Study On Simulation And Optimization Of Low Metamorphic Coal Pyrolysis-gasification Coupling Technology

Coal is the primary energy source of China, in which low metamorphic coal includinglignite, long flame coal, non-caking coal and light sticky coal are abundant and have highquality, and the proportion of mining are increaseing improved. Coal staged conversion whichwas proposed considering that low metamorphic coal had the character of high volatile matter,according to the different reaction features of different coal in different conversion period,implement classification conversion about pyrolysis, gasification and combustion. Thistechnology can raise coal utilization, simplify gasification, reduce the investment and cost,and effectively solve the problem of removal of contaminants of coal.Reference to the"combined thermal-conversion technologies", based on the analysis andstudy on pyrolysis and partial gasification technology of domestic and oversea, the thesis putforward the low metamorphic coal pyroglysis-partial gasification coupling technology, andthis process was simulated and analyzed to provide reference and guidance for the furtherdevelopment of specific method and operational control.Through the analysis of coal pyrolysis reaction dynamics, based on distribution activationenergy model (DAEM), the lumped reaction kinetics model was established to represent thepyrolysis process, and kinetics equations which can estimate the relation among thecomposition and distribution of pyrolytic products and final pyrolysis temperature and heatingrate were determined. The research showed that the emission rate of volatile matterapproached the ultimate production rate with the rising of final pyrolysis temperature, whilesemi-coke yield reduced, of which C content increased and the others including H, N, O and Scontent decreased. Therefore, the rising of final temperature favored the desulfurization anddenitrification of semi-coke. The most volatile except H2 basically released and elementschange range of semi-coke decreased at 600℃. When pyrolysis temperature remained constant, slow heating was beneficial to the full emission of volatile matter. Analysis resultsshowed that controlling the temperature at 550℃and heating rate of 10℃/min volatile mattercan wholly release.Based on ASPEN PLUS, the simulation method of the two-stage gasification technologyintegrated with pyrolysis model of coal and partial gasification of semi-coke was presented.The results showed that the established gasifier model can accurately simulate the two-stagetechnology which the thesis put forward. Tar yield of the pyrolysis-stage was 12.23%, andsemi-coke yield was 65.11%. By regulating the segmentation rate of splitter at 0.53:0.47, thewet coal can be preheated to the specified temperature at 110℃. Finally, the gasification-stagewas optimized based on performance parameters adjustment and sensitivity analysis. Whenratio of oxygen to coal (O2/C) was 0.33 and ratio of steam to coal (H2O/C) was 0.2, or O2/Cand H2O/C were 0.356 and 0.25 respectively, the temperature of gasifier can maintain at 900℃and the cold gas efficiency was highest.