Design of a hear recovery system in an aluminium casthouse

Increasing energy prices as well as environmental considerations make waste heat to power conver-sion very attractive. This is especially the case for energy intensive industry sectors like aluminium industry. An energy flow survey has been performed for the casting furnace at Sunndalsøra (Hydro Aluminium, Norway). Opportunities for waste heat to power conversion are identified. Both exhaust gas from the furnace and cooling water from the casting ingot machine are considered. Steam cycle, organic Rankine cycles and organic flash cycles are optimised for several working fluids. The furnace has the greatest potential as the exhaust gas temperature is high, but this heat source is not stationary and leads to operation challenges. The casting ingot machine is interesting as the heat source is easily recoverable, but today's low water return temperature limits the potential. Solutions are proposed to improve the heat to power conversion efficiency.