RESUMO
The Heshan coal and the Wansheng coal were selected to investigate the effects of Ca/S molar ratio, combustion temperature and other factors on the desulfurization efficiency when limestone as a desulfurizer. And then the possible effects of various desufurizing systems on the mineral constituents of their residues were discussed by using the X-ray diffraction analyzer. Moreover, the phase diagrams of the ternary system CaO-Al2O3-SiO2 were further used in order to find out the transformation behaviors of inorganic mineral matters in the desulfurizing processes of burning coal on the basis of the XRD results. The results show that the combustion temperature and the Ca/S molar ratio are the key factors affected the desulfurization efficiency and their residues' mineral constituents. When the temperature raised and the Ca/S ratio increased, the solid-phase reactions between CaO and some inorganic matters in coal ash will be obviously accelerated, which thus are good for the formaion of many mineral matters such as C4AF,C2AS and beta-C2S. Yet the anhydrite formed will decompose if the temperature is above 1050 degrees C and then the desulfurization efficiency will decrease. The desulfurization efficiency in different temperature is mainly decided by the existence form of the sulfur-contained mineral matters and their contents in the residue. In the experiment, the best desulfurization efficiency for the HS coal was about 90% when the Ca/S ratio was 2 or 3 and the range of the temperature was from 850 degrees C to 950 degrees C.
