Suppression of sodium fires with liquid nitrogen

Sodium has unusual fire hazards, including autoignition when heated in air or exposed to liquid water. Owing to limitations of existing suppression agents for sodium pool fires, suppression using liquid nitrogen (LN2) is examined here. Sodium pools of 5-80 g were heated in stainless steel beakers. At about 290 degrees C, pool surface autoignition occurred and caused a rapid pool temperature increase. Vapor phase combustion occurred when the pools reached 320-450 degrees C, ultimately leading to pool temperatures up to 700 degrees C. For suppression tests, LN2 delivery (at 2.7 g/s) began when the fires became fully-developed, near a pool temperature of 600 degrees C. Liquid nitrogen was found to be an effective suppression agent. The minimum amount of LN2 required to suppress a fully-developed sodium pool fire was found to be about three times the initial sodium pool mass. (C) 2013 Elsevier Ltd. All rights reserved.