Abstract: There is a short-circuit problem of regenerated catalyst particles during the operation of a fluidized bed reactor in an industrial methanol-to-olefin (MTO) unit, accompanied by abnormal catalyst loss. In this study, the Multi-Phase Particle-in-Cell (MP-PIC) model was used to simulate the hydrodynamic behavior of the reactor in equal proportion and analyzed together with field data. The results show that the two distributors in the reactor, especially the distributor near the outlet of spent catalyst, are prone to short circuit of regenerated catalyst particles. After the installation of three overflow buckets, the short circuit of regenerated catalyst particles can be suppressed to a certain extent. Under normal conditions, the catalyst loss in the reactor mainly come from the extremely small particle size fine powder (particle size below 10 μm) produced by particle wear. In the MTO unit, the probabilities of abnormal catalyst loss from the reactor and the regenerator are 18.19% and 54.51%, respectively; the much higher probability in the regenerator is attributed to its higher dense bed level and to the cyclone wing valves being located below the bed level. Through simulation, the possibility of short circuit of regenerated catalyst particles and the necessity of installing overflow buckets were clarified, and follow-up improvement suggestions were proposed to mitigate abnormal catalyst loss in the unit.

Key words: methanol-to-olefin, reactor, fluidized bed, particle distributor, entrainment, MP-PIC, simulation