Iranian Journal of Chemistry and Chemical Engineering
Year:2011 | Volume:30 | Issue:3 (59)|Papers Count:15

The miscible displacement process appears to be an increasingly feasible method for the extraction of oil from depleted reservoirs. How­ever, there is a lack of fundamental understanding of how fracture geometrical characteristics impact the oil recovery efficiency in this type of enhanced oil recovery technique. In this work, a series of experimental tests were conducted whereby the n-Heptane as a solvent displaced n-Decane in the glass micro-models having different fracture geometries. It has been observed that the breakthrough time is decreased with increasing the fractures’ length. In contrast, breakthrough time is increased when increasing the fractures orientation angle related to flow direction. A correlation has been presented for the breakthrough time as a function of fracture length and its orientation.

Water injection is an enhanced oil recovery method which is applied for number of reservoirs especially in the offshore fields around the world. Sea-water injection process is usually associated with important concerns affecting the efficiency, safety, and economy of the operation like formation damage, mineral scaling, early breakthrough and corrosion. Incompatibility between injected and formation waters may result in inorganic scale precipitation in the reservoir and then reduction of oil production rate (productivity loss) and water injection rate (injectivity loss).A comprehensive study supported by reliable modeling and experimental investigation will therefore, significantly improve the success of the operation. In this paper, mineral scale deposition phenomenon in Sirri-C offshore carbonate oil field under water injection is studied and its influence on reservoir performance and production rate is investigated. For this purpose, a seriesAmount and type of scales formed as the result of mixing different portions of these waters have been applied and incorporated with simulation studies. STARS simulator (from CMG 2005) that is capable of evaluating the effect of scale formation on reservoir performance allowing for alteration of permeability and the flow path has been used in simulation study. One of the major contributions of this work is to incorporate the equilibrium conditions, reaction rates and solubility parameters for various scale types in reservoir simulation, so the results can be more realistic.The simulation results show that in Sirri-C oil field, scale formation undermines the productivity index and has a major impact on reservoir performance.

This paper describes the theoretical and experimental investigations of the key components and also the performance analysis of a rotary wheel for using as a solid desiccant dehumidifier and also indirect evaporator cooling system. Solid desiccants have long been used in dehumidification and cooling systems for energy efficiency or reduce electricity. Although many mathematical models on the rotary desiccant wheel have been proposed, the effect of air speed on wheel performance as a momentum equation combined with heat and mass transfer has not been studied. In this study, for the first time the two dimensional mathematical modeling of a desiccant wheel and its numerical simulation using an explicit method considering momentum equation and Ackermann correction factor were described. The results indicated that Ackermann correction factor had a significant effect on performance efficiency. Air stream velocity was one of the most effective parameter on performance and dehumidification rate of wheel. The performance was increased when process air stream velocity decreased. The model suggested the optimum air stream velocity and rotational speed of wheel as 1.86 m s-1 and 10 rad h-1, respectively, obtaining maximum efficiency.

A Real-Time Optimization (RTO) strategy incorporating the fuzzy sets theory is developed, where the problem constraints obtained from process considerations are treated in fuzzy environment. Furthermore, the objective function is penalized by a fuzzified form of the key process constraints. To enable using conventional optimization techniques, the resulting fuzzy optimization problem is then reformulated into a crisp programming problem. The crisp programming problem is solved using both Sequential Quadratic Programming (SQP) and Heuristic Random Optimization (HRO) techniques for comparison purposes. The proposed fuzzy RTO strategy is demonstrated via the Tennessee Eastman benchmark process, and is also compared with a crisp RTO strategy from the literature. Remarkable economical improvement is found over the crisp RTO. In spite of the fuzzified constraints, the proposed strategy yields smooth operation of the process, while maintaining the product quality within the acceptable range.

In this theoretical study, the effect of various types of bypass graft angles on the flow field, has been investigated specially on the temporal Wall Shear Stress (WSS) on the toe, heel and some locations on the bed of the Left Anterior Descending (LAD) artery at the anastomoses areas in the Aorto-Coronary (AC) and Coronary-Coronary (CC) bypasses. Flow fields in both bypasses with angles of 20o, 30o and 40o by 75% stenosis were simulated using Fluent software. The results show high restenosis potential in the side-to-end anastomosis, heel and host artery bed in the CC bypass, and also high restenosis potential at end-to-side in comparing of the AC bypass. Effects of variable graft angles on the WSS on the upper and lower heels in the CC bypass were negligible and the length of the bed influenced by variation of the graft angle was restricted to one diameter distal to the toe in AC bypass and one diameter distal to the lower toe in the CC bypass and finally use of graft angles near 30o was of other important results.

Thermal decomposition of two coal samples obtained from Top Seam Sibi (TSS) and Sore Range Quetta (SRQ) coal fields in their raw and acid washed forms were carried out in an open type tubular pyrolyzer coupled to a gas chromatograph with FID. Elemental analyses were carried out with Scanning Electron Microscope-Energy Dispersive X-rays (SEM-EDX) analyzer. Effect of inherent mineral contents on the yields of pyrolysis products was investigated using acid washed coal samples. It was observed that total volatiles decreased as compared to raw form samples. Deductions in tar and liquid fractions were observed for both the acid washed Top Seam Sibi and Sore Range Quetta coals as compared to their raw forms where as an increase in the gas yield was noted in both the cases.

Free radicals involved in a number of diseases due to the oxidative damage to DNA, lipids, and proteins and which can result in failure of cellular functions. Dried plant bulbs and leaves methanolic and ethanolic extracts were prepared. Total antioxidant activities of the methanolic extracts of Romulea ramiflora and Gagea fibrosa were determined using -carotenlinoleic acid assay. Romulea-Bulb-Ethanol (RBE) extract showed the highest (89.64±1.25%) but, Romulea-Leaves-Ethanol (RLE) extract showed the lowest (33.23±1.13%) antioxidant activity.The lowest antioxidant activity of the Gagea leaves extract (GLE - Gagea-Leaves-Ethanol, 46.18±0.09%) was higher (p<0.05) then Romulea Leaves Extract (RLE - 33.23±1.13%). This may be related with the structure of the plant’s leaves cells. The DPPH radical scavenging assay was used to determine the antiradical activities. Gagea-Leaves-Methanol extract (GLM - 61.16±1.46%) has higher DPPH radical scavenging activity than Romulea-Bulb-Methanol extract (RBM - 51.27±0.94%).Generally leaf extracts have the highest free radical scavenging activity. The total phenolic content of extracts was determined using to the Folin-Ciocalteu method. RBE has the highest phenolic content (74,12±4,6 mg/100 g plant extract). R. rami flora and G. fibrosa have the antioxidant and free radical scavenging activities. These properties are due to the number of the hydroxyl groups of the phenolic compounds, but not amount of them.

In this work, a simple and effective way to modify the support surface is developed and a nanostructure ceramic support to facilitate deposition of a defect-free overlying micro and meso (nano) porous membrane is obtained. To achieve high performance nanocomposite membranes, average pore size of outer surface of support was reduced by dip-coating in submicron and nano a-alumina slurries. In this respect, the effects of several parameters such as: solid content, dipping time, vacuum pressure, heating rate and number of coated layers on microstructure of the fabricated layers were investigated. The obtained results showed that the optimum routine for this technique was twice coating of 5wt% submicron slurry without applying vacuum followed by vacuum dip-coating of 5wt% submicron and 1wt% nano alumina slurry. Pore size of the unmodified membrane support was calculated using permeance data and the obtained result was 540 nm. After twice modification with submicron alumina slurry without vacuum, average pore size of surface decreases significantly. More surface modification by vacuum dip-coating of alumina submicron and nano particles slurries results in decreasing of average pore size of intermediate layers to nanometric scale (<100 nm), respectively. The obtained results are confirmed by mercury porosimetry measurements.

Nanocrystalline ZnO particles were prepared by a novel sonochemical route from zinc acetate and sodium hydroxide without any requirement of calcination steps at high temperature and without surfactants. Variations in several parameters and their effects on the structural (crystal size and morphology) properties of nanoparticles were investigated. Characterizations were carried out by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), IR spectroscopy, Thermal Gravimetry Analysis and Diffrential Thermal Analysis (TGA/DTA).

Nanosized Al2O3 powder is synthesized by thermal Metal Organic Chemical Vapor Deposition (MOCVD) combined with plasma. The effects of reaction temperature, pressure, Al (CH3) 3 (TMA) concentration and reactant gases (CO2 and O2) on the characteristics of the synthesized Al2O3 powders are investigated. The experimental results demonstrate that very fine Al2O3 powders with mean particle size of about 2.5 nm can be obtained at 5.3kPa reactor pressure and 1000oC by the thermal MOCVD. As the pressure is increased from 5.3kPa to 100 kPa, the mean diameter of Al2O3 powders also reaches to 10 nm. In other words, the increase in pressure has a negative effect on the synthesis of nanosized Al2O3. Meanwhile, it is also observed that the increment of temperature can promote the synthesis of fine Al2O3 powder.

Keep in mind the importance of cadmium, cobalt and nickel ions as environmentally and economically strategic heavy metals, the application of two acidic extractants, named bis (2-diethylhexyl) phosphoric acid (DEHPA) and 2-thenoyltrifluoroacetone (HTTA), was assessed for the extraction-recovery of these ions from leached solution of spent rechargeable Ni-Cd batteries.The conditions for leaching of metal contents in solid materials of the batteries were optimized.The effect of parameters influencing the process for achieving to an efficient and selective extraction of Cd, Co and Ni ions from synthetic samples and leach liquor of spent Ni-Cd batteries was investigated.

Absorptive characteristics of polyaniline synthesized in different solvents were studied.Water and mixture of water with other solvents were implemented for polyaniline synthesis.Synthesized polyanilines in powder shape is used as an adsorbent to remove toxic hexavalent chromium from aqueous solutions. Experiments were conducted in batch mode. Removal mechanism involving polyaniline is the combination of surface adsorption and reduction. The kind of solvent used at synthesizing stage can affect the capacity of produced polyanilines for removal of heavy metals including chromium. Synthesized polyaniline in water had the maximum chromium removal efficiency. The morphology study of polyanilines show that the type of solvent used for polymer synthesis affect the morphology of polyaniline.

A new method for the determination of trace copper (II) in food samples by Cloud Point Extraction (CPE) combined with Flame Atomic Absorption Spectrometry (FAAS) is presented and evaluated. The method is based on the fact that hydrophobic complex of copper (II) with sodium diethyldithiocarbamate (DDTC) was formed at pH 6.0 and subsequently the hydrophobic complex was extracted into surfactant-rich phase. Copper (II) in surfactant-rich phase was analyzed by FAAS after dilution the surfactant-rich phase to 0.5 mL by nitric acid in methanol (0.1 mol L-1). The main factors affecting CPE, such as pH, concentration of DDTC and Triton X-114, equilibrium temperature and incubation time, sample volume were investigated in detail. The effect of coexisting ions on the recovery of copper (II) was also investigated. Under the optimum conditions, the detection limit (3s) of this method was 1.1 ng mL-1 for copper (II), and the relative standard deviation was 3.4% (c=100 ng mL-1, n=7). The analytical results for the certified reference tea sample (GBW07605) were in a good agreement with the certified value. The proposed method was successfully applied to determination of trace copper (II) in milk powder and mineral water with satisfactory results.

Riboflavin and protoporphyrin IX are two molecules that participate in oxidation and reduction reactions in the living cell. Changing some functional groups of riboflavin and protoporphyrin IX can provide compounds with self-assembled monolayer properties with wide applications in designing the molecular electronic devices. In this study, the amphiphilic structure of riboflavin and protoporphyrine IX is resulted from the reaction of stearic acid with riboflavin and phosphatidyl ethanol amine with protoporphyrin IX. The reaction products were purified and analyzed by different spectroscopy techniques such as IR, Uv-Vis, fluorimetry and NMR.The electron transfer ability was confirmed by cyclic voltametry. The finding approves that the produced amphiphilic compounds have kept theirs intrinsic properties as well.

FOX-7 (1, 1-diamino-2, 2-dinitroethylene) recently is expected as a relatively new energetic material with high-performance and low sensitivity. The RHF and MP2 levels and DFT method with B3LYP functional with aug-cc-pVDZ basis set have been used for obtaining equilibrium geometry and Rho function (electron density distribution). By the aid of fundamental physical theorems implemented in the Quantum Theory of Atoms In Molecules (QTAIM), the structure, the physical nature of chemical bonds and all Bond Critical Points (BCPs) properties have been determined for FOX-7 at the mentioned theoretical levels. Existence of resonance due to "electron-withdrawing" nitro groups and "electron-donating" amine groups in ethene backbone and intra-molecular hydrogen bonding are shown with AIM analysis and then the resonance structures of FOX-7 are found. Also the calculated IR spectrum of FOX-7 is compared with the experimental IR spectrum. It is demonstrated that the mathematical properties of molecular graph derived from charge density analysis are in good correlation with that of the vibrational normal modes derived from ab initio computations.