Explosion at a Chlorine Production Plant
An explosion occurred at a chlorine production plant during the restart of the installation. An hydraulic syphon had probably been blocked by fire extinguishing products following a previous fire on the hydrogen exhaust system. While restarting the chlorine production unit, the hydrogen pressure started to increase, allowing hydrogen to permeate through the electrolyzer membrane into the chlorine compartment. The chlorine /hydrogen mixture then entered the chlorine drying unit before exploding. The explosion was probably initiated by a discharge of static electricity or UV radiation. The internal emergency plan was started. The were not victim. The desiccation towers were destroyed and the chlorine manifold damaged.The increase in the chlorines hydrogen content had been detected by an on-line analyzer 15 minutes prior to the explosion.
Event Date
September 11, 1991
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause was the clogging of the hydrogen venting pipe. The root cause were ill-designed procedures: inappropriate hydrogen firefighting means or insufficient with regard to (i) inappropriate hydrogen firefighting means, (ii) detection of overpressure in the hydrogen manifold, (iii) detection of hydrogen in the chlorine compartment, (iv) operating procedures to reduce these values.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
gas vents, drying tower
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
A fire had occurred on the hydrogen exhaust system, which required the use of fire extinguishing products. These had blocked the hydraulic guard on the hydrogen exhaust.
Currency
Lessons Learned
Lessons Learned
The accident demonstrated that the preventive measure for hydrogen fire were inappropriate or insufficient: in particularly the (i) detection of overpressure in the hydrogen manifold, (ii) the analysis of hydrogen in the chlorine compartment, (iii) inappropriate operating procedures mitigating these events. CORRECTIVE MEASURES were implemented: (1) Elimination of the possibility of pressure build-up in the H2 manifold, (2) Reinforcement of hydrogen overpressure detection systems (3) Reinforcement of the detection of hydrogen in the chlorine, (4) Adaptation of the operating procedures for these cases.
Event Nature
Emergency Action
Unknown
Emergency Evaluation
Fire fighting means were not appropriate and monitoring procedures were not adapted to hydrogen overpressure or pollition of chlorine with hydrogen.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/14987_en/?lang=…
(accessed December 2020)