When high yield chemimechanical sulphite pulp fibres were suspended in water, both lignin and carbohydrate were leached out of the pulp. The rate of leaching fitted a theory developed previously for the diffusion of macromolecules through the water-swollen fibre wall. The average intrafibre diffusion coefficients for lignin and carbohydrate were several orders of magnitude lower than the free diffusion of these macromolecules in solution. Leaching over a long period indicated a polydispersity of diffusion coefficients. This was related to an increase with time in the molecular weights of macromolecules removed from the fibre. Although the rate of leaching increased markedly with temperature, the diffusion coefficient of lignin decreased, while that of carbohydrate increased by a factor higher than that predicted by the Stokes-Einstein equation. These contrasting results were interpreted in terms of the molecular weights of the diffusing species and hydrogen bonding of carbohydrate to the fibre wall. The rate of leaching decreased with an increase in pulp yield, increasing cationic strength and pH of the wash water, decreasing refining energy, pretreatment of pulp with formaldehyde, and the use of polyethyleneoxide/alum retention aid in the wash water. Decreasing pH of the cooking liquor and the use of anthraquinone in the pulping increased the leaching of lignin but did not affect the leaching of carbohydrate. The effects observed could be related either to swelling or degradation of the fibre wall.

No description available.

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.

SAPPI SAICCOR is a pulp and paper mill situated in Umkomaas, 50 kms south of the port of Durban in South Africa. It was the first company to produce high grade dissolving pulp from the Eucalyptus tree and is currently the world's largest manufacturer of chemical cellulose. SAICCOR is one of the few pulp and paper mills that produces its dissolving pulp by the acid sulphite process using both calcium and magnesium as bases in the form of calcium bisulphite and magnesium bisulphite. Four streams of effluent are produced during their process, namely, the calcium spent liquor, the magnesium pulp condensate and two streams from the bleaching stages. An acid hydrolysis of the effluent streams yielded a range of organic compounds such as lignans and lignin - type precursors as well as a triterpenoid. Column chromatography and thin layer chromatography, using various ratios of hexane, dichloromethane, ethyl acetate and methanol, were carried out in isolating and purifying the compounds. The structures of these compounds were determined using NMR spectroscopic and mass spectrometric techniques. / Thesis (M.Sc.)-University of Natal, Durban, 2003.

The chemistry of the batch cooking process at Sappi Saiccor, relating to both the pulp and liquor, was investigated with the aim of using kinetic expressions to develop an improved process control model. The mill produces dissolving pulps using the acid sulphite method. Three process reactions were identified as important: cellulose hydrolysis, delignification and hemicellulose dissolution. Of these, cellulose hydrolysis is the most important since the primary aim is to achieve a targeted cellulose degree of polymerisation (DP) or viscosity (DP is commonly expressed in terms of this measurement). This is directly determined by the rate of this reaction during the cook, and the acidity of the cooking liquor was found to be the key factor. As existing equipment was not suitable for obtaining the data required to perform a kinetic analysis, a pilot plant was constructed. A commercially available probe was used for the first time to measure pH directly. The measured acidity is not directly equivalent to hydrogen ion activity at these temperatures and pressures; however, since the conditions of each cook are similar the errors incurred were found to be constant from cook to cook. The probe was found to be prone to drift due to ageing and this was accounted for by using an 'on line' calibration based on a liquor analysis. The kinetics of the cellulose hydrolysis reaction were determined using the on-line measurement of acidity and the concept of degradation increase (DI) which relates the reduction in DP value to the rate at which the polymeric chains are split. Delignification and hemicellulose dissolution were examined, since it is beneficial to maximise these reactions to reduce the quantities of chemicals consumed during the bleaching process. A model for controlling cooks to a set target cellulose DP value within a set time was developed based on the reaction kinetics. This was capable of predicting cooking conditions required with sufficient accuracy to control the cellulose DP value to within ±6 cp SNIA on the viscosity scale. / Thesis (M.Sc.Eng.)-University of Natal, 1992.

Made available in DSpace on 2016-01-13T13:27:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-07-28. Added 1 bitstream(s) on 2016-01-13T13:33:18Z : No. of bitstreams: 1 000855548.pdf: 1685828 bytes, checksum: e3301ca45c4c1e600e9478296606f770 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A indústria de polpa de celulose kraft de eucalipto no Brasil possui grande importância para a economia do setor de celulose e papel. Os parâmetros de carga alcalina e de temperatura devem ser controlados durante o processo de polpação e otimizados para que se obtenha polpa de alta qualidade e alto rendimento. A etapa de refino é uma das que mais consome energia nas indústrias e deve ser bem controlada para a economia de custos, podendo-se atrelar as variáveis de cozimento com a necessidade de refino da polpa. Deste modo, o objetivo deste estudo é avaliar a influência da carga alcalina e da temperatura da polpação kraft de eucalipto na branqueabilidade e refino. O material utilizado foi uma amostra de cavacos de Eucalyptus grandis x E. urophylla. Os cavacos foram caracterizados e submetidos a cozimentos com as temperaturas de 155 °C, 160 °C e 165 °C, e para cada um deles, foi aplicada a carga alcalina para que se obtivesse polpas com número kappa de 13, 15 e 17. Posteriormente, parte das amostras foi branqueada pela sequência OAHTD(Ep)D. Ambas polpas, branqueada e nãobranqueada, foram refinadas em moinho PFI para diferentes níveis de refino e realizados testes físico-mecânicos. Este trabalho está dividido em quatro Capítulos, a saber: (1) avaliação do efeito da temperatura e da carga alcalina na classificação de fibras, refino e testes físicomecânicos da polpa marrom; (2) impacto da polpação na branqueabilidade e no refino da polpa celulósica branqueada de eucalipto; (3) potencial da sequência curta de branqueamento AHTDP de polpa kraft de eucalipto para a obtenção de 90% ISO de alvura; (4) composição química da lignina residual de polpas kraft de eucalipto, provenientes de cozimentos realizados em 155, 160 e 165 °C por métodos da oxidação por nitrobenzeno e ressonância magnética nuclear (RMN)... (Resumo completo, clicar acesso eletrônico abaixo) / The eucalyptus kraft industry in Brazil has great importance for the sectors economy. The alkali charge and temperature parameters must be controlled during the kraft pulping and optimized in order to obtain high quality and high yield pulp. The refining is the process that consumes most energy in the mill and should be well controlled to the capital reduction. Thus, the aim of this study is to evaluate the influence of alkali load and final temperature of eucalyptus kraft pulping on refining and bleachability. Eucalyptus grandis x E. urophylla chips were characterized and cooked to different temperatures of 155 °C, 160° and 165 °C, and for each of them, the alkali charge that was applied to obtain pulps with a kappa number of 13, 15 and 17. Subsequently, part of the samples was bleached by the sequence OAHTD(Ep)D. Both bleached and unbleached pulps were refined in PFI mill and physical and mechanical tests were performed. This work is divided into four chapters, namely: (1) evaluation of temperature, alkali charge and its influence on fiber fractionation, refining and physical-mechanical testing; (2) the impact of the pulping parameters on its bleachability and refining; (3) the potential of a short sequence bleaching, AHTDP, of kraft eucalyptus pulp to 90% ISO brightness; (4) analysis of the chemical composition of the residual lignin in kraft eucalyptus pulp by nitrobenzene oxidation and nuclear magnetic resonance (NMR). The main conclusions of these chapters are: Chapter 1: lower cooking temperatures are beneficial to the cooking performance, selectivity, viscosity, and preservation of xylans. The use of low alkalinity in pulping increased the mechanical strength of the paper due to better preservation of carbohydrates; the final cooking temperature did not affect the refining with the same intensity as the alkali charge; Chapter 2: higher ... (Complete abstract click electronic access below)

Orientador: Gustavo Ventorim / Coorientador: José Cláudio Caraschi / Banca: Augusto Batagin Neto / Banca: Claudio Angeli Sansigolo / Banca: Dalton Longue Júnior / Banca: Danielle Goveia / Este trabalho contou com o depósito de Patente no instituto Nacional de Propriedade Industrial sob número de registro BR1020140166920 em 04/jul/2014, através da Agencia Unesp de Inovação / Resumo: A indústria de polpa de celulose kraft de eucalipto no Brasil possui grande importância para a economia do setor de celulose e papel. Os parâmetros de carga alcalina e de temperatura devem ser controlados durante o processo de polpação e otimizados para que se obtenha polpa de alta qualidade e alto rendimento. A etapa de refino é uma das que mais consome energia nas indústrias e deve ser bem controlada para a economia de custos, podendo-se atrelar as variáveis de cozimento com a necessidade de refino da polpa. Deste modo, o objetivo deste estudo é avaliar a influência da carga alcalina e da temperatura da polpação kraft de eucalipto na branqueabilidade e refino. O material utilizado foi uma amostra de cavacos de Eucalyptus grandis x E. urophylla. Os cavacos foram caracterizados e submetidos a cozimentos com as temperaturas de 155 °C, 160 °C e 165 °C, e para cada um deles, foi aplicada a carga alcalina para que se obtivesse polpas com número kappa de 13, 15 e 17. Posteriormente, parte das amostras foi branqueada pela sequência OAHTD(Ep)D. Ambas polpas, branqueada e nãobranqueada, foram refinadas em moinho PFI para diferentes níveis de refino e realizados testes físico-mecânicos. Este trabalho está dividido em quatro Capítulos, a saber: (1) avaliação do efeito da temperatura e da carga alcalina na classificação de fibras, refino e testes físicomecânicos da polpa marrom; (2) impacto da polpação na branqueabilidade e no refino da polpa celulósica branqueada de eucalipto; (3) potencial da sequência curta de branqueamento AHTDP de polpa kraft de eucalipto para a obtenção de 90% ISO de alvura; (4) composição química da lignina residual de polpas kraft de eucalipto, provenientes de cozimentos realizados em 155, 160 e 165 °C por métodos da oxidação por nitrobenzeno e ressonância magnética nuclear (RMN)... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The eucalyptus kraft industry in Brazil has great importance for the sectors economy. The alkali charge and temperature parameters must be controlled during the kraft pulping and optimized in order to obtain high quality and high yield pulp. The refining is the process that consumes most energy in the mill and should be well controlled to the capital reduction. Thus, the aim of this study is to evaluate the influence of alkali load and final temperature of eucalyptus kraft pulping on refining and bleachability. Eucalyptus grandis x E. urophylla chips were characterized and cooked to different temperatures of 155 °C, 160° and 165 °C, and for each of them, the alkali charge that was applied to obtain pulps with a kappa number of 13, 15 and 17. Subsequently, part of the samples was bleached by the sequence OAHTD(Ep)D. Both bleached and unbleached pulps were refined in PFI mill and physical and mechanical tests were performed. This work is divided into four chapters, namely: (1) evaluation of temperature, alkali charge and its influence on fiber fractionation, refining and physical-mechanical testing; (2) the impact of the pulping parameters on its bleachability and refining; (3) the potential of a short sequence bleaching, AHTDP, of kraft eucalyptus pulp to 90% ISO brightness; (4) analysis of the chemical composition of the residual lignin in kraft eucalyptus pulp by nitrobenzene oxidation and nuclear magnetic resonance (NMR). The main conclusions of these chapters are: Chapter 1: lower cooking temperatures are beneficial to the cooking performance, selectivity, viscosity, and preservation of xylans. The use of low alkalinity in pulping increased the mechanical strength of the paper due to better preservation of carbohydrates; the final cooking temperature did not affect the refining with the same intensity as the alkali charge; Chapter 2: higher ... (Complete abstract click electronic access below) / Doutor