Attrition of catalyst particles in a laboratory-scale fluidized-bed reactor

• Catalyst attrition arises from mixed particle fragmentation and surface abrasion.
• A relative attrition rate is suggested to represent the attrition process.
• The relative attrition rate tends to a constant after nonsteady-state attrition.
• An exponential decay model is proposed to describe the time-dependent attrition.

Attrition of fluid catalytic cracking catalysts is investigated in a laboratory-scale fluidized bed. It is shown that the catalyst attrition arises from a mixed mechanism of particle fragmentation and surface abrasion. The measured conventional attrition rate always decreases with time, even for a long-time attrition; therefore, a relative attrition rate is suggested. Experiments indicate that after a nonsteady-state attrition where the measured relative attrition rate decreases with time, the attrition gets into a steady state and the measured relative attrition rate tends to a constant value. Furthermore, the time-dependence of particle attrition is discussed. It is seen that the widely-used Gwyn equation cannot model the catalyst attrition accurately. Alternatively, an exponential decay attrition model is proposed and confirmed to describe the time-dependent attrition behavior. It is found that the model parameters have definite meanings and are strongly related to the particle properties, fluidization conditions and fluidized bed structure.