Earlier today, KrAZ commissioned a new gas treatment plant, the 23rd in succession, which marked the completion of the environmental modernisation programme launched in 2004. The aims of ‘Clean Soederberg’ – a modernisation programme developed by RUSAL’s Engineering and Technology Centre - were to reduce environmental impact and improve efficiency of the smelting facility. As part of the programme, KrAZ equipped its potrooms with automatic alumina feeding systems, installed new gas treatment equipment, converted to dry anodes, and raised amperage in its potrooms.

The programme, a RUSAL proprietary solution, helps Soederberg smelting facilities, built several decades ago, to improve their environmental performance to an acceptable level and stay environmentally competitive with pre-baked anode smelters. For example, the modernisation programme resulted in a reduction of KrAZ’s emissions per tonne of aluminium output, including a 1.5-fold reduction in HF, a 2.7-fold reduction in tar, and a 2.5-fold reduction in benz(alpha)pyrene.

‘We believe in the great potential of Soederberg pots, which represent over 60% of global aluminium production.’ said Victor Mann, Technology Development Director at RUSAL. ‘This Clean Soederberg project of unprecedented size and results has given a second life to KrAZ. Certain emissions are now almost three times lower than before the project was commenced. We see our biggest challenge as being to apply this experience at RUSAL’s other Soederberg plants and to secure global leadership in the highest international environmental standards.’

About the modernisation of KrAZ (2004-2009):

Dry anodes
During 2008, the smelter converted all its pots (8 potlines) to ‘dry’ anodes as part of the modernisation programme. This leading-edge technology contributed to a reduction in tar and benz(alpha)pyrene emissions and an improvement in the working conditions in the potrooms. The economic effect was brought about by a major decrease in raw material and electricity consumption.

Dry gas scrubbing system
Another major part of the modernisation programme was the construction of new dry gas scrubbers. The new installations, manufactured by Alstom, employ dry scrubbing of gases, the most effective process according to international experts. Following the commissioning of the scrubbing system, the smelter saw a notable increase in tar collection – from 58% to 99% in HF collection – to 99.6%. KrAZ operates a total of 23 gas treatment plants that use dry scrubbing as an additional phase of the gas treatment process.

Automatic alumina feeding system
In August 2004 the Krasnoyarsk aluminium smelter began to build automatic alumina feeding systems in its potrooms. The work was finished in 2008 by which time all the pots of the 21 potrooms had been equipped with automatic feeding.

The new system follows a chosen algorithm and feeds alumina automatically into the pots through small openings. It improves the production environment, lowers demand for crust breaking and feeding vehicles, and reduces the risk of shop-floor injuries. With the new system, the smelter was able to reduce harmful emissions per tonne of aluminium output, the most impressive result so far. HF was reduced by 10%, tar and benz(alpha)pyrene – by 30%. Pots equipped with the new feeding system have a reduced the frequency of anode effects, resulting in significantly lower per-fluorocarbon emissions (greenhouse gases).

Industrial and storm water post-treatment plant
At the end of 2008, KrAZ completed the construction of an industrial and storm water post-treatment plant. From 2004 the smelter was improving its water circulation system and creating an industrial and storm water treatment system. Completion of the wastewater post-treatment plant marked the end of the five-year modernisation of the smelter’s water circulation system. Because of the new system the water released from the treatment system will meet any legal sanitary requirements. The smelter will also be able to use more reclaimed water and, consequently, less fresh water from the Yenisei River. Over RUB 102 mln was invested in the new system.

About UC RUSAL

RUSAL (www.rusal.com) is the global leader in the aluminium industry and accounts for approximately 12% and 15% of the global production of aluminium and alumina respectively. RUSAL sells its products in 70 countries worldwide and employs 90,000 people in 19 countries across five continents.

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