350MW燃煤锅炉在富氧下掺烧生物质气的数值模拟

Numerical Simulation of Biomass Gas Blending in 350MW Coal-Fired Boiler under Oxygen Enrichment

摘要: 为了研究火力燃煤锅炉的碳减排与低氮燃烧技术，本文通过数值模拟方法研究了不同O₂/CO₂体积分数比的富氧条件下四角切圆锅炉内生物质气与煤粉混燃情况。结果表明：当O₂浓度高于29%时，炉膛整体速度梯度提高，有利于煤粉的充分混合燃烧，从而改善了煤粉的燃烧特性；随着O₂/CO₂体积分数比的增加，炉膛内温度整体是提高的，有利于提高炉膛内的换热性能；随着O₂/CO₂体积分数比的增加，炉膛内整体的CO₂浓度逐渐提高，炉膛出口的CO₂浓度是70%~77%，有利于CO₂的捕集，同时，炉膛内NOx的浓度也逐渐提高，主要原因是炉膛内的温度随着O₂浓度的增加而上升，由此热力型NOx的产生量更大。

Abstract: In order to study the carbon reduction and low-NOx combustion technology of thermal coal-fired boiler, this paper investigates the mixing and combustion of biomass gas and pulverized coal in a four-corner cut circle boiler under oxygen-rich conditions with different O₂/CO₂ volume fraction ra-tios by numerical simulation, and analyzes the flow, heat transfer and combustion processes in the furnace. The results show that: when the O2 concentration is higher than 29%, the overall velocity gradient in the furnace increases, which is favorable to the full mixed combustion of pulverized coal, thus improving the combustion characteristics of pulverized coal; with the increase of O₂/CO₂ vol-ume fraction ratio, the overall temperature in the furnace is increased, which is favorable to the improvement of heat transfer performance in the furnace; with the increase of O₂/CO₂ volume frac-tion ratio, the overall CO₂ concentration in the furnace gradually increases. The CO₂ concentration at the furnace outlet is in the range of 70% to 77%, which is conducive to the capture of CO₂. Mean-while, the concentration of NOx in the furnace chamber also gradually increases, mainly because the temperature in the furnace chamber increases with the increase of O₂ concentration, and thus the generation of thermal NOx is greater.