Page 1






Editor: Nadine Bloxsome







Kiln lining 5 - The future of kiln lining fibres

Tel: +44 (0) 1737 855115 June 2018

Production Editor: Annie Baker

Regenerative furnaces 8 - Reappraising the role of port-necks in regenerative furnaces

Sales/Advertisement production: Esme Horn

Sustainability 12 - Environmentally friendly multi-chamber furnace marks major investment in Aludium Amorebieta Tel: +44 (0) 1737 855136

Sales Manager:

Blast furnace 16 - Increasing BF hot blast temperature

Nathan Jupp +44 (0) 1737 8555027

Manuel Martin Quereda +44 (0) 1737 855023

Partnership 20 - Plibrico adds Upstate Refractory Services as newest partner Furnce guide cover_FINAL.indd 1

6/11/18 11:03 AM

Front cover:

Expansion 21 - Can-Eng Furnaces selected for North American expansion

Subscriptions: Elizabeth Barford

Future of furnaces 22 - Future challenges and Sorg’s approach to environmental limits 28 - What is the future of furnaces? 29 - Stuart Hakes, Chief Executive, FIC (UK) 30 - Richard Stormont, Managing Director, Electroglass, UK 32 - Andy Reynolds, Business Development Director, Fives Stein, UK

Managing Director: Steve Diprose Chief Executive Officer: Paul Michael

Published by


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Furnaces International June 2018


Comment and News

Mechatherm signs contract According to reports, Mechatherm International has created 20 jobs after securing a £25 million order from Bahrain, with support from the Department for International Trade (DIT). The new contract is to supply and

maintain a series of furnaces with one of the largest aluminium producers in the Middle East. It also intends to open its first office in Dubai later in 2018 to bolster its presence in the Middle East.


Jiangxi Huifeng Glass chooses Sorg furnace design Chinese cosmetic packaging and flacon manufacturer Jiangxi Province Huifeng Glass Products has selected Sorg to build its new furnace. Furnace number 2 will be a 60tpd modern gas-heated regenerative endfired furnace and be 35m² in size. It will be built alongside the existing furnace number 1. The working end and five forehearths as well as all necessary equipment will also be supplied by the German glass

furnace maker. The furnace needs to fulfil high quality criteria, but at the same time has to be highly energy efficient and low in emissions As well as the manufacture of highquality glass products, Jiangxi Huifeng also produces enhanced packaging for added value of the articles in-house. This includes various kinds of painting and print processes as well as caps and packages.

Pictured: General Manager of Huifeng Glass, Mr. Bingling Xu; Member of Management, Mrs. Cheng; President of Jisheng Glass, Mr. Waisheng Chen (Business partner of Huifeng); President of Guanghua Glass, Mr. Genhua Ling (Business partner of Huifeng), Owner of Huifeng Glass, Mr. Huitai Guo;

Welcome to the June 2018 issue of Furnaces International. I’m writing this not long after the dust has settled from running the first ever Future Aluminium Forum in Milan. With my ‘aluminium’ hat on, the forum hosted more than 150 delegates from across the aluminium manufacturing industry to discuss the integration of Industry 4.0 and smart technologies.

Sales Director & Marketing Director of SORG, Dr. Hartmut Hegeler; Commercial Director of SORG, Mr. Willi Schromm; Sales of SORG, Mr. Tony Zhang

Extra papers for Furnace Solutions event More papers have been added to the Training Day at next week’s Furnace Solutions conference. Chris Windle, of DSF Refractories and Minerals, will discuss the key to high float glass yield is the performance of the tin containment material; the tin bath blocks. Tin bath block characteristics have been the root cause for many glass defects over decades of manufacture. Chris will review the tests and solutions devised to achieve the high level of performance expected from

float glass manufacture today. Richard Hulme of Guardian Glass will present a paper titled Safety In Numbers? Why some process variables are key to safe, consistent and optimided furnace operations. The two-day Furnace Solutions conference and Training Day takes place on June 6 and 7 at Lucideon, Stoke-on-Trent, UK. For more details about the conference and book your place at this years’ event visit

The topic of furnaces came up over and over again, with one particular paper highlighting a process that can allow your furnace to talk to you! We will have more on this in the September issue, so hold tight... I’m interested to know what the furnace of tomorrow looks like and how it might be safer, better connected, more flexible and more efficient. If anyone out there has the answer to this question, then please don’t hesitate to get in touch! In the meantime, I hope you enjoy this issue. Nadine Bloxsome Editor, Furnaces International 1

Furnaces International June 2018

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SGD celebrates second furnace at Saint Quentin site

Christophe Rogier, the plant director of SGD Pharma’s Saint Quentin La Motte site

SGD Pharma celebrated the lighting of furnace number 2 at its Saint Quentin La Motte plant, northern France. More than 70 people attended the inauguration ceremony for the all electric furnace. The project leader Mme Marie Lurquin (pictured right) had the honour of lighting up the new furnace at the ceremony as she was named the ‘Marraine’ - godmother of the furnace. The furnace will produce borosilicate Type 1 glass for the pharmaceutical industry

and was installed after nearly 40 days of rebuild work. The furnace was rebuilt by the plant’s staff – with help from external contractors and the capacity had increased by 10% of the previous furnace’s 300 million vials a year. Saint Quentin La Motte Plant Manager, Christophe Rogier, said he was proud of the team. “We have some very experienced and experimental people within both the group and the plant so we were able to manage this project.

“I’m very proud because we have a beautiful plant and we are very proud of this first rebuild of the furnace. The restart was very good and we have reached high production standards in very few days. We were inside the budget and we built it four to five days ahead of schedule. “The team did a great job and I have already had great feedback from our customers who have visited.” The company decided to use an electric furnace after a successful experience of a similar furnace at its former

Mers le Bains plant, supplied from furnace group Fives. The Saint Quentin plant produces vials dedicated to the injectable, nasal needs and baby bottles sector. Its main geographical markets are Europe and the USA.

Forglass completes major float furnace projects Polish glass engineering company Forglass recently completed three major hot repairs of float furnaces for Saint-Gobain in Germany, UK and Romania. Forglass deployed a full team of employees on

site for the jobs, including managers, supervisors and safety inspectors. The main task facing the Forglass team was a hot overcoating of the furnace Melting Tank, including Dog house, Tank sides, Exit wall

and Waist. The preheated tiles were placed and the steel structure was adapted accordingly. Some minor repairs were also performed at the Melting End superstructure. Following the completion

at each of the three locations, Forglass received a letter from Saint-Gobain emphasising the fact that all work was performed in a safe manner, as a result of which there were no accidents nor injuries. 3

Furnaces International June 2018

Kiln lining

The future of kiln lining fibres Successful trials have confirmed that Superwool® XTRA, the latest generation of low-biopersistent fibre from the Thermal Ceramics business of Morgan Advanced Materials, delivers a long-awaited alternative to Refractory Ceramic Fibre (RCF), also known as Alumino Silicate Wool (ASW), materials used in furnace linings. Morgan’s Fibre Centre of Excellence lead, Gary Jubb explains how they developed a new material with high temperature tolerance, improved pollutant resistance and a chemical formulation that meets stringent Environmental Health & Safety requirements.

Lining iron and steel furnaces is critical to extend the life of the furnace and to protect the purity of the metals being heat treated. Therefore, choosing the best material to meet these needs is crucial. For many years, the first-choice material for the industry has been RCF, which can withstand the extreme temperatures within the furnace and has strong resistance to pollutants. However, RCF has environmental, health and safety (EHS) concerns. After numerous studies, RCF was classified as a category 1b carcinogen in Europe and is considered a substance of very high concern (SVHC) under REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals). There’s already pressure from European legislators to find safer alternatives, ‘Under the Carcinogens Directive, where technically possible, substitutes to RCF should be used. RCF is currently under

consideration for further regulation in Europe, which will make the use of RCF more difficult with constraints and stringent controls likely to come into force. This is compounded by the increasing commitment of major industrial companies and trade associations to improve ‘green’ standards, placing the onus on the fibre industry to find alternatives that match the performance of RCF without adverse effects. Backed by almost 10 years of research and development and more than 30 months in trials at customer furnaces, our Thermal Ceramics business has launched Superwool® XTRA, a material that delivers the performance of RCF without the inherent EHS risks associated with it.

Reinventing RCF Since the 1990s, the Superwool® brand has been a mark of quality in creating

low bio-persistent (LBP) fibres that minimise health risk to furnace installers, operators and other factory employees. We’ve achieved major advances in the performance of LBP fibres through our Superwool® HT™ and Superwool® Plus™ grades. The evolution of the Superwool® family of materials has been recognised with the Queen’s Award for Enterprise: Innovation (2003), as our insulating fibre experts have continued to innovate to meet – and anticipate – market demand. This demand is now for a material that balances the performance of RCF with more stringent environmental safety. This is a significant challenge, because RCF has really strong characteristics that make it ideal for use in chemical processing, iron & steel processing and ceramics factories. For example, RCF is very resistant to attack by alkai-based pollutants, something that needs to be considered when developing a viable alternative.


FURNACES Morgan.indd 1

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11/06/2018 14:25:11

Kiln lining

That’s why, in recent years, the focus at our Fibre Centre of Excellence in Bromborough, UK has been to challenge the assumptions in LBP chemistry. Rather than keep trying to make marginal gains in LBP performance, we’ve flipped our approach and revisited the RCF itself. What the industry wants is an RCF equivalent that has low bio-persistence, so that’s how we’ve approached our development. Superwool® XTRA is an Alkali Metal Silicate fibre, especially combined to deliver the optimum combination of RCF and LBP properties.

A different fibre Superwool® XTRA delivers the strength that industrial applications need, both in terms of its resistance to high temperatures and pollutants, but also its improved EHS credentials. With a classification temperature of 1450°C, Superwool® XTRA offers a performance equal – and in many cases superior – to RCF. The fibre is unusual in that it expands when heated up to close shrinkage gaps at high temperatures, this is reversible so when it cools down the shrinkage gaps return and are visible. Once heated again it expands and closes the gaps again. This means there is no reason to fill the shrinkage gaps with blanket – the normal practice for RCF. With a 2% shrinkage, open gaps with RCF normally require an installer to fill these gaps with thin blanket, this is not only time consuming but more material is required adding to costs. In terms of EHS qualities, Superwool® XTRA is exonerated from any carcinogenic classification under nota Q of directive 97/69EC. A key benefit is that Superwool® XTRA does not form crystalline silica, a common by-product when many refractories are heated to high temperatures. Having a fibre that produces no crystalline silica is a major breakthrough for the industry, which enhances EHS compliance.

A class of its own Superwool® XTRA has been extensively tested by Dillinger, at its mill for heavy plates in Germany. At the mill, as well as the pusher type furnaces used for slab reheating, three shuttle kilns are existing for ingot reheating and for support of the pusher type furnaces on maintenance or heavy load. This environment was

chosen for testing because of the high temperatures and high levels of impurities in their atmospheres, including sodium, potassium, iron and chromium. Over time these impurities weaken the lining, leading to high shrinkage and surface degradation. This in turn increases thermal conductivity and increases heat losses and often damage to the steel infrastructure of the furnace. A small section of wall in shuttle kiln no. 2 was selected for an initial feasibility test, because the risk of any problems resulting in long downtime issues was considered to be low. Tested against the existing lining material used in this application, after six months of firing, Superwool® XTRA showed 50% less shrinkage compared RCF. Where the existing lining material was hard, full of cracks and had discoloured noticeably into a dark brown, the surface of Superwool® XTRA remained softer, with no surface cracks and there was little change in colour. This proves that the material is outperforming existing RCF solutions in environments with high pollutant levels. This success led the customer to reline half of the roof of shuttle kiln No. 3 for further testing, with similarly positive results. The customer has now decided to switch entirely to the new Superwool® XTRA grade, for the benefit of both the non-regulated status of this product and its superior chemical resistance and

shrinkage performance, relative to RCF. The refractory maintenance department has since presented Superwool® XTRA to Dillinger’s EHS Department as a working alternative to RCF. The key messages in their presentation is that Superwool® XTRA will reduce risk for workers as well as reducing costs for installation, wrecking and disposal. There are additional benefits in no or little maintenance for the filling any shrinkage gaps and no reduction in the insulating performance. As a result of this, Dillinger decided to set Superwool® XTRA as their new standard, replacing the formerly used Cerachem® Fibre. This example confirms the potential of Superwool® XTRA. EHS concerns are an increasingly important driver in terms of meeting legislative compliance – and Superwool® XTRA offers exceptionally performance alongside low bio-persistence and no formation of crystalline silica. From a commercial standpoint, the bigger benefit of this breakthrough in LBP is that it matches, and even exceeds, the established performance of RCF. Superwool® XTRA is the future for applications requiring high temperature fibrous insulation.

To find out more about Superwool® XTRA, please visit: http://www.morganthermalceramics. com/SuperwoolXTRA

6 Furnaces International June 2018

FURNACES Morgan.indd 2

11/06/2018 14:25:12

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A Division of Glass Service

Regenerative furnaces

Reappraising the role of port-necks Ernesto Cattaneo, Giorgio Minestrini, Alessandro Mola* and Alessandro Spoladore** discuss how, within the Prime Glass project, two techniques were developed to contain NOx in regenerative end-port furnaces.

Today’s glass industry faces the problem of nitrogen oxides that come from its typical high-temperature diffusive combustion systems. The first step to contain NOx pollution is to proceed at the level of the combustion chamber employing primary containment measures, which are techniques for the non-generation of nitrogen oxides. Within the Prime Glass project, Stara Glass, together with the University of Genova and Stazione Sperimentale del Vetro (SSV), developed and patented two techniques for the primary containment of NOx in regenerative end-port glass furnaces that gave excellent field results thanks to the percentages of NOx abatement in the order of 30/40%.

Strategic waste gas recirculation (SWGR) Figure 1. SWGR system layout.

Recirculation test: 10%-20%-30% of waste gas in combustion air 1300 Nox [mg/Nm3 @8% O2]

It is scientifically known that a combustion, even at a high temperature, if it is developed in an atmosphere that presents an oxygen concentration, which is lower than the atmospheric one, will produce a lower amount of NOx. In different industrial fields, it is common to lead a part of combustion gas flow inside the combustion airflow, in order to reduce oxygen concentration and, consequently, NOx production. Stara Glass, within the Prime Glass project, has developed a system that allows applying the waste gas recirculation technique to regenerative glass furnaces maximising the general benefits (Figure 1). The obtained abatement levels have been >35 % (Figure 2). In the near future, Stara Glass will explore a coupled design of chambers and recirculation system. Please visit for more details about the SWGR system and its interesting energy implications.



1000 Recirculation 900


ON 10%

Recirculation OFF









Figure 2. NOx furnace’s production during the SWGR system test.

8 Furnaces International June 2018

Regenerative furnaces

s in regenerative furnaces

High-Efficiency Air-Staging (HEAS) This technique can be seen as an evolution of the cold air staging, which consists in the development of a reduced combustion inside the combustion chamber, followed by the admission of a post-combustion air inside the waste gas port in order to complete the oxidation. From the point of view of thermal NOx formation, this technique is effective, because of the reduced oxidation level of the flame. The cold air staging technique consists of inserting a cold airflow inside the port obtaining a good mix between waste gas, still rich in CO, and post combustion cold air, but with a high decay of energy efficiency (≈-3.5%), due to the low

temperature of the post-combustion air. With the aim of developing an air staging system without affecting the global efficiency of the furnace, Stara Glass studied a hot air staging system connecting the two ports with a ceramic duct, but it was evident since the beginning that to recover of energy efficiency (≈-0.5%) corresponded to a poor mixing. In front of this challenge Stara Glass, thanks also to the CFD support, decided to mix the two-previous systems: cold and hot air staging realising a hybrid one i.e. the HEAS system (Figure 3). In the final solution, an external double cold air flow (CFD optimised air jets with 10-15% of total staging air) at high velocity (250-300m/s) drives the hot air

through the connection duct between the ports, thus achieving an energy efficiency that is absolutely comparable to the hot solution (> -0.5/-1.0%) and a satisfactory oxidation of the waste gas flow. The two air jets are always working, in fact a minimum of compressed air mass flow must be guaranteed in the metallic spears to keep them in good working condition. Synchronously with the inversion of the regenerative cycle, one of the two spears, the closer at the waste gas port, introduces a higher compressed air flow to realise a localised head loss in order to control the preheated air extraction. As shown by Figure 4 the real results went beyond expectations, in effect since the first test, the NOx abatement has been ≥ 40% (Figure 4)

Figure 3. HEAS system layout.


Furnaces International June 2018

Regenerative furnaces

thermodynamic mixer. Thanks to the observation of the Reynolds number, it is defined as turbulent and therefore mixing the motion regime inside the port. From this point, the possible design relapse goes in the direction of a probably longer port, or in general with different geometries, to promote the rapid consumption of CO in the waste gas before their arrival in the regenerator, always guaranteeing low NOx emissions. All theoretical considerations and CFD results have been confirmed during the Prime Glass project by the field analysis of Stazione Sperimentale del Vetro (SSV) with its innovative Multipoint Continuous Monitoring System (MCMS) that was able to collect a grid of chemical analysis data, that proved to be absolutely in line with the CFD models and were useful to further fine tune them. After the experimental plant of the Prime Glass project, Stara Glass received different orders for the HEAS system, thus having the chance to explore different optimising solutions.

HEAS off



800 NOx RC a 400

NOx RC p HEAS on

NOx Torrino

0 0




Figure 4. NOx furnace’s production during the HEAS system test.




ppm CO

3500,0 3000,0

CO RC1 mg/Nmc 8%O2


NOx RC1 mg/Nmc 8%O2 NOx RC2 mg/Nmc 8%O2


NOx RC2 mg/Nmc 8%O2


The port-neck is not just a duct, today it is a reactor too


The trend for glass furnace combustion today is to use reduced combustions, in order to avoid a higher NOx formation, thus paying the price of a residual quota of CO in the waste gas flow. Naturally, either by physiological air infiltration or by advanced post-combustion systems like HEAS, all waste gas CO ends up oxidised to CO2 before leaving the heat recovery system. The point is: while until a little time ago the waste gas port was just a duct for a fluid whose composition was constant, nowadays the port has raised itself to a more central role in the combustion process, it is in fact a reactor, whose possibilities to affect the furnace ambient and energy performance are yet quite unexplored. Stara Glass is focused on analysing how a new generation of port design can lead a glass furnace to better achievements.



mg/Nm3 8%O2


1500,0 1000,0


500,0 0,0

0,0 0














Figure. 5 NOx (O2), CO (O2).

The system as well as being easily manageable is also reversible by using the damper in the middle of the duct and then closing the by-pass duct, creating two separate and independent ports. The experimental data show that the HEAS utilisation has consequences on the smoking point; more in detail the CO in the backward position is negligible even at low O2 level and the linear equation of NOx f(O2) are substantially overlapping. This underlines that working at the level of 2% of O2 in the backward position, which is the reference value (which

corresponds to approximately 3.2 to 3.5% of the forward position) the NOx values are always below 600mg/Nm3. (Figure 5). The combination between the DeNOx effect of reduced combustion and high efficiency in removing CO reveals an important advantage: the increment of extraction flow strongly increases the turbulence and shows a fast CO reduction in the top of regenerator, this means a more efficient mixing due to high-speed jet with quicker CO decreasing. This phenomenon highlights the new role of the port as a reactor, as a

Acknowledgements The project has been co-funded by the LIFE instrument of the European Community.

*Stara Glass, Genova, Italy, ernesto. **UniversitĂ degli Studi di Genova, Italy

10 Furnaces International June 2018


Environmentally friendly multi-cham investment in Aludium Amorebieta

12 Furnaces International June 2018


mber furnace marks major

Aludium has announced that the company will install a multi-chamber furnace to improve the sustainability of its operations. The new furnace will be installed in the Amorebieta cast house and will increase Aludium’s ability to melt lacquered scrap. That will enable Aludium to create one of the most flexible metal production units in the world. The ₏20 million investment is due to come onstream during 2019.

13 Furnaces International June 2018


The multi-chamber furnace selected is a Hertwich Ecomelt PS275, a proven technology and one of the largest shaft furnaces in the world. The PS275 is a toploading system and can be charged with many different types and shapes of scrap and has a throughput of 275 tonnes per day. The PS-type furnace ordered by Aludium Amorebieta is suitable for scrap with the highest contamination rates. The scrap is fed into a preheating shaft from above through a material lock. The hot gases flow through the charged material in the shaft from the bottom upwards. The pyrolysis gases produced during this stage are combusted in the main chamber. Thanks to the advanced design of the furnace, the reuse of the pyrolysis gases reduces gas consumption to around 300 kWh/tonne (depending on the scrap input). This increases the sustainability of Aludium’s operations, and results in minimal emissions of gases including CO2, CO, NOx, dioxins, volatile organic compounds (VOCs), and salts.

All melting technologies under one roof “With the installation of the new multichamber furnace, Aludium will have a range of furnaces of different sizes and all

melting technologies on one site. That will enable us to produce slabs in the most flexible way,” explains Mario Allet, Program Director. The Aludium Amorebieta cast house already houses three standard reverb melting furnaces which utilise primary metal and clean scrap as feedstock. It also contains a rotary furnace which runs in batch mode, allowing the cast house to quickly change the alloy produced. Many different types of scrap can be melted in the furnace including painted scrap and dross. By contrast, the multi-chamber furnace operates continuously and will produce large volumes of alloys from the 3xxx and 5xxx families. The de-coating and re-melting process steps are separated to maximise recovery and production. External after-burning is not required as all emerging pyrolysis gases are combusted in the main chamber in a controlled manner. At the lower end of the shaft, the pre-heated and de-coated material is immersed in the melt bath, which is moved by a liquid metal pump. The material melts instantaneously with minimal melt loss. The melting furnace includes a separate feed for scalper chips. These are fed into the furnace immediately after rolled slabs are machined. They are also melted using

the submersion melting process, ensuring the greatest possible yield. Multi-chamber furnace increases sustainability of Aludium’s operations When it comes onstream in 2019, with the new MultiChamber Furnace, Aludium will increase it’s output of Sheet Ingots by 55000 tons per year. Compared to primary metal production, recycling aluminium reduces energy consumption by 95% or 14 megawatt hours (MWh) per tonne of aluminium. With this project, Aludium expects to reduce CO2 emissions by 250,000 tonnes annually. During the works to install the furnace, the existing scrap yard in Amorebieta will be enlarged and a new 65-tonne scrap holder will be installed. The unit will be optimised for safety including features such as a hands-free casting machine. The entire system will also comply with OHSAS 18001 and European standards. The total cost of the investment is €20 million. Work on the improvements and furnace installation are scheduled to begin during the first half of 2018 and will take 18 months in total. At the same time, pit #3 will also be enlarged to allow five sheet ingots to be cast in each drop. The multi-chamber furnace is expected to become fully operational in the second half of 2019.

14 Furnaces International June 2018


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Furnaces International June 2018


Blast furnace

Increasing BF hot blast temperature

Process optimisation at the blast furnace preheat stoves at SAIL’s Durgapur Steel Plant have enabled the blast temperature to be raised from 910° to 1000°C resulting in increased productivity of the furnace by 257t/d or 10.8%, along with a reduction in coke rate of 5.2%, an increase in coal injection of 450% and O2 enrichment up 42%. By R K Singh, S Sudhir, R R Kumar, V K Jha, B K Das, A Mallick, S K Pan & A Arora

The Hot Blast Temperature (HBT) is the most important parameter and frequently used to control the supply of thermal heat into the blast furnace. Higher blast temperature or higher thermal heat input through the tuyeres decreases the total heat requirement generated in the furnace. A high hot blast temperature is one of the enablers to enhance pulverised coal injection (CDI). The hot blast temperature also directly influences the combustion raceway adiabatic flame temperature (RAFT). A rise in blast temperature of 10°C increases the combustion raceway temperature by 8.4°C. Such a rise in blast temperature decreases the coke rate by 1.23kg/thm, lowers the blast volume by 5.65Nm3/thm and reduces the top gas volume (800Kcal/ Nm3 basis) by 4.04 Nm3/thm. HBT is thus an important parameter for controlling the heat content inside the blast furnace. A number of advantages are associated with high HBT in blast furnace operation. To achieve higher HBT, the blast preheat stoves must be operated efficiently. The major factors affecting HBT are the gas rate, air-gas

ratio (excess air coefficient), waste gas temperature, draught at chimney, cold blast temperature and its leakage into the flue tunnel, the calorific value of blast furnace top gas (BF gas) and blast furnace gas temperature, among others. The use of a high blast temperature results in a saving of coke and in an increase in productivity. The saving is mainly due to an increased supply of sensible heat from the blast which reduces coke consumption at the tuyere. Generally, 85% of heat to the furnace is supplied by coke consumption at the tuyere and 15% by the hot blast. The blast temperature directly influences the theoretical combustion temperature in the raceway which exerts substantial influences on the cohesive zone configuration and also on burden descent. The blast enters through the tuyeres and causes combustion of coke and auxiliary fuels in the combustion zone or raceway. The character of the raceway plays a vital role in intensifying smelting. The raceway is a cavity, immediately in front of the tuyeres, in which coke particles are found loosely packed. The Raceway Adiabatic

Flame Temperature (RAFT) is the maximum flame temperature, which is attainable by burning incandescent coke in front of the tuyeres using atmospheric or enriched oxygen in the hot blast. The RAFT is a function of blast temperature, blast humidity, granulated or pulverised coal injection (CDI) and the oxygen content of the blast. A number of advantages are associated with high HBT. To achieve high HBT, the air pre-heater stoves must be operated efficiently, but additional important factors are gas rate, air-gas ratio (excess air coefficient), waste gas temperature, draught at the chimney, cold blast temperature and its leakage into the flue tunnel, calorific value and temperature of the Blast Furnace top gas, and others.

Measures for improvement The condition of the stoves requires a number of measures to be taken both in operation and maintenance. Only operational aspects are discussed here.

High dome temperature The resulting HBT depends on the stove

16 Furnaces International June 2018

Blast furnace

Ratio BF to coke

oven gas

Calorific Value

Maximum dome


BF adiabatic flame

temperature achievable (0C)

α = 1.1

temperature at α = 1.1(0C)

α = 1.2



















































Table 1. Maximum dome temperature for different calorific values of fuel gas

dome temperature and the degree of heat soak in the checker brickwork of the stoves. Efforts should be taken to maximise the dome temperature. This is dependent on the calorific value of fuel gas used in heating the stoves, normally a blend of blast furnace (BF) top gas and coke oven gas. However, this must not exceed the maximum allowable temperature for the refractory used in the combustion chamber, dome and the top layers of checker work. It can be maximised by improving the combustion of the fuel gas by correct setting of the air-to-gas ratio, or by use of higher calorific value gases for preheating the furnace blast. Correct dome temperature protects the refractories from overheating and so prevents premature failure and the appearance of hot spots in the combustion chamber and dome. Normally, the dome temperature is kept about 150-200°C higher than the Hot Blast Temperature (HBT) required. The dome temperature is lowered by increasing the air to fuel gas ratio (α). Once the dome temperature reaches its set value the air-gas ratio is increased automatically to maintain the set dome temperature. This reduces the BF top gas fuel into the stoves in order to keep the total generated

Excess air ratio

waste gas at a constant level. It is essential to improve the insulation of stove and hot blast delivery system to achieving higher HBT. Table 1 shows the effect of calorific value of the stove fuel gas and the air-gas ratio (α) on stove dome temperature.

Calorific value of gas The calorific value (CV) of the fuel gas blend determines the maximum achievable dome temperature. The flame temperature is purely a function of the calorific value of gas and the amount of excess air coefficient (α) in the waste gas. The higher the calorific value, the higher the flame temperature resulting in a higher dome temperature. It is, therefore, essential to work out the exact requirement of the calorific value of fuel gas to achieve the required dome temperature. If the condition of the stoves and hot blast delivery system are unsatisfactory, unblended BF gas is used with a higher air-gas ratio to maintain lower dome temperatures, otherwise mixing coke oven gas or coal bed methane (CBM) in the ideal ratio may be employed to increase the adiabatic flame temperature which will lead to increased HBT. The blast furnace top gas calorific value

can be calculated from an analysis of the gas. The main gases with a fuel value are CO and H2. CV kCal/Nm3 = 30.2 kCal x %H2 + 30.0 Kcal x %CO + 93.9 KCal x %CH4

BF top gas temperature The effect of BF gas temperature on stove dome temperature is significant. The BF top gas undergoes wet-cleaning to remove dust. If the gas temperature exiting the cleaning plant is high then the moisture content of the gas will also be fully saturated at a level dependent on gas temperature. As a result, the maximum attainable dome temperature decreases as the BF gas temperature increases. With almost the same BF gas, the maximum attainable dome temperature decreases by 70°C, if the BF gas temperature increases from 30 to 45°C and the corresponding moisture content increases from 35 to 85gm/Nm3 of dry gas. If the dome temperature decreases, the HBT will also be lower for the same CV of BF gas. Therefore, it is desirable to cool the BF gas in the gas cleaning plant to about 3035°C.

Air requirement

Waste gas generation

Gas flow rate




(Nm3/Nm3 of gas)

(Nm3/Nm3 of gas)


flame temp (0C)

temp (0C)











































Table 2. Effect of excess air on heat input to stove


Furnaces International June 2018

Blast furnace










Production (t/d) 2383

2388 2493 2428 2329 1410 2578 2640

Productivity (t/d/m3) 1.58

1.58 1.66 1.61 1.58 1.17 1.69 1.74

Coke rate (kg/thm) 516

499 462 470 481 515 502 489

CDI rate (kg/thm) 10

19 57 56 62 36 58 55

Wind volume (Nm3/min) 2133

2200 2183 2133 2050 1750 2250 2200

Blast pressure (kg/cm2) 1.52 1.57 1.56 1.59 1.58 1.22 1.66 1.67 O2 enrichment (Nm3/h) 4526 4706 5484 5077 5146 2178 6198 6438 HBT (oC) 910

914 921 984 1007 970 908 1000

Table 3 Operating parameters of BF # 4, Durgapur Steel Plant

Air-to-gas ratio The Air to Gas ratio is also equally important to achieve a higher dome temperature for a given CV. Excess air not only lowers flame temperature, but also increases the waste gas volume resulting in increased load on the chimney. Finally, it will affect the gas input to the stove, thereby lowering hot blast temperature. It is essential, therefore, have the air-gas ratio correctly set by using automatic mode. The effect of excess air coefficient (α) on the gas input to stoves is shown in Table 2.

Waste gas temperature The temperature of the waste gas exiting the stoves is an indication of the level of the temperature of the stove checker bricks. A higher waste gas temperature at exit indicates more heat retained in the checker brickworks. Gas exit temperature should be maintained in the range of 375 to 400°C. This will ensure a higher hot blast temperature for a longer duration. It also ensures higher chimney draughts resulting in higher gas input to the stove. The trend of waste gas temperature is also important in achieving higher hot blast temperature. If the waste gas temperature at exit increases or remains constant, the thermal stability of the stove improves, otherwise it deteriorates. This means that the heat input to the stove is below that required to maintain a constant hot blast temperature. The waste gas temperature should be 190 - 200°C at the end of an on blast heating period and is 25-30°C above the unheated (cold) blast temperature. This, with a temperature of 375- 400°C of the stove waste gas, will help improve the chimney base draught leading to increased BF top gas input to the stoves. Corrective action is to be taken either by increasing fuel gas input or reducing the hot blast temperature, otherwise hot blast temperature will keep on falling

until the heat input to the stove by the fuel gas becomes higher than the heat taken by hot blast and losses.

Cold blast valve & chimney valve The cold blast valve should be completely closed when the stove is on the fuel gas period, otherwise there will be leakage of cold air into the checker. This will dilute the waste gas, lowering its temperature and increasing the waste gas volume, thereby reducing the draught and this will reduce the gas input into the stove thereby decreasing hot blast temperature and loss of cold blast. Similarly, the chimney valve should also be completely closed during the blast preheat period. If it does not hold, then there will be leakage or loss of cold blast and it will dilute the waste gas temperature coming from other stoves and increase chimney load. This will again affect the gas input in the other stoves thereby decreasing hot blast temperature.

Draught The draught is a very important parameter for gas input to the stoves. It is dependent on the waste gas temperature at the chimney base for a given chimney. It is therefore essential to maintain a waste gas temperature 20°C higher than the cold blast temperature at the end of the blast period and 350-400°C at the end of the gas period. Further, It is also essential to stop cold blast leakage into the stove and atmospheric air, and water infiltration into the flue tunnel.

Stove availability Stove availability is a very important factor which affects HBT. In cases of three stove operation, one stove is on blast and two stoves are on fuel gas. If, due to any reason, one stove is down, then only one stove will be heating on gas. This adversely affects the gas input to the stove. Similarly, for four stove operation, two

stoves are on blast and two on gas. If one stove is down then one stove is on blast and two stoves remains on gas. But if out of four stoves, one stove is under capital / long repair then it becomes a three stoves operation and if any stove out of three is down, it adversely affects gas input to the stoves. Therefore, it is essential to improve stove availability by good maintenance and stocking critical spares. Due to ageing of stoves, the gas input decreases resulting in lower HBT. Where four stoves are available, three stoves can be kept on gas and the other on blast. If three stoves are put on gas, the total gas input into the stoves increases by about 25 - 30%, which will meet the hot blast temperature of 1000°C with BF gas alone. It is, therefore, essential to ensure high availability of stoves by proper maintenance.

Operational aspects for high HBT The hot blast temperature (HBT) depends on stove dome temperature and the level of soaking of the checker brickwork. A high dome temperature will give a high blast temperature, but it will not sustain this for long. Therefore, both the dome temperature and the stove waste gas temperature, being a measure of the checker brick soak, are equally important. If higher CV gas is used, the higher dome temperature is achieved within half an hour from the start of the fuel gas period even at lower gas input. But, it will not ensure proper soaking of the checker bricks. The waste gas temperature will be in the range of 225-275°C against the desired 375-400°C required for proper soaking. If the waste gas temperature is at about 250°C, the bottom checker will only be at about 150-175°C. The cold blast temperature, enters the checker at about 150-170°C, so there is hardly any temperature difference between the cold blast and checker bricks resulting in no heat transfer. In this situation, utilisation of the bottom part of the checker is very

18 Furnaces International June 2018

Blast furnace

poor. There is a loss of effective surface area of the stove for heat transfer resulting in lower hot blast temperature. To achieve higher hot blast temperature, it is essential to have properly soaked checker brickwork. The gas input into the stove has to be increased. Increasing the gas CV alone will not improve soaking, it will only increase dome temperature and may damage the top checker and dome refractory.

Gas to stoves when BF off blast

To increase the gas input into the stoves, the following measures can be adopted: • Increase and maintain the gas line pressure. • Cool the BF gas in the gas cleaning plant to reduce moisture carried to the stove. • Three stoves on fuel gas instead of two stoves, wherever four stoves are available. • Increase the stove availability by good maintenance. • Improve chimney draught by eliminating leakages from the cold blast valve. • Close chimney valve and avoid water logging in flue tunnel/ chimney base. • Fully open the fuel gas valve. • Auto operation of air-gas ratio.

Waste gas temperature enhancement

Case study HBT of BF#4 DSP The stoves of BF 4 at Durgapur Steel Plant, SAIL are based on HTS technology. HBT was in the range of 920-930°C in the months of Jul-Aug’ 2012, which was on the low side, hence measures were taken to increase the HBT to 1000°C.

During a shutdown of the furnace continuous heating of the stoves is very important to maintain the heat inside the stoves for later providing heat to the blast furnace. Excessive cooling is also not good for the stove refractories as it creates greater thermal stress. Hence during short shutdown periods (6-8hr) BF gas is provided to the stoves to maintain heating.

Initially the set point of HBT was reducing in steps of 10°C to improve the thermal status of the stoves as the waste gas temperature at the end of the blast period was less than 300°C. Once a waste gas temperature of above 300°C was achieved at the end of the on blast period, gradually the HBT was increased in steps of 10°C.

Optimisation of blowing parameters Furnace RAFT was maintained at around 2050 ± 50oC in BF# 4. Adequate steam of 3-4 t/hr was added to maintain the desired RAFT with a HBT of 1000-1020°C along with oxygen enrichment of 60007000 Nm3/hr (3-4%), and CDI of 6-8 t/hr. Operating parameters of BF#4 are given in Table 3.

Bibliography 1) A K Biswas: Principles of Blast Furnace Iron making: Theory and Practice, Cootha publishing house, Brisbane, (1981). 2) CBR Applications in Combustion Control of Blast Furnace Stoves”, Proceedings of the International Multi Conference of Engineers and Computer Scientists 2008 Vol I IMECS 2008, 1921 March, 2008, Hong Kong by SUN Jinsheng, Member, IAENG 3) AM Dalley, “Failure Analysis of a Section of Bustle Pipe from the No. 13 Blast Furnace at Gary Works,” U. S. Steel Research Interorganisation Correspondence, November 6. 4) M L Wei, and T. E. James, “Design, Maintenance and Repair of Blast Furnace Bustle Pipes,” Iron and Steel Engineer, August 1981, pp. 51-59. 5) Investigation of Blast Furnace Bustle Pipe Failures and Repair by D. J. Radakovic and Y. Zhao, United States Steel Corporation Research & Technology Centre. 6) Blast temperature optimisation philosophy and practice by Yasushi Ishikawa, Shin Hashimoto and Hiromitsu Yoshimoto.

Conclusions The combined effect of various process optimisation measures – the installation of drip pots, optimisation of the air/ gas ratio in all the three stoves by flue gas analysis, maintaining a higher stove waste gas temperature leading to higher chimney draughts – have resulted in

Install drip pot in gas lines








960 940 HBToC

The installation of drip pots in the gas line of all three stoves was undertaken with significant effect on the dome temperature. Before drip pots were installed the gas was absorbing moisture from water present in the gas line. Drip pots have enabled continuous removal of water from the gas line leading to less moisture carry by the fuel gas.

improving the hot blast temperature from 920°C to about 1000°C during Nov-Dec 2012 and beyond (Figure 1).



921 908


Stove flue gas analysis


The Air-to-Gas ratio is equally important to achieve higher dome temperature for a given gas CV. Initially, the air-gas ratio of all three stoves was in the range of 0.951.0. The ratio was optimised at 0.80-0.85 with the help of a flue gas analyser on the basis of % CO and % O2 in the flue gas.

860 840

Base (Jul-Aug)



Nov Month




Figure 1. Hot blast temperature variation Jul 2012 to Feb 2013. *BF was under CR in Dec’12 for top repair and stabilisation in Jan’13


Furnaces International June 2018


Plibrico adds Upstate Refractory Services as newest partner Furthering its commitment to growth and providing value to customers, Plibrico is pleased to announce its new partnership with Upstate Refractory Services (URS), a company dedicated to providing customers with cost-effective solutions to refractory related problems in the New York Region.

Headquartered in Newark, NY, URS is a contractor, installer and distributor of refractory materials. URS will join Plibrico’s global network of refractory distribution specialists offering Plibrico branded high-quality refractories, along with turnkey installation, repair services. “It is exciting to welcome a distributor of the caliber of URS to our PliPartner network,” said Brad Taylor, President and CEO of Plibrico. “URS operates with the same high quality and safety standards that Plibrico embraces. I am confident that our new partnership will provide value to customers and expand Plibrico’s market position in the New York area.” In March of this year, URS acquired long-time PliPartner Hanyan-Higgins Company, Inc. Owners John Higgins and Dave Higgins, as well as the company’s core employees, have joined the URS team. The acquisition has elevated URS’s refractory knowledge - the management team now has more than 300 years of refractory industry experience, and provided it with a wider pool of technical expertise, experience and skill to assist its industrial, commercial and municipal

customers. “Since 2002, our customers have looked to us to provide them with solutions that include quality refractory materials from trusted suppliers to help with difficult problems,” said Dave Wetmore, URS President. “Plibrico materials will help provide value to our customers through improved refractory life, saved energy and reductions in installation time.” Wetmore went on to say, “Plibrico is an innovative, customer-driven and qualityfocused manufacturer with a long history of supporting its distributors with its PliPartner program. We’re looking forward to using our real-world experience and deep expertise in industrial furnaces and combustion solutions to help introduce the company’s outstanding refractory products to our customers.”

For more information on Plibrico products and services, visit To learn more about Upstate Refractory Services visit

20 Furnaces International June 2018


Can-Eng Furnaces selected for North American expansion Can-Eng Furnaces International Limited was recently awarded a contract from an India based conglomerate to design, manufacture, install, and commission an Aluminum Automotive Casting Heat Treatment system for their new green field North American expansion in South Carolina. Can-Eng was chosen for this project largely due to the unique Modular Design concept which offers efficient product, process, and production flexibility for our partners new line of Die Cast Light Weight

Aluminum Automotive Components. This Solution Treatment, Water Quench and Artificial Aging system are arranged to provide both T5, T6 and Homogenizing Processes. The new system will service three distinct aluminum product groups with unique treatment cycles. This new project is yet another modular system for Can-Eng, which have been a valuable offering to Can-Eng’s Partners since 2005. Most beneficial to users is the ability to plan, and scale their equipment capital

needs to their production capacity needs. Can-Eng Furnaces International is a global provider and leader of stateof-the-art thermal processing systems. Headquartered in Niagara Falls, ON, Canada, Can-Eng is an ISO 9001:2015 certified company.


Automatic Heat Treatment Line Profitherm P80, Austria, 2017

Laboratory furnaces 1100–1600°C

Chamber furnaces 600–1100°C

Industrial ovens 250-400°C

Heat treat furnace 1050°C with quenching tank Retort furnace 650°C with controlled atmosphere


Furnaces International June 2018

Future of furnaces

Future challenges and Sorg’s approach to environmental limits Dr Matthias Lindig* highlights some of the future challenges facing furnace makers and Sorg’s approach to forthcoming EU environmental legislation.

Beside statutory emission limits other tools have been introduced to encourage the industry to invest in new waste gas cleaning systems, the reuse of waste heat or in new processing from renewable energy sources. One of these tools is the so-called emission trading system (ETS), which is addressed to all European countries. It is a long term measure with different time intervals associated with intermediate goals. Every year we have to face about 1.9 billion tons of CO2 per year emissions or more correct CO2 equivalents (called EUA) EU-wide. Among the EU partners, Germany is the one with the highest share in emission. From 2005 to 2007 it was almost 500 million tons. During the so-called first and second trading period from 2005 to 2012 emission sources were allocated and the total amount of emissions was ‘capped’ i.e. limited EU-wide. Each country committed to continuously reduce these emissions. The first complimentary emission allowances were granted to the industry based on average values received during the allocation period. For the third trading period from 2013 to 2020 these complimentary allowances were cut annually by 1.74%. For all emissions exceeding this number of complimentary allowances company sites need to purchase allowances by auctions. What is the glass industry’s contribution to CO2 emissions and what

is it in comparison to the entire national emissions? Glass production emissions in Germany are about 0.9% of the total emissions. Two thirds are emitted by power plants. The entire industry and power plants are causing in total 45% of the national emissions in Germany. Over 50% is traffic and buildings’ heating (Literature - DEHSt Report 2015) (Figure 1). For the next trading period the policy is searching for new options to shorten

the available allowances in the market. An increase in an annual cut by more than 1.74%, maybe 2.2%, is very likely to be established. The excess number of available allowance will be withdrawn for a certain time period (backloading). In consequence the market price for the EUA will rise.

National emission limits and laws The overall mass of greenhouse gases (CO2 and equivalent gas species) will definitely

0,9 mineral industry

emissions % glass


emissions % other combustions


paper + pulp


non metal industry


chem. industry


iron + steel




power plants

73,3 0,0









Figure 1. Annual emissions in kT/year CO2 equivalent of all industrial fields in Germany 2015. Source: Emissionen in Zahlen, DEHSt Germany 2015

22 Furnaces International June 2018

Future of furnaces

be restricted in the near future. But the specific emissions, the concentration of flue gas species in particular, are restricted by law as well. In Germany the first technical instruction for emission reductions was established in 1974. The decree has undergone several updates with tighter emission limits. The emission limits are now harmonised EU-wide. The limitations are based on investigations of the so-called Best Available Technology (Literature - Industrial Emission Directive 2010/75 EU). As a consequence, there are two driving forces (the self-commitment and the legal emission limits) pushing the industry towards more efficiency and prevention of emissions. What are the expectations for the near future? A new draft of emission directive will come into force within a short time. The new emission limits for NOx concentration cannot be observed only with primary measures. Additional flue gas cleaning facilities will be necessary and raise the overall production costs for one ton of glass. New dust limitations might also require an exchange of the existing filter systems.

Figure 2. Endport furnace for container glass: 85m2, 250t/d, 65% cullet, heat balance (energy inlet 100%).

QF +94 QRL -7 Qflue gas -23

QL +47

QB +6

QC-7 QWall-21,5 Q F Q B Q C Q Glass Q Wall Ql Q Flue gas Q Reg. wall


Fuel Boosting Chem. heat demand Glass delivery Total wall losses Combustion air Waste gas behind regenerator Wall losses regenerator

Conclusions for the glass industry The European Countries have contracted in achieving a significant reduction of CO2 emission within the next decades. The German policy agreed on a CO2 reduction by 90% until 2050. As a consequence of this goal, an industrial production, which implies thermal processing steps in this country, will only be feasible in future by using either electric power or hydrogen - also generated by electric power. A number of projects have been established by the government but also industrial associations are promoting and supporting technical solutions and striving to achieve these ambitious goals. The SORG company was invited to some of these activities and has given technical support. Sorg has offered solutions applicable for the near future demands as well as solutions for the distant future. Before explaining these solutions it might be necessary to illustrate the present glass furnace performances and pinpoint opportunities of improvement without significant changes in processing.

Glass melting furnaces today Today’s furnaces are strongly insulated. The outside wall has less than 150°C. Nevertheless, there are still sections which need to be free from insulation

like metal lines or scewbacks. This minor share, about 10% of the total wall surface, contributes to more than 30% of the entire furnace heat loss. Minor improvements might be still possible and it is a matter of reconsideration during each present furnace project (Figure 2). Other drawbacks in efficiency are leakages and trapped false air. An open doghouse or open joints might cause about 3% of the entire energy used for melting. A sealed doghouse, sensitive furnace pressure control, continuous inspection and hot sealing could help to reduce these heat losses. With the EME-NEND batch charger and the IRD Doghouse, Sorg supplies a completely sealed charging area for the furnace. After furnace heat-up, a ceramic welding and sealing to close joints between the side wall and crown from outside might be highly recommended (cold face welding). Hot face welding to close joints with lances from inside the furnace is also a proven technology. By now, this technology is state-of-the-art and successfully carried out by the Sorg subsidiary Fuse Tech. The implementation of additional sensors for CO2 measurement or gas quality is required when the combustion efficiency needs more control. More

unpredictable gas quality and variations in the public net are caused by feeding low LCV bio gases and hydrogen. Sorg has developed a control loop using natural gas analyses, calorific value and air demand calculation. With this loop system the total energy input into the furnace will be kept constant. It is a pre-set control system and not a re-adjustment. In conclusion all of these issues are relevant for energy savings and minor CO2- emission reductions.

Sorg approach - facts Looking at CO2 reduction one may not forget all the operation parameters influencing the energy consumption. The replacement of natural gas input by electric heating is a large contribution to CO2-reduction. Looking at the public traffic, the conversion to electric power is a measure without any alternatives. This is justified by the increasing share of electric power generated with renewable sources. In Germany 2014 more than 25% of the total power was generated using renewable sources and with a progressive trend. In case of glass melting furnaces the use of about 15% electric power instead of fuel can save more than 15% of CO2 in


Furnaces International June 2018

Future of furnaces

modeling calculations. A large number of end-fired furnaces built by Sorg are already equipped with an enlarged doghouse proving the feasibility and the advantage of such a concept. The risk of further increase of this charging section is controllable (Figure 6). It seems to be inevitable that electrically boosted or all-electric glass melting furnaces will be the most suitable technology in future. On the other hand it is unlikely that large end-fired furnaces will be replaced by all-electric melters. The limitation in capacity of those furnaces is well known. In the past, Sorg has built all-electric melters with capacities up to 180t/d for container glass and up to 250t/d for C-glass. The limitation in capacity is accounted for the cold top and vertically orientated melting processing. The batch has to insulate the melt surface. The melting of the batch layer is only from underneath with no support from top with fossil firing. Due to this the specific pull is limited up to about 2.5 to 3.0t/m2/d depending on glass type. The critical path proceeds directly from top batch layer down to the throat. The fining, blister release has to be performed just below batch in the hottest section. The minimum residence time depends strongly on the basin depth. Melting larger quantities all-electrically requires substantial changes in the furnace design. Since the official schedules for emission limitation are almost for the long term, it might be a feasible solution to perform





100 0,00






Boosting of total energy input in %

Figure 3. 90m2 endport furnace with 60% cullet – CO2 emissions versus boosting share.

the flue gas. The use of boosting is directly correlated to the CO2-emissions (Figure 3). The energy input and CO2 emissions can be reduced by using recycled cullet. An increase in the use of recycled cullet by 20% equates to more than 5% CO2 reduction (Figure 4). Also a pull increase, increase of pull compared to melting area, results in a specific decrease in CO2 emissions. The higher the pull, the lower are the emissions related to one ton of produced glass. An increase in melting performance together with the reuse of flue gas heat for batch preheating can result in more than 20% of CO2 reduction (related to the ton of produced glass) (Figure 5).

In conclusion a new furnace concept is required for flexible boosting and high specific pull. Sorg has made a proposal based on the well-known end-fired furnace concept. The charging section should be enlarged and equipped with boosting. In this section a pre-melting of the batch will be performed. The high crown in this section allows radiation heat transfer with the batch surface. The melter itself needs special features to control the flow pattern regardless of the heat flow ratio from inside the melt with boosting or from the combustion space. The feasibility of the concept is proven by


Sorg approach - concept



300 CO2 batch


250 Total CO2 emissions in kg/t glass

In summary there are still various measures available to improve the emissions of existing furnaces. The next cold repair of a furnace would allow for the implementation of new design features to increase specific pull, apply flue gas reuse and batch preheating as well as implement more capacity for electric boosting. The increase in use of renewable sources for electric power generation also implies changes in availability or temporary shortage in supply which has to be balanced EU-wide with neighbouring countries. Consumers will be asked in the near future to be more flexible in using the various heat sources. Melting furnaces should run with more or less electric boosting depending on short term changes in availability in the public power net.


25,0 200 20,0 150 15,0 100

CO2 batch/(batah + combustion)

CO2 emissions in kg/t glass


10,0 50



0,0 30





Cullet content in %

Figure 4. 90m2 endport furnace with 260 t/d pull – CO2 emissions versus cullet share

24 Furnaces International June 2018

Future of furnaces


4,00 CO2


Spec. energy


3,90 3,80







180 3,40


Specific energy in Gj/t glass


Total CO2 emissions in kg/t glass

the change from fossil to all-electric or highly boosted in several steps. The next CO2 trading period starts from 2020. The runtime might last for about eight years. The costs for emission allowances will definitely rise. The complementary allowances will drop for each manufacturer. Sorg has calculated the benefit of one production line of a three lines fossil-fired furnace to all-electric. From the technological point of view this change does not imply any risk. The use of electric power instead of fossil fuel needs to be mirrored with increasing costs for emission allowances. An increase in costs for 1EUA up to â‚Ź40 justifies the decision in running on line all-electric. The CO2 emission of the fossil-fired furnace with reduced pull is reduced and does not require emission purchases. In a calculation example a 100m2 furnace for 280t/d pull with three production lines is used. One of the lines, preferentially the one with long run production items, is converted to an allelectric melter with one line. The fossil




150 2,5




Specific pull in t/m2*d

Figure 5. 70m2 endport furnace with 60% cullet – pull increase versus spec. CO2 emissions and specific energy consumption.

Figure 6. Sorg’s end-fired furnace with an enlarged pre-melting system EPMS.


Furnaces International June 2018

Future of furnaces

Endport furnace with 3 lines pull 280 tpd and cullet content 75% CO2 from combustion 5130 t/a Difference in CO2 emission Cost of 1 EUA Cost of allowances

1476t/a 9,37€ 13.746€/a

Endport furnace with 2 lines pull 200 tpd All electric furnace with 1 line pull 80 tpd and cullet content 75% CO2 from combustion 3663 t/a

Figure 7. Calculation example for one line conveted to all electric heating – Impact on CO2 emissions and in case for purchasing EUA allowances.

fired furnace continues with reduced capacity. The savings in CO2- emission equates to almost 28% of the previous emissions (Figure 7). The emission savings might be in the range of what manufacturers can anticipate looking the requested overall reduction rate during the next CO2 trading period. The decision is based on proven technology and without any risk. A stepwise change in melting technology might be the most appropriate approach. As mentioned above increasing demand in flexibility raises expectations to operate a furnace within a large range of boosting between 10 and 90%. Sorg has done extensive studies to investigate the thermal conditions and melting conditions resulting from these very diverging boundaries. The crown temperature might vary in a range of 200°C. The glass temperature charge end might change by more than 100°C. For those changes in temperature, a suitable refractory still needs to be invented. For today’s refractory availability, boosting rate changes between 10 to 35% might be feasible. Semi-cold top melters would allow running between 70 to 90% boosting

rate. For these operation conditions the melter design needs changes to ensure suitable fining conditions as already mentioned above. Various solutions have been considered and published in the path. In practice only a few have been realised, mostly for smaller capacities and for special coloured glasses. Today, the mathematical simulation allows investigating the melting, fining and refining conditions in detail. The former furnace solutions for all-electric melters are based on the model of large cross-fired furnaces, which were recalculated and severe disadvantages in fining performance were identified. Completely new approaches in design features inside the basin are required. Sorg is presently developing a large all-electric melter using mathematical modeling. One of the key criteria for evaluation is the bubble tracing. Typically about 12,000 blisters with 0.1mm in diameter and with typical gas content are placed under the batch layer in the charge end of the model. Experimental growth functions are derived from laboratory tests. The path, growth and release at the surface or in the glass exit flow is calculated

and compared with similar gas-air-fired furnaces well-known regarding their fining performance. It will depend on several criteria in the future whether we need this kind of special melting furnace solution. Availability of electric power, cost conditions, and cost increase for emission allowances might have a strong influence in the decision making.

Summary The obvious changes in climate and the impact on environment need a response from the energy - intensive industry. Climate and resources are compulsory reasons for inventing new ways of production with less greenhouse gas emissions. Sorg is trying to find new approaches with increase in productivity and in substitution of fuel by electric power. New furnace concepts are required and Sorg is preparing solutions for larger furnaces for containers but also for float furnaces using high fraction of electric power.

*Research and Development Manager, SORG, Lohr am Main, Germany.

26 Furnaces International June 2018

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, Tomorrow s Technology Today

The structure for glass is as simple as the structure for success...


...the only electric glass melting company which can supply all of your needs l All-electric furnaces l Electric boosting

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A Division of Glass Service

Future of furnaces

What is the future of furnaces? Tough new environmental legislation will be implemented in the next few years by policymakers, which will impact the number of emissions glassmakers can produce during the manufacturing process. Over the next few pages furnace makers give their views on what the future holds for them and describe the actions they are taking to meet environmental objectives.

28 Furnaces International June 2018

Future of furnaces

Stuart Hakes, Chief Executive, FIC (UK) 1. What is your company’s involvement in the furnace industry for glassmaking? We are a major supplier of equipment to all types of glassmaking furnaces. As well as the design and build of all-electric furnaces we also supply various other electrical heating solutions to improve productivity and/or glass quality. These solutions include electric boosting, electric forehearths and isothermal units to eliminate top to bottom and side to middle temperature differences in forehearths. We also supply water-cooled bubbler systems that eliminate erosion of the refractory floor. We have a range of unique electrode holders and supply both molybdenum and tin oxide electrodes. 2. In your opinion, is the glass furnaces sector evolving quickly enough with new ideas to address the new wave of environmental thinking and meet the Paris climate agreement? And can you indicate what your company has done to address this? The glass furnace sector has been too slow to wake up to the ramifications of the Paris climate agreement. We have been pushing energy substitution for some years now and the idea of super-boosting to reduce both carbon dioxide and NOx. We have developed proposals for large scale all-electric furnaces in the range of 250 – 600 tonnes per day.

4. How do you foresee furnaces evolving over the next say, five to 10 years? The glass industry will try and take small steps but in reality these steps will be bigger than they realise. New control systems that optimise reduced emissions based on low carbon fuels including renewable electricity, oxy and syngas will become standard and super-boosting will be introduced.

6. What will the furnace of the future look like? Will it be run entirely on renewable fuels or a hybrid of energy sources? Future furnaces will have a smaller footprint and run entirely on low carbon renewable fuels. These furnaces will be hybrid furnaces switching between various fuels based upon optimal cost.

5. Do you think it possible furnaces will have shorter lifetimes in future? Or can you see their lifetimes increasing? Furnace life will become shorter enabling more cost effective options to be considered.

FIC UK, Penzance, UK.

3. What are the technological challenges facing the furnaces sector in terms of meeting environmental legislation? Is the legislation realistic? The technological challenges require a paradigm shift. This means that decision makers have to move out of their comfort zone and accept radical solutions are required to meet the emissions objectives. The legislation is nothing short of ambitious and will involve huge investments, but if there is a will then there is a way of achieving these objectives.


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Future of furnaces

Richard Stormont, Managing Director, Electrogla 1. What is your company’s involvement in the furnace industry for glassmaking? Electroglass develops, designs and supplies electric glass melting and conditioning systems for glassmakers worldwide. Over its 42-year history the company has supplied continuous all-electric furnaces ranging from less than one tonne/day to 250 tonnes/ day capacity, producing glass for containers, tableware, lighting, fibre, insulation glass wool, pharmaceutical and special technical glass products. The company also designs and supplies electric boosting systems for fuel-fired furnaces to increase furnace output and glass quality and to reduce overall energy consumption and emissions per tonne of glass produced. 2. Is the glass furnaces sector evolving quickly enough with new ideas to address the new wave of environmental thinking and meet climate legislation? Glassmaking is an energy-intensive process and conventional fuel-fired furnaces are both of limited energy efficiency and generate significant emissions from the combustion process, making them prime targets for environmental concerns. There have been and will no doubt continue to be incremental improvements in the energy efficiency of fuel-fired furnaces and in technologies and equipment for the reduction or ‘capture’ of harmful emissions, but much more than this is needed to meet some of the targets being set and the expectations of all concerned for our environment. Our focus has always been on energy efficiency and minimising or eliminating harmful emissions in the glassmaking process, both achieved through the development of so-called cold-top all-electric melting and immersed electrode boosting for fuelfired furnaces.

3. What are the technological challenges facing the furnaces sector in terms of meeting environmental legislation? Is the legislation realistic? Although very many furnaces incorporate electric boosting systems, by far the greatest proportion of glass being made today is produced using fossil fuel energy. Few purely fuel-fired glass furnaces reach or exceed thermal efficiencies of 40% to 45%, and then typically only in the largest of container glass furnaces and only when operating at full design output. The large majority of fuel-fired glass furnaces are significantly less efficient than this, especially smaller capacity units and those melting more difficult glass types. Low thermal efficiency means not only higher costs but also greater levels of emissions for each tonne of glass produced. It is difficult to see where the step changes needed to meet today’s targets can come from without much greater adoption of alternative and fundamentally more efficient technologies, either replacing fuel-fired melting or at least in the form of hybrid melters with a heavy reliance on highly efficient electric melting technologies. 4. How do you foresee furnaces evolving in the next few years? Electricity needs to be generated. While the use of renewable energy sources in the electricity generation is of course increasing rapidly, fossil-fuel-fired (oil, gas or coal) power stations still provide the majority in most regions. These also have a level of inefficiency, but firstly the thermal efficiency of an average fuel-fired power station is significantly higher that an average fuel-fired glass furnace, and secondly emissions arising in a small number of power stations are both far easier and far cheaper to deal with than those emissions transferred to a large number of glass furnaces. A well-designed all-electric furnace of

over say 100 tonnes/day capacity can have a thermal efficiency of 80% to 85% and produces no combustion emissions. Even a small furnace of say 10 tonnes/day can have an efficiency of 70%. On this basis all-electric melting is an obvious candidate for environmentally friendly glass making. There is to date limited experience in all-electric furnaces of the size of today’s larger capacity container glass furnaces for instance. However one of the main reasons for size in this context is the better fuel efficiency of larger furnaces. In all-electric furnaces, the difference in the energy consumption of say two furnaces of 150 tonnes/day and one furnace of 300 tonnes/day will be very small. In other words there is not necessarily a significant energy cost penalty in a greater number of smaller capacity units. The interim position is increased use of ‘hybrid’ melters, essentially fuel-fired with high levels of electric boosting, accounting for perhaps 50% of the furnace’s output. The technology is well proven, and capital cost, overall energy consumption and emissions per tonne of glass produced are all greatly reduced. 5. Do you think furnaces will have shorter lifetimes? In our field of electric furnaces, we continue to lengthen furnace lifetimes, through ever better understanding of energy, temperature distributions, the resulting convection currents, glass flow and refractory wear patterns. 6. What will the furnace of the future look like? Will it be run entirely on renewable fuels or a hybrid of energy sources? It will be a long time before fuelfired furnaces are replaced, but everincreasing renewable energy sources for the electricity generation will, I believe, continue the movement to heavily boosted fuel-fired furnaces and for many industry sectors, the most environmentally friendly solution of allelectric melting.

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Future of furnaces

ass, UK

Electroglass Ltd, Benfleet, UK


Furnaces International June 2018

Future of furnaces

Andy Reynolds, Business Development Director 1. What is your company’s involvement in the furnace industry for glassmaking? Fives (Glass) supplies melting furnaces, conditioning systems and associated ancillary equipment, for all types of glass manufacture. Fives Stein Limited (FSL) in the UK, serves the non-float sector (the float sector being served by Fives Stein SA in France). In respect to melting technology, FSL specialises in electric melting, oxy-fuel and hybrid furnaces; consequently, most of our business at present is in the pharmaceutical, cosmetic, technical and fibre markets rather than container production (where FSL involvement is focused on working ends and conditioning forehearhs).

2. In your opinion, is the glass furnaces sector evolving quickly enough with new ideas to address the new wave of environmental thinking and meet the Paris climate agreement? And can you indicate what your company has done to address this? Converging forces have, I believe, triggered the ‘wake-up’ call for what is a technically conservative industry. Even without the pending legislation on emissions, the fact is that the availability of conventionally extracted fossil-fuels will decline within 30 years – that’s

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r, Fives Stein, UK less than two furnace campaigns in the container or float sector. We already see larger players in container production investigating ‘new’ technologies with the aim of reducing or eliminating dependence on gas. The next two to three years will show us if these thoughts translate into positive steps. Producers will not move without being pushed – technical ‘quantum leaps’ are not in this industry’s nature. Fives is already investing in programmes to assess how electric melting and hybrid technologies can be extended further into the higher-volume (lower-value) product sectors of container, float and reinforcement fibre. Some of this work is done in partnership with furnace users; one of the key objectives being how to reduce risks when ‘up scaling’ technologies only well proven at smaller furnace capacities.

3. What are the technological challenges facing the furnaces sector in terms of meeting environmental legislation? Is the legislation realistic? Environmental objectives will only be achieved by a move away from fossil-fuel technology; we should not underestimate the challenge, considering that much of the focus in recent years has been at honing the same technologies to what are now impressive levels of performance across all criteria. Legislation that is both ambitious and binding must be enforced through the economics of cost – we have no choice if we wish to avert global warming. 4. How do you foresee furnaces evolving over the next say, five to 10 years? The use of higher electrical boosting levels (super-boosting) will be the first step to reduce emissions and in such cases furnace design will not change so much. The step-change will be to allelectric melting and we see at least one big container player taking this step very soon. Furnaces will be cold-top vertical melting as used already in higher value glass production such a cosmetics and pharmaceutical.

5. Do you think it possible furnaces will have shorter lifetimes in future? Or can you see their lifetimes increasing? Investment in furnaces with very long campaigns (15-20 years) really makes little sense now (certainly in Europe at least). Short campaigns give more opportunities to adapt and evolve – from all aspects including capacity and technology. Shorter campaigns work if rebuild times and costs are also significantly reduced – as is the case with all-electric systems. At FSL we also promote consideration of ‘modular’ melting units, where individual parts of the system can be rebuilt while production continues. 6 What will the furnace of the future look like? Will it be run entirely on renewable fuels or a hybrid of energy sources? At FSL we believe it is inevitable that in the future all glass furnaces will be fully electric. As the contribution of renewal electricity increases, countries where it is still environmentally preferable to burn fossil-fuel directly in furnace rather than in a power station will diminish. If electricity is generated ‘cleanly’ and costs become favourable, then there is simply no technical argument for thermal intensive industries such as glass melting not to use it. In the short to mid-term, the legislation will impact heavily on the capex and opex for fuelfired furnaces; electric boosting reduces the problem but does not eliminate it – the future is therefore electric.

Fives Stein, Didcot, UK


Furnaces International June 2018


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Furnaces International June 2018  
Furnaces International June 2018