Coal waste management practices in the USA:an overview

This paper provides an overview of coal waste management practices with two case studies and an estimate of management cost in 2010 US dollars.Processing of as-mined coal typically results in considerable amount of coarse and fine coal processing wastes because of in-seam and out-of-seam dilution mining.Processing plant clean coal recovery values run typically 50%-80%.Trace metals and sulfur may be present in waste materials that may result in leachate water with corrosive characteristics.Water discharges may require special measures such as liner and collection systems,and treatment to neutralize acid drainage and/or water quality for trace elements.The potential for variations in coal waste production and quality depends upon mining or processing,plus the long-term methods of waste placement.The changes in waste generation rates and engineering properties of the coal waste during the life of the facility must be considered.Safe,economical and environmentally acceptable management of coal waste involves consideration of geology,soil and rock mechanics,hydrology,hydraulics,geochemistry,soil science,agronomy and environmental sciences.These support all aspects of the regulatory environment including the design and construction of earth and rock embankments and dams,as well as a wide variety of waste disposal structures.Development of impoundments is critical and require considerations of typical water-impounding dams and additional requirements of coal waste disposal impoundments.The primary purpose of a coal waste disposal facility is to dispose of unusable waste materials from mining.However,at some sites coal waste impoundments serve to provide water storage capacity for processing and flood attenuation.

The Future Resources for Eco-building Materials:Ⅱ. Fly Ash and Coal Waste

To use fly ash and coal waste effectively, the current technologies for reprocessing and recycling these wastes into eco-building materials were reviewed, such as utilizing fly ash as the component of fly ash cement and low heat cement after the processes of separation, removal of carbon remains and fine comminution, calcining coal waste into kaolin and meta-kaolin with suspension technology, and preparing clinkerless alkali-activated geopolymer materials with fly ash and meta-kaolin.

Facultative-anaerobic microbial digestion of coal preparation waste and use of effluent solids to enhance plant growth in a sandy soil

Coal preparation solid waste,which is a major environmental issue for coal-producing areas in China,may be microbiologically digested and transformed into a product suitable as a soil amendment to increase soil organic matter content and prevent and enhance plant/crop growth.Coal preparation waste collected from a coal sorting plant in Inner Mongolia,China was digested in bioreactors inoculated with microbial enrichments prepared from activated sludge and cow manure.The effluent solids from the coal preparation waste bioreactors were analyzed for their suitability as organic soil amendments,which complied with China standards.Plant growth tests were conducted in sandy soil from a semi-arid region in Colorado,which was amended with the effluent solids.Kentucky bluegrass(Poa pratensis L.)and chives(Allium schoenoprasum)were used as the representative plants for the growth tests,where results indicated substantially higher yields of Kentucky bluegrass and chives for the sandy soils amended with the effluent solids when compared to a commercial organic fertilizer.The number and average length of Kentucky bluegrass shoots were 10 and 5.1 times higher,respectively,in soils amended with the effluent solids.Similarly,the number and average length of chives shoots were 10 and 1.7 times higher,respectively,in soils amended with the effluent solids.Overall,the microbial digestion of coal preparation waste for application as an organic soil amendment is a viable alternative and beneficial use of coal preparation solid waste.

Negative-pressure pneumatic separator:a new solution for hard-coal beneficiation

Hard coal is an important source of energy worldwide.Owing to the imperfections of excavation technology,most run-of-mine coals must be processed before they can be utilised as fuel.In this study,tests on the dry separation process were performed with numerous different raw hard coal and coal waste material samples,using a newly designed and constructed negative-pressure pneumatic separator(NPPS).The experiments revealed the effects of the feed-material properties and material processing conditions.These experiments were preceded by additional tests for evaluating the influence of each device operating parameter on the process,to determine the optimal method of supplying the feed material.The calorific value of the processed materials was improved by 5%–40%,while a minimal output yield of products(60%–70%)was maintained.The trials indicated that in coal material processing,the developed NPPS can be used for not only raw coal enrichment but also coal recovery from materials stored at coal-waste dumps.The main advantages of the device are its mobility,low material processing cost,and lack of water consumption during operation.

Classification of fires in coal waste dumps based on Landsat,Aster thermal bands and thermal camera in Polish and Ukrainian mining regions

A self-heating intensity index(SHII)based on the highest(pixel max.)and lowest(pixel min.)values taken from satellite thermal maps of burning coal waste dumps are proposed.The index enables the classification of such fires in Ukrainian-and Polish coal waste dumps.Both in Ukraine and in Poland,varying thermal intensities during 1985–2019 are revealed,using the SHII and following thermal intensity threshold values,namely,extreme thermal activity([7),advanced(3–7),moderate(3–1.5),initial(1.5–1),no activity(<1).The SHII shows decreasing thermal activity in the selected Ukrainian coal waste dumps during 2017–2019.It aids in reconstructing the thermal history of the dumps.Analysis of satellite images revealed a large number of burning coal waste dumps in the Donetsk Coal Basin(Ukraine)with high thermal activity.Such burning likely reflects large amounts of organic matter and sulphides in the dumped material subjected to self-heating and self-burning processes,lack of compaction of the coal waste and/or high methane contents.Comparison of SHII values calculated from satellite-and drone thermal-camera images were compared to show that SHII from drone thermal images have much higher values than those from satellite images;the former have better resolution.Thus,SHII from Landsat-and drone images should be used separately in dump heating studies.

Ladle Slag of Electric Steelmaking as Alkaline Agent on Controlling of Acid Mine Drainage Generation

Commercial coal production in the southern region of Brazil (comprising the Paraná, Santa Catarina, and Rio Grande do Sul states) has been occurring since the beginning of the twentieth century. Regarding the Santa Catarina coalfields, about 60% - 65% of the ROM coal is discharged at dump deposits as waste. These wastes can lead to the formation of acid mine drainage (AMD), a source of ground and surface water pollution. One of the technologies used for preventing AMD consists of the alkaline additive method. Thus, the aim of this work was to study, at laboratory scale, the DAM control by blending coal waste with a metallurgical slag. A coal-tailing sample was collected from a coal mine, and the slag was obtained from a semi-integrated steel plant. Static tests were carried out by the acid-base account method to determine the balance between the acid-producing and acid-consuming (neutralizing) mineral components of the samples. Kinetic tests were conducted in humidity cells, following the ASTM D 5744-96 method, for a period of 80 weeks. The results showed that the coal tailing generates AMD. However, environmental problems can be minimized by mixing the coal waste with the metallurgical slag in 1:1 or 1:1.5 proportions. The kinetic experiments proved that, in this condition, the lixiviation presents a higher pH and a lower concentration of acidity, metals, and sulfate. Finally, it is possible to conclude that the blending slag in coal tailing deposits can be a viable alternative for DAM control in coal mining.

Pyrolysis of scrap tyres pretreated by waste coal tar

For disposal of scrap tyres,there have been a lot of studies done by previous researchers,but it yet remains a longstanding challenge in practice.To find a solution for this problem,the feasibility of a proposed approach in a laboratory scale was tested.The pyrolysis of scrap tyres pretreated by waste coal tar(noted as "as-pretreated" tyres)was performed in a batch reactor at atmospheric pressure.Waste coal tar was used to modify the scrap tyres to improve the pyrolysis efficiency of scrap tyres input and the quality of the product tar.The swelling behavior of scrap tyres soaked in waste coal tar at 10℃,effect of pyrolysis temperature on the product yields,and the synergies during pyrolysis of the as-pretreated tyres and co-pyrolysis of scrap tyres/waste coal tar mixture were all investigated in detail.The results observed found that by comparison of the calculated yields and the observed experimental yields for pyrolysis products,the synergy from co-pyrolysis of scrap tyres/waste coal tar mixture boosted the gas yield without increasing the tar yield.In contrast,the synergy during pyrolysis of the as-pretreated tyres could enhance the tar yield,but reduced the gas and char yields.According to the distillation range analyses of the tar,more light fractions were found in the tar from pyrolysis of the as-pretreated tyres,in which the gasoline fraction,diesel fraction and kerosene fraction were 38.4 wt%,46.8 wt%and 50.2 wt%,respectively.This work is expected to be helpful in further use of scrap tyres.