Dry water fire extinguishing agents with bentonite

Abstract

Efficient and environmentally friendly means for fire extinguishing can reduce extreme economic losses from fires and protect people's lives and property. A separate problem is extinguishing oil products on the water surface. Dry water is a new type of environmentally friendly fire extinguishing agent. It is a powder with a water content of more than 90 %, so it has excellent fire extinguishing properties.

The purpose of this work was to obtain dry water fire extinguishing powders based on pyrogenic hydrophobic methyl silica with bentonite and to study their fire extinguishing properties in case of extinguishing gasoline on water surface.

To obtain dry water fire extinguishing powders, there were used distilled water, Dashukovsky bentonite (Ukraine), and pyrogenic methyl silica (AM-300 brand, S_sp = 300 m²/g, particle size 5–7 nm) (Kalush, Ukraine). Dry water fire extinguishing powder was prepared by mixing the components at a speed of 15000 rpm for 10 s. Were made samples containing 10 wt. % methyl silica, 3, 6, 10, and 15 wt. % bentonite and the corresponding amount of water. The bulk density was 0.423, 0.453, 0.459, and 0.464 g/cm³ for samples of 3, 6, 10, and 15 wt. % bentonite, respectively.

Optical microscopy has shown that the particles of the dry water powder have a clearly visible core-shell structure. Dry water fire extinguishing powder is a polydisperse system - most of the particles are single fine particles with a size of 1 micron or less, and there are also agglomerates with a size of more than 5 microns. As a result of the mechanical destruction of individual bentonite particles during high-speed mixing of components, bentonite particles are destroyed, therefore, individual bentonite particles are surrounded by a hydrophobic-hydrophilic mixture of hydrophobic silica nanoparticles and bentonite nanoparticles formed during exfoliation.

The study of the fire-extinguishing properties of the dry water powder was carried out by spraying it onto a layer of burning gasoline A92 on water surface. The time to complete extinguishing of the fire and the consumption of the substance per unit area of burning were determined. It has been determined that the time for extinguishing gasoline and the consumption of dry water fire extinguishing powder for extinguishing it depend on the concentration of bentonite and are for 3, 6, 10, and 15 wt. % 9, 7, 6, and 9 s and 0.333, 0.309, 0.284, and 0.260 g/cm³, respectively.

The developed dry water fire extinguishing powders are environmentally friendly, have good fire extinguishing properties, and can be used to extinguish oil products on the surface of water bodies.