Nashrieh Shimi va Mohandesi Shimi Iran
Year:2001 | Volume:20 | Issue:1|Papers Count:8

In the research work, several series of experiments are carried out by a ten-stage progress horizontal mixer-settler. In the first series of experiments, the effect of impeller speed on the overall volumetric mass transfer coefficients at a constant and specific volumetric flow rates for both phases is studied. In the second series of experiments, the effect of volumetric flow rates of dispersed phase on the overall volumetric mass transfer coefficients at a constant impeller speed for all stages is studied. In the third series of experiments, the effect of volumetric flow rates of continuous phase on the overall volumetric mass transfer coefficients at a constant impeller speed for all stages is studied. According to the experiments, the following conclusions can be made: -An increase of impeller speed results to an increase of the overall volumetric mass transfer coefficients, but after a specific speed (critical speed) the overall volumetric mass transfer coefficients decrease. - An increase of raffinate volumetric flow rate results to an increase of the overall volumetric mass transfer coefficients. - An increase of extract (solvent) volumetric flow rate results to an increase of the overall volumetric mass transfer coefficients. - The obtained results show that the resistance against mass transfer in both phases is considerable high and cannot be neglected none of them.    

In fixed bed reactors, velocity distributions have a direct effect on heat transfer properties. Therefore, in this study we first examined different flow models and solved the modified Brinkman flow model numerically where cannot be tackled analytically. Then, from a heat transfer point of view, plug and non-plug flow models with respect to velocities obtained from the modified Brinkman model have been solved and its effect on Biot number have been examined. In this paper, it has been shown that the correct choice of flow model can have a great impact on the heat transfer properties of such systems.    

Agitated vessels in form of stirred tank reactors and mixed fermentors are being used in large numbers of industry. It is more important to develop good and theoretically sound models for scaling up and design of the agitated vessels. In this article, two phase flow (gas-liquid) in a agitated vessel has been investigated numerically. A two-dimensional computational fluid dynamics (CFD) model is used to predict the gas-liquid flow. The effects of gas phase, varying gas flow rates and variation of bubbles shape on flow filed of liquid phase are investigated. The numerical results are verified against the experimental data.

Coal could be used for production of coke and as feed stock. Sulfur and ash are the most notorious impurities in coal. Sulfur increases the difficulty and the cost of making steel and ash decreases coke heat value. They contribute to the wear and tear of equipment and create pollution problems and corrosion. Among the different methods for desulfurization of coal, the "Molten Caustic Leaching" method has been selected in this research since it is feasible for reducing the sulfur content of Iranian coal. This method is used, for the first time, at atmospheric pressure to reduce the sulfur content of one type of coal used in Isfahan Steel Plant. The results showed 15% reduction in sulfur and 38% reduction in ash with no loss in coking properties of coal. The effect of different parameters on coal desulfurization and product efficiency has been investigated.      

A series of catalysts with perovskite type structure, LaNi (l-x-y) CoxfeyO3 were synthesized by a sol-gel method. The samples were characterized by powder x-ray diffraction (XRD) and elemental analysis. The lattice parameters of the unit-cell in these compounds were calculated and the surface areas of the catalysts were measured by BET method. The catalytic properties of the compounds were studied for the partial oxidation of methane to synthesis gas.