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The article presents a study which determines the effect of high temperature on the drying rates of recycled paper and the sheet properties. It assesses the functionality and efficiency of a gas-fired paper dryer (GFPD) in both pilot- and full-scale set-ups. It cites that the best location for installing a high-temperature dryer is near the middle of the dryer chain. It notes that the findings aim to boost paper machine drying and production rates and improve overall mill power efficiency.

The article discusses a study on nitrogen oxide (NOx) formation in recovery boiler in paper making. It states that the study uses a methodolgy of computational fluid dynamics (CFD) combined with a detail reaction mechanism. It mentions that in investigating the origin of nitrogen emissions in this study, they carried out the CFD analysis of a black liquor using a highly detailed model. In conclusion, it mentions that black liquor spray characteristics play an important role in paper making. However, it states that increasing the average particle diameter has an opposite effect.

The article discusses the utilization of fractionation and refining in tailoring softwood kraft pulp properties in manufacturing paper. It notes that the materials used in this experimental methodology include softwood kraft pulp, conical filling, and narrow-bar disc filling. In conclusion, it mentions that fractionation indicates better potential for softwood pulp for different paper products. In addition, it states that the said methodology will benefit certain facilities interested in manufacturing softwood pulp fibers into different paper grades.

The article presents an experimental research on the effect of eucalyptus globulus wood density on papermaking potential. It states that understanding the morphological features of eucalyptus globulus in tree selection and genetic improvement programs can help papermakers keep off the negative impact on light scattering coefficient and refining energy usage. Eucalyptus globulus kraft pulp has been used for printing and writing papers because of its strength, bulk, opacity, and smoothness. Different charts reflecting provenance, temperature, climate conditions and density of the wood are shown. It also includes diagrams showing the correlation between paper density and wood basic density, and the results and conclusions obtained from the study.

The article presents an experimental research on the process to produce high-quality precipitated calcium carbonate (PCC) by the causticizing process in a kraft pulp mill. It states that the purpose of this study is that rotary lime-kiln operation could also be cut down or avoided, and the consumption of fuel oil and consequent discharge of carbon dioxide gas could be decreased. PCC, which is produced mainly by the carbonation process, has been used widely as a paper filler due to its brightness and opaqueness effects, and its low cost. Included also are the experimental procedures, schematics of the causticizing process, photographic views of the various shapes of causticizing calcium carbonate, and the derived results and discussions.

The article presents an experimental research on the continuous time domain characterization of mixing in agitated pulp chests. It states that this study can help engineers to consider the use of new characterization algorithm in improving the design and performance of agitated pulps for better paper quality and machine efficiency. The authors point out that mixing is to be highly considered in stock blending, consistency control, chemical generation, and deinking. Included are mathematical models showing a flow diagram of mixing, optimization problem presentations, and the associated solutions. It also mentions that anticipated results were based on the inherent limitations of the discrete-time approach.

The article examines the effect of press and paper variables on linting during the offset printing of newsprint. The results of printing take-off angle, ink tack, print coverage, and paper two sidedness on linting in offset printing were investigated with printing trials conducted on a small commercial Heidelberg GTO-52 and a large commercial Man-Roland Uniset press. It reveals that the take-off angle at which the web exits the printing nip have the largest influence on lint, with the lint weight increasing fivefold when the take-off angle was increased from 27° to 153°.

The article presents a study which demonstrates the drying behavior of water saturated cellulose fibers to better understand the fiber-water interaction during the drying process in papermaking. The authors examine the relationship between the hard-to-remove (HR) water content and the water retention value (WRV) by using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). They found that free bound water evaporated first, followed by trapped water, freezing-bound water and then nonfreezing-bound water. Based on the results, they suggest that a qualitative drying model of wood-based cellulose fibers must be used relative to its decreasing moisture ratio.

The article reports on the benefits gained from the use of pulp and paper power boiler ash residues. A major part of the solid residues produced by pulp and paper mills is comprised by ash residuals obtained from recovery and power boilers combusting wood residues, sludges or auxiliary fuels. Different types of ashes have increased since the mid-1990s. The primary disposal method of ashes is through landfilling. However, there are also potential applications for the ashes, such as, large-scale opportunities and small scale applications.

Multicylinder sections of paper dryers consume the most energy in an industrial plant. They are also responsible for the final characteristics of the paper produced. In this context, the modeling of the paper drying process is very important, and is normally done by phenomenological approaches. An interesting and promising alternative, due to the possibilities of its application, is through the identification of an operational standard behavior, obtained by the use of neural networks in the simulation of the final paper moisture content. This alternative was implemented in the drying section of the KIabin Paraná Papeis S.A. (Klabin-PR) MP-7 paper machine. For this study, we collected operational data related directly and indirectly to the drying process, composing a database with 110 preselected variables. These data were analyzed with the help of Statistica Neural Network software, which, besides its use for training and choosing the more capable neural networks to model the chosen variable, allows the selection of the group of variables of larger influence in the studied process. The results obtained by the use of the neural network modeling were quite satisfactory, with an average error of less than 2% in the prediction of the final paper moisture content Application: Neural networks may be useful to help control moisture content and increase dryer efficiency. [ABSTRACT FROM AUTHOR]

This study investigated the influence of different calendering conditions on newsprint surface and absorption characteristics, strength, and compression uniformity. We used a combination of traditional and new measurement techniques to evaluate newsprint calendered using a hard-nip, a conventional soft-nip, and an extended soft-nip. This study points out and compares the advantages and disadvantages of the respective calendering techniques. In all cases, flocs carried the greater part of the load. The different calendering techniques yielded dissimilar compression patterns. At constant process parameters, flocs were flattened most in hard-nip calendering, which had a positive effect on smoothness, gloss, thickness uniformity, and ink hold out. However, it negatively affected tensile strength, gloss uniformity, and print mottle. Extended soft-nip calendering produced opposite effects, including a rougher surface, non-uniform thickness, and less print mottle. Application: A combination of traditional and new measurement techniques to analyze the effects of calendering on paper properties is introduced. [ABSTRACT FROM AUTHOR]

We applied catalytic oxidation using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxy radical), sodium bromide, and sodium hypochlorite to aqueous kraft pulp slurries at pH 10.5 under various conditions at room temperature to chemically modify pulp fiber surfaces. This TEMPO-mediated oxidation can effectively introduce aldehyde and carboxylate groups into accessible regions of the pulp fibers. When the amount of sodium hypochiorite (NaClO) added in the oxidation was optimum (about 0.3 mmol/g pulp in this study), we observed almost no loss in pulp yield, and the handsheets prepared from the oxidized pulp had maximum wet and dry tensile strengths. Interfiber covalent bond formation through hemiacetal linkages between hydroxyl groups of cellulose/hemicellulose and aldehyde groups brings about the clear wet tensile strength improvement. These linkages form at the C6 primary hydroxyl groups of cellulose through TEMPO-mediated oxidation. Moreover, wet tensile strength of the handsheets was further improved when aluminum sulfate was used in handsheet-making in combination with TEMPO-oxidized pulps, while dry tensile strength decreased to some extent. Formation of aluminum carboxylate linkages between pulp fibers in the dried handsheets may have an additive effect on the wet tensile strength improvement. [ABSTRACT FROM AUTHOR]

Comparative analyses were carried out on the properties of birch, maple, and spruce for conventional kraft pulping and kraft pulping with sodium metaborate added to correspond to 35% autocausticizing. A 1.8% increase was noticed in the screened yield for the kraft-borate pulping of spruce at H-factors higher than 1000. Also, at kappa numbers lower than 50, sodium metaborate increased the total yield in spruce pulping. Sodium borate did not affect the brightness nor the contents of extractives and hexenuronic acid groups (HexA) of the kraft pulps for the species studied. The kappa number corrected for the HexA component, which is a more accurate estimate of the lignin content, showed that kraft delignification was not changed by sodium metaborate at the increasing H-factor. An increase of holocellulose retention was found for the kraft-borate pulps of spruce at the kappa numbers lower than 60, indicating that sodium metaborate has the potential to protect carbohydrates in kraft pulping. Application: With no detrimental effects observed for maple, spruce, and birch pulps, autocausticizing with sodium metaborate added in the white liquor appears to be an easy way for a causticizing-limited mill to increase its capacity without new equipment. [ABSTRACT FROM AUTHOR]

Digital particle image velocimetry (DPIV) was used to study the question of how headboxes generate machine-direction streaks. Experiments were conducted in a water tunnel with slice geometries and conditions similar to those of headboxes. An initially steady flow past a channel was terminated by a partial blockage to represent the slice knife. DPIV vector fields showed turbulent streamwise vortices being generated and an unsteady cross-direction vortex forming in the corner of the channel that resembled the top nozzle wall and knife. The size and spacing of the streamwise vortices correspond closely to MD streak spacings found in paper. Not surprisingly, headbox manufacturers indicate that paper streaks can be reduced when headboxes are designed without slice knives. Application: The slice knife can generate streaks by producing streamwise vortices in flow entering the wire section of a paper machine. Modern headbox designers are eliminating the slice knife. [ABSTRACT FROM AUTHOR]