The Coupling Integration Process Of Coal Pyrolysis And Coal Tar Hydrogenation Upgrading

Coal pyrolysis technology is an effective way to realize the clean and efficient utilization of low-rank coal.Under the two themes of high-quality development of China’s energy reform and the"double carbon"goal,it is particularly important to choose a suitable and efficient clean coal utilization process.In order to solve the problems of poor tar quality in low-rank coal pyrolysis process.The catalytic activated hydrogen as coal pyrolysis atmosphere to regulate its product distribution was used in this work,and the aromatic-rich tar production by in-situ catalytic upgrading coupling process of coal pyrolysis tar under hydrogen and coke oven gas atmosphere was proposed.Finally,the mechanism of these processes was investigated by isotope tracer method.The main research results of the paper are as follows:（1）Firstly,the effects of temperature on product distribution,tar quality,tar composition and gas composition of coal hydropyrolysis were investigated.The research results show that hydrogen improves the pyrolysis conversion of Shenmu coal and plays a significant role in promoting the formation of tar and gas,and the highest temperature of tar yield is at 650°C.Hydrogen can promote the production of CH₄ and improves the content of light oil fractions and aromatics in tar.Subsequently,the effects of catalytic activated hydrogen with different catalysts on coal pyrolysis product distribution,tar quality and tar composition were investigated.The results show that at 650°C,the catalyst of Cat-3 has the best hydrogen catalytic activation and obtains the highest tar yield of 18.26 wt.%.The light oil content increased,the asphalt content decreased,and the benzene and naphthalene content increased significantly.（2）Secondly,the effects of the coupling process of coal pyrolysis and in situ catalytic upgrading of tar under hydrogen atmosphere on the tar yield,yield and content of light tar,tar quality and tar composition were investigated.The results shows that the catalyst of Cat-1 shows the best tar catalytic upgrading effect at 650°C,obtaining the highest tar and light tar yields of16.06 wt.%and 10.45 wt.%,respectively.Meanwhile the light tar content increased from 50.78wt.%to 65.05 wt.%.The content of benzenes,phenols and naphthalenes in tar increased,while the content of long-chain aliphatic hydrocarbons,3-ring and 4-ring aromatic hydrocarbons decreased,indicating that the catalyst of Cat-1 can promote the ring-opening reaction of PAHs.Subsequently,the coupling process of coal pyrolysis and in situ catalytic upgrading of tar under coke oven gas atmosphere was investigated.The results still showed that at 650°C,the highest tar and light tar yields were obtained with the catalyst of Cat-1,14.34 wt.%and 8.75 wt.%,respectively.The light tar content also increased from 53.96 wt.%to 61.03 wt.%.（3）Finally,the mechanisms of the above processes were studied by the deuterium isotope tracer method.The deuterium contents of char,tar and gas were analyzed by isotope mass spectrometry（IRMS）combined with elemental analyzer（EA）,the distribution of deuterium in tar was studied by deuterium nuclear magnetic（²H-NMR）,and the distribution of deuterium in typical components of tar and gas were analyzed by GC/MS.For the mechanism the coal pyrolysis process under catalytic activation of hydrogen,the results shows that the reactivity of hydrogen with coal is improved by the catalysts,and there are more hydrogen atoms entering into the char and gas,while there is no significant increase of hydrogen into the tar.For the mechanism of the coupling process of coal pyrolysis and in situ upgrading of tar,the results shows that more hydrogen involved in the reaction combined with the volatile radicals into the tar and gas,and the hydrogen preferentially enter theαcarbon atoms on the side chain of the benzene ring in tar.The radicals generated by catalytic cracking of tar were stabilized by active hydrogen radicals,thus improving the content of light tar.