| Case Name |
Explosion caused due to a catalytic effect of contaminant in the reactor at a resin intermediate manufacturing plant |
| Pictograph |
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| Date |
June 10, 1996 |
| Place |
Kitakyushu, Fukuoka, Japan |
| Location |
Chemical factory |
| Overview |
An explosion occurred at a plastic intermediate plant. Raw material was decomposed explosively by contaminant on heating and agitating after charging the raw material into the reactor. The reactor exploded and a fire occurred. Due to imperfect valve operations during vacuum distillation work for a previous run, sodium hydroxide for exhaust gas neutralization flowed in reverse to the reactor. As this alkali became a catalyst, a runaway reaction occurred. Human error or lack of understanding of contamination hazards with alkali is considered to be the root cause. |
| Incident |
To manufacture an epoxy resin intermediate, raw materials were heated and agitated after being charged. Contaminant in the reactor became a catalyst and the raw material reacted violently. A temperature rise in the reactor continued, the reactor finally exploded, and a fire occurred. |
| Processing |
Manufacture |
| Individual Process |
Reaction |
| Process Flow |
Fig2.Unit process flow
|
| Chemical Reaction |
Condensation |
| Substance |
Maleic anhydride, Fig3 |
| Methyl-1,2,3,6-tetrahydrophthalic anhydride, Fig4 |
| Sodium hydroxide, Fig5 |
| Type of Accident |
Explosion, fire |
| Sequence |
In the morning on June 9th, 1996. An operator had forgotten to close a valve in the manufacturing lot before last. For this reason, a sodium hydroxide solution in a water-sealing tank and sodium hydroxide adhering to piping was sucked into the reactor. This was clarified later.
21:50 on June 10th. The reactor was agitated and heated. Pressure was 2 KPaG.
23:30. Operators noticed that the temperature rise rate of the reactor was faster than usual. They judged that it was because the quantity of the raw material in the reactor was small, and heating was continued.
23:35. As the temperature of the reactor reached a specified temperature at 202 °C, an operator checked the situation. Then, gas leaked from the gasket at the upper side and the pressure gauge of which the limit was 0.5 MPaG swung out of the limit. Immediately, the reactor was cooled by supplying cooling water to the jacket. However, the temperature reached 206 °C, and did not stop rising. As the circumstances were filled with gas, the operator took refuge in the boiler room 20 m away.
23:42. An explosion occurred and a fire spread.
23:45. The fire department was notified about the fire. 22 fire engines and 95 fire fighters turned out.
00:06 on June 11th. The fire was extinguished. |
| Cause |
An operator forgot to close one of the valves of piping in vacuum distillation operations in the manufacturing lot before the last. Therefore, the pressure was reduces in the reactor. Due to this decompression, a reverse flow of sodium hydroxide in the water sealing drum and attached to the inside wall of the piping was generated and it flowed into the reactor through piping.
As this sodium hydroxide became a catalyst, one of the raw materials of maleic anhydride decomposed explosively. |
| Response |
Stopping heating.
A shutdown.
Spraying water to extinguish the fire.
Spread of the fire to a methyl isobutyl ketone plant was prevented by fire fighting activities. |
| Countermeasures |
Re-checks of facilities and equipment.
Employees' education for disaster prevention.
Thorough training for emergencies.
Rechecking by another operator after the valve being opened or closed. |
| Knowledge Comment |
Information from a company about the quality of materials, possibility of fire fighting with water, etc. is indispensable in the case of a chemical fire.
Establishment of an information exchange system between the administration side and the enterprises side and a quick response system if an accident occurs are desired.
In water sealing, if the pressure difference between an inlet and an outlet is more than the designed value, water will flow to the low-pressure side. If water flows out and the water level falls, the water sealing function will be lost. |
| Background |
The safety manager did not understand the hazard of maleic anhydride, which explodes in the presence of an alkali. Therefore, it seems that operators were not informed about the hazard. Probably, attention would have been paid to the reverse flow from the water-sealed tank if they understood the hazard of alkali contamination, and probably the situation would have been properly checked by conducting a double-check of opening and closing of valves or a check before use. Otherwise, there was human error caused by negligence. |
| Sequel |
The characteristics of the burning material and propriety of extinguishing fire with water were notified to the fire brigade.
This plant was decommissioned in July, 1996. |
| Incidental Discussion |
There was a report that a runaway reaction could not be stopped although the operator performed cooling operation based on the operation manual when he noticed the abnormal reaction. Countermeasures against unusual conditions might have been insufficient. It is important not only to analyze a reaction at the design stage, but also to analyze the abnormalities during operation using some special methods such as HAZOP. |
| Reason for Adding to DB |
Example of explosion caused due to a broken water seal during vacuum operation |
| Scenario |
| Primary Scenario
|
Ignorance, Insufficient Knowledge, Insufficient Study, Poor Value Perception, Poor Safety Awareness, Insufficient Safety Education/Training, Carelessness, Insufficient Precaution, Carelessness of Operator, Planning and Design, Poor Planning, Poor Design, Regular Operation, Erroneous Operation, Not Confirm the Valve Closed, Bad Event, Chemical Phenomenon, Abnormal Reaction, Secondary Damage, External Damage, Explosion/Fire, Bodily Harm, Injury, 2 person injured
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| Sources |
Fire and Disaster Management Agency, Fire and explosion of reactor. Accident cases of dangerous materials. 1996, pp.428-429.
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| Physical Damage |
Complete collapse of the east side of the plant, and the third and fourth floors. Debris was scattered within a radius of 350 m. Windows of neighboring apartments and offices were damaged. |
| Consequences |
The fire department received a large number of reports that the sky was orange. |
| Multimedia Files |
Fig3.Chemical formula
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Fig4.Chemical formula
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Fig5.Chemical formula
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| Field |
Chemicals and Plants
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| Author |
ITAGAKI, Haruhiko (Japan National Institute of Occupational Safety and Health)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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