Master of Engineering Science
Chemical and Biochemical Engineering
Fluid Coking is a continuous process to thermally upgrade heavy hydrocarbons into lighter, higher-value products. Fouling of the cyclones in commercial Fluid Coker reactors significantly reduces unit runtimes. The main objective of this thesis is to improve unit reliability by identifying process levers that can mitigate against this phenomenon while minimizing reductions in product quality. This thesis expanded a previous freeboard region model to consider vapour phase cracking and adsorption and developed a novel reactor region model to consider the impact of liquid and vapour phase cracking, vapour-liquid equilibrium, and residence time distribution on product composition. By changing the temperature and flowrate of key process inlets, these two parallel models noted the impact of raising specific process temperatures on increased light end yields, while identifying increasing steam and scouring coke flows as the most effective methods to reduce cyclone fouling while minimizing the impact on Fluid Coker products.
Summary for Lay Audience
Canada has an abundance of natural resources, including the third largest oil reserve in the world. However, this oil is found in a thick, heavy, tar-like form, referred as bitumen, which cannot be used in its natural state. By taking this heavy oil and heating it up to high temperatures (between 500 and 550°C), the large hydrocarbon molecules can break, or crack, into smaller, useful compounds like gasoline and diesel. One reactor that is used for this conversion is called a Fluid Coker, which can run continuously as long as it is fed heavy oil and sufficient heat is provided. However, droplets of the heavy oil can form, adhere and solidify at the wall of the reactor outlet, causing it to be plugged and shut down. Previous studies showed that increasing the reactor temperature would prevent the droplets from forming and clogging the outlet, thus increasing the unit run length. Nonetheless, if the feed into the reactor is heated too much, it will continue to react, thus breaking down into smaller molecules like propane or natural gas, which have a lower value, instead of the desired products. This thesis therefore investigates methods to prevent the droplets from forming and plugging the reactor outlet without overheating the feed in the reactor. This thesis builds two process models, one that investigates near the reactor outlet to study droplet formation, and a second which investigates the products made inside the reactor. Both model predictions are analyzed to ensure that the changes made to prevent fouling at the reactor outlet do not significantly reduce the reactor product quality.
Heaslip, Andrew J., "Mitigation of Fluid Coker Cyclone Fouling with Consideration to Reactor Performance" (2021). Electronic Thesis and Dissertation Repository. 7768.