Experimental Study On Fluidization Modification And Ash Melting Characteristics Of Coal And Gasified Fly Ash

One of the important technologies for clean and efficient coal utilization is coal gasification technology.In recent years,fluidized bed gasification technology has been rapidly developed and widely used.Fluidized bed gasification technology has the advantages of low gasification temperature,high strength,wide adaptability of coal,good heat and mass transfer in the furnace,uniform temperature distribution.However,large heat loss,high content of effluents in gas,low effective components and low carbon conversion rate are also shortcomings that cannot be ignored.At the same time,with the strict national environmental protection laws and regulations,the melting technology that can realize the efficient and environmentally friendly utilization of gasification fly ash will also become a new market trend.In the direction of the development of modern coal gasification for solid-state discharge to develop in the direction of liquid slag discharge,national developing clean coal utilization technology of big background,in view of the gasifier tail flue emissions low volatile gasification of fly ash,puts forward the fluidization melting gasification technology for gasification of fly ash,fly ash gasification efficiency,to improve resource utilization,low pollutant emission targets.In 15 kg/h preheating gasification test-bed,we use shenmu bituminous coal,inner Mongolia lignite,suqian gasification of fly ash and shenmu gasification of fly ash,using X-ray diffraction,scanning electron microscope,laser particle size analyzer,thermogravimetric differential thermal analyzer,specific surface area and porosity analyzer on the fluidization modification and quality improvement of semi coke in fluidized process is studied: the research,gasification agent and particle size of coal,steam coal than factors such as characteristics of coal and the structure of modified carbocoal and gasification reactivity of different effects.The results show that compared with pyrolysis coal coke,the modified semi-coke has more secondary pores,more developed pore structure,more ordered carbon microcrystalline structure and better gasification reactivity.After the fuel is fluidized and modified,the physical and chemical properties will change,mainly reflected in that the median particle size can be reduced,the specific surface area and pore volume of the semi-coke can be increased,and the carbon conversion rate of the semi-coke changes faster with time.Under this action,fluidization modification can improve the reactivity of semi-cokegasification.After the fuel is modified by fluidized gasification,the physical and chemical properties will change,mainly reflected in the reduction of the median particle size,the increase of the specific surface area and pore volume of the semi-coke,and the improvement of the carbon conversion rate and the cold gas efficiency.The carbon conversion rate of the semi-coke changes faster with time,and the gasification reactivity is better.Under this action,fluidized gasification modification can improve the reactivity of semi-coke gasification.By changing operating parameters,the optimum operating conditions for fuel modification and improvement were studied.The research shows that the increase of temperature will lead to the increase of reaction rate and the positive deviation of reaction equilibrium,which will strengthen the reaction of water gas.Increasing the oxygen concentration of primary gasifier depends on reducing the air flow rate and increasing the oxygen flow rate,which promotes the reaction of water gas.The increase of steam-coal ratio can enhance the modification and improvement of fuel particles by promoting the reaction of water gas.The gasification reactivity of semi-coke obtained by fluidized gasification modification of steam coal is better than that obtained by fluidized gasification modification of 0.87kg/kg.The high temperature melting characteristics of semi-coke modified by convection state were studied: the changes of coal type and atmosphere on the viscosity temperature characteristics and the melting point characteristics of ash from raw coal to fluidized modified semi-coke were studied.The results show that calcium oxide has a melting effect on fly ash of shenmu coal gasification,and there is an optimal addition interval.Calcium feldspar and calcium silicate in ash appear in large quantities to form low-temperature eutectic bodies.The continuous addition of CaO may lead to the occurrence of calcium silicate with high ash melting point and single crystal calcium oxide,thus leading to the increase of characteristic temperature of ash melting.The effect of fluidization modification on reducing the melting point of fly ash of godswood gasification is obvious and stable.In addition,the fluidization modification also has the same effect on reducing the melting temperature of soot in the same stable way for shenmu bituminous coal and suquan gasification fly ash.Fluidization modification can improve the viscosity-temperature characteristics of gasification fly ash.Gasification fly ash after fluidization of modified fly ash in the content of silica,alumina drastically,calcium oxide content increased,viscosity-temperature curve becomes more smooth,along with the change oftemperature and compared to the raw material,the phenomenon of the left deviation,critical temperature viscosity ratio reduces the raw materials,and by not suitable for the crystallization of liquid slag discharge slag slag into the vitreous,viscosity-temperature characteristics better,more conducive to liquid slag discharge.