二次热解对污泥热解产物影响的研究

The Second Reaction of Pyrolysis Volatiles from Sewage Sludges in a Fixed-bed Reactor

针对上海市污水污泥,以提高热解气体、抑制热解焦油为目标,利用两段固定床反应器,研究二次热解温度对污泥一次热解挥发分的热解特性的影响。利用气相色谱定量研究不同二次热解温度下热解气中H2、CO、CO2、CH4的含量变化。利用全二维气相色谱-飞行时间质谱联用仪(GC×GC-TOFMS)定性研究不同二次热解温度下热解油化学组分。结果表明:二次热解温度高于600℃时,热解气体产率明显增加,液体产率明显减少。这表明,在仅改变上段固定床二次热解温度的条件下,一部分污泥热解油通过高温二次热解转化为气体。其中CH4是受二次热解影响最大的气体,相比于一次热解,当二次热解温度高达700℃时,CH4的累计释放量增加了7.0倍,这表明热效应明显促进了污泥热解挥发分的脱甲烷反应。为了更好地揭示污泥热解油转化成热解气的机理,运用GC×GC-TOFMS分析污泥热解油中上千种化合物。我们猜测长链脂肪含氮化合物主要通过脱甲烷反应产生CH4。酮类通过脱羧反应生成CO。

The sewage sludge was pyrolyzed in a fixed bed reactor at a heating rate of 10℃and a final temperature of 700℃, and the resultant volatiles were allowed to be secondarily cracked through a tubular reactor in a temperature range of 500-700℃. The thermal effect on the cracking of tar was investigated. It was found that the thermal effect was catalytically active for the tar cracking at 600-700℃ . CH4 was dominantly affected among the secondary pyrolysis gas, indicating that the second reaction dramatically influenced the demethylation. In order to reveal the mechanism of transforming pyrolysis oil into gas, we used the GCXGCTOFMS to analyze thousands of compounds in the pyrolysis oil. Long chain aliphatic amides, nitriles generated CH4 through demethylation, while ketones produced CO by decarboxylation.