Numerical Simulation On Influence Of Wall SOFA On Combustion Characteristics Of A 660MW Coal-fired Boiler

Separated overfire air(SOFA)technology is one of the most important methods for deep coal grading and low NOx combustion in coal-fired boilers.The location,mode and operating parameters of the SOFA have an important impact on the combustion characteristics of the boiler,which in turn affects the safety,efficiency and low NOx emission performance of the boiler.In this paper,a 660MW tangential pulverized coal combustion boiler equipped with wall SOFA is used to study the arrangement position and mode of different SOFA and different SOFA operation parameters,such as wind rate,vertical swing angle and horizontal pendulum.According to the actual structure and size of the boiler,reasonable geometric and mathematical models were established to carry out detailed numerical simulation of boiler flow,combustion,heat transfer and NOx generation characteristics,and compared with the test results,the rationality of the model was verified.The influence of angle on the combustion characteristics of the boiler,the temperature,O2,CO and NOx distribution characteristics under different working conditions were analyzed.The combustion efficiency and NOx emission were counted,and the optimized SOFA arrangement and operating parameters were obtained.It provides reference information for the optimal design and operation of the boiler's low NOx combustion.Firstly,The results of research on changing SOFA rate,vertical swing angle and horizontal swing angle show that with the increase of SOFA rate,NOx emission decreases,but the pulverized coal burn-up rate decreases.The SOFA nozzle upper swing angle increases,NOx emissions decrease,and pulverized coal burnout rate decreases;SOFA spout horizontal swing angle changes,NOx emissions increase,and pulverized coal burnout rate increases.Considering the combustion efficiency and NOx emissions,when the SOFA rate is 22.6%,the swing angle is 10~o,and the horizontal swing angle is 0~o,the combustion condition is better.Secondly,the effects of SOFA bias and momentum enhancement on boiler combustion characteristics were studied.The results show that the wind speed of SOFA is offset according to the left and right wall.The wind speed of SOFA on the right wall can be increased by 10%to obtain lower NOx emission,which has little effect on the burnout rate.It is offset according to the diagonal mode,burnout rate and NOx.Emissions have declined slightly;SOFA momentum increases can increase burnout rates,but NOx emissions increase.Finally,the effects of SOFA four-wall layout,wall staggered and angular arrangement on the combustion characteristics of the boiler were studied.The results show that when four wall layout,staggered arrangement and four-corner arrangement are used,compared with the wall type hedge arrangement,the upper space of the furnace is not fully utilized,the pulverized coal burnout rate is decreased,and NOx emissions are increased.