Modeling a coupled fluidized-bed process for extraction of tar sand bitumen

A thermal process involving coupled fluidized-bed reactors has been developed at the University of Utah for thermal extraction of tar sand bitumen. The development of a comprehensive model for the process was completed during the work reported here. It incorporates models for fluidization hydrodynamics, pyrolysis and combustion kinetics, mass and heat transfer, material and energy balances, and the heat pipes that couple the two fluidized beds. The model can be used to determine the optimum process conditions for maximizing the oil yields and minimizing the energy requirement of the process. It predicts that a pyrolysis temperature of 475°C and a combustion temperature of 600°C are optimum. The simulation results compare well with experimental results obtained for Whiterocks tar sand. The model accounts for differences in yields of different tar sands on the basis of the chemical nature of compounds present in the bitumen. However, due to the complexity of the pyrolysis process, accurate correlations are not possible and more information about the chemistry of pyrolysis of bitumen is needed for making predictions with more certainty.