Browsing by Author "Sadeghi Yamchi, Hassan"

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    Effect of Refining on Asphaltene Property Distributions
    (2014-07-10) Sadeghi Yamchi, Hassan; Yarranton, Harvey
    Asphaltenes are a solubility class and are defined as the part of a crude oil that is soluble in toluene and insoluble in n-heptane. Asphaltene precipitation, and subsequent fouling, is a potential issue in refining when feedstock and/or process streams are blended. While asphaltene precipitation from native crude oils can be predicted from a small set of measurements using regular solution based models, these precipitation models have not been applied to reacted crude oils. This study is part of a larger project to extend a previously developed regular solution based precipitation model to reacted crude oils. The three properties required for this model are density, molecular weight, and solubility parameter. The objectives of the study are: 1) to determine the distributions of these properties for self-associated asphaltene nanoaggregates; 2) model asphaltene precipitation from solutions of n-heptane and toluene (heptol) using regular solution theory. To determine these distributions, n-heptane extracted asphaltenes from hydrocracked and thermocracked samples were fractionated into solubility cuts. The asphaltenes were dissolved in toluene and then partially precipitated at specified ratios of heptane-to-toluene to generate sets of light (soluble) and heavy (insoluble) cuts. The molecular weight and density were measured for each cut. The refractive index and elemental analysis were also measured for potential use as correlating parameters. The density distributions were determined directly from the data. The molecular weight data were fitted with a self-association model in order to predict the distributions at any given concentration. Asphaltene solubility parameters were determined by fitting the regular solution model to asphaltene precipitation yield data. The asphaltenes were found to include both associating and non-associating asphaltenes. The amount of non-associating material and the density of the asphaltenes increased as the extent of reaction increased. Thermal cracking appeared to have little effect on asphaltene average monomer molecular weight or the distribution of nanoaggregate molecular weights. Hydrocracking significantly decreased both the average monomer and nanoaggregate molecular weights. It was found that both hydrocracking and thermal cracking made asphaltenes denser and significantly less soluble. The onset point of precipitation for both cases moved to zero concentration of n-heptane in heptol solutions. A previously developed regular solution model was adapted to calculate solubility parameter distribution reacted asphaltenes. The model was modified as follows: density was correlated to the cumulative mass percent of asphaltenes; 2) the correlation of the asphaltene solubility parameter to molecular weight was retuned. Two methods were used to represent the asphaltene molecular weight distributions: the gamma distribution and the distribution from an association model. Since the solubility model predictions are affected by the shape of the molecular weight distributions, different sets of solubility parameter were calculated for each. In general, the gamma distribution adequately represented the molecular weight distributions for both native and reacted asphaltenes and better fit asphaltene yield data.
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    Liquid-Liquid Equilibrium Studies of Solvent and Bitumen Systems
    (2021-01-13) Sadeghi Yamchi, Hassan; Hazzanzadeh, Hassan; Abedi, Jalal; Li, Xiaoli; Jasso, Martin; Moore, Robert; Mehta, Sudarshan
    Solvent-aided and solvent-based heavy oil recovery methods have gained interest as alternatives to the conventional steam-based thermal recovery methods. Dimethyl ether (DME), propane, butane, and their mixtures (LPG) are considered proper solvents for low temperature upgrading and solvent-based bitumen and heavy oil recovery processes. One key prerequisite for simulation and optimization of these recovery processes is the liquid-liquid thermodynamic equilibrium (LLE) data of solvent and bitumen mixtures. This study presents measurements and modeling studies of the LLE of solvent (butane, DME, and LPG) and Athabasca bitumen mixtures. Phase behavior measurements including equilibrium compositions (K-value), density, and viscosity of the light phase as well as saturation pressures of the mixtures are measured at temperatures and pressures up to 100 °C and 3.5 MPa, respectively. To model LLE data of solvent/bitumen system, detailed characterization of the light and heavy cuts (upgraded oil and asphaltenes) are conducted using a methodology that combines the gel permeation chromatography (GPC) with the simulated distillation results (SD) to provide a molecular weight distribution. Then, two pseudocomponents (one representative of maltenes and the other representative of asphaltenes) are defined based on the characterization, and LL K-values are estimated for each component. Non-Random Two Liquid (NRTL) model is then tuned to represent the experimental compositional data and K-values. Finally, the implementation of LL K-values for simulation of asphaltene deposition in porous media is described. A modified approach is presented based on the LL K-values and a reaction-based non-equilibrium mass transfer model. The interplay of viscous fingering and asphaltene deposition during the injection of solvent is studied and sensitivity of the simulation results on grid size is investigated.