| 1. |
- Bhatnagar, Amit, et al.
(författare)
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Utilization of industrial waste for cadmium removal from water and immobilization in cement
- 2009
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 150, s. 145-151
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the adsorption potential of metal sludge (a waste product of the electroplating industry) for the removal of cadmium from water. The adsorption capacity of the waste sludge for cadmium was ca. 40 mg g−1 at 25 °C. The adsorption was studied as a function of contact time, concentration and temperature by batch experiments. The adsorption has been found to be endothermic and data conform to the Langmuir model. The analysis of kinetic data indicates that the present adsorption system followed pseudo-first-order kinetics. After the adsorption studies, the metal-laden sludge adsorbent was immobilized in cement for its ultimate disposal. Physical properties such as initial and final setting time and the compressive strength of cement-stabilized wastes were tested to investigate the effect of the metal-laden sludge. The results of the present study clearly reveal that waste metal sludge can be used beneficially in treating industrial effluents containing cadmium and safely disposed of by immobilizing into cement. The proposed technology provides a two-fold advantage of wastewater treatment and solid waste management.
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| 2. |
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| 3. |
- Gopala, Vinay, 1979, et al.
(författare)
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Volume of fluid methods for immiscible-fluid and free-surface flows
- 2008
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 141:1-3, s. 204-221
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Tidskriftsartikel (refereegranskat)abstract
- This article reviews and analyzes a number of numerical methods to track interfaces in multiphase flows. Several interface tracking methods can be found in literature: the level-set method, the marker particle method, the front tracking method and the volume of fluid method (VOF) to name a few. The volume of fluid method has an advantage of being conceptually simple, reasonably accurate and phenomena such as interface breakup and coalescence are inherently included. Over the years a number of different techniques to implement the VOF method have been devised. This article gives a basic introduction to the VOF method and focuses on four VOF methods: flux-corrected transport (FCT) by Boris et al. [J.P. Boris, D.L. Book, Flux-corrected transport. I: SHASTA, a fluid transport algorithm that works, J. Comput. Phys. 11 (1973) 38-69], Lagrangian piecewise linear interface construction (L-PLIC) by van Wachem and Schouten [B.G.M. van Wachem, J.C. Schouten, Experimental validation of 3-d Lagrangian VOF model: bubble shape and rise velocity, AIChE 48 (12) (2002) 2744-2753], Compressive interface capturing scheme for arbitrary meshes (CICSAM) by Ubbink [O. Ubbink, Numerical prediction of two fluid systems with sharp interfaces, Ph.D. Thesis, Imperial College of Science, Technology and Medicine, 1997] and inter-gamma scheme by Jasak and Weller [H. Jasak, H.G. Weller, Interface-tracking capabilities of the InterGamma differencing scheme, Technical Report, Imperial College, University of London, 1995]. A detailed description of these schemes is given and implemented into an in-house fully coupled solver. Further, the performance of these schemes is examined employing a number of tests to analyze their strengths and weaknesses. Their advantages and limitations are discussed. (C) 2008 Elsevier B.V. All rights reserved.
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| 4. |
- Henda, Redhouane, et al.
(författare)
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Heat and mass transport in a nonlinear fixed-bed catalytic reactor: Hot spots and thermal runaway
- 2008
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 143:1-3, s. 195-200
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Tidskriftsartikel (refereegranskat)abstract
- Transient heat and mass transport in a wall-cooled tubular catalytic bed reactor is numerically investigated. A two-dimensional pseudo-heterogeneous model, accounting for transport in the solid and fluid phases, with axial and radial dispersions is used to describe transport in the reactor. The effects of inlet process conditions, viz., temperature and concentration, are investigated and their impact on the development of thermal runaway and hot spots in the reactor is analyzed. Under typical process conditions the calculation results show the development of a hot spot downstream the reactor inlet. At reduced feed temperature thermal runaway develops for an inlet concentration of 0.505 mol/m(3). A criterion for thermal runaway limit has been developed whereby runaway can be detected at a point in time during the process when the time derivative of temperature increases monotonously with time throughout the bed. Under low feed concentration and temperature a simpler pseudo-homogeneous model can be used to describe the reactor. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.
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| 5. |
- Lilja, J., et al.
(författare)
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Esterification of propanoic acid with ethanol, 1-propanol and butanol over a heterogeneous fiber catalyst
- 2005
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 115:02-jan, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Esterification kinetics of propanoic acid with ethanol, 1-propanol and butanol over a fibrous polymer-supported sulphonic acid catalyst (Smopex-101) was studied. Experiments were carried out in a batch reactor operating isothermally at three different temperatures: 60, 70 and 75 degrees C (80 degrees C for butanol) and with different initial molar ratios of propanoic acid and alcohol (1:1, 1:2 and 2:1). The fiber catalyst was active and stable in all the experiments. The experimental results were modeled according to a Langmuir-Hinshelwood model and with an advanced adsorption-based model. The activity coefficients were calculated according to the UNIFAC model. The activation energy of esterification of propanoic acid with ethanol was found to be 52.6 kJ/mol, 49.9 kJ/mol with 1-propanol and 47.3 kJ/mol with butanol. The kinetic model, which includes the adsorption of carboxylic acid and water combined with the activities of the species, explained the experimentally recorded concentrations well.
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| 6. |
- Lundström, Andreas, 1980, et al.
(författare)
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Urea thermolysis studied under flow reactor conditions using DSC and FT-IR
- 2009
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 150:2-3, s. 544-550
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Tidskriftsartikel (refereegranskat)abstract
- The thermal decomposition of urea has been studied under flow reactor conditions using a differential scanning calorimeter (DSC) and Fourier transformed infrared spectroscopy (FT-IR). Samples of urea were administered using either a cordierite monolith impregnated with a urea/water solution or a silica cup with a dry urea sample. The samples were heated between 25 and 700 degrees C with heating rates of 10 and 20 K/min and the thermal response of the sample and off gas concentrations of ammonia and isocyanic acid were recorded. Biuret and cyanuric acid were decomposed in a separate set of experiments to verify some of the features observed in gas phase data during urea decomposition. Results show that depending on the way the sample is administered, i.e. cup or monolith different behavior in the evolved gases are observed. This is due to different reactions taking place in the vessel induced by the different conditions under which the pyrolysis of urea is preformed. (C) 2009 Elsevier B.V. All rights reserved.
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| 7. |
- Nilsson, Marita, et al.
(författare)
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Assessing the adaptability to varying fuel supply of an autothermal reformer
- 2008
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 142, s. 309-317
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Tidskriftsartikel (refereegranskat)abstract
- The present paper describes the study of an autothermal reformer and its fuel-flexible capabilities. Experiments have been performed in a reactor designed to generate hydrogen by autothermal reforming for a 1-5 kW(e) polymer electrolyte fuel cell. Both logistic fuels (diesel, gasoline, and E85) and alternative fuel candidates (methanol, ethanol, and dimethyl ether) were tested in the reformer. The same catalyst composition, Rh supported on Ce/La-doped gamma-Al2O3 and deposited on cordierite monoliths, was used for all fuels. The practical feasibility of reforming each fuel in the present reactor design was tested and evaluated in terms of fuel conversion and selectivity to hydrogen and carbon dioxide. Temperature profiles were studied both in the axial and radial direction of the reformer. It was concluded from the experiments that the reformer design was most suitable for use with hydrocarbon mixtures Such as diesel, gasoline, and E85, where it represents a good basis for an optimized multifuel-reformer design.
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| 8. |
- Rownaghi, Ali, et al.
(författare)
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Solvothermal synthesis of vanadium phosphate catalysts for n-butane oxidation
- 2009
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 155:1-2, s. 514-522
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we have developed a simple, low-cost, template-free and surfactant-free solvothermal process for synthesis of vanadyl hydrogen phosphate hemihydrate (VOHPO4·0.5H2O) with well defined crystal size. The synthesis was performed by reaction of VPO4·2H2O with an aliphatic alcohol (isobutyl alcohol, 1-pentanol, 1-hexanol, 1-heptanol or 1-decanol). This afforded well crystallized VOHPO4·0.5H2O by solvothermal methods at 120°C temperature. This new method significantly reduced the preparation time and lowered production temperature (50%) of catalyst precursor (VOHPO4·0.5H2O) when compared to conventional hydrothermal synthesis methods. By varying the reducing agent, the solvothermal evolution process from layered tetragonal phase VOPO4·2H2O to orthorhombic phase VOHPO4·0.5H2O was observed. It was found that the length of carbon chain in an alcohol in the solvothermal condition had a great impact on chemical and physical properties of resulting catalysts. Interestingly, there was no trace of VO(H2PO4)2an impurity noted to be readily formed under solvothermal preparation condition. Therefore, this study introduces a more facile synthetic pathway to V(III) compounds. In addition, the microwave-synthesized catalysts exhibited some properties superior to those of conventionally synthesized catalyst such as better stability, crystallinity, and catalytic activity in the production of maleic anhydride. The characterization of both precursors and calcined catalysts was carried out using X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometer (ICP-AES), N2physisorption, temperature programmed reduction (H2-TPR) and scanning electron microscopy (SEM). The XRD pattern of the active catalyst prepared by this solvothermal method confirmed the presence of smaller crystal size (between 6 and 13nm along 020 planes) of vanadium phosphate catalyst with higher specific surface area. Finally, the yield of maleic anhydride was significantly increased from 29% for conventional catalyst to 44% for the new solvothermal catalyst.
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| 9. |
- Ström, Henrik, 1981, et al.
(författare)
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Choice of urea-spray models in CFD simulations of urea-SCR systems
- 2009
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 150:1, s. 69-82
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Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of modeling choices to obtained results for Eulerian–Lagrangian CFD simulations of urea-SCR systems has been investigated for a system consisting of an AdBlue-spray located at the exhaust pipe wall, directed into the exhaust gas flow. The decomposition of urea is modeled as being heat transfer limited and taking place at a constant temperature (425 K). It is shown that modeling choices may affect the predicted extent of wall hit, which types of droplets that are predicted to hit the wall, and also where they will do so.The influence of the different forces due to drag, buoyancy, lift effects, thermophoresis and history effects was investigated, proving that only the forces due to drag and buoyancy are necessary to correctly describe droplet motion within this system. It is necessary to use a droplet drag coefficient that takes the current level of droplet distortion into account.A stochastic particle tracking model will describe the effects of turbulent dispersion, but also make the simulation results sensitive to the quality of the turbulence model's prediction of the turbulent fluctuating velocities. Using such a model will also resolve some of the enhancement of heat and mass transfer caused by the continuous acceleration/deceleration of droplets by turbulent eddies.
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