Influence Of Different Coal Macerals Interaction On Formation Mechanism Of Residual Carbon From Coal Gasification Fine Slag

The high carbon content of the fine slag from entrained flow gasification restricts its resource utilization and brings a series of environmental problems.In essence,fine slag is a comprehensive reflection of the gasification interaction of various maceral in coal.Vitrinite and inertinite have unique properties in carbon,hydrogen,volatile content and so on,which have an important effect on the formation of carbon residues.In order to provide theoretical support for rational coal blending based on maceral structure characteristics and emission reduction of gasification fine slag source,three typical gasification coals,namely Zhundong coal(ZD),Meihuajing coal(MHJ)and Yangchangwan coal(YCW),are selected as research objects in this paper.Vitrinite was separated and prepared by isopycnic centrifugation.On this basis,five groups of maceral mixtures containing 10%,30%,50%,70%and 90%vitrinite were prepared by adding different proportions of inertinite.In the condition of rapid temperature rise,use high-frequency gasification reactor and the gasification residual carbon of different conversion levels was prepared.The physicochemical structure and reactivity of the residual carbon were systematically characterized and evaluated,so as to reveal the influence mechanism of different maceral components on the formation of residual carbon in fine slag during the gasification process.The main research results are as follows:(1)The microstructural characteristics of coal were analyzed by digital coal rock analyzer and high purity maceral were separated by isopycnic centrifugation.The vitrinite random reflectance of ZD,MHJ and YCW is 0.644,0.516 and 0.677 and the active and inert ratio is 0.41,0.18 and 1.20.ZD and MHJ are single type of coal,while YCW is the mixed coal with one concave.Different maceral were prepared from ZD and HJ by isopycnic centrifugation.The purity of vitrinite is 92.4%and 91.3%.The purity of inertinite is 90.1%and 90.7%.(2)XRD,FT-IR,13C-NMR and other characterization methods were used to reveal the maceral structure of the two coals.The results show that the aromatic lamellar accumulation height Lc,aromatic lamellar diameter La and aromatic degree fa of vitrinite are all smaller than those of inertinite.Vitrinite has more fatty carbon structure,while inertinite has orderly carbon arrangement and tends to graphitic structure.The peak intensities of aliphatic C-H absorption peaks and aromatic C-H absorption peaks of different maceral components were different.Vitrinite had more aliphatic functional groups,while inertinite had more aromatic functional groups.The aromatic carbon structure region of maceral is the most obvious,and the aliphatic carbon peak intensity of vitrinite is greater than that of inertinite.(3)The residual carbon of different conversion levels was prepared in a high frequency gasification reactor under 1100℃,CO2 atmosphere and different gasification time.The change rule of gasification reaction process was analyzed by combining with the micro-imaging system of high temperature hot table and thermogravimetric analyzer.The results show that the carbon conversion rate of vitrinite content of 70%and 90%samples is higher in the early stage of gasification reaction.The reaction rate of vitrinite is faster because of the high content of active sites and the low degree of structure order.In the middle stage of gasification reaction,the reactivity and gasification reaction rate of vitrinite-rich samples decreased gradually due to the rapid depletion of active sites.When vitrinite content is 10%and 30%,although the initial active site content of inertinite is small,due to its easy to be crushed and contracted by heat,the specific surface area of inertinite is constantly increased and new active sites are released,which enables it to maintain high reactivity,so its gasification reaction rate is gradually enhanced.At the later stage of gasification reaction,the carbon conversion rate of vitrinite sample is 97%,5%higher than that of vitrinite sample.The carbon conversion rate of vitrinite content of 50%samples is higher than that of other samples.The interaction of maceral promotes the gasification reaction.