In the natural gas desulphurization workshops of a gaseous fuel production and underground storage plant, a pressure rise of between 1.7 and 3 bar occurred at 5:47 p.m. in the amine-regeneration unit after part of the process had been shut down at around 5 p.m. The restart sequence started at around 5:40 p.m. and caused an abnormal release through a vent at the top of the oxidiser at 5:48 p.m. This vent is equipped with a flame arrester that directs the gaseous discharge downwards which then rises upward toward a flare and ignites. The fire, located at the outlet of the vent’s flame arrester at the top of the oxidizer (14 m), went out after 17 minutes before the fire brigade intervened. The facilities were shut down and 64,000 Nm³ of natural gas (41.5 t of methane) was vented. Part of the production process was shut down for two weeks. However, no operating losses were reported since production was adequately compensated by the site’s other storage facilities. The internal emergency plan was activated, and the operator alerted the fire-fighters, which mobilised 14 emergency response vehicles.

The desulphurization facilities were shut down one hour after being started due to a series of control issues. An in-depth analysis of the event showed that the accident was due to the design of the vent’s flame arrester that directs the release downwards, and its location near a flare. The oxidizer had not been taken into account in the site’s safety report. The event was given a “high” severity level rating on an internal scale which consists of 4 rating levels (low, medium, high, severe). Putting the facility back into service depends on how part of the facilities are managed, following a new risk analysis using the HAZOP (HAZard and OPerability study) methodology.