Review of the Preparation and Application of Porous Materials for Typical Coal-Based Solid Waste

Research status of comprehensive utilization of coal-based solid waste (CSW) and key technologies of filling mining in China: A review

Coal-based solid waste (CSW) is the solid waste generated in the process of coal mining, washing and pyrolysis, which is an important industrial solid waste. The comprehensive utilization of CSW is a key link in the process of clean and efficient utilization of coal, and the use of CSW for coal mine filling mining is an important means of "harmless, resourceful and large-scale" utilization. In order to study the research status of comprehensive utilization of CSW and key technologies of filling mining in China, this paper combs and analyzes the current situation of comprehensive utilization of CSW from three parts, namely, physical and chemical properties of CSW, Industry-related policies, and ways and means of comprehensive utilization. It is found that coal mine filling mining is a green disposal method with relatively reliable technical means, low supervision cost and large-scale disposal of CSW in the comprehensive utilization of CSW in China. Furthermore, an analysis was conducted on the current research status of key technologies in the CSW filling and mining process, including the integration of "mining, selection and filling", adsorption and complexation passivation of heavy metals in CSW, the preparation of CSW collaborative filling materials, and monitoring and control of the whole filling process, etc. Based on the above analysis and research, it was pointed out that there were some problems, namely: (1) large output of CSW and low level of comprehensive utilization; (2) high investment and high cost of CSW filling and mining; and (3) imperfect CSW waste filling mining theory and technology. In response to these issues, prospects have been made from the aspects of policy incentive mechanisms, collaborative utilization of CSW with multi-industry links, and the theory and technology of CSW filling mining. This study provided reference and inspiration for the comprehensive utilization of CSW in the world, and provides guidance for the large-scale promotion and application of CSW filling mining methods.

Research on preparation and related properties of macro-micro porous mullite ceramic skeletons via twice pore-forming technology

A lot of solid waste coal gangue is produced every year in the process of coal mining and coal washing, which poses a great threat to human health. How to deal with coal gangue properly is still a serious problem. In this study the macro-micro composite porous mullite ceramic skeletons were successfully prepared using solid waste coal gangue and α-Al2O3 as main raw materials via twice pore-forming technology. The main phase composition of the porous ceramic skeletons was mullite tested by X-ray Diffractometer (XRD). The morphology and microstructure of the porous ceramic skeletons were analyzed by Scanning Electron Microscope (SEM). The results show that the microstructure of porous ceramic skeletons was mainly composed of mullite whiskers. With the increase of sintering temperature from 1200 °C to 1350 °C, the maximum length of mullite whiskers grew up from 2.68 μm to 8.10 μm and their average length grew up from 0.78 μm to 2.98 μm. The maximum compressive strength of the porous ceramic skeletons with 30 PPI and 45 PPI were 1.25 MPa and 1.54 MPa tested by Universal Testing Machine (UTM) at the sintering temperature of 1250 °C, respectively. The linear shrinkage, bulk density and pore stem density of the porous ceramic skeletons became larger with the rising of sintering temperatures from 1150 °C to 1350 °C. However, the corresponding performance values of 45 PPI porous ceramic skeletons were greater than that of 30 PPI at the same sintering temperature. The prepared porous ceramic skeletons will be used in ceramic-metal wear-resistant composites for the later research and the study provides a new idea for coal gangue on the comprehensive utilization with high added value and brings both good environmental and economic benefits.

Study on the macro-micro evolution of compaction characteristics of coal gangue with different grain sizes under side-limit compression conditions

Currently the main method of mine solid waste disposal and utilization is to apply gangue to underground filling. For the grading characteristics of coal gangue in the hollow zone in underground filling, the state of pressure and the mechanical properties of coal gangue filling materials under different particle sizes. In this paper, through laboratory tests and numerical simulations, the bearing characteristics and deformation damage of gangue are deeply investigated and analyzed from both macroscopic and microscopic perspectives. The results of the study show that when the axial pressure reaches a certain threshold, the strain increases accordingly with the increase in grain size. Under the axial pressure condition of 15MPa, the bearing capacity of gangue with different grain sizes under the lateral pressure of steel cylinder showed obvious positive correlation. In the software PFC3D simulation, as the particle size of gangue particles increases, it has a significant effect on the natural stacking porosity of the specimen, and gangue particles are more prone to force chain instability and failure. Mixed particle size gangue can significantly reduce the natural accumulation porosity of the specimen, thus improving its overall stability. Significant displacement triangles existed in the top and lateral directions of the B1 (0-5 mm), B2 (5-10 mm), and B5 (0-20 mm) specimens under the same circumferential pressure conditions. The results of the study are of great significance for further selection of reasonable gangue gradation and determination of its mechanical properties.

Recovery of Non-Ferrous Metal from Metallurgical Residues

Non-ferrous metals and alloys are essential resources for the development of modern industries [...].

Eco-Friendly Sustainable Concrete and Mortar Using Coal Dust Waste

Finding the solution to the problem of the accumulating waste from the mining and processing industries, as well as reducing their carbon footprint, is among the most important tasks today. Within the construction industry, in the field of the production of building materials such as concrete, these problems may be solved through the use of waste and by saving the binder component. The purpose of this study is to substantiate the feasibility of using waste coal dust (CD) in concrete and cement-sand mortars as a partial replacement for cement. Test samples were made by partially replacing cement with CD in an amount from 0% to 10% in increments of 2% by weight. The following main characteristics were studied: mobility and density of mixtures, as well as density, compressive strength, bending strength and water absorption of concrete and mortars. X-ray diffraction and microscopic analysis methods were used in this work. The introduction of CD to replace part of the cement, up to 10%, did not have a significant effect on the density of concrete and mortar mixtures but reduced their workability. The best values of physical and mechanical characteristics were recorded for concrete and mortar with 4% CD. The increases in the compressive strength of concrete and mortars were 6.6% and 5.7%, and in flexural strength 6.1% and 5.6%, respectively. Water absorption decreased by 9.7% for concrete and by 9.3% for mortar.