19,543 research outputs found

    A Study of the Use of Borates in Semi-Chemical Pulping

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    The purpose of this project was to identify sodium metaborate as a pulping chemical in semi-chemical pulping with soda ash. The experimental design included four digester cooks with 0%, 10%, 20%, and 40% addition of.the borate compound. The resulting yields were 81. 3 %, 79. 2%, 77.4 %, and 7 4. 5% respectively. Therefore, under the definition of pulping, sodium metaborate was considered a pulping chemical. The pulps were mechanically refined. The resulting screened rejects increased with increasing borate addition. Handsheets were made and tested for strength and optical properties. The tensile and mull en strengths of the handsheets increased with addition of borates up to 20%, but degradation of the bonding properties occurred at high addition levels (40%). The tear strength increased dramatically (up to 24.1%) with the addition of borates to the pulping liquor. Brightness and visual color were slightly improved. The results indicate that the sodium metaborate was an effective pulping chemical with a tendency to be selective in delignification. Further work should be performed to compare the effect of substitution against conventional non-borate pulping, and possible changes in bleached pulp quality

    Variables Affecting Impregnation during Kraft Pulping

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    Introduction The purpose of this report was twofold. First, a pulping aid was evaluated for its effects on pulp properties. Then, the pulping aid was used in conjunction with a reduction in the times to temperature for several cooks, to see if the pulping aid could be used to reduce the total cooking time for kraft cooks. To gain some background as to how the pulping aid might affect the cook, variables affecting impregnation are presented and discussed

    A Study of the Feasibility of Using a Pulping Aid with Polysulfide Kraft Cooks

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    The purpose of this paper was to determine the feasibility of using a pulping aid with a polysulfide kraft cook. Since any change in an operation such as pulping must yield a product such that the quality is better or not appreciably reduced and at the same time must be economically acceptible, the feasibility was based on these factors. Tests were made on a standard kraft cook, a polysulfide cook, a cook using the pulping aid alone and a cook using the pulping aid with the polysulfides. From the work conducted, there were no significant changes in the physical and optical tests performed while at the same time, a slight increase in the yield over the standard kraft cook was noted

    Preliminary Investigation on Bamboo Pulping

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    A preliminary investigation on bamboo pulping by Semi-Keebra process reveals that a higher pulp yield than that obtained by most of the known methods of pulping bamboo can be attained by Semi-Keebra process.* The chemical requirement for pulping is lower than the conventional processes and the spent liquor also contains a higher per cent of solids. The pulp obtained by Semi-Keebra pulp would also require a considerable lesser time for obtaining the desired freeness value, resulting in lower power consumption for stock preparation, than that for the conventional sulphate bamboo pulp of bleachable grade. A comparison of the various hand-sheet properties of the two pulps show that all properties other than density and breaking length are, however, lower in the case of Semi-Keebra bamboo pulp. It is, however, hoped that further investigation on optimum condition of Semi-Keebra process for bamboo pulping would show some further improvement in the strength properties

    Ultrastructural characterization (morphological and topochemical) of wood pulp fibres

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    Different electron microscopy techniques including SEM (scanning electron microscopy), FE-SEM (field emission-scanning electron microscopy), TEM (transmission electron microscopy) and Immuno-gold TEM (immuno-gold transmission electron microscopy) were applied in order to gain a better understanding of the influence of the native softwood fibre cell wall ultrastructure including morphology and topochemistry (i.e. lignin and glucomannan distribution) during mechanical pulping. In thermomechanical pulp (TMP) processing, wood fibres undergo structural changes (cell wall delamination and fibrillation) that are regulated by the native fibre micro- and ultrastructure. In addition, novel information was obtained on the fibre cell wall architecture. In contrast, the stoneground wood (SGW) process inflicted severe damage to the fibre structure resulting in transverse and longitudinal fibre breakage. However, juvenile wood SGW fibres showed improved properties (strength and light scattering) compared to mature wood. Ultrastructural aspects of fibre processing and development explained the differences in physical properties observed. During the SGW process, the native morphological fibre cell wall ultrastructure and microfibrillar organization governed the manner of juvenile wood fibre development similar to TMP fibres. Ultrastructural studies on Norway spruce and Scots pine TMPs revealed fundamental features that governed the different behaviour exhibited by the two wood species. Specific ultrastructural characteristics of pine TMP fibre cell walls were explored in relation to both morphology and topochemistry and that regulating the different pine fibre development mechanisms compared to spruce. The negative behaviour shown by Scots pine during TMP processing was most likely attributable to the observed fibre development mechanism. Histochemical techniques were applied to study wood resin associated problems during mechanical and kraft pulping. Studies provided information on the spatial micro-morphological distribution/redistribution of lipophilic extractives that were visualized on single fibre and cell wall fractions. Results from histochemical staining and chemical analysis performed on Norway spruce and Scots pine TMPs showed that there were morphological and chemical differences in the redistribution of extractives between the two species. This may further contribute to the effects of extractives on pulp- and paper properties and processing. Localization of lipophilic birch wood extractives involved in pitch problems was performed using histochemical techniques. Correlated information from gas chromatography-mass spectrometry and specific staining methods gave details on how extractives are removed during processing as well as information on the mechanisms of removal

    The Pulping of Hardwood Sawdust by the Neutral Sulfite Semichemical Process for Use in Corrugating Medium

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    The need for using less expensive raw materials is ever increasing. Here the use of hardwood sawdust as one of these raw materials was investigated for use in Semichemical Corrugating Medium. It was found that 20 to 30% sawdust could be used in the furnish without a significant loss in sheet strength. It was also found that sawdust could be pulped either separately or combined with hardwood chips giving the same product quality. This was accomplished by either a regular neutral sulfite semichemical cook or by a vapor phase cook. The conventional disk refiner was found to do the best job of refining, when the plate clearance is very close. The use of 20 to 30% sawdust in the furnish could lead to a substantial cost savings, and would aid in pollution control in that it would end the disposal problem of the sawdust

    Determination of the permeability parameters of bagasse pulp from two different sugar extraction methods

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    The permeability, the specific surface area and the swelling factor have been determined for Australian bagasse pulp derived from bagasse from two different sugar extraction processes. The sugar extraction process was not found to affect the permeability of the pulp. The results for bagasse pulp are compared to those of eucalypt pulp, which is widely used in Australia for paper manufacture. The fibre length distribution showed a high fraction of small fibres in all of the bagasse pulp samples. Surprisingly, the permeability properties of the bagasse pulp samples were better than that that of eucalypt. It is presumed that this is due to the relatively large fraction of longer fibres in the bagasse pulp compared to the eucalypt pulp

    Kraft Smelt Solidification In A Fluidized Bed Reactor

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    An improved black liquor recovery system for use in a kraft pulping mill is provided. Molten kraft smelt from a black liquor recovery boiler or recovery system is fed into a fluidized bed reactor where it is cooled and solidified to form solid kraft smelt particles. The solid kraft smelt particles are then fed into a dissolving tank containing an aqueous solution to form a green liquor. The green liquor, after clarification, is treated with lime to form a white liquor containing the regenerated pulping chemicals. Waste steam is an especially preferred fluidizing gas for use in the fluidized bed reactor. This process provides improved energy recovery and process productivity, reduction in gaseous sulfur-containing emissions, reduction in landfilled wastes, and improved safety as compared to a conventional kraft smelt treatment process.Institute Of Paper Science And Technology, Inc

    Estimating Pure Diffusion Contributions in Alkaline Pulping Processes

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    A model that predicts isothermal alkali diffusion and reaction with acetyl groups in moist wood chips was derived and approximated. System parameters were estimated from unsteady-state experimental data. Simulation results reinforce the idea that the diffusion effect is not fully exploited in pulping processes. Traditionally, digestion is conducted at high temperature, where delignification reaction kinetics is enhanced and the reaction effect is predominant. This approach is being reviewed by modern industry since energy and environmental savings associated with low temperature operation might compensate for high-yield productivity. The concentration of alkali at the center of the chip is a measure of the completeness of wood deacetylation, which translates into the aptitude of the final product for pulping purposes. This concentration is predicted here from the solution to a pair of coupled ODE’s. Since alternatives combining both low and high-temperature processes are being studied, the results in this paper provide basic data for optimization analysis.Fil: Costanza, Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Costanza, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin

    Modeling of acetosolv pulping of oil palm fronds using response surface methodology and wavelet neural networks

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    Mathematical models based on response surface methodology (RSM) and wavelet neural networks (WNNs) in conjunction with a central composite design were developed in order to study the influence of pulping variables viz. acetic acid, temperature, time, and hydrochloric acid (catalyst) on the resulting pulp and paper properties (screened yield, kappa number, tensile and tear indices) during the acetosolv pulping of oil palm fronds. The performance analysis demonstrated the superiority of WNNs over RSM, in that the former reproduced the experimental results with percentage errors and mean squared errors between 3 and 8% and 0.0054–0.4514 respectively, which were much lower than those obtained by the RSM models with corresponding values of 12–40% and 0.0809–9.3044, further corroborating the goodness of fit of the WNNs models for simulating the acetosolv pulping of oil palm fronds. Based on this assessment, it validates the exceptional predictive ability of the WNNs in comparison to the RSM polynomial model
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