Mechanism Of Desulphurization During Coal Combustion And Composition Control Of Desulphurization Residues

With the swift developing of our economics, the contradiction between the increasingly demanding of natural resource and the mothball resource scarcity, especially deficient of energy sources, as well as the environment pollution have become acute. To settle such problems, enhancing utilization of coal sources, which performs a vital role in our energy mix, optimizing manufacturing process to reduce emission, developing technology to low fuel consumption are being enforced.In allusion to the discharge of flue-gas such as SO2and solid waste pollutants, this paper focusing on the high-sulfur inferior coal from Heshang, investigated the solid state reaction mechanisms of desulphurization during coal combustion with sulfur fixative CaCO3, and in-depth studied the influence of sulfur fixation rate and the product composition when changing temperature and proportion between calcium and sulfur. By means of chemical methods and test equipments such as X-ray diffraction, SEM, fuel-gas analyzer and so on, we found the corresponding relationships between temperature and solid state behaviors, also got the methods adjusting the Ca/S and temperature according to the need of practical production.Further, to meet the application demands and control the components of the residues, three additives Al2O3, Fe2O3, and MgO, which are common in fly ash, have being taken to optimize the composition of the solid product in this article. And through systematic experiment, the reasonable mechanisms of the additives were explored, the outcomes as follow:(1) Combining with Si in coal, Al2O3becomes gehlenite going against reclamation; moreover, the hydration activity and gelation will depress with too much Al2O3. Inversely, lack of Al2O3will reduce the formation of C4A3S, causing the decline of desulphurization efficiency. In Heshang coal, the very ratio of Al/S is1.(2) The formation temperature will be lowered by adding Fe2O3, and the diffusion rate will be raised, so the desulphurization will be increased at low temperature. However, the decomposition temperature also be decreased, which does harm to the desulphurization and the recycle in the end.(3) Adding MgO, the composition of desulphurization residues will be strikingly improved. And with more CaSO4and C4A3S, the desulphurization and recycle demands can both be satisfied. However, the by-product periclase in the ash should be concerned in practice.Through this research, some feasible methods have been gained to raise the desulphurization rate, and to improve the composition of ash, which we are aiming at all the time. Such outcomes also give advices to the reclamation of sulfur-fixed ash in processing.