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Journal articles
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The solubility of calcium carbonate in green liquor handling systems, TAPPI Journal October 2019
ABSTRACT: The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.
Journal articles
Magazine articles
Case study: Paper mill power plant optimization—balancing steam venting with mill demand, TAPPI Journal June 2020
ABSTRACT: Most Power departments are tasked with generating steam to support mill wide operations, generate electricity, and reduce operating costs. To accomplish these tasks, power boilers generate high pressure steam that is reduced to intermediate and low pressures for process utilization in the mill by means of steam turbine generator extraction or pressure reducing valves. The most economical method to reduce steam pressure is the use of steam turbine generators, as electricity is generated from the steam when it is reduced in pressure. Electricity that is produced by these generators provides a substantial financial benefit and helps offset overall operational costs. To achieve tangible financial gains, the mill must evaluate the overall cost of steam production and the price of electricity.The current work provides a case study of power plant optimization that evaluated electricity production and steam production costs balanced with mill steam demand. Process and cost optimization led to a significant reduc-tion in low pressure steam venting, resulting in reduced fuel consumption and reduced operating cost.
Journal articles
Magazine articles
Effects of different ammonium lignosulfonate contents on the crystallization, rheological behaviors, and thermal and mechanical properties of ethylene propylene diene monomer/polypropylene/ammonium lignosulfonate composites, TAPPI Journal January 2020
ABSTRACT: Thermoplastic elastomer (TPE), made from ethylene propylene diene monomer (EPDM) and polypropylene (PP) based on reactive blending, has an excellent processing performance and characteristics and a wide range of applications. However, there are currently no reports in the literature regarding the usage of TPE in making composite boards. In this paper, EPDM, PP, and ammonium lignosulfonate (AL) were used as the raw materials, polyethylene wax was used as the plasticizer, and a dicumyl peroxide vulcanization system with dynamic vulcanization was used to make a new kind of composite material. This research studied the influences of the AL contents on the crystallization behaviors, rheological properties, thermal properties, and mechanical properties of the composites. The results showed that the AL content had a noticeable impact on the performance of the composite board. Accordingly, this kind of composite material can be used as an elastomer material for the core layer of laminated flooring.
Journal articles
Magazine articles
Quantification of hardwood black liquor contamination in pine black liquor, TAPPI Journal February 2024
ABSTRACT: The presence of hardwood black liquor contamination in pine black liquor can negatively impact brownstock washer and evaporator operation, as well as reduce soap separation and yield. It is also believed to negatively impact commercial kraft lignin production. It was desired to develop a method of quantitatively determining the amount of low-level hardwood liquor contamination in pine black liquor. A method employing pyrolysis-gas chromatography mass spectrometry (py-GCMS) was developed to perform the desired measurement. Laboratory cooks with carefully controlled blends of pine and hardwood chips were prepared, and the resulting liquor was measured using this technique. Additionally, samples of pine and hardwood black liquors were blended in known quantities and analyzed. All these samples were submitted as blind samples. The resulting analysis suggests the py-GCMS method was able to accurately determine the level of hardwood contamination between 1% to 10% hardwood liquor using a low-level calibration curve prepared with coniferyl alcohol and sinapyl alcohol as standards.
Journal articles
Magazine articles
Quantification of hardwood black liquor contamination in pine black liquor, TAPPI Journal February 2024
ABSTRACT: The presence of hardwood black liquor contamination in pine black liquor can negatively impact brownstock washer and evaporator operation, as well as reduce soap separation and yield. It is also believed to negatively impact commercial kraft lignin production. It was desired to develop a method of quantitatively determining the amount of low-level hardwood liquor contamination in pine black liquor. A method employing pyrolysis-gas chromatography mass spectrometry (py-GCMS) was developed to perform the desired measurement. Laboratory cooks with carefully controlled blends of pine and hardwood chips were prepared, and the resulting liquor was measured using this technique. Additionally, samples of pine and hardwood black liquors were blended in known quantities and analyzed. All these samples were submitted as blind samples. The resulting analysis suggests the py-GCMS method was able to accurately determine the level of hardwood contamination between 1% to 10% hardwood liquor using a low-level calibration curve prepared with coniferyl alcohol and sinapyl alcohol as standards.
Journal articles
Magazine articles
Editorial: Special issues in March and May TAPPI Journal focus on the latest pulp manufacture and engineering research, TAPPI Journal March 2024
ABSTRACT: This issue, organized by Editor-in-Chief Peter Hart, features content from the 2023 PEERS/IBBC Conference that has been peer reviewed for publication in TAPPI Journal. The papers encompass a range of topics:œ Two papers, from researchers Suarez et al. at WestRock, examine pulp from nonwoods like wheat straw and sugar-cane bagasse using a holistic life cycle analysis approach to project environmental performance in packaging products. The results can help mills make decisions about which fibers ensure a low carbon footprint.
Journal articles
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Evaluating the effect of recovery boiler operation on green liquor dregs concentration using multivariate analysis, TAPPI Journal June 2023
ABSTRACT: Poor settling and filterability of green liquor dregs has been a persistent problem in many kraft pulp mills. While the concentration and settling/filtering behaviors of dregs are expected to be related to how black liquor is burned in recovery boilers, the effect of boiler operation is not well understood. A systematic study was conducted to examine how recovery boiler operation may affect the dregs concentration in the raw green liquor (RGL) at three kraft pulp mills using SIMCA, a multivariate data analysis (MVDA) program. Daily average boiler operating data from three kraft mills were analyzed over a 3-year period. Results of both principal component analysis (PCA) and partial least squares regression (PLS) suggest that the main boiler operations contributing to high dregs concentrations in RGL are low liquor firing load, low bed temperature, poor char burning, and unstable char bed.
Journal articles
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Combatting lime kiln ringing problems at the Arauco Constitución mill, TAPPI Journal July 2020
ABSTRACT: The lime kiln at the Arauco Constitución mill experienced severe ringing problems requiring it to be shut down for ring removal every 3 to 6 months. The mill controlled the problems by blasting ring deposits off during operation with its existing industrial shotgun and a newly installed Cardox liquid carbon dioxide (CO2) cartridge system. Various ring blasting procedures were tested to determine the optimum ring location and thickness to blast; the optimum depth to insert the CO2 cartridge into the kiln; and the most effective blasting frequency and sequence to employ. The best strategy was found to be the weekly blasting operation that alternated between the liquid CO2 cartridge and the industrial shotgun, with the CO2 cartridge inserted into the ring mass, 20 cm (8 in.) away from the refractory brick surface, and the shotgun aimed at rings at about 28 m (92 ft) from the kiln discharge end. With each blasting event removing considerably more rings than before, it takes a longer time for rings to rebuild, allowing the kiln to run continuously between annual maintenance shutdowns with only a few short (< 4 h) downtimes for ring removal. This substantially reduces the costs associated with ring removal and lime replacement during unscheduled shutdowns.
Journal articles
Magazine articles
Incorporation of post-consumer pizza boxes in the recovered fiber stream: Impacts of grease on finished product quality, TAPPI Journal March 2021
ABSTRACT: Grease and cheese contamination of used pizza boxes has led to misunderstanding and controversy about the recyclability of pizza boxes. Some collection facilities accept pizza boxes while others do not. The purpose of this study is to determine whether typical grease or cheese contamination levels associated with pizza boxes impact finished product quality. Grease (from vegetable oil) and cheese are essentially hydrophobic and in sufficiently high concentration could interfere with interfiber bonding, resulting in paper strength loss.Findings from this study will be used to determine the viability of recycling pizza boxes at current and future con-centrations in old corrugated containers (OCC) recovered fiber streams. These findings will also be used to inform the acceptability of pizza boxes in the recycle stream and educate consumers about acceptable levels of grease or cheese residue found on these recycled boxes.
Journal articles
Magazine articles
Extension of a steady-state chlorine dioxide brightening model for Z-ECF bleaching of softwood kraft pulps, TAPPI Journal March 2021
ABSTRACT: Earlier studies developed a steady-state model to predict the brightness and/or bleach consumption during the chlorine dioxide brightening (D1) of softwood pulps produced by conventional elemental-chlorine-free (ECF) sequences. This model relates the chlorine dioxide consumed to the brightness gains predicated upon an asymptotic D1 brightness limit, an incoming D1 pulp brightness, and an equation parameter (ß11). The current investigation examines the application of this model to ECF sequences that use ozone delignification (Z-ECF). Literature D1 data from various Z-ECF bleaching studies, which investigated OZ, OD0/Z, and OZ/D0 delignification, were fitted to the model. The ß11 parameter was found to be linearly correlated to the entering kappa number. Interestingly, this linear relationship was found to be identical to the relationships observed when modeling the D1 stage for conventional ECF and chlorine-based bleach sequences. Subtle differences in D1 brightening response in the model among the various bleach sequences are reflected by incoming pulp brightness (at the same kappa number). The current model is used to illustrate how alterations to Z-ECF delignification affect D1 brightening and chlorine dioxide consumption.