In a petrochemical plant, a butane leak occurred around 6:30 p.m., at the height of 30 m, on a flange in an elbow of an insulated pipe (DN 800) feeding the condenser of a 2,000 m³ oxidation reactor.

The reactor operates at a pressure of 30 bar and at a temperature of 130 °C. The reaction mixture, consisting of 50% butane, peroxide and butanol, ignited at the leak, and the plant’s internal contingency plan was initiated. The response team used internal means to extinguish the fire and dilute the leak. One technician was slightly burned and treated on site.

To stop the leak, the facility operator decided to decompress the damaged piping and the reactor. The reaction mixture was conveyed to the flare stack to be burned. The flaring operation generated black smoke visible from a distance, as well as organic peroxides (toxic and corrosive products) when the butane sent to the flare came into contact with the oxygen in the air. In a second step, the operator trapped the butane contained in the reactor without sending it to the flare. Butane is recirculated in the preheating exchangers which feed the reactor while the superheated steam circulating in these exchangers is replaced by water. By liquefying butane through water cooling, this manoeuvre reduced the reactor pressure from 25 to 10 bar and gradually stopped the leak rate on the pipe.

Once the leak had stopped, the insulation on the flange was removed, and a leak box was installed. The leak was located on the flange seal. The fire was of low intensity and short duration, so property damage was minor. Operating losses were related to the destruction of the reaction mixture during production and the installation of a sealing collar.