A large explosion occurred at a TNT manufacturing plant, injuring 8 people and making considerable damage to surrounding buildings: collapse of 40 buildings including 4 by fire, partial collapse of 14 buildings including 2 by fire, partial damage of 65 buildings including 1 by fire, 40.6 ha of a forest burned. The costs are estimated at 6.3 M euros.

On 13/11, damage to glass of the denitrification tower was found at the end of the batch. It was decided to shut down the plant to repair. Repair work was carried out from the 14/11 to 18/11. However, it was interrupted for some reason and it was decided that TNT manufacturing operation would restart from the next day.

On the 19/11, at 08:15 a.m., after preparatory work, mixed acid was poured into the third-order nitration reactor and the temperature rose to 90 °C. Although many problems occurred, charging of raw materials was finished and warm-up operation progressed.

A ring-like crystal was found when the sodium carbonate tank was checked for preparing the crystallization process. Then, as the valve was checked, it froze and would not open. After melting a sticky material, the valve was opened at 11 a.m. and about 1 L of sodium carbonate (20% solution) collected into the crystallization drum.

The tank was heated to 108.5 °C to receive “trioil” (liquid once the nitration is finished – mixture of TNT and residual acids). At about 14:13, heating was stopped and “trioil” was received into the drum. The operator looked into the drum because the amount of NOx generated was less than usual. He found that the flow rate was half of the normal rate.

A sound was heard afterwards and a large amount of NOx was generated. The amount of generated NOx gradually increased, and it changed into dark smoke. A metallic sound was heard afterwards. As flames of about 30 cm high had been observed from the manhole at the upper part of the drum, the worker sensed danger and escaped to the shelter.

After 2 minutes, a large explosion occurred, followed by a large secondary explosion 3 minutes later.

15-20 kg of TNT from the former batch remained in the crystallization drum when the sodium carbonate flowed into the drum and was heated for four hours at 100 °C. Due to an incompatible reaction, the content of the tank changed to a material with a very low initial exothermic temperature. A decomposition reaction began, accelerated, and exploded when the “trioil” was received. In addition, it is presumed that the trioil in the third-order reactor and DNT in the DNT store tank exploded (2nd explosion heard) due to a fire subsequent to the first explosion.

Knowledge of hazardous reactions of manufactured hazardous materials was insufficient. When a problem occurred, it was solved by a temporary measure without sufficient hazard study. The manufacturing system was moved from batch to continuous and the safety management system was improved.