The extraction unit of hexane, which is a highly flammable substance, makes it possible to switch from seed to vegetable oil. The first step consists of extraction by hexane percolation. The cake (solid) and miscella (a mixture of oil and hexane) are obtained. Miscella is vacuum distilled to separate the oil from the hexane that is recycled into the process. The cake is desolvated in a toaster desolvator that cooks it and evaporates the recycled hexane as well. Considering the required temperature, the loss of steam leads to the unit stopping the recycling of hexane and its condensation.
At about 9:45 p.m. in a vegetable oil factory, a fire broke out in a capacitor bank cabinet in the main LV switchboard room. The employees were able to set up 2 water hoses to combat the fire. The sprinklers went off, causing the HV breaker to trip on the transformer’s incoming feeder. The power outage caused the steam production and other units to stop, including the hexane extraction system. The emergency services arrived at 10 p.m., and the employees were evacuated. A 100-metre safety perimeter was set up around the hexane unit, and the traffic was stopped. Hexane condensation was stopped due to lack of cooling. Considering the hexane risk, the facility operator activated the plant’s internal contingency plan but did not set it in motion. The hexane unit’s explosimeters detected a concentration in the industrial water sewers. These devices are slaved to a shut-off valve, which is closed if hexane is detected. To accelerate hexane condensation, a cooling pump powered by the emergency genset was started.
Starting at 11:30 p.m., situation updates were sent out between the emergency services, the operator and the Inspection authorities for classified facilities (IIC). The LEL fluctuated between 0 and 20% causing the unit’s shut-off valve to open and close. The compressed air supply was shut off to maintain the valve in the closed position. At 1:05 a.m., the LEL was between 0 and 0.2%, eliminating any danger. The emergency services left the premises at around 2:45 a.m. On 26 June, the plant was still shut down owing to a steam production problem. A monitoring plan was established with temperature monitoring of each unit and periodic rounds. While waiting for the utilities to restart, the site was up and running thanks to the genset that keeps all the safety barriers in place.
Property damage was concentrated in the electrical room. Before restarting operations, the installations were drained, and 428 tonnes of canola seed and oil cake waste were eliminated by methanisation.
The outbreak of fire was caused by an overheating capacitor bank which had been replaced in 2011. The last thermographic inspection, conducted in 2017, had revealed overheating on the circuit breaker supplying power to the bank. It too had been replaced.
The operator, in consultation with the IIC, took the following measures:
- modification of the internal contingency plan, specifying the procedures triggering it;
- training of staff on communication and crisis management, regular exercises on the implementation of the internal contingency plan;
- enhanced training of authorised personnel on electrical transformer fires (use of 2 water hoses by personnel, the misunderstanding of the risk of electrocution);
- revision of the ER (Etablissement Répertorié, listed establishment) plan with the rescue services;
- study of the loss of utilities to identify the causes and the consequences. The study helps define compensatory measures and establish emergency procedures.
