摘要:

The ΔP instrument measures the rate of gas release from coal under standard conditions. The original development of the technique took place in the USSR and France for use as an indicator of a coal seam's susceptibility to gas outburst in underground operations. In Canada, the ΔP technique was applied to coal degradation, oxidation and handling problems

ISSN:0734-9343    

DOI:10.1080/07349348908960525

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Improved pyrite rejection during fine coal flotation can be achieved by chemical pretreatment of the coal prior to flotation. The process involves conditioning the suspension with potassium monopersulfate or other peroxy compounds followed by conventional flotation. The ambient-temperature treatment seems to improve the hydrophobic character of certain low-rank coals as is evident from induction time measurements and bench-scale flotation experiments. In addition, the chemical pretreatment leads to an improvement in ash rejection and to enhanced depression of pyrite.

ISSN:0734-9343    

DOI:10.1080/07349348908960526

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A Seta ram C-80 heat flux calorimeter was used to study the surface and interfacial properties of fine coal particles in water containing flotation agents via heat of immersion measurements. Heat of immersion (ΔHimm) is usually a small exothermic quantity1and can be used to characterize a solid in terms of its relative hydrophobicity or hydrophilicity. The effects of coal type, surface oxidation, mineral matter content, kerosene concentration, and pH on the wetting characteristics were investigated. Results obtained from the calorimetry experiments correlated well with results from independent flotation experiments.

ISSN:0734-9343    

DOI:10.1080/07349348908960527

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

High pressure waterjets attack, fragment and comminute coal. The purpose of this research is to determine the effect of selected waterjet parameters on the specific energy required to create particles less than 75 μm in size. The selected parameters are waterjet pressure, nozzle diameter, relative velocity between moving coal sample and stationary waterjet nozzle and nozzle standoff distance, defined as the distance between nozzle and target. This information is necessary as a starting point for the design of coal comminution equipment based on waterjet technology. Over 980 individual specimens of bituminous coal from Moberly, Missouri USA, were subjected to controlled attack by waterjet. Trials were executed with waterjet pressures up to 100 MPa, and with nozzle standoff distances between 0.80- to 44.5 × 10−3m. Nozzle diameters of 1.14-, 0.81 -, and 0.41 × 10−3m were used, and coal sample feedrates varied up to 0.127ms−1relative to a stationary nozzle. The most important parameter was found to be feed rate. At feedrates less than 0.254ms−1, specific energy is quite high, more than 200kWg−1s−1, in some trials. At feedrates of 0.51 ms−1or more, the specific energies are typically in the range of 20-50 kWg−1s−1. These results are attributed to stagnation pressure within existing fractures in the coal. At high feedrates, the jet plays on the surface of the coal for a short time, thereby permitting only shallow fractures – to form. Low feedrates permit deep cutting of the coal and much larger particles thereby form, consuming much more energy.

ISSN:0734-9343    

DOI:10.1080/07349348908960528

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The effect of poly(acrylic acid), poly(acrylamide), and poly (vinyl alcohol) on the attrition grinding of Illinois No. 6 coal was examined. The grinding efficiency was significantly increased by poly(acrylic acid), slightly decreased by poly(acrylamide), and unaffected by poly(vinyl alcohol). The beneficial effect of poly(acrylic acid) was most pronounced when it was used as an additive in a 55% solids slurry. The beneficial effect decreased with increasing grinding time and was most effective at lower pH values where the poly(acrylic acid) existed in the acid or partially neutralized form. When the mixture of coal slurry plus poly(acrylic acid) was neutralized with alkali to pH 6.62, the beneficial effect disappeared. Subsequent froth flotation, using kerosene and MIBC, of coal ground with poly(acrylic acid) was essentially unaffected by the presence of the additive. Some potential economic advantages of using poly(acrylic acid) as a grinding aid are pointed out.

ISSN:0734-9343    

DOI:10.1080/07349348908960529

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A polyanionic biopolymer known as alpha-emulsan was found to flocculate fine particle suspensions of pyrite quite readily, but other materials including silica (quartz), kaolin, and a particular bituminous coal required activation in order to respond in large measure. Activation of these materials was achieved with small amounts of ferric iron which is known to hydrolyze to form ferric hydroxy complexes and colloidal particles of ferric hydroxide. When the positively charged hydrolyzed species of iron(III) were adsorbed by the negatively charged particles, the latter experienced a charge reversal which made them more receptive to adsorption of the polymeric anions. Larger amounts of ferric iron interfered with the flocculation of all the materials except pyrite, and the interference seemed due to the formation of ferric iron complexes with emulsan. Since high concentrations of ferric iron and low pH favored the flocculation of pyrite with emulsan but not the flocculation of the other materials, these conditions were applied to the selective flocculation of binary mixtures of pyrite and either silica, kaolin, or coal. Partial separation of the mixtures was achieved.

ISSN:0734-9343    

DOI:10.1080/07349348908960530

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Since there has been a growing interest in using gravity concentration techniques for the processing of fine coal (less than about 0.5 mm in size), it is important that a performance prediction procedure is used which is capable of showing differences in the operating conditions of the separator. The generation of fractional recovery or partition curves is one such procedure. A fractional recovery curve is a plot of the fraction of or probability that a given size feed material of a given density reports to the product against the density. This paper derives a mathematical model, based upon the physics of the separation process, from which fractional recovery values can be obtained. The heart of this derivation is the convection-diffusion equation which takes into account both the settling and the mixing of particles within a free-settling-type separator. The fractional recovery curve can be obtained by fitting these values to an appropriate mathematical function. Although the fractional recovery curves can be described by model parameters such as viscosity, etc., the common industrial practice is to derive certain characteristic parameters directly from the curves. Therefore, if these values are fitted to an appropriate mathematical function, then the derived parameters can be obtained using a parameter estimation technique. Thus, by analyzing the variation of these parameters with operating and design conditions, a valuable technique for studying separator performance is established.

ISSN:0734-9343    

DOI:10.1080/07349348908960531

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The mechanism of the LICADO process has been investigated in terms of the surface and interfacial properties of gaseous CO2, liquid CO2, and water in contact with feed coal, clean coal products, and refuse materials. Contact angles of water on the coal surface measured utilizing two different drop-deposition techniques were used to simulate the wetting characteristics of coal in the LICADO process under various mixing conditions. The clean coal particles show a strong hydrophobic behavior which results in their agglomeration and transfer to the liquid CO2phase while the refuse particles, being more hydrophilic, remain in the water phase. The results also showed that an optimum mixing speed is necessary in order to provide enough shearing force to expose the clean coal particles to the CO2droplets. The CO2adsorption on coal surfaces at pressures up to 6.2 MPa and the Dubinin-Polanyi coal surface area measurements indicate that the clean coal samples have higher adsorption isotherms and larger surface areas than those of the corresponding refuse. Consequently, the film pressure and the surface tension of the coal sample were found to increase with increasing ash content. The experimental evidence clearly shows that the LICADO process is a surface property-driven process, governed by the interaction among the interfacial, shearing and body forces present in the coal particle-liquid CO2-water system.

ISSN:0734-9343    

DOI:10.1080/07349348908960532

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348908960533

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348908960534

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor