Covering Best Practices for the Industry
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For Two Lions Fine Chemicals, success comes in pairs Page 7
IN THIS ISSUE > > > > Market Outlook: COVID-19’s ongoing impact on the sulfuric acid market page 10
Wet Electrostatic Precipitators: A proven technology for sulfuric acid gas and mist cleaning page 24
Latest in process gas dewpoint/moisture leak detection Page 30
Clean Technologies
Making everyday life better, safer, cleaner For 100 years, we have partnered sulfuric acid producers with innovative technology and expert trouble-shooting technical support. And our tradition of designing advanced solutions to solve site-specific challenges continues – so we can together deliver cleaner air productively, efficiently and reliably. Learn more on www.cleantechnologies.dupont.com
MECS® Sulphuric acid & environmental technologies Copyright © 2019 DuPont. The DuPont Oval Logo, DuPont™, is registered trademarks or trademarks of E.I. du Pont de Nemours and Company or its affiliates. All rights reserved.
Sulfuric Acid
Covering Best PraCtiCes for the industry
Sulfuric Acid T
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For Two Lions Fine Chemicals, success comes in pairs Page 7
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Vol. 26 No. 2
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IN THIS ISSUE > > > > Market outlook: Covid-19’s ongoing impact on the sulfuric acid market page 10 Wet electrostatic Precipitators: a proven technology for sulfuric acid gas and mist cleaning page 21
FROM THE PUBLISHER
Latest in process gas dewpoint/moisture leak detection page 32
On the Cover … 7
Two Lions installs twin HRS units to become benchmark facility in China.
Departments 4
News items about the sulfuric acid and related industries
14 Product News Latest sulfuric acid technology 16 Lessons Learned Case histories from the sulfuric acid industry
Dear Friends, Welcome to the Fall/Winter 2020 issue of Sulfuric Acid Today. We have dedicated ourselves to covering the latest product and technology for those in the industry, and hope you find this issue both helpful and informative. As we move into the fourth quarter of the year, the sulfuric acid market continues to have challenges due to COVID-19. In the first half of the year, sulfur production dropped sharply, due to COVID-19 related manufacturing slowdowns. Things are starting to look up as the world adjusts to the “new normal,” though, setting the tone for a more positive 2021 for the industry. For in-depth information on the sulfuric acid market, please see Acuity Commodities article ‘COVID-19’s ongoing impact on the sulfuric acid market’ on page 10. COVID-19 has also affected industry conferences and meetings for 2020. Notably, this is the first issue of Sulfuric Acid Today that does not include our popular ‘Faces and Places’ section with photos from our Sulfuric Acid Roundtable and other industry conferences. The CRU Group’s Sulphur + Sulphuric Acid conference will host the first fully virtual event in the conference’s 36-year history November 9-11, 2020. Additionally, due to restricted international travel associated with COVID-19, we have rescheduled our Australasia Sulfuric Acid Workshop this year to Sept. 12-15, 2021 in Brisbane, Queensland, Australia.
Sincerely, Kathy Hayward
FEATURES & GUEST COLUMNS
PUBLISHED BY Keystone Publishing L.L.C. PUBLISHER Kathy Hayward
In this issue, we have several informative articles regarding state-of-the-art technology and projects. Our cover story, on page 7, focuses on China’s Two Lions Fine Chemicals facility. With two sulfuric acid plants online, the facility has gained national recognition as a model for energy savings and environmental stewardship in China. Clark Solutions presents their new SAFEHX® Heat Exchanger (page 26), while Acid Piping Technology and Gecko Robotics offer an option for safe, convenient robotic inspections (page 12). Breen offers a look at new leak detection for sulfuric acid plants on page 30. I would like to welcome our new and returning Sulfuric Acid Today advertisers and contributors, including: Acid Piping Technology Inc., Acuity Commodities, Alphatherm Inc., Beltran Technologies, Breen Energy Solutions, Central Maintenance & Welding, Chemetics Inc., Clark Solutions, DuPont MECS, Integrated Turbomachinery, Koch Knight LLC, Mercad Equipment Inc., NORAM Engineering & Constructors, Optimus, Southwest Refractory of Texas, Spraying Systems Co., VIP International, and Weir Minerals Lewis Pumps. We are currently compiling information for our Spring/ Summer 2021 issue. If you have any suggestions for articles or other information you would like included, please feel free to contact me via email at kathy@h2so4today.com. I look forward to hearing from you.
10
COVID-19’s ongoing impact on the sulfuric acid market
EDITOR April Kabbash
12
Ultrasonic technology helps keep infrastructure sound
EDITOR April Smith
14
Sulfur gun improvements
Marketing ASSISTANT Tim Bowers
18
Weir Minerals’ provides one-of-a-kind engineering expertise
DESIGN & LAYOUT 281-545-8053 Mailing Address: P.O. Box 3502 Covington, LA 70434 Phone: (985) 807-3868 E-Mail: kathy@h2so4today.com www.h2so4today.com SUBSCRIPTIONS U.S. Plant Personnel —‑Complimentary U.S. Subscription —‑ $39 per year (2 issues) Internat’l Subscription —‑$59 per year (2 issues) Subscribe Online: www.h2so4today.com
12
20 Evolution of the safety professional 22
NORAM fast tracks a converter–order to door in 5 months
24
Wet Electrostatic Precipitators: A proven technology for
22
sulfuric acid gas and mist cleaning 26 SAFEHX®: Safe Heat Exchanger 30
The latest in sulfuric acid plant process gas dewpoint/ moisture leak detection
26
Department
Industry Insights Metso, Outotec complete merger
HELSINKI, Finland—Finland-based equipment maker Metso Corp.’s board of directors and Finland-based Outotec Oyj recently announced that the combination of Metso’s Minerals business and Outotec is complete. Outotec is a designer and builder of minerals processing and metals refining systems. The companies announced a demerger plan and combination agreement in July 2019. The companies received unconditional merger control clearance from the European Commission in May. As a result of the transaction, Outotec is now Metso Outotec Corp. The new company is focused on sustainable minerals and metals processing and recycling technologies. Headquartered in Helsinki, Metso Outotec employs more than 15,000 people in more than 50 countries and its combined sales for 2019 were about $4.7 billion. The company will offer crushing and screening equipment for the production of aggregates as well as equipment and solutions for minerals processing, metals refining, chemical processing, and metal and waste recycling. Metso Outotec’s service capabilities are complemented with a range of spare and wear parts, refurbishments, and professional services. “It is our core expertise to help our customers transform the industry,” says Pekka Vauramo, president and CEO of Metso Outotec. “We offer sustainable technologies and services that reduce the consumption of energy and water by increasing process efficiency, recycling, and reprocessing of tailings and waste. Our extensive offering and expertise help our customers improve their business and lower their risks.” For more information, please visit www.mogroup.com.
Haldor Topsoe and Comprimo® offer sulfur recovery solution
LYNGBY, Denmark—The TopClaus® sulfur recovery solution combines two well-proven technologies–Topsoe’s energy-efficient wet gas sulfuric acid (WSA) process and Comprimo’s industry-leading Claus process. The TopClaus solution will enable operators to handle acid gases and achieve sulfur removal efficiency (SRE) above 99.9%– at a significantly lower cost of ownership. TopClaus is suitable for greenfield projects and revamps. It is also ideal for debottlenecking existing acid gas treatment plants, enhancing uptime, increasing capacity, and lowering emissions. The Claus part of the TopClaus process recovers elemental sulfur from acid gases. The tail gases from the Claus unit are treated in the WSA unit where the remaining sulfur compounds are converted into sulfuric acid. The sulfuric acid is returned to the Claus reaction furnace for reprocessing to elemental sulfur, with no sulfuric acid left as by-product. However, sulfuric acid can be extracted for specific uses or for sale, as needed. “Customers will benefit from a simpler, more robust and efficient plant design at a lower cost of ownership,” said Rasmus Atle Breivik, product line director, Topsoe. “TopClaus sulfur removal and recovery will enable them to comply with strict environmental regulations while protecting their profit. We are proud to be working with Comprimo, the world’s largest technology licensor of gas treating and sulfur recovery solutions.” Frank Scheel, senior vice president, Comprimo, added, “We share Topsoe’s commitment to provide customers around the world with smarter and more sustainable solutions to protect the environment.” For more information, please visit www.topsoe.com.
HOMESTEAD, Fla.—
Conshohocken, PA.
industry and Sulfuric
his vast knowledge
sulfuric
acid
Ed enjoyed sharing
Acid Today lost a
and experience with
valued member of
others, through both
the community with Edward
his membership in the
Fowler’s
American Institute of
passing on July 16. After
earning
degree in chemical engineering
Chemical Engineers
his
from
Drexel University in
and as a participant Edward Fowler January 26, 1959 - July 16, 2020
in several Sulfuric
Acid
Roundtable
Philadelphia, Ed embarked on a 32-year
conferences.
Before joining Kimre, Inc. as a Senior
Carolyn Dares Fowler, son Daniel and
years ago, he worked for CECO Filters of
granddaughters Lily and Angela. q
career in the sulfuric acid industry.
Technical Manager in Homestead nine
his wife Andrea, son Timothy, and
PAGE 4
First Quantum Minerals files updated NI 43-101 for Kansanshi
TORONTO—First Quantum Minerals Ltd. recently announced the filing of an updated National Instrument 43-101–Standards of Disclosure for Mineral Projects (“NI 43-101”) Technical Report dated June 30, 2020 for the Kansanshi Operations located in the North West Province, Zambia. The updated Kansanshi Technical Report is based on 1.5 million meters of resource expansion drilling and resulting assay data to provide an updated Mineral Reserve and Resource estimates showing an increase of 70% and 40%, respectively, over reserves and resources reported in the last update in May 2015, and extends the mine life to 24 years. This plan assumes a 25 million tonnes per annum (mtpa) expansion of the sulfide ore processing facility and associated increase in mining capacity, increasing annually throughout to 52 mtpa. The timing of capital expenditure for this expansion is proposed for 2023/24 and commissioning envisaged in late 2024. This timing could be accelerated or delayed depending on capital availability, commodity prices, and the Zambian fiscal regime. For more information, please visit www.first-quantum.com.
Pure Minerals secures government grant
In Memory of Edward Fowler The
TopClaus ® sulfur recovery solution combines two well-proven technologies–Topsoe’s energy-efficient wet gas sulfuric acid (WSA) process and Comprimo’s industry-leading Claus process.
Ed leaves behind his beloved wife
WEST PERTH, Australia—Pure Minerals has secured a A$2.55 million grant via its wholly owned subsidiary Queensland Pacific Metals Pty Ltd (QPM) for the Townsville Energy Chemicals Hub (TECH) project. QPM and project partners Direct Nickel Projects Pty Ltd (DNi) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) successfully applied for the Federal Government grant. The TECH project will process imported, high-grade nickel-cobalt laterite ore from New Caledonia to produce nickel sulfate, cobalt sulfate, and other valuable co-products. If it proceeds it will be the first commercial application of the DNi Process™. Using a bulk sample from ore supply partners in New Caledonia, a pilotplant test program is the next step. For more information, please visit www.pureminerals.com.au.
DuPont Clean Technologies Avon Plant awarded American Chemistry Council’s Responsible Care® Certificate of Excellence
WILMINGTON, Del.—The DuPont Clean Technologies Avon plant in Martinez, CA, has been awarded the American Chemistry Council’s (ACC) Responsible Care® Certificate of Excellence in recognition of its prevention of occupational injuries and illnesses in 2019. The site manufactures MECS® catalyst for the sulfuric acid industry, which has been in production at this site since 1970. DuPont recorded zero fatalities, zero days away from work cases, and zero job transfer or restriction cases at the plant last year for both employees and contractors. The certificate from ACC honors the cooperative and individual effort that went into realizing this achievement. DuPont places the utmost emphasis on safety and has a strong safety culture that encourages and embraces ideas for continual improvement. The company is committed to protecting the safety and health of employees, contractors, customers and the people in the communities where they operate. “I am proud of the Avon team for its safety record and the efforts made by each and every employee to ensure a safe work environment,” said Eli BenShoshan, global business leader, DuPont Clean Technologies. The Avon site also received the Responsible Care® Certificate of Excellence from the American Chemistry Council in 2018. The sulfuric acid industry has been relying on high-performance MECS® Catalyst products since 1915 to convert sulfur dioxide (SO2) to sulfuric trioxide (SO3) reliably and economically. As a world leader in sulfuric acid process technologies and catalyst production, DuPont supports the sulfuric acid producers around the world with high-quality catalysts that boost plant capacity, improve efficiency and, at the same time, reduce SO2 emissions. For more information, please visit www.cleantechnologies.dupont.com. Sulfuric Acid Today • Fall/Winter 2020
Australian Mines secures government funding
QUEENSLAND, Australia — The Queensland government has offered Australian Mines a conditional financial support package for the development of the Sconi cobalt-nickel-scandium project in north Queensland, the mine developer says. Australian Mines recently became the first mineral resources company to be certified a “Carbon Neutral Organisation” under the Australian Government’s Climate Active program. The package will be subject to a number of conditions including a timetable for securing an offtake agreement for all of the nickel sulfate and cobalt sulfate production; delivery of a detailed execution plan, obtaining approved financing for construction, and making a final investment decision; appointing an engineering, procurement, construction management contractor; and completion of construction by July 2023. For more information, please visit australianmines.com.au.
Ravensthorpe restarts
PERTH, Australia—The First Quantumowned Ravensthorpe nickel mine in Western Australia is continuing with a restart plan despite coronavirus challenges, the company recently reported. The acid plant and atmospheric leaching operations restarted in March 2020, with the first high pressure acid leach (HPAL) circuit brought on stream in mid-April, followed by product drying and containerizing of nickel mixed hydroxide product. The second HPAL circuit is scheduled to come online soon. Roughly 1,979 t of nickel was produced at the facility in the 2nd quarter of 2020. The company has previously said that the mine plans to ramp-up production to between 20,000-30,000 t/y of nickel over the next few years. For more information, please visit www.first-quantum.com.
Worley awarded Indonesian acid plant contracts
JAWA TENGAH, Indonesia—Shell Global Solutions International recently awarded Worley two contracts for PT Pertamina EP Cepu’s (PEPC) new sulfuric acid plant in Indonesia. The plant is part of the JambaranTiung Biru utilized gas field project for PEPC, which is a subsidiary of PT PertaminaIndonesia’s state-owned energy company. Under the contracts, Worley will supply Chemetics’ cooled oxidation reactor (CORE) technology. This is the first time this Chemetics technology will be applied with Shell’s Cansolv SO2 capture technolSulfuric Acid Today • Fall/Winter 2020
WASTE HEAT RECOVERY BOILERS SUPERHEATERS ECONOMIZERS
ogy. Cansolv controls the emissions and captures additional by-product value from the sulfur dioxide emitted from various refinery flue gas streams (such as cracking units, process heaters, and boilers), sulfur plants, and spent acid regeneration units. Sulfur dioxide can be recycled to the sulfur recovery unit to be produced as marketable sulfur or it can be converted to sulfuric acid. “We are excited to apply our Chemetics CORE sulfuric acid technology in the natural gas sector and look forward to supporting both PEPC and Shell on this significant project,” said Worley CEO Chris Ashton. In addition to the Chemetics’ contract, Worley has won another contract with the Indonesian sulfuric acid plant—this one is with PT Environmate Technology International (ETI). Under this contract, Worley will design and engineer a new sulfuric acid plant using CORE technology. It will supply key equipment and materials. The company will also provide technical services for building the plant, operator training, commissioning, and testing. “We are pleased to work with ETI and PEPC on this exciting project and look forward to supporting Indonesia as it continues to grow into the natural gas sector,” Ashton said. For more information, please visit www.worley.com.
Teck’s Chile mine commits to renewable power
VANCOUVER, B.C., Canada—Teck Resources Limited recently announced that their Chilean affiliates had entered an 11year power purchase agreement to provide 100% renewable power to Carmen de Andacollo. Teck said the operation would source 72 megawatts (550 GWh/year) from AES Gener’s growing renewable portfolio of wind, solar, and hydroelectric energy. The transition will replace previous fossil fuel power sources and eliminate about 200,000 tonnes of greenhouse gas emissions annually, the equivalent to removing over 40,000 passenger vehicles from the road. “Teck is tackling the global challenge of climate change by reducing the carbon footprint of our operations and working towards our goal of becoming carbon neutral,” said Don Lindsay, president and CEO of Teck. “This agreement takes Teck a step closer to achieving our sustainability goals, while also ensuring a reliable, longterm clean power supply for CdA at a reduced cost to Teck.” The company is aiming to source all its power needs in Chile from renewable energy by 2030, as a milestone on its path to being a carbon neutral operator by 2050. For more information, please visit www.teck.com. q
Op�mus delivered its rst sulfuric acid plant waste heat recovery system in 1996. Across the power and process industries, we’ve produced more heat recovery boilers, HRSGs, superheaters, and economizers than any ac�ve company in the USA. Op�mus and its Chanute Manufacturing plant have a long‐standing rep‐ uta�on for high‐quality workmanship and on‐�me performance. Cus‐ tomers trust our unique manufacturing exper�se and have condence in our quality control and comprehensive project execu�on.
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PAGE 5
Department
Industry Insights
+ The world leader in reliable and cost effective products has partnered with the leading robotic inspection services in the sulfuric acid industry. Acid Piping Technology has been supplying high quality equipment like MONDITM Piping Systems since 1991. Being on the forefront of technology, APT has partnered with Gecko Robotics to provide the sulfuric acid industry with a data-dense inspection solution to enable their customers to focus on preventative maintenance.
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Cover Story
For Two Lions Fine Chemicals, success comes in pairs By: April Smith, Editor, Sulfuric Acid Today
W
hen your new sulfuric acid plant heat recovery system works so well, why not install another? This line of thinking led Two Lions (Zhangjiagang) Fine Chemicals Co., Ltd., to add a second identical unit five years after its 2005 HRS™ installation was such a success. When the first acid plant came online in 2005, the 3,000 MTPD unit with MECS® HRS™ became the largest single-train sulfur burning acid plant and the first HRS™ plant in China. Two Lions built the unit to supply steam to its chemical production line so the company could avoid purchasing coal-generated steam and reduce production costs. Beyond the highly efficient sulfuric acid production and its significant environmental benefit, Two Lions adds carbon credits to the list of advantages. With plant one just two years in operation, Two Lions signed on for a second, twin acid plant with the same capacity and design. The second facility started in 2010. With both units now running, the Two Lions facilSulfuric Acid Today • Fall/Winter 2020
ity has gained national recognition as a model for energy savings and environmental stewardship in China. The site has even become a training school for the MECS® Heat Recovery System (HRS™).
About Two Lions
Two Lions’ sulfuric acid operation has a long history dating back to 1958. Based in Zhangjiagang, in Jiangsu Province in Eastern China, the company currently produces sulfuric acid, oleum, ion membrane caustic soda, and chlorosulfonic acid as well as other chemicals for the domestic and international market. The facility is located in the Yangtze River International Chemical Industrial Park, which covers an area of 1.4 square kilometers. Being near the Yangtze, the company’s private berth in Zhangjiagang port offers a great logistical advantage. The company also operates a 103 MW power station. The company took the Two Lions name when it
incorporated in 2003 as a joint investment between Suzhou Fine Chemicals Co., Ltd., producer of the famous Two Lions brand saccharin, and Flying Glory Enterprises (Canada) Ltd. That same year, China became a member of the World Trade Organization, and the newly branded organization began planning major upgrades to optimize efficiency and meet current emissions standards. It moved its operation from an urban site to the much larger industrial park where it could expand and upgrade its facilities.
Ambitious goals
Planners at Two Lions had their work cut out for them. “When China became a member of the World Trade Organization in 2003,” said Two Lions general manager, Yafei Yuan, “Two Lions set itself ambitious goals: to employ state-of-the-art sulfuric acid technology to achieve optimal energy efficiency, to meet the highest emissions PAGE 7
Cover Story
standards, to maximize ROI, and, of course, to comply with industrial policies and regulations.” In essence, the challenge became how to be economically viable while achieving the necessary environmental stewardship and operational safety. Choosing the right technology provider was a major factor in meeting that challenge. “The choice of project technology was not only based on technical aspects but also on national policy,” Technical Manager Ziling Chen explained. “Our selection process therefore followed strict procedures and standards. As the world leader in sulfuric acid technology, DuPont Clean Technologies (DuPont) had numerous references and proven quality technology. That gave us the confidence to work with them.”
Plant one
For the first plant, the MECS® engineering team developed a process design evenly balancing capital and operational efficiency. The plan focused on the co-generation of electricity-use high pressure steam and HRS steam which would more than satisfy the chlor-alkali power demand. Essentially, the acid plant became a power plant for the chemical facilities.
The plant achieved this using MECS® HRS™ technology to recover the heat generated during the absorption and dilution of the sulfur burning process and use it to produce steam. The heat recovery system was configured to meet plant-specific requirements for varying steam pressure, from 0.4 MPag to 1 MPag. In the case of Two Lions, the system also produces high pressure steam at 6.4 MPag from the waste boiler and superheater to generate more electricity for the downstream chlor-alkali facility, while the conventional sulfuric acid steam pressure is 3.8 MPag. The MECS® steam injection technique makes full use of exhaust steam exiting the steam turbine producing 0.6 MT steam/MT acid. In this way, the Two Lions plant recovers 95 percent of the heat generated and supplies approximately 220 MT/h steam to the turbo-generator and other steam users. Utilizing steam recovered from the sulfuric acid process also prevents the emission of approximately 400,000 MT/annum carbon dioxide that would have occurred from burning coal at the plant site to generate the same level of steam. By avoiding coal burning, the company also meets the mandatory limits on greenhouse gas emissions as set in the international Kyoto treaty. The process design also conserves water. Because much of the heat is recovered from sulfuric acid production to produce steam, less cooling water is needed. As a result, Two Lions has reduced cooling water usage by 65 percent in the main acid plant, saving 360,000 MT/annum of process water.
Plant two
The Two Lions sulfuric acid plant.
In 2007, after another in-depth evaluation of technology providers, Two Lions signed a contract with DuPont for a second, identical acid plant with the same capacity and design. The second plant, which started up in 2010, employs the same MECS® HRS™ technology. “The MECS ® sulfuric acid unit had proved itself economically and shown itself to work safely,” explained Chen. Since then, the new Two Lions acid plant has been regarded as a model for energy saving and environmental stewardship in China. Because of the facility’s success as the largest sulfur burning acid plant and the first to employ a heat recovery system, more than 300 people have come to Two Lions for MECS® HRS training.
MECS® HRS™ Plant 1 at Two Lions.
2.62 lbs of sulfur dioxide per ton of sulfuric acid) emissions guarantee without the use of a cesium catalyst. The large size of the converter further minimizes heat loss during hot shutdown, which means the plant can be restarted after just 16 hours in summertime without requiring prior heating. The heat recovered from the process gas can generate approximately 160 MT/h HP steam at 6.4 MPag.
Maintenance practices
Reliability of equipment is of prime importance for Two Lions—and their strict maintenance program reflects it. If, for example, a tiny cooling crack forms on the ceramic sleeve of the waste heat boiler inlet tube sheet, Two Lions will replace all the sleeves, even though the risk of their failing is only 1 percent. Because of these stringent maintenance protocols, the plant has run for long periods without stopping for preventive upkeep or repairs. In fact, the main equipment of the facility required no unplanned maintenance at all in the first five years after start-up. In addition, total unplanned shutdown time for the plant has been less than 40 hours in the last five years. Maintenance costs have
Training from the start
Even before the construction of the plants began, the Two Lions operations team received detailed operation training and was actively involved in engineering and construction work. In addition to group training one month before start up, Two Lions employees have been able to access technical training any time as more than four MECS® design engineers remained on site for six months — five months prior to start up and one month after operations began. DuPont Clean Technologies further supported Two Lions with extensive technical services during detail engineering, construction, commissioning, and start-up. All that learning paid dividends. Over the last 15 years, not a single injury or accident has been recorded.
Converter efficiencies
The performance of the converter has exceeded target over the past 15 years with conversion rates above 99.8 percent. This easily met the 800 mg/Nm3 (equivalent to PAGE 8
Outdoor training at Two Lions.
Sulfuric Acid Today • Fall/Winter 2020
Cover Story
Project Achievements • Use of steam recovered from the sulfuric acid process saves approximately 400,000 MT/ annum carbon dioxide. • Steam recovery translates into gains of millions of dollars through carbon trading in accordance with the Kyoto protocol. • The MECS® HRS™ system enables the Two Lions plant to recover 95% of the heat generated and supplies approximately 220MT/h steam to the turbo-generator and other steam users.
MECS® Brink® CK mist eliminators in the Two Lions drying tower.
been extremely low—below 1 percent annually of overall capital expenditure. Careful upkeep of the air filter and filtration of the liquid sulfur have kept the catalyst bed pressure drop below 2kPa for five years. Methodical maintenance of the drying tower, especially regular cleaning of its mist eliminators, has held acid mist downstream of the drying tower at a level of 20 mg/Nm3. The acid concentration of the HRS™ system has been maintained within the design range, so the HRS™ equipment and acid piping have not been subject to any serious corrosion in fifteen years. Nor has the compressor impeller shown any signs of corrosion over the same period.
Overall performance Since coming on stream in 2005 and 2010 respectively, the plants operate to very ambitious emissions and energy consumption targets that go far beyond current governmental specifications (see Table 1). The site holds the best record for turnaround shifts and online time (> 98 percent) for the entire sulfuric acid industry in China, bringing high efficiency and yield with it. Currently, turnarounds take place every two years and last between 12 to 14 days. Overall, the cost of turnarounds accounts for less than 2.5 percent of the total cost of equipment change-out. The Two Lions production manager, Wenqing Yu, sums up the performance of the plant, “Generally, the operation parameters of the acid plant has matched the design. The control of processes is superb and consistent. The key equipment has a very high reliability. Over an operating
Since coming on stream, the Two Lions HRS™ plants have become a showpiece in China for efficient and energy-saving acid plant operation.
period of 15 years, it is very rare to have an unplanned acid plant shutdown caused by equipment. Environmental emissions are better than the national standard.” In fact, sulfur dioxide and acid mist emission have never exceeded national or local limits or posed a risk to local residents. Nor have the facilities had to close due to accident in the past 15 years. Two Lions has moreover managed to obtain considerable Clean Development Mechanism (CDM) rewards through its output of HRS™ steam amounting to a total of 947,670 Certified Emission Reduction (CER) credits by the end of 2013. Since 2005, the two acid plants have also been supplying sufficient, cheap electric power to the company’s ion membrane caustic soda plant. Mr. Chen says, “The ion membrane caustic soda plant has benefited hugely from the acid plant and the MECS® Heat Recovery System (HRS™). If we did not have the MECS® acid plant and HRS™, the higher cost of electric power would kill Two Lions.” With the help of DuPont Clean Technologies and MECS® technology, Two Lions has created a model sulfuric acid plant, leading the way for energy efficiency and environmental stewardship in China. q
• Total unplanned shutdown time for new plant has been less than 40 hours in last five years • Uptime has been > 98%. • Over the last 15 years, plant 1 has seen a conversion rate above 99.8%. • Cheap electric power generation for the company’s ion membrane caustic soda plant. • Minimal heat loss through converter section means the plant can restart after just 16 hours in summer without prior heating. • The costs of turnarounds account for less than 2.5% of the total cost of equipment change-out. • Accidental shutdowns in last 15 years = zero. • Injuries and accidents in last 15 years = zero. • Last 15 years: Annually, less than 1% of overall investment spent on maintenance and spare parts.
Table 1: Two Lions emission and steam production Design
Actual (in December of 2019)
Overall conversion
99.8%
99.94% @ 70% rate
SO2 emissions prior scrubber (mg/Nm3)
800
215 outlet of bed 4 68 exit of scrubber
HRS™ steam MT/MT acid
0.48
0.52
HP steam MT/MT acid
1.2
1.24
Sulfuric Acid Today • Fall/Winter 2020
• Reduction in cooling water usage by 65% in the main acid plant saves 360,000 MT/annum of process water.
• Project execution on time and on budget. • Emissions well below Chinese regulatory requirements (see Table 1). Two Lions operates to very ambitious emissions and energy consumption targets that go beyond current governmental specifications.
PAGE 9
Feature
market outlook
COVID-19’s ongoing impact on the sulfuric acid market
Fiona Boyd, Acuity Commodities
Freda Gordon, Acuity Commodities
By: Fiona Boyd and Freda Gordon, Directors of Acuity Commodities
At the time of writing of our last article for the Spring/Summer 2020 issue of Sulfuric Acid Today, the world was in the very early stages of COVID-19, which was largely focused in China. Since then, the virus developed into a global pandemic with significant impacts across the globe. Today, the world is adjusting to a “new normal” including social distancing and facial covering requirements. As the northern hemisphere prepares for the arrival of Fall/Winter, there is uncertainty over the evolution of COVID-19 at a time when other rapidly spreading viruses, namely the flu, are at seasonal peaks. In our last article we focused on China, then the epicenter of the virus, as its sulfuric acid balance has shifted from a net importer to a net exporter. We noted a 1.3m t shift in its balance last year due to a 70% increase in sulfuric acid exports compared with 2018. Amid the COVID-19 pandemic, China’s industrial activities were significantly constrained, thereby reducing domestic consumption of sulfuric acid while the impact on production, mainly from base metals smelters, was less notable even though there were indeed some slight interruptions. As an indication of the impact on China’s balance, in 1Q its imports were down around 40,000t compared with 1Q19 while its exports were down marginally by around 4,000t. The decreased demand in China did leave some volume from the key South Korea market looking for alternative homes, resulting in prices reaching double-digit negative values for the first time since early 2017. By the end of 1H of 2020, the impact in China was less apparent as activity began to rebound as the virus subsided there while growing in other regions. By the end of June, China’s imports were actually up around 10,000t versus 1H19. Exports saw a sharper decrease of around 100,000t, however, which was mostly driven by tighter availability of sulfur production to feed onpurpose production, which is sold to Morocco under a contractual basis. Reduced sulfur production has been one of the most notable impacts of the COVID-19 pandemic on the sulfuric acid market due to lower availability of the key raw material. As the graph below reflects, refinery utilization
PAGE 10
dropped below 60% in Canada and below 70% in the United States in April/May. This is a reflection of refineries slowing throughput as demand for refined products, namely gasoline and jet fuel, was significantly hampered by the impacts of COVID-19 as lockdowns were put in place to help slow the spread of the virus. As a result, by-product production of sulfur from refining was reduced accordingly. At the time of writing, refinery utilization rates remained well below typical seasonal levels. At the same time, however, we saw demand for sulfuric acid stay relatively stable, highlighting its use as a key chemical for many applications including fertilizer production, water treatment, and production of some pulp and paper products. With many of these products essential and critical to everyday living, most production sites continued to hum along. We did, however, see some weaker demand for applications such as ethanol and automotive uses, but it was not enough to result in significant market impacts. This explains in part why, despite the tighter availability of sulfur, we did not see a run up in sulfur or sulfuric acid pricing as the graph below reflects.
While Chile could have been a viable outlet, beginning in May pressure began to mount there too as some consumers were beginning to slow consumption due to COVID-19. This was amid improved domestic production compared with 2019 and a healthy lineup of import contractual supply for 2020. As a result, there was little interest in spot cargoes and buyers were in fact trying to delay shipments with suppliers inflexible in moving shipping dates around. Inventory began to climb, and buyers were already discussing carryover volume for 2021 under 2020 contracts despite the year not being even halfway over. As the situation in Chile began to intensify India was beginning to emerge from its lockdown, which allowed cargoes from Asia to be diverted to India, again at attractive pricing. By 3Q, prices had recovered slightly as the world began to adjust to COVID-19. Some commodity prices have firmed notably, particularly in the base metals sector on bullish sentiment around demand. For example, copper pricing has improved notably in recent weeks due to demand in China surging as it catches up following pandemic impacts earlier in the year.
As the graph reflects, we did see more downward pressure on sulfuric acid pricing compared with sulfur pricing. This was first triggered by the aforementioned need to find markets outside of China when demand there was hampered. India was able to take advantage of this and secure spot cargoes at attractive pricing, including for as far out as August shipment. There was also some opportunistic buying of spot sulfuric acid by sulfur consumers as a way to augment their sulfurbased production amid the tight raw material supply conditions. Then, however, India began a nationwide lockdown in April due to COVID-19, resulting in its demand for sulfuric acid declining accordingly. Some Indian buyers declared force majeure on contracted acid amid unplanned port disruptions, and secured spot tonnes at much lower prices for delivery in the second and third quarters. This put pressure once again on smelters in Asia, namely Japan and South Korea, with the need to find alternative markets.
This is setting the tone for a more positive outlook for 2021 as planning begins there, including for the key market of Chile, which has been grappling with high inventory levels for most of the year. Despite the current bullish outlook on copper, with acid there imported for leaching, we are aware of export activity for 4Q to help manage length. The question is whether the copper rally is sustainable and will incentivize buyers to consume more acid and have greater ability to absorb higher sulfuric acid pricing. However, uncertainty is still hanging over the market as we approach the end of the year, largely due to the lingering concerns around COVID-19. Acuity Commodities provides insight into the sulfur and sulfuric acid markets through price assessments, data and supporting analysis. Offerings include weekly reports on the global sulfur and sulfuric acid markets and a biweekly report focusing on North America as well as bespoke consulting work. Please visit www.acuitycommodities.com for detailed information. q Sulfuric Acid Today • Fall/Winter 2020
Feature
Ultrasonic technology helps keep infrastructure sound Acid Piping Technology and Gecko Robotics have combined forces to provide an elegant solution to keeping acid plant infrastructure sound. Sulfuric acid industry supplier, Acid Piping Technology is now offering its customers a method of examining pipes and vessels by sending a hydraulically powered robot crawling along the equipments’ exterior. As the robot rolls along, it measures thickness ultrasonically and maps the information to precise locations along the vessel. The test is called rapid ultrasonic gridding (RUG), by Gecko Robotics, Inc. of Houston, Texas. Sticking to surfaces like its amphibious namesake, the Gecko Robotics robot traverses industrial vessels left, right, under and over until all areas have been measured and plotted on a grid. Ultrasonic gridding is a nondestructive examination method using multiple ultrasonic thickness probes to gather thickness measurements in a predefined or ad hoc space. The robot is small enough to be lifted by a single technician and brought to customer sites via commercial airline. This solution was the brainchild of engineering student Jake Loosararian who got the idea to build the robot in 2012 after talking with a local plant manager who couldn’t afford to keep his plant running because of frequent infrastructure failures. Manual inspection of plant equipment was too time consuming and too inaccurate. And in the case of this plant, almost deadly. So Loosararian decided to build a wall-climbing robot to automate dangerous and costly inspections. In 2013, he founded Gecko Robotics, LLC, and spent the next few years developing his robot. With $300 to his name and sleeping on a friend’s floor, Loosararian was offered a lucrative buyout opportunity from a huge energy company.
Mapping wall thickness by manual inspection—slow and tedious.
Mapping wall thickness by robot – faster and easier. The method can eliminate the need for costly and time consuming scaffolding or rope.
PAGE 12
External and internal views of the Rapid Ultrasonic Gridding (RUG) device.
But Loosararian wanted to see his vision through—to ensure any plant in any industry had a chance to maintain sound infrastructure. So he turned the offer down. In 2016, with the help of friend Troy Demmer, now the company’s chief operating officer, Gecko applied for a grant with startup accelerator Y Combinator (YC) and was awarded $2.1 million in funding. From there the young company worked with other startup innovators to grow the business; and changed its name to Gecko Robotics, Inc. 2017 saw record growth with the Gecko Robotics Inspection Team (GRIT) performing 25 inspections in 17 states. Gecko engineers also produced a new generation robot, the TOKA® series, enabling teams to inspect more types of equipment, including boilers, tanks, and silos. The next few years brought additional funding and more growth. Gecko expanded operations to the paper, oil, and gas industries. Further enhancements to the TOKA® robot offered more inspection angles, greater speed, improved mobility, and localization abilities. In 2019 Gecko expanded into Houston, where it continues to innovate on this solution. Currently operating in the refining, chemical, power, and paper industries, the robots can test many vessel types including piping, stacks, towers, spheres, boilers, heaters, tubes, roofs, and floors. Integrated software provides various reports for each inspection, including a spreadsheet with thickness plotted on XY coordinates and an interactive map where clients can drill down to photos and other data for a specific area. A robot and a team of two technicians can be deployed within 48 hours. Based on vessel size, the appropriate size robot is put to work. The TOKA® series can cover up to 150
GeckoRobotics, Inc. founder and CEO, Jake Loosararian, testing robot prototype in college, 2012.
sq. ft./minute collecting 144 - 11,000 A-Scans per square foot traversed. Each robot needs about one gallon of water per minute and 110v power. Paint or other surface coatings are okay, as long as the surface temperature remains below 250 degrees F and the vessel is ferromagnetic. Gecko’s RUG testing robots reduce costs and safety risks related to manual inspections, such as setting up and using scaffolding or ropes, manually cleaning internals, and high hourly costs. Reports are available 24-72 hours after inspection. Acid Piping Technology, having been a longtime supplier of high quality equipment like MONDI™ Piping Systems since 1991, has partnered with Gecko Robotics to provide the sulfuric acid industry with this efficient datacentric inspection solution so its customers can focus on preventative maintenance. For more information about rapid ultrasonic testing, contact Chris Wolfe, Sales Manager, at 203-979-7490 or chris.wolfe@geckorobotics.com. Or visit www.geckorobotics.com. For more information about Acid Piping Technology, contact Alex Knoll, Sales, at 314-478-5772 or aknoll@ acidpiping.com. Or visit www.acidpiping.com. q
Each inspection provides various reports, including a spreadsheet with thickness plotted on XY coordinates and an interactive map where clients can drill down to photos and other data for a specific area.
Sulfuric Acid Today • Fall/Winter 2020
Draft one of our all-star converters into your line-up. NORAM is a world leader in extending the life of existing facilities, improving operating economics and cost-effectively meeting stringent emission standards.
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sulfuric acid products & services
Department
Product News Haldor Topsoe launches new potassium-promoted catalyst VK38+
LYNGBY, Denmark—Haldor Topsoe, global leader in supply of catalysts, technology, and services to the chemical and refining industries, recently launched a new potassium-promoted catalyst VK38+ to their line of sulfuric acid catalysts. Selecting the right catalysts for a SO2 converter has always been about balancing expenses and gains. Haldor Topsoe’s new potassium-promoted catalyst VK38+ helps create that balance–and more. As the highest performing potassiumpromoted catalyst on the market, VK38+ enables their customers to: • Reduce emissions by ~35% over existing VK38/48 loading. • Lower catalyst waste and raw material use by about 50%. • Reduce power consumption by about 10% due to capacity for higher feed concentration. • Increase power output with higher steam production at the same load. • Decrease or avoid chemical consumption in existing scrubbers. • Reuse more existing catalyst. The VK38+ catalyst is part of a range of proven, top-performing sulfuric acid cat-
alysts from Topsoe and can be used in all SO2 converter beds. The development of VK38+ comes at the heels of tightening legislation that poses challenges to sulfuric acid plants worldwide, many of which already operate with fully loaded converter beds. Sulfuric acid producers can now keep up with the changing requirements without costly revamps or increasing catalyst consumption. Combined with Topsoe’s unparalleled service and advisory team, producers can now get more from their catalyst investments and tip the scales to their advantage by enhancing performance, improving efficiency, and reducing climate footprint. For more information about Haldor Topsoe catalysts, including VK38+, visit www.topsoe.com.
Haldor Topsoe lauches new potassiumpromoted catalyst VK38+.
DuPont’s Sennuba™ offers cost-effective, reliable answer to steam plume control
WILMINGTON, Del.–DuPont Clean Technologies, the supplier of world-leading scrubbing and other environmental technologies, has introduced a new, advanced steam plume suppression solution for its MECS® DynaWave® scrubbers in SRU applications. Called Sennuba™ plume suppression technology, it employs two heat exchangers and a heat-transfer medium to heat stack gas from the wet scrubbers that are used to remove pollutants from flue gases, with steam produced from the heat of the gas at the inlet of those scrubbers. This solution avoids the high operating costs associated with other methods of steam plume control as it recovers otherwise lost heat from the process to generate the necessary steam to suppress the visible plume. Sennuba™ is designed with a heat-transfer medium so there is no chance of leakage of the process gas directly to the stack gas. In this design, there is no forced circulation of the heattransfer medium. “Our aim was to develop a solution that would offer the refining industry a cost effective, simple to operate, low maintenance
DuPont’s Sennuba™ new plume suppression technology for MECS® DynaWave® scrubbers.
plume suppression technology for its SRU scrubbers,” says Yves Herssens, global licensing manager, scrubbing technologies, DuPont Clean Technologies. “Sennuba™ offers reliable plume suppression and corrosion control in a scrubbing system that is at minimal risk of plugging.” For more information on Sennuba™ technology, as well as the MECS® DynaWave® wet scrubbing technology, please visit www.cleantechnologies.dupont.com. q
THE BREEN-SA PROBE Real-Time Moisture Leak Detection and Periodic Acid Dew Point Measurement
SULFURIC ACID PROCESS EQUIPMENT PROTECTION • Moisture Leak Detection • Periodic Dew Point Measurement • Economizer Water Tube Temperature Control COPPER SMELTER APPLICATIONS • Control of Weak Acid Production • Control of Sulfurization Air • ESP Performance
Breen Sensor Technology
AcidDewpoint.com Patent pending
PAGE 14
Breen is a Mississippi Lime FGT Business Unit Company.
Sulfuric Acid Today • Fall/Winter 2020
Tip the scales with the new VK38+ catalyst
Choosing catalysts is a percentage game. Here’s a cheat code. Choosing sulfuric acid catalysts is about balancing expenses and gains. The new VK38+ not only makes it easier to find the right balance. Bringing enhanced performance, efficiency and a reduced climate footprint, it tips the scales to your favor.
www.topsoe.com
Feature
lessons learned: Case histories from the sulfuric acid industry
How much moisture really enters your acid plant?
By: Evan Uchaker, Steve A. Ziebold, and Doug E. Azwell, DuPont Clean Technologies, owner of MECS® sulfuric acid technology
In sulfur-burning sulfuric acid plants, high moisture in the process can typically be traced back to one of the following conditions: • Improper drying tower operation. • Moisture created from combustion of trace hydrocarbons in sulfur burning plants. • Tube leaks (waste heat boiler or economizer). • Moist air ingress due to equipment under negative pressure/vacuum. This article focuses on measuring dry tower performance.
shortened element life. This plant site had three sulfur burning sulfuric acid plants with suction dry towers. All dry tower outlet gas ducts had a series of four sampling ports with valves for stick testing, and these locations were selected for dew point testing. An analog dew point apparatus (Lectrodryer Dew Cup) was used for the dry tower dew point temperature measurements (Fig. 2).
Dew point measurement
Moisture in the gas exiting the dry tower can be directly measured on site by a dew point measurement. The dew point is defined as the temperature at which air becomes saturated with water vapor when air is cooled by removing sensible heat. Higher moisture level bypassing the dry tower can lead to an undesired or uncontrolled combination of SO3 and water vapor downstream to produce sulfuric acid. The principle issue with an unchecked level of water vapor leaving the dry tower as measured by dew point is that sulfuric acid may condense out of the process downstream where it is undesirable; e.g., in heat exchangers and ductwork where acid will cause corrosion and eventual (premature) equipment failure. Excessive sulfuric acid mist formation may also occur, leading to overloaded mist eliminators with higher than desired pressure drop. One client recently noted some of the impaction elements in their drying tower deteriorated prematurely from corrosion on the wire mesh. Some elements of the overall installation exhibited severe corrosion (Fig. 1), while the remaining elements were in much better condition.
Fig. 2: Lectrodryer dew point testing apparatus.
The Lectrodryer apparatus provides a relatively fast and simple check of dry tower performance. The dew point is measured when condensate is formed on a cooled polished metal surface in contact with a gas sample leaving the dry tower. Dry ice, broken into 4 cc bits, and acetone are used inside a polished cup to provide cooling. The moisture level is then derived from the dew point temperature measurement. For world areas where dry ice is not available, a CO2 fire extinguisher discharged into a bucket can produce dry ice powder that works well in mixing with acetone in the Lectrodryer cup to control cup temperature. The dew point measurement takes some practice to perform properly. Cycling the cup’s metal surface temperature up and down several times helps establish an average temperature when moisture condensing occurs. A healthy operating dry tower has a dew point temperature of -40 degrees C or lower. Lower dew points are achievable with well operating dry towers.
Traverse Point
Fig. 1: Corroded dry tower impaction element.
To help determine the cause of corrosion, dew point temperature was measured at the exit of the dry tower as excess moisture was the most likely culprit leading to PAGE 16
Dew Point (°F) DT X
DT Y
DT Z
1
- 12.5
- 10.0
- 27.5
2
- 50.0
N/A
- 37.5
3
- 75.0
- 70.0
- 35.0
4
+ 26.3
+ 22.5
- 10.0
Table 1. Measured and averaged dew point temperatures.
The Lectrodryer measurements can be accurate within ±3 degrees C of the gas dew point, and the device (when using acetone) is capable of detecting dew points as low as -76 degrees C. Actual measured dew point temperatures for the previously mentioned client issue are shown in Table 1. The dry towers in all plants tested showed variable dew points indicating insufficient drying leading to downstream mist eliminator corrosion. Variable velocity profiles and zones can develop within a dry tower as packing becomes plugged with sulfates over the course of its lifetime and/or if the distributor is not properly performing. In this location the dry tower packing depth provided little margin for acid distribution or any additional issues and had been in service for approximately 25 years. Therefore, it is within reason to assume that the gas and/or acid distribution through the packing in the dry tower of each plant is contributing to maldistribution through the impaction of fiber bed mist eliminators. The mist eliminators with shortened lifetime bore the preferential brunt of this distribution with the root cause being moisture slip, localized formation of weak acid, and consequent corrosion of some areas of the mist eliminators. It was recommended that the client replace the dry tower packing at the earliest convenient opportunity, after which mist eliminator corrosion was no longer an issue. Thus, the lessons learned from this client experience include: 1. Dew point profile measurements in the exit gas ducts indicated the gas was not well mixed at the sampling location, thus taking only one measurement would not be representative of dry tower performance. Therefore, when measuring dew point downstream of the dry tower, make sure enough points are taken in the exit gas duct to get a representative sample. 2. Dew point temperature profiles indicated there were areas in the drying tower that had moisture slip. 3. A well-performing dry tower should result in the same dew point temperatures across the gas duct being lower than -40 degrees C. 4. Since dew point measurements are relatively easy to perform, if not currently installed, consider adding more sampling points after the dry tower in the exit gas duct to allow measuring dew point temperature profiles to better monitor dry tower performance. The Clean Technologies division of DuPont is a global leader in process technology licensing & engineering, offering critical process equipment, products, and services that enable an array of industrial markets to minimize their environmental impact. We provide extensive global expertise across our portfolio of offerings in key applications–MECS® sulfuric acid production, STRATCO® alkylation, BELCO® wet scrubbing, and IsoTherming® hydroprocessing. For more information, visit www.cleantechnologies.dupont.com. q Sulfuric Acid Today • Fall/Winter 2020
Feature
Weir Minerals’ provides one-of-a-kind engineering expertise Since brothers James and George Weir founded what would become the Weir Group with their 1871 invention of the Weir boiler feed pump, engineering expertise has been the driving force of its success. For almost 150 years, Weir has built its business on the principle that if something’s worth doing, it’s worth doing right, and to do something right in a mine, you need the right team. “We need integrated solutions now more than ever. With this approach, we continually listen to our customer’s pain points and identify ways in which we can improve their process,” says John McNulty, vice president of global engineering and technology for Weir Minerals. “Integrated solutions also align closely with the Weir Group’s sustainability strategy. We often talk to our customers about the challenges they face in terms of energy consumption, water usage, and waste, and we brainstorm ways we can help reduce their environmental impact. In this current climate, this approach is absolutely critical.” When confronted with a problem that requires more than a single piece of equip-
ment, Weir Minerals draws on its integrated solutions teams, made up of process engineers, design engineers, product experts, materials scientists, and supply chain and logistics experts, as well as local sales teams who know the customer’s site back-to-front. These multi-disciplinary teams ensure that a problem is considered from all perspectives, identifying potential issues and opportunities to optimise the circuit with upstream and downstream benefits. With almost 10,000 employees operating in more than fifty countries, Weir Minerals can build teams with experience working in every kind of mine and quarry, in environments ranging from Canada’s frozen oil sands region and Indonesia’s rain-prone coal mines, to remote deserts in Chile, Mongolia, and Australia. In Florida, the USA’s phosphates region, the ability of the integrated solutions team to help understand and select the right type of material is important as well. “While material selection always plays an important role in selecting the right equipment, it’s a particularly impor-
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PAGE 18
9/14/17 4:06 PM
Weir employee inspecting a Warman pump at an underground mine in Montana.
tant task in the phosphate industry,” says Paul Mattson, a process optimization engineer for Weir Minerals. “Not only does the phosphate industry face high erosion concerns, as all of the mining industry does, it also faces high corrosion concerns. The best materials for corrosion and the best materials for erosion do not typically overlap, making the importance of the material selection that much more critical.” In addition to selecting the right material and equipment to provide maximum efficiency and wear life in any given situation, the integrated solutions team’s expertise allows them to tailor solutions for the unique challenges facing each location: using epuipment that can be flown to a site when the roads freeze in the winter, preventing crocodiles climbing onto floating equipment, and using waste products like tailings as a resource. “For us, we believe nothing is impossible and we continually look for better ways of doing things,” says Seda Kahraman, a regional process engineering manager for Weir Minerals. “Our team is made up of specialists, each possessing different process system expertise including, but not limited to: troubleshooting, designing tools, and process simulation programs. We combine this wealth of knowledge to deliver innovative solutions that address our customers’ varied needs.” The key to Weir Minerals’ integrated solutions approach is the entire team of experts collaborating to identify all the root causes of a customer’s challenge, considering all the contributing factors. That’s where Weir Minerals’ unique interdisciplinary expertise is so important for customers. The team performs process audits during
Weir employees at a pump house in Finland.
site visits to identify bottlenecks, and then using flowsheets, mass balances, 3D layouts, and feasibility studies, advises on the most appropriate solution for the customer to not just resolve the problem they came to Weir Minerals with, but to optimise their process to save energy, reduce water waste, or increase capacity, and ultimately save the customer money. Weir Minerals delivers end-to-end solutions worldwide for all mining, dewatering, transportation, milling, processing, and waste management activities. Weir Minerals has an advanced product range incorporating brands such as Warman® centrifugal slurry pumps, GEHO® PD slurry pumps, Linatex® rubber products, Vulco® wear resistant mill linings, Cavex® hydrocyclones, Trio® crushers and screens, Enduron ® comminution equipment, Isogate® slurry valves, Multiflo® mine dewatering solutions, and Lewis® Pumps— covering virtually any application, in any environment. The Weir Minerals global network ensures proximity to its customer wherever they are located. For more product information, visit www.global.weir. To find out how the integrated solutions team can optimize your site, visit www.problemsolved.weir. q Sulfuric Acid Today • Fall/Winter 2020
We are everything sulphur As the recognized world leader for sulphur-related projects, Worley has over 65 years of providing unique total sulphur and sulphuric acid management solutions globally. Worley can provide leading technology, plants, equipment and solutions for all parts of the sulphur chain. We are everything sulphur. ComprimoÂŽ Sulphur, ChemeticsÂŽ Sulphuric Acid, and Advisian Port and Logistics solutions provide world wide focus on site reliability, environmental solutions, plant economics and workforce development.
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Feature
Evolution of the safety professional
By: Cody Savoy, CSP, VIP International
The evolution of workplace safety
of the Occupational Safety and Health
to prevent injury, illness, and death in the
is no secret. There is more emphasis and
Administration (OSHA) in 1971. While
workplace. The things that have changed
attention on safety in the workplace now
the initial regulations mandated by OSHA
over the years are the laws that regulate us,
than ever before. Companies and corpora-
were not much, it was a building block
information that is available at our dispos-
tions now realize the benefits and impor-
that sparked change in the right direction.
al, knowledge and qualifications required
tance of having an effective safety program
Over the last 50 years, OSHA has been
of safety personnel, and technology.
and safety culture. Safety professionals
constantly changing and evolving for the
past and present have worked and will
better and safety professionals have had to
pational safety and health professionals:
continue to work in order to protect their
keep up. Companies quickly realized that
occupational safety, industrial hygiene,
companies, but most importantly, ensure
having a safety department may not make
occupational medicine, and occupational
that each and every employee goes home
them any money, but they save money and
health nursing. For the purpose of this arti-
safely.
help protect the company’s most important
cle, occupational safety is the focus. The
asset: its employees.
roles and responsibilities of occupational
very different than their predecessors.
The safety profession started around
safety professionals varies by industry and
Safety professionals have had to evolve and
the same time as workers compensation in
region, but may include: evaluation of work
adapt to ever-changing regulations in order
the United States. The first state to adopt
to protect their companies and employees.
workers compensation was Wisconsin in
In 1970, as a response to dangerous work-
1911, and the last was Mississippi in 1948.
ing conditions across the nation, Nixon
From the beginning until now, the ulti-
signed the Occupational Safety and Health
mate goal of safety professionals has not
Act into law. This led to the development
changed. The goal has and always will be
Modern day safety professionals are
encouraging measures to prevent injuries and illness; providing relevant safety information to employees and employers; and evaluating the success of safety and health programs that are in place. The majority of early safety profes-
sionals were experienced workers that were removed from the field. They were employees with extensive knowledge of the process in which they worked. Once removed from the field they assumed the
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responsibility of managing and carrying out the responsibilities of the company’s safety department. Most had a high school education with no formal training in hazard identification or remediation; they just knew how to identify the hazards involved in the specific work conducted. Some of
”
of Certified Safety Professionals (BCSP) created a way to further ensure competency of safety professionals by evaluating candidates’ academics, experience, skills, and knowledge through proctored examinations. The BCSP offers many certifications today, with the greatest being the Certified Safety Professional (CSP). The CSP has always been the gold standard of certifications in safety. In order to sit for this exam, you must have minimum of a bachelor’s degree, four years of safety experience, and a BCSP qualified credential. Furthermore, to maintain certification after passing an exam, you must recertify every five years by earning 25 CEUs from approved continued education courses, attending safety conferences, etc.
these safety professionals were employees
who were hurt on the job and moved to
sional must have many different skills
the safety department because they “had
sets as well as a comprehensive knowl-
a story to tell.” Without a doubt there is
edge of regulations. Some primary skills
a need for safety professionals with this
needed include hazard recognition, teach-
type of field-based knowledge, since they
ing ability, effective communication skills,
can serve as an outstanding resource. But
understanding psychological behaviors of
as times have changed, regulations have
employees, accident investigation, etc. As
become more prevalent and non-compli-
workplace safety evolves, we, as safety
ance fines have increased. Obviously, there
professionals, must evolve with it. We must
is a need for more experienced and edu-
do so in order to maintain compliance with
cated professionals.
the ever-changing regulations, and most
A survey of American Society of
importantly, to ensure each employee goes
Safety Engineers (ASSE) members con-
home safely to their families at the end of
ducted in 1997 showed that only 17 percent of safety professionals have less education than a bachelor’s degree. In 1969 the Board PAGE 20
As workplace safety evolves, we, as safety professionals, must evolve with it.
There are four core types of occu-
environments; developing, endorsing, and
“
Today, the modern-day safety profes-
their shift. For more information, please visit www.vipinc.com. q Sulfuric Acid Today • Fall/Winter 2020
Feature
NORAM fast tracks a converter–order to door in 5 months
By: John Orlando, Brian Gilliland, Werner Vorster, Kam Sirikan, Andres Mahecha-Botero, and Guy Cooper* of NORAM Engineering and Constructors Ltd., Vancouver, Canada.
Out of gas
In late July 2019, NORAM received an urgent request from a client to help replace a failing converter. The converter’s stainless-steel vessel shell had developed a series of cracks attributed to sigma phase embrittlement, making repairs difficult. Due to the cracks, the client could not delay replacement until the scheduled shutdown in 2022. For plant reliability, the converter had to be replaced sooner, during a planned outage in February 2020. The sulfuric acid plant receives spent acid and acid gases from its crude oil refinery. Loss of the acid plant would jeopardize operation of the refinery—crude oil futures were on the line!
How much time to supply a converter?
There is wide variation among clients in terms of the timespan from when they first start thinking about replacing a converter to the actual installation. Some plan two to four years ahead, starting with a process study, followed by basic engineering, detailed engineering, and finally equipment supply. In the case of a fast-track converter replacement project, some of these steps are condensed or eliminated. That was certainly the case for this client.
Designing the replacement converter
A replacement converter gives the owner the opportunity to upgrade materials of construction, converter mechanical design, and catalyst volumes. NORAM’s converter design features a catenary (aka “blooper”) plate. This improved design uses a dished shape for the catalyst support and division plates which can easily accommodate thermal growth while being fully welded to the shell to eliminate division plate gas slippage. The catalyst load is supported through the shell and, for larger diameter converters, also with internal welded support posts. This simple and elegant design allows full use of the converter cross sectional area for catalyst loading; an important feature because the diameter is typically dictated by the old converter for ducting and equipment layout reasons. The client had been eyeing NORAM’s converter design for years. They liked the absence of internal support posts which were not required in this 18’ diameter converter. Also, the reduced stresses of the elliptical nozzles were appealing. The client had stringent quality control requirements and they visited prospective fabrication shops with NORAM to make sure PAGE 22
NORAM three-bed stainless steel converter.
the shop procedures were up to snuff. The design basis for this replacement was simple–same diameter (18’), same number of beds (3), and same nozzle elevations and orientation to minimize ducting changes.
Start the clock
NORAM received the go-ahead in late August 2019 to design and sup-
The three converter rings ready to ship to client.
ply the converter with delivery required by mid-January 2019—less than five months. A few things were working in the company’s favor. The fabricator had been pre-selected and 304H material was readily available. The converter dimensions, catalyst volumes, and emissions were unchanged from the ‘old’ converter with the major changes being NORAM’s
One of the three converter rings under fabrication at the shop.
catenary plate design and changing the rectangular nozzles to elliptical and eliminating external stiffeners. For transport, NORAM evaluated shipping the 18’ diameter converter in one piece by both truck and barge. After analysis, shipping in three rings with two circumferential welds on site (by the client) resulted in a significantly lower total cost.
A catalyst bed support with ceramic and stainless-steel support.
Sulfuric Acid Today • Fall/Winter 2020
Feature
Fabrication
NORAM placed an order with a fabricator immediately upon receipt of the client order. The nature of a fast-track project is events must be finely choreographed down to the last minute. NORAM was in daily contact with the fabricator days before and after receipt of the order. The fabricator ordered the stainless-steel materials within a day of award, starting the fabrication process. Paramount for short duration projects is safety and quality. Several face-toface meetings were held with the fabricator prior to and immediately after award as well as during vessel fabrication with the client, NORAM’s local inspector, and NORAM. Inspection reports were received on a frequent basis and weekly progress phone calls were held with all parties. And in fewer than 20 weeks from getting the goahead, a truck convoy with three converter modules hit the highway with numerous police escorts for the 2,200-mile, two-week journey to the site.
Site assembly
The delivered converter modules required, as they say on children’s toys, some assembly. For this converter, erection was simple. The client set the lower module on a temporary foundation, and the middle section was then promptly placed on top and tack welded. A circumferential weld was then made, and the process was repeated for the top section. It took less than a week, and it saved a lot of money
The new converter being lifted into place.
compared to shipping in one piece. The internal saddles and expanded metal catalyst supports were installed at this time and the vessel was insulated.
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Moving day
The shutdown move was routine. The catalyst was removed and screened from the old converter, that converter was lifted out, and the new NORAM converter was dropped into place. New and used catalyst was loaded into the new converter, the manways were buttoned-up, and the plant started up.
Setting converter in position.
End result
NORAM and the client executed a successful fast track project with the design supply of a NORAM stainless steel of and Rotating Equipment converter. The elapsed time from the client’s first contact with NORAM until startup was 7 months. The time from receipt of order to delivery at the plant site was only 5 months. What is normally a marathon was turned into a 10-kilometer race! NORAM followed rigorous quality control procedures to ensure a high-quality final product. For the replacement of a
Newly installed converter.
converter and other acid plant equipment NORAM recommends a longer lead time, but if you get in a squeeze, NORAM will work hard to deliver! NORAM Engineering and Constructors Limited designs and supplies sulfuric acid plant equipment. It designs and supplies converters ranging in diameter from 12 to 46 feet. For more information, email sulfuric@noram-eng.com. *Corresponding Author: C. Guy Cooper, P.Eng. gcooper@noram-eng.com, 604-724-8219. q
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PAGE 23
Feature
Wet Electrostatic Precipitators: A proven technology for sulfuric acid gas and mist cleaning By: Gary Siegel, Marketing Director, Beltran Technologies Inc.
The extremely high collection efficiency of sub-micron particulate and sulfuric acid mist makes the wet electrostatic precipitator an ideal choice for gas cleaning of processes with a very high concentration of emissions, like metallurgical and spent acid regeneration plants and sulfur recovery units (SRU). These plants typically produce fine particulate and sulfuric acid mist in the sub-micron range. This particulate and mist, if allowed to pass into the contact section of the acid plant, will result in fouling of the catalyst bed, excessive corrosion, and potentially the production of “black” or low quality acid. Due to the high dust and acid removal requirements that are necessary, the wet electrostatic precipitators operate at collection efficiencies of 99.5 to 99.9 percent in various metallurgical process facilities, such as a sulfuric acid regeneration plants, zinc roasting plants, nickel flash smelters, copper smelters, and sulfur recovery units (SRU). Acid mist precipitators or wet electrostatic precipitators (WESPs) are used in metallurgical acid plants to protect the catalyst beds. These plants are usually non-ferrous smelters, processing copper, zinc, lead, nickel, molybdenum, zirconium, and gold ores. WESPs are also used in spent acid recovery sulfuric acid plants where reprocessed or “spent” acid is converted into SO2 feedstock for the formation of new sulfuric acid. Another application for WESPs is protecting the sulfuric acid plants used to reduce SO2 and SO3 emissions from heavy oil- and coalfired boilers where the fuel has high concentrations of sulfur. WESPs efficiently collect sub-micron dusts and acid mists. These fine particulates usually contain heavy metals, such as arsenic, lead, zinc, cadmium and, other metals depending upon the content of the ores. The emission from these metallurgical processes can contain flotation oils used to separate the various constitutes in the ore, such as sulfides. These oils evaporate in the high temperature of the metallurgical process and condense into mists, in the quenching section of the gas cleaning plant, and are then collected by the WESP. WESPs are also used for tail gas cleaning where it is necessary to remove particulate, mists, and aerosols, as well as reduce visible emissions.
Advantages of wet electrostatic precipitators
WESPs have several advantages over other types of gas cleaning equipment, including high efficiency collection of submicron particulate, mist, and aerosols; and low pressure loss since the internal structure is open tubes, which do not easily plug or restrict gas flow. Another advantage of WESPs is that they can remove dusts that are conductive or have high resistivity, which are problematic for dry ESPs. Since a lot of metallurgical dusts have high resistivity, the wet environment of the WESP coats the PAGE 24
Tubular electrostatic precipitator
particulate with moisture, which makes the dust conductive and enables collection with high efficiency. WESPs operate by charging and collecting the particulate, mists, and aerosols with a corona formed by the collector surfaces and the sharp pointed discharge electrodes. High voltage power supplies charge the WESPs at high voltage, usually between 30 and 75 kilovolts, depending upon the WESP design and the process gas conditions. The WESP is usually formed with a collector of tubes or plates, with discharge electrodes held in the center of the collector structure by a high voltage frame supported by non-conducting insulators. Since the process gases are saturated and contain electrically conductive mists and aerosols, the insulators have to be operated dry, purged by dry, clean, and heated purge gases (usually ambient air). The WESP can be operated by the collection of liquid acid droplets, mists, and aerosols, flushing the collector plates, or with the operation of continuous fogging sprays into the collector section. WESPs usually have deluge or wash nozzles mounted to periodically wash the WESP of solids and collected particulate, which may not be removed by the draining acid/water collected by the WESP.
Beltran WESP design
The collection efficiency of the WESP is expressed in the DA equation and is an exponential function of the three parameters: 1) collector surface area (A); 2) gas flow rate (F); and 3) drift velocity (W). These are really two parameters, A/F, which are related to the size of the WESP box, and W, which is proportional to the electrical power applied to the process gases. Since the efficiency is proportional to the product of these two parameters, it is possible to design a WESP either with a large box and low power, or a smaller box and higher power, for the same efficiency. The consumption of electrical power
for WESPs is usually low compared to other gas cleaning equipment such as venturi scrubbers, bag filters, or other types of high pressure devices. WESPs are constructed of expensive, corrosion-resistant materials, making it better to maximize W and minimize A/F, the size of the WESP. The exponent in the DA equation can be substituted with the parameters voltage, tube or plate length, inter-electrode spacing, and gas velocity through the collector. The efficiency increases with greater field strength (operating voltage divided by inter-electrode spacing), collector length, and reduced process gas velocity. The collection efficiency of the WESP varies with the size of the particulate, mist, or aerosol. Since gas phase reaction and evaporation/ condensation form particles around 0.1 to 1.0 microns, considerable acid mist and particles form in this size range. As particles increase in size from the submicron range they are more easily collected since field charging increases. Also, as particles decrease in size from the submicron range they are more easily collected, since diffusion charging increases. Therefore the collection efficiency curve versus particle size forms a U-shaped curve with its minimum in the submicron range. The collection efficiency is also related to corona power of the WESP, with the minimum efficiency increasing with greater corona power. To minimize the size of the WESP and maximize the operating efficiency, the WESP should be designed to maximize W, the drift velocity, or the rate at which particulate, mists and aerosols move to the collector plates. Although the basic principle and design of the electrostatic precipitator have been around since the early 1900s, recent innovations have produced dramatic advances in efficiency, cost effectiveness, ease of maintenance, and wider applicability. Beltran Wet Electrostatic Precipitators in particular have demonstrated a level of performance that environmental and plant engineers appreciate. However, it is important for engineers to recognize that there are key differences in features and benefits offered by the various precipitator systems. Although they may share the similar operating principles and basic structures, WESPs can vary greatly in design, materials, gas flow rate, durability—as well as collection efficiency. A basic WESP is comprised of an array of ionizing electrodes such that negatively charged discharge rods generate a strong electric field and corona. These are surrounded by or interfaced with positively charged or grounded collection surfaces, which attract and hold the charged particles. In operation, the source gas is passed through the electrode array, which induces a negative charge in even the most minute, submicron-size particles, propelling them toward the grounded collection surfaces, where they adhere as the cleaned gas is passed through. The captured particles are cleansed
Beltran WESPs at copper smelting plant.
from the plates by recirculating water sprays; residues, including aqueous sulfuric acid, are extracted for further use or disposal. The cleaned gas is ducted to downstream equipment or to the stack, depending on the application. The round tube design has the disadvantage of wasting space in the vessel due to the nesting of the round tubes, so round tube WESPs require larger size vessels. If the size of the vessel is not increased, the gas will flow through at a greater velocity and require longer tubes for comparable collection efficiencies. This then requires the WESP to be considerably taller and the tubes longer for the same efficiency. This has a further disadvantage in that the high voltage discharge electrodes are longer and the electrodes have a greater likelihood of swinging or vibrating during operation. This causes sparking and the WESP to operate at lower field strengths and voltages, lowering operating power and efficiency. In addition, longer tubes are more difficult to clean, since the wash sprays have more difficulty penetrating into the high L/D tubes. This causes dust build-up in the tube, which increases sparking and reduces operating voltage, operating power, and collection efficiency. There is a major economic disadvantage to designing WESPs with round tubes, in that the surface area on the outside of the round tube is wasted. Only the surface area of the inside of the tube is utilized for collection; therefore, the round design has to use twice the collector material to obtain the same collector surface as the flat plate, hexagonal, or square tube design. Beltran WESPs are designed with the use of advanced materials of construction, and utilize the advantages of other shape collector tubes, such as the hexagonal and square tubes. Flat plate electrostatic precipitators have operated efficiently since the early part of the last century. This design does not have uniform field strength, since the field is greatest opposite the discharge electrode wire or spike and weakest at the area between the discharge electrodes. This difference is overcome by making the plate length slightly longer to compensate for the field asymmetry. Flat plate ESPs have operated at high efficiency for over 100 years. Beltran WESPs are available with two designs: the hexagonal tube design and the square Sulfuric Acid Today • Fall/Winter 2020
design. The hexagonal design has the advantage that its shape is almost the same as a round tube (field strength symmetry) but it takes advantage of the fact that both sides of the hexagonal wall material are utilized for the collection surface. However, when hexagonal tubes are nested into a round, square, or rectangular housing vessel, because of the nesting shape of the hexagonal tubes, about 15 percent of the cross-sectional area is wasted. This then requires an increase in tube length to compensate for the increased velocity for the same collection efficiency. The most efficient design when considering collection efficiency, compactness, and economic design is the square tube collector configuration. The square tube collector completely utilizes the cross-section of a square or rectangular vessel and can be effectively utilized in a round vessel, as well as the hexagonal. Due to the square tube’s high utilization of the vessel cross-section it can be operated at a
rations, such as: single WESPs, two WESPs in series, two WESPs in parallel, or multiple WESPs in parallel or in series. Smaller gas flows are usually treated with one WESP. This also depends on the efficiency requirements; however one WESP unit can produce reliable service at 99.5 percent efficiency, for smaller flows. Typical plants have two WESPs in series so that one WESP can be washed while one operates. Sometimes two WESPs are designed to be utilized in parallel, for similar purpose. Two in series has the advantage of the first WESP overcoming the current suppression condition while the second WESP operates at full power. This will depend on the gas flow rate, inlet and outlet process conditions, amount of particulate, mist and aerosol at inlet and outlet, etc. Larger plants will require more WESPs in parallel and usually two WESPs in series; so one WESP can be taken offline for washing or maintenance, or washed online.
Materials of WESP construction
Beltran WESPs are built of metal alloys, thermoplastic materials, thermosetting materials, and conductive graphite composite materials. Metal alloys are expensive and have extended delivery time, but their biggest disadvantage is the unreliable performance with regard to corrosion. The sulfuric acid WESP operates in highly corrosive environments, including sulfuric, hydrochloric, and hydrofluoric
acid and other impurities, as well as increased temperature. Because of the high cost of more robust chrome-nickel-molybdenum alloys, like C-276, C-22 and C-2000, designers are attempting to utilize less of these materials. • Conductive graphite composite materials have these advantages: • Highly corrosion resistant • Good mechanical properties • Electrically conductive • Homogenous • Do not require water/acid film to ground WESP • Fire retardant and thermally robust • Cost effective Beltran WESP systems are designed with advanced electronic controls, which can optimize operating parameters such as gas flow, saturation temperature, corona intensity, etc., to achieve maximum efficiency. Since the WESP operates at cooler temperatures—usually at the process gas saturation temperature between 100-170° F— the WESP is uniquely adept at capturing condensable organic materials and acid mists, making this technology an invaluable component for sulfuric acid production plants, petrochemical refineries, and spent acid recovery plants. Beltran Technologies has more than 1,000 installations worldwide and over 100 WESPs operating at sulfuric acid plants. For more information visit www.beltrantechnologies.com. q
416.444.4880 admin@mercad.com ● www.mercad.com
Sulfuric Acid Today • Fall/Winter 2020
PAGE 25
Feature
Beltran WESPs at zinc roasting operation.
lower velocity, so that the required tube length is lower, making it more efficient and easier to wash since the wash sprays penetrate the collector. The high voltage frame is more rigid, does not swing, and stays more accurately aligned, resulting in more efficient and reliable performance. Because of the shorter tube length, lower stabilizing insulators are not required, and the insulators can be mounted on the clean gas side of the WESP, reducing the requirement for heated purge air and resulting in more reliable WESP operation. The Beltran WESP collection efficiency is increased with increasing corona power. Multipointed star discharge electrodes are utilized to maximize corona power and WESP operating efficiency. Multi-pointed star discharge electrodes overcome the problems of current suppression of the space charge effect, whereby the corona power is significantly reduced by the high concentration of submicron particles, mists, and aerosol present in the process gases. This reduces the corona power of the WESP operation and can lower the collection efficiency. Multi-pointed star discharge electrodes overcome this issue by enabling the multi-pointed stars to charge and repel some of the submicron particles, then enabling the next star to increase its corona power, and further repeating this phenomenon almost 100 times as the gases flow up the tube. This type of electrode can produce considerable efficiency in single or multiple pass WESPs, usually utilized in acid plants. WESPs can be utilized in various configu-
Feature
SAFEHX™: Safe Heat Exchanger
By: Breno Avancini, Bruno Ferraro, and Nelson Clark of Clark Solutions
In 2016 Clark Solutions introduced the SAFEHR® heat recovery technology to the sulfuric acid industry. As in other commercial technologies, SAFEHR® uses hot sulfuric acid heat of absorption (180-220 °C) to generate steam instead of releasing this heat to the environment. The major advantage of SAFEHR® in comparison to conventional technologies is that the process eliminates any risk of hydrogen generation and/or severe corrosion in the acid cooling equipment, that will happen in standard technologies, by physically separating the hot acid from the water by means of an inert fluid. This not only dramatically increases the safety of the system but also allows the energy recovered to be shifted to high pressure steam. Strong acid heat exchanger and boiler failures are extremely dangerous occurrences commonly experienced in sulfuric acid manufacturing. Leaks between concentrated acid and cooling water lead to acid dilution with highly corrosive diluted spots, whose corrosiveness is exacerbated by acid heat of dilution, creating a hazardous chain reaction. SAFEHR®’s use of inert fluid brings proven benefits. The first plant is up and running with all the guarantees met, but also adds some extra equipment to the system—two exchangers instead of one and an intermediate piping and pumping system. In order to improve the design and reduce the overall cost without giving up the safety and performance advantages offered by SAFEHR®, Clark Solutions developed and patented a new, breakthrough heat exchanger technology: SAFEHX™ (SAFE Heat eXchanger). The technology not only fits standard heat recovery systems but also any kind of “risky” cooling where the contact between fluids may be harmful or dangerous. SAFEHX™ is a patented multi-fluid heat exchanger technology developed to be a safe, compact and reliable part of the SAFEHR® operation. The SAFEHX™ design reduces the intermediate inert fluid circuit into one single, multi-fluid heat exchanger. Water flows in one tube bundle while sulfuric acid flows in another tube bundle. The chosen inert fluid is encapsulated inside the heat exchanger shell, working as a temperature buffer, which constantly boils at the hot bottom bundle and condenses at the top cold bundle. This creates a chemically inert heat exchanging barrier that prevents the dangers of acid dilution in leakage scenarios while reducing the fluid volume and amount of pipes and control valves required in the intermediate circuit, thus leading to a simpler and safer design. Since SAFEHX™ heat exchangers work via a boil– condensation cycle, most of the heat exchanged is due to phase change, so a temperature buffer forms that stays reasonably constant depending on the fluid mixture chemistry. In the event of an acid or water leak, the leaking fluid (acid/water) will not come in contact with the other fluid (water/acid) eliminating the risk of accelerated corrosion, hydrogen release, and plant upset. Since the corrosive acid is contained inside the lower tube bundle, SAFEHX™’s shell and top tube bundle can be built with inexpensive materials, as these are unlikely to contact hot acid. SAFEHX™ PAGE 26
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SAFEHX™ is a patented multi-fluid heat exchanger technology developed to be a safe, compact and reliable part of the SAFEHR® operation.
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brings to Clark Solutions SAFEHR® and to the sulfuric acid industry a new, intrinsically safe and reliable way to cool and recover energy from hot acid.
SAFEHR® Heat Recovery
In a conventional sulfuric acid plant arrangement, there is no heat recovery from the SO3 absorption step. Strong acid is admitted at the top of absorption towers at temperatures around 80°C and the bottom acid temperatures are controlled to not exceed 115°C. Cooling water used to refrigerate this circulating acid is employed at outlet temperatures usually no higher than 45°C, which do not allow any quality heat recovery. The energy is returned to the environment in the site’s cooling tower in the form of water vapor. Hot water obtained from cooling the acid may be used in projects such as city district heating or for electrolyte heating, but the temperature does not allow the energy to be recovered as a useful form of steam. Increasing absorption temperatures allows energy to be recovered at a higher grade, such as low or
medium pressure steam. Acid at 200-225°C bottom temperatures can easily boil pressurized water at 8-10 bar or pre-heat high pressure boiler feedwater while reducing cooling water consumption and related treatment costs. However, these benefits come associated with a definitively non-negligible risk: since heat recovery takes place on an acid/water boiler, a failure or leak in
the system can, and a few times did, prove disastrous. To completely eliminate this dangerous scenario, which some argue to be one important disincentive to the widespread implementation of heat recovery in the absorption step, Clark Solutions introduced SAFEHR® technology. This technology circulates an intermediary cooling fluid that is non-toxic, non-flammable, immiscible with water and sulfuric acid, and arranged in a circuit that completely separates both fluids even in a simultaneous leakage event. Conventional cooling temperature considerations: Acid is introduced at the top of the absorption tower at a temperature of about 80°C and reaches up to 115°C at the bottom. This hot acid is cooled back to 80°C by 30° C water that is heated to about 40°C in doing so. The water is cooled back to 30°C by evaporation in a cooling tower. Conventional absorption heat recovery temperature considerations: Acid is introduced at the top of the absorption tower at a temperature of about 180°C and reaches up to 225°C at the bottom. This hot acid is cooled back to 180°C, which is enough temperature to generate steam with the transferred heat. In doing so, 105° C water from the deaerator system is heated generating steam of about 170°C. SAFEHR® absorption heat recovery temperature considerations: Acid absorption temperatures are equivalent as with the conventional heat recovery system. But to cool hot acid back to 180°C, an inert
circulating fluid is used, heating up from 170°C to 210°C. This heated fluid is then used to generate the steam, heating water from 105°C to 170°C. Studies of corrosion progression developed by Clark Solutions, utilizing the apparatus shown below, demonstrate that the corrosion rate of a 316L plate with 1 mm hole in an acid-water system at ambient temperature and pressure can be as high as 145 mm per year in these mild lab conditions. When in a heat recovery system, a water leak Continued on page 28
Sulfuric Acid Today • Fall/Winter 2020
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Continued from page 26
into the acid can dilute the strong acid in the system. The corrosion effects will occur inside the acid plant equipment and will release hydrogen, that accumulates in high spots. The leaking spot is a hot weak acid location that auto-catalyzes the corrosive process. This may further increase operations risk. Several hydrogen incidents have been reported by the industry in the recent past. In the SAFEHR® system, regardless of the exposure time, the leakage situation using inert fluid does not speed corrosion as it does not dilute the acid. The interfacial tension and density differences between the fluids make a liquid-liquid coalescer an excellent storage tank for the system itself. Acid will settle at the bottom of the coalescer and water will stay at its top, so, even in the improbable case of both leaking, there would still be no contact between them. The coalescer/ settling tank is designed to easily segregate the fluids. Conductivity and level control guarantee that a leak is quickly identified. The immiscibility of the process fluids, having the inert fluid sitting in a middle density layer between acid and water, is portrayed in the next image:
SAFEHX™: SAFE Heat EXchanger
SAFEHX™ heat exchanger technology represents a further step in SAFEHR® process operation. It is a buffer-fluid heat exchanger designed to maximize the process heat exchanging capabilities while minimizing the intermediary circuit. The buffered heat exchanger concept has the advantage of using an inert fluid that has a boiling temperature in between the process fluid temperatures. In other words, when exchanging heat with the hot side, the buffer fluid will boil, vapors will ascend, condense, and descend in the cold side.
The buffer fluid selection addresses the exchanged process temperatures to give the optimal thermodynamic and chemical properties in the heat exchange working range. The internal convection promoted by the density gradients gives motion to the inert fluid sitting in between the hot and the cold heat exchanging sides. This gives the process a strong advantage by continuously exchanging fluid latent heat, which is substantially more efficient than exchanging only sensible heat, and performing the heat recovery without an extra circuit, thus reducing the required system size. The pressure inside the exchanger shell is con Instead of just an interesting idea, SAFEHR® is now a proven reliable technology, which is fully operational at a Clark Solutions technology designed plant with the following key features: • Clark Solutions Technology and Design • 150 MTPD production • Sulphur Burning • Single Absorption • Hydrogen Peroxide Tail Gas Scrubber • CSX®(UNS S32615) Highly Resistant Alloy Acid Piping • Horitontal SO2 converter • SAFEHR® Heat Recovery Technology PAGE 28
trolled by the flow of the cold fluid; the higher the flow, the more condensation and consequently the lower the internal pressure of the vessel. Safety fluid partly fills the volume of the shell, covering the hot side tubes, similar to a steam generating boiler. The top is out of contact with the liquid level and works as a condenser. In addition to the safety features delivered by the SAFEHR® solution, the SAFEHX™ concept and design also brings economic advantages through higher global heat exchange coefficients, lower volume of safety fluid required, and a reduced system with fewer circulation pipes, control valves, flanges, and heat exchangers, all combined into one single piece of equipment. In order to validate the proposed heat exchanger, an experimental bench was designed to obtain operational data to evaluate the mathematical model’s accuracy, establish operation procedures, validate equipment to its application, and evaluate inert fluid thermal properties. The bench operates with two circuits of water and the heat exchanger half-filled with the inert fluid. One circuit of water is heated to 85°C by a resistor and the other water circuit is kept cooled at 25°C by an air radiator. In order to have the equipment working properly, the safety fluid is selected so its boiling temperature is 55°C—between 85°C and 25°C. The bench design is simple because this new technology is complex only in terms of the equipment, not the process itself. The bench is made of two pumps, one heater (resistor), one cooler (air radiator) and three tanks (two for the water circuits and one to drain the liquid from the heat exchanger interior, if necessary). Furthermore, the heat exchanger was made to allow flow patterns inside the shell to be viewed through glass windows and with several ports for thermoresistors and pressure transmitters.
Conclusion
The SAFEHX™ heat exchanger adds a further safety feature to heat recovery technologies and one that is not restricted to the sulfuric acid industry. The technology improves process temperature control because the boiling safety fluid temperatures stay reasonably constant due to the heat transfer being focused on the fluid latent heat. The SAFEHR® system’s smaller size, achieved by transforming the closed loop of safety fluid into a single component, brings multiple advantages, including reduced maintenance costs, fewer control valves, less instrumentation, lower fluid volume requirements, and smaller footprint. For more information, please visit www.clarksolutions.com. q Sulfuric Acid Today • Fall/Winter 2020
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Feature
The latest in sulfuric acid plant process gas dewpoint/moisture leak detection By: Daniel T. Menniti, Director of Business Development, Mississippi Lime, Breen and Stuart Hinze, Senior Process Engineer, J.R. Simplot
Over the past several years, Breen and the sulfuric acid industry have collaborated to develop a commercially available, permanently installed Sulfuric Acid Dew Point Monitor. Its development objective has been to establish long term reliability for the measuring device, as well as prove its capability for measuring the sulfuric acid manufacturing process gas dew point, while simultaneously detecting the ingress of moisture into the process. The gas laden with SO3 in the process is kept moisture free and the only time moisture gets introduced in the gas is when there is a process upset. Moisture in the process gas combines with the SO3 which will condense on the process equipment surfaces, and is generally indicative of one of the following conditions, among others: • drying tower malfunction • contamination in sulfur feed • waste heat boiler tube leaks • economizer tube leaks • superheater tube leaks • sulfur gun steam jacket leaks. The presence of moisture and therefore weak acid vapor in the gas stream is detrimental to equipment health and can cause extreme corrosion. This is a highly undesirable condition and can be potentially hazardous. A secondary impact of moisture in the process gas can be the formation of hydrogen gas creating an explosion hazard [1]. • SO3+H2O —> H2SO4 • Fe+H2SO4 —> FeSO4+H2 The H2 formed in the equations above can create an explosion hazard in the presence of O2 and an ignition source.
Moisture leak detection
Traditional detection methods currently used include the manual inspection of economizer drains, dilution water flow, and economizer temperatures. Monitoring each of these individual process points for malfunction and moisture ingress becomes expensive, manpower intensive, and most importantly, not useful for the detection of small amount of moisture ingress. Understanding this, it was desired to measure the acid dew point to indicate such moisture leaks. In theory, a moisture leak would affect a step change increase in gas dew point temperature response should moisture enter the upstream process. After several iterations of design as reported in previous editorials, there was consensus that a 24/7 continuous dew point measurement was not required, but only a periodic dew point measurement with continuous monitoring of condensation on the sensor.[2]
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The presence of moisture and therefore weak acid vapor in the gas stream is detrimental to equipment health and can cause extreme corrosion.
Fig. 1: Breen-SA Probe for Sulfuric Acid manufacturing plants.
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change, in process gas dew point. The commercial design for the Breen-SA Probe can be seen in Fig. 1.
Moisture leak detection commercial design
In late September/early October 2018, Breen installed the commercial design into a sulfuric acid plant in California (Fig. 2). The probe system was allowed to run at the above dew point mode, with weekly “Check Cycle” cooling the sensor to the process gas dew point. The probe cycle and check cycles are shown in Fig. 3. On January 23, 2019, the plant performed a test to verify that the system would indeed detect a moisture leak. At approximately 10:45 (Fig. 4) there was a probe response when a pressure point line was cleared out with instrument air. A compressor was then hooked up to the line to pump ambient air into the duct; no response was seen, and it was assumed that the air pressure was not powerful enough to push sufficient air into the duct. Subsequently, the process engineer put water into the pressure point line and used instrument air to push that water into the duct. The amount of water added was approximately one gallon. At 13:15, the probe immediately responded to the event. It was concluded, with a fairly strong certainty, that the probe is very responsive to even small amounts of moisture. There were also other minor responses in the previous
Fig. 2: Breen-SA Probe installation at J.R. Simplot’s Lathrop plant.
Fig. 3: Breen-SA Probe Normal Cycle and Check Cycle. weeks, which were believed to have been caused when other pressure point lines were cleaned out.
Further evidence of response to moisture ingress and leaks
In July 2019, a second and third system were installed in another acid plant in the Western U.S. One SA-Probe was installed at the waste heat boiler outlet and one probe at the final economizer exit (Fig. 5). During start-up operations, this plant experienced a small leak. As the graph in Fig. 6 shows, the Breen-SA Probe detected the leak when it was still very small—at
“Above dew point” measurement
To keep the sensor free of process condensables for the long term and provide moisture leak detection, it was decided to operate the system at an “above dew point cycle.” The above dew point cycle allows the probe to operate in the duct at a temperature higher than the process gas dew point, but low enough to detect an increase, or step PAGE 30
Fig. 4: Leak detection simulation.
Continued on page 32
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Continued from page 30
about 05:00 on June 27th. The first plant’s DCS indicated
“
that there was an issue at about 13:30 on the 27th when the
dilution water flow started to drop, indicating the leak is large enough that less water is needed to maintain the acid
The dew point measurement provides solid trend of the process gas dew point over time as well as insitu verification of sensor function while continuously monitoring for condensation of process gas vapors.
concentration balance in the plant.
Clearly, the probe provided almost eight hours advance
notice compared to the traditional method of leak detection Fig. 5: Breen-SA Probe installation points.
at the plant.
Advanced detection of “undetectable” leaks
The same plant referenced above had run leak free
for almost a year, until June 16, 2020 when the Breen
SA-Probe system started indicating a high process dew
”
point at the waste heat boiler outlet and the economizer
outlet systems. Multiple dew point measurements were taken from June 14-June 30 to verify the higher dew points, as shown in Fig. 7. Fig. 6: Leak detection from Breen-SA Probe vs. dilution water flow
As can be seen above, from June 16th through July
14th, the dew point temperatures progressed upwards over time.
SA-Probe health
of the condensate rose above the process gas temperatures
and cleaned the probes. They were both fit for service and
Finally, around July 16th, the evaporation temperature
and the condensate could not be evaporated from the sensor (Fig. 8).
Having little experience with the Breen technology,
the plant hesitated to take the unit offline until these traditional methods indicated a leak.
Traditional Methods (Fig. 9) include:
2. Condensate in the economizer drains
Fig. 7: Progressive increase in dew point.
1. Economizer Temperature 3. Dilution water flow
a. This did not show any significant change.
Root cause analysis showed that there was a very
small leak in the waste heat boiler shell close to the tube sheet/shell weld. This small leak was most likely the source of the original moisture ingress and all indications show
that the SA-Probe responded to the leak as expected. The
leak then propagated into the tube sheet, causing the further rise in dew points and conductivity and ultimately (30 days later) condensate was detected in the economizer drain. Fig. 8: Moisture ingress causing high temperature condensation without evaporation.
During the unit downtime, the site removed, inspected,
re-installed prior to start-up (Fig. 10).
Summary
Further to the commercialization of the Breen
SA-Probe, the measurement philosophy has been proven effective to detect both large and small moisture leaks,
consistently responding to moisture ingress into the process
in real-time and demonstrably quicker than a traditional methods.
The dew point measurement provides solid trend
of the process gas dew point over time as well as insitu verification of sensor function through the automatic and periodic system “check cycle” dew point measurement.
As of this writing, all the commercial systems have
been running continuously with no failures, or maintenance outside of cleaning during unit turnarounds. The first
installation has been running for over two years and the subsequent systems more than one year each.
For more information, please visit www.breenes.com. q
Acknowledgments Note [1] Information developed and presented by the Hydrogen Safety Workgroup. Note [2] “Detecting real-time moisture leaks in acid plant process gas” Sulfuric Acid Today, Spring/Summer 2020, Vol. 26 No. 1, pages. 32-33 “Process
gas
dew
point/moisture
leak
detection
measurement system”
Fig. 9: Economizer temperature and dilution water flow. PAGE 32
Fig. 10: Left, SA-Probe as found. Right, SA-Probe cleaned prior to unit start-up.
Sulfuric Acid Today, Fall/Winter 2019 Vol. 25 No. 2, pages 28-29
Sulfuric Acid Today • Fall/Winter 2020
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