Linde makes fighting large smouldering fires safer

Tag : liquid carbon dioxide


Dangerous fires in silos storing organic material, such as woodchips, grain and increasingly raw material for bio fuels areunfortunately frequent events. Extinguishing these fires can bevery dangerous and has even resulted in deaths of fire fighters.Smouldering fires often begin when moist organic matter starts toferment. Fermentation creates heat which can lead to a potentiallyexplosive, smouldering fire.

"Our new carbon dioxide extinguishing process will not onlysignificantly reduce the risk of explosion, increasing safety forfire fighters, but because it is a clean agent any material whichis not burned by the fire can remain undamaged, maintaining productvalue" said Michael Heisel, Project Manager Refining and ProcessChemistry, Linde Gases Divison.

With Linde's new process a smouldering fire in a container issealed off by a blanket of carbon dioxide injected through aproprietary nozzle. As carbon dioxide is heavier than air it sinksto the lowest level once injected into a silo and as the firecontinues underneath, the remaining air is consumed, creating adownwards vacuum. Carbon dioxide fills this vacuum and stifles thefire as the injected gas itself does not burn. Additionally, thecarbon dioxide efficiently catches sparks from the fire andextinguishes them, further reducing risk of explosion. The methodcan also be applied from a distance, protecting fire fighters.

Traditional methods of fighting large smouldering fires have untilnow been limited to the use of water and nitrogen, neither of whichhas produced optimal results. Water slowly permeates the organicmaterial rendering any unburned stock water damaged. It alsointroduces more oxygen into the silo increasing the risk ofexplosion. As nitrogen is lighter than oxygen, it rises to thehighest point in the silo, creating an upwards vacuum which canflare up the fire. In addition, highly flammable gas is generatedduring the smouldering process of organic materials and collects inthe head space in the silo. The upward vacuum created by injectingnitrogen can carry dangerous sparks up to the head space resultingin an explosion.