Numerical Simulation Of Combustion Optimization For A 600MW Swirl-opposed Firing Boiler

The opposed combustion mode has strong adaptability to coal types and better filling degree of flame in the furnace.Therefore,the opposed combustion mode is widely used in coal-fired power plants.In actual operation,the uneven distribution of the flow of the secondary bellows burner,the unreasonable operating parameters of the burner and the unreasonable operating parameters of the boiler will have a greater impact on the thermal efficiency of the boiler and the pollutant discharge.In this paper,a numerical simulation method is used to simulate the combustion optimization of a 600MW front and rear wall pulverized coal combustion boiler,which provides scientific guidance and suggestions for the normal operation of the boiler unit.According to the actual boiler structure and size,the geometric and mathematical models of single-layer bellows,swirl burner and full furnace are established respectively.The numerical simulation of combustion is carried out.The velocity distribution,temperature distribution and concentration distribution of each component are reasonable.The error between the simulation results of the exit parameters and the actual measurement results are less than 10%.The flow characteristics and optimization of single-layer bellows is studied by numerical simulation.The flow of each burner presents certain non-uniformity and deviation characteristics under the same secondary air valve opening.With the decrease of the secondary air valve opening,the flow heterogeneity and deviation between the burners increases.Appropriately reduce the secondary damper opening of the burners on the middle and middle sides,the flow deviation of each burner is reduced,and the flow distribution is more uniform.The parameter optimization of a new low NOx swirl burner is studied by numerical simulation.Appropriate increase of DC secondary air volume can reduce NO_x production.Excessive DC secondary air volume will weaken the reductive atmosphere and increase NO_x production.Appropriately increasing the swirl angle of the third and fourth winds will delay the mixing of the third and fourth winds with the pulverized coal,which can effectively reduce the amount of NOx generated.When swirl angle is too large,the burnout rate decreases rapidly and the production of NO_x increases.Combined with various factors,the swirl burner operates better under the condition of air rate and swirl angle of 35~40.The numerical simulation of pulverized coal combustion in a 600 MW fired boiler with front and rear walls was carried out.The results show that with the increase of exhaust air rate,the temperature level in the burner area decreases,the CO concentration level increases,and the NO_x concentration level in the furnace decreases significantly;when the exhaust air rate is constant,the lower exhaust air volume increases,the concentration of NOx in the lower exhaust area increases significantly.Under the air distribution mode of inverted pagoda,the CO concentration in the furnace is higher and the NOx concentration level is lower.On the contrary,the burnout rate of pulverized coal is higher under the condition of equal air distribution.Considering comprehensively,the operation of the boiler under the air distribution mode of equal air distribution can realize high efficiency and low pollution combustion.