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Bratislava, Slovakia

Fiserova M.,Pulp and Paper Research Institute | Opalena E.,Pulp and Paper Research Institute
Wood Research | Year: 2014

Mixed hardwood chips were pre-extracted with green liquor and hot water prior to kraft pulping. The hot water extraction rate was higher by a factor of 1.3 compared to extraction with green liquor solution corresponding to 3 % Na2O charge on ODW. The total monosaccharides content in hydrolysed hot water extract was approximately twice higher than in hydrolysed green liquor extract at the same wood weight loss. The total kraft pulp yield decreased with increase of wood weight loss in pre-extraction. Pulp yield from green liquor pre-extracted chips was approximately the same as from original chips, while pulp yield from hot water pre-extracted chips at 10 % wood weight loss was by about 4 % lower. Addition of 0.1 % AQ in kraft pulping of pre-extracted chips increased total pulp yield by about 1%. Effective alkali charge in kraft pulping was reduced by 3 % in kraft pulping of green liquor pre-extracted chips, and by 1 % of hot water pre-extracted chips in comparison with original chips. The fibre characteristics of kraft pulps from green liquor pre-extracted chips at 10 % wood weight loss were only slightly lower as of kraft control pulps at the same kappa number. Fibre strength (FS number), length (L number) and bonding ability (B number) of pulps from hot water pre-extracted chips were lower by about 3 %, and by about 6 % respectively for bonding ability as fibre characteristics of kraft control pulps. Strength properties of pulps from pre-extracted chips showed similar dependencies. Tensile index of pulps from hot water pre-extracted chips decreased by about 12 %, burst index by about 15 % and tear index by about 5.5 % in comparison with kraft control pulps at a same kappa number. Source


Gigac J.,Pulp and Paper Research Institute | Fiserova M.,Pulp and Paper Research Institute
Cellulose Chemistry and Technology | Year: 2010

The influence of velocity gradient on the anisotropy of tensile stiffness index, tensile energy absorbance, tensile index, tear strength, tensile stiffness orientation, formation and curl of MG paper, as well as on the anisotropy of coating raw paper, was investigated. The maximum strength of MG paper was achieved in the 0.93-1.05 range of the jet-to-wire speed ratio. The best formation and the lowest curl with fibre orientation ±1.7° was achieved at a jet-to-wire speed ratio around 1.0, while CMT and SCT of fluting from a mixture of semi-chemical pulp and recovered fibres produced at a constant speed difference of the jet and wire are influenced by basis weight and semi-chemical pulp content. Source


Russ A.,Pulp and Paper Research Institute | Fiserova M.,Pulp and Paper Research Institute
Wood Research | Year: 2011

PCA analyses of hardwood NIR spectra showed high separation capabilities between ten various hardwood species. A series of measurements in various combinations were made with emphasis on standards and unknown samples drawn from the same lot and at around the same time span. We explain this approach to have a profound effect on the overall selectivity gain. Separation of hardwood species based on their density and classifying them according to the first PCA model led to classification success rate of 96.5%. Separation of all hardwood species into independent components led to lower success rate of 79%. Still, due to switched misidentification on the long run, only the total counts matter, not every single independent identification. Considering this, the selectivity success rises to 85%. Source


GlGAC J.,Pulp and Paper Research Institute | Flserova M.,Pulp and Paper Research Institute
Wood Research | Year: 2011

Near infrared spectroscopy offers monitoring of raw materials and paper properties. The data from near infrared spectroskopy (NIR) spectra can by scanned directly on the surface of the handsheets and commercial paper. Data of NIR spectra of semichemical fluting correlate with the filler content, Kappa number as well as directly with strength properties. Concora medium test (CMT), short span compression test (SCT) and burst strength of semichemical fluting may be controlled by semichemical pulp and recovered fibers content in the furnish. Increasing filler content by 1% results in decrease of CMT and SCT by 6.9-7.4%, and burst strength by 12%. Decreasing of strength may be compensated with increased semichemical pulp content in the furnish by around 9.5%. Source


Fiserova M.,Pulp and Paper Research Institute | Gigac J.,Pulp and Paper Research Institute
Wood Research | Year: 2015

Beech chips were pre-extracted with hot water and green liquor prior to kraft pulping. The total pulp yield of green liquor pre-extracted chips equivalent to 10% wood weight was approximately the same as that from the original chips, while the pulp yield from hot water pre-extracted chips was lower by 4.2%. Effective alkali charge was reduced by about 3% in kraft pulping of green liquor pre-extracted chips, and by about 1% in kraft pulping of hot water pre-extracted chips when compared with original chips. The pulps from pre-extracted chips demonstrated higher oxygen delignification efficiency and bleachability in the sequence D0(EO)D1D2 as in case of reference pulp from original chips. Consumption of chlorine dioxide in bleaching of pulps from hot water pre-extracted chips was lower by about 17% at 5% wood weight loss and 20.5% at 10% wood weight loss, while in case of pulp from green liquor pre-extracted chips it was lower only by about 5% at the same weight loss compared with the reference pulp. The overall yield of bleached pulps from hot water pre-extracted chips was lower by 1.2 and 3.1%, respectively (at 5 and 10% wood weight loss), of the pulp from green liquor pre-extracted chips by 0.2% in comparison with the reference pulp. Brightness reversion and beatability of bleached pulps from pre-extracted chips was lower as compared with the reference pulp, mainly in case of pulps from hot water pre-extracted chips. Tensile index of bleached pulps prepared from pre-extracted chips was lower, however tear index was higher in comparison with the bleached reference kraft pulp. © 2015, Statny Drevarsky Vyskumny Ustav. All rights reserved. Source

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