Study On Sulfur Release And Removal During Coal Pyrolysis And Gasification In A Fluidized Bed

A review was made on the research advancement as well as analysis methods of gaseous sulfur release and removal during coal pyrolysis and gasification, based on which the mechanism of sulfur release and retention in fluidized bed was studied extensively.The mechanism of limestone sulfidation was studied using a bench-scale bubble fluidized bed. An experimental analysis was made on the factors affecting the desulfuration of sorbent, such as the reaction temperature, particle size of absorbent, sulfidation atmosphere, flow rate in fluidized bed, species of limestone, and calcination conditions, based on which, the characteristics of sulfur release during coal pyrolysis, and the capability of desulfurization in the bench-scale fluidized bed under the conditions of different temperatue, pyrolysis atmospheres and Ca/S mole ratio of sorbent, were further studied.In order to analyze the mechanism of sulfur removal by limestone, the scanning electron microscope (SEM) and Mercury Porosimeter were used to observe and analyze the micropore strctures and properties of the uncalcined, calcined and sulfided limestone particles as sorbent, which revealed the variation laws of the micropore structures and properties of limestone particles and also provided explanations for the different performance of sulfur removal by limestone under various reaction conditions.Based on the research of tests above, experiments were conducted on 1MW polygeneration system of CFB partial gasification and combustion to testify the results obtained in former experiments. Recycle gas pyrolysis and air partial gasification were carried out individually to get different desulfuration properties of limestone under the conditions of various temperature, atmosphere and Ca/S mole ratio. The results of the experiments results supported the assumption of realization realizing low discharge of pollutant gas in polygeneration system.A synthetic mathematical model concerning sulfur release and retention by limestone during partial gasification in CFB gasifier on the basis of percolation theory of a voronoi tessellation of microscopic polyhedra was established. The synthetic model includs the CFB hydrodynamic model, the sulfur release model during partial gasification of coal and the desulfuration mechanism model, which may predict the properties of sulfur release and removal by limestone under various conditions.By comparing the calculation values of the model and the results obtained by experiments, the primary laws of sulfur release and removal in polygeneration system of CFB were obtained, which implied the advantages of the system, and also provided some references for the industrialized application of system in the future.