Fluidization of coked sands and pyrolysis of oil sands in a fluidized bed reactor (Abstract only)

A 7.62 cm diameter fluidized bed oil sands pyrolysis system was designed, installed, and operated. The studies conducted with this system included coked sands and oil sands feeding using a bin discharge auger feeder, the withdrawal of solids from a fluidized bed using a modified Lvalve, fluidization-defluidization experiments using different fluidization modes, and the determination of minimum fluidization velocities at ambient and elevated temperatures and pyrolysis of the PR Spring oil sands. The feeder study results indicated that the modified Acrison bin discharge feeder with a water cooled E-auger provided linear and reproducible oil sands feed rates from 1 to 10% of the full range of the feeder motor speed controller. The feeder study confirmed that predictable and reproducible feed rates were possible with a solid fight C-auger when feeding coked sands. The coked sands withdrawal device was a modified pneumatic L-valve with an auxiliary aeration port. The variables studied included the lengths of the vertical and horizontal sections, the location of the primary gas injection port, and the injection gas flow rates. The results indicated that the effect of the length of the vertical section on solids withdrawal rate was not a significant variable. Solids flowed freely due to gravity when the length of the horizontal section was less than two times its diameter. The solids flow rate decreased as the length of the horizontal section increased. The maximum solids flow rate was obtained when the injection gas port was located 1.3 cm behind the center line of the vertical section. The solids flow rate decreased when the gas injector was moved in either direction. Fluidization studies were conducted with the coked sands produced from previous oil sands pyrolysis experiments. The fluidization experiments indicated that the coked sands, which were group B particles according to Geldart's classification system, had a minimum fluidization velocity of 1.41 cm/s in the regular fluidization mode, 1.35 cm/s in the reduced pressure fluidization mode, and 1.62 cm/s in the pull fluidization mode. Three different fluidization modes have been identified and the pressures in the reactor for the three modes have also been analyzed. The fluidization curves obtained with a tapered gas distributor have been obtained. Fluidization studies at elevated temperatures (>373 K) indicated that empirical minimum fluidization velocity correlations developed at ambient temperatures were incapable of predicting minimum fluidization velocities at elevated temperatures. An alternative relationship was developed in this study in which the minimum fluidization velocity was determined to be 2.03-2.02x10~3T cm/s in the temperature range from 297 to 623 K. The mined oil sands ore used in the pyrolysis studies was obtained from the PR Spring oil sands deposit. The influence of reactor temperature and solids retention time on the product distribution and yields and on the total liquid product qualities was determined in the pyrolysis process variable study. The total liquid yields increased as the reactor temperature increased in the range from 723 to 773 K at a fixed solids retention time of 30 minutes. A maximum yield of 84.2 wt% was obtained at a reactor temperature of 773 K. The liquid yields decreased slightly as the reactor temperature was increased from 773 to 798 K. The coke yields decreased as the reactor temperature increased from 723 to 773 K. The coke yield was insensitive to the reactor temperature above 773 K. The hydrocarbon gas (Cj to C4) yields increased with reactor temperature from 723 to 798 K. The total liquid product yields ranged from 80 to 84 wt% based on bitumen fed to the reactor as the solids retention time increased from 18.5 to 39 min at a constant reactor temperature of 773 K. The coke yields increased slightly with solids retention time. The hydrocarbon gas (C] to C4) yields were insensitive to solids retention time. The shortest solids retention time achieved for the pyrolysis of the PR Spring oil sands in this system was 18.5 min. The reactor had a tendency to plug with unreacted oil sands at solids retention times below about 20 min. The total liquid products produced in the pyrolysis studies were significantly upgraded relative to the bitumen.