Search
Use the search bar or filters below to find any TAPPI product or publication.
Filters
Content Type
Publications
Level of Knowledge
Committees
Collections
Journal articles
Magazine articles
External fibrillation of wood pulp, TAPPI Journal June 2023
ABSTRACT: Pulp refining produces external fibrillation consisting of fibrils tethered to fiber surfaces, in addition to loose fibrils and fines. Both contribute to a larger bonding area that increases paper strength, but tethered fibrils have less likelihood of being washed out during papermaking. This study postulates the mechanism by which refining produces external fibrillation and the optimum conditions for doing so.The postulated mechanism is surface abrasion during sliding of fibers in refiner gaps. External fibrillation occurs when forces are great enough to partially dislodge fibrils from fiber surfaces, but not large enough to break the fibrils. The refining intensities to achieve these forces were determined by a mathematical model and experiments using a laboratory disc refiner. The optimum intensities in terms of specific edge load (SEL) for chemical pulps were about 0.1 J/m for hardwoods and 1.0 J/m for softwoods. An extension of this study suggested that abrasion may also account for most of the energy consumed in the mechanical pulping process.
Journal articles
Magazine articles
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
Optimization of energy efficiency and condensate production in evaporation plants for a modern softwood pulp mill, TAPPI Journal April 2026
ABSTRACT: To meet the need to further improve thermal efficiency and environmental performance of kraft pulp mills, new systems and techniques have been developed within the evaporation plant. This paper describes these novel approaches and how they were implemented in a project completed in 2018 for a new evaporator and condensate treatment system supplied by Valmet at the SCA Östrand market pulp mill in Sweden. This project was part of a stepwise upgrade of the complete mill to increase the production capacity of the mill from 430,000 to 900,000 air-dried metric tons/year (ADt/y). As part of this upgrade, the mill had the objectives to increase the energy efficiency of the pulp mill and to minimize the air emissions as much as possible, the effluent volume, and the water usage in the mill. The mill also wanted to have the disposal of the biosludge in the black liquor, and the production of tall oil from black liquor soap, liquid methanol, and turpentine. This required that the new evaporation and condensate treatment system be very closely integrated into the other process departments of the mill, including integration of the hot weak black liquor flash vapor from the digester directly into the evaporator train and the production of multiple streams of clean evaporation plant condensate at the correct temperature for the bleach plant. Heat and mass balance calculation values, which were found to do very well in predicting the effect on actual mill operation, are also presented in this paper.
Journal articles
Assessing lignin content in Nordic hardwood and softwood species using models based on near-infrared (NIR) spectral data and partial least squares regression (PLSR), TAPPI Journal September 2025
ABSTRACT: Continuous kraft cooking digesters face challenges affecting product quality, making it valuable to improve control through advanced techniques like near-infrared (NIR) spectroscopy, model predictive control, and machine learning models. The primary goal of this study was to use NIR spectra to predict the amount of lignin in hardwood and softwood samples. This study investigated the correlation of NIR derivative spectra with the amounts of lignin relative to other constituents, namely cellulose, hemicellulose, and water, in wood chip samples of varying chip sizes and shapes from six Nordic wood species. It employed partial least squares regression (PLSR) on the NIR data to construct a model that predicted the lignin fraction and the relative fraction of acid-soluble lignin. When trained on a group of five wood species, the model achieved a satisfactory predictive ability, striking a balance between a wide range of lignin content and a consistent chemical environment. The accuracy increased further when the model was restricted only to spruce and pine, reflecting the benefits of a more homogenous dataset. Additionally, the optimal number of latent variables was identified as two, indicating that three distinct chemical components — cellulose, lignin and water — can be effectively differentiated using NIR.
Journal articles
Materials performance considerations in hydrothermal liquefaction conversion of biomass, TAPPI Journal June 2025
ABSTRACT: Hydrothermal liquefaction (HTL) is a promising thermochemical route developed to convert woody biomass and biowaste to biochemicals and bio-oils. However, the operating conditions are rather harsh to biorefinery structural metallic components. These conditions include alkaline catalysts such as potassium carbonate (K2CO3); hot, pressurized (sub-critical) water reaction; and medium and aggressive anions chlorine (Cl•) and hydrogen sulfide (H•) released from biomass feedstocks. Thus, selection of suitable structural alloys for biorefinery components involves striking a balance between mechanical properties, corrosion resistance, and cost. Alloys currently being considered for this application include ferritic-martensitic steels and austenitic stainless steels. From a corrosion perspective in hot pressurized water, the former typically exhibits higher stress corrosion cracking resistance, whereas the latter exhibits higher corrosion resistance. This study reviews cost-effective corrosion control strategies aimed at increasing the chromium (Cr) content for protective surface oxide formation, as screened by testing in simulated HTL alkaline water, to support materials selection and design. Corrosion control strategies include surface modification (increasing surface Cr content), alloying (increasing bulk Cr content), and stainless-steel type (ferritic vs. austenitic). Of the alloys considered (including those subjected to surface modification), ferritic stainless steels exhibit a promising balance between corrosion and stress corrosion cracking resistance, adding another family of candidate alloys for structural biorefinery component materials selection and design.
Journal articles
Magazine articles
Modeling the dynamics of evaporator wash cycles, TAPPI Journal July 2024
ABSTRACT: Kraft pulping is a process that utilizes white liquor, composed of sodium sulfide (Na2S) and sodium hydroxide (NaOH), for wood delignification and pulp production. This process involves washing the dissolved organics and spent chemicals from the pulp, resulting in the generation of black liquor. Prior to its use as fuel in the recovery boiler, the black liquor is concentrated in multiple-effect evaporators. During the evaporation process, the inorganic salts present in the liquor become supersaturated and undergo crystallization. Fluctuations in sodium, carbonate, sulfate, and oxalate can give rise to severe sodium salt scaling events, which significantly impact the thermal efficiency of the evaporators, and ultimately, pulp production. Dynamic modeling provides insights into fluctuations in liquor chemistry in the evaporators. The primary objective of this study was to employ dynamic modeling to evaluate the effects of wash liquor recovery from evaporator wash cycles. The dynamics associated with wash cycles encompass variations in the concentrations of salts and solids in the recovered wash liquor, changes in the flow rate of wash liquor recovery, and fluctuations in liquor volume within the liquor tanks. The dynamic model was developed using Matlab Simulink and applied to the evaporation plant of a pulp mill in South America. By utilizing one month of mill process data, the model enabled the evaluation of fluctuations in liquor chemistry due to evaporator wash cycles. The developed model has demonstrated the potential to estimate the concentration of key ions responsible for scaling and to contribute to enhancements in evaporator washing strategies.
Journal articles
Magazine articles
Online monitoring of the size distribution of lime nodules in a full-scale operated lime kiln using an in-situ laser triangulation camera, TAPPI Journal June 2024
ABSTRACT: To maximize efficiency of the recausticizing process in a pulp mill, producing a reburned lime with high and consistent reactivity is process critical. Prior investigations have demonstrated a correlation between the reactivity of lime and its nodule size, as well as the dusting behavior of the kiln. Therefore, monitoring the nodule size produced in the lime kiln could be a promising indirect method to measure the performance of the lime kiln. The objective of this investigation was to evaluate the utility of a laser triangulation camera for online monitoring of nodule size distribution for the lime kiln. A series of full-scale trials were performed in a lime kiln of a kraft pulp mill in which a camera was installed at the exit conveyor to analyze the lime discharging from the kiln. The nodule size distribution was analyzed for correlation with the lime temperature, flue gas temperature, and rotational speed of the kiln. The monitoring demonstrated temporal stability, and the results showed that the lime temperature had the most significant effect on the nodule size. The rotational speed of the lime kiln and the flue gas temperature showed limited effect on nodule size, but they had significant impact on the specific energy demand. The overall conclusion of the study is that the camera methodology effectively correlates lime temperature with nodule size distribution, and it advocates for the methods of implementation in automating lime temperature control, facilitating the production of consistently reactive lime at a lower specific energy consumption.
Journal articles
Magazine articles
Understanding the energy and emission implications of new technologies in a kraft mill: Insights from a CADSIM Plus simulation model, TAPPI Journal June 2024
ABSTRACT: Kraft mills play a vital role in energy transition because they have significant potential to reduce their own energy utilization and produce energy/products to decarbonize other sectors. Through biomass combustion and potential biogenic carbon emissions capture, these mills can contribute to offsetting emissions from other sectors. This research investigates the departmental and cross-departmental implications of technology upgrades on energy, steam, emissions, water, and chemicals using a CADSIM Plus simulation model. The model provides a comprehensive analysis of mass and energy balances, offering valuable insights into the benefits and limitations of each technology. The model facilitates scenario analysis and comparisons of process configurations, enabling data-driven decision-making for sustainable and competitive operations. Six high-impact technologies, including additional evaporator effects, weak black liquor membrane concentration, belt displacement washer for brownstock washing, oxygen delignification, and improvements to the pulp machine shoe press and vacuum pumps, are evaluated. Individual technologies resulted in energy savings of 1.2% to 5.4%, biomass consumption reductions of 8.6% to 31.6%, and total emissions reductions of 1.6% to 5.9%. Strategic decision-making must consider existing mill limitations, future technology implementation, and potential production increases. Future research will explore product diversification, biorefineries, and pathways to achieve carbon-negative operations, aiming to reduce emissions and secure a competitive future for kraft mills.
Journal articles
Magazine articles
Editorial: TAPPI Standards development: Authors and reviewers are welcome, TAPPI Journal July 2021
ABSTRACT: Readers of TAPPI Journal (TJ) and those involved with R&D and process and product quality will be familiar with TAPPI Standard Test Methods. These test methods are necessary for validating research and ensuring the quality of end products. In addition to test methods, TAPPI also publishes information that isn’t directly related to test methods, such as technical information and definitions, which include specifications, guidelines, and glossaries. All Standards information is developed with the consensus of a technical working group that adheres to set procedures.
Journal articles
Magazine articles
Lignin-based resins for kraft paper applications, TAPPI Journal November 2019
ABSTRACT: We investigated miscanthus (MS) and willow (W) lignin-furfural based resins as potential reinforce-ment agents on softwood and hardwood kraft paper. These resins might be sustainable alternatives to the commercial phenolformaldehyde (PF) resins. Phenol is a petrochemical product and formaldehyde has been classified as a carcinogen by the U.S. Environmental Protection Agency. The lignin used in this study was derived from hot water extraction (160ºC, 2 h) of MS and W biomass, and may be considered sulfur-free. These biorefinery lignins were characterized for their chemical composition and inherent properties via wet chemistry and instrumental techniques. The resin blends (MS-resin and W-resin) were characterized for their molecular weight, thermal behavior, and mechanical properties. Mechanical properties were measured by the resin’s ability to reinforce softwood and hard-wood kraft papers. The effect of adding hexamethylenetetramine (HMTA), a curing agent, to the resin was also examined. Mixtures of PF and lignin-based resins were investigated to further explore ways to reduce use of non-renewables, phenol, and carcinogenic formaldehyde. The results show that lignin-based resins have the potential to replace PF resins in kraft paper applications. For softwood paper, the highest strength was achieved using W-resin, without HMTA (2.5 times greater than PF with HMTA). For hardwood paper, MS-resin with HMTA gave the highest strength (2.3 times higher than PF with HMTA). The lignin-based resins, without HMTA, also yielded mechanical properties comparable to PF with HMTA.