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Browsing by Author "Ali, Zulfiqar"

Now showing 1 - 4 of 4
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    High Pressure Oxydesulphurisation of Coal Using KMnO4—Effect of Coal Slurry Concentration, pH and Alkali
    Ghauri, Moinuddin; Shahzad, Khurram; Inayat, Abrar; Ali, Zulfiqar; Cliffe, Keith R. (MDPI, 2016-04-16)
    A high pressure oxydesulphurisation technique was investigated to reduce sulphur content, especially at ambient temperature. Prince of Wales coal was chosen for this study. The focus of the study was on the reduction of both pyritic and organic sulphur. The effects of pressure, coal slurry concentration, pH and KOH concentration in a fixed time interval on sulphur removal were studied with a series of experimental runs at ambient temperature. Heating value recovery was found to be increased with decreased pressure and with increased coal slurry concentration. It was found that sulphur removal was enhanced with an increase in pressure, with a more significant effect on the organic sulphur. With increase in the coal slurry concentration reduction, sulphur was found to be decreased.
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    High Pressure Oxydesulphurisation of Coal—Effect of Oxidizing Agent, Solvent, Shear and Agitator Configuration
    Ghauri, Moinuddin; Shahzad, Khurram; Inayat, Abrar; Ali, Zulfiqar; Khan, Waqar Ali; Akhtar, Javaid; Cliffe, Keith R. (MDPI, 2016-06-30)
    The ambient temperature high pressure oxydesulphurisation technique was investigated to reduce the sulphur content. Prince of Wales coal was chosen for this study. The focus of the study was to investigate the reduction of both pyritic and organic sulphur while changing the KMnO4/Coal ratio, agitation speed, agitator configuration, and shear. The effect of different concentrations of acetone as a solvent and effect of particle size on the sulphur removal was also studied by a series of experimental runs at ambient temperature. Heating value recovery was found to be increased with the decreased KMnO4/Coal ratio and with decreased acetone concentration. It was found that sulphur removal was enhanced with the increase in shear using a turbine impeller. The effect of particle size was more significant on the pyritic sulphur removal as compared to the organic sulphur removal while heating value recovery was found to increase with decreased desulphurization tome for both, under atmospheric and high pressure.
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    Identification of Improved Stratigies for Processing Fine Coal
    Ali, Zulfiqar (Virginia Tech, 2012-12-11)
    In modern coal preparation plants, solid-solid and solid-liquid separation processes used to treat fine coal are least efficient and most costly operations. For example, field studies indicate that the froth flotation process, which is normally used to treat minus (-0.2 mm) fine coal, often recovers less than 65 to 70% of the organic matter in this size range. Fine coal separation processes are also inherently less effective in removing pyrite than that of coarse coal separations. Moreover, while fines may represent 10% or less of the total run-of-mine feed, this size fraction often contains one-third or more of the total moisture in the delivered product. In order to address these issues, several multistage coal processing circuits were set up and experimentally tested to demonstrate the potential improvements in fine coal upgrading that may be realistically achievable using an "optimized" fine coal processing flowsheet. On the basis of results obtained from this research, engineering criteria was also developed that may be used to identify optimum circuit configurations for the processing different fine coal streams. In the current study, several fine coal cleaning alternatives were evaluated in laboratory, bench-scale and pilot-scale test programs. Fine coal processes compared in the first phase of this work included spirals, water-only cyclones, teeter-bed separators and froth flotation. The performance of each technology was compared based on separation efficiencies derived from combustible rejection versus ash rejection plots. The resulting data was used to identify size ranges most appropriate for the various alternative processes. As a follow-up to this effort, a second phase of pilot-scale and in-plant testing was conducted to identify new types of spiral circuit configurations that improve fine coal separations. The experimental data from this effort indicates that a four-stage spiral with second- and fourth-stage middlings recycle offered the best option for improved separation efficiency, clean coal yield and combustible recovery. The newly developed spiral circuitry was capable of increasing cumulative clean coal yield by 1.9% at the same clean coal ash as compared to that of achieved using existing conventional compound spiral technology. Moreover, the experimental results also proved that slurry repluping after two turns is not effective in improving separation performance of spiral circuits. The third phase of work conducted in this study focused on the development of methods for improving the partitioning of pyrite within fine coal circuits. The investigation, which included both laboratory and pilot-scale test programs, indicated that density-based separations are generally effective in reducing sulfur due to the large density difference between pyrite and coal. On the other hand, the data also showed that sulfur rejections obtained in froth flotation are often poor due to the natural floatability of pyrite. Unfortunately, engineering analyses showed that pyrite removal from the flotation feed using density separators would be impractical due to the large volumetric flow of slurry that would need to be treated. On the other hand, further analyses indicated that the preferential partitioning of pyrite to the underflow streams of classifying cyclones and fine wire sieves could be exploited to concentrate pyrite into low-volume secondary streams that could be treated in a cost effective manner to remove pyrite prior to flotation. Therefore, on the basis of results obtained from this experimental study, a combined flotation-spiral circuitry was developed for enhanced ash and sulfur rejections from fine coal circuits. Finally, the fourth phase of work conducted as part of this investigation focused on evaluating a new mechanical, non-thermal dewatering process called Nano Drying Technology (NDT™). Experimental results obtained from bench-scale testing showed that the NDT™ system can effectively dewater fine clean coal products from more than 30% surface moisture to single-digit moisture values. Test data obtained using a pilot-scale NDT™ plant further validated this capability using a continuous prototype facility. It was also observed that, unlike existing fine coal dewatering processes, the performance of the NDT™ system is not constrained by particle size.
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    Improved strategies for processing fine coal streams
    Ali, Zulfiqar (Virginia Tech, 2012-12-20)
    In modern coal preparation plants, solid-solid and solid-liquid separation processes used to treat fine coal are least efficient and most costly operations. For example, field studies indicate that the froth flotation process, which is normally used to treat minus (-0.2 mm) fine coal, often recovers less than 65 to 70% of the organic matter in this size range. Fine coal separation processes are also inherently less effective in removing pyrite than that of coarse coal separations. Moreover, while fines may represent 10% or less of the total run-of-mine feed, this size fraction often contains one-third or more of the total moisture in the delivered product. In order to address these issues, several multistage coal processing circuits were set up and experimentally tested to demonstrate the potential improvements in fine coal upgrading that may be realistically achievable using an "optimized" fine coal processing flowsheet. On the basis of results obtained from this research, engineering criteria was also developed that may be used to identify optimum circuit configurations for the processing different fine coal streams. In the current study, several fine coal cleaning alternatives were evaluated in laboratory, bench-scale and pilot-scale test programs. Fine coal processes compared in the first phase of this work included spirals, water-only cyclones, teeter-bed separators and froth flotation. The performance of each technology was compared based on separation efficiencies derived from combustible rejection versus ash rejection plots. The resulting data was used to identify size ranges most appropriate for the various alternative processes. As a follow-up to this effort, a second phase of pilot-scale and in-plant testing was conducted to identify new types of spiral circuit configurations that improve fine coal separations. The experimental data from this effort indicates that a four-stage spiral with second- and fourth-stage middlings recycle offered the best option for improved separation efficiency, clean coal yield and combustible recovery. The newly developed spiral circuitry was capable of increasing cumulative clean coal yield by 1.9 % at the same clean coal ash as compared to that of achieved using existing conventional compound spiral technology. Moreover, the experimental results also proved that slurry repluping after two turns is not effective in improving separation performance of spiral circuits. The third phase of work conducted in this study focused on the development of methods for improving the partitioning of pyrite within fine coal circuits. The investigation, which included both laboratory and pilot-scale test programs, indicated that density-based separations are generally effective in reducing sulfur due to the large density difference between pyrite and coal. On the other hand, the data also showed that sulfur rejections obtained in froth flotation are often poor due to the natural floatability of pyrite. Unfortunately, engineering analyses showed that pyrite removal from the flotation feed using density separators would be impractical due to the large volumetric flow of slurry that would need to be treated. On the other hand, further analyses indicated that the preferential partitioning of pyrite to the underflow streams of classifying cyclones and fine wire sieves could be exploited to concentrate pyrite into low-volume secondary streams that could be treated in a cost effective manner to remove pyrite prior to flotation. Therefore, on the basis of results obtained from this experimental study, a combined flotation-spiral circuitry was developed for enhanced ash and sulfur rejections from fine coal circuits. Finally, the fourth phase of work conducted as part of this investigation focused on evaluating a new mechanical, non-thermal dewatering process called Nano Drying Technology (NDT"). Experimental results obtained from bench-scale testing showed that the NDT" system can effectively dewater fine clean coal products from more than 30% surface moisture to single-digit moisture values. Test data obtained using a pilot-scale NDT" plant further validated this capability using a continuous prototype facility. It was also observed that, unlike existing fine coal dewatering processes, the performance of the NDT" system is not constrained by particle size.