Originally published in

ALUMINIUM • 1-2/2018, pages 24-28

Successful revamp of Anode Baking Furnace No. 3

at Aluminium Bahrain

“Everyone involved in the revamp

did a splendid job”

Volume 94 · January / February 2018International Journal for Industry, Research and Application 1/2

© E

GA

� ALUMINIUM · 1-2/2018

A L U M I N I U M S M E L T I N G I N D U S T R Y

� ALUMINIUM · 1-2/2018 ALUMINIUM · 1-2/2018 �

S P E C I A L

Successful revamp of Anode Baking Furnace No. 3 at Aluminium Bahrain

“Everyone involved in the revamp did a splendid job”Beginning of 2016, as part of a compre-hensive modernization project Riedham-mer GmbH in Nuremberg, Germany, reconstructed the Anode Baking Furnace No. 3 at Aluminium Bahrain (Alba). The reconstruction took place between March and June, in only 100 days, which for an anode furnace with 68 sections was a very demanding task. In a talk with this journal Thomas Janousch, head of the Carbon business at Riedhammer, explains the jobs and challenges entailed in order to implement this turnkey project, which included engineering, delivery of materi-

als, the execution of the construction work, the adaptation of the existing firing system and the supervision of construc-tion including HSE management proce-dures.

After an operating life of around 25 years the anode baking furnace ABF #3 had definitely reached the end of its useful life. It is true that the refractory material and the flue walls had been replaced at regular intervals, “but with this kind of continual partial renewal, after a few years a furnace will operate in a sub-op-timal condition,” explains Janousch. Among

other things this becomes evident in that the quality of the anodes deteriorates, the reject rate increases, and in addition the energy con-sumption no longer comes up to technologi-cally feasible standards.

The decision to demolish the furnace lin-ing completely and rebuild it anew was also motivated by the fact that Alba needs larger anode dimensions, and the height and width of the pits therefore had to be changed. A par-ticular challenge was that the reconstruction had to be carried out during on-going produc-tion, so as to have to buy in as few anodes as possible during the 100-day time window involved.

The height of the anode furnace was in-creased by 500 mm and the pits were made wider. Since the furnace tub and the number of seven pits per section had to remain the same, a modified sidewall had to be built in and the flue walls adapted accordingly. The firing system, especially the exhaust and cool-ing ramps, also had to be adapted to the new dimensions.

Besides these ‘external’ features, it was mainly necessary to considerably improve the conditions inside the anode furnace, namely the flow and pressure situation in the flue walls, since if the oxygen content of the flue gas is insufficient combustion can no longer take place cleanly, and because of that tar deposits can be produced in the flue gas ring main. Owing to the entry of false air due to leaks in the refractory material, a larger vol-ume has to be heated and this in turn increases the energy consumption. Overall, no optimum operation can then be ensured, the anode quality deteriorates and rejects are more fre-quent: in short, the performance of the plant as a whole was, and would remain in such a case, unsatisfactory.

Boost in production output, better anode quality and lower energy consumption

The diagram illustrates the fact that by re-constructing the furnace the flow situation in the flue walls was optimized for the new flue wall (on the right). By means of CFD (Com-putational Fluid Dynamics) the optimum flow conditions were simulated and calculated “and measurements have shown that the cal-culated values can be attained very accurately in practice,” says Janousch. On the left of the diagram (the old flue wall) the red areas indi-

Demolition of the old ABF #3

© R

iedh

amm

er

A particular challenge was the reconstruction during on-going production

� ALUMINIUM · 1-2/2018� ALUMINIUM · 1-2/2018 ALUMINIUM · 1-2/2018 �

S P E C I A L A L U M I N I U M S M E L T I N G I N D U S T R Y

cate that the flow velocity of the flue gases is almost zero at a number of points. From this it can be concluded that the heat distribution is clearly less uniform. With the new flue wall the flow distribution and consequently the temperature distribution as well are substan-tially more uniform, with a positive effect on the quality of the baked anodes.

“For optimum operation of an anode bak-ing furnace and for good anode quality, there must be as uniform a distribution of flue gases as possible. Accordingly it is advantageous to demolish the flue walls and partially also the headwalls after an operating period of around eight years or some 200 firing cycles, instead of renewing the flue walls continually. Mean-while, this philosophy of complete renovation has proved its worth in numerous projects,” explains Janousch. “By virtue of such a gen-eral renovation, including optimization, the furnace can now be operated more quickly, meaning that the firing times and firing cy-cles are made shorter, which in this case has brought about a production boost of around 25 percent and energy savings of at least ten percent. In addition the furnace now provides a homogeneous process with consistent anode quality, a low reject rate and generally better working conditions for the furnace operating personnel,” he summarizes.

As was shown by a performance test after commissioning, the modernized anode fur-nace now has a projected performance rating of 211,360 tonnes per year, with energy con-sumption less than 1.8 gigajoules per tonne of baked anode. The effective temperature difference of the baked anodes in the pit is ± 15 °C within a window between 1 100 °C minimum and 1 130 °C maximum.

In reply to a question Janousch explains the Riedhammer concept of furnace reno-vation as follows: “In accordance with our philosophy an anode furnace should be op-erated without part-modernizations until the wear-related end of its useful life (the life cycle of its refractories, particularly the flue walls) has been reached after around eight years of operation or 180 to 200 firing cycles. During that period the furnace can be oper-ated with relatively little maintenance work.

After this a major reconstruction takes place, in which after the first life cycle all the flue walls and after a further life cycle all the headwalls as well are replaced. In contrast, if one replaces the furnace walls continually this has to begin after only the fourth year so that by the eighth year almost all the flue walls have been replaced. But after that the replacement cycles become progressively shorter because the prefabricated flue walls

used no longer last as long. Over a period of 25 years or around three life cycles this en-tails replacing more flue walls and thus using substantially more refractory material than with two complete renovations in accordance with the Riedhammer concept. Furthermore, the continual replacement of the flue walls creates additional problems for the operation since the old and new walls have different process-technological properties in a section. Another advantage of our concept is that with-

together as possible, so as to dismantle and then rebuild the furnace over an area of 22 sections,” explains Janousch. For the rebuild-ing of the first section Riedhammer had a time allowance of around 28 days. After that, one new section had to be handed over each day, since the fire moves after 28 to 30 hours and comes close to the demolition and building work. Accordingly a detailed plan for the rebuilding was worked out, with an exact timetable and data for which day and

Velocity profile of the existing (left) and new flue wall (right)

Fire direction>

The new ABF #3 will produce around 210,000 tonnes of anodes per year

in certain limits the geometry of the furnace can be changed if the customer wants differ-ent anode dimensions. And in that way we can incorporate newly gained knowledge into the furnace design.”

�.� million bricks used

A complete renovation as for ABF #3 has to be planned in great detail. “We only removed one fire and brought the other three as close

in which position the fires should be in place. The reconstruction of the four fires also has to be planned in detail, since the old ramps no longer matched the new dimensions. As Janousch stressed, the planning was carried out on a 1:1 basis. “Everyone involved in the reconstruction, including the customer, did a splendid job,” he emphasized.

For the reconstruction outlined 3.2 mil-lion bricks were used, this corresponding to a weight of 15,200 tonnes. 350 people worked

� ALUMINIUM · 1-2/2018

A L U M I N I U M S M E L T I N G I N D U S T R Y

Alba to entrust Riedhammer again with the new building of a further anode baking fur-nace for the Potline 6 currently under con-struction. This turnkey order is the largest furnace project in the company’s history since the building of an anode baking furnace for KAS (Kazakhstan Aluminium Smelter) in 2011. The new furnace for Alba will consist of 68 sections each with eight pits, which will be deeper, wider and longer than in the ABF #3. For this new anode furnace Riedhammer will supply the refractory material (at around 26,500 tonnes, about twice as much as for the ABF #3), it will be responsible for the brick lining, it will supply the firing system and is also responsible for the supply lines and the electric equipment in the production hall. The new furnace will produce approximately 305,000 tonnes of anodes per year and will enable the production of 514,000 tonnes of primary aluminium for Potline 6.

“There’s always something to do in the repair field”

Asked about his expectations about the gener- al development of orders, Janousch expressed confidence that Riedhammer would have plenty of work in the coming years. He does not expect a marked boom of new smelter construction with new carbon plants. How-ever: “In the field of repair there is always something to do – modernizations, recon-structions and optimizations of existing anode furnaces, as well as working out systems for larger anodes or faster cycle times. In this field we think we are well placed. And wherever the opportunity arises, we want to strengthen our image as a supplier for turn-key projects, since we offer customers a full service and thereby make it easier for them to concentrate on their core business. Our core competence is refractory design, refrac-tory materials, refractory linings, renova-tion strategies and the firing system (process know-how). That is an interlocked package which determines the performance of a plant and that best comes from one source if pos-sible, to avoid interface problems. With the ABF #3 project for Alba we have shown that Riedhammer can implement a complex reno-vation in a very limited time-frame without problems. And with the new-build of an an- ode furnace for Alba’s Potline 6, we will suc-cessfully be implementing one of the largest turnkey project in our company’s history.”

on the project – in two shifts, day and night for six days a week. In total, 325,000 work- ing hours were spent.

And as mentioned, all this during on-go-ing operation with three fires running. The demands on the safety and co-ordination of the work had to be correspondingly strict. The aim was Zero Lost Time Injuries, and this was achieved in every respect thanks to our own installed safety management, permanent- ly in charge of staff’s instruction and control of the HSE orders, in close collaboration with the safety team of the client. Apart from two minor first-aid incidents, there were no ac-

cidents, serious injuries or other damage on site.

With this project Riedhammer once again demonstrated that the company has the exper-tise to reconstruct an anode baking furnace on a turnkey basis, even during on-going opera-tion, which spared the customer from having to buy in several ten thousand tonnes of an-odes.

“A very important factor for the success-ful implementation of such a project is that the co-operation between all those involved should function frictionlessly, with the correct resources for the project and competent con-tact partners on the customer side. Suppliers and local partners must be carefully chosen and there should be clear areas of responsi-bility. And of course, the engineering has to be first-rate. All this happened in an optimum way during this project,” says Janousch.

The exemplary project implementation was certainly a decisive factor that motivated

Alba ABF #3

Pit usage [%] 67.3

Production factor [kg/h/pit] 800

Production per fire [t/a] > 50,000

Anodes per pit [t/pit] 19.5

Pits per section 7

Energy consumption [GJ/tba] < 1.8

Open top anode baking furnace technology – Riedhammer references since 2014Project Location Year Type Sections

Dubal ABF 3 Dubai, UAE 2014 Revamping 32

Trimet St.-Jean-de-Maurienne, France 2014 Cross-over revamping n/a

Dubal ABF 1 Dubai, UAE 2015 Revamping 32

Dubal ABF 2 Dubai, UAE 2015 Height increase 32

Emal Phase 1 Al Taweelah, UAE 2015 Height increase 2 x 64

Alba ABF 3 Askar, Bahrain 2015 Revamping 68

Sual (Rusal) Volgograd Russia 2016 New construction 52

Rusal ABF 1 Taishet, Russia 2016 Height increase 64

Alba Potline 6 Askar, Bahrain 2016 New construction 68

Hindalco ABF 5 Renukoot, India 2017 Revamping 32

“Everyone involved in the reconstruction, including the customer, did a splendid job,” Janousch emphasized.

Riedhammer GmbH Industrie-Ofenanlagen, Klingenhofstr. 72, D-90411 Nürnberg

Tel: +49 (0)911 52 18-0, Fax: +49 (0)911) 52 18-231, Email: mail@riedhammer.de, www.riedhammer.de

■