Fire on a methanation reactor

A fire developed on a mathanation reactor. The methanation reactor vessel was found to be deformed and had a 3-4 inch rupture at a position corresponding to the top of the catalyst bed.
It is thougth that the incident was caused by ethylene entering the reactor. The ethylene reacted with hydrogen on the nickel catalyst, resulting in a very rapid release of energy. The corresponding temperature rise was sufficient to cause a ductile failure of the vessel.

According to the ICHEME report (See References), the assumed INITIATING cause was a runaway reaction caused by the accidental injection of ethylene into the methanation reactor.
The proposed mechanism for the accident is that ethylene vapour entered the methanation reactor via the cold box where there was a low pressure/high temperature following a trip. When re-pressuring, the ethylene was carried forward through the 90% hydrogen line to the methanation reactor. This suggests a mistake in the design of the plant.

methanator

The methanation reactor was damaged.