Numerical exploration of hydrodynamic features in a methanol-to-olefins fluidized bed reactor with two parallel reaction zones

A novel methanol-to-olelins (MTO) reactor in which two parallel reaction zones were created by introducing a draft tube to a column bed was numerically investigated using a combination of multi-fluid model and two types of EMMS drags, in order to explore the favorable hydrodynamics. The further numerical comparison of the novel reactor and a conventional reactor found that the introduction of a draft tube helps increase the gas velocity substantially, building an approximate plug flow in the center and concurrent downward flow in the annulus. The gas-solid contact time and solids backmixing in the draft tube were thus greatly reduced, being favorable to MTO reactions, while the gas and solids backmixing in the annulus was enhanced. Besides, severe gas bypassing from the annulus to the draft tube was detected. A gas tracer method was then adopted to quantify the gas bypassing and internal gas circulation for further optimization. (C) 2020 Elsevier B.V. All rights reserved.