A tank glazed with 85% H2SO4 ruptured leading to a workshop to close down for five days in an explosives factory. Given the waste acid storage autonomy period of four days for production, 3 tank trucks hired in February and not dispatched following a leak in the waste acid tank were reused and three additional tank trucks were hired. Tank truck 2 was half filled with waste acid from the production of dinozebe on 26/02, and completed on 23/03 with waste acid from the production of DNTCBB (dinitro 2-6 tertiobutyl 4 chlorobenzene), a crop protection intermediate. On 27/04, nitrous vapours were emitted from the manhole of tank truck 2. The internal emergency plan was triggered. The insulated tank truck was cooled with water hose nozzles. A water curtain was used to disperse the nitrous vapour cloud that was 30 m high and 180 m long. The tank truck exploded since the situation was aggravated by its insulation and closed vents. An acid aerosol was projected over 135 m, metal debris of 3 kg reached 195 m and 15 m³ of matter was spilt on the ground. Two technicians affected by the accident at the boundary of the site were treated onsite. Despite the projections, three lifeguards located at 25 m remained intact. Ground pollution in the town of OUVEZE was limited and the spill was neutralised with calcium carbonate.
After an enquiry was conducted, it was shown that at room temperature and under adiabatic conditions, dinozebe starts to decompose after 15 days of contact with waste acids from the production of DNCTBB along with the formation of nitrous vapours. There was a slow decomposition reaction between the contents of the tank truck and the trace of dinozebe during the month of storage accompanied by an increase in pressure of the airtight and insulated tank truck. The accident resulted from inadequate cleaning between the two uses and the mixing of incompatible materials that triggered the sudden reaction. Measures were taken for other tank trucks containing the same acids: opening of manholes, cooling devices for tank trucks, etc. The use of temporary mobile storage containers without retention tanks was not allowed. Furthermore no risk assessment studies were carried out on the storage and treatment of waste acids. Material damage was evaluated at 0.36 MF.
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