Similitude studies in three-phase ebullieted bed reactors

The length of a commercial reactor, in three-phase ebullieted bed processes with pelleted catalysts, for the processing of heavy oils, bitumen and bitumen-derived liquids are long due to the requirement of low space velocities. The reactor length, for laboratory scale studies of such processes, can be reduced by reducing the superficial liquid velocity. Consequently, the catalyst size has to be reduced to achieve circulation within the reactor. It is important to ensure that, with these changes, the values of the phase holdups are maintained the same in the commercial and the laboratory units. Through extensive similitude studies, similarity criteria that would ensure identical holdups in the commercial and laboratory units were identified, which required the equality of six dimensionless numbers. These criteria were validated using the generalized wake model. It was found that it was impractical to establish all the parameters in the set of dimensionless numbers at the desired values. Therefore, a method to achieve similarity by varying a minimum number of parameters, such as liquid and gas velocities and particle size, was developed using the generalized wake model. This resulted in a set of two conditions, which when satisfied, yielded practically equal holdups in the two reactors.