The production process of Aluminum involves conversion of Alumina to Aluminium through an electrolytic process that takes place in a pot. These pots are steel containers lined with refractory brick with an inner lining of carbon. The carbon liner is usually up to 15 inches thick and serves as the cathode in the electrolysis process that transforms aluminum ions from the molten bath to molten aluminum. Spent Pot Liner (SPL) is a waste that is generated during this conversion. Depending on the life of the pot, SPL is chipped off from the pot for disposal and relining. SPL is considered hazardous because of the presence of cyanide, soluble fluoride and volatile compounds. The most commonly adopted practice of its disposal is through secured land fill, which is not seen as an acceptable option for the future. It is subjected to close regulatory control including the Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal.
The issue of management of SPL has remained a challenge for the Aluminium industry. The industry has been systematically working to minimize the amount of SPL produced during the production process by extending the life of the lining in the smelter pots. However, the quantity of SPL that needs to be managed is still high.
The management of SPL seems a challenge, if it is viewed purely as a waste material. However, if it is treated as a resource, in line with the principles of circular economy, SPL has the potential for use as input to other industries. Other than its toxic contents, SPL has certain characteristics, which if properly harnessed can not only provide a source of useful energy but also help in mitigating carbon dioxide emissions and in addressing the local environmental issues arising out of the present disposal methods.
This technical article, written by Mr. Nitin Kumar Tiwari, Head- Planning and Waste Management, Bharat Aluminium Company Limited, is prepared to provide general information on processing of SPL. There are a number of ways including direct charging in cement kilns as fuel substitute or feed mix received after detoxification process can be used in various Steel & clay bricks manufacturing. This detailed report would shed light on SPL usage in Indian Industrial scenario and creating awareness about its positivity with complete corporate responsibilities in line with environmental norms. There are more aspects reviewed such as transportation and technical aspects that come with the implementation of each selected option.
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