Study On Catalytic Steam Gasification Of Caking Bituminous Coal

China’s coking industry produces a large amount of washed coal every year.These washed coals are generally used for direct boiler combustion due to their low calorific value and high ash content.Catalytic gasification is a potential use of coal in washing,which enables clean and efficient use of coal samples.In this thesis,the effects of different catalysts（KCl,Na₂CO₃ and K₂CO₃）and different catalyst loadings（3%,5%and 7%）on the debonding effect of coal samples were investigated.The catalysts（K₂CO₃）and composite catalysts（K₂CO₃ and CaO）which achieved complete debonding effect were selected for fixed bed gasification experiments on coke samples prepared at 950°C.First,the coal coke volume（2g,3g,4g and 5g）and the water vapor flow rate(0.4L·min^-1,0.6L·min^-1,0.8L·min^-1 and1.0L·min^-1)were investigated.The effects of different gasification temperatures（700℃,750℃,800℃and 850℃）and different catalyst loadings on coal coke conversion were then investigated.Finally,a model for catalyzing gasification reaction kinetics（harmonious model（HM）,shrink core model（SCM）,and random pore model（RPM））was established.Research indicates:（1）The order of the different catalysts for the debonding effect of coal samples is K₂CO₃>Na₂CO₃>KCl.The coal sample loaded with K₂CO₃ can achieve complete debonding;the larger the catalyst loading,the better the debonding effect.（2）When the coal coke amount is 3g and the water vapor flow rate is 0.8L·min^-1,the influence of coal coke internal and external diffusion can be basically eliminated.（3）The higher the temperature,the larger the catalyst loading,and the higher the carbon conversion rate of coal char.Among them,the K₂CO₃ loading per gram of YZ is 7%,and the carbon conversion rate of coal char can be 100%when the temperature is 850°C.The gasification activity of PDS is slightly lower than that of YZ.（4）The main components of the gas products are H₂,CO,CO₂ and CH_4,of which H₂ content is the highest and CH₄ content is the lowest.CaO in the composite catalyst can modulate the gas product composition and increase the H₂ production.（5）The harmonious model（HM）and the shrink core model（SCM）have better fitting results at lower temperatures,and the results are worse when the temperature is higher.The random pore model（RPM）has a poor fitting effect when the conversion rate reaches 100%.The final results show that the correlation coefficient of the random pore model（RPM）simulation increases with the increase of temperature,and the correlation coefficient is higher than the harmonious model（HM）and the shrink core model（SCM）,and the simulation effect is the best.