Study on the Minimum Fire-Extinguishing Concentration of Several Commonly Used Extinguishing Agents to Suppress Pyrolysis Gas of Red Pine Wood

The suppression of forest wood burning has been one of the important research directions in the field of solid combustible fire safety. The process of forest wood flame propagation is a coupled process of solid-phase pyrolysis and gas-phase combustion chemical reactions; therefore, as long as the solid-phase pyrolysis or gas-phase combustion can be suppressed, the forest wood flame propagation can be suppressed and an important contribution can be made to the subsequent suppression of forest wood fires. Previous studies have focused on the inhibition of solid-phase pyrolysis of forest wood, so this paper examines the effectiveness of several common fire suppressants for suppressing forest wood gas-phase flames, starting with the inhibition of forest wood gas-phase combustion. In this paper, for the convenience of the study, we narrowed the scope of the research object to the previous research ideas for gas fires, established a simplified small-scale flame model for forest wood fire suppression, took red pine wood as the research object, analyzed the pyrolysis gas components after high-temperature pyrolysis, and constructed a Cup burner suitable for N₂, CO₂, fine water mist, and NH₄H₂PO₄ powder to extinguish the pyrolysis gas flame of red pine wood, respectively. The experimental system, together with the 9306 fogging system and the improved powder delivery control system, shows the process of extinguishing fuel flames such as red pine pyrolysis gas at 350, 450, and 550 °C with various types of fire-extinguishing agents on this device. It was found that the flame morphology was related to the composition of the gas and the type of extinguishing agent. At the same time, NH₄H₂PO₄ powder appeared to burn above the cup mouth when pyrolysis gas interacted with it at 450 °C, but this phenomenon did not occur when other extinguishing agents interacted with it and only appeared when pyrolysis gas interacted with it at 450 °C, so it was judged that this phenomenon was related to the CO₂ content of the gas component and the type of extinguishing agent. The study found that the four extinguishing agents extinguish red pine pyrolysis gas flame MEC value. There’s a big difference. The worst performance is N₂. Compared with N₂ suppression of red pine pyrolysis gas flame, CO₂ suppression effectiveness is 60% higher, but compared to the suppression effectiveness of fine water mist and far away, the suppression effectiveness of fine water mist is much higher than the suppression effectiveness of CO₂. However, the difference in effectiveness between fine water mist and NH₄H₂PO₄ powder is almost double. In summary, in the suppression of red pine gas-phase flame, four kinds of fire-extinguishing agents are ranked as follows: N₂ < CO₂ < fine water mist < NH₄H₂PO₄ powder. Finally, the suppression mechanism of each type of extinguishing agent was analyzed. The study of this paper can provide some data to support the extinguishing of open fires in forest fires or suppressing the rate of forest fire spread.