Experimental study of flame extinguishing of red pine wood pyrolysis gas by NH4H2PO4 powder based on Cup-burner

Abstract

Suppression of forest fires has been one of the important research directions in the field of fire safety, ammonium phosphate and its mixture of inhibitors commonly used in solid combustible fires, for forest fire scenarios, also has a good fire suppression effectiveness, inexpensive and easy to store, but also the current suppression of forest fires is one of the main inhibitors. However, there are few studies on the interaction between ammonium phosphate and forest fires. In this paper, to facilitate the study, we enter the previous research ideas for gas fires, reduce the scale of the research object, establish a small-sized simplified flame model for suppressing wood fires, take red pine wood as the research object, analyze the pyrolysis gas components after high-temperature pyrolysis, and construct the Cup-burner experimental system, together with an improved powder delivery control system, so that the process of NH4H2PO4 powder quenching fuel flames such as red pine pyrolysis gas at 350 °C, 450 °C and 550 °C was well presented on this device. It was found that the flame morphology was not only related to the gas composition but also the amount of NH4H2PO4 powder added and the particle size; the Minimum fire extinguishing concentration(MEC) value was not only related to the gas composition but also the particle size of NH4H2PO4 powder. This is because the CO2 content decreases and the H2 and CH4 content increase significantly in the gas composition at 550 °C compared to the 450 °C gas composition. Among the same pyrolysis gas components, the MEC value gradually increased as the particle size of NH4H2PO4 powder decreased, and the MEC value of 30 μm–40μm particle size powder was the lowest, and the difference between the particle size MEC value and the other two particle sizes was large, while the difference between the MEC values of 20 μm–30μm particle size powder and 10 μm–20μm particle size powder was small; according to the Cup-burner test The chemical thermodynamic analysis was carried out according to the results of the Cup-burner test to obtain the proportion of NH4H2PO4 powders playing a physical role in fire extinguishing. When NH4H2PO4 powder is involved in syngas/air combustion, the end product is P2O5 and xsp = 2.35%. When the end product is HPO3, xsp = 7.29%. The products were collected after the interaction of NH4H2PO4 powder with the synthesis gas flame, and the analysis of the products revealed that the products were sticky and not dry solids, and the material analysis of them revealed that they contained more HPO3 and its mixture, which shows that the physical heat absorption played a greater role when NH4H2PO4 powder interacted with the synthesis gas flame.