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On the usage of online fiber measurements for predicting bleached eucalyptus kraft pulp tensile index — an industrial case, TAPPI Journal July 2022
ABSTRACT: Cellulose pulp’s physical-mechanical properties are determined by laboratory tests obtained from prepared handsheets. However, this procedure is time intensive and presents a lead time until the results are available, hindering its utilization for monitoring and decision-making in a pulp mill. In this context, developing real-time solutions for physical-mechanical properties prediction is fundamental. This work applied a mathematical modeling approach to develop a soft sensor for tensile index monitoring. The mathematical model considers online morphology measurements obtained from the last bleaching stage outlet stream and important process variables for tensile index prediction. The results obtained are satisfactory compared to laboratory results, presenting a mean absolute percentual error of 2.5%, which agrees with the laboratory testing method’s reproducibility.
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Kraft pulp bleaching with a P-stage catalyzed by both bicarbonate and TAED, TAPPI Journal July 2019
ABSTRACT: Peroxide bleaching of softwood and hardwood (eucalypt) kraft pulps was performed in solutions of sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH). The conventional P stage (hydrogen peroxide + sodium hydroxide; H2O2 + NaOH) was the most effective brightening system without an additional activator. However, peroxide activation by bicarbonate anion (HCO3•) was obvious in all cases where NaHCO3 or Na2CO3 was used. When N,N,N’,N’-tetraacetylethylenediamine (TAED) was added to the bleaching sys-tem, Na2CO3 as the alkali source afforded equal or slightly higher bleached brightness compared to NaOH usage for both the softwood and hardwood pulps. This outcome is attributed to simultaneous peroxide activation by HCO3• and TAED. When applied to the eucalypt pulp, the H2O2/Na2CO3/TAED bleaching system also decreased the bright-ness loss due to thermal reversion.
Journal articles
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Rewet suppression through press felt engineering, TAPPI Journal June 2022
ABSTRACT: Due to the immense energy and associated financial cost of drying paper, achieving a drier web entering the dryers is a key objective in paper manufacture. One major research thrust has been finding a way to increase press solids by mitigating or eliminating rewet in the press section. For decades, solutions to this problem have remained elusive. In this work, we develop a novel approach that significantly reduces rewet by rupturing the liquid channels between felt and web. We illustrate the effects that altering the mechanical and surface properties of the press felt matrix have on the stability of these liquid channels. In a laboratory-scale platen press, a 40% reduction in the residual water of 120 g/m2 southern bleached softwood kraft (SBSK) pulp handsheets after pressing was observed, corresponding to an increase in press solids from 48% to 61%. For reference, pressing under identical conditions with paper blotters, in which minimal rewet is presumed to occur, resulted in 64% solids. Furthermore, we observed enhanced dewatering across a range of basis weights, applied pressures, and felt types. In addition to measuring the solids content of pressed sheets, we capture and analyze video evidence of the mechanisms at play in our improved dewatering technology.
Journal articles
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Comparative analysis and benchmarking of commercial and emerging fast pyrolysis technologies, TAPPI Journal May 2023
ABSTRACT: It is well established that producing sustainable fuels and replacing the fossil-based ones is one of the key solutions to achieving net-zero emissions goals. One of the most advanced commercial-scale pathways to biofuels available today is fast pyrolysis. However, due to the need for a supportive regulatory environment and mitigation strategies for uncertainties related to costs and feedstock quality, fast pyrolysis is not yet being widely implemented. In this case study, three fast pyrolysis technologies with a technology readiness level (TRL) of 6 and above have been compared to distinguish between them and identify the conditions under which they are economically viable. The circulating fluidized bed (CFB), rotating cone (RC), and mechanically assisted fluidized bed (MFB) fast pyrolysis technologies were considered. First, the flow diagram and a mass and energy balance comparison were addressed. It was revealed that the RC configuration has better bio-oil yields because it can handle smaller particles. The MFB configuration has a progressive condensation unit at the end of the process, which produces a nearly dry oil having a higher energy content. Four implementation scenarios were studied. The first was the fast pyrolysis standalone process, where all options had marginal economic attractiveness, and the RC configuration economically outperformed the other two. Integration of a fast pyrolysis plant into a sawmill in the second scenario was found to bring significant improvements in revenues and internal rate of return (IRR). Realization of the full value of bio-oil (the third scenario) brought significantly more revenues for the MFB. Finally, the fourth scenario involved adding a progressive condensation unit, which increased the capital expenditure (CAPEX) by 3%•4% while increasing revenues by 32%•35%. A sensitivity analysis highlighted the importance of financial support towards capital cost and the full valuation of bio-oil for the economic viability of fast pyrolysis processes. Progressive condensation leading to more added-value bio-oil makes the standalone fast pyrolysis process more profitable.
Journal articles
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Multilayering of conventional latex-based dispersion coatings containing small amounts of silica nanospheres: Runnability on a pilot scale flexographic coater and barrier performance, TAPPI Journal November 2023
ABSTRACT: The addition of functional coatings to packaging materials is a key requirement for increasing their performance and creating innovative packaging solutions. Flexography, a cost-effective printing method commonly used to print information and graphics directly onto a wide variety of packaging substrates, shows good potential for applying functional coatings. In this study, conventional clay-latex coating formulations containing approximately 1.3 wt% silica nanospheres were applied to a linerboard using a pilot scale flexographic printing web press. The performance of multilayered silica nanosphere-based coatings was compared with conventional coatings containing talc and/or wax dispersion in terms of coating grammage, runnability, and barrier performance. Coating grammage increased with an increased number of coating layers and a significant decrease in both the water vapor transmission rate (WVTR) and the direct water uptake of water (Cobb 120 wettability test) was observed for coatings containing silica nanoparticles. In general, the silica nanosphere-based coatings performed better than talc-based coatings. Talc/wax-based coatings had the highest variation in surface roughness due to an uneven distribution and variations of coating layers.
Journal articles
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Development of a fast brightness testing method for mechanical pulp based on microwave oven drying, TAPPI Journal June 2020
ABSTRACT: Brightness is an important quality parameter for pulp products, and it is important to have reliable measurement of pulp brightness in a timely manner for process control and/or quality control purposes. In these circumstances, a quick testing method for pulp brightness is highly desirable.A rapid handsheet brightness testing method for lignin-rich mechanical pulp has been developed, which is based on the use of tap water to make handsheets and microwave ovens to rapidly dry the handsheet. Microwave oven fast drying decreased the handsheet brightness of mechanical pulp by 5•6 points due to the lignin-originated discol-oration reactions. The spray of ascorbic acid and ethylenediaminetetraacetic acid (EDTA) solutions to the handsheet can effectively inhibit these lignin discoloration reactions.With 0.2% ascorbic acid and 0.2% EDTA spraying on the wet pulp handsheet, the brightness of the handsheet from a peroxide-bleached stone groundwood pulp after the microwave oven fast drying method was similar to that obtained from the same pulp but following TAPPI Standard Test Method T 272 sp-12 “Forming handsheets for reflectance testing of pulp (sheet machine procedure)”. The effect of handsheet dryness on the handsheet brightness was also studied, and the results showed that the brightness reading was almost constant in the dryness range of 70% to 90%. The method developed is a reliable, fast brightness testing method for lignin-rich pulp that is of practical interest in industrial operations.
Journal articles
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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
Novel test method for measuring defects in barrier coatings, TAPPI Journal November 2022
ABSTRACT: In the last several years, activity to develop water-based barrier coatings (WBBCs) that meet challenging packaging performance requirements has increased dramatically. Cellulose-based packaging solutions can provide a more sustainable packaging option for replacing single-use plastic-based options like extrusion-based and laminated materials. An advantage of WBBCs is the opportunity to reduce the coating thickness applied, as long as the barrier requirements can be met. A challenge that must be overcome is the ability to maintain a defect and pin-hole-free coating layer after coating and drying to retain the barrier performance. Many formulation and coating parameters can affect the barrier coating layer quality; however, methods for detecting more subtle differences in these types of studies are not widely available. Work was carried out to develop a quantitative technique for detecting and measuring the quantity and size of defects in the barrier coating layer. A test method has been developed using a combination of dyed oil and image analysis to be able to characterize the imperfections in the coating surface. The use of dyed oil serves two purposes. First, it better simulates the types of materials, in this case, oils and grease, for which the barrier coating is expected to hold out. Second, it also provides contrast between the coating and failure points for testing. An image analysis technique is employed to characterize the number and size of the imperfections. For the former, it reduces the testing time required if a quality control or laboratory technician counts the dots. For the latter, it assists with judgment on the source of the root cause of the imperfection, such as base sheet defects, coating dispersion issues, or perhaps micro-blisters in the coating, as some examples.To show the benefit of this technique, several pilot coating studies were designed to see if the new technique could be utilized to detect differences in WBBC performance. Both process and chemical variables were evaluated. With refinement, it is believed this technique can be utilized in development work, as well as for a potential quality control technique for manufacturing of coated paper and paperboard products.
Journal articles
Magazine articles
Application of fuzzy TOPSIS in the Analyze phase of the DMAIC cycle to aid decision-making, TAPPI Journal April 2020
ABSTRACT: This paper reports the use of multicriteria analysis in the Analyze phase of the DMAIC (Define-Measure-Analyze-Improve-Control) cycle for continuous improvement. The research was carried out in a tissue paper factory located in southern Brazil. A sample of 64 parts of 16 different reels of recycled paper was used. A problem regarding paper quality variability was detected, presenting a scrap index ranging between 9% and 23%, compromising machine productivity and product sales. This motivated the implementation of a structured project supported by the application of the DMAIC cycle. The project team (machine operators, maintenance staff, supervisor, and data analyst) defined the evaluation criteria and determined the control intervals and their equivalence with linguistic variables to support the necessary evaluations for the application of fuzzy TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). The criteria were C1-Longitudinal Strength (Kgf), C2-Longitudinal Elongation (mm), C3-Cross-strength (kgf), C4-Cross-elongation (mm), C5-Weight (g/m²), and C6-Humidity (%). The results showed that samples with the same ranking had the lowest scrap indexes in the subsequent process. Also, the criterion C5 had a more significant impact on the quality of the product than the other criteria, which was determined from the DMAIC sequence. Improvements related to C5 should be prioritized. The fuzzy TOPSIS method presented is a flexible tool, adapting itself to the solution of the problem and contributing to the decision-making process.
Journal articles
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Equilibrium moisture content in wet pressing of paper, TAPPI Journal July 2020
ABSTRACT: Equilibrium moisture is a limiting factor in achieving high solids in the later stages of pressing or pressing low basis weight grades. We have developed a model that relates equilibrium moisture directly to the pore size distribution of fibers as measured by the solute exclusion technique. The model shows that chemical pulping and refining increase equilibrium moisture by increasing pore volume at given pore sizes in fibers, which leads to lower pressed solids and greater energy expenditure in the dryer section. Means to increase equilibrium moisture without compromising pulp strength are briefly discussed.