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Wheat straw as an alternative pulp fiber, TAPPI Journal January 2020
Author: Peter W. Hart | ABSTRACT: The desire to market sustainable packaging materials has led to an interest in the use of various fiber types as a raw material. It has been suggested that the use of annual crops for partial replacement of wood fiber would result in more sustainable products. Several life cycle analyses (LCA) have been performed to evaluate these claims. These LCAs provided conflicting and contradictory results because of the local conditions and the specific pulping processes investigated. Selected LCAs are reviewed and the underlying reasons for these conflicting results are analyzed.
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Editorial: TAPPI Journal 2019 Best Research Paper addresses hard scale formation in green liquor pipelines, TAPPI Journal March 2020
ABSTRACT: TAPPI and the TAPPI Journal (TJ) Editorial Board would like congratulate the authors of the 2019 TAPPI Journal Best Research Paper Award: Alisha Giglio, Vladimiros Papangelakis, and Honghi Tran. Their paper, “The solubility of calcium carbonate in green liquor handling systems,” appeared on p. 595 of the October 2019 issue. This kraft recovery cycle research was recognized by the TJ Editorial Board for its innovation, creativity, scientific merit, and clear expression of ideas.
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Considerations in managing wastewater odor at pulp and paper operations, TAPPI Journal March 2022
ABSTRACT: Many pulp and paper mills are, at least periodically, faced with the release of odors that can migrate offsite and be considered a nuisance by nearby residents. At chemical pulp mills, perceptible odors associated with reduced sulfur compounds (RSCs) are common, many of which are highly perceptible owing to their low odor thresholds. As releases of RSCs and other odorous substances from production processes are progressively controlled, the proportional contribution from wastewater treatment systems to areal odors can increase. This review paper summarizes important fundamentals of odor generation, source identification, and control. Common odorous substances are identified, and mechanisms for their generation are summarized. Approaches for measuring odorous substances are detailed to enable more effective management, and various odor control strategies are discussed.
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Alternative “green” lime kiln fuels: Part II—Woody biomass, bio-oils, gasification, and hydrogen, TAPPI Journal May 2020
ABSTRACT: This paper is the second of a two-part series on “green” lime kiln fuels. The first part of this work reviews the use of pulp mill and recovery byproducts as either full or partial replacement of oil or natural gas in the kiln. The second part reviews the use of various forms of woody biomass, bio-oils, gasification and hydrogen as potential carbon neutral or carbon-free lime kiln fuels. Several of these options require specialized burners to supply the fuel to the kiln and high-quality metallurgy to withstand the acidic conditions of the fuel.
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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.
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Effects of different soda loss measurement techniques on brownstock quality, TAPPI Journal July 2024
ABSTRACT: The efficiency of the kraft recovery plant, bleaching process, and paper machine are affected when black liquor carryover from the brownstock washers is not controlled well. Measuring soda loss within a mill can vary from using conductivity, either in-situ or with a lab sample of black liquor filtrate squeezed from the last stage washer, to measuring absolute sodium content with a lab sodium specific ion probe or spectrophotometer. While measuring conductivity has value in tracking trends in black liquor losses, it is not an acceptable method in reporting losses in absolute units, typically in lb/ton of pulp. This is further complicated when trying to benchmark soda loss performance across a fleet of mills with multiple washer lines. Not only do the testing methods vary, but the amount of bound soda on high kappa pulps can be significant. This variability creates inconsistent results, and studies are needed to understand the effect of different testing methods on the pulp quality. In this study, soda loss is expressed as sodium sulfate (Na2SO4). Four different methods to measure soda content in pulp off commercial brownstock washers were studied: full digestion (FD), washing soaking overnight and washing (WSW), soaking in boiling water and stirring 10-min (SW-10), and squeeze-no wash (Sq). Total, washable, and bound sodium sulfate calculations were determined for each soda content measuring technique using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results showed bound and washable sodium sulfate amounts significantly depend on which soda measurement technique was used. In addition, the soda results were correlated with the pulp kappa numbers. As the kappa number increases, bound soda increases, regardless of the soda measurement method used. Impacts of high sodium sulfate in brownstock are also discussed.
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Understanding extensibility of paper: Role of fiber elongation and fiber bonding, TAPPI Journal March 2020
ABSTRACT: The tensile tests of individual bleached softwood kraft pulp fibers and sheets, as well as the micro-mechanical simulation of the fiber network, suggest that only a part of the elongation potential of individual fibers is utilized in the elongation of the sheet. The stress-strain curves of two actual individual pulp fibers and one mimicked classic stress-strain behavior of fiber were applied to a micromechanical simulation of random fiber networks. Both the experimental results and the micromechanical simulations indicated that fiber bonding has an important role not only in determining the strength but also the elongation of fiber networks. Additionally, the results indicate that the shape of the stress-strain curve of individual pulp fibers may have a significant influence on the shape of the stress-strain curve of a paper sheet. A large increase in elongation and strength of paper can be reached only by strengthening fiber-fiber bonding, as demonstrated by the experimental handsheets containing starch and cellulose microfibrils and by the micromechanical simulations. The key conclusion related to this investigation was that simulated uniform inter-fiber bond strength does not influence the shape of the stress-strain curve of the fiber network until the bonds fail, whereas the number of bonds has an influence on the activation of the fiber network and on the shape of the whole stress-strain curve.
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How to use total dissolved solids measurements to evaluate the performance of diffuser washers—A mill study, TAPPI Journal April 2020
ABSTRACT: Various types of pulp washing equipment are available. Each washing device has a unique mechanical construction, and the washing principle is often a combination of dilution, thickening, and displacement washing. In this work, the performance of the pressure diffuser washer is studied. In stepwise trials, the effect of the feed and discharge consistencies on the performance of the diffuser was studied. The effect of the downward velocity of the screen on the pressure diffuser’s washing efficiency was also studied. The measurement of total dissolved solids (TDS) by a process refractometer was used as a wash loss measurement unit and the refractometer’s results were used in the calculations of standardized Nordén efficiency (E10) values. The chemical oxygen demand (COD) and conductivity values were also measured and their results compared to the TDS results.The results indicated that feed consistency has a significant effect on the performance and effectiveness of the diffuser washers in the mill. It can also be stated that when the downward velocity of the screen is adjusted to too high a level, the washing efficiency of the pressure diffuser decreases. As a conclusion from the mill tests, it can be stated that even small process parameter changes can provide enhanced diffuser washing at the beginning of the washing line, which has a direct effect on the performance of post-oxygen washing.
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Lignin-based resins for kraft paper applications, TAPPI Journal November 2019
ABSTRACT: We investigated miscanthus (MS) and willow (W) lignin-furfural based resins as potential reinforce-ment agents on softwood and hardwood kraft paper. These resins might be sustainable alternatives to the commercial phenolformaldehyde (PF) resins. Phenol is a petrochemical product and formaldehyde has been classified as a carcinogen by the U.S. Environmental Protection Agency. The lignin used in this study was derived from hot water extraction (160ºC, 2 h) of MS and W biomass, and may be considered sulfur-free. These biorefinery lignins were characterized for their chemical composition and inherent properties via wet chemistry and instrumental techniques. The resin blends (MS-resin and W-resin) were characterized for their molecular weight, thermal behavior, and mechanical properties. Mechanical properties were measured by the resin’s ability to reinforce softwood and hard-wood kraft papers. The effect of adding hexamethylenetetramine (HMTA), a curing agent, to the resin was also examined. Mixtures of PF and lignin-based resins were investigated to further explore ways to reduce use of non-renewables, phenol, and carcinogenic formaldehyde. The results show that lignin-based resins have the potential to replace PF resins in kraft paper applications. For softwood paper, the highest strength was achieved using W-resin, without HMTA (2.5 times greater than PF with HMTA). For hardwood paper, MS-resin with HMTA gave the highest strength (2.3 times higher than PF with HMTA). The lignin-based resins, without HMTA, also yielded mechanical properties comparable to PF with HMTA.
Journal articles
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Using bleaching stage models for benchmarking hardwood ECF bleach plants, TAPPI Journal October 2023
ABSTRACT: Steady-state models estimated the performance of the D0(EOP)D1 bleach sequence at two mixed hardwood bleach plants in the southern United States. At Mill 1, the full sequence’s chlorine dioxide charge that brightens the pulp to ~84% ISO was monitored for two weeks. Mill 2 considered the partial sequence that brightens the pulp to ~86% ISO for nearly four weeks. Elevated levels of chlorine dioxide were linked to increased washer carryover in brownstock and extraction areas. For Mills 1 and 2, an extra 0.24% and 0.33% chlorine dioxide was consumed in the D0 stage. This extra bleach demand was equivalent to an additional 4.8 and 5.5 kappa load to the brownstock, respectively. Some differences were observed for the D1 stage. Mill 1 had extraction carryover that averaged 1.1 units higher than was measured, contributing to use of an extra 0.22% of chlorine dioxide. Mill 2 had extraction carryover that averaged between 0 and 0.7 kappa units and consumed up to 0.13% more chlorine dioxide. Another data set from Mill 2 showed high brownstock and extraction carryover, leading to ~0.90% more total chlorine dioxide usage to brighten to 84% ISO. Overall, this investigation illustrated that the models could be employed as benchmarks.