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A novel approach for determining the reactivity of dissolving pulp based on the COD method
ABSTRACT: A novel approach for determining the reactivity of dissolving pulp according to the chemical oxygen demand (COD) of water has been discussed. First, a sample of dissolving pulp was subjected to mercerization and xanthation in order to obtain dissolved cellulose fractions. Next, the fractions were digested with a testing solution as applied in COD procedures. Finally, the resulting liquid was rapidly tested by ultraviolet-visible spectrophotometry (UV-Vis). By quantifying the absorbance of Cr3+ at a wavelength of 600 nm, the reactivity of dissolving pulp was indirectly calculated. The results measured by this novel COD method correlated well with the most accepted Fock test results with less than 10% relative difference. Meanwhile, this newly developed COD method required less time-consuming procedures as compared to the Fock test.
Journal articles
Magazine articles
Integrated study of flue gas flow and superheating process in a recovery boiler using computational fluid dynamics and 1D-process modeling, TAPPI Journal June 2020
ABSTRACT: Superheaters are the last heat exchangers on the steam side in recovery boilers. They are typically made of expensive materials due to the high steam temperature and risks associated with ash-induced corrosion. Therefore, detailed knowledge about the steam properties and material temperature distribution is essential for improving the energy efficiency, cost efficiency, and safety of recovery boilers. In this work, for the first time, a comprehensive one-dimensional (1D) process model (1D-PM) for a superheated steam cycle is developed and linked with a full-scale three-dimensional (3D) computational fluid dynamics (CFD) model of the superheater region flue gas flow. The results indicate that: (1) the geometries of headers and superheater platens affect platen-wise steam mass flow rate distribution (3%•7%); and (2) the CFD solution of the 3D flue gas flow field and platen heat flux distribution coupled with the 1D-PM affect the platen-wise steam superheating temperature (45%•122%) and material temperature distribution (1%•6%). Moreover, it is also found that the commonly-used uniform heat flux distribution approach for the superheating process is not accurate, as it does not consider the effect of flue gas flow field in the superheater region. These new observations clearly demonstrate the value of the present integrated CFD/1D-PM modeling approach.
Journal articles
Investigating the causes of severe economizer tube thinning in a spent sulfite liquor (SSL) boiler, TAPPI Journal August 2026
ABSTRACT: In this study, the causes of tube thinning in the economizer of an ammonia-based spent sulfite liquor (SSL) boiler in a Canadian pulp mill are investigated. The tube thinning was most severe in the upper tube rows of the lowest economizer sections where the tube surface temperature ranges between about 180°C and 210°C. The location, the temperature range, and the results of a tube failure analysis indicate that some form of corrosion- erosion is the main cause for the tube thinning. The process is likely initiated by the formation of potassium bisulfate in tube deposits. We hypothesize that some areas in the economizer, including gaps in tube shields, have allowed for temporary buildup of deposits that were not fully removed by sootblowing. Potassium bisulfate is highly hygroscopic, so it readily absorbs moisture, forming an acidic solution leading to corrosion. The corrosion products are removed by the erosive effects of high velocity gas movement, causing the tube thinning. The high-speed fluid flow may be a result of sootblower action and/or enhanced flue gas velocity due to channeling. The tube thinning eventually leads to perforation and leakage.
Journal articles
Effects of calcium on sodium salt scaling with the presence of resin acids and fatty acids, TAPPI Journal June 2026
ABSTRACT: Reintroducing tall oil soap or its related products into high dry solids black liquor has been found to reduce sodium salt scaling in falling film evaporators. Aside from resin acids and fatty acids, which are the likely scale inhibitors, calcium is reintroduced into black liquor because of the relatively high calcium content of tall oil soap. One concern is that this increase in calcium content might lead to the formation of additional calcium and sodium scales in evaporators. In this work, we investigated the relationship among trace amounts of calcium, sodium salts, resin acids, and fatty acids in a controlled system using a model salt solution and a benchtop setup. We studied the effects of the calcium carbonate addition and calcium carbonate scales on sodium salt scaling in the presence of resin acids and fatty acids. We found that some calcium carbonate is incorporated in the precipitated sodium crystals, and the suspended sodium crystals become larger and more compact with increasing calcium carbonate concentration. Experiments in the benchtop setup show that precipitating calcium carbonate scale on the heat exchanger does not lead to a higher rate of sodium salt scaling. The solubility of calcium carbonate is not affected by the addition of resin acids and fatty acids. These findings indicate that the reduction in sodium salt scaling through the addition of tall oil soap is primarily related to resin acids and fatty acids, rather than to calcium or to interactions between calcium and mixtures of resin and fatty acids.
Journal articles
Magazine articles
In-situ green synthesis and adsorption on methylene blue of copper-based metal organic framework/cellulose/chitosan (CCTSA/HKUST-1) composite aerogel, TAPPI Journal October 2024
ABSTRACT: In order to explore the application of metal-organic frameworks (MOFs) in environmental and water treatment fields, a new composite aerogel of HKUST-1/cellulose/chitosan (CCTSA/HKUST-1) with better hydrostability was synthesized by an in-situ synthesis method combining covalent cross-linking and solvothermal methods as an efficient adsorbent for methylene blue (MB). The composite aerogel (CCTSA) obtained by covalent cross-linking of cellulose (CE) and chitosan (CTS) exhibited excellent stability under strong acid and solvent-thermal conditions. With the increase of CTS content, it was beneficial to the in-situ synthesis of HKUST-1, as well as to increase the mass loading rate of HKUST-1 to 37.06%, while the Brunauer-Emmett-Teller (BET) specific surface area of CCTSA/HKUST-1 composite aerogel reached 945.123 m2·g-1, which was much higher than that of the CCTSA composite aerogel (14.489 m2·g-1). The CCTSA/ HKUST-1 composite aerogel exhibited excellent adsorption capacity (537.6 mg·g-1) on MB solution, and cyclic adsorption could be achieved. This study proposes a concept of valorization of alkaline peroxide mechanical pulping (APMP) waste liquor to hemicellulose-based hydrogel. This hemicellulose-based hydrogel exhibits a sensitive temperature/pH dual response. Hemicellulose-based hydrogels swell or shrink through the change of hydrogen bond/electrostatic repulsion/charge screening. They also show good water absorption and water retention properties.
Journal articles
Magazine articles
Biofuels in lime kilns • Operating experience in the Nordic pulp and paper industry, TAPPI Journal October 2024
ABSTRACT: The lime reburning process is a central part of the chemical pulp mill. It is energy intensive and consumes large amounts of fossil fuel, globally consuming about 50 terawatt-hours (TWh) of fuel per year. Conversion to operation with biofuel is interesting, both to reduce carbon dioxide emissions and to reduce costs. Researchers interviewed managers in mills that use solid, liquid, or gasified biofuels to replace fuel oil or natural gas in their lime kilns, and they conducted surveys related to fuel consumption and operations and maintenance. In Sweden and Finland, there were ten mills in 2020 using biomass powder or gasified biomass as the primary fuel, and two more installations were under construction. There were also nine installations in operation or under construction outside the Nordic countries. Fourteen mills in Sweden and two mills in Finland used tall oil pitch as the main fuel. Fuel consumption in Swedish lime kilns was 3.8 TWh in 2020, and 90% of this energy was supplied with biofuels. Of about 4.2 TWh used in Finnish lime kilns, approximately 45% was supplied with biofuels. Developments in the design of the fuel supply system include belt dryers being used in all new installations and mass flow metered dosing systems being used in most new pulverized fuel installations. Bark gasifiers have increased considerably in size. Lignin powder firing has been established as a proven option. A solution for many Swedish and Finnish mills is the use of tall oil pitch as a replacement for fuel oil.
Journal articles
Recovery of Sulfur from Spent Semichemical Pulping Liquors,
Recovery of Sulfur from Spent Semichemical Pulping Liquors, 1991 Engineering Conference Proceedings
Journal articles
Influence of voids on the engineering constants of paper par
Influence of voids on the engineering constants of paper part 2: void modeling, TAPPI JOURNAL, December 1994, Vol. 77(12)
Journal articles
The Impact of the Summer Effect on Ink Detachment and Remova
The Impact of the Summer Effect on Ink Detachment and Removal
Journal articles
Liquor-To-Liquor Differences in Combustion and Gasification
Liquor-To-Liquor Differences in Combustion and Gasification Processes: Nitrogen Oxide Formation Tendency, 1995 Engineering Conference Proceedings