摘要:

The deleterious effect of oxidation processes on coal flotation is generally recognized by researchers in the field. The present study, however, demonstrates that properly controlled low-temperature heating can actually improve coal flotation and its separation from mineral matter especially for low-rank coals. With a lignite sample, low-temperature heating at 130°C for a given time under ambient atmosphere leads to a higher yield and greater ash rejection during subsequent bench-scale flotation experiments. By combining experimental results from Hallimond-tube and bench-scale flotation experiments, bubble attachment-time measurements, wetting phenomena, and FTIR spectroscopy, it is clear that thermal treatment under the above conditions, which involves dehydration and oxidation reactions, changes the coal sample to a more hydrophobic state. These new results provide further evidence of the complexities involved in the analysis of coal surface chemistry as related to flotation phenomena.

ISSN:0734-9343    

DOI:10.1080/07349348808960511

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The surface of Upper Freeport coal was oxidized by air at 150°C for up to 144 h, and the behavior of this coal during oil agglomeration was studied at various pH values. With increased oxidation time the surface concentration of both carboxyl and hydroxyl groups was increased, and the recovery of coal with a given amount of oil was decreased. Spherical agglomeration was possible only with the unoxidized or mildly oxidized coal. The effect of oxidation on the zeta potential and three-phase contact angle was studied as well as the relation between these parameters and the agglomeration behavior. The recovery of coal was also measured as a function of pH, oil dosage, and addition of the surface-active agents sodium oleate and cetyl trimethyl ammonium bromide. The results indicate that the relative oleophilic/hydrophilic nature of the coal surface is more important to the oil agglomeration process than the electrokinetic properties of the system.

ISSN:0734-9343    

DOI:10.1080/07349348808960512

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The technical feasibility of removing ultrafine pyrite from high sulfur coals by selective flocculation using poly acrylate-acrylodithiocarbonate (or polyxanthate) dispersant was examined. The sulfur removal efficiency of the polyxanthate dispersant was tested on coal samples of the Pittsburgh No. 8 seam which were precleaned by heavy liquid separation (S.G. = 1.6gm/cc) and then were dried and ground to − 25μm size.

ISSN:0734-9343    

DOI:10.1080/07349348808960513

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This study investigates the influence of different operating parameters on the performance of the two density separators to determine their applications and limitations within the fines cleaning circuit. Two types of spirals are tested and results of different operating conditions are compared with those of the water-only cyclone. The following operating parameters are examined: cutpoint control and limitation in relation to size, particle size in relation to sharpness of separation and influence of clay slimes on the performance. The spiral's cutpoints show limited change with decrease in particle size and are mainly influenced by change in feed rate. Generally the spirals cutpoints are lower for the finer particles and higher for coarser particles ( + 0.3 mm) than those of the cyclones. However, the cutpoint control is easier to achieve in the cyclone, particularly for coarser particles. A single spiral is capable of achieving an equal or better separation efficiency (Epand error area) than a two stage water-only cyclone but at higher cutpoint for the 0.6–0.15 mm fraction. The sharpness of separation in the spiral deteriorates slower with decrease in particle size than that of the cyclone. Furthermore, the increase in clay amounts in the feed has no influence on the spiral separation and performance while deteriorating rapidly for the cyclone, particularly with clay contents over 30%.

ISSN:0734-9343    

DOI:10.1080/07349348808960514

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Tests were carried out on a 600 mm industrial heavy medium cyclone treating coal in the size range − 13.0 to +0.5 mm. The results indicate that the yield and ash content of the clean coal can be controlled by manipulating both the relative density of the feed and the spigot diameter. It has been shown that for the same proportion of heavier fraction in the clean coal, larger spigot openings accompanied with high relative density of the feed give more yield than smaller spigots operating with a low relative density of the feed medium. The misplaced heavier fraction in the clean coal has been found to be much finer than the misplaced lighter material in the discard.

ISSN:0734-9343    

DOI:10.1080/07349348808960515

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

When evaluating the separation made by a coal cleaning device, particularly when examining new applications, it is important to have a procedure that is independent of the feed consist to the device and thus can show differences arising from various operating conditions. One such procedure is the generation of fractional recovery values, defined as the fraction of feed material in a given relative density interval for a given size interval which reports to the product, and the resulting curves. The methodology has been developed so that subjectivity on the part of the engineer is eliminated. This is achieved by first establishing a mass balance around the coal cleaning device, reconstituting the feed stream and then interpolating the feed and product streams into narrow size and narrow relative density intervals. Using these interpolated data, the fractional recovery values can be calculated and in turn fit to a mathematical function from which descriptive parameters, separation modulus, distribution modulus and material bypass parameters, can be obtained. Not only can the function parameters be estimated, but confidence limits can be placed on them. These parameters can be analyzed according to how they vary with operating conditions. An example comparing the results obtained from using this methodology to those obtained using a “standard” technique is presented in which published data for heavy media fine coal cleaning development is used.

ISSN:0734-9343    

DOI:10.1080/07349348808960516

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Process waters and coal wastes from the physical cleaning of coals were collected at heavy media cyclone and water washing plants. The process wastewaters and leachates of the wastes were extracted and the organic compounds in these extracts were characterized by gas chromatography (GC) and combination gas chromotography/mass spectrometry (GC/ MS). Most of the identified compounds were aliphatic acids present at less than 1 mgL−1. Base/neutral compounds were present at less than 10μgL−1in 22 different samples.

ISSN:0734-9343    

DOI:10.1080/07349348808960517

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348808960519

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348808960520

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0734-9343    

DOI:10.1080/07349348808960521

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor