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Novel type of two-impinging-jets reactor for solid-liquid enzyme reactions
, Article AIChE Journal ; Volume 52, Issue 2 , 2006 , Pages 692-704 ; 00011541 (ISSN) ; Sharif University of Technology
2006
Abstract
The isomerization of D-glucose to D-fructose using the immobilized glucose isomerase, as a typical model system of solid-liquid enzyme reactions has been carried out in a novel type of two-impinging-jets reactor (TIJR), which is characterized by a rotating inner cylinder in a stationary one. Because of the impinging process, turbulence, and complex trajectory of the solid particles within the reactor, the fractional conversion of glucose obtained in the TIJR increased dramatically compared to that obtained by conventional reaction systems. A compartment model was considered to describe the pattern of flow [residence time distribution (RTD) of solid particles] within the TIJR. Considering...
Catalytic wet peroxide oxidation of phenol : H2O2 gradual addition study
, Article 2008 AIChE Annual Meeting, AIChE 100, Philadelphia, PA, 16 November 2008 through 21 November 2008 ; November , 2008 ; 9780816910502 (ISBN) ; Ebrahimi, A. A ; Shahalami, S ; Sharif University of Technology
2008
Population balance modeling of barium sulfate nanoparticle synthesis via inverse microemulsion including coagulation effect
, Article Industrial and Engineering Chemistry Research ; Vol. 53, issue. 32 , 2014 , Pages 12705-12719 ; ISSN: 08885885 ; Shahrokhi, M ; Molaei Dehkordi, A ; Sharif University of Technology
2014
Abstract
A deterministic model based on the discrete population balance equation (PBE) is used to examine the precipitation of barium sulfate nanoparticles in nonionic inverse microemulsion systems. It is shown that coagulation can have a significant effect at low initial reactants concentration. The simulation results show that a bimodal particle size distribution (PSD) observed in experimental analysis reported in the literature cannot be predicted by neglecting the coagulation effect. A coagulation kernel is proposed that takes into account the effect of interparticle forces through the Fuchs' stability ratio. The effect of electrolyte concentration on the surfactant headgroup area is also...
A novel model for predicting the dense phase behavior of 3D gas-solid fluidized beds
, Article Chemical Engineering and Technology ; Volume 37, Issue 1 , January , 2014 , Pages 103-112 ; ISSN: 09307516 ; Ghafari, M ; Molaei Dehkordi, A ; Sharif University of Technology
2014
Abstract
A novel phenomenological discrete bubble model was developed and tested for prediction of the hydrodynamic behavior of the dense phase of a 3D gas-solid cylindrical fluidized bed. The mirror image technique was applied to take into account the effects of the bed wall. The simulation results were validated against experimental data reported in the literature that were obtained by positron emission particle tracking. The time-averaged velocity profiles of particles predicted by the developed model were found to agree well with experimental data. The initial bubble diameter had no significant influence on the time-averaged circulating pattern of solids in the bed. The model predictions clearly...
Numerical investigation of gas bubble behavior in tapered fluidized beds
, Article Particuology ; Volume 38 , June , 2018 , Pages 152-164 ; 16742001 (ISSN) ; Askaripour, H ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this article, the behavior of gas bubbles in tapered fluidized beds is investigated with the use of a two-fluid model incorporating kinetic theory of granular flow. The effects of various parameters such as apex angle, particle size, and particle density on the size distribution and the rise velocity of gas bubbles were examined. In addition, the simulation results for the bubble fraction and axial velocity of gas bubbles were compared with experimental data reported in the literature and good agreement was observed. As the apex angle was increased, the fraction of gas bubbles with large sizes increased and the fraction of bubbles with small sizes decreased. As the particle size...
Gas absorption enhancement in hollow fiber membrane contactors using nanofluids: Modeling and simulation
, Article Chemical Engineering and Processing: Process Intensification ; Volume 119 , 2017 , Pages 7-15 ; 02552701 (ISSN) ; Rahimi, M ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
In this article, a comprehensive 2D mathematical model has been developed to simulate process intensification of carbon dioxide absorption in the presence of nanoparticles in hollow fiber membrane contactors (HFMCs). The influences of nanoparticle were taken into account considering Brownian motion and Grazing effect as dominant phenomena of mass-transfer enhancement in nanofluids. The obtained simulation results were validated against experimental data reported in the literature and excellent agreement was obtained. It was found that by adding 0.05 wt % silica nanoparticles, the absorption rate could be enhanced by 16%, while the corresponding value is 32% for CNT nanoparticles. High...
Numerical investigation of gas bubble behavior in tapered fluidized beds
, Article Particuology ; 2017 ; 16742001 (ISSN) ; Askaripour, H ; Molaei Dehkordi, A ; Sharif University of Technology
2017
Abstract
In this article, the behavior of gas bubbles in tapered fluidized beds is investigated with the use of a two-fluid model incorporating kinetic theory of granular flow. The effects of various parameters such as apex angle, particle size, and particle density on the size distribution and the rise velocity of gas bubbles were examined. In addition, the simulation results for the bubble fraction and axial velocity of gas bubbles were compared with experimental data reported in the literature and good agreement was observed. As the apex angle was increased, the fraction of gas bubbles with large sizes increased and the fraction of bubbles with small sizes decreased. As the particle size...
Numerical simulation of a cubic spout-fluid bed: influences of inlet gas temperature and jet to bed cross-section ratio
, Article International Journal of Chemical Reactor Engineering ; Volume 18, Issue 3 , 2020 ; Tamtaji, M ; Molaei Dehkordi, A ; Sharif University of Technology
De Gruyter
2020
Abstract
In this paper, we study the role of inlet gas temperature and jet to bed cross-section ratio on hydrodynamics and circulation patterns of particles in a spout-fluid bed. The system is modeled using CFD-TFM approach based on Eulerian-Eulerian method. Simulation results are validated by experimental data measured by (Link 2008. "PEPT and Discrete Particle Simulation Study of Spout-fluid Bed Regimes." Aiche Journal 54 (5): 1189-202). First, the sensitivity analysis of simulation results versus the most significant parameters are conducted to find the optimum values for each parameter. Subsequently, the role of inlet gas temperature and cross-section ratios are studied in detail. The simulation...
Investigation on various types of ion-exchange membranes in vanadium redox flow batteries: Experiment and modeling
, Article Journal of Energy Storage ; Volume 54 , 2022 ; 2352152X (ISSN) ; Rahimi, M ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Choosing the appropriate ion exchange membrane in vanadium redox flow batteries plays an important role in achieving optimal system performance. In this article, the implementation of commercial cation exchange membranes (Nafion 115, Nafion 117, and Nafion 212), anion exchange membranes (FAP 450 and QA-PFE), and the combination of them are investigated. In this regard, the effects of membrane type, thickness, electrical conductivity, and the transfer of vanadium species at different current densities are examined carefully. In addition, the influences of the flow rate and the concentration of electrolytes are investigated using a comprehensive developed model. The model predictions are...
Gas bubble diameter and rise velocities in tapered fluidized beds: experiment and computational fluid dynamics simulation
, Article Industrial and Engineering Chemistry Research ; Volume 62, Issue 9 , 2023 , Pages 4175-4190 ; 08885885 (ISSN) ; Sarafan, K ; Molaei Dehkordi, A ; Sharif University of Technology
American Chemical Society
2023
Abstract
The two-dimensional two-fluid model (TFM) incorporating the kinetic theory of granular flow was used to simulate the hydrodynamic behavior of gas bubbles in tapered fluidized beds. Because numerous previous works conducted were mainly focused on the hydrodynamic behavior of the beds such as pressure drop, minimum fluidization velocity, and bed expansion ratio, it is required to investigate one of the most significant parameters in tapered fluidized beds (i.e., gas bubble diameter and rising velocity). The experimental data obtained in our laboratory were compared with the simulation results, and good agreement was found. Effects of the superficial gas velocity, apex angle, particle size,...
Transient and steady-state analysis of heat, mass, and momentum transfer in developing and fully-developed regions of homogeneous tubular reactors with non-Newtonian fluid flow
, Article Energy Conversion and Management ; Volume 65 , 2013 , Pages 308-321 ; 01968904 (ISSN) ; Hashemi Amrei, S. M. H ; Molaei Dehkordi, A ; Haghi, M ; Sharif University of Technology
2013
Abstract
In this article, the problem of simultaneous heat, mass, and momentum transfer in the developing region of tubular reactors with homogeneous chemical reaction and laminar power-law fluid flow under unsteady-state conditions has been solved. In this regard, the general governing equations were solved using finite-difference method and analyzed carefully. Moreover, the influences of various parameters and dimensionless numbers such as power-law index, heat of reaction, reaction order, and Damköhler number value on the numerical results were investigated. In addition, the numerical results obtained for the fully-developed velocity distribution of Newtonian fluid flow and Sherwood number value...
Oxidative desulfurization of Non-hydrotreated kerosene using hydrogen peroxide and acetic acid
, Article Chinese Journal of Chemical Engineering ; Volume 17, Issue 5 , 2009 , Pages 869-874 ; 10049541 (ISSN) ; Sobati, M. A ; Nazem, M. A ; Sharif University of Technology
2009
Abstract
The oxidative desulfurization of a real refinery feedstock (i.e., non-hydrotreated kerosene with total sulfur mass content of 0.16%) with a mixture of hydrogen peroxide and acetic acid was studied. The influences of various operating parameters including reaction temperature (T), acid to sulfur molar ratio (nacid/nS), and oxidant to sulfur molar ratio (nO/nS) on the sulfur removal of kerosene were investigated. The results revealed that an increase in the reaction temperature (T) and nacid/nS enhances the sulfur removal. Moreover, there is an optimum nO/nS related to the reaction temperature and the best sulfur removal could be obtained at nO/nS8 and 23 for the reaction temperatures of 25...
Numerical Study of Bubble Behavior in Two-and Three-Dimensional Gas-Solid Fluidized Beds
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Because of the importance of gas-solid fluidized beds in chemical industrial plants, many experimental and modeling efforts have been conducted the prediction of their behaviors up to now. Gas bubbles have a pivotal role in the hydrodynamics of bubbling gas-solid fluidized beds; so, fundamental understanding of the bubbling behavior of fluidized beds is required to describe bubble-related phenomena such as solids mixing and segregation, reaction conversion, heat and mass transfer, erosion of heat-transfer tubes and particle entrainment. In this work, the effects of different parameters such as bed aspect ratio, bed width, superficial gas velocity, and particle size distribution on the...
Numerical investigation on the solid flow pattern in bubbling gas-solid fluidized beds: Effects of particle size and time averaging
, Article Powder Technology ; Vol. 264, issue , September , 2014 , p. 466-476 ; Salehi, M. S ; Molaei Dehkordi, A ; Sharif University of Technology
2014
Abstract
The effects of particle size on the solid flow pattern in gas-solid bubbling fluidized beds were investigated numerically using two-fluid model based on the kinetic theory of granular flow. In this regard, the set of governing equations was solved using finite volume method in two-dimensional Cartesian coordinate system. Glass bead particles with mean sizes of 880. μm, 500. μm, and 351. μm were fluidized by air flow at excess gas velocities of 0.2. m/s and 0.4. m/s. For particle diameters of 880 and 351. μm, the predicted characteristic times for solid dispersion were 0.14. s and 0.15. s, respectively, while characteristic times for solid diffusivity were 1.68. ms and 0.75. ms in the same...
Experimental investigation and process intensification of barium sulfate nanoparticles synthesis via a new double coaxial spinning disks reactor
, Article Chemical Engineering and Processing: Process Intensification ; Volume 115 , 2017 , Pages 11-22 ; 02552701 (ISSN) ; Shahrokhi, M ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier B.V
2017
Abstract
In this article, a new double spinning disks reactor (DSDR) has been proposed and tested successfully for the synthesis of barium sulfate nanoparticles by means of the reactive precipitation. The proposed DSDR consists of two coaxial rotating disks placed horizontally in a cylindrical chamber. Continuous precipitation of barium sulfate nanoparticles as a chemical test system was carried out using this new contacting device and the effects of operating and design parameters such as the disk rotational speed, distance between the disks, feed concentration, feed flow rate, free ion ratio, feed location, and feed distribution pattern on the mean size, size distribution, and morphology of the...
Tuning the wetting properties of SiO2-based nanofluids to create durable surfaces with special wettability for self-cleaning, anti-fouling, and oil-water separation
, Article Industrial and Engineering Chemistry Research ; Volume 61, Issue 23 , 2022 , Pages 8005-8019 ; 08885885 (ISSN) ; Ghazanfari, M. H ; Molaei Dehkordi, A ; Sharif University of Technology
American Chemical Society
2022
Abstract
Surfaces with special wettability have aroused lots of attention due to their broad applications in many fields. In this work, we systematically report selective and various fabrications of nanofluids based on readily available materials such as SiO2 nanoparticles and polydimethylsiloxane to create superhydrophobic, superoleophobic, superhydrophilic/superoleophobic, and underwater superoleophobic coatings. The efficiency of prepared coatings is investigated on mineral rock plates as porous substrates via the straightforward and cost-effective solution-immersion technique. The static water contact angle of 170°, effortless bouncing of water droplets, and self-cleaning property with a near...
Investigation of a two impinging-jets contacting device for liquid-liquid extraction processes
, Article Chemical Engineering Science ; Volume 61, Issue 12 , 2006 , Pages 3942-3950 ; 00092509 (ISSN) ; Ebrahimzadeh Zonouzian, S. A. R ; Molaei Dehkordi, A ; Sharif University of Technology
Elsevier Ltd
2006
Abstract
A two impinging-jets contacting device (TIJCD) for liquid-liquid extraction processes was proposed and tested through the standard test system recommended by the European Federation of Chemical Engineering (EFCE), toluene-acetone-water, as a typical example of liquid-liquid extraction processes. The results obtained for the overall volumetric mass transfer coefficient (capacity coefficient) were more than three times higher than those reported in the conventional contactors and in an air-driven two impinging-streams contactor. These experimental results clearly indicate the greater performance capability of TIJCD relative to those of conventional contactors. To have a perfect study on the...
Reactive Crystallization in an Impinging Jets Reactor
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Reactive crystallization or precipitation is an important industrial process. Many chemicals and biochemicals such as catalysts and pigments are produced by precipitation. Because of the advantages of impinging jets in chemical engineering processes, the main aim of this research was to investigate the application of this method in precipitation and to study the effects of different operating and design parameters on the product’s quality and properties. Two chemical models of barium sulfate and copper oxalate were used as main products. Each of these chemicals was produced by a liquid-liquid reaction of two aqueous solutions, which were fed to an impinging-jets reactor. Effects of...
Solid-Liquid Heterogeneous Catalytic Reactions in a New Two-Impinging-Jets Reactor
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
In this work the transesterification reaction of waste cooking oil in the present of solid catalyst as a type of solid-liquid catalytic reaction, has been studied. For this purpose, two types of alkali solid catalysts were synthesized. CaO-ZrO2 and KOH/γ-Al2O3 catalysts were prepared by co-precipitation and impregnation method, respectively. These catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), BET surface area, and temperature programmed desorption of CO2 (TPD-CO2). The obtained results for the CaO-ZrO2 catalysts indicate that with increasing Ca/Zr atomic ratio, the activity of catalysts increases, but the stability...
Adsorption of xylene isomers on Na-BETA zeolite: Equilibrium in batch adsorber
, Article Microporous and Mesoporous Materials ; Volume 172 , 2013 , Pages 136-140 ; 13871811 (ISSN) ; Khademi, M ; Sharif University of Technology
2013
Abstract
In this article, adsorption of p-xylene, m-xylene, o-xylene, and ethylbenzene on Na-BETA type zeolite in liquid phase at 15, 25, and 35 °C has been studied and the single adsorption isotherms have been obtained and reported. The Langmuir isotherm model was used to describe the experimental adsorption isotherm data. It was found that p-xylene is more strongly adsorbed component followed by ethylbenzene, m-xylene and o-xylene. This means that this adsorbent is selective for p-xylene. Using Langmuir isotherm model, the saturation adsorption capacities of the adsorbent were obtained as follows 143 mg/g for p-xylene, 105 mg/g for ethylbenzene, 83 mg/g for m-xylene, and 68 mg/g for o-xylene at 25...