Investigation on the Regulation Mechanisms of Viscosity–Temperature Characteristics of High Calcium–Iron Coal by Coal Blending

Entrained-flow bed gasification was an important way to realize clean coal conversion. However, the high calcium–iron coal ash had a low flow temperature, low viscosity, and strong fluctuations in viscosity, which severely affected the service life of the gasifier. It was necessary to regulate its ash fusion temperature and viscosity–temperature characteristics (AFV). In the paper, the AFV of Datong coal (DTC, a high calcium–iron coal) and its regulation mechanism were investigated by ash fusion temperature tester, high-temperature viscometer, Raman spectrometer, differential scanning calorimetry, X-ray diffractometer, FactSage software, and activation energy calculation. With the increasing Pingdingshan coal (PDS, a high silicon–aluminum coal) mass ratio, the AFV of DTC mixtures increased, and the viscosity fluctuation of DTC mixtures disappeared gradually. When PDS mass ratio is in the range of 18%–24%, the flow temperature and viscosity of DTC ash were 1375°C–1400°C and 18–22 Pa·s, respectively. The increasing PDS mass ratio, the formation of high melting point anorthite and its increasing content, the polymerization degree of DTC mixed ash increasing, and a gradual increase in activation energy as well as their corresponding crystallization behavior led to the increase in the AFV. The mineral transformations and the position variation in the ternary phase diagram of ash compositions with PDS addition by FactSage calculation also explained the variations in the viscosity–temperature characteristics.