生物质掺混煤粉无焰富氧燃烧燃料氮转化数值模拟

Numerical simulation on fuel nitrogen conversion in flameless oxy-fuel combustion of biomass-pulverized coal blends

无焰富氧燃烧能在捕集高浓度CO_(2)的同时显著降低了NO_(x)排放,是清洁低碳燃烧技术的前沿发展方向之一。生物质作为一种来源广泛的可再生能源,与煤粉的掺混燃烧可有效减少CO_(2)排放。为探究无焰富氧燃烧模式下生物质掺混煤粉燃料氮转化特性,基于0.58 MW燃烧炉,采用Fluent进行模拟,耦合适用于富氧燃烧的反应机理以及辐射模型,在完成模型和算法的验证后进行燃料N转化机理研究。结果表明,随着掺混生物质比例从0增加到100%,炉内低氧区域增大,CO分布区域更广,炉内峰值温度升高,当掺混比为50%时相比纯煤粉燃烧升高了47 K,掺混比为70%时升高了55 K,纯生物质燃烧时峰值温度达到1850 K,较纯煤粉燃烧升高了71 K;生物质掺混比例从0增加到50%时,NO再燃还原比例相比纯煤粉大幅下降了61%以上,且随着掺混比继续增加,NO再燃还原基本不变;随着掺混比从0增加到100%,虽然生物质挥发分含量比煤粉高,但掺混后挥发分NO总和基本不变,由于生物质焦碳含量低,掺混后焦炭氮大幅降低,NO排放整体呈降低趋势,掺混比从0增加到100%,NO排放量降低了51%;表明生物掺烧可有效减少NO的排放。

Flameless oxy-fuel combustion significantly reduces NO_(x) emissions and captures high concentrations of CO_(2),positioning it as a leading technology in clean and low-carbon combustion.Biomass,a widely available renewable energy source,can effectively reduce CO_(2) emissions when co-fired with pulverized coal.This study investigates the nitrogen conversion characteristics of biomass-coal blends under flameless oxy-fuel combustion through simulations conducted on a 0.58 MW combustion furnace.The simulations incorporate a reaction mechanism and radiation model suitable for oxy-fuel combustion.After verifying the model and algorithms,the study examines the fuel nitrogen conversion mechanism.The results indicate that as the biomass blending ratio increases from 0 to 100%,the lowoxygen zone in the furnace expands,and the distribution of CO widens.Additionally,the peak temperature inside the furnace rises.Specifically,when the blending ratio is 50%,the temperature increase compared to pure pulverized coal combustion is 47℃,and at a blending ratio of 70%,the increase is 55℃.For pure biomass combustion,the peak temperature reaches 1850 K,which is 71℃higher than that of pure pulverized coal combustion.When the biomass blending ratio increases from 0 to 50%,NO reburning decreases significantly by more than 61%compared to pure coal combustion and remains relatively unchanged with further increases in the blend ratio.Despite the higher volatile content of biomass compared to coal,the total NO from volatiles remains almost constant after blending.The fixed carbon nitrogen decreases significantly after blending due to the lower fixed carbon content in biomass,leading to a reduction in NO emissions.When the blending ratio increases from 0%to 100%,NO emissions decrease by 51%.