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PEERS 2023 Poster Session: a competition for students and young professionals, TAPPI Journal April 2023
ABTRACT: Originating in the field of scientific research and academia, poster sessions at conferences may date back to the mid-20th century, although the origins aren’t quite clear. Some sources have said as early as the 1950s and others later, while the term “poster session” itself may not have been coined until the 1975 American Physics Conference. The original concept behind poster sessions was to provide a platform for researchers to share their work in a more visual and interactive format as compared to the traditional long-form oral presentation.
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Black liquor evaporators upgrade — How many effects?, TAPPI Journal April 2023
ABSTRACT: Black liquor evaporation is generally the most energy intensive unit operation in a pulp and paper manufacturing facility. The black liquor evaporators can represent a third or more of the total mill steam usage, followed by the paper machine and digester. When considering an evaporator rebuild or a new system, the key design question is how many effects to include in the system. The number of effects is the main design feature that deter-mines the economy of the system and the steam usage for a given evaporation capacity. A higher number of effects increases steam economy and reduces energy cost to a point, but additional effects also have higher initial capital cost and increased power costs. This research paper uses life-cycle cost analysis (LCCA) as a method to determine the optimum number of evaporator effects for a new evaporator system. The same basic principles and method can also apply to existing evaporator rebuild projects.
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Dynamic CFD modeling of calcination in a rotary lime kiln with an external dryer, TAPPI Journal August 2023
ABSTRACT: Mid-kiln ring formation is a problem in lime kilns that may be related to fluctuations in the start location of calcination. To calculate fluctuations in bed and gas temperature profiles within a lime kiln with an external dryer, a dynamic two-dimensional (2D) axisymmetric computational fluid dynamics (CFD) gas model with a methane burner implemented in ANSYS Fluent, coupled by mass and heat balances to a one-dimensional (1D) bed model, was developed. The dynamic model was used to calculate changes in the location where calcination starts with fluctuations in operational conditions using pulp mill data. This model simulates radiative, convective, and conductive heat transfer between the gas, wall, and bed to determine the axial bed temperature in the kiln. The calcination reaction is described using a shrinking core model that allows for the prediction of the location at which calcination begins and the degree of calcination achieved. The solid motion within the kiln is modeled using Kramer’s equation modified for transient response. Steady-state and dynamic simulation results were compared to data from an industrial dry lime kiln, and good agreement was found. A sensitivity analysis was also performed to provide insight on how operating conditions and model variables impact the calcination location and degree of calcination. Of the variables examined, the fuel rate and the feed temperature had the largest impact on both the calcination location and degree of calcination in the kiln. Model predictions of a period of ring formation in the industrial kiln showed that the start location of calcination fluctuated by more than 2 m on either side of the mean of regular operation, warranting further investigation of the importance of these fluctuations on mid-kiln ring formation.
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Totally chlorine-free peracetic acid pulping for nanocellulose isolation from hemp and poplar, TAPPI Journal August 2023
ABSTRACT: Nanocellulose is a promising and sustainable feedstock for developing advanced and functional materials. However, the characteristics of nanocellulose, such as crystallinity, surface energy, and aspect ratio, can vary depending on biomass source and pretreatment methods, leading to variable performance of the nanocellulose-based materials. In this study, cellulose nanocrystals (CNCs) were isolated from hemp and poplar using totally chlorine free (TCF) peracetic acid and sodium chlorite delignification and bleaching pretreatments to probe the influences of biomass source and treatment methods on the isolation and characteristics of CNCs. Our results showed that hemp and poplar were almost completely delignified by peracetic acid treatment, whereas sodium chlorite treatment left 5%•6% lignin in the pulp. The yields of CNCs from raw hemp and poplar biomass ranged from 9.8% to 21.9% and 10.9% to 28.3%, respectively, depending on the treatment methods. The dimensions of CNCs from TCF-treated biomass generally maintained a larger width and aspect ratio than those from sodium chlorite-treated biomass. The poplar-derived CNCs exhibited slightly higher crystallinity of 53%•58% than hemp-derived CNCs of 49%•54%. The zeta potential of the CNCs, ranging from -20.1 mV to -31.1 mV, ensured a well-dispersed aqueous solution. The surface energy (dispersive energy of 40•80 mJ/m2 and specific energy of 2•10 mJ/m2), water interaction, and thermal stability of the CNCs were comparable, regardless of the biomass source and pretreatment methods. Our finding suggests that the TCF technique with peracetic acid treatment is a promising delignification and bleaching approach to obtain cellulose-rich pulps from herbaceous and hardwood biomass for nanocellulose isolation.
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SCC susceptibility of chromized type 409 stainless steel in alkaline chloride solutions at ambient temperature and pressure, TAPPI Journal August 2023
ABSTRACT: Biomass hydrothermal liquefaction (HTL) is operated in a harsh reaction medium that contains hot pressurized water, inorganic acidic or basic catalyst, and inorganic/organic corrosive components released during the conversion. Candidate alloys for this application require suitable resistance to both corrosion and stress corrosion cracking (SCC) to withstand the HTL process conditions (250°C•374°C and 4•22 MPa). Ferritic iron-chromium (Fe-Cr) steels are more prone to corrosion but less susceptible to SCC compared to austenitic iron-chromium-nickel (Fe-Cr-Ni) steels. Chromizing can significantly reduce corrosion of Type 409 stainless steel (Fe-11Cr) in a simulated aqueous HTL solution. The objective of this study is to determine the SCC susceptibility of chromized Type 409 stainless steel, relative to the bare (non-chromized) case. The slow strain rate testing (SSRT) technique was used for this purpose. For simplicity of experimentation, SSRT was conducted using simulated HTL water containing 800 ppm potassium chloride (KCl), 1 M potassium carbonate (K2CO3), and 10 wt% acetic acid at ambient temperature and pressure. Complementary potentiodynamic polarization measurements and surface analysis by X-ray photoelectron spectros-copy (XPS) were also made to help interpret the SSRT results. The SSRT results show no significant difference in SCC susceptibility, regardless of the starting surface. Thus, chromizing, while significantly reducing the corrosion of Type 409 stainless steel, does not adversely affect SCC susceptibility, at least under the conditions tested.
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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.
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Editorial: Surface energy in printing is the focus of runner-up, TAPPI Journal May 2024
ABSTRACT: The runner-up to the 2023 TAPPI Journal Best Re-search Paper was “Surface energy considerations for offset printing of coated paper and pa-perboard,” co-authored by Janet Pres-ton, Andrew Findlay, Jonathan Keen, and Eli Gaskin of Imerys Minerals in Par, England, UK. Their research appeared in the November 2023 special coating issue organized by TAPPI Journal Editorial Board Members Steve Ottone, Gregg Reed, and Greg Welsch.
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Remembering Dr. Peter W. Hart: Dedicated leader, mentor, friend, TAPPI Journal May 2024
ABSTRACT: Dr. Peter W. Hart, a true pioneer in the pulp and paper industry, passed away on May 11, 2024. His legacy will be celebrated for many years. As we reflect on Hart’s remarkable life and achievements, we celebrate his positive impact on TAPPI and the industry. He was a beloved TAPPI member, editor, author, instructor, and mentor.
Journal articles
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Enhancing tissue wet pressing performance and dry end material efficiency for cost savings, TAPPI Journal May 2024
ABSTRACT: The steadily growing global tissue paper demand lays a foundation for new technologies targeting tissue production optimization, as well as improved material and time efficiency. Tissue making is an especially energy-intensive field of paper industry, creating unique demands for performance in wet pressing and drying processes to cut energy usage. Intelligent roll solutions offer new tools for tissue making to achieve these goals. These tools aim at improving press nip, moisture, and tension profiles; reeling nip and parent roll hardness profiles; rewinder runnability; and end product web handling characteristics in converting. Intelligent rolls can be utilized in all the main processes and positions on tissue production lines. With these tools, production cost reductions and energy savings can be obtained by optimizing the press nip-to-Yankee cylinder contact, avoiding moisture profile errors requiring overdrying with the Yankee hood and reducing reeling/winding broke under low nip load conditions typical to tissue windups. The intelligent roll system consists of a helically mounted force or temperature sensors, roll covers, measurement electronics, digital radio transmission, and a receiver system connected to a user interface or the mill automation system. What distinguishes these implementations is that no layout changes or added external measurement devices are required, helping to fit into compact tissue machine environments, regardless of the equipment type • traditional, hybrid, or through-air drying (TAD) concept. In tissue processing equipment, the optimal positions for these rolls are press nip rollers, reeling cylinders, rewinder or converting line paper lead rolls, or rewinder winding drums. In addition to these, temperature profile measurements are utilized, with the main application being the sheet temperature profile detection after Yankee drying for moisture profile and drying process optimization.
Journal articles
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Editorial: New coating grades require new tests: Barrier performance inside the package, TAPPI Journal November 2024
The TAPPI Journal special Coating issue is an annual issue that focuses on paper coating and coated papers. It is drawn from presentations at TAPPICon and from other submissions on the topic of paper coating. The TAPPICon 2024 Coating track was rich in high-quality technical content. In fact, the papers were of such significance that Coating members of the TAPPI Journal Editorial Board, which include me, Gregg Reed, and Gregory Welsch, decided that a second paper coating-related special issue would be appropriate for the TAPPI Journal editorial calendar. In addition to the current issue on Barrier Coating Testing, there will be another issue on Coating Fundamentals in early 2025.