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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
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Continuous digester rapid thinning, TAPPI Journal June 2024
ABSTRACT: Carbon steel continuous digesters built after the early 1980s are fully stress relieved, so stress corrosion cracking has been less of a concern. However, these newer digesters were designed to run modified cooking processes that have turned out to be much more corrosive than those running with conventional cooking. This corrosion is mainly associated with softwood digesters and appears to be flow related. Average corrosion rates of 40 mil/year are possible on the exposed shell between the wash and extraction screens. The corrosion patterns are visually distinct from surfaces in the upper digester and below the wash screens. This paper goes into practical detail on where it occurs, the causes, visual identification, inspection planning and results evaluation, and finally, how to mitigate this damage, which consists of applying a corrosion resistant barrier. Some discussion on dealing with general corrosion throughout the digester is included.
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.
Editorial: The innovation engine and the forest products industry value chain, TAPPI Journal October 2023
ABSTRACT: The forest products industry (FPI • pulp, paper, paperboard, building products, allied products, and byproducts) has been continuously innovating as it manufactures and delivers value-added products to consumers worldwide. Integrated pulp and paper mills produce pulp, paper, paperboard, and byproducts like turpentine, tall oil, methanol, lignin, and other chemicals.
Pulp and paper mills: The original biorefineries — past performance and limitations to future opportunities, TAPPI Journal October 2023
ABSTRACT: Pulp mills have been biorefineries since the invention of the Tomlinson recovery boiler. Unfortunately, the paper industry has done a poor job explaining that concept to the general public. A number of bioproducts in everyday use have been produced by pulp mills for several decades, and new products are routinely being developed. Modern research efforts over the last couple of decades have focused on producing even more products from pulp and paper mills through capacity enhancement and the development of value-added products and liquid transportation fuels to enhance paper mill profitability. Some of these efforts, often referred to as modern biorefineries, have focused so heavily on product development that they have ignored operating and process realities that limit the transformation of pulp and paper mills from the current limited number of bioproducts produced today to economic scale production of these value-added products. In this paper, several of these limitations are addressed. In addition, there are several supply chain, marketing, product quality, and economic realities limiting the value potential for these wholesale conversions of pulp mills into multiproduct modern biorefineries. Finally, the conservative nature and capital intensity of the pulp and paper industries provide a difficult hurdle for conversion to the modern biorefinery concept. These issues are also reviewed.
Rice straw-based sustainable food packaging material with improved strength and barrier properties: Development and characterization, TAPPI Journal October 2023
ABSTRACT: Sustainable food packaging paper with high barrier and strength properties was developed with rice straw nanocellulose materials. Pulping and bleaching of rice straw were performed using an organosolv pulping and DED (D: chlorine dioxide bleaching; E: sodium hydroxide extraction) bleaching sequence. Bleached rice straw pulp was refined to 90°SR using a laboratory Valley beater. The laboratory handsheets were prepared using pulp slurry at 40°SR and 90°SR. The handsheets of cellulose nanofibrils (CNFs) made of highly refined pulp (90°SR) were surface sized using alkyl ketene dimer (AKD) wax to increase the barrier properties of paper for selective food packaging applications. The paper samples were tested for mechanical, optical, surface, and barrier properties, including tensile index, burst index, tearing index, bending stiffness, elongation, porosity, apparent density, opacity, Cobb value, water vapor transmission rate (WVTR), oil and grease resistance, and contact angle. The refined pulp (90°SR) was analyzed using field-emission scanning electron microscopy (FE-SEM), and it was observed that the morphology of the developed fibers changes to the nanoscale (<100 nm) for at least one dimension. The particle size distribution of the refined pulp using DLS analyzer also confirmed the cellulose fibers to near nanoscale. It was concluded that nanofibers were formed by a high degree of the mechanical pulp refining process and found to be much more economical than alternative processes in this direction. The sample handsheets of CNFs showed good strength and barrier properties. The barrier properties further increased when surface sizing was done using low-cost, nontoxic, and biodegradable AKD wax.
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) — Fibrous substrates, TAPPI Journal September 2023
ABSTRACT: Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been implemented during the finishing process of textiles such as upholstery, clothing, personal protective equipment, and sports gear to provide water resistance. Currently, PFAS are still present at quantifiable levels in consumer products and food, even though many companies have started to phase out PFAS treatment with non-toxic water repellant replacements given the possible detrimental health effects suggested by current research. This paper is a detailed review that focuses on how PFAS are implemented in textile production and sources of PFAS contamination during chemical treatments. This review also addresses current legislation on PFAS emissions and trade regulations to decrease exposure of consumers due to toxicokinetics and mechanisms of action through-out the body that are still not well understood. This paper includes a literature review on possible PFAS related health conditions shown from past research and contains suggested toxicity levels, exposure routes, duration, and pathways detailed to the best of our ability.
Filtration efficiency and breathability of selected face masks, TAPPI Journal September 2023
ABSTRACT: Face masks have been used as physical barriers to stop respiratory infections for many years. Due to insufficient and low supply of certified masks, alternative face covers such as face shields, neck gaiters, and fabric reusable masks gained attention during the COVID-19 pandemic. However, for these alternate face masks to fulfill their intended function, they must be effective. Additionally, the level of breathability provided by the makeshift masks must be at a certain level. The work reported in this paper was carried out to determine the relationship between filtration efficiency (FE), breathability, and important physical characteristics of mask substrates. The fiber diameter of the core filter layer was determined using a scanning electron microscope. Five types of face masks (two types of N95, two types of surgical masks, and a 100% knitted cotton fabric) were tested for their FE and breathability using moisture vapor transmission rate (MVTR). The cotton knitted mask had the lowest FE (5.10%•26.47%), while the National Institute for Occupational Safety and Health (NIOSH)-certified N95 mask had the highest FE values (92.10%•99.65%). However, the cotton mask outperformed the N95 in terms of the pressure drop, meaning higher comfort. In general, the N95 face mask provided the best protection against aerosolized particles. According to the regression analysis, the fiber diameter of the mask filter substrate serves as an important predictor of FE of mask substrates. In this study, it was confirmed that fiber diameter is inversely related to the filtration ability. Results show that compact structure with finer fibers will enable higher filtration efficiency. The study lends itself to developing layered face masks to obtain optimum filters with good filtration, better fit, and acceptable comfort for the wearer.
Cross-flow separation characteristics and piloting of graphene oxide nanofiltration membrane sheets and tubes for kraft black liquor concentration, TAPPI Journal September 2023
ABSTRACT: Dewatering of weak black liquor (WBL) in the kraft cycle by evaporation is highly energy intensive. Membranes are an attractive alternative for energy-efficient dewatering, but existing commercial polymeric or ceramic membranes are either degraded in BL or have high capital costs. Our recent works have demonstrated the engineering of graphene oxide (GO) nanofiltration membranes, their stability and promising performance in BL conditions, and preliminary scale-up into sheets and tubes. Here, we describe in detail the separation characteristics of GO membrane sheets and tubes under real BL conditions and crossflow operation. Recycle-mode piloting of a GO tubular membrane showed average “production flux” of 16 L/m2/h (LMH) and high rejections of lignin (98.3%), total solids (66%), and total organic carbon (83%), with no signs of irreversible fouling identified. A corresponding GO sheet membrane produced an average flux of ~25 LMH and maintained high lignin rejection of ~97% during a slipstream pilot at a kraft mill site using WBL with ~16 wt% total solids (TS). Finally, we piloted a Dow/DuPont XUS1808 polyamide composite reverse osmosis (RO) membrane for last-mile processing of the GO nanofiltration membrane permeate. The RO membrane showed a steady state flux of 19 LMH at 65 bar and produced ~0.02 wt% TS water product, which is highly suitable for reuse in pulp washing operations in the kraft process. The results have strong positive implications for the industrial application of GO membranes in BL concentration and other related applications.
Editorial: PEERS and IBBC: TAPPI fall conferences address current and evolving challenges, TAPPI Journal August 2023
On November 5-8, TAPPI will host its 2023 Pulping, Engineering, Environmental, Recycling and Sustainability (PEERS) Conference. This year’s conference will be held in Atlanta and is co-located with TAPPI’s International Bioenergy & Bioproducts Conference (IBBC). Below are some highlights about what is in store for attendees.