Study On Catalytic Gasification Of Crushed Coke

Metallurgical coke is an important material for blast furnace iron making process,which needs a given size distribution of fragmentation.However,in the process of production and transportation,some coke will be broken into crushed coke,which can not be filled into blast furnace.Resulting of the above-mentioned,crushed coke becoming a kind of waste.The gasification technology will convert coke into synthesis gas for further processing of methanol,alkene and other chemical products,not only increasing the added value of coke but also solving the problem of low coke price with put market demand,receiving obvious environmental and economic benefits.However,crushed coke was characterized by low gasification activity and a high gasification initiation temperature.Therefore,improving the gasification rate of coke is a critical problem.The catalytic gasification technology of coal is used to promote the coal gasification reaction by adding a catalyst,which can significantly improve the gasification reaction rate,it is suitable for solving the problems of high temperature and slow gasification rate of crushed coke gasification.In this paper,a series of studies have been carried out on the catalytic gasification of crushed coke and the structural changes in the gasification process.The main contents of this study are as follows:Firstly,the effects of three cheap catalysts:Na2CO3,Fe2O3 and CaO on the gasification performance and gasification temperature of crushed coke were investigated by a TG-MS with steam as gasifying agent.At the same time,the proper amount of catalyst supported and the kinetics of catalytic gasification reaction of crushed coke were discussed.The results show that the catalytic activity of Na2C03 is the highest among three catalysts,The gasification reaction rate of CaO for crushed coke was not improved;Fe2O3 has a certain lifting effect on the gasification reaction activity of crushed coke,but the effect is weak;after adding Na2CO3,the gasification temperature of crushed coke was reduced by about 170℃,and the maximum gasification rate was raised from 0.351/℃ to 0.365/℃.With the increase of Na2C03 load,the gasification rate of coke increases gradually.The loading amount of Na2C03 reached saturation at about 5%,and excessive catalyst could not effectively increase the gasification rate of coke.For the gasification reaction of char with Na2CO3,SCM model can reflect the kinetic law of gasification very well.Secondly,the structure change of crushed coke gasification/catalytic gasification reaction were studied,coke samples under different reaction times were prepared using a tube type furnace.A specific surface area and porosity analyzer,an X-ray diffraction apparatus and a Raman spectra apparatus were used to characterize the structure of the cokes.BET data indicated that the addition of Na2CO3 can effectively corrode the pores on the surface of the coke to produce many small holes on the surface of the coke and widen the aperture of the coke.When Na2C03 is added to the channel of the coke,the smaller porosity of the coke becomes more crowded.Coke loaded with Na2C03 has a larger average pore diameter,which is more beneficial to the reaction with steam.Raman spectra analysis demonstrated that the degree of graphite-like structures in the graphite layer increases as the reaction proceeds and that Na2C03 inhibits the growth of large aromatic ring structures and decreases the content of graphite-like crystal structures.The XRD results suggested that some of the sodium atoms are inserted into the coke matrix and distort the orientation of carbon crystallites,thus effectively hindering the trend of carbon graphitization in the process of gasification.The XRD analysis result is in accordance with the results of Raman analysis.Finally,the effects of gasification conditions on the catalytic gasification of char were investigated,and it was found that the catalyst loading mode,reaction temperature,steam/carbon ratio and water vapor partial pressure had some effects on the gasification of crushed coke.For char catalytic gasification,the loading mode of Na2C03 by impregnation method is better than that by mechanical mixing method.With the increase of temperature from 800 ℃ to 1000℃,the conversion rate and gasification rate of crushed coke catalytic gasification increased obviously,and the highest gasification rate reached when the temperature reached 1000℃;With the increase of steam/carbon ratio from 1:1 to 5:1,the gasification rate of catalytic gasification is obviously increased,but continue to improve the steam/carbon ratio has little effect on the gasification rate of crushed coke.Different water vapor partial pressures have little influence on catalytic gasification reaction of crushed coke,as water vapor partial pressure increases,the reaction rate of crushed coke gasification is increased,but the increase data were small.When the water vapor partial pressure is 100%,it has the fastest gasification rate.