Direct hydroliquefaction characteristics of lignite in eastern area of Xinjiang

In order to find a clean and high efficient technology for economic utilization of Xinjiang coal,the coal quality and composition of lignite in East Xinjiang were analyzed.In Lignite of eastern Xinjiang and hydrogenation solvent as raw materials,hydrogenation regulation test was carried out in 500 m L stirring autoclave to investigate influences of temperature,pressure and residence time on hydrogen consumption,gas,conversion,oil and asphaltene.The effects of process parameters on liquefaction performance and distribution of various products were investigated.A verification test was finished in 0.01 t/d BSU and the structural characteristics of liquefied primary oil products were analyzed in depth.The results show that the active component is 90% in the lignite of eastern Xinjiang with the characteristics of high volatile and H/C atom ratio.Under the moderate conditions( 430 ℃,15 MPa and 60 min),the conversion of coal is up to 94% and the oil yield is 57%,which is similar to that under the traditional conditions( 450 ℃,17 MPa and 60 min).The lignite is a high quality raw material for direct liquefaction.Moderate conditions contribute much to smooth temperature control of reactor,which is conducive to reducing energy consumption of large equipment.Process regulation test shows that the conversion of coal and asphaltene to oil and gas is promoted effectively,resulting in the increase of coal conversion and oil yield by increasing temperature especially at 430 ℃.High hydrogen pressure is conducive to the dissolution of H_2 in reaction system,the stability of radical fragment and the hydrogenation of polycyclic aromatic hydrocarbons in asphaltene to small molecules.The lignite is possessed of favorable liquefaction effect and reaction performance at 30 min.Due to the phase transform of iron based catalyst in reaction system from active Fe7 S8 to nonactive Fe9 S10 and Fe S at 90 min,the catalytic ability decreases significantly,which leads to the condensation reaction of asphaltene,the increase of asphaltene yield and the decrease of coal conversion and oil yield.Retaining some structural characteristics of coal,the primary oil from hydrogenation liquefaction continuous test of the lignite in eastern area of Xinjiang has the characteristics of high density,high aromatic hydrocarbon,high nitrogen and low sulphur.The20 ℃ density of <220 ℃ fraction is 851.2 kg/m~3.The 20 ℃ density of 220-350 ℃ fraction is 953.5 kg/m~3.The main structure in the primary oil of <220 ℃ and 220-350 ℃ fraction is mononuclear aromatics( 60%) caused by the easy hydrogenation of polycyclic aromatic hydrocarbon and the difficult ring opening reaction of mononuclear aromatics.Nitrogen content in <220 ℃ fraction is 2 500×10~(-6) and 4 800×10~(-6) in 220-350 ℃ fraction,which is one order higher than sulphur content respectively.