Date of Award
Master of Engineering Science
Mechanical and Materials Engineering
Dr. Cedric Briens
Dr. Franco Berruti
Fluidized bed reactors are used extensively in many industrial applications due to attractive features such as good solids and gases mixing, and rapid heat and mass transfer. Fluid Coking is a process that utilizes these attractive properties. It is a non-catalytic thermal conversion process that is used to upgrade bitumen from oil sands in order to produce synthetic crude oil. Particle size control is crucial in Fluid Coking in order to maintain a well fluidized bed and a satisfactory production rate. Therefore, steam is injected through supersonic nozzles in the reactor section of the Fluid Coker, to attrit the coke particles and maintain the desired particle size distribution. Currently, a large quantity of steam is used by the Coker attrition nozzles. If the steam consumption of the attrition nozzles could be reduced, it would reduce the energy consumption and lead to a higher reactor throughput. This is the primary research objective for this thesis work.
The first portion of the research work was focused on the optimization of supersonic nozzle operating conditions, in terms of maximizing the grinding efficiency to minimize the flowrate of attrition gas. The attrition nozzle operating pressure, attrition time, and nozzle scale were tested to determine their effect on the grinding efficiency. Attrition gas consumptions were compared for the same new surface area created in order to find the optimal operating conditions, for which a minimum flowrate of attrition gas is used.
The effect of fluid bed hydrodynamics on jet attrition was investigated next. A specially designed fluidized bed was used to create two hydrodynamics zones, where the superficial gas velocity could be independently adjusted.
Supersonic attrition jets were tested under different hydrodynamic conditions, with different nozzle penetrations where the attrition jet could either straddle both hydrodynamic zones, or be completely enclosed within one hydrodynamic zone. Local bed pressure gradient was measured along the width of the bed to help explain the effect of bed hydrodynamics on jet attrition.
Finally, the effect of the nozzle inclination angle on jet attrition was studied. A supersonic nozzle was used and able to adjust from 0° to 90°. The optimal nozzle inclination angle was found, which generated the largest new surface area. Particle size distribution analysis was carried out to determine the amount of coarse particles ground and fine particles generated for each nozzle angle.
Zhang, Qi, "IMPROVING JET ATTRITION IN FLUIDIZED BEDS" (2011). Digitized Theses. 3399.