Heat recovery systems and power generation systems

In an improved system for recovering heat from a combustion gas produced by burning combustibles, said combustion gas or a gas produced by partial burning of combustibles is subjected to dust removal in a temperature range of 450 - 650 DEG C at a filtration velocity of 1 - 5 cm/sec under a pressure of from -5 kPa (gage) to 5 MPa before heat recovery is effected. The dust removal is preferably performed using a filter medium which may or may not support a denitration catalyst. The heat recovery is preferably effected using a steam superheater. The dust-free combustion gas may partly or wholly be superheated with an auxiliary fuel or a gasified product to a sufficiently high temperature to permit heat recovery. The combustion furnace may be a gasifying furnace which, in turn, may be combined with a hot melting furnace. If desired, the superheating to a higher temperature may be performed under pressure and the obtained hot combustion gas is supplied to a gas turbine to generate electricity, followed by introduction of the exhaust gas from the turbine gas into a steam superheater for further heat recovery. The system can raise the temperature of superheated steam to a sufficient level to enhance the efficiency of power generation without potential for the corrosion of heat transfer pipes by the combustion gas.