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Factors affecting phosphorus uptake/dissolution during slaking and causticizing, TAPPI Journal March 2024
ABSTRACT: Hydroxide is regenerated in the recovery cycle of kraft pulp mills by the addition of lime (CaO) to green liquor. Phosphate in green liquor can react with the lime during slaking/causticizing. Total titratable alkali (TTA), sulfidity, the concentration of phosphate in the green liquor, temperature, and the liming ratio were all variables explored in this work to determine their influence on phosphorus uptake and dissolution. Experiments were also run in which the lime was slaked before being added to the green liquor to separate reactions with phosphate during slaking and reactions that occur during causticizing. Both reburnt lime and technical grade CaO were used. The experiment results indicate that phosphorus primarily reacts with slaked lime (Ca(OH)2), and that the final concentration of phosphate in the white liquor at the end of slaking and causticizing is nearly independent of the initial concentration of phosphorus and only mildly dependent on the carbonate concentration in the green liquor. There do appear to be differences in the rate at which phosphate reacts with reburnt lime and technical grade CaO, though the reason for this was not determined.
Journal articles
Magazine articles
Z-directional testing of paperboard in combined tensile and compression loading, TAPPI Journal May 2024
ABSTRACT: The out-of-plane properties of paperboard are important in several converting applications such as printing, sealing, creasing, and calendering. A juxtaposed tensile and compression curve in the z direction (ZD) will, however, appear to have a kink or discontinuity at 0 stress. The purpose of the present work is to capture the continuous transition between tension and compression and to increase the understanding of the complex ZD properties of paperboard by cyclic testing. In this attempt to unify the ZD tensile and compressive behavior of paperboard, samples were laminated to the testing platens using heat seal laminate film. The method for adhering the samples was compared to samples that were laminated and glued to the testing platens. The edge effects of the cutting method were evaluated in compression testing with samples not attached to the testing platens. The flat slope seen in the initial part of the pure compression curve disappeared when the samples were laminated to the testing platens. The flat slope was instead replaced by a continuous response in the transition across 0 N. The stiffness in the transition region resembled the response in tensile testing. When the testing is cycled, the material exhibits a history dependence. Starting the cycle in either compression or tensile will show an effect on the stiffness at the transition, as well as the compressive stiffness. However, the ultimate tensile strength is unaffected.
Journal articles
Magazine articles
Utilization of Areca leaf residues for sustainable production of greyboard, TAPPI Journal May 2024
ABSTRACT: This study primarily focused on the production of greyboard using waste materials from small scale industries, and specifically using Areca leaf waste fibers as a sustainable and environmentally friendly resource. Areca leaf waste fibers were employed as the primary raw material for greyboard manufacturing. The resulting greyboard exhibited commendable properties, including a tear index of 7.53 mN·m2/g, tensile index of 18.34·N·m/g (i.e., breaking length of 1870 m), burst factor of 9.24 (gf/cm2)/(g/m2) and stiffness factor of 33.1. This greyboard was created through a series of steps, including hydrothermal treatment of the material at 155°C and mechanical pulping refinement. The produced greyboard met the specifications outlined in the Indian Standard 2617 (1967) for greyboard. The key objective of this work was to leverage agricultural waste resources to develop a chemical-free greyboard, resulting in reduced waste disposal in open fields and a decrease in chemical usage within the greyboard manufacturing industry. Various characterization techniques, including field emission scanning electron microscopy (FE-SEM), attenuated total reflection•Fourier transform infrared (ATR-FTIR) analysis, and X-ray diffraction (XRD), were used to assess the fiber quality, including aspects such as functional groups, morphology, and crystallinity for the materials used in the manufacturing process.
Journal articles
Nonlinear modeling of batch digester discharge dynamics with rheology-driven hydraulic transport and drainability coupling, TAPPI Journal September 2026
ABSTRACT: Batch digester blowdown constitutes a strongly nonlinear transient transport process governed by the coupled evolution of pulp consistency, slurry density, hydraulic resistance, liquid inventory, and discharge line dynamics. A control-oriented nonlinear formulation is developed by coupling dry fiber and free liquor mass balances with phase volume reconstruction, consistency-dependent hydraulic resistance, channeling and drainability effects, and a power law head flow relationship derived within a lumped hydraulic inertance framework. A fixed-gain PI controller obtained from local linearization is employed as the conventional benchmark, whereas an integral sliding mode controller (SMC) explicitly compensates the nonlinear time-varying hydraulic structure and bounded disturbances. Both strategies are evaluated under identical actuator constraints and sequential perturbations involving opposing head, hydraulic resistance, channeling, drainability, and dilution. Numerical results demonstrate lower rootmean- square error, integral absolute error, and peak flow-tracking error for the SMC, with rapid recovery toward the prescribed sliding boundary layer and improved robustness to variations in the nonlinear flow exponent n. Cumulative electrical energy and batch-specific specific energy consumption remain comparatively similar, indicating that the principal SMC benefit is enhanced hydraulic regulation rather than substantial batch energy reduction. Specific energy consumption is an established metric for energetic assessment of slurry transport. Model-based hydraulic demand, electrical power, and sliding manifold surfaces further characterize the nonlinear operating domain. The resulting framework provides a computational proof-of-concept for modeling and control of transient batch digester discharge systems.
Journal articles
Pressure drop characteristics of steam condensation flow in triangular channels for multi-channel cylinder dryers, TAPPI Journal September 2026
ABSTRACT: This study investigates the condensation pressure drop characteristics of steam in the channels of multi-channel drying cylinders, which remain insufficiently understood. An experimental system was established using a horizontal mini-channel with a triangular cross-section and a hydraulic diameter of 4.09 mm. Flow visualization combined with a high-precision data acquisition system was employed to systematically examine the effects of steam mass flux (10•60 kg/(m²·s)), inlet temperature (110°C•140°C), and cooling water flow rate (100•500 kg/h) on the frictional pressure drop during condensation. The results indicate that the two-phase frictional pressure drop increases with rising steam mass flux but decreases with increasing saturation temperature, while the effect of cooling water flow rate becomes more pronounced under lower temperature conditions. In addition, several existing two-phase flow pressure drop correlations were evaluated against the experimental data. Based on a comparative assessment of eight existing correlations, a new predictive model was developed through regression analysis, achieving a mean absolute percentage error (MAPE) of 19.56%. These findings elucidate the pressure drop mechanism of steam condensation in triangular channels and establish a high-precision predictive model, providing theoretical guidance and a critical tool for the engineering design and energy consumption optimization of multi-channel drying cylinders.
Journal articles
Magazine articles
In-process detection of fiber cutting in low consistency ref
In-process detection of fiber cutting in low consistency refining based on measurement of forces on refiner bars, TAPPI JOURNAL April 2017
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Low consistency refining of mechanical pulp — system design
Low consistency refining of mechanical pulp — system design, TAPPI JOURNAL July 2017
Journal articles
Magazine articles
Kinetics of sulfur dioxide-alcohol-water (SAW) pulping of su
Kinetics of sulfur dioxide-alcohol-water (SAW) pulping of sugarcane straw (SCS), TAPPI JOURNAL June 2017
Journal articles
Magazine articles
Operational limits of blade coating associated with high aspect ratio pigments: Part I—bench top blade coater, TAPPI Journal February 2019
Operational limits of blade coating associated with high aspect ratio pigments: Part I—bench top blade coater, TAPPI Journal February 2019
Journal articles
Magazine articles
Operational limits of blade coating assocciated with high aspect ratio pigments: PartII—cylindrical laboratory coater, TAPPI Journal February 2019
Operational limits of blade coating assocciated with high aspect ratio pigments: PartII—cylindrical laboratory coater, TAPPI Journal February 2019