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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
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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.
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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
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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.
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Characterization and evaluation of antioxidation of lignin from bamboo powder using a formic acid-catalyzed ethanol organosolv process, TAPPI JOURNAL January 2019
Characterization and evaluation of antioxidation of lignin from bamboo powder using a formic acid-catalyzed ethanol organosolv process, TAPPI JOURNAL January 2019
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Nano-magnesium oxide as hard template synthesis of lignin carbon-based solid acids and its application for cellulose hyrdrolysis, TAPPI JOURNAL January 2019
Nano-magnesium oxide as hard template synthesis of lignin carbon-based solid acids and its application for cellulose hyrdrolysis, TAPPI JOURNAL January 2019
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Kraft pulp bleaching with a P-stage catalyzed by both bicarbonate and TAED, TAPPI Journal July 2019
ABSTRACT: Peroxide bleaching of softwood and hardwood (eucalypt) kraft pulps was performed in solutions of sodium bicarbonate (NaHCO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH). The conventional P stage (hydrogen peroxide + sodium hydroxide; H2O2 + NaOH) was the most effective brightening system without an additional activator. However, peroxide activation by bicarbonate anion (HCO3•) was obvious in all cases where NaHCO3 or Na2CO3 was used. When N,N,N’,N’-tetraacetylethylenediamine (TAED) was added to the bleaching sys-tem, Na2CO3 as the alkali source afforded equal or slightly higher bleached brightness compared to NaOH usage for both the softwood and hardwood pulps. This outcome is attributed to simultaneous peroxide activation by HCO3• and TAED. When applied to the eucalypt pulp, the H2O2/Na2CO3/TAED bleaching system also decreased the bright-ness loss due to thermal reversion.
Journal articles
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The sticky behavior of pulp and paper mill biosludge during drying, TAPPI Journal June 2019
ABSTRACT: Pulp and paper mill biosludge becomes sticky after being dried to a certain solids content. As bio-sludge becomes sticky, it agglomerates and adheres to the heat transfer surfaces of the dryer. This undesirable property can lower the dryer efficiency and cause the drying equipment to fail.A systematic study was conducted to examine the sticky behavior of biosludge. The stickiness was evaluated by measuring the adhesive force between a sludge cake and a stainless steel substrate, and the cohesive force between a sludge cake and a sludge substrate. The results show that: i) both adhesive and cohesive forces increase markedly as the solids content increases, reaching a maximum value at about 13% solids, and then decrease steadily at a high-er solids content; ii) cohesive force is stronger than adhesive force, implying that biosludge tends to agglomerate rather than adhere to smooth equipment surfaces; and iii) mixing wood fines or fly ash from a biomass boiler reduc-es the stickiness of the mixture. These findings may help mills improve the thermal efficiency of biosludge dryers and to turn biosludge into a more attractive fuel for burning in biomass boilers.
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Fabrication of cross-linked starch-based nanofibrous mat with optimized diameter, TAPPI JOURNAL June 2019
ABSTRACT: The design and synthesis of natural and synthetic polymer blends have received recent and wide attention. These new biomaterials exhibit progress in properties required in the field of medicine and healthcare. Herein, the aim of present study is to fabricate starch (ST)/polyacrylic acid (PAA) electrospun nanofibrous mat with a smooth and uniform morphology, lowest fiber diameter (below 100 nm) and the highest possible starch content. Starch itself is poor in process-ability, and its electrospinning could be quite a challenging process. To address this, we carried out the response surface methodology (RSM) technique for modelling the electrospinning process. In order to have ST/PAA nanofibers with the finest possible diameter, optimized processing parameters (applied volt-age, nozzle-collector distance and feed rate) obtained from RSM technique were applied. ST/PAA electrospun nano-fibers with an average diameter of 74±13 nm were successfully achieved via the electrospinning method for the first time. The structure, preparation and properties of the nanofibrous structure were discussed. Results indicated that drug loaded ST/PAA blend nanofibrous structure has a great potential to be used in controlled drug release systems.
Journal articles
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Editorial: TAPPI Journal 2018 Best Research Paper delves deeper into press section rewet to address drying efficiency, TAPPI Journal March 2019
ABSTRACT: TAPPI and the TAPPI Journal (TJ) Editorial Board would like to congratulate the authors of the 2018 TAPPI Journal Best Research Paper Award: J. David “Dave” McDonald and Richard J. “Dick” Kerekes. Their paper, “Rewet in wet pressing of pa-per,” appeared on p. 479 of the September 2018 issue. This research was recognized by the Editorial Board for its in-novation, creativity, scientific merit, and clear expression of ideas.