CO2气化反应对O2/CO2气氛中煤焦燃烧特性影响

为探讨CO2气化反应在低氧气体积分数下对煤焦燃烧及燃烬过程的影响，利用热天平对比研究了大同煤焦在O2/N2/和O2/CO2气氛中的燃烧行为，主要探讨CO2气化反应对煤焦富氧燃烧特性的影响。实验结果表明，在5%氧气体积分数下，煤焦在O2/CO2气氛下的燃烧速率要低于O2/N2气氛下。当氧气体积分数降低到2%，且温度高于900 ℃时，在CO2气化反应的作用下，煤焦在O2/CO2气氛中的整体反应速率逐渐高于O2/N2气氛中的燃烧速率，使得燃烬提前。随着环境温度的升高，煤焦在O2/CO2和O2/N2气氛下的反应速率均有所增加，但在O2/CO2中增幅更显著。动力学分析显示，在5%氧气体积分数时，大同煤焦在O2/N2中的活化能要低于O2/CO2中。当氧体积分数减少到2%时，由于高温下煤焦的燃烧和气化反应同时进行，较高的气化反应活化能使得煤焦在O2/CO2中的整体反应活化能有明显增加。

Effect of CO2 gasification on the combusiton characteristics of char under O2/CO2 atmosphere

In order to investigate the effect of CO2 gasification reaction of coal char combustion and combustion process under low oxygen concentration，the burning behaviors of Datong char under O2/N2 and O2/CO2 atmosphere were comparatively investigated by thermo-gravimetric analyzer，in particular，the influence of CO2 gasification to the oxy-fuel combustion characteristics of char were mainly studied.The results generally indicate that at 5% oxygen concentration the burning rate of char is slower in O2/CO2 than in O2/N2 mixture.When the oxygen concentration reduces to 2% and the temperature is above 900 ℃，the overall reaction rate of char in O2/CO2 is higher than the burning rate of char in O2/N2 mixture，which results in an earlier burnout.With the rise in temperature，the both burning rates of char under O2/CO2 and O2/N2 atmosphere increase，but the growth amplitude in O2/CO2 mixture is more significant.The kinetic analysis shows that at 5% oxygen concentration the activation energy in O2/N2 is lower than in O2/CO2 mixture.As the combustion and gasification of char occur simultaneously at high temperature with 2% oxygen concentration，the overall reaction activation energy under O2/CO2 atmosphere increases obviously due to the higher activation energy of CO2 gasification.