Semester

Summer

Date of Graduation

2004

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Chemical and Biomedical Engineering

Committee Chair

John W. Zondlo.

Abstract

Hydrotreatment of coal in the presence of hydrogen donor solvents is considered to be a potential route for developing value-added carbon products. The aim of this research was to investigate the use of coal-derived solvents as replacements for expensive hydrogendonor solvents like tetralin, in the production of hydrogen rich carbon products. Three coal-derived solvents obtained from the metallurgical coke ovens, namely Heavy Creosote Oil (HCO), Carbon Black Base (CBB) and Refined Chemical Oil (RCO), were utilized as hydrogen donor solvents in the hydrotreatment process. The coal-alone conversion in producing THF solubles decreased in the order as CBB>HCO>RCO. Process-derived (recovered) solvents were isolated as vacuum distillation overheads and tested for their effectiveness towards producing THF solubles. The coal-alone conversion for these recovered was found to be comparable to the starting fresh solvents. An average mass loss of 7-10% was observed for the fresh solvents whereas the mass loss increased slightly to 10-13% for the recovered solvents during the hydrotreatment runs. The residue from the vacuum distillation i.e. the pitch, was characterized by testing for softening point, ash content, elemental analysis and optical texture. The coke yield and softening point of the pitch followed a linear dependence on the amount of solvents distilled from the product mixture. The effect of temperature and reaction atmosphere was also studied on the hydrotreatment process. The coal-alone conversion increased with higher temperature and a hydrogen atmosphere was found to be crucial. The optimum process temperature was found to be 450°C under 500 psig hydrogen pressure. Reaction conditions did not affect the recovered solvent performance upon recycle in producing THF solubles. The ash content of the pitches was found to be low i.e 0.2%. The optical texture of the cokes was found to have an anisotropic structure. The elemental composition of the pitches showed higher hydrogen-to-carbon ratio than the starting coal and was found to be similar irrespective of reaction conditions. Finally, successive use of only recovered solvents and/or blends of fresh and recovered solvents were studied to mimic a continuous hydrotreament operation. The coal-alone conversion decreased after going through a maximum in both the cases. While the decreasing trend continued for the pure recovered solvents, the coal-alone conversion was found to stabilize for the blends.

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