Dissertation > Industrial Technology > Chemical Industry > Coal gasification industry > Gasification process

Catalytic Cracking of Coal Pyrolysis Product for Oil and Gas Upgrading Over Char-based Catalysts

Author WangXingDong
Tutor LuJiangYin; XuGuangWen; GaoShiQiu
School Xinjiang University
Course Chemical Engineering and Technology
Keywords Coal pyrolysis Catalytic upgrading Char catalyst Coal tar Coboltcatalyst
Type Master's thesis
Year 2012
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China is a major coal mining and consumption country,which has the coalstorage ranking number3in the world, and the coal resource is the dominant resourcein its primary energy structure. Now the coal in China is mainly used to directcombustion for industrial and civilian use, and the coal utilization rate is low andproduces serious pollution to the environment. At the same time, China is in greatshortage of oil and gas resources and the oil import volume increases year by year. Toincrease the efficiency of coal use and decrease the oil import amount, the use of coalpyrolysis technique for the production of liquid fuel and coal gas to replace oil andnatural gas is imperative. The catalytic pyrolysis technique could be used to producehigh-quality oil and gas production under mild reaction conditions,So the dual-stage fixed bed reactor which was composed of upper pyrolysis stageand lower catalytic stage, was used in this dissertation to compare the effects ofdifferent pyrolysis techniques on Fugu coal pyrolysis products. It was found that thechar could be used to control the primary pyrolysis products with the catalyticcracking technique, and improve the quality of oil and gas effectively.Then the catalytic cracking upgrading of coal pyrolysis oil and gas products wasconducted in a dual-stage reactor using char or de-ashing char and Ni,Co-impregnated char or de-ashing (Co-char and Ni-char) as the catalyst. The testedcoal was Fugu coal, and the upper stage of the dual-stage reactor was used forpyrolysis. It was shown that the catalytic cracking of coal pyrolysis productsdecreased the tar yield and increased the gas yield and also the fraction content oflight oil (boiling points <360℃) in tar, while the yield of light tar remainedconstantly or increased slightly. Compared with the direct pyrolysis of coal at600℃,When the Co-char was used as the catalyst, the cracking at500℃over the catalyst of5%coal mass increased the light oil yield by8.8wt.%and the light oil content in thetar by28.8wt.%, although the gas yield increase was only21.5vol.%. Thus, in coal pyrolysis the upgrading effects of the secondary catalytic cracking appeared to be theeffective way to convert heavy oil components into pyrolysis gas.Finally, the catalytic pyrolysis effect of Al2O3-supported Co on coal pyrolysisproducts was investigated. It was found that the catalytic pyrolysis effect wasstrengthened with Al2O3, and tar removal catalytic cracking reaction is dominantwhen the quantity of Al2O3-supported Co equals20%quantity of the coal sample.Compared with the coal pyrolysis without catalyst,, the tar yield decreased by56.8%,while the light component in oil and gas yield increased by48.1%and108.3%,respectively.

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