| Coal is a high-quality chemical raw material,but at the present stage,the main method of coal utilization in my country is direct combustion,which not only causes a waste of resources,but also brings more environmental problems.Therefore,the clean and efficient utilization of coal has always been one of the important research directions of scientific researchers.Coal is a complex mixture composed of a variety of chemical components and molecular structures.The microscopic components in coal have different origins,different compositions,and different structures,resulting in different properties of different microscopic components.Therefore,their roles in coal conversion technology are also different.The study of the basic properties of coal and rock components and the targeted development of the separation and utilization of coal and rock components are important ways to improve the efficiency of comprehensive and high-efficiency coal utilization.Compared with the high hydrogen consumption of direct coal liquefaction and the high energy consumption of indirect coal liquefaction,coal pyrolysis can obtain gas,liquid and solid products under mild conditions.Carrying out the grading and comprehensive utilization of coal resources based on pyrolysis is of great strategic significance to our country’s economic development and energy security.Tar is the product with the highest added value in the process of coal pyrolysis.Tar can not only be hydrogenate to make fuel oil,but also can extract chemical products such as phenol,benzene,naphthalene,etc,so by improving the quality and yield of tar with high added value,the overall benefit of the pyrolysis process can be significantly improved.On the basis of full analysis of relevant research work at home and abroad,our research group proposed the concept of catalytic depolymerization.This method is based on the catalytic principle and uses the effect of catalysts on certain specific bonds in coal to destroy as little as possible in the coal.Based on the original structure（that is,breaking the chemical bond）,it realizes the gentle depolymerization of coal,improves the oil yield,and obtains high value-added chemicals and liquid fuels.Based on this,this study selects Shaanxi Yanchang coal as the research object,and uses the established flotation-centrifugation method to separate and obtain high-purity micro-component enrichment,and analyzed its pyrolysis reaction characteristics.Combined with the catalytic depolymerization concept proposed by the group investigated the catalytic depolymerization effects of Fe Cl3 and Zn Cl2 catalysts on the enrichment of different microscopic components.The main research contents are as follows:Study on the separation of microscopic components of Yanchang coal in Shaanxi.Using the flotation-centrifugal combined separation method,the vitrinite content in the vitrinite enrichment obtained increased from 37.25%of the raw coal to 79.56%,and the inertite content in the inertite enrichment increased from 45.76%of the raw coal to 72.25%.Compared with raw coal,vitrinite enrichment has higher hydrogen and oxygen content and higher hydrogen to carbon ratio and volatile content.Inertite enrichment has lower hydrogen content,lower hydrogen-carbon ratio,and lower volatile content.Study on the low-temperature pyrolysis characteristics of the enrichment of microscopic components in coal.The vitrinite enrichment pyrolysis tar yield,pyrolysis water yield and pyrolysis gas yield are higher,and the yield of char is lower.This is because the relative content of aliphatic hydrocarbons in its structure is higher,and the length of the fatty side chain is longer.Long,relatively high amorphous carbon content,consistent with the characteristics of high volatile matter and H/C ratio,which is conducive to the generation of low-molecular free radical fragments and combines with H free radicals to form small molecular compounds to escape.At the same time,its contains oxygen is relatively high,and mainly exists in the form of phenolic hydroxyl group.The relative content of H2 and CH4 in the pyrolysis gas is relatively high.The content of aliphatic hydrocarbon compounds and phenolic compounds in the tar is relatively high;The yield is relatively high.The tar yield,pyrolysis water yield and pyrolysis gas yield are relatively low.There are relatively more polycyclic aromatic hydrocarbons,fused-ring aromatic hydrocarbons and heteroatomic compounds in tar,which are compared with the higher degree of graphitization.The stable aromatic structure and the rich oxygen-containing functional groups are consistent with the characteristics.The rich carboxyl,carbonyl and aromatic ethers are conducive to the generation of CO and CO2 small molecule gases.Research on the effect of different catalysts on the catalytic depolymerization of microscopic components in coal.The Fe Cl3 catalyst can significantly promote the increase in the yield of tar from the pyrolysis of the microscopic components,which is conducive to the progress of the dehydrogenation reaction,and at the same time promotes the progress of the decarboxylation reaction,inhibits the combination of H free radicals and methyl groups,resulting in tar The relative content of aliphatic hydrocarbons and benzene series is increased.The addition of Fe Cl3 catalyst promotes the shedding of aliphatic hydrogen and the scission of side chains,which enhances the thermal reactivity of the coal,while inhibiting the polymerization of char and retarding the development of graphitization of char,To promote the cracking of large molecules in coal.The Zn Cl2 catalyst only promotes the pyrolysis tar yield of the vitrinite-enriched material,which is beneficial to promote the scission of the side chain and the precipitation to generate more small molecular compounds and the progress of the dehydrogenation reaction,which promotes the generation of H2 and CH4,and inhibits The phenolic hydroxyl groups are separated from the main body of coal,which promotes the combination of free radicals and single benzene ring compounds to increase the relative content of benzene series.At the same time,the aromatic structure in the tar has a certain catalytic cracking effect;the addition of Zn Cl2 catalyst promotes the side chain The cleavage and generation of more small molecule compounds and H free radicals,at the same time,will increase the aromaticity of the vitrinite and inertite enrichment pyrolysis char,and increase the degree of condensation.This thesis explored the influence of coal micro-component separation and micro-component structure on the pyrolysis and catalytic depolymerization process,and provided basic data and support for more targeted research on coal conversion and utilization. |
