摘要:

In the present study a set of 101 coal samples of various ranks from different countries have been used to establish correlations between helium density (HDdaf) and compositional parameters of H/C, O/C and O/H ratios. The absolute average percentage error and correlation coefficient of recommended models (Eqs. 2 and 3) based on dry-ash-free (daf) basis are found to be 1.20; 0.97 and 1.19; 0.97 respectively. Statistical analysis and comparison of the models with other existing model (Eq. 1) suggested the superiority of the proposed models over earlier one's.

ISSN:0734-9343    

DOI:10.1080/07349349808945570

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The fundamental principles governing the filtration of fine (nominally -0.5 mm) coal are not well understood. This has recently been recognised by the Australian coal industry as a major hurdle to significantly improving dewatering technology and performance. This study quantifies and compares the respective influences of filter cake microstructure, and coal surface and bulk properties on the vacuum filtration of fine bituminous coal slurries. It is shown that filter cake microstructure is the dominant factor, particularly in determining the kinetics of cake formation and desaturation. Although variations in coal properties probably have little effect on the filtration kinetics, they can significantly influence residual cake moisture. Moreover, the results obtained in this study indicate that there does not exist a single microstructure capable of providing both a high filtration rate and a low product moisture. Such a result is expected to influence future dewatering research efforts and possibly drive the design of new fine coal filtration technologies.

ISSN:0734-9343    

DOI:10.1080/07349349808945571

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The characteristic separation performance achievable from the treatment of fine coal using a froth flotation process is commonly estimated using either the release or tree analysis procedure. The two flotation characterization procedures differ substantially in the method of achieving selectivity between particles having varying degrees of hydrophobicity. From the treatment of -180 μm coal, the separation performance curves generated using the release analysis method were superior to those produced by tree analysis on the basis of both product ash and total sulfur contents. However, after grinding to reduce the amount of middling particles, the separation performance achieved by the tree procedure on the basis of product ash content was nearly equal, and in some cases, exceeded the performance provided by release analysis. In terms of product total sulfur content, the results obtained from release analysis remained superior. The differences in the separation performances achieved from the two flotation characterization methods are a result of the presence of middling and coal pyrite particles, which degrade the froth product upon flotation. Improvements in the two traditional procedures, such as the use of high feed solid concentrations to ensure a significant amount of selective reflux between the froth and collection zones, are presented in this publication.

ISSN:0734-9343    

DOI:10.1080/07349349808945572

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A modified coal flotation characterization procedure, referred to as the Advanced Flotation Washability (AFW) technique, has been developed which, compared to traditional procedures, provides a more accurate prediction of the optimum separation performance achievable by a froth flotation process. The AFW procedure uses a batch-operated flotation column packed with corrugated plates which provides enhanced selectivity among particles of varying degrees of hydrophobicity due to a selective bubble-particle detachment mechanism. This mechanism is more pronounced in a flotation column operating under carrying-capacity limited condition with a deep froth zone. In addition, the plug-flow environment resulting from the apparent high length-to-diameter ratio provides an improved performance over the near perfectly-mixed conventional cells used in the traditional procedures. The separation performance provided by the AFW procedure was superior to that obtained from multiple stage cleaning provided by commercially-available flotation columns under both kinetic and carrying-capacity limiting conditions. The separation performance improvement provided by the AFW technique has been illustrated using three different coal samples having varying feed characteristics.

ISSN:0734-9343    

DOI:10.1080/07349349808945573

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Fractal geometry is beginning to find wide ranging practical applications in technology. It enables the description of structures that exhibit some degree of self-similarity or scale invariance, and has been found to be applicable to the characterisation of coal froths. The exact dimension used was the Sierpinski fractal, which gives a measure of the efficiency with which the entities of a system are covering the available space.

ISSN:0734-9343    

DOI:10.1080/07349349808945574

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A full-scale Microcel™ flotation column was trialled at the BHP Coal Peak Downs Mine and Saraji Mine coal preparation plants for the treatment of 0.5 mm × 0 (−500 μm) coal. By using deep froths and counter-current froth washing, the Microcel™ columns have been demonstrated to achieve substantially lower product ash compared to conventional flotation cells when treating slimes fractions. This paper reports the results of modelling the pulp behaviour in a full-scale Microcel™ treating −500 μm coal. The results suggest that the conventional theory and scale-up design criteria need to acknowledge a very significant degree of mixing when applied to the treatment of coarse ( −500 μm) coal.

ISSN:0734-9343    

DOI:10.1080/07349349808945575

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Pulverized coal combustors are the principal means for converting coal to electricity in the United States. Coals used in these combustors have to be beneficiated because of escalating specifications on fuel quality that help to increase boiler efficiency and decrease acid gas emmissions. Because coal is pulverized before its combustion in PC boilers, during which time substantial mineral liberation occurs, it may be beneficial to remove mineral matter from the combustibles by using dry beneficiation techniques after the pulverizers and within the burner pipes leading to the coal burners. One such technique is based on triboelectrostatics. It relies on establishing a differential charge on coal and mineral matter and then separating this charged mixture in an electrostatic field.

ISSN:0734-9343    

DOI:10.1080/07349349808945576

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor