Steam Gasification Of Low Rank Coal At Low/Medium Temperature And The Catalytic Effect Of Inherent Minerals

Baganuur lignite (BN), Nalaihk lignite (NL), Alagtogoo (AT) and Shengli lignite (SL)were chosen as the samples and Tavantolgoi anthracite (TT) was chosen as the referenceobject for the study. The basic components of the coal samples, surface functional groups,pyrolysis properties, physical and chemical adsorption properties were characterized. Coalsamples were processed by hydrochloric acid and coal samples processed by hydrochloricacid were added minerals in. This article focuses on studying performance of TPSG(Temperature programmed steam gasification) about the raw, the coal sample afterhydrochloric acid treatment and the coal sample after adding mineral. Gasification reactionwas analyzed on thermodynamics and kinetics, reaction mechanism of Minerals in situcatalytic about low rank coal steam gasification reaction was proposed.The results show that there are little difference among four kinds of low rank coal onthe respects of volatile matter, fixed carbon and the elements of C and O, but significantlydifference with anthracite TT-Raw. There is no significant difference between low rankcoal and anthracite. But low-temperature oxidation activity of low rank coal is significantlyhigher than anthracite. Its molecular structure is more stable than the anthracite’s, it hasbetter thermal properties of chemical reactions. The initial temperatures of gasificationreaction for four kinds of lignite are about600℃, the maximum synthesis gas generationrate temperatures are all about700℃. And gasification reaction starting temperature ofTT-Raw is730℃and the maximum temperature of the synthesis gas generation rate is850℃.They are significantly higher than lignite. After removal of some minerals byhydrochloride, the initial temperatures of coal gasification for SL BN and NL increase by102℃,96℃and90℃respectively. Among the kinds of gasification syngas, thecumulative yield of H2reduces more than46%, the cumulative yield of CO2reduces morethan75%, the cumulative yield of CO increases more than4.9times. Before the treatmentof hydrochloric acid, the AT’s cumulative H2/CO molar ratio of syngas is6.94. After thetreatment of hydrochloric acid, it becomes to9.05. And after the treatment of hydrochloricacid, for SL, BN and NL, the cumulative H2/CO molar ratio of syngas are1.28,1.58and1.63, much lower than their raw about20. And after the treatment of hydrochloric acid, forSL, BN and NL, the activation energy of gasification reaction and the activation energy of the main products of gasification reaction are lower than the raw. However, due to thefrequency factor greatly reduce the gasification reactivity of the three kinds of coal aresignificantly lower than their raw. After the treatment of hydrochloric acid, AT frequencyfactor is7-9orders of magnitude higher than SL, BN and NL. It shows that impact ofhydrochloric acid on the gasification kinetics primarily associated with coal types. Ca canimprove gasification rate and carbon conversion rate of low rank coal in low temperature(600-750℃). However, the catalytic steam gasification reaction of anthracite is not obvious.Na and K can improve the gasification rate and carbon conversion rate of low rank coal inhigh temperature (750-850℃). And there is no significant catalytic effect to use Al, Mnand Fe. The catalytic effect of minerals is mainly achieved by WGSR in catalyticgasification process. The catalytic effect can reduce the vaporization temperature, increasethe content of H2and CO2, and reduce the content of CO.