Dissertations / Theses on the topic 'Sulfate pulping process Costs'

Environmental concerns and cost reduction have been the focus of pretreatment and extended delignification in Kraft pulping for some time now. Previous work has looked at the diffusion of tritiated water into softwood chips. This thesis looks at the diffusion of Na2S into southern pine softwood chips. Two size fractions were used. The measured diffusion data were compared to the equilibrium of mixing between the HS ion and water alone. Since pine is porous, effective diffusivities were calculated for each size fraction using a 1-dimensional model. Tortuosities were then calculated for the HS / pine wood system. These diffusivities are compared to values previously obtained for tritiated water.

Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2005.
Empie, Jeff, Committee Chair ; Banerjee, Sujit, Committee Member ; Deng, Yulin, Committee Member. Includes bibliographical references.

A unique penetration instrument has been developed to evaluate the role of surfactants in kraft pulping process. This instrument can screen surfactants which can improve the wood impregnation more effectively and much faster than pilot-plant experiment. The role of surfactants in wood penetration has been explored. Surfactants can improve wood impregnation by dispersing the extractives in the wood structure and optimizing the interfacial properties between wood surface and kraft liquor. The addition of two blends of anionic and nonionic surfactants into kraft pulping process results in a significant reduction of the screen rejects and an increase of screened yield at the same delignification rate.
Six wood species were tested in this study including both non-resinous and resinous wood species. Both sapwood and heartwood of these species were tested. Surfactants were found to have no improvement on sapwood, but a significant improvement on heartwood. The critical micelle concentrations (CMC) of surfactants in kraft liquor were determined. The best dosages of surfactants based on CMC were also determined in this study.

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

This study-investigated the use of cationic polymers, and a surfactant, EHDABr, in the color removal treatment of Kraft pulp and paper wastewater. Four polymers were evaluated for their color removal performance by jar test procedures. The polymers removed between 77 and 87% of the wastewater color. The affect of pH upon polymer performance varied with the polymer tested. Powdered activated carbon addition improved the performance of the polymers. The color removal ability of EHDABr was evaluated by jar test, and by continuous-flow foam flotation.. EHDABr removed 77% of the wastewater color by jar test and was relatively unaffected by pH variation. The addition of powdered activated carbon improved EHDABr performance in jar tests. EHDABr removed 90% of the wastewater color by continuous-flow, foam flotation. Color bodies were precipitated in the foaming system before being removed by flotation. Total suspended solids removal improved with increasing column detention time.
Master of Science

Xylanase production from a Bacillus subtilis gene cloned into a strain of Escherichia coli was measured. Although this gene was expressed in E. coli at several temperatures, efficient normal xylanase secretion did not occur, the observed protein release apparently depending on cell leakage or lysis. Screening for a better microbial protein secretor free of cellulase selected B. cereus #259. The strain had wild plasmids that were hard to eliminate using acridine orange and elevated temperature curing techniques. While still bearing 5 wild plasmids, attempts to transform B. cereus #259 were unsuccessful using conventional methods and electroporation. Another strain, B. cereus #518, found to be free of wild plasmids, was then used. A bidirectional vector shuttle plasmid (pMK3) was employed to carry the cloned gene into this B. cereus strain. Transformation was carried out by high voltage electroporation. Xylanase production by the new B. cereus clone was similar to that from E. coli, but was shown to be continuously and normally secreted. The xylanase gene products from the E. coli and B. cereus hosts were shown to function identically. Both xylanases improved the delignification of unbleached softwood and hardwood kraft pulps, thus reducing the Cl$ sb2$ required to achieve a given degree of bleaching, without altering the physical properties of the fibers. Using a target kappa number lignin content) of 5, xylanase pretreatment of aspen kraft pulp led to a 22% saving of chlorine. Adsorbable organic halogens in the bleachery effluent were also lowered by more than 50%.

Thesis (MSc)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: The extractive materials in wood often cause pitch problems in pulp mills. During pulping and bleaching extractives are released from the wood and pulp and later stick to ceramic and metal parts, forming pitch deposits. Pitch deposits impair both product quality and production rates. It decreases the efficiency of pulp washing, screening, centrifugal cleaning, and refining, and can disrupt many paper machine operations. The deposits also break loose from equipment and cause spots in the final product. There are a few triggering mechanisms that induce pitch deposition. Hydrodynamic or mechanical shear can destabilise the colloidal pitch emulsion, causing pitch to agglomerate and deposits to form. Similarly, sudden temperature drops and/or pH shocks and/or the introduction of water hardness ions from fresh water inlets or showers can also cause pitch deposits by destabilising the colloidal pitch emulsion. Inorganic salts, such as calcium carbonate, can catalyse pitch deposition by acting as the building blocks for the sticky pitch. Calcium ions in the white water can react with fatty acids, forming insoluble, sticky calcium soaps. Triglycerides have also been shown to be a major contributor to pitch deposition in kraft pulping and bleaching mills. It forms a sticky deposit to which less sticky particles attach. To attain an improved understanding of pitch problems associated with the kraft pulping and bleaching of Eucalyptus spp., various analyses were done on wood- and pulp extractives and pitch from a South African kraft pulp mill. High molecular weight compounds (involatile) constituted a large portion of the extracts and pitch. Approximately 40% of volatile Eucalyptus grandis extract was f3-sitosterol, with fatty acids (22.8%) and triglycerides (15.5%) also making a substantial contribution. Fatty acid amides were a prominent fraction of pulp extracts from the latter stages of bleaching. The amides constituted 38.3% and triglycerides 10.1% to total volatile pitch deposits. Lipases hydrolyse triglycerides and could therefore help to reduce pitch problems. Consequently 381 filamentous fungi isolated from indigenous and commercial forests in South Africa were screened for lipase activity on tributyrin and Tween 80. Eight strains were selected and the tributyrin and Tween 80 assays were repeated by monitoring lipase activity over a seven-day period. The selected strains were also assayed for their activity toward p-nitrophenyl palmitate. Ophiostoma piliferum Cartapip 58™ and Phanerochaete chrysosporium BKM-F-1767, two strains known for respectively their biodepitching and biopulping ability, were' used as controls. A few of the strains compared well and even outperformed the control strains, indicating their potential for use in pitch control. The effect of pretreatment with the eight selected fungal strains on E. grandis wood- and pulp extractives was determined. Cartapip 58™ and P. chrysosporium BKM-F-1767 were used as control strains. Several of the strains compared well to the control strains in their ability to reduce the triglyceride content of wood extract. The South African isolate, white-rot fungus Phanerochaete psuedomagnoliae nom. prov., reduced triglyceride content significantly. Consequently it can act as an agent for both biopulping and biodepitching. The treated wood samples had a lower triglyceride content than the sterile controls. Consequently more triglycerides would be released into process waters by the sterile controls than the treated samples. The effect of commerciallipases on deposited brown stock pulp extract was also evaluated. The lipases did not reduce the triglyceride content of the deposited extract. The addition of lipases in pulping and bleaching processes would therefore not affect already deposited pitch.
AFRIKAANSE OPSOMMING: Die ekstrakstowwe van hout veroorsaak dikwels 'n neerslag tydens verpulping. Gedurende verpulping en bleiking kom ekstrakstowwe van die hout enpulp vry en kleef aan keramiek- en metaalonderdele. Gevolglik benadeel dié neerslag produkkwaliteit en produksietempo. Dit verlaag die effektiwiteit van pulpwas, sifting, sentrifugale skoonmaakprosesse en suiwering, en kan die werkverrigting van papiermasjiene ontwrig. Die neerslag kan ook later los breek en kolletjies op die finale produk veroorsaak. Verskeie meganismes kan die neerslag veroorsaak. Hidrodinamiese of meganiese wrywing kan die kolloïdale ekstrakstofemulsie destabiliseer en sodoende die ekstrakstof laat konglomereer en neerslaan. Op soortgelyke wyse veroorsaak skielike temperatuurverlaging en/of pH-skokke en/of die toevoeging van ione in varswater om waterhardheid te beheer ook die neerslag deur die kolloïdale ekstrakstofemulsie te destabiliseer. Anorganiese sout soos kalsiumkarbonaat kan neerslagvorming kataliseer omdat dit optree as bousteen vir die klewerige, sementagtige ekstrakstowwe. Kalsiumione in die proseswater kan ook reageer met vetsure om onoplosbare, klewerige kalsiumsepe te vorm. Dit is bewys dat trigliseriede een van die hoofoorsake is in die vorming van die neerslag tydens kraft verpulpingen bleikingprosesse. Om die neerslagreaksie wat met die kraft verpulping en bleiking van Eucalyptus spp. geassosieer word, beter te verstaan, is verskeie analises op hout- en pulpekstrakte asook die neerslag van 'n Suid-Afrikaanse kraft verpulpingsaanleg uitgevoer. Hoë molekulêre massa (nie-vlugtige) stowwe het 'n groot gedeelte van die ekstrakte en neerslag uitgemaak. Ongeveer 40% van die vlugtige Eucalyptus grand is ekstrak bestaan uit ~-sitosterol met vet sure (22.8%) en trigliseriede (15.5%) wat ook aansienlike bydraes lewer. Vetsuuramiede verteenwoordig 'n beduidende komponent van pulpekstrak by die laaste stadiums van bleiking. Die amiede het 38.3% en trigliseriede 10.1%tot die vlugtige fraksie van die neerslag bygedra. Lipases hidroliseer trigliseriede en kan dus help om neerslagprobleme te voorkom. Gevolglik is 381 filamentagtige fungi geïsoleer uit inheemse en kommersiële woude van Suid-Afrika en hul lipase-aktiwiteit op tributyrin en Tween 80 geëvalueer. Agt rasse is geselekteer en die tributyrin en Tween 80 toetse is herhaal deur lipase-aktiwiteit oor 'n sewe-dag periode te monitor. Die geselekteerde rasse is ook getoets vir lipase-aktiwiteit met p-nitrofenielpalmitaat. Ophiostoma piliferum Cartapip 58™ en Phanerochaete chrysosporium BKM-F-1767, twee rasse wat daarvoor bekend staan vir onderskeidelik hul vermoë om houtekstrakstowwe te verminder en te bioverpulp, is as kontroles gebruik. 'n Paar van die geselekteerde rasse het goed vergelyk en selfs beter presteer as die kontrolerasse; 'n aanduiding van hul potensiaal om neerslagreaksies te beheer. Die effek van voorafbehandeling met die agt geselekteerde fungi rasse op E. grandis hout- en pulpekstrak is vasgestel. Cartapip 58™ en P. chrysosporium BKM-F-1767 is gebruik as kontrolerasse. Verskeie rasse het goed vergelyk met die kontrolerasse in hul vermoë om die trigliseriedinhoud van die houtekstrak te verlaag. Die Suid-Afrikaanse isolaat, witverrottingswam Phanerochaete pseudomagnoliae nom. prov., het ook die trigliseried inhoud beduidend verminder. Gevolglik sou dit as 'n middel kon dien vir beide neerslagvoorkoming en bioverpulping. Die trigliseriedinhoud van die behandelde monsters was laer as dié van steriele kontroles. Gevolglik sal meer trigliseriede in proseswater vrygestel word deur die steriele kontroles as die behandelde monsters. Die effek van kommersiële lipases op ongebleikte kraft pulpekstrakneerslag is ook geëvalueer. Omdat lipases nie die trigliseriedinhoud van die neerslag kon verlaag nie sal die gebruik van lipases dus nie die ekstrakstofneerslag in verpulpings- en bleikingsprosesse beïnvloed nie.

Gasification of black liquor is an alternative to the combustion of black liquor, which is currently the dominant form of chemical recovery in the paper industry. Gasification of black liquor offers the possibility of higher thermal efficiencies than combustion, reducing manufacturing costs and creating new revenue streams through a forest biorefinery. Pressurizing the gasification reactor further enhances the efficiency advantage of gasification over combustion. This study uses a pressurized entrained flow reactor (PEFR) to study black liquor gasification behavior under pressures, temperatures, and heating rates similar to those of next-generation high-temperature black liquor gasifiers. The effects of pressure on black liquor char morphology, gasification rates, pyrolysis carbon yields, and sulfur phase distribution were studied. These characteristics were investigated in three main groups of experiments at 900oC: pyrolysis (100% N2), gasification with constant partial pressure (0.25 bar H2O and 0.50 bar CO2), and gasification with constant mole fraction (10% CO2, 2% H2O, 1.7% CO, 0.3% H2), under five, ten, and fifteen bar total pressure. It was found that pressure had an impact on the char physical characteristics immediately after the char entered the reactor. Increasing pressure had the effect of decreasing the porosity of the chars. Pressure also affected particle destruction and reagglomeration mechanisms. Surface areas of gasification chars decreased with increasing pressures, but only at low carbon conversions. The rate of carbon conversion in gasification was shown to be a function of the gas composition near the particle, with higher levels of inhibiting gases slowing carbon conversion. The same phenomenon of product gas inhibition observed in gasification was used to explain carbon conversions in pyrolysis reactions. Sulfur distribution between condensed and gas phases was unaffected by increasing total pressure in the residence times investigated. Significant amounts of sulfur are lost during initial devolatilization. With water present this gas phase sulfur forms H2S and did not return to the condensed phase.

Mise en uvre d'un procede de delignification utilisant un reacteur a lit fixe et faible temps de passage, concernant plus particulierement le traitement du bois de peuplier par les procedes a la soude, soude-anthraquinone et kraft. Dans chaque cas, l'etude cinetique fait apparaitre trois regimes distincts et confirme le role essentiel du ph. L'addition de na#2s et/ou de aq ameliore remarquablement la cinetique et la selectivite de la delignification. L'analyse des procedes montre que les reactions de recondensation de la lignine sur les fibres sont peu prononcees. Ceci permet d'obtenir plus rapidement des pates mieux delignifiees et moins degradees qu'en reacteur clos. Ce phenomene est confirme par la caracterisation chimique, spectrometrique et macromoleculaire des lignines recuperees en cours de traitement. Les resultats mettent en evidence des reactions d'hydrolyse et de degradation diverses. Ils confirment le role selectif de na#2s. Il apparait que, quel que soit le type de delignification alcaline, ces reactions de degradation sont les memes

Submitted in the fulfillment of the requirements for the degree of Master of Technology, Durban University of Technology, Durban, South Africa, 2011.
The main objective of this study was to evaluate the feasibility of conversion of crude tall oil and tall oil fatty acids into biodiesel. During the Kraft pulping process, Crude Tall Oil originates as tall oil soap, which is separated from recovered black liquor. The soap is then converted to Crude Tall Oil by acidulation with sulphuric acid. The Crude Tall Oil is then fractionated by distillation to produce tall oil fatty acids (TOFA), rosin and pitch. There were a number of conversional methods that were considered but proved to be inappropriate. A base-catalyzed method was inappropriate with due to the high free fatty acid content on the feedstock, and the acid-base catalyzed method was inappropriate due to the long reaction times and large excess of methanol required. An enzyme based conversion method was also found to be inappropriate because of the high price attached to the purchasing of the enzymes and the stability of the enzyme. A procedure of choice was the supercritical methanol treatment, due to the fact that it requires no separate catalyst. A procedure was developed for both the feedstocks (i.e. crude tall oil and tall oil fatty acids) using the supercritical methanol treatment. In supercritical methanol treatment, feedstock and methanol were charged to a reactor and were subjected to temperatures and pressures beyond the critical point of methanol (Tc = 240 °C, Pc = 35 bar). The maximum biodiesel yield obtained from Crude tall oil was 66% and was 81% for the tall oil fatty acids that was produced in a single stage process. The temperature and methanol to feedstock ratio effects was also found to yield a maximum biodiesel yield at 325°C and 40:1 respectively. A 20 minutes reaction time was found to be appropriate for the maximum yield of biodiesel. The final biodiesel produced was also evaluated against a commercial biodiesel product and its parameters measured. The biodiesel resulting from the tall oil fatty acid yielded parameters that were acceptable according to ASTM D6751 specifications for biodiesel. The biodiesel produced from the crude tall oil did not meet the ASTM D6751 specification, and this was mostly attributed to the presence of unsaponifiables which hindered the conversion of oil into biodiesel.
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