Commercial ebullated bed hydroprocessors, such as the LC-Finer, are used for the production of synthetic crude oil by upgrading bitumen extracted from the Alberta oil sands. The objective of this thesis was to investigate the impact of an increased vacuum distillation tower bottoms feed fraction on the reactor fluid dynamics (e.g., bed and freeboard phase holdups, bubble characteristics and local fluidization behaviour). Industrial conditions were simulated in a high pressure gas-liquid-solid fluidization system based on dimensional and geometric similitude. Considering important geometric characteristics and matching dimensionless groups, base-case conditions resulted in an ebullated bed of nitrogen, 0.5 wt.% aqueous ethanol, and aluminum cylinders (average lengths and diameters of 7.5 and 3.2 mm, respectively) operating at 6.5 MPa and a gas-to-liquid superficial velocity ratio of 0.78. The proposed scale-down method resulted in high gas holdup conditions similar to industrial measurements. The use of the Sauter mean diameter to account for particle size and shape at the simulation conditions was investigated by comparing glass spheres with diameters of 4 and 1.5 mm to aluminum cylinders with equivalent volume-to-surface area ratios. Local bubble characteristics, including gas holdups, bubble rise velocities, and chord lengths, were then investigated under various operating conditions using a monofibre optical probe. Overall fluid dynamics were studied when increasing the liquid viscosity and varying the gas and liquid superficial velocities due to their relevance for industrial ebullated bed hydroprocessors. Freeboard and bed region gas holdup relations were studied and correlations were developed for gas and solid holdups at the simulation conditions based on the dimensionless groups. Mesophase generation in hydroprocessors due to undesired secondary reactions was also considered for an increased vacuum residue feed fraction. Adding a dispersed immiscible liquid phase which preferentially wetted the particles was therefore experimentally studied at non-simulating conditions using nitrogen, biodiesel, glycerol and various particles, where fluidization behaviour and phase holdups were considerably affected due to particle clustering. A study on the impacts of particle size, shape and material demonstrated the influences of fluid and particle properties, specifically the relative surface energies and viscous forces, on agglomeration due to interparticle liquid bridging.

Commercial ebullated bed hydroprocessors, such as the LC-Finer, are used for the production of synthetic crude oil by upgrading bitumen extracted from the Canadian oil sands. The objectives of this thesis were to experimentally determine bubble characteristics at industrially relevant operating conditions for the design and optimization of the reactor’s recycle pan, as well as to investigate the impact of a catalyst density distribution on the reactor’s fluidization behaviour. High gas holdups have been reported for this type of industrial unit. As a result, high gas holdup conditions were required to assess the commercial unit fluid dynamics. Industrial conditions for the bubble characteristics in the reactor freeboard were simulated in a high pressure gas-liquid bubble column operating at 6.5 MPa using nitrogen and a 0.5 wt.% aqueous ethanol solution. Local bubble characteristics, including gas holdups, bubble rise velocities, and chord lengths, were investigated under various operating conditions using a novel monofibre optical probe designed for high gas holdup and elevated pressure. High gas holdups were achieved (up to 60%) and relatively narrow chord length distributions were observed, where 90% of the bubbles diameters were 1.0 mm or less. The energy dissipated through the distributor plate was shown to have a significant impact on the initial bubble size generated and high gas holdups were also achieved at atmospheric pressure by varying the open-surface area of the distributor. As a result, the impact of catalyst density distribution on local fluidization behaviour was investigated at atmospheric pressure using the previously designed high energy dissipation gas-liquid distributor plate and a 0.5 wt.% aqueous ethanol solution. Fresh and spent hydroprocessing catalysts having relatively narrow and wide density distributions were compared. The introduction of gas greatly impacted the fluidized bed dynamic by rendering the bed-freeboard interface diffuse at low superficial liquid velocity. Bed interface fluctuations were significantly reduced at elevated liquid flow rate due to average bubble size reduction caused by high shearing through the gas-liquid distributor plate. Solid holdup was most affected by the density distribution where bed expansion/contraction was dependent of the liquid flow rate due to varying particle-bubble dynamics.

La sécurité des procédés est une préoccupation majeure dans l'industrie du raffinage et de pétrochimie. Pour les procédés très exothermiques, l'emballement thermique doit être évité. Ainsi, l'objectif de la thèse est la mise en place d'une méthodologie d'étude de la stabilité thermique dans les réacteurs chimiques qui permet de déterminer les zones opératoires de fonctionnement stable du réacteur. Après le développement d'un modèle dynamique de réacteur, la méthodologie consiste à cartographier les zones de stabilité et d'instabilité du système réactionnel en régime stationnaire et dynamique. Le critère de Van Heerden (régime stationnaire) à été généralisé pour application à des systèmes réactionnels complexes. La méthode de perturbation des états stationnaires (régime dynamique) a aussi été intégrée à la méthodologie avec l'analyse des valeurs propres.Cette méthodologie a été appliquée au procédé d'hydroconversion en lit bouillonnant de charges pétrolières lourdes, ceci à l'échelle pilote et industrielle. Des modèles dynamiques adaptés au procédé pilote et industriel ont été développés. Ils tiennent en compte la complexité de la charge ainsi que le schéma des deux procédés. L'étude de la stabilité stationnaire et dynamique a été réalisée. Des cartographies de stabilité/instabilité en fonction des principaux paramètres du procédé ont été tracées. D'après les résultats obtenus, la plage stable pour réacteur pilote est plus large que pour le réacteur industriel. La variation des paramètres du procédé ont le même effet sur les deux réacteurs. Les cartographies de stabilité obtenues sont un outil indispensable pour l'ingénieur lors du design des procédés ou leur opération. / In refining and petrochemistry process safety is a major issue. For highly exothermic processes it is necessary to ensure in a rigorous way the safe that the process operates in safe conditions, hence avoiding thermal runaway. The objective of this thesis was to develop a methodology to determine the operating conditions of reliable operation of chemical reactors. The methodology relies on stationary and dynamic analysis. The stationary stability analysis based on the Van Heerden criterion was generalized to complex chemical systems. The dynamic analysis applies the perturbation theory to definitely determine if a stationary point is stable according to eigenvalue analysis.The methodology was applied to ebullated-bed technology for residue hydroconversion at pilot and industrial scale. Two comprehensive dynamic models that accurately represent the ebullated-bed pilot plant and industrial process were developed for the study. The models take into account a detailed description of the reactive system and the configuration of the pilot and industrial plants: three phases, kinetics and flow characterization. A stationary and dynamic thermal stability analysis was carried out for both configurations and stable/unstable operating regions were identified. The study showed that the pilot plant reactor can operate in a larger domain of operating conditions compared to the industrial reactor while the parameters have the same effect on both reactors. The resulting reactor operation diagrams are a essential guide for engineers in the reactor design and operation practice.