The Numericl Simulation Research Of Flow And Combustion Characteristic On 1000MW Grade W Fired Boiler

As the world's largest country in anthracite coal production and consumption,anthracite coal is accounts for about 16.4% of proven coal reserves in China.For the high carbonization degree,low volatile,high ash,anthracite is difficult to ignition,stable combustion and burnout.Anthracite is always uesd to generate electricity as the fuel of W fired boiler.At present,1000 MW grade of W fired boiler is in the stage of development in the world.Considering the larger furnace capacity and two layers of the burners,the boiler is very complex.In order to obtain a better flow distribution and temperature distribution in the furnace and guarantee the performance of the boiler,it is necessary to simulate on structure and air distribution.The Fluent software is used to numerically simulate the combustion process of 1000 MW grade of W fired boiler in this paper.It studied the infact on flow and combustion characteristic in furnace under the following conditions: The burner and OFA use direct flow or cyclone flow.Staged-air rate is 13.43%,15.93% or 18.43%.The outer secondary air blade opening of the burner is 45°,60° or 75°.Different OFA nozzle locations.Combined with the background of saving energy and emission reduction,the paper studied impaction of the OFA nozzle position on nitrogen oxides generating.According to the results of numerical simulation: At the optimum conditions,the deviation of relevant section average temperature is small between the result of numerical simulation and thermo dynamic calculation.Direct flow has big difference with actual conditions.Cyclone flow has better performance on gas flow,temperature,O2 distribution.When staged-air rate is 13.43% or 18.43%,the lower speed zone flow of cold hopper has an obvious deflection;and the front cold hopper paint the wall.When the outer second air blade opening of the burner is 45°,burner air became weaker,cyclone intensity and entrainment effect became stronger,combustion process became shorter;the lower speed zone flow of cold hopper has an obvious deflection;the cold area of ash hopper is not obviously.When the outer second air blade opening of the burner is 75°,burner air became stronger,cyclone intensity and entrainment effect became weaker;combustion process became longer;the lower speed zone flow of cold hopper has an obvious deflection;the cold area of ash hopper is not obviously.When staged-air rate is 15.93% and the outer second air blade opening of the burner is 60°,the cylone air intensity and entrainment effect is moderate;the flow distribution and temperature distribution is uniform.If the coal fineness is better,the coal is more flammable,and we can increase OFA nozzle height to reduce nitrogen oxides generating.If the coal fineness is poorer,we can reduce OFA nozzle height to strengthen coal burning,reduce the carbon content in fly ash,improve the efficiency of the boiler.The result of the study is already used in the design of this type boiler,and it will provide some reference in the future operation.