Abstract:
The A4 coal seam of the Naomaohu coalfield in Xinjiang has a characteristic of high-quality for direct liquefaction by previous experiments.This research took the A4 coal seam of the Naomaohu coalfield as the object to carry out the study on coal for direct liquefaction,which is important for the quality characteristics and genetic understanding of the high-quality direct liquefaction coal.The research samples were collected at the Baishihu open-pit mine in the Naomaohu coalfield.The test results show that the average ratio of H/C in the A4 coal seam is 0.94,and the average volatile production rate is 49.2%.The active components of directly liquefied (vitrinite+chitin) content are as high as 97.7%,while the average ash content of A4 coal seam is 5.2%,which is extremely low,and the ash content has a low contents of SiO2 and Al2O3,which harm direct hydro liquefaction.The Fe2O3 content has a higher value,which has a catalytic effect on liquefaction.Therefore,the characteristics of three high and one low coal quality (high H/C ratio,high volatile and high active components,and low ash content) of the Naomaohu coalfield have brought favorable conditions for the direct liquefaction process.The average maximum reflectance of the vitrinite group is 0.42% in the Naomaohu coal sample,which stays in the best coalification stage of direct liquefaction.The results of coal facies studies indicate that the early Jurassic Badaowan Formation deposits formed by the A4 coal seam in the Naomaohu coalfield are in a calcium-rich peat swamp environment,which ensures the early humification and biochemical gelation of peat accumulation.The stratigraphic sequence belongs to the water inlet sequence,which can be quickly covered by the overlying-sediments after the peat is accumulated,ensuring that the peat stays in an oxygen-deficient and reducing environment so that the gelation is fully carried out.Meanwhile,the overlying and underlying strata have good water resistance,which ensures that the evolution process of maceral specification is not easily affected by the oxygen-rich water from the roof and floor.The above factors form the ultra high direct liquefaction active component (vitrine of the Naomaohu coalfield).The important factors of the group (vitrinite and exinite group) provide favorable conditions to the formation of high-quality coal for direct liquefaction.