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Kappa Number (kappa + number)
Selected AbstractsEffect of xylanase on ozone bleaching kinetics and properties of Eucalyptus kraft pulpJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2003M Blanca Roncero Abstract Environmental pressure has led the pulp and paper industry to develop new technologies in order to reduce or suppress the presence of various pollutants in effluents from bleaching plants. One of the choices for this purpose is enzyme-based biotechnology. This study deals with the effect of using a xylanase-based enzymatic pretreatment, in a TCF (Totally Chlorine Free) sequence, on the properties of the resulting paper pulps. The hexenuronic acid content in the pulp and the physical properties of the paper were also studied. The performance of the xylanase was analysed through kinetic studies on ozone bleaching. The enzymatic pretreatment results in easier bleaching and delignification of the pulp, causing a bleach-boosting effect. The decreased consumption of reagent is related to a decreased content of hexenuronic groups. The physical properties of the treated pulp are similar to those of untreated pulps. Cellulose degradation, delignification and chromophores' removal show first-order kinetics. Enzyme pretreatment leads to differences between the kinetic constants of cellulose degradation and chromophores' removal, due to an increased accessibility to bleaching agents. The xylanase treatment leads to a lower floor kappa number (IK,) during the ozone stage. Copyright © 2003 Society of Chemical Industry [source] Delignification of Pinus taeda wood chips treated with Ceriporiopsis subvermispora for preparing high-yield kraft pulps,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2002Régis Mendonça Abstract Pinus taeda wood chips were treated with the white-rot fungus Ceriporiopsis subvermispora in 20-dm3 bioreactors for periods varying from 15 to 90 days. Decayed samples, non-inoculated controls and extractive-free wood samples were submitted to kraft pulping using 25% of sulfidity and different active alkali concentrations in the cooking liquor. Cooking reactions were carried out isothermally at 170,°C. Residual lignin contents of pulps prepared from biotreated wood chips were lower than those observed in pulps from the undecayed control. Delignification kinetic studies showed that the initial delignification phase was accelerated and shortened by the fungal pretreatment. At a cooking time fixed before the end of the bulk delignification phase, the fungal pretreatment provided pulps with significantly lower kappa numbers or pulps with a fixed kappa number were obtained by reducing the amount of active alkali added to the liquor. Pulps of kappa 80 were obtained both from the undecayed control cooked with 20.8% of active alkali and from the 15-day-biotreated sample cooked with only 15% of active alkali. The biopulping benefits were neither proportional to the extent of the biodelignification nor to the biological removal of some specific wood component. DFRC-determination (derivatization followed by reductive cleavage) of the amount of aryl,ether linkages in residual lignins of biotreated samples indicated an extensive depolymerization during the initial stages of biodegradation, which suggested that bio-depolymerized lignin was easily released during the first stages of cooking, resulting in a faster and shorter initial delignification phase. © 2002 Society of Chemical Industry [source] The Effect of Particle Size Distribution on Pressure Drop through Packed Beds of Cooked Wood ChipsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2005Quak Foo Lee Abstract The pressure drop of process liquors through columns of wood chips determines the operability, efficiency and control of both batch and continuous pulp digesters and the quality of the pulp produced from them. Pressure drop was measured through columns of industrial white spruce chips (produced with a chipping head-rig) as a function of the chip size distribution and the extent of delignification. Flow resistance depended on the porosity of the chip bed which was affected by the kappa number of the chips (which affected their flexibility) and chip size distribution, the compaction forces applied to the column, and the liquid superficial velocity. The chip beds were compressible and inelastic. Previous work from the literature using the Ergun equation to characterize pressure losses through chip beds is examined and compared with results of this work. La perte de charge des liqueurs de procédés dans des colonnes de copeaux de bois détermine l'opérabilité, l'efficacité et le contrôle des digesteurs de pâtes discontinus et continus, ainsi que la qualité de la pâte produite. La perte de charge a été mesurée dans des colonnes de copeaux d'épinette (produits avec une machine de fabrication de copeaux) en fonction de la distribution de taille des copeaux et du degré de délignification. La résistance à l'écoulement dépend de la porosité du lit de copeaux qui est influencée par le nombre de kappa des copeaux (qui influe sur leur flexibilité) et la distribution de taille des copeaux, les forces de compaction appliquées à la colonne ainsi que la vitesse de liquide superficielle. Les lits de copeaux sont compressibles et inélastiques. Un travail antérieur de la littérature scientifique faisant appel à l'équation d'Ergun pour caractériser les pertes de charge dans les lits de copeaux est examiné et comparé aux résultats du présent travail. [source] Delignification of Pinus taeda wood chips treated with Ceriporiopsis subvermispora for preparing high-yield kraft pulps,JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2002Régis Mendonça Abstract Pinus taeda wood chips were treated with the white-rot fungus Ceriporiopsis subvermispora in 20-dm3 bioreactors for periods varying from 15 to 90 days. Decayed samples, non-inoculated controls and extractive-free wood samples were submitted to kraft pulping using 25% of sulfidity and different active alkali concentrations in the cooking liquor. Cooking reactions were carried out isothermally at 170,°C. Residual lignin contents of pulps prepared from biotreated wood chips were lower than those observed in pulps from the undecayed control. Delignification kinetic studies showed that the initial delignification phase was accelerated and shortened by the fungal pretreatment. At a cooking time fixed before the end of the bulk delignification phase, the fungal pretreatment provided pulps with significantly lower kappa numbers or pulps with a fixed kappa number were obtained by reducing the amount of active alkali added to the liquor. Pulps of kappa 80 were obtained both from the undecayed control cooked with 20.8% of active alkali and from the 15-day-biotreated sample cooked with only 15% of active alkali. The biopulping benefits were neither proportional to the extent of the biodelignification nor to the biological removal of some specific wood component. DFRC-determination (derivatization followed by reductive cleavage) of the amount of aryl,ether linkages in residual lignins of biotreated samples indicated an extensive depolymerization during the initial stages of biodegradation, which suggested that bio-depolymerized lignin was easily released during the first stages of cooking, resulting in a faster and shorter initial delignification phase. © 2002 Society of Chemical Industry [source] | ||||||||||