The Numerical Simulation Research On Combustion Optimization Of Circulating Fluidized Bed Boiler

Circulating fluidized bed boiler has advantages of wide fuel applicability and low pollutant emission,which has great vitality at energy area at home and abroad.So it has great significance to study its combustion process and products.Considering the status of domestic and foreign research on circulating fluidized bed boiler combustion,this paper,employing FLUENT software,invetigate the combustion processes of circulating fluidized bed boiler at different air distribution conditions and coalfeed methords.The main research content is as follows:1.Based on the combustion principle of the circulating fluidized bed boiler and combustion characteristics of coal particles inside the furnace,the effects on combustion of various factors were analyzed,e.g.the feeding types and methods,excess air coefficient,fluidization velocity,bed temperature,circulation ratio of separator,and so on.2.Utilizing a 130t/h circulating fluidized bed boiler as the prototype.,the aerodynamic characteristics of circulating fluidized bed boiler under different air distribution conditions were simulated and the effects on combustion from the changes of secondary air ratio were analyzed.according to the results,aerodynamic characteristics of furnace performs best when the air ratio of primary and secondary wind are 55% and 45% respectively,since this ratio benefits burning.3.This paper simulated the combustion characteristics of circulating fluidized bed boiler respectively under two conditions of coalfeed,i.e.Coalfeed at the front wall or at the front and back wall.Results show that under the condition of coalfeed at front wall,the velocity gradient is uniform and the burning is full,however,the high temperature area deflects the front wall.Under the condition of coalfeed at front wall,combustion temperature field distribution is symmetrical,but the temperature gradient is large,and combustion mainly concentrates in the lower part of furnace.4.NO_x emission numerical simulations were carried out under two combustion conditions,and the pollutants discharge of circulating fluidized bed boiler were analyzed.The effects of ammonia concentration on the denitration efficiency and NO_x distribution in circulating fluidized bed boiler were analyzed by using SNCR denitration technology.The results provide references for cleaning boiler combustion.