Thesis (Ph. D.)--University of Washington, 1993. / Vita. Includes bibliographical references (leaves [60]-61).

Thesis (M.Sc.). / Written for the Dept. of Chemistry. Title from title page of PDF (viewed 2009/13/07). Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1972. / Vita. Digitized and made available by the University of Wisconsin Digital Collections Center as part of Minds@UW. Description based on print version record. WU Includes bibliographical references.

Thesis (Ph. D.)--Institute of Paper Science and Technology, Georgia Institute of Technology, 2004. / Includes bibliography.

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 95-96).

Thesis (MSc)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Autocausticizing, a new method to regenerate sodium hydroxide from the sodium carbonate, is intended to replace the conventional Kraft Recovery System which uses calcium hydroxide produced in a lime kiln for this purpose. It is defined as the self-induced expulsion of carbon dioxide bound in the smelt by using certain amphoteric oxides. Thus autocausticizing can eliminate the need for a lime cycle and hence reduce the Kraft process capital and operating costs. The reactions between sodium carbonate and a number of amphoteric oxides have been reported in the literature. Patents have been issued on the use of titanium dioxide, iron oxide and sodium borates for this purpose. The sodium borates have the advantage of a high reaction rate, but are totally soluble and must be carried throughout the whole Kraft cycle. In this research colemanite (calcium borate) which is mined as a cheap mineral in California and in Turkey was studied as an autocausticizing agent. Since it is partially soluble and most likely can be recycled, it would eliminate the problems associated with the use of soluble borates. Experiments were performed both isothermally and under constant heating rate conditions. Isothermal studies were made with Ti0₂, alumina and colemanite to compare their performances as autocausticizing agents at 900°C and 1000°C for various reaction times in an electric furnace. The second group of experiments was made using a differential Chermogravimetric (TG) analyzer. In these experiments mixtures with 20 to 80 weight percent colemanite in sodium carbonate were heated at a constant heating rate of 10°K/min in the range of 190-1000°C. The results indicate that two reaction were involved. Above the stoichiometric colemanite concentration the colemanite and sodium carbonate had reacted completely by a temperature of about 700°C. Above that temperature the impurities in the colemanite appeared to catalyze the decomposition of sodium carbonate if the colemanite concentration was less than the stoichiometric amount needed. TG data were analyzed for the first and second reactions between the temperature ranges of 190-700°C and 700-1000°C respectively. Kinetic models were developed In terms of the reaction order, activation energy and frequency factor. The first reaction was found to be zero order on sodium carbonate concentration. The results also showed that the activation energy and frequency factor were functions of the colemanite concentration in the mixtures. As a result the rate was affected by the amount of colemanite used. The same was true for the second reaction except the reaction was first order. The concentrations predicted for the isothermal tests by the model were compared with the results of the isothermal study for various colemanite concentrations. Reasonable agreement was found except for the values at lower conversions, which might be due to the Increased importance of the diffusion of CO₂ from the mixtures in the case of Isothermal runs. It was also found that it is possible to obtain conversions as high as 85 percent with 40 percent colemanite in 20 minutes. Promising results were obtained from the recycle tests as well. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Submitted in fulfillment of the requirements for the Degree of Doctor of Technology: Biological Sciences, M.L. Sultan Technikon, 2002. / The extent of diffusion and surface modification of a purified 23.6 kDa xylanase isolated from Thermomyces lanuginosus on bagasse pulp was evaluated. Polyclonal anti-xylanase antibodies were raised in two rabbits and in conjunction with immunogold labeling and microscopic studies enzyme diffusion and degradation studies were performed. The purity of the xylanase was confirmed by SDS-PAGE and western blots confirmed the antigen-antibody hybrid on the nitrocellulose membrane. / D

The pulp and paper industry uses pulping chemicals for the treatment of bagasse, straw and wood chips. Spent liquor or effluent liquor, with high carbon content is produced and sent to chemical recovery to recover pulping chemicals. In addition, energy from the spent liquor is recovered and utilised to generate steam for electricity supply, thereby reducing fossil fuel power consumption. Spent liquor is destroyed using conventional incineration technology, in a recovery furnace or recovery boiler, which is the heart of chemical recovery. These units have over the past few decades been prone to numerous problems and are a major concern to the pulp and paper industry. They pose a threat to the environment, are expensive to maintain and constitute a safety hazard. Thus the pulp and paper industry is now looking at a replacement technology; an alternative that will effectively regenerate pulping chemicals and recover energy for generating electricity, ultimately to make the plant energy self-sufficient. Gasification technology may be the chosen technology but is yet to be applied to the pulp and paper sector. However, this technology is not new. It has been integrated and used successfully in the petroleum industry for decades, with applications in coal mining and the mineral industry. The overall objective of tills study is to develop a better understanding of gasification using a pilot-scale fluidised bed reactor which was designed and developed at the University of Natal. The reactor, "the Gasifier", is operated at temperatures below the smelt limits of inorganic salts (<750°C) in the spent liquor. In this investigation, spent liquor is injected directly into an inert bed of alwninium oxide grit, which is fluidised by superheated steam. The atomized liquor immediately dries when it contacts the grit in the bed, pyrolyses and the organic carbon is gasified by steam. Pyrolysis and steam gasification reactions are endothennic and require heat. Oxidised sulphur species are partially reduced by reaction with gasifier products, which principally consist of carbon monoxide, carbon dioxide and hydrogen. The reduced sulphur is said to be unstable in the gasifier environment, and reacts with steam and carbon dioxide to form solid sodium carbonate and gaseous hydrogen sulphide. (Rockvam, 2001). The focus of this study will be to determine the Gasifier's ability to gasify spent liquor, from soda and sulphite pulping of bagasse, at different operating conditions. In addition, the fate of process and non-process elements will be investigated. The product gas generated in the gasification of spent soda and sulphite liquors consisted of hydrogen, carbon dioxide, carbon monoxide and methane. In the gasification of spent sulphjte liquor, hydrogen sulphide was also produced. The water-gas shift reaction, which was the main reaction, was found to be temperature dependent. In adilition, organic carbon conversion increased with temperature. Furthermore, most of the sulphur in the bed predominated in the form of hydrogen sulphide with very little sulphur in the form of sulphate. This indicated that gasification would reduce sulphate levels, which are responsible for dead load in a chemical recovery cycle. Finally, an important result was that the aluminium oxide grit was successfully coated. It was previously speculated that this would not be possible. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2004.

The work described in this thesis was aimed at obtaining a better understanding of the neutral sulphite semichemical pulping process employed by Mondi Kraft's Piet Retief mill, and to investigate ways to improve this process. The unique feature of the process in this mill is that hardwood and softwood species are pulped simultaneously in a continuous digester. The pulping trials described were carried out in a laboratory batch digester which was build as a part of this project. Pulps were evaluated for yield, Hypo number as an indication of the residual lignin content and strength properties. The first part of the experimental work focused on the effect that different pulping variables have on the process and the resulting pulp. Variables investigated were the chemical charge, pulping temperature, chip composition and anthraquinone dosage. The second part of the work was to investigate ways in which the process can be improved. In particular it was investigated whether it would be advantageous to pulp hardwood and softwood separately and mix the two pulps together after pulping. The effect of changing to an alkaline sulphite process was also briefly investigated. It was found that the current process is optimized as far as the chemical charge and pulping temperature is concerned. Increasing the softwood percentage used to 50 % (from current value of 41 %) increases the tear strength, whilst decreasing it to 30 % increases the tensile strength of the resulting pulp. It was also determined that increasing the AQ dosage from 0.1 % to 0.5 % might bring savings in chemical costs. It is suggested that this is investigated in a mill trial. It was further found that pulping the two species separately improves the tear strength of the pulp by about 20 % compared with that which was pulped simultaneously. The results indicate that no benefits concerning the chemical costs, pulping temperature, pulp yield, burst strength or tensile strength are to be gained from separate pulping. Preliminary results indicated that significant strength increases and possible chemical cost savings are to be gained by changing from a neutral sulphite to an alkaline sulphite process. Further work to determine the reproducibility of these results, as well as the effect of different chemical charge and ratios is suggested. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.