Abstract: Addressing technical challenges in the reactor-regenerator section of a 1.2 Mt/a catalytic cracking unit, such as afterburning in the regenerator dilute phase and severe catalyst loss, a systematic revamp focused on flow field optimization was implemented during the 2021 overhaul. Key technical measures included optimizing the main air distribution system, improving the catalyst distributor, applying PLS-type dual-inlet cyclones, and adding dense phase grids. These measures fundamentally improved gas-solid distribution uniformity and carbon-air matching efficiency. Post-revamp, afterburning in the dilute phase was eliminated, catalyst loss reduced from 3―7 t/d to 1.5 t/d, achieving long-term, stable, and safe operation.

Key words: catalytic cracking, dilute phase afterburning, cyclone separator, main air distribution, catalyst loss, flow field optimization