A polyethylene manufacturing workshop was shut down inside a chemical plant, subsequent to a temperature rise in a tank containing 2.6 t of peroxides (tertiary butyl peroxypivalate diluted to 20% in isododecane). The internal emergency plan was activated as a preventive measure. According to the site operator, temperature rose in the 2-m³ tank due to high ambient heat. Since these peroxides were themselves releasing heat (i.e. an exothermic reaction), the risk of a runaway reaction was very real, i.e. leading to fire or even explosion.
Workshop personnel were evacuated. Internal fire-fighters sprinkled the building in order to lower its temperature. Thanks to sprinklers turning on inside the building, as well as to partial drainage of the reactor into a displaced sump and additional dilution of product remaining in the tank, the temperature progression could be brought under control. The sump slightly overflowed, but all water was collected in a storm basin, thereby preventing any pollution of the natural environment. The remainder of the storage contents, along with sump contents, were then pumped to the backup basin designed to accommodate concentrated peroxides in the event of an incident. The peroxide concentration of this basin was analysed, and foam ramps were laid out around the sump to avoid any risk of fire.
Workshop activity was suspended for 48 hours to allow enough time to install an industrial refrigeration system. No trace of hydrocarbons or peroxides was detected on the storage building floor, and the local atmosphere was verified. A second tank containing the same mix was transferred into a refrigerated container. The other tanks, which contained less sensitive peroxide mixes, were conserved until their ultimate destruction. The peroxides were diluted to 1% concentrations to enable their elimination via incineration.
According to Inspection Authorities, this temperature rise might have been due to the extended storage time (3 days) of catalyst solution at the tank bottom, as the catalyst had been delivered in solid form before being diluted on-site to produce the catalytic solutions. Following this incident, an emergency order was issued, requesting the operator to improve safety conditions relative to the dissolution procedure and response protocol in the event the preparation temperature rises.
