燃煤锅炉一次风掺混氢氧对炉膛温度影响的数值模拟

Numerical Simulation of Effect of Primary Air Mixed with Hydrogen and Oxygen on Furnace Temperature of Coal-fired Boiler

为提高1 000 MW超超临界四角切圆燃煤锅炉低负荷工况(300 MW)燃烧稳定性,在一次风中掺混不同比例氢气和氧气,采用数值模拟方法对比分析了低负荷掺混氢氧前后炉膛平均温度场和CO体积分数等参数。研究结果表明:一次风掺混氢氧加强了低负荷工况下的火焰温度,进而提升炉内整体平均温度,改善低负荷燃烧不稳定现象;掺混5%体积分数的氢气,主燃区炉内截面平均温度达到1 603 K,比初始工况平均温度高了37 K;掺混8%~15%体积分数的氢气,随着氢气燃烧产生水份比例增高,炉膛截面平均温度逐步降低;掺混5%体积分数的氢气和10%体积分数的氧气,主燃区炉内截面平均温度达到了1 696 K,比只掺混5%体积分数的氢气平均温度提高了93 K,比初始工况平均温度提高了130 K,此工况是该四角切圆锅炉低负荷下改造后较为理想的工况。

In order to improve combustion stability of 1 000 MW ultra-supercritical tangentially fired coal-fired boiler under low load condition(300 MW),different ratios of hydrogen and oxygen are mixed in primary air, and parameters such as average temperature field and CO volume fraction before and after low load mixing of hydrogen and oxygen are compared and analyzed by means of numerical simulation. The results show that mixing primary air with hydrogen and oxygen strengthens the flame temperature under low load conditions, thus increasing the overall average temperature in the furnace and improving the combustion instability under low load. By mixing 5% volume fraction hydrogen, the average cross-section temperature in the main combustion zone reaches 1 603 K, which is 37 K higher than the average temperature under initial conditions.By mixing 8%~15% volume fraction hydrogen, the average temperature of furnace section decreases gradually as the proportion of water produced by hydrogen combustion increases. By mixing 5% volume fraction hydrogen and 10% volume fraction oxygen, the average cross-sectional temperature in the main combustion zone reaches 1 696 K, which is 93 K higher than that of only mixing 5% volume fraction hydrogen, and 130 K higher than the average temperature in the initial working condition. This working condition is an ideal one after the low load retrofit of the tangentially fired boiler.