摘要:

Small scale “frothless” flotation tests were carried out on narrow size fractions of several coal samples, in a series of aqueous methanol solutions of decreasing surface tension. The results presented as variation of cumulative yield versus cumulative ash content constitute optimum flotation response curves analogous to washability curves in sink-float tests. Flotation behaviour of different coals from the East Kootenay coalfield, British Columbia, was assessed relative to petrographic composition, rank, extent of weathering and inherent ash content. Differences in coal floatability caused by small degrees of weathering could be detected despite lack of differentiation by conventional tests on bulk coal properties.

ISSN:0734-9343    

DOI:10.1080/07349348408945536

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The reverse flotation of pyrite from coal was studied to determine surface chemical aspects of this system. Included in the research was determination of the effect of dextrin on the adsorption of xanthate by pyrite, measurement of rest (mixed) potentials for crystal- and coal-pyrite electrodes and evaluation of the bench scale flotation response with respect to the understanding of the adsorption reactions. Although little dextrin is adsorbed by crystal pyrite in the absence of xanthate, significant adsorption of dextrin in the presence of xanthate occurs. These results further support the general hypothesis that dextrin adsorption involves a hydrophobic bonding mechanism, In this system hydrophobic bonding is thought to occur at the surface between the non-polar portion of the dextrin and the dixanthogen oil which forms on the crystal pyrite surface. On the other hand, the slightly hydrophobic character of coal pyrite (pyrite associated with locked coal) exhibits a higher adsorption potential for dextrin in the absence of xanthate. The coal impurities presumably provide hydrophobic sites for the adsorption process. As with crystal pyrite, the dextrin adsorption density is increased further when potassium amyl xanthate is added. Most importantly, the coadsorption of dextrin and xanthate does not affect the flotability of pyrite in the range of concentrations tested. From these results it was inferred that the dixanthogen either wets surface dextrin molecules or that the dixanthogen forms in surface patches, providing the necessary hydrophobic character to permit xanthate flotation of pyrite even in the presence of coadsorbed dextrin. Unlike crystal pyrite electrodes, the rest (mixed) potential of a locked coal-pyrite electrode was not a strong function of either the xanthate or dextrin concentration. In fact the rest (mixed) potential of the locked-electrode was very close to the potential of crystal pyrite in the absence of xanthate (0·42 V at pH 7). It seems that the coal portion of the locked electrode may act as the anodic half cell which determines the electrode potential. In any event, coal pyrite exhibits the necessary electrochemical characteristics for the discharge of xanthate to dixanthogen. Bench scale flotation of pyrite from a ROM Illinois No.6 coal was studied by factorially designed experiments. The separation effectiveness was evaluated as a function of xanthate addition, dextrin addition, and acidity by surface response methodology. The pyrite flotation behavior was explained to some extent in terms of the coadsorption of collector and depressant.

ISSN:0734-9343    

DOI:10.1080/07349348408945537

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Fine coals (less than 0·5 mm) having high mineral matter content in intimate association with the different organic coal components (macerals), poses problems in their preparation. In order to study the preparation characteristics of such coal fines, broad specific gravity fractions of a particular Indian coking coal were separately subjected to froth flotation and oil agglomeration tests. Flotation concentrates as well as the oil-agglomerated products were collected separately and their petrographic constituents were analysed under microscope. The different coal macerals showed characteristic selectivity in flotation as well as in oil-agglomeration processes. In both the cases vitrinites were found to get selectively concentrated in the cleans. The petrographic make up of the flotation concentrates collected at time intervals of 15 s revealed that pure vitrinite particles tend to respond in the initial stage of flotation, while in the later stage other microlithotypes, e.g., vitrinertite, trimacerite, inertite were collected in the concentrates, Proper selection of collection time and other process variables may be helpful in controlling the petrographic composition of the concentrates.

ISSN:0734-9343    

DOI:10.1080/07349348408945538

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The notation response of coals containing pyrite has been observed to vary with time over a period of months. This behaviour could not be attributed to coal oxidation in the normal sense. The objective of the present work was to examine whether the oxidation products of the contained pyrite were contributing to observed depression of the coal flotation response. This was achieved by examining the influence of iron sulphide oxidation products, iron(II), iron(III), sulphate and hydrogen ions on the flotation response of a number of coals. From the results it was concluded that withcleancoal, i.e., coal with little or no liberated clays associated with it, that pyrite oxidation products had little effect. However withrawcoals, i.e., flotation feeds with significant associated clays, the flotation response was markedly influenced by pyrite oxidation products particularly hydrogen ions. The effect was attributed to the presence of oleophilic organic material adsorbed on the surface of the clay.

ISSN:0734-9343    

DOI:10.1080/07349348408945539

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In this paper, an attempt is made to shed light on the relationship between particle characteristics and the complex mechanism of the filtration/dewatering operations of fine coal. The effects of particle segregation, particle and pore sizes as well as air bubbles were studied micrographically. These results were compatible with those obtained from dynamic and equilibrium experiments on Pittsburgh-Bruceton coal. A three-dimensional network model is utilized to simulate the characteristics of coal filter cakes. The model could predict both equilibrium and dynamic properties of filter cakes, including the moisture content and cake permeabilities, under different operating conditions.

ISSN:0734-9343    

DOI:10.1080/07349348408945540

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

This report describes a quantitative method for calculating overdesign factors for coal preparation plant design. A Monte Carlo technique was used to account for uncertainties in design data and plant operation, and a statistical consideration of possible plant performance enables the selection of an appropriate overdesign factor with respect to the required level of confidence in the design. The uncertain design factors considered were percentage of fines, coarse coal yield, fine coal yield, amount of out-of-seam dilution and availability. In general, the justifiable overdesign factor increased with increasing uncertainty in data and with a greater number of variables in which there was uncertainty. The variability of parameters which had a large impact on overall yield contributed significantly to overdesign factors. From this study the most important variables for determining overdesign factors were uncertainties in coarse coal yield and plant availability with the variability in out-of-seam dilution having a lesser but still important effect. Although aspects of fine coal treatment had little impact on overall overdesign, the design capacity of the fines plant should be considered separately. The required degree of confidence in plant design has a strong influence on the over-design factor, with a steady increase in overdesign factor up to 90% confidence, but a very rapid increase above 90%

ISSN:0734-9343    

DOI:10.1080/07349348408945541

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348408945542

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor