Fire at a desulphurisation unit

The incident occurred at the recycle hydrogen compressor of a hydro-desulphurisation unit. The compressor was equipped with a suction rectifier. The drainpipe of this rectifier had been corroded internally by a combination of hydrogen sulphide and ammonia residues. The corrosion produced a 2mm wide x 90mm long hole, through which hydrogen escaped. The process condition (45C and 3.7Mpa) had created the conditions for the corrosion to take place, including presence of steam. The drainage piping had a horizontal section of approximately 10 m, with an upward outlet. This upward outlet made it impossible to drain out completely the pipe. "
The leak was detected thanks to an abnormal noise was heard in the operator cabin. The workers checking the site detected the smell of hydrogen sulphide, upon which the plant operator gave the order to shut down the operation immediately.

[Note of the HIAD validator: the original data in the database RISCAD reported the development of a fire. The KHK database mentions only a leak].

The INITIATING CAUSE was internal corrosion leading to a pipe opening.
The ROOT CAUSE was a design of the drainpipe which could not be fully drained.

pipe, recycle hydrogen compressor,