Hazardous aluminium waste can be converted into fuel-grade carbon

Nagpur-based JNARDDC develops detoxifying process that destroys 98 per cent of cyanide from the aluminium waste and converts it into Carbon that can be used in place of coal.

Dealing with hazardous waste, especially destroying cyanide contents from Spent Pot Lining (SPL), was a cause of concern for aluminium industry in the country. Nagpur-based Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC) has developed a revolutionary detoxifying process to deal with cyanide contents from SPL and convert it into Carbon of the grade which can be used in place of coal.

“Aluminium industry of the country produces about 50,000 tonnes of SPL every year which contains 90 per cent of poisonous cyanide and remaining are valuable materials such as high fuel value carbon,” Dr Upendra Singh, Scientist, JNARDDC, told ‘The Hitavada’. Calorific Value (CV) of this carbon is more than 6000 KCal/KG which is as good as Grade-A coal that can be put to domestic use also. In fact, an Odisha-based company is going to establish a plant that will commercialise and convert SPL into energy source.

JNARDDC developed the process in collaboration with National Aluminium Company Limited (NALCO).

SPL is the largest solid waste generated in aluminium smelter. It is categorised as hazardous waste due to cyanide contents. Along with cyanide, SPL also contains carbon that can be utilised in place of coal as fuel. SPL arises during production of metallic aluminium after a complicated series of industrial processes. It is a contaminated graphite or ceramics cell lining waste, which is obtained from production of primary aluminium. Bauxite, a common aluminium ore is used as alumina source and it is the feedstock for smelting operation, such as aluminium metal production, where alumina is fluxed/dissolved with cryolite in large carbon or graphite lined steel electrolytic cells known as ‘pots’.

According to Dr Singh, “It is estimated that generation of SPL is in the range of 3-5 per cent of aluminium production in the country. The process we developed is helpful in destroying cyanide contents in SPL upto 98 per cent without burning of carbon.”

Since the Environmental Protection Agency (EPA) guidelines restrict total cyanide contents for land disposal, containment and safe disposal of SPL becomes a matter of great concern to aluminium industry. In most of the countries, disposal of SPL in land-fillings is banned. But, this process will provide a big relief to aluminium industry and also provides a fuel option. The developed process has been filed for obtaining patents, Dr Singh added.

The process developed by JNARDDC and NALCO is approved by Central Pollution Control Board, New Delhi for its commercialisation. The research and development project work has been done by M T Nimje, Senior Principal Scientist, and a team of scientists under the guidance of Dr Anupam Agnihotri, Director, JNARDDC.

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