Fluidized Bed Boiler Plants and Methods of Preheating Flue Gases in Fluidized Bed Boiler Plants

摘要

A method of preheating a fluidized bed boiler plant (10) and a flue gas fluidized bed boiler plant, the boiler plant comprising a furnace (12), and flue gas channels (24, 24b), and an evaporator section (26), a superheater (30' at the end) ) and a superheater section comprising a steam turbine 34, and a water-steam cycle comprising a superheating path carrying steam from the evaporator section 26 through the superheater section to the steam turbine, and a first flue gas preheater 38, 38b), wherein the fluidized bed boiler plant comprises a second combustion gas preheater (40, 40b), a superheat path at a location upstream of the last superheater (30') for conveying steam from the superheat path to the second combustion gas preheater; and a steam extraction line (46, 46b) attached in flow connection with the second combustion gas preheater, wherein the method for preheating the combustion gas is from a position upstream of the last superheater to the second combustion gas preheater through the steam extraction line. conveying steam from the superheat path of the furnace, and transferring heat from the steam to the combustion gases in a second combustion gas preheater.