燃烧中气化半焦孔隙结构特性变化实验研究

针对工业气化炉二级旋风分离器捕集的气化后半焦,利用高温携带流反应器进行高温燃烧反应特性实验。对1273和1573 K两个温度,5%和20%两个烟气含氧量,在反应器轴向不同停留时间下采得半焦样。采用自动吸附仪(ASAP 2020)测定半焦样氮吸附等温线,对氮吸附等温线形态、BET比表面积及BJH孔容积等孔结构参数进行了分析,并结合分形维数测量和扫描电镜对燃烧过程中气化半焦孔隙结构变化规律进行研究分析。研究表明所采集的半焦样吸附等温线为典型Ⅱ类吸附等温线,高温和较高烟气含氧量对半焦孔隙结构变化有促进作用,半焦燃烧反应中比表面积变化趋势与半焦燃烧反应速率变化趋势相似,后期燃尽速率主要由焦炭本征反应活性决定。

Experimental Study on Pore Structure Changing of Gasified Coal Char Under Combustion

The combustion characters and pore structure changing of the gasified coal char obtained from the secondary cyclone of the Jincheng industrial gasifier were experimental studied at high temperature in a simulator of high-temperature entrained flow reactor.Gasified Chars were burned at the temperature of 1273 and 1573K,the oxygen contain of 5% and 20% and sampled along the reactor at different axial residence time.Automatic adsorption instrument(ASAP 2020) was employed to measure absorption isotherms of sampled chars.Cryogenic nitrogen absorption isotherms,parameters such as BET specific surface area,BJH pore volume and average pore diameter were measured and analyzed.Surface morphology of the char was further studied by scanning electron microscopy(SEM) and with fractal theory.The isotherms of char samples at different residence time were all type II.Higher temperature and more oxygen concentration both can improve the changing of char pore structure.The changing of specific surface areas during the combustion is consistent with the trends of reacting rates for chars.The char reacting rates in finial reacting period is mainly dominated by char intrinsic reactivity.