Search

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.

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.

Editorial: Changing of the guard: Dr. Arthur Ragauskas assumes TAPPI Journal editor-in-chief role, TAPPI Journal January 2026

TAPPI is pleased to announce that Dr. Arthur J. Ragauskas has assumed the editor-in-chief role for TAPPI Journal. Ragauskas, who is a professor at University of Tennessee (UT) in Knoxville, TN, has been a member of the TAPPI Journal Editorial Board since 2011 and is a TAPPI Fellow, as well as recipient of the TAPPI Gunnar Nicholson Gold Medal Award, among his many accomplishments. As a member of the Editorial Board, Ragauskas has curated eight special issues on a range of topics, including nanocellulose, lignocellulose, lignin valorization, and the forest biorefinery.

Full-scale operation of a membrane-based black liquor concentrator, TAPPI Journal January 2026

ABSTRACT: For years, black liquor concentration by reverse osmosis has been an aspiration for reducing mill energy consumption and costs. Building on a 2023 report of an 81% reduction in the energy intensity for concentrating black liquor using its membrane platform at the pilot scale, this paper reports on the fabrication, installation, startup, and operation of the world’s first full-scale membrane-based black liquor concentration system at the International Paper Grande Prairie mill in Canada. The majority of the membrane modules in this system have reliably exceeded permeability expectations by more than 50%. In addition to strong membrane performance, the system has been a significant source of learnings for material specifications and system design. Incorporating these learnings and comparing to typical multiple effect evaporators, the system demonstrates a 43% reduction in capital cost for the same capacity, a 30% reduction in the lifetime cost of removing water from black liquor, and an 86% reduction in energy use. The impact on washer optimization was also considered, and net energy and chemical costs were reduced by US$3.8 and US$6.8/a.d. metric ton for a typical brown and bleach mill, respectively, when incorporating this technology. Completed in less than 12 months, the facility has demonstrated successful black liquor concentration at the 500 gpm scale with monthly uptime as high as 96%.

Energy and emission implications of optimized white liquor causticity, TAPPI Journal January 2026

ABSTRACT: Optimizing the causticizing plant offers significant opportunities for energy and emissions savings in kraft mills by minimizing the chemical and water deadload introduced into the recovery cycle via white liquor. Modern control strategies utilize both feedforward and feedback loops to manage causticity, enabling more aggressive targets closer to equilibrium levels. This paper evaluates the benefits of optimizing white liquor chemistry through a detailed CADSIM Plus simulation model, replicating the chemistry of a Canadian bleached kraft mill that adopted an automated causticizing control system. The control system increased causticity from 77.0% to 82.3% at a fixed total titratable alkali (TTA) of 126.5 grams of sodium dioxide per liter (gNa2O/L). Modeling this chemistry change indicated a 1.5 metric tons per hour (t/hr) reduction in evaporator steam demand and a 2.8% increase in black liquor higher heating value. Consequently, the improved heating value resulted in a 1.5% rise in recovery boiler steam production and a 5.3% reduction in biomass energy consumption in power boilers, leading to a 4.8% decrease in biogenic carbon dioxide (CO2) emissions. Additionally, reducing the inorganic and water deadload throughout the recovery cycle may support higher as-fired dry solids targets, enhancing recovery boiler energy efficiency by lowering the water evaporation requirement during black liquor combustion. However, implementing a causticizing control system requires careful assessment of potential lime kiln bottlenecks, as increased causticity demands may affect kiln operations depending on broader mill conditions. Overall, an automated causticizing control system enhances process efficiency, reduces energy consumption and emissions, and positions kraft mills for improved productivity and longterm sustainability.

Effects of variability of wood chip composition on recovery cycle operation, TAPPI Journal January 2026

ABSTRACT: Fluctuations in wood chip properties in kraft pulp mills, which often follow seasonal patterns, can lead to changes or disruptions in the operation of the recovery cycle whereby the root causes are not immediately obvious. In some cases, these changes are attributed to operational adjustments in the digester or brownstock washing areas resulting from the variability in wood characteristics. Varying wood chip characteristics that have the most significant impact on the recovery cycle operation include the content of non-process elements (NPEs), extractives, and properties influenced by chip storage conditions. Elevated levels of NPEs, often associated with a higher influx of wood bark into the digester, can negatively affect the entire recovery cycle. Increased levels of chlorine and potassium can lead to severe fouling and corrosion in the recovery boiler. Higher concentrations of silicon, aluminum, phosphorus, magnesium and calcium in the chips may accelerate scaling in the evaporation plant, impair dregs and lime mud settling and filtering, reduce lime mud solids content and lime availability, and increase the amounts of dregs, grits, and purged lime mud. This technical review provides an overview of the most significant effects that changes in wood chip quality can potentially exert on various processes within the kraft recovery cycle.

TAPPI Journal Summaries, Paper360º November/December 2022

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.

Economic and competitive potential of lignin-based thermoplastics using a multicriteria decision-making method, TAPPI Journal September 2022

ABSTRACT: As a result of new lignin extraction plants hatching and increasing volumes of technical lignin becoming available, a variety of lignin derivatives, including phenolic resins and polyurethane (PU) foams, are reaching the marketplace or being used as intermediate products in many industrial applications. In the spectrum of possible lignin derivatives, thermoplastics appear particularly attractive due to a symbiosis of market, policy, and technology drivers. To assess the preferredness for lignin-based thermoplastics, this paper adapted a risk-oriented methodology formerly applied to assess lignin usage in various applications (phenol-formaldehyde [PF] resins, PU foams, and carbon fiber applications) to the case of lignin-based thermoplastics using hydroxypropylated lignin (HPL) and miscible blends of lignin and polyethylene oxide (PEO). The HPL is considered for garbage bags and agricultural films applications, while lignin-PEO blends are used as replacement for acrylonitrile butadiene styrene (ABS) in applications such as automotive parts. In the methodology, two phased-implementation strategies were defined for each thermoplastic derivative, considering perspectives for profit maximization (90 metric tons/day integrated units) and revenue growth (350 metric tons/day overall capacity), which were considered for implementation within a softwood kraft pulping mill. A set of six criteria representative of the main economic and market competitiveness issues were employed, and their respective importance weights were obtained in a multicriteria decision-making (MCDM) panel.Early-stage techno-economic estimates were done as a basis for the calculation of decision criteria. Compared to product derivatives previously assessed, capital investment for thermoplastic strategies appeared marginally higher due to the required lignin modification steps (on average 30% higher at similar capacity, and 6% for higher-scale revenue diversification strategies). Higher operating costs were also observed due to increased chemical expenses for all thermoplastic strategies, which are ultimately balanced by revenues associated with targeted thermoplastic products, leading to greater annual margins and cash flow generation over the project lifetime for thermoplastic strategies compared to other product applications (58% to 66% higher on average, at similar scale). Benefits of improved economics were reflected in economic criteria, internal rate of return (IRR), and cash flow on capital employed (CFCE), as well as in the price competitiveness criterion, CPC. Overall, the combination of relatively high lignin content in the plastic formulation and the less costly modification method contributed to lignin-PEO strategies, gaining the top two rankings. Based on their overall scores, both strategies defined for HPL would also integrate the group of “preferred” strategies, but are outranked by strategies that consider lignin positioning on PU foam applications.

Fiber-based characterization of pulp refining, TAPPI Journal September 2022

ABSTRACT: Fiber development in pulp refining can be characterized by three parameters: number of impacts on pulp, N; energy per impact, I, and bar force on fibers, F. These parameters enable comparisons of radically different refining conditions; determination of intensity for hardwoods and softwoods; assessment of effect of bar width on fiber shortening; and predictions of tensile strength increases.