Effect Of Coal Gangue Research Articles

Low-temperature preparation of lightweight ceramic proppants using high-proportioned coal-based solid wastes

Lightweight ceramic proppants are prepared using coal gangue, fly ash, and bauxite as raw materials, and a mixture of manganese dioxide and magnesium oxide is used as composite additives. The total content of the coal gangue and fly ash in the raw materials reaches up to 70 wt%. The effects of coal gangue and fly ash precalcination, sintering temperature, and composite additive content on the phase compositions, microstructures, and performances of the resulting ceramic proppants are studied in detail. The ceramic proppant prepared at 1285 °C using 1 wt% of the composite additive is composed of quartz, corundum, and mullite. It also presents the desired sphericity, roundness, and microstructure. The apparent density, bulk density, and breakage ratio of the ceramic proppant described above are 2.55 ± 0.06 g/cm3, 1.03 ± 0.02 g/cm3, and 8.30 ± 0.68% at 35 MPa, respectively. This ceramic proppant belongs to lightweight ceramic proppants and meets the requirement of the 5K grade in the standards of SY/T 5108-2014 and API STD 19C-2018.

Effects of coal gangue on the ash initial deformation temperature and gasification characteristic of biomass

AbstractThe effects of coal gangue (CG) on the ash initial deformation temperature (IDT) and CO2 gasification characteristic of biomass (chestnut shell [CS] and soybean straw [SS]) were investigated by ash fusion tester and thermogravimetric analyzer, respectively. The IDTs of CS and SS ashes were low because of the presence of abundant low melting point (MP) airchildite (K2Ca(CO3)2) and arcanite (K2SO4), and they were efficiently improved by the CG additions of 2%–10% mass ratios. The increases in the IDTs of CS and SS ashes were resulted from the conversions of fairchildite and arcanite into high MP K‐Al silicates (kalsilite [KAlSiO4], leucite [KAlSi2O6], etc.). The gasification reactivities of CS/CG mixtures stayed below that of CS, and they decreased with increasing CG mass ratios (4%–10%) and increased with increasing temperatures (900–1000°C). At 900°C, CG addition caused a decrease in the gasification reactivity of SS. When the temperature reached 950°C, the CG addition of 4% mass ratio increased the gasification reactivity of SS instead. The synergistic effect between biomass and CG during cogasification was more significant at low CG mass ratio and high temperature, and the synergistic effect between SS and CG was more intense than that between CS and CG.

Effects of coal gangue on soil property and plant growth in mining area.

With indoor and outdoor treatments, coal gangue with different ratios (10%, 20%, 30%, 40% and 50%) and different particle sizes (0-2, 2-5, 5-8 and 8-10 mm) were mixed into soil, and formed reconstructed soil with different soil bulk densities (1.3, 1.35, 1.4, 1.45 and 1.5 g·cm-3). The effects of soil reconstruction modes on soil water condition, structure stability of aggregate and the growth of Lolium perenne, Medicago sativa, and Trifolium repens were investigated. Soil saturated water (SW), capillary water (CW), and field water capacity (FC) were decreased with increasing coal gangue ratio, particle size, and bulk density of reconstructed soil. >0.25 mm particle size aggregate (R0.25), mean weight diameter (MWD), and geometric mean diameter (GMD) increased first and then decreased with the increases of coal gangue particle size, reaching the peak at 2-5 mm coal gangue particle size. R0.25, MWD and GMD were significantly and negatively correlated with coal gangue ratio. Based on boosted regression tree (BRT) model, the coal gangue ratio contributed 59.3%, 67.0% and 40.3% to the variation of SW, CW and FC, respectively, which was a main influencing factor of soil water content. The coal gangue particle size contributed 44.7%, 32.3% and 62.1% to the variation of R0.25, MWD, and GMD, respecti-vely, which was the greatest influencing factor. Coal gangue ratio had a great effect on the growth of L. perenne, M. sativa, and T. repens, which contributed to 49.9%, 17.4% and 10.3% of their variations, respectively. Soil reconstruction mode of 30% coal gangue ratio and 5-8 mm coal gangue particle size was the best condition for plant growth, indicating that coal gangue could change soil water content and structure stability of aggregate. The soil reconstruction mode of 30% coal gangue ratio and 5-8 mm coal gangue particle size was recommended.

Effects of Coal Gangue on the Hydrochemical Components under Different Types of Site Karst Water in Closed Mines

In order to explore the potential effects of abandoned coal mines on the water quality of Ordovician limestone aquifers, water-rock interaction simulations were conducted. After the closure of the coal mine, the karst water in the goaf area and the waste gangue had a geochemical reaction, and the above-mentioned water-rock process was simulated by an indoor static immersion experiment to explore the differences in the effect of different types of karst water on the dissolution of gangue. The basic water quality parameters pH, EC (electrical conductance), and ORP (oxidation-reduction potential) showed different trends in karst hydro-immersion solution and ultra-pure hydro-immersion solution; pH and EC had greater fluctuations in two sets of ultrapure hydro-immersion solutions, while ORP fluctuated more widely in three groups of karst hydro-immersion solutions. In addition, gangue minerals dissolved more significantly in bodies of water where limestone was added. The results of chemical component clustering showed that TDS (total dissolved solids) and EC were homopolymerized in each immersion solution, and subsequent correlation analysis showed that TDS and EC clusters were more significantly affected by mineral properties in ultrapure water-immersion solutions, and more affected by dominant ions in karst water-immersion solutions.

Utilization of coal gangue as coarse aggregates in structural concrete

In this paper, coal gangue is utilized as a replacement of coarse aggregate in structural concrete. The effects of coal gangue on the mechanical properties of concrete material, circular reinforced concrete column and concrete-filled steel tubular column are experimentally studied and discussed in detail. The mechanical behavior of coal gangue concrete is reduced by increasing the coal gangue replacement ratio. A model is proposed for predicting the compressive strength of coal gangue concrete. Some constants are proposed based on test results to predict the splitting tensile strength and elastic modulus of coal gangue concrete. The increase of coal gangue replacement ratio decreases the axial compressive strength and elastic modulus of reinforced coal gangue concrete stubs and coal gangue concrete-filled steel tubular stubs linearly. The enhancement factor and the confinement factor both approximately increase with the increase of coal gangue replacement ratio which indicates that concrete-filled steel tube is a more preferable product than reinforced concrete for the usage of coal gangue as coarse aggregates. A modified design method for reinforced concrete and concrete-filled steel tube towards cleaner products is proposed by considering the coal gangue replacement ratio. The full-range prediction analysis for the strength degradation of coal gangue concrete-filled steel tube implies that relative higher steel strength and lower concrete strength should be used in the preparation of concrete-filled steel tube using coal gangue as coarse aggregates in structural stubs.

The effects of coal gangue and fly ash on the hydraulic properties and water content distribution in reconstructed soil profiles of coal‐mined land with a high groundwater table

AbstractSoil water systems have been severely degraded in coal‐mined and subsiding land, where a shallow groundwater table is also present. The present paper discussed the effects of fly ash (FA) and coal gangue (CG) as filling materials on the hydraulic properties and water content distribution in a profile for the purpose of rehabilitating subsided lands. The saturated water content, water characteristic curve, and water diffusivity of local soil, FA, CG, and a mixture of FA and CG (“mixed filling”) were characterized. A column experiment was conducted to investigate the changes of water content in profiles reconstructed from the combination of soil and filling materials, including soil only, FA, CG, and a mixture of FA and CG, which were used to fill the lower part of the reconstructed profile. The mixture of FA and CG was found to possess similar hydraulic properties to those of the soil, particularly high water‐holding capacity and permeability. Moreover, the volumetric water contents in the whole profile containing the mixture of FA and CG were consistent with those of the profile reconstructed with soil only. As a result, it is recommended to adopt the mixture of FA and CG for reconstructing the lower profile of the land to alleviate or rehabilitate subsided land in coal mines.

Effects of Coastal Coal Gangue Highway on Groundwater

At present, the cumulative coal gangue piles up about 4.5 billion tons and annual discharge capacity reaches 300 million tons in China. Emissions of coal gangue wastes national resources and will take up a lot of land. Besides, the ecological environment will be polluted and damaged. Using coal gangue as roadbed filling material can not only solve the difficulty of land expropriation, but also consume a large amount of accumulated coal gangue, which has huge economic and environmental benefits. Through laboratory soak test and leaching test, this paper analyses the inorganic salt content and heavy metals of coal gangue used in Xing Fen expressway. Groundwater in Xing Fen highway was captured, detected, evaluated and its quality was good or excellent. In this project, the effects of coal gangue on groundwater meet the regulatory requirements and coal gangue as a new filler can be applied to coastal highway roadbed.

Effect of coal gangue with different kaolin contents on compressive strength and pore size of blended cement paste

The effects of activated coal gangue on compressive strength, porosity and pore size distribution of hardened cement pastes were investigated. Activated coal gangue with two different kaolin contents, one higher and one lower, were used to partially replace Portland cement at 0%, 10%, and 30% by weight. The water to binder ratio(w/b) of 0.5 was used for all the blended cement paste mixes. Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content. The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.