Cost Optimised CO2 Capture from Aluminium Production

Abstract

The process gas from aluminium production generally has a CO2 concentration close to 1 vol%, which is usually considered too low for economically viable CO2 capture. Changes made to the current technology, the Hall-Héroult, together with advances in mechanical and automotive components can facilitate for a higher CO2 concentration in the process gas. However, the assessment of the feasibility of achieving this is outside of the scope of this article. The aim of the work presented in this article is to investigate the optimal CO2 concentration from a CO2 capture perspective. Capture of CO2 from aluminum production has been simulated using CO2 concentrations of 1, 4, 7 and 10 vol%, the current 1 vol% case is included for references purposes. Generic MEA based CO2 capture models have been built-up in Aspen Hysys and Aspen Plus. The results from these simulations provide input to the cost estimation of the CO2 capture process. Based on the results from the economic assessment with the current assumptions, the overall recommendation is to increase the CO2 concentration to 4 vol%. Further increase to 7 and 10 vol% shows only minor savings potential. In addition, the potential for extracting energy from the process gas for utilization in the CO2 capture process has been assessed. The results show that the highest capture rate, around 55%, can be achieved, further affirming that the optimal CO2 concentration in the process gas is 4 vol%.