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A feasibility study of using the organic Rankine cycle for power generation from the flue gases of recovery boilers, TAPPI Journal August 2022
ABSTRACT: Almost 415 tons/h of flue gases with a temperature of 160°C are released to the atmosphere from the recovery boiler of a pulp mill with capacity of 1000 air dried (a.d.) metric tons of pulp per day. This is a large waste heat stream that can be used to generate power, to decrease the operating costs of a pulp mill, and to save carbon dioxide (CO2) emissions. In this work, the feasibility of using an organic Rankine cycle (ORC) with ammonia as the working fluid to generate power from the flue gases of recovery boilers is studied. CHEMCAD and Taguchi methods are used for simulation of the process and for optimization of operating conditions, respectively. The temperature of the ammonia and flue gases at the exit of evaporator, exit pressure of the pump and turbine, and the degree of subcooling of ammonia at the exit of the condenser are five operating parameters that are manipulated to optimize the process. Three different scenarios are defined: minimizing the net power cost, maximizing the ORC efficiency, and maximizing the net profit. Different aspects of these scenarios, such as net power generation, cost, efficiency, and CO2 emission savings are discussed, and optimum operating conditions are reported.
Journal articles
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Causes of poor dregs settling in a green liquor clarifier, TAPPI Journal August 2022
ABSTRACT: A study was conducted to examine the most likely parameters responsible for poor dregs settling at a kraft mill over a 2.5-year period, using multivariate data analysis (MVDA) and machine learning (ML) techniques. The dregs settling behavior seems to be seasonally influenced, implying that wood quality variation can be a factor. The results from the MVDA/ML analysis show that poor dregs settling is correlated to incomplete combustion and/or low load conditions in the recovery boiler, low sulfidity in the causticizing plant, and high flow in the green liquor•weak wash cycle. Compositions of dregs and black liquor were also examined to identify correlations with impaired dregs settling. The results show that poor dregs settling strongly correlates with high silicon (Si) content in dregs and moderately correlates with high iron (Fe) and high aluminum (Al) contents, and with low bulk density in dregs. For mills that experience dregs settling or green liquor filtering issues, regular compositional analyses of dregs, green liquor, weak wash, and black liquor are recommended in order to monitor the dynamics of silicon and other constituents in the recovery cycle.
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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Utilization of palm fiber as papermaking materials: Microscopic structure and chemical pulping, TAPPI Journal October 2022
ABSTRACT: The microscopic structure and pulping properties of palm fiber were explored. Soda cooking and sulfate cooking were conducted and compared in terms of physical strength of the obtained pulps. Sulfate pulp showed better performance than soda pulp, as indicated by the 23% higher tensile index, 49% higher tear index, and 36% higher burst index. To further elevate physical strength, long fibered pulp (LFP), namely commercial softwood sulfate pulp, was mixed with sulfate pulp of palm fiber at levels from 20% to 50%. At the blend level of 50%, tensile index of 52.13 Nœm/g, tear index of 15.63 mNœm2/g, and burst index of 3.42 kPaœm2/g were attained. The lignin in spent liquor from pulping was isolated and characterized. Soda lignin of palm fiber was mainly composed of guaiacyl and syringyl units, and showed weight-average molecular weight of 3616 g/mol.
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Effects of different ammonium lignosulfonate contents on the crystallization, rheological behaviors, and thermal and mechanical properties of ethylene propylene diene monomer/polypropylene/ammonium lignosulfonate composites, TAPPI Journal January 2020
ABSTRACT: Thermoplastic elastomer (TPE), made from ethylene propylene diene monomer (EPDM) and polypropylene (PP) based on reactive blending, has an excellent processing performance and characteristics and a wide range of applications. However, there are currently no reports in the literature regarding the usage of TPE in making composite boards. In this paper, EPDM, PP, and ammonium lignosulfonate (AL) were used as the raw materials, polyethylene wax was used as the plasticizer, and a dicumyl peroxide vulcanization system with dynamic vulcanization was used to make a new kind of composite material. This research studied the influences of the AL contents on the crystallization behaviors, rheological properties, thermal properties, and mechanical properties of the composites. The results showed that the AL content had a noticeable impact on the performance of the composite board. Accordingly, this kind of composite material can be used as an elastomer material for the core layer of laminated flooring.
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.
Journal articles
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Characterization of chia plant (Salvia hispanica) for pulping, TAPPI Journal October 2020
ABSTRACT: In this paper, chia plant was characterized in terms of chemical, morphological, and anatomical properties. Chia plant was characterized with low a-cellulose (30.5%); moderate lignin (23.2%) with syringyl to guaiacyl ratio of 1.41; and shorter fiber length (0.67 mm) with thinner cell wall (1.91 µm) and good flexibility coefficient (71.44). Anatomical features showed that chia plant consists of vessels, fibers, parenchyma cells, and collenchyma cells. Chia plant pulping was evaluated in soda-anthraquinone (soda-AQ) and formic acid/peroxyformic acid (FA/PFA) processes. Chia plant was difficult to delignify in the alkaline process. The FA/PFA process produced higher pulp yield at the same kappa number than the soda-AQ process. Unbleached soda-AQ chia pulp exhibited good properties in terms of tensile, bursting, and tearing strengths, even at the unrefined stage, due to high drainability of the pulps. Alkaline peroxide bleached FA/PFA pulp exhibited better papermaking properties and 2% higher brightness than the D0(EP)D1 bleached soda-AQ pulp.
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
Journal articles
Magazine articles
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
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.