| Case Name |
Spouting of high-temperature liquid from the reactor due to a hot spot formed on stopping the agitator |
| Pictograph |
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| Date |
January 1, 1974 |
| Location |
Chemical factory |
| Overview |
There was a spouting accident of high-temperature liquid from a reactor in an aluminum sulfate manufacturing plant. Work of putting about 25 tons of aluminum hydroxide sludge into a reactor that stocked concentrated sulfuric acid was underway. In the middle of the operation, charging work was stopped, the agitator stopped, and the operators took a break. A high-temperature spot was locally generated by reaction heat and dilution heat of sulfuric acid. The pressure in the reactor rose locally, and high-temperature liquid spouted out from the reactor after about one and a half hours. Four operators got burnt. |
| Incident |
Agitation stopped during a reaction in a reactor of a aluminum sulfate manufacturing plant. After a while, high-temperature reaction liquid spouted out, and four operators got burnt.
Aluminum sulfate: Produced by reaction of 10% hydroxide aluminum sludge with concentrated sulfuric acid. It is used for various purposes, as flocculants for water purification, sizing material of paper, and a mordant ,etc. |
| Processing |
Manufacture |
| Individual Process |
Reaction |
| Process Flow |
Fig3.Unit process flow
|
| Chemical Reaction |
Other |
| Chemical Equation |
Fig2.Chemical reaction formula
|
| Substance |
Sulfuric acid, Fig4 |
| Aluminum hydroxide, Fig5 |
| Aluminum sulfate, Fig6 |
| Type of Accident |
Leakage |
| Sequence |
About 25 tons of hydroxide aluminum sludge had been charging into the reactor where concentrated sulfuric acid had been charged, spending three hours. When about six tons sludge was charged, operators stopped the agitator, and took a break. The high-temperature reaction liquid spouted out from reactor after one and a half hours. |
| Cause |
The aluminum sulfate formation reaction is an exothermic reaction. Simultaneously, heat of dilution of sulfuric acid due to generated water is added. A high-temperature spot is locally generated in the reactor because the agitator stopped. Pressure of the part in the reactor rose and the contents spouted out. |
| Countermeasures |
1. Safety education and training.
2. The operation standard is improved. |
| Knowledge Comment |
Stopping agitation during reaction has frequently caused accidents. |
| Background |
1. Knowledge of workers was insufficient (The danger when the agitator stopped was not understood.). Education to workers by the manager and the engineer was insufficient.
2. It seems that the work standard was incomplete. |
| Reason for Adding to DB |
Example of accident caused due to an insufficient understanding about process hazards of the operators |
| Scenario |
| Primary Scenario
|
Ignorance, Insufficient Knowledge, Insufficient Study, Organizational Problems, Inflexible Management Structure, Insufficient Education/Training, Misjudgment, Misunderstanding, Relation between Reaction Progress and Dangerousness, Other Reaction, Regular Operation, Erroneous Operation, Opration without Thinking Timing, Bad Event, Chemical Phenomenon, Abnormal Reaction, Secondary Damage, External Damage, Leakage, Bodily Harm, Injury, 4 person burnt
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| Sources |
Masamitsu Tamura, Masahide Wakakura, High-temperature reaction liquid spouting, Reaction danger - Accident case and analysis - p.136(1995).
|
| Number of Injuries |
4 |
| Multimedia Files |
Fig4.Chemical formula
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Fig5.Chemical formula
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Fig6.Chemical formula
|
| Field |
Chemicals and Plants
|
| Author |
OGAWA, Terushige (Graduate School of Environment and Information Sciences, Yokohama National University)
TAMURA, Masamitsu (Center for Risk Management and Safety Sciences, Yokohama National University)
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