Numerical Study On Optimizing Combustion And Reducing NOx Generation Of Pulverized Coal Boiler

With the deepening of the engineering degree of combustion theory and the rapid development of computer technology,numerical simulation technology has been applied to the research of boiler combustion more and more,and has played an important role in optimizing boiler combustion,reducing pollutant generation and relevant transformation of boiler.In this paper,a 330 MW tangentially fired pulverized coal boiler in a power plant is taken as the research object.In the actual operation of the boiler in the power plant,there are some conditions such as high NOx generation and unstable combustion.It is hoped that through the method of numerical simulation,the relevant operating conditions and parameters can be improved,and the method of reasonable transformation of the burner can be found to reduce NOx generation and optimize combustion.Based on this,this paper mainly studies the effects of excess air coefficient,air distribution mode,burnout air rate and burnout air position height on boiler combustion and NOx generation characteristics,analyzes the velocity field,temperature field,component concentration field in the furnace,NOx concentration at the furnace outlet and flue gas temperature deviation,and obtains the appropriate excess air coefficient,air distribution mode,burnout air rate and burnout air position height during the operation of the boiler,Then optimize the combustion and reduce the generation of NOx.With the increase of excess air coefficient,the average velocity of flue gas in the furnace increases,the temperature in the burn out air area and the upper part of the furnace decreases,the NOx concentration at the furnace outlet increases,and the uneven coefficient of temperature distribution at the furnace outlet decreases slightly.Properly reducing the excess air coefficient is conducive to reducing the generation of NOx in the furnace and reducing NOx emission.The temperature of the burner area is higher when the air distribution of the main pagoda and the equal air distribution,and the temperature of the burner area is lower when the air distribution of the inverted pagoda and the waist retraction.Under the four air distribution modes,the NOx concentration at the furnace outlet from high to low is: positive pagoda air distribution,equal air distribution,inverted pagoda air distribution and waist contraction air distribution.From high to low,the uneven coefficient of temperature distribution at the furnace outlet is: equal air distribution,inverted pagoda air distribution,waist shrinking air distribution and positive pagoda air distribution.With the increase of burnout air rate,the temperature in the burner area shows a downward trend.When the burnout air rate changes from 15% to 30%,the temperature decreases by 87 k.With the increase of burnout air rate,the generation of CO in the burner area increases,the degree of incomplete combustion in this area intensifies,and the effect of air staged combustion is improved.With the increase of burnout air rate,the generation of NOx in the furnace decreases significantly,the concentration of NOx at the furnace outlet decreases,and the uneven coefficient of temperature distribution at the furnace outlet decreases,which reduces the flue gas temperature deviation at the furnace outlet.The change of the position and height of the burn out air has a great impact on the generation of NOx in the furnace.With the increase of the position of the burn out air,the generation of NOx in the furnace decreases and the emission of NOx at the furnace outlet decreases.Moreover,when the position of the burn out air increases by 2.5m and the position of the burn out air is not adjusted,the uneven coefficient of the temperature distribution at the furnace outlet is also small,which provides a direction for the transformation of the low NOx burner of the boiler.