| 15.6% of my country’s coal reserves are anthracite,which is mainly used for thermal power generation due to its high degree of carbonization,low heating value and low volatile content.The W-type flame boiler is suitable for burning anthracite due to its advantages of long flame stroke,small air volume in the ignition zone,good combustion stability and high combustion efficiency.This article takes as the background the problems of water wall bursting,poor combustion stability,furnace coking and high NOX emission concentration in a 600MW subcritical W-type flame boiler in a certain power plant,and use FLUENT software to numerically simulate the combustion process in the furnace before and after the transformation,and analyze the changes in the velocity field,temperature field and component concentration field in the furnace before and after the transformation,and carry out the corresponding combustion modified industrial test.First,establish the mathematical model of the boiler combustion numerical simulation,establish the physical model according to the actual size of the boiler,and set the meshing,boundary conditions and wall conditions of the physical model.Then the BMCR working conditions of the boiler are numerically simulated,through the analysis of the velocity field,the temperature field and the component concentration field in the furnace,the combustion characteristics and the furnace slagging in the furnace are studied.Numerical simulation results show that:in the original plan,the pulverized coal gas flow descended for a short distance and then turned into the upper furnace,the flame center moved upward,and the pulverized coal particles burned to a low degree,the speed field of the modified plan showed a perfect "W" shape,and the flame in the furnace was full;the temperature field distribution of the original plan is uneven,the high-temperature area is concentrated,and the temperature field of the modified plan is evenly distributed,and the average temperature in the furnace is reduced;in the original plan,the NOx generation was concentrated in the burner layout area and near the wall of the upper furnace,the modified plan reduced the amount of NOx generated at these two locations due to the addition of burning wind;the CO concentration field and O2 concentration field of the modified plan have also been improved to a certain extent;the modified plan made reasonable adjustments to the area and position of the refractory belt,and solved the problem of easy coking of the wing wall,side wall and furnace arch when the upper furnace is under oxygen combustion.Finally,the boiler before and after the transformation was carried out on the combustion transformation industrial test,and the preliminary performance test results and the numerical simulation results were compared and analyzed,the analysis found that the industrial test results are highly consistent with the numerical simulation results.Through the low-nitrogen combustion transformation,the velocity field and temperature field in the furnaces of#1 and#2 in this power plant have been improved to a certain extent;and judging from the test data before and after the transformation,the NOx emission concentration of the#1 boiler of the power plant decreased from 1453～1507mg/Nm3 to 754～812mg/Nm3,and the NOx emission concentration was reduced by about 697mg/Nm3 on average;the NOx emission concentration of the#2 boiler decreased from 1265～1305mg/Nm3 to 550～595mg/Nm3,and the NOx emission concentration was reduced by about 713mg/Nm3 on average.The research results have been applied to the design of the low-nitrogen combustion modification plan for the W-type flame boiler in JinZhuShan Power Plant,and will provide some references for the future low-nitrogen combustion modification of the same type of boiler. |
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