Master of Engineering Science
Chemical and Biochemical Engineering
Professor Franco Berruti and Professor Cedric Briens
Fluid CokingTM is a major refining process to upgrade heavy crude oil or bitumen from oil sands. In Fluid CokingTM bitumen is atomized with steam and sprayed inside a high temperature fluidized bed of coke particles where it thermally cracks into smaller molecules. Fluid CokingTM is a carbon rejection process as solid carbon residues are formed during fragmentation into lighter hydrocarbon vapors. New coke deposits over existing coke particles and, consequently, the particle size increases. In addition, particles agglomeration occurs when the injected liquid does not disperse uniformly on individual hot coke particles but reaches, instead, local concentrations sufficiently large to act as a binder for several solid particles. Attrition nozzles are used to control the particle size to maintain the desired flow properties and reactor operability. In fact, fluidization quality degrades while there are too many particles smaller than 50 μm or larger than 600 μm. Some of the large agglomerates may interact with the stripper sheds near at the bottom of Fluid CokersTM, resulting in their fouling and can cause premature reactor shut down.
The simultaneous particle agglomeration and attrition observed in Fluid CokersTM has been simulated at elevated temperature in laboratory scale fluidized unit to study these processes and to develop and apply new technological solutions to reduce the generation of large agglomerates. An experimental technique has been developed to simultaneously perform the spray injection and attrition processes utilizing different nozzle designs and operating conditions, measuring, the initial and the final bed particle size distribution. Various interactions of spray and attrition jets have been tested and a novel liquid dispersion technique has been proposed and studied to reduce the production of large agglomerates.
The results show that, when an attrition jet hits at the base of a spray jet, the formation of large agglomerates is significantly reduced, but a large amount of unwanted fines is then generated. On the other hand, the application of satellite jets at the periphery of spray jets achieved better control of large agglomerates while minimizing fines generation.
Saha, Mithun, "Simultaneous particle agglomeration and attrition in a high temperature fluidized bed" (2012). Electronic Thesis and Dissertation Repository. Paper 876.