Impact of Quality Changes in Calcined Petroleum Coke(CPC)on Anodes Used for Aluminium Production

CPC(calcined petroleum coke)has been in use for more than 120 years to produce the carbon anodes used in the Hall-Heroult Aluminium electrolysis process.Performance of the anodes in the aluminium electrolysis process depends on many properties of CPC.It is seen that over the last several years quality and availability of anode grade petroleum coke have been impacted by changes in the petroleum refining industry.Refineries have started using sour crudes that have high sulphur and metallic impurities due to shortage of sweet crudes coupled with high demand for oil.As a result,RPC(raw petroleum coke)from refineries is having higher sulphur content and metal impurities.Therefore,smelters worldwide are using CPC with higher sulphur content to meet their requirements.The increasing trend of impurities in CPC used by Indian industry is a major concern for the industry.In this paper,the quality variations observed in CPC used by NALCO(National Aluminium Company)and their impact on anode quality are highlighted along with presentation of few R&D studies carried out at NALCO,the findings of which may be helpful to deal with expected future quality changes in CPC.