Influence of chip presteaming conditions on kraft pulp composition and properties (original) (raw)
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O PAPEL, 2011
Two treatments, an induced autohydrolysis and an acid hydrolysis, were applied to Eucalyptus globulus wood chips prior to the cooking stage to extract the hemicellulosic fraction that otherwise would be dissolved in the black liquor and burnt in the recovery boiler. The obtained hydrolysates, rich in xylose, were detoxified by overliming and used for ethanolic fermentation. Impacts of each wood pretreatment on the kraft cooking process and on the quality of the produced pulp were evaluated. Both pretreatments promoted an increase in the cooking rate, but had a negative effect on pulp quality and overall yield. Autohydrolysis showed a less negative influence. However, autohydrolysates led to lower values of ethanol concentration, productivity and yield compared to the fermentation of acid hydrolysates. To get more profit from the autohydrolysates they were also submitted to secondary acid hydrolysis and vacuum evaporation processes. Overliming followed by evaporation (with a concentration factor of 3) gave better results than the inverse method. This procedure raised the fermentable sugar content and led to the production of ethanol with a concentration of ~10 g eth L -1 (productivity of 0.23 g eth L -1 h -1 and yield of 0.50 g eth g xyl eq -1 ) which compares well with the results obtained with the fermentation of acid hydrolysates.
EFFECTS OF HEMICELLULOSE STABILISATION AND RAW MATERIAL ON THE BEATABILITY OF SOFTWOOD KRAFT PULPS
2000
A linear correlation has been found between the beatability and the hemicellulose content of Scandinavian softwood laboratory pulps. In addition to increasing yield, especially of hemicellulose, additives like polysulfide and/or anthraquinone can thus improve the beatability of softwood pulps. At similar hemicellulose content, pulps manufactured from Norway spruce (Picea abies) is still better than pulps manufactured from Scots pine (Pinus
Influence of Green Liquor and Hot Water Pre- Extraction of Hardwoods on Kraft Pulping
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 % Na 2O 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 chip...
Study of chipper type influence on chip quality and unbleached softwood kraft pulp characteristics
2008
The study was conducted to define chip quality characteristics (chip distribution) variation influence on kraft cooking process selectivity, fiber fundamental properties and pulp strength characteristics. To estimate the chip geometry contribution laboratory cookings were held using chips produced by two types of chippers: traditional chipper "Norman-66" with inclined feeding and modern chipper "HHQ 11-XL-16" with horizontal feeding. Chip distribution, cooking temperature, alkali demand and final temperature standing were taken as variation factors.
The method of increasing of pulp yield with kraft cooking
Digest of Technical Papers. PPC-2003. 14th IEEE International Pulsed Power Conference (IEEE Cat. No.03CH37472), 2003
The increasing of pulp yield in cooking process is very important for pulp-paper industry. The modified kraft cooking, such as polisulfide process, is one of the directions in increasing of pulp yield.
Bioresources, 2022
The uniformity of pulp and the amount of rejects are influenced by many factors, but impregnation can be the most important. The opportunities for improving impregnation of kraft white liquor start in description of the parameters affecting the process. The first parameter is the chip itself (its basic density, moisture, and pH) and the second is the process parameters set by the technological possibilities of the digester. During outside storage, the chips deteriorate via the fungal stains, brittleness, and high acidity. The moisture content also decreases. Understanding the relationships of chip parameters in the impregnation step and amount of rejects requires the assignment of effective alkali consumption. This study shows the effects of selected physical parameters, such as bulk density, moisture, and pH, of spruce chips on alkali consumption during impregnation step of a Super Batch process.
Effect of hemicellulose content in kraft brownstock on oxygen delignification
Kraft pulping experiments were performed on mixed Northeastern hardwood chips to investigate the effect of hemicellulose content on the response of brownstock pulps to medium consistency oxygen delignification. High levels of anthraquinone were used to produce pulps with high pulp yield which coincided with high hemicellulose content brought about by elevated levels of xylan.
On the Recovery of Hemicellulose Before Kraft Pulping
Bioresources, 2012
To assess the feasibility of implementing hemicellulose recovery stages in kraft mills, Eucalyptus globulus wood samples were subjected to aqueous treatments with hot, compressed water (autohydrolysis processing) to achieve partial dissolution of xylan. Autohydrolyzed solids were subjected to kraft pulping under selected conditions to yield a pulp of low kappa number, and to an optimized TCF bleaching sequence made up of three stages (alkaline oxygen delignification, chelating, and pressurized hydrogen peroxide), with minimized additions of pulping and bleaching chemicals. The final product had a relatively low kappa number (1.4), 641 mL/g ISO intrinsic viscosity, and 86.4% brightness.