Construction Of Structural Model And Study On The Liquefaction Performation Of Long Flame Coal And Its Macerals

Coal plays an irreplaceable role in China's rapid economic development,but the unclean utilization of coal,such as combustion,has caused serious environmental pollution.Coal direct liquefaction?DCL?is a clean conversion technology for coal to liquid fuel oil.It is of great significance to balance China's energy status,maintain the sustainable development of energy and society,protect the environment and ensure national security.The nature of matter is determined by its structure.At the molecular level,it is significant for the development of coal direct liquefaction to explore the structural differences and liquefaction reactivity of coal and its macerals.In this study,Heidaigou coal was selected as the representative of long flame coal,and the raw coal,and its vitrinite and inertinite were analyzed and characterized.The structural differences were explored and the structural models of three samples were constructed.In addition,based on the structural models,the liquefaction properties of the three samples were investigated by quantum chemical calculation,pyrolusis and liquefaction autoclave test.The experimental results show that:The raw coal and its inertinite contain more aromatic structure,while the vitrinite contains more fat structure.The main aromatic structures in the raw coal are pyrene,phenanthrene,naphthalene,benzene,pyridine and pyrrole.The vitrinite structure does not contain pyrene and phenanthrene with higher degree of aromatic ring condensation,but only naphthalene with lower degree of aromatic ring condensation and benzene,pyridine and pyrrole with zero degree of condensation.In the inertinite structure,the content of pyrene,phenanthrene and naphthalene with higher degree of condensatioon of aromatic ring is high,and the number of benzene ring structure with zero degree of condensation is less.In addition,the inertinite structure does not contain pyridine,but only pyrrole.The structural formulas of raw coal,vitrinite and inertinite are C₁₈₉H₁₉₄N₂O₂₀,C₂₁₄H₂₁₈N₂O₂₀and C₁₇₀H₁₆₂N₂O₂₀,respectively.The bond length and bond order distribution information can reflect the reactivity of coal to some extent.The content of the longer bond decreases in turn according to vitrinite,raw coal and inertinite,and the content of the larger bond increases in turn according to vitrinite,raw coal and inertinite.During the pyrolysis of the three samples,the chemical bonds were broken in the same order,but the difference lies in the number of breaking chemical bonds.Vitrinite contains the most fragile bonds,followed by raw coal and inertinite.In addition,some C_al-C_al were destroyed before the release of CO₂.In the pyrolysis process,the variation trends of different substances with the same carbon number in raw coal,vitrinite and inertinite are similar with temperature.The gases escaped during the pyrolysis of the three samples are the same,and can be roughly divided into four categories according to the escaping time and variation law.The optimum liquefaction temperature and time of the raw coal and its vitrinite are 455oC and 60 min,respectively.At the optimum liquefaction temperature and time,the liquefaction conversion rate of raw coal was 83.50%,the oil yield was 56.32%;the liquefaction conversion rate of vitrinite was 93.55%,and the oil yield was 72.44%.Compared with raw coal,the vitrinite shows higher liquefaction conversion and oil yield.