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Pressurised hot water extraction of wood : three wood species prior to pulpingMji, N. (Ntuthuzelo) 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2005. / No english abstract available. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van warm water uitloging van
houtspaanders by hoë temperature en onder hoë druk voor alkaliese verpulping te
ondersoek. Warm water uitloging van houtspaanders onder druk voor alkaliese
verpulping was baie belowend, aangesien dit ekstrakstowwe verwyder het wat andersins
verteringschemikalieë sou opgebruik het en ook verbertede verpulpingstoestande
meegebring het. Gedurende uitloging het die houtstruktuur verander agv die verwydering
van die ekstrakstowwe. Dit het veroorsaak dat die houtstruktuur meer toeganglik geword
het, en dit het gelei tot 'n verbeterde diffusie van die kookloog. Die versnelde
kookloogdiffusie het 'n verbeterde en meer gelykmatige delignifikasie meegebring.
Warm water uitloging by verhoogde druk is ondersoek vir drie houtsoorte nl. Eucalyptus
grandis, Acacia mearnsii en Pinus patuia. 'n Twee-uur en 'n een-uur uitlogingstyd van
die houtspaanders voorafgaande Kraft en soda-AQ verpulping is ondersoek.Vergelyk met
'n een-uur uitloging is daar gevind dat die twee-uur uitloging van die houtspaanders te
drasties was, met 'n gevolg van 'n vermindering in pulpopbrengs, vesellengte en
pulpsterkte. Die verlaging III pulpsterkte kon toegeskryf word aan
polisaggariedafbreking. Die een-uur uitloging het 'n hoër opbrengs opgelewer as beide
die kontrole (nie uitgeloogde houspaanders) en die twee-uur uitgeloogde houtspaanders.
Die een-uur uitlogingsperiode het besonder goeie verpulpingsresultate vir die ekstrakstofryke
Acacia mearnsii houtspaanders getoon, met 'n bykomstige verbetering in
pulpsterkte eienskappe.
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Gas hydrodynamics and mass transfer in low- and medium-consistency pulp suspensions in a retention towerIshkintana, Linda Kate 11 1900 (has links)
In the pulp and paper industry, the interaction between the gas, liquid, and solid phases occurring in various unit operations is often not clearly understood. Such multi-phase operations include flotation deinking (a separation process of paper fibres in the recycling process) as well as the delignification and bleaching operations in the kraft pulping process. Much of the design, operation, and optimization of such processing equipment are dependent upon past experience as well as trial-and-error methodologies.
Pulp fibre suspensions possess a complex and unique rheology. The unpredictability of the behaviour of pulp suspensions at any given mass concentration is due to the bonding between the fibres resulting in network formation (which depends on suspension consistency) with this interaction creating complexity in fluid flow in various unit operations.
This thesis describes the gas hydrodynamic behaviour and gas-liquid mass transfer characteristic in low- and medium-consistency pulp suspensions in batch operation. First, the hydrodynamic behaviour of the gas phase (air) in water and pulp suspensions having mass concentrations up to Cm = 7% is examined by visually observing and recording the bubble shape, size, and rise velocity in a rectangular channel. Results are obtained using a high-speed video camera. Second, the hydrodynamic behaviour is described in terms of the gas holdup along with axial and radial gas phase distributions in water and kraft pulp suspensions having mass concentrations between Cm = 0.5 and 9% in a batch-operated cylindrical bubble column. The gas holdup results are compared using three methods: the suspension height method, the pressure difference method, and the electrical resistance tomography (ERT) method. Finally, the volumetric gas-liquid mass transfer characteristic of air in water and kraft pulp suspensions having mass concentrations up to Cm = 4% is examined in the same bubble column in batch-operation using a dissolved oxygen probe.
Experimental results were comparable to that in literature for water and for pulp fibre suspensions having Cm < 2%. The presence of fibres had a significant effect on the gas holdup and mass transfer characteristic with results providing insight on the limitations that exist in industrial pulp unit operations. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
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Paper tensile properties as determined by fibre origin in the coniferous wood matrixSun, Bernard Ching-Huey January 1970 (has links)
This study examines the hypothesis that coniferous wood fibre origin is maintained even when purified pulps are subjected to severe mechanical (beating) and chemical (decrystallizing) treatments.
Four to five intra-incremental sulphate pulps obtained from each of three species, eastern larch (Larix lariaina (Duroi) K. Koch), Douglas fir (Pseudotsuga menziessii (Mirb.) Franco) and balsam fir (Abies balsamea (L.) Mill), were purified and machined to one or three levels EL (170 ± 45 ml Csf), DF (615 + 90 ml Csf; 328 + 43 ml Csf; 168 ± 62 ml Csf) and BF (190 + 30 ml Csf). Thereafter, cellulose supermolecular structures were altered by monoethylamine swelling, with changes (48 ± 2% vs. 68 ± 2%) quantified as fibre crystallinity index measured by X-ray diffractometry. Paper sheet apparent densities and tensile parameters (maximum strength, "stretch," modulus of elasticity and rupture energy) were determined. Fibre surface areas and sheet bonded states were estimated by light scattering coefficient measurements.
The effects of wood origin on paper sheet physical-mechanical properties reported by other researchers were reaffirmed in this study, with all factors decreasing progressively across growth increments. The differences of wood intra-incremental, as well as species origins, were not removed by conventional pulping and papermaking processes, or additional treatments such as severe beating or major alteration of the basic cellulose structures as practiced in the study.
Paper sheet tensile properties were related directly to sheet apparent density. Correlation coefficients as high as 0.979 and 0.989 were obtained for 00% and 82% monoethylamine decrystallized fibre sheets, respectively. Sheet density was inversely related to wood specific gravity
and was found to be independent of wood species, degree of beating and decrystallization treatments.
It is shown that fibre bonding potential is not the only factor influencing paper sheet strength. Intrafibre characteristics, such as cellulose supermolecular structures, have a highly significant effect on paper sheet strength as well.
In addition, specific energy of "bond failure" (irreversible energy consumed per unit sheet surface formed as result of tensile straining)
was higher for earlywood than for latewood sheets. This energy quantity
depends on beating degree and differs according to species, as well as intra-incremental origin.
The paper sheet light scattering coefficient (L.S.C.)-density relationship
also depended on wood fibre origin. Earlywood sheet L.S.C. decreased with increased beating and sheet density, but latewood sheet L.S.C. remained almost unaffected. This observation explains why whole-wood fibre sheet L.S.C.-density relationships vary with pulp types as recorded in the literature. / Forestry, Faculty of / Graduate
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The economic outlook for the woodpulp industry in British ColumbiaWood, William Fordham Johnson January 1966 (has links)
The Honourable Mr. Ralph Loffmark, British Columbia's Minister of Trade and Commerce, has taken the position that demand for woodpulp will greatly exceed the supply during the next five years. On the other hand, leaders of British Columbia's pulp and paper industry fear that a large surplus of pulp is inevitable. In this thesis, the difference of opinion was examined by forecasting demand for paper and paperboard for the period of 1965 to 1975. From this estimate was derived the expected requirements for chemical pulp and bleached sulphate market pulp for the same period. The demand for bleached sulphate was then compared with the potential supply, leading to the judgement that a surplus condition will exist. Finally, the principal factors which would affect the financial outcome for an independent bleached sulphate pulp mill were analyzed. The conclusion was reached that an independent firm would be profitable in spite of the anticipated surplus. / Business, Sauder School of / Graduate
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Detoxification of bleached kraft mill effluents by foam separationNg, Kong Seng January 1977 (has links)
Foam separation has been successfully developed on a 4-1 laboratory column, an 80-1 field column installation and a 6000 gal pilot plant trough type system as a novel process for detoxifying bleached kraft mill effluents.
Toxic surface active materials such as resin and unsaturated fatty acids collect at the gas-liquid interface of rising air bubbles and concentrate
in the foam. The highly toxic collapsed foam represents 1-2% by volume of the influent and is subsequently detoxified by biological treatment. Process parameters controlling detoxification efficiency are pH, gas-liquid interfacial area, initial toxicity level and mode of operation. The gas-liquid interfacial area and pH are of utmost importance.
For a typical effluent with MST of 3-4 hr, approximately 20-2
30 m²/l of interfacial area given to an effluent at pH > 7.0 are required for detoxification.
Foam separation is universally applicable and reliable for detoxifying
kraft whole mill effluent. Over 80% of 205 samples from 10 Canadian mills were detoxified. A 1 gal/min, one and two stage continuous
flow systems detoxified over 90% of samples at pH 8 and 1-2 hr retention time over 80 days of operation period.
Study of detoxification mechanism indicated that foam fractionation accounts for 77.5% of detoxification, volatization for 5.4% and unidentified
mechanisms for 17.1%. Depending on the mode of operation, up to 5% of effluent volume was discharged as foam. The foam volume could be reduced to < 2% by increasing foam retention time and enhancing internal
reflux. Collapsed foam was readily detoxified by a biodisc or aerated lagoon process.
In addition to detoxification, foam separation removed 20-60% of suspended solids, 66% resin acids, 12% B0D5 (10% TOC), 8% color and 80% foaming tendency. Suspended solids removal could be increased to 88% if an expensive dissolved air system were used for bubble generation.
Commercially available equipment for foam generation and foam breaking was reviewed. Jet aerators and turbine systems were assessed as most suitable for commercial application. Pilot plant evaluation of this equipment indicated that reliable and consistent operation could be obtained. The results were used to establish empirical formulae for use in process scale up.
During a 4 month continuous flow study, approximately 5-7 m²/l of gas-liquid interfacial area was provided to detoxify 80-100 gal/min of mill A effluent with MST of 6-10 hr. The detoxification success rate of a large number of samples increased from 50 to 86 and to 100% as the operation changed from 1 to 2 to 3 stages. The foam produced by the pilot plant was collapsed by a 12" diameter turbine at 100% efficiency all the time.
Costs of foam separation were examined for a projected 3 stage foam separation process, treating 25 M gal/day of bleached kraft whole mill effluent. Capital costs for pH control, foam generation, foam breaking and foam treatment were estimated at $2.26 M. Operating costs were estimated at $2.35/ton of pulp. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
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A histological study of gingival implants into the dental pulp and connective tissue of dogsHenry, Millicent, 1936- January 1967 (has links)
Indiana University-Purdue University Indianapolis (IUPUI)
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A critical clinical and television radiographic evaluation of indirect pulp cappingTraubman, Lionel January 1967 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to quantitatively measure the
rate and amount of calcification and secondary dentin deposition
below deep carious lesions of otherwise radiographically and
clinically sound teeth treated by calcium hydroxide - methyl
cellulose indirect pulp capping. Standardized, reproducible
serial radiographs of 50 treated young posterior teeth were
exposed preoperatively at one, three, six, nine and, in some
cases, 12 months. At the final appointment, the silver amalgam
restorations were removed and all residual caries was excavated.
A barium sulphate radiographic indicator paste identified the
pulpal floor level at the first and last appointments. Ninety
per cent of the teeth studied remained asymptomatic and were
not pulpally exposed. Television density and linear measurement
instrumentation was utilized to register calcification
changes, pulpal floor thicknesses, and secondary dentin deposition.
Following treatment, increased secondary dentin deposition and
Calcification activity, or sclerosis, was initiated.
Higher levels of calcification activity were related to increased
thickness of pulpal floors, but this dimension had little influence
on the total amount of reparative dentin formed. The
rate of reparative dentin formation was highest during the first
month and steadily diminished with time. Calcification activity
experienced a cyclical change, or "exchange," with an initial
activity peak. This was followed by an apparent, but temporary
mobilization of mineral content •out of the affected dentin.
With time, a steady rise in calcification level was observed.
Measurement of longitudinal records showed that apparent pulp
exposures can be avoided by allowing significant amounts of
protective secondary dentin to form, before complete caries
excavation.
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Evaluation of a new pulp capping agent: a clinical investigationNirschl, Ronald Francis January 1979 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This study compared clinical results of two calcium hydroxide bases
used in indirect pulp therapy on human teeth.
Thirty-four teeth with deep carious lesions were treated with indirect
pulp therapy. Eighteen teeth were treated with commercially available
Improved Dycal and 16 teeth were treated with an experimental calcium
hydroxide formula.
Evaluation was made at intervals of three and six months. After
three months, periapical and bitewing radiographs were made and the teeth
were examined clinically for signs of pulpal degeneration. At the six-month
evaluation, in addition to the radiographic and clinical examinations,
cavities were re-entered and the unsound residual dentin was removed to
ascertain the presence of a so1id dentinal base. Removal of all unsound
residual dentin without an exposure of the pulp, as well as the clinical
and radiographic examinations, were used to determine clinically successful
treatment.
In the experimental group 15 teeth were successfully treated; a
success rate of 94.4 percent. Seventeen teeth in the control group
demonstrated successful indirect pulp therapy; a success rate of 93.75 percent.
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The effect of formocresol and calcium hydroxide on the dental pulps of rhesus monkeysSpedding, Robert H., 1931- January 1963 (has links)
Indiana University-Purdue University Indianapolis (IUPUI)
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Displacement washing of wood pulpPoirier, Nicole A. January 1986 (has links)
No description available.
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