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<p> </p><p>The correlation between pulp properties and operating conditions in high consistency (HC) refiners at Holmen Paper AB were studied. Two types of HC refiners were investigated: the Andritz RTS refiner at the Hallstavik Mill and the Sprout-Bauer Twin 60 refiner at the Braviken Mill. The objective of the study was to clarify the relationship between the pulp properties and refining conditions such as electrical energy input, housing- and feed- pressure and plate wear in high consistency refining.</p><p>The results of this project show that worn segments reduce the operating energy maximum input and the pulp and handsheet properties in negative aspects such as lower tensile- and tear index, and shorter average fibre length. Energy input is an important factor in the refining process and influence Canadian Standard Freeness and the tensile index as evident from the probability residuals. Housing pressure and feed pressure influence the pulp quality and should be adjusted in order to optimise the refining process, although the effect is not as great as for energy input or plate wear.</p><p>The results of the study indicate that Braviken Mill is operating at its optimum for the parameters measured in this project. Hallstaviks goal, to avoid fibre shortening and to obtain better tensile index, can be reached by making slight changes in pressure condition.</p><p> </p>

Thesis (M. Eng.)(Chemical)--University of Pretoria, 2003. / Summaries in Afrikaans and English. Includes bibliographical references (leaves 83-86) and index. Available on the Internet via the World Wide Web.

Este trabalho teve como objetivo analisar os cavacos de dimensões reduzidas inseridos em cozimentos que se utilizam de menores tempos e maiores temperaturas, de maneira a se obter as bases para o estabelecimento de um novo processo e/ou a otimização dos sistemas atualmente utilizados em escala industrial. Amostras de cavacos de referência (3,6 mm, obtidas pelo processo convencional de picagem) e de cavacos com espessura de 0,5 mm, 1 mm e 2 mm (obtidas por um gerador de partículas), do híbrido de Eucalyptus urophylla x Eucalyptus grandis com 7 anos foram analisadas quanto à densidade básica, composição química e morfologia das fibras. Após a caracterização, os materiais foram submetidos à polpação kraft pelo processo convencional e foram testados três níveis de fator H com quatro níveis de álcali ativo de maneira a se estabelecer uma equação que representasse o processo e pudesse ser utilizada em cozimentos futuros. Através das equações obtidas foi possível calcular os parâmetros de rendimento depurado, álcali ativo residual, álcali ativo consumido, teor de sólidos secos, fator H e álcali ativo em função de um número kappa 18. Os resultados mostram que a densidade básica, a composição química e a morfologia das fibras da madeira não foram afetadas pelo processo de picagem. No entanto, a densidade a granel foi afetada pela espessura dos cavacos, sendo de 0,037, 0,081, 0,110 e 0,141 g.cm-³ para os cavacos de 0,5 mm, 1 mm, 2 mm e 3,6 mm respectivamente. No processo de polpação, as espessuras se comportaram de maneira semelhante, no entanto, a espessura de 2 mm apresentou o melhor número kappa para o fator H de 451, o de maior interesse, com o mesmo rendimento que as demais espessuras. Na análise de regressão, a espessura de 2 mm apresentou melhor rendimento, menor teor de sólidos e menor fator H (de 461), compatível com o que se pretende utilizar em processos de polpação com tempo reduzido de cozimento. / The objective of this work was to evaluate the performance of thin chips inserted on a short time and higher temperatures in cooking process, to obtain the basis for the establishment of a new process and / or the optimization of the currently systems used on an industrial scale. Samples of the reference chips (3,6 mm obtained by the conventional process of chipping) and thin chips with 0,5 mm, 1 mm and 2 mm (obtained by a particle generator) of the Eucalyptus urophylla x Eucalyptus grandis hybrid with 7 years of age had their density, chemical composition and fibers morphology evaluated. After the characterization, the materials were submitted to conventional kraft pulping process and three levels of H factor with four levels of active alkali were tested to establish an equation to represent the process that can be used on future cookings. Yield, residual active alkali, consumed active alkali, dry solids, H factor and active alkali were calculated through equations, according to a kappa number 18. The results show that the basic density, chemical composition and morphology of the wood fibers were not affected by the chipping process. However, the bulk density of 0,037, 0,081, 0,110 and 0,141 g.cm-³ for the 0,5 mm, 1 mm, 2 mm and 3,6 mm chips, respectively, was affected by the chip thickness. On the pulping process, the different chips had the same behavior, however, 2 mm chips showed the best kappa number to H factor 451, with the same yield as the other thickness. On the regression analysis, the 2 mm chips showed better performance, lower solids content and lower H factor (461), consistent with a short time pulping process.

O presente estudo teve como objetivo avaliar e comparar os processos de polpação kraft convencional e SuperBatchTM para Bambusa vulgaris visando a produção de polpa celulósica não branqueável (número kappa 58±2). A matéria prima foi caracterizada com relação à densidade básica, composição química e dimensões de fibras; foi realizado um estudo de pré-extração aquosa com as temperaturas de 50, 70 e 90°C durante 5 horas pesando-se os cavacos a cada 15 minutos para avaliar a absorção de água. Este mesmo procedimento foi feito à temperatura de 110°C com tempos de 15 minutos, 1, 2 e 5. Posteriormente foram avaliados os teores de extrativos totais e lignina dos cavacos oriundos das temperaturas 50, 70, 90 e 110°C nos tempos de 1 e 5 horas. Para os processos de polpação avaliou-se, o rendimento bruto, rendimento depurado, teor de rejeitos, ácidos hexenurônicos e alvura, além da eficiência da adição de um estágio de préextração aquosa. Os resultados obtidos mostram que a matéria-prima apresentou valores típicos para a espécie em questão no que diz respeito à densidade básica, composição química e morfologia das fibras. Através de uma regressão com os resultados de absorção de água e extrativos totais nas diferentes temperaturas foi estabelecido a temperatura 80°C e tempo de 1 hora como a ideal para a préextração aquosa. Para o processo de polpação kraft convencional o nível de deslignificação foi obtido com carga alcalina de 14% (base NaOH); para o processo SuperBatchTM o nível de deslignificação estabelecido foi obtido com uma carga de reagentes químicos de 16% (base NaOH). A impregnação aquosa contribuiu para uma melhor deslignificação somente no processo convencional. / The present study aimed to evaluate and compare the kraft pulping conventional processes and SuperBatchTM for Bambusa vulgaris aiming the production of pulp unbleached (kappa number 58 ± 2). The raw material was characterized with respect to basic density, chemical composition and morphology of fibers, was analyzed an aqueous pre-extraction temperatures of 50, 70 and 90 ° C for 5 hours weighing the chips to every 15 minutes to evaluate the absorption of water. The same procedure was done for 110 ° C were used time of 15 minutes, 1, 2 and 5 hours. After this stage were evaluated the total extractives and lignin content from the chips of the temperatures 50, 70, 90 and 110 ° C for 1 and 5 hours. For the pulping processes were evaluated, the total yield, screened yield, reject content, HexA and brightness, besides the efficiency of the addition of a pre-stage aqueous extraction. The results show that the raw material had values typical for the species in question with regard to density, chemical composition and fibers morphology. Through a regression with the results of water absorption and extractives was set at different temperatures the temperature 80 ° C as optimal for pre-aqueous extraction. For the conventional kraft pulping process the level of delignification was obtained with the alkali charge of 14% (based on NaOH); SuperBatchTM process for the level of delignification has been achieved with a set of chemical reactants load 16% (base NaOH). The aqueous pre-extraction contributed to a better delignification only in the conventional process.

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.