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Fine slag (FS), which is a by-product from coal gasification, is composed of inorganic minerals and residual carbon. Acid treatment has high efficiency to separate the residual carbon in FS but the changes of properties of FS treated by acid remain unclear. To have a deep understanding of effects of acid treatment on physicochemical properties and gasification activity of FS, FS was subjected to different acid treatment, and then were characterized using Nitrogen adsorption technique, Raman spectroscopy and thermo-gravimetric analyzer. The results showed that the combined treatment with hydrochloric acid and hydrofluoric acid can remove the almost all mineral matters. Acid treatments did not modify the continuous and complete pores structure of FS. While, hydrochloric acid has a major influence on carbon structure, which produces the highest carbon actives and amorphous carbon. Nitric acid has positive influence on carbon structure transformation to crystalline structure. Notably, the gasification time can be shortened by the reduction of ash content. The carbon active sites in samples governed the initial reactivity while at the late stage of gasification the amount of inorganic elements controlled the gasification rate.

There are abundant resources of low-rank coal powder in the world. Powder briquetting technology has opened up a new avenue for large-scale utilization of low-rank coal. Water repellency is of grea...

Fine slag (FS) is byproduct of the coal gasification process, consisting of mineral-rich particles (MRP) and discrete residual carbon (DRC). MRP were separated using froth flotation method from FS and the ash content of separated MRP was higher than 98%. MRP were sieved into five sized fractions and its properties were studied by SEM/EDS, XPS, XRD, FT-IR and Raman spectroscopy. The results show that MRP are heterogeneous material which contain not only minerals but also residual carbon. The minerals in MRP contain most amorphous glass, together with minor proportions of crystal quartz. The MRP mainly consist of aluminosilicate and smallest (0–23 µm) particles have the most of aluminosilicate. Except for discrete residual carbon particles, there are also another two types of residual carbon within MRP. The first is embedded in the MRP matrix. The second is associated in chemical and/or physical way with the inorganic matter within MRP matrix. Residual carbon within MRP has a low degree of crystalline order. The main functional groups of residual carbon within MRP matrix are C-C, C-H and C-O. C-O which chemically bound with inorganic elements in the MRP forming C-O-M (M represents inorganic elements existing in MRP) groups.

An accurate and quantitative description of the pore structure of gasification-coke using fractal geometry could be of great significance to its industrial utilization. In this study, gasification-coke was prepared with low-quality coal blending at different high-temperature residence times to investigate the variation in the pore structure, fractal dimensions, reactivities, and their relationship. The pore structure parameters (e.g., specific surface area, pore volume, and average pore diameter) of gasification-coke were investigated by low-temperature N2 adsorption/desorption and mercury intrusion porosimetry. Fractal dimensions D1 and D2 (at relative pressures of 0–0.5 and 0.5–1, respectively) were calculated using the fractal Frenkel–Halsey–Hill model, and the fractal dimension D3 was obtained using the Menger sponge model. The results show that the pore structure systems of gasification-coke prepared at different high-temperature residence times are continuous and complete, which contributes to the gasification reaction. The variation trend of the macropore structure parameters is more complex than that of micropore and mesopore with the extension of the high-temperature residence time. It is found that D1 is linearly correlated with the micropore specific surface area, indicating that D1 is more suitable for reflecting the roughness of the micropore surface; D2 is linearly correlated with the mesopore volume and can describe the volumetric roughness of the mesopore; and D3 reflects the irregularities and surface roughness of the macropores. Gasification reactivity is closely related to the D2 value, and the reactivity of the gasification-coke may be improved if the number of mesopores is increased by controlling the high-temperature residence time or other pyrolysis conditions. The research results will provide theoretical reference for controlling the gasification reaction of gasification-coke and gasifier design.

Residual carbon can be recycled from the solid-waste gasification fine slag by froth flotation which is suspended into bio-oil to produce a new type of slurry fuel, so the comprehensive utilization...

The coal fly ash produced by gasification is estimated to be over 80 million ton per year in China by 2021. It has mainly been disposed as solid waste by landfill. There is lack of study focused on its utilization. In this paper, the coal fly ash produced by gasification was at first analyzed and then applied to synthesize zeolite as an adsorbent. The effects of synthesis conditions on the cation exchange capacity (CEC) of zeolite were investigated. The results from X-ray diffraction and scanning electron microscope indicated that the crystallinity of the synthesized zeolite is the most important factor to affect the CEC. When the synthesized zeolite with the highest CEC (275.5 meq/100 g) was used for the adsorption of Cr(VI) from aqueous solution, the maximum adsorption capacity for Cr(VI) was found to be 17.924 mg/g. The effects of pH, contact time and initial concentration on the adsorption of Cr(VI) were also investigated. The adsorption kinetics and isotherms can be well described by the pseudo-second-order model and Langmuir isotherm model, respectively.

As new gasification materials for gasification industry, gasification-coke can be produced with coking coal, coal by-product, and a high ratio of low-rank coal. Microscopic structure of gasificatio...

Fine slag (FS), a byproduct of coal gasification, consists of mineral-rich particles (MRP) and residual carbon particles (RCP). The characteristics of the MRP were investigated by laser particle si...

A large amount of coal gasification slag is produced every year in China. However, most of the current disposal is into landfills, which causes serious harm to the environment. In this research, coal gasification fine slag residual carbon porous material (GFSA) was prepared using gasification fine slag foam flotation obtained carbon residue (GFSF) as raw material and an adsorbent to carry out an adsorption test on waste liquid containing methylene blue (MB). The effects of activation parameters (GFSF/KOH ratio mass ratio, activation temperature, and activation time) on the cation exchange capacity (CEC) of GFSA were investigated. The total specific surface area and pore volume of GSFA with the highest CEC were 574.02 m2/g and 0.467 cm3/g, respectively. The degree of pore formation had an important effect on CEC. The maximum adsorption capacity of GFSA on MB was 19.18 mg/g in the MB adsorption test. The effects of pH, adsorption time, amount of adsorbent, and initial MB concentration on adsorption efficiency were studied. Langmuir isotherm and quasi second-order kinetic model have a good fitting effect on the adsorption isotherm and kinetic model of MB.

Using bamboo powder biochar as raw material, high-quality meso/microporous controlled hierarchical porous carbon was prepared—through the catalysis of Fe3+ ions loading, in addition to a chemical activation method—and then used to adsorb copper ions in an aqueous solution. The preparation process mainly included two steps: load-alkali leaching and chemical activation. The porosity characteristics (specific surface area and mesopore ratio) were controlled by changing the K2CO3 impregnation ratio, activation temperature, and Fe3+ ions loading during the activation process. Additionally, three FBPC samples with different pore structures and characteristics were studied for copper adsorption. The results indicate that the adsorption performance of the bamboo powder biochar FBPC material was greatly affected by the meso/micropore ratio. FBPC 2.5-900-2%, impregnated at a K2CO3: biochar ratio of 2.5 and a Fe3+: biochar mass ratio of 2%, and activated at 900 °C for 2 h in N2 atmosphere, has a very high specific surface area of 1996 m2 g−1 with a 58.1% mesoporous ratio. Moreover, it exhibits an excellent adsorption capacity of 256 mg g−1 and rapid adsorption kinetics for copper ions. The experimental results show that it is feasible to control the hierarchical pore structure of bamboo biochar-derived carbons as a high-performance adsorbent to remove copper ions from water.

As a kind of solid waste from coal chemical production, the disposal of coal gasification fine slag poses a certain threat to the environment and the human body. It is essential for gasification slag (GS) to realize rational utilization. GS contains fewer combustible materials, and the high heating value is only 9.31 MJ/Kg, which is difficult to burn in combustion devices solely. The co-combustion behavior of the tri-fuel blends, including bituminous coal (BC), gasification slag (GS), and bamboo residue (BR), was observed by a thermogravimetric analyzer. The TGA results showed that the combustibility increased owing to the addition of BC and BR, and the ignition and burnout temperatures were lower than those of GS alone. The combustion characteristics of the blended samples became worse with the increase in the proportion of GS. The co-combustion process was divided into two main steps with obvious interactions (synergistic and antagonistic). The synergistic effect was mainly attributed to the catalysis of the ash-forming metals reserved with the three raw fuels and the diffusion of oxygen in the rich pore channels of GS. The combustion reaction of blending samples was dominated by O1 and D3 models. The activation energy of the blending combustion decreased compared to the individual combustion of GS. The analysis of the results in this paper can provide some theoretical guidance for the resource utilization of fine slag.

Landfill is the major waste disposal method of high-moisture coal gasification fine slag (GFS) which causes the pollution of soil and water and brings the waste of resources. GFS efficient dewatering is an urgent problem to be solved, which is beneficial to realize its resource utilization. In this paper, mechanical pressure and vacuum coupling energy fields are applied to carry out the dewatering processes of GFS. The pressure field provides strong power for water migration, which makes water leave the particle system, while the vacuum field provides traction for water removal from system. The fine slag produced from Coal-to-methanol (named JC) with larger size particles tends to form "bridging" frameworks among particles, which provides water occurrence space and increases the moisture migration resistance. The mechanical dewatering process has an energy advantage interval, when the sample moisture is reduced to a certain degree, the mechanical force field is mainly used for particle friction and breakage but not for moisture migration. Through dewatering process energy optimization, high moisture gasification fine slag can be removed about 15% water within 30s and energy consumption of efficient dewatering is 2.63 kJ/g which is much lower than that of drying. Efficient dewatering is benefit to the GFS recycling which reduces hazardous materials release to environment. The potential effects of high efficiency dewatering process on GFS resource utilization and the possible eco-design framework for products recycled from the waste GFS were proposed. The research results will provide theoretical guidance for the gasification fine slag efficient dewatering and is benefit to the environment.

From the perspective of environmental protection and resource utilization, the feasibility of treating m-cresol wastewater with coal gasification fine slag (GFS) as particle electrodes in an electrocatalytic system was evaluated to achieve the purpose of treating waste with waste. Characterization by scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), Raman, and fourier transform infrared spectroscopy (FTIR) confirmed that the GFS featured a diverse inorganic framework, large specific surface area (as large as above 155 m

The abundant coal powder generated as a waste by-product during the lignite upgrading process is harmful to the environment. Lignite briquetting offers a practical solution for lignite usage. Altering the process parameters of briquetting can significantly improve briquette quality. In this paper, the characteristics of lignite briquettes, including drop strength and compressive strength were investigated. A combination of quadratic orthogonal rotation combination designs and regression equations established the best process parameters to be 40% weight of #2 upgraded coal, 20% weight of briquetting moisture, 25 MPa of briquetting pressure, and 12 h of drying time. The low error variance of the drop strength and compressive strength, at 0.01% and 1.83% respectively, verified the feasibility of the model. The analysis by scanning electron microscope (SEM) showed that the surface morphology of briquette was denser than that of raw coal. Finally, the combustion test of briquettes revealed that the particulate matter emission (PM2.5) of briquette was 16.7% lower than that of raw coal. In summary, these data provide a theoretical reference for realizing the reasonable utilization potential of waste products derived from industrial processes.

To replace the high-cost lump coals for fixed bed/moving bed gasification and broaden the utilization of the coke ovens with periodic overcapacity problems, the gasification coke with a large amoun...

The coal gasification fine slag (CGFS) from the entrained-flow coal gasification unit faces the challenge of safe disposal and clean utilization in the Ningdong region, China. This study aims to provide complete and thorough understanding of the distribution features, chemical speciation, environmental impact, and leaching behavior of typical heavy metals (i.e., V, Cr, Mn, Ni, Cu, Zn, Ba, and Pb) in the CGFS with different size fractions. The results show that the distribution of selected heavy metals in the CGFS has evident particle size dependence. Except for Zn, the other heavy metals in different size fractions mainly exist in chemical speciation of residual form with the ratio of 50.11-86.69 wt%. Moreover, it is found that the heavy metals in the different-sized CGFS show different RAC (risk assessment code) environmental risk levels and TCLP (Toxicity Characteristic Leaching Procedure) leaching concentrations. Especially, Zn in SGFS-C and SGFS-D posed a high-risk level to the environment, while the heavy metal elements of Cr, Mn, Ni, Zn, and Ba in other size fractions are classified as a medium environmental risk. In addition, the TCLP test results indicate that the leaching concentration of Cr, Mn, Ni, Zn, Ba, and Pb exceeds the groundwater-related regulatory limit in China. The pH-dependent leaching experiments suggest that Pb shows the amphoteric behavior, while the leaching mode of other heavy metals seems to be the cationic pattern. Furthermore, the leachability of the selected heavy metals in small-size fractions of the CGFS should be given more consideration at both acid and alkaline pH ranges. The leaching kinetic results demonstrate that the most effective mechanism to describe the leaching process of Cr, Ni, Zn, and Pb in different CGFS size fractions is the diffusion-controlled theory, which is supported by the different morphological traits of spherical mineral particles and carbon particles in the CGFS.

This study aims to further reveal the properties of coal gasification fine slag (CGFS) and provide the essential basis for the efficient and environmentally friendly utilization of solid waste CGFS. In this work, the physicochemical properties, combustion reactivity, and heavy metal environmental impact of CGFS with different particle size fractions were comparatively studied. The results show that the fractions of >115 μm (SGFS-A) and 38–75 μm (SGFS-C) contain more carbon particles with a higher disorder degree due to the low degree of gasification reaction. The increase of pore roughness with the rise of particle size fractions of CGFS could be attributed to the different carbon-mineral particles occurrence patterns in four fractions. Moreover, the kinetic parameters were determined by using different model-fitting methods. The first order reaction model could best elucidate the combustion reaction mechanism of SGFS-A. Due to the transport limitation of reaction gas through the pore structure into the carbon matrix, the three-dimensional diffusion model is the most effective mechanism for the combustion process of SGFS-B (75-115 μm), SGFS-C, and SGFS-D (0-38 μm). In addition, the overall combustion reactivity of the samples follows the sequence of SGFS-A>SGFS-D>SGFS-C>SGFS-B. The sequential chemical extraction results suggest that the combustion volatility of heavy metals is negatively correlated to the residual fraction ratio of heavy metals in different particle size fractions of CGFS. The potential adverse effects of some heavy metals in CGFS on the environment should be noticed due to the high mobility.

The drying processes are always applied prior to the transportation or utilization of lignite, and result in notable changes in the stabilities of lignite. In this paper, the study on the effects of nitrogen and MTE drying process on the physico-chemical properties and stabilities of Zhaotong lignite was carried out. The briquettes produced by MTE drying in this study were 150 mm in dimension, and so had a much larger particle size than nitrogen-dried samples. Nitrogen adsorption, mercury intrusion porosimetry and scanning electron microscopy all suggested that drying was accompanied by the transformation of larger pores into smaller ones. Compared to nitrogen drying, the pore structures could be stabilized by the MTE process. The soluble salts were removed during MTE drying which resulted in the decrease in ash and the concentrations of some of the major metals. The removal of water enhanced the hydrophilicity of nitrogen dried samples, but did not affect the hydrophilicity of MTE dried samples. The moisture holding capacity of MTE dried samples reduced faster than nitrogen dried samples with the decrease of residual moisture content. The moisture readsorption processes of MTE dried samples were strongly inhibited due to the much larger particle size of sample produced by MTE drying than nitrogen drying. The susceptibility to spontaneous combustion, indicated by cross point temperature and self-heating tests, of nitrogen and MTE dried samples increased with the decrease of residual moisture content. The MTE dried samples are more liable to spontaneous combustion than nitrogen dried samples with the same residual moisture and particle size. However, the larger particle size of the MTE product made it more stable with respect to spontaneous combustion and also moisture readsorption.

Coal gasification fine slag (FS)-based activated carbons (ACs) for CO2 capture provided a new method to realize the value-added utilization of FS. Furthermore, pre-oxidation treatment of carbonaceous materials is one of the most efficient possibilities to obtain developed pore structure of activated carbons to enhance the CO2 adsorption capacity. In this study, four types of oxidizing agents (HNO3, NaClO, H2O2, and air) carefully modified the coal gasification fine slag residual carbon (RC) to fix the oxygen content at about 12 wt%, 15 wt%, and 18 wt%. The samples were characterized by XPS, volumetric sorption analyzer, SEM, Raman spectroscopy, TEM, TG, and TG MS. Results suggested that the specific surface area and total pore volume of the ACs were observed to increase after oxidation. The types of oxygen-containing groups also affected the pore structure of the ACs. The results showed that the content of O C O groups were the most predominant factors for high surface area, and the C O group could hinder the development of pore structure. The ACs facilitated by RC oxidation by HNO3 had a high CO2 storage capacity of 12.4 % at 30 °C and a fast adsorption rate, around 86 % of CO2 uptake occurring in a span of 1 min.

Coal tar pitch (CTP) is abundant and widely used, but its properties will be affected due to oxidation aging during storage. In this study, CTP was oxidized by simulating the air oxidation process, and the change of chemical structure has been analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and both gas chromatography and mass spectrometry (GCMS). The effects of the oxidized and unoxidized CTP co-carbonization with coal on the polycyclic aromatic hydrocarbons (PAHs) emission were detected by GCMS. The small and medium-molecule aromatic substances were reduced during CTP oxidation, while the intermolecular condensation reaction increased the macromolecules content. The catalytic can effectively facilitate the dehydrogenation and condensation reaction of CTP and the entry of oxygen molecules, which leads to the increase of oxygen-containing groups and the decrease of PAHs. Compared to the raw CTP, the catalytic oxidized CTP significantly reduced the emissions of toxic PAHs during the co-carbonization with coal. A possible catalytic mechanism of CTP catalytic oxidation is proposed.

The conversion of solid waste into energy through combustion is sustainable and economical. This study aims to comprehensively evaluate and quantify the co-combustion characteristics, synergistic catalysis, and gaseous pollutant emission patterns of sewage sludge (SS) and coal gasification fine slag residual carbon (RC) as well as their blends through thermogravimetry coupled with mass spectrometry (TG-MS). The results showed that the co-combustion of SS and RC can not only improve the ignition and burnout property but also maintain the combustion stability and comprehensive combustion performance at a better level. The kinetic analysis results showed that a first-order chemical reaction and three-dimensional diffusion are the reaction mechanisms during the co-combustion of SS and RC. The synergistic catalysis between SS and RC can well explain the changes in activation energy and reaction mechanism. Furthermore, the blending ratio of SS is recommended to be maintained at 40% because of the lowest activation energy (Ea = 81.6 kJ/mol) and the strongest synergistic effect (Xi = 0.36). The emission of gaseous pollutants is corresponding to the primary combustion stages of SS, RC, and their blends. In co-combustion, the NH3, HCN, NOx, and SO2 emissions gradually rise with the increase of SS proportion in the blends due to the high content of organic compounds in SS.

In this study, the water distribution and adsorption behaviors of two typical coal gasification fine slag (GFS) samples with different moisture contents were studied. Both of the samples were collected from entrained-flow coal gasifiers with the same coal as feedstock from Ningxia Region. The GFS sample collected from a GSP gasifier (2.5–4.0 MPa, 1400–1750 °C), with lower moisture content, was named as GFS-L, and the sample collected from a Texaco gasifier (4.0–6.5 MPa, 1300–1400 °C), with higher moisture content, was GFS-H. As the water distribution and adsorption behaviors in GFS samples, largely depending on the pore structure, had not been extensively analyzed, this study was investigated by the means of nitrogen adsorption analysis, mercury intrusion porosimetry (MIP), low field nuclear magnetic resonance (LF NMR) and dynamic water vapor sorption analysis (DVS). Experimental results revealed that the surface area, pore volume and average pore diameter of GFS-L were all lower than those of GFS-H. The fractal dimension analysis results illustrated that the GFS-L sample had smoother surface but more complicated internal pore structure than the GFS-H sample. Accordingly, the moisture content in GFS-L (45.42%) was slightly lower than that in GFS-H (48.78%). Water distributed in macropores decreased significantly during dehydration process, whereas decrease of water in mesopores was not apparent. And negligible water was found in micropores. Moreover, it was found that the water adsorption behaviors in both of the GFS samples could be characterized by the monolayer adsorption and multilayer adsorption over the relative humidity (RH) range of 0–0.7. Beyond the RH range of 0.7, it was found that water adsorption in the GFS-H sample transitioned to the capillary condensation, leading to higher moisture content. This study is envisaged to provide some new insights into developing GFS dehydration technology.

Taking coal and herb residue as the main research object, the thermal analysis law of inorganic chlorine in the mixture of coal and herb residue was studied by dual-temperature tube furnace, Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Results showed that comparing the distribution of chlorine in solid, liquid as well as gases produced during pyrolysis, it could be seen that when the pyrolysis temperature and the sample percentage changed, the distribution of chlorine in the solid and gas phases varied greatly, but the change in the liquid phase was little. Their ranges of chlorine variation were 23.35%, 6.05% and 17.29% in solid, liquid and gas phase from 300 °C to 900 °C at the herb residue addition of 50 wt%. The ranges were 30.83%, 2.43% and 33.26% about the additive quantity of herb residue from 10 wt% to 90 wt% at the pyrolysis temperature of 500 °C. When the addition of the herb residue was 0–70 wt%, the content of chlorine in the coke increased with the increasing herb residue. When the addition of the herb residue reached 70 wt%, it reached the maximum, which was 0.0806%. There was synergism between herb residue and coal. The content of chlorine in semi-coke (or coke) decreased with the increasing temperature at 300–900 °C. The major materials of the coke for herb residue and coal at 500 °C consisted of SiO2, KCl and CaCO3 by EDS and XRD. It provides a method for harmless co-utilization of coal and herb residue.

Coal gasification fine slag is a kind of industrial waste produced from coal gasification process, and high-moisture coal gasification fine slag filter cake has brought challenges to environment and coal energy suatainable development. It is an important prerequisite for the development of fine slag efficient dewatering technology to investigate the water migration laws during the water removal process. In this study, the volume of water was ~56.95% of the filter cake according to the advanced micro-CT analysis which shows the spatial distribution information of water. The non-freezable water in the gasification fine slag filter cake occupied ~13 wt% which requires more energy to achieve the removal of this part of water. The larger water pore in the filter cake evolved into smaller pores in the drying process was confirmed which provides information for water migration behavior among pores. During the heating process, the change of weak hydrogen bonds intensity is more obvious than that of strong hydrogen bonds at the initial stage, implying that the different types of water have differences in the removal process. The hydrogen bond energy at 85 °C exceeds 40 kJ/mol, which is twice of that at 80 °C, indicating that more effective dewatering energy would be required in the future to remove water with strong hydrogen bonds. The investigations of water migration behavior and dewatering energy consumption provide potential guidance for efficient dewatering of gasification fine slag, which benefits to the environment and energy security.

This study aims to systematically investigate the physiochemical properties, co-combustion characteristic and kinetic behavior of sawdust char and residual carbon in order to guide its combustion as the potential solid fuel in the industrial-scale furnace. The froth flotation process to recycle the residual carbon from coal gasification fine slag increases the higher heating value from 7.81 to 17.70 MJ/kg and upgrade the fuel quality by effectively removing spherical mineral particles attached to the carbon particles surface or entrained in the pores. The addition of sawdust char into residual carbon could obviously improve the ignitability and combustibility of residual carbon. In the co-combustion process, both synergistic and antagonistic effects (Interaction index x d varies from −3.89 to 13.6) exist between sawdust char and residual carbon, while the synergistic effect was dominant. The first-order chemical reaction (O1) and diffusion-controlled reaction (D3 and D4) are the most effective mechanisms (all the correlation coefficient R2>0.98) for the multi-step co-combustion process. The percentage of sawdust char in blends is recommended to be maintained at 40 wt% because of the lowest combustion total activation energy (105.77 kJ·mol−1) and the strongest synergistic effect (Interaction index x d =13.6). The results provide theoretical reference for realizing the sustainable utilization of coal gasification fine slag and biomass waste resources.

Coal gasification fine slag is one of the major industrial wastes produced from coal gasification technology and its landfill disposal of the high-moisture product has brought harmful environmental impacts. The characteristic of water occurrence modes in gasification slag filter cake has positive effects on guiding high-efficiency dewatering processes which benefits to the environment. Gasification fine slag particles and water exist simultaneously in the gasification fine slag filter cake, and the physicochemical properties of the gasification fine slag have significant influences on the water occurrence mode and the effective dewatering process. The hydrophilic components and abundant macropores in the gasification slag are favorable for water occurrence. The water in the gasification fine slag filter cake was classified according to the freezing types and size distribution by low-temperature DSC and LF-NMR, respectively. ∼86 wt% of total water corresponding to the free water form which would be removed first during drying process. The visualization of water was determined by three-dimensional reconstruction technology, there are distinct water channels in the gasification fine slag filter cake from the direction in which the filter cake is formed, and the volume of water was estimated at ∼56 %. The drying behaviors were tested by TGA with the heating rates of 2, 7, and 15 K/min, and the maximum drying rate and critical water content increased as the increasing heating rates. The two-dimensional growth kinetic model was applied for describing the drying kinetic process, and the activation energy decreased as the increasing heating rate, and the drying rate reduction stage has higher activation energy compare to the increasing and constant drying stage.

Gasification fine slag is one of the industrial wastes of the coal gasification, and the efficient dewatering is indispensable for further dispose. The enhanced dewatering process of gasification fine slag was achieved by innovative coupled mechanical dewatering force fields and dewatering mechanisms were explained in this study. The results showed that the dewatering process under pressure presented a three-stage process, the filtration and compaction stages of the dewatering process were accelerated at higher pressures. Vibration field improved the dewatering process linearly by filling the gaps among particles and accelerating particle compaction. Synergistic action of pressure and vibration frequency on dewatering was confirmed. The dewatering promotion effect of vibration frequency was obvious at high pressure. In dewatering process, the energy consumption of coupled mechanical dewatering is only 37.4% of that of evaporation dewatering, which presents the advantage of coupled mechanical dewatering process in energy consumption. In this paper, 13% moisture reduction of sample within 3 min via coupled mechanical dewatering force fields was studied, which will provide references for deep dewatering process and cleaner production of gasification fine slag in industry.

Gasification fine slag is a kind of solid waste, and there is a large number of fine slags need to be recycled and reused for environmental consideration. The froth flotation kinetics experiment was adopted to recycle the residual carbon, carbon recovery percentage of 52.65% and the loss on ignition (LOI) of 64.47% were obtained. The pore structure and fractal characteristics of fine slag and its flotation residual carbon are essential factors which will influence their physical and chemical properties, including mechanical, adsorption and fuel properties and it is imperative to understand these parameters. In this study, BET, HK, BJH and FHH models of low-temperature N2 adsorption/desorption were used to compare the differences of specific surface area, pore size/volume and fractal characteristics among samples, respectively. As a result, there are larger surface area and fractal dimension value (D), smaller pore volume and average pore diameter of fine slag than that of flotation residual carbon, which is caused by the spherical-ash particles covering the surface and pores of the rough carbon matrix. Comparing the fine slag and flotation residual carbon, surface area decreases from 145 to 111 m2/g, pore volume increases from 0.1288 to 0.1833 cm3/g, and average pore width increases from 5.2141 to 6.0436 nm. Moreover, the values of D2 and D1 decreased by 6.77% and 2.89%, correspondingly. From the perspective of energy utilization, the HHV value of gasification fine slag is elevated from 6.22 to 19.48 MJ/kg after flotation kinetics process and LOI value increases from 24.49 to 64.47% respectively. TGA shows that the flotation residual carbon has better reactivity than raw fine slag. Froth flotation is an efficient approach to recycle residual carbon from fine slag, while the low-temperature N2 adsorption/desorption technology can be innovatively applied to characterize the pore structure and fractal characteristics of gasified fine slag.