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Vajda Papír Takes a Big Step Forward, Tissue360º Spring/Summer 2021
Vajda Papír Takes a Big Step Forward, Tissue360º Spring/Summer 2021
Journal articles
Magazine articles
Continuous tannin extraction by use of screw reactor, TAPPI Journal February 2021
ABSTRACT: A pilot-size screw reactor (extraction unit) was used for tannin extraction of spruce. Yield of the same magnitude or better was obtained when comparing a screw reactor with batch reactors. A longer presoaking time in water seemed to be better than a short one for obtaining higher yield. A higher yield is obtained with lower dry-water ratio, which suggests that the internal diffusion in bark does not determine mass transfer as much as is the case without presoaking of bark. The higher dry-water ratio decreased the yield. The prior soaking of the bark also minimized the mechanical reactor feeding problems (clogging). The benefits of a screw reactor likely are that run time changes for different process conditions are flexible; it simplifies design and construction of an industrial unit for tannin production; and it saves space because of the need for fewer and smaller intermediate storage tanks.
Journal articles
Magazine articles
An evaluation of household tissue softness, TAPPI Journal February 2021
ABSTRACT: This study extends our 2019 paper, a study of the softness of household tissues using a tissue softness analyzer (TSA) and hand-felt panels. It revisits the softness theory of Holger Hollmark by applying a reciprocal matrix approach to measure sheet bulk softness and surface softness, and then make comparisons with the results obtained using a TSA instrument. We ascertained that there was a high correlation of R=0.904 between panel-corrected hand-felt (CHF) softness and TSA softness (TSA-HF); and a low correlation of R=-0.678 between panel-corrected hand-felt surface softness (CHSS) and TSA smoothness (TS-750). Three hunches about TSA measurements were confirmed: 1) Hollmark’s theory was confirmed by a high correlation coefficient (R=0.895) between CHF and CHSS softness, indicating that the two parameters are mutually dependent; 2) TS-750 differs from CHSS and has partial influence on TSA-HF results with a correlation of R = -0.510; and 3) although TS-750 has only limited influences on TSA-HF, further opportunities for their application can be provided using pertinent regression equations.
Journal articles
Magazine articles
Co-ground mineral/microfibrillated cellulose composite materials: Recycled fibers, engineered minerals, and new product forms, TAPPI Journal January 2021
ABSTRACT: When pulp and minerals are co-processed in suspension, the mineral acts as a grinding aid, allowing costeffective production of mineral/microfibrillated cellulose (MFC) composite materials. This processing uses robust milling equipment and is practiced at industrial scale. The resulting products can be used in many applications, including as wet- and dry-strength aids in paper and board production.Previously, we have reported that use of these MFC composite materials in fiber-based applications allow generally improved wet and dry mechanical properties with concomitant opportunities for cost savings, property improvements, or grade developments. Mineral/MFC composites made with recycled pulp feedstocks were shown to offer at least equivalent strength aid performance to composites made using virgin fibers. Selection of mineral and fiber allows preparation of mineral/MFC composites with a range of properties. For example, the viscosity of such formulations was shown to be controlled by the shape factor of the mineral chosen, effective barrier formulations were prepared, and mineral/MFC composites with graphite as the mineral were prepared.High-solids mineral/MFC composites were prepared at 75% total solids (37% fibril solids). When resuspended and used for papermaking, these high-solids products gave equivalent performance to never-dried controls.
Journal articles
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SetPoint: Under the Influence, Paper360º July/August 2021
SetPoint: Under the Influence, Paper360º July/August 2021
Journal articles
Magazine articles
The Paper360° 2021 TOP 50 POWER LIST, Paper360º July/August 2021
The Paper360° 2021 TOP 50 POWER LIST, Paper360º July/August 2021
Journal articles
Magazine articles
Rheological behavior of magnetic pulp fiber suspensions, TAPPI Journal June 2021
ABSTRACT: This paper is focused on the rheology of magnetic pulp suspensions in absence and presence of an external magnetic field. Magnetic fibers were prepared by the lumen loading method using bleached eucalyptus fibers and cobalt ferrite (CoFe2O4) nanoparticles. The effect of mass consistency, temperature, concentration of magnetic fibers, and magnetic field strength on yield stress and apparent viscosity of the suspensions were investigated. In the absence of an applied field, a dependence of yield stress with consistency, as well as with the percentage of magnetic fibers present in the suspension, was found. In flow tests, all the suspensions exhibited shear-thinning behavior, showing that the viscosity is only affected by the consistency of the suspension. On the other hand, magnetorheological measurements show a negative effect of the applied magnetic field on the viscosity of the suspension.
Journal articles
Magazine articles
New learnings and strategies for meeting future recovery boiler particulate emission limits with existing electrostatic precipitators, TAPPI Journal June 2021
ABSTRACT: It is foreseeable that recovery boiler particulate emission limits in the United States and Canada will continue to get more stringent with time. Because of this, continued improvement of emission control equipment, as well as a better understanding of how operating parameters affect performance, are necessary. Although electrostatic precipitators (ESPs) are often viewed as a mature technology, many improvements in ESP technology continue to be developed. In recent years, academic efforts have improved the understanding of recovery boiler operating conditions on ESP performance. Additionally, advancements in materials, power supplies, and design continue to improve the efficiency and reliability of ESPs.This paper discusses how recovery boiler and electrostatic precipitator (ESP) operating factors affect ESP perfor-mance based on process simulations and practical experience, and how these learnings can be implemented to improve future operation of existing ESPs.
Journal articles
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Repulping of wet strength paper towel with potassium monopersulfate, TAPPI Journal September 2020
ABSTRACT: Potassium monopersulfate (KMPS) was used in repulping of polyamide-epichlorohydrin (PAE)-containing paper towel. The effectiveness of the repulping aid was compared with that of sodium hypochlorite. Addition of a 2.4% KMPS repulping aid achieved complete repulping of the paper towel, resulting in 88% screen yield and about 5% rejects. To reach a similar pulping result, two times the oxidative equivalent amount of sodium hypochlorite had to be used. Compared to the pulp fibers obtained from sodium hypochlorite repulping, those obtained from KMPS repulping had higher physical strength, longer fiber length, and lower fines content. This study demonstrated that KMPS was superior to sodium hypochlorite in repulping of PAE-containing paper towel in terms of effectiveness and pulp quality.
Journal articles
Magazine articles
Numerical analysis of slot die coating of nanocellulosic materials, TAPPI Journal November 2020
ABSTRACT: Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parame-ters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume meth-od is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to poten-tial defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted.