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Surface areas of most American coals are small when measured by N2 adsorption at 77 K and large when measured by CO2 adsorption at 298 K, implying that the majority of the pores are less than 5 Å in diameter. This small pore size would restrict many gaseous and liquid reactants from entering the internal pore system of the coal, and hence, reduces the efficiency of coal conversion. Therefore, if the surface area, as measured by N2 (77 K), could be increased, that is, to increase the pore size, the conversion of coal into useful products should be accomplished more efficiently. Determining the surface properties of coal during treatment is important if one wishes to maximize any future process. Therefore, this research project is undertaken to gain knowledge of the surface properties (in particular the surface area) of coals undergoing treatment with various gaseous and liquid reactants. In particular, the effects of heat treatment in a stream of N2 up to 600oC and of oxidation in a stream of O2:N2 (5%:95%) at various temperatures between 350° and 450°C are studied with three coals of various ranks. The effect of pyridine extraction, at room temperature, before heat and oxidation treatments are examined for two of the coals, in addition to treatment with chromyl chloride at l00°C. Finally, the effects of hydrogen and oxygen atoms on the surface area of the coals are also investigated.

Plasticity, which typically develops at 380-420°C, is a unique property of mid-ranked coals. The phenomenon of plasticity in coals has been known for a long time but is still poorly understood. Even among coals of identical subrank and chemical composition, large differences in plastic behavior are commonly encountered. Plastic coals go through a softening and swelling state upon heating before they resolidify. Concurrent with the plastic state of the coal, thermal decomposition of the coal takes place. The coking ability of a coal can be directly related to the plasticity of the coal. In liquefaction reactions, plastic coals tend to give higher yields than nonplastic coals, a fact very useful in the synfuel industry. Plastic coals, however, tend to agglomerate in fluidized bed reactors thereby impairing their function. Currently, the ASTM approved method used to determine plasticity is by means of a Gieseler plastometer. Gieselers are inconsistent; therefore, an easier and more efficient method is needed. A current and widely accepted idea is that the extractable portion of the mid-ranked coal is responsible for initiating the plasticity mechanism. It has been shown that plasticity can be correlated to the total aliphatic C-H content of a bituminous coal. This extractable portion is the bitumen in the coal. It is logical, then, to assume that the bitumen in the coal could be analyzed for the aliphatic content and be used as a predictor of plasticity. Tetrahydrofuran (THF) was used as the solvent for the Soxhlet extraction of 40 highly characterized bituminous coals. The extracts were purified and analyzed by Fourier Transform Infrared Spectroscopy and Proton Magnetic Resonance Spectroscopy.

The effects of air oxidation on coal may change many important attributes of the coal such as calorific values, solubilities and solvent swelling values. By studying the effects of air oxidation on the soluble portion of coal, we were able to study coal oxidation in a new light.

M.Phil. (Mineral Economics) / Please refer to full text to view abstract

M.Phil. / The study was undertaken at Bosjesspruit, one of the Sasol Collieries, to investigate aspects that contribute to the degradation of coal. Bosjesspruit is penalised with more than nine million rands per year for fine coal that exceeds the set limits. Compliance to quality is the main reason. The cost is directly deducted from the profit. The quality of coal is of importance for the effectiveness of the gasifying process. A feasibility study has indicated that this study is viable. Various factors in the process were studied to identify the system deviations such as: coal bunkers, section and main conveyor belts, geology, production section activities and coal production equipment. A literature study was done and time was spent to become conversant with the coal transport system. The process is described from where the coal is mined, through the handling action up to where it is fed into the Sasol plant gasifiers. Several coal samples of the identified bottleneck areas were taken and analysed. The four main areas that were studied are: Loading actions at East 700 bunker. Incline shaft transfer chute. The horizontal bunker on surface. The South section conveyor chutes. The free-flow technology was researched and developed for an acceptable chute design. The design is now computerised and in use at Sasol Collieries. The current design and its restrictions are compared with the proposed designs to indicate the improvements. A detailed cost analysis was done to determine the expenditures such as: Penalties for fine coal. The cost of adaptability and redesign. - Forecast cost savings after the redesigns are implemented. - Cost to produce coal as well as the income for Bosjesspruit. An economical evaluation indicates that all the suggested solutions are economically justifiable. The results of the study indicate several suggested solutions to overcome the identified bottlenecks. It is further suggested that results of this study are also implemented at the other Sasol mines as well as the mines that are being developed.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 29 August 2016 / This study discusses underground coal gasification (UCG) and the analysis thereof. Two main methods were used. The first is the Bond Equivalent Diagram, which gives an ideal of where operations should take place in relation to their coal and product gas compositions. This method was used to analyze several real life sites for their idealized and actual operations. The second consisted of a comparative exergy simulation study. This was done for an air-blown UCG plant with a downstream Fischer-Tropsch reactor and an oxygen-blown UCG plant with upstream air separation. The plants were analyzed by their overall exergy efficiency as well as their exergy outputs with respect to coal inputs (fuel). It was discovered that the air-blown simulation with downstream Fischer-Tropsch was the better choice from an exergy point of view due to it having higher efficiencies (1.5 for overall, 1.38 for fuel) as opposed to the oxygen-blown simulation (0.77 overall, 0.8 for fuel). This coupled with other design and safety factors led to the conclusion that the air-blown simulation was better. / MT2017

PhD, Faculty of Engineering and the Built Environment, 1993

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaf 93. / by Ronald Alan Dictor. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 238-245. / by Mark Steven Dershowitz. / M.S.