Experimental Study Of The Effect Of Coal Blending On Ash Fusibility And Slag Viscosity

Advanced gasification process often employs high temperature, high pressure slagging gasifier. The ash flow temperature of feedstocks should be lower about 50°C than operating temperature and the slag viscosity should be less than 25Pa-s at operating temperature in the process. In order to use Huainan coals (their ash flow temperature is over 1500°C)in the slagging gasifier, their ash melting temperature and slag viscosity should be lowered to the requirement of the gasification process.In this paper, four Huainan coals (I , II, III, IV) and three low ash fusion temperature coals (A, B, C) were selected. The ash fusion characteristics and slag viscosity at different blending ratios were studied. The ash fusion temperature and slag viscosity of coal blending were measured, and mineral composition and type at various temperatures and coal blending ratios were determined by X-ray diffraction (XRD). Some results are obtained.1. Ash melting temperature of Huainan coals can be decreased to less than 1380°C by coal blending. The relationship between ash fusion temperature and coal blending ratios is nonlinear. The high blending ratio of Huainan coal with B coal can be achieved.2. Ash chemical composition, temperature and blending ratios have significant effects on the mineral behavior of coal blending. As the temperature increases, thermal decomposition, transformation, and reaction occured between the components, and some iron inclusion compounds melted to become glassy phase matter. In weak reducing atmosphere, metakaolinite reacted with ferrous oxide to form hercynite and reacted with lime to form anorthite. Mullite derived from the clay mineral in high temperature can increase ash fusion temperature. Quartz, anorthite and fayalite coexisting in blends will produce a low-melting eutectic mixture which decreases the ash fusion temperature. The ash fusion temperature of blended coal is nonlinear with blending ratio of raw coals can be explained by nonlinear temperature distribution in ternary system phase diagram.3. Coal blending can efficiently decrease slag viscosity. The viscosities lower than 25Pa.s at 1380°C were detected for 60% Huainan coal III+40%B coal blending...