Gas Recycling and Energy Recovery. Future Handling of Flue Gas from Aluminium Electrolysis Cells

Flue gas recycling and energy recovery provide an excellent opportunity for the aluminium industry to reduce the total energy consumption and to prepare for possible future carbon capture and storage or utilisation. Gas recycling enables increased CO2 concentration and more efficient recovery of heat from the flue gas. The present paper addresses some of the challenges with this technology, including increased concentrations of other pot gases such as CO, SO2, and HF and possible increased fugitive emissions due to reduced suction. Increased concentration of CO is particularly unwanted, since it is a lethal compound. Thus, catalytic conversion of CO to CO2 is crucial for HES (Health, Environment and Safety) reasons, and it also increases the amount of collectible heat. However, high concentration of SO2 can pose problems to equipment, including the heat exchanger units, due to the formation of sulfuric acid when the acid dew point is reached.