Fire in an ammonia synthesis reactor

In a fertiliser plant, an ammonia synthesis unit stopped following the malfunction of an alternator due to a thunderstorm.
The safety features were operating normally, yet the synthesis gas (N2 / H2) emitted into the atmosphere ignited in the chimney (possibly sparked by lightning).
Alerted by the noise and after noticing the flames raging for 15 min, neighbours contacted the fire department. During this time, the facility operator cut the natural gas intake that supplied the unit and secured the installation.
Fire-fighter presence was not required at the site.

INITIATING CAUSE is the malfunction of an alternator, which stopped the ammonia production.
Despite the correct safe procedure was in place, the hydrogen released via the chimney ignited (perhaps sparked by lightning).
A CAUSE CONTRIBUTION was adverse environmental conditions

chimney at an ammonia synthesis unit

Due to a thunderstorm, the alternator was malfunctioning.

An investigation was undertaken to identify the causes of alternator malfunction. Unfortunately its results are unknown.

Alerted by the noise and after noticing the flames raging for 15 min, neighbours contacted the fire department.
During this time, the facility operator cut the natural gas intake that supplied the unit and secured the installations.
Fire-fighter presence was not required at the site.