جستجوی مقالات مرتبط با کلیدواژه « crude oil » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Hydrocarbon fouling of preheat exchangers causes several detrimental impacts on operation, environment, safety, as well as economy of oil refineries. To investigate threshold fouling models, a variety of hydrocarbon fouling data, such as temperature, oil flow, fluid properties, and geometries of such exchangers, has been gathered from the literature. The most accurate models for predicting the fouling rate are the Polley, Ebert, and Panchal models, with slopes of 0.352, 0.108, and 0.022, respectively, based on fitted curves on the computational fouling rates in terms of comparable experimental values. The sensitivity analysis indicates that the two factors that profoundly affect the fouling rate are the surface temperature and Reynolds number. Using the Polley's equation, the fouling rate in preheat exchangers may be predicted with the highest degree of accuracy, mean sensitivity analysis of 0.29, based on the consistency of calculated and experimental data.

Fouling in heat exchangers is main causes of energy losses in oil and gas refineries. One way to reduce this energy loss in these refineries is to predict fouling resistance. In this paper, the fouling resistance rate is first estimated using the Buckingham's dimensionless groups. The resistance rate is then validated with the experimental data derived from the literature. The results show the relative error of 26.79% with the experimental data, which is rather low and acceptable as compared by those reported in the literature ranged from 40-59%. In general, by estimating the fouling resistance rate, the fouling threshold curve can be plotted and the position of the exchangers relative to it can be checked. The position of the exchangers would allow to reduce the amount of fouling and to stay in non-fouling area with the proper justifications of the operating conditions. The curve is also used to estimate the deposition resistance in the unstable state with the asymptotic model. This model has also been validated with the experimental data from the Australian light oil and Tehran refinery data. It is worthy to mention that the prediction of fouling instability has been less considered in the literature, although with this estimate it is possible to have a better and more regular cleaning program for exchangers and to reduce the problems caused by deposition in exchangers leading to lower operational costs.

Mixing or dispersing operation is an important section in chemical processes. Because of several advantages like: low capital cost, low operating cost, low maintenance cost and low required space; static mixers are applied in many industries. In crude oil desalting process, static mixers for dispersion of the dilution water in crude oil is proposed by this study; which conventionally a mixing valve is used. Type of the static mixer in the applied operating conditions effects on the properties and the stability of the resulted emulsion. In a pilot scale setup, three types of SMV, HMS and LPD static mixers have been investigated; for different conditions of water fraction (2-15%) and crude oil flow rate (86-144 l/h). The experimental results show that SMV outcomes the most stable emulsion which is not appropriate for desalting process. Against, LPD is the optimal choice for the said application, regarding to the emulsion properties.

One of the most important aspects of governing physical processes through rough-walled fractures is the non-linear behavior of flow. The onset of non-linear flow in rock fractures is characterized by critical Reynolds number, which is the main object of this paper. In this paper, the technical aspects of non-linear flow of crude oil through open rock fractures and critical Reynolds number were studied. These issues were studied based on the results of three-dimensional numerical simulation of the Navier-Stokes equations for crude oil flow through rough-walled fractures. The finite volume simulation of crude oil flow through three-dimensional space of rough-walled fractures was performed for a wide range of Reynolds numbers or flow rates. The results of crude oil flow simulations were analyzed based on the Forchheimer’s law. The coefficients of energy losses due to viscous and inertial dissipation mechanisms were derived from the Forchheimer’s law regression on the results. Then, the role of linear and nonlinear energy losses with viscous and inertial dissipation mechanisms was evaluated based on the relation between Reynolds and Forchheimer non-dimension numbers. Finally, the critical Reynolds number was determined for onset of non-linear flow through rough-walled fractures. The results of this study indicate that the Forchheimer’s law appropriately describes the non-linear crude oil flow through rough-walled fractures. By increasing the Reynolds number (or flow rate), the ratio of viscous energy lose from total energy losses decreases non-linearly and simultaneously, the inertial dissipation becomes the dominant mechanism of energy lose. The critical Reynolds number for crude oil is in the range of 30 to 46 for the open fractures of this study. The maximum and minimum of critical Reynolds number follow the minimum and maximum of inertial dissipation coefficient and also the gradient of Reynolds- Forchheimer curve, respectively.

Oil extracted from the underground oil reservoirs contains heavy hydrocarbons.Heavy hydrocarbons include waxes,asphalts and resins that can appear as solids in compounds,which waxes are of particular importance.Changes in factors such as temperature,pressure,compounds of light components in petroleum compounds,etc.Cause the formation of solid paraffin wax deposits in these compounds.The wax precipitate formed mainly contains paraffins,naphthenes and to a lesser extent aromatics.The formation of these sediments in the first stage can block the underground pores, reduce their permeability and reduce the efficiency of oil extraction.In the next stages,the formation of deposits will lead to many problems. For example,it can clog pipes and increase flow resistance, resulting in a drop in flow pressure and,in addition to increasing the power required to pump fluid, cause premature depreciation of the facility.The issue of wax sediment formation and the factors affecting it have been discussed by researchers for many years and different methods have been studied to control it.In this project,by examining 1 nanoparticle of SiO2,as chemical inhibitor, acceptable results were obtained in reducing the wax appearance temperature(WAT).First,using differential scanning calorimetry analysis,a temperature of 250C was obtained for the crude oil cloud point.Then,by adding nanoparticles in different concentrations,this temperature was significantly reduced for different amounts of nanoparticles.Analysis of polarized optical microscopy also shows the change in structure of wax crystals to a disk like after the addition of nanoparticles. To investigate the flow behavior of crude oil,the apparent viscosity parameter was used at shear rates of 0.01,0.1 and 1 rpm and higher and lower temperatures of WAT temperature.Then,using wax deposition of oil samples by two analyzes of X-ray diffraction(XRD) and scanning electron microscopy(FESEM) with EDAX additive to study the dispersion of nanoparticles in wax deposits and changes resulting from the addition of nanoparticles in depositions was paid.In this regard,according to X-ray diffraction analysis,it was found that the nanoparticles had no chemical interaction with wax molecules,but was a confirmation of the results obtained in the analysis of differential scanning calorimetric analysis.The layered structure of the wax precipitate by adding nanoparticles to a fine-grained structure was also one of the results of scanning electron microscopy analysis.

Today, constant economic development at a global scale has become a nationwide demand that cannot be met unless oil production and export are boosted. A central treatment/export plant (CTEP) is a facility for the initial treatment and refining of crude oil. The originally produced crude oil contains a wide range of different compounds that must be removed before the oil can be exported. The CTEP is designed based on the type and quality of the locally available crude oil. It has a handful of different units which are responsible for separating different compounds from the crude so as to produce export-ready oil. For each ppm of increase in the water and/or brine content of the oil, its per-barrel price is expected to drop by 0.08 – 1.3 USD, clearly emphasizing the importance of the initial treatment of the crude.

The dielectric properties of a substance are the properties by which the effect of the utilization of electromagnetic waves can be studied. These properties should be investigated to study the electromagnetic heating method and optimization. In this study, seven oil samples from different fields were investigated, including Asmari, Sarvak, Sohrab, Fahlian, Kuh Mond, Mansouri, and Yaran. In this study, organic compounds and functional groups in crude oil were identified, and their effect on the dielectric property of oil was investigated. By examining the parameters affecting the dielectric property, it was concluded that the more polar compounds the compound has, the higher the dielectric and, therefore, the higher the ability to absorb microwave waves. The amount of dielectric property of Kuhmand, which is part of super heavy oil equal to 2.853 and Fahlian which is part of light oil is equal to 2.006, which shows that the heavier the oil between these two oil samples, the more Its electricity is higher and ultimately has a higher ability to absorb electromagnetic microwave waves. On the other hand, the bonds in the oil themselves also affect the dielectric. According to the FTIR test, the OH, NH, CN and SH bonds in the samples are directly related to the dielectric. The higher the concentration of these bonds is, the higher the dielectric is. In this project, the required links and functional groups within oil samples have been studied and discussed.

During recent years, Gemini ionic liquids (ILs), as a new type of surfactants, have gained much attention due to their significant interfacial activity. Accordingly, use of these materials to reduce crude oil-water interfacial tension (IFT) and to enhance oil recovery is much advantageous. In this study, effects of concentration, temperature and pH on the crude oil-water IFT in the presence of Gemini IL surfactants were investigated. For this aim, alkyl chain length imidazolium based gemini ILs of [C4im-C4-imC4][Br2] and [C8im-C4-imC8][Br2] were synthesized and used. By measuring IFT of the system, under different conditions, the corresponding variations were considered. Results revealed the strong effect of alkyl chain length and concentration on the IFT, leading to, respectively, 72.5 and 97.5% reductions under critical micelle concentrations and temperature of 298.2 K. The Gemini IL surfactants were stable at high temperatures and under a wide range of pH, and that their performance was significantly promoted with these factors. In theoretical investigation, it was revealed that the experimental data were nicely consistent with the Frumkin adsorption isotherm and the obtained parameters with reasonable variations.

Oil-associated salts, depending on their origin, usually contain sodium, potassium, and magnesium. One of the best and most effective ways to separate salt water from crude oil is to use an electrostatic field. In this method, the droplets are polarized in the presence of an electric field and an electrostatic force is created between them, which causes the droplets to approach and coagulate. Using an electric field, the coagulation rate of a dispersed phase in an emulsion can be increased. Therefore, methods based on electric current have been proposed. From an energy efficiency point of view, electrical separation is the best way to break the emulsion and desalinate the oil. Therefore, an electric current is used when the salt water droplets are difficult to separate from the oil. The basic principles of electrostatic desalination of crude oil can be summed up as the application of small droplets of water under an electric field and the formation of larger droplets of water with higher settling velocities.

Asphaltene not only increases the viscosity of crude oil, but it can block oil extraction, transportation, and separation equipment. In the present study, effects of frequency and addition of n-heptane on rheological behavior of two oil samples (i.e., 23 and 71) from Mansouri oil reservoir (Iran) are investigated. Variation of viscosity is used as a criterion for amount of asphaltene separation, and loss factor is employed for distinguish the viscos as well as elastic (liquid or gel-like) behavior of the oil samples. Both viscosity and frequency tests have been conducted at different concentrations of n-heptane. The viscosity tests revealed that addition of n-heptane to the oil samples results in separation of high amount of their asphaltene. Moreover, viscosity of the oil samples continuously decreases by increasing the concentration of n-heptane. Afterwards, the numerical values of loss factor for the oil samples having different concentrations of n-heptane are measured using the frequency test. It’s simply possible to understand liquid or gel-like behavior of oil using this factor.  Finally, by focusing on viscosity decrease as well as liquid-like behavior of oil, the optimum range for frequency and concentration of n-heptane are determined. The results revealed that by adding 75 volume percent of n-heptane to oil sample of 23 in frequency of higher than 33.6 rad.s-1, the liquid-like behavior is seen, and viscosity decreased more than 97%. Moreover, the best results for the oil sample of 71 is obtained during adding 75 volume percent of n-heptane in frequency of higher than 23.4 rad.s-1. The oil sample experiences more than 96% decrease in its viscosity, and it also shows a liquid-like behavior in this condition.

The impact of brine salinity and ion composition on wettability alteration of carbonate reservoir has been studied extensively in recent years. In these researches, the effect of salt water without considering the water-soluble amphiphilic compounds of crude oil has been investigated. In this study, the effect of water-soluble amphiphilic compound of crude oil beside ionic composition of MgCl2 and CaCl2 salt, on wettability alteration of oil-wet calcite surface were investigated. In this turn, distilled water and salt water of MgCl2 and CaCl2 with ionic strength of 0.5 molar were contacted to the crude oil for two weeks to be saturated with crude oil amphiphilic compounds. The effect of these compounds on water properties are examined with pH and total organic carbon (TOC) tests. In the next step, the effect of these compounds on wettability alteration of oil-wet calcite surface were investigated with exposing the oil-wet surfaces to the saturated and pure (without contact with crude oil) water samples and measuring the contact angle of oil droplet. The obtained results show that a low amount of acidic and basic compounds of crude oil (with higher portion of acidic compounds) were dissolved in contacted waters. The wettability of both surfaces which exposed to the pure and saturated waters changed toward water-wet. However, the changes in the presence of pure waters are much more than saturated waters. The results reveal that as well as water-soluble amphiphilic compounds the presence of similar rock composition ions in water can prevent the wettability alteration. In this turn, the wettability alteration of surfaces exposed to the CaCl2 salt waters (in both group of waters) were low and in saturated water was lower.

Measuring the relationship of metallic elements in crude oil and petroleum source rock characteristics is important. The samples were collected in various petroleum refineries and Sample preparation using microwave digestion procedure was performed and the amounts of nickel and vanadium samples by graphite furnace atomic absorption was measured. Crude oil was digested with standard methods and the results obtained with these methods were compared. For sample digestion, factors such as the microwave energy and time required for complete digestion of the sample were optimized in order to have 800 W and 10 minutes. The relative standard deviation of 4.8 and 4.5 per cent and the linear range for nickel and vanadium 0.1 - 100 and 1.0 - 150 micrograms per liter micrograms per liter respectively.

Nowadays, biosurfactants are widely used in various industries due to their wide range of applications. In this paper, the production of rhamnolipid biosurfactant from Pseudomonas aeruginosa PTCC 1340 as one of the most important biosurfactants was investigated using a sunflower oil carbon source. For this purpose, soil samples were contaminated by crude oil with API 33 artificially. In this study, the production of biosurfactant in the removal of crude oil was investigated. Moreover, the results of this study showed that the maximum amount of rhamnolipid production was 4.3 g/L. Rhamnolipid structure was examined and verified by TLC and FTIR analyzes. The study of the properties of the produced rhamnolipid showed that these substances had a high potential in reduction of surface tension, as the produced rhamnolipid reduced the surface tension of water from 69 mN/m to 26.8 mN/m. It  also showed that a considerable stability in mixing with NaCl salt up to a concentration of 15%. Finally, the results showed that Rhamnolipid supernatant  eliminated 75.17% of the crude oil in the soil, while the highest removal efficiency of the crude oil from the soil was 76.92% by SDS surfactant. According to the successfull results, it can be suggested that the produced rhamnolipid biosurfactant can be used as an alternative to chemical surfactants in various industries.

One of the most important aspects of governing physical processes through rough-walled fractures is the non-linear behavior of flow. The main aim of this paper is to investigate the effect of non-linear flow on the hydraulic parameters and deviation from Darcy’s law. To reach this goal, the three-dimensional simulation of crude oil flow inside rough-walled fractures was performed by numerical solving the Navier-Stokes equations supplemented by the continuity equation through application of finite volume technique. The crude oil flow through three-dimensional space of rough-walled fractures was numerically simulated for a wide range of inlet velocity of flow rates. Then, the regime of flow, the deviation of crude oil flow through rough-walled open fractures from Darcy’s law, nonlinear relationship between hydraulic gradient and flow rate, and the effect of non-linear flow on the hydraulic aperture and permeability of fractures were investigated by analysis of crude oil flow simulation. The results of this study indicate that the crude oil flow through rough-walled fractures is non-linear; therefore the hydraulic parameters such as hydraulic aperture and permeability are not constant and highly depend on the flow rate of crude oil. In fact, hydraulic aperture and permeability of fractures decrease non-linearly by increment of flow rate, where these parameters show 10% and 20% of relative decrement, respectively. In addition, the results of regression analysis show that the Forchheimer’s law appropriately describes the behavior of crude oil flow through rough-walled fractures than Darcy’s law. Moreover, the accuracy of Forchheimer’s law is much more than 98%, but the relative error of Darcy’s law reaches to 27%.