Fire Extinguishing Performance of Chemically Bonded Struvite Ceramic Powder with High Heat-Absorbing and Flame Retardant Properties

Abstract

Struvite is a chemically bonded ceramic product in the pipeline of a sewage treatment plant. In order to explore the fire extinguishing potential of struvite, a new type of struvite ultrafine dry powder with excellent performance was prepared by a simple process, and its fire extinguishing performance and mechanism were analyzed in depth. Under the same process conditions, the refinement degree (D50 = 5.132 μm) and the specific surface area (BET = 25.72 m2/g) of ultrafine struvite were larger than those of NH4H2PO4 (D50 = 8.961 μm, BET = 13.64 m2/g), making struvite more suitable for fire extinguishing. Besides, the pyrolysis process of struvite was relatively concentrated and absorbed more heat in a short time. Its heat absorption (458.4 J/mg) was higher than that of NH4H2PO4 (156.4 J/mg). Water, ammonia, and PO· were released during the pyrolysis of struvite, which effectively reduced fire temperature, diluted oxygen concentrations and captured free radicals. At the same time, the final products were magnesium orthophosphate and magnesium pyrophosphate, which formed a dense flame-retardant ceramic layer with good thermal insulation and environmental protection functions. In these cases, the fire extinguishing mechanism of struvite was determined to have three stages: the cooling effect, the asphyxiation effect, and the chemical effect. Correspondingly, the fire extinguishing time of struvite was three seconds faster than that of ammonium phosphate under 0.2 MPa based on the local oil basin test.

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

“…Figure 4 shows the N 2 adsorption isotherms of CSPMS, CSP, and Mg(OH) 2 , all exhibiting type IV isotherms according to the IUPAC classification, which is characteristic of porous materials 21 . In Table 1, the surface area of chitosan, not determined here, is 2 m 2 g −1 , while the surface area of NH 4 H 2 PO 4 is 13 m 2 g −1 , and the CSP material has an increased surface area of 19 m 2 g −1 22 . This is believed to be due to the particle size and size distribution of the samples.…”

“…The measured results of CO emissions during the fire also show that can adsorb CO gas down below 400 ppm, while using ADP powder results in a CO concentration of 800 ppm (Figure 7). To achieve such superiority, the fire extinguishing mechanism of CSPMS powder is believed to involve all three factors: chemical, combustion inhibition, and fire cooling 9,22 …”

“…all three factors: chemical, combustion inhibition, and fire cooling. 9,22 Mg(OH) 2 acts as an inhibitor and coolant, adsorbing a large amount of heat released from the fire, reducing the flame temperature, and inhibiting flame propagation. CSP has a heat-adsorbing effect and decomposes into diluted oxygen-concentration gases such as NH 3 and H 2 O.…”

“…21 In Table 1, the surface area of chitosan, not determined here, is 2 m 2 g −1 , while the surface area of NH 4 H 2 PO 4 is 13 m 2 g −1 , and the CSP material has an increased surface area of 19 m 2 g −1 . 22 This is believed to be due to the particle size and size distribution of the samples. The nano-sized NH 4 H 2 PO 4 particles protrude like snowflakes on the surface of chitosan, increasing the surface area and roughness of the powder compared to individual NH 4 H 2 PO 4 .…”

A Novel Inorganic Aluminum Phosphate-Based Flame Retardant and Thermal Insulation Coating and Performance Analysis

“…Currently, there are mainly three fire prevention modes: sensor warning, active extinguishing with fire-extinguishing agents, and passive fire prevention [ 4 , 5 , 6 ]. The sensor early-warning system adopts a physical method of non-contact temperature measurement, combined with a fire alarm algorithm built into the monitoring front-end hardware for intelligent judgment and a timely alarm, to prevent imminent fire crises [ 7 , 8 ].…”