Pyrolysis of bitumen impregnated sandstones: A comparison of fluidized-bed and rotary-kiln reactors

The recovery of hydrocarbon values from the bitumen impregnated sandstones of Utah can be accomplished by any of several mining-surface recovery techniques. These processing strategies include aqueous separation, diluentassisted aqueous separation and solvent extraction of the bitumen from the sand and pyrolysis of the tar sand to produce a bitumen-derived hydrocarbon liquid. A series of stationary state pyrolysis experiments have been completed with the mined ore from the Whiterocks tar sand deposit in both rotary-kiln and fluidized-bed reactors. Four stationary-state experiments were conducted in the rotarykiln at a reactor temperature of 798 K and solids retention times ranging from 9 to 31 minutes. The sweep gas flow rate, 77.5 SCFH, was the same in all four experiments. The C5 plus hydrocarbon liquid yield decreased with increasing solids retention time at a fixed operating temperature in both the fluidized bed and the rotary kiln. The liquid yield obtained with the rotary kiln was higher than that obtained with the fluidized bed at comparable operating conditions. The bitumen-derived hydrocarbon liquids produced in the rotary kiln reactor were significantly upgraded relative to the native bitumen: the viscosity was decreased by several orders of magnitude when compared at the same temperature; the pour point was reduced by 110 - 125 "F; the Conradson Carbon residue was decreased by a factor of 3-6; the API gravity increased from 11.9 API to 18-20 API; and the residual fraction (>1000 F) was reduced from 59.5 wt.Z to 8-13 wt.Z. The total asphaltene content as determined by gradient elution chromatography was reduced by 50-63Z.