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Toward valorization of lignin: characterization and fast pyr
Toward valorization of lignin: characterization and fast pyrolysis of lignin recovered from hot-water extracts of electron-beam irradiated sugar maple, TAPPI JOURNAL April 2017
Journal articles
Magazine articles
Visual discrimination of hygiene tissue softness in the abse
Visual discrimination of hygiene tissue softness in the absence of haptic feedback, TAPPI JOURNAL August 2017
Journal articles
Magazine articles
How old are fibers in paper for recycling and what is their
How old are fibers in paper for recycling and what is their life expectancy? A contribution to the life cycle assessment of wood fiber-based products, TAPPI JOURNAL July 2017
Journal articles
Magazine articles
Accelerated aging of bio-oil from lignin conversion in subcr
Accelerated aging of bio-oil from lignin conversion in subcritical water, TAPPI JOURNAL March 2017
Journal articles
Magazine articles
Analysis of economically viable lignin-based biorefinery st
Analysis of economically viable lignin-based biorefinery strategies implemented within a kraft pulp mill, TAPPI JOURNAL March 2017
Journal articles
Magazine articles
Numerical analysis of the impact of rotor and screen hole plate design on the performance of a vertical pulper, TAPPI Journal April 2025
ABSTRACT: The dissolving of mechanical pulp is one of the most important process steps in stock preparation, since pulping occurs at the very beginning of the papermaking process. Efficient mixing of the pulp in a short amount of time is essential to achieve high furnish volume flow rates. The design of the rotor, as well as the pulper vat and inserts, significantly affects the overall performance of the pulper, such as mixing efficiency and power demand. Using advanced numerical methods such as computational fluid dynamics (CFD) can accelerate the development process. The CFD simulations allow for detailed analysis of flow phenomena, making it possible to study a real-size machine numerically. This approach is particularly advantageous because it can reduce the need for timeconsuming and costly experiments associated with scaling up test rigs. In this study, we compared two different rotor designs utilized in a vertical pulper and evaluated the numerical results with experimental data. Rotor A is designed for low turbulence and low power demand, while rotor B is designed for high turbulence with high power demand. The CFD results showed good agreement with the experimental measurements. We investigated how the rotor design influences the free fluid surface and the mixing efficiency. Our study also highlights the differences in results depending on whether water or furnish is simulated, which exhibit Newtonian or, respectively, non-Newtonian fluid behavior. Additionally, a detailed numerical investigation of various screen hole plate designs revealed that the newly developed hole design significantly reduces pressure loss compared to a standard drilled hole. This outcome was consistent for both types of fluids investigated: water and furnish.
Journal articles
Reinforcing folding boxboard ply stock with refined pulp and its effect on dewatering potential, TAPPI Journal February 2025
ABSTRACT: The folding boxboard (FBB) filler ply typically contains a significant amount of mechanical pulp such as bleached thermomechanical pulp (BTMP), bleached chemi-thermomechanical pulp (BCTMP), and chemi-thermomechanical pulp (CTMP), etc. It is usually reinforced with either refined broke from the same paper machine line and converting process or by utilizing traditional bleached kraft pulp (BKP). In response to the drive for improved/increased ply bond (to avoid undesired delamination), increased bulk, reduced basis weight, and minimized energy consumption, papermakers have experimented with various options and strategies. In between the common approaches, choices have been made between reducing the refining of the mechanical pulp, increasing the broke refining (more frequently practiced on the production scale), or increasing the BKP refining (a potentially superior choice). This study focused on a simplified approach to assess the impact of three reinforcement pulps with different refining levels on the dewatering of the filler ply. The reinforcement pulp was added to the core stock for the FBB filler ply — a mechanical pulp, BCTMP, with a drainability of 25 °SR. The proportions of the reinforcement pulp, hardwood bleached kraft pulp (HWBKP), were 20% of 30-35 °SR, 10% of HWBKP 50-55 °SR, and 5% of HWBKP 70-75 °SR. The intention behind using varying percentages of reinforcement pulp was to attain a controlled internal bond while enhancing bulk through increased mechanical pulp content. The dewatering potential of the stock mixtures was assessed at three vacuum levels — 4, 10, and 25 kPa — that can be found in progressive stages within production- scale forming sections. Our goal was to find an optimal reinforcement strategy for filler ply that would minimize the use of the reinforcement pulp, give better strength, retain bulk, and lower basis weight. The success of this strategy was verified with an actual FBB machine.
Journal articles
Water-based adhesive penetration into paperboard and coated paperboard, TAPPI Journal January 2025
The setting of water-based adhesives in contact with paperboard is important in the production of boxes and other packaging, but the topic has received little attention in the literature. The penetration of the adhesive into the paper surface is important to get good bond strength through mechanical interlocking. The influence of the process conditions and the paper properties on this penetration is lacking. A water-based adhesive was applied to an uncoated and coated paperboard. The coating layer had two latex levels. Samples were characterized in terms of air permeability, void fraction, average pore size, and coat weight. The adhesive was applied to the samples in a mechanical press, squeezing a drop between two samples. The penetration of the adhesive was characterized with a silicone oil absorption method that measured the decrease in pore volume after the adhesive had been applied to approximate the pore volume taken up by the adhesive. The bond strength was measured with a peeling test. The penetration depth into uncoated paper did not depend on the application method parameters such as pressing time, pressure, or initial solids of the adhesive. The penetration depth ranged from 35•40 mm. The penetration into 10 pph latex content coated paper was similar to the uncoated samples, but reduced penetration was observed into the 40 pph latex content coatings. The results were compared to the limiting amount of adhesive that was obtained from the weight gain of the samples and to a simple model that is based on flow in porous media. Peel tests revealed that good penetration was needed, as well as a strong coating layer to obtain high peel forces.
Journal articles
Data-efficient determination of machine-specific process windows in thermoforming using the example of PCR materials, TAPPI Journal July 2025
ABSTRACT: In an industrial context, process windows for thermoplastics in thermoforming processes are still often determined through time-consuming trial-and-error approaches. This results in increased effort when commissioning new machines, implementing new technologies, or substituting sheet materials. One key reason is the lack of methods that allow for efficient, process-related assessment of material behavior and a quantitative definition of a “target state” of the heated sheet in relation to geometry and process conditions. In this study, we present the In-Situ Thermoforming Characterization (ITC) method as an application-oriented approach that enables format-independent evaluation of material behavior directly within the forming station of a thermoforming system. The method was successfully applied to a material substitution case, replacing conventional virgin polypropylene (PP) with post-consumer recyclate (PCR) — in this case, recycled PP (rPP) — in the production of a defined cup geometry. The results enabled the transfer of existing process knowledge from the virgin material to the recyclate, thereby accelerating material qualification. Based on the collected data, material behavior under process conditions could be mapped within the design space, making it possible to identify machine settings that deliver equivalent forming results in our test setup. Overall, the method shows strong potential for efficient and precise determination of machine-specific process windows.
Journal articles
Materials performance considerations in hydrothermal liquefaction conversion of biomass, TAPPI Journal June 2025
ABSTRACT: Hydrothermal liquefaction (HTL) is a promising thermochemical route developed to convert woody biomass and biowaste to biochemicals and bio-oils. However, the operating conditions are rather harsh to biorefinery structural metallic components. These conditions include alkaline catalysts such as potassium carbonate (K2CO3); hot, pressurized (sub-critical) water reaction; and medium and aggressive anions chlorine (Cl•) and hydrogen sulfide (H•) released from biomass feedstocks. Thus, selection of suitable structural alloys for biorefinery components involves striking a balance between mechanical properties, corrosion resistance, and cost. Alloys currently being considered for this application include ferritic-martensitic steels and austenitic stainless steels. From a corrosion perspective in hot pressurized water, the former typically exhibits higher stress corrosion cracking resistance, whereas the latter exhibits higher corrosion resistance. This study reviews cost-effective corrosion control strategies aimed at increasing the chromium (Cr) content for protective surface oxide formation, as screened by testing in simulated HTL alkaline water, to support materials selection and design. Corrosion control strategies include surface modification (increasing surface Cr content), alloying (increasing bulk Cr content), and stainless-steel type (ferritic vs. austenitic). Of the alloys considered (including those subjected to surface modification), ferritic stainless steels exhibit a promising balance between corrosion and stress corrosion cracking resistance, adding another family of candidate alloys for structural biorefinery component materials selection and design.