Fluidized bed boiler plant and method for preheating combustion gas in fluidized bed boiler plant

Abstract

A fluidized bed boiler plant (10) and a method for preheating combustion gases in a fluidized bed boiler plant comprising a furnace (12) and combustion gas channels (24, 24b), and water-steam cycle, the water-steam cycle includes: an evaporator section (26); a superheater section including a final superheater (30') and a steam turbine (34) and a The evaporator section (26) is delivered via the superheater section to the superheat path of the steam turbine; and a first combustion gas preheater (38, 38b), wherein the fluidized bed boiler plant comprises a second two combustion gas preheaters (40, 40b), and a steam extraction line (46, 46b), said steam extraction line (46, 46b) being located upstream of said last superheater (30') from said first A second combustion gas preheater is attached in flow connection with said superheating path for delivering steam from said superheating path to said second combustion gas preheater (40, 40b), wherein said for The method of preheating combustion gases comprises conveying steam from said superheating path to said second combustion gas preheater (40) via said steam extraction line (46, 46b) from a location upstream of said last superheater , 40b); and transferring heat from the steam to the combustion gas in the second combustion gas preheater.

Description

technical field [0001] According to the preambles of the adjacent independent claims, the invention relates to a fluidized bed boiler plant and a method for preheating combustion gases in a fluidized bed boiler plant. More particularly, the present invention relates to a fluidized bed boiler plant and a method for preheating combustion gases in a fluidized bed boiler plant, which enable an advantageous operation of the boiler plant at particularly low loads. Background technique [0002] Today, fluidized bed boilers are often required to meet highly variable load requirements and thus to operate the boiler at very low loads. Conventional fluidized bed boilers typically have a minimum load of about 40% of full load, but today it would often be desirable to operate fluidized bed boilers at even lower loads (eg, 30-20%) of full load. Operating conventional fluidized bed boilers at very low loads is generally prevented by the requirement to maintain the bed temperature in the f...

AI Technical Summary

Problems solved by technology

However, this causes increased investment costs for the gas recirculation path and larger hot surfaces required due to the larger total exhaust flow, and increased auxiliary power consumption in the recirculation gas fan and the flue gas fan

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