CO_2/H_2O气化反应作用下煤恒温富氧燃烧特性

利用自制恒温热分析系统研究了不同气氛中(O_2/N2,O_2/CO_2和O_2/H2O_/CO_2)煤粉在温度(800~1 200℃)和氧气体积分数(2%~21%)范围内的燃烧行为,主要关注CO_2/H2O_气化反应作用下的燃烧特性。结果表明:在800℃时,大同烟煤在O_2/N_2中相对O_2/CO_2较快的燃烧速率主要源于N_2和CO_2物性的差异。温度升高到1 000℃进而到1 200℃,CO_2气化反应影响增强,大同煤在O_2/CO_2中整体反应速率逐步接近并超过O_2/N_2中的燃烧速率。但是当氧气体积分数超过10%后,气化反应影响减弱,大同煤在O_2/CO_2中的反应速率又逐渐落后于O_2/N_2中。因为H_2O比热和氧扩散能力介于N_2和CO_2之间,在气化反应作用之前,大同煤在O_2/CO_2/H_2O中的燃烧速率低于O_2/N_2而高于O_2/CO_2。在2%氧气体积分数下,温度的升高强化了CO_2/H_2O协同气化的影响,使得大同煤在O_2/H_2O/CO_2中的整体反应速率始终要高于O_2/CO_2中;但是氧气体积分数增加到10%后,协同气化作用减弱,导致大同煤在3种气氛中的反应过程较为接近。与大同烟煤相比,阳泉无烟煤在气化反应作用下的整体反应速率增幅更加明显,说明气化对高阶煤反应过程改善可能更为显著。

Oxy-fuel combustion characteristics of pulverized coal under the cction of CO2/H2O gasification at constant temperature

The burning behaviors of pulverized coal under different atmospheres (O2/N2,O2/CO2 and O2/H2O/CO2) in the range of temperature (800-1 200 ℃) and oxygen concentration (2%-21%) were comparatively investigated using the isothermal thermal analysis system.The combustion characteristics of coal samples under the action of CO2/H2O gasification were mainly studied.The results indicate that at 800 ℃ the burning rate of Datong bituminous coal (DT) in O2/N2 is faster than that in O2/CO2 due to the different physical properties between N2 and CO2.The effect of CO2 gasification is enhanced with the increase of temperature from 1 000 ℃ to 1 200 ℃ and as a result,the overall reaction rate of DT in O2/CO2 approaches and exceeds the burning rate in O2/N2.But the effect of gasification is weakened with the increase of oxygen concentration (e.g.≥10%),and the reaction rate of DT in O2/CO2 gradually lags behind that in O2/N2.Because the specific heat and the oxygen diffusion rate of H2O are between those of N2 and CO2,the combustion rate of DT in the O2/CO2/H2O is lower than that in O2/N2 but higher than that in O2/CO2 without the effect of gasification.At 2% oxygen concentration,the influence of CO2 and H2O synergistic gasification is enhanced by increasing temperature and thus the overall reaction rate in the O2/H2O/CO2 is always higher than that in O2/CO2.But a higher oxygen concentration (e.g.10%) weakens the effect of synergistic gasification which leads to the similar burning processes in different atmospheres.With the effect of gasification,the overall reaction rate of Yangquan anthracite (YQ) increases more significantly compared to DT,which indicates that the gasification has remarkable influences on the reaction process of high-rank coal.