Iranian Journal of Chemistry and Chemical Engineering
Volume:26 Issue: 1, Jan-Feb 2007

Two pure bacterial strains capable of rapid degrading methyl tert–butyl ether (MTBE) were isolated from an industrial wastewater treatment plant, identified and characterized. These strains are able to grow on MTBE as the sole carbon and energy sources and completely mineralize it to the biomass and carbon dioxide. The strains were identified as Bacillus cereus and Klebsiella terrigena. Both strains are able to grow in the presence of 48 gl -1 MTBE in water, which is almost the maximum concentration of MTBE in the water. They were able to completely degrade 10 gl -1 MTBE in less than a day. The specific degradation rate of MTBE at optimum conditions were 5.89 and 5.78 g(MTBE) g(cells)-1 h-1 for B. cereus and K. terrigena, respectively. The biomass yield was 0.085 and 0.076 gg-1, respectively. The cultivations were carried out successfully at 25, 30 and 37 °C, while they showed the best performance at 37 °C. Neither of the strains was able to grow and degrade MTBE anaerobically.

An extensive study of Fischer-Tropsch synthesis (FTS) on alumina-supported cobalt catalysts with different amounts of cobalt is reported. Up to 40 wt % of cobalt, is added to the catalysts by impregnation method. The effect of the cobalt loading on the reducibility of the cobalt oxide species, dispersion of the cobalt, average clusters size, water-gas shift (WGS) activity and activity and selectivity of FTS is investigated. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4, decreasing the cobalt surface interaction with the support and decreasing the dispersion of cobalt. The maximum concentration of active surface Coo sites and FTS activity are achieved for the 34 wt% cobalt loading. While the maximum WGS activity is achieved for the 40 wt % cobalt loading. The methane selectivity in the catalyst with 40 wt % of cobalt loading was about 43.7 % less compared to that of the less reducible 8 wt % cobalt catalyst. The C5+ selectivity for the 40 wt % cobalt catalyst was 60.8% higher than that of the 8 wt % Cobalt catalyst.

In this work we have applied the Dense System Equation of State (DSEOS) to electrolyte solutions. We have found that this equation of state can predict the density of electrolyte solutions very accurately. It has been tested for different electrolytes solutions at different temperatures and compositions. A hypothetical binary model has been applied to find the dependencies of parameters of this equation of state on solution temperature and composition. Using such a simple model the heat capacity of NaCl solution was calculated for which the absolute percent deviation is less than 2 %. The DSEOS is tested for the following electrolytes: Na2SO4, MgCl2, MgSO4, KCl, NaCl, and NaBr. We found that the DSEOS predicts the density of aqueous electrolyte solutions mentioned above accurately so that its percent error in density is less than 0.04.

In this work the effect of electrolytes on hydrate formation was investigated. To do so, a new model was used in predicting the hydrate formation conditions in presence of both single and mixed electrolyte solutions. The new model is based on the van der Waals - Platteeuw hydrate equation of state. In order to evaluate the values for the activity of water in electrolyte solutions the simplified version of the Ghotbi-Vera Mean Spherical Approximation (SGV-MSA) model was used. According to the SGV-MSA model the ions in the solutions are considered as charged hard spheres with different sizes. The values of the parameters for the SGV-MSA model are independent of temperature and depend only on the nature as well as concentration of electrolytes studied in this work. These parameters were obtained using the experimental data for the mean ionic activity coefficient of the single electrolyte solutions at 298.15 K. In the case of the mixed electrolyte solutions a new mixing rule was introduced to obtain the activity of water in aqueous electrolyte solutions. The results show that the proposed model can predict the hydrate formation for the systems containing single or mixed electrolyte solutions with good accuracy compared to the experimental data available in the literature. In addition, the results obtained from the proposed model were favorably compared with those obtained from the previously used models.

Thirty five fungal strains which isolated from vegetable wastes, were screened for the use of polygalacturonic acid as the sole carbon source. Twenty five isolates were positive for polygalacturonase activity in cup-plate assay, as evidenced by clear hydrolysation zones. The most productive strain was determined by measuring clear zones formed around colonies stained with ruthenium red. The highly pectinolytic fungal strain was tentatively identified as Tetra-occosporium sp. according to morphological characterization. The cultivation of the selected strain (Tetracoccosporium sp.) in liquid media resulted in high quantities of polygalacturonase enzyme. Maximum polygalacturonase activity was reached in 48 h of growth in the pectate medium. The collected polygalacturonase had optimum activity at pH 5.0 and maximal activity of the enzyme was determined at 35 °C. Mn2+, Ag3+ and surface active detergents such as tween 20 and triton X-100 increased the polygalacturonase activity by 37 % and EDTA enhanced the activity up to 125 %.

Micro flora of the effluents from a dairy factory in Tehran(Pegah Dairy Processing Plant) were isolated and screened for their ability to reduce the organic matter content and COD of the effluents. 10 bacteria were selected due to reduction in COD content from the 4th to 6th day of incubation at 30 °C and pH =11. Highest COD reduction were obtained by two isolates, BP3 and BP4, 70.7 % and 69.5 %,, respectively (The initial COD concentration was 3000 mg/l and reduced to 880 and 920 mg/l).After optimization of the condition for test organisms, big reductions in COD, carbohydrate, fat and protein content of the effluents were observed by BP3 up to 84.70 %, 98 %, 45.30 % and 53 %, respectively. The mixture of BP3 and BP4 did not show the good results as the BP3 alone. Therefore, BP3 has been selected as the most efficient microorganism for the system.The overall efficiency of the system will be increased if it is added to anaerobic activated sludge tank

The effect of membrane molecular weight cut off (MWCO) at three levels (10, 20 & 50 kD) on dynamic behavior of permeate flux (JP), hydraulic resistances (total hydraulic resistance, RT; reversible fouling resistance, Rrf; irreversible fouling resistance, Rif and membrane hydraulic resistance, Rm) and milk solutes rejection (protein, RP; fat, RF; lactose, RL; minerals, RM and total solids, RTS) are studied for the ultrafiltration of milk. Experiments are carried out using the pilot plant UF membrane system equipped with a spiral wound module and a polysulfone amide membrane. A three-stage strategy based on a resistance-in-series model (boundary layer-adsorption) was used to determine the different hydraulic resistances. The results showed that the JP decreases greatly with increasing the process time, but the JP values obtained for 20 kD were considerably higher than 10 kD & 50 kD during the whole process. RT increased during operation at all levels of MWCO, but the hydraulic resistance values for 50 kD were significantly greater than 10 & 20 kD. Results for milk solutes rejection showed that the RP and RF are almost constant with process time at the corresponding MWCO, whereas the RL, RM and RTS significantly increased.

An Artificial Neural Network (ANN) was used to analyse the capillary rise in porous media. Wetting experiments were performed with fifteen liquids and fifteen different powders. The liquids covered a wide range of surface tension (15.45-71.99 mJ/m2) and viscosity (0.25-21 mPa.s). The powders also provided an acceptable range of particle size (0.012-45 μm) and surface free energy (25.54-63.90 mJ/m2). An artificial neural network was employed to predict the time of capillary rise for a known given height. The networks inputs were density, surface tension, and viscosity for the liquids and particle size, bulk density, packing density, and surface free energy for the powders. Two statistical parameters namely the product moment correlation coefficient (r2) and the performance factor (PF/3) were used to correlate the actual experimentally obtained times of capillary rise to: i) their equivalent values as predicted by a designed and trained artificial neural network; ii) their corresponding values as calculated by the Lucas-Washburns equation as well as the equivalent values as calculated by its various other modified versions. It must be noted that for a perfect correlation r2=1 and PF/3=0. The results showed that only the present approach of artificial neural network was able to predict with superior accuracy (i.e. r2 = 0.91, PF/3=55) the time of capillary rise. The Lucas-Washburns calculations gave the worst correlations (r2 = 0.11, PF/3 = 1016). Furthermore, some of the modifications of this equation as proposed by different workers did not seem to conspicuously improve the relationships giving a range of inferior correlations between the calculated and experimentally determined times of capillary rise (i.e. r2 = 0.24 to 0.44, PF/3 = 129 to 293).

The bubble effectiveness in liquid phase cylohexane non-catalytic oxidation process is discussed in this paper. Then the bubble effectiveness and a new proposed kinetic model are used in the mathematical model of the industrial reactor for the cyclohexane non-catalytic oxidation process. Furthermore, simulation and optimization based on this reactor model are carried out. The results of simulation show that the reactor model using the concept of bubble effectiveness agrees better with the plant data, and the results of optimization are much better than the present industrial production level, which will help to improve the operation of the reactor section and design of new installations.

This study concerns the scope to improve water flooding in heterogeneous reservoirs. We used an existing, in-house developed, optimization program consisting of a reservoir simulator in combination with an adjoint-based optimal control algorithm. In particular we aimed to examine the scope for optimization in a two-dimensional horizontal reservoir containing a single high permeable streak, as a function of reservoir and fluid parameters, which we combined in the form of 10 dimensionless parameters. We defined the parameter NPVimprovement to indicate the improvement in net present value (NPV) that can be achieved through optimization. For initial screening of the effect of the dimensionless parameters, a two-level D-optimal design of experiments (DOE) technique was used to obtain a linear response surface model with the aid of 11 water-flooding simulations. As a result 8 dimensionless groups were selected for more detailed analysis, and a full quadratic NPVimprovement model was constructed using a three-level D-optimal design using 50 simulations. It should be reminded that all the D-optimal matrix designs were generated by using commands of statistics Toolbox of MATLAB software. Finally, Pareto charts were plotted to visualize the sensitivity of the model as a function of the dimensionless parameters. Based on the present model we can draw the conclusion that the parameters (relative streak length), (relative streak permeability) and the ratio of water cost and oil price have the largest effect on the scope for obtaining a high value of NPVimprovement

FThis study aimed to construct the hydrate three-phase equilibrium curves for two typical Iranian gas reservoir samples using a high-pressure visual cell. To do so, complete analysis of the reservoir fluids was obtained by different techniques of composition analysis i.e. gas chromatography (GC) and detailed hydrocarbon analysis (DHA). Using high-pressure visual cell the hydrate phase equilibrium curve was obtained by measuring the hydrate formation temperature in each pressure level. By means of commercial hydrate software, hydrate formation temperature was predicted in each specified pressure level. Comparing the results showed that the experimental data are in good agreement with the simulator results. Using the experiments results, hydrate phase equilibrium curves were constructed in order to depict the safe and unsafe regions of the hydrate formation zones for two typical Iranian gas reservoir samples.

Ammonium perchlorate particles have been dried in a laboratory spouted bed dryer (screen-bottomed type) which is categorized as a fluidized bed dryer. The solid particles obtained in this process of drying were semi-porous and known as the group D of Geldart classification. The variations of moisture content with resident time, the effects of bed height on the pressure drop, and the influence of moisture content on drying rate were investigated. In this project, the air flow rate and the moisture diffusivity were determined. A model to determine the minimum spout velocity and also a model based on the Fick’s law were obtained which predicted the experimental data very well.