GRETA - value adding heat recovery - report heat treatment furnace

Recovering heat from exhaust gas from heat treatment furnaces is technically simple and provides high temperature heat, e.g. 100°C heating water/district heating or steam. The process has been evaluated at Swedish steel foundry. A fairly rough estimate is that just under 50% of the used fuel (net calorific value a.k.a lower heating value) can be recovered from the flue gas assuming a standard burner is used. If the burner is regenerative/recuperative or oxy-fuel type, the amount of residual exhaust heat is significantly reduced, to perhaps 15-20% of the fuel input. Additional heat is available at lower temperatures, e.g. for preheating ventilation air. In the longer term, the transition to a sustainable society may change the amount of available exhaust gases, e.g. if electric furnaces without exhaust gases take over the market from combustion furnaces, or if e.g. fuel and oxygen prices in the future favour oxy-fuel burners. An accumulator tank that holds the heat equivalent to a batch is likely to be needed if the heat is to be used for comfort heating or similar purposes.