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Furnishing autohydrolyzed poplar weakly alkaline P-RC APMP to make lightweight coated base paper, TAPPI Journal February 2022
ABSTRACT: This work investigated the effects of autohydrolysis pretreatment severity on poplar (Populus tomentosa Carr.) woodchips used to make a type of high-yield pulp (HYP) known as preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulp (P-RC APMP). It also investigated the ratios for partially replacing sodium hydroxide (NaOH) with magnesium oxide (MgO) in the high-consistency (HC) retention stage of the P-RC APMP process on the obtained HYP’s properties. The results show that the pretreatment severity of autohydrolysis at combined hydrolysis factor (CHF) = 10.77 and the 50 wt% ratio for partially substituting NaOH with MgO were the optimum conditions for making light-weight coated (LWC) base paper. Compared to the conventional P-RC APMP, the optimized P-RC APMP had similar bulk and higher tensile, burst, and tear indices, as well as opacity, but a slightly lower ISO brightness. When the optimized P-RC APMP and commercial softwood bleached sulfate pulp (SBKP) were blended to make LWC base paper, the most favorable pulp furnish was comprised of 50% optimized P-RC APMP and 50% commercial SBKP. The obtained LWC base paper handsheet had better bulk, and its other properties could also meet the require-ments of LWC base paper.
Journal articles
Magazine articles
Upscaling of foam forming technology for pilot scale, TAPPI JOURNAL August 2019
ABSTRACT: The need for production cost savings and changes in the global paper and board industry during recent years have been constants. Changes in the global paper and board industry during past years have increased the need for more cost-efficient processes and production technologies. It is known that in paper and board production, foam typically leads to problems in the process rather than improvements in production efficiency. Foam forming technology, where foam is used as a carrier phase and a flowing medium, exploits the properties of dispersive foam. In this study, the possibility of applying foam forming technology to paper applications was investigated using a pilot scale paper forming environment modified for foam forming from conventional water forming. According to the results, the shape of jet-to-wire ratios was the same in both forming methods, but in the case of foam forming, the achieved scale of jet-to-wire ratio and MD/CD-ratio were wider and not behaving sensitively to shear changes in the forming section as a water forming process would. This kind of behavior would be beneficial when upscaling foam technology to the production scale. The dryness results after the forming section indicated the improvement in dewatering, especially when foam density was at the lowest level (i.e., air content was at the highest level). In addition, the dryness results after the pressing section indicated a faster increase in the dryness level as a function of foam density, with all density levels compared to the corresponding water formed sheets. According to the study, the bonding level of water- and foam-laid structures were at the same level when the highest wet pressing value was applied. The results of the study show that the strength loss often associated with foam forming can be compensat-ed for successfully through wet pressing.
Journal articles
Magazine articles
Effects of tissue additives on copy paper forming and properties, TAPPI Journal February 2024
ABSTRACT: Laboratory tests were conducted in an effort to determine the effects on paper machine process attributes and the properties of paper made from recycled copy paper furnish upon the addition of chemical agents that are commonly used in the production of hygiene tissue products. Due to continuing growth in tissue and towel grades of paper, such agents are experiencing greater usage. Charge titration test results revealed that certain dry strength agents associated with tissue manufacturing have the potential to shift the balance of charge in papermaking furnish to less negative or even positive values. Creping adhesive was found to contribute to fine particle retention, especially when present at relatively high levels. Release aid and a polyacrylate dispersant had the opposite effect. Low addition levels of both a creping adhesive and a debonding agent surprisingly increased a wide range of strength attributes of paper handsheets in comparison to sheets prepared from unaltered recycled copy paper furnish. The debonding agent decreased paper strength at higher levels of addition. Such effects appear to depend not only on the expected effects of agents themselves, but also on how they affect the charge balance of the wet-end system.
Journal articles
Magazine articles
Amphoteric dry strength chemistry approach to deal with low-quality fiber and difficult wet-end chemistry conditions in the Asian and North American markets, TAPPI Journal January 2024
ABSTRACT: With Japan’s high recycling rates and low access to fresh fiber sources, reaching strength targets in manufacturing packaging materials is a challenge. Declining quality of recycled fiber and minimal freshwater con-sumption results in difficult wet-end chemistry conditions in terms of high conductivity and elevated levels of dissolved and colloidal substances (DCS). These trends are somewhat typical of other Asian regions. Due to global trade, Asian packaging materials have become a part of the North American (NA) raw material pool. The gradual closing of mill water circuits for fresh water and energy savings results in more difficult wet-end chemistry conditions experienced in North America. China’s ban on the import of mixed paper and the consequent ban on all waste-paper imports triggered a significant price drop in recycled raw material, resulting in plans for increased manufacturing capacity in North America. Between increased demand, decreasing fiber quality, and movement towards more closed white water systems associated with packaging grade paperboard (even a virgin fiber mill uses a fair amount of recycled fiber), new methods to overcome strength reduction in raw materials must be proactively considered for North America. Reviewing the strategies currently used in the Asian industry regarding strength development is an excellent starting place for NA producers. A clear difference between Asian and NA wet-end chemistry is the dominant position of amphoteric dry strength agents. This paper reviews the fundamentals of dry strength development that explain the trend towards the increased application of amphoteric dry strength technology for poor-quality fiber and highly contaminated water circuits in Asian markets. This paper discusses the development and application perfor-mance of the novel 4th generation amphoteric polyacrylamide (AmPAM) dry strength technology, based on selected laboratory and mill case studies.
Journal articles
Magazine articles
Flocculation of fiber suspensions studied by Rheo-OCT, TAPPI Journal September 2024
ABSTRACT: When dealing with papermaking fiber suspensions, particle flocculation takes place even before the paper web is formed. The particle flocculation depends on several aspects, including particle mass concentration (consistency), particle collisions, electrochemical interactions promoted by chemical additives, etc. Due to its importance, fiber suspension flocculation has been studied for a long time in papermaking, and several methods have been developed for this purpose. The traditional techniques include, for example, focused beam reflectance microscopy (FBRM) and high-speed video imaging (HSVI). Recently, a new optical method, optical coherence tomography (OCT), has emerged for flocculation analysis. The advantages of OCT are the possibility to study opaque suspensions, its micron-llevel resolution, and its high data acquisition speed. The OCT measurements can be combined with rheological (Rheo) measurements, allowing simultaneous measurement of both the time evolution of the floc size and the suspension viscosity. In this work, we used this approach, Rheo-OCT, to study the flocculation of suspensions of various papermaking furnishes. We analyzed the time evolution of the floc size and the fiber suspension viscosity when the studied papermaking suspensions were treated with highly refined furnish (HRF) — a furnish that contained a significant amount of micofibrillated cellulose (MFC)-type fibrils — and/or chemical additives. Such studies can lead to a better understanding of the impact of flocculation on the produced paper web in terms of qualities like formation, drainage potential, and strength behavior.
Journal articles
Magazine articles
Viscoelastic web curl due to storage in wound rolls, TAPPI Journal July 2020
ABSTRACT: Winding is often the final operation in a roll-to-roll manufacturing process. Web materials, i.e., materials that are thin compared to their length, are wound into rolls because this form is the only practical means to store them. The resulting bending strains and associated stresses are large for thick webs and laminates. As many webs are viscoelastic on some time scale, bending stresses lead to creep and inhomogeneous changes in length. When the web material is unwound and cut into discrete samples, a residual curvature remains. This curvature, called curl, is the inability for the web to lie flat at no tension. Curl is an undesirable web defect that causes loss of productivity in a subsequent web process. This paper describes the development and implementation of modeling and experimental tools to explore and mitigate curl in homogenous webs. Two theoretical and numerical methods that allow the prediction of curl in a web are developed: a winding software based on bending recovery theory, and the implementation of dynamic simula-tions of winding. One experimental method is developed that directly measures the curl online by taking advantage of the anticlastic bending resulting from the curl. These methods are demonstrated for a low-density polyethylene web.
Journal articles
Magazine articles
Improving paper wet strength via increased lignin content and hot-pressing temperature, TAPPI JOURNAL October 2020
ABSTRACT: It is known that the strength properties of wood-based paper materials can be enhanced via hot-pressing techniques. Today, there is a desire not only for a change from fossil-based packaging materials to new sustainable bio-based materials, but also for more effective and eco-friendly solutions for improving the dry and wet strength of paper and board. Against this background, hot pressing of paper made from high yield pulp (HYP), rich in lignin, becomes highly interesting. This study investigated the influence of pressing temperature and native lignin content on the properties of paper produced by means of hot pressing. Kraft pulps of varied lignin content (kappa numbers: 25, 50, 80) were produced at pilot scale from the same batch by varying the cooking time. We then studied the effect of lignin content by evaluating the physical properties of Rapid Köthen sheets after hot pressing in the temperature range of 20°C•200°C with a constant nip pressure of 7 MPa. The pilot-scale cooked pulps were compared with reference samples of mill-produced northern bleached soft-wood kraft (NBSK) pulp and mill-produced chemithermomechanical pulp (CTMP).Generally, the results demonstrated that lignin content had a significant effect on both dry and wet tensile index. All of the pilot cooked pulps with increased lignin content had a higher tensile index than the reference NBSK pulp. To obtain high tensile index, both dry and wet, the pressing temperature should be set high, preferably at least 200°C; that is, well above the glass transition temperature (Tg) for lignin. Moreover, the lignin content should prefera-bly also be high. All kraft pulps investigated in this study showed a linear relationship between wet strength and lignin content.
Journal articles
Magazine articles
Furnishing autohydrolyzed poplar weakly alkaline P-RC APMP to make lightweight coated base paper, TAPPI Journal February 2022
ABSTRACT: This work investigated the effects of autohydrolysis pretreatment severity on poplar (Populus tomentosa Carr.) woodchips used to make a type of high-yield pulp (HYP) known as preconditioning followed by refiner chemical treatment, alkaline peroxide mechanical pulp (P-RC APMP). It also investigated the ratios for partially replacing sodium hydroxide (NaOH) with magnesium oxide (MgO) in the high-consistency (HC) retention stage of the P-RC APMP process on the obtained HYP’s properties. The results show that the pretreatment severity of autohydrolysis at combined hydrolysis factor (CHF) = 10.77 and the 50 wt% ratio for partially substituting NaOH with MgO were the optimum conditions for making light-weight coated (LWC) base paper. Compared to the conventional P-RC APMP, the optimized P-RC APMP had similar bulk and higher tensile, burst, and tear indices, as well as opacity, but a slightly lower ISO brightness. When the optimized P-RC APMP and commercial softwood bleached sulfate pulp (SBKP) were blended to make LWC base paper, the most favorable pulp furnish was comprised of 50% optimized P-RC APMP and 50% commercial SBKP. The obtained LWC base paper handsheet had better bulk, and its other properties could also meet the require-ments of LWC base paper.
Journal articles
Magazine articles
The Shendye-Fleming OBA Index for paper and paperboard, TAPPI Journal March 2022
ABSTRACT: We are proposing a new one-dimensional scale to calculate the effects of optical brightening agents (OBA) on the bluish appearance of paper. This index is separate from brightness and whiteness indices.In the paper industry, one-dimensional scales are widely used for determining optical properties of paper and paperboard. Whiteness, tint, brightness, yellowness, and opacity are the most common optical properties of paper and paperboard. Most of the papers have a blue cast generated by addition of OBA or blue dyes. This blue cast is given because of the human perception that bluer is whiter, up to a certain limit. To quantify this effect, it is necessary to determine how much blue cast paper and paperboard have. As the printing industry follows the ISO 3664 Standard for viewing, which has a D50 light source, this also plays a very important role in showing a blue cast. Color perception is based on light source and light reflected from an object. The ultraviolet (UV) component in D50 interacts with OBA to provide a reflection in the blue region of the visible spectrum. Use of a UV blocking filter results in measurements without the effect of emission in the blue region. This difference is used in determining the OBA effect in the visible range of the paper. This equation is known as the Shendye-Fleming OBA Index.
Journal articles
Magazine articles
Recovery boiler back-end heat recovery, TAPPI Journal March 2023
ABSTRACT: Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%•4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.