A reaction kinetic model for the fluorination of plasma dissociated zircon (PDZ, pr ZrO2.SiO2) with hydrogen fluoride was developed. The model uses reaction as rate-limiting step, with a shrinking core of PDZ in a porous matrix of zirconia (ZrO2).: This model was used to develop models for a multi-stage fluidized bed reactor. These models facilitated the determination and design of an optimally configured multi-stage fluidized bed reactor for the fluorination of PDZ. It was shown that a combination cross-/countercurrent multi-stage fluidized bed reactor could yield significant improvement over the conventional countercurrent multi-stage fluidized bed reactor for certain reaction kinetic conditions.