فهرست مطالب

Chemical Engineering - Volume:5 Issue: 2, 2008
  • Volume:5 Issue: 2, 2008
  • تاریخ انتشار: 1387/02/11
  • تعداد عناوین: 7
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  • Y. Babazadeh1, S. M. Mousavi1, M. R. Akbarzadeh2 Page 3
    Prediction of the dynamic crossflow ultrafiltration rate of a protein solution such as milk poses a complex non-linear problem as the filtration rate has a strong dependence on both the solution physicochemical conditions and the operating conditions. As a result, the development of general physics-based models has proved extremely challenging. In this study an alternative dynamic neuro-fuzzy model for milk ultrafiltration that describes the variation in dynamic permeate flux decline with temperature, transmembrane pressure (TMP), fat percentage, pH and molecular weight cut off (MWCO) has been developed with the experimental data of the pilot spiral wound membrane test rig. By increasing the temperature, TMP, and pH the permeate flux is increased, and by increasing fat concentration the permeate flux is decreased. The MWCO variation indicates a paradoxical permeate flux. Additionally, a hybrid physical model for dynamic prediction of total resistance in the milk ultrafiltration by combination of two neuro-fuzzy (ANFIS) models and a physical model (BLA model) is developed. By increasing the TMP and fat concentration, the total resistance is increased. But by increasing the pH and temperature, the total resistance is decreased. Also, MWCO variation indicates a paradoxical total resistance value.
    Keywords: ultrafiltration, dynamic modeling, milk, neuro, fuzzy, hybrid model
  • S. A. Mousavi Dehghani1, M. Vafaie Sefti2, H. Mehdizadeh2 and H. Shirkhanloo1 Page 23
    Precipitation of solid paraffins is one of the most common problems in the oil industry, imposing high operating costs. There have been a great many efforts for the prediction of solid paraffins precipitation up to now. Most of them were based on activity coefficient models accounting to solid phase non-ideality or the multi-solid model to calculate the number of precipitated solid phases. In this work, solid phase behavior is predicted by a solid equation of state. At first, by using the thermodynamic method (subcoled liquid) for pure solid phase fugacity from pure liquid fugacity, the solid EOS parameters are tuned.
    The tuned solid EOS can then be directly applied for the prediction of the amount of precipitated solid paraffins (waxes) in the oil samples. The proposed equations system in this work is solved by a proper mathematical method. The obtained results of wax precipitation in this work are in good agreement with the experimental data.
    Keywords: Solid Paraffin, Solid Phase Equation of State, Wax Precipitation, Multi, solid model
  • M.M. Parnian and Sh. AyatollahiF Page 34
    Uncontrolled release of light non aqueous phase liquids (LNAPL) such as diesel, gasoline, fuel oils and lubricating oils from transporting vehicles, pipeline and underground storage tanks (UST) could lead to the migration of contaminants to the subsurface soil and ground water. There is a high interfacial tension (IFT) between LNAPL molecules and water molecules that makes water a non-efficient cleaning material for removing LNAPL from the soil. Nowadays, surfactants (surface active agents) can promote the enhanced removal of LNAPL from the subsurface through mobilization and solubilization. Encouraging results were achieved from laboratory and field results. The aim of this study is to improve the clean up efficiency of surfactant-flooding for two different surfactants; Triton X-100 and Sodium Dodecyl Sulfate which are known as mobilizing and solubilizing surfactants, respectively, by adding alkaline (increasing pH) and foam producing substances. It is shown here that adding alkaline improves the performance of Triton X-100 in removing LNAPL from the contaminated soil by about 8 percent, but spoils the remediating capability of Sodium Dodecyl Sulfate by about 3 percent. Also, adding a foaming agent helps the surfactant solution in removing the LNAPLs out of the soil by more than 5 percent.
    Keywords: LNAPL, Surfactant, Remediation, Alkaline, Foam
  • Preparation and Characterization of Polyaniline/CaCO3 Composite and its Application as Anticorrosive Coating on Iron
    A. Olad, A. Rashidzadeh Page 45
    Composites of polyaniline with calcium carbonate particles (PANI/CaCO3) with different CaCO3 content (0-40 %w/w) were prepared. Two different methods of in situ polymerization and solution mixing were used for PANI/CaCO3 composite preparation. The composite was characterized using FT-IR, SEM, electrical conductivity measurement and cyclic voltammetry techniques. The incorporation of CaCO3 particles in polyaniline matrix in both methods of composite preparation was confirmed by FT-IR results. Electrical conductivity measurements showed that the conductivity of the composite decreases by increasing the CaCO3 loading in polyaniline. Also, the anticorrosive property of the PANI/CaCO3 composite coating on iron samples was investigated in various corrosive environments. According to the results, the corrosion rate or corrosion current of PANI/CaCO3 composite coated iron coupons was much lower (96.75%) than polyaniline coated samples. Also, results showed that the corrosion current of composite coated samples varies with the variation of the CaCO3 content in composite coating, and the optimum CaCO3 content of composite coating to achieve the best anticorrosive performance on iron is 10 %w/w.
    Keywords: Composite, Conducting polymers, Polyaniline, Calcium carbonate, Corrosion
  • M. Amouei, P. Khadiv, Parsi, M. M. Moosavian, N. Hedayat and A. A. Davoodi Page 55
    Phase inversion phenomenon occurs in many industrial processes including liquid- liquid dispersions. Some parameters such as energy input or the presence of mineral compounds in the system affect this phenomenon.
    The aim of this research is to study the speed of rotation or energy input at a range of 400 to 800 rpm in a batch liquid-liquid system containing toluene and water. The presence of sodium chloride and magnesium sulphate in the system was also studied.
    It was shown that the increase of energy input had a more obvious effect on oil in water (O/W ) dispersion at lower values of holdup. It was also shown that the ambivalence (o/w  w/o) region of the phase inversion curve shifted downward and became wider as a result of the decrease in interfacial tension.
    It was observed that inorganic salt, used in both single and dual (mixed) shapes, enhanced phase inversion for O/W dispersion. Therefore, the greater the ionic strength of salt, the greater the tendency to phase inversion is.
    Keywords: phase inversion, holdup, ambivalence region, delay time, O/W dispersion
  • M. Irani1, A. Nakhaei, Pour, Sh. Tehrani2 Page 64
    The influence of SiO2 and Al2O3 binders on the catalyst performance and products selectivity of the precipitated Fe-Cu-K catalyst physically mixtured with HZSM-5 was studied in a fixed bed tubular reactor. The iron catalyst was mixed with HZSM-5 zeolite and shaped to cylinders form by alumina and or silica as a binder for increasing the mechanical strength of bifunctional catalyst. The catalyst activity was tested under reaction condition, P=17 bar, T=290 oC , H2/CO=1 and GHSV= 3.07 NL.h-1.g.Fe-1. The results showed that the catalyst activity for Fischer – Tropsch and water gas shift reactions for silica binders is lower than alumina and secondary reactions in the presence of alumina is higher .
    Keywords: Fischer  Tropsch synthesis_HZSM5 Zeolite_Iron Catalysts_Silica binder_Alumina binder_Secondary reaction
  • Notes for Authors
    Page 71