The Improvement And Application Research Of The Zonal Model Of Radiation Heat Transfer In The Furnace Of Large Capacity Utility Boiler

The safety,stability,and economic operation of generator sets are of great significance to the development of China’s power industry.When the type of coal burned or the operating mode changes,or the structure and area of the furnace heating surface change,It is necessary to make a reasonable estimation of parameters such as the distribution of heat load in the furnace and the temperature of flue gas at the outlet of the furnace under the new operating conditions.The furnace thermal calculation is the prerequisite and basis for the calculation of other parts of the boiler.This paper mainly investigates the thermal calculation and application of large-scale power station boiler furnace.Aiming at the current structural layout and combustion characteristics of large-scale power station boilers,an improved one-dimensional heat transfer model is proposed on the basis of the Mildo section method in the Soviet "Standard Method for Thermal Calculation of Boiler Units".Divide into five sections along the height of the furnace from the bottom of the cold ash hopper to the folding angle.Each section adopts iterative calculation of heat balance equation.In the calculation,the heat transfer and contamination of each section are considered separately,and important parameters such as the one-dimensional temperature distribution of the flue gas in the furnace,the heat absorption of the water wall,and the wall heat load are obtained.Select a 600MW supercritical pressure pulverized coal furnace.The improved one-dimensional zone heat transfer model of the furnace is used for thermal calculation under different working loads,and the calculation results are compared with the traditional zero-dimensional model.The errors of the improved model under 100%BMCR,75%BMCR,and 50%BMCR are 13K,12K,and 18K respectively,which are smaller than the zero-dimensional model,which verifies the accuracy of the model.At the same time,other important parameters in the furnace under different loads can be obtained,such as the flame blackness of each section,the blackness of the furnace,the temperature and pressure of the inlet and outlet of the working fluid,and so on.Select a 600MW subcritical pressure pulverized coal furnace.Aiming at the problem of low reheating steam temperature in actual operation,a comprehensive analysis of the wall-type reheater renovation plan is proposed.The improved furnace one-dimensional partitioned heat transfer model is used to calculate the furnace outlet flue gas temperature under different loads.Under a 300MW load,the steam temperature at the outlet of the final reheater reaches 528℃,which is 8℃ higher than before the transformation;under a 450MW load,the steam temperature at the exit of the final reheater reaches 540℃;under a 600MW load,the steam temperature at the exit of the final reheater reaches 540℃;The calculation results are used to calculate the thermal power of the reheater,which effectively increases the temperature of the reheated steam and ensures the economic operation of the unit.