Mist Suppression Research Articles

Reliability Analysis Based on Fuzzy Comprehensive Evaluation for Cooking Fire Extinguishing System

Large cooking fires, occurring in industrial oil cookers, present a severe hazard to food processing plants. There lots of reasons and usually the fire extinguishing system invalid turned to be getting more and more attention. The fire extinguishing system has many complex components, and very difficult to evaluate. In view of the existing fuzziness and randomness in reliability comprehensive evaluation for the suppression system, a two-stayed fuzzy assessment model for the evaluation of the petrochemical production unit is established by using the theory of fuzzy mathematics. Average fault ratios, mean time between failures, effectiveness, mean-time-to-repair, and maintenance cost rate, spatial variability and fault density are used as evaluation index system. It is found from the result of evaluation that the variability of the water mist suppression system is reliability step.

Physical Scaling of Water Mist Suppression of Wood Crib Fires in Enclosures

Physical Scaling of Water Mist Suppression of Wood Crib Fires in Enclosures

Stability of 6:2 fluorotelomer sulfonate in advanced oxidation processes: degradation kinetics and pathway

Perfluorooctane sulfonate (PFOS), a widely used mist suppressant in hard chrome electroplating industry, has been listed in the Stockholm Convention for global ban. 6:2 Fluorotelomer sulfonate (6:2 FTS) acid and salts have been adopted as alternative products in the market, but no data about their abiotic degradation has been reported. In the present study, the degradability of 6:2 FTS potassium salt (6:2 FTS-K) was evaluated under various advanced oxidation processes, including ultraviolet (UV) irradiation, UV with hydrogen peroxide (H2O2), alkaline ozonation (O3, pH = 11), peroxone (O3/H2O2), and Fenton reagent oxidation (Fe(2+)/H2O2). UV/H2O2 was found to be the most effective approach, where the degradation of 6:2 FTS-K followed the pseudo-first-order kinetics. The intermediates were mainly shorter chain perfluoroalkyl carboxylic acid (C7 to C2), while sulfate (SO4 (2-)) and fluoride (F(-)) were found to be the final products. The high yields of SO4 (2-) and F(-) indicate that 6:2 FTS-K can be nearly completely desulfonated and defluorinated under UV/H2O2 condition. The degradation should firstly begin with the substitution of hydrogen atom by hydroxyl radicals, followed by desulfonation, carboxylation, and sequential "flake off" of CF2 unit. Compared with PFOS which is inert in most advanced oxidation processes, 6:2 FTS-K is more degradable as the alternative.

First Report of a Chinese PFOS Alternative Overlooked for 30 Years: Its Toxicity, Persistence, and Presence in the Environment

This is the first report on the environmental occurrence of a chlorinated polyfluorinated ether sulfonate (locally called F-53B, C8ClF16O4SK). It has been widely applied as a mist suppressant by the chrome plating industry in China for decades but has evaded the attention of environmental research and regulation. In this study, F-53B was found in high concentrations (43-78 and 65-112 μg/L for the effluent and influent, respectively) in wastewater from the chrome plating industry in the city of Wenzhou, China. F-53B was not successfully removed by the wastewater treatments in place. Consequently, it was detected in surface water that receives the treated wastewater at similar levels to PFOS (ca. 10-50 ng/L) and the concentration decreased with the increasing distance from the wastewater discharge point along the river. Initial data presented here suggest that F-53B is moderately toxic (Zebrafish LC50-96 h 15.5 mg/L) and is as resistant to degradation as PFOS. While current usage is limited to the chrome plating industry, the increasing demand for PFOS alternatives in other sectors may result in expanded usage. Collectively, the results of this work call for future assessments on the effects of this overlooked contaminant and its presence and fate in the environment.

Fire Behavior and Mist Suppression of a Room Lined with Glass Reinforced Polymer (GRP) Panels

Six water mist suppression experiments were conducted in an ISO 9705 size room lined with GRP panels with a small wooden crib as a fire initiation source. A four-nozzle water mist suppression system was used to extinguish the fires.Heat release rate (HRR) from the fires was measured, as well as: room temperature; wall surface temperature of GRP panels, and; heat flux to the wall at specific locations within the room. The concentration of oxygen, carbon monoxide and carbon dioxide was also measured in one corner of the room. It was found that the mist suppression method used was an effective system for extinguishing fires from 500kW – 1.5 MW in magnitude. However, in one experiment in which only a single, centrally located nozzle was used the fire could not be completely extinguished.The GRP material was characterised using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone calorimetry. The TGA results showed that the resin component of the GRP underwent pyrolysis over a temperature range of 225°C to 450°C when most of the resin mass was gasified leaving a solid char. The char material was completely consumed over a temperature range of 375°C to 430°C when heated in air. The DSC showed that, when heated in air, these two degradation steps released large amounts of energy.Cone calorimetry tests were conducted to measure the combustion behavior of the panel material (e.g. heat release rate (HRR) and time to ignition) when subjected to a constant incident radiant heat flux. The results showed that the panel material was flammable with a peak HRR of between 350 – 400kW/m2 and the minimum heat flux for ignition was determined to be 16.5kW/m2

Experimental Data on Water Mist Suppression

Action of water mist in suppressing gasoline spray fires, asphalt spray fires and diesel spray fires in confined spaces will be reported in this paper. Relevant experimental works reported earlier are reviewed with key points summarized. Factors affecting the properties of the water mist suppression systems are investigated. The characteristics of water mist are studied using the Phase Doppler Particle Analyzer with key results compiled. Results are firstly applicable in directly drafting out design guides on water mist suppression systems on oil fires. Secondly, it is also useful for justifying numerical models studying water mist suppression on oil fires.

Research Progress of the Methods of Acid Mist Suppression

Abstract: Acid mist suppression has always been a huge challenge, which troubled in metallurgy and metal products processing industries. According to the physical and chemical processes, the methods of acid mist suppression are discussed systematically in this paper. The application prospect of a new type of polymer microspheres used as acid mist suppressants is also presented in detail.

Performance evaluation of acid mist reduction techniques in copper electrowinning

The effectiveness of various acid mist suppression techniques has been analysed in the present work. The two important factors that influenced the performance of a floating barrier were its coverage of the solution's surface area and its height above the solution line. When comparing single layered floating barriers, spheres reduced acid mist the most due to their higher buoyancy and higher coverage of the solution surface. In general, barriers made of high density polyethylene were 3.4% more effective in reducing acid mist than those made of polypropylene due to their lower density which enabled them to be more buoyant in the solution and intercept acid mist more effectively.Acid mist was reduced noticeably with the addition of FC-1100 (a chemical reagent widely used to suppress acid mist) to the solution up to 30ppm. Further addition of FC-1100 made much less difference in the suppression of acid mist. When FC-1100 was used in combination with floating barriers (such as spheres), the reduction in acid mist improved by an average of 29% in comparison to the use of FC-1100 alone.

Full-scale experimental study on fire suppression performance of a designed water mist system for rescue station of long railway tunnel

Rescue stations have been newly designed in some super-long mountain railway tunnels of China such as over 30 km long, as a new type of strategic counteract design for fire accident in tunnels. Water mist fire suppression systems are needed to be installed in such rescue stations to control the train fire. However, there is no design engineering experience for it. In this article, a full-scale experimental facility was built to study the fire suppression performance of water mist system in such railway tunnel rescue station. A series of full-scale tests was preliminarily conducted considering the fire position was on top of, inside, and under the train carriage with gasoline pool fire and wood crib fire used as fire sources. A design of water mist suppression system for such a fire scenario was presented, and its performance was tested. Experimental data on temperature, CO concentration, and radiation flux were collected and analyzed. The results showed that the water mist system could control fires, cool the air temperature in the rescue station, and strongly reduce the radiant heat flux in the vicinity of the fire source under various ventilation conditions. However, the visibility of the rescue station was much deteriorated after the injection of water mist, so that emergency lights and evacuation lights are necessary for personnel evacuation. The changes of fire extinguishing time with longitudinal ventilation velocities showed that longitudinal ventilation could provide both favorable and unfavorable conditions for water mist fire extinguishment. So, to achieve efficient fire suppression performance of water mist system, attention might be paid to the controls of tunnel ventilation system in the event of a fire in a railway tunnel rescue station. The design of the water mist system and the full-scale experimental data on the fire suppression performance presented in this article may serve as a reference for such engineering applications.

The effects of mixtures of acid mist suppression reagents on zinc electrowinning from spent electrolyte solutions

The effects of Dowfroth 250 (D) and Tennafroth 250 (T) in combination with saponin (S) on zinc deposition current efficiency and power consumption during electrowinning of zinc from industrially supplied spent electrolyte solutions were investigated. The surface morphology and crystallographic orientations of the zinc deposits were also examined by scanning electron microscopy and X-ray diffraction techniques, respectively. Acid mist suppression efficiencies were measured and investigated by frothing behavior of the additives and by surface tension measurements. Concentrations of 5, 10, and 15 ppm of each of the additives were mixed with all possible combinations into spent electrolyte to study the effects. Results showed that addition of Dowfroth 250/Tennafroth 250 as well as saponin decreased the current efficiency, increased the energy consumption while maximum acid mist suppression efficiencies of 86.1% and 87.0% were obtained at D5 + S5 and T5 + S5, respectively. The increase in saponin concentration resulted a change in preferred crystal orientation from (104) (112) (103) (102) (101) at low saponin concentrations to (101) (112) at higher saponin concentration. Bright and compact deposits were obtained at a mixture concentration level of T5 + S5 and D5 + S5.

Physical Scaling of Water Mist Suppression of Pool Fires in Enclosures

A series of fire suppression experiments was conducted in two geometrically similar enclosures of 1-to-3 ratio to evaluate whether the Froude-modeling-based scaling methodology could reasonably reproduce the pool fire development under water mist application in different scales. The parameters considered in the evaluation were: enclosure size, door opening size, water mist spray condition, fire size, fire location and fire-shielding condition. The two enclosures measured 1.22x1.22x1.22 m and 3.66x3.66x3.66 m. Two door opening sizes were tested for each enclosure: 0.30x0.61 m high and 0.61x0.61 m for the Scale-1 enclosure, and 0.91x1.83 m high and 1.83x1.83 m for the Scale-3 enclosure. Two heptane fire sizes were selected for each enclosure. The quasi-steady heat release rates of the two pool fires for the Scale-1 enclosure were 25 and 57 kW, and the corresponding heat release rates were 380 and 860 kW for the two pool fires used in the Scale-3 experiments. Besides matching the quasi-steady heat release rates according to the scaling requirement, the fire developments under free-burn were also carefully scaled. Two water mist nozzles were used to produce the water mist sprays in the Scale-1 and Scale-3 enclosures; these two nozzles were operated at the designated pressures of 13.8 bar and 41.4 bar, respectively. In each enclosure, nine ceiling-mounted nozzles were arranged in a 3 x 3 pattern with equal nozzle-to-nozzle and nozzle-to-wall spacing. The experiments showed that the fire development in terms of heat release rate could be reasonably reproduced during free-burn and water mist application in the Scale-1 and Scale-3 enclosures, so was the oxygen concentration inside the enclosure.

Suppress flashover of GRP fire with water mist inside ISO 9705 Room

Water mist suppression tests for glass-reinforced polyester (GRP) panels were conducted in ISO 9705 Room. GRP panels covered part of the room and a wood crib fire was used as fire source to ignite GRP fire. A four-nozzle water mist suppression equipment was used inside test room on the time of flashover. Heat release rate of the combustion inside the room, room temperature, surface temperature of GRP panels, total heat flux to wall, ceiling and floor in specific positions were measured. Gas concentration of O2, CO, and CO2 was also measured in the corner of the room at two different levels. A thermal image video was used to record the suppression procedure inside room. Test results show that the water mist system is efficient in suppressing the flashover of GRP fire and cooling the room within short time.

Physical Scaling of Water Mist Suppression of Pool Fires in Enclosures

Physical Scaling of Water Mist Suppression of Pool Fires in Enclosures

Experimental and numerical study on water mist suppression system on room fire

Full-scale experiment and numerical simulations are carried out on a room fire to study water mist suppression system with heat release rate of 6 MW. A computational fluid dynamics (CFD) model of fire-driven fluid flow, FDS (Fire Dynamics Simulator), is used to solve numerically a form of the Navier–Stokes equations for fire. A fire experiment without water mist is performed and the temperatures are measured to validate the predictions of FDS code against the experimental data. Then a fire experiment with water mist suppression system is performed and the temperatures and extinguishing time are measured. The validated numerical model is used to simulate the experiment; the temperatures, oxygen concentration and extinguishing time are compared and studied. In numerical simulations, the cell size sensitivity is analyzed. The experimental results of temperatures and extinguishing time are compared with the results of numerical simulations. It appears that the numerical results are in good agreement (qualitatively) with the experimental data in temperature fields. These useful data can be helpful in accomplishing the design of water mist suppression system and the design regulations for fire safety management.

An Investigation on the Effects of Organic Additives on Zinc Electrowinning from Industrial Electrolyte

The influence of Saponin, Licorice, Tennafroth 250, and Dowfroth 250 at different concentration levels (0, 5, 10, and 15 ppm) were investigated during zinc electrowinning from industrially supplied spent electrolyte. Acid mist suppression efficiency, polarization behavior, current efficiency and energy consumption were investigated for a current density of 500 A.m-2. Surface tension measurements were used to find a correlation between the concentration of the different additives and the acid mist suppression efficiencies. Morphological and crystallographic orientation studies indicated dense and well defined crystalline grains with homogeneous distribution mostly at the 5 ppm level of suppressant. The electrowinning in presence of Saponin and Tennafroth were found to have high current efficiencies of 90% each with low energy consumptions of 2641 and 2675 kWh/t, respectively and the deposited crystals were found to be oriented preferably in the [101], [102], [103] and [112] planes for both.

Suppress flashover of GRP fire with water mist inside ISO 9705 Room

Water mist suppression tests for glass-reinforced polyester (GRP) panels were conducted in ISO 9705 Room. GRP panels covered part of the room and a wood crib fire was used as fire source to ignite GRP fire. A four-nozzle water mist suppression equipment was used inside test room on the time of flashover. Heat release rate of the combustion inside the room, room temperature, surface temperature of GRP panels, total heat flux to wall, ceiling and floor in specific positions were measured. Gas concentration of O2, CO, and CO2 was also measured in the corner of the room at two different levels. A thermal image video was used to record the suppression procedure inside room. Test results show that the water mist system is efficient in suppressing the flashover of GRP fire and cooling the room within short time.

Effects of pairwise, donor–acceptor functional groups on polymer solubility, solution viscosity and mist control

Homologous series of functionalized polymers were used to compare the solution properties of donor–acceptor (DA) interpolymer mixtures with those of self-associating and non-associating polymer analogues. Polymer analogous synthesis was used to produce a series of polymers from a specific, anionically-polymerized prepolymer (1250 kg/mol polybutadiene), using thiol-ene coupling to incorporate systematically-varied contents of side groups: either tertiary amines (as proton acceptors) or carboxylic acids (both as proton donors in donor–acceptor mixtures, or as self-associating moieties in single-polymer solutions). Comparison with controls reveals that, relative to the effects of self-associations, DA interpolymer interactions more strongly affect solution properties such as phase behavior, interpolymer aggregation, shear viscosity, and elastic response in extensional flow. Specifically, DA associations lead to (i) greater reductions in polymer solubility in hydrocarbon solvents, (ii) interpolymer aggregation into larger clusters, and (iii) greater shear viscosity in solution. Nevertheless, DA associations reduced solution elasticity and mist suppression—a highly unanticipated result in light of the prior literature.

Experimental Studies on Water Mist Suppression of Liquid Fires with and without Additives

The purpose of this article is to examine the effect of additives on the extinguishment of liquid pool fires with water mist. Tests are conducted using gasoline, diesel, and ethanol pool fires in a 3.0 × 3.0 × 3.0 m well ventilation compartment. The additives included representative kinds of metal compound, NaHCO3, film-forming agent, AFFF, and a multi-component agent, MC additive. Results showed that the suppression performance varied greatly depending on fuel type, additive type, and concentration. The higher the fire point, the easier it is to extinguish the hydrocarbon liquid pool fires with water mist. But for the polar fuel, small fractal flames existing around the pool edge after the fire is suppressed increased the suppression difficulty. The benefit of adding film-forming additives is observed in the suppression of hydrocarbon fires when forming a thin film layer by fluorinated surfactant on the surface. However, too much film-forming additive decreased the marginal fire extinguishing effectiveness due to the saturation effects of surfactants. Addition of a small quantity of film-forming additives did not improve the performance of water mist for ethanol fires, which is considered to be eroded by the fuel. Addition of metal compounds increased the effectiveness of water mist gradually both for ethanol and hydrocarbon fires, but there also existed upper agent limit because of the associated limiting vapor pressure of the active metal compound. The multi-component additive showed a combined suppression effect of film-forming agent and metal chemicals. It effectively extinguished both ethanol and hydrocarbon fires though coupling the physical and chemical fire suppression mechanisms and seems worth further exploration.

Evaluation of Surfactant Enhanced Water Mist Performance

Water-mist technology provides efficient fire suppression for compartments while minimizing water usage. Even with the many advantages of water mist systems, there is still room for improvement. Water mist systems have demonstrated effectiveness at suppressing flammable liquids (Class B) fires in compartments. However, an especially challenging fire suppression scenario for water mist systems is the small Class B fire. This scenario is often realized after a large fire has been reduced in size or ‘controlled’ by water mist. The small fire scenario is challenging because a small fire may not be able to generate enough vaporized water to displace sufficient oxygen for complete extinction. It should also be noted that even if the Class B fire is extinguished with a water mist system, re-ignition from the hot surrounding surfaces may occur at any time. In the present work, an additive is introduced into the water supply and its effect on the water mist suppression performance is studied. This ForafacTM additive is a specific formulation, which includes fluorinated surfactants for creating a robust fire suppression foam. The enhanced suppressant exiting the mist nozzle is dispersed in the form of small droplets (not as a continuous foam) similar to a pure water mist spray. However, these droplets create a foam blanket on the surface of the fire, which acts to isolate the fuel from the air. With this formulation, the efficiency of the water mist system is improved even on small fires and most importantly the re-ignition of class B fires is prevented.

Preliminary Experimental Study and Numerical Simulations on Suppressing Spray Bitumen Fire with Water Mist in a Confined Space

Spray bitumen fires often occur in buildings and industrial processes. To investigate this type of hazard, the burning behavior of this flammable mixture was tested under practical conditions. Investigations of the suppression of this typical kind of fire were also included. CFD simulations were used as supplementary validation of tests that assessed the suppression of this type of fire by application of water mist. The water mist was generated from a centrifugal nozzle operating at low pressure about 1.0 MPa. The characteristics of the water mist were tested by LDV/APV system. The fuel was sprayed using the same sprayer as the sub-sprayer of the water mist nozzle. The flame structure was observed by the Thermograph (TG, SATHY6850). The various temperatures were tracked every 1 second by the K-type thermocouple. The flame suppression processes were observed and analyzed using a Charge Coupled Device (CCD) video camera. All the experiments were carried out in a 3 m × 3 m × 3 m confine space. Results indicated that the highest temperature of the spray bitumen fire was recorded in the core of the spray. The spray bitumen fire could be suppressed effectively by using the water mist fire suppression system. For lower pressure of the spray bitumen, the water mist suppression demonstrated higher efficiency. The test results showed that there was a short-lived “fire enhancement” phenomena as long as the water mist was released into the spray fire. Also, using the FDS to simulate the spray bitumen fire, we found comparative results between the numerical and experimental results.