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Analysis of economically viable lignin-based biorefinery st
Analysis of economically viable lignin-based biorefinery strategies implemented within a kraft pulp mill, TAPPI JOURNAL March 2017
Journal articles
Magazine articles
A guide to eliminating baggy webs, TAPPI Journal June 2021
ABSTRACT: Slack or baggy webs can cause misregistration, wrinkles, and breaks in printing and converting operations. Bagginess appears as non-uniform tautness in the cross direction (CD) of a paper web. The underlying cause is uneven CD tension profiles, for which there are few remedies once the paper is made. Precision measurements of CD tension profiles combined with trials on commercial paper machines have shown that uniform CD distribution of moisture, basis weight, and caliper profiles at the reel are key to avoiding bagginess. However, the most important but infrequently measured factor is the CD moisture profile entering the dryer section. Wetter areas entering the dryers are permanently elongated more than dry areas, leading to greater slackness in the finished paper. In storage, wound-in tension can amplify baggy streaks in paper near the surface of a roll and adjacent to the core. Unwrapped or poorly wrapped rolls exposed to low humidity environments may have baggy centers caused by moisture loss from the roll edges.All of the factors that impact bagginess have been incorporated in a mathematical model that was used to interpret the observations from commercial trials and can be used as a guide to solve future problems.
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Using novel DNA methods to achieve higher process efficiency and performance, TAPPI Journal January 2023
ABSTRACT: Uncontrolled microbiological activity is a challenge for recycled fiber (RCF) mills as it can have negative effects on production and end-product quality. The microbes that exist in these systems have been largely unknown, and the strategies employed to control microbiology have been non-specific. Understanding the specific microbial groups present in RCF mills, their properties, and where they exist, as well as having the ability to accurately measure the true troublemakers, are key to targeted control of the bad actors. In this study, we present the results of a global survey of over 40 RCF paper machines. The same RCF-specific problem-causing bacterial groups were found on different continents, including large densities of newly identified bacteria in paper processes. Those can degrade cellulose and starch, produce acids and odorous substances, and have a significant impact on fiber strength and additive consumption. We also demonstrate how modern DNA tools can quantify the impact of biocidal countermeasures against the actual troublemakers, including bacteria found to degrade cellulose during RCF pulp storage, which may be linked to a negative impact on end-product strength. These novel DNA tools give producers updated biocide program key performance indicators (KPIs) and actionable information to more effectively design and adjust microbiological control to achieve higher process efficiency and performance.
Journal articles
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Non-process elements in the recovery cycle of six Finnish kraft pulp mills, TAPPI Journal March 2023
ABSTRACT: In this work, the aim was to study the distribution and accumulation of the non-process elements (NPEs) in the recovery cycle of Finnish pulp mills and look at whether the geographical location (North vs. South) correlates with the current Finnish NPE levels. In addition, a comparison to older similar Finnish measurements was made with an attempt to analyze the reasons behind differences in the most typical non-process elements, aluminum (Al), silicon (Si), calcium (Ca), phosphorus (P), magnesium (Mg), manganese (Mn), chlorine (Cl), and potassium (K), taking into account the main elements in the white liquor, sodium (Na) and sulfur (S). The extensive laboratory results gained in this study are from seven sampling points at six pulp mills and present analytical data of metal concentrations. The data obtained presents an update to previous NPE studies. The levels found did not statistically differ between North and South Finland. The NPE levels, apart from phosphorus, found in Finnish pulp mills today have not changed considerably compared to the levels in earlier investigations in the 1990s. In the newest data, the phosphorus concentration was consistently higher in the as fired black liquor, electrostatic precipitator (ESP) ash, lime mud, and green liquor than in the previous results. In addition, the levels of Al, Si, Ca, P, and Mg in recovery boiler ESP ash were consistently higher compared to the older results. As the mills start to close their systems more, a stronger accumulation of NPEs can be expected, increasing the likelihood of more operational problems in the process. Further understanding of where the NPEs accumulate and how they can be most effectively removed will be valuable knowledge in the future.
Journal articles
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Paper bending stiffness and web tension measurement from a running web using a vacuum and computer imaging, TAPPI Journal May 2023
ABSTRACT: A novel method for measuring the bending stiffness of paper online during manufacturing is introduced. The method uses photometric stereo imaging to detect the shape of the deflection surface caused by a controllable pressure difference over the paper’s surfaces. The hardware for the measurement is based on a combination of two existing sensors, which has accelerated and facilitated the development of the implementation. The deflection and loads are tied together by the governing differential equation for the bending of an orthotropic elastic plate with selected simplifications. An approach to resolve material parameters and in-plane loads without knowledge of traditional boundary conditions is suggested. The presented method was tested in a paper mill during manufacturing. For bending stiffnesses measured online, correlation coefficients 0.88 and 0.92 were obtained compared to state-of-the-art laboratory measurements. However, the results gained from a moving web are noisy and the data requires correction of the slope and an off-set. Although several issues remain to be resolved before the method can be considered as an accurate measurement for industrial use, the theoretical background, the performance of online implementation, and the results are promising. Possible causes for the observed discrepancies and the future development of the method are discussed.
Journal articles
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Surface modification of TiO2 with MPS and its effects on the wettability and physical properties of Kawayan Kiling (Bambusa vulgaris Schrad ex. Wendl) handsheets, TAPPI Jouranl April 2024
ABSTRACT: The need for hydrophobic papers has steadily increased over past years. These papers are often sought after as packaging materials and have high demand in the food industry and medicine. In this study, various concentrations of surface-modified TiO2-MPS were added to Kawayan Kiling (B. vulgaris) pulp at the wet-end section of handsheet formation. Surface-modified TiO2-MPS was made from nano-titanium (IV) oxide using 3-(trimethoxysilyl)propyl methacrylate as a coupling agent. The wettability of handsheets and physical properties were tested using various standard methods. Results reveal that the handsheets without surface-modified TiO2-MPS had the lowest water contact angle (WCA), while the handsheet with 12.34% (w/w) surface-modified TiO2-MPS had the highest WCA. At 17% (w/w) surfacemodified TiO2-MPS, the WCA rapidly declined. Handsheets with surface-modified TiO2-MPS have a rougher surface compared to the handsheets without chemicals and handsheets with unmodified TiO2. This roughness made the handsheet hydrophobic. The handsheet with 12.34% (w/w) unmodified TiO2 has a smoother surface than the control handsheet. Energy-dispersive X-ray spectroscopy (EDS) analysis shows that the handsheet with 12.34% (w/w) unmodified TiO2 contained titanium, while the handsheet with 12.34% (w/w) surface-modified TiO2-MPS contained both titanium and silicon. Generally, the physical properties of handsheets improved with surface-modified TiO2- MPS, especially grammage, bulk thickness, tensile index, and water absorptiveness, which showed statistically significant differences across treatments. The tear index did not differ between treatments.
Journal articles
Magazine articles
Effects of different soda loss measurement techniques on brownstock quality, TAPPI Journal July 2024
ABSTRACT: The efficiency of the kraft recovery plant, bleaching process, and paper machine are affected when black liquor carryover from the brownstock washers is not controlled well. Measuring soda loss within a mill can vary from using conductivity, either in-situ or with a lab sample of black liquor filtrate squeezed from the last stage washer, to measuring absolute sodium content with a lab sodium specific ion probe or spectrophotometer. While measuring conductivity has value in tracking trends in black liquor losses, it is not an acceptable method in reporting losses in absolute units, typically in lb/ton of pulp. This is further complicated when trying to benchmark soda loss performance across a fleet of mills with multiple washer lines. Not only do the testing methods vary, but the amount of bound soda on high kappa pulps can be significant. This variability creates inconsistent results, and studies are needed to understand the effect of different testing methods on the pulp quality. In this study, soda loss is expressed as sodium sulfate (Na2SO4). Four different methods to measure soda content in pulp off commercial brownstock washers were studied: full digestion (FD), washing soaking overnight and washing (WSW), soaking in boiling water and stirring 10-min (SW-10), and squeeze-no wash (Sq). Total, washable, and bound sodium sulfate calculations were determined for each soda content measuring technique using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results showed bound and washable sodium sulfate amounts significantly depend on which soda measurement technique was used. In addition, the soda results were correlated with the pulp kappa numbers. As the kappa number increases, bound soda increases, regardless of the soda measurement method used. Impacts of high sodium sulfate in brownstock are also discussed.
Journal articles
Magazine articles
Understanding the energy and emission implications of new technologies in a kraft mill: Insights from a CADSIM Plus simulation model, TAPPI Journal June 2024
ABSTRACT: Kraft mills play a vital role in energy transition because they have significant potential to reduce their own energy utilization and produce energy/products to decarbonize other sectors. Through biomass combustion and potential biogenic carbon emissions capture, these mills can contribute to offsetting emissions from other sectors. This research investigates the departmental and cross-departmental implications of technology upgrades on energy, steam, emissions, water, and chemicals using a CADSIM Plus simulation model. The model provides a comprehensive analysis of mass and energy balances, offering valuable insights into the benefits and limitations of each technology. The model facilitates scenario analysis and comparisons of process configurations, enabling data-driven decision-making for sustainable and competitive operations. Six high-impact technologies, including additional evaporator effects, weak black liquor membrane concentration, belt displacement washer for brownstock washing, oxygen delignification, and improvements to the pulp machine shoe press and vacuum pumps, are evaluated. Individual technologies resulted in energy savings of 1.2% to 5.4%, biomass consumption reductions of 8.6% to 31.6%, and total emissions reductions of 1.6% to 5.9%. Strategic decision-making must consider existing mill limitations, future technology implementation, and potential production increases. Future research will explore product diversification, biorefineries, and pathways to achieve carbon-negative operations, aiming to reduce emissions and secure a competitive future for kraft mills.
Journal articles
Magazine articles
Colloid chemical aspects of paper formation in the presence of nanofibrillated cellulose and cationic starch, TAPPI Journal September 2024
ABSTRACT: A series of experimental tests were carried out to examine colloidal-scale consequences of optionally treating nanofibrillated cellulose (NFC) with cationic starches of different charge density and dosage (0.5% or 2.0% by weight), adding that material to a furnish prepared from 100% recycled copy paper, and then subjecting the mixture to very different levels of hydrodynamic shear. Tests included optical microscopy, sediment volume tests, sediment velocity tests, and “percent fines” assessment by means of a fiber quality analyzer (FQA). In addition, the zeta potential and charge demand of the studied materials were evaluated. Optical imaging revealed that cationic starch treatment of the NFC tended to agglomerate it into multiparticle clusters, which sometimes could be mostly redispersed by hydrodynamic shear. Subsequent addition of the starch-treated NFC to the default furnish resulted in much of the colloidal material becoming attached to fibers. Subsequent shearing of the mixtures was at least partly effective in separating the clusters of NFC from the fiber surface, resulting in essentially a two-component mixture. Multiparticle NFC clusters coexisted with the fiber suspension, sometimes attached and sometimes not, depending on the details of treatments. Sediment volume tests showed that systems containing cationic starch-treated NFC tended to have a higher density after settling in comparison to untreated NFC; these findings are consistent with the cationic starch acting as a stabilizer on the solid surfaces, allowing them to slide past each other during the settling process. Application of intense hydrodynamic shear tended to result in denser sediment. Results of tests with the sediment velocity messurement and the FQA percent fines assessment did not correlate well with changes in test conditions considered in this study.
Journal articles
Magazine articles
Stiffness and strength properties of five paperboards and their moisture dependency, TAPPI Journal February 2020
ABSTRACT: Five commercial multiply folding boxboards made on the same paperboard machine have been analyzed. The paperboards were from the same product series but had different grammage (235, 255, 270, 315, 340 g/m2) and different bending stiffness. The paperboards are normally used to make packages, and because the bending stiffness and grammage varies, the performance of the packages will differ. Finite element simulations can be used to predict these differences, but for this to occur, the stiffness and strength properties need to be deter-mined. For efficient determination of the three-dimensional properties in the machine direction (MD), cross direction (CD), and Z direction (ZD), it is proposed that the paperboard should be characterized using in-plane tension, ZD-tension, shear strength profiles, and two-point bending. The proposed setups have been used to determine stiff-ness and strength properties at different relative humidity (20,% 50%, 70%, and 90% RH), and the mechanical proper-ties have been evaluated as a function of moisture ratio.There was a linear relation between mechanical properties and moisture ratio for each paperboard. When the data was normalized with respect to the standard climate (50% RH) and plotted as a function of moisture ratio, it was shown that the normalized mechanical properties for all paperboards coincided along one single line and could therefore be expressed as a linear function of moisture ratio and two constants.Consequently, it is possible to obtain the mechanical properties of a paperboard by knowing the structural properties for the preferred level of RH and the mechanical property for the standard climate (50% RH and 23°C).