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A study of the softness of household tissues using a tissue softness analyzer and hand-felt panels, TAPPI Journal March 2019
ABSTRACT: This study applied the reciprocal matrix approach to deduce the correlation between hand-felt (HF) and tissue softness analyzer (TSA) instrumental measurements of tissue softness. The research was conducted in three phases, which are discussed separately. In the phase one study, results indicated that systematic collection of samples and preparation of test specimens were the foundation of successful tests. TSA-HF and tensile strength exhibited a strong negative correlation. In the future, same-unit physical properties can provide a basis for discuss-ing the commonality and complementary natures of hand-felt and TSA softness measurements. In phase two, through the reciprocal matrix approach, subjective softness assessments performed by humans were reliably quan-tified. The quantified values were further applied to a statistical analysis using the t-test to distinguish and train pro-fessional panelists. In phase three of HF panel test results, all independent panels were compared to one another under a uniform scale established by four standard samples. The calibrated HF panel values were incorporated with TSA-HF results to establish technical curves between the softness and tensile strength, which were helpful for onsite workers to carry out process controls.
Journal articles
Magazine articles
Evaluation of novel drum chipper technology: pilot-scale production of short wood chips, TAPPI Journal October 2019
ABSTRACT: Impregnation of wood chips with acidic pulping liquors is improved when using short chip lengths. If the average wood chip length is too short, conventional chipping technology will generate excess small material, such as pin chips and fines. The possibility of using newly developed drum chipping technology to produce short-length wood chips was evaluated with a pilot drum chipper operating at different drum velocities and in-feed angles. With a drum velocity of 30 m/s, the average wood chip lengths and the combined fractions of pin chips and fines were 24 mm and 3.3%, 22 mm and 4.2%, and 17 mm and 8.5%. The highest fractions of total accept chips (large and small accepts), 89% to 90% without screening, were observed for drum velocities of 30•34 m/s and average wood chips lengths of 21•22 mm. The results indicate the potential of drum chipping technology for producing short wood chips with relatively high fractions of accept chips and tolerable fractions of pin chips and fines.
Journal articles
Magazine articles
Exergy and sensibility analysis of each individual effect in a kraft multiple effect evaporator, TAPPI Journal October 2019
ABSTRACT: The multiple effect evaporator (MEE) is an energy intensive step in the kraft pulping process. The exergetic analysis can be useful for locating irreversibilities in the process and pointing out which equipment is less efficient, and it could also be the object of optimization studies. In the present work, each evaporator of a real kraft system has been individually described using mass balance and thermodynamics principles (the first and the second laws). Real data from a kraft MEE were collected from a Brazilian plant and were used for the estimation of heat transfer coefficients in a nonlinear optimization problem, as well as for the validation of the model. An exergetic analysis was made for each effect individually, which resulted in effects 1A and 1B being the least efficient, and therefore having the greatest potential for improvement. A sensibility analysis was also performed, showing that steam temperature and liquor input flow rate are sensible parameters.
Journal articles
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Utilization of kraft pulp mill residuals, TAPPI Journal February 2022
ABSTRACT: Kraft pulp mills produce on average about 100 kg of solid residuals per metric ton of pulp produced. The main types of mill waste are sludge from wastewater treatment plants, ash from hog fuel boilers, dregs, grits, and lime mud from causticizing plants and lime dust from lime kilns. Of these, about half is disposed of in landfills, which highlights the need and potential for waste recycling and utilization. Sludge is either incinerated in hog fuel boilers to generate steam and power or used in various forms of land application, including land spreading, composting, or as an additive for landfill or mine waste covers. The majority of hog fuel boiler ash and causticizing plant residues is landfilled. Alkaline residuals can be conditioned for use in land application, manufacture of construction materials, and production of aggregates for road work. This technical review summarizes residuals utilization methods that have been applied in pulp and paper mills at demonstration- or full-scale, and therefore may act as a guide for mill managers and operators whose goal is to diminish the costs and the environmental impact of waste management.
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
Magazine articles
Probing the molecular weights of sweetgum and pine kraft lignin fractions, TAPPI Journal June 2021
ABSTRACT: The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physico-chemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to determine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weight-lignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.
Journal articles
Magazine articles
New learnings and strategies for meeting future recovery boiler particulate emission limits with existing electrostatic precipitators, TAPPI Journal June 2021
ABSTRACT: It is foreseeable that recovery boiler particulate emission limits in the United States and Canada will continue to get more stringent with time. Because of this, continued improvement of emission control equipment, as well as a better understanding of how operating parameters affect performance, are necessary. Although electrostatic precipitators (ESPs) are often viewed as a mature technology, many improvements in ESP technology continue to be developed. In recent years, academic efforts have improved the understanding of recovery boiler operating conditions on ESP performance. Additionally, advancements in materials, power supplies, and design continue to improve the efficiency and reliability of ESPs.This paper discusses how recovery boiler and electrostatic precipitator (ESP) operating factors affect ESP perfor-mance based on process simulations and practical experience, and how these learnings can be implemented to improve future operation of existing ESPs.
Journal articles
Magazine articles
Fate of phosphorus in the recovery cycle of the kraft pulping process, TAPPI Journal March 2020
ABSTRACT: The accumulation of nonprocess elements in the recovery cycle is a common problem for kraft pulp mills trying to reduce their water closure or to utilize biofuels in their lime kiln. Nonprocess elements such as magnesium (Mg), manganese (Mn), silicon (Si), aluminum (Al), and phosphorus (P) enter the recovery cycle via wood, make-up chemicals, lime rock, biofuels, and process water. The main purge point for these elements is green liquor dregs and lime mud. If not purged, these elements can cause operational problems for the mill. Phosphorus reacts with calcium oxide (CaO) in the lime during slaking; as a result, part of the lime is unavailable for slaking reactions. The first part of this project, through laboratory work, identified rhenanite (NaCa(PO4)) as the form of P in the lime cycle and showed the negative effect of P on the availability of the lime. The second part of this project involved field studies and performing a mass balance for P at a Canadian kraft pulp mill.
Journal articles
Magazine articles
Synthesis of filtrate reducer from biogas residue and its application in drilling fluid, TAPPI Journal March 2020
ABSTRACT: Biogas residues (BR) containing cellulose and lignin are produced with the rapid development of biogas engineering. BR can be used to prepare the filtrate reducer of water-based drilling fluid in oilfields by chemical modification. BR from anaerobically fermenting grain stillage was alkalized and etherified by caustic soda and chloroacetic acid to prepare filtrate reducer, which was named as FBR. The long-chain crystalline polysaccharides were selected as dispersing agents (DA), and the water-soluble silicate was used as the cross-linking agent. After the hot rolling of FBR in saturated saltwater base mud for 16 h at 120°C, the filtration loss was increased from 7.20 mL/30 min before aging to 8.80 mL/30 min after aging. Compared with the commercial filtrate reducers, FBR had better tolerance to high temperature and salt, and lower cost.
Journal articles
Functional surfaces produced by foam coating, TAPPI JOURNAL
Functional surfaces produced by foam coating, TAPPI JOURNAL August 2016