Heat recovery – profitable and environmentally friendly
By recovering energy from the casting process in steelmaking, energy use and environmental impact can be reduced. Energy recovery can potentially replace other heat sources in steelmaking.
Steelmaking is a high-temperature process (1500–1600 degrees Celsius). During subsequent casting the temperature of the liquid steel is lowered, so that the steel solidifies (about 800 degrees). This is achieved with water-cooled moulds, through heat transfer or by spraying water on the steel.
Often, significant amounts of energy are lost. For the Swedish steel industry, this amounts to approximately 1200 GWh/year, enough to heat about 60,000 small homes.
Reduced energy use
By recovering this heat it could be possible to reduce the use of fossil fuels, for example, for producing steam for district heating.
Swerea has studied the potential of various types of energy recovery from the casting process. The project shows that the available energy is 257 kWh/tonne steel, about half of which is dissipated during casting. The highest energy loss is to the cooling water system, at temperatures below 50 degrees Celsius, followed by radiation and steam losses.
Heat residue replace other energy sources
The greatest potential for economically viable energy recovery is in replacing other heat sources in steelmaking.
“The project has given us greater insight into what is or isn’t possible. This also gives us a clue as to the potential for recovering residual heat from the casting processes,” says Susanne Lindqvist, energy manager at Sandvik MT.
A successful implementation would reduce the environmental impact from steelmaking while at the same time reducing costs.