Coal Mine Waste Rock Research Articles

3D geometallurgical characterization of coal mine waste rock piles for their reprocessing purpose

Jerada coal mining generates extensive coal mine waste rock (CMWR) piles rich in valuable minerals, posing environmental challenges and economic opportunities. This study examines reprocessing feasibility through 3D geometallurgical characterization. Sampling used down the hole hammer drilling technique (DTH) and drone surveys for topographical precision. Over 620 samples from (T01, T02, T08) underwent comprehensive analyses including particle size distribution, x-ray fluorescence (XRF), total sulfur/carbon analysis (S/C), and inductively coupled plasma mass spectrometry (ICP-MS) for physical–chemical characterization. Mineralogical aspects were explored via optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Quantitative mineral evaluation by scanning electron microscope (QEMSCAN) provided mineral insights. Chemical data was used in a 3D block model to quantify residual coal. Results for the three examined CMWR piles (T01, T02, and T08) showed varying D80 from 160 to 300 µm, notable carbon content averaged 12.5 wt% (T01), 16 wt% (T02), and 8.5 wt% (T08). Sulfur presence exceeded 1 wt% in T08, and potential environmental concerns due to iron sulfides. Anthracite liberation was below 30 wt%. 3D modeling estimated a total volume of 7 Mm3, mainly from T08, equaling 11.2 Mt. With its high carbon content and substantial tonnages, re-exploitation or alternative applications could minimize these CMWR piles environmental impact.

Integrated 3D geo-environmental assessment of acid-forming materials in historic coal waste piles for sustainable management.

Integrated 3D geo-environmental assessment of acid-forming materials in historic coal waste piles for sustainable management.

On the technology of waste rock dump development in coal mines

Purpose. Analysis, systematization, and visualization of technological schemes for developing waste rock dumps in coal mines, considering the types and specifications of mining equipment. Methodology. To achieve the stated objective, a comprehensive approach was applied, which included summarizing the current state of waste rock dump formation and existing methods for their development. The visualization of technological schemes for developing coal mine waste rock dumps, considering mechanization complexes, involved using the AutoCAD software, enabling the geometrization of dump development parameters, optimization of mining equipment movement routes, and identification of the most efficient sites for its placement. Results. Various forms of mine waste rock dumps were analyzed, allowing for the identification of their main types, geometric characteristics, and formation methods. The obtained data made it possible to determine the specific configurations of the dumps and propose a mechanization complex for their development. It was found that the foundation for the efficient and safe development of waste rock dumps consists of seven technological schemes, each having both common and distinctive features. It was determined that using modern tracked transport vehicles allows for overcoming steeper slopes. Additionally, considering the rotation of the dump body platform with the cabin around the base chassis, it is possible to reduce the required working platforms. Originality. A scientific classification of technological schemes has been developed based on comprehensive mechanization tools for reclamation waste dumps. This classification is determined by the dump height, available equipment (when designing the technology), natural (geographical), climatic, and geological conditions, as well as the main parameters of the dump. Practical implications. A new technological scheme for waste rock dump development was proposed, involving the use of tracked dump trucks, which allows for the operation of steep slopes and a steep transport incline. The study examined the staged development of dumps using various technological schemes.

Optimizing aggregate grading and residual mortar coefficient in low-cement concrete by using crushed coal mine waste rock as base layers for low-traffic roads

Optimizing aggregate grading and residual mortar coefficient in low-cement concrete by using crushed coal mine waste rock as base layers for low-traffic roads

Experimental evaluation of shrinkage properties in concrete incorporating coal mine waste rock

This research investigates the properties of concrete utilizing coal mine waste rock (CMWR) as a substitute for river sand. The workability of fresh concrete is assessed through slump tests, revealing a decrease in a slump as the percentage of CMWR replacement increases. The density of the concrete mixtures increased with curing time, and the compressive strength also exhibited an upward trend but with lower values compared to the control concrete when CMWR was used as a replacement. The reduction in compressive strength ranges from 11.4% to 47.6% for CMWR replacement levels of 25% to 100%. The study also examines the influence of climate conditions, including temperature and humidity. Shrinkage deformation tests indicate that CMWR concrete demonstrates higher plastic and dry shrinkage than river sand concrete. CMWR concrete exhibits significantly higher drying shrinkage, attributed to the enhanced water absorption capacity of CMWR particles. These findings provide valuable insights into the performance of concrete incorporating CMWR and propose potential strategies for mitigating its effects. The research outcomes contribute to the knowledge base in the field and offer practical implications for the operation of CMWR in concrete applications

Mechanical properties and durability of concrete containing coal mine waste rock, F-class fly ash, and nano-silica for sustainable development

Mechanical properties and durability of concrete containing coal mine waste rock, F-class fly ash, and nano-silica for sustainable development

Towards an integrated approach for zero coal mine waste storage: solutions based on materials circularity and sustainable resource governance

ABSTRACT Around 25 million tons of coal mine waste rock (CMWR) are stored in many places in Morocco due to coal mining activities. As a result, air and water quality of the neighborhood is polluted and large lands are occupied. This study aimed to investigate the use of an integrated and circular approach based on coal recovery and waste rock recycling. More than 30 drill core samples were taken from the big coal dump reaching a depth of 60 m and analyzed to evaluate the chemical composition variability. Froth flotation was used to recover coal particles using diesel as a collector and Methyl Isobutyl Carbinol as a frother, 100 g/t each. The tailings of coal flotation process (CFT) were used to manufacture fired bricks at a pilot scale. The results of this study highlighted the possibility to valorize the whole waste material toward an objective of zero waste in the future. On a basis of 100t feed, (i) 10-15t can be recovered as high-quality anthracite coal with a calorific value over 7500 kcal/kg using flotation processing at a recovery yield over 80%, (ii) 45-60t can be reused as shales for bricks production with a compressive strength over 16MPa, (iii) 20-30t can be reused as aggregates for concrete production with a compressive strength over 20MPa. The remaining material can be reused as sand. The recovered anthracite can be reused to manufacture coal briquettes or used at it is in the thermal power plant next to the dump site.

Parameters updating and calibrated double-yield model methods to simulate the compaction behaviour of waste rock backfill materials in coal mine gob

Coal mine waste rock can be filled into the gob to control strata movement and protect the mine environment. However, the compaction behaviour of the waste rock backfill materials (WRBM) must be considered when the they are filled into the coal mine gob. Based on the compaction properties of the WRBM tested by a purpose-made compaction device, Salamon's and Terzaghi's models are used to describe the stress–strain relationship of the WRBM, and the parameters updating (PU) and calibrated double-yield model (CDM) methods to simulate the WRBM are proposed in this paper. An engineering application in a backfill panel is used to validate the reliability of this method by numerical simulation and field measurement. Comparison of the vertical stress inside the WRBM obtained by the numerical simulation using the proposed method with those from field measurement indicates that the proposed method is reliable. The proposed method gives an opportunity to obtain the stress distribution accurately when the WRBM are filled into the coal mine gob.

Co-disposal of lignite fly ash and coal mine waste rock for neutralisation of AMD

Waste rocks (WRs) from a lignite-producing coalfield and fly ash (FA) produced from the same lignite have been investigated in this study with a primary objective to determine the potential for co-disposal of WRs and FA to reduce the environmental contamination. Mixing WRs with FA and covering WRs with FA have been investigated. Particle size effect caused ≤2 mm particles to produce low pH (~2) and metal-laden leachates, indicating higher sulphide minerals’ reactivity compared to larger particles (≤10 mm, pH ~ 4). Co-disposal of FA as mixture showed an instantaneous effect, resulting in higher pH (~3–6) and better leachate quality. However, acidity produced by secondary mineralisation caused stabilisation of pH at around 4.5–5. In contrast, the pH of the leachates from the cover method gradually increased from strongly acidic (pH ~ 2) to mildly acidic (pH ~ 4–5) and circumneutral (pH ~ 7) along with a decrease in EC and elemental leaching. Gradually increasing pH can be attributed to the cover effect, which reduces the oxygen diffusion, thus sulphide oxidation. FA cover achieved the pH necessary for secondary mineralisation during the leaching experiment. The co-disposal of FA as cover and/or mixture possesses the potential for neutralisation and/or slowing down AMD and improving leachate quality.

The spatial distribution of soil heavy metals and ecological restoration of Datong Abandoned Coal Mine in Huainan City

Based on laboratory analysis of soil samples collected from abandoned coal mine in Datong area, content of heavy metals in the soils was monitored and the soils were evaluated for heavy metal pollution. The spatial distribution of heavy metals was study with means of Kriging method by under ArcGIS environment in the abandoned coal mine in Huainan area. The results show: (1) the content of 5 types of heavy metals( Hg, Cd, Cr, Pb, Cu) were all higher than Huainan area background value of soil elements, among of these heavy metals, the enrichment of Cd was higher and polluted quite seriously; the enrichment of Hg, Cr, Pb and Cu was lower, and polluted lightly comparatively. (2) The coal mine waste rock pile and abandoned chemical plant were the main pollution sources. (3) The heavy metal concentrations and space distribution were mainly affected coal mine waste rock pile, and abandoned chemical plant. (4) Positive correlation between concentrations of most heavy metals was significant, and there is a certain relationship between concentrations of heavy metals and organic matter, nitrogen, available phosphorus. On the basis of the above research, some countermeasures were put forward for ecological restoration in Datong abandoned coal mine.

A texture fused superpixel algorithm for coal mine waste rock image segmentation

ABSTRACT In coal production, it is necessary to separate waste rock from raw coal. With the development of computer vision technology, the image recognition method with simple equipment and high efficiency has become a research hotspot. Image segmentation is a very important step before the image analysis in image recognition method. Traditional image segmentation takes pixel as processing unit, without considering the influence of space and texture; therefore, it is difficult to segment the coal and waste rock images when the target and the background are with similar color and the existence of weak edges and fuzzy regions. In this paper, a new superpixel segmentation algorithm that combines color, spatial position, and texture in clustering is proposed, which integrates texture information into SLIC algorithm. After test of a great number of coal and waste rock images, the segmentation results of SLIC and SLFTIC algorithms were evaluated that SLFTIC can better fit the edge. According to the evaluation index of superpixel algorithm, undersegmentation error and boundary recall of SLFTIC are superior than SLIC, and compactness score is slightly improved. For the images with similar foreground and background and complex texture, such as mineral images and medical images, this kind of superpixel cutting method has better segmentation effect.

Potential of coal mine waste rock for generating acid mine drainage

Potential of coal mine waste rock for generating acid mine drainage

Electro-biochemical reactor (EBR) technology for selenium removal from British Columbia’s coal-mining waste waters

The weathering of coal mine waste rock releases iron, calcium, sulfate and associated trace elements like selenium (Se). Nitrogen species are also found in association with coal-mining drainages mainly due to the leaching of residual blasting compounds. Elevated concentrations of Se are a ubiquitous occurrence in coal-mining environments in British Columbia. A major concern with waterborne Se in British Columbia is the potential for its bioaccumulation in aquatic food chains. Treatment to remove Se from coal-mining waste waters has proven to be challenging for conventional water-treatment technologies. Compounding this challenge, many streams are characterized by high flows and low selenium concentrations. Conventional membrane and ion exchange treatments produce concentrated brine streams that are difficult to treat or require disposal. Conventional biotreatment systems use excess nutrients to provide the required electrons to compensate for inefficient and variable electron availability, as well as to adjust reactor chemistry. This paper’s electro-biochemical reactor (EBR) technology provides a controllable and consistent supply of useable electrons to the microbes directly at a low voltage potential (1–3 V) and low current. In this manner, the EBR technology overcomes the shortcomings found in conventional systems, as it reduces the required nutrient addition and provides a more controllable, efficient, economical and robust biotreatment system. Additionally, the EBR process does not produce excess solids or biomass; therefore, solids management post-treatment is not required. Laboratory EBR bench-scale and on-site pilot-scale systems were used to treat five British Columbia coal-mine waste waters; influent Se concentrations ranged from 35 µg/L to 531 µg/L. Se treatment targets for the tested waters ranged from 5 to 10 µg/L. Mean Se concentrations in EBR effluents ranged from 0.5 µg/L to 1.4 µg/L, while reducing sulfate concentrations. The test data demonstrate that the EBR technology is an effective Se removal option for British Columbia’s coal-mining waste waters.

Assessment of Unsaturated Flow for a Large Coal Mine Waste Rock Pile

Some waste rock piles create some problems such as acid mine drainage (AMD), leaching of heavy metals, and slope stability concerns. These problems are related to the flow of water through the rock pile. Understanding the physical and hydrological properties of the waste rock piles is important for flow and solute transport modeling. To study physical properties and unsaturated flow in rock pile, some soil samples were collected from surface of the large coal waste rock pile and tested for some common geotechnical parameters in the laboratory. The results showed that materials are so heterogeneous and highly supporting segregation and natural gravity sorting of waste rock materials from top to toe. Numerical simulation was performed to investigate the unsaturated flow conditions in the pile. The results obtained showed that pile is unable to fully saturate and drain during the simulated period. It was also found that high evaporation and also coarse grain nature of waste rock materials results holding few amounts of water in the system.

Reduction and utilization of coal mine waste rock in China: A case study in Tiefa coalfield

Reduction and utilization of coal mine waste rock in China: A case study in Tiefa coalfield

Selenium Adsorption onto Iron Oxide Layers beneath Coal-Mine Overburden Spoil

A field experimental study to determine the feasibility of sequestering dissolved selenium (Se) leached from coal-mine waste rock used an iron (Fe)-oxide amendment obtained from a mine-drainage treatment wetland. Thirty lysimeters (4.9 × 7.3 m), each containing 57.7 t (1.2-1.8 m thickness) of mine-run carbonaceous shale overburden, were installed at the Hobet mine in southeastern West Virginia. The fine-grained Fe-oxide was determined to be primarily metal oxides (91.5% ferric and 4.37% aluminous), with minor (<3%) SO and Ca, perhaps as gypsum. The mineralogy of the Fe was goethite, although residual ferrihydrite may have been present. Various thicknesses of this amendment (0.0064, 0.057, 0.229, and 0.457 m, plus a zero-amendment control) were used, ranging from 0 to 2.2% weight percent of the spoil. The control and each treatment were replicated six times to estimate uncertainty due to compositional and hydrological variation. Infiltration of rainfall created leachate that drained to individual batch-collection tanks that were sampled 46 times at approximately 2-wk intervals from 2010 to 2012. Basal Fe-oxide layers in the three highest amendment categories removed up to 76.1% selenium (in comparison to unamended piles) from leachate by adsorption. Only lysimeters with very thin Fe-oxide layers showed no significant reduction compared with unamended piles. Reproducibility of replicates was within acceptable limits for amended and unamended lysimeters. Results indicate that in situ amendment using Fe-oxide obtained from treatment of mine water can sequester Se by adsorption on surfaces of goethite and possibly also ferrihydrite. This process is demonstrated to substantially reduce dissolved Se in leachate and improve compliance with regulatory discharge limits.

Identification of the Former and after Transformation of a Steel Headframe

This article is studied a coal mine waste rock mine shaft steel headframe which is used more than 20 years and the need of the headframe process transformation. The main components of steel headframe (for example: headframe column, beams and bracing) is sampling inspected the geometry and weld size. At last, SAP2000 is used by analyzing the steel headframe the former and after transformation on the basis of the on-site detection. Field testing and theoretical analysis showed that: the main steel headframe and the envelope structure is largely intact and the only part of the rod local area is a certain degree of corrosion, the connected nodes are basically in line with the requirements of the original design; The steel headframe structure which has transformed and components meet the requirements of national norms.The Identification and reinforcement of the project, will provide a reference for future similar projects.

Distribution characteristics of Zn,Pb,Cd,Cu in soil and crops around Xinzhuangzi Coal Mine waste rock pile

Samples of soils and crops were collected around Xinzhungzi Coal Mine waste rock pile by the intercept method.The concentrations of Zn,Pb,Cd,Cu in the soils and crops were analyzed by inductively coupled plasma optical emission spectrometer(ICP-OES).The results showed that the soil is alkaline,and the max concentrations of Zn,Pb in the soils are 43.08 mg·kg-1 and 15.61 mg·kg-1 at the depth of 20~40 cm,which are below the background values of Huainan soil.The concentrations of Cd and Cu in the soil with the depths of 0~20 cm and 20~40 cm,respectively,are the highest and 106.76% and 0.46% higher than the background value of Huainan soil.The concentrations of Zn,Pb,Cd,Cu are incorrelate with the depth of soil.The Zn and Pb in the top soil(0~20 cm) reach their peak values at a distance away from the coal mine spoil,which may be caused by the grain from the burst of coal mine spoil transported by the wind.The stepwise regression analysis indicated that total P affects the concentrations of Zn and Pb in soil,and organic matter affects the concentrations of Pb and Cu in soil.Cd accumulates in the roots of soybean and rice,while Zn transports into the aerial parts of the two plants.The enrichments of Zn in the aerial parts of soybean and rice are much higher.The order of Zn,Pb,Cd,Cu enrichments in the leaf,hull and seed of soybean and rice is ZnCuCdPb.The max value of Pb in the grain of rice is 0.52 mg·kg-1(dry weight),1.3 times higher than the national food hygiene standard.The risk from the Pb in the seed of rice should not be overlooked.

An Evaluation on the Physical and Chemical Composition of Coal Combustion Ash and Its Co-Placement with Coal-Mine Waste Rock

In the last few decades, the utilization of coal to generate electricity was rapidly increasing. Consequently, the production of coal combustion ash (CCA) as a by-product of coal utilization as primary energy sources was increased. The physical and geochemical characteristics of CCA were site-specific which determined by both inherent coal-source quality and combustion condition. This study was intended to characterize the physical, chemical and mineralogical properties of a coal-combustion ash (CCA) from a site specific power plant and evaluate the leachate characteristic of some scenario on the co-placement of CCA with coal-mine waste rock. The physical properties such as specific gravity, dry density, porosity and particle size distribution were determined. Chemically, the CCA sample is enriched mainly in silica, aluminum, iron, and magnesium along with a little amount of calcium and sodium which includes in the class C fly ash category. Moreover, it is found that the mineral phases identified in the sample were quartz, mullite, aragonite, magnetite, hematite, and spinel. Co-placement experiment with mudstone waste rock shows that the CCA, though it has limited contribution to the decreasing permeability, has important contributed to increase the quality of leachate through releasing higher alkalinity. Moreover, addition of CCA did not affect to the increase of the trace metal element in the leachate. Hence, utilization of CCA by co-placement with coal mine waste rock in the dumping area is visible to be implemented.

Environmental Impact on an Arctic Soil–Plant System Resulting from Metals Released from Coal Mine Waste in Svalbard (78° N)

Impact of acid mine drainage (AMD) from a coal mine waste rock pile deposited within a permafrost-affected Arctic ecosystem was investigated near Longyearbyen (Svalbard, 78° N). Analyses included metal concentrations (Al, Fe, Mn, Zn, Ni, Cr, As and Pb) in runoff, soil and plants. It was observed that impacts of AMD, such as plant degradation, were similar to impacts reported from non-arctic ecosystems. It was found that bio-available metal concentrations in soil samples were not useful in assessing potential plant toxicity, as metals were not accumulated in the most impacted area due to low soil pH (pH < 4). Native graminoid plants in the high impacted area showed accumulation of all the investigated elements. Al, Mn and As were found at phyto-toxic concentrations. Metal uptake in two native graminoid plants was studied in the laboratory. Positive correlations were noted between metal concentrations and plant uptake for all metals investigated, except Fe. High Fe concentrations found in plant samples in the impacted area are considered a result of Fe-oxide precipitation (plaque) on leaves during the spring flush when runoff covers the plants. We conclude that the weathering products Al, Mn and Fe induce the largest negative impact on vegetation in the area, and that a major fraction of the annual uptake of metals occurs during spring flushes. During these flushes, metals produced from weathering processes throughout the winter are released in high concentrations, coinciding with low pH values, low infiltration rates due to permafrost and the start of the plant growth season.