Nashrieh Shimi va Mohandesi Shimi Iran
Year:2002 | Volume:21 | Issue:1-2|Papers Count:10

A Series of experiments have been conducted to study gas phase hydrodynamic in a fluidized bed reactor. Experimental results show that under bubbling conditions around the gas injection devices, bubbles tend to keep their identity, forming the train of bubbles around the nozzle wall. In this investigation, the gas mixing was studied by measuring the radial and axial dispersion of a gas tracer injected to a hot fluidized bed reactor of FCC particles. In addition, the effect of gas injection devices on tracer gas mixing was examined experimentally.

Ejector is important equipment in the chemical industry. It is mainly used for vacuuming and mixing of flows. In the present work a computer modeling of the flow inside an ejector is used to give a better understanding of the principle of the operation of an ejector. Since the fluid inside an ejector passes through sub sonic, sonic and super sonic regimens, the pressure field is used as the controlling variable and the density is found through the constitutive equations. The control volume method with a co-location grid, attached to the boundary is used to discretize the domain. The overall solution is obtained by the SIMPLE method and to dissociate the pressure and the velocity grid Rhie-Chow interpolation method is employed A central difference approximation method is used to approximate the density on the element borders and the upwind approximation is used to correct the density correction factors. Both upwind, quick and minimum gradient methods were used to approximate the momentum variables on the control volumes. The resultant matrices are solved with the tri-diagonal method the accuracy of the model is checked by simulating a flow regimen in a converging-diverging nozzle, and comparing the results with the available experimental data. The results show that for an inviscid fluid the first order approximation produce as accurate results as the higher order approximations while it has a better stability. However, for the viscous fluid the second order approximation produces a better understanding of the physics of the problem. The solution also shows that the flow field inside an ejector is a complex one and the shock wave has a great influence on the pressure field especially close to the walls. The upper convective quick method did not converg well in the shock calculations while the slowest descent method had a very stable behavior in the analysis of the shock behavior.

Pistachio is considered one of the most important and strategic products among export products in Iran. To design suitable dryer in order to dry pistachio perfectly, and to keep goods in a good situation, it is considered to have adjusting equilibrium moisture curve. These curves are very important information, which are used in solving equivalent mass and energy transfer for designing a dryer system. By using the experimental standard method (COST- 90) these curves in temperature of 15, 25, 35 and 40°C for pistachio powder and the temperature of 15, 35CC for pistachio core (kernel) and unhulled pistachio (whole) were studied. By using the experimental data, the adsorption and desorption isotherm curves of pistachio have been presented and also by using them the net isosteric heat of sorption was obtained.

Equilibrium adsorption isotherms of CH4 and N2 on the Zeolite5A, and the two kinds of Carbon Molecular Sieves (CMS955 and CMS938 produced by Takeda Company) were obtained at 299K and the pressure range of 1-10 bar using volumetric methods. The equilibrium data were analyzed and compared with the prediction of four models; Langmuir, Langmuir-Freundlich (Sips), Toth and the Extended Langmuir Model. Also the Equilibrium Isotherms for binary system of methane and nitrogen with the initial mole fractions of nitrogen equal to 0.035, 0.05, and 0.10 at the same conditions were determined and the experimental data were compared with the prediction of Extended Langmuir model. Experimental results indicated that CMS955 is a superior adsorbent for separation of nitrogen from methane. The kinetic behavior of N2-CH4-CMS955 at two different pressures and three different inlet mole fractions of nitrogen was studied and the corresponding breakthrough curves were obtained. 

Conventional methods are useful for destruction of NOx and CO air pollutants but these technologies are not able to destroy solvents such as acetone, alcohol, halogenated compounds, sulfuric compounds and surfactants. These pollutions cause some problems for human, animals, plants and also for semiconductors that are used in electronic devices. Photocatalytic reactions have been found to be able to overcome the problem. In this research, a catalyst was prepared by sol-gel technique and evaluated by the amount of co conversion. Some adsorbents were added to the catalyst to improve its conversion efficiency. The results show that, for % 80 conversion, the space time of TiO2 -Al2O3 is 4*106 g.s/mol while of TiO2 catalyst is 15*106 g.s/mol. As a result, it can be said that Al2O3 improves conversion efficiency.

The solubility of 1, 3-5 Trioxane in four binary solvent mixtures containing 1-butanol with methanol, ethanol, 2-propanol and 1-propanol are measured at 30°C. The results are used for determining of the activity coefficients of the Trioxane by Wilson, UNIQUAC, Margules and Van Laar models. The Parameters of the mentioned models are presented The Comparison of the calculated and measured solubilities indicate the applicability and accuracy of the models.

In this investigation the clay treating process which have used in petrochemical industries for olefine removing from aromatic products (benzene, toluene and xylenes) have been studied. The presence of olefines in aromatic products are objectionable because of their higher reactivity than aromatics. Olefines produce undesirable by-products in severe conditions which are required for downstream processing. The process was carried out through the fixed bed microreactor which can simulate industrial conditions (200 psi and liquid phase). The selected range of temperature was 75-225 °C and the olefines were linear and cyclic. The obtained results from GC and GC/MS analysis of products showed that optimized temperature was 150-175°C and in these conditions the process carried out by alkylation reactions.