The Oxidative Hydrothermal Dissolution (OHD) process was developed at Southern Illinois University to convert solid organic material to low-molecular-weight, water-soluble products using small amounts of dissolved oxygen in liquid water at high temperature and pressure. The process is environmentally friendly; it does not involve the use of solvents or catalysts, and there is little emission of CO2 and no emission of NOx or SOx. Previous studies of the effects of OHD on organic matter have focused on coal, coal waste, and biomass. This study explores the application of OHD to organic-rich shales, providing a baseline investigation into how highly aliphatic materials react under OHD conditions, what types of products are created during the process, whether the products are economically valuable, and whether they provide novel structural and biomarker information that complements typical bulk organic matter characterization methods. Furthermore, typical oil shale utilization methods are plagued by environmental concerns akin, in some respects, to the environmental concerns associated with the coal industry. The successful application of OHD to these materials would provide a cleaner, more efficient way to process oil shale, resulting in an aqueous product that can be transported through pipelines and refined using conventional processing technology. To examine how OHD affects oil shale kerogen, a series of partial conversion experiments were conducted on an Alpha Torbanite sample at varied temperatures, reaction times, and oxidant inputs. Using a fixed-bed type reactor, over 90% carbon conversion was achieved in just 10-12 minutes under relatively mild reaction conditions (300°C) with little gas production, approximately twice as fast as OHD coal conversion. GC-MS analyses of the product distributions for these experiments demonstrate that they do not change significantly under varying reaction conditions, which can be adjusted for maximum carbon conversion. A sample of each type of oil shale (torbanite: Alpha Torbanite, lamosite: Green River Formation, marinite: New Albany Shale, tasmanite: Tasmanian tasmanite, kuckersite: Decorah Formation, cannel: Cannel King) was reacted and analyzed for product distributions. All of the oil shales produced a complex mixture of aliphatic carboxylic acids, dicarboxylic acids, keto-acids, aromatic acids, and poly-acids, some of which include phenolic structures. These products include materials that are useful as chemical feedstocks for the manufacture of plasticizers, nylons, polymers, lubricants, nylons, paints, and a variety of other materials, most of which are currently produced from petroleum derived precursors. Results of OHD biomarker analysis were not comparable to conventional solvent extraction results. With the exception of the Green River sample which did produce favorable results, analyzed steranes and hopanes were not present in measurable/identifiable amounts in the OHD products. It is unclear whether the biomarker peaks are buried under unresolved products or if the biomarkers are oxidizing/degrading under OHD conditions. However, a comparison of OHD product distributions to pyrolysate product distributions demonstrates that this method provides novel information regarding the original macromolecular structure of the kerogen. Since OHD converts a larger fraction of the original carbon, this approach may provide a more complete/correct representation of the initial structure than conventional methods.

PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2010 / Dual Energy X-Ray Transmission (DE-XRT) Imaging is a multi-sensor technique employed to conduct particle-by-particle sorting. The system makes use of a dual energy x-ray line scan sensor, which generates images of the transmitted x-rays, similar to images generated for suitcase inspection in airport security applications. The dual energy x-ray system allows for rapid approximation of atomic number range, which is utilised to evaluate the mineral and maceral content of a variety of minerals, including coal. The process is independent of particle surface condition, and can thus be utilised as a dry process. A unique application of this technology is in the removal of torbanite from a coal deposit located in Mpumalanga, South Africa. The separation of coal from torbanite has been a problem for the coal industry for a long time. The separation of coal and torbanite by conventional gravity separation techniques is difficult, due to the overlapping densities of torbanite and coal. The commercial value of both commodities is significantly compromised if contaminated with the other, thus impacting negatively on the financial viability of mining such a deposit. Preliminary laboratory DE-XRT testwork results on high quality coal and torbanite products were promising. In order to evaluate the separation of typical Run of Mine (ROM) material on pilot scale, a production scale Mikrosort X-Tract Sorter was purchased. This was the first DE-XRT sorter available in South Africa, and was housed at Mintek in Johannesburg. A 150t sample was provided from a box cut adjacent to the coal deposit under investigation in order to conduct bulk and pilot sorting tests, the focus of which was on obtaining coal products of low ash and torbanite content. Clear distinctions between the coal, torbanite and shale fractions were observed using this technique. The sorter feed (-80mm+20mm) could be upgraded from a CV of 22MJ/kg to 28MJ/kg. Ash content could be reduced from 26% to 10%, which meets export quality standards. Petrographic analysis of the coal product indicated that a high purity coal product (in terms of torbanite and ash content) was attainable (91% by volume) at a mass yield of 42.9% to the coal product, with shale and mixed humic/sapropelic coal as contaminants. Under these conditions, torbanite contamination was marginal. It was demonstrated that shale could be removed from the torbanite product via a second sorting stage. This however was not the primary focus of the study, and was not optimised for this investigation. Two major limitations of the sorting process were identified, viz.; poor liberation and limited sorter feed size range. These impacted on the process as follows:- • The effects of poor liberation on coal quality could be counteracted by adjusting the sorting criteria of the algorithm to reject additional material. This would result in a lower coal product mass yield. In addition, interlocked coal/shale particles would report to the torbanite fraction. • A significant proportion of the ROM feed reported to the -20mm size fraction, and therefore did not fall part of the sorter feed. This resulted in a very low coal mass yield as a proportion of the ROM feed. If this process were to be adopted, means of minimizing fines production during mining and crushing would need to be investigated to improve overall yield to coal product. The capability to process coarse materials (-80mm+20mm) allows for throughputs in excess of 40t/hr. Consequently, this technique may be applied in simpler coal upgrading processes, such as coal deshaling in arid regions.