Papers by Keyword: Coal Gangue

Abstract: The effective recycling of industrial waste is a globally significant issue. In this study, a geopolymer binder was synthesized using an alkaline activator derived from brown coal gangue and blast furnace slag, along with silica fume as an industrial waste material. Also, the properties of these geopolymer binders are examined using them as a briquette binder. At temperatures above 700°C, roasted brown coal gangue is more active than the initial state. The optimum dosage of alkaline activator is 10M NaOH, silica fume/NaOH ratio of 3, specific gravity of 1.42, and the addition of binder of 6%. The main polymerization products of the alkali activated brown coal gangue geopolymer samples are N-A-S-H gel and amorphous aluminosilicate gel, while the main polymerization products of the alkali activated brown coal gangue -blast furnace slag geopolymer samples are N-A-S-H gel, C-(A)-S-H gel and amorphous aluminosilicate gel. Blast furnace slag is added during the preparation of briquette binder by brown coal gangue geopolymer, which increase the mechanical strength of the geopolymer binder and the optimum dosage is 30%. This study demonstrates a high-value and sustainable pathway for co-utilizing multiple industrial by-products.

Abstract: China's coal resources are extremely rich, and the degree of coal mining is high. During the formation of coal, a large amount of coal gangue will be produced, which not only accumulates land and wastes resources, but may also cause natural disasters such as fires. In this paper, coal gangue is used as the main raw material, and a certain amount of kaolin, steel slag and other auxiliary materials are added to prepare coal gangue ceramsite through a high-temperature sintering process. The research results show that as the sintering temperature increases, the porosity of the ceramsite decreases first. After increasing, the water absorption rate of ceramsite also decreases first and then increases with the increase of the firing temperature, while the compressive strength first decreases and then increases with the increase of temperature. With the increase of the holding time, the porosity of the ceramsite first decreases and then increases. The water absorption rate of the ceramsite also first decreases and then increases with the increase of the firing temperature, while the compressive strength decreases first and then increases with the increase of the temperature. Elevated. With the increase of coal gangue content, the porosity of ceramsite gradually decreases, the water absorption rate of ceramsite also gradually decreases, and the compressive strength gradually increases with the increase of coal gangue content. The optimization can be obtained, the coal gangue content (mass fraction) is 100%, the calcination process system is 1200°C, and the heat preservation time is 60min as the better parameters. At this time, the compressive strength is 29.57MPa and the porosity is 4.36%.

Abstract: Massive coal gangue waste delivers environmental disasters in China. Finding an effective, efficient, practical and value-added approach for large-scale disposal of coal gangue waste is very urgent. In this study, thermal treatment approach was conducted on coal gangue waster with the goal to improve its pozzolanic activity so that considerable replacement of Portland cement can be realized. XRD analysis, IR analysis as well as the evaluation on mechanical properties of mortar specimen were carried out to optimize thermal treatment program. The results indicate that coal gangue waste can be efficiently treated at 850°C in less than 30min to obtain pozzolanic activity of 108% at 7 days and 124% at 28 days. And an industrial product also shows similar improvement in pozzolanic activity to the lab results, and indicates the potential for producing eco-efficient cementitious materials.

Abstract: The current statistics show coal gangue discharge is 100 million tons per year, and the accumulated discharge has been as high as 4.5 billion tons. It comprises the largest portion of solid waste in our country. Its storage not only requires valuable land resources, but also pollutes the air, water and soil of the storage sites, resulting in waste of resources. This article firstly introduces the physical characteristics, influence and application of coal gangue. And then applications of coal gangue in cement-based materials and new wall materials are illustrated as examples of application of coal gangue in building materials. This section is composed of the following particular aspects: 1) concrete application: replacement of cement by 20% coal gangue can effectively extend the setting time, increase the compressive strength, and has little influence on workability; 2) Grouting material application: coal gangue can completely substitute filling material used in grouting material; 3) Hollow brick application: compared to conventional hollow bricks, in terms of density, density of coal gangue hollow bricks is not larger; in terms of void fraction, coal gangue hollow block is also slightly better. Finally several limitations in applications are discussed and improvements are suggested.

Abstract: In-situ growth of mullite whisker from waste coal gangue and different aluminium source mixtures by dry pressing were investigated aiming at the preparation of mullite - corundum lightweight refractory by controlling mullite whisker precursor pseudo particle size and quantity in corundum matrix. The phase composition and microstructure were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. Apparent porosity and bending strength were also measured. The samples exhibited characteristic alumina and mullite phases. The formation mechanism and influence factors for mullite whiskers materials were discussed. The experimental results showed that the whisker of the obtained sample changed from the accumulated short column to mesh cross acicular whisker shape, and the length to diameter ratio increases. When the aluminium source was aluminium hydroxide, the length to diameter ratio and apparent porosity reached the maximum of 17.6 and the minimum of 2.15%. The bending strength of all the samples was similar, that of the sample prepared by calcined bauxite was the largest (84 MPa), that of the sample prepared by calcined alumina was inferior, and the sample prepared by aluminum hydroxide was the lowest.

Abstract: Life cycle assessment (LCA) was carried out to quantify and analyze the environmental impact and benefit caused by the utilization of coal gangue as alternative raw material and fuel in cement clinker production. The optimal dosage of coal gangue was determined by comparing among different mixing amount scenarios and Portland cement clinker (clinker without adding any waste) considering the phases of coal gangue disposal, transportation, and raw meal grinding and clinker calcination. The results showed that: 1) After adding coal gangue to the raw meal, almost all the considered environmental impacts of cement clinker including human toxicity potential, photochemical smog potential, especially abiotic depletion potential decreased significantly. However, global warming potential and acidification potential increased slightly in comparison with Portland cement clinker. 2) Compared with the Portland cement clinker, the single environmental indicator reduced after adding coal gangue and the indicator decreased gradually with the dosage increasing.

Abstract: Anorthite good sintering properties and strength, there promotion prospects in oil and gas fields in the ceramic proppant fracturing. In this experiment, fly ash, coal and limestone as raw materials by high-temperature reaction sintering ceramics, Explore mineral composition, the sintering temperature of the final preparation phase of the resulting composition and physical properties of the impact, better product performance obtained at 1250 °C.

Abstract: Shear wall is the main component that resists the lateral force for high-rise buildings. With the rapid development of high-rise buildings, especially the super high-rise buildings, requirements for seismic performance of shear walls have become more sophisticated. This introduction summarizes the commonly used in embedded development and existing problems of steel plate shear wall, which are stiffened steel plate shear wall, non-stiffened steel plate shear wall, composite steel plate shear wall, preventing buckling of steel plate shear wall and low yield point steel plate shear wall.

Abstract: The hydrophobic SiO₂ aerogel was prepared by using coal gangue as the starting material—which is viewed as waste in most coal mining and preparation plant—via ambient pressure drying through sol-gel method. The effects of different temperature, time to keep the temperature,vary in mass ratio of coal gangue to sodium hydroxide on the leaching ratio of SiO₂ from coal refuses are discussed in this paper. Results showed that the leaching ratio of SiO₂ extracted from gangue will be made up to 35.23% compared with the other tests on the condition that the temperature is given 750°C, holding time 2h, the value of ratio of coal gangue to sodium hydroxide 1:0.8, concentration of NaOH 20%. Trimethylchlorosilane (TMCS) is used as modifier to obtain hydrophobicity through solvent exchange and surface modification. We achieved SiO₂ aerogel with low density of 0.2559g/cm³, high porosity 88.97%,Strong hydrophobicity (contact angle with water 140.61^。) respectively, which demonstrated that the final product exhibits excellent property. Differences among SiO₂ aerogel properties were discussed between industrial sodium silicate as precursor and sodium silicate drew from coal gangue as precursor. Results revealed that the the latter is better than the former on properties .Our work provided a potential way to synthetize high value-added product from abandoned by-product coal gangue.

Abstract: The ways of using coal gangue in electricity generation, chemical utilization and building-material production are introduced and national coal gangue utilization status and development trend is analyzed in this paper. Pointing out the main problems in present utilization of coal gangues, suggestions on coal gangue resource utilization are given that provide reference for eliminating coal gangue pollution, enhancing environmental protection and saving up energy.