Abstract: In response to the severe erosion problem of the main air distribution pipe in the Methanol to Olefins (DMTO) unit regenerator, this study focuses on the industrial system at a certain company. By integrating field operating data with numerical simulation results, the underlying erosion mechanism is elucidated. Within the branched distribution pipes, the abrupt change in airflow direction from branch to sub-branch causes the near-wall flow to be hindered and locally detached, giving rise to a typical flow separation phenomenon. Under these conditions, the velocity on the windward side exceeds that on the leeward side, and pressure drop anomalies create low-pressure recirculation zones that entrain external catalyst particles back into the pipes. The entrained particles, subjected to the combined action of forward airflow and reverse recirculation, impinge upon and erode the nozzle surfaces. To mitigate this effect, structural optimization strategies were introduced, including elliptical cross-section design and gradually expanding transitions for the sub-branches, reinforcement of ceramic nozzle edges, and the application of high-hardness protective coatings. The results demonstrate that these measures effectively suppress catalyst backflow, restore the designed pressure drop characteristics of the main air distribution pipe, and ensure stable fluidization within the regenerator.

Key words: methanol to olefins, main air distribution pipe, erosion mechanism, catalyst particle backflow, numerical simulation