Prediction of dense phase voidage for group C⁺ fluidized bed reactor

Group C⁺ fluidized bed reactor exhibited better reactor performance than conventional fluidized bed reactors, due to the larger specific surface area of the catalysts and the more homogeneous fluidization, especially the extraordinary dense phase expansion which contributes to higher gas–solid contact efficiency. As a critical parameter affecting the reactor performance, the dense phase voidage (ε_d) was thoroughly characterized and general correlations for predicting ε_d were derived based on both Richardson-Zaki and Kozeny-Carman approaches. In addition, a new method for predicting the minimum fluidization velocity of Group C⁺ particles with the consideration of the particle cohesion was proposed. The bed voidage at minimum fluidization (ε_mf) and the maximum dense phase voidage (ε_d,max) were shown to correlate well with a dimensionless cohesion index (σ*). All these new correlations showed good agreements with the experimental data for various types of Group C⁺ particles.