Pulp & Paper Canada March 2009

March 2009

www.pulpandpapercanada.com

PAPTAC Annual Meeting & EXFOR review

deas new i ing

Exp lor

Journal of Record, pulp and paper technical association of canada HE: Adding Optical Brightening Agents to High-Yield Pulp at the Pulp Mill

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February 2009

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MARCH 2009 Vol. 110, No. 3 A Business Information Group Publication ISSN 0316-4004 EXFOR

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PROCESS CONTROL

14

Oxygen DELIGNIFICATION

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FEATURES

8 10 14 38

Safest Mill in Canada Congratulations to the employees at Domtar/Windsor, Weyerhaeuser/ Grande Prairie, and Sonoco/Brantford, winners of Pulp & Paper Canada’s annual contest.

EXFOR & Annual Meeting 2009: Exploring new ideas Hundreds gathered in Montreal to share ideas and renew personal connections at PAPTAC’s EXFOR and Annual Meeting 2009.

Taking the pulse of process control Effective process control can be a key factor in profitability, so we checked in with some leading players to see what they’re working on.

Open sesame!

The team at SFK-Pâte developed a simple tool to safely open railcar doors.

TECHNICAL PAPERS

18 24 29

High Yield Pulp Adding optical brightening agents to high-yield pulp at the pulp mill Z. He (University of New Brunswick), H. Zhang (Tianjin University of Science and Technology), Y. Ni (University of New Brunswick), and Y. Zhou (Tembec) T19 Mechanical Pulps Impact of machine whitewater on brightness of mechanical grades X. Hua (FPInnovations- Paprican) and M. Laleg (FPInnovations – Paprican) T25 Oxygen Delignification Rate determining step and kinetics of oxygen delignification Y. Ji (National Renewable Energy Laboratory), E. Vanska (Helsinki University of Technology), and A. van Heiningen (University of Maine) T30

MISSION STATEMENT:

To promote the pulp and paper industry in Canada by publishing news of the people and their innovations in research, technology, management and financing, as well as forecasts of future trends.

Authorized to publish papers of the Pulp and Paper Technical Association of Canada, which are identified by the symbol

IN EVERY ISSUE

4,5 6 28 35 36 36 37

Editorial Industry News On the Move Events Technology News Classified Ads Advertiser Index

Serving the industry since 1903.

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Pulp & Paper Canada March 2009

3

Changes at the Pulp & Paper Canada group of magazines Dear readers, As the pulp and paper industry faces numerous changes in response to the current global economic situation, magazines must also adapt.

The Pulp & Paper Canada Magazine Group is currently going through a transformation in order to continue serving the industry and our valued readers, as we have been for over a century.

Our French-language publication, Les Papetières du Québec, and electronic newsletter, Le Parchemin, are not economically viable at this time. With regret, we have suspended production of these two publications. We continue to bring you headlines, analysis, and coverage of industry issues through Pulp & Paper Canada and the website

Editorial Editor CINDY MACDONALD 416-510-6755 cindy@pulpandpapercanada.com Contributing Editors HEATHER LYNCH YVES LAVERTU ELYSE AMEND Advisory Board Richard Foucault Greg Hay Dr. Richard Kerekes Barbara van Lierop Dr. David McDonald Dennis McNinch Dr. Yonghao Ni Bryant Prosser Dr. Paul Stuart Ross Williams Administration Publisher EILEEN WALTERS eileen@pulpandpapercanada.com President, Business Information Group BRUCE CREIGHTON Vice President, Publishing ALEX PAPANOU Editorial And Sales Offices: 12 Concorde Place, Suite 800 Toronto, ON M3C 4J2 Phone: 416-442-5600.

Toll Free: c da 800-268-7742; usa 800-387-0273

4

Production Art Directors RON TAYLOR rtaylor@bizinfogroup.ca VALERIE PERROTT vperrott@bizinfogroup.ca Circulation Manager CINDI HOLDER cholder@bizinfogroup.ca

­pulpandpapercanada.com.

In addition, we welcome our new editor, Cindy Macdonald, who will maintain the journalistic standards and quality our magazine has prided itself on since 1903. Cindy has 18 years of experience as an editor in the automotive, manufacturing, and forestry sectors.

As always, Pulp & Paper Canada remains dedicated to being your authoritative source for developments in our industry.

Sincerely, Eileen Walters Publisher

Scandinavia and Finland: Jyri Virmalainen, Exomedia Oy, Latokartanontie 7A, 4 krs, 00700, Helsinki, Finland; Phone: +3589-61500100; Telex 121394 tltx sf (Att: Exomedia); Fax 358-9-61500106.

E-mail: jyri.virmalainen@exomedia.fi

Market Production Manager KIMBERLY COLLINS kcollins@bizinfogroup.ca Print Production Manager PHYLLIS WRIGHT pwright@bizinfogroup.ca Reprint requests: Marisa Sementilli 416-510-6829 News and Press Releases media@pulpandpapercanada.com Sales Representation North America: Eileen Walters, Publisher, Phone: 514-630-5955, Fax: 514-630-5980, eileen@pulpandpapercanada.com Inside Sales and Classified Ads: Jim Bussiere, Senior Account Manager, Phone: 514-630-5955, Fax: 514-630-5980, jim@pulpandpapercanada.com We acknowledge the financial support of the Government of Canada through the Publications Assistance Program towards our mailing costs.

March 2009 Pulp & Paper Canada

Sustaining member, Pulp and Paper Technical Association of Canada; Member, Canadian Business Press and Audit Bureau of Circulation.

Indexed by: Canadian Business Periodicals Index; Abstract Bulletin, The Institute of Paper Science and Technology; Materials Science Citation Index PULP & PAPER CANADA (ISSN 03164004) is published by a division of Business Information Group Magazines, Limited Partnership, 12 Concorde Place, Suite 800, Toronto, ON, M3C 4J2.

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All rights reserved. The contents of this publication may not be reproduced in part or in full without the consent of the copyright owner.

From time to time, we make our subscription list available to select companies and organizations whose product or service may interest you. If you do not wish your contact information to be made available, please contact us via one of the following methods.

Phone: 1-800-668-2374; fax: 416-442-2191; e-mail: privacyofficer@businessinformationgroup.ca; mail to: Privacy Officer, Business Information Group, 800-12 Concorde Place, Toronto, ON, M3C 4J2 Canada Postmaster: Please forward 29B and 67B to 6600 Trans Canada Highwary, Suite 209 Pointe Claire, QC H9R 4S2. Legal deposit Quebec National Library. Canada Post Publications Product Agreement No. 40069240. Publications Mail Registration No. 09777. USPS 751-630. US office of publication: 2424 Niagara Falls Blvd., Niagara Falls, NY 14304-5709. Periodicals Postage paid at Niagara Falls, NY. US postmaster: Send address changes to Pulp & Paper Canada, 2424 Niagara Falls Blvd., Niagara Falls, NY 14304. Printed in Canada. Return undeliverable Canadian addresses to Circulation Dept. – Pulp & Paper Canada, 800-12 Concorde Place, Toronto, ON, M3C 4J2.

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editorial

Pulp & Paper Canada: a world of its own

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magazine is a world of its own.

The headlines, the words and images chosen to tell the stories, the angles taken, the opinion columns, the integrity of the authors, the principles defended, and the commitment to a mission - this all creates a unique meeting ground for the writers and artists, the people making the news, and the readers.

With every issue comes the chance to renew the trust and relationship between readers and writers. Sometimes these relationships are built recently, over a few months, but often they are established over many years, with investments made throughout decades.

A publication like Pulp & Paper Canada has a history of over 100 years, and has a duty to its writers and artists, and its readers. It is this unique relationship that has made Pulp & Paper Canada the authority in the Canadian industry, as well as on an international scale.

A recent restructuring brought on by the current global economic situation means I will be passing the torch to our new editor, Cindy Macdonald.

Cindy has worked in the forestry sector before. I first met her when she worked here, in Montreal, on both Pulp & Paper Canada and Canadian Forest Industries. I am sure she will keep Pulp & Paper Canada’s flame burning bright.

I am happy to have had the opportunity to add my building blocks to this historic institution, and I value the relationships built with the numerous writers and artists, figures in the industry, and readers. It has been a privilege and an unforgettable experience, and I thank you for it.

Yves Lavertu

pulpandpapercanada.com

New beginnings in a familiar place I

am thrilled, and a little awed, to be at the helm of Pulp & Paper Canada. This magazine was the first publication I worked on after graduating from journalism school. For several years during Peter Williamson’s reign as editor, I was an editorial assistant, writing news stories and preparing technical papers for publication.

That early exposure introduced me to the traditions and values espoused by the Pulp & Paper Canada group of publications. In recent weeks, I’ve seen that the magazine continues to be an authority in the industry, and have a strong connection with its readers, as well as outstanding technical content.

In the intervening years, I have edited several Cindy Macdonald Editor magazines at Business Information Group, the parent company of Pulp & Paper Canada. I now have news releases first-hand knowledge of logging operations, how to media@pulpandpapercanada.com mold plastic parts, and how to repair vehicles. letters to the editor While some concerns are consistent among cindy@pulpandpapercanada.com businesses in different sectors, a readership survey performed last spring has provided me with valuable insight to what Pulp & Paper Canada readers want from their magazine. It helped to crystallize my own ideas about the direction our content should take. Pulp & Paper Canada needs a bit of a return to its roots, with more input from mills, more case histories, and more voices from the industry. For that, I’ll be drawing on you, the readers. Feel free to send me your ideas and comments, or talk to me in person at industry events.

Yves Lavertu has laid the groundwork for some timely and relevant stories in the upcoming issues. The April edition will have articles on energy conservation strategies and the emergence of energy issues on the public agenda.

In May, we present an update on biorefining, reviewing the projects of a few leaders in this sector and outlining strategies for business ventures in this new realm of forest products.

It’s invigorating to join a sector in the midst of transforming itself, as the forest products sector is doing. There’s much to talk about, much to learn, and a challenging role for me to fill in bringing the news to you quickly and accurately. My first opportunity to meet everyone will be at PacWest in June. I’m looking forward to it.

You can reach me at cindy@pulpandpapercanada.com or 416-510-6755, or toll-free at 800-268-7742, ext. 6755. For our friends south of the border, call 800-387-0273, ext. 6755.

Cindy Macdonald cindy@pulpandpapercanada.com Pulp & Paper Canada March 2009

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industry news ECONOMY EXPANSION

Cascades announces investments at Norampac plant

Kingsey Falls, Que. – Cascades Inc. has announced an investment of $5 million at its Norampac plant in Kingsey Falls Que., to streamline the manufacturing of linerboard made from 100% recycled fibre. The current project consists of expanding the building to replace the winder as well as to create additional space for future investments.

Since its inception in 1964, the plant, formerly called “Division Papier” (Paper Division), has invested $55 million in order to increase its annual production capacity to 90,000 tonnes. At the end of this current project, production capacity at the plant will be greater than 125,000 tonnes per year. Subsequent phases of the upgrade are planned for 2010 and 2011.

In 2008, more than $12 million was invested in Cascades’ seven production units in Kingsey Falls alone. In 2009, depending on the status of the global economic situation and its financial performance, Cascades intends to invest approximately $100 million in capital costs.

MILL

Superior Fine Papers to restart TBFP mill

Thunder Bay, Ont. – After months of uncertainty, the former Thunder Bay Fine Papers (TBFP) mill in Thunder Bay, Ont., appears to have been saved again.

A local group of investors that goes by the name of Superior Fine Papers Inc. purchased the mill in early February for an undisclosed amount.

The facility has had a tough history.

The former Cascades Fine Papers Group Inc. mill was closed in 2006, and was then bought and restarted by TBFP in early 2008. However, due to a surplus of inventory and a lack of customers, the mill had to shut down again in July of the same year.

Following an October 2008 Supreme Court hearing in Toronto, Deloitte & Touche Inc. was given possession of the mill. It was saved from going to scrap by the Superior Fine Papers acquisition.

An exact start date for the mill has not yet been determined, but according to a press release issued by the new owners, it will be “a matter of weeks as opposed to a matter of months.”

The press release also stated the start-up would return most of the former jobs and “countless spin-off jobs” to Thunder Bay. The Superior Fine Papers mill will be the only coated free sheet mill in Canada.

According to Marc Goguen, Superior Fine Papers’ vice-president sales and mar-

keting, the group’s sales team is talking to customers and has secured a level of commitment.

“The reaction has been overwhelming.

In fact, we have letters of commitment from our key customer base in excess of 90,000 tonnes, which is half of the mill’s output; we are all overwhelmed by the support,” Goguen says.

PACKAGING

Smurfit-Stone files for Chapter 11

Wimington, Del. – Smurfit-Stone Container Corp. and its U.S. and Canadian subsidiaries filed petitions for reorganization under Chapter 11.

According to an article on Bloomberg. com, the company listed US$5.6 billion in consolidated debt and US$7.5 billion in consolidated assets as of Sept. 30, 2008. The article also stated 24 affiliates sought court protection as well.

In a company press release, SmurfitStone’s chairman and chief executive officer, Patrick Moore, is quoted as saying the low demand for packaging spurred by the global economic recession and frozen credit markets were behind the move.

According to the article, SmurfitStone will continue to operate normally while it moves to reorganize its debt.

Smurfit-Stone – North America’s second largest corrugated packaging producer – employs about 22,000 people in the United States, Canada, Mexico and Asia.

According to the company, its operations outside Canada and the United States are excluded from the bankruptcy process.

Tembec cuts costs through salary freeze, reduced expenses

Montreal, Que. – Tembec Inc. is taking further measures to cut costs. The company recently announced plans to slash 100 white-collar jobs and to shutter an Ontario sawmill, Canadian Press confirmed. Tembec has also frozen all salaries for 2009, cut bonuses for its executives, and is seeking to reduce travel expenses as well as participation in associations and research institutes in order to save money.

The moves come on top of previously announced plans to lay off close to half of its work force in B.C., Manitoba, and Ontario.

“The actions announced today are extraordinary measures for our company,” Jim Lopez, president and CEO, said.

“However, these are extraordinary times for the economy generally, and for forest products in particular.”

Tembec is also seeking a 10% reduction from material suppliers and a 20% reduction from service suppliers.

At Tembec Inc.’s annual meeting in Montreal in January, Lopez also said the company will increase its focus on becoming more environmentally friendly and gaining Forest Stewardship Council certification, a status he was noted as saying brought in $10 million for Tembec last year.

MILL

UPM’s Miramichi paper mill sold, will produce solar panels

Helsinki, Finland – UPM has sold its former paper mill and related assets in Miramichi, New Brunswick, to Umoe Solar AS of Norway. The sale includes the paper mill, a groundwood pulp mill, woodlands operations, and two sawmills located nearby in Bathurst, N.B., and Blackville, N.B. The sale price was not disclosed.

The Miramichi paper mill, with an annual production capacity of 450,000 tonnes of light-weight coated magazine paper, was permanently closed in December 2007. The disabled paper machines can no longer be used for paper production.

Umoe Solar has revealed plans to build a solar panel facility at the site, and will continue to run the Bathurst sawmill.

……Visit www.pulpandpapercanada.com for details: West Fraser cuts back....Fraser Papers offloads specialty tons...Canfor take s s s

industry news SHUTDOWN

B.C. government takes responsibility for keeping Mackenzie mill warm

Victoria, B.C. – British Columbia’s Ministry of Environment was compelled take over operation of the idled Worthington pulp mill in Mackenzie, B.C., to prevent the facility from freezing and potentially leaking or releasing dangerous substances, including chlorine dioxide and caustic soda.

The provincial government declared an environmental emergency at the site in January when it became clear the mill’s owners were not taking the necessary actions to properly maintain the site and employees who had not been paid for weeks were prepared to walk away.

Under the wintry conditions of northern B.C. in January, failure to maintain and operate the boiler would likely result in pipes, tanks, and other equipment freezing, and possibly rupturing.

In a further development, the Canadian Nuclear Safety Commission ordered radioactive nuclear instruments at the mill be removed, saying there was the poten-

tial for a risk to health and safety, and to the security of the nuclear substances.

Following the provincial government’s intervention, the mill’s owner, Edmonton-based Worthington Industries, did pay back wages for the staff who were maintaining critical operating systems.

In mid-February, Worthington’s plans for the mill were still unclear. research

NSERC Chair renewed, will study forest biorefinery in second term

The NSERC Environmental Design Engineering Chair celebrated last month the renewal of its mandate to study process integration in the pulp and paper industry. The emphasis in this second mandate will be on the forest biorefinery.

Professor Paul Stuart of the department of chemical engineering at École Polytechnique de Montréal directs the Chair.

Representatives from NSERC, Natural Resources Canada, and many industrial partners of the program were present at the ceremony on Feb. 2.

PAPERCLIPS

Canadian graduate students come together during EXFOR and PAPTAC annual meeting The Canadian Pulp and Paper Graduate Student Seminars, co-sponsored by PAPIER (the Canadian Pulp and Paper Network for Innovation and Research) and the PAPTAC (Pulp and Paper Technical Association of Canada) Research Committee, took place all day Feb. 5 at the Fairmont Queen Elizabeth Hotel in Montreal.

Nineteen students from universities across the country presented their research on a number of topics, including cellulosic nanofibres, low-consistency refining, biorefining, and bio-active fabrics.

“It’s nice to see the program is as successful as ever,” seminar moderator Prof. Theo van de Ven of McGill University said before leaving the floor to the students.

Richard Kerekes, professor emeritus of pulp and paper engineering at the University of British Columbia and PAPIER director, said he had received positive feedback about the graduate student events, especially the PAPIER student poster session that took place on Feb. 4 during EXFOR and the PAPTAC annual meeting. He added that giving the seminars their own day this year allowed the graduate students to take part in the EXFOR and Annual Meeting events of the previous two days, and also gave industry

Paul Stuart, chair of NSERC’s Environmental Design Engineering Chair.

Among the issues the Chair will study are: - What is the biorefinery and how can it revitalize the forestry industry while also reducing greenhouse gas emissions?

- How should the environmental performance of the forest biorefinery be evaluated?

- What products of biorefining should be considered by Canadian forestry companies to ensure their long-term competitiveness?

- How should forest companies change their supply chain to effect the transformation to the forest biorefinery? fessor Richard Kerekes, pro paper d an lp pu of tus eri em iversity Un the engineering at d an bia lum Co h of Britis uced rod int or, ect dir R PIE PA Paper d an lp Pu the Canadian nars mi Se nt de Stu te Gradua on Feb. 5

members the time to learn about the students’ research.

Awards were presented for the three best presentations of the day, as well as the three best posters.

Alkis Karnis Memorial Prize 2009 (for best poster) 1st – Ali Soltanzadeh, University of British Columbia, Mixing Evaluation in Pulp Stock Chests 2nd – Ali Chami Khazraji, Université du Québec à Trois-Rivières, Physicochemical Study of Factors Inducing Piling in Heatset Offset Lithography 3rd – Antti Luukkonen, University of British Columbia, Understanding Low Consistency Refining of Mechanical Pulps

Henry I. Bolker Prize 2009 (for best seminar) 1st – Zeinab Hosseinidoust, McGill University, Cellulose-phage Interactions 2nd – Azadeh Bagherzadeh-Namazi, University of Toronto, Conversion of Pulp Mill Sludge into Activated Carbon 3rd – Lijun Wang, University of Toronto, Characterization of Two Novel Esterases from Streptomyces avermitilis and Rhodopseudomonas palustris

es downtime...Further shutdowns for AB in Thunder Bay...Atlas Paper Mill receives green stamp of approval...Catalyst Paper seek s s s

health and safety

Safest Mill in Canada Contest F

or more than 70 years, Pulp & Paper Canada magazine has recognized mills which achieve an outstanding safety record. The presence of repeat winners this year clearly demonstrates that these facilities have succeeded in creating a culture of safety in the workplace. The staff of Pulp & Paper Canada magazine congratulates the category winners and commends them for maintaining high safety standards in the current cost-conscious climate.

Category A

Domtar Inc., Windsor, Que. This is Domtar/Windsor’s second consecutive year in first place. The mill achieved total recordable frequency of 0.99, with 1,411,959 hours worked in 2008. This is a drop from last year’s frequency of 1.53 with 1,439,532 hours worked.

Category B

Weyerhaeuser Canada, Grande Prairie, Alta.

The team at Weyerhaeuser’s Grande Prairie mill achieved a perfect score of zero recordable incidents in 2008. This facility placed second in this category last year, with frequency of 0.96.

Category C

Sonoco Canada Corporation, Brantford, Ont. This is the fourth year in a row that Sunoco Canada/Brantford tops the Category C list. In 2008, the facility recorded a perfect score of zero recordable incidents. Second place finisher, Catalyst Paper/Paper Recycling of Vancouver also has zero recordable incidents, but had fewer total hours worked.

Safest Mill in Canada Contest 1-1-2008 to 31-12-2008 Category A (more than 100,000 man-hours per month) Domtar Inc., Windsor, Que. Catalyst Paper, Crofton, B.C. Catalyst Paper - Elk Falls, Campbell River, B.C.

Total Recordable Incidents 7 41 37

Total Hours Worked 1,411,959 1,546,145 1,280,388

TRI Frequency 0.99 5.30 5.78

Category B (50,000 to 100,000 man-hours per month) Total Recordable Incidents Weyerhaeuser Canada, Grande Prairie, Alta.

0 Irving Pulp & Paper Ltd., Saint John, N.B. 5 Hinton Pulp (Div. of West Fraser Mills), Hinton, Alta.

5

Total Hours Worked 608,065 783,874 679,499

TRI Frequency 0.00 1.28 1.47

Category C (less than 50,000 man-hours per month) Sonoco Canada Corp., Brantford, Ont. Catalyst Paper - Paper Recycling, Vancouver Kruger Inc., Montreal

Total Hours Worked 115,790 102,656 306,608

TRI Frequency 0.00 0.00 0.65

8

March 2009 Pulp & Paper Canada

Total Recordable Incidents 0 0 1

pulpandpapercanada.com

“One simple upgrade brought amazing results.”

With optical module improvements and technology for continuous, single line measurement of total and true ash consistencies, the kajaaniRM3 retention sensor is the latest proven edition to the Kajaani™ family of products.

“The new kajaaniRM3 is much better at ash measurement and requires almost no maintenance,” explains Norske Skog, Norway, PM3 Instrument Engineer, Oddvar Maås (on the right).

Simple to install using existing RM-200 frames and connections, “RM3 is a practical, economical and effective way to upgrade to state-of-the-art retention measurement technology,” states Jan-Ola Claesson, Line Maintenance Manager for Automation (on the left).

With instant results, it’s not hard to smile.

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cover story

Exploring new ideas

By Elyse Amend

Hundreds gathered in Montreal to share ideas and renew personal connections at PAPTAC’s EXFOR and Annual Meeting 2009.

W

By Elyse Amend

ith just over 1000 people attending from mills, research organizations, and industry suppliers from Canada and around the world, the Pulp and Paper Technical Association of Canada’s EXFOR trade show and 95th annual meeting in Montreal, Que., garnered its fair share of positive feedback.

Taking place at the Fairmont Queen Elizabeth Hotel from Feb. 3-4, this year’s event was consolidated so the technical and business programs plus the EXFOR trade show ran simultaneously on the convention floor.

“It’s a smaller format, and I think it’s a little more intimate,” comments Buckman Laboratories’ president Tom Johnstone, a long-time exhibitor at EXFOR. “It’s not about the quantity of people, but we’ve got some good quality decision makers, and we’re quite pleased.”

Over the two days, participants at the event were able to learn about new technologies in a number of fields, including biofuels, recycling, process control, and many more, as part of the technical program. The business programs featured presentations from industry leaders on timely issues, such as managing energy costs, carbon strategy, innovation, and surviving the current economic storm.

The EXFOR trade show gave suppliers and industry members the chance to discover the new technologies available, exchange ideas, and network with their peers. Students also had the opportunity to participate in the PAPIER (Canadian Pulp and Paper Network for Innovation and Research) poster session during the two days of EXFOR and the annual meeting, as well as the graduate student seminars held at the Fairmont Queen Elizabeth Hotel on Feb.5.

Yves Lavertu (right), formerly of Pulp & Paper Canada presented the Energy Conservation Awards. Surendra Singh (left) of Alberta Newsprint Company accepted first prize.

Gerry Pageau (left) presented the I.H. Weldon Award to Dominique Lachenal (right), Guillaume Pipon and Christine Chirat of École française de papeterie.

Dan Davies presented Adriaan van Heiningen of the University of Maine with the Howard Rapson Award for the best chemical pulp bleaching paper.

The PAPIER student poster session took place Feb. 4 on the convention floor. All posters were eligible for the Alkis Karnis Memorial Prize.

10

March 2009 Pulp & Paper Canada

Dr. George Rosenberg of SENTINEL/Paprican in Vancouver received a certificate of appreciation for his contributions to PAPTAC and to the research community.

Industry experts at the mechanical pulping panel gave overviews on different steps that can be taken to reduce energy consumption at the mill. pulpandpapercanada.com

cover story Pettigrew sees a positive future for Canada

“This is a very unique event where you see most of your customers and partners. It generates a lot of discussion and a lot is happening,” says Jean Hamel, FPInnovations-Paprican’s director of research. “Right now, it’s as important as ever to participate in these kinds of events … with the economic situation and the state of the industry. Now, innovation is the key to change. And you cannot change if you don’t see what’s going on around you.”

Outgoing PAPTAC chairman Marie Dumontier agrees that the exchange of knowledge and personal connections are what makes this annual event so important.

“If we stay in our own mills, our resources are rather limited,” she says. “Yes, there is the Internet, but it’s never like having a conversation with a supplier, with somebody else from another mill, with a speaker, with the experts.”

Patrice Mangin, head of the CIPP at the Université du Québec à Trois-Rivières (UQTR), presented the F.G. Robinson Award to Sylvain Robert, also of the CIPP/ UQTR and chairman of the PAPTAC Research Committee for outstanding leadership and service.

Robert Lanouette (left) of the CIPP/UQTR presented the Douglas Atack Award to Zhibin He (centre) and Yonghao Ni (right) from the University of New Brunswick, Hongjie Zhang of Tianjin University of Science and Technology, China, and Yajun Zhou of Tembec Inc., Témiscaming, QC. Martin Fairbank (right) of AbitibiBowater presented the John S. Bates Award for the Best Branch Paper to Brian O’Connor (left) of FPInnovations in Pointe-Claire, QC and Chris Walton of AbitibiBowater (not pictured).

pulpandpapercanada.com

By Elyse Amend Thanks to its management of the economy and the solid condition of its financial institutions, Canada is in the best situation to survive and emerge from the current global financial crisis, said former federal Foreign Affairs Minister Pierre Pettigrew during the Tuesday morning plenary session of EXFOR & Annual Meeting 2009 at the Fairmont Queen Elizabeth Hotel Pettigrew in Montreal.

“As Canadians, we’ve always had this kind of inferiority complex...that when the U.S catches a cold, Canada gets pneumonia,” said Pettigrew, who is now executive advisor, international, at Deloitte & Touche LLP. He added, however, that compared to the United States, our economy has been more resilient, and that recessions in the past have tended to affect Canada’s southern neighbour more deeply.

“It’s when America has pneumonia, we have a cold,” Pettigrew said.

Canada is based on the notion of peace, order, and good government, Pettigrew said, compared with the American ideal of life, liberty, and the pursuit of happiness. Thanks to our public finance, relatively low debt, balancing of trade, and good social support systems, Pettigrew said Canada is in a very solid position to weather the financial crisis. The country’s commodities, he added, will also play an important role.

“Watch us in 2010, and you’ll see, we’ll carry a lot,” he forecast.

On a global level, Pettigrew said that while the United States will continue to represent “a huge power”, emerging markets, including China and India, will play a significant role in the future. However, he feels the world’s economic powerhouses need to start treating these emerging markets differently, integrating them into the world’s institutions.

EXFOR 2009 Pulp & Paper Canada March 2009

11

cover story

Annual meeting wraps up a year of changes

T

he 95th Annual General Meeting of PAPTAC on Feb. 4 was an occasion to acknowledge changes that have streamlined the association, and recognize the contributions of ­PAPTAC’s dedicated members. An annual meeting also looks to the future, and in this case, a vote on the bylaws governing the composition of the executive council opens the doors to some fresh input for the group in 2009.

Marie Dumontier, outgoing chairman of the executive council, gave a brief review of association events in 2008.

“This was a year of transition for the pulp and paper industry, as well as PAPTAC,” she remarked. “There were hard decisions made to ensure a viable future for the association.”

However, there were positive outcomes to the association’s ability to economize and streamline. “We reduced office space by 60% as well as introduced our online bookstore, to provide access to PAPTAC publications 24/7,” Dumontier noted. The Journal of Pulp and Paper Science continues to be published, under a revised budget.

An amendment to PAPTAC’s bylaws that will allow up to two supplier representatives to sit on the association’s nine-member executive council was supported unanimously by all eligible voting members present. Until now, industry suppliers have only been indirectly represented by the voting members on council, although this group makes up about 35% of PAPTAC’s total membership. With this bylaw revision, suppliers will be able to directly communicate with the council, and help in planning PAPTAC’s future activities. Under the amendment, supplier councillors will be able to serve as full members on the executive council, and have the ability to move, second, and vote on council business. Their participation will also be factored in to have quorum during meetings.

Achievements and excellence were acknowledged during the awards portion of the annual meeting.

12

March 2009 Pulp & Paper Canada

By Janelle Jordan The Dr. John S. Bates Gold Medal Award was awarded to Dr. Donald B. Mutton. This award is bestowed upon individuals for long-standing contributions to the science and technology of the pulp and paper industry.

“A prestigious award like this isn’t won alone,” Dr. Mutton commented. “This award belongs to all of us.” Dr. Mutton also paid tribute to his wife who passed away last year, attesting that “her support was the wind beneath my wings.”

The Honorary Life Member Award, given to C. Scott Travers, recognizes outstanding service to PAPTAC and to the pulp and paper industry as a whole.

Marie Dumontier, PAPTAC’s outgoing chairman, with André Bernier, who has been elected chairman for 2009.

Dr. Dominique Lachenal received the I.H. Weldon Award, accepting it on behalf of his students Christine Chirat and Guillaume Pipon from the École française de papetrie in St-Martin d’Hères, France. The award is granted to the best paper by a member of PAPTAC. Dr. Lachenal and his students won for their paper entitled Final Pulp Bleaching

by Ozonation: Chemical Justification and Practical Operating Conditions.

Before Dumontier passed the reins of her two year chairmanship over to André Bernier, she praised the efforts of current and retiring councilors, as well as welcomed the newly elected councilors.

“This two-year term as chairman has been rewarding and a great learning experience. Nowhere else could I have gained an experience like this in such a short amount of time,” she stated.

André Bernier will be following in the footsteps of Dumontier as the PAPTAC chairman for 2009. Bernier, mill manager at Catalyst Paper - Crofton Division, praised her contribution to PAPTAC. “Marie is a source of inspiration, exceptional leadership, and service as chairman,” he said.

Other awards

Dumontier presented C. Scott Travers with the Honorary Life Member Award during the PAPTAC annual general meeting Feb. 4.

Gadget Competition: Steve Pellerin of Kruger Inc., Trois-Rivières, Que., for his cable winder.

Douglas Jones Award: Mike Van Ham, Lesley Dampier, Kerry Morton, and Sophie Mullen, for Pulp and paper sludge as a barrier layer in landfill closure: a new opportunity.

Jasper Mardon Award: X. Hua and M. Laleg, for Impact of machine whitewater on brightness of mechanical grades.

Certificate of Appreciation: Robert Lanouette, Université de Québec à TroisRivières.

Certificate of Appreciation: Natacha Houde, Kruger Wayagamack Inc, TroisRivières, Que.

Dumontier presented Donald B. Mutton with the John S. Bates Memorial Gold Medal.

For more news on EXFOR and the PAPTAC Annual Meeting, visit ­pulpandpapercanada.com/exfor. pulpandpapercanada.com

cover story

T

Innovation and climate change: From concept to reality

he business seminars at the PAPTAC Annual Meeting 2009 were ripe with practical information relating to how pulp and paper companies can integrate the concepts of innovation and carbon management into their dayto-day operations.

Discussing his company’s carbon strategy, Phillipe Riebel said at the top of UPM-Kymmene’s list are decreasing greenhouse gas emissions and its carbon footprint.

“Defined by Carbon Trust, carbon footprints are total emissions of greenhouse gases and carbon equivalents from a product across the life cycle, from the production of raw materials used in its manufacture to disposal of a finished product,” he explained.

“The decrease of greenhouse gases itself improves energy efficiency, by replacing fossil fuels with non-fossil energy.

Energy-efficient logistics, such as using eco-efficient transport, shifting volume to rail and sea, or using a low-sulfate/alternative bio diesel, is an efficient choice,” he continued.

Riebel also commented on the “carbon profile” his organization created as a testimony to the importance of transparency.

“You can only know the influence of a carbon footprint if you measure it,” he stated. “We have a carbon report card if you want to know carbon per tonne of paper.”

Paul Lansbergen, director and secretary of the Forest Products Association of Canada, highlighted that climate change touches provincial, federal and U.S. congressional borders. “Climate change is a multi-jurisdictional action which overlaps and also presents potential confusion due

to various baselines and provisions on carbon off-sets.”

Climate change director Frédéric Gagnon-Lebrun of EcoRessources delved into the opportunities for the pulp and paper industry as an off-set provider through voluntary carbon market initiatives.

“There are certain steps to develop a project: you must document the project to get voluntary credit,” he said. These steps include the Preparation Phase, which could cost approximately $70,000 including feasibility studies and marketing to potential buyers. The Validation Phase could reach upwards of $30,000. This phase entails validation from a third party, certification, and product registration.

This investment translates into marketing opportunities to sell carbon neutral products, in addition to having increased consumer awareness.

Also touting the value of carbon management was the Sustainable Practice Group of Raymond Chabot.

“Climate strategy should be an overall strategy, not just an add-on,” advised Michelle Régis. “It needs to be integrated from strategy to action and you need commitment from management, clear policies and objectives.”

Take action on innovation

The Wednesday morning session on “Innovation: A Key for the Future” discussed how organizations could transform traditional concepts and products into tangible innovation.

Keynote speaker Brian Engleman from SRI International (Stanford Research Institute) spoke about the five key aspects of innovation. SRI is the pio-

neer of several well-known inventions – the computer mouse, hypertext protocol, and low-cost solar grade silicon. “The five steps of innovation are customer and market needs; value creation; innovative champions; innovative teams; and organization alignment (from the top-down that provides goals to the bottom-up that provides ideas), all of which that are critical for improving innovation,” Engleman explained.

“Much of what is taught [about innovation] is wrong and counterproductive,” he continued. “Saying it is all about creativity, that discipline destroys creativity or that shareholders come first is wrong.

This is why most organizations score a ‘C-’ on innovation.”

Roger Gaudreault, R&D manager of Cascades Canada Inc., talked about the importance of implementing innovation.

“Traditional strategies make it difficult to win new markets. Innovation can increase competitiveness,” Gaudreault said. “Innovation at Cascades is defined as a new process, new product, and new method.”

Gaudreault also introduced the notion that people can be either conceptual thinkers or experimental ones. Ultimately, an assimilation of both frameworks is essential for innovative success, he explained.

“We want a quick answer, therefore we use a conceptual framework. But, we need a portfolio of both, even as we are increasingly faced with problems that can only be solved in a slow, steady way,” concluded Gaudreault, referring to the characteristics of the experimental model.

With files from Janelle Jordan.

PPC

Rewarding energy conservation ideas

Yves Lavertu, past editor of Pulp & Paper Canada and Les Papetières du Québec, presented the Energy Conservation Awards during the Energy Session. Surendra Singh of Alberta Newsprint Company accepted first prize for Improving heat recovery by utilizing grit cleaner reject, which he co-authored

pulpandpapercanada.com

with Darrel Stang, Jim Johnson, Sean Cairns, Chad Gurney, Andrew World, Jan Lupens, and Mike Putzke, also of Alberta Newsprint Company.

Second prize went to Marco Veilleux of Fraser Papers, Thurso, Que., for Heat recovery from smelt dissolving tank vent to pre-heat boiler make-up

water with implementation through an off-balance sheet.

Scott Shannon of Millar Western Forest Products was awarded third prize for Synergies between low energy refining and ultra fine slotted screening producing cost effective high quality BCTMP.

Pulp & Paper Canada March 2009

13

process control

Taking the pulse of process control Effective process control can be a key factor in profitability. Pulp & Paper Canada checked in with some of the leading players in the process control industry to learn more about what they are

By Heather Lynch working on and how an edgy economy has changed the control landscape.

Brad MacDonald, marketing manager, and Sachin Jari, sales manager, ABB: Specifically in process control for pulp and paper, last year we introduced a new QCS scanner called the Network Platform, as well as a broad suite of services and tools that enable customers to more cost effectively ensure the best performance and highest reliability of their assets. The new platform can coexist with the existing Smart Platform on the same machine and doesn’t require modifications to the existing QCS.

current pulp and paper market condition has prevented a deeper penetration of these solutions.

We have also focused on system integration using standard PLC. These control-based systems replace old manual controls and improve process control.

These kinds of upgrades are focused on reducing the workload for operators, improving process control, and decreasing energy costs. Many mills in North America are trying to eliminate old, energy consuming refiners by improving low consistency refining, which typically demands less energy.

Steven W. Schoenborn, product specialist, industrial process applications,

Optek: In the past year, our primary focus for instrumentation into the pulp and paper industry has been measuring turbidity of white liquor in a way such that fouling of the sensor’s optical windows does not interfere with the reliability of the measurement.

Steve Glover, integrated architecture marketing, Canada, and Kevin DeWitt, global process technical consultant, Rockwell: The PlantPAx portfolio is the next step in our commitment to help customers achieve process automation excellence. It unifies our core capabilities and technologies with those of our market leading partners.

Sylvain Renaud, sales director for North America, Andritz Automation, Ltd.: We focused on advanced model predictive control in 2007-2008. We had great success on lime kiln control, bleach plant, and kappa control. Model predictive controllers (MPCs) have been used for 20 years in the mining, glass and food industries, but are really just starting in pulp and paper. MPCs are used to control non-linear and complex processes that cannot be controlled with standard PID. Our MPC, BrainWave, stabilizes complicated processes, which allows the user to decrease set point for saving energy or chemicals.

While it has been deployed in more than 10 pulp and paper mills in North America, the Refining is one target for process control improvements.

14

March 2009 Pulp & Paper Canada

In a challenging North American industry, how important is process control research and development in a quest to remain competitive?

Photo: ABB

PPC: What developments in the area of process control have you focused on in the past year?

Rockwell: For mills to be competitive in today’s economic conditions, research and development are very important, not only in product development, but also on how the machines are set up to run. The product grades the machines are running and how to reduce the amount of scrap and waste rejects is also important. Knowing what the specific issues are and finding how to eliminate them can potentially save the mill a significant amount of money, which is necessary to survive in the paper industry pulpandpapercanada.com

PACWEST CONFERENCE JUNE 10-13, 2009 Join us at:

Closing the Loop: Profiting from our Green Potential

SUN PEAKS BC

TECHNICAL SESSIONS * KRAFT * PAPER MACHINE TECHNOLOGY * ENERGY * ENVIRONMENT

and network with industry leaders and technical experts. Learn about and showcase new technologies and process improvements.

Enhance professional development …

* MECHANICAL PULPING * NEW TECHNOLOGIES Pacwest 2008 Program Chair, Carlo Dal Monte, Catalyst Paper and Conference Chair, Brett Robinson, CanforPulp LP

PROGRAM OUTLINE

2009 COMMITTEES

WEDNESDAY, JUNE 10

Program Committee: Carlo Dal Monte -Catalyst Paper Ralph Lunn - Zellstoff Celgar Paul Watson - Canfor Pulp Sales Randy Reimer – Al-Pac

* Industry Meetings: (TBC) * PAPTAC Councillors * Mill Managers * Purchasing Committee * Roundtable Discussions * Pulp Machine Superintendents * Maintenance Superintendents * Short Courses * Trade Fair

IBMP Organizing Committee: Alan Humber – AES Consulting Paul Leyen – ERCO Worldwide Ken Harman – ADI Sales Al Parsons – Bancroft Western Tony Vandendool – Oval Int’l

THURSDAY, JUNE 11

* Conference Forum featuring leading Industry Managers & Analysts * 2 Technical Sessions * Trade Fair

* * * * * *

* MAINTENANCE

FRIDAY, JUNE 12

5K Fun Run 4 Technical Sessions Feature Luncheon Trade Fair Awards Dinner Dance Honorary Peddler Inductee

SATURDAY JUNE 13

Annual Delegates and Spousal Golf Tournaments Full SPOUSAL Program

2008 H.R. MacMillan Trophy winner, Jeff Bennett, Canfor Pulp LP

AWARDS presented in 2008: * H.R. MacMillan Trophy and George Sedgwick (ARC) Memorial Award for BEST MILL PAPER awarded to Jeff Bennett, Canfor Pulp Limited Partnership * RUNNER-UP for full length paper (open to consultants and researchers) awarded to: Jean Bouchard, FPInnovations - Paprican, PointeClaire, QC * BEST SUPPLIER PAPER awarded to: Jay. A. Shands, Johnson Foils, Springfield, MA * BEST NOVICE PAPER for first presentation by author (excluding presentation at Branch Meetings) awarded to: Gwen Vernham, Zellstoff Celgar Ltd. Partnership

2009 CALL FOR PAPERS: Please check the website for details and submit your abstract to the 2009 Program Chair: Ralph Lunn at ralphl@celgar.com

For further information, log on to www.pacwestcon.net

process control today. Sustainability (doing more with less) also plays into the formula and mills need to figure out how to reduce waste and work more efficiently. This usually starts in the research and development process with an initial study to reduce cost of manufacturing and downtime, and produce product more cost effectively.

ABB: R&D is critical to the long-term survival of process control suppliers. We continue to leverage our position as the market share leader in controls systems for a tremendous war chest of R&D funds. ABB is unique in the world of process control suppliers in that we have industry-specific business units devoted to development, sales, installation, and service. In a challenging environment our customers find comfort in knowing that we understand their business.

Andritz: The industry has focused on mechanical upgrades for a decade without always looking at ways to improve control of existing equipment. Now that many types of equipment have reached their peak mechanical performance, it is essential to look at improving control of that equipment. It is critical for mills to look at ways to improve control and this is typically achieved through R&D but also through partnerships with suppliers who have readily available control solutions. It is unfortunate to see mills trying to reinvent the wheel using outdated technology.

Have your relationships with Canadian forestry, pulp, and paper firms changed in terms of increased expectations and requirements in the face of economic downturns?

ABB: Our customers are doing more with less and with fewer people. We recognize this and have recently improved our technical offering to enable us to put an expert in every mill using remote access capabilities. We can respond with our best experts almost immediately. This helps our customers reduce downtime and increase production.

Optek: Of course, a difficult economic environment could preclude a mill from becoming as efficient as possible in terms of controlling their processes. But given 16

March 2009 Pulp & Paper Canada

the industry’s tendency to lag behind technological innovation by preferring to “wait until someone has tried this first,” it is no surprise that the pulp and paper industry has minimal expectations. Quite frankly, this is the attitude that presently separates the mills that are viable and somewhat profitable, from those which are struggling or already closed.

Rockwell: Our relationships with customers is always changing in the forestry industry. With downturns in the industry, this can be challenging. The key for automation solutions vendors is to know who has the authority to make key decisions on purchasing cost-effective solutions. Most manufacturers can provide a solution, and the challenge is to fully

“Expectations are higher now than they have ever been, since capital and money in general has become a challenge.”

— Glover and DeWitt, Rockwell

convince the customer that we can provide a comprehensive solution that will meet their goals and needs. Expectations are higher now than they have ever been, since capital and money in general has become a challenge.

Andritz: Our relationship has always been excellent with all the pulp and paper players. The economic downturn is more challenging and has brought more innovative ways to approach project execution and justification. A good example is our BrainWave Model Predictive Controller, which we offer at no-risk to mills, meaning the mill only pays if they see benefits.

What advice do you have for pulp, paper, and forestry companies who are trying to differentiate themselves from their competitors, while carving out niche markets for themselves?

Optek: That is the advice — look for niche markets and products and get away from the commodity newsprint, copy, and other uncoated freesheet type products. In addition, touting the expanded use of recycled paper in their products will appeal to the “greens” of the world.

ABB: Niche markets require flexibility and adaptability. This in turn requires that process control systems be in peak condition. If a customer made a good investment in world-class control systems, then they need only focus on getting the most out of these systems.

Andritz: Improve your process control: that is often an untapped sector where mills make very little investment. After working for many years in Europe, I can comment that Scandinavian mills have invested much more in process control than North American mills, which resulted in a lower cost per tonne and improved process performances.

Rockwell: In any mill, you need to meet the challenges of global competition, higher production costs, and increasingly strict environmental standards. That means streamlining manufacturing processes while minimizing water, energy and material costs, improving product quality, productivity and capacity, while reducing downtime. Executing real-time control and maintaining critical process parametres means you can respond to diverse customer demands.

Being able to use one platform throughout a mill allows you to have all the information at your fingertips when required. This saves time by not having to go through multiple systems to get the basic operational performance of the mill.

Dashboard type displays are popular as they collect a large amount of data and the end user can look at one single screen.

Similar to a car dashboard, the information is easy to read and understand.

Hiring an external company that remotely monitors the operational equipment in the mill is another available solution. This lets the mill know about problems with a machine before it goes down, and so it can be shut down and fixed before it becomes a much larger problem.

This can be a very cost-effective tool. pulpandpapercanada.com

process control

If I Had A Million Dollars PPC: If a mill has a budget of less than $1 million, what process control improvements would you suggest it make?

instrument can be purchased for $20,000 per measuring point, increasing their profits while reducing down time.

Andritz: For a kraft mill, I would suggest focusing on improving controls on the digester, lime kiln, recaust area, and bleaching. Those areas provide very good potential for energy and chemicals reduction. There are readily available solutions for all those applications using advanced process control. Simply looking at control strategies, often dating from the mill start-up, can provide real opportunities as well.

In a TMP application, improving high consistency refining control can substantially reduce energy costs in a market where electricity is limited and expensive. Reducing load variation in order to reduce load set point is usually a sure investment. In some mills, improving performance of low consistency refiners can decrease the number of refiners. Many projects consisting of removing refiners have been executed in the last few years, providing very good return on a minimum investment. Investing in process control is a permanent improvement that will provide savings year after year.

Rockwell: Customers need to be aware of their aging infrastructure and reduced human resources. Many times, equipment can be upgraded and productivity gains can be realized. Gains can be made with a better view by business systems, faster grade changes, and increased up-time. Deciding between various strategies isn’t easy; that’s why proper planning is essential.

Well thought-out migration solutions are instrumental to your competitive position. They help you achieve productivity gains, lessen the risk of maintaining legacy equipment, and allow you to migrate at a pace that is comfortable for the company.

Optek: From our point of view, we want mills to upgrade their ClO2 monitoring (both in solution and as a scrubber gas) and to begin monitoring their turbidity of white liquor. Each

ABB: Most process control systems are being underutilized.

A mill with less than $1 million to spend would be best served by having a company like ABB come in and evaluate the status of their control system to propose an improvement plan. We call this a “finger print.” It provides both a benchmark and an improvement plan. ABB’s recommendations from a fingerprint also include an ROI estimate. This ROI has both an estimated cost to fix the problem and an estimate of the return. Most recommendations have less than a one-year return. P&PC

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Pulp & Paper Canada March 2009

17

T19

high yield pulp

Adding optical brightening agents to high-yield pulp at the pulp mill

WINNER OF THE DOUGLAS ATACK AWARD

By Z. He, H. Zhang, Y. Ni and Y. Zhou Abstract: Optical brightening agents (OBAs) can effectively improve the optical properties of high-yield pulp (HYP). We developed a new method for this purpose and found that the OBA brightening process can be conveniently incorporated into the alkaline peroxide bleaching process. By combining peroxide bleaching with an optical brightening agent, one can decrease the bleaching cost to reach the same brightness target.

There are a number of advantages of adding OBA to HYP at the pulp mill over the conventional wet-end addition of OBA.

T

he bleached chemi-thermo-mechanical pulp (BCTMP), also known as high-yield pulp (HYP) has many unique properties such as high bulk and high light scattering coefficient that are desirable for printing and writing paper products [1-5]. However, based on currently available bleaching technologies, the economical brightness levels of HYP are still significantly lower and its yellowness (b*) higher than those of fully bleached kraft pulp (BKP) [1-2].

Pretreatments of HYP with optical brightening agents (OBAs) and/or blue dyes can be a solution to improve the optical properties of HYP. Optical brightening agents (OBAs) or fluorescent whitening agents (FWAs) are commonly used to improve the optical properties of printing and writing paper during the papermaking process [6]. Both the paper brightness and whiteness can be increased with the addition of OBA. Also, OBA can decrease the photo-yellowing (photoreversion) of HYP by acting as an UV screen [7,8,9]. It has also been reported that the overall environmental impact of using OBA might be better than peroxide for a certain level of brightness gain of mechanical pulps [9].

Conventionally, OBA is applied to pulp at the wet-end of the papermaking process. OBA molecules adsorb on pulp fibres by forming hydrogen bonding with cellulose in fibres. When OBA is added to a mixed furnish, HYP will have to compete with BKP for OBA. Ideally, OBA adsorbed on HYP fibres would be more effective in whitening HYP-containing paper sheets. To have more OBA on HYP fibres rather than on BKP fibres, OBA may be added to HYP at the pulp mill during the HYP production process. Another factor affecting OBA efficiency is its retention on fibres. It has been reported that OBA retention decreased with the increase of HYP substitution rate due to the lower affinity of OBA molecules to HYP fibres [10]. As 18 

March 2009  Pulp & Paper Canada

a result, the OBA efficiency decreased. Although the white water circulation system can improve the overall retention of OBA, the un-absorbed OBA molecules in the white water can undergo a transformation from trans- to cis- configuration and loses its fluorescent properties [6].

While many results are available in the literature about the application of OBA in the papermaking process, none has been reported on the application of OBA on mechanical pulps during the pulp manufacturing process. The objective of this paper was to investigate the effect of applying OBA to HYP at the pulp mill on the optical properties of HYP, as well as on the overall OBA efficiency.

The results were also compared with those from the conventional wet-end addition of OBA.

EXPERIMENTAL

A softwood bleached kraft pulp (SW BKP, 87.2% ISO), a hardwood (eucalyptus) bleached kraft pulp (HW BKP, 88.4% ISO) and commercial aspen high yield pulps (HYPs) were obtained from Tembec Inc. The kraft pulps were refined in a PFI mill to about 450 and 500 ml CSF freeness, respectively, and the high yield pulps were used without refining. Optical brightening agents were obtained from Ciba. The charge of OBA in this study was based on the liquid products.

The procedure for adding OBA to HYP pulp or mixed furnish was as follows. The pulp samples were disintegrated for 15,000 revolutions in a standard disintegrator at 1.2% pulp consistency, and then diluted to 1% suspension. An aliquot of the pulp suspension (equivalent to 3 g o.d. pulp) was transferred to a 500 ml beaker, and CaCl2 solution was added to reach a Ca2+ concentration of 100 ppm (as CaO). The pH of the mixture was adjusted to about 6.5 followed by the OBA addition. Magnetic stirring was provided for 20 minutes under room temperature. The content of

Z. He, Limerick Pulp and Paper Centre, University of New Brunswick Fredericton, NB

H. Zhang, Tianjin Key Laboratory of Pulp and Paper, Tianjin University of Science and Technology Tianjin, China

Y. Ni, Limerick Pulp and Paper Centre, University of New Brunswick Fredericton, NB yonghao@unb.ca

Y. Zhou, Tembec Inc. Temiscaming, QC pulpandpapercanada.com

peer reviewed Table I. Effect of OBA on the optical properties of HYP in comparison to hw.

Pulp

OBA dosage, %

HYP HYP HYP HYP HW BKP

0 0.1 0.2 0.4 0

Brightness, % ISO 84.6 86.4 87.6 88.9 88.4

CIE whiteness b*

65.7 70.6 74.0 76.6 76.2

5.85 4.86 4.14 3.55 3.84

Other conditions: Di-sulfonic OBA; 1.0% pulp consistency; 100ppm Ca2+; pH 6.5; 20 minutes contact time.

the beaker was then made into a handsheet and tested according to the TAPPI standard methods [11,12].

For the simulation of applying OBA to the manufacturing process of HYP production, OBA was added either to the bleach liquor or to the bleached pulp-slurry after peroxide bleaching. In the latter case, the pulp slurry was mixed with OBA at 5-10% pulp consistency and 80°C for 20 minutes, and then adjusted to about pH 6 and pressed to 25% pulp consistency in a Büchner funnel. The pressed pulp was air-dried before being used for the subsequent experiments (designated as the OBA-treated HYP).

When the OBA-treated HYP (air-dried) was used to partly substitute for HW BKP, it was soaked with deionized water overnight, and disintegrated with the SW BKP and HW BKP for 15,000 revolutions in a standard disintegrator at 1.2% pulp consistency. For the co-refining experiments, the OBA-treated HYP was soaked and disintegrated with the HW BKP, and then refined in a PFI mill at 10% consistency for 2,000 revolutions.

The co-refined pulp was then disintegrated for 15,000 revolutions and made into handsheets.

For the OBA affinity experiments on the OBA-treated HYP, the air-dried pulps were soaked with deionized water overnight, and then disintegrated at about 1.0% pulp consistency for 15,000 revolutions in a standard disintegrator. The pulp suspension was then made into handsheets for determining the optical properties.

For the hot water extraction, the disintegrated pulp suspension was heated in a water bath at 50°C for one hour before making handsheets.

The photo-reversion of handsheets was performed in a photoreactor, with a total intensity of either 9-10 mW/cm2 (approximately 53 times greater than the intensity of normal office light) fluorescent light or 2.7 mW/cm2 UV light (with a nominal wavelength of 350 nm). A fan is installed in the back of the photoreactor for temperature control.

RESULTS AND DISCUSSION

OBA is Effective in Improving the Optical Properties of HYP As shown in Table 1, OBA can improve the optical properties of HYP (Aspen 325/85) significantly. With 1 kg/t OBA (Tinopal UP), the brightness increased by about 2 units, and the whiteness by 5 units. The yellowness (b*) dropped from 5.85 to 4.86.

With 4 kg/t OBA, the optical properties of HYP (brightness, whiteness, b*) are similar to those of a typical hardwood bleached kraft pulp. It has been reported that the brightening efficiency of OBA is determined by its retention and effectiveness on pulp fibres [13,14]. The retention of OBA is affected by the types of pulpandpapercanada.com

Table II. Effect of the substitution of OBA-treated HYP for hardwood BKP on the OBA efficiency at the paper machine.

OBA dosage

0

0.1

0.2

0.5

1.0

BKP 91.20 97.14 0.56 1.21 87.30 3.58

92.60 97.19 0.90 0.38 91.17 4.91

94.66 97.25 1.33 -0.72 96.25 6.97

95.95 97.25 1.59 -1.35 99.08 8.38

10 % OBA-HYP Brightness (%ISO) L* a* b* CIE Whiteness Fl. Comp. (%ISO)

+ 30% SW BKP + 60% HW BKP 90.15 91.40 92.36 93.97 97.05 96.97 96.99 97.05 0.32 0.76 0.96 1.25 1.92 0.90 0.33 -0.52 83.88 88.25 90.90 94.85 2.95 4.55 5.47 7.10

95.16 97.12 1.37 -0.97 97.08 8.34

15 % OBA-HYP Brightness (%ISO) L* a* b* CIE Whiteness Fl. Comp. (%ISO)

+ 30% SW BKP + 55% HW BKP 90.20 91.55 92.35 93.78 96.90 96.99 97.04 97.08 0.40 0.70 0.90 1.22 1.71 0.93 0.48 -0.29 90.32 93.92 84.42 88.20 3.52 4.84 5.62 7.06

94.87 97.12 1.29 -0.75 96.09 8.24

25 % OBA-HYP Brightness (%ISO) L* a* b* CIE Whiteness Fl. Comp. (%ISO)

+ 30% SW BKP + 45% HW BKP 90.75 91.68 92.27 93.41 96.93 96.99 97.01 97.04 0.51 0.73 0.82 1.09 1.43 0.90 0.58 -0.02 85.78 88.33 89.84 92.60 4.53 5.38 5.97 7.04

94.30 97.05 1.21 -0.41 94.40 8.17

30% SW BKP + 70% HW Brightness (%ISO) 87.63 L* 97.07 a* -0.41 b* 3.70 CIE Whiteness 75.87 Fl. Comp. (%ISO) 0

Note: The OBA-HYP had a brightness of 91.7% ISO. Other conditions for OBA addition to the mixed furnish: Tetra-sulfonic type of OBA; 1.0% pulp consistency; 100ppm Ca2+; pH 6.5; 20 minutes contact time.

OBA, fixing agents, temperature and contact time [10]. The presence of cations such as Ca2+ in the white water can increase the OBA retention. Also, a higher temperature and longer time of OBA with pulp fibres improved the OBA retention [10].

The effectiveness of OBA at a given amount of OBA adsorbed on HYP fibres was affected mainly by the properties such as the original brightness of HYP [13]. OBA is less effective on the lower-brightness HYP. This is because the blue light re-emitted

by OBA is absorbed by the colorants such as lignin in pulp fibres.

The higher the HYP brightness, the higher the OBA efficiency.

Incorporating OBA Brightening into the Alkaline Peroxide Bleaching Process in HYP Production Conventionally, OBA is used at the wet-end of the papermaking process. When HYP is substituted for HW BKP in printing and writing paper to take advantages of its high bulk and light scattering, the brightness and whiteness are affected negatively due to the inferior brightness and whiteness of HYP. However, the negative effect of HYP on brightness and whiteness can be compensated for by adding more OBA at the wet-end [10].

We proposed that OBA can be added to HYP at the pulp mill, as the higher temperature and longer contact time can improve Pulp & Paper Canada March 2009

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FIG. 1. Proposed addition points for the application of OBA to HYP at the pulp mill. table iII. Comparison of the OBA efficiency between two addition methods.

Addition Method

OBA dosage (%, on total furnish) Brightness, % ISO Whiteness b*

A: OBA added to HYP at the pulp mill

0.25 90.7 84.1 1.97

0.50 91.9 87.2 1.30

FIG. 2. Comparison of the adsorption of OBA on HYP and BKP (Tetra-sulfonic OBA, pH 6.5, 2-hour contact time, room temperature).

B: OBA added to mixed furnish at the wet-end

0.25 0.3 3.0 2.21

0.50 91.5 86.5 1.38

Note: Furnish composition: 30% SW BKP+ 20% HW BKP + 50% HYP; OBA: Di-sulfonic OBA; wet-end conditions: 1% pulp consistency, pH 6.5, 100 ppm Ca2+, 5 minutes of contact time.

OBA retention and thus its brightening efficiency. If OBA has no interference to the alkaline peroxide bleaching, and peroxide has no effect on the fluorescent properties of OBA, the application of OBA can be conveniently incorporated into the bleaching process. Based on experimental results, we confirmed that there is no reaction between OBA and the peroxide-containing bleach liquor under the normal bleaching conditions. Furthermore, our experimental results show that different levels of peroxide concentration and DCS have negligible effect on the brightening efficiency of OBA. In the mill operation, OBA can be added to the pulp along with the bleach liquor or at the bottom of the bleaching tower with the dilution water, as shown in Figure 1.

To bleach HYP to high brightness (e.g. 85% ISO), stronger bleaching conditions (higher peroxide charge, alkalinity and temperature) are usually needed, which can decrease the bulk and light scattering coefficient of HYP. If the brightness target of HYP is lowered from 85% ISO to 83% ISO in peroxide bleaching, the production cost of HYP will decrease significantly, while the bulk and light scattering of HYP can be preserved. The concept can decrease the production cost. For example, for peroxide bleaching to increase 83% ISO to 85% ISO, an additional 2% peroxide is required; for using OBA to achieve the same brightness gain, about 0.2% Tinopal UP is needed. The cost for the OBA and hydrogen peroxide is about $2,000/t and $800/t respectively, thus the economic benefit of using OBA is rather evident.

Adding OBA to Pulp Furnish Containing OBA-treated HYP For high brightness printing and writing paper grades (>88% 20 

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FIG. 3. Comparison of the brightening efficiency of OBA between two addition methods with the presence of PEI (30% SW BKP, 20-60% HW, 10-50% HYP (Aspen 325/85), 0.05-0.25% Di-sulfonic OBA, 0.2% PEI).

ISO), OBA is normally added at the wet-end of the papermaking process. When the OBA-treated HYP is partly substituted for hardwood BKP, a question arises as to whether the brightening efficiency of OBA added at the wet-end will be affected negatively.

We designed a set of experimental trials, whereby, the hardwood BKP was partially substituted with the OBA-treated HYP (Grade 325/90); OBA was then added to the mixed furnish at 1% pulp consistency, 100 ppm calcium concentration, pH 6.5. Theses conditions were similar to the wet-end addition of OBA in the papermaking process. Handsheets were then made to determine the brightness. Results in Table 2 show that for a brightness level up to 92% ISO, the presence of the OBA-treated HYP has negligible effect on the final brightness for the HYP substitution of 15% or lower. However, at a brightness higher than 92% ISO (achieved with more OBA), or a HYP substitution rate of higher than 15%, slightly more OBA than the control (0% HYP) is needed to reach the same brightness and whiteness.

In general, OBA-treated HYP can be used to replace part of BKP in printing and writing paper with negligible effect on the brightness, whiteness and yellowness of paper products even when OBA is used as well at the wet-end of the papermaking process. pulpandpapercanada.com

peer reviewed table iV. Comparison of the effect of PEI on OBA efficiency between the two OBA addition systems.

PEI dosage, % HYP %

OBA dosage % Brightness % ISO b* CIE whiteness

A: OBA was added to HYP at the pulp mill 0.05 87.54 0.10 88.78 0.15 88.72 0.25 89.27 0.15 90.68

0.2 0.2 0.2 0.2 0

10 20 30 50 30

0.2 0.2 0.2 0.2

B: OBA was added to mixed furnish at the wet-end 10 0.05 86.22 20 0.10 87.05 30 0.15 87.49 50 0.25 87.30

3.38 2.72 2.46 2.67 2.05

76.44 79.66 80.31 80.16 83.70

3.62 3.38 3.42 3.82

74.35 75.84 76.12 74.51

Furnish: 30% SW BKP, 20-60% HW BKP and 10-50% HYP (Aspen 325/85); OBA type: Di-sulfonic; 0.2% PEI; OBA was added first, followed by the addition of PEI after 2 minutes of mixing, and a handsheet was made after another 5 minutes of mixing.

table V. Effect of time interval between oba and pei addition on oba efficiency.

OBA addition Time interval Brightness method between OBA and (% ISO)

PEI addition, (min.)

Method Method Method Method

B B B A

2 20 60 -

87.51 87.79 87.68 88.72

Bright. gain b* CIE due to OBA whiteness (% ISO) 1.89 2.04 2.01 2.75

3.42 3.28 3.18 2.46

76.12 76.83 77.11 80.31

Other conditions: 30% SW BKP + 40% HW BKP + 30% HYP, 0.15% OBA (Di-sulfonic); OBA was added to the mixed furnish before the addition of PEI (0.2%).

Under normal conditions, the efficiency of OBA added at the paper machine remains similar whether there is OBA already on HYP fibres or not.

HYP fibres. As shown in Table 3, at the same OBA dosage, the whitening efficiency of OBA was slightly better when it was added to HYP at the pulp mill.

Advantages of Adding OBA to HYP during the HYP Manufacturing Process The advantages of adding OBA to HYP during the HYP manufacturing process over the conventional wet-end OBA addition are discussed below.

Minimizing the Interference from Cationic Polymers such as PEI It is well known that cationic polymers and metal ions have negative effects on the performance of OBA [6,14]. PEI is a cationic polymer that is commonly used in the retention systems to neutralize the negative effect of anionic trash. It can react with OBA to form complexes and reduce the brightening efficiency of OBA. A pre-adsorption of OBA onto pulp fibres before PEI addition may reduce their interaction, leading to an improved OBA efficiency. Table 4 compares the efficiency of two OBA addition methods (A and B) at various HYP substitution rates and OBA dosages, in the presence of PEI (0.2%). Method A is a lab simulation of adding OBA to HYP at the pulp mill, and Method B is a lab simulation of the conventional wet-end addition of

Improving the OBA Efficiency OBA molecules adsorb on pulp fibres by forming hydrogen bonding with cellulose fibres. When OBA is added to a furnish that contains both HYP and BKP, OBA will adsorb preferably on BKP fibres as they are essentially free of lignin. As shown in Figure 2, at the same OBA concentration in the liquid phase, the BKP fibres adsorbed much more OBA than the HYP fibres.

It would be beneficial to have more OBA adsorbed on HYP fibres. OBA may cover up and/neutralize the yellowish colour of HYP fibres more effectively when it is on pulpandpapercanada.com

OBA. The results show that at the same HYP substitution rate and OBA dosage, Method A always gave higher brightness and whiteness, and lower yellowness (b*).

The higher OBA efficiency of Method A is due to less quenching effect from PEI. Figure 3 compares the brightness gain from OBA (fluorescent component) of the two systems at various conditions, which demonstrates the superior OBA performance when added during the HYP manufacturing process.

For Method B, OBA is usually added to the pulp fibres first and as far as possible from the addition point of PEI to decrease their interactions. However, the conclusion does not change even when the time interval between OBA and PEI additions was up to 60 minutes for Method B (Table 5). To minimize the interference of PEI more effectively, OBA would have to be absorbed and fixed on fibres. The drying process after OBA addition in the HYP manufacturing process may help fix OBA molecules on fibres by forming more and stronger hydrogen bonding.

Minimizing the Interference of Metal Ions in the White Water Metal ions such as Al3+ and Fe3+ are present in the white water system, in particular for the acidic papermaking system. These metal ions can react with OBA molecules to form deposits and thus decrease the OBA efficiency [6]. Fixing OBA molecules onto fibres by adding OBA to HYP at the pulp mill can reduce their reactivity towards the harmful metal ions. In Table 6, various amount of Al3+ and Fe3+ ions were added to pulp suspension, and the tolerance of OBA to the metal ions was compared between the two addition methods, with all other conditions unchanged.

The results show that the interference of metal ions is significantly less when OBA is added to HYP at the pulp mill (Method A), evidenced by the constantly higher brightness, fluorescence composition and whiteness, and lower yellowness.

Decreasing the Color Reversion Another advantage of adding OBA to HYP at the pulp mill is that OBA on HYP fibres may also act as a UV screen and thus decrease the photo-yellowing (colour reversion) of HYP during shipping, storage and application [15]. As shown in Figure 4, the photo-reversion of Pulp & Paper Canada  March 2009 

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high yield pulp table VI. Effect of metal ions on oba efficiency.

Wet-end conditions

Blank A Al3+ 2.5ppm Al3+ 5.0ppm Al3+ 10 ppm Al3+ 20 ppm Fe3+ 0.1ppm Fe3+ 0.2ppm Fe3+ 0.4ppm Fe3+ 0.8ppm

Brightness (% ISO)

Bright. gain due to OBA (% ISO)

b*

CIE Whiteness

A: OBA was added to HYP at the pulp mill (0.15% Di-sulfonic OBA) 90.4 3.6 2.5 90.3 3.6 2.5 90.2 3.6 2.6 89.6 3.5 2.8 89.4 3.4 2.9 90.1 3.6 2.6 90.0 3.5 2.5 89.0 3.4 2.5 88.2 3.3 2.6

82.0 81.7 81.3 80.2 79.6 81.4 81.3 80.5 79.3

B: OBA was added to the mixed furnish at the wet-end (0.15% di-sulfonic OBA) Blank B 90.5 3.6 2.5 81.9 Al3+ 2.5 ppm 88.3 2.7 3.4 77.1 Al3+ 5.0 ppm 88.2 2.3 3.5 76.5 Al3+ 10 ppm 88.1 1.9 3.5 76.7 Al3+ 20 ppm 88.0 1.7 3.8 75.7 Fe3+ 0.1ppm 87.8 1.4 3.8 75.3 Fe3+ 0.2ppm 87.6 1.4 3.9 74.9 Fe3+ 0.4ppm 87.3 1.5 3.7 75.0 Fe3+ 0.8ppm 86.4 1.5 3.7 74.1 Other conditions: 30% SW BKP + 30% HYP + 40% HW BKP; pH 4.5; 5 minutes.

table VII. Comparison of the two OBA addition methods with co-refining of hyp and bkp.

Wet-end conditions

Brightness (% ISO)

Bright. gain due to OBA (% ISO)

b*

CIE Whiteness

A: OBA was added to HYP at the pulp mill (0.25% Di-sulfonic OBA) Blank A, pH 6.5 89.6 4.81 2.83 0.2% PEI, PH=6.5 89.2 4.06 2.73 0.5% PEI, PH=6.5 87.2 3.95 3.65 20 ppm Al3+, pH 4.5 88.2 4.21 3.41 20 ppm Al3+, PH=6.5 90.1 4.86 2.45 1.0 ppm Fe3+, PH=4.5 84.7 4.11 2.79 1.0 ppm Fe3+, PH=6.5 85.0 4.26 2.53

80.0 79.7 74.9 76.6 81.6 74.7 76.0

B: OBA was added to mixed furnish at the wet-end (0.25% Di-sulfonic OBA) Blank B, pH 6.5 89.7 3.96 3.18 79.1 0.2% PEI, PH=6.5 * 86.3 1.67 4.23 72.0 0.5% PEI, PH=6.5 * 85.2 2.12 4.87 68.8 0.5% PEI, pH=6.5 ** 85.4 2.72 4.60 70.0 20 ppm Al3+, pH 4.5 85.7 2.14 4.69 70.2 20 ppm Al3+, PH=6.5 89.4 4.53 2.55 80.7 1.0 ppm Fe3+, PH=4.5 83.1 2.45 3.80 69.9 1.0 ppm Fe3+, PH=6.5 84.9 3.85 2.64 75.6 Furnish: 50% HYP + 50% HW BKP; OBA treated HYP was air-dried to simulate the commercial HYP process. Co-refining of HYP and HW BKP: 2000 PFI revolution to about 450 ml CSF. * PEI was added before OBA; ** OBA was added before PEI.

OBA-treated HYP is much less than the regular HYP when exposed to UV radiation under the same conditions.

The same benefit can also be seen when using the OBA-treated HYP in the production of HYP-containing paper. If OBA is added to HYP at the pulp mill, 22

March 2009 Pulp & Paper Canada

more OBA will stay on HYP fibres to protect them from light radiation and thus decrease the photo-reversion of the paper. As shown in Figure 6, a noticeable reduction in reversion was observed for the paper sheet with OBA-treated HYP in both of the UV light treatments.

Other Practical Considerations In some paper mills, HYP is co-refined with hardwood BKP. A question arises as to whether the strong mechanical force and interaction between HYP and BKP fibres during co-refining will diminish the benefits of OBA-treated HYP. To answer this question, we designed another set of experiments as shown in Table 7. For Method A, 50% OBA-treated HYP was co-refined with 50% HW BKP in a PFI mill to 450 ml CSF, and was then made into handsheets under different wet-end conditions; for Method B, 50% regular HYP was co-refined with 50% HW BKP, and then OBA was added. The results in Table 7 show that Method A is still much better than Method B with respect to the brightening efficiency of OBA. Therefore, one can conclude that the benefits of the OBA-treated HYP can be maintained after the co-refining process.

Another question is the affinity of OBA on HYP fibres, once added in the HYP manufacturing process. Water extraction at 50°C is a good simulation of the situation in a paper mill where the OBA-treated HYP will be used in the process. Our results showed that hot water extraction (50°C, 1 hour) changed the optical properties of the OBA-treated HYP only slightly.

To test the affinity of OBA on HYP fibres under a high shear force environment, a standard disintegrator operated at 3,000 rpm was used to simulate the repulping, refining and pumping processes in a paper mill. Results showed that the change of the optical properties of the OBA-treated HYP was small, indicating that the OBA-treated HYP can survive the typical mechanical treatments in a paper mill.

CONCLUSIONS

OBA can be a cost-effective solution to improve the optical properties of HYP. A partial substitution of HW BKP with the OBA-treated HYP has negligible influence on the final paper brightness and whiteness, which would be an encouragement to more HYP applications in more paper grades. Neither OBA has interference to the alkaline peroxide bleaching process, nor the bleaching chemicals on the performance of OBA. Therefore, the OBA brightening process can be incorporated into the peroxide bleaching process pulpandpapercanada.com

Brightness (% ISO)

UV exclusive brightness (% ISO)

peer reviewed

conveniently.

Adding OBA to HYP at the pulp mill can have several advantages over the conventional wet-end addition of OBA. First, the quenching effect on OBA by the wet-end cationic polymers such as PEI can be decreased by fixing OBA on HYP fibres before going into the papermaking process. Moreover, the negative impact of metal ions in the white water system on the OBA performance can be minimized when OBA is pre-adsorbed and fixed on HYP fibres. Furthermore, the photo-yellowing (colour reversion) of HYP and HYP-containing paper sheets can be decreased when more OBA is on HYP fibres to protect them from harmful UV radiation. OBA has good affinity to HYP fibres when it is added in the HYP manufacturing process, and it retains well when subjected to water extraction (50°C), disintegration and co-refining treatments.

LITERATURE

1. Zhou, Y., “Overview of High Yield Pulps (HYP) in Paper and Board”, PAPTAC 90th Annual Meeting, 2004, B143-148, Montreal, Canada.

2. Cannell, E.; Cockram, R., “The Future of BCTMP”, Pulp and Paper, 74(5): 61-76 (2000).

3. Reis, R., “The increased use of hardwood high yield pulps for functional advantages in papermaking”, Proceedings of the 2001 Papermakers Conference, 2001, 87-108 (Cincinnati, OH, USA) .

4. Levlin, J.E., “On the Use of Chemi-mechanical Pulps in Fine Papers”, Paperi ja Puu - Paper and Timber, 72(4): 301-308 (1990).

5. Ford, M.; Sharman, P., “Performance of High Yield Hardwood Pulp is Investigated as it should be the Choice of the Future”, Pulp & Paper International, 38(10): 29 (1996).

6. Neimo, L. (Book Editor), Papermaking Science and Technology, Book 4, Papermaking Chemistry, 1999, Fapet Oy, Helsinki, Finland.

7. Ragauskas, A.J.; Allison, L.; Lucia, L.A.; Li, C., “Brightness Reversion of Mechanical Pulps XIV: Application of FWAs for High-brightness, High-yield pulps”, Solutions!, 84 (11): 55 (2001).

8. Bourgoing, S.; Robert, S., “Inhibition of Light Induced Colour Reversion by Diaminostilbene Derivatives Fluorescent Whitening Agents - Molecular Simulation Correlation”, Proceedings of PAPTAC 87th Annual Meeting, 2001, B47-B54.

9. Scheringer, M.; Halder, D.; Hungerbühler, K., “Comparing the Environmental Performance of Fluorescent Whitening Agents with Peroxide Bleaching of Mechanical Pulp”, Journal of Industrial Ecology, 3(4): 77-95 (1999).

10. Zhang, H.; Hu, H.; He, Z.; Ni, Y.; Zhou, Y., “Retention of Optical Brightening Agents (OBA) and their Brightening Efficiency on HYP-containing Paper Sheets”, J. Wood Chem. Tech., 27(4): 153 (2007).

11. “Forming Handsheets for Reflectance Testing of Pulp (Sheet Machine Procedure)”, TAPPI Test Methods T272 (1992).

12. “Diffuse Brightness of Pulp (d/0°)”, TAPPI Test Methods, T525 (1992).

13. Zhang, H.; He, Z.; Ni, Y.; Hu, H.; Zhou, Y., “Effectiveness of Optical Brightening Agent (OBA) on High Yield Pulps (HYP)”, Proceedings of 93rd PAPTAC

pulpandpapercanada.com

CIE Whiteness

FIG. 4. Effect of OBA on the accelerated photo-reversion of HYP under intensive UV radiation (Photo reactor: 350 nm nominal wavelength, 2.7 mW/cm2 intensity).

FIG. 5. Comparison of the UV reversion of HYP-containing paper sheets between the two OBA addition methods (50% HYP + 50% HW BKP, 0.25% Tinopal UP; Photo reactor: 350 nm nominal wavelength, 2.7 mW/cm2 intensity).

Annual Meeting, Feb. 2007, B235-240, Montreal, Canada.

14. Crouse, B.W.; Snow, G.H., “Fluorescent Whitening Agent in the Paper Industry: Their Chemistry and Measurement”, Tappi J., 64(7): 87-89 (1981).

15. Bourgoing, S.; Leclerc, É.; Martin, P.; Robert, S., “Use of Fluorescent Whitening Agents to Inhibit Light-induced Colour Reversion of Unbleached Mechanical Pulps”, Journal of Pulp and Paper Science, 27(7): 240-244 (2001).

Résumé: Les agents de blanchiment optique (ABO) peuvent réellement améliorer les propriétés optiques de la pâte à haut rendement (PHR). Nous avons à cette fin mis au point une nouvelle méthode et constaté que le blanchiment aux agents de blanchiment optique peut sans problème être intégré au blanchiment au peroxyde alcalin. En combinant le blanchiment au peroxyde à un agent de blanchiment optique, on peut réduire le coût du blanchiment et obtenir la même blancheur désirée. L’ajout d’un ABO à la PHR à l’usine de pâte comporte de nombreux avantages par rapport à l’ajout habituel d’un ABO à la partie humide.

Reference: HE, Z., ZHANG, H., NI, Y., ZHOU, Y. Adding Optical

Brightening Agents to High-Yield Pulp at the Pulp Mill. Pulp & Paper Canada March 2009:T19-24. Paper presented at the 94th Annual Meeting in Montreal, February 5-7, 2008. Not to be reproduced without permission of PAPTAC. Manuscript received December 18, 2007. Revised manuscript approved for publication by the Review Panel December 29, 2008.

Keywords: BRIGHTNESS, HIGH-YIELD PULP, OPTICAL BRIGHTENING AGENT, PEROXIDE BLEACHING, PULP MILL, OBA EFFICIENCY, BLEACHING COST.

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Impact of machine whitewater on brightness of mechanical grades

WINNER OF THE JASPER MARDON AWARD

By x. Hua and m. Laleg Abstract: We have studied the effect of machine whitewater on brightness loss for 16 mechanical pulp furnishes, in the presence and absence of calcium carbonate filler. Dilution of pulps with paper machine whitewaters collected from the same mill caused decreases in brightness, up to 8 points, with an average of 4.6 points for newsprint machines. The reasons for the brightness loss varied from mill to mill. Proper identification of the sources of brightness loss is the first step toward effective strategies to minimize the loss and reduce chemical costs.

C

alcium carbonate is bright filler widely used in the manufacture of wood-free papers. Many wood-containing-grade mills have also switched from an acidic clay system to a neutral calcium carbonate system. However, the production of mechanical grades with calcium carbonate filler is not straightforward, mainly due to its alkaline nature. The pH of calcium carbonate suspensions varies between 8.5 and 10.5, depending on its origin. Since lignin in mechanical pulp turns yellow in alkaline media, the expected brightness gain from calcium carbonate addition could be significantly reduced. This pulp darkening presents a great challenge for the mechanical paper producers who wish to convert their paper machines to neutral or alkaline operation. Nevertheless, the brightness of paper increases when the proportion of carbonate is increased above a minimum level [1,2].

In previous work, we have investigated the combined effects of pH, temperature, and storage time on brightness and other properties of TMP. Brightness dropped rapidly as the pH increased from acid to alkaline. This darkening was partially reversed by acidification; however, more irreversible darkening was produced as the storage time increased [3]. We have also shown that the initial alkali darkening of mechanical pulp caused by the addition of a small amount of carbonate filler depends on the bleaching processes to which the pulp was subjected [4]. On exposure to alkaline calcium carbonate, hydrosulphite-bleached TMP and unbleached TMP exhibited a greater brightness loss than did peroxide-bleached TMP. There was no significant darkening with peroxidebleached TMP at a pH close to 7.

To minimize the darkening caused by the alkalinity of calcium carbonate filler, paper containing mechanical pulp should be produced under slightly acidic or neutral conditions. According to the 24 

March 2009  Pulp & Paper Canada

relationship between pH and alkaline darkening observed in the previous studies [3], the brightness loss at the wet end of a paper machine should not exceed 3 points if the machine changes from acidic to neutral operation. However, the brightness loss due to calcium carbonate addition was often much greater and in some mill trials reached 6 points. Furthermore, it is often observed that brightness loss occurs even under acidic conditions whether filler is present or not. The mechanism of this excessive brightness loss is not yet completely understood. It was speculated that machine whitewater could play an important role in brightness loss. In the presence of calcium carbonate there might be interactions between calcium carbonate filler and some whitewater components causing an increase in dark materials in the finished paper.

The purpose of the present work was to determine the effect of machine whitewater on brightness loss when a paper machine converts from acidic to neutral operation and to shed some light on the mechanism causing the excessive brightness loss of mechanical pulps. We have also conducted several case studies to understand the reasons for the excessive brightness loss. This report summarizes the main findings from this work.

EXPERIMENTAL

Sample Collection Pulp and whitewater samples were collected from eight newsprint machines and eight SC, LWC, and wood-containing specialty paper machines of Canadian paper companies. To minimize the contamination from machine whitewater, the individual pulp components for each furnish were taken before the blending chests. Pulp and whitewater samples were blended in the laboratory according to the ratio provided by the mills to form the specific furnish for each machine studied in this work.

Thus, the blended furnish did not contain broke

X. HUA, FPInnovations - Paprican Pointe-Claire, QC

M. Laleg, FPInnovations - Paprican Pointe-Claire, QC pulpandpapercanada.com

peer reviewed Table i. Impact of pcc addition at pH 7 on the brightness of various furnishes diluted with deionized water.

PM no.

Furnish

Pulp pH without PCC

Brightness without PCC

Brightness with 2% PCC at pH7

Brightness loss due to increased pH

1 2 3 4 5 6 6 7 7

TMP, DIP1, kraft TMP, DIP, kraft TMP TMP TMP, PBTMP TMP TMP TMP, PBTMP2, kraft TMP, PBTMP, kraft

4.8 4.8 5.1 5.5 5.6 7.0 5.5 7.0 5.5

Newsprint Furnishes 61.8 61.4 62.5 62.6 59.2 59.5 60.83 58.7 60.73

59.2 58.8 60.7 61.2 57.1 59.0 59.0 59.1 59.1

2.6 2.6 1.8 1.4 2.1 0.5 1.8 –0.4 1.6

8 9 11 12 14

SGW, kraft TMP, PBTMP, kraft PBTMP, kraft PBTMP SGW, kraft

5.3 5.3 5.6 4.8 5.0

SC and LWC Furnishes 69.4 69.2 74.7 70.0 66.7

67.5 67.7 73.9 68.6 62.4

1.9 1.5 0.8 1.4 4.3

DIP: de-inked pulp.

PBTMP: Hydrogen peroxide-bleached TMP. 3.

This is the brightness of pulp after being acidified to pH 5.5 before heating. The original pH of the samples was about 7.

1.

2.

Table ii. Impact of whitewater on the brightness of mechanical furnishes in the absence of PCC. PM no.

Furnish

Brightness Brightness Brightness with deionized with loss water whitewater Newsprint Furnishes 61.8 53.8 61.4 55.0 62.5 61.5 62.6 58.2 59.2 56.2 59.5 57.11 60.8 56.42 58.7 55.51 60.7 57.22 62.5 56.1

Increase in ash content (%)

1 2 3 4 5 6 6 7 7 15

TMP, DIP, kraft TMP, DIP, kraft TMP TMP TMP, PBTMP TMP TMP TMP, PBTMP, kraft TMP, PBTMP, kraft TMP

8.0 6.4 1.0 4.4 2.9 2.4 4.4 3.2 3.5 6.4

3.7 4.6 0.3 0.2 1.0 5.1 0.9 4.7 0.8 n/a

8 9 11 12 13 14

SC, LWC and High Brightness Grade Furnishes SGW, kraft 69.4 67.9 1.5 TMP, PBTMP, kraft 69.2 71.5 –2.3 PBTMP, kraft 74.7 76.0 –1.3 PBTMP 70.0 72.2 –2.2 –1.8 PBTMP 77.3 79.1 SGW, kraft 62.4 62.8 -0.4

9.6 8.1 20.9 15.4 7.6 7.8

Note:

1.

2.

The WW from PM 6 and 7 contained about 16.7 and 8% PCC, respectively.

The furnish and WW had been acidified to pH 5.5 to remove calcium carbonate.

Table iii. The brightness of fresh fines and whitewater solids collected from PM 15.

Sample

Brightness (%)

Fresh fines WW

64.1 47.6

pulpandpapercanada.com

and saveall pulp. Fresh water samples were also collected from some of the mills.

The precipitated calcium carbonate (PCC) used in this work was Albacar HO from Specialty Minerals Inc., and had a scalenohedral crystal form.

Effect of PCC and Whitewater Pulp samples prepared as described above were further diluted with either de-ionized water to 1% consistency, or the corresponding machine whitewater (WW). When machine whitewater was used for dilution, the ratio of WW/pulp solids was fixed at 0.46, which resulted in pulp consistencies close to 1%. Because whitewater consistency varied from one machine to another, the consistency of the diluted pulp in each case was not exactly 1%. The diluted pulp blend was then agitated at 50°C for 30 minutes in the presence or absence of PCC. After 30 minutes, brightness pads were prepared without further dilution. When PCC was added, the pulp pH was adjusted to 7.0 with phosphoric acid. The dosage of PCC was 2% based on pulp solids. The pH was re-adjusted to 7.0 before forming pads. At this dosage and pH level, most of the PCC dissolved. The ash content in brightness pads was increased by about 0.5% in most cases. Therefore, the contribution of PCC filler to sheet brightness was negligible.

Tests and Chemical Analyses Brightness and Eric (Effective residual ink concentration) of the pads were determined according to PAPTAC Standard Testing Method E1 using a Technibrite Eric 950, Technidyne Corporation (New Albany, IN). The metal ions content and colour of the WW and fresh water were determined by following the PAPTAC Standard Testing Methods G.34P and H.5, respectively.

RESULTS AND DISCUSSION

Impact of PCC on Mechanical Furnishes in the Absence of Whitewater Table I shows the effect of PCC on the brightness of newsprint furnishes (PM 1-7) in the absence of whitewater. The brightness loss caused by adding PCC was between 1.4 and 2.6 points, which is in the same range as we had observed previously. The loss in brightness was caused by increasing pH from 4 or 5, to neutral.

PM 6 and 7 were running under neutral conditions. To assess the impact of alkalinPulp & Paper Canada March 2009

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mechanical pulps Table iv. Consistency, pH and conductivity of whitewater from newsprint machines.

PM no.

Furnish

1 2 3 4 5 6 7 15

TMP, DIP, kraft TMP, DIP, kraft TMP TMP TMP, PBTMP TMP TMP, PBTMP, kraft TMP

Brightness loss due to WW 8.0 6.4 1.0 4.4 2.9 4.4 3.5 6.4

ity from PCC on the samples from PM 6 and 7, one set of the samples was acidified to pH 5.5 before heating. As also shown in the table, the differences in brightness between the two acidified furnishes and the two neutral samples were 1.8 and 1.6 points for PM 6 and 7, respectively. Thus, the brightness drop on neutralisation on these machines was similar to that found for other paper machines operating under acidic conditions. Table I also shows that similar brightness losses were obtained when PCC was added to SC and LWC furnishes, except for one furnish (PM 14) which was much more sensitive to pH change.

Impact of PCC on Mechanical Furnishes in the Presence of WW While in some mill trials the addition of PCC caused a brightness loss of 5 to 6 points, only a minor brightness loss was observed in the laboratory when PCC was added to the furnishes diluted with the corresponding machine whitewater (data are omitted for conciseness). The brightness losses were not higher than those obtained with deionized water. For the five newsprint machines (PM 1 to 5), the brightness loss due to PCC addition to the furnish at pH 7 ranged between 1.2 and 2.2. Similar brightness loss was observed with the SC and LWC furnishes, ranging between 1.1 and 2.6 points. Obviously, whitewater did not generate additional dark substances with calcium carbonate, other than those caused by alkaline darkening.

Whitewater Contribution to Pulp Darkening When brightness was compared at the same pH in the presence or absence of whitewater, it was found that the machine 26

March 2009 Pulp & Paper Canada

Consistency pH %

0.40 0.27 0.39 0.69 0.29 0.38 0.38 0.63

Conductivity µS/cm

4.3 1026 3.7 813 5.1 1740 4.7 1365 3.9 1531 7.8 2910 7.6 3450 4.7 1206

whitewater reduced the brightness of the furnishes much more than the addition of calcium carbonate. Table II shows the brightness values of pulps with and without whitewater in the absence of PCC. The dilution with whitewater reduced pulp brightness by as much as 8 points, with the average being 4.6 points for the newsprint furnishes. Considering the high bleaching cost to gain each point of brightness, especially when brightness is already high, a loss of 4.6 points represents a significant bleaching cost. For SC, LWC and other groundwood specialties, the whitewater did not cause a significant loss in brightness. In most cases, there was a small gain when whitewater was used for dilution.

This is because the whitewater for these grades usually contains a large amount of filler, most of which was retained in the pulp pad. One would also expect a loss in brightness if the filler was removed from the whitewater. The effect of filler in whitewater can be seen for the samples of PM 6 and 7 in Table II. The brightness loss increased when PCC was removed by acidification.

In this work, the brightness was measured on the pads formed on a filter paper.

In this way the fines in the whitewater should be completely retained. In a paper machine, the first pass retention is never 100%. Thus, the impact of whitewater on the brightness of paper products would depend on the retention of the dark fines materials in the whitewater. This might explain why brightness losses varied in several PCC trials even on the same machine with the same furnish. The negative impact on brightness of the machine whitewater might also explain why in many mills producing newsprint and mechanical grades, their finished products often have a signifi-

cantly lower brightness than the incoming pulp furnishes.

The effect of retention on paper brightness manifested itself in one mill that produced PCC-filled mechanical grades.

The machine operated under neutral conditions, which increased the darkening of the fines in the whitewater system. Since the PCC addition level was low, the use of PCC could not mask the darkening effect of the dark whitewater fines. When the mill increased retention aid flow to have more PCC in the paper, the actual brightness was reduced (Figure 1).

Mechanism of Brightness Loss Caused

by Whitewater As mentioned earlier, fines in the furnish and whitewater cannot be 100% retained on a commercial paper machine. Most of them pass through the forming fabric and end up in the whitewater. These fines circulate in the whitewater system until they are retained or purged out of the system.

The fines in mechanical pulps usually contain more lignin than the whole pulp [5]. The circulation of these fines generates chromophores in the lignin component, and increases their chances of interaction with contaminants presented in the whitewater. Thus, the fines in whitewater are darker than fibres and, when retained, cause a reduction in the paper brightness.

Table III shows the enormous difference in brightness between the fresh fines fractionated from a virgin TMP and whitewater fines collected from the same mill.

Whitewater Characteristics From Table II, it can be seen that two furnishes (PM 1 and 2) with the largest brightness losses contained deinked pulp.

It was suspected that the whitewater from these machines might contain residual ink, which was confirmed by their high Eric values (Effective residual ink concentration). The Eric values of the PM1 and PM2 furnishes diluted with whitewater were 178 and 189 ppm respectively. Most of the residual ink originated from the whitewaters. The contribution from the two whitewater samples was estimated to be 132 ppm and 106 ppm, respectively.

According to a statistical analysis, based on a number of newsprint samples, an increase of 100 ppm in Eric for a newsprint furnish would reduce the paper brightness by 5-6 points. Therefore, the residual ink in the pulpandpapercanada.com

peer reviewed

PM no.

Brightness loss due to WW

3 1.0 4 4.4 6 4.4 7 3.5 15 6.4 PCC Clay

Copper ppm

Iron ppm

Manganese ppm

10.9 8.2 18 18 16 1 7

83.9 78.3 184 289 488 280 709

1348 701 552 684 480 24 14

Paper Brightness (%)

TABLE V. Metal ions in the selected ww and filler samples.

Note: The ion concentration, “ppm”, was based on dry solids.

whitewater might be the main reason for the greatest brightness losses for PM 1 and 2.

Table IV shows that whitewater that caused high brightness loss in the absence of ink had high consistency, pH or conductivity (see the highlights in the table). A high whitewater consistency implies a low first-pass retention. For PM 15, the first pass retention of fines was only about 15%. A low fines retention means the fines circulate much longer in the whitewater system, and consequently become darker. For PM 6, and 7, the neutral pH combining with high conductivity was probably responsible for the darker whitewater fines. As we previously reported [3], at the same pH, high conductivity increases the pH inside the fibre wall, thus accentuating the effect of neutral pH. Metal Ions in the Whitewater Samples It is well known that some heavy metal ions, like copper and iron, can accelerate the thermal darkening of mechanical pulp, and form colour complexes with lignin and phenolic compounds.

To see if metal ions also play an important role in the whitewater darkening, copper, iron, and manganese contents were determined in some of the whitewater samples. According to Table II, besides the two that contained residual ink, the whitewater from PM 4, 6, 7, and 15 had the most darkening effect, while the whitewater from PM 3 had the least effect. The metal ion contents of these whitewater samples are listed in Table V. None of the samples tested contained an significant amount of copper, but they all had a great quantity of manganese. Interestingly, the whitewater with the least impact on brightness had the highest manganese content. This implies that manganese was not the prevalent cause for the low brightness of the whitewater fines.

On the other hand, the whitewater from PM 15, which caused the highest brightness loss, did have the highest content of iron, about six times that of the whitewaters from PM 3 and 4. Further analysis indicated that the mill fresh water was the source of this high iron content. This high iron content might explain, at least partially, why this mill experienced a significant brightness loss in the wet-end.

The significant amount of iron in samples from PM 6 and 7 was probably due to the presence of PCC in the whitewater, because the PCC contained a large amount of iron, as also indicated in Table V. Besides PCC, clay also contains a significant amount of iron. Our laboratory study shows that the iron in PCC and clay does not have measurable effect on pulp brightness, probably because the iron in these fillers is not soluble under papermaking conditions. pulpandpapercanada.com

FIG. 1. Increasing filler content decreased paper brightness because more dark fines were also retained.

Other Factors Causing Brightness Loss in the Wet End of a Paper Machine Our mill case studies have shown that, besides the factors discussed above, there are other factors contributing to the brightness loss in machine wet ends; for example, chip quality, pulp storage, broke usage, and accumulation of dyes. These will be discussed in a separate report.

CONCLUSIONS

This benchmark study based on 16 paper machines shows that adding calcium carbonate to mechanical furnishes at neutral pH, either in the absence or presence of whitewater, causes a brightness loss of the pulp, which is in most cases less than three points.

This brightness loss is consistent with our previous study, in which no whitewater was used, which implies that the brightness loss is caused mainly by increasing pH due to the alkaline nature of calcium carbonate, not by complexion or a reaction between whitewater components and calcium ions.

All the whitewater investigated in this study had a detrimental effect on paper brightness in the absence of filler, whether the paper machine was run under neutral conditions or not. The brightness loss ranged from 1 to 8 points, depending on the individual paper machine, when the paper furnish was diluted with the corresponding whitewater. This brightness loss was mainly caused by the dark whitewater fines.

The common factors causing dark fines materials in whitewater include residual inks from DIP, contaminants from fresh water, low fines retention and increased wet-end pH. Each paper machine might have different causes of brightness loss. Long pulp and broke storage time, and an accumulation of dyes in the fines may also contribute to the low brightness of finished paper products. The analysis described in this report can be used to identify the sources of the brightness loss and to develop strategies to minimize the loss and save bleaching chemicals.

ACKNOWLEDGMENTS

The authors would like to thank Tom Owston and Françoise Forel for their technical assistance, the chemical analysis groups for metal ions and colour determination, and all the mill partners for assisting in sample and process data collection.

Pulp & Paper Canada March 2009

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mechanical pulps LITERATURE

1. Evans, D.B., Drummond, D.K. and Koppelman, M.H., “PCC Fillers for Groundwood Papers”, Proceedings of 1991 TAPPI Papermakers Conference, 321-330 (1991).

2. Ain, R. and Laleg, M., “Mill Experiences with AT™ Precipitated Calcium Carbonate (PCC) in Papers Containing Mechanical Pulp”, Pulp & Paper Can., 98(12): 172-176 (1997).

3. Hua, X., Laleg, M., and R. Poole, “Effect of Neutral Conversion on TMP Properties”, Paprican, PPR 1392 (1998).

4. Hua, X., “Effect of Neutral Papermaking on Brightness and on Bleaching Processes of Mechanical Pulps”, Paprican, PPR 1496 (2000).

5. Kangas, H. and Kleen, M., “Surface Chemical and Morphological Properties of Mechanical Pulp Fines”, Nord. Pulp Pap. Res. J. 19(2): 191-199 (2004).

Résumé: Nous avons étudié l’effet de l’eau blanche de la machine à papier sur la perte de blancheur de 16 pâtes mécaniques, en présence ou en l’absence d’une charge composée de carbonate de calcium. La dilution des pâtes à l’aide d’eaux blanches provenant de la même usine a entraîné des réductions de blancheur allant jusqu’à 8 points et d’en moyenne 4,6 points dans le cas des machines à papier journal. Les causes de cette perte de blancheur variaient d’une usine à l’autre. Il est primordial d’identifier d’abord correctement les sources de ce phénomène afin de développer des stratégies efficaces pour réduire cette perte et les coûts des produits chimiques.

Reference:

HUA, X. AND LALEG, M. IMPACT OF MACHINE WHITEWATER ON BRIGHTNESS OF MECHANICAL GRADES. Pulp & Paper Canada March 2009:T25-29. Paper presented at PAPTAC 94th Annual Meeting in Montreal, February 6-7, 2009. Not to be reproduced without permission of PAPTAC. Manuscript received December 2007. Revised manuscript approved for publication by the Review Panel December 2008.

Keywords: BRIGHTNESS, CALCIUM CARBONATE, CONDUCTIVITY, DEINKED STOCK, FILLERS, FINES, FRESH WATER, MECHANICAL PAPERS, MECHANICAL PULPS, NEUTRAL PAPERS, PAPER MAKING, PH, INK, RETENTION, WET ENDS, WHITE WATER

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oxygen delignification

Rate determining step and kinetics of oxygen delignification

WINNER OF THE HOWARD RAPSON AWARD

By Y. Ji, E. Vanska and A. van Heiningen Abstract: A differentially operated, continuous stirred tank reactor (CSTR) was used to study the kinetics of oxygen delignification. The delignification kinetics and reaction rate were determined at different temperatures, oxygen pressures and caustic concentrations on softwood kraft pulps. The kinetics are first order in residual lignin content (HexA corrected). The kinetics of phenolic delignification can be described by assuming that the decomposition of the hydroperoxide anion at carbon 3 of the aromatic ring is the rate determining step. The cellulose degradation kinetics were described by two contributions: one due to radicals produced by phenolic delignification, and the other due to alkaline hydrolysis.

M

any studies have been performed to determine the kinetics of oxygen delignification1-5. Almost all kinetic equations were derived using experiments performed in laboratory batch reactors. However it is difficult to determine the reaction orders in alkali concentration and residual lignin content when operating a batch reactor at medium consistency (MC) because these variables are continuously changing with time. Also mass transfer of oxygen from the gas to the liquid phase must be efficient enough so that the oxygen concentration in the liquid phase is close to saturation throughout the experiment. Another difficulty is that pulp properties can only be determined after an experiment so that many experiments at different reaction times must be run, thereby increasing experimental error.

In the present study, a constant flow of an oxygenated caustic solution is fed to a MC pulp bed.

The pulp bed is retained inside a basket placed inside a pressured reactor. The caustic solution circulates rapidly through the pulp, while fresh oxygenated caustic solution is added to the reactor and spent liquor is removed simultaneously at the same rate. In other words, the device is a differentially operated continuous stirred tank reactor (CSTR) in which the concentrations of the dissolved oxygen and NaOH are close to that of the feed.

Oxygen delignification kinetics previously reported have mathematical forms which were mostly chosen to obtain a good fit with the experimental data rather than derived based on fundamental chemical mechanisms. This leads to kinetic equations with high reaction orders in residual lignin content or to arbitrary identification of so called “fast reacting” and “slow reacting” lignin. Another aspect of the reported delignification equations is that the lignin content is generpulpandpapercanada.com

ally derived from the kappa number, i.e. they do not distinguish between real lignin, hexenuronic acids (HexA) and non-lignin based oxidizable structures as identified by Li and Gellerstedt6.

Since it is known that hexenuronic acids are stable during oxygen delignification, the lignin content in the present study is corrected for the presence of HexA7. The delignification data are then fitted to kinetics which are derived based on elementary reactions identified in a chemical mechanism of oxygen delignification. The cellulose degradation kinetics are described by two contributions: one due to radicals produced by phenolic delignification, and the other due to alkaline hydrolysis.

Experimental

Reactor setup A flow diagram of the CSTR system is shown in Figure 1. Oxygen is bubbled overnight into a caustic solution in a pressurized (0.9 MPa maximum) heated stainless steel container of 11 liter. A 280 mL Berty reactor (Autoclave Engineers) with a 100 mL stationary basket holds the pulp bed. A rotor underneath the basket induces flow through the pulp mat. Any gas inside the reactor is vented at the top of the reactor so that the entire reactor is filled with liquid during operation. The reaction is started by feeding the oxygenated caustic solution at constant flow rate and oxygen pressure. The reactor pressure and temperature, and flow rate and UV-VIS absorption of the outflow stream are continuously recorded.

Pulps and analyses Unbleached southern pine kraft pulps were used.

The dissolved lignin concentration was determined from UV absorption at 280 nm using Indulin AT lignin (MeadWestvaco) for calibration8.

The HexA content of pulp was determined by the

Y. Ji, National Renewable Energy Laboratory Golden, CO, USA E. Vanska, Helsinki University of Technology Espoo, Finland

A. van Heiningen, University of Maine Orono, ME, USA

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oxygen delignification

Fig. 1. Flow diagram of the continuous stirred tank reactor (CSTR) system.

method of Tenkanen et al. scaled down to 200 mg pulp9. The residual lignin content in pulp, Lc, was calculated as

(

)

(

)

mg lignin HexA 31.5 –—––––– Lc = Kappa – ––––– (1) 10 g pulp

where the kappa number is calculated as the initial pulp kappa number minus the amount of lignin dissolved as measured by UV. The kappa number is corrected for the HexA content (in µmol/g pulp). Since 10 µmol/g of HexA is equivalent to one kappa unit10, the HexA content is divided by 10. The factor 1.5 is the standard conversion of kappa to mg lignin per gram of pulp. Ji has shown that the HexA content of pulp does not change during oxygen delignification except when a severe yield loss occurs so that HexA groups are removed together with the carbohydrates11.

The phenolic hydroxyl group content of the liquor and the pulp was determined from the difference in UV absorbance of neutral and alkaline solutions at 300 and 350 nm11-12. To avoid lignin precipitation, 100 µl of dioxane was added to the samples.

Fig. 2. Delignification rate vs. residual lignin at different O2 pressures.

– . .– L* + O2 $ L* + O2

(2) .–

forming a superoxide anion radical, O2 , . and a lignin radical L* . Therefore the rate expression of oxygen delignification may be written as: dLC – – ––––– = k [L* ]·[O2]ads dt

(3)

–

where [L* ] is the reactive lignin site concentration and [O2]ads is the adsorbed oxygen concentration on the reactive lignin site. The equilibrium constant KHL* of the protonation of the lignin active site is: –

[L* ][H+] KHL* = –––––––– [HL*]

(4)

When the total number of active lignin – sites is defined as HL*total = L* + HL*, it can be derived that: dL KHL*[HL*total][OH –][O2]ads – ––––C = k ––––––––––––––––––––– (5) dt Kwater + KHL*[OH–]

Data analysis procedure Details about the data analysis procedure can be found in earlier publications8, 11.

where Kwater = [H+] 3 [OH-]. If it is now assumed that the active sites are uniformly distributed throughout the residual lignin Lc, then [HL*total] = C·LC, where C is a proportionality constant. Thus, equation (5) becomes:

Development of rate expression and determination of rate constants It is well accepted that the first step involving oxygen delignification is dissociation of phenolic groups forming an active lignin – anion site3, 5,. L* . Oxygen delignification kinetics can be interpreted as the result of the rate determining reaction between adsorbed oxygen and the active lignin – anion site, L* , as:

where the constant Kc = KHL*·[HL*total]·C. The reaction rate constant, k, is obtained from the slope of the delignification rate versus Lc curve shown in Figure 2 for a commercial unbleached southern pine kraft pulp (Kappa 26). The linear decrease in delignification rate with HexA-free residual lignin content, LC, can be inter-

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dLC [OH–][O2]ads – –––– /LC = k = KC = ––––––––––––– (6) dt Kwater+KHL*[OH–]

preted as a first order reaction in lignin.

The wavy character of the data is caused by slow small temperature fluctuations (± 1°C) in the CSTR due to imperfect control.

Equation 6 predicts that when [OH–] is very high, the reaction order in [OH–] approaches zero, and that the reaction order in [OH–] should approach first order when [OH–] is close to zero. By taking the inverse of equation 6, we obtain 1 KHL* Kwater 1 – = ––––––– + –––––––– · –––––– k KC[O2]ads KC[O2]ads [OH –]

(7)

The terms KHL* /Kc[O2]ads and Kwater/ KC[O2]ads are constant when the temperature and oxygen pressure are kept constant.

Thus, by plotting 1/k versus 1/[OH–] at constant temperature and oxygen pressure, but at variable [OH–], a linear relationship should obtained. This is indeed the case as shown in Figure 3. From the abscissa and slope of Figure 3 one obtains that KHL*/Kc[O2]ads = 29.54 and Kwater/KC[O2]ads * = 3.28 or KHL = 9.01·Kwater. Since the pKw of water, –log(Kwater), at 90°C is 12.40 (Palmer et al. 2004), the pKa of the active lignin sites at 90°C is calculated as 11.5.

This value is almost two units higher than 9.8 measured for Indulin AT at this temperature13, indicating that the lignin active site is not a phenolic group.

To include the effect of oxygen pressure in equation 6, a relationship was derived between [O2]ads and PO2 based on the following assumptions: 1. Oxygen adsorption follows a Langmuir type adsorption isotherm, 2. The total number of adsorption sites is constant, pulpandpapercanada.com

peer reviewed

FIG. 3. 1/k (min) vs. 1/[OH].

FIG. 4. 1/k (min) vs. 1/PO2.

3. The adsorption/desorption equilibrium can be described by equation 8.

L*– +O2,dis O2,ads

(8)

where O2,dis is oxygen dissolved in the caustic solution.

As the adsorption and desorption of oxygen from the active lignin sites is fast, [O2]ads is at quasi-equilibrium, and the adsorption rate, ra = ka[L*–][O2,dis] is equal to the desorption rate, rd = kd[L*–][O2,]ads. The total number of active sites is constant, i.e.

[HL*-] + [O2]ads = Ct , thus it may be derived that KeCt[O2]dis [O2]ads = –––––––––– 1 + Ke[O2]dis ka where Ke = ––– kd

(9)

Equation 9 shows that when [O2]dis is very large, the reaction is zero order in dissolved oxygen concentration, while it is first order in dissolved oxygen concentration at very low oxygen concentration. The dependence of [O2]dis in water on the NaOH concentration and temperature has been reported by Tromans14. The data in the quoted paper show that for the present experimental conditions (0.5M [NaOH], 0.55 MPa, and 110°C) the saturated oxygen concentration at oxygen delignification conditions is: [O2]dis = 6.4310 3PO2 –3

(10)

where [O2]dis is expressed in mol/l and PO2 in MPa. Table 1 shows the saturated oxygen concentration at different oxygen partial pressures for the present experiments performed at 90°C. PH2O is the saturated steam pressure at 90°C. Inserting equations 9 and 10 into equation 6 gives dL [OH–] PO2 – ––––C = C1 ––––––––––––––– · ––––––––– · LC dt Kwater + KHL*[OH–] 1 +KePO2

(11)

where C1 = k · KHL*C · KeCt At constant temperature and [OH –], equation 11 can be rearranged as

1 1 Ke 1 –––––––––– = ––– = –––– + ––––– dLc k C2 C2PO2 (– ––––)/L C dt pulpandpapercanada.com

(12)

table i. Oxygen concentrations at different partial pressures at 90°C. PO2 = Ptotal-PH2O + 0.1. total at 363K P (MPa)

0.24 0.38 0.52 0.66

PO2 at 363K (MPa)

O2 Conc. [O2]dis (mol l–1)

0.27 0.41 0.55 0.69

0.001748 0.002632 0.003517 0.004401

where C2 is a constant. For the four conditions listed in Table 1, the slope of plots of – dLC /dt versus Lc is equal to k. A plot of the inverse of the slope (or 1/k) versus 1/PO2 is presented in Figure 4. It can be seen that a relative straight line behavior is obtained, supporting the assumption that [O2]ads is governed by a Langmuir-type adsorption. The value of Ke obtained from Figure 4 is Ke = 47.91/14.13 = 3.39 (1/MPa).

The constant C1 in equation 11 was calculated using all the CSTR experiments performed at 90°C. The value of C1 is 0.175 with a standard derivation of 0.0127. Thus, the final oxygen delignification kinetic equation at 90°C is: dL [OH –] PO2 – –––C = –––––––––– – · –––––––– · LC dt 0.111+[OH ] 1 + 3.39PO2

(13)

with –dLC/dt expressed in mg lignin/g pulp/min, [OH–] in mol/l and PO2 in MPa. Based on equation 13, the first order reaction rate constant, k, can be defined as [OH–] PO2 k = 0.175 –––––––––––– – · –––––––– 0.111 + [OH ] 1+3.39PO2

(14)

Figure 5 illustrates that k calculated with equation (14) compares well with the measured reaction rate constant (slope of the experimental curves of –dLC/dt versus Lc).

Finally, the activation energy was determined from the temperature dependence of the rate constant, k, in the present study as 53 kJ/mol15. This value is in agreement with that of a reaction controlled process.

To confirm the first order is behavior in LC, –dLC/dt was measured for three Loblolly Pine kraft pulps of different initial kappa numbers; 23, 26, and 34 (see Figure 6)16. The initial higher faster delignification may be due to additional peeling delignification Pulp & Paper Canada March 2009

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oxygen delignification

FIG. 5. Slope (1/min) vs. predicted reaction rate constant k.

FIG. 6. Oxygen delignification rate of Loblolly pine kraft pulps at different kappa no. levels.

FIG. 7. Phenolic group content of liquor and pulp at different reaction times.

FIG. 8. Three experiments; (1) experiment in Berty CSTR during 3 h; (2) 60 min batch reactor + 80 min Berty CSTR; (3) 20 min batch reactor + 75 min Berty CSTR.

as has been discussed by van Heiningen et al17.

The first order behavior in LC can be interpreted that the lignin active sites, L*–, are uniformly distributed throughout the lignin, and have the same reactivity during the entire oxygen delignification process.

It is generally accepted that the first step during oxygen delignification is the dissociation of the phenolic groups. This is the reason why the phenolic group content of residual lignin was measured before and after oxygen delignification. In agreement with literature data7 we obtained values for the phenolic fraction of lignin in the original pulp of around 0.41 and after 60 min at 90°C, 0.52 MPa oxygen pressure and 3.3 g/l of NaOH of around 0.27. After 3 h of oxygen delignification, the phenolic fraction of the residual lignin in pulp decreases further to 0.22, i.e. to half the initial value.

Based on this and on the high pKa value of the lignin active sites, L*– we suggests that the rate determining step of oxygen delignification is not a direct attack of oxygen on the dissociated phenolic groups.

The phenolic lignin content of the 32

March 2009 Pulp & Paper Canada

liquor was also measured. Figure 7 shows these values and that of the pulps at different reaction times as well as the sum of the phenolic group content in the pulp and liquor based on original pulp. As can be seen, the reduction in the amount of phenolic groups in the pulp is nearly equal to the amount of phenolic groups removed with the liquor since the sum of phenolic groups does not change significantly during oxygen delignification. This suggests that the dissolved lignin is still mostly aromatic in nature.

Finally, we found that the ratio (MeOH formation rate/32) / (delignification rate/185), as determined from the methanol and lignin content of the liquor samples, remains mostly constant during delignification at about 0.9 ± 0.2. This means that methanol is released essentially quantitatively from lignin monomer units when they are solubilized11 The delignification rate versus residual lignin of three brown stock pulps cooked to different kappa numbers from the same Loblolly Pine (Figure 6) shows an initial fast rate. However, after oxygen delignifi-

cation of the fresh 24.4 kappa brownstock pulp for different times (20 and 60 minutes) in a batch reactor, continued delignification in the CSTR does not display the initial fast rate (Figure 8). The absence of the initial fast rate for the latter two pulps has been explained by the absence of hemicelluloses with reducing ends and attached lignin fragments in these pulps17.

Figure 8 also shows that the oxygen delignified pulp obtained in a batch reactor has a similar delignification rate as the original pulp. This implies that lignin condensation is insignificant in a batch reactor since the pulps are exposed to high concentrations of dissolved lignin at the end of the delignification process.

Delignification mechanism Based on the presented data we propose that the active lignin site is not the phenolic group, but another less acidic site which is uniformly distributed throughout the residual lignin to satisfy the first order in lignin rate behavior. Because hydroperoxides have a pKa of 12 – 13 compared to about 10.5 for Indulin AT at room pulpandpapercanada.com

peer reviewed R1

a)

R1

OH-

R2

R1

OCH3 R2 OH pKa 10-11

OCH3 R2

OCH 3

O

O

R1

R1

O2

R1 O2 -

O-O R2

OCH3 R2 O

O pKa 12-13

b) R1

R2 O-O

R2

O-OH

OCH3 R2

OCH3 O

R1

CO2 CO2

+ CH3OH

FIG. 10. Cellulose degradation in CSTR and batch reactors; Experimental and predicted data.

R1

OCH3 O

+ CH3OH R2

O O

is that almost all residual softwood lignin monomer units contain

this moiety, thus explaining the uniform reactivity and first order Figure 9 Reaction mechanism of lignin with oxygen from Chang and(adopted Gratzl, 1980 18). a) FIG. 9.

Reaction mechanism of (adopted lignin with oxygen Formation of cyclohexadienon hydroperoxides by attack of oxygen. b) Homolytic and heterolytic kinetics in residual lignin for oxygen delignification. from Chang and Gratzl, 1980 18). a) Formation of cyclofragmentation of para-cyclohexadienone hydroperoxidases hexadienon hydroperoxides by attack of oxygen. b) Homolytic and heterolytic fragmentation of para-cyclohexadienone hydroperoxidases.

temperature13, a mechanism proposed by Chang and Gratzl18 was adopted to explain the present kinetics. Figure 9 shows the formation of cyclohexadienone hydroperoxide by attack of oxygen at alkaline conditions on phenolic lignin.

As illustrated, a hydroperoxide anion is formed by reaction of superoxide radical anion with the phenolate radical located at the carbon 3 position. Chemical computational modeling19 to calculate the enthalpies of reactions of lignin model shows that the reaction pathway in Figure 19 9a is possible. Other phenolate radical intermediates have been proposed (McDonough 1996) where the radical is located on carbon 1 and the beta carbon in addition to the carbon 3 shown in Figure a. All these three structures are part of the same resonance structure in which the odd electron formally resides at each of the three carbon positions.

The explanation, why the coupling of the superoxide anion radical with the radical at the carbon 1 and beta carbon is not effective for delignification, is likely that the formation of the respective oxirane and carbonyl structures is much more difficult than the formation of the muconic acid and quinone structures shown in Figure 9b when the hydroperoxide anion is located at the carbon 3 position.

Figure 9b shows that the hydroperoxide anion forms either a muconic acid structure and MeOH or an orthoquinone structure and MeOH. Since the hydroperoxide anion is the dominant species at pH > 12~13, based on the present kinetics is probable that the carbon at the 3 position of the lignin aromatic ring is the active site for oxygen delignification. Thus the present kinetics may be interpreted that the rate determining step is the unimolecular decomposition of the formed hydroperoxide anion, i.e. the rate is determined by the dissociated hydroperoxide concentration.

The latter is determined by the concentration of adsorbed oxygen on methoxyl groups at the carbon 3 (the lignin active site, L*), as well as by the pKa of the hydroperoxide. Further support that the carbon 3 with a methoxyl group is the lignin active site, L*, pulpandpapercanada.com

The pH dependence of the kinetics implies that the protonated hydroperoxide does not fragment into muconic acid or quinone structures. Also, the fact that dissolved lignin mostly retains its aromatic nature, and that MeOH is released essentially quantitatively during delignification, further support the hypothesis that quinone formation is the dominant pathway.

Kinetics of cellulose degradation The cleavage of cellulose was modeled by Iribarne and Schroeder19 as the increase in number-average moles of cellulose per gram of pulp (mn ). Similarly one can describe the cellulose degradation by the number of cellulose chain scissions during oxygen delignification. Violette and van Heiningen20 calculate the number of cellulose chain scissions from the average degree of depolymerization of cellulose (DP) in the pulp at time t=0 and time t=t, as 1/ DPt-1/DP0. DP can be obtained from the intrinsic viscosity [h] by equation (15). This formula considers the actual weight of cellulose rather than the pulp weight being responsible for the viscosity, and makes a correction for the small contribution of the hemicelluloses to the pulp intrinsic viscosity21.

(

)

1.65[h] – 116H 1.111 DP of Celluose = ——————— G

(15)

where [h] is intrinsic viscosity of the pulp in cm3/g, and G and H are the mass fractions of cellulose and hemicellulose in the pulp (see Table 2). This formula considers the actual weight of cellulose rather than the pulp weight being responsible for the pulp viscosity, and makes a correction for the small contribution of the hemicelluloses to the intrinsic viscosity.

The number of moles of cellulose per gram of pulp, mn, can be calculated by equation (16) as22:

(

)

1 1 Moles _ ––––––– mn = ––––––––– .

––––––––––

162DPn+18 162DPn Gram Pulp

(16)

The content of cellulose (G) and hemicellulose (H) in the pulp was measured by high pressure anion exchange chromatography (HPAEC) on double hydrolyzed pulp samples23. The results for the pulp samples are listed in Table 2.

Pulp & Paper Canada March 2009

33

T34

T35

oxygen delignification table Ii. Properties of CSTR oxygen delignified pulps (at 3.3g/l NaOH, 90°C and 0.52MPa).

Time Kappa (min) 0 10 20 40 60 180

24.4 20.1 18.5 14.3 12.7 7.6

Viscosity (ml/g)

Cellulose, G (g/g pulp)

Hemicellulose, H (g/g pulp)

DP of cellulose

1189 1079 1033 877 828 592

0.714 0.732 0.734 0.746 0.750 0.763

0.142 0.139 0.142 0.140 0.138 0.135

6561 5724 5435 4445 4144 2784

table iII. Properties of Batch oxygen delignified pulps (3% NaOH, 90°C, 0.52 MPa, 10% Cons.).

Time Kappa (min) 0 10 20 40 60 180

24.4 20.8 18.5 15.0 13.5 10.1

Viscosity (ml/g)

Cellulose, G (g/g pulp)

Hemicellulose, H (g/g pulp)

DP of cellulose

1189 1058 1011 924 898 829

0.714 0.723 0.723 0.729 0.736 0.736

0.142 0.139 0.138 0.139 0.140 0.141

6561 5674 5394 4831 4629 4230

Based on these results the cellulose degradation was modeled by two contributions: one due to radicals produced by phenolic delignification, and the other due to alkaline hydrolysis. The model can be described as equation (17):

dmn dK –––– = –kc –––– + kh [OH –] dt dt

(17)

where kc is the rate constant for radical attack, and kh is the alkaline hydrolysis rate constant.

[OH –] is the alkali concentration in g/L. Integration of equation (17) gives: mn = m0 + kc (K – K0) + kh [OH–]t

(18)

Comparable results for the same brown stock pulp oxygen delignified in a batch reactor samples are given in Table 3. Since NaOH is rapidly consumed during the initial phase of oxygen delignification in a batch reactor, the influence of the term kh[OH–]t in equation (18) may be neglected for t ≥ 20 minutes. This allows calculation of kc by fitting the batch reactor as 3.60 x 10-8 (moles/g pulp·kappa). Using this value in the analysis of the CSTR data gives a value for kh of 1.07 x 10-9 (liter·mol cellulose/g pulp·g NaOH·minute). These two values provide a good fit of the cellulose degradation in the CSTR and batch reactor as can be seen in Figure 10.

Conclusions

The kinetics of oxygen delignification are first order in residual lignin content (HexA 34

March 2009 Pulp & Paper Canada

corrected), and follow a Langmuir-type behavior for adsorption of oxygen on the active aromatic lignin sites. The reaction order in NaOH of the kinetics implies that the rate determining step involves an acidic lignin active site with a pKa almost 2 units higher than that of phenol in lignin. Based on these results it is proposed that the lignin active site is the 3 carbon of the aromatic ring where oxygen reacts to form a hydroperoxide. The rate determining step is identified as the unimolecular decomposition of the formed hydroperoxide anion.

The almost uniform presence of aromatic methoxyl groups in residual lignin further supports the first order in lignin kinetics.

Further supporting evidence is the close relationship between delignification and demethoxylation. The significant reduction in phenolic group content of the lignin during oxygen delignification is consistent with the hypothesis that the rate determining step of oxygen delignification is not a direct attack of oxygen on the dissociated phenolic groups. The cellulose degradation during oxygen delignification was modeled by two contributions: one due to radicals produced by phenolic delignification, and the other due to alkaline hydrolysis.

Acknowledgement

Financial support by the Technology Development Agency of Finland (TEKES), Helsinki University of Technology and the Ober Chair is gratefully acknowledged. The discussions with Dr.

Raymond Fort Jr. at the University of Maine were essential for our understanding of the mechanism, and are greatly appreciated.

Literature:

1. Edwards L. and Nordberg S-E. (1973) Alkaline Delignification Kinetics, a General Model Applied to Oxygen Bleaching and Kraft Pulping, TAPPI, 56(11), 108-111 2. Teder A. and Olm L. (1981) Extended delignification by combination of modified kraft pulp and oxygen bleaching, Paperi Puu, 63(4a), 315-326 3. Ljunggren, S.C.H and Johansson ,E.C. (1987) Reaction Kinetics of Lignin Structures during Oxygen Bleaching-Effects of Solvent, Oxygen Pressure and pH, In: International Oxygen Delignification Conference, Tappi Proceedings, 125 4. Kovasin K., P. Uusitalo P., M. Viilo, (1987) Dimensioning of oxygen delignification reactors, International Oxygen Delignification Conference, June 7-12, San Diego, USA, pp. 223-230 5. Johansson, E., Ljunggren, S., (1994) The Kinetics of Lignin Reaction During Oxygen Delignification, Part 4. The Reactivates of Different Lignin Model Compounds and the Influence of Metal Ions on the Rate of Degradation, J. Wood Chem. Technol. 14(4), 507-525 6. Li, J. and Gellerstedt, G., (2002) Oxymercuration – Demercuration Kappa Number: an Accurate Estimation of the Lignin Content in Chemical Pulps, Nordic Pulp Paper Res. J. 17(4), 410-414 7. Rööst, C., Lawoko, M., Gellerstedt, G. (2003) Structural Changes in Residual Kraft Pulp Lignins. Effects of Kappa Number and Degree of Oxygen Delignification, Nordic Pulp Paper Res. J. 18(4), 395-399 8. Ji Y. and van Heiningen A. (2007) A new CSTR for Oxygen Delignification Mechanism and Kinetics Study, Pulp Paper Canada, 108(5), 38-42 9. Tenkanen, M.,G. Gellerstedt, T. Vuorinen, A. Teleman, M. Perttula, J. Li, and J. Buchert (1999) Determination of Hexenuronic Acid in Softwood Kraft Pulps by Three Different Methods, J. Pulp Paper Sci. 25(9), 306-311 10. Vuorinen, T. et al., (1999) Selective Hydrolysis of Hexenuronic Acid Groups and its Application in ECF and TCF Bleaching of Kraft Pulps, J. Pulp Paper Sci. 25(5), 155-162.

11. Ji, Y. (2007) Kinetics and Mechanism of Oxygen Delignification, PhD thesis, University of Maine, Orono, USA 12. Gartner, A., Gellerstedt G. and Tamminen T. (1999) Determination of Phenolic Hydroxyl Groups in Residual Lignin using a Modified UV-Method.

Nordic Pulp Paper Res. J. 14(2), 163-170 13. Norgren, M., and Lindstrom B., (2000) Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures Holzforschung, 54, 519-527 14. Tromans D., (1998) Oxygen Solubility Modeling in Inorganic Solutions: Concentration, Temperature and Pressure Effects, Hydrometallurgy, (50), 279-296 15. Ji, Y., Wheeler M. C. and van Heiningen A. (2007) Oxygen Delignification Kinetics: CSTR and Batch Reactor Comparison, AIChE J. 53(10), 2681-2687 16. Vanska, E., (2007) Kinetics of Oxygen Delignification in a Continuous Stirred Tank Reactor, M. Sc. Thesis, Helsinki University of Technology, Espoo, Finland 17. Van Heiningen, A., Ji, Y., Vänskä, E., (2008) New kinetics and mechanism of oxygen delignification: International Pulp Bleaching Conference, June 2-5, Quebec City, Canada. 91-98 18. Chang H. and Gratzl J. S. (1980) Ring Cleavage Reactions of Lignin Models with Oxygen and Alkali, In. Chemistry of Delignification with Oxygen, Ozone and Peroxide, Uni Pub. Co. Ltd, Tokyo, Japan, pp.

151-163 19. Hausman, M.C., Elder, T.R. and Fort, R.C. Jr. (2003) How Do Phenoxyl Radicals Form During Oxygen Delignification? 12th International Symposium on Wood and Chemistry (ISWPC), June 9-12, Madison, WI, USA, Poster presentations pp. 59-62 20. McDonough, T. J. (1996) Chapter IV 1: Oxygen Delignification, in Pulp Bleaching – Principles and

pulpandpapercanada.com

peer reviewed Practice, Dence, C. W. and Reeve, D. W. Editors, Tappi Press, Atlanta, GA., 220-223 21. Iribarne J. and Schroder L.R. (1997) High-Pressure Oxygen Delignification of Kraft Pulps, TAPPI, 80(10), 241-250 22. Van Heiningen A. and Violette S., (2003) Selectivity Improvement during Oxygen Delignification by Adsorption of a Sugar-based Polymer, J. Pulp Paper Sci. 29(2), 48-53 23. Da Silva Perez, D. and van Heiningen A.R.P. (2002) Determination of Cellulose Degree of Polymerization in Chemical Pulps by Viscosimetry, 7th European Workshop on Lignocellulosics and Pulp (EWLP) Conference, Turku, Finland 393-396 24. Davis, M.W. (1998) A Rapid Modified Method for Compositional Carbohydrate Analysis of Lignocellulosics by High pH Anion-Exchange Chromatography with Pulsed Amperometric Detection (HPAEC/PAD), J. Wood Chemistry and Technology, 18(2), 235-252

Résumé: Un réacteur à fonctionnement continu et à commande différentielle a été utilisé pour étudier la cinétique de la délignification à l’oxygène. La cinétique de la délignification et la vitesse de réaction ont été déterminées à des températures, des pressions d’oxygène et des concentrations caustiques différentes avec des pâtes kraft de résineux. La cinétique joue un rôle de premier ordre dans la teneur en lignine résiduaire (HexA corrigé). On peut décrire la cinétique de la délignification phénolique en partant de l’hypothèse que la décomposition de l’anion de peroxyde d’hydrogène à carbone 3 du noyau aromatique constitue l’étape cinétiquement déterminante.

Deux contributions expliquent la cinétique de la dégradation de la cellulose : l’une attribuable aux radicaux produits par la délignification phénolique et l’autre, à l’hydrolyse alcaline.

Reference: JI, Y., VANSKA, E., VAN HEININGEN, A. Rate determining step and kinetics of

oxygen delignification. Pulp & Paper Canada March 2009:T30-36. Paper presented at the 2008 International Pulp Bleaching Conference in Quebec City, QC Canada, June 2-5, 2008. Not to be reproduced without permission of PAPTAC. Manuscript received August 1, 2008. Revised manuscript approved for publication by the Review Panel December 29, 2008.

Keywords: oxygen delignification kinetics; rate determining step, cellulose degradation kinetics.

International Colloquium on Eucalyptus Pulp April 14-17 Laboratorio Tecnológico Del Uruguay, Montevideo, Uruguay www.4thicep.com/english/index.html

10th International Conference on Wood & Biofibre Plastic Composites & Cellulose Nanocomposites Symposium May 11-13 Madison, WI conferences@forestprod.org

Papricourse 2009 May 11-15 FPInnovations-Paprican, Pointe-Claire, Que. H. Avedesian, 514-630-4101, ext. 2349; heather.avedesian@fpinnovations.ca

BCIT Pulp and Paper Technology Summer Institute May 11-15 Prince George, B.C. www.pulp.bcit.ca

2009 TAPPI 12th European PLACE Conference May 18-20 Budapest, Hungary www.tappi.org; 800-446-9431

PaperCon ’09 May 31-June 3 St. Louis, Mo. www.tappi.org; 800-446-9431

International Mechanical Pulping Conference June 1-4 Sundvall, Sweden G. Hay 514-392-6964

International Paper and Coating Chemistry Symposium June 10-12 McMaster University, Hamilton, Ont. G. Hay 514-392-6964

PACWEST Conference June 10-13 Delta Sun Peaks Resort, Kamloops, B.C. M. Barnes 604-988-9829; barnesmm@shaw.ca

International Symposium on Wood and Pulping Chemistry June 15-18 Oslo, Norway G. Hay 514-392-6964

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XIVth Fundamental Research Symposium Sept. 13-18 Oxford, UK frc14oxford2009.org.uk; www.frc14oxford2009.org.uk

International Conference on Wood Adhesives Sept. 28-30 Lake Tahoe, NV cfrihart@fs.fed.us

TAPPI Engineering, Pulping, Environmental Conference Oct. 11-14 Memphis, TN www.tappi.org

Events

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Pulp & Paper Canada March 2009

35

T36

technology news All-purpose blade holder system

Kadant Web Systems Inc. has launched its Uniset™ blade holder featuring an integrated T-rail holder removal system.

This patent-pending holder is designed

to upgrade the popular DST-style blade holder, as well as competitive blade holders.

The all-composite construction of the Uniset system is lightweight and facilitates easy removal of the holder for cleaning and maintenance. The heat- and corrosion-resistant material works in nearly all mill environments and permits easy inventory management as spare holders can be “cut-to-fit” prior to installation in the particular position.

Uniset blade holders are available for both light-duty cleaning applications and for heavy-duty sheet shedding applications. Both models use conventional load and unload tubes and doctor blades.

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Professional Connect Equipment

Paper testing in the lab or on the mill floor The new-generation kajaaniPaperLab automated paper testing laboratory from Metso emphasizes modularity and scalability. The goal was to design a flexible device that responds to the industry’s demands for enhanced productivity.

Its new design takes ergonomics and ease of use to a new sophisticated level.

Many safety features, such as the automatic module frame opener, make operation easier so that users need not be highly skilled laboratory personnel.

Suitable for testing all grades of paper and board, kajaaniPaperLab offers a wide selection of industry-standard tests for more than 400 properties. Testing can be done equally well in the laboratory or at the production line. When used at-line, the machine operation team can run the most critical tests on their own and keep machine operation on-spec, as results transfer immediately to the automation system for process management control purposes.

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Online system for standardized pulp measurements To optimize and control the pulp and papermaking processes, operators need frequent and fast pulp quality information. According to Lorentzen & Wettre, it is possible with the L&W Pulp Tester to get standardized measurement results online with the same accuracy as in the

36

March 2009 Pulp & Paper Canada

laboratory.

The L&W Pulp Tester is a comprehensive system for automatic quality control of the pulping process.

“The system provides reliable and fast fibre measurements. A small measurement gap according to the standard for fibre length measurements secures a perfect alignment of the fibres in the measurement cell, which is unique for online fibre analyzers,” says Håkan Karlsson, product manager for the L&W Pulp Tester.

The system is built up of different modules, for example: fibre morphology (length, width, deformations, fines, etc.) including fully automatic measurement of

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Jim Bussiere 800-363-1327, ext 222 Fax: 514-630-5980 coarseness; optical properties (brightness, colour, and ERIC 950); and standard freeness (Canadian Standard Freeness and Schopper-Riegler). Shives content and distribution are measured with optical technique and with better statistical significance than ever.

Gravimetrical consistency measurements give a new dimension to many pulp properties besides coarseness.

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37

health & safety

Open sesame!

The team at SFK Pâte developed a simple and ingenious key to open even the most stubborn railcar with ease.

By Yves Lavertu

W

hen railcars arrive at a warehouse – whether at SFK Pâte in St-Félicien, Qué., or any other similar plant – a number of door cranks arrive positioned vertically, while others are horizontal, or at various positions in between. They are often badly positioned for workers to turn them. As a result, they have to struggle to turn the cranks, and the mechanism can get stuck, preventing the railcar doors from sliding open.

A team at SFK Pâte has addressed the problem with a homemade device that has garnered multiple awards from regional and provincial safety organizations.

Makeshift levers risk injury

The 1,050 tonnes of bleached kraft pulp produced at StFélicien every day is delivered to clients by truck and train.

Employees load the pulp into no less than 40 railcars on a weekly basis. According to Jérôme Laprise, the plant’s security superintendent, the wagon doors are difficult to open about 40% of the time.

Before developing the new device, the factory’s workers used a much more rudimentary system when faced with this problem: they would insert a steel pipe into the end of the crank to create a lever. While this system did make it possible to turn the cranks, it involved much effort and carried a high risk of injury. If the lever was badly positioned, the workers were susceptible to falls and muscle strains.

Thanks to a key system developed at SFK Pâte in St-Félicien, workers are well-positioned to open the door, no matter what position the door crank is in.

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March 2009 Pulp & Paper Canada

“Sometimes, it took two men,” Laprise says. “And sometimes, the crank would break.”

Furthermore, the situation was similar when it came time to close the doors.

SFK Pâte lodged a number of complaints with the carrier, but did not get any concrete results. A number of investigations into how other plants were solving the problem were made. StFélicien workers looked into the device developed on-site at the Domtar plant in Lebel-sur-Quévillon, for example.

Light and easy solution

Not finding a ready-made solution, the St-Félicien workers began to discuss their expectations and criteria in order to come up with an in-house solution.

“It needed to be something light,” says Laprise. “A simple, manual tool, which we would be able to use in all positions, no matter what position the crank was in.”

In 2000, things started to get moving.

“Every plant has its own ‘inventor,’” explains Laprise. At St-Félicien, his name is Aimé Bureau, a welder. After listening to suggestions from the operators, Bureau started to work on the desired tool. His creation would eventually help things go a lot quicker.

The device is made up of a metal piece that has been designed to fit around the principal section of the crank. At the centre of this steel component – which is in the form of a large bar – a 24-inch ratchet key has been welded on. The device is held by a safety pin, which makes sure the system stays in place.

When the time comes to open a railcar door, the worker fits the device on the crank. The ratchet key then does the rest. In an ergonomic sense, the worker is always positioned correctly for the job, no matter what position the crank is in.

“If he has to position the bar horizontally, he places the key horizontally,” Laprise says. “He is then in the right position to force, pull, push, and turn the crank.”

The operators have been very satisfied, says the superintendent. Not only does this system allow workers to better manage the force they apply, but it has also eliminated the potential risks of injury associated with this type of manoeuvre.

This innovation developed at St-Félicien is easily exportable, says Laprise. It could, of course, be used in other paper plants, but also in other types of factories that transport their merchandise by train. SFK Pâte has welcomed papermakers from Baie-Comeau and other corners of the province, and manufacturers from the aluminum industry have also come to PPC see the invention. pulpandpapercanada.com

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Š2008 Buckman Laboratiories