دوماهنامه مهندسی شیمی ایران
پیاپی 30 (آبان 1386)

Because of the various applications of xylene isomers, their separation for use in downstream industries is essential. One of the above-mentioned isomers is meta-xylene whose separation by an adsorption bed packed with molecular sieve adsorbents to achieve purities in excess of 99.5% for production of isophthalic acid is of interest. After reviewing the feasibility of various existing methods of separation of meta-xylene from a mixed xylenes mixture, the Xylene-Simulator version 1.4 developed in the Process Simulation and Control Department of the Research Institute of the Petroleum Industry by the order of the Isphahan Aromatics Petrochemical Complex was used to investigate the effect of various parameters on this separation process. The most important objective of this process is the transfer of meta-xylene to the extract phase and the production of an extract stream rich in meta-xylene and the desorbent in the adsorption tower which would facilitate their separation with high purity using distillation in the next step. The results obtained validate the possibility of achieving this goal by optimizing the studied parameters.

Extraction of essential oil from medicinal and flavored plants by the method of distillation has been used for a long time and has been developed later. In the early of 80s it was observed that steam distillation had a high yield as well as low expense. In this article the influence of microwave heater, isolation of distillation column, steam flow rate, temperature, pressure and degree of grinding of plant were studied.Overall, we can say that addition of all factors discussed above, except temperature and pressure and microwave heater caused an increase in extraction of essential oil without any unfavorite effect on color and fragrance, but using microwave heater just decreased process time. Increasing temperature and pressure probably caused undesirable components that they could change the color of the essential oil and made unfavorite fragrance.

Study of adsorption models and concentration profile is very important in order to determine efficiency and mass transfer coefficients. A non-linear partial differential equation (PDE) was obtained using mass balance on the spherical element at resin by four isotherm models (Langmuir, Freudlich, Redlich-peterson and Toth). The PDE turn to linear equation with Approximation Method and it solved with converge Implicit Method and lead to concentration profile. The most advantage of this work is presentation of general PDE that it is independent of type of isotherm models. Also, a general matrix is obtained for this type of problems. Generally, the solution of matrix presented a comparison between experimental data and mathematical calculations. Therefore, one can compute the deviation of the theoretical calculations with the experiments.

In boiling, high heat flux levels are possible driven by relatively small temperature differences, which make its use increasingly attractive in aerospace applications, such as compact evaporators in the thermal control of spacecraft environments, and cooling of electronic equipment. Such characteristics have led to research efforts aimed at quantifying boiling behavior in variable gravitational environments. What is discussed in this article includes brief introduction to different experimental methods to prepare microgravity condition and analysis of forces acting on bubble such as buoyancy, surface tension and inertia induced by fluid motion and on the other hand, evaluates the parameters affecting this phenomenon like subcooling, in order to achieve better understanding of the boiling fundamentals under this condition.

Metal nanoparticles have attracted attention due to their unique electrical, magnetical and optical properties. Due to the metal nanaparticles instability because of their high surface energy, these unique properties can be affected by coagulation and growth of cluster size. In this research, the effective parameters on the synthesis of metal nanoparticles via reduction of metal ions in the polymeric matrix (in situ method) from organometal and metal salts precursors were investigated and the effects of the investigated parameters were presented. In the synthesis of metal nanoparticles via in-situ method, polymeric matrix plays as reducing agent and stabilizer to prevent coagulation of the synthesized nanoparticles which have very important and strategic applications. The obtained results of the studies on the synthesis of Au and Ag nanoparticles showed that the metal nanoparticles synthesized via this method have narrow particle size distribution. Also, polymer matrix as stabilizer to metal precursor ratio and reducing agent type and content are key parameters in the controlling of the synthesized nanoparticles size in this method.

In the present article, the ability of silica gel and 4A zeolite in the process of adsorption of water from toluene at different toluene flow rate has been examined in a dynamic adsorption system.In a duration of 7 hours, toluene with a water content of 220 ppm was admitted to flow in a column filled with different adsorbents and the residual water was measured in the outgoing toluene from the column.The results indicated that the residual water content in toluene was increased with the flow rate while the performance of zeolite was greater than that of the silica gel.

In This investigation to produce Single cell protein was done by using cheese whey as substrate. The used microorganism was Trichosporon yeast as fermented, that is separated from chees- making factory in fusion. Fermentation process was done by using external loop air lift bioreactor. In temperature 30 c○ and pH 3.5, and various aeration intersity rate of cheese whey COD reduction was measured. The experimental results showed that in aeration intensity 2.5 v.v.m rate of cheese whey COD from 70000 p.p.m reduced to 7000 p.p,m, that is, approximately, 90 percent of cheese whey COD rate was reduced. By attention to, in production any cheese Ky, almost, 8ky cheese whey is produced. While it wasn,t used from this cheese whey, we will encounter the difficulty of environment. Then future investigation over cheese whey, to produce kinds of foodstuffs by formentation processing will be important.

Shaping of heterogeneous catalysts is so important in catalyst producing process. Catalyst perovskite Nickel prepared via sol-gel method and shaped in different cylindrical shape with one, two, four and no holes. The factors that affects catalyst‘s shaping includes kind and amount of binder, device’s pressure, heating operation after shaping, and raw materials. Catalyst’s strength is measured and conditions for catalyst’s shaping eventually are optimized by standard methods. Results shown optimum conditions are: the furnace temperature: 700(ºC), pressing machine: 800 bar, mass ratio of binder to catalyst: 1/7, binder: PVA, Alumina: mesh 250.

Regarding to exhaustion of fossil energy resources and side effect problems which are originated from consumption of these fuels (air pollution and global warming), several efforts to substitute clean energy carrier are being done. In this situation, hydrogen for many reasons such as: emitting no pollution during burning, diversity in production methods, and capability of being stored in high scales, fascinated many researchers. Also, increase in transportation fuel demand, and it's dependability on gasoline and diesel, inspired many governments to develop the infrastructures of hydrogen application in transportation sector. In this paper, review of hydrogen energy system technologies, and technical comparison of hydrogen with conventional fuels, were done. The most important advantage of using hydrogen is this that well to wheel efficiency of hydrogen is higher, in comparison of conventional fuels.