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Journal articles
Application of AI-based approach to control the papermaking process, TAPPI Journal March 2025
ABSTRACT: This paper explores AI’s role in revolutionizing the pulp and paper industry, and specifically in predicting wet tensile strength (WTS) for specialty-grade papers. Leveraging eLIXA technology, a 90-day study achieved a 15% reduction in chemical dosage and an 80% decrease in wet tensile standard deviation. The real-time dosage prediction led to optimizing the wet strength resin (WSR) consumption and improved process reliability. The self-learning models exhibited adaptability to changing variables, ensuring their robustness. Overall, this study highlights AI’s transformative impact on efficiency, cost savings, and product quality within the dynamic landscape of papermaking. The approach used for wet strength optimization has been used to optimize other aspects of pulp and paper production.
Journal articles
Reducing aox by increasing oxidation potential in the first caustic extraction stage, TAPPI Journal December 2024
Authors: Peter W. Hart and Jeffrey S. Hsieh | Tappi J. 74(11): 117(1991) - ABSTRACT: An increase in the standard oxidation potential of the reinforcing agent in the first caustic extraction stage will reduce the amount of AOX in the stage's effluent. A chlorinated broumstock pulp was treated alternatively in a basic caustic extraction (E) stage, an oxygen-reinforced caustic extraction (EO) stage, and an extraction stage reinforced with oxygen and peroxide (EOP). An AOX reduction of up to 30% was obtained in the effluent from the peroxide-reinforced extraction stage. In addition to the brownstock work, using two different model lignin compounds, we ran tests using oxyen, potassium permanganate, hydrogen peroxide with oxygen, and ozone with oxygen-reinforced caustic stages. In all cases, increasing the oxidation potential of the reinforcing agent decreased the amount of AOX detected in the effluent.
A new method of studying the fundamental mechanisms involved in pigment liberation from recycle papers, TAPPI Journal October 2022
ABSTRACT: Deinking flotation is the most efficient and widely used method of removing ink particles from printed papers to improve the recyclability. A prerequisite for successful deinking flotation is detachment of pigments from paper fibers, a subprocess known as liberation. The degree of liberation is usually determined via hyperwashing tests, which are costly and time consuming. Furthermore, they provide no information on the fundamental mechanisms controlling liberation. In the present work, we developed a new method in which ?-potentials of the particles in a pulp are measured and analyzed. If pigments are not liberated from paper fibers, a frequency distribution plot gives a single peak, while two peaks appear when they are liberated. One can readily determine the degrees of liberation from the peak positions and peak heights. In addition, the ?-potential data can be used to construct disjoining pressure isotherms using the DLVO theory that are useful to better understand the fundamental mechanisms involved and the roles of different reagents used to improve pigment liberation.
Nanocellulose–cationic starch– colloidal silica systems for papermaking: Effects on process and paper properties, TAPPI Journal October 2022
ABSTRACT: Laboratory tests were conducted to better understand effects on the papermaking process and handsheets when recycled copy paper furnish was treated with combinations of nanofibrillated cellulose (NFC), cationic starch, colloidal silica, and cationic retention aid (cPAM; cationic polyacrylamide). Dosage-response experiments helped to define conditions leading to favorable processing outcomes, including dewatering rates and the efficiency of fine-particle retention during papermaking. Effects were found to depend on the addition amounts of cationic starch and colloidal silica added to the system. It was shown that the presence of a polymer additive such as cationic starch was essential in order to achieve large strength gains with simultaneous usage of NFC.
Journal articles
Corrosion Monitoring and Root Cause Identification in High Solids Concentrators
Black liquor high solids (about 80%) concentrators have often been found to suffer from aggressive corrosion. In particular, the first and second effect bodies are susceptible to corrosion attacks resulting in tube leaks and wall thinning, which limit the availability and lifetime of evaporator lines. Corrosion dynamics and construction materials have been studied extensively within the pulp and paper industry to understand the corrosion process. However, it has been challenging to identify root causes for corrosion, which has limited proactive measures to minimize corrosion damage. Corrosion of the first phase concentrator was studied by defining the potential regions for passive area, stress corrosion cracking, pitting corrosion, and general corrosion. This was achieved by using a technique called polarization scan that reveals ranges for the passive area in which the equipment is naturally protected against corrosion. The open circuit potential, also known as corrosion potential, and linear polarization resistance of the metal were monitored online, which allowed for definition of corrosion risks for stainless steel 304L and duplex stainless steels 2205 and SAF 2906. An online temperature measurement added insight to the analysis. A process diagnostics tool was used to identify root causes of the corrosion attacks. Many of the root causes were related to process conditions triggering corrosion. Once the metal surface was activated, it was difficult to repassivate the metal naturally unless a sufficient potential range was reached.
Journal articles
Commissioning Brownstock Washing Controls for an Evaporator Limited Mill
An automated shower water control system has been implemented to reduce the volume and vari-ability of weak black liquor being sent from the pulp mill to the evaporators. The washing controls attempt to bal-ance the need for consistent and low soda carryover to the bleach plant with consistently high weak black liquor solids being sent to the evaporators. The washer controls were implemented on two bleachable grade hardwood lines (one with oxygen delignification, one without oxygen delignification) and one pine line. Implementation of the con-trol program resulted in an increase in black liquor solids of 0.6 percentage points for the hardwood lines. Significant foam reduction was realized on the pine line since the pine black liquor solids were able to be consistently maintained just below the soap separation point. Low black liquor solids excursions to the evaporators were eliminated. Bleach plant carryover was stabilized and no negative impact on chemical consumption was noticed when control-ling weak black liquor solids to recovery.
Journal articles
Research pathways and outreach to drive cellulosic nanomater
Research pathways and outreach to drive cellulosic nanomaterials development, TAPPI JOURNAL June 2016
Journal articles
Magazine articles
Preparing prehydrolyzed kraft dissolving pulp via phosphotungstic acid prehydrolysis from grape branches, TAPPI Journal January 2022
ABSTRACT: Dissolving pulp was successful prepared via phosphotungstic acid (PTA) prehydrolysis kraft (PHK) cooking followed by an elementary chlorine-free (ECF) bleaching process from grape branches. The effects of prehydrolysis temperature, reaction time, and PTA concentration that potentially affect the quality of dissolving pulp product on chemical components of pulp were studied via an orthogonal experiment. The structure of lignin was activated during the PTA prehydrolysis phase, and lignin was easily removed during the following cooking process. Thus, relatively mild conditions (140°C, 100 min) can be used in the cooking process. During the prehydrolysis phase, temperature exhibited the most significant influence on the cellulose purity of the obtained pulp fiber, followed by reaction time and PTA concentration. The optimized prehydrolysis conditions were as follows: prehydrolysis temperature, 145°C; reaction time, 75 min; and PTA concentration, 1 wt%. Whether the excessively high prehydrolysis temperature or prolonging the reaction time did not favor the retention of long chain cellulose, the delignification selectivity for the cooking process could not be further improved by excessive PTA loading. Under these prehydrolysis conditions, 94.1% and 29.0% for a-cellulose content and total yield could be achieved after the given cooking and bleaching conditions, respectively. Moreover, the chemical structure and crystal form of cellulose were scarcely changed after PTA prehydrolysis, which could be confirmed by results from Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). PTA prehydrolysis could be considered as an alternative method for preparing PHK dissolving pulp under relatively mild cooking conditions.
Journal articles
Magazine articles
Kraft recovery boiler operation with splash plate and/or beer can nozzles — a case study, TAPPI Journal October 2021
ABSTRACT: In this work, we study a boiler experiencing upper furnace plugging and availability issues. To improve the situation and increase boiler availability, the liquor spray system was tuned/modified by testing different combinations of splash plate and beer can nozzles. While beer cans are typically used in smaller furnaces, in this work, we considered a furnace with a large floor area for the study. The tested cases included: 1) all splash plate nozzles (original operation), 2) all beer can nozzles, and 3) splash plate nozzles on front and back wall and beer cans nozzles on side walls. We found that operating according to Case 3 resulted in improved overall boiler operation as compared to the original condition of using splash plates only. Additionally, we carried out computational fluid dynamics (CFD) modeling of the three liquor spray cases to better understand the furnace behavior in detail for the tested cases. Model predictions show details of furnace combus-tion characteristics such as temperature, turbulence, gas flow pattern, carryover, and char bed behavior. Simulation using only the beer can nozzles resulted in a clear reduction of carryover. However, at the same time, the predicted lower furnace temperatures close to the char bed were in some locations very low, indicating unstable bed burning. Compared to the first two cases, the model predictions using a mixed setup of splash plate and beer can nozzles showed lower carryover, but without the excessive lowering of gas temperatures close to the char bed.
Journal articles
Using white liquor as the alkali source in oxygen delignific
Using white liquor as the alkali source in oxygen delignification, TAPPI JOURNAL September 2016