EXTINGUISHING OF PROPANE-AIR FLAME BY SODIUM AND POTASSIUM HYDROCARBONATES

Powders of sodium and potassium hydrocarbonates are good fire extinguishing agents however their impact on the flames is not implicit. The study included analysis of both the hydrocarbonates and their mixtures with 1:1 mass ratio. Extinguishing occurred from the preflame zone of the preliminarily mixed propane-air flame by means of less than 80 m diameter particles. Thermogravimetric analysis of the hydrocarbonates and their mixtures shows that potassium hydrocarbonate decomposes similarly to sodium hydrocarbonate. Thermal decomposition results in water and carbon dioxide, the thermometric parameters of the mixture dissociation are additive with regards to its components. Prior to the flame zone, sodium hydrocarbonate looks like transparent irregular-shaped crystals of more than 40 m diameter, while after the flame effect most particles retain the same shape and their size ranges from 40 to 60 m. The x-ray phase analysis of the particles exposed to the flame proves that they consist of sodium carbonate (073 %) as well as sodium carbonate with three water molecules (027 %). Prior to the flame zone, the basic KHCO3 particles are transparent crystals sized less than 15–20 m (090 %). After the flame zone effect most particles (080 %) are bigger than 50 m, more than one half of them being of the spherical shape. Basically the particles are transparent and become whiter with time that phenomenon being typical for K2CO3. Prior to the flame zone most hydrocarbonate mixture particles size is below 15 m. Approximately 29 % particles pass the flame zone without evaporation, out of which about 10 % are less than 1 m. Big particles are of irregular shape sized from 50 up to 80 m and also of spherical form sized from 30 up to 60 m, that in accordance with the roentgenogram, are related to KNaCO3. Fire extinguishing mixture corresponds to the additive nature of extinguishing with regards to individual components. The contribution of thermal losses in the flame extinguishing by means of hydrocarbonates and their mixtures is quite small. Fire extinguishing most likely is homogeneous. The powder particles undecomposed in the flame and having melting temperature below 1000 °Ñ have been melted off and acquired a spherical shape.