Abstract: A typical vertical-inclined combined standpipe with length of 3 600 mm and diameter of 80 mm was built to investigate the flow patterns of catalyst particles and their evolution under various mass flow rates. The flow patterns were identified by the distribution of the axial pressure and dynamic pressure. The results indicated that with the increase of the catalyst mass flow rate, the flow patterns of catalyst particles in the riser were changed from dilute to dense phase flow, and the axial pressure gradient was gradually decreased. When the catalyst mass flow rate was 720 kg/(m².s), the axial pressure was reversed with the filling flow at the bottom of the risers. The filling flow can be avoided by setting the aerating air. The main frequency range of different flow patterns is 0 - 0.5 Hz.

Key words: combined standpipe, catalyst flow pattern, dynamic pressure, aerating air