Integrated desalination and primary aluminium production.

The possibility is discussed of valorising the heat extracted from pot gases to produce fresh water, particularly in areas where water is in scarce supply. A case study is presented based on a hypothetical smelter in a Middle Eastern country with one potline operating at 400 kA and producing 403 000 t Al/y. Two gas treatment centres (GTC) are installed with filters with integrated heat exchangers, and plant fresh water consumption is assumed to be 403 000 m3/y. Pot gas heat typically accounts for more than 30% of the total energy dissipated by the pot and can be estimated based on pot gas flow rate and temperature. A revised equation for the pot gas heat is presented assuming that a heat exchanger is installed upstream of the GTC. Up to 20% of the pot gas heat daily average is recoverable in summer, with a yearly average close to 10%, and this can be increased by reducing ductwork losses, for example by installing the heat exchanger as close as possible to the pot outlet. Energy required for the desalination plant is provided by extracting heat from the pot gas, with water being used in a closed-loop circuit to convey energy from the heat exchanger to the desalination plant. Robust heat exchangers of shell and tube design are used to minimise the risk of scaling and the formation of deposits from the pot gas. Multi-effect distillation is considered to be the most effective desalination technology for the particular application.
The possibility is discussed of valorising the heat extracted from pot gases to produce fresh water, particularly in areas where water is in scarce supply. A case study is presented based on a hypothetical smelter in a Middle Eastern country with one potline operating at 400 kA and producing 403 000 t Al/y. Two gas treatment centres (GTC) are installed with filters with integrated heat exchangers, and plant fresh water consumption is assumed to be 403 000 m3/y. Pot gas heat typically accounts for more than 30% of the total energy dissipated by the pot and can be estimated based on pot gas flow rate and temperature. A revised equation for the pot gas heat is presented assuming that a heat exchanger is installed upstream of the GTC. Up to 20% of the pot gas heat daily average is recoverable in summer, with a yearly average close to 10%, and this can be increased by reducing ductwork losses, for example by installing the heat exchanger as close as possible to the pot outlet. Energy required for the desalination plant is provided by extracting heat from the pot gas, with water being used in a closed-loop circuit to convey energy from the heat exchanger to the desalination plant. Robust heat exchangers of shell and tube design are used to minimise the risk of scaling and the formation of deposits from the pot gas. Multi-effect distillation is considered to be the most effective desalination technology for the particular application.