Oscillations induced by bubble flow in a horizontal cylindrical vessel

- An interesting oscillation was observed in the horizontal cylindrical vessel.
- Circulating flow induced by the gas bubble flow was a cause of the oscillation.
- Height of the liquid surface had also an effect on the oscillatory phenomenon.
- Oscillation frequency was constant regardless of the operational conditions.

Oscillations induced by bubble flow in a horizontal cylindrical vessel were experimentally investigated. These oscillations disturb the stable operation of complicated successive reactions and lead to the breakdown of the aeration system in the vessel. Therefore, they should be prevented. Understanding the generation mechanism of these oscillations could help improve the safety design of the reactor. A series of experiments were performed to examine the causes of the oscillations. The gas feed rate, height of the liquid surface, and length of the cylinder were varied as operational parameters. It was found that the oscillations occurred in the horizontal cylindrical vessel at specific conditions. In order to deepen the understanding of these oscillations, the operational conditions that maintained the stable state and the boundary conditions that caused the oscillations were investigated. The results provided two important suggestions. First, increasing the gas feed rate caused the oscillations. It was considered that the circulating flow induced by the gas bubble flow was a cause of the oscillations. Second, the height of the liquid surface influenced the oscillatory phenomenon. In particular, distance from the aeration tube to the liquid surface was important. The oscillation frequency was measured and it was constant regardless of the operational conditions, and it could be estimated based on the natural frequency of the vessel.