High-yield Pulp Research Articles

Coating

The ability of coating colours to obstruct ultraviolet (UV) radiation in the 300-385 nm region was examined with the aim of finding the best photo-stabilising formulation to inhibit discoloration of high-yield pulps. The influence of pigment type, bleaching of the pigments, pigment size, pigment size distribution, type of binder and addition of U-V-absorbing compounds were examined using a newly developed method for studying the reflectance and transmittance properties of thin coating layers. The pigment type and coat weight was found to be the most important factors for reducing the transmittance of UV-radiation. Kaolin clays were more effective than calcium carbonate pigments and are therefore a better coating pigment for photostability reasons. Bleaching of the pigments, resulted in an overall minor decrease in transmittance for both kaolin and ground calcium carbonate (GCC) pigments, especially at low coat weights. Bleaching of the pigments changed the particle size distribution somewhat, which probably alters the structure in the coating layer. Precipitated calcium carbonate (PCC) pigments have a higher UV-screening potential compared to GCC pigments and should therefore be a better choice among the calcium carbonates. It was further concluded that a narrow pigment size distribution was beneficial for reducing the amount of transmitted UV-radiation that reaches the base paper. Styrene butadiene latex and polyvinylpyrrolidone were better in reducing the transmittance in the UV-region than polyvinyl alcohol. Adding a fluorescent whitening agent to a coating colour decreased the transmittance in the UV-region when the pigment was of the GCC type, and increased the transmittance when kaolin pigment was used. Addition of titanium dioxide (3 parts) to a coating colour containing kaolin pigment blocked about 90% of the UV-radiation at a coat weight of 10 g/m(2), which is a common coat weight for a single coated paper. Another possibility is to double coat to increase the coat weight, which turns the transmittance factor closed to zero.

Dye Stability in the Presence of Hydrogen Peroxide and Its Implication for Using Dye in the HYP Manufacturing Process

Dye can be used to improve the optical properties of high-brightness market high yield pulp (HYP). In this study, we aimed to develop a practical method of using dye for this purpose. The dye performance in the presence of residual hydrogen peroxide at different pH levels was determined. At a pH of 7.5, the dye performance was not affected by the presence of hydrogen peroxide; at a pH of 8.5, the dye performance decreased slightly; at a pH of 9.5 or higher, the dye effectiveness decreased significantly. Based on these results, a method of using dye to decrease the yellowish hue of the HYP in its manufacturing process is proposed.

Path analysis for some fruit properties of passion fruit (Passiflora edulis f. flavicarpa Deg.)

In Colombia, no studies of path analysis to maximize the selection progress in passion fruit (Passiflora edulis f. flavicarpa Deg.) breeding have been reported. The objectives of this work were, therefore, to estimate two path analysis, one for weight per fruit and the other one for seed weight with aril under environmental conditions of the city of Monteria (Cordoba, Colombia). Genetic and phenotypic correlations obtained from the analysis of 400 fruits, collected from ten commercial lots, ten plants/lot and four fruits/plant (repetitions) were used under a hierarchical design with plants within lot and fruits within plant. Path analysis for weight per fruit showed that the direct effects were positive and 2.28 to 16.50 times, compared to indirect effects, when phenotypic correlations were used and, 1.93 to 6.90 times, when genetic correlations were employed. Peel weight was the variable that caused the largest direct effect on fruit weight. Path analysis for seed weight with aril, when the phenotypic or genetic correlations were used, showed that in fruit weight the direct effects were 3.2 to 80 times, compared to indirect effects. Fruit weight was the variable that showed the largest direct effect on seed weight with aril. The indirect effects through fruit weight were higher than the direct effects within the other variables. Fruit weight can be used as selection criteria for obtention of passion fruit cultivars of high pulp yield.

Refiner bleaching with magnesium hydroxide (Mg(OH)2) and hydrogen peroxide

Conventional bleaching of mechanical pulp with magnesium hydroxide and hydrogen peroxide shows significant economic benefits over bleaching with caustic soda and sodium silicate. Magnesium hydroxide [Mg(OH)2] bleaching generates lower effluent BOD/COD, higher pulp yield, lower anionic trash in the paper machines, reduced oxalate scaling and, in some cases, higher bulk. NORPAC has developed this bleaching process into a commercial, patented refiner bleaching technology. The excellent mixing, high temperature, and high consistency of the refining environment solubilize the magnesium hydroxide and provide an excellent bleach reactor with the addition of hydrogen peroxide. We have shown that by adding magnesium hydroxide into the refining system, refiner energy demand is reduced by 100-200 KW-hr/odmt and pulp strength is improved by 5-10%. In this paper, we describe NORPAC’s development of refiner bleaching, University of Maine lab refiner studies that support NORPAC’s work, and the additional benefits this technology provides to the mill.

Caracterização física de frutos e sementes de goiaba-da-costa-rica, produzidos em Manaus, Amazonas

A goiaba-da-costa-rica (Psidium friedrichsthalianum) é uma espécie frutífera nativa da América Central, cultivada em pomares domésticos. Visando a contribuir para o estabelecimento de técnicas de implantação e condução de plantios comerciais, foi realizada a caracterização física de frutos e sementes dessa espécie. Assim, foi verificado que o valor médio da massa fresca dos frutos foi 42,19 g, da polpa foi 39,72 g e das sementes foi 2,47g, com número em torno de 72,8 sementes por fruto. As sementes apresentam formato irregular, com valores médios de comprimento, largura e espessura de 4,29 mm, 4,11 mm e 2,68 mm, respectivamente. O fruto apresenta atributos favoráveis ao aproveitamento industrial, como o elevado rendimento em polpa (94%) e o formato globoso, levemente achatado nos pólos (valor da relação diâmetro longitudinal/diâmetro transversal = 0,83). O número elevado de sementes por fruto representa uma característica facilitadora à propagação e produção de mudas.

Effect of HYP fibers on bulk and surface roughness of wood-free paper

Two typical high-yield pulps (HYPs) used in wood-free paper grades, aspen HYP and birch HYP, were investigated for their effects on the bulk and surface roughness when substituting for hardwood kraft pulp in wood-free fine paper production. Results show that paper bulk, bending stiffness, and opacity can be improved significantly by both aspen and birch HYPs. Birch HYP has greater effects since birch fibers are larger and have higher coarseness. However, increasing HYP substitution rate increases paper surface roughness and decreases paper strength. Selection of HYP species and substitution rate should be made based on the needs of a specific paper grade.

Micromorphology and topochemistry of extractives in Scots pine and Norway spruce thermomechanical pulps: a cytochemical approach

Due to the increasing demand for Norway spruce as prime raw material for high-yield pulping, recent interest has focused on Scots pine as an alternative. However, the intrinsic properties of Scots pine, particularly the high amounts of extractives and the fiber properties, have been considered a disadvantage for thermomechanical pulping. A study was therefore conducted on the variations in the spatial distribution and redistribution of lipophilic extractives in spruce and pine wood and thermomechanical pulp (TMP) using cytochemical staining methods and chemical analysis. Chemical analyses showed chips from pine thinnings and sawmill slabs to contain three to five and two to three times, respectively, more extractives than found in spruce; in particular, the amount of triglycerides differed significantly. Results from staining techniques on the abundance and distribution of extractives (i.e., fats) between pine and spruce correlated with amounts detected by Fourier transform infrared spectroscopy and gel permeation chromatography. Cytochemical observations revealed information pertaining to species-specific distribution and redistribution of extractives among TMP fines and fibers and indicated the presence of a molecular film of extractives. Results indicate that the high concentrations of extractives in pine ray parenchyma are released during TMP processing and are redistributed onto the surfaces of the pulps, negatively affecting energy usage during primary refining.

Discoloration of mechanical and chemimechanical pulps: Influence of wood raw material, process and ageing method

The change in colour of a wide range of unbleached and bleached high-yield pulps was assessed using the CIELAB colour system. The influence of ageing method, pulping process and wood raw material i ...

Selection criteria of Eucalyptus globulus Labill. for production of chemithermomechanical pulps (CTMP)

Abstract Utilization of rapidly growing trees, such as eucalypts, for high-yield mechanical pulps is limited by low brightness owing to high contents of alkali and neutral extractives. Wood supply problems have developed in many areas of the world and new sources of high-yield pulp are needed. Ten Eucalyptus globulus trees were selected from two plantation sites to evaluate suitability as raw material for high-quality and high-yield pulp. Chemithermomechanical pulp (CTMP) was prepared from tree chips pretreated with sodium sulfite prior to refining. Characteristics of the CTMP were correlated with chemical and physical properties of the wood. There was a linear relationship between the content of alcohol-benzene extractives in wood and CTMP brightness. Klason lignin content in wood was inversely correlated with pulp sheet density, which is an important characteristic affecting the physical properties of pulp. The content of alkali extractives were inversely correlated with pulp yields. Color reversion was tested by exposing CTMP sheets to heat and light. Heat-induced yellowing of CTMP was of a low level and satisfied requirements for printing paper. The rate of yellowing was inversely associated with extractives and can be reduced by antioxidants.

Retention of Optical Brightening Agents (OBA) and their Brightening Efficiency on HYP‐Containing Paper Sheets

Optical brightening agents (OBA) or fluorescent whitening agents (FWA) are commonly used in the paper industry to improve the optical performance of paper products. The increased use of bleached chemi‐thermo‐mechanical pulp (BCTMP) or high‐yield pulp (HYP) in printing and writing paper grades has initiated research topics on the brightening efficiency of OBA on mechanical pulp‐containing furnishes. In this study, process parameters that may affect the retention of OBA were investigated, such as furnish composition, OBA charge, contacting time, water hardness, anionic trash, and fines in HYP. It was found that OBA had lower retention on HYP fibers than on bleached kraft pulp (BKP) fibers. Efforts were also made to understand the underlying mechanism.

Inhibition of light-induced brightness reversion of high-yield pulps: The UV-screening properties of coating layers containing kaolin or calcium carbonate pigments

A newly developed method making it possible to study the reflectance/transmittance of thin coating layers and to link this to the inhibition of the light-induced yellowing, was used to describe the ...

Pulping and papermaking properties of pati ( Typha)

Pati grown in the northern and eastern region of Bangladesh was submitted to chemical and morphological analysis. The results of general chemical analysis have evidenced the different relative abundance of holocellulose, lignin, extractive and ash. The eastern region pati had higher holocellulose and lower lignin and extractives than the northern region pati. Morphological properties of both regions pati were similar. Pulping of northern and eastern region pati was done with varying active alkali and cooking time at boiling temperature. The viscosity of pati pulp was increased with decreasing kappa number. Eastern region pati had higher pulp yield and lower kappa number than northern region pati. Initial SR value and strength properties of pati were higher than other nonwood. Eastern region pati showed higher strength properties than northern region pati.

Chemistry of Wheat-and Rice-Straw Based CTMP Black Liquor

"Chemithermomechanical pulping (CTMP) is an ideal process for producing highyield pulp from wheat and rice straw. It involves low concentrations of cooking chemicals and ultimately elutes black liquor with very low dissolved solids, high in organics and relatively low in inorganic components. This work characterizes the behavior of this liquor in the chemical recovery process. Chemical analysis of the black liquor reveals a high silica content, which indicates a risk of silica scaling in the concentrators. High proportions of total sodium (10.96% o.d. basis) and total sulfur (2.42% o.d. basis) in the inorganic components allow efficient recovery of both these key elements. High organics content helps to maintain low density and high viscosity. This high viscosity increases the solubility of sodium carbonate and sodium sulfate and decreases the risk of burkeite scaling in the concentrators, but increases the risk of heavy scaling after the recovery boiler. For these reasons, chemical recovery of this black liquor will be possible only through decreasing the high viscosities and designing the recovery boiler to generate high steam rates as a result of the high heating values of the relatively higher quantities of organic components."

Assessment of potential approaches to improve Eucalyptus globulus kraft pulping yield

AbstractThe main goal of this work is to study the potential approaches to improve polysaccharides retention during Eucalyptus globulus kraft pulping. The addition of anthraquinone to kraft pulping leads to the highest pulp yield while the addition of urea promotes lower depolymerization of polysaccharides (higher pulp viscosity), but does not have a significant effect on yield. The early interruption of kraft cooking followed by oxygen delignification is a reliable approach to increase pulp yield, particularly when pulping is interrupted at the end of the faster and more selective kinetic regime (bulk phase). Yield loss during oxygen delignification is considerably lower than that incurred in the last phase of kraft pulping. Pulping with OH−/HS− charge profiling, carried out with liquor injection in three different phases leads to a yield increase. However, this increase results from a lower total alkali charge applied when profiling pulping is compared to standard pulping conditions, rather than to alkali profiling. Standard kraft pulping with different active alkali (AA) charges demonstrated that this operational variable is determinant for pulp yield and viscosity. Pulping experiences with lower AA (14%) resulted in a higher and almost constant pulp viscosity and in a higher pulp yield, assigned to improved retention of both cellulose and xylan. During the last stage of pulping, cellulose content decreases, this being mainly responsible for the decrease of pulp yield, while xylan content is almost constant, a feature attributed to the peculiar structure of this E. globulus's hemicellulose. Copyright © 2007 Society of Chemical Industry

Proteins in Norway spruce thermomechanical pulp

Two methods of cytochemical staining using Coomassie dye and Cu+-bicinchoninic acid, respectively, showed that there are proteins in thermomechanical pulp (TMP) of Norway spruce. Protein isolated from TMP was analyzed for amino acid composition. There was about twice the amount of acidic amino acid material compared with basic amino acids, and the presence of glucosamine indicated that the isolated polypeptides also contained glycoproteins. The presence of proteins in ray cells and fiber tracheids in TMP adds to the chemical heterogeneity of the structurally complex high-yield pulp.

Pulping of holm oak wood. Influence of the operating conditions

This paper reports on the influence of independent variables in the pulping of holm oak wood ( Quercus ilex L.) [viz. temperature (135–195 °C), cooking time (30–90 min) and soda concentration (10–20%)] on the yield, holocellulose content, α-cellulose content, brightness and viscosity of the resulting pulp. By using a central composite factorial design, equations relating each dependent variable to the different independent variables were derived that reproduced the experimental results for the dependent variables with errors less than 5–15% in all cases. The highest pulp yield (56.9%) was obtained with the lowest values of the operating variables. However, obtaining the optimum holocellulose content, α-cellulose content and viscosity (viz. 94.5%, 78.5% and 1395 ml/g, respectively) entailed using values of the independent variables above their mean levels. Also, ensuring optimal brightness (viz. 24.3%) required using higher temperatures and soda concentrations. A compromise that saves equipment immobilized capital and about 25% of soda is using a soda concentration of 15% at 195 °C for 30 min. The yield thus obtained differs by less than 29.5% from the highest level; also, the resulting holocellulose content, α-cellulose content and brightness differ by less than 12% from their respective optimum values.

Comparison of two multicriteria decision aid methods: Net Flow and Rough Set Methods in a high yield pulping process

This investigation presents a synthesis of two multicriteria analysis methods, Rough Set Method (RSM) and Net Flow Method (NFM), applied to the multicriteria optimisation for the manufacture of paper using jack pine as the source of fibres. This work is the result of a collaboration between different Canadian and French laboratories. The two optimisation methods, based on different approaches, are applied to the same Pareto domain of non-dominated operating conditions. The Rough Set Method (RSM) uses a set of decision rules that are based on the preferences of experts, when presented with a small set of diverse conditions extracted from the Pareto domain. These rules are then applied to the entire Pareto domain to determine the preferred zone of operation. In the Net Flow Method (NFM), the preferences of experts are defined with three threshold values and one set of weights that are used to classify the entire Pareto domain. The NFM is a hybrid of two methods between ELECTRE and PROMETHEE. To compare these two methods, they were used to optimise the identical process. Results clearly show that the two methods gave nearly identical optimal solutions and well within inherent experimental errors.

A systematic approach for determination of optimal conditions for Lo-Solids™ kraft pulping of Eucalyptus nitens

Abstract Kraft pulping of thin chips of Eucalyptus nitens was performed in laboratory flow-through reactors under isothermal condition. The effects of process variables on the dissolutions of the lignocellulosic components, i.e. lignin, pentosans and cellulose, of the chips were studied. It was found that at a target kappa number, higher pulp yields could be obtained by pulping at a temperature below 150 °C and with an effective alkali concentration below 0.5 M. The effects of all process conditions were combined using the Nuclei Growth kinetic models.

Light-induced yellowing of mecanical and chemimecanical pulp sheets – influence of wood raw material, process and aging method

The light-induced brightness reversion of different types of unbleached and bleached high-yield pulps was studied under both accelerated and long-term ambient light-induced ageing conditions. It wa ...

Brightness stabilisation of bleached high-yield pulps by novel sulfur-containing inhibitors

Abstract The stabilisation of a peroxide-bleached chemothermomechanical pulp against light-induced yellowing by novel sulfur-containing radical-scavenging compounds was investigated. Substances were identified that lack the unpleasant odour typical for compounds containing thiol groups. High inhibition effects were observed when the sulfur compounds were combined with small amounts of hindered amines and UV absorbers. A novel group of thiols isolated from biomatter was among the sulfur-containing inhibitors. Photoyellowing could be avoided for 3 years in real conditions when the inhibitors were applied as part of a coating. The ability of the thiol compounds to scavenge phenoxy radicals was demonstrated by ESR spectroscopy of irradiated chemithermomechanical pulp sheets. The results are encouraging for efficient brightness stabilisation of high-yield pulps.