Coal Ash Low Temperature Molten Matrix Formation Characteristics Under Fluidized Gasification

Coal ash fusibility is an important characteristic in pulverized coal combustion and coal gasification, which determines how to utilize coal resources in coal combustion or gasification. Because the fluidized gasification technology has the characteristics of high adaptability in coal resources and the release of pollutants easily controlled, it will become an direction of coal gasification technology development. But there are some operation problems such as bed fusion, bed agglomeration and deposition in fluidized gasification technology, this paper mainly did experimental and theoretical research on coal ash fusibility which is important to solving these problems.First of all, this paper did literature summary on the effects of coal ash chemistry composition, mineral composition, atmosphere and pressure on coal ash fusibility and introduced different kinds of methods to measure coal ash fusion temperature.Studied the influences of coal ash characteristics and operation environment conditions such as atmosphere, temperature and pressure on coal ash fusibility by combining the advantages of the intelligent ash melting point apparatus, Differential Scanning Calorimetry(DSC), pressurized thermobalance, XRD and FactSage software. The fusion temperature under both oxidizing and reducing atmosphere is higher than that under weakly reducing atmosphere. The fusion temperature under H₂/CO₂ atmosphere is lower than that under CO/CO2. Increasing pressure can promote the production of low temperature molten matrix and the process of low temperature fusion. The temperature range of coal ash fusion can be achieved by using FactSage which can be used to estimate coal ash fusibility. Activation energy and frequency factor are obtained using DSC curve.Finally, this paper studied the effects of ash arrangement and time on the sintering process, atmosphere (inertia, oxidizing, reducing atmosphere) and coal ash chemical composition on the coal ash sintering temperature. The sintering temperature under inertia atmosphere is similar to that under oxidizing atmosphere. The sintering temperature under reducing atmosphere is lower than that under oxidizing atmosphere. The sintering temperature under CO atmosphere is higher than that under H₂ atmosphere. In oxidizing atmosphere, with the increase of CaO and Na₂O content, the sintering temperature decreases. In typical fluidized bed gasification atmosphere (weakly reducing atmosphere), with the increase of Fe₂O₃, CaO and Na₂O content, the sintering temperature decreases. After reaching the set-up temperature, with the increase of time, the pressure drop across the ash pellets decreases gradually, but after a certain time, kept constant. The research consequences show the coal ash sintering characteristics can be changed by mixing different kinds of coals or adding addition agent to make the process of fluidized gasification operate safely.This paper studied the effects of pressure on coal ash fusibility, and the influences of ash chemistry composition and atmosphere on the coal ash sintering characteristics preliminarily. It may have certain guidance on the design and the operation of fluidized gasification technology.