Reaction Engineering, Kinetics and Catalysts,
A. Irankhah; Y. Davoodbeygi
Abstract
One of the effective catalysts for hydrogen purification and production via medium temperature shift reaction, is Cu-Ce solid solution. Cu0.1Ce0,9O1.9 was produced using co-precipitation method and then was utilized as support for 5Cu/Ce0.9Cu0.1O1.9 catalyst which was synthesized employing wet impregnation ...
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One of the effective catalysts for hydrogen purification and production via medium temperature shift reaction, is Cu-Ce solid solution. Cu0.1Ce0,9O1.9 was produced using co-precipitation method and then was utilized as support for 5Cu/Ce0.9Cu0.1O1.9 catalyst which was synthesized employing wet impregnation method. X-ray diffraction (XRD) analysis showed that crystalline sizes of Ce0.9Cu0.1O1.9 and 5Cu/Cu0.1Ce0,9O1.9 were 9.22 and 18.33 nm, respectively. The Catalysts were evaluated in medium temperature shift reaction at 300-390 °C and at gas hourly space velocities (GHSV) of 12000 and 30000 h-1, in a fixed bed reactor. Due to higher concentration of Cu and synergic positive effects of both active metal and support, 5Cu/Cu0.1Ce0,9O1.9 catalyst showed better performance. It was also concluded that, because of low residence time at high levels of GHSV, increasing GHSV leads to decrease CO conversion. Then 5Cu/Cu0.1Ce0,9O1.9 was evaluated in microchennel reactor in 2 GHSVs of 12000 and 30000 h-1 and results were compared with the fixed-bed reactor. It can be concluded that microchannel reactor is better in higher GHSVs (lower residence time of gas flow). A microchannel reactor provides a high surface-to-volume ratio and gases pass over the thin layer of catalyst on the coated plates. Hence, due to the better access to the catalytic bed, the reactants react even in a short time, which improves the microchannel performance compared to the fixed bed reactor
Separation Technology,
M. Yasemi; M. Rahimi; A. Heydarinasab; M. Ardjmand
Volume 15, Issue 3 , September 2018, , Pages 15-33
Abstract
In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence ...
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In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence angles and diameters were examined. Microchannels with different confluence angles and diameters were examined. The effects of pH, temperature, and volumetric flow ratio and contact time of the two phases were investigated. The response surface methodology was used to optimize extraction yield of tannin from Quercus leaves in the employed microchannels. Based on this optimization, maximum yield was achieved at pH=2, temperature=33.1℃, volumetric flow ratio =1.2 and contact time of 25.35s. Results show that extraction-using microchannel has many advantages over traditional methods, including shorter time and higher economic efficiency. Moreover, microchannel provides smaller volume of fluids resulting in lower solvent consumption, lower waste production, shorter analytical times, smaller space requirements, and lower energy consumption.
Reaction Engineering, Kinetics and Catalysts,
F. Mohammadi; M. Rahimi; A. Parvareh; M. Feyzi
Volume 15, Issue 1 , February 2018, , Pages 102-114
Abstract
In the present study, Choline hydroxide (ChOH) as an ionic liquid catalyst was used for transesterification of soybean oil into biodiesel in a microchannel reactor. The effects of three variables i.e. reaction temperature, catalyst dosage and total flow rate on fatty acid methyl ester (FAME) content ...
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In the present study, Choline hydroxide (ChOH) as an ionic liquid catalyst was used for transesterification of soybean oil into biodiesel in a microchannel reactor. The effects of three variables i.e. reaction temperature, catalyst dosage and total flow rate on fatty acid methyl ester (FAME) content (wt. %) were optimized using Box–Behnken experimental design. In order to predict the FAME content a quadratic polynomial model was obtained. The optimal conditions from the model were reaction temperature of 53.53 °C, catalyst dosage of 2.6 wt. % and total flow rate of 11.82 mL/min. At these conditions, the predicted FAME content was 96.45 wt.% and the experimental FAME content was obtained 97.6 wt. %. The proximity of the experimental results and predicted values showed that the regression model issignificant. Using the ionic liquid catalyst in the studied microreactor for transesterification leads to diminish the reaction time to the order of seconds compared to conventional batch systems. In addition, the reusability of ChOH catalyst was investigated. The results revealed that the catalyst had perfect utility after several runs without much loss in the activity.
Separation Technology,
Mo. H. Almasvandi; M. Rahimi
Volume 14, Issue 4 , December 2017, , Pages 17-31
Abstract
This paper reports the results of experimentally removing ammonia from synthetically prepared ammonia solution using a micro scale mixing loop air stripper. Effects of various operational parameters (such as: pH, air flow rate, wastewater flow rate and initial ammonia concentration) were evaluated. By ...
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This paper reports the results of experimentally removing ammonia from synthetically prepared ammonia solution using a micro scale mixing loop air stripper. Effects of various operational parameters (such as: pH, air flow rate, wastewater flow rate and initial ammonia concentration) were evaluated. By increasing the pH from 10 to 12.25 the amount of KLa increased from 0.26 to 0.73 hr-1. A considerable enhancement, about 150%, can be found for KLa by changing the air flow rate from 280 to 700 mL/min under fixed condition. The wastewater flow rate can also the value of KLa from 0.22 to 0.59 hr-1. The values of KLa increased only about 20% by changing the initial concentration of ammonia in the range between 50 and 500 mg/L. The results showed that improving in air stripping using microchannel was successfully carried out with enhancing overall volumetric mass transfer coefficient (KLa) and providing higher mass transfer capabilities compared with other types of strippers, even for lower amounts of used air. The enhancement of mass transfer is happened by efficient mixing induced by the employed microchannel. It has been demonstrated that wastewater flow rate and air flow rate have significant effects on KLa. The optimal stripping conditions and mathematical modeling for ammonia removal and the relation between the parameters were determined using Response Surface Methodology (RSM) with Central Composite Design (CCD) method. The results demonstrate the advantages the proposed system over convention stripper types.
Transport Phenomena,
Hossein Hadi Najafabadi; Mostafa Keshavarz Moraveji
Volume 13, Issue 4 , November 2016, , Pages 46-61
Abstract
In this paper, three-dimensional incompressible laminar fluid flow in a rectangular microchannel heat sink (MCHS) using Al2O3/water nanofluid as a cooling fluid is numerically studied. CFD prediction of fluid flow and forced convection heat transfer properties of nanofluid using single-phase and two-phase ...
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In this paper, three-dimensional incompressible laminar fluid flow in a rectangular microchannel heat sink (MCHS) using Al2O3/water nanofluid as a cooling fluid is numerically studied. CFD prediction of fluid flow and forced convection heat transfer properties of nanofluid using single-phase and two-phase model (Eulerian-Eulerian approach) are compared. Hydraulic and thermal performance of microchannels are investigated according to the results of the friction factor, pumping power, average heat transfer coefficient, thermal resistance, average temperature of the walls and entropy generation. In addition, due to the CFD results, two correlations for predication of Nusselt number and friction factor are presented. Comparing the predicted Nusselt number using single-phase and two-phase models with experimental data shows that the two-phase model is more accurate than single-phase model. The results show that increasing the volume fraction of nanoparticles leads to increases the heat transfer coefficient and reduces the heat sink wall temperature, but it leads to the undesirable effect of increase in pumping power and total entropy generation.
Transport Phenomena,
Volume 6, Issue 4 , October 2009, , Pages 44-61
Abstract
A numerical investigation was carried out to solve the flow dimensionless partial differential equations through rectangular microchannels. A purely viscous power law model was used to characterize the flow behavior of non-Newtonian fluids. The flow was assumed to be steady and laminar, and slip conditions ...
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A numerical investigation was carried out to solve the flow dimensionless partial differential equations through rectangular microchannels. A purely viscous power law model was used to characterize the flow behavior of non-Newtonian fluids. The flow was assumed to be steady and laminar, and slip conditions were used as boundary conditions at the walls. The problem was solved for different power law indices as well as for various rectangular aspect ratios. Results showed that the effects ofslip velocity on dilatant fluids are more pronounced than that for pseudoplastic fluids. An increase in the power law index enhances the product of the friction factor and the Reynolds number, as well as the dimensionless incremental pressure drop and the dimensionless maximum velocity, while the hydrodynamic entrance length decreases. Results emphasize the significant effects of channel aspect ratio on the hydrodynamic flow behavior through microchannels.