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Journal articles
Magazine articles
Effects of carboxymethyl starch as a papermaking additive, TAPPI Journal February 2024
ABSTRACT: Carboxymethyl starch (CMS) is a bio-based, anionic polymer that has potential as part of a dry-strength additive program for papermaking. Due to its negative charge, its effects can be expected to depend on its interactions with various cationic agents. In this work, the effects of CMS were observed following its sequential addition after one of three selected cationic strength agents at different dosage levels. In selected tests, the furnish was pretreated at the 1% level by a dispersant, sodium polyacrylate, which might represent a high level of anionic contaminants in a paper mill system. Laboratory tests were conducted to show the effects on dewatering, fine-particle retention, and flocculation. These tests were supplemented with measurements of charge demand, zeta potential, and handsheet properties. Sequential addition of cationic glyoxylated acrylamide copolymers (gPAM) and CMS were found to strongly promote dewatering. Two gPAM products and a poly(vinylamine) product in sequential addition with CMS were very effective for promoting fine-particle retention. These same sequential treatments of the stock contributed to moderate fiber flocculation, though severe flocculation was caused by further treatment of the furnish with colloidal silica. Handsheet strength results were mixed. In the default recycled copy paper furnish, the average breaking length for the sheets made with cationic additives followed by CMS was not greatly different from the blank condition. Superior strength resulted when the default furnish was treated with a dispersant alone. When the dispersant-contaminated furnish was treated with the same combinations of cationic additives and CMS, the strength returned to the baseline achieved in the absence of the dispersant. The results were discussed in terms of the charged character of the different additives and their interactions not only with the fiber surfaces but also with each other.
Journal articles
Magazine articles
Quantification of hardwood black liquor contamination in pine black liquor, TAPPI Journal February 2024
ABSTRACT: The presence of hardwood black liquor contamination in pine black liquor can negatively impact brownstock washer and evaporator operation, as well as reduce soap separation and yield. It is also believed to negatively impact commercial kraft lignin production. It was desired to develop a method of quantitatively determining the amount of low-level hardwood liquor contamination in pine black liquor. A method employing pyrolysis-gas chromatography mass spectrometry (py-GCMS) was developed to perform the desired measurement. Laboratory cooks with carefully controlled blends of pine and hardwood chips were prepared, and the resulting liquor was measured using this technique. Additionally, samples of pine and hardwood black liquors were blended in known quantities and analyzed. All these samples were submitted as blind samples. The resulting analysis suggests the py-GCMS method was able to accurately determine the level of hardwood contamination between 1% to 10% hardwood liquor using a low-level calibration curve prepared with coniferyl alcohol and sinapyl alcohol as standards.
Journal articles
Magazine articles
Editoral: Investing in the future: Writing and peer-reviewing for TAPPI Journal, TAPPI Journal July 2024
ABSTRACT: Those who actively participate in TAPPI realize how much there is to gain from the networking, educational resources, career development, and other opportunities that come with this involvement. One important opportunity is the ability to share your work and expertise with others in your field, and an excellent way to do this is by taking part in the TAPPI Journal peer-review process, either as an author or a reviewer or both.
Journal articles
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Tetraethyl orthosilicate-containing dispersion coating — water vapor and liquid water barrier properties, TAPPI Journal September 2021
ABSTRACT: An aqueous styrene-butadiene latex dispersion coating containing in-situ processed tetraethyl orthosilicate (TEOS) applied on paperboard demonstrated improved water barrier performance. Coatings containing TEOS equivalent to 0.8% silicon dioxide (SiO2; dry basis) exhibited water vapor performance of < 25 g/m2/day (23°C, 50% relative humidity [RH]) and liquid water barrier performance Cobb 1800 s of < 6 g/m2, when applied as a single-layer 18 g/m2 coating. Cobb 1800 s barrier performance was still good (< 11 g/m2) at coat weights of 7•10 g/m2. The use of filler materials such as kaolin improved the vapor barrier properties of the coating, but this was not critical to the liquid water barrier properties.
Journal articles
Magazine articles
Commercially relevant water vapor barrier properties of high amylose starch acetates: Fact or fiction?, TAPPI Journal September 2021
ABSTRACT: Starches have recently regained attention as ecofriendly barrier materials due to the increased demand for sustainable packaging. They are easily processable by conventional plastics processing equipment and have been utilized for oil and grease barrier applications. While starches have excellent oxygen barrier properties and decent water barrier properties at low relative humidity (RH), they are moisture sensitive, as demonstrated by the deterioration of the barrier properties at higher RH values. Starch esters are chemically modified starches where the hydroxyl group of the starch has been substituted by other moieties such as acetates. This imparts hydrophobicity to starches and has been claimed as a good way of retaining water vapor barrier properties of starches, even at high RH conditions. We studied the water vapor barrier properties of one class of starch esters, i.e., high amylose starch acetates that were assumed to have good water vapor barrier properties. Our investigations found that with a high degree of substitution of hydroxyl groups, the modified starches did indeed show improvements in water vapor response as compared to pure high amylose starch films; however, the barrier properties were orders of magnitude lower than commercially used water vapor barriers like polyethylene. Even though these materials had improved water vapor barrier response, high amylose starch acetates are likely unsuitable as water vapor barriers by themselves, as implied by previous literature studies and patents.
Journal articles
Magazine articles
Viscoelastic web curl due to storage in wound rolls, TAPPI Journal July 2020
ABSTRACT: Winding is often the final operation in a roll-to-roll manufacturing process. Web materials, i.e., materials that are thin compared to their length, are wound into rolls because this form is the only practical means to store them. The resulting bending strains and associated stresses are large for thick webs and laminates. As many webs are viscoelastic on some time scale, bending stresses lead to creep and inhomogeneous changes in length. When the web material is unwound and cut into discrete samples, a residual curvature remains. This curvature, called curl, is the inability for the web to lie flat at no tension. Curl is an undesirable web defect that causes loss of productivity in a subsequent web process. This paper describes the development and implementation of modeling and experimental tools to explore and mitigate curl in homogenous webs. Two theoretical and numerical methods that allow the prediction of curl in a web are developed: a winding software based on bending recovery theory, and the implementation of dynamic simula-tions of winding. One experimental method is developed that directly measures the curl online by taking advantage of the anticlastic bending resulting from the curl. These methods are demonstrated for a low-density polyethylene web.
Journal articles
Magazine articles
Case study: Paper mill power plant optimization—balancing steam venting with mill demand, TAPPI Journal June 2020
ABSTRACT: Most Power departments are tasked with generating steam to support mill wide operations, generate electricity, and reduce operating costs. To accomplish these tasks, power boilers generate high pressure steam that is reduced to intermediate and low pressures for process utilization in the mill by means of steam turbine generator extraction or pressure reducing valves. The most economical method to reduce steam pressure is the use of steam turbine generators, as electricity is generated from the steam when it is reduced in pressure. Electricity that is produced by these generators provides a substantial financial benefit and helps offset overall operational costs. To achieve tangible financial gains, the mill must evaluate the overall cost of steam production and the price of electricity.The current work provides a case study of power plant optimization that evaluated electricity production and steam production costs balanced with mill steam demand. Process and cost optimization led to a significant reduc-tion in low pressure steam venting, resulting in reduced fuel consumption and reduced operating cost.
Journal articles
Guest Editorial: Carrying forward the tradition of fundamental research, TAPPI Journal June 2026
Since its first symposium in 1957, the Fundamental Research Symposium has evolved around fundamental research themes aimed at scientifically understanding papermaking. The symposium is organized by the Fundamental Research Committee (FRC), which is operated by the Fundamental Research Society (FRS). The unique format of the symposium, held at universities such as Oxford and Cambridge where participants stay together, fosters intensive academic exchange and collegial interaction.
Journal articles
Magazine articles
Eucalyptus black liquor properties in a lignin extraction process: density, dry solids, viscosity, inorganic, and organic content, TAPPI Journal March 2023
ABSTRACT: Extracting lignin from black liquor is becoming more common, although only a few research papers discuss the impact of the process on the liquor’s primary properties. This work aims to determine the changes in black liquor properties as it undergoes a lignin extraction process using carbon dioxide (CO2). A diluted eucalyptus black liquor sample (DBL) was acidified with CO2 to a final pH of 8.5. After filtration, the kraft lignin was removed, and the filtrated lignin lean black liquor (LLBL) was collected. Five acidified black liquors (ABL) samples were collected during acidification at pH 10.5; 10.0; 9.5; 9.0; and 8.5. The samples were analyzed regarding lignin content in solution, sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), density, dry solids content, and viscosity. While Na2SO4 remained almost constant, Na2CO3 presented an enormous increase in its concentration when comparing DBL with LLBL. As pH decreased, the lignin content in the solution was also reduced due to lignin precipitation. The results showed similar behavior for dry solids, density, and viscosity of the supernatant, but an increase in density was observed around pH 9.00. In light of this, the density of LLBL turns out to be closer to the one in the initial DBL. The significant increase in carbonate content could explain this behavior during acidification with CO2 once the inorganic content significantly influences the property. The viscosity was determined from 10 s-1 to 2000 s-1. We observed a Newtonian behavior for all samples. The increase in carbonate content in the sample is crucial information to the recovery cycle, especially for calculating the mass and energy balance when targeting the use of the LLBL.
Journal articles
Magazine articles
On the diagnosis of a fouling condition in a kraft recovery boiler: combining process knowledge and data-based insights, TAPPI Journal March 2023
ABSTRACT: Fouling is still a major challenge for the operation of kraft recovery boilers. This problem is caused by accumulation of ash deposits on the surfaces of heat exchangers in the upper part of the boiler over time. The first consequence is the reduction of steam production due to loss of heat transfer and, finally, the shutdown of the boiler due to clogging. The present work investigated the operational condition of a modern kraft boiler under a critical fouling condition. This boiler had even faced a manual cleaning due to a clogging event. This analysis combined process knowledge, plant team experience, and a data-driven approach, given the complexity of the process. In this sense, historical data covering this critical period of operation were collected. After a cleaning procedure, they were used to obtain a predictive neural network model for the flue gas pressure drop in the boiler bank, which is an indirect measure of ash deposit accumulation. Once validated, it was used for sensitivity analysis, with the aim of quantifying the effects of the model inputs. Five variables out of eighteen accounted for nearly 60% of the total effect on pressure drop. Namely, primary air temperature (21.6% of the total effect) and flow rate (11.1%), black liquor flow rate (9.9%) and temperature (8.4%), and white liquor sulfidity (8.6%). The analysis of these results mainly suggested an excess of carryover, which composes the ash deposits. Recommended actions to mitigate the fouling condition involved adjustments to the primary air system before the more drastic solution of reducing the boiler load.