Simulation of the effects of blending out-furnace and in-furnace on combustion performance under low load

In order to study the difference in combustion performance between out-furnace blending and in-furnace blending under low load, the combustion of a 350MW tangential boiler under the conditions of lignite blending with different proportions of bituminous coal was simulated and analyzed based on Fluent software. The results show that the blending of bituminous coal can increase the combustion temperature and is conducive to the complete combustion of pulverized coal. When blending outside the furnace, the temperature change in the furnace is gentler, which is safer than in-furnace blending. Under blending conditions, lignite and bituminous coal compete for O₂ seriously, which is most obvious under 40% coal blending conditions. Blending outside the furnace, especially in the 40% working condition, has a good effect on reducing NOx emissions. However, In-furnace blending has side effects and increases NOx emissions by 30%.