Combustion and emissions analysis of Spent Pot lining (SPL) as alternative fuel in cement industry

Spent Pot lining (SPL) is a carbonaceous material generated during the primary aluminum smelting process. SPL is a hazardous waste but the high energy density (carbon rich fraction) and good environmental impacts (toxic materials such as cyanides are destroyed at temperature well above 1000 °C) of the treated SPL (water washed followed with and NaOH and H₂SO₄ treatments) makes it a valuable material for use as fuel feedstocks in cement and steel industries. The principal objective of this study is to investigate the combustion performance and emission characteristics of SPL as alternative fuel in cement industry. The goal is to develop sustainable process systems by using solid waste materials such as SPL from Aluminum industry as a fuel in the cement industry. The proximate (moisture, volatile, fixed carbon, and ash contents) and ultimate (C, H, O, N, S) analyses and the heating value (MJ/kg) of the raw and treated SPL materials are determined first. Computational Fluid Dynamics analysis based on gas and discrete phase modeling (DPM) approach and probability density function/mixture fraction turbulent non-premixed combustion model are used to test the combustion performance and pollutants emissions (flame temperature, fuel particle devolatization and burnout rates, and species concentration formations inside and at the exit of the combustor) of the SPL fuel. The results of the SPL or the alternative fuel combustion are compared with conventional fuel (coal) combustion used in cement industry. The final treated SPL fuel (water washed SPL followed with NaOH and H₂SO₄ treatments) combustion shows lower temperature and NO and CO₂ emissions at the exit from the furnace compared to coal. The results show that the final treated fuel can be used as alternative fuel in cement industry to displace coal fuel and reduce the pollutant emissions from the combustor in cement industry.