Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xvi, 135 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 107-109).

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xvi, 214 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 199-208).

Thesis (MSc.(Chemistry)) - University of Pretoria, 2008. / Summary in English.

Thèses (Ph.D.)--Université de Sherbrooke (Canada), 2001. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xvi, 182 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 98-100).

M.Sc. (Chemistry) / Catalyst deactivation is a process that plays an important role in many catalytic processes. The forming of coke is in this respect the most common cause for deactivation. The research that has been done here has tried to give some insight into the mechanism of cokeforming with the help of Fourier Transform Infrared Spectroscopy (F)'IR). For this purpose a cobalt catalyst on an alumina carrier was used. The influence of the reaction time, the carbon monoxide to hydrogen ratio and the temperature on the rate and amount of coke formed was determined. A cell was developed that could be heated up to 500°C and could simultaneously be used in FTIR-spectroscopy in situ research. This enabled the determination of spectra at certain time intervals. In this way the development of the characteristic bands could be followed. Two other methods were used to support the transmission spectra : Diffuse Reflectance Spectroscopy and the burning of the coke from the catalyst. The latter was done to determine the amount of coke that had formed on the catalyst surface during the run. The amount of coke decreased with an increase of the hydrogen to carbonmonoxide ratio in the feed. Temperature also had a marked influence on coke formation: It decreased at higher temperatures. As expected the amount of coke increased with reaction time. In general the coke contained only a small hydrogen content. In conclusion it may be mentioned that the results obtained can contribute to the characterization of coke formed on Fischer-Tropsch catalysts.

The influence of coking conditions, with respect to position in a commercial coke-oven, on the mechanical behaviour of blast furnace coke has been studied. This involved the determination of density, porosity, the characterization of microstructure and assessing the influence of all three on the compressive strength of coke. The plastic flow properties were also investigated at temperatures greater than 1000°C. Three coke batches, originating in a 5m commercial coke-oven at three different positions with respect to height (0.8m, 3.3m and 5m below the coal line), along with three coke batches produced in a 460mm test-oven, were supplied by Energy, Mines and Resources (CANMET) in Ottawa. A warf coke batch was also provided as a control sample. Several hundred core-drilled specimens (≃1.3cm diameter and 1.3cm length) were produced from the seven coke batches. The bulk density of each cylindrical coke specimen was determined. Also, a detailed microstructural analysis, using a Leitz Image Analyzer, of the flat faces of the coke cylinders was performed to quantitatively characterize the pore and cell wall size, and the pore geometry. The compressive strength of each coke cylinder was determined both at ambient temperature and at 1400°C. In addition, the plastic flow behaviour of the commercially produced coke batches was studied. Results indicate that the coke product bulk density was affected by the coke-oven pressure (static load). Studies of the test-oven coke batches revealed that coke bulk density increased with higher oven pressure. Furthermore, the pore size was found to be larger for cokes produced at lower oven pressures. The cell wall size did not appear to be affected by coke-oven pressure. The bulk density of the commercially produced samples increased with depth below the coal line. This was attributed to a higher temperature and static load that existed at the bottom of the battery. The pore size was larger in cokes extracted from higher regions. No correlation of cell wall size with depth below the coal line was found. However, an oven size effect on the pore and wall size was noticed. Both the pore and wall size was smaller in the test-oven coke batches. The compressive strength of coke was higher in batches subjected to higher coke-oven pressures. Similarly,' the compressive strength of commercial coke batches was higher for coke batches extracted from regions near the sole of the coke-oven, than that for coke batches extracted from higher regions. It was concluded that high oven pressures resulted in cokes exhibiting a lower porosity and small pores which had the combined effect of producing stronger coke. Coke strength was generally shown to be higher at 1400°C than at room temperature. The test-oven cokes were always stronger than cokes produced in the 5m commercial coke-oven. Constant load tests revealed that coke exhibited plastic flow behaviour at temperatures above 1000°C. The time dependent strain data was described using an interactive-double-Kelvin element visco-elastic model. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The influence of aggregate and binder phase characteristics on formcoke products has been studied. This involved investigating the compaction kinetics of the system and determining the mechanical strength of the briquettes produced. The char phase was characterized in terms of density, hardness, porosity and residual volatile matter content and the rheological properties of the binder phases used were established elsewhere. The strength and wetting behaviour of the aggregate-binder interface were studied using model materials (an SRC pitch binder and a graphite rod aggregate) as well as those produced in this work. Analysis of compaction curves was carried out using the CCWL Hot Compaction Model for Char-Binder Coal systems which was found to adequately describe the observed compaction behaviour. Briquette strength was characterized by ultimate compressive strength and comparisons were made for a constant briquette bulk porosity of 35% (by volume). Results indicate that binder phase fluidity affects compaction viscosity during the particle flow stage of compaction and that char porosity influences final briquette bulk density by affecting the amount of total compaction required to obtain a given bulk density. In general, increased total compaction was shown to result in higher product bulk density and high bulk density was found to yield higher gross composite strength. The latter relationship was seen to be approximately linear over the range of bulk porosity encountered in this study. A higher briquette strength was found for systems with aggregates carbonized at lower temperatures. This was attributed to a combination of higher porosity and stronger char-binder interfacial strength, although the former effect was considered to predominate in the systems considered here. Binder phase fluidity was also seen to affect briquette strength, higher fluidity resulting in higher strength. It was concluded that this was due to increased binder penetration of the aggregate phase. With no significant pore structure in the aggregate, as found with high temperature char, briquette strength was seen to become approximately constant for the three binder coals used. It was concluded that a good formcoke product was aided by a highly fluid binder and a char pore structure accessible to the binder phase. / Applied Science, Faculty of / Materials Engineering, Department of / Unknown

Of all coke properties the influence of the catalytic mineral matter on reactivity of metallurgical cokes is least understood. There is limited information about the form of minerals in the metallurgical cokes and no information about their relative concentration. A comprehensive study was undertaken for characterisation of mineral matter in coke (qualitative and quantitative), which enabled quantification of the effect of catalytic minerals on the reaction rate, and establishment of the effect of gasification on the mineral phases. Also, the relative importance of coke properties on the gasification reaction rate was determined. The reactivity experiments were performed at approximately 900??C using 100% CO2 under chemically controlled conditions. The mineralogical composition of the investigated cokes was found to vary greatly as did the levels of catalytic mineral phases. These were identified to be metallic iron, iron sulfides and iron oxides. The gasification reaction rate at the initial stages was strongly influenced by the content of catalytic mineral phases and also by the particle size of the catalytic mineral matter. The reaction rate increased as the contact surface between catalyst and carbon matrix increased. Catalytic mineral phases showed a strong influence on the reaction rate at early stages of reaction. But their influence diminished during gasification. At later stages of reaction the influence of micropore surface area became more important. The influence of the catalytic mineral phases diminished during gasification because the catalyst was inactivated to some degree and the contact surface between the catalyst and carbon matrix diminished due to the strong gasification of the carbon around the catalyst particles. The partial inactivation of the catalytic mineral phases occurred because metallic iron and pyrrhotite were oxidised by CO2 to iron oxide, and in turn iron oxide reacted with other mineral phases, which it is associated with, to form minerals that are not catalysts. It is noteworthy that a significant percentage of the mineral matter present in the investigated cokes was amorphous (44 - 75%). The iron, potassium and sodium present in the amorphous phase did not appear to catalyse gasification, but their potential contribution to gasification could not be completely excluded.

Thesis (Ph.D.)--University of Wollongong, 2009. / Typescript. Includes bibliographical references: leaf 248-256.