The Research On Catalytic Coal Pyrolysis And Partial Gasification And Its Directional Control

In view of the present situation of resources and energy,coal will be the major primary energy in China in the foreseeable future.The multi-generation technology based on coal pyrolysis and partial gasification can achieve the efficient and clean utilization of coal by offering a certain place the most suitable resources and energy.Firstly,in this paper,the pyrolysis of coal at ultra-high-temperature was studied.Then,because of the controversy about the effect of catalyst on coal pyrolysis and the lack of the work in the investigation of the catalytic mechanism and the catalytic effect on the coal gasification in the H₂O and CO₂ mixed gas,the catalytic pyrolysis and gasification in H₂O and CO₂ mixed gas were studied by on-line measuring technology.In addition,the products controlling and catalytic mechanism were also included in this paper.Firstly,the pyrolysis characteristics of Shenmu bituminous coal and Baorixile lignite in the range of 5 0??1600 ? were studied by ultrahigh temperature thermogravimetric analysis.when the pyrolysis temperature exceeds 1000?,the volatilization yield increases very slowly;although there is still a weight loss peak between 1200 ? and 1500?,the little volatility yields does not dezerve the pyrolysis temperature up to 1500 ?.In the next chapter,Ca,Na,K and Fe were choosed as the catalysts,and then the effect of them was studied.As a result of the addition of them,At different temperatures,the formation rate and the yield of CO and CH₄ were always decreasing,while the formation rate and yield of CO₂ and H₂ varied with coal,catalyst and temperature.The varies of the yields of different products can be divided into three categories:The first type of these processes is represented by Fe and Ca-catalyzed pyrolysis of Pingzhuang lignite.The yields of CO,CO₂,CH₄ and H₂ are all reduced,resulting in the increasing of H₂O yield.The second type of these processes is represented by Ca-catalyzed pyrolysis of Shenmu coal at 800 0 C,the key progress in which was the trassmition of H and O from CO and CH₄ to CO₂,H₂ and H₂O.The last type was represented by Shenmu coal pyrolysis catalyzed by K and Na.The main process of that is the reduction of CO,CH₄ and H₂O yields,which induced the increase of the CO₂ and H₂ yields.Then,a mechanism is proposed to explain the different effects of these catalysts on coal pyrolysis at different conditions,according to the characteristics of the catalyst and the experiments.Finally,the effects of these catalysts on the gasification reaction were studied and more attention was paid to the effect of CaCl₂ and K₂CO₃ on the gasification rate and product composition of coal in H₂0 and CO₂ mixed gas.Because of the effect of CaCl₂,although the interaction between H₂O and CO₂ is still the strongest and the conversion is also the lowest in 50%H₂O and 50%CO₂ mixed gas,the reaction rate is lower than that in other mixed gases,due to the faster formation of the inertial carbon,which has a greater effect on the formation of CO,especially at the latter stage.Due to the contradiction between the catalytic effect of K₂CO₃ and the mutual effect between CO₂ and H₂O,the formation rate of H₂ in the early stage was not significantly increased comparing with the weighted value.So the average gasification rate did not increase much.However,the amount of residue in each atmosphere after the addition of the catalyst is lower due to the effect of the catalyst.After the addition of the catalyst,the formation rates of CO and H₂ were both increased in 30%H₂O and 70%CO₂ mixed gas.The interaction between H₂O and CO₂ benefited the increasing of H₂/CO,and so do the catalysts.Through the range of the atmospheres,catalysts and the degree of gasification,the ratio between H₂ and CO yields can be effectively controlled.At the same time,it was also found that the effect of the interaction between H₂O and CO₂ on the same coal when gasification varies with the inorganic matters and the composition of the gasifying agent.