Slurrying Property and Mechanism of Coal–Coal Gasification Wastewater–Slurry

Abstract

The co-slurrying technology of coal and organic wastewater, which achieves the simultaneous disposal and utilization of wastewater, has attracted extensive attention in recent years. The emission of coal gasification wastewater causes serious environmental hazards, because of its large amount, high organic content, and high toxicity. In the present study, two types of wastewater, namely, gasifier wastewater (GW) and wastewater from a secondary sedimentation tank (SW), were used to prepare coal water slurry (CWS), which was labeled as coal−GW−slurry (CGS) and coal−SW−slurry (CSS), respectively, with coal−deionized water−slurry (CDS) as a reference. The surface property of coal and the dispersing mechanism were characterized using zeta potential and contact angle analyses. Results showed that the fixed viscosity loading decreased with the addition of the two types of wastewater, and the decrease was more considerable with GW. All the slurries exhibited pseudoplastic behavior and thixotropy, with the following order: CGS > CSS > CDS. Wastewater, particularly GW, strengthened the stability of CWS. The influences of ammonium and volatile phenols on slurry viscosity were also investigated. The effect of ammonium was related to the pH value of the solution. The effect of volatile phenols on the range of wastewater organic content was limited. The stability of CWS was obtained by combining the result of ammonium with organic matter. Ammonium affected the surface charge of coal particles and changed the electrostatic repulsion between coal particles. The amphiphilic organic molecules enhanced the hydrophilicity of coal, which weakened the hydrophobic interaction between particles and thickened the hydration layer. Consequently, the agglomeration of coal particles was weakened.

Slurryability and combustion characteristics of coal‐coking wastewater‐slurry

“…Phenols can be absorbed on the surface of the coal particles through benzene rings, and the adsorption results in the improvement of the particle surface polarity. The thickness of the hydration layer increases and the content of free water decreases . Therefore, the apparent viscosity increased because of the existence of phenols, and the SC 1000 value of CCWS became lower than that of CWS.…”

Maximum solid concentrations of coal wastewater slurries predicted by optimized neural network based on wastewater composition data

“…2. Some studies have pointed out that ammonia nitrogen can be adsorbed on the surface of coal particles, [28] so that a thicker and more stable hydration film is formed around the particles, which increases the difficulty of releasing water molecules from the hydration film, thereby reducing MSC of CWWS. [29] Therefore, ammonia nitrogen is also one of the indispensable input factors.…”

Adsorption of Surfactants on Coal Surfaces in the Coking Wastewater Environment: Kinetics and Effects on the Slurrying Properties of Coking Wastewater–Coal Slurry

“…Several research papers have been published on the slurryability and rheology of coal slurries prepared with different types of wastewater−coal slurries, such as hydrothermal treatment waste liquid, 9 coal waste liquid, 10 gasification furnace wastewater, and secondary sedimentation tank wastewater. 11 Previous experiments have shown that slurrying is promoted by some types of wastewater, such as hydrothermal treatment waste liquid and coal waste liquid, but not by others, such as gasification furnace wastewater and secondary sedimentation tank wastewater. These responses can be mainly attributed to the different internal components of wastewater.…”

“…CWS must have good slurrying properties, specifically, high concentration (heat value) and low viscosity, to ensure the economic efficiency of CWS-based combustion and gasification. Several research papers have been published on the slurryability and rheology of coal slurries prepared with different types of wastewater–coal slurries, such as hydrothermal treatment waste liquid, coal waste liquid, gasification furnace wastewater, and secondary sedimentation tank wastewater . Previous experiments have shown that slurrying is promoted by some types of wastewater, such as hydrothermal treatment waste liquid and coal waste liquid, but not by others, such as gasification furnace wastewater and secondary sedimentation tank wastewater.…”