Washability evaluation of coal gasification slag via an integrated sieving-water flow classification.

In a slagging entrained-flow coal gasifier, a large portion of the inorganic matter will form liquid slag that may have strong physical and chemical interactions with char. Understanding the char-slag interaction is important for improving the modeling and design of gasifiers. This paper reports the characteristics of residual carbon in both coarse and fine slag from a typical entrained-flow coal water slurry gasifier. The surface characteristics of slag and residual carbon in slag were evaluated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The reactivity of the residual carbon in slag was compared through thermal gravimetric analysis. It was observed that fine inorganic matters in the slag tend to exist in spherical shape whereas residual carbons tend to stay as loose floccule. A melting test on fine carbon-slag mixture validated that inorganic matters have a tendency to agglomerate into large carbon-free spheres when melting in a carbon powder matrix due to surface tension change. It was also found that the reactivity of the carbon in fine slag was lower than carbon in coarse slag, which implies the formations of the carbon in fine and coarse slag are different.

Characterisation of residual carbon from entrained-bed coal water slurry gasifiers

Kinetic analysis on the mesoporous formation of coal gasification slag by acid leaching and its thermal stability

Structure characteristics and gasification activity of residual carbon from entrained-flow coal gasification slag

Preparation and application of porous materials from coal gasification slag for wastewater treatment: A review

Structure characteristics and composition of hydration products of coal gasification slag mixed cement and lime

Gasification technology enables the clean and efficient utilization of coal. However, the process generates a significant amount of solid waste—coal gasification slag. This paper focuses on the Jinhua furnace coal gasification slag (fine slag, FS; coarse slag, CS) as the research subject, analyzing its composition and structural characteristics, and discussing the thermochemical conversion performance of both under different atmospheres (N2 and air). The results show that the fixed carbon content in FS is as high as 35.82%, while it is only 1% in CS. FS has a large number of fluffy porous carbon on its surface, which wraps around or embeds into smooth and variously sized spherical inorganic components, with a specific surface area as high as 353 m2/g, and the pore structure is mainly mesoporous. Compared to the raw coal (TYC), the types of organic functional groups in FS and CS are significantly reduced, and the graphitization degree of the carbon elements in FS is higher. The ash in FS is mainly amorphous and glassy, while in CS, it mainly has crystalline structures. The weight loss rates of TYC and FS under an inert atmosphere are 27.49% and 10.38%, respectively; under an air atmosphere, the weight loss rates of TYC and FS are 81.69% and 44.40%, respectively. Based on the analysis of the thermal stability of FS and its high specific surface area, this paper suggests that FS can be used to prepare high-value-added products such as porous carbon or high-temperature-resistant carbon materials through the method of carbon–ash separation.

A study on the occurrence modes and distribution characteristics of sulfur and mercury in coal gasification slag

The dissimilarity in chemical speciation and release properties of heavy metals will result in varying levels of environmental hazards and potential applications of coal gasification coarse and fine slags. The distribution, chemical speciation, leaching features, and potential environmental risks of heavy metals (Cr, Cu, Cd, Zn, Pb, and Mn) in coarse and fine slags from different coal gasification processes were revealed and compared by the sequential chemical extraction method, Horizontal vibration method, and pH-dependent leaching experiments. The results show that Cr (516.78 mg/kg) in coarse slag, Zn (348.50 mg/kg) and Pb (214.78 mg/kg) in fine slag are highly enriched and the content exceeds the screening value, indicating the need for better management during stockpiling and landfilling. The distribution of Cr, Cu, Pb, and Mn in residual state, Zn in Fe-Mn oxide bound state, and Cd in unstable bound state is the highest in both coarse slag and fine slag. The leaching toxicity of heavy metals (HMs) does not exceed the standard, but the leachate is classified as Level V surface water or groundwater quality due to the leaching concentration of Pb exceeding 0.1 mg/L. Furthermore, leaching of Cr, Zn, Cd, and Pb in fine slag is much more dependent on pH compared to coarse slag, and the concentrations of Zn and Pb exceed emission standards at pH < 3.0. The high concentration of heavy metals caught on the surface of fine slag is more harmful to the environment. The properties of HMs in the slags and pH of the application environment must be comprehensively considered before coal gasification slag disposal, especially fine slag.

Fractal analysis and pore structure of gasification fine slag and its flotation residual carbon

The properties of solid wastes (fly and bottom ashes) generated from an industrial-scale pressurized entrained-flow gasifier were investigated. Bottom ashes consist of coarse slag granules and fine slag particles, both retrieved from the quench bath but characterized by distinctively different morphological and physicochemical properties. Characterization of fly ash, coarse slag, and fine slag has been accomplished by a combination of experimental techniques: elemental, granulometric, and X-ray diffractometric analyses, scanning electron microscopy, and energy-dispersive X-ray analysis. Analysis of results gives useful information on the properties and partitioning of carbon among the three main ash streams (coarse slag, slag fines, and fly ash). Residual carbon in slag granules is present in a segregated embedded form, while slag fines are composed of both porous (high-carbon) and compact (low-carbon) material. Carbon partitioning and properties of the different phases of which bottom ashes are composed are further analyzed in light of the flow patterns that establish the gasification chamber, with a focus on char–slag micromechanical interaction and char segregation. The properties of the three ash residues are consistent with a mechanistic framework, developed in a recent study (Montagnaro, F.; Salatino, P.Combust. Flame 2010, 157, 874−883), according to which extensive bulk-to-wall transfer of char is followed by the establishment of a segregated dense-dispersed char phase in the near-wall region of the gasification chamber.

Enrichment and utilization of residual carbon from coal gasification slag：A review

Ash composition, structural characteristics and thermal conversion performance of Texaco gasifier based on Zhundong coal

Properties of flotation residual carbon from gasification fine slag

Optimizing calcination temperature to improve the compressive strength of coal gasification slag-based alkali-activated materials by reducing carbon content and adjusting polymerization degree