摘要:

A model based on the potential energy minimization principle allowing for the dispersive effects due to panicle-particle and particle-fluid interactions is developed and applied to the jigging of coal. The model requires only a single parameter, the specific stratification constant. The model generates the equilibrium stratification profile for all components in the jig bed and the separation of each component is then calculated as a function of the total yield of solids. The model is validated against experimental data obtained from a laboratory batch jig and against operating data from several industrial single and two-compartment Baum and Batac jigs. The model calculates the performance of continuous jigs for arbitrary compositions of the feed and is paticularly useful for the reliable simulation of washing plant performance.

ISSN:0734-9343    

DOI:10.1080/07349349508905291

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper details the use of a batch hindered-settling model to investigate dense-medium cyclone separations, particularly with respect to variable interactions. The model parameters are based on those obtained for various dense-medium cyclones processing fine coal. Simulations were run over a wide range of test conditions to investigate changes in volumetric flow rate, cyclone diameter, pulp split, medium density, and magnetite size distribution. The performance is analyzed in terms of the fractional recovery (partition) curves and corresponding parameters. Comparisons are made to the results obtained from the actual dense-medium cyclone separations.

ISSN:0734-9343    

DOI:10.1080/07349349508905292

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The control and stability of the air core and factors affecting the flow split to the underflow or ‘heavy’ product are two of the least understood aspects in the operation of hydrocyclone and dense medium separators. Existing methods for assessing these factors using conventional and lomographic measurement instrumentation are described. New results obtained using electrical resistance tomography (ERT) are described for a pilot-scale large diameter coal dense medium separator (LARCODEMS). Such data have important implications for the development of: (a) empirical correlations to describe air core characteristics as a function of operational variables (feed rate, feed slurry viscosity, feed density, etc.) and their role on separation efficiency, and (b) computational fluid dynamics models of liquid and slurry flow in centrifugal separators.

ISSN:0734-9343    

DOI:10.1080/07349349508905293

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new technique involving a rotational (coaxial cylinder) viscometer and a vibrating sphere viscometer was developed for the rheological characterization of coal slurry process streams as either Newtonian or non-Newtonian. Both viscometers were able to measure apparent viscosity as low as one centipoise, and special precautions were taken to allow measurement of rapidly settling coal suspensions. In this technique, the vibrating sphere viscometer was used to measure the apparent viscosity at a high shear rate, while the rotational viscometer was used to measure the apparent viscosity at a low shear rate. Together, the two instruments could determine the shear-rate dependency of the viscosity, and thus provide an estimate of the total slurry Theology. The technique was first verified using two types of fluid with known Theological properties; sucrose solutions ranging from 10 to 60% by weight (Newtonian fluids), and solutions of Dow Methocel A4M ranging from 0.5 to 2% by weight (Pseudoplastic fluids). Following verification with the known fluids, a high-ash Pittsburgh seam bituminous coal was ground to 80% passing 34 micrometers, and was used to prepare slurries ranging from 10 to 45% solids by weight in distilled water. Apparent viscosity of each slurry sample was measured simultaneously by both viscometers and the results were then compared. With this technique, the onset of non-Newtonian flow behavior was clearly observed for slurries of this particular coal when the solids loading exceeded 20% solids by weight.

ISSN:0734-9343    

DOI:10.1080/07349349508905294

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The problem of generating a balanced set of density or size separation data is considered. A technique utilizing the least-squares approach is used to generate optimum estimates of products mass yields and balanced direct mass distributions of feed and products. The estimated separation data set satisfies mass balance conditions of the mass distributions for the feed and product streams. The technique can be applied to three- and two-product separations. Actual data are utilized to demonstrate the technique for balanced scaled and normalized data sets.

ISSN:0734-9343    

DOI:10.1080/07349349508905295

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Stripa is an autogeneous heavy medium separator originally developed in Sweden for the processing of iron ores. The major difference between a Stripa and a conventional heavy medium separator is that a Stripa employs heavy medium or the ore itself. Although the Stripa has been used for concentrating ores such as iron and chromite, it has not been applied in coal preparation. In this study, a pilot scale Stripa with a capacity of 2.5 t/h is tested on − 50 + 10 mm bituminous, subbituminous and lignitic coals. The effects of medium density and buoyancy force as a function of panicle size have been investigated. The performance of the Stripa was evaluated for each size using the parameters, the probable error of separation (Ep) and the degree of washability (N). Under the optimum conditions, both parameters indicate that the Stripa performs better with increasing particle size, the optimum being − 50 + 19 mm. The comparison of the performance of the Stripa with that of the Baum jig indicates that Stripa can be used in coal preparation circuits as an alternative to jigs in the size range of − 100 + 10 mm. Simplicity, low initial investment, and low operating and maintenance costs make the Stripa a plausible candidate for coarse coal cleaning.

ISSN:0734-9343    

DOI:10.1080/07349349508905296

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349349508905297

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor