Oil Desalting Research Articles

Crude Oil Desalting Using Hydrocyclones

Dilute dispersion/emulsion of ultrafine water droplets containing a variety of salts is usually present in crude oil. It is very useful to remove the water and the dissolved salts, so that corrosion, plugging, and fouling of equipment can be prevented. Electrical desalter is an effective method in crude oil desalting. In order to overcome the shortcomings of electrical desalting system, such as larger equipment volume, complex high tension electricity system, a new process of crude desalting that are based on hydrocyclone technology is designed. Preliminary industrial experiments have been carried out to prove the feasibility of desalting using hydrocyclone. The effects of several dimensionless units, such as Reynolds number, Euler number and pressure drop ratio were studied. An increase in inlet Reynolds number will decrease the pressure drop ratio. With an increase in inlet Reynolds number, Euler number increases gradually. Under the condition that Reynolds number of inlet is ranging from 5000 to 5800, the water concentrations can decrease from 5 vol% ∼ 8 vol% to less than 0.40 vol% and the salt concentrations is reduced from less than 8 mg L −1 to 3 mg L −1 after handled.

06/02528 Building inferential estimators for modeling product quality in a crude oil desalting and dehydration processAbdul-Wahab, S. et al. Chemical Engineering and Processing, 2006, 45, (7), 568–577

06/02528 Building inferential estimators for modeling product quality in a crude oil desalting and dehydration processAbdul-Wahab, S. et al. Chemical Engineering and Processing, 2006, 45, (7), 568–577

Building inferential estimators for modeling product quality in a crude oil desalting and dehydration process

Desalting/dehydration plants (DDP) are often installed in crude oil production units in order to remove water-soluble salts from an oil stream. This paper describes the development of simple inferential estimators for product quality of the desalting/dehydration process. The inferential estimators were constructed to capture the relationship between the product quality of the plant and the process input variables. Five input process variables that are known to influence product quality were considered. These include temperature, settling time, mixing time, chemical dosage, and dilution rate. The product quality of the desalting/dehydration process was identified by the salt removal and water cut efficiencies. Hence, inferential estimators were used to infer the salt removal and water cut efficiencies from the five input process variables. These inferential estimators were constructed based on the application of both multiple linear and principal component analysis as well as non-linear regression. The results indicate that the settling time and dilution water were the common variables in estimating both the salt removal and water cut efficiencies. On the other hand, temperature contributed insignificantly in predicting the two efficiencies. Furthermore, the inferential model predictions were compared with the experimental readings. It was found that the actual dependence of the performance of the desalting/dehydration process on process parameters could not be described only by linear relationships. Addressing the non-linearity of the process variables overcame the problem of inaccurate predictions. Future studies based on the use of computational intelligence techniques and design of experiments to get better models are suggested as well as the use of response surface methodologies to determine the set of parameters that will optimize the process efficiencies.

A Computational Intelligence Based Approach for the Analysis and Optimization of a Crude Oil Desalting and Dehydration Process

Water and salt associated with oil production can cause considerable operational problems. Therefore, desalting/dehydration plants are often installed in crude oil production units to remove water-soluble salts from an oil stream. The performance of the desalting/dehydration process depends on various process parameters interacting with each other. These parameters include concentration of demulsifying agents, heating, wash water, salt concentration, and rate of mixing with wash water. In this study, the performance of the desalting/dehydration process was evaluated by calculating the salinity and water cut efficiencies that are expected to depend on the values of these five process parameters. The work concentrated on modeling and optimizing the performance of the desalting/dehydration process system. It was an attempt to develop and apply an artificial neural network (ANN) as a modeling technique for simulating and optimizing the desalting/dehydration process system. ANNs were selected due to their potential for modeling highly nonlinear relationships of the parameters involved in the desalting/dehydration process system. The neural network model predictions were compared with the actual observations, and the results were shown to be consistent. The prepared neural network model was then used to optimize the performance of the process. A composite objective function for measuring the performance of the desalting process was used in conjunction with the prepared ANN within an optimization model. The outcome of this research will help in improving oil production operations and therefore in lowering the cost per barrel produced.

Experimental investigation of crude oil desalting and dehydration

Oil produced in most oil fields is accompanied by water in the form of an emulsion that must be treated. In addition, this water normally contains dissolved salts, principally chlorides of sodium, calcium, and magnesium. If crude oil is left untreated, when it is processed in a refinery the salt can cause various operating problems. This paper investigates experimentally the effect of five factors (gravity settling, chemical treatment, freshwater injection, heating, and mixing) on the efficiency of the dehydration/desalting process for a Kuwaiti crude oil and a commercial demulsifier (Servo CC 3408). These factors are systematically varied and efficiency is analyzed. Two efficiencies are defined: a Salt Removal (S/R) efficiency and a Water Cut (W/C) dehydration efficiency. The investigation was carried out through changes made to a single factor at a time as well as multiple variations of factors. Plots, based on experimental data, showing the variation of the two efficiencies as a function of the various factors are given. Two main conclusions are drawn for the system studied. First, excessive amounts of a demulsifying agent had adverse effects on the desalting/dehydration process. Secondly, the most important factor that improved both efficiencies (S/R and W/C) was found to be the settling time. Efficiencies up to 75% were obtained at settling times of 5min. This factor was simulated in the experimental runs through the use of a centrifuge. The implication of this finding is that future desalting/dehydration systems for the oil and demulsifier studied should be based on centrifugal techniques.

5591326 Catalytic process for crude oil desalting: Shih Stuart S Cherry Hill, NJ, United States assigned to Mobil Oil Corporation

5591326 Catalytic process for crude oil desalting: Shih Stuart S Cherry Hill, NJ, United States assigned to Mobil Oil Corporation

5591326 Catalytic process for crude oil desalting: Shih Stuart S Cherry Hill, NJ, United States assigned to Mobil Oil Corporation

Biological removal of organic sulfur from petroleum feedstocks offers an attractive alternative to conventional thermochemical treatment due to the mild operating conditions afforded by the biocatalyst. In order for biodesulfurization to realize commercial success, it will be necessary to design reactors that allow for sufficient liquid/liquid and gas/liquid mass transfer while simultaneously reducing operating costs. In this study, the use of electric field contactors for the biodesulfurization of the model compound dibenzothiophene (DBT) as well as actual crude oil was investigated. The emulsion phase contactor (EPC) creates an emulsion of aqueous biocatalyst in the organic phase by concentrating forces at the liquid/liquid interface rather than by imparting energy to the bulk solution as is done in impeller-based reactors. Characterization of emulsion quality and determination of rates of DBT oxidation to 2-hydroxybiphenyl (2-HBP) were performed for both batch stirred reactors (BSR) and the EPC. The EPC was capable of producing aqueous droplets of about 5 μm in diameter using 3 W/1 whereas the impeller-based reactor formed droplets between 100 and 200 μm with comparable power consumption. The presence of electric fields was not found to adversely affect biocatalytic activity. Despite the greater surface area for reaction afforded by the EPC, rates of DBT oxidation in both reactors were similar, demonstrating that the biocatalyst used (Rhodococcus sp. IGTS8) was not active enough to be mass transport limited. The EPC is expected to have tremendous impact on reactor operating costs and biocatalyst utilization once advances in biocatalyst development provide systems that are mass transport limited.

Dehydration of oil waste emulsions by means of flocculants

Oil waste emulsions are formed in the course of pumping petroleum crudes and products and are collected from the surfaces of equipment in recirculating water systems and wastewater disposal facilities (oil separators, sand traps, oil traps, holding pits for accidental spills, settlers, ponds, sludge accumulators, and so on). Emulsions are also obtained in the course of cleaning equipment in crude oil desalting and dehydration units. Such emulsions are stable, structurized systems that are very resistant to dewatering by heating and settling in separator tanks. In order to break stabilized emulsions, i.e., in order to ensure complete coalescence of drops when they collide, it is not sufficient to increase the forces of mutual attraction of drops at the moment of collision; in addition, the protective shell must be either destroyed or weakened. Demulsifying agents, or surfactants, will displace the stabilizers. This report is concerned with demulsifier efficiency.

Dielectric strength and electric conductivity of liquid dielectrics containing water

1. The breakdown resistance of all liquid dielectrics is independent of the amount of dissolved water but is dependent on the quantity of emulsified and microemulsified water. 2. Changes in the diameter of the emulsified water droplets in liquid dielectrics within the range of 0.5 to 50 μ has no effect on dielectric strength of the dielectrics. 3. Secondary processes in a series of other processes have a relatively minor effect on the reduction in dielectric strength of liquid dielectrics (for crude oil containing 0.3% water, this effect does not exceed 10% of the total); as the water content is increased, the effect of secondary processes in reducing the dielectric strength becomes more important. 4. For aqueous emulsions of organic liquids, there is a limit depending on water content that governs whether they can be regarded as liquid dielectrics or as conductors of the second type; for crude oils, this limit corresponds to a water content of about 1%. 5. The theories of Hemant and Boning do not reflect the physical significance of the breakdown process of liquid dielectrics containing water and hence cannot be regarded as correct. 6. The breakdown of pure liquid dielectrics, as is evident from the results of our investigations, can be explained by the gas theory of shock ionization in the bulk. 7. The results obtained from these studies can be used in controlling and monitoring the process of crude oil dehydration and desalting, in the design of instruments to determine the amount of emulsified water in crude oil, and in the design of electrodehydrators and development of an automatic control system for operation of such equipment [11, 12].

Desalting of oils from the Kotur-Tepe field

1. Oil from the Kotur-Tepe field belongs to the group of oils that are hard to desalt because of their capacity to form stable, highly dispersed, hydrophobic emulsions which are only slightly broken down in electrodehydrators without utilization of deemulsifiers. 2. Two-stage desalting of oil in the electrolytic desalting unit with the NChK deemulsifier and a supply of 3–5% fresh washing water does not warrant the required oil quality. At a supply of 1.2 kg of NChK/ton, the content of chlorides in the desalted oil equals 150–250 mg/liter. Analogous results are obtained during desalting of oil with NP-1 sulfonol containing 36% active substance (83 g/ton). 3. When effective nonionic deemulsifiers are used, the emulsion is broken down completely, and the salt content of the oil is lowered to 37 mg/liter by disolvan 4411 supplied at the rate of 43 g/ton and to 35 mg/liter by proxanol supplied at the rate of 38 g/ton. 4. The rather complete clarification of the water in the electrodehydrators during operation with effective nonionic deemulsifiers enables us to replace fresh water by sea water for the washing of the oil, which is very important in the Krasnovodsk Oil Refinery. When fresh water is replaced by sea water (6–8% water supply), the residual salt content in the oil changes: from 38 to 33 mg/liter during operation with disolvan 4411, from 30 to 40 mg/liter with proxanol 146 and from 53 to 79 mg/liter with OZhK. 5. Since there is a severe shortage of fresh water in the Krasnovodsk Oil Refinery, and the cost of this water is high (35–70 kopecks per m3), utilization of nonionic deemulsifiers is very profitable (radical improvement of the desalting of oil and saving of fresh water).

Technical and Commercial Developments-Crude Oil Desalting

Technical and Commercial Developments-Crude Oil Desalting