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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
Print quality of flexographic printed paperboard related to coating composition and structure, TAPPI Journal January 2018
Print quality of flexographic printed paperboard related to coating composition and structure, TAPPI Journal January 2018
Journal articles
Magazine articles
Evaluation of the out-of-plane response of fiber networks with a representative volume element model, TAPPI JOURNAL June 2018
Evaluation of the out-of-plane response of fiber networks with a representative volume element model, TAPPI JOURNAL June 2018
Journal articles
Magazine articles
Decreased water usage in a softwood ECF bleaching sequence— full mill simulations, TAPPI JOURNAL June 2018
Decreased water usage in a softwood ECF bleaching sequence— full mill simulations, TAPPI JOURNAL June 2018
Journal articles
Magazine articles
Photo-catalytic degradation of gaseous pollutants in paper mills of southern China, TAPPI JOURNAL March 2018
Photo-catalytic degradation of gaseous pollutants in paper mills of southern China, TAPPI JOURNAL March 2018
Journal articles
Magazine articles
Use of vent stack temperature as a feedforward variable for dissolver total titratable alkali (TTA) control, TAPPI JOURNAL May 2018
Use of vent stack temperature as a feedforward variable for dissolver total titratable alkali (TTA) control, TAPPI JOURNAL May 2018
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
Magazine articles
Guest Editorial: Still working (overtime): Life-saving nonwovens and continued innovation, TAPPI Journal August 2021
ABSTRACT: Recently, the United States federal government has recommended the need for a booster shot to combat COVID-19, highlighting the highly contagious nature of its Delta variant. This variant is surging in countries as far apart as Thailand, Brazil, and the United States. While the availability of the vaccine is not an issue in the United States, African, Latin American, and South Asian countries are in dire need of the vaccine. This scenario necessitates the need for continued safety measures. Among the recommended safety measures, use of face masks has been proven to be effective. Recent analysis showed that two-thirds of the 32 states in the United States with face mask mandates found them helpful for lowering infection rates.
Journal articles
Magazine articles
Rheological characterization of tack and viscoelasticity of compositions of crepe coating used in the Yankee dryer, TAPPI Journal November 2019
ABSTRACT: The vast majority of tissue production uses creping to achieve the required set of properties on the base sheet. The Yankee coating helps to develop the desired crepe that in turn determines properties such as bulk and softness. The adhesion of the sheet to the Yankee surface is a very important characteristic to consider in achieving the desired crepe. The coating mix usually consists of the adhesive, modifier, and release. A good combination of these components is essential to achieving the desired properties of the tissue or towel, which often are determined by trials on the machine that can be time consuming and lead to costly rejects. In this paper, five compo-sitions of an industrial Yankee coating adhesive, modifier, and release were examined rheologically. The weight ratio of the adhesive was kept constant at 30% in all five compositions and the modifier and release ratios were varied. The normal force and work done by the different compositions have been shown at various temperatures simulating that of the Yankee surface, and the oscillatory test was carried out to explain the linear and nonlinear viscoelastic characteristic of the optimal coating composition.