O2/CO2气氛煤焦的燃烧及其孔隙结构变化

采用热力工况与实际煤粉炉相近的沉降炉实验装置，制备了不同环境气氛下（O₂/N₂及O₂/CO₂气氛）、不同燃尽率的煤焦试样，并采用低温氮吸附仪和扫描电子显微镜测定了其孔隙结构和表面形貌。结果表明，在相同的操作条件下，相同O₂浓度的O₂/CO₂气氛下煤焦的燃烧速率较慢、燃尽率较低，各试样的孔比表面积和比孔容积均较小。两种气氛下燃尽过程孔结构参数（SBET和VBJH）均呈减小趋势，且在孔径变化较明显的区域内（<5 nm）在CO₂气氛下煤焦的孔径分布较小且与煤种相关。SEM图像显示CO₂气氛下的煤焦表面致密，孔隙较少，其定性结果与N₂吸附法的定量测量结果吻合较好。

Combustion of pulverized coal in O2/CO2 mixtures and its pore structure development

In a drop tube furnace with the similar combustion conditions of actual furnace, coal char samples with various burn-off rates, were prepared in different environments and analyzed with N₂ adsorption analyzer at a low temperature and scanning electronic microscope (SEM).The results showed that both burning rates and burn-off rates of chars in O₂/CO₂ environment were lower than those in O₂/N₂ environment with equivalent O₂ concentration and same operating conditions.The CO₂ char (derived in O₂/CO₂ environment) showed lower specific surface area and specific pore volume than that of the N₂ char (derived in O₂/N₂ environment).During the combustion processes, pore structure parameters of all samples, such as S_BET and V_BJH decreased with the increase in burn-off rate.The results also indicated that the CO₂ char showed poor pore distribution among a region less than 5 nm but correlated with coal rank.SEM results also indicated the same regularity and agreed well with those determined by the N₂ adsorption method.