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Measurement of forces in a low consistency refinerPrairie, Brett Cameron 30 November 2009 (has links)
A piezo-ceramic sensor was developed to measure normal and tangential shear forces applied to a bar at one location in the refining zone of a Sunds Defibrator Conflo® JC-00 refiner. Testing was completed at the Pulp and Paper Research Institute of Canada in Vancouver. BC using CTMP pulp with a stock consistency of 3.15%. Distributions have been determined for peak normal and shear forces. peak coefficient of friction. shear work. and shear lead. These distributions were analysed to assess possible correlations with specific edge load. Force magnitudes were found to increase with an increase in specific edge load. The peak coefficient of friction was calculated that ranged from 0.13 to 0.16. Both the normal and shear force magnitudes varied by as much as a factor of 3, due to rotor out-of-tram of only 0.06 mm. These distributions could provide greater insight to the mechanisms responsible for fibre development in papermaking and thus "In Process" control of various refiner conditions.
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Factors Affecting the Resistivity of Recovery Boiler Precipitator AshSretenovic, Ivan 16 August 2012 (has links)
Electrostatic precipitators (ESPs) are commonly used to control particulate emissions from recovery boilers in the kraft pulping process. The electrical resistivity of entrained particulates is known to affect the performance of ESPs. There are many factors which influence resistivity of particulate matter, such as field strength, time of exposure, particle size, particle composition, temperature, and flue gas composition. The objective of this study was to identify the ideal operating conditions and dust particle characteristics which lead to an optimum dust resistivity and maximized ESP efficiency. The effect of these factors was examined through a variety of experimental and analytical techniques on kraft recovery boiler ash samples and synthetically prepared samples. It was concluded that particle composition, gas composition, and ambient temperature had the most pronounced effects, while the other factors, such as field strength and exposure time, had a smaller impact on particle resistivity.
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Factors Affecting the Resistivity of Recovery Boiler Precipitator AshSretenovic, Ivan 16 August 2012 (has links)
Electrostatic precipitators (ESPs) are commonly used to control particulate emissions from recovery boilers in the kraft pulping process. The electrical resistivity of entrained particulates is known to affect the performance of ESPs. There are many factors which influence resistivity of particulate matter, such as field strength, time of exposure, particle size, particle composition, temperature, and flue gas composition. The objective of this study was to identify the ideal operating conditions and dust particle characteristics which lead to an optimum dust resistivity and maximized ESP efficiency. The effect of these factors was examined through a variety of experimental and analytical techniques on kraft recovery boiler ash samples and synthetically prepared samples. It was concluded that particle composition, gas composition, and ambient temperature had the most pronounced effects, while the other factors, such as field strength and exposure time, had a smaller impact on particle resistivity.
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Mechanisms of pulp loss in flotation deinking /Ajersch, Michael. January 1997 (has links)
Thesis (Ph.D) -- McMaster University, 1997. / Includes bibliographical references. Also available via World Wide Web.
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Control of an acid sulphite batch pulp digester based on a fundamental process modelKilian, André. January 1999 (has links)
Thesis (M.Eng.(Control Engineering))--University of Pretoria, 1999. / Summaries in Afrikaans and English. Includes bibliographical references (leaves 196-199).
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Détoxification d'un effluent de pâte chimico-thermomécanique par voie anaérobie /Patoine, Alain, January 1992 (has links)
Mémoire (M.Ress.Renouv.)-- Université du Québec à Chicoutimi, 1992. / Résumé disponible sur Internet. CaQCU Bibliogr.: f. [67]-71. Document électronique également accessible en format PDF. CaQCU
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Alkaline pulping deadload reduction studies in chemical recovery system /Chandra, Yusup. January 2004 (has links) (PDF)
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.
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Implementation and performance analysis of a model-based controller on a batch pulp digesterSandrock, Carl. January 2003 (has links)
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.
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Thermomechanical pulping (TMP), chemithermomechanical pulping (CTMP) and biothermomechanical pulping (BTMP) of bugweed (Solanum mauritianum) and Pinus PatulaVena, P. F. 12 1900 (has links)
Thesis (MSc (Forest and Wood Science))—University of Stellenbosch, 2005. / In this study the mechanical pulping characteristics of Solanum mauritianum (Bugweed) were investigated using Thermomechanical (TMP), Chemithermomechanical (CTMP) and Biothermomechanical (BTMP) methods. Results were compared with those obtained from Pinus patula pulps treated under similar conditions. In the TMP pulping trials, the pretreatment of wood chips involved soaking of chips in water overnight prior to refining. The CTMP pulping trials involved first the impregnation of wood chips with 3% sodium sulfite and 2% sodium carbonate solution for 24 hours before refining. Coculture of hemicellulolytic Aspergillus flavipes and ligninolytic Pycnoporus sanguineus were inoculated to the wood chips in BTMP trials, to enhance wood chip breakdown.
Solanum mauritianum (Bugweed) wood chips produced the highest pulp yields and less shive content compared to Pinus patula treated under similar pulping conditions. This could be ascribed to easier fibre separation and lesser fibre damage, as well as its lower extractive content. Results showed that the pretreatment of wood chips prior to TMP pulping increased paper strength properties compared to the pulp prepared from the untreated wood chips. Chemically pretreated wood chips consumed a larger amount of refining energy. With regard to brightness levels, handsheets from Pinus patula pulps recorded lower brightness values than those from Bugweed pulps. This was related to the lighter colour of the Bugweed wood chips and the higher extractive content of Pinus patula. The high brightness level of the CTMP pulps could be attributed to a modification of the lignin chromophores and the extractive removal, which contributed to a lower absorption coefficient of the pulp. Handsheets from BTMP pulps showed a reduction in brightness compared to the TMP and CTMP pulps. This was caused by the darkening of the wood chips during the fungal incubation period. Pulp and paper properties of Bugweed compared favourably to those results published for other hardwoods. The results of this study suggest possibilities for using Bugweed in high yield pulping processes.
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Enzymatic pitch control in the kraft pulping and bleaching of Eucalyptus spp.Scheepers, Gerhardus C. (Gerhardus Coenraad) 03 1900 (has links)
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.
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