Improving Water Spray Efficacy for Fire Suppression via CO2 Addition at High Pressures and Low Temperatures: Evidence for CO2 Clathrate Hydrate Formation

This paper describes a technique for achieving a compact aqueous spray that incorporates CO 2 into the spray at low temperatures ( T < 10 °C) and high pressures ( P > 10 MPa). A high-pressure spray apparatus was used to explore the effects of temperature (4−25 °C), nominal CO 2 mole fraction (0−0.12), in-line filter pore size (0.5−7 μm), and additives on the high-pressure (12−19 MPa) water spray patterns. Divergence of the high-pressure H 2 O−CO 2 spray was significantly reduced at low temperatures, with addition of sodium lauryl sulfate or aqueous film-forming foam (AFFF), and with a small-pore-size (0.5 μm) filter. The observed trends, based on digital images, can be explained by the formation of CO 2 clathrate hydrate within the continuous-flow system. The concepts discussed herein may be applied to conventional H 2 O/AFFF fire-suppression systems, where the introduction of CO 2 as a foaming agent can increase fire-suppression efficacy.