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The sticky behavior of pulp and paper mill biosludge during drying, TAPPI Journal June 2019
ABSTRACT: Pulp and paper mill biosludge becomes sticky after being dried to a certain solids content. As bio-sludge becomes sticky, it agglomerates and adheres to the heat transfer surfaces of the dryer. This undesirable property can lower the dryer efficiency and cause the drying equipment to fail.A systematic study was conducted to examine the sticky behavior of biosludge. The stickiness was evaluated by measuring the adhesive force between a sludge cake and a stainless steel substrate, and the cohesive force between a sludge cake and a sludge substrate. The results show that: i) both adhesive and cohesive forces increase markedly as the solids content increases, reaching a maximum value at about 13% solids, and then decrease steadily at a high-er solids content; ii) cohesive force is stronger than adhesive force, implying that biosludge tends to agglomerate rather than adhere to smooth equipment surfaces; and iii) mixing wood fines or fly ash from a biomass boiler reduc-es the stickiness of the mixture. These findings may help mills improve the thermal efficiency of biosludge dryers and to turn biosludge into a more attractive fuel for burning in biomass boilers.
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A study of the softness of household tissues using a tissue softness analyzer and hand-felt panels, TAPPI Journal March 2019
ABSTRACT: This study applied the reciprocal matrix approach to deduce the correlation between hand-felt (HF) and tissue softness analyzer (TSA) instrumental measurements of tissue softness. The research was conducted in three phases, which are discussed separately. In the phase one study, results indicated that systematic collection of samples and preparation of test specimens were the foundation of successful tests. TSA-HF and tensile strength exhibited a strong negative correlation. In the future, same-unit physical properties can provide a basis for discuss-ing the commonality and complementary natures of hand-felt and TSA softness measurements. In phase two, through the reciprocal matrix approach, subjective softness assessments performed by humans were reliably quan-tified. The quantified values were further applied to a statistical analysis using the t-test to distinguish and train pro-fessional panelists. In phase three of HF panel test results, all independent panels were compared to one another under a uniform scale established by four standard samples. The calibrated HF panel values were incorporated with TSA-HF results to establish technical curves between the softness and tensile strength, which were helpful for onsite workers to carry out process controls.
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Optimazation of coating with water-based barriers, TAPPI Journal February 2019
Optimazation of coating with water-based barriers, TAPPI Journal February 2019
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Editorial: TAPPI Journal 2018 Best Research Paper delves deeper into press section rewet to address drying efficiency, TAPPI Journal March 2019
ABSTRACT: TAPPI and the TAPPI Journal (TJ) Editorial Board would like to congratulate the authors of the 2018 TAPPI Journal Best Research Paper Award: J. David “Dave” McDonald and Richard J. “Dick” Kerekes. Their paper, “Rewet in wet pressing of pa-per,” appeared on p. 479 of the September 2018 issue. This research was recognized by the Editorial Board for its in-novation, creativity, scientific merit, and clear expression of ideas.
Journal articles
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Effect of eucalyptus bark contamination during pulping of mi
Effect of eucalyptus bark contamination during pulping of mixed southern hardwoods, November 2016 TAPPI JOURNAL
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Chemical addition to wet webs using foam application, TAPPI Journal January 2023
ABSTRACT: In papermaking, the conventional way to add chemicals to the web is to dose them into the fiber stock and form the paper afterwards. However, in many cases, adding chemicals directly to the stock is challenging. For example, strength aids tend to increase flocculation in the stock, which limits the addition amounts of those aids. The need for better performance of paper (and paperboard) products has given rise to the need for functionalization of paper. Adding such functional chemicals to the stock is usually rather inefficient. Hence, novel methods are needed to add chemicals to the paper bulk. One such method is dosing chemicals to the wet web via foam application. In this study, we built a laboratory-scale sheetfed dynamic foam application device and utilized it to study addition of starch to wet bleached chemithermomechanical pulp (BCTMP) paper handsheets. The impact of parameters such as vacuum level, the amount of added chemical, and the viscosity of the foaming liquid on the penetration of starch into the wet web was explored. Starch penetration into wet webs was measured via iodine-potassium iodide staining, followed by image analysis. According to our results, controlling the viscosity of the foaming liquid gives the best possibility to control the penetration.
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Z-direction chemical analysis for new application methods, TAPPI Journal January 2023
ABSTRACT: In conventional wet-end chemical addition during paper production, chemical distribution through the z-direction of the sheet is usually not considered an important characteristic. With a nontraditional chemical dosing approach, such as foam-assisted additive addition, the chemistry can appear at different concentrations throughout the sheet, typically in a z-direction gradient. To fully understand the strength properties of the sheet, it is helpful to view or quantify the chemical distribution through the sheet in the z-direction. One qualitative method uses a dye technique along with confocal laser scanning microscopy to generate an image where the relative chemical concentration can be observed. A quantitative method involves compiling nitrogen analyses of layered subsections of the sheet into a composite graph of relative chemical concentration vs. the z-direction of the sheet. Chemical distribution analysis can be paired with traditional z-direction strength tests, such as Scott bond and z-direction tensile, to help one understand and improve the chemical addition process and its effects.
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Convolutional neural networks enhance pyrolysis gas chromatography mass spectrometry identification of coated papers, TAPPI Journal August 2024
ABSTRACT: In the evolving paper industry, accurate identification of coated paper components is essential for sustainability and recycling efforts. This study employed pyrolysis-gas chromatography mass spectrometry (Py-GCMS) to examine six types of coated paper. A key finding was the minimal interference of the paper substrate with the pyrolysis products of the coatings, ensuring reliable analysis. A one-dimensional convolutional neural network (1D-CNN) was employed to process the extracted ion chromatograms directly, simplifying the workflow and achieving a predictive accuracy of 95.2% in identifying different coating compositions. Additionally, the study high-lighted the importance of selecting an optimal pyrolysis temperature for effective feature extraction in machine learning models. Specific markers for coated papers, including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene succinate (PBS), polylactic acid (PLA), and waterborne polyacrylates (WP), were identified. This research demonstrates a novel approach to coated paper identification by combining Py-GCMS with machine learning, offering a foundation for further studies in product quality and environmental impact.
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Factors affecting deposit formation in foul condensate stripping systems, TAPPI Journal June 2024
ABSTRACT: In kraft pulp mills, foul condensates are often steam-stripped to produce clean condensate for use as process water. The formation of organic deposits in the stripped condensate is a common problem. A systematic study was conducted to examine the deposit composition and the most likely operating parameters responsible for stripped condensate contamination experienced at a kraft mill in Brazil. Daily averaged data of 170 operating parameters over a 15-month period were analyzed by means of multivariate discriminant analysis and random forest classification analysis. The results showed that the deposit formation is related to high temperature, pressure, and dry solids operations in various evaporator effects. These conditions, combined with the poor demisting efficiency in these effects, may have increased black liquor carryover mist in the vapor. Deposit formation also appeared to be related to increased throughput of the foul condensate stripping system and increased pressure in the stripper. Results of Fourier transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography mass spectrometry (Py-GCMS) analyses show that the deposit consists of mostly organic matter that likely originated from wood extractives and lignin.
Journal articles
Magazine articles
Effect of high sulfate content on viscosity of recovery boiler molten smelt, TAPPI Journal March 2024
ABSTRACT: A systematic study was conducted to examine the effect of high sulfate content on the freezing temperature of molten smelt and how this may contribute to the formation of viscous jellyroll smelt in recovery boilers. The results show that even for recovery boilers with a smelt reduction as low as 70%, the sulfate content in smelt has no or little effect on smelt freezing temperature, and hence, on molten smelt fluidity. The perceived adverse effect of high sulfate content on smelt fluidity and on jellyroll smelt formation comes from the high sulfate content in deposits that have fallen from the upper furnace. Fallen deposits may or may not form jellyroll smelt, depending on whether or not they can melt and be well-mixed with molten smelt by the time they reach the smelt spouts. It is not the high sulfate content in smelt resulting from the low smelt reduction efficiency that makes molten smelt viscous and forms jellyroll smelt, but rather, it is the incomplete melting of fallen deposits that results in one of the proposed mechanisms for jellyroll smelt formation.