496 / 2018-12-31 18:08:19

Influence of Bypass Flue Gas Flow Ratio and Inlet Air Temperature on Thermal Performance and ABS Deposition of Air Preheater in Flue Gas Waste Heat Recovery System

Air preheater；Flue gas waste heat recovery system based on boiler-turbine coupling；Deposition of ammonium bisulfate；Steam turbine heat rate

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Taking a 660 MW unit as an example, with the finite difference method and the equivalent enthalpy drop method, this paper calculates and illustrates the influence of the design and operating parameters, such as the bypass flue gas flow ratio and the air preheater inlet air temperature of the flue gas waste heat recovery system based on boiler-turbine coupling, on the heat transfer process entropy production of the air preheater, the outlet flue gas/air temperature of the air preheater, the ammonium bisulfate(ABS) and sulfuric acid vapor deposition area location, and the economic indicators such as steam turbine heat rate. Respectively, the calculation in the cases of 5%, 10%, 15%, and 20% bypass flue gas flow ratio was conducted, and the results show that, if the temperature of the bottom of the cold-end is kept constant, the temperature of the bottom of the intermediate layer is lowered, and the ABS deposition area is moved up; while if the temperature of the bottom of the intermediate layer is kept constant, the ABS deposition area moves down, and the sulfuric acid vapor deposition shrinks, but the reduction in steam turbine heat rate and coal consumption rate decrease. The improvement of the structure of the air preheater and the arrangement of an additional pre-displacement heat exchanger are proposed. While maintaining the ABS and sulfuric acid vapor deposition areas unchanged, the steam turbine heat rate reduction has increased by 29%-53%.