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Journal articles
Toward environmental resilience in pulp and paper manufacturing: Water consumption and carbon dioxide emission reductions, TAPPI Journal September 2025
ABSTRACT: Pulp and paper manufacturing is a water- and energy-intensive industrial sector, necessitating improvement of its operational efficiency, as well as reduction of emissions to the maximum extent possible. This review focuses on the reduction of water consumption and carbon dioxide (CO2) emissions that originate in the pulp and paper industry (PPI). First, process simulation and optimization techniques used for water consumption reduction are reviewed. Then, techno-economic analyses of solvent-based CO2 capture from PPI are discussed. Additionally, key actions are proposed for enhancing water consumption reduction and CO2 capture in PPI.
Journal articles
Effect of pulp refining on thixotropy of cellulose fiber suspensions, TAPPI Journal September 2025
ABSTRACT: This paper presents results on the thixotropic behavior of low-consistency bleached eucalyptus fiber suspensions that had been mechanically treated. The pulps were refined in a PFI mill at different numbers of revolutions (0, 3000, and 6000) to study the effect of refining intensity on the viscosity time-response of fiber suspensions. In steady rheological tests, all the suspensions exhibited shear thinning behavior and no significant differences were observed after mechanical treatment. Stepwise experiments showed that viscosity continuously increased with time when shear rate was suddenly reduced. Additionally, a delay in time evolution of viscosity was observed as the pulp was more refined. A stretched exponential model was fitted to the experimental results of viscosity.
Journal articles
Support for innovation and workforce development, TAPPI Journal August 2026
Advanced manufacturing is gaining attention in developed economies due to national security issues, calls for developing domestic supply chains, and more importantly, the need for creating jobs. COVID-19 exposed vulnerabilities in the manufacturing of lifesaving and critical items such as N95 masks. Tariffs are considered one avenue to protect domestic manufacturing, but in the case of manufactured products like commodity textiles, a tariff barrier alone will not be able to bring back manufacturing. It is a beneficial move by the U.S. government to boost manufacturing through investments in research and development (R&D), enhancing the advanced manufacturing sector focusing on defense and medical items through the establishment of centers like the Advanced Functional Fabrics of America. Additionally, schemes to grow a skilled workforce both at factory and R&D levels will be valuable.
Journal articles
Comparative evaluation of conical and double disk refiners: Effects of operating mode, refining intensity, and device geometry on energy consumption and paper properties, TAPPI Journal August 2026
ABSTRACT: This study investigates the effects of refiner operating mode and refining intensity adjusted via pulp flow rate, applied power, and refiner speed on the refining characteristics of high-yield southern softwood. We compared Valmet’s OptiFiner PRO (conical) and DD6700 (double disk) refiners under matched specific edge load (SEL) conditions. Batch and one-pass modes were evaluated for their impact on energy efficiency and physical paper properties. The results showed that while SEL provides a useful baseline, it does not fully account for differences in refiner geometry, particularly angular parameters. With the chosen plate sets, C-factor analysis revealed that the OptiFiner PRO delivers a lower number of fiber impacts at a higher intensity per impact compared to DD6700 at similar SEL, influencing fiber length, short-span compression test (STFI) index, and tear strength development. These findings offer actionable insights for mills seeking to optimize refining efficiency and cost. In summary, conical refiners may provide advantages in compression strength at mid-range energies, while double disk refiners maintain higher tear strength at elevated energies due to better fiber length preservation.
Journal articles
Simplified modeling of a complete rotary lime kiln at a pulp mill, TAPPI Journal February 2026
ABSTRACT: Rotary lime kilns are essential and complex components in pulp mills using the kraft process. They are primarily used to produce lime (CaO), which is then employed to make white liquor, the reagent used to separate wood fibers. To understand and improve the performance of the kiln, modeling its behavior is essential. However, the kiln operates through a complex combination of thermal and chemical phenomena. That is why a simplified approach was used to tackle this challenge. A zero/one-dimensional steady-state analysis was performed based on first principles to simplify the modeling process and reduce the need for experimental data. Additional assumptions, such as steady-state operation and the absence of a refractory lining, were introduced to further simplify the model so that it can be used for daily analysis. Moreover, the auxiliary equipment of the plant, such as the intercooler and preheat cyclone, is also modeled. The final model was validated using data from the literature and a two-month analysis of experimental measure-ments from the Burgo Ardennes lime kiln in Virton, Belgium. It shows good agreement with the available data, with a 6% deviation for the adiabatic flame temperature and a 17% average error in predicting the kiln shell outside temperature. For the fuel and lime flow rate predictions, also validated over the same two-month period, the errors were -6.6% and 0.6%, respectively.
Journal articles
Development of a packaging test method, TAPPI Journal February 2026
ABSTRACT: Innovation in packaging design will be facilitated by a simple test method to indicate whether a product is compatible with paper recycling. Three laboratories cooperated on the development of a method and used it on linerboard, coated paperboard, wet-strength paperboard, and white copy paper. This test method includes pulping and screening. The data presented here illustrate the factors affecting the results of a bench-scale test. Our observations show that a bench-scale test can give reproducible results for yield, < 5%. We also present an approach to contaminant assessment based on current published test methods. A specification with a lower limit on yield of 70% and a contaminant level of less than 5,000 particles/kg is proposed.
Journal articles
Magazine articles
Experiments and visualization of sprays from beer can and turbo liquor nozzles, TAPPI Journal February 2022
ABSTRACT: Industrial scale swirl-type black liquor nozzles were studied using water as the test fluid. Simple water spraying experiments were found to be very beneficial for studying and comparing nozzles for black liquor spraying. These kinds of experiments are important for finding better nozzle designs. Three nozzle designs were investigated to understand the functional differences between these nozzles. The pressure loss of nozzle 1 (“tangential swirl”) and nozzle 3 (“turbo”) were 97% and 38% higher compared to nozzle 2 (“tan-gential swirl”). Spray opening angles were 75°, 60°, and 35° for nozzles 1, 2, and 3, respectively. Video imaging showed that the nozzles produced sprays that were inclined a few degrees from the nozzle centerline. Spray patter-nation showed all the sprays to be asymmetric, while nozzle 2 was the most symmetric. Laser-Doppler measure-ments showed large differences in spray velocities between nozzles. The spray velocity for nozzle 1 increased from 9 m/s to 15 m/s when the flow rate was increased from 1.5 L/s to 2.5 L/s. The resulting velocity increase for nozzle 2 was from 7 m/s to 11 m/s, and for nozzle 3, it was from 8 m/s to 13 m/s. Tangential flow (swirl) directed the spray 6°•12° away from the vertical plane. Liquid sheet breakup mechanisms and lengths were estimated by analyzing high speed video images. The liquid sheet breakup mechanism for nozzle 1 was estimated to be wave formation, and the sheet length was estimated to be about 10 cm. Sheet breakup mechanisms for nozzle 2 were wave formation and sheet perforation, and the sheet length was about 20 cm. Nozzle 3 was not supposed to form a liquid sheet. Nozzle geometry was found to greatly affect spray characteristics.
Journal articles
Magazine articles
Application of ATR-IR measurements to predict the deinking efficiency of UV-cured inks, TAPPI Journal January 2022
ABSTRACT: In recent years, ultraviolet (UV)-curable ink has been developed and widely used in various printing applications. However, using UV-printed products (UV prints) in recovered paper recycling causes end-product dirt specks and quality issues. A new method was developed that can distinguish UV prints from other prints by means of attenuated total reflectance infrared (ATR-IR) spectroscopy. Application of this method could allow more efficient use of UV prints as raw materials for paper recycling.First, a mill trial was performed using UV prints alone as raw materials in a deinked pulp (DIP) process. Second, test prints were made with four types of UV inks: a conventional UV ink and three different highly-sensitive UV inks. Each print sample had four levels of four-color ink coverage patterns (100%, 75%, 50%, and 25%). Next, deinkability of all prints was evaluated by laboratory experiments. Finally, each print was measured using the ATR-IR method, and the relationship between the IR spectra and deinkability was investigated. Mill trial results showed that UV prints caused more than 20 times as many dirt specks as those printed with conventional oil-based ink. There were variations in recycling performance among UV prints taken from bales used for the mill trial. Lab tests clearly revealed that not all UV-printed products lead to dirt specks. In order to clarify the factors that affected deinkability of UV prints, the print samples were investigated by lab experiments. Key findings from lab experiments include: œ The number of dirt specks larger than 250 µm in diameter increased as the ink coverage increased. œ Higher ink coverage area showed stronger intensity of ATR-IR spectral bands associated with inks. These results indicate that deinkability of UV prints could be predicted by analysis of ATR-IR spectra. œ Finally, the method was applied for assessment of recovered paper from commercial printing presses. It was confirmed that this method made it possible to distinguish easily deinkable UV prints from other UV prints. Based on these findings, we concluded that the ATR-IR method is applicable for inspection of incoming recovered paper.
Journal articles
Magazine articles
Using bleaching stage models for benchmarking softwood ECF bleach plants, TAPPI Journal July 2022
ABSTRACT: Steady-state bleaching delignification and brightening models were used to gauge how well elemental chlorine-free (ECF) bleach plants were using chlorine dioxide to bleach 25-kappa softwood brownstocks. Case 1 examined the D0(EOP)D1 portion of Mill 1’s five-stage sequence that brightens the pulp to 86% ISO. Case 2 studied the D0(EO)D1 portion of Mill 2’s four-stage sequence, which brightens the pulp to 82% ISO, and Case 3 re-examined the same bleach plant several years after it made improvements around the extraction stage. The models highlighted days in the previously mentioned cases where high bleach usage occurred, presumably because of high brownstock and/or extraction washer carryover, and days where bleach usage was normal. In Case 2, the model esti-mated that 10 kg of the 44 kg chlorine dioxide/metric ton pulp consumed in bleaching was likely reacting with washer carryover sources; approximately two-thirds of this extra consumption was assumed to be reacting with extraction filtrate. Changes that Mill 2 made (Case 3) reduced the unproductive chlorine dioxide usage from 10 to 5 kg/metric ton pulp. When the delignification and brightening models were simultaneously solved, the models predicted somewhat different optimized distributions of chlorine dioxide to D0 and D1 vs. actual values used in bleach plants. However, the forecasted chlorine dioxide totals agreed with the actual values when washer carryover sources were considered. This study showed the bleaching models could be used as hypothetical benchmarks for softwood ECF bleach plants.
Journal articles
Magazine articles
On the usage of online fiber measurements for predicting bleached eucalyptus kraft pulp tensile index — an industrial case, TAPPI Journal July 2022
ABSTRACT: Cellulose pulp’s physical-mechanical properties are determined by laboratory tests obtained from prepared handsheets. However, this procedure is time intensive and presents a lead time until the results are available, hindering its utilization for monitoring and decision-making in a pulp mill. In this context, developing real-time solutions for physical-mechanical properties prediction is fundamental. This work applied a mathematical modeling approach to develop a soft sensor for tensile index monitoring. The mathematical model considers online morphology measurements obtained from the last bleaching stage outlet stream and important process variables for tensile index prediction. The results obtained are satisfactory compared to laboratory results, presenting a mean absolute percentual error of 2.5%, which agrees with the laboratory testing method’s reproducibility.