Search
Use the search bar or filters below to find any TAPPI product or publication.
Filters
Content Type
Publications
Level of Knowledge
Committees
Collections
Journal articles
Magazine articles
Control of malodorous gases emission from wet-end white water with hydrogen peroxide, TAPPI Journal October 2021
ABSTRACT: White water is highly recycled in the papermaking process so that its quality is easily deteriorated, thus producing lots of malodorous gases that are extremely harmful to human health and the environment. In this paper, the effect of hydrogen peroxide (H2O2) on the control of malodorous gases released from white water was investigated. The results showed that the released amount of total volatile organic compounds (TVOC) decreased gradually with the increase of H2O2 dosage. Specifically, the TVOC emission reached the minimum as the H2O2 dosage was 1.5 mmol/L, and meanwhile, the hydrogen sulfide (H2S) and ammonia (NH3) were almost completely removed. It was also found that pH had little effect on the release of TVOC as H2O2 was added, but it evidently affect-ed the release of H2S and NH3. When the pH value of the white water was changed to 4.0 or 9.0, the emission of TVOC decreased slightly, while both H2S and NH3 were completely removed in both cases. The ferrous ions (Fe2+) and the copper ions (Cu2+) were found to promote the generation of hydroxyl radicals (HOœ) out of H2O2, enhancing its inhibition on the release of malodorous gases from white water. The Fe2+/H2O2 system and Cu2+/H2O2 system exhibited similar efficiency in inhibiting the TVOC releasing, whereas the Cu2+/H2O2 system showed better perfor-mance in removing H2S and NH3.
Journal articles
Magazine articles
Sulfur makeup in an unbleached kraft pulp mill, TAPPI Journal August 2024
ABSTRACT: Sodium sesquisulfate or “sesqui” (Na3H(SO4)2) is a by-product of chlorine dioxide production at kraft pulp mills. It is typically used for sodium and sulfur makeup in the liquor loop. Mondi Hinton Inc. (MHI) in Hinton, AB, Canada, was converting from bleached to unbleached kraft pulp production and was thus losing this source of makeup. The only option that was readily available as a substitute was sodium hydrosulfide (NaHS), which was cost prohibitive. Other options such as sodium sulfate (Na2SO4), emulsified sulfur, sulfuric acid (H2SO4), and sodium bisulfite (NaHSO3) were compared. The mill concluded that pelletized sulfur plus sodium hydroxide or “caustic soda” (NaOH) was the best option. Laboratory-scale experiments showed that pelletized sulfur dissolved in white liquor (WL). A mill-scale trial revealed that pelletized sulfur added to a causticizer had no adverse impacts on the downstream pressure filters or kiln operation. The sulfur reacted to produce polysulfide upstream of the WL storage tank, giving the liquor an orange hue. This polysulfide appeared to partially degrade into thiosulfate before being fed to the digester. The heavy black liquor (HBL) sulfur:sodium (S:Na) ratio did not change significantly, even though the sulfur/soda addition location was upstream of the original one. In addition, other properties such as liquor heating value and elemental analysis did not significantly change. Due to polysulfide/thiosulfate concentration in the white liquor, it was determined that the carbon steel equipment was at risk for corrosion. During the annual turnaround that occurred eight months after the addition of sulfur was started, the wash zone of the digester showed no signs of thinning/damage. The mill has been running exclusively with pelletized sulfur for 22 months (as of August 2024), realizing significant cost savings compared to the use of NaHS or other sulfur/soda addition options.
Journal articles
Magazine articles
The role of hornification in the deterioration mechanism of physical properties of unrefined eucalyptus fibers during paper recycling, TAPPI Journal February 2024
ABSTRACT: Physical properties of cellulosic paper deteriorate significantly during paper recycling, which hinders the sustainable development of the paper industry. This work investigates the property deterioration mechanism and the role of hornification in the recycling process of unrefined eucalyptus fibers. The results showed that during the recycling process, the hornification gradually deepened, the fiber width gradually decreased, and the physical properties of the paper also gradually decreased. After five cycles of reuse, the relative bonding area decreased by 17.6%, while the relative bonding force decreased by 1.8%. Further results indicated that the physical property deterioration of the paper was closely related to the decrease of fiber bonding area. The fiber bonding area decreased linearly with the reduction of re-swollen fiber width during paper recycling. Re-swollen fiber width was closely related to the hornification. Hornification mainly reduces the bonding area of unrefined eucalyptus fiber rather than the bonding force. The work elucidates the role of hornification in the recycling process of unrefined eucalyptus fibers and the deterioration mechanism of paper physical properties, which will be helpful to control the property deterioration of paper and achieve a longer life cycle.
Journal articles
ABSTRACT: Water hardness, which can be defined as the concentration of calcium and magnesium ions, is known to vary greatly depending on geographical locations. Laboratory tests were carried out to evaluate effects of large differences in water hardness o
ABSTRACT: Water hardness, which can be defined as the concentration of calcium and magnesium ions, is known to vary greatly depending on geographical locations. Laboratory tests were carried out to evaluate effects of large differences in water hardness on the performance of certain wet-end additives to the paper machine process. Tests were carried out at hardness levels of 25, 125, and 225 ppm (as calcium carbonate equivalents). Increased water hardness was found to have a generally negative effect on the performance of a cationic acrylamide- type retention aid, although the extent of performance loss depended on experimental details. Likewise, rates of dewatering in systems containing cationic retention aid were adversely affected by increasing hardness, though the effects were not statistically significant in all cases considered. The tendency of bridge-forming flocculants (cationic retention aid or sequential addition of a cationic additive and then anionic retention aid) fell slightly with increasing water hardness.
Journal articles
Optimizing Water and water vapor barrier properties of water-based barrier coatings
Functional coatings are applied to paper and paperboard substrates to provide resistance, or a barrier, against media such as oil and grease (oil and grease resistance; OGR), water, water vapor (moisture vapor transmission rate; MVTR), and oxygen, for applications such as food packaging, food service, and other non-food packaging. Typical functional barrier coatings can be created by applying a solid coating or extruded film, a solvent-based coating, or a water-based coating to the paper substrate using various means of coating applicators. Today, there is increasing interest in developing recyclable and more sustainable approaches to producing these types of packages. This paper focuses on water-based barrier coatings (WBBC) for water resistance and MVTR for medium barrier performance. The main goal was to improve the performance of existing barrier polymers using additives such as waxes. Barrier coated systems were evaluated in single layer laboratory coating studies. This paper reviews examples of improving the performance of barrier polymers studied, including styrene butadiene and styrene acrylate, using wax additives. Regulatory challenges with paraffin waxes have resulted in the focus on bio-waxes. The results showed that small amounts of bio-wax can significantly improve barrier properties, especially for water resistance and MVTR. The choice of the best combination of binder and wax is essential. The influence of the bio-wax additive on blocking tendency, coldset glue strength, or heat seal strength is negligible.
Journal articles
Magazine articles
Modeling the dynamics of evaporator wash cycles, TAPPI Journal July 2024
ABSTRACT: Kraft pulping is a process that utilizes white liquor, composed of sodium sulfide (Na2S) and sodium hydroxide (NaOH), for wood delignification and pulp production. This process involves washing the dissolved organics and spent chemicals from the pulp, resulting in the generation of black liquor. Prior to its use as fuel in the recovery boiler, the black liquor is concentrated in multiple-effect evaporators. During the evaporation process, the inorganic salts present in the liquor become supersaturated and undergo crystallization. Fluctuations in sodium, carbonate, sulfate, and oxalate can give rise to severe sodium salt scaling events, which significantly impact the thermal efficiency of the evaporators, and ultimately, pulp production. Dynamic modeling provides insights into fluctuations in liquor chemistry in the evaporators. The primary objective of this study was to employ dynamic modeling to evaluate the effects of wash liquor recovery from evaporator wash cycles. The dynamics associated with wash cycles encompass variations in the concentrations of salts and solids in the recovered wash liquor, changes in the flow rate of wash liquor recovery, and fluctuations in liquor volume within the liquor tanks. The dynamic model was developed using Matlab Simulink and applied to the evaporation plant of a pulp mill in South America. By utilizing one month of mill process data, the model enabled the evaluation of fluctuations in liquor chemistry due to evaporator wash cycles. The developed model has demonstrated the potential to estimate the concentration of key ions responsible for scaling and to contribute to enhancements in evaporator washing strategies.
Journal articles
Magazine articles
Online monitoring of the size distribution of lime nodules in a full-scale operated lime kiln using an in-situ laser triangulation camera, TAPPI Journal June 2024
ABSTRACT: To maximize efficiency of the recausticizing process in a pulp mill, producing a reburned lime with high and consistent reactivity is process critical. Prior investigations have demonstrated a correlation between the reactivity of lime and its nodule size, as well as the dusting behavior of the kiln. Therefore, monitoring the nodule size produced in the lime kiln could be a promising indirect method to measure the performance of the lime kiln. The objective of this investigation was to evaluate the utility of a laser triangulation camera for online monitoring of nodule size distribution for the lime kiln. A series of full-scale trials were performed in a lime kiln of a kraft pulp mill in which a camera was installed at the exit conveyor to analyze the lime discharging from the kiln. The nodule size distribution was analyzed for correlation with the lime temperature, flue gas temperature, and rotational speed of the kiln. The monitoring demonstrated temporal stability, and the results showed that the lime temperature had the most significant effect on the nodule size. The rotational speed of the lime kiln and the flue gas temperature showed limited effect on nodule size, but they had significant impact on the specific energy demand. The overall conclusion of the study is that the camera methodology effectively correlates lime temperature with nodule size distribution, and it advocates for the methods of implementation in automating lime temperature control, facilitating the production of consistently reactive lime at a lower specific energy consumption.
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
Determining operating variables that impact internal fiber bonding using Wedge statistical analysis
ABSTRACT: In this study, Wedge statistical analysis tools were used to collect, collate, clean up, plot, and analyze several years of operational data from a commercial paper machine. The z-direction tensile (ZDT) and Scott Bond tests were chosen as representative of fiber bond strength. After analyzing thousands of operational parameters, the ones with the most significant impact upon ZDT involved starch application method, starch penetration, and the amount of starch applied. Scott bond was found to be significantly impacted by formation and refining. Final calendering of the paper web has also shown an impact on internal fiber bonding.
Journal articles
Magazine articles
A novel predictive method for filler coflocculation with cellulose microfibrils, TAPPI Journal November 2019
ABSTRACT: Different strategies aimed at reducing the negative impact of fillers on paper strength have been the objective of many studies during the past few decades. Some new strategies have even been patented or commercialized, yet a complete study on the behavior of the filler flocs and their effect on retention, drainage, and formation has not been found in literature. This type of research on fillers is often limited by difficulties in simulating high levels of shear at laboratory scale similar to those at mill scale. To address this challenge, a combination of techniques was used to compare preflocculation (i.e., filler is flocculated before addition to the pulp) with coflocculation strategies (i.e., filler is mixed with a binder and flocculated before addition to the pulp). The effect on filler and fiber flocs size was studied in a pilot flow loop using focal beam reflectance measurement (FBRM) and image analysis. Flocs obtained with cationic polyacrylamide (CPAM) and benonite were shown to have similar shear resistance with both strategies, whereas cationic starch (CS) was clearly more advantageous when coflocculation strategy was used. The effect of flocculation strategy on drainage rate, STFI formation, ash retention, and standard strength properties was measured. Coflocculation of filler with CPAM plus bentonite or CS showed promising results and produced sheets with high strength but had a negative impact on wire dewatering, opening a door for further optimization.