Effect Of Ca/Fe On Thermal Evolution And Reaction Activity Of Semi-Coke Structure

Anthracite is an ideal gasification raw material due to its high degree of coalification and low impurity content,but its poor gasification activity has been a difficult problem to solve.The study on the physicochemical structure and reactivity of anthracite semi-coke is not only helpful to the application of anthracite in the gasification field,but also of great significance to the clean and efficient utilization of coal.In this paper,anthracite coal was used as the research object.And demineralized anthracite coal was obtained by HCl-HF pickling raw coal,and its physicochemical properties and reactivity changes of coal samples before and after pickling were detected.Based on the acid-eluted demineralized coal,the influence of Ca/Fe catalyst on the thermal evolution progress of the physicochemical structure of the demineralized coal and the activity of CO₂ gasification reaction was investigated.The kinetic model suitable was established by fitting the experimental data for catalytic gasification reaction,which provides theoretical basis and data support for the catalytic gasification technology of anthracite industry.The main contents and results were summarized as follows:Demineralized coal samples were prepared by HCl-HF pickling.Scanning electron microscope（SEM）,X-ray diffractometer（XRD）,Fourier transform infrared spectrometer（FT-IR）,Raman spectrometer（Raman）and thermogravimetric analyzer（TGA）were used to analyze the influence of mineral removal process on the physical and chemical properties of coal samples.The results showed that the acid elution demineralization process reduced the dry ash content of coal samples from 19.76%to 0.21%,the median diameter of coal particles decreased from 67.02 um to 54.75 um,and the surface of coal particles was rough.In addition,the content of-OH groups in demineralized coal samples were increased by acid elution.At the same time,the accumulation height of the aromatic layer of coal samples was reduced from 3.133 nm to 3.033 nm,and the aromaticity was increased from 73.25%to73.59%through demineralization progress.The degree of graphitization of coal samples was basically not affected,and the degree of carbon skeleton ordering was slightly reduced.The pyrolysis rate and weight loss of demineralized coal were higher than that of raw coal.At the same time,although the reaction rate of demineralized coal in the early stage of gasification reaction was lower than that of raw coal,the overall reaction rate was similar to that of raw coal.The impregnation method was used to add a single catalyst of Ca and Fe and a composite catalyst with a ratio of Ca-Fe to the demineralized coal.TGA was used to analyze the effect of the amount and type of catalyst on the pyrolysis performance of the demineralized coal.In addition,XRD,FT-IR and SEM were used to characterize the effects of different catalysts on the physical and chemical structure of semi-coke at different pyrolysis temperatures.The results showed that the effect of Fe catalyst was better than that of Ca catalyst,and Fe catalyst has a better catalytic effect than the same amount of Ca;the Ca-Fe composite catalyst was more complicated for the pyrolysis process,and the overall heat was3%Ca-2%Fe.The degree of decomposition was greatest.Ca,Fe and Ca-Fe composite catalysts can all promote the reduction of the stacking height of semi-coke crystallites and inhibit the increase of the crystallite diameter size.The composite catalysts were more effective than single-component catalysts.The Ca catalyst helps the retention of unsaturated functional groups,while the Fe catalyst promotes the decomposition of the unsaturated functional groups.The Ca-Fe composite catalyst promotes the decomposition of C-O more effectively than a single catalyst.Ca mainly promotes surface erosion,Fe mainly develops surface pore structure,and the Ca-Fe composite catalyst promotes surface erosion and pore development.Constant temperature CO₂ reaction was carried out in TGA,and the reaction activity of gasification temperature,catalyst loading type and catalyst content on the semi-coke produced by pyrolysis of demineralized coal was explored.The results showed that the catalytic effect of the Ca catalyst on the CO₂ gasification rate of semi-coke increases with the increase of the added amount,and the difference of the reaction index decreases with the increase of temperature.The catalytic performance of Fe catalyst is similar to that of Ca catalyst.The Ca-Fe composite catalyst has a higher increase in the gasification rate of semi-coke CO₂ than a single pure component catalyst,and the3%Ca-2%Fe composite catalyst has the best synergistic effect.The fitting coefficient is low when the classical kinetic model was used to fit the experimental data of catalytic gasification.Modifying the pore structure parameters of the random pore model can improve the correlation coefficient of curve fitting.The larger the correction coefficientα,the stronger the catalytic ability of the catalyst.Compared with the activation energy of semi-coke gasification reaction without adding catalyst,the activation energy of adding 5%Ca catalyst is reduced by about 64%,the activation energy of adding5%Fe catalyst is reduced by about 44%,and the activation energy of adding 3%Ca-2%Fe catalyst,the activation energy is reduced by about 78%.Figure[43]Table[20]Reference[129]...