Gasification Slag Research Articles

Experimental study on pore structure and mechanical dehydration of coal gasification fine slag

ABSTRACT Coal gasification fine slag is a kind of solid waste with high carbon content produced in the process of coal gasification. There is an urgent need to analyze the various pore sizes and their characteristics, and then design a proper method for dewatering gasification fine slag. In this study the low-temperature adsorption analysis, high-pressure injection analysis (mercury porosimetry) as well as the two types of filter press are used to first analyze the gasification slag pore characteristics and then dewatering efficiency, respectively. Results show that the full pore size combined analysis method portray that the pore size increases rapidly between 100 ~ 2000 nm, which is significantly different and larger than the pore size at low-temperature nitrogen adsorption analysis (4.37 nm). As a result, the combined pore size method of high-pressure mercury injection and low-temperature nitrogen adsorption predicts more precise results. Micropores, transition pores, mesopores, and macropores account for 6.62%, 7.84%, 18.46%, and 67.08% of the total. A filter press with a diaphragm plate and frame is an efficient dewatering device for fine coal gasification slag. The final filter cake moisture is 50.87%, which is significantly lower than the vacuum belt filter with 69.22%. A new option for coal gasification fine slag dewatering equipment is the ultra high-pressure filter press; the moisture content of filter cake obtained is 44.70%, and the dewatering effect is outstanding. This study will help to better design the dehydration methods of the wet slags. Ultimately, it will help recycling the water, reducing the ash quantity as well as the cost of the ash landfill.

Effect of Coal Gasification Slag on Improving Physical Properties of Acid Soil

Coal gasification slag (CGS) is a coal-based solid waste formed by the transformation of inorganic mineral components and carbon components in raw coal into slag during coal gasification. To explore its influence on the physical characteristics of acid soil and study the influence mechanism on the water holding capacity of acid soil, the coarse and fine CGS were used as materials to mix with acid soil in different proportions. The volume weight, particle size composition, and water retention performance of the mixed soil were tested, and the changes of soil water characteristic curve were analysed. The results showed that, after mixing the acid soil with CGS, the particle size composition of acid soil was significantly improved, the sand content increased by 13.27–195.46%, the clay and silt content decreased by −2.14–38.62% and 3.22–40.06%, respectively; and the soil bulk density decreased significantly (P < 0.05), with a decrease range of 3.38–28.12%. The soil texture also changed from silty loam to sandy loam, and the water retention performance showed an upward trend, which significantly affected the soil saturated water content, capillary water capacity and field water capacity, with an increase range of 2.87–38.09%, 1.73–27.92% and 4.18–22.27%, respectively. The Van Genuchten (VG) model could fit the soil water characteristic curve well, indicating that the water retention of acid soil was significantly improved by adding CGS. In conclusion, CGS could improve the water physical properties effectively, and improve the water retention and water holding properties of acid soil significantly. This feature is conducive to the environmentally friendly utilization of CGS to improve agricultural acid soil.

Removal of mercury from flue gas using coal gasification slag

Coal combustion often produces mercury emissions. Coal gasification fine slag (FS) was used to remove Hg0 from flue gas. To increase the removal efficiency, two ionic liquids (IL-T and IL-B) were immobilized on the surface of FS. The mercury removal performance was evaluated in a fixed-bed reactor in the presence of SO2 + O2. The experimental results showed that the mercury removal efficiency increased when the adsorbents were supported by ionic liquids (FS-T and FS-B). The effect of 0.6% SO2 on the capture of Hg0 was negligible for all three adsorbents. The total mercury removal efficiencies exceeded 90% for FS-T and FS-B in the atmosphere of 0.6% SO2 + 6% O2. When the initial mercury concentration was 60 μg/m3, the effective adsorption time was about 80 min for FS and longer than 120 min for FS-T and FS-B. In the presence of 0.6% SO2 + 6% O2, Hg0 and Hg2+ were detected in exhaust gas using FS and FS-B and in solid phase using the three adsorbents. According to XPS analysis, an oxidation reaction occurred on the surface of FS and FS-T. For FS-B, the Br− anion of IL-B was the active site and oxidized Hg0 to Hg2+ on the surface as well as in the gas phase.

Enhanced flotation mechanism of coal gasification fine slag with composite collectors

In this study, different composite collectors were used to analyze the flotation separation of residual charcoal and ash materials in fine coal gasification slags. The effects of collector type, stirring speed, and conditioning time on the flotation separation were investigated. The experimental results showed that composite collectors containing dodecylamine polyoxyethylene ether (AC1201) and kerosene could effectively separate charcoal-ash when treating the fine coal gasification slags of Ningxia Coal Industry Company. The ash content of the residue carbon product was approximately 60%, and that of the ash material product was more than 95%. Compared with kerosene, AC1201-kerosene collector can be dispersed more easily and lower interfacial tension in collector-deionized water system, resulting in better selectivity of the collector. The composite collector containing 15% AC1201 has stronger adsorption on residual charcoal compared with kerosene at the same dose, owing to electrostatic mechanism. The addition of AC1201 in kerosene resulted in better adsorption on residual charcoal than ash material, the hydrophobicity difference of two materials can be further expanded, resulting in increased tailings ash and combustible recovery. The flotation products, including the concentrate and tailings of fine coal gasification slag, were evaluated by means of infrared spectrum analysis, X-ray photoelectron spectroscopy (XPS) analysis, and scanning electron microscope energy spectrometer (SEM-EDS) to characterize the different compositions and elemental distributions. The results of this study provide a reference for analyzing charcoal-ash flotation separation and its mechanism.

High‐value application of glass beads/porous carbon obtained from coal gasification fine slag as alternative for carbon black in natural rubber composite

AbstractCoal gasification slag is a by‐product of entrained‐flow coal gasification, and the improper disposal of the slag causes environmental pollution. Coal gasification fine slag (CGFS) filtered cakes were treated in a spin flash dryer. The CGFS products with different particle sizes (coarse particles (CGFS‐C) and fine particles (CGFS‐F)), loss on ignition (unburned carbon), and silica content were obtained. Morphology analysis revealed that the CGFS‐F particles had a hybrid structure of unburned carbon embedded by glass beads and a higher structural degree of the unburned carbon. The effects of carbon black (CB), CGFS‐C, and CGFS‐F on the comprehensive properties of filled natural rubber (NR) were studied. Compared with CB, CGFS‐F had little effect on the cure characteristics of NR and delayed the scorching. The CB dispersion status and rubber processing analysis showed that the hybrid structure of the CGFS‐F can prompt the fillers to disperse well in NR. Owing to the hybrid structure and higher structural degree, the overall properties of the NR composites filled with CGFS‐F having a yield of 39.46 wt.% were better compared to those of the CB‐filled NR composite. In summary, CGFS‐F particles can replace CB (N660) used in NR products.

Effect of Fe2+/Fe3+ on high-strength ceramsite prepared by sintering geopolymers using iron ore tailings

Iron ore tailings (IOTs) and coal gasification slag (CGS) were used to prepare novel ceramsites via high-temperature sintering. The IOTs were activated by NaOH to form a geopolymer that was sintered at 650 °C, 850 °C, and 1050 °C to obtain ceramsites. The formation of the geopolymer was confirmed by the characteristic peaks of Si–O–T (T = Si, Al) in the Fourier transform infrared spectra. X-ray diffractograms showed that Fe 3+ participated in the geopolymerization reaction, whereas Fe 2+ did not; hence the effect of the Fe 2+ /Fe 3+ ratio was investigated. This ratio increased with increasing sintering temperature, thereby facilitating nucleation within the sample. The mullite–pyroxene network that formed upon sintering at 1050 °C improved the strength of the prepared ceramsite and its structure became more compact. Specifically, the cylinder compressive strength increased from 10.5 to 35.5 MPa after sintering at 1050 °C. Overall, this method of preparing high-strength ceramsites from IOTs and CGS can be used for the preparation of high-strength lightweight concrete. • Compressive strength of ceramsite tripled after alkali-activated pretreatment. • Fe 3+ ions participated in the geopolymerisation reaction; Fe 2+ ions had no effect. • Fe 2+ /Fe 3+ ratio had a notable effect on the internal crystallization of ceramsite. • Mullite pyroxene network structure enhanced the strength of ceramsites.

Investigation on the utilization of coal gasification slag in Portland cement: Reaction kinetics and microstructure

Gasification slag is a solid waste generated by the coal chemical industry which has emerged in recent years. In this paper, the effect of coal gasification slag (CGS) powder content on the reaction kinetics, gel structure and the compressive strength of Portland cement was investigated for the potential application of CGS powders in cementitious materials. The reaction and gel structure of Portland cement blended with CGS was analyzed by using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy tests. The results show that the unreacted CGS power exists mainly in an agglomerated state in cement matrix, and a low dosage of CGS powder (10%) can play a role in nucleation and pozzolanic effect in Portland cement, which is conducive to the formation of hydration reactions of Portland cement, shortening the setting time and improving the compressive strength. If the CGS content is >30%, the hydration product content decreases, and the microstructure of the sample becomes loosened. The setting times are significantly prolonged with the increase of CGS content dosing and the compressive strength is considerably reduced as well.

Durability of Concrete With Coal Gasification Slag and Coal Gangue Powder

Lack and quality decrease of supplementary cementing materials (SCMs) such as fly ash and granulated blast-furnace slag is increasingly prominent in China. Thus, the use of coal gangue (CG) and coal gasification slag (CGS) as SCMs in concrete attracted more researcher’s attention. This paper investigated the mechanical strength, porosity, and durability of CG-and CGS-added concrete. Experimental results showed that the activity of the treated CG and CGS is better than that of ordinary mineral SCMs, indicating that CG and CGS concrete can satisfy the requirements of ordinary construction under reasonable processing technology. Both CG-added and CGS-added concrete illustrated better chloride penetration resistance. The aluminum element contained in CG and CGS causes the C3S hydration to generate ettringite which is an erosion product under sulfate erosion, and it will intensify the damage of sulfate erosion. After 125th freeze-thaw cycles, the CGS-added concrete has no obvious failure which indicates that CGS-added concrete has great capacity in the frost resistance.

Simultaneous adsorption of ammonia and phosphate using ferric sulfate modified carbon/zeolite composite from coal gasification slag

Removal of nutrients in water is crucial to control eutrophication. Fly ash has been increasingly used to synthesize zeolite to remove nutrients, but it is still poorly understood about the removal capacity of zeolite synthesized from coal gasification slag (CGS), which has not been well recycled in many countries. In this study, the CGS was acid leached, alkali dissolved, and synthesized to carbon/zeolite composite (C/ZC) under induction by medical stone. After being modified by ferric sulfate, the composite was analyzed for the adsorption of NH4+ and PO43−. Results showed that the maximum adsorption capacity by C/ZC is 5.17 mg/g, but C/ZC has no adsorption capacity of PO43−. The ferric sulfate was used to modify C/ZC to obtain carbon/zeolite composite modified by iron (M-C/ZC). M-C/ZC has a higher specific surface area (348.3 m2/g), and the negatively charge of M-C/ZC can adsorb NH4+ and form Fe–O–P between PO43− and Fe–OH bonds. The maximum adsorption capacity of NH4+ and PO43− by M-C/ZC are 7.44 mg/g and 6.94 mg/g, respectively. The removal efficiency of NH4+ and PO43− are up to 88% and 99% under initial NH4+ (5 mg/L) and PO43− (10 mg/L) concentration. The regeneration capacity of M-C/ZC of NH4+ was stronger than that of PO43−. After three cycles, the regeneration rate of M-C/ZC of NH4+ was still up to 76.96%. Our findings suggest the good application potential of M-C/ZC for removing NH4+ and PO43− from wastewater.

Fluidity Influencing Factor Analysis and Ratio Optimization of New Filling Slurry Based on the Response Surface Method

The filling mining method is important in realizing the green mining of mineral resources. Aiming at the problems of land resource occupation, environmental pollution, and rational utilization of coal-based solid wastes such as coal gangue, fly ash, and desulfurization gypsum, a new paste filling material was developed with coal gangue, fly ash, and desulfurization gypsum as raw materials. The microstructure of the raw materials was analyzed by XRD and SEM. Combined with the Box-Behnken experimental design, the effect of each component on the fluidity of the filling slurry was analyzed through the response surface analysis. The significance of each component on its bleeding and fluidity was determined, and the optimal ratio of the filling slurry was obtained. Experimental results show that the microcosmic morphology of coal gangue, desulfurization gypsum, and gasification slag presents an irregular block and rough particle surface; the microcosmic morphology of fly ash and bottom slag presents first out spherical or quasi spherical particles. Moreover, obvious sintering traces exist on the surface of the bottom slag. The main crystal mineral of coal gangue and fly ash is SiO2, the desulfurization gypsum is composed of Ca(SO4) (H2O) and Ca(CO3) crystal minerals, the gasification slag is composed of carbon and nitrogen compounds, and the main crystal mineral components in the bottom slag sample are SiO2 and AlxSiyOz compounds. The order of significance of each key factor on slurry fluidity is as follows: C (desulfurization gypsum) > D (gasification slag and bottom slag 1:1) > A (coal gangue) > B (fly ash). The order of the significance of each key factor on slurry bleeding is as follows: B (fly ash) > C (desulfurization gypsum) > D (gasification slag and bottom slag 1:1) > A (coal gangue). Considering the material preparation, field application, and other conditions, the mass percentage of each factor content of the new paste filling material is as follows: 49.5% coal gangue, 8.3% fly ash, 4.1% desulfurization gypsum, 6.2% gasification slag, and 6.2% bottom slag.

Optimization Analysis of Mechanical Properties of Fly Ash‐Based Multicontent Gasification Slag Paste Filling Material

In view of the difficult utilization of a large amount of coal‐based solid waste produced by coal electrification in the Ningdong mining area, especially the large storage and low utilization rate of gasified slag, combined with the advantages of high paste filling concentration, fast efficiency, and low construction cost, it is of great significance to study the appropriate proportion of fly ash‐based multicontent gasified slag paste filling material for green mining and large‐amount utilization of gasified slag. Based on the microstructure, composition, and particle size distribution of gasification slag, fly ash, broken coal gangue, furnace bottom slag, and desulfurization gypsum tested by XRD, SEM, and particle size sorting screen, the mass fraction (X1), gasification slag content (X2), m (c): m (FA) (X3). 29 groups of schemes are designed by four factors : mass fraction X1 refers to the proportion of solid in the filling paste, the amount of gasification slag in the solid X2 refers to the proportion of gasification slag in the solid, and m (c): m (FA) X3 refers to the proportion of fly ash and cement in the solid excluding gasification slag, coal gangue, desulfurization gypsum, and furnace bottom slag. The amount of desulfurization gypsum in the solid X4 refers to the proportion of desulfurization gypsum in the solid. The flow and strength characteristics of each group are analyzed. It is found that before proportioning, coal gangue of 2.5∼5 mm accounts for 80.8%, furnace bottom slag of less than 2.5 mm accounts for 56.5%, fly ash of 20∼80% μm accounts for 80%, and fly ash of 10∼20% μm accounts for 90%. XRD patterns reveal that the main components of four solid wastes and cement are SiO2 and Ca3SiO5, and the chemical composition of desulfurization gypsum is Ca(SO4)(H2O)2. The regularity of size change tends to be consistent, and the uniaxial compressive strength of 3 days later in group thirteenth exceeds 0.991 MPa. Combined with the flow characteristics, it is determined that there are 6 optimization groups in the inclined ladder area with the expansion of 200∼250 mm and the uniaxial compressive strength of 0.6∼1.4 MPa. The compressive strength increases with the increase of the mass fraction of single‐factor analysis. The response surface method of C shows that the significance of X1, X2, X3, and X4 decreases in turn. The central combination design is used to predict that the mix proportion of X1 is 84%, X2 is 15%, X3 is 1 : 5, and X4 is 7%, the content of coal gangue is 10%, and the content of furnace bottom slag is 5% which is the best. The supplementary experimental results show that σ3d is 1.35 MPa and the expansion is 200 mm. Combined with SEM, it is found that the microstructure before and after optimization is rich in hydration products and the internal structure is well cemented, which further explains σC. The above research provides important basic parameters for large‐scale disposal and green filling mining which is difficult to deal with a large amount of stockpiled gasification slag.

A Facile Synthesis Process and Electromagnetic Absorption Performance of High Alumina Fly Ash and Gasification Slag- Based Ceramic Composites

A Facile Synthesis Process and Electromagnetic Absorption Performance of High Alumina Fly Ash and Gasification Slag- Based Ceramic Composites

Study on the Conversion Mechanism of Iron- Containing Coal Gasification Slag to No in High Temperature Flue Gas of Cement Kiln

Study on the Conversion Mechanism of Iron- Containing Coal Gasification Slag to No in High Temperature Flue Gas of Cement Kiln

Insight into the Mechanism of Gasification Slag Enhanced Flotation with Selective Dispersion Flocculation

Insight into the Mechanism of Gasification Slag Enhanced Flotation with Selective Dispersion Flocculation

Study on The Conversion Mechanism of Iron-Containing Coal Gasification Slag to No in High Temperature Flue Gas of Cement Kiln

Study on The Conversion Mechanism of Iron-Containing Coal Gasification Slag to No in High Temperature Flue Gas of Cement Kiln

Study on the composition and structure characteristics and dry decarbonization separation of coal water slurry gasification fine slag

Efficient separation and high-valued utilization of coal gasification ash or slag limit the clean and green development of coal chemical industry. In this paper, a coal-water slurry gasification fine slag (CWSFS) was studied by wet screening and classification. The relationship between the particle composition with different sizes and the structural characteristics was investigated by means of proximate analysis, XRF, XRD, BET and SEM. A classification method of CWSFS was proposed to guide the high-valued utilization of coal gasification slag. Then, dry separation of a coal-water slurry gasification fine slag was carried out using a combined treatment method of crushing and dissociation and airflow classification. The results show that the CWSFS particles of different sizes have obvious differences in fixed carbon content, ash composition and mineral types. For the CWSFS with the particle size above 74 μm, the fixed carbon content is more than 60%, the calorific value is more than 20 MJ/kg, the specific surface area is relatively high and the main component is the residual carbon that contains magnetite and brookite. For the CWSFS with particle sizes between 13–74 μm, the fixed carbon content is between 20%–60%, the calorific value is between 11–19 MJ/kg, the specific surface area is small and the main mineral types are pyroxene, marcasite and hematite, etc. For the CWSFS with a particle size between 0–13 μm, the fixed carbon content is less than 20% and the calorific value is less than 10 MJ/kg, which mainly includes the amorphous glass phase that was rich in aluminum, iron and calcium, quartz and a small amount of fayalite, muscovite and other minerals. According to the fixed carbon content of CWSFS with different particle sizes, the above three components with varying particle size ranges are defined as high-carbon component, medium-carbon component and low-carbon component, respectively. The dry separation test shows that the air flow crushing and classification process can achieve a higher product yield of 29.60% and a high ignition loss of 93.76%, compared to the traditional disc crushing-classification process. Airflow crushing was proved to be able to effectively increase the dissociation degree of residual carbon and greatly improve the separation and enrichment rate of residual carbon.

Study on the proportion of coal gasification slag paste filling material

Aiming at the utilization of coal gasification slag, it is proposed to prepare coal gasification slag as mine filling material. The optimum ratio of cement: coal gasification slag: gangue is 1:5:1, the mass fraction is 70%, and the dosage of quicklime is 4%. The strength of backfill reaches 4.23mpa, which can meet the requirements of mine backfill strength.

Universality of mesoporous coal gasification slag for reinforcement and deodorization in four common polymers

Mesoporous adsorbents and polymer deodorants are difficult to implement on a large scale because of their complicated preparation methods. Herein, a mesoporous adsorbent (CGSA) with a specific surface area of 564 m2 g−1 and a pore volume of 0.807 cm3 g−1 was prepared from solid waste coal gasification slag using a simple acid leaching process. The adsorption thermodynamics and adsorption kinetics results verified that the adsorption mechanism of propane on CGSA was mainly physisorption. Then the universality of CGSA in different polymers was investigated by introducing CGSA and its commercialized counterparts (CaCO3, and zeolite) into four common polymers. When the filler content was 30 wt%, the average reinforcement effect of CGSA on the tensile, flexural, and impact strengths of the four polymers was 46.68%, 83.62%, and 211.90% higher than that of CaCO3, respectively. Gas chromatography results also showed that CGSA significantly decreased total volatile organic compound emissions from the composites, and its optimal deodorization performance reached 69.58%, 81.33%, and 91.09% for different polymers, respectively, far exceeding that of zeolite. Therefore, this study showed that low-cost, high-performance, and multifunctional mesoporous polymer fillers with excellent universality can be manufactured from solid contaminants.

Study on compatibility of fresh cement paste mixed with modified coal gasification slag and superplasticizer

Study on compatibility of fresh cement paste mixed with modified coal gasification slag and superplasticizer

Adsorption mechanism of a new combined collector (PS-1) on unburned carbon in gasification slag

Coal gasification fine slag (CGFS) is a type of solid waste produced during coal gasification, in which unburned carbon (UC) severely restricts its resource utilization. The removal of UC from CGFS is considered an urgent problem. This study applies PS-1 (a mixture of kerosene and oleic acid at the ratio of 7:3) to improve the flotation separation effect of carbon from CGFS. The flotation adsorption mechanism of PS-1 on UC is revealed by experiment/molecular dynamics simulation and characterization analysis. Results show that long-chain hydrocarbons in PS-1 are adsorbed on the non-polar region of UC by Van der Waals force, while –COOH groups in PS-1 are adsorbed on the polar sites of –COOH and –OH of UC by hydrogen bonds. The synergistic effect of long-chain hydrocarbons and –COOH groups in PS-1 improves the hydrophobicity of the UC surface. Compared with traditional collector kerosene, the combustible recovery rate of foam products can be increased to 68.0%. Collector dosage can be reduced by approximately 50% using PS-1. This study can provide essential guidance for the design of CGS flotation collectors and help realize the comprehensive utilization of coal gasification solid waste.