Thermal Numerical Simulation and Engineering Transformation of Combustion System of 3100t/h Ultra-Supercritical Boiler

In the operation of a 3100t/h ultra-supercritical boiler, there are some problems such as high combustible content of slag, low reheat steam temperature, poor combustion stability and uneven distribution of primary air at four corners of the furnace. The combustion conditions in the furnace before and after the transformation of the four-corner tangential combustion boiler are numerically simulated by numerical calculation. The calculation results show that the amount of pulverized coal falling into the cold ash hopper is reduced from 0.065kg/m
³
before the transformation to 0.052kg/m3 after the transformation, which is reduced by about 20%. The centralized arrangement of secondary air at the bottom layer enhances the lifting ability of pulverized coal. In the direction of the burner section, the low temperature zone in the center of the furnace is reduced, the annular high temperature zone around the furnace is increased, and the heat load of the furnace section is increased. Along the height direction of the furnace, the average temperature of the section of the burner area at the bottom of the furnace is increased by about 50°C~80°C, which is conducive to the ignition and combustion of the pulverized coal gas. The average cross section temperature of the main combustion zone in the upper part of the furnace is increased by about 20°C~30°C, which is conducive to improving the temperature of reheated steam. The conversion rate of pulverized coal carbon in the four corners of the bottom burner nozzle is increased from 92.2% before the transformation to 93.1% after the transformation. The reconstruction of the primary and secondary air nozzles at the bottom, the installation of backburner belt in the lower group of burners, and the installation of adjustable shrinkage holes in the primary air pipeline are proposed. After the transformation is completed, the boiler can be stable combustion at 500MW low load without oil injection, the combustible content of slag is reduced to 2.5%~5.5%, the temperature of reheated steam is improved to a certain extent, the boiler is in good running condition, and the boiler efficiency is increased by about 0.3 percentage points.