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Showing 1 to 17 of 17 for “"ultrafine coal"”.
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Low Temperature Drying of Ultrafine Coal
… drying, has been developed to remove water from ultrafine (minus 325 mesh) coal particles. The process subjects partially dewatered solids to intense mechanical shearing in the presence of unsaturated air. Theoretical analysis of the thermodynamic properties of water indicates residual surface …
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Developing a Novel Ultrafine Coal Dewatering Process
Dewatering fine coal is needed in many applications but has remained a great challenge. The hydrophobic-hydrophilic separation (HHS) method is a powerful technology to address this problem. However, organic solvents in solvent-coal slurries produced during HHS must be recovered for the method to be …
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The cleaning of ultrafine coal using microbubbles
… mining techniques that are commonly used in the coal industry produce a large amount of fine particles. These fines are extremely difficult to recover by conventional flotation methods, mainly because of the large size of the bubbles produced relative to the size of the particles. Hydrodynamic …
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Continuous column flotation of ultrafine coal using microbubbles
… to remove ash-forming minerals from micronized coal. The microbubble generator used In this work has been characterized and found to yield a very narrow size distribution. Microbubble column flotation tests have been conducted to study a series of operating variables such as time, bubble size, …
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Development of the selective-shear coagulation process for ultrafine coal cleaning
In order to produce coal containing less than 2% ash using a physical cleaning process, the coal must initially be ground to liberate the mineral matter. The result is a micronized feed material that cannot be efficiently treated using the commercial methods currently available. Therefore, an …
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An evaluation of separation methods for the selective coagulation of ultrafine coal
… for selectively coagulating and separating coal from dispersed mineral matter has been developed at Virginia Tech. The process, which is known as Selective Hydrophobic Coagulation (SHC), differs from oil agglomeration, shear or polymer flocculation, and electrolytic coagulation processes in …
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The effect of particle size distribution on the rheology of ultrafine coal-water slurries
Recent interest in producing superclean coal has lead to the development of coal cleaning techniques which require the grinding of coal to sizes below 10 microns. Coal in this size range has inherent material handling problems, most of which can be eliminated by the utilization of this ultrafine …
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Environmental Performance Assessment of Froth Flotation for Coal Recovery and Sulfur Removal from Ultrafine Coal Waste
The South African coal mining industry generates large volumes of coal ultrafine waste (< 150 microns) each year, with a significant amount being dumped in tailing slurry dams. These slurry dams have been associated with prolonged pollution and loss of valuable resources. In the two stage flotation …
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Reverse flotation : a novel process for the beneficiation of fine coal
The beneficiation of ultrafine coal by froth flotation is a widely used process, and its importance for the treatment of -0.1 mm coal has been appreciated of late in South African coal washing plants. A number of problems adversely affect the efficiency of this process, such as poor liberation, …
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The Production of Low Ash Coals Using the Hydrophobic-Hydrophilic Separation Process with Novel Developments
… as particle size is reduced. Because of this ultrafine particles are often discarded prior to froth flotation, and contributes to a substantial amount of coal waste in impoundments. An impoundment is a dam built using coarse reject to hold fine reject in slurry. Because of the land-use and …
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Combining froth flotation and reflux classification to mitigate ARD generating potential of the Waterberg and Witbank coal ultrafines via sulfide removal
In South Africa, over 10 million tons of ultrafine coal wastes are discarded every year, typically in the form of ultrafine slurries. These fines have a high calorific value, and contain sulfur minerals, particularly pyrite. The high calorific value of these discards leads to a waste of energy that …
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An economic analysis of coal desulpharisation by froth flotation to prevent acid rock drainage (ARD) and an economic review of capping covers and ARD treatment processes
… feasibility using porphyry copper tailings, fine coal and more recently gold tailings. Historically, ultrafine coal was not treated by most collieries in South Africa, but disposed as waste. Oxidation of the pyrite in the coal leads to generation of acidic water. In this project, an economic …
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Bioaugmentation and biostimulation of a South African coal-based Technosol as a mine rehabilitation strategy
… over 70 million tonnes of material are added to coal waste dumps in South Africa. To alleviate the environmental and social burdens of unsightly mine waste dumps, improved management of existing discarded materials and new wastes, and fertile soils for land rehabilitation are essential. To …
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Methods of Improving Oil Agglomeration
… that oil can spontaneously displace water from coal's surface if the coal particle has a water contact angle greater than 90°. However, the clean coal products obtained from laboratory-scale dewatering-by-displacement (DbD) test work assayed moistures substantially higher than expected. These …
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Advancement of the Hydrophobic-Hydrophilic Separation Process
… regarded as the best available technology for ultrafine particles separation. However, froth flotation has extreme deficiencies for recovering ultrafine particles that are less than 30-50 μm in size for coal and 10-20 μm for minerals. Furthermore, dewatering of flotation products is difficult …
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Characterizing the potential environmental risks of South African coal processing wastes
The environmental impacts of coal processing wastes are a challenge in South Africa as large amounts of coal wastes are produced annually, pegged at 60 million tons per year according to Eberhard (2011). Whilst the fossil fuel-based industry is in decline globally, coal is likely to remain the …
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NEW APPROACHES FOR MITIGATING ENVIRONMENTAL CONCERNS ASSOCIATED WITH COAL AND COAL COMBUSTION PRODUCTS
Currently, coal combustion plays an important role in meeting the energy needs of the United States. It is expected that the effective utilization of coal will be crucial for attaining energy independence for the nation in the next 25 to 30 years, if not longer. The United States burns about 20% of …