Corrosion Mitigation in Crude Oil Process by Implementation of Desalting Unit in Erbil Refinery
The aim of this study is to reduce the percentage of salt and water in the Khurmele crude oil which is chosen for this study in order to mitigate the corrosion of the equipment’s involved in the refining process. The produced oil in Khurmele oil ﬁeld, received by a refinery, usually contains water, mineral salts, and sediments, which should be treated before starting the refining process. In addition, this water normally contains dissolved mineral salts which are usually soluble in the water phase such as chlorides of sodium, calcium, and magnesium. If crude oil is left untreated, it can cause various operating problems such as scaling, corrosion and inorganic fouling of the equipment, and catalyst poisoning of the hydrotreating unit. This study focuses on the optimization of the salt removal and dehydration efficiency of the desalter unit, which currently is a single-stage desalter. Five parameters which are affecting the efficiency of the desalter unit are; temperature, demulsifier injection rates, wash-water injection rates, differential pressure, and electrical current. A systematic study was carried out by variation of one parameter while keeping the other four parameters constant at each time. Basic Sediments & Water (BS&W) will be measured to evaluate the effect of each parameter. Samples were taken with every changed factor and analyzed.., For multiple tests, the extent of the changes and the difference between the results of the first sample with the results of other samples, on the basis of the analysis of the percentage removal of salts and separation of water, were determined in order to get the best results at the end. This leads to the improvement of the operational conditions to good working conditions. It was found that at a crude oil flow rate of 70 -200m3/hr.
The optimum result of salt and water removal was at the temperature 125 °C. The optimum injected concentration of Embreak 2W157D was 20ppm for salt and water removal. The highest efficiency for salt and water removal was reached at 1.3bar differential pressure (∆P = 1.3bar). The best ratio of wash water injection to desalter unit for optimum salt and impurities removal from the crude oil was found to be 6m3/hr. Also, It was found that the electrical voltage value of 23 Kv. gave the optimum collection of water drops. Finally, the overhead system corrosion was due to the hydrogen chloride dissolved in crude oil passed through bad desalting process to downstream of the desalter unit.
4 Effect of the water dilution
Water-related with crude oil can cause huge operational problems. The removal of this water can be readily able by using a desalting/dehydration unit. Wash water rate should be increased to improve the contacting of the oil and water streams. We tried to use different water flow rate to desalter that water flow increased up step-by-step start from 2m3/hr. to 10m3/hr. at the 100m3/hr. crude flow rate, the best efficiency of desalter was at 6m3/hr. water flow rate by depending on the laboratory results. In figure 9 & 10 shows the result. The quality of the wash water is important. Wash water with a high pH can cause stable emulsions. This is normally and an indication of caustic in the system, which can cause the attendance of sodium naphthenates (soaps). These soaps can also be formed with a naphthenic acid containing in crude oil with acid numbers more than 1.0. Five values of wash water were added to desalter were analyzed: (2, 4, 6, 8, and 10) m3/hr. it was confirmed that water injected equal 6% of crude oil flow rate was the best condition.
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