علی اکبر میران بیگی

Determination of wax appearance temperature is a crucial specification in the transportation and storage of crude oil or heavy refinery products same as fuel oils. In this work, to determine wax appearance temperature different applicable methods were tested and developed. At first, the microscopic experiments were applied to different samples. Then the variation of viscosity versus temperature was monitored. To determine a feasible method to be applied in the fields, the variation of viscosity versus temperature was monitored. It was declared that at the wax appearance temperature a deep change in viscosity happened. Eventually, the wax appearance temperature of different crude oil including Iranian or heavy crude oil can be determined by the viscosimetry method. In the related experiments, the negative effect of water sediments and wax crystals was eliminated. It was also declared that the wax appearance temperature could be varied by variation of density, wax content, pour point, and asphaltenes of the samples. To correlate between input and output variables three different modeling methods were tested and implemented. The Artificial neural networks, Neuro-fuzzy, and regression models were tested to derive the most accurate correlation. The statistical studies approved that the regression models have suitable accuracy. The results of the regression model declared that the interaction effect of density and pour point and the effect of asphaltenes as one of the main input variables have the greatest impact on the wax appearance temperature.

In this work, the influence of substituted fullerene on the pour point and rheological behavior of a waxy crude oil sample was investigated. The compositional analysis of crude oil was performed and then the influence of the substituted fullerene on the viscosity and pour point of waxy crude oil was evaluated. The results show that the substituted fullerene reduces the pour point of the waxy crude oil is in all concentrations. Also, the results indicate that viscosity reduces by increasing the concentration of substituted fullerene at constant temperature and shear stress. While viscosity increases by decreasing the temperature of crude oil. It is obvious that by increasing the shear rate the viscosity decreases dramatically. Results show that the shear rate has considerable effect on decreasing viscosity particularly at temperatures below the pour point.

A survey of the literature shows that the source of total acidity in crude oils is due to naphthenic acids available in their hydrocarbon matrices. On the contrary، our studies show that the emulsion water in crude oil is responsible for the main part of total acid number (TAN)، especially for heavy crude oils. In order to avoid metal corrosion in refining facilities and transport lines of crude oil، a special care is needed to control the acidity level of heavy crude oils. In the current work، a new technique based on chemical treatment and centrifugal separation was developed in order to decrease the total acid number of off-spec heavy crude oils. This method was ideally suited for the acid removal of heavy crude oils including water and salt at the level of 0. 05-20 vol% and 10-10000 ptb respectively.

In response to the quality upgrading of producing sweet crude oil for export، four different types of chemical scavengers have been formulated and produced in laboratory and scaled up to bench scale. Cold stripping، affective technical reducing، and removal parameters of the process have been studied on four different sour crude oils by each formulated scavenger. Experimental design was performed to optimize effective parameters by using Minitab-14 software package. Main parameters such as concentration، temperature، and effective time were studied. Under optimal values of 1100 ppm scavenger concentration، 50 °C temperature، and 15 minutes contact time، the H2S content was significantly removed from 950 ppm to less than 15 ppm for an Iranian light sour crude oil.

Hydrogen sulfide is one of the most important impurities in crude oil and natural gas, which is required to be separated before crude refining or gas transport. From the viewpoint of environmental and quality control aspects, many problems rise due to organosulfur compounds available in crude oils especially in oil refining and oil product consumption. In spite of a variety of methods such as stripping and extraction requiring long term programs and high cost processes, chemical scavengers are recently introduced as short-time solutions with a suitable economic potential—especially in sweetening processes of gas and oil industry. One of the methods used for removing hydrogen sulfide is using chemical scavengers. Nowadays, the present technology is ideally used for upgrading gas and crude oil for export purposes. Unfortunately, no standard method has been established for evaluating H2S scavengers yet. Herein, conventional methods for evaluating H2S scavengers are initially studied due to lack of standard methods. Owing to the disadvantages of the conventional methods, a novel method (named RIPI Method) is described to evaluate the performance of synthetic and commercial H2S scavengers in crude oil matrices. The method is basically so dynamic and rapid that at least 20 real samples can daily be analyzed with a relative error of 2.4%.

In this paper, one of the most recent methods of desulfurization of fuel on which there has been a large number of researches since 2001, has been used. To achieve low sulfur levels in fuel, desulfurization of domestic and imported gasoline has been assessed by using several types of ionic liquids (green solvents). Additionally, by using experimental design and statistical software, the variables affecting the desulfurization efficiency have been determined and optimum conditions have been used for higher desulfurization efficiency. In this study, physical and chemical properties of gasoline especially the amount of sulfur content have been determined before and after each extraction. By evaluating the achieved results, it was found that ionic liquids or green solvents have a great impact on removing aromatic sulfur compounds. As a result, ionic liquid extraction can be used as a complementary method for HDS in deep desulfurization.