Catalyst-scale investigation of polydispersity effect on thermophysical properties in a commercial-scale catalytic MTO fluidized bed reactor

Abstract

The methanol-to-olefin (MTO) process is commercialized worldwide, yet the understanding of in-furnace phenomena is still lacking. Accordingly, this work explores the multiphase flow and thermochemical characteristics in a commercial-scale MTO fluidized bed reactor using a three-dimensional multiphase particle-in-cell model. After model validations, the intrinsic relationship of solid transportation and thermochemical properties is elucidated together with the study of the polydispersity effect on reactor performance. The non-uniform gas-solid distribution in the reactor demonstrates the turbulent fluidization regime. Heat transfer coefficients (HTCs) of about 300 and 200 W/(m2·K) are observed in the medium and upper regions, respectively. The small velocity, particle Reynolds number, temperature, and HTC correspond to those large-size catalysts in the dense region where particles are nearly close packing with a large solid volume fraction. Increasing particle size distribution (PSD) width increases the catalyst HTCs and the mass fraction of C2H4, promoting reactor performance. Besides, increasing the PSD width enlarges gas viscosity, gas specific heat capacity, and gas thermal conductivity but decreases gas density.