Study On Co-Gasification Characteristics Of Straw Stalks And Yongcheng Anthracite

Yongcheng anthracite and Xuzhou rice straw were selected as raw materials in the paper.The Yongcheng anthracite ash was removed by HCl-HF combined acid-washing and the structure and properties difference of coal samples after removing ash were explored by FTIR,SEM,BET and other methods.Then the co-pyrolysis,non-isothermal co-gasification and mixed semi-coke isothermal co-gasification experiments of rice straw,Yongcheng coal,and deashed coal were developed by thermogravimetric analyzer,and the experimental results were analyzed using a kinetic model.The experimental content and conclusions are as follow(1)The pore diameters of the raw coal are basically micropores,but the demineralized coal samples are mainly mesopores and the pore diameters are about2-3.8nm,the specific surface area of the coal samples increases from 0.607 m²/g to3.868 m²/g.The surface of the raw coal is relatively rough.After removing the coal ash,the surface of the coal sample is destroyed and the mineral particles are dramatically decrease,also appearing some fold structures.FTIR showed that the number of absorption peaks of the coal sample was reduced,removing the alkyl side chains and small molecules mainly containing oxygen functional groups.(2)The co-pyrolysis experiment of rice straw and Yongcheng coal was conducted through thermogravimetric analyzer.The results showed that with the rawcoal sample blending ratio increased from 5%to 15%,the initial pyrolysis temperature decreased,and the depressed pyrolysis weight loss rate peak and corresponding temperature.After removing the ash,the pyrolysis temperature increases and maximum weight loss peak peak value increases.It is speculated that the pyrolysis reactivity is dominated by the AAEM catalysis in the coal,and thediffusion of the pore structure effect failed to control.Selecting the n-level reaction model to analyze the activation energy of the reaction.Compared with the co-pyrolysis of rice straw and Yongcheng anthracite,the activation energy of the mixing demineralized coal sample increased,which may be related to the large amount of AAEM removed from the coal sample.(3)The non-isothermal co-gasification experiment of Yongcheng coal,demineralized Yongcheng coal and rice straw was carried out through the thermogravimetric analyzer under the condition of the final gasification temperature of 1100?and the heating rate at 15K/min.The results show that when the blending ratio of Yongcheng coal increases from 5%to 15%,the starting gasification temperature of the sample,the peak temperature and the peak value of the weight loss rate increase.After removing the ash,the absolute value of the gasification weight loss rate peak increases.The removal of ash is beneficial to the diffusion of the gasification agent between the pores,it is possible that the gasification reaction rate is greatly affected by the diffusion of the pore structure in the middle and late stages of the reaction.The shrinking nucleus model is selected to analyze the reaction activation energy.The reaction activation energy decreases with the increase of the raw coal blending amount.After removing the ash,the reaction activation energy of the mixed sample increases,which may be combined with catalysis of some alkali metals in the coal ash for gasification reactivity.(4)The effects of gasification temperature,coal sample blending ratio and ash content on the isothermal cogasification reactivity of mixed semi-coke were studied.The results showed that when the Yongcheng coal-coke blending ratio increased from5%to 15%,the sample's carbon conversion rate decreases,sample gasification reaction time increases,gasification reactivity indexes R_0.5 and R_0.9 decrease,and the maximum gasification reaction rate decreases.As the gasification temperature increased from 950?to 1100?,the gasification reactivity index increases and the maximum gasification reaction rate increases.The gasification reaction rate of the sample is lower at low temperature with ash acid-washing,as the temperature rises to 1100?,the gasification rate is higher than that of raw coal.It may be attribute to the catalysis of alkali metals at lowtemperature has a greater impact on the gasification reactivity,and catalysis weakens with the increase of the gasification temperature,and finally is determined by the diffusion of the pore structure.The random pore model was selected to analyze the activation energy of the reaction,and the activation energy of the sample blended with demineralized coal char was lower than that of blending raw coal sample.