Browsing by Author "Al-Shamlan, Yousef Easa"

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    Mechanistic Investigation of Asphaltene-Induced Fouling in Preheat Trains of Refinery Crude Distillation Units
    (2022-12-02) Al-Shamlan, Yousef Easa; Chapman , Walter G
    Asphaltene precipitation and its subsequent deposition is a growing problem for the oil and gas industry. Not only does it hinder the output of oilfields, but it also causes significant issues in downstream refining. Blending incompatible oils and operations at high surface temperatures are some of the key causes of the instability of asphaltenes, which may lead to fouling and reduction in performance for refinery equipment, such as heat exchangers. In this work, a systematic investigation of crude oil properties and asphaltene behavior at high temperatures and pressures was done for the first time to understand the occurrence and the magnitude of asphaltene-induced fouling in heat exchangers. The physico-chemical characterization of the oil samples used in this study included the application of a novel methodology to separate the crude oil into asphaltene and multiple maltene fractions, with known properties such as molecular weights and densities. Asphaltene polydispersity, onsets of asphaltene precipitation and the amount of precipitated asphaltenes were also investigated, as well as the rheological behavior of the crude oils of interest. A novel experimental apparatus that can operate in batch and continuous flow modes was built and operated to investigate the behavior of crude oil blends at high temperatures and pressures. In batch mode, the setup was used to investigate the effect of temperature on asphaltene stability and precipitation tendency. The extent of fouling at high temperatures was further explored using the configuration in a continuous mode of operation. According to evidence obtained in this work, asphaltene solubility decreases with increasing temperature, which leads to the formation of asphaltene deposits on the wall of the heat exchanger tubes. This mechanism, which might seem counterintuitive, is different from the asphaltene behavior reported in upstream conditions. This study provides a solid foundation and valuable laboratory data to facilitate the development of computer models to predict the occurrence and the magnitude of asphaltene-induced fouling, and for the development of best practices to mitigate this challenging problem commonly found in refineries worldwide.
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    Mechanistic Investigation of Fouling of Heat Exchangers Caused by Asphaltene Deposition in Oil Refineries
    (2019-04-19) Al-Shamlan, Yousef Easa; Vargas, Francisco M.
    Asphaltene precipitation and subsequent deposition is a growing problem for the oil and gas industry. The so-called “cholesterol of the oil” is the heaviest and the most polar fraction of the oil that is well-known to cause flow assurance problems in the near-wellbore region and production tubing. It is also responsible for water-in-oil emulsion stabilization and problems in surface facilities, such as catalyst poisoning and heat exchanger fouling. Extensive research has been conducted over the last few decades to better understand and predict the precipitation and deposition of asphaltenes in the wellbore. However, the knowledge and tools to forecast and mitigate the fouling caused by asphaltenes in downstream facilities are somewhat limited. Refineries all over the world suffer from this problem that has been declared inherent to the heating process itself, which causes a loss of approximately $ 5 million per year on average. In this work, I provide a comprehensive analysis of the general mechanisms by which asphaltenes precipitate and deposit and analyze the variables that govern this multi-step process. A comparison is made between the phase behavior of asphaltenes in upstream and downstream facilities. Moreover, a novel mechanism of inhibition for asphaltene deposition is proposed and validated experimentally. Furthermore, a modeling method has been adapted for the precipitation and deposition of asphaltenes at high temperatures based on the combination of the Perturbed Chain version of the Statistical Associating Fluid Theory Equation of State (PC-SAFT EOS) and a computational fluid dynamics (CFD) model. New insights into the effect of temperature on the asphaltene precipitation and deposition tendencies have been drawn from the experimental and the modeling work performed in this thesis. Unlike the well-known asphaltene precipitation phenomenon driven by pressure depletion in the wellbore, in the case of the heat exchangers, where the temperature is much higher, asphaltene precipitation and subsequent deposition is driven by a temperature gradient. It has been confirmed, that as the temperature increases above a certain range, the solubility of asphaltenes in oil decrease, resulting in a higher accumulation of asphaltene deposits on the tube surface. The simulation results are consistent with field observations. The proposed methods can enable both the manipulation of the process variables to minimize fouling in heat exchangers and the development of alternative methods that have the potential to remove asphaltenes and increase the temperature of the oil to the desired conditions. With this work, I aim to contribute to the understanding and ultimate solution to a long-standing problem that threatens the cost-effective production and refining of crude oils.