温度和停留时间对煤热解挥发分二次反应的影响

在两段固定床反应器中考察了温度和停留时间对煤热解挥发分二次反应产物分布的影响. 结果表明，温度和停留时间对二次反应的影响相互关联. 温度≤600℃、停留时间小于2 s时，挥发分基本不发生气相二次反应. 随温度升高和停留时间延长，挥发分二次反应加剧，焦油产率下降，气体产率和积碳产率增加. 温度低于700℃时，焦油主要转化为气体产物，气相二次反应由二次裂解反应控制；高于700℃时，焦油转化为气体和积碳，气相二次反应由裂解反应和结焦反应共同控制. 提高二次反应温度和延长停留时间，热解气中的H2, CH4和CO产率增加，CO2产率减少，焦油中杂原子化合物及其中的酚、甲酚和二甲酚产率降低，大于3环的重质多环芳烃(PAHs)产率增加，H/C和O/C原子比降低，特别是在900℃时，随停留时间延长，H2和重质PAHs产率快速增加.

Influences of Temperature and Residence Time on Secondary Reactions of Volatiles from Coal Pyrolysis

The influences of temperature and residence time on secondary reactions of coal pyrolysis volatiles were investigated in a dual-stage fixed bed reactor. The results showed that the effects of temperature and residence time on secondary reactions are closely related. The secondary reactions of volatiles hardly occurred in general at the secondary reaction temperature≤600℃ and under residence time 2 s. The tar yield decreased while corresponding gas and deposited carbon yields increased by increasing temperature and residence time due to the intensified secondary reaction of volatiles. At lower temperature (below 700℃), the tar mainly converted into gas product by secondary cracking of tar. At higher temperature (above 700℃), the tar transformed into gas and deposited carbon products by the secondary cracking and coking of tar. With the increase of the temperature and the residence time of secondary reactions, the yields of H2, CH4 and CO increased while CO2 yield decreased, and also lead to the increase of the heavy PAHs (polycyclic aromatic hydrocarbons of more than 3 ring) and the decrease of the phenol, cresol, xylenol and atom ratio of H/C and O/C. Especially at 900℃, the yields of H2 and heavy PAHs increased rapidly with increasing the residence time, due to the occurrence of the violent condensation reactions among aromatic rings.