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Coal water slurry technology and gasification technology are used to simultaneously treat wastewater and CO2; coal water slurry is prepared from fixed‐bed coal gasification wastewater; and then, thermogravimetric analysis, Fourier‐transform infrared spectrometry, scanning electron microscopy, energy‐dispersive spectrometry, and X‐ray diffraction are used to analyze the characteristic parameters of CO2 gasification and the products that formed. The results reveal the following: (a) compared with coal water slurry, coal gasification wastewater slurry shows decreases in the gasification start temperature, gasification weight loss peak temperature, and gasification end temperature of 12°C, 22°C, and 17°C, respectively, and shows increases in the maximum and average reaction rates. In addition, the reactivity index for coal gasification wastewater slurry is found to be 14.29% higher than that for ordinary coal water slurry. (b) Coal gasification wastewater slurry produces more methane and other aliphatic hydrocarbon gases in the pyrolysis stage and more CO in the coke gasification stage than coal water slurry. (c) Coal gasification wastewater slurry contains many small particles and flocs on the surface of the coal and a high Na content (up to 8.07%) in the microarea. In addition, a richer pore structure exists on the surface of the gasification residue of the coal gasification wastewater slurry. (d) The components of the gasification residue for coal gasification wastewater slurry show relatively larger changes. Moreover, the catalytic effect of alkali metal may be weakened due to the reaction of the minerals in the coal to form a complex. [ABSTRACT FROM AUTHOR]

Abstract: Coal gasification wastewater (CGW) contains high concentrations of pollutants and varying chemical components and thus is difficult to treat. CGW slurry (CGWS), which is prepared by blending coal, CGW, and additives, is a new wastewater utilization technology that can be used to efficiently and conveniently treat CGW. This work mainly investigated the slurryability, rheology, stability, and combustion properties of CGWS prepared from Shenhua and Yima coals. Results showed that (a) the maximum solid loading of CGWS was slightly lower than that of ordinary coal–water slurry (CWS), but CGWS exhibited better pseudoplastic rheology and stability than CWS; moreover, increasing the solid loading of CGWS resulted in an increasingly pseudoplastic trend and enhanced stability; (b) CGW strengthened the combustion capacity of coke and CGWS demonstrating better ignition, burning, and burnout properties than CWS. These findings suggest that the use of CGWS technology in CGW treatment is beneficial economically and environmentally. [ABSTRACT FROM AUTHOR]

Solvents have been considered to show a profound influence on the charge storage of electric double-layer capacitors (EDLCs). However, the corresponding mechanisms remain elusive and controversial. In this work, the influences of solvent dipole moment on the EDL structures, kinetic properties, and charging mechanisms of graphene-based EDLCs are investigated with atomistic simulations. Specifically, electrolyte structuring is conspicuously modulated by solvents, where a sharp increment of capacitance (~325.6%) and kinetics (~10-fold) is documented upon the slight descent of polarity by ~33.0%. Unusually, such an impressive enhancement is primarily attributed to the suppressed interfacial electric fields stimulated by strong-polarity solvents in the proximity of electrodes, which goes beyond the previously observed issues that stemmed from the competitive interplays between ions and solvents. Moreover, a distinctive polarity-dependent charging mechanism (i.e., from pure counterion adsorption to coion desorption) is identified, which for the first time delineates the pivotal role of solvent polarity in manipulating the charge storage evolutions. The as-obtained findings highlight that exploiting the solvent effects could be a promising avenue to further advance the performances of EDLCs. [ABSTRACT FROM AUTHOR]

• CWWS is prepared using various types of coal chemical wastewater. • GWW, SW, IW, and MW promote slurryability, while CW shows a negative effect. • All CWWSs exhibit pseudoplastic fluid property and good stability. • CMWS shows high carbon conversion rate and cold gas efficiency when being gasified. The coal water slurry gasification combined with ammonia synthesis process produces various complex wastewaters that are difficult to handle, and the improper disposal of these wastewaters causes great harm to the environment. In this paper, coal wastewater slurry was prepared from these wastewaters, and its slurryability, rheology and stability were measured. The gasification characteristics were studied in a coal water slurry gasifier. Results show that (a) The gas washing wastewater, sulfur wastewater and industrial wastewater can promote slurryability, whereas carbonized water is not conducive to promoting slurryability. The mixed wastewater, that comprises all four types of wastewater mentioned above, promotes slurryability and has a slurry concentration of 62.0%. All coal wastewater slurries exhibit pseudoplastic fluid property, which are beneficial for industrial pumping and atomization. The stability of the samples was evaluated by analyzing the water separation rate, and all coal wastewater slurries show better stability than the coal deionized water slurry. (b) In the industrial application process, the active component of the syngas produced from the gasification of the coal mixed wastewater slurry can reach 78.6% and has a higher H 2 content than the syngas produced from ordinary coal water slurry. Moreover, using the coal mixed wastewater slurry can increase cold gas efficiency by 1.57% and carbon conversion rate by 0.45% in industrial processes. Therefore, preparing and using coal mixed wastewater slurry in coal water slurry gasification combined with ammonia synthesis process not only treats high-concentration wastewater but also achieves sustainable development and a circular economy model. [ABSTRACT FROM AUTHOR]

• A novel full nonlinear mathematical model of asymmetric hydro turbine governing system established. • The multi-stability characteristics of as well as its generation mechanism are revealed. • The effect mechanism of water diversion system topology on the system stability is revealed. • The recommended setting values of system parameters under different topologies are provided. This paper aims to study the stability and nonlinear dynamics of hydro-turbine governing system with asymmetric water diversion system, i.e. asymmetric hydro turbine governing system, by using Hopf bifurcation theory. Firstly, the full nonlinear mathematical model of asymmetric hydro turbine governing system is established by all system components and nonlinear head loss. This model contains two units with different capacities which share a common pipeline. Based on the nonlinear mathematical model, the multi-stability characteristics of asymmetric hydro turbine governing system under load disturbance is studied by using stable domain and verified by numerical simulation. Moreover, the multi-time scale oscillation is revealed and its relationship to system multi-stability is investigated. Furthermore, the effect of system parameters and topological parameters on system stability is analyzed. Results indicate that: two stable domains are emerged under load disturbance, the overall stability of asymmetric hydro turbine governing system is determined by the intersection area of the two stable domains. In addition, the system parameters and topological parameters both have obvious effect on system stability, which can be significantly improved by reasonable tuning of system parameters and optimization of water diversion system layout. [ABSTRACT FROM AUTHOR]

Here, a novel approach to the detoxification and reuse of waste activated carbon (WAC) through co-gasification with coal-water slurry (CWS) is proposed. To evaluate the harmlessness to the environment of this method, the mineralogical composition, leaching characteristics, and geochemical distribution of heavy metals were investigated, enabling the leaching behavior of heavy metals in gasification residues to be explained. The results showed that the gasification residue of coal-waste activated carbon-slurry (CWACS) contained higher concentrations of Cr, Cu, and Zn, while those of Cd, Pb, As, Hg, and Se were well below 100 μg/g. Further, the spatial distributions of Cr, Cu, and Zn in the mineral phases of the gasification residue of CWACS were relatively uniform overall, and no obvious regional enrichment was observed. The leaching concentrations of various heavy metals in the gasification residues of the two CWACS samples were all lower than the standard limit. Following the co-gasification of WAC with CWS, the stability of the heavy metals in the environment was enhanced. Meanwhile, the gasification residues of the two CWACS samples showed no environmental risk for Cr, low environmental risk for Pb and Hg, and only a moderate environmental risk for Cd, As, and Se. [Display omitted] • Detoxify and reuse the waste activated carbon through co-gasification with CWS. • The leaching behavior of heavy metals in gasification residues was explained. • The residue after co-gasification of WAC and CWS is non-hazardous. • Modified BCR method was used to study the geochemical distributions. • The environmental risk of the CWACS gasification residues was evaluated. [ABSTRACT FROM AUTHOR]

• The effect of the electrolyte itself on the coal particles cannot be ignored. • Judging the reactivity of coal only from the current density will produce errors. • Most of the liquid phase organics are oxygenated, and oxidative shedding dominates. Coal-assisted water electrolysis for hydrogen production can effectively reduce electricity consumption and improve the economics of electrolytic hydrogen production technology. However, the influencing factors of this process, especially the mechanism of the electrolyte itself on the coal particles, are not clear. The influence of electrolyte on the electrooxidation process of coal particles is of great importance in practical applications. In this paper, detailed controlled experiments were designed to investigate the effect of electrolyte concentration on coal-assisted water electrolysis. And the laws of the acid leaching and electrooxidation processes on the macrostructure and organic structure of coal particles were investigated by various characterization methods. Information on the small molecules of organic matter stripped from coal molecules under different experimental conditions was also obtained by GC–MS. The results showed that the reactivity of coal particles decreased with increasing electrolyte concentration, and judging reactivity from current density alone would produce some errors. The rebound of current density in high concentration of sulfuric acid mainly came from more fragmentation of coal particles. The C O structure played a facilitating role in the oxidation of coal, while the C O and COOH structures would hinder the further oxidation of coal particles due to their stability. Small organic molecules were released from coal particles into the electrolyte during acid leaching and electrolysis, and the amount of small organic molecules detached was positively correlated with sulfuric acid concentration and oxidation charge, where oxidation detachment dominated. [ABSTRACT FROM AUTHOR]

• High concentration organic waste liquids was investigated to reduce clean water consumption. • Mixing two types of organic waste liquids that are insoluble in each other evenly. • The total interaction energy in the entire WCWS system is greater than 0. • The steric stabilization energy is introduced into the system by xanthan gum. • Xanthan gum serves as a bridge in the system based on its molecular characteristic. High-concentration organic waste liquids have complex components and their treatment is difficult. These liquids also contain hydrophobic organic pollutants. The preparation of waste liquid coal water slurry (WCWS) can aid with environmental protection and resource utilization. In this study, xanthan gum was selected from 11 types of additives because it overcomes the problem of solution incompatibility during the mixing of various high-concentration organic waste liquids. The experimental results showed that with 0.08 wt% addition of xanthan gum, no stratification occurred in the mixed waste liquid and the apparent viscosity of the WCWS was 921.1 mPa ∙ s. In this study, the role of xanthan gum was studied, and the effect of its addition on the coal particle surface was characterized by zeta potential and contact angle measurement. In addition, various interaction energies in the WCWS system were calculated using the extended DLVO theory. The results showed that xanthan gum introduced steric hindrance interaction energy into the WCWS system, enabling the system to be stably dispersed. [ABSTRACT FROM AUTHOR]