(81a) Operating an Unstable Acetylene Hydrogenation Reactor after a Runaway

Acetylene reactors in a front-end de-ethanizer ethylene plant typically operate in a stable manner. Swings in a few key parameters such as CO, C2H2, and temperature may cause breakthrough of acetylene, but can be handled temporarily as a minor plant upset. Acetylene is a known poison for downstream customers and is operated under a tight range.

In an unfortunate circumstance of a major plant upset, an operating and process automation error occurred which caused the guard catalyst bed to have a significant exotherm. This led to hot spot formations in the catalyst bed due to maldistribution of cracked gas flow.

Through the ups and downs of the series of exotherms, root cause investigations and execution of the catalyst change out, significant learning has been gained on operating these catalyst beds.

This presentation will share some of the details of this incident, the impact on reactor operations, and the development of new operating discipline with unstable catalyst.