The Effect Of Coal Blending On The Ash Fusibility Characteristics And Gasification Characteristics Of Coal

Clean coal technology is the inevitable choice to realize the clean and effective utilization of coal resources.Coal gasification technology is the key technology of clean coal technology.Circulating fluidized bed coal gasification technology has been widely applied in engineering due to its advantages of mild gasification conditions,strong gasification intensity and less pollutant emission.However,there is a certain requirement for the ash fusion temperature and activities of raw coal because of its characteristics of dry ash and mild gasification temperature.Coal blending is a common method to reduce the cost of a coal gasification project and realize the localization of coal utilization.The trend of ash fusion point and gasification activity is very complicated and it is not linear superposition of raw coal characteristics,after mixing of different coal types,due to the complexity of coal and its ash components.Therefore,it is necessary to study the effect of coal blending ratio on the ash fusibility and the characteristics of gasification reaction of blended coal,to provide guidance for selecting appropriate proportions of coal blending for engineering projects to reduce the cost of gasification.In this dissertation,the influence of coal blending ratio on melting characteristics and mineral evolution of coal ash during coal gasification,the change of gasification characteristics of mixed coal,ware investigated to select suitable coal blending ratio for engineering application,at the same time,the feasibility of improving operation temperature in lean phase of fluidized bed gasifier was explored.The ash composition and fusibility characteristics ware studied by muffle furnace and ash fusion analyzer.The results show that the ash melting point of mixed coal is between Guanghui coal and Hongshagang coal,and decreases with the increase of coal blending ratio,however there is no linear relationship between the melting point of mixed coal and the blending ratio.The softening temperature of blended coal ash is higher than 1100?,when the blending ratio of Hongshagang coal is less than 40%,which meets the requirements of CFB gasifier 's operating temperature.In addition,the content of each component in blended coal ash is between the raw coal.The influence of coal blending ratio and gasification temperature on mineral evolution of blended coal was studied by horizontal tube furnace test platform.The results show that when the coal blending ratio increased from 0 to 40%at 950?,the content of CaO gradually decreased,on the contrary,Ca2Al2Si07 increases gradually,thus CaO gradually transformed into Ca2Al2Si07.The content of Ca2Al2Si07 gradually decreases,while CaS increases gradually,meanwhile SiO2 appears and gradually increased,when increasing blending ratio from 50%to 60%,CaO gradually transformed into CaS increasing blending ratio,the nepheline content will gradually decrease.With the increase of coal blending ratio,the surface of mixed coal gasification residues tends to be smooth,the surface attachments change from bulk to fine particles,and the adhesion phenomenon gradually decreases.It is appropriate blending ratio is from 30%to 40%on the basis of adhesion phenomenon.The influence of temperature and coal blending ratio on the gasification activity of mixed coal was investigated by thermogravimetric analyzer.The results show that the gasification temperature has a great influence on the gasification activity of mixed coal under the experimental conditions adopted in this study,The increase rate of blended coals' activity is related to the gasification temperature and blending ratio.The gasification activity of mixed coal decreases with increasing blending ratio,and increases with the increasing gasification temperature.Moreover,there is no linear relationship between the gasification activity and the blending ratio,while the maximum gasification rate of mixed coal is linear with the ratio of coal blending.According to the gasification activity and melting characteristics,it is more suitable to choose coal blending ratio of 30%-40%.The fusion behavior and gasification activity of mixture of char and ash were studied by ash fusion analyzer and thermogravimetric analyzer.The results show that the ash fusion temperature increases significantly after mixing with char,and decreases gradually to the coal ash fusion temperature with the increasing of ash blending ratio.There is no obvious difference of gasification activity between the mixture and the char in the experimental temperature range.The operating temperature of the lean phase can be increased without the limit of the coal ash melting temperature.