Fire in an Ammonia Production Plant
The accident took place in a tank-type pressurised separator on the synthesis gas line of an ammonia production plant. The pressurised separator operates at nominal values of 25 bar and 5C. It contains a mixture of hydrogen and nitrogen (75%/25%). It is located slightly upstream of the synthesis gas compressor (on the low pressure side) that was shut down. The connector connecting the separator to its level measuring instrument is located outside, near the building containing the compressors. The connector is thermally insulated (gas inside at 5C) over its entire length.The leak took place at the point of connection between the separator and its level measuring instrument. 1.First a compressor on the synthesis gas circuit was shut down following a malfunction. 2.When the compressor stopped, there was a slight increase in pressure (25 -> 29 bar) upstream (at the low pressure end). Normal pressure is roughly 25 bar, and the system is protected by a 30 bar pressure relief valve. 3.The pressure of 29 bar, although not too high for the installation, caused the connecting pipe to break because of heavy wear resulting from undetected corrosion under the insulation. 4.A leak of hydrogen (25 bar) occurred and caught fire. A flame jet approximately 10 metres high then damaged various surrounding installations (domino effect). Equipment containing oil that became engulfed by the flame jet also caught fire. The flame jet was extinguished by closing a valve located upstream of the hydrogen leak. Once the valve had been closed, the flame jet gradually became smaller and smaller until the hydrogen from the installations between the valve and the leak had burnt off completely. The companys emergency response team fought the (oil) fire and cooled the equipment near the flame jet so as to minimise damage. Although no one was hurt in the accident, the damage caused (solely on the companys premises) was significant, and the plant had to be shut down for several months for repairs. We estimate that roughly 700 kg of hydrogen was released during the leak.
Event Date
January 14, 2014
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
Immediate cause was failure of a pipe below the nominal operative values due to undetected corrosion.Root cause is lack of procedure for preventive inspection of damage.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
pressurized separator, synthesis gas line, ammonia reactor
Storage/Process Medium
Actual Pressure
29
Design Pressure
25
Location Type
Location description
Industrial Area
Pre-event Summary
First a compressor on the synthesis gas circuit was shut down following a malfunction. When the compressor stopped, there was a slight increase in pressure (25 -> 29 bar) upstream (at the low pressure end). Normal pressure is roughly 25 bar, and the system is protected by a 30 bar pressure relief valve.
Consequences
Number of Injured Persons
1
Lessons Learned
Lessons Learned
The accident happened because corrosion was no detected because not visible. The following improvements were implemented:1.Improvement of the system for inspecting insulated pipes; 2.Installation of an automatic fire extinguishing system in the compressors; 3.Moving equipment containing oil away from the compressors.For a more complete (older) reviews of hazard related to hydrogen in ammonia plants, see references.
Event Nature
Emergency Action
15.30 The leak starts15:45 The gas ignites. The companys emergency response team fight the (oil) fire and cooled the equipment near the flame jet so as to minimise damage. 16.10 The oil fire is brought under control (also the time at which the fire fighters arrived).till 16:45 Waiting for the flame jet to stop burning because of lack of hydrogen, the neighbouring installations are cooled
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Release Duration (s)
2400
Release Amount (kg)
700.00
Release Pressure (bar)
25.00
Ignition Source
Ignition Delay (s)
900
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
eMARS dtabase
https://emars.jrc.ec.europa.eu/en/emars/accident/view/1e305b4e-894f-08d…
(accessed Deember 2020)
ARIA data base
event no. 52743
A review of the problems relatd to ammonia plants can be found here:
M. Ojha, A. K. Dhiman
Problem, Failure and Safety Analysis of Ammonia Plant: a Review
International Review of Chemical Engineering (I.RE.CH.E.), Vol. 2, N. 6 November 2010
Publicly available at:
http://hristov.com/jordan/pdfs/Problem%2C%20Failure%20and%20Safety%20An…
(accessed 2020)