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Critical parameters for tall oil separation I: The importance of ration of fatty acids to rosin acids, TAPPI Journal September 2019
ABSTRACT: Tall oil is a valuable byproduct in chemical pulping of wood, and its fractions have a large spectrum of applications as chemical precursors, detergents, and fuel. High recovery of tall oil is important for the economic and environmental profile of chemical pulp mills. The purpose of this study was to investigate critical parameters of tall oil separation from black liquor. To investigate this in a controlled way, we developed a model test system using a “synthetic” black liquor (active cooking chemicals OH- and HS- ions), a complete process for soap skimming, and determination of recovered tall oil based on solvent extraction and colorimetric analysis, with good reproducibility. We used the developed system to study the effect of the ratio of fatty acids to rosin acids on tall oil separation. When high amounts of rosin acids were present, tall oil recovery was low, while high content of fatty acids above 60% significantly promoted tall oil separation. Therefore, manipulating the content of fatty acids in black liquor before the soap skimming step can significantly affect the tall oil solubility, and hence its separation. The findings open up chemical ways to improve the tall oil yield.
Journal articles
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A new technique for the measurement of show-through mottle of fine paper, TAPPI Journal September 2019
ABSTRACT: Mottling within print-through and show-through is caused by the variability of the local optical properties of the sheet. This mottling is visually disturbing and a mark of poor paper quality. The ability to predict print-through mottle of printed paper by measuring show-through mottle on the unprinted sheet would be a valuable asset for paper machine control.We examined the relationship between print-through mottle and show-through mottle. We worked with nine samples of 60 lb. uncoated fine paper (90 g/m2), from various North American paper companies, that were printed on an offset press, 400K (400% Black), on both sides. A show-through mottle instrumental determination technique was developed using an existing Fast Fourier Transform-based algorithm. The nine samples examined were ranked similarly by the visual evaluation of print-through mottle and by the instrumental determination of show-through mottle. We thus established that show-through on the unprinted sheet can be used as a reliable predictor of print-through, therefore saving time and money for papermakers. We also found a significant two-sidedness in show-through for some of the samples.
Journal articles
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Evaluation of folding effects on coating damage, TAPPI Journal November 2024
ABSTRACT: Barrier coatings on paperboard need to maintain integrity during converting and end-use for effective barrier performance. Folding is one of the most common deformations during converting; however, factors that affect damage during folding are not well defined. This is partly because methods to fold specimens and characterize damage are not standardized and the results are generally not transferable. In this work, we describe a method to fold paper specimens precisely and reproducibly. The keys to folding include using a defined geometry and controlled deformation. Multiple methods can be used to quantify damage; in this case, we use differences in permeability as a measure of how the coating becomes more open. Damage is sensitive to the degree of compression after the initial folding. Using a shim for support provides a defined amount of compression and minimizes the sensitivity to the applied pressure.
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On increasing wet-web strength with adhesive polymers, TAPPI JOURNAL February 2020
ABSTRACT: Fiber-fiber adhesion, called “bonding” in the old paper physics literature, is a critical component of the overall strength of dry paper. With freshly formed very wet pulp fiber webs, all evidence suggests there are no fiber-fiber crossings with significant adhesive joint strength. With water removal, a point will be reached where fiber-fiber adhesion starts to contribute to the overall wet-web strength.The literature reveals very few examples of polymers that increase fiber-fiber joint strength in freshly formed webs. Here, we summarize the literature and explain why it is so difficult to promote fiber-fiber wet adhesion with polymers. Nevertheless, ongoing research in areas as diverse as tissue engineering scaffolds and biomimetic adhesives gives clues to future developments. Advances in paper machine engineering have lessened the importance of wet-web strength. By contrast, a critical issue in many of the evolving nanocellulose technologies is the strength of objects first formed by aqueous processing, the green strength—the strength of wet bodies before drying. For exam-ple, 3-D printed nanocellulose objects and ultralow density cellulosic aerogels can be destroyed by capillary forces during drying. There is a need for adhesives that strengthen freshly formed, wet lignocellulosic joints.
Journal articles
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Effects of phosphogypsum whiskers modification with calcium stearate and their impacts on properties of bleached softwood paper sheets, TAPPI Journal September 2021
ABSTRACT: By combining the structural properties and characteristics of phosphogypsum whiskers, a preliminary study on the modification of phosphogypsum whiskers and their application in papermaking was carried out. The effects of reaction temperature, reaction time, and reaction concentration on the solubility and retention of modified phosphogypsum whiskers and the effects of phosphogypsum whiskers on the physical properties of paper under different modified conditions were explored. The research results show that, after the phosphogypsum whiskers are modified with calcium stearate, a coating layer will be formed on the surface of the whiskers, which effectively reduces the solubility of the phosphogypsum whiskers. The best modification conditions are: the amount of calcium stearate relative to the absolute dry mass of the phosphogypsum whisker is 2.00%; the modification time is 30 min, and the modification temperature is 60°C. The use of modified phosphogypsum whiskers for paper filling will slightly reduce the whiteness, folding resistance, burst resistance, and tensile strength of the paper, but the tearing degree and retention of the filler will be increased to some extent.
Journal articles
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Three-dimensional pore structure visualization and character
Three-dimensional pore structure visualization and characterization of paper using X-ray computed tomography, TAPPI JOURNAL September 2017
Journal articles
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Calender barring review with experiences, TAPPI Journal July 2022
ABSTRACT: Excessive calender vibration affects all styles of calender stacks from single to multi-nip, all hard rolls, or a combination of hard and soft rolls. Calender vibration can be forced vibration or self-excited vibration. Forced vibration occurs at the first few harmonics of the calender roll rotational speeds and is caused by imbalance, misalignment, eccentricity, etc. Self-excited vibration, the focus of this paper, occurs at higher frequencies. Feedback paths for self-excited vibration must be understood in order to ameliorate the problem. This is presented in the context of the historical development of the theory of self-excited feedback mechanisms, followed by a survey of self-excited feedback mechanisms in various types of calender stacks. Methodology to determine which feed-back path is present and techniques to control or eliminate the resulting vibration follow. To obtain a flavor of the types of problems faced and practical remedial actions, a variety of experiences with barring issues are provided.
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Discrete element method to predict coating failure mechanisms, TAPPI JOURNAL January 2018
Discrete element method to predict coating failure mechanisms, TAPPI JOURNAL January 2018
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Quantification of vegetable oil in recycled paper, TAPPI JOURNAL September 2020
ABSTRACT: Vegetable soybean oil is commonly used in cooking foods that are packaged in takeaway paper-board containers. Vegetable oil is hydrophobic, and in sufficiently high concentration, could interfere with interfiber bonding and result in paper strength loss. In order to quantify the effect of oil on the resulting paperboard strength, it is necessary to quantify the oil content in paper. A lab method was evaluated to determine the soybean oil content in paper. Handsheets were made with pulps previously treated with different proportions of vegetable oil. Pyrolysis gas chromatography-mass spectrometry (pyGCMS) was used to quantify the amount of oil left in the handsheets. The results revealed a strong correlation between the amount of oil applied to the initial pulp and the amount of oil left in the handsheets.In addition, the effect of vegetable oils on paper strength may be affected by the cooking process. Vegetable oil is known to degrade over time in the presence of oxygen, light, and temperature. The vegetable oil was put in an oven to imitate the oil lifecycle during a typical pizza cooking process. The cooked oil was then left at room temperature and not protected from air (oxygen) or from normal daylight. The heated, then cooled, oil was stored over a period of 13 weeks. During this time, samples of the aged oil were tested as part of a time-based degradation study of the cooked and cooled oil.
Journal articles
Magazine articles
Chemical addition to wet webs using foam application, TAPPI Journal January 2023
ABSTRACT: In papermaking, the conventional way to add chemicals to the web is to dose them into the fiber stock and form the paper afterwards. However, in many cases, adding chemicals directly to the stock is challenging. For example, strength aids tend to increase flocculation in the stock, which limits the addition amounts of those aids. The need for better performance of paper (and paperboard) products has given rise to the need for functionalization of paper. Adding such functional chemicals to the stock is usually rather inefficient. Hence, novel methods are needed to add chemicals to the paper bulk. One such method is dosing chemicals to the wet web via foam application. In this study, we built a laboratory-scale sheetfed dynamic foam application device and utilized it to study addition of starch to wet bleached chemithermomechanical pulp (BCTMP) paper handsheets. The impact of parameters such as vacuum level, the amount of added chemical, and the viscosity of the foaming liquid on the penetration of starch into the wet web was explored. Starch penetration into wet webs was measured via iodine-potassium iodide staining, followed by image analysis. According to our results, controlling the viscosity of the foaming liquid gives the best possibility to control the penetration.