فهرست مطالب

Chemical Engineering - Volume:11 Issue: 1, Winter 2014

Iranian journal of chemical engineering
Volume:11 Issue: 1, Winter 2014

  • تاریخ انتشار: 1394/01/18
  • تعداد عناوین: 7
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  • S. Titiz, Sargut, P. Sayan, A. Masum, B. Kiran Pages 3-18
    Struvite crystallization was investigated in the presence of different amino acids at 37°C and pH 8.0 in a continuous crystallization system. Crystal size distributions, filtration rates and morphologies of struvite crystals were determined and discussed as a function of amino acid concentration. The change of morphology depending on the amino acid type and concentration affected the filtration characteristics of struvite crystals. The crystal size distributions of the final products obtained at investigated experimental conditions were evaluated by using modified form of Abegg, Stevens and Larson (ASL) model. Thermogravimetric and differential thermal analysis have been used for thermal characterization of struvite crystals by measuring the changes in their physicochemical properties as a function of increasing temperature with time. The Coats-Redfern integral method was used to evaluate the kinetic parameters in the decomposition sequence observed in the TGA curves. In the presence of all investigated amino acids, the form of precipitate was struvite and newberyite formation was not observed.
    Keywords: Struvite, Amino Acids, Size Dependent Growth, ASL Model, Coats, Redfern Method
  • A.A. Amooey, M. Fazlollahnejad Pages 19-29
    In this work, the surface tension () of aqueous solutions of PEGs (poly ethylene glycol) with molecular weights of 200, 300 and 6000 in water, and poly (propylene glycol) (PPG) with a molecular weight of 2000 in ethanol, were measured in the (293.2-338.2) K temperature range and atmospheric pressure. The results of the measurements were modeled by an Artificial Neural Network(ANN) with input of mass fraction of polymer and solution temperature. The predictions of the artificial neural network model fit the experimental data perfectly.
    Keywords: Surface Tension, Polymer Solutions, Polyethylene Glycol, Propylene Glycol Neural Network
  • M. Aghayarzadeh, R. Alizadeh, S. Shafiei Pages 30-41
    Due to wide application of styrene for production of different materials, it is considered as an important product in industry. Therefore, optimizing styrene production conditions is of great importance in petrochemical industry. In this paper, styrene production reactors of Tabriz Petrochemical Complex are modeled using Artificial Neural Network (ANN) model and Adaptive Neuro Fuzzy Inference System (ANFIS). Comparison of two models revealed that the neural networks are more reliable. The process of design and evaluation of models are carried out using industrial data which show credibility of designed models. The neural networks are designed to predict the styrene output from reactors as a function of effective input parameters on the styrene production. Predictions of designed neural networks were used to study the effect of each variable, such as oxygen flow rate and steam oil ratio, on the amount of styrene produced. Also, the optimal values of effective variables for maximum production of styrene were obtained. Furthermore, in order to obtain accurate results, catalyst deactivation of styrene reactors has been modeled using Fuzzy Inference System. As a result, catalyst activity as a function of time is obtained.
    Keywords: Styrene Monomer, Artificial Neural Network, Catalyst Deactivation, Fuzzy Inference System
  • M. Takht Ravanchi, S. Fadaeerayeni, M. Rahimi Fard Pages 42-54
    In the present research, egg-shell Pd-Ag/α-Al2O3 catalysts prepared by impregnation method using self-improved spherical alumina support with BET 13.34m2/g and pore volume 0.36cm3/g were used for the hydrogenation of acetylene in the presence of a large excess of ethylene (tail-end cuts) and their activity-selectivity patterns were compared with the commercial one. All of the synthesized catalysts were tested under 60C, 10bar, space velocity 6500h-1 and H2/C2H2 ratio 1.5 (mol/mol) which is the same as an industrial plant.The effect of impregnation operating parameters, such as pH of the impregnation solution and impregnation type, on palladium penetration depth and palladium uptake was investigated.pH 1.5 is best for impregnation solution.Catalytic performance tests showed that for Pd-Ag/α-Al2O3 catalysts,sequential impregnation was a suitable method for the active metal. By controlling the synthesis condition, the best Pd-Ag/α-Al2O3 sample was an egg-shell one in which Pd was loaded evenly in a layer with thickness 20-30µm. This sample gave ethylene selectivity of 100% and acetylene conversion of 58% which is higher than the commercial one.
    Keywords: Acetylene, Selective Hydrogenation, Palladium, Impregnation
  • M. Shafiee, A. Ramazani S.A., H. Bahrami, A. Kheradmand Pages 55-62
    The ultra-high molecular weight polyethylene (UHMWPE) was prepared using titanium tetrachloride (TiCl4) supported by MgCl2 (ethoxide type), accompanied by triisobutylaluminium (TIBA) as co-catalyst. These all constituted the Ziegler–Natta catalytic system. MgCl2 is one of the best supports for Ziegler-Natta catalyst in order to increase its yield.In the present study, the process variables were investigated through response surface methodology (RSM) to optimize the productivity of the catalyst and also the molecular weight of the polymer. Taking this into consideration a three-level Box-Behnken design for three factors with temperature (X1), monomer pressure (X2), and [Al]/[Ti] molar ratio (X3) as the independent variables were selected. Different molar ratio of [Al]/[Ti] is achieved by changing the amount of the co-catalyst.The dependent variables were productivity and molecular weights of the prepared polymers. Specifically, using these three parameters at three levels including 50, 60, and 70°C for temperature; 4, 6, and 8 bar for pressure; and 150, 250, and 350 for [Al]/[Ti] molar ratio. The RSM yielded optimum reaction conditions equal to: temperature of 55°C, pressure of 8 bar, and [Al]/[Ti] molar ratio of 230. Under these optimum conditions, the productivity and molecular weight were 2628 g PE/mmolTi.h and 5.09×106 g/mol, respectively.
    Keywords: UHMWPE, Ziegler, Natta, Optimization, Response Surface Methodology
  • A. Kumar Jhankal, M. Kumar Pages 63-68
    The plane Poiseuille flow with unequal wall temperatures of an incompressible fluid having temperature dependent viscosity in the presence of transverse magnetic field is studied. The coupled differential equations of momentum and energy are solved numerically by RKF45 (Runge-Kutta-Fehlberg fourth-fifth) method. Numerical results for the dimensionless velocity profiles, the temperature profiles and the heat transfer coefficient are presented and discussed graphically for various parameters. The study provides quantitative information of interest; in general, it is observed that the maximum velocity does not occur in the middle of the channel but moves towards the upper wall as the magnetic field increases. The temperature and heat transfer coefficient increases with the increasing value of magnetic field and EPr.
    Keywords: Poiseuiller Flow, Variable Viscosity, Unequal Wall Temperature, Numerical Study
  • A. Hosseinnia, M. Pazouki, M. Banifatemi Pages 69-74
    The sintered glass filters with 90–150 µm porosity were coated with titanium oxide/silver composite. For deposition of titanium oxide, the filter was deep coated in the titanium oxide sole. Subsequently the solution of silver nitrate in methanol was used for silver deposition. The ultra violet (UV) radiation with 254 nm wave length was used for reducing silver ions to metallic silver. The prepared filters were characterized by X-ray diffraction and scanning electron microscopy. The photo-catalytic efficiency of TiO2 and TiO2/Ag coated sintered glass filters was investigated for photocatalytic decomposition of epichlorohydrin. The 67% of 1 and 20 mg/lit of epichlorohydrin solution in ethanol was decomposed by TiO2 /Ag coated filter after 3 hours UVA radiations.
    Keywords: TiO2, Ag, Epichlorohydrin, Photocatalyst, Coated Sinter Glass Filter