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Journal articles
Physico-mechanical and ethylene scavenging properties of active packaging from Bambusa fibers modified with TiO2 /Cu2O composite, TAPPI Journal February 2026
ABSTRACT: The physico-mechanical and ethylene scavenging properties of active packaging consisting of paper prepared from bamboo (Bambusa vulgaris) fibers loaded with varying concentrations of nano titanium dioxide/cuprous oxide (TiO2/Cu2O) composite was investigated for its ability to delay ripening of Philippine climacteric fruits. Tests of paper containing 1% to 5% TiO2/Cu2O showed no or limited negative impact on its physical, optical, and mechanical properties. Images from a field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy (FESEM-EDS) showed dispersion and agglomeration of TiO2/Cu2O nanoparticles on the paper surface. The percent weight of titanium and copper increased with increasing metal oxide composite concentration used in this study. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy indicated small shifts in band intensity at 3330 cm-1 and 1100 cm-1 in the hydroxyl (O-H) and C-O regions, respectively, suggesting possible chemical or physical interactions between the metal oxide and paper. Contact angle measurement suggest- ed that TiO2/Cu2O nanoparticles may have imparted paper hydrophobicity at 3% & 5% concentration, possibly through increased microscale roughness. The ethylene scavenging experiment indicated that there was a significant delay in the ripening process of mango and tomato when packed in paper doped with 3% and 5% TiO2/Cu2O. The fruits were greener with a firmer texture compared with untreated control after three days of storage under natural light and ambient condition. The preliminary results suggested that 3% &5% TiO2/Cu2O active packaging modification can remove ethylene from the fruit's storage environment, extending shelf life and maintain quality for three days. This simple technique could have potential economic benefits for the fruit industry by directly reducing post-harvest waste, and the delayed ripening could provide flexibility in supply chain management.
Journal articles
Black liquor spray properties in-furnace conditions for swirl cone nozzles, TAPPI Journal July 2026
ABSTRACT: Recovery boiler furnace operation is controlled for high chemical recovery, high steam production, and low emissions. Good control allows long runs with minimum cleaning without expensive shutdowns. An essential variable affecting boiler operation is black liquor spraying into the furnace. Poorly controlled black liquor spraying causes difficulties, e.g., in chemical recovery, fouling of heat transfer surfaces, and decreased energy production. A challenging measurement strategy with three different swirl cone nozzles . types A, C, and T . was carried out at a mill in the United States. Black liquor spray properties were measured under in-furnace conditions for flow rates of 2.0 L/s to 3.0 L/s. Three spraying temperatures of 119™‹C, 122™‹C, and 126™‹C, which were 2™‹C, 5™‹C, and 9™‹C above the boiling point (ƒ¢Te), were tested. These flow rates and temperatures are typical for industrial nozzle sizes with exit orifice sizes of 17 mm and 22 mm. An imaging method to measure droplet size in a highly challenging furnace environment was developed. Droplet volume median diameter (Dv50) for nozzles A, C, and T varied between 7 mm to 4 mm, 7 mm to 5 mm, and 8 mm to 6 mm, depending on the flow rate and temperature. The high number of droplets detected by the analysis program enabled data fitting into statistical correlations. The size and width parameters for the Rosin™]Rammer droplet size distribution function could be defined. The droplet size distribution was found to be surprisingly wide, probably because of swollen droplets. Spray velocity was measured in two locations, 5 cm from the nozzle and 1.8 m from the nozzle. Near the nozzle, the average velocity increased from 7.3 m/s to 13 m/s when the flow rate was increased from 2 L/s to 3 L/s. Increase of black liquor temperature increased spray velocity in most of the cases. At the distance of 1.8 m from the nozzle, average spray velocities varied between 4.0 m/s to 11 m/s, depending on nozzle geometry, flow rate, and temperature. The opening angles of the spray for nozzles A and C varied between 57™‹ to 78™‹. The opening angle of nozzle T with flow guide varied between 48™‹ to 56™‹. The highest penetration of the spray was estimated for nozzle T because of the narrow spray and large droplets.
Journal articles
Magazine articles
Pilot scale black liquor concentration using pressure driven membrane separation, TAPPI Journal April 2023
ABSTRACT: Black liquor concentration using pressure driven membrane separation has long been proposed as a means of achieving energy savings and breaking production bottlenecks. To date, limitations in membrane performance and stability under black liquor process conditions have prevented those promises from being realized out-side of tightly controlled laboratory settings. In this work, we describe the first successful pilot scale field deployments of a membrane system for black liquor concentration. Using a purpose-built system and commercial sized, spiral wound graphene oxide membrane elements, we have logged nearly 6000 h of runtime across deployments to multiple mill sites. We demonstrate concentration of black liquor from 14% to >20% total solids, while generating permeate water comparable in quality to that of evaporator condensate and an 81% reduction in energy consumption relative to evaporation. At a commercial scale, these results translate to $2 M/year in net energy savings for a typical mill, as well as an opportunity to support production increases or mill expansions. These results represent a significant leap forward in the ability of membrane systems to deliver substantial value via black liquor concentration.
Journal articles
Magazine articles
Evaluation of soap recovery efficiency from black liquor — analytical tools, TAPPI Journal April 2023
ABSTRACT: Soap skimmings (“soap”) are typically recovered from black liquor in kraft mills that process a high percentage of softwood. In many mills, the recovery of soap is inefficient, negatively impacting performance of evaporators and recovery boilers and resulting in loss of potential revenue. A thorough evaluation of soap recovery performance in a kraft mill requires measurement of soap content in black liquor at various sampling locations, especially around the soap skimmer.The standard laboratory method for evaluating soap content in black liquor is a complex, multi-step process that relies on solvent extraction and titration; most mills send these samples to an outside laboratory for this analysis. In this study, 100 black liquor samples, with a wide range of soap concentrations, were tested by the standard solvent extraction method. After additional dilution, each sample was also tested for surface tension with a bubble pressure tensiometer. The results were found to correlate very closely with the solvent extraction tests results. This alternate method, using surface tension measurements of diluted black liquor samples, produces rapid results and can be easily implemented in most kraft mills, which would facilitate much more frequent in-house evaluations of soap recovery performance.
Journal articles
Magazine articles
Advantages of lean duplex stainless steels in the pulp and paper industry, TAPPI Journal April 2023
ABSTRACT: The performance of lean duplex stainless steels has been utilized by the pulp and paper industry since their introduction to the market almost 20 years ago. Experience has shown that this group of stainless steels has exceptional performance in, for example, alkaline environments towards typical deterioration mechanisms, i.e., uniform corrosion and stress corrosion cracking. The chemistry of the “lean” duplex steels is designed so that the content of volatile and expensive elements like nickel and molybdenum can be reduced to an absolute minimum without sacrificing the technical performance. This reduces the raw material cost and most importantly provides predictability of the steel price, which is often challenging with conventional austenitic and duplex stainless steels.Thanks to a dual phase microstructure and high nitrogen content, lean duplex steels have at least two times higher strength compared to standard austenitic stainless steels. This is often a preferred feature in pulp and paper construction, as it enables lighter structures and less material to be utilized. Today, lean duplex steels are widely available in various dimensions, from thin cold rolled sheets up to thick hot rolled plates. Lean duplex steels are also fully recyclable after the decommissioning stage of the equipment, thereby contributing to the circular economy.
Journal articles
Magazine articles
Energy saving potential of interstage screen fractionation for production of board grade BCTMP, TAPPI Journal August 2023
ABSTRACT: Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.
Journal articles
Exploratory study on how sub-ply fiber orientation affects t
ABSTRACT: The transition to 100% biobased packaging presents considerable challenges, particularly in the development of a petroleum-free barrier. Generally, biobased barriers exhibit lower flexibility compared to traditional barriers, thereby increasing the risk of cracking during the converting process. The present study examines the possibility of optimizing the substrate to reduce cracking in brittle barriers. Five three-ply composites were fabricated using commercial paperboard to enable a composite with different fiber orientation in the individual plies. The different orientations achieved varying mechanical properties, including strain-atbreak and folding resistance, with a ranking that is comparable to a standard multi-ply paperboard. The composites were subjected to creasing at five distinct depths to assess the area percent of barrier cracks across the crease bead. Micro-cracks appeared on the surface before larger coating cracks were registered. As expected, the area percent of barrier cracks increased significantly with greater creasing depths. The orientation of the bulky middle ply showed little difference in the cracking propensity. However, by replacing the stiffer bottom ply with a ply of lower stiffness, the cracking propensity was significantly reduced without a substantial loss in mechanical properties. Hence, these findings indicate that it is possible to reduce the cracks in the barrier by modifying the fiber orientation in the different plies.
Journal articles
Improving barrier performance of coated paper and paperboard
ABSTRACT: Market demand for barrier coated packaging paper and paperboard has been on a steady rise and is forecasted to further increase. As a result, there is a continued interest in improving barrier coating functionalities, which is currently an active area of investigation. In this work, a multi-layer approach was adopted that involved applying a biowax emulsion, latex, or a combination of biowax and latex top coating layer onto the kaolin/latex (20/80, 50/50, 65/35, or 70/30) precoated solid bleached sulfate (SBS) paperboard. Our main objective was to demonstrate the effect of these top coating layers on various barrier properties, especially water vapor transmission rate (WVTR) at high relative humidity (RH) and high temperature (90% RH; 38°C), known as tropical/jungle test conditions. While the top coat with latex and/or biowax showed dramatic improvement in both water resistance (Cobb) and WVTR, the biowax coating increased contact angle significantly compared to the latex top coat. Contact angle increased from about 65° for the latex top coat to as high as 96° for the biowax top coat. Generally, it is much more difficult to improve WVTR at the jungle conditions below 100 g/m2/day, even with the high aspect ratio platy pigment. However, using the coating strategies adopted in this study, we were able to achieve WVTR values notably below 50 g/m2/day at the tropical test conditions, as well as significant improvements in regard to fold crack barrier integrity at high kaolin clay usage.
Journal articles
Prediction of residual calcium carbonate (CaCO3) in the lime
ABSTRACT: In a kraft pulp mill, the rotary lime kiln is responsible for converting calcium carbonate (CaCO3) into calcium oxide (CaO) to be reused in the causticizing plant. An important parameter of the calcination efficiency and the product quality is the amount of CaCO3 not converted to CaO, commonly defined as residual carbonate. This parameter is usually determined through laboratory analysis, which introduces delays in process control and limits the ability to make timely operational adjustments. This work presents a predictive model that functions as a soft sensor for the residual carbonate in a lime kiln of a Brazilian kraft pulp mill. This model was able to estimate residual CaCO3 every 30 min using routinely measured online process variables, which is a considerable reduction from the 6-h average laboratory measurement. The correlation coefficient (r) between the model predictions and the mill values was 0.83, with a mean absolute error (MAE) of 0.33%. Considering the effect of the residence time throughout the lime kiln proved to be decisive in obtaining a satisfactory prediction result. After model validation, a variable importance analysis showed that the carbon monoxide (CO) concentration in the stack flue gas (in ppm), secondary air temperature (in oC), and fan speed (in %) were the most influential variables in predicting the residual carbonate content. Combined with commonly used operation expertise, this subset of variables can serve as additional information to achieve smoother lime kiln operation.
Journal articles
Magazine articles
Value creation by converting pulp mill flue gas streams to green fuels, TAPPI Journal March 2023
ABSTRACT: Climate change mitigation induces strong growth in renewable electricity production, partly driven by shifts in environmental policies and regulation. Intermittent renewable electricity requires supporting systems in the form of sustainable hydrocarbon chemicals such as transportation fuels. Bulk chemical production fits well into a pulp mill environment, given their large volumes, stable operation, and ample supply of biomass-based carbon feed-stock in the form of flue gases. Until now, the utilization of the flue gases from conventional operation of a pulp mill has received little attention. Harnessing these flue gases into usable products could offer additional value to mill operators, while also diversifying their product portfolio. However, electricity-based fuels and products require extra energy in the conversion step and may not be commercially competitive with current fossil products under the current regulation. There might also be uncertainties about future commodity prices. Thus, the objective of this study is to estimate the economic competitiveness and the added value of selected side products that could be produced alongside conventional pulp and paper products. A typical modern pulp mill is modeled in different product configurations and operational environments, which allows testing of various development paths. This illustrates how the overall energy and mass balance of a pulp mill would react to changes in different final products and other parameters. The focus of the study is in synthetic methanol, which is produced from flue gases and excess resources from the mill, with minimal interference to the pulping process. The results aid in assessing the necessity and magnitude of a premium payment for subsidizing green alter-natives to replace current fossil fuels and chemicals. Additionally, the results function as an indicator of the development state of the pulp and paper industry in the turmoil of climate change regulation. The results indicate that power-to-X systems offer one more viable pathway alternative for broadening the product portfolio of the pulp and paper sector, as well as opening new flexibility measures and services to grid stabilization. Market conditions were found to have a significant impact on the perceived profitability.