热态半焦和冷态半焦催化裂解煤焦油研究

Research on coal tar catalytic cracking over hot in-situ chars

对比研究了热态半焦(原位热解半焦)和冷态半焦(热解后温度降至常温的半焦)对煤焦油的催化裂解特性。结果表明,相同条件下,热态煤半焦比冷态煤半焦具有更高的催化裂解焦油能力。当裂解温度为1 100℃,热解气体在热态半焦层中的停留时间为1.2 s时,催化裂解后燃气中焦油含量可降至100 mg/m3。BET分析结果表明,热态半焦比冷态半焦具有更大的比表面积和更发达的微孔结构。同时,在不可避免经历相对明显的高温过程中,冷态半焦的碳微晶结构有序度增加,进而导致其活性有所降低。随着气体停留时间的延长或催化裂解温度的提高,燃气中焦油含量迅速降低,但热态半焦与冷态半焦催化裂解焦油的活性差异也变小。半焦催化裂解焦油后,活性明显降低,但使这种半焦与水蒸气发生部分气化反应后,其活性基本得到恢复。

A comparison of coal tar catalytic cracking over hot char from in-situ coal pyrolysis and cooling char w as investigated.The results show that the in-situ char has a higher capability of removing tar than the cooling char under the same reaction conditions.The tar content in the product gas is reduced to as low as 100 mg / m3 w hen the temperature of the in-situ char bed and the gas residence time in the bed are 1 100 ℃ and 1.2 s,respectively.BET analysis show s that the in-situ char has larger specific surface area and more micro pores than the cooling char,w hile the uniformity of the carbon crystallite structure in the cooling char increases,causing the decrease of the char＇s catalytic activity for tar removal.With the increase of gas residence time in the char bed or of cracking temperature,the tar content in the product gas decreases greatly,w hile the difference of catalytic activity for tar cracking betw een in-situ char and cooling char also decreases.The activity of the spent char is decreased significantly.How ever,the activity of the spent char can be basically recovered w hen it is partially gasified w ith steam.