Fire in the hydrogenation reactor of a alcohols an acids production plant

A fire started on the primary hydrogenation reactor of a chemical plant synthesizing alcohols and acids by reactions between olefins and a H2 / CO gas mixtures. The alcohols are synthesised in 3 steps: HP (280b) / BP (<3b) ozonisation, primary hydrogenation (63b), vacuum distillation and final hydrogenation (63b).

A pressure drop was noted on the hydrogenation unit, caused by a leak from a thermally insulated pipe (DN 50, 3.6 mm). The pipe was containing hydrogen at 40 bar and was connected to a separator. The unit was depressurized, but 15 minutes later the hydrogen ignited generating a jet fire directed towards the inside of the unit.
The emergency plan was triggered, with four water jets cooling the unit. The fire was put under control by means of fire extinguishers do that the firefighters did not need to intervene.

Property damage and environmental impact (smoke) were limited.

An investigation of the pipe has revealed a 30 mm long crack perpendicular to the axis of the pipe in the outer part of an elbow, corrosion I nth direction of the flange of connection with the condenser and also internal corrosion at the elbow. The pipeline was corroded / eroded and the stresses due to insufficient support weakened the elbow. Thickness checks were carried out, the pipe was replaced (5.6 mm thick) and a suitable support was put in place.

INITIATING CAUSE was the self-ignition of hydrogen released via a crack in a pipe.
The crack was probably caused by corrosion and consequent reduction of the stress-bearing section of the pipe.

hydrogen pipe, hydrogenation reactor

Property damage and environmental impact (smoke) were limited.

Since the cause was failure to bear stress at a corroded pipe elbow, a thicker tube was used to replace the cracked pipe (5.6 mm thick instead of 3.6) and a suitable support was put in place to reduce stress at the elbow. .