Extinguishing Properties Research Articles

Monitoring and Leak Diagnostics of Sulfur Hexafluoride and Decomposition Gases from Power Equipment for the Reliability and Safety of Power Grid Operation

Sulfur hexafluoride (SF6) is a typical fluorine gas with excellent insulation and arc extinguishing properties that has been widely used in large-scale power equipment. The detection of SF6 gas in high-power electrical equipment is a necessary measure to ensure the reliability and safety of power grid operation. A failure of SF6 insulated electrical equipment, such as discharging or overheating conditions, can cause SF6 gas decomposition, resulting in various decomposition products. The decomposed gases inside the equipment decrease the insulating properties and are toxic. The leakage of SF6 can also decrease the insulating properties. Therefore, it is crucial to monitor the leakage of SF6 decomposed gases from electrical equipment. Quantitative testing of decomposition products allows us to assess the insulation state of the equipment, identify internal faults, and maintain the equipment. This review comprehensively introduces the decomposition formation mechanism of SF6 gas and the current detection technology of decomposition products from the aspects of principle and structure, materials, test effect, and practicability. Finally, the development trends of SF6 and decomposition gas detection technology for the reliability and safety of power grid operation are prospected.

Sub-ppm NDIR [formula omitted] gas sensor using ICEEMDAN-SG joint denoising algorithm

Due to the excellent insulation and arc extinguishing properties of SF6 gas, it is widely used in power equipment such as gas insulated switchgear or gas circuit breaker. Therefore, detection of SF6 gas leakage with high sensitivity is necessary. Non dispersive infrared (NDIR) technology have advantages such as miniaturization, low power consumption, simple structure, low cost, and non-destructive testing, making it suitable for building large-scale sensor networks. However, NDIR sensors are susceptible to noise coming from the emitter, the detector and the circuits, which receives little research attention. In this study, we propose a new denoising method by combining improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) with Savitzky-Golay (S-G) to the noise suppression, which achieves a 7 dB signal-to-noise ratio improvement over the traditional wavelet threshold denoising, making the detection limit of the sensing system reach the level below 1 ppm.

Mono-Ammonium Phosphate Treated Blankets’ Effectivity to Different Classes of Fires

According to Monaghan County Council, the fire begins when a flammable and combustible object is exposed to enough heat and has access to enough oxygen or another oxidizer. Fire aids in our daily activities and improves our quality of life. On the other hand, fires can potentially endanger human life. A large number of casualties are reported in the Philippines due to very simple causes, such as an unattended candle or an open stove, which significantly increases the number of resources lost in large-scale fires. Fires are necessary for our existence, yet numerous incidents have contradicted this notion, turning them into dangerous forces when left unattended with flammable objects. According to the concept of fire-extinguishing tools, the researchers hypothesized that the so-called mono-ammonium phosphate, a dry chemical present in the chemical composition and combination of fire extinguishers, could be used as a key component of alternative fire blankets to put out Classes A, B, D, and K fires. These fire blankets provide similar functions to the existing ones but offer convenience to the less fortunate people vulnerable to fire-related hazards. The researchers seek to determine the effectiveness of extinguishing different classes of fires using MAP Treated Blankets and the extent of the treated fire blanket in terms of quality and performance. The research procedure has 3 phases, the preparation of the MAP- Treated Blankets, Methods of Testing such as the Ability and Fire Retardancy Test, and lastly the Extinguishing Properties of MAP-Treated Blankets in terms of Quality and Performance. Results revealed that the MAP-treated Blanket was very effective as it perfectly extinguished different classes of fire such as Class A, B, D, and K. Also, it is very good in quality for it follows the British Kite mark Standard for the fire Blanket system, and the property such as cost-efficient, user and environmentally friendly.

Hollow waveguide CO2 laser sensing system for rapid detection of trace sulfur hexafluoride (SF6) gas

Sulfur hexafluoride (SF6) has been widely applied in electrical facilities due to its excellent electrical insulation and high-voltage arc extinguishing properties, although it is a potent greenhouse gas. Rapid detection of trace SF6 gas is significant for monitoring the operation safety of high-voltage power grid facilities and greenhouse gas emissions. In this work, a SF6 gas sensing system was proposed and built using a CO2 laser as the light source and a 700 μm bore Ag/AgI hollow glass waveguide (HGW) as the gas chamber and laser transmission channel. Sensing performances of the SF6 gas HGW sensors with different lengths were investigated. The gas sensing sensitivity and standard deviation (SD) of blank increase as the waveguide length increases. The limit of detection (LOD) decreases with waveguide length increase but the decline becomes less pronounced after the length exceeds 120 cm. The HGW length exhibits minor effect on the response and recovery time of the sensor system. The sensor sensitivity undergoes a slight reduction as the HGW is bent. Optimization of the sensing performance was achieved based on the straight 120 cm-length HGW SF6 gas sensor system. Its sensitivity reaches 0.384 dB/ppm and the LOD is 148 ppb with good cyclic response characteristics (response and recovery time 2–3 s). The present work provides a feasible idea for building up a trace SF6 gas sensing system with simple structure, easy operation and high performances.

Experimental research on bimetallic ion crosslinked gel to inhibit the spontaneous combustion of coal

To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new type of mine fire prevention and extinguishing gel was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-δ-lactone (GDL) as the pH modifier. The preferred ratio was 2.5 % CMC + 4 % Fe-AlCit + 2 % GDL of No. 23 gel material by gelation time, thermal stability, strength, and permeability performance tests. The results show that the gelation time of No. 23 gel was 10 min, and its complete water loss time was 1.97 times that of water at a high temperature of 180 °C. The gel for sealing the surface of the coal body still maintained good stability after two weeks. Furthermore, A metal coordination bond favorable to the stability of gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ ionized by Fe-AlCit. No. 23 gel exhibits excellent fire prevention and extinguishing properties. The temperature-programmed test showed that the CO and C2H4 gas inhibition rate of the coal sample treated with No. 23 gel reached 33.42 % and 56.86 % at 220 ℃, and the activation energy growth rate reached 26.5 % and 21.1 % in the first and second stages, respectively. The fire extinguishing test indicated that No. 23 gel can significantly reduce the temperature of the coal sample and extinguish the coal fire quickly. The study is useful to develop efficient and environmentally friendly coal mine fire prevention and extinguishing materials.

In Ukrainian

Efficient and environmentally friendly means for fire extinguishing can reduce extreme economic losses from fires and protect people's lives and property. A separate problem is extinguishing oil products on the water surface. Dry water is a new type of environmentally friendly fire extinguishing agent. It is a powder with a water content of more than 90 %, so it has excellent fire extinguishing properties. The purpose of this work was to obtain dry water fire extinguishing powders based on pyrogenic hydrophobic methyl silica with bentonite and to study their fire extinguishing properties in case of extinguishing gasoline on water surface. To obtain dry water fire extinguishing powders, there were used distilled water, Dashukovsky bentonite (Ukraine), and pyrogenic methyl silica (AM-300 brand, Ssp = 300 m2/g, particle size 5–7 nm) (Kalush, Ukraine). Dry water fire extinguishing powder was prepared by mixing the components at a speed of 15000 rpm for 10 s. Were made samples containing 10 wt. % methyl silica, 3, 6, 10, and 15 wt. % bentonite and the corresponding amount of water. The bulk density was 0.423, 0.453, 0.459, and 0.464 g/cm3 for samples of 3, 6, 10, and 15 wt. % bentonite, respectively. Optical microscopy has shown that the particles of the dry water powder have a clearly visible core-shell structure. Dry water fire extinguishing powder is a polydisperse system - most of the particles are single fine particles with a size of 1 micron or less, and there are also agglomerates with a size of more than 5 microns. As a result of the mechanical destruction of individual bentonite particles during high-speed mixing of components, bentonite particles are destroyed, therefore, individual bentonite particles are surrounded by a hydrophobic-hydrophilic mixture of hydrophobic silica nanoparticles and bentonite nanoparticles formed during exfoliation. The study of the fire-extinguishing properties of the dry water powder was carried out by spraying it onto a layer of burning gasoline A92 on water surface. The time to complete extinguishing of the fire and the consumption of the substance per unit area of burning were determined. It has been determined that the time for extinguishing gasoline and the consumption of dry water fire extinguishing powder for extinguishing it depend on the concentration of bentonite and are for 3, 6, 10, and 15 wt. % 9, 7, 6, and 9 s and 0.333, 0.309, 0.284, and 0.260 g/cm3, respectively. The developed dry water fire extinguishing powders are environmentally friendly, have good fire extinguishing properties, and can be used to extinguish oil products on the surface of water bodies.

Self-Healing Gels Based on Bimetallic ion Cross-Linking for Mining Fire Prevention and Extinguishing

ABSTRACT To address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, a new biomass gel material was prepared using sodium carboxymethyl cellulose (CMC) as the matrix, ferro aluminum citrate (Fe-AlCit) as the cross-linking agent, and gluconic acid-δ-lactone (GDL) as the pH modifier. Through performance tests of gel micromorphology, thermal stability, viscoelasticity and yield stress, it was found that the CMC-3 gel material with a ratio of 2.5% CMC + 4% Fe-AlCit +2% GDL had a dense surface structure, good thermal stability and moderate viscosity, which was the most suitable for pipeline transport. A metal coordination bond favorable to the stability of CMC-3 gel is formed by the carboxylate ion in CMC and the double high-valent metal ions Fe3+ and Al3+ dissociated by Fe-AlCit. CMC-3 gel exhibits excellent fire prevention and extinguishing properties. The results of the programmed warming experiments showed that the inhibition rate of the coal sample treated with CMC-3 gel against CO and C2H4 gases reached 44.84% and 46.57% at 220°C, respectively, and the growth rate of the activation energy in the first and second stage reached 17.63% and 22.68%, respectively, which plays a significant inhibitory role. The infrared spectroscopy test showed that after adding CMC-3 gel, the content of -OH and Ar-C-O in the coal samples was reduced by 49.58% and 40.82%, respectively, and the content of stable C=C in the aromatics was increased by 6.14%, which effectively blocked the coal-oxygen chain reaction and reduced the tendency of coal spontaneous combustion. The thermogravimetric test showed that the characteristic temperature points of the coal sample treated with CMC-3 gel were all increased to different degrees. The fire extinguishing test showed that CMC-3 gel could significantly reduce the temperature of coal sample and extinguish the coal fire quickly. Moreover, the CMC-3 gel material also has excellent self-healing properties, which can self-repair the damaged network through the abundant reversible hydrogen and ionic bonds inside the gel in only 90 s. The study has certain guiding significance for the development of efficient and environmentally friendly self-healing mining fire prevention and extinguishing materials.

Synthesis and application of cationic fluorocarbon surfactants

In this paper, a series of cationic polyurethane fluorinated surfactants were synthesized using a series of isocyanates, and 1H, 1H, 2H,2H-tridecafluoro-1-octanol, 2-(dimethylamino)ethanol, and iodomethane as raw materials in a three-step sequential reaction. These fluorinated surfactants exhibited high surface activity and low critical micelle concentration. In addition, these fluorinated surfactants exhibited excellent wetting and emulsification properties at very low concentrations of 0.1 wt%. In addition the cationic polyurethane fluorinated surfactants are compounded into aqueous film-forming foam extinguishing agents, which exhibit excellent fire extinguishing properties. The desirable properties coupled with the simple and green preparation process make this strategy a new way to prepare sustainable alternatives to long fluoroalkyl chain surfactants.

Wafer-Scale Field-Effect Transistor-Type Sensor Using a Carbon Nanotube Film as a Channel for Ppb-Level Hydrogen Sulfide Detection.

Sulfur hexafluoride is widely used in power equipment because of its excellent insulation and arc extinguishing properties. However, severe damage to power equipment may be caused and a large-scale collapse of the power grid may occur when SF6 is decomposed into H2S, SOF2, and SO2F2. It is difficult to detect the SF6 concentration as it is a kind of inert gas. Generally, the trace gas decomposed in the early stage of SF6 is detected to achieve the function of early warning. Consequently, it is of great significance to realize the real-time detection of trace gases decomposed from SF6 for the early fault diagnosis of power equipment. In this work, a wafer-scale gate-sensing carbon-based FET gas sensor is fabricated on a four-inch carbon wafer for the detection of H2S, a decomposition product of SF6. The carbon nanotubes with semiconductor properties and the noble metal Pt are respectively used as a channel and a sensing gate of the FET-type gas sensor, and the channel transmission layer and the sensing gate layer each play an independent role and do not interfere with each other by introducing the gate dielectric layer Y2O3, giving full play to their respective advantages to forming an integrated sensor of gas detection and signal amplification. The detection limit of the as-prepared gate-sensing carbon-based FET gas sensor can reach 20 ppb, and its response deviation is not more than 3% for the different batches of gas sensors. This work provides a potentially useful solution for the industrial production of miniaturized and integrated gas sensors.

Preparation and properties of a new core–shell-modified gel dry-water powder

To improve the spray fire extinguishing performance of magnesium-hydroxide gel dry-water powder, this paper studied the preparation speed, material mass ratio, fluidity, bulk density, pressure resistance, and fire extinguishing performances of modified dry-water powders. A pure-water dry-water powder was modified by applying an effective extinguishing component, magnesium hydroxide, and a coagulant, Gellan gum. The preparation process parameters of the pure-water dry-water powder system were optimized. The results showed that the optimal process parameters for the preparation of dry-water powder were a rotation speed of 4000 rpm, an SiO2:H2O ratio of 9:100, and a stirring time of 3 min. The resting angle of magnesium-hydroxide gel dry-water powder was below 28°, with good fluidity. The bulk density of the dry-water powder was lower than that of the BC-class dry powder extinguishing agent, and the bulk density of the magnesium-hydroxide gel dry-water powder was 0.467 g·mL−1. With the increase in pressure, the damage rate of the dry-water powder increased. The addition of magnesium hydroxide and Gellan gum significantly improved the pressure resistance of the dry-water powder. At a pressure of 1.4 MPa, the magnesium-hydroxide gel dry-water powder was only 11% damaged. The performance of the magnesium-hydroxide gel dry-water powder was improved by 37.21% compared with the average cooling rate of the BC-class dry powder extinguishing agent used as a control fire extinguishing group. The dry-water powders produced by modifying the dry-water powders with magnesium hydroxide and Gellan gum could withstand higher driving pressures, and they had improved powder diffusion, reduced powder charge volume, and increased fire extinguishing properties compared with those of the other dry-water powders.

An Intelligent Recognition Method of a Short-Gap Arc in Aviation Cables Based on Feature Weight Enhancement

The cases of loose pin of electrical connectors and broken wire harnesses easily occur in aviation cables due to vibration and thus cause the short-gap arc fault. When the vibration frequency exceeds 30 Hz, the short-gap arc fast burning and extinguishing properties make the changes in time domain and frequency domain of fault signals weak, thus increasing the difficulty in the identification of such a fault. In this article, an arc recognition method based on weight enhancement (WE) and principal component analysis (PCA) is proposed to solve the identification problem of the short-gap arc fault caused by its unapparent frequency-domain characteristics. In the proposed method, the currents under different conditions were measured and analyzed based on the considerations of different vibration conditions and loads. The measured current signals were first decomposed with the empirical modal decomposition (EMD) method, and then, optimal intrinsic mode functions (IMFs) were selected based on the correlation coefficient and kurtosis index to reconstruct the signals with WE algorithm. The time-domain, frequency-domain, and sample entropy characteristics extracted from reconstructed signals were used to establish the 3-D eigenvectors with direct fusion algorithm. Finally, the short-gap arc fault was identified with a principal element analysis and dimension reduction method. The experimental results proved that WE could improve the selection of the optimal direction of PCA dimensional reduction projection and that the short-gap arc fault of aviation cables could be quickly and effectively identified with the proposed method.

Robust superhydrophobic and flame-retardant coatings based on hierarchical epoxy textured with gas barrier structure; efficient oil-water separation devices under extreme conditions

Inspired by the biomaterial nacre, we report a versatile and facile strategy to rugged, flame retardant superhydrophobic materials by embedding a nacre-like montmorillonite (MMT) based gas barrier layer into hierarchical epoxy-resins. The well-aligned MMT layer imparted excellent oxygen and water barrier properties that rendered the coating surface water repellent yet protected the substrate materials from fire by suppressing heat and oxygen transfer. The hierarchical epoxy not only provided the robust superhydrophobic structure but offered strong adhesion to MMT layer. After application of this coating to a flammable sponge, it demonstrated superhydrophobicity with a contact angle of ∼153°. Furthermore, the material was rugged, resisting 1200 compression cycles and induced marked flame retardancy. The coated sponge delayed ignition (689% delay in ignition time) and promoted significant flame extinguishing property, compared with the uncoated material (demonstrated by LOI, CONE combustion, and fire scenario tests). Owing to its robustness and multifunctionality, the coated sponge was able to efficiently separate oil from multi-environments including strong corrosive, icy, boiling or vibrating mixtures. Additionally, the versatile application to wood, cotton, textile and other lignocellulosic substrates has been verified. This research opens up a new direction for durable waterproof and fireproof materials.

Laboratory and Bench Methodology to Test Fire Suppressant Effectiveness in Aviation Method of Extinguishing of Forest Fires

Laboratory and bench tests for evaluation of fire retaining and fire extinguishing properties of agents used for fighting forest fires are described. The methodology gives not only a possibility to understand the effectiveness of the agents themselves but also to determine the characteristics of their discharge from an aircraft, in particular, the length and width of the wetted strip, the irrigation density and the flight altitude. Laboratory experiments confirm high fire retaining efficiency of aqueous solutions of magnesium halides and diammonium phosphate which cause significant delay in ignition time and substantial increase in ignition temperature for wood treated with these solutions. The efficiency of the halides significantly increases in the row MgCl2 < MgBr2 < MgI2. It was also shown by the experiments that the irrigation density by aqueous solutions necessary to extinguish grassroots and crown forest fires decreases when using Firex wetting agent and increases for bischofite and bentonite.

Study on the stability of foamed gel and its structural evolution characteristics

ABSTRACT Foamed gel is an efficient material for coal spontaneous combustion prevention and control, which effectively combines the fire prevention and extinguishing properties of foam and gel. In this paper, the formation principle, structural evolution, stability, and fluidity of foamed gel are elaborated. Foamed gel is mainly formed by foaming agent, cross-linking agent and water through physical foaming and gelling reaction, and its formation process is divided into two stages: the first stage is physical foaming and forming foam; the second stage is adding cross-linking agent to foam and generating foamed gel through gelling reaction. The first stage of foamed gel mainly reflects the fluidity and stacking of foam, and in the second stage, with the increase of gel amount, foamed gel reflects the temperature resistance of gel. The basic structure of the foamed gel is the same as that of the water-based foam, and the gel particles constitute the basic skeleton of the foamed gel, which slows down the gravitational drainage and foam disproportionation rate. The evolution process of foamed gel structure includes liquid film rupture, gel formation and skeleton collapse, which eventually forms a gel layer to fill the residual coal fissure. The flow of foamed gel in the mining area is subject to the combined effect of grouting pressure, gravity and resistance, and the lateral flow velocity is larger than the longitudinal flow velocity, and the contour line of its diffusion front peak is ellipsoidal.

Modifying of air-mechanical foams using organosilicone compounds

The results of studying the fire foams’ modification using organosilicone compounds are presented in this article. The results of comparative fighting flammable liquid fires (diesel fuel) using non-modified foam and modified foam are also studied. It is shown that fire fighting using foam, modified with organosilicone compounds is much more effective, because of the increasing isolating capacity of such foam due to high-solidifying formation of foam which prevent the liquid vapors from getting in the area of chemical reactions and also isolate the flammable liquid from the oxygen of the air. Such a result is possible due to the presence of the mixture of solutions of foaming agent and the organosilicone modifying compound in the structure of the foam – tethraethyl silicate (TES). The results of the study confirm the perspective of using the organic compounds of the silica for improvement the fire extinguishing properties of the foam and its further applying for the fighting with flammable liquid fire.

A novel biomass sodium alginate gel foam to inhibit the spontaneous combustion of coal

In order to address the environmentally friendly issue of fire prevention and extinguishing materials in coal mines, A new biomass sodium alginate gel foam (SC-GF) was prepared by using sodium alginate (SA), calcium L-lactate (CL), alkyl glycoside (APG) and tea saponin (TS). The effect of different concentrations of CL on the properties of SC-GF was analyzed by studying the gelation time, foaming volume and half-life of the SC-GF. The results show that the gelation time of SC-GF is successfully controlled by using the weak electrolyte CL as the cross-linking agent. When SA: CL: APG: TS = 4 : 1 : 2 : 1, the gelation time of SC-GF is 10 min with half-life of 16 days. Furthermore, A metal coordination bond favorable to the stability of SC-GF is formed by the carboxylate ion of α-L-gulonic acid in SA and Ca2+ ionized by CL. SC-GF exhibits excellent fire prevention and extinguishing properties. The CO concentration of the coal sample treated with SC-GF decreases from 7556.8 to 34.92 ppm in the process of oxidation at room temperature for 48 h. The temperature-programmed oxidation test shows that SC-GF can delay the accelerated oxidation temperature from 120 to 160 °C, and the CO inhibition rate is as high as 60.5 % at 200 °C. The fire extinguishing test indicates that SC-GF can significantly reduce the temperature of the coal sample and extinguish the coal fire quickly. The study is useful to develop efficient and environmentally friendly coal mine fire prevention and extinguishing materials.

Preparation and characterization of a lignin based hydrogel inhibitor on coal spontaneous combustion

Although organic hydrogel fire-fighting materials have excellent properties in fire prevention and extinguishing, the harsh experimental conditions, combined with expensive synthetic raw materials, make organic gel fire-fighting marginally visible. This issue could be addressed by introducing lignin to the network of gel. Lignin is a macromolecular organic matter, which consists of phenyl propanol units and aromatic rings, and has excellent thermal stability and biocompatibility. The addition of lignin would improve the thermal stability of the hydrogel, increase the water absorption capacity, and make the hydrogel more porous. Copolymerization of lignin, N-isopropyl acrylamide (NIPAm) and acrylic acid (AA) through stirring at room temperature, followed by Fourier transform infrared spectrometry (FT-IR), thermogravimetry and differential scanning calorimeter (TG-DSC) analysis of the effect of lignin-based hydrogel on coal oxidation, the consumption of aliphatic hydrocarbons on the surface of coal slowed down, and the characteristic temperatures including critical temperature, initial exothermal temperature and the ignition temperature all increased significantly, while releasing less heat during the process of coal oxidation. The distributed activation energy showed that the presence of lignin-P(NIPAm-co-AA) increased the activation energy barrier throughout the entire oxidation process, with maximum increase of 37 kJ/mol, suggesting that lignin-P(NIPAm-co-AA) inhibited the coal oxidation effectively. Thus, the incorporation of lignin into P(NIPAm-co-AA) hydrogel represents positive benefits in terms of realizing high-value utilization, reducing the cost of hydrogel, and improving the fire extinguishing properties of hydrogel on coal oxidation.

A novel biomass thermoresponsive konjac glucomannan composite gel developed to control the coal spontaneous combustion: Fire prevention and extinguishing properties

Spontaneous combustion in coal mines continues to pose a significant risk. A novel biomass composite thermoresponsive gel produced by mixing konjac glucomannan (KGM) with fly ash (FA) was prepared to prevent coal spontaneous combustion. The composite gel had a controllable gelation time, a good seepage capacity, a high water retention capacity, a good combustion inhibition effect and an excellent fire extinguishing effect. Scanning electron microscopy indicated that the FA strongly interfacially adhered to the three-dimensional KGM framework and the gel wrapped around the coal surfaces well. Energy dispersive X-ray spectroscopy element mapping indicated that the FA was mixed uniformly with the KGM gel. The KGM@FA gel oxidation characteristics were analyzed by thermogravimetry infrared analysis and low-temperature coal oxidation system. The KGM@FA gel was found to effectively inhibit coal temperature increases, heat accumulation and CO generation during the process of oxidation and combustion, which would decrease the likelihood of coal spontaneous combustion. Fire-extinguishing experiments indicated that the gel covered the surfaces of burning coal well and markedly decreased the fire temperature and CO emissions and therefore stably extinguished the fire without combustion restarting. The KGM@FA gel is therefore an effective fire prevention and extinction material.

Preparation of foamed gel for preventing spontaneous combustion of coal

As a fire prevention and extinguishing technology, foamed gel was developed to control spontaneous combustion of coal effectively. Foamed gel is a compositional system formed by a foaming agent, polymers, and N2 through physical foaming. It controls spontaneous combustion of coal by integrating the fire prevention and extinguishing properties of gel and foams. In this study, the influences of the compositional system and the dosage of foaming agent, as well as the type and dosage of polymers, on foam properties were analyzed by experiments. A compositional foaming agent system was prepared by mixing two surfactants at a mass ratio of 1:2. Results show that the foamed gel prepared when the mass fractions of the compositional foaming agent system and the polymer X are 6 and 3 g/L is optimal. Moreover, the retardation performance of the foamed gel was studied. Results demonstrate that the TTI of coal samples with foamed gel is 334 s, which is considerably higher than those of coal samples with MgCl2 and raw materials (167 and 27 s, respectively). The highest HRR of coal sample with foamed gel is only 38.46 kW/m2, which is significantly lower than those of coal samples with MgCl2 and raw materials (62.32 and 68.08 kW/m2). The THR of coal samples with foamed gel is the lowest (28.87 kW/m2) within 1,200 s; meanwhile, the THR of coal samples with MgCl2 and raw coal samples is 45.46 and 49.97 kW/m2, respectively. Therefore, the coal samples with foamed gel have outstanding retardation performance.

Огнетушащая эффективность перфторизогексенов

Показана нехватка современных веществ для газового пожаротушения, вызванная борьбой с глобальным потеплением. Описаны подходы к поиску перспективных газовых огнетушащих веществ (ГОТВ), применявшиеся ранее. Предложен новый подход и найдены с его помощью принципиально новые огнетушащие вещества, полностью удовлетворяющие современным экологическим и токсикологическим требованиям. The paper is devoted to investigation of perfluoro-isohexenes as new gaseous fire suppressants. The current situation in the field of fire protection with chemically active gases is analyzed. The problem of greenhouse gases replacement during fire suppression is discussed. The disadvantage of existing alternative agents is short atmospheric lifetime. It is also shown that the existing approach to development of new gaseous fire extinguishing substances is almost exhausted. New group of gaseous agents for fire suppression - perfluoro-isohexenes - is proposed based on new approach. These substances are non-toxic and have very short atmospheric lifetime. Two types of experimental equipment were used in this work to investigate properties of aforesaid substances as extinguishing agents. It was implemented to determine flammability limits of gaseous mixtures and fire extinguishing concentration of gaseous fire suppressants having high boiling point. It was shown that perfluoro-isohexenes are non-flammable and their extinguishing properties are substantially better than properties of the nearest equivalent - perfuoroethyl-isopropylketone. These results are discussed from the point of view of the features of transformation of considered fire extinguishing substances in a flame.