Blowdown stack

In chemical engineering a blowdown stack is a vertical stack or chimney into which the contents of a chemical or petroleum process unit are emptied in case of an operational emergency, for example in the event of overpressure in a refining vessel. A blowdown stack can be used to compliment a flare stack or as an alternative. The purpose is to prevent 'loss of containment' of volatile liquids and gasses. The failure of the blowdown stack to contain hydrocarbons vented from a raffinate splitter led to a catastrophic explosion at the Texas City Refinery (BP).