دوماهنامه مهندسی شیمی ایران
پیاپی 24 (مهر و آبان 1385)

The bioleaching of zinc sulfide ore using acidophilic autotrophic microorganisms has been studied. The effect of temperature, microorganism, and concentration of Fe(II) in the zinc extraction were assessed. Extraction of zinc from low-grade ores up to 60% after 30 days could be obtained with optimized conditions, and 15% after 30 days without any optimization. The extraction of zinc without any optimization is because of high temperature and acidic environment.

In this research the kinetic of propane hydrate production In constant volume was performed using simple laboratory instruments. For modeling, one-parameter Varaminian-Danesh model was used. Since the propane comprises the structure II of hydrate, the performance of the aforementioned model was evaluated at this state. The experiment was conducted at the temperature range of 274 to 276 K, and the pressure range of 2.9 to 4.3 bar.

Dividing Wall distillation Column (DWC) is one of the thermally coupled distillation columns that has been interested for separation of multi-component mixtures in the recent years. This type of columns has energy and equipment cost saving ability compared with conventional columns. To obtain design and simulation parameters of this column with existing softwares, this column must be modeled to simpler columns. In this paper, design and simulation of a DWC for purification of 1-Butene from the feed of distillation part of 1-Butene unit of Tabriz Petrochemical Complex has been performed. A DWC has been modeled, designed and simulated based on the available data of the unit by HYSYS. The results show that by replacing the two existing sequenced columns with a DWC, a considerable energy saving can be achieved. For existing concentrations in the unit, condenser and reboiler duties reduce 13.3% and 15.4%, respectively.

In this study, the effect of recycle flow, in different configurations on the performance of a set of mixed flow reactors for isothermal and non-isothermal conditions has been investigated. In addition, the effect of operational factors, such as feed temperature, feed flow rate, and heat transfer on temperature distribution and concentration of the reactors, for hydrolysis of ethyl acetate, has been studied.The mathematical equations for mass and energy balances for different configurations of recycle stream for a set of three reactors in series have been derived. The equations have been solved using analytical and numerical methods. For this purpose, an effective computer program has been prepared in order to study the effects of operational parameters on the performance of the system.The results show that the role of recycle flow, especially in non-isothermal conditions, is considerable. It is shown that in some situations, the conversion increases with an increase in recycle flow ratio by increasing temperature.

Separation of water from mine tailing in mining process as well as wastewater resulted from highly concentrated tailings can play a significant role in water recycling and reduce water demand in the mines. An understanding of flow and turbulence can contribute a major task to design hydro cyclone. Therefore, construction of an experimental model with a known characteristic in put can help to analyze hydro cyclone process. This model could possibly be simple, albeit it can behave very closely to prototype. Results and analysis from the model may be employed to verify a numerical simulation.

In this research, unsteady state behavior of gas-solid fluidized beds has been investigated using CFD simulation methods. For this reason, a two dimensional system of jet gas flow in a fluidized bed with axial symmetry has been studied. In order to model this system Eulerian-Eulerian approach has been applied for both gas and solid phases. The model includes continuity equations as well as momentum equations for both phases and the equations for granular temperature of solid particles. MFIX software that applies finite volume method has been employed to solve the model equations. The effects of jet velocity on the bed hydrodynamic as well as the influence of particle density and size, jet velocity, and initial bed height on the bed pressure drop were investigated. The results revealed that, compared with jet velocity and particle size, initial bed height and particle density have more impact on pressure drop. A comparison of predicted bubble size with the corresponding data in the literature indicates a good agreement between them. Also gas flow inside the bubble compared with Davidson model and result of this simulation shows good agreements with this model.

Catalytic and solvent dewaxing are the current major processes for removing wax from refined wax distillate. The proposed hydro-isomerization scheme would be superior to the other lubricant dewaxing processes because of their high yield and high quality of dewaxed products. In this work, at first, it has been collected useful information about hydroisomerization of n-alkenes (isodewaxing process) with various catalysts. Then it is pointed to the kinetic modeling and process reactor simulation approach. For the kinetic modeling it has been developed 6 possible models for this process. We examine hydroisomerization of n-hexadecane as a vehicle to establish a modeling protocol and kinetic parameters.Girgis and Tsao have published data for the hydroisomerization of n-hexadecane on various catalysts [1]. These data have been used in the present work to determine and evaluate lump kinetic models.The rate constants were determined by minimizing a merit function which contained the weighted sum of the square of the residual. The non-linear regression analysis was carried out with a computer program which uses nedler-mead algorithm for the minimization of the merit function. In the experimental section of this work a high pressure batch reactor was designed. 5 final experiments has been done with n-hexadecane at 350 °C, 60 bar and with catalyst to feed ratio of 10% in various retention times of 0.5, 1.5, 3, 5 and 7 hr. with respect to the experiment's results, properly model was suggested. Another experiment was carried out with same condition but with difference in catalyst to feed ratio of 15% at 3 hr. it was seen that 5% increasing in the catalyst to feed ratio was leaded to 200% increasing in total conversion. Analysis of the all experimental samples has been done with mass chromatography.

Packed bed towers are used in many industries for absorption of gases. For example, they are used for absorbing and control of gaseous air pollutants (like SO2 and NOx, …) and absorption of CO2 from flue gases of fuel combustion for using in drink industries.In this work with respect to many uses of packed bed towers and necessity for having this kind of towers in research centers and university research and educational laboratories, a packed bed tower in laboratory scale was designed and made. After that, by doing some experiments on CO2 absorption, tower was started-up and its working guide manual as a laboratory equipment was prepared. Now, this tower is used in unit operation laboratory of Sahand university of technology.

In general, about 30 percent of crude oil can be recovered naturally. To recover the rest of crude oil, it is necessary to use enhanced oil recovery (EOR) methods. Based on the scientific investigations, there are about ten billion barrels of unrecovered crude oil in Iranian reservoirs. This point indicates the importance of enhanced oil recovery methods. In this paper, the improvements of water injection methods are reviewed. In water injection method, scale formation is one of the main problems. This problem decreases the permeability of core. To prevent this problem, the formation water and injection water should be compatible. In this regard, selection of proper source of water is also important. It can be concluded that the thermodynamic models can be used to predict scale formation. These methods are used to increase the oil recovery efficiency.

Cement industry is categorized in energy intensity industries for high consumption of energy. Energy in cement factories consists of 88% thermal energy and 12% of electric energy. Thermal and electric energy optimization strategies can perform separately or simultaneously.These strategies are divided in to short-term and long-term (with the term of return more than 5 years). Control of the burnability of raw material is known as a short-term strategy and avoidance of quality fluctuation in raw material as long-term strategies. Production of various types of blended cement can reduce both thermal and electric energy simultaneously. This method is determined as a short-term strategy due to its volume of investment. Cement and raw material mills are considered as the main consumers of electric energy. Applying the new mill technologies can also reduce electric energy significantly. But due to the high cost of these technologies these methods are only applied in new projects.