How to preheat combustion gases in fluidized bed boiler plants and fluidized bed boiler plants

摘要

A method of preheating a fluidized bed boiler plant (10) and a flue gas fluidized bed boiler plant, wherein the boiler plant comprises a furnace (12), and combustion gas channels (24, 24b), and an evaporator section (26), the last superheater (30 '). ) And a superheater section comprising a steam turbine 34, and a superheater path that carries steam from the evaporator section 26 through the superheater section to the steam turbine, and a first combustion gas preheater 38 ( 38b), the fluidized bed boiler plant includes a second combustion gas preheater (40, 40b), the superheat path at a position upstream of the last superheater (30 ') for conveying steam from the superheat path to the second combustion gas preheater. And steam extraction lines 46, 46b attached in flow connection with the second combustion gas preheater, wherein the method of preheating the combustion gas comprises steam extraction from a position upstream of the last superheater. In the first step of transporting the superheated steam from the second path to the pre-heater the combustion gas, and a second combustion gas through the pre-heater comprises the step of transferring heat from the combustion gas steam.