Fire-extinguishing Powders Research Articles

Experimental study on the inhibition of hydrogen deflagration by flame retardant compounded ultrafine dry powder fire extinguishing media containing magnesium-aluminum hydrotalcite

Experimental study on the inhibition of hydrogen deflagration by flame retardant compounded ultrafine dry powder fire extinguishing media containing magnesium-aluminum hydrotalcite

Investigating the Potential Use of End-of-Life Fire Extinguisher Powder as a Soil Amendment in Different Soil Types: A New Approach Following a Circular Economy Model

A first attempt to assess the potential alternative use of fire extinguisher filler powder after its exhaustion has been investigated in the present research. The chemical composition of fire extinguisher filler powder, specifically type ABC 40%, consists of monoammonium phosphate and ammonium sulfate. As its nitrogen and phosphorus content is particularly high, the thought of its possible use as a fertilizer and/or a soil amendment is a challenge. For this purpose, a pot experiment was carried out and two leafy vegetables (spinach and lettuce) were used as biomarkers. Two soil samples from rural areas, one acidic (pH = 5.8 ± 0.1) and one alkaline (pH = 8.2 ± 0.7), were selected for the experiments. Filler powder from a used fire extinguisher was added to the soil samples in two levels (1 and 2% v/v). It was found that the addition of fire extinguisher filler powder caused no toxicity to either of the two plants studied. On the contrary, an increase in their above-ground biomass was observed, proportional to the amount of powder added. It was established that in the pots where the powder was added, in both plant species observed, the plant height, root length, and chlorophyll content of leaves increased, the total antioxidant capacity was enhanced, and the concentrations of nitrate and phosphate in the leaves and roots of plants also increased, compared to the soil without the addition of fire extinguisher powder. The early signs appear to be encouraging, as an increase was observed in almost all aspects. The mandatory end of the life cycle of the powder as a fire-extinguishing agent and its disposal is also a challenge in the context of the circular economy, as reducing the energy requirements for fertilizer production is one of the objectives of sustainable development.

EFFICIENCY OF USING PORTABLE FIRE EXTINGUISHERS WHEN EXTINGUISHING LITHIUM-ION BATTERIES

The article substantiates the trends in using electric energy storage systems consisting of a battery, an inverter, connecting conductors, safety automation, and, if necessary, solar panels. Such systems typically use lithium-ion batteries because of several technical advantages: high specific energy capacity, high discharge-charging currents, and many charge-discharge cycles, i.e., longevity. The chemical and electrochemical reactions that occur during the charge-discharge cycles of lithium-ion batteries can lead to irreversible electrothermal processes. Such processes cause an uncontrolled increase in temperature, the release of hazardous gases, fires, and explosions, often accompanied by fire. Therefore, the authors conducted a successful full-scale field study of the effect of various extinguishing agents of the most common portable fire extinguishers in Ukraine on the efficiency of extinguishing lithium-ion batteries. Based on the experiment, we found that extinguishing the lithium-ion module using a portable carbon dioxide fire extinguisher is the least effective among the extinguishers studied, with the resumption of flame combustion occurring within 3–4 s after the cessation of carbon dioxide supply to the combustion centre. When using a portable powder fire extinguisher, the flame combustion of the test module resumed after 18–20 s. The desired extinguishing effect was achieved using low-density air-mechanical foam from the VVK-5 fire extinguisher and sprayed water with salt additives from a water extinguisher. Based on the obtained research results, we proposed recommendations for the selection of standards for the availability and use of portable fire extinguishers for the effective extinguishing of lithium-ion batteries at the rate of at least 5 kg of charge of working solution or water with salt additives per 5 kWh of energy capacity of a lithium-ion battery. Further research will identify influence patterns of the intensity of extinguishing agent supply on the efficiency of extinguishing lithium-ion batteries. Keywords: lithium-ion battery, fire, irreversible electrothermal process, fire safety.

Analysis of the Influence of Nozzle Structure of Dry Powder Fire Extinguishing System on Supersonic Jet Characteristics

Analysis of the Influence of Nozzle Structure of Dry Powder Fire Extinguishing System on Supersonic Jet Characteristics

Numerical Simulation and Experimental Study of Gas–Solid Two-Phase Spraying of Dry Powder Fire-Extinguishing System Based on Fire-Extinguishing Inspection Robot

In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems.

Experimental study on the inhibition of hydrogen deflagration by flame-retardant compounded ultrafine dry powder fire extinguishing media containing zinc hydroxystannate

With the rapid development of global hydrogen energy industry, the issue of hydrogen energy safety has emerged, it is prone to cause a serious explosion accident once hydrogen leaks. Therefore, it is urgent to develop efficient suppression media to reduce the severity of hydrogen explosion accidents. In this paper, a new compounded powder composed of ordinary ultra-fine dry powder extinguishing agent (ODPEA) and zinc hydroxystannate (ZHS) is prepared. On the basis of material preparation, an experimental system of hydrogen explosive suppression is established to explore the inhibitory effect of ODPEA-ZHS. In terms of explosion overpressure, the results show that the peak overpressure suppression rates of ODPEA-ZHS are 90.12 %, 92.31 %, and 93.04 % for hydrogen release pressures of 2.0, 4.0, and 6.0 MPa, respectively. Besides, the flame front propagation velocity under the action of ODPEA-ZHS reaches a suppression rate of 40.55 %. Furthermore, the overpressure suppression efficiency of ODPEA-ZHS exceeds 90 % when ignites 1.0 m axially from leak port. Ultimately, the physicochemical synergistic inhibition mechanism of ODPEA-ZHS is revealed by combining material characterization and pyrolysis results. This study can provide effective countermeasures for accident prevention in hydrogen energy industry, and also contribute to the establishment of hydrogen energy safety standards and norms.

NUMERICAL JUSTIFICATION OF THE LABORATORY TECHNIQUE FOR TESTING OF FIRE-EXTINGUISHING POWDERS

Improvement of firefighting means and methods for measuring their effectiveness are important tasks in the field of fire safety. The paper presents the results of experimental measurements of the minimum extinguishing concentration of powder mixtures that can be applied as effective explosion-suppressing barriers. Measurements of the minimum extinguishing concentration of the investigated powders were carried out using a laboratory method with their pulsed delivery to a microfire of class B using compressed air. In order to justify and assess possible errors of the mentioned laboratory method for measuring extinguishing efficiency, numerical 3D modeling of the interaction of a multiphase flow with a model combustion focus was performed. The analysis of the numerical modeling results has shown that, for the applied laboratory method, almost the entire portion of the investigated powder enters the combustion zone. Additionally, the numerical calculations indicate that under the specified experimental conditions, the particle size of the powder has no noticeable effect on their loss into the surrounding flame space. Thus, these results justified the use of the mentioned laboratory method for he comparative evaluation of fire-extinguishing powders with a wide range of dispersity. The application of this laboratory method for assessing the effectiveness of the fire-extinguishing powder allowed for the development of an optimal powder composition for explosion suppression, incorporating inert mineral particles as the main component and an additive of a chemically active potassium-containing combustion inhibitor.

КОМПЛЕКСНЫЙ ПОДХОД В ИССЛЕДОВАНИИ ОГНЕТУШАЩИХ ПОРОШКОВЫХ СРЕДСТВ ПРИ ЭКСПЕРТИЗЕ ПОЖАРОВ

The article discusses the possibility of using a set of instrumental methods, such as morphological analysis, elemental analysis, X-ray phase analysis, infrared spectroscopy, ion chromatography or capillary electrophoresis to study the chemical composition of fire extinguishing powders during fire-technical examinations. Examples of the use of these methods in the investigation of real fires are given. It is described in detail how studies of fire extinguishing agents are carried out to answer questions related to establishing their composition, as well as identifying the compliance of the fire extinguishing powder submitted for study with technical documentation. It is shown that in order to obtain complete information about the chemical composition of the fire extinguishing agent, it is necessary to use a set of methods, since each of the considered methods provides additional information during the study.

Study on Flowability Enhancement and Performance Testing of Ultrafine Dry Powder Fire Extinguishing Agents Based on Application Requirements

Flowability greatly affects the application of ultrafine dry powder fire extinguishing systems, while hydrophobicity and acute inhalation toxicity are concerns for fire extinguishing agents. In the present study, we examined the impact of hydrophobic fumed silica on the hydrophobicity and flow properties of ammonium dihydrogen phosphate as the base. Our findings revealed that incorporating 6 wt.% of hydrophobic fumed silica resulted in optimal flowability, accompanied by a hydrophobicity angle of 126.48°. The excessive inclusion of hydrophobic fumed silica impeded powder flow within the ammonium dihydrogen phosphate particles. Furthermore, the investigations indicated that the incorporation of a small quantity of bentonite (0.5 wt.%) amongst the three functional additives—bentonite, magnesium stearate, and perlite—offered further enhancements in powder flowability. In fire extinguishing experiments’ total flooding conditions (1 m3), the designed UDPA exhibited a minimum required extinguishing concentration of merely 41.5 g/m3, which is better than the publicly reported value. Moreover, observations on the well-being of mice subjected to nearly three times the extinguishing concentration at 60 s, 10 min, and 3 days, respectively, demonstrated the absence of acute inhalation toxicity associated with the designed UDPA. Collectively, the developed ultrafine dry powder fire extinguishing agent displayed promising performance and possesses broad applicability.

Preparation of NaHCO3 fire extinguishing agent with perfluoropolyether groups to inhibit rapid re-ignition of Class B fires

To enhance the fire suppression effectiveness of dry powder extinguishing agents against Class B fires, the environmentally friendly surface modification of dry powder fire extinguishing agents using long-chain perfluoropolyether silanes (LCPS) was designed to modify the extinguishant. LCPS was synthesized by combining perfluoropolyether methyl ester (PME, Mw=4000 g/mol) and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AAPS). A novel hydrophobic and oleophobic ultrafine dry powder fire extinguishing agent (LCPS-Na) was obtained by the introduction of LCPS into tetraethyl orthosilicate (TEOS)-modified ultrafine NaHCO3 powder (Na-UDP). The contact angles of water (WCA) and oil (OCA) on LCPS-Na are 151.4° and 145.8°, respectively. The hydrophobicity and oleophobicity of LCPS-Na are determined to be 94.2% and 85.6%, respectively. Moreover, the required concentrations of LCPS-Na powder to extinguish n-heptane and aviation kerosene fires are found to be 38.3 g/m3 and 39.7 g/m3, respectively, with a reduction of 31.6% and 31.0% compared to that of Na-UDP. The rekindling time for aviation kerosene after fire suppression was significantly prolonged to 40.6 s compared to Na-UDP (0.20 s), owing to the superior floating capability of LCPS-Na.

A Comparative Approach Study on the Thermal and Calorimetric Analysis of Fire-Extinguishing Powders

This study offers a comprehensive evaluation of the effectiveness of expansible graphite (EG) and potassium bicarbonate (KHCO3) in suppressing metal fires, which are known for their high intensity and resistance. Our assessment, utilizing thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), revealed that compositions of EG–KHCO3 can endure temperatures of up to 350 °C, indicating their thermal resilience. The 3:1 EG–KHCO3 mixture demonstrated exceptional performance in fire suppression tests by extinguishing sodium flames in a mere 20 s, using approximately 50 g of the agent. This highlights a substantial improvement in efficiency. In addition, FTIR analysis identified important gaseous compounds released during decomposition, while XRD and SEM techniques confirmed the advantageous insertion of KHCO3 into the EG matrix, enhancing its resistance to heat and chemical reactions. The mixture with a ratio of 3:1 also demonstrated a higher cooling rate of 2.34 °C/s within the temperature range of 350 to 200 °C. The results emphasize the potential of EG–KHCO3 compositions, specifically in a 3:1 ratio, for efficient fire management by integrating fire suppression, heat resistance, and quick cooling. Subsequent investigations will prioritize the evaluation of these compositions across different circumstances and the assessment of their environmental and industrial viability.

Synthesis of magnesium hydroxide powder and dry powders for application in extinguishing petroleum fires

AbstractFire extinguishing agents are an important factor in the fight against fires. In this study, a new composite powder (CSPMS) was synthesized and used to extinguish fires caused by petroleum products. SiO2 nanoparticles, Mg(OH)2 nanoparticles, and nanocomposites of NH4H2PO4/chitosan (CSP) were combined to generate CSPMS powder. The structure and morphology of the material were characterized using methods such as XRD, SEM, FTIR, etc. The results showed that the synthesized Mg(OH)2 nanoparticle size ranged from 20 to 30 nm, and the NH4H2PO4 nanoparticle size ranged from 800 to 900 nm on the chitosan surface. The CSPMS material had particle sizes ranging from 2 to 3 µm, with a uniform distribution of SiO2 nanoparticles (50–100 nm) and Mg(OH)2 nanoparticles on the surface. The powdered materials were applied to extinguish gasoline and oil fires. CSPMS sample demonstrated the best fire extinguishing time and powder consumption (5.8 s and 12.2 g, respectively) and CO emission below the threshold of 400 ppm. Small‐scale fire extinguishing tests showed that CSPMS powder had better fire extinguishing capability, cooling time, and CO gas adsorption ability compared to commercial fire extinguishing powder.

Study on the hydrophobic nano silica particles as flow-enhancing additives for ultrafine dry powder fire extinguishing agent

Sodium bicarbonate-based ultrafine dry powder fire extinguishing agents (UDEAs) exhibit high hygroscopicity and a tendency to agglomerate, which result in poor flowability and diminished extinguishing efficiency, thus proving to be crucial concerns in the UDEA design. The integration of hydrophobic nano silica (HNS) has been recognized as an effective strategy to tackle these challenges, but the precise optimal quantity of HNS in UDEA has been a subject of confusion. Consequently, the impact of HNS as an additive on the flowability of sodium bicarbonate UDEA was thoroughly examined. Through high-speed stirring, the surface of UDEA was evenly coated with HNS particles, resulting in a notable increase in the contact angle of the modified extinguishing agent to approximately 135.4°. Notably, the UDEA formulation with an 8% HNS addition exhibited the least cohesion, the highest flow function value, and the lowest spray resistance. Moreover, the study unveiled the underlying flow mechanism of sodium bicarbonate UDEA influenced by the HNS additive. The findings indicated that the most effective incorporation of HNS into sodium bicarbonate UDEA was 8%, considering both its hydrophobic properties and flow characteristics.

Numerical Study of the Effect of Primary Nozzle Geometry on Supersonic Gas-Solid Jet of Bypass Injected Dry Powder Fire Extinguishing Device

A two-way coupled model between polydisperse particle phases with compressible gases and a density-based coupling implicit solution method, combining the third-order MUSCL with QUICK spatial discretization scheme and the second-order temporal discretization scheme, are constructed based on the discrete-phase model (DPM) and the stochastic wander model (DRWM) in the Eulerian–Lagrangian framework in conjunction with a unitary particulate source (PSIC) approach and the SST k-ω turbulence model. The accuracy of the numerical prediction method is verified using previous supersonic nozzle gas-solid two-phase flow experiments. Numerical simulation of a two-phase jet of dry powder extinguishing agent gas with pilot-type supersonic nozzle was performed to analyze the influence of geometrical parameters, such as the length ratio rL and the area ratio rA of the main nozzle on the two-phase flow field, as well as on the jet performance indexes, such as the particle mean velocity vp,a, velocity inhomogeneity Φvp, particle dispersion Ψp, particle mean acceleration ap,a, etc. By analyzing the parameters, we indicate the requirements for the combination of jet performance metrics for different flame types such as penetrating, spreading, and dispersing.

Investigating the efficacy of expanded graphite/NaCl composite powder as an extinguishing agent for metal combustion suppression

Advancements in fire safety technology have led to the development of expanded graphite (EG)/NaCl composite powder, a dry powder fire extinguishing agent specifically for metal fires. This study used custom apparatus to examine the fire suppression properties of this composite powder in relation to its constituent elements, EG and NaCl. Compared to pure EG, this composite powder has a smaller particle size and better thermal stability. The flames of a sodium metal fire were effectively suppressed using only 8 g of the EG/NaCl composite powder. The powder suppressed the flames within 22 s. This performance surpassed that of the use of EG or NaCl alone. Moreover, after the fire was extinguished, the temperature decreased at a rate of 1.23 °C/s within the temperature range of 350–250 °C. This rate was 15.44% and 44.78% faster than those of EG and NaCl, respectively. The suppressive effects of the EG/NaCl composite powder are primarily attributed to heat absorption—which prevents contact between combustible metals and air—and the adsorption of depleting H∙ and OH∙ radicals. These results indicate that EG/NaCl composite powder has promising firefighting applications, particularly in fires involving the burning of metals.

The effectiveness of mechanisms of heterogeneous and homogeneous inhibition of flame particles taking by extinguishing powder particles, into account the rate of their formation

The relevance of the work is due to the need to improve the technology of extinguishing fire with extinguishing powders based on the study of the laws of the physicochemical processes of interrupting chain combustion reactions, in particular, heterogeneous and homogeneous mechanisms of inhibition of active flame centers by powder particles. The aim of the work is to evaluate the effectiveness of non-stationary mechanisms of heterogeneous and homogeneous inhibition of active flame particles by fire extinguishing powder particles taking into account the rate of their birth, as well as to compare the contributions of each of the mechanisms to the result of fire extinguishing. Mathematical modeling of the mechanisms of heterogeneous and homogeneous inhibition of active flame particles by fire extinguishing powder particles is carried out, taking into account the rate of birth of active particles of in flame. The theoretical dependences of the rates of reactions of heterogeneous and homogeneous inhibition of active flame particles on the dispersed characteristics of powder particles, their residence time in the zone of flame and the characteristic durations of inhibition reactions are obtained. It is established that the condition for the effective recovery inhibition of active particles of flame by the mechanisms under consideration is exceeding the time of interaction of powder particles with active flame particles over the duration of inhibition processes, as well as an excess of the rate of inhibition of active flame particles over the rate of their birth. The rate of inhibition of active particles of flame depends on the particle size of the extinguishing powder, namely, the smaller the particle size of the powder, the greater the rate of inhibition. This dependence is observed explicitly for the mechanism of heterogeneous inhibition of active particles of flame and implicitly for the mechanism of homogeneous inhibition through the dependence of the rate of thermal production of metal oxide radicals of the extinguishing powder involved in this process on the size of the powder particles. The presence of two stages in the implementation of the mechanism of homogeneous inhibition of active flame particles (thermal production of metal oxide radicals of the powder substances used and the inhibition process itself) allows us to consider this mechanism of extraction of active particles longer than the mechanism of heterogeneous reduction, and, therefore, it does not significantly contribute to the chemical process of extinguishing a fire.

Влияние кристаллогидратов солей в огнетушащем порошковом составе на его удельную эффективность тушения легковоспламеняющейся жидкости

The article presents the comparative evaluation of specific fire extinguishing efficiency of powder compositions containing crystalline hydrate salts as a gas-generating component. Thermodynamic calculations and experimental tests have shown a reduction in the consumption of powder compositions for extinguishing highly flammable liquids by at least 30% when hexahydrate of magnesium-ammonium phosphate MgNH4PO4∙6H2O is used as a component of fire extinguishing powders. The research has shown the advantage of implementing fine particles of crystalline hydrates (d<10 μm) obtained during the controlled precipitation process compared to analogs manufactured by mechanical grinding (d < 100 μm).

Increasing the effectiveness of extinguishing fires in the undercarriage of the subway with gel-forming compounds

The effectiveness of extinguishing fires in the undercarriage space of cars at subway stations has been increased due to the use of a special trolley for supplying gel-forming compounds to hard-to-reach places under subway cars. In order to ensure the delivery of the gelling system to hard-to-reach places under the subway cars, it is proposed to use a special cart that moves inside the main track of the subway in the deepened tray of the water collector, thanks to a cable winch on the «pull-push» principle with an autonomous electric reversing drive. To confirm the effectiveness of extinguishing, on a special stand that allowed changing the position of the model hearth in space, to the position of the conventional ceiling-floor, comparative experiments were conducted for three types of the most common fire extinguishing agents, with the determination of the average values of the time and consumption of fire extinguishing agents for fire extinguishing, with at different angles of inclination of their submission. It is recognized that the use of gel-forming compounds when extinguishing equipment elements in the undercarriage space helps to reduce extinguishing costs and allows to extinguish the fire under the car 2,5 times faster. It was established that the change in the angle of inclination of the burning surface significantly affects the effectiveness of extinguishing with water and fire-extinguishing powder. The obtained data confirm the expediency of creating special carts for undercarriage extinguishing using fire-extinguishing gelling compounds. The obtained results are useful and im-portant, as they confirm the increase in the effectiveness of extinguishing the weighted space with gel-forming compositions, reflect a reduction in times of time and consumption of fire extinguishing agent when using gel-forming compositions. The use of a special weighted extinguishing cart with gel-forming compositions allows automated remote extinguishing in hard-to-reach places of the weighted space, which significantly increases the safety of rescuers when extinguishing such fires.

A novel approach for enhancing fire suppression efficiency of dry powder extinguishant: From the synergistic effect of dawsonite

A novel superfine dry powder extinguishing agent (DW-SDE) was developed by combining dawsonite (NaAl(OH)2CO3, DW) with superfine ABC dry powder fire extinguishing agent (SDE). The micro-morphology of DW transforms into a near-spherical shape (D90 = 8.33 μm) under optimal conditions including a mass ratio of 1:10 for citric acid (ZS) to aluminum hydroxide, a reaction time of 8 h, and a reaction temperature of 150 °C. The D90 of DW-SDE is 11.20 μm which is less than that of SDE (D90 = 14.46 μm). The activation energy (E) of DW-SDE is lower (E = 102.0 kJ/mol) and the thermal decomposition of DW-SDE can absorb more heat (388.7 J/mg). Moreover, the flowability of DW-SDE is superior to that of SDE and commercial ABC dry powder extinguishing agent (CDE). Furthermore, the DW-SDE can completely extinguish a fire in 8.7 s at 0.6 MPa, which is 47.4% and 27.1% faster than that of CDE and SDE.

Analysis of combustion characteristics of wood stack and absolute ethanol in fire extinguishing experiment

For the purpose of researching the rules of combustion heat release, ammonium phosphate dry powder extinguishing agent and water-based fire extinguishing agent were utilized before and after the class A fire common wood stack ignition fuel and class B fire anhydrous ethanol ignition fuel fire extinguishing. For wood stack fire, 0.5A wood stack was used for blank combustion test, and the pan fire ignition method for the same type and scale of wood stack fire extinguishing experiment. For absolute ethanol fire, fire suppression was studied using a 13B scale. The change characteristics of the combustion field before and after action of the dry powder extinguishing agent and water system extinguishing agent were measured by thermocouple, heat flow meter and digital camera. The findings of the experiment demonstrated that in the combustion experiment of wood stack, the temperature of 0.5A wood stack of the blank group could reach 800 °C, and the temperature reduction rate of free combustion was 2.62 °C/s. It took an average of 36.5s and 2.25 kg of ammonium phosphate dry powder to put out the fire，and the temperature reduction rate was 4.18 °C/s. The average amount of water-based extinguishing agent used to extinguish a fire was 1.21 kg, yet the average time to do so was just 12.5 s, and the average rate of temperature drop was 10.14 °C/s. In the experiment where an ethanol pool fire was being burned, the typical amount of water-based fire extinguishing chemical used was 3.44 kg, and the typical extinguishing time was 18 s, the maximum temperature drop rate could reach 35.6 °C/s in the initial stage of fire extinguishing, despite the fact that the dry powder fire extinguisher containing ammonium phosphate was used, the fire was not properly controlled.