The preparation and fire extinguishing mechanism research of a novel high-efficiency KHCO3 @HM dry powder

Abstract

Hydromagnesite (HM) is a widely distributed primary natural carbonate mineral. To expand the application range of hydromagnesite and tap its fire-extinguishing potential, a new type of high-efficiency KHCO3 @HM dry powder was prepared by coating potassium bicarbonate on the surface of hydromagnesite with a dip coating method. KHCO3 @HM dry powder obtained a chemical inhibition effect through this method, and the fire extinguishing efficiency has been further improved. A series of tests were carried out to confirm the excellent physical and chemical inhibition effect of KHCO3 @HM dry powder. Specific surface area tests showed that the specific surface area of KHCO3 @HM dry powder (31.405 m2/g) was higher than NH4H2PO4 dry powder (12.766 m2/g). Flowability tests showed that KHCO3 @HM dry powder (0.04 g/s) achieved the same flowability as NH4H2PO4 dry powder (0.04 g/s). Local oil basin fire experiments showed that the average fire extinguishing time of KHCO3 @HM dry powder was shorter with less powder consumption. Under 0.2 MPa driving pressure, the fire extinguishing time of KHCO3 @HM dry powder was 2.2 s faster than NH4H2PO4 dry powder, and the dry powder consumption was 3.71 g less than NH4H2PO4 dry powder. The cooling effect of KHCO3 @HM dry powder (208 ℃) in 10 s was better than NH4H2PO4 dry powder (157 ℃), and KHCO3 @HM dry powder (399 ppm) showed a better smoke suppression effect than NH4H2PO4 dry powder (545 ppm). The pyrolysis of KHCO3 @HM dry powder reduced the fire temperature, diluted the oxygen concentration, and captured free radicals. The final pyrolysis products formed a thick oxide film to provide good heat insulation and asphyxiation effects. The excellent cooling, dilution, asphyxiation, and chemical inhibition mechanisms of KHCO3 @HM dry powder were demonstrated, and finally achieved a comprehensive performance comparable to NH4H2PO4 dry powder.