Journal of Chemical and Petroleum Engineering
Year:2017 | Volume:51 | Issue:2|Papers Count:8

Catalytic reforming is a chemical process utilized in petroleum refineries to convert naphtha, typically having low octane ratings, into high octane liquid products, called reformates, which are components of high octane gasoline.In this study, a mathematical model was developed for simulation of semi-regenerative catalytic reforming unit and the result of the proposed model was compared with the plant data to verify accuracy of the model. Then, an extra fixed bed reactor was added for upgrading the semi-regenerative process to cyclic process. The optimal condition of the cyclic process was calculated mathematically. The results show that the proposed configuration is capable to enhance the octane number, yield of product, hydrogen production rate, and hydrogen purity by 1.5%, 7.14%, 8.1%, and 13.2%, respectively. The modifications improve the performance in comparison with the current facilities. The results indicate that aromatic and hydrogen production and hydrogen purity improve in comparison with the semi-regenerative reformatting process. Due to the additional swing reactor, which is a spare one, each of the reactors must be removed for regeneration process and, then, be replaced with a rebuilt one.

There has been little interest in the application of hydraulic fracture treatment in Iranian oil fields, thanks to the primarily suitable production rates of the vast oil fields. In this paper, hydraulic fracturing treatment was simulated by different models for a carbonate reservoir in the southwest of Iran. Suitable pay zones were nominated based on the lithology, water-oil saturation, geomechanical properties, and finally in-situ stress conditions – with the optimum option chosen based on a pseudo three-dimensional (P3D) model. In this work, modeling with P3D, finite different method (FDM), and the methods proposed by Perkins, Kern, and Nordgren (PKN) and Khristianovic, Geertsma, and de Klerk (KGD) were performed in order to determine and compare fracture growth geometrical aspects and the required pressure. Comparison of the above-mentioned models confirmed that P3D and FDM provides more reasonable results, while neither of PKN and KGD models was suitable for such a complex condition. Eventually, sensitivity analysis of input data, such as in-situ stress, injection rates, and reservoir geomechanical properties, was performed to evaluate the variation influence of these factors on fracture growth aspects, such as required pressures and geometrical specifications. The results showed that successful hydraulic fracturing treatment not only depended on the controllable parameters like fluid and proppant specifications, but also uncontrollable parameters such as reservoir properties and in-situ stress had to be taken into account. This study can help to select the optimum model in future hydraulic fracture design and implement it in carbonate reservoirs with similar conditions.

In this study, the effect of operating parameters on dispersed phase holdup in liquid-liquid extraction process has been investigated. Three chemical systems (Toluene/Water, Butyl acetate/Water, and n-Butanol/Water) were utilized and holdup was considered in a wide range of interfacial tensions through a Scheibel extraction column. Various rotor speeds were examined on the certain velocities of dispersed and continuous phases. It was found that with increasing rotor speed in a Scheibel extraction column, the drop size was reduced and drops were trapped inside the packed so that an increase in the dispersed phase holdup happened. An obvious increasing trend of dispersed phase holdup was observed as a result of increase in dispersed phase velocity for all systems operating under 2 different rotor speed, namely, 100 and 140rpm. However, the results showed that increase in the velocity of continuous phase would not make significant effect on the holdup. During examining the effect of both rotor speed and dispersed phase velocity, it was found that the holdup would be higher in the chemical system with the lowest interfacial tension compared with two other systems. An empirical correlation was also proposed to predict the dispersed phase holdup with AARE of 8.72%.

In this study, characterization of vanadia supported on Al-modified titania nanotubes (TiNTs) synthesized by the alkaline hydrothermal treatment of TiO2 powders has been reported. A promising catalyst for oxidative dehydrogenation (ODH) of propane was prepared via the incipient wetness impregnation method. The morphology and crystalline structure of TiNTs were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). TiNTs provided large specific surface areas of about 408 m2/gr and 1.603 cm3/gr for pore volume. Rapid sintering and anatase to rutile phase transformation occurred in presence of vanadia in the catalysts at high calcination temperature. Al-promoted TiNTs considerably inhibited the loss of surface area so that a superior catalytic activity was observed in the ODH of propane along with amelioration of structural properties. The results showed 49.7% increase in propane conversion and 22.6% increase in propylene production at 500οC for Al-modified catalyst.

Separation of a racemic mixture of ibuprofen at a low concentration level by supercritical fluid chromatography in a simulated moving bed (SFC-SMB) is investigated by simulation. The feasibility of ibuprofen enantiomers separation has been experimentally examined in the literature. Our simulation results show that separation of ibuprofen enantiomers is feasible by this method, and R-ibuprofen and S-ibuprofen products with purity of over 99% can be obtained, which agrees with experimental data in the literature. For initial studies, the triangular theory is used to find the operating conditions. This simulation shows that the application of the triangular diagram is valuable in cases where none of the operating conditions is available. The operating point conditions, such as streams flow rates and switching time, are obtained with this method. Also, the effect of the location of the selected operating points in the triangular diagram on operating conditions, purity, and concentration of the products are investigated. In triangle theory, the optimal operating point should be near the vertex of the triangle diagram with a safety margin, to obtain products with high purity. The simulation also confirms that selecting the operating point away from the vertex of the triangular diagram will lead to diluted products.

3D modeling of Pd/a-Al2O3 hollow fiber membrane by using computational fluid dynamic for hydrogen separation from H2/N2 mixture was considered in steady and unsteady states by using the concept of characteristic time. Characteristic time concept could help us to design and calculate surface to volume ratio and membrane thickness, and adjust the feed conditions. The contribution of resistance between the membrane and the gas phase could be analyzed by considering characteristic times. The effect of temperature on quasi-steady time (t99) was examined at constant feed flow rate and pressure. As a result, when thickness of membrane was less than the critical amount, the surface resistance was important. According to the results, about 50% mass separation was obtained in the initial 8% period of permeation time. By enhancing temperature, membrane permeation and, consequently, hydrogen separation increased. The CFD results showed good agreement with experimental data.

Butyl stearate as a phase change material was microencapsulated within melamine-formaldehyde resin using emulsion polymerization. Morphology and thermal specification of produced microcapsules were studied by Fourier transform infrared spectroscopy, FT-IR, scanning electron microscopy, SEM, and Differential scanning calorimetry analysis, DSC. FT-IR spectra validated the existence of the butyl stearate in the core of microcapsules. SEM graphs showed that melamine formaldehyde polymer without core was spherical and almost uniform with an approximate size of 2μm and microcapsules of butyl stearate in melamine formaldehyde shell were also spherical with the average diameter of 4mm. DSC results showed that microencapsulation reduced the latent heat of melting and freezing of butyl stearate and increased melting point. The performance of the produced microcapsules was obtained 36.64%. Moreover, the efficiency of energy storage by the microcapsules was obtained about 40%. It was observed that the rate of thermal energy conservation was high during the phase change process of microcapsule core and it was reducing after completion of the melting process.

Wettability alteration has been a sophisticated issue for scientists and reservoir engineers since early 20th century; thus, many investigations have been carried out to determine wettability and enhance it to ideal conditions, which leads to improvement in oil recovery. Dilute surfactant flooding has been ap-proved as one of the noteworthy methods in chemical flooding. Several petroleum reservoirs were rec-ognized as suitable nominees for surfactant/water flooding when screening criteria were established. Surfactant flooding was applied to mobilize the trapped oil in reservoirs. The key mechanism to enhance oil recovery by surfactant flooding was defined as rock wettability alteration. Experimental investigations into the impact of aging and temperature on wettability alteration were performed. Subsequently, core flooding test of surfactant was performed to define the effect of thinned cationic surfactant slug with cyclic 7 days technique (Multi-slug injection) on displacement sweep efficiency in the carbonate core of Bangestan reservoir with its heavy oil reservoir. Moreover, contact angle and interfacial tension (IFT) measurements were made to gain the supplementary information for a surfactant/water flooding. The best concentration of C19TAB was determined by measuring interfacial tension values of the crude oil in contact with surfactant solutions prepared in synthetic brackish water. Results displayed a decrease in residual oil saturation by changing the contact angle and IFT reduction between oil and water. Moreover, aging was known as a significant constraint to change the wettability index to make similar oil-wet condition. Besides, laboratory experiments verified that the influence of wettability alteration was higher than IFT reduction.