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Experiments and visualization of sprays from beer can and turbo liquor nozzles, TAPPI Journal February 2022
ABSTRACT: Industrial scale swirl-type black liquor nozzles were studied using water as the test fluid. Simple water spraying experiments were found to be very beneficial for studying and comparing nozzles for black liquor spraying. These kinds of experiments are important for finding better nozzle designs. Three nozzle designs were investigated to understand the functional differences between these nozzles. The pressure loss of nozzle 1 (“tangential swirl”) and nozzle 3 (“turbo”) were 97% and 38% higher compared to nozzle 2 (“tan-gential swirl”). Spray opening angles were 75°, 60°, and 35° for nozzles 1, 2, and 3, respectively. Video imaging showed that the nozzles produced sprays that were inclined a few degrees from the nozzle centerline. Spray patter-nation showed all the sprays to be asymmetric, while nozzle 2 was the most symmetric. Laser-Doppler measure-ments showed large differences in spray velocities between nozzles. The spray velocity for nozzle 1 increased from 9 m/s to 15 m/s when the flow rate was increased from 1.5 L/s to 2.5 L/s. The resulting velocity increase for nozzle 2 was from 7 m/s to 11 m/s, and for nozzle 3, it was from 8 m/s to 13 m/s. Tangential flow (swirl) directed the spray 6°–12° away from the vertical plane. Liquid sheet breakup mechanisms and lengths were estimated by analyzing high speed video images. The liquid sheet breakup mechanism for nozzle 1 was estimated to be wave formation, and the sheet length was estimated to be about 10 cm. Sheet breakup mechanisms for nozzle 2 were wave formation and sheet perforation, and the sheet length was about 20 cm. Nozzle 3 was not supposed to form a liquid sheet. Nozzle geometry was found to greatly affect spray characteristics.
Journal articles
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Displacement washing of softwood pulp cooked to various levels of residual lignin content, TAPPI Journal September 2021
ABSTRACT: This study investigates the influence of the degree of delignification of kraft spruce pulp cooked at seven different kappa numbers, ranging from 18.1 to 50.1, on the efficiency of displacement washing under laboratory conditions. Although the pulp bed is a polydispersive and heterogeneous system, the correlation dependence of the wash yield and bed efficiency on the Péclet number and the kappa number of the pulp showed that washing efficiency increased not only with an increasing Péclet number, but also with an increasing kappa number. The linear dependence between the mean residence time of the solute lignin in the bed and the space time, which reflects the residence time of the wash liquid in the pulp bed, was found for all levels of the kappa number. Washing also reduced the kappa number and the residual lignin content in the pulp fibers.
Journal articles
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A hundred years of corrosion in the pulp and paper industry, TAPPI JOURNAL May 2018
A hundred years of corrosion in the pulp and paper industry, TAPPI JOURNAL May 2018
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Laboratory method for determining the source of brightness loss at a southern United States bleached paperboard mill, TAPPI Journal October 2018
Laboratory method for determining the source of brightness loss at a southern United States bleached paperboard mill, TAPPI Journal October 2018
Journal articles
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Comprehensive fault detection and isolation method applied t
Comprehensive fault detection and isolation method applied to a recovery boiler, TAPPI JOURNAL May 2016
Journal articles
Magazine articles
Fundamental molecular characterization and comparison of the O, D0, and E stage effluents from hardwood pulp bleaching, TAPPI Journal 2019
ABSTRACT: The present study characterized effluents from the O, D0, and E stages using nuclear magnetic reso-nance (NMR) and gel permeation chromatography (GPC) techniques to better understand the chemical nature of the dissolved organics formed from the bleaching of a high-yield hardwood kraft pulp. Understanding the structures and molecular weight distribution of these organics is the first step in developing methods to mitigate these contam-inates in the discharged effluents. The results indicated that the molecular weight distribution (MWD) of the dis-solved organics from oxygen delignification effluent is broader than those from D0 and E stage effluents. In addition, the O stage filtrate contained considerable amounts of lignin and xylan fragments, which showed its efficiency in removing such materials. The effluent from the D0 stage contained a lower amount of high molecular weight frag-ments and a higher amount of low molecular weight fragments versus the O-stage filtrate. Aromatic structures were nearly absent in the D0 stage filtrate, but the degraded organic material, presumably from oxidized lignin, contained olefinic (C=C) and carbonyl (C=O) functional groups. Furthermore, higher molecular weight fragments were detected in the E-stage effluent, presumably due to the extensive solubilization and removal of the oxidized lignin generated from the D0 pulp.
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
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Kraft pulp viscosity as a predictor of paper strength: Its uses and abuses, TAPPI Journal October 2023
ABSTRACT: For bleached kraft pulps, two factors govern paper strength: the individual fiber strength, and the bond strength that adheres the individual fibers together in the paper matrix. Inherent fiber strength is related to the length of the carbohydrate polymers, also known as the degree of polymerization (DP). Average DP (DP) is inferred by performing pulp viscosity measurements. Under certain circumstances during kraft pulping and bleaching, the average polymer lengths can be shortened, resulting in lower pulp viscosity, and may indicate fiber damage. Fiber damage typically manifests itself as a reduction in tear strength for well-bonded handsheets.This paper will review the literature on how pulp viscosity can predict paper/fiber strength and how it can be used as a diagnostic tool. It can be a means to monitor pulp quality during pulping and bleaching, as well as to alert when such operations approach a critical threshold. However, viscosity losses must be carefully and judiciously analyzed. Like most diagnostic tools, viscosity measurements can be misused and abused, which can lead to incorrect inferences about intrinsic fiber strength. This review will also cover these misuses. The overall goal is to provide the papermaker a better understanding of what pulp viscosity is, how it correlates to potential sheet strength, and what its limitations are. It will be illustrated that when pulp viscosity drops below a critical value, it will indicate an appreciable deterioration in the paper’s tear and tensile strength.
Journal articles
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Biofuels in lime kilns • Operating experience in the Nordic pulp and paper industry, TAPPI Journal October 2024
ABSTRACT: The lime reburning process is a central part of the chemical pulp mill. It is energy intensive and consumes large amounts of fossil fuel, globally consuming about 50 terawatt-hours (TWh) of fuel per year. Conversion to operation with biofuel is interesting, both to reduce carbon dioxide emissions and to reduce costs. Researchers interviewed managers in mills that use solid, liquid, or gasified biofuels to replace fuel oil or natural gas in their lime kilns, and they conducted surveys related to fuel consumption and operations and maintenance. In Sweden and Finland, there were ten mills in 2020 using biomass powder or gasified biomass as the primary fuel, and two more installations were under construction. There were also nine installations in operation or under construction outside the Nordic countries. Fourteen mills in Sweden and two mills in Finland used tall oil pitch as the main fuel. Fuel consumption in Swedish lime kilns was 3.8 TWh in 2020, and 90% of this energy was supplied with biofuels. Of about 4.2 TWh used in Finnish lime kilns, approximately 45% was supplied with biofuels. Developments in the design of the fuel supply system include belt dryers being used in all new installations and mass flow metered dosing systems being used in most new pulverized fuel installations. Bark gasifiers have increased considerably in size. Lignin powder firing has been established as a proven option. A solution for many Swedish and Finnish mills is the use of tall oil pitch as a replacement for fuel oil.
Journal articles
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Rethinking the paper cup — beginning with extrusion process optimization for compostability and recyclability, TAPPI Journal June 2021
ABSTRACT: More than 50 billion disposable paper cups used for cold and hot beverages are sold within the United States each year. Most of the cups are coated with a thin layer of plastic — low density polyethylene (LDPE) — to prevent leaking and staining. While the paper in these cups is both recyclable and compostable, the LDPE coat-ing is neither. In recycling a paper cup, the paper is separated from the plastic lining. The paper is sent to be recycled and the plastic lining is typically sent to landfill. In an industrial composting environment, the paper and lining can be composted together if the lining is made from compostable materials. Coating paper cups with a compostable performance material uniquely allows for used cups to be processed by either recycling or composting, thus creating multiple pathways for these products to flow through a circular economy.A segment of the paper converting industry frequently uses an extrusion grade of polylactic acid (PLA) for zero-waste venues and for municipalities with ordinances for local composting and food service items. The results among these early adopters reveal process inefficiencies that elevate manufacturing costs while increasing scrap and generally lowering output when using PLA for extrusion coating. NatureWorks and Sung An Machinery (SAM) North America researched the extrusion coating process utilizing the incumbent polymer (LDPE) and PLA. The trademarked Ingeo 1102 is a new, compostable, and bio-based PLA grade that is specifically designed for the extrusion coating process. The research team identified the optimum process parameters for new, dedicated PLA extrusion coating lines. The team also identified changes to existing LDPE extrusion lines that processors can make today to improve output.The key finding is that LDPE and PLA are significantly different polymers and that processing them on the same equipment without modification of systems and/or setpoints can be the root cause of inefficiencies. These polymers each have unique processing requirements with inverse responses. Fine tuning existing systems may improve over-all output for the biopolymer without capital investment, and this study showed an increase in line speed of 130% by making these adjustments. However, the researchers found that highest productivity can be achieved by specifying new systems for PLA. A line speed increase to more than 180% and a reduction in coat weight to 8.6 µm (10.6 g/m2 or 6.5 lb/3000 ft2) was achieved in this study. These results show that Ingeo 1102 could be used as a paper coating beyond cups.