Physicochemical structure, combustion characteristics and SiO2 properties of entrained flow gasification ash

During the gasification process of coal, fine ash (FA) and coarse slag (CS) solid waste are produced, which contain a large amount of residual carbon and ash (mainly SiO2), resulting in energy waste and environmental pollution. Therefore the main goal of this research is to recover the wasted energy from FA and CS. The investigation of the physicochemical structure, combustion characteristics and SiO2 properties of entrained flow gasification ash (EFGA) is an important basis for the valorization of EFGA. The physicochemical, combustion characteristics and SiO2 properties of EFGA in a entrained flow bed of 112,000 Nm3/h gas-forming capacity were investigated, showing that FA and CS undergo different gasification processes, with FA having a more developed pore structure and high specific surface area. FA and CS have different degrees of graphitization, with defects or heteroatoms in FA causing a scattered carbon layer structure with an irregular graphitic carbon crystal structure, and organic molecular functional group fragments forming an indeterminate structure and active sites. The organic molecule functional group fragments constitute an indeterminate structure and active sites. Kinetic analysis shows that the influence of chemical structure on the combustion characteristics of EFGA is higher than that of physical structure. Compared to CS, FA has fewer active sites and a small number of oxygen-containing functional groups, resulting in a weaker combustion reactivity of FA. The combustion activity of EFGA is lower than that of circulating fluidized bed gasification ash and anthracite, making it difficult to be eliminated by direct combustion, although co-combustion is feasible. The specific surface area of SiO2 prepared by EFGA after acid treatment and calcination is small (< 39.7086 m(2)/g), SiO2 exists as crystals and the elemental silicon exists mainly in the form of Si-O, O-Si-O and hydrated silicon dioxide Si-O-2- nH(2)O, which can be used as a raw material for the preparation of silica. (c) 2022 Elsevier Ltd. All rights reserved.