| 1. |
- Berezowski, M., et al.
(författare)
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Dynamics of heat-integrated pseudohomogeneous tubular reactors with axial dispersion
- 2000
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Ingår i: Chemical Engineering and Processing. - 0255-2701 .- 1873-3204. ; 39:2, s. 181-188
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Tidskriftsartikel (refereegranskat)abstract
- The study concerns a theoretical analysis of pseudohomogeneous autothermal tubular reactors with axial dispersion of mass and heat. Based on analysis and simulations it is demonstrated that such a system can generate complex oscillatory profiles of temperature and concentration-periodic or chaotic. These profiles, especially those of aperiodic character, can seriously impair the performance of the system. The effect of three parameters on the reactor dynamics is studied, namely, the cooling medium temperature, the Lewis number and the Peclet number. We consider only relatively small values of the Lewis number in this paper.
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| 2. |
- Aldehani, Mohammed, et al.
(författare)
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Kinetics and reactive stripping modelling of hydrogen isotopic exchange of deuterated waters
- 2016
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Ingår i: Chemical Engineering and Processing. - : Elsevier BV. - 0255-2701 .- 1873-3204. ; 108, s. 58-73
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Tidskriftsartikel (refereegranskat)abstract
- This work presents results of experimental kinetics and modelling of the isotopic exchange between hydrogen and water in a reactive stripping column for water dedeuteriation. The missing physical properties of deuterium and tritium isotopologues in hydrogen gas and water forms were predicted and validated using existing literature data. The kinetic model relevant to a styrene-divinyl-benzene copolymer-supported platinum catalyst was used for modelling, by Aspen plus modular package, impact of design parameters including temperature, total pressure, gas to liquid flowrate ratio, pressure drop and flow mixing, on the separation of deuterium and further the separation of tritium. The modelling by the rate-based non-equilibrium, including design correlations of model of mass and heat transfers, chemical kinetic constants, mass transfer coefficients and overall exchange rate constants, allowed access to separation trends in a good agreement with published data. The synergy between the rates of chemical isotopic exchange and gas/liquid mass transfer, and by inference the performance of reactive stripping, was particularly sensitive to high temperatures, low hydrogen flow rates, pressure drops and internals properties. Extension to tritium confirmed a slightly slower mass transport compared with deuterium leading to potentially under-estimated design features for detritiation processing when deuterium is used instead.
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| 3. |
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| 4. |
- Fitzpatrick, J.J., et al.
(författare)
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Food powder handling and processing : Industry problems, knowledge barriers and research opportunities
- 2005
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Ingår i: Chemical Engineering and Processing. - : Elsevier BV. - 0255-2701 .- 1873-3204. ; 44:2, s. 209-214
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Tidskriftsartikel (refereegranskat)abstract
- This paper highlights some of the outcomes from a EU Accompanying Measure focussing on food powders. The main goals of the work were to outline the major industrial problems, knowledge barriers, and research challenges and opportunities in relation to food powders, and to promote the creation of a sustainable network of excellence in the area of food powders. Food powders are powders first and foremost, thus many of the research challenges and opportunities are similar to handling and processing of other powders. As a result, much can be learned from other industries that deal with powders. What makes food powders different from many other powders is their composition, which is mainly of biological origin, and that they are eventually consumed by people and animals. Consequently, stability of food ingredient functionality and prevention of contamination are major issues right through from powder production to final application of the powder, which is usually in the form of a wet formulation. © 2004 Elsevier B.V. All rights reserved.
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| 5. |
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| 6. |
- Herrara, Victor A. Sifontes, et al.
(författare)
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Sugar hydrogenation in continuous reactors : from catalyst particles towards structured catalysts
- 2016
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Ingår i: Chemical Engineering and Processing. - : Elsevier BV. - 0255-2701 .- 1873-3204. ; 109, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The density, viscosity and hydrogen solubility of selected sugars (l-arabinose, d-galactose, d-maltose and l-rhamnose) were determined at different temperatures (generally 60, 90 and 130 °C). The role of internal diffusion resistance in porous catalyst layers for sugar hydrogenation was confirmed by numerical simulations based on kinetic data and physical properties. The simulations suggested the use of small catalyst particles or structured catalysts in continuous hydrogenation of the sugars to sugar alcohols. Continuous hydrogenation of l-arabinose was carried out in a laboratory-scale fixed bed reactor with ruthenium catalysts on three different supports (active carbon clothes, carbon nanotubes on sponge-like metallic structures, conventional active carbon catalyst particles). It was proved that continuous hydrogenation is a feasible alternative to batch technology for sugar hydrogenation over conventional catalyst particles and structured catalysts: l-arabinose was converted to arabitol with a very high selectivity.
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| 7. |
- Jogunola, Olatunde, et al.
(författare)
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Rates and equilibria of ester hydrolysis: Combination of slow and rapid reactions
- 2011
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Ingår i: Chemical Engineering and Processing. - : Elsevier. - 0255-2701 .- 1873-3204. ; 50:7, s. 665-674
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics and thermodynamics of ester hydrolysis were studied experimentally in a laboratory-scale batch reactor by using ethyl formate as the model molecule. The effects of the reaction conditions, such as temperature, excess water, complexing agent and initial acid charge upon the ester hydrolysis process were investigated and a kinetic model was developed for the system. Autocatalytic kinetics was observed experimentally, which was due to the carboxylic acid formed during the reaction. The reaction rate was further enhanced and the equilibrium was shifted to the product side by adding a complexing agent into the reaction mixture. A mathematical model comprising the mass balances and rate equations were developed for the system by assuming quasi-equilibrium hypothesis for the reaction involving the complexing agent. A robust calculation scheme was developed for the estimation of the kinetic and thermodynamic parameters from experimental data. The proposed model was able to predict the experimental results satisfactorily.
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| 8. |
- Pamidi, Taraka, et al.
(författare)
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Hydrodynamic and acoustic cavitation effects on properties of cellulose fibers
- 2024
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Ingår i: Chemical Engineering and Processing. - : Elsevier. - 0255-2701 .- 1873-3204. ; 203
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Tidskriftsartikel (refereegranskat)abstract
- The cellulose pulp refining process is crucial for achieving high-quality paper characteristics. This research aims to enhance energy efficiency while maintaining good fiber quality using hydrodynamic and acoustic cavitation (HAC). Experiments were conducted with an in-house developed flow-through sonicator combined with a novel Venturi nozzle for hydrodynamic cavitation. The Venturi design was determined by analytical modeling and verified by CFD simulation with multi-phase turbulence models to balance cavitation intensity and turbulence against the acoustic cavitation effect. Experimental evaluation of two batches of CTMP fibers, pre-processed in different ways, showed significant improvements in paper strength and fiber properties. The best results for Batch 1 (HC and LC) were obtained with 386 kWh/bdt for AC and 350 kWh/bdt for HC (60 °C, 2 % concentration). The tensile strength index increased by 26 %, and the TEA-index, related to freeness, increased by 55 %. HAC treatment (750 kWh/bdt, 70 °C, 1.5 % concentration) of the less refined Batch2 (HC) yielded results better than the Batch 1 reference. These findings confirm the energy-efficient potential of the sonicator concept compared to traditional industrial processes. The conclusion is that HAC-refining of softwood pulp requires a proper balance between hydrodynamic and acoustic cavitation intensities. Both fiber concentration by weight and temperature are critical for an energy-efficient process.
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| 9. |
- Pamidi, Taraka Rama Krishna, et al.
(författare)
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Acoustic optimization of a flow through sonicator for fibrillation of cellulose fibers
- 2022
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Ingår i: Chemical Engineering and Processing. - : Elsevier. - 0255-2701 .- 1873-3204. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- Fibrillation is identified as the most energy intensive process step in pulp and paper manufacturing and improved energy efficiency is the motivation for development of alternative technologies. The aim of this study is to explore the potential of a new refining concept based on cavitation, focusing on the optimization of acoustic cavitation efficiency of the proposed flow-through sonicator concept. The simulations utilize the linearized wave equation in the frequency domain with an addition of nonlinear attenuation introduced by cavitation bubbles. Verification is made by pressure measurements, calorimetry, and foil tests. The fibrillation capability was validated on chemi-thermo mechanical pulp fibers at low consistencies. Fiber properties was characterized by ultrasonic spectroscopy, fiber analysis and SEM. The objective is to optimize the energy transfer efficiency from electrical input power to acoustic cavitation intensity for efficient fibrillation of cellulose fibers. Results showed changes in fiber dimensions and fiber morphology, however, improvements in tensile strength index, measured and predicted by ultrasonic spectroscopy, was limited to 20 % at an energy level of 804 kWh/bdt. To enhance energy efficiency and paper strength properties, it is suggested to add a hydrodynamic cavitation device prior to the sonicator to initiate cavitation bubbles and to increase turbulence intensity.
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| 10. |
- Sadegh-Vaziri, Ramiar, et al.
(författare)
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Modeling of slow pyrolysis of various biomass feedstock in a rotary drum using TGA data
- 2018
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Ingår i: Chemical Engineering and Processing. - : Elsevier. - 0255-2701 .- 1873-3204. ; 129, s. 95-102
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Tidskriftsartikel (refereegranskat)abstract
- Design and optimization of biomass gasification faces the challenge of feedstock variation. Specifically, design calculations require kinetic rate expressions for the given feedstock, whose rigorous determination is demanding and often exceeds available recourses in an early development stage. In this work, we model the slow pyrolysis of biomass for the production of biochar. The aim is to predict the conversion of raw biomass to biochar as a function of the process conditions. Here, we will show that TGA data processed with an isoconversional method is enough to obtain an effective rate expression which allows for predicting the behavior of the biomass at an arbitrary temperature evolution. Such rate expressions can then be used in the process model to simulate conversion of raw biomass to biochar. To illustrate the feasibility of this approach we consider four vastly different biomass, namely spruce wood, pulp, lignin and xylan–lignin, undergoing slow pyrolysis in an indirectly heated rotary kiln reactor. The results of our modeling are compared to experimental data obtained from a 500 kW pilot plant pyrolyzer and to a more detailed process model.
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