Heat is recovered indirectly from the incinerator exhausting gas by passing them either through a gas tube heat exchanger or across a radiant tube boiler. Energy is exchanged between the gases and water to produce steam for heating or industrial processing. When used for electrical power production, the steam is further heated within a super-heater to produce a dry steam to drive a turbine/generator set. Economisers are fitted to the boiler outlet to recover additional energy from the flue gas.