Compressed air foam fire extinguishing technology is a new type of foam fire extinguishing technology that has been widely used at home and abroad for more than 20 years. The core component is compressed air foam system, which can reduce the foam fire extinguishing agent reserve and reserve space, further highlighting the fixed The performance advantages of compressed air foam systems for tank fire protection. Therefore, this study used the method of simulating oil tank fire extinguishing to evaluate the technical feasibility and effectiveness of the compressed air foam system for liquid injection, and thus the fund project: National Science and Technology Support Program (2011BAK03B04).
The engineering application of a stationary compressed air bubble system provides advantageous technical support.
1 test materials and test methods 1.1 test materials GB50151-2010 <bubble fire extinguishing system design specifications specified 61, when using liquid injection system, non-water-soluble liquid storage tanks of type A, B, C liquid storage tanks should use protein, Fluorin, film-forming fluoroprotein or aqueous film-forming foam; when using water-forming membrane foam, the anti-burning level should not be lower than the C grade specified in the current national standard GB15308-2006. When using a system to simultaneously protect water-soluble and water-insoluble liquids of type A, B, and C, anti-foaming liquid must be used. In summary of the above requirements, 3% protein foam fire extinguishing agent (P), 6% fluoroprotein foaming agent (FP), 3% aqueous film forming bubble qualified by GB15308-2006 (bubble fire extinguishing agent standard test) were selected in this study. Extinguishing agent (AFFF) and 3% anti-solvent film-forming foam extinguishing agent (AFFF/AR) are used as fire-extinguishing materials for testing. 71. According to GB15308-2006, the test results of fire-extinguishing performance of the above-mentioned several kinds of foaming agents are as follows: Table 1 shows.
Fire extinguishing performance of test foam fire extinguishing agent name Mixing ratio /% fuel fire extinguishing time 25% anti-burning time fire extinguishing performance grade rubber industrial solvent oil industry acetone rubber industrial solvent oil spray fire test fuel for 90 motor gasoline, vehicle Gasoline has a larger range of solvent oils than standard fire test fuel rubber industry, and although there is no clear flash point (usually between 50 and 10C), it is classified according to GB5(1)16-2006 Building Design Fire Code. It should be a non-water-soluble class A liquid. 18 Currently, methyl tert-butyl ether 91 is often added to unleaded gasoline which is currently commercially available, which further increases the difficulty of fire extinguishing. Therefore, the choice of vehicle gasoline as the test fuel in this paper is equivalent to selecting a relatively harsh and unfavorable fire extinguishing condition.
1.2 Test equipment Considering that there is no special standard or small-scale model, the actual fire-extinguishing performance of the fire-extinguishing agent against the oil tank fire can be effectively evaluated. However, the solid fuel fire test requires a large amount of test fuel, and the general financial and material resources. It is difficult to guarantee multiple repetitive and regular exploration experiments. Therefore, the research team designed a simulated oil tank to evaluate the feasibility of the compressed air bubble generation method for the fixed foam fire extinguishing system. ). Specifically, the simulated oil tank is an open design with a diameter of 1.7 m and a tank wall height of 1.7 m. The flow rate of the bubble mixture in the test is fixed at 11.4 L/min, and the cross-sectional area of ​​the simulated oil tank is 2.26 m2, so the study The medium bubble solution supply strength was 5 L/(min m2). Furthermore, a bubble bypass outlet is provided after the inlet of the compressed air bubble, so that the expansion ratio can be determined during the test, and the drain pipe is arranged at the bottom of the tank to facilitate the venting of the water layer.
The bubble generation system used in the test is a standard compressed air bubble system 1101 developed by the research team and meets the requirements of GB27897-2011 Class A foam fire extinguishing agent. The 30m long hose at the bubble outlet is connected with the compressed air bubble inlet of the simulated oil tank. .
The test method for jetting compressed air bubble fire on the tank liquid is as follows: add tap water to the tank to make the water layer height 1.2m. Start the standard compressed air bubble system, adjust the system pressure, and maintain the outlet flow of the bubble solution in the test requirements. Within the scope. Further adjust the standard compressed air bubble system to make the bubble state to the corresponding expansion ratio required by the test, and record the relevant pressure parameters.
Add 90 car gasoline to the tank to maintain the fuel layer thickness above the water layer at 30 mm. The tank car is ignited with gasoline and a standard compressed air foam system is activated. After the system is stable, open the foam bypass outlet valve and test the expansion ratio. After pre-combustion for 60 s, open the foam into the tank valve to apply the fire-fighting foam and record 90% of the fire control time and extinguishing time.
2 Test results and discussion 2.1 The influence of different supply strengths on the effect of the supply strength of the foam solution on the control and fire extinguishing effect under the condition of 2/3, the test results are shown in Table 2. The test results show that a higher foam supply strength can achieve better fire extinguishing effect. Although a more detailed supply strength test has not been carried out, it can be preliminarily judged that 5LAmin m2) is already close to the critical supply strength. GB50151-2010 <Design Specification for Foam Fire Extinguishing System> The supply strength of the foam mixture of the non-water-soluble liquid storage table 2 tank liquid injection system is defined as: protein 6L / (minm2), fluorine protein, water film formation and film formation fluorine Protein 5L / (minm2). Although the test results of this study do not reflect the advantages of compressed air foam production in the foam supply strength, the test conditions are 2/3 of the design mix ratio. It can be speculated that the compressed air foam fire extinguishing technology is used in the amount of foam fire extinguishing agent. Have certain advantages. In addition, the further extension of this test results can be considered that in the future fixed compressed air foam system for oil tank liquid injection engineering design, the protein foam fire extinguishing agent design supply strength should also be higher than the water film forming foam fire extinguishing agent.
Different foaming fluid types affect the control of different supply strengths. Fire extinguishing performance test result sample number mixing ratio /% supply strength eight 1 /! 11 - 1 m a foaming multiple 90% control fire time 10 minutes without fire extinguishing In fact, from Table 2 has been able to initially reflect the impact of foam type on fire performance. The anti-solvent film-forming foam fire extinguishing agent contains a fluorosurfactant, so its fire extinguishing performance is superior to that of the ordinary protein foam fire extinguishing agent, which can be reflected from the fire extinguishing performance level of Table 1. Specifically, in this test, at a supply intensity of 3L/(minm2), although the fire extinguishing time of 3% AFFF/AR is longer than 3'55", 3% of Table 3p cannot be extinguished at this supply strength. The effect of liquid type on fire extinguishing performance, this study also compared the control and fire extinguishing performance of 3% AFFF and 6% FP under the same supply strength. The control and fire extinguishing performance data of foam fire extinguishing agent used in this study are shown in the table. 3 is shown.
For the 90% control time, the data in Table 3 shows the following control at 51/(min.m2) supply intensity. Fire extinguishing performance test results Sample name mix ratio /% supply intensity eight! /! 1-1 foaming ratio 90% fire control time fire test time test results can also be expressed as: the foam liquid added with fluorosurfactant, its fire control performance is better than the fluorosurfactant-free variety, and added fluorine surface Among the active agent varieties, "film forming" foam fire extinguishing agents are superior to "non-film forming" foam fire extinguishing agents. According to the current level of foam fire extinguishing agent formula, in addition to protein foam fire extinguishing agent, in order to improve the fluidity of other fire-fighting foams of low-fold foam fire extinguishing agents used in Class B fire fighting, the fluorine will be added to the formula. The surfactant component, while the added fluorosurfactant has different ability to reduce the surface tension of the foam solution, and the foam fire extinguishing agent is divided into two types of "film forming type" and "non-film forming type". Although the "film formation" depends on the surface tension of the foam solution itself, it depends on the surface tension of the liquid to be protected, but the surface tension of the foam solution is always the key factor determining the fluidity of the fire-fighting foam on the oil surface, that is, for the same kind of In terms of protecting the liquid, the lower the surface tension of the foam solution under the condition of similar expansion ratio, the better the fluidity of the fire-extinguishing foam on the liquid surface.
Although the actual test has not been carried out, the order of surface tension from low to high for different types of foam fire extinguishing agents in the test should be: FFFAFFF/AR For the fire-extinguishing time, the same rule of "film-forming" foam fire extinguishing agent is better than "non-film forming" foam fire extinguishing agent. For AFFF/AR, the fire control time is longer than AFFF, and the fire extinguishing time is shorter than AFFF. The main reason is that AFFF/AR has better foam stability than AFFF, which makes it easier to control edge fire and shorten the fire extinguishing time. . 2.3 The effectiveness analysis of the fixed compressed air foam system is limited by factors such as funding and time, and the single representative sample does not have the overall representativeness. In this case, the impact of the expansion ratio on the wider range has not been More experimental samples for in-depth research must be thoroughly explored and confirmed in subsequent studies using a large number of basic experiments on a relatively small scale. The experimental results of this study still have strong theoretical and practical significance, and it is proved that the fixed compressed air foam system adopts the liquid injection method with technical feasibility. Use the protein foam fire extinguishing agent, fluoroprotein foam fire extinguishing agent, water film forming foam fire extinguishing agent and anti-solvent film forming foam fire extinguishing agent specified in the current foam fire extinguishing system design specification to be no more than 5L/(min m2). Under the supply strength of the foam solution required by the standard design, the fire test was successful, indicating that the fixed compressed air foam system has a relatively reliable technical feasibility. Although the fire extinguishing time of the selected foam fire extinguishing agent in the test is affected by external factors such as wind speed, wind power and temperature at each test, and there is only a small edge fire that is not extinguished, resulting in an extended fire extinguishing time, so that each time The fire extinguishing time of the test is not fully comparable, but this does not affect the final technical feasibility conclusion. This study further proves that the compressed air foam fire extinguishing method has better fire extinguishing performance than the aspirating foam generating method. In all the tests, the mixing ratio of the low-multiple foam fire extinguishing agent was lower than the designed mixing ratio, such as 3% aqueous film-forming fire extinguishing agent. The fire extinguishing success was achieved according to the 2% mixing ratio, which further confirmed the compression. The air foam fire extinguishing method has better fire extinguishing performance than the aspirating foam generating method, and has the potential and application value for the oil tank fire protection. The future research direction of fixed compressed air foam fire extinguishing technology should be the application of fixed compressed air foam system engineering, including the design of gas supply, liquid supply mode, gas-liquid mixing mode and gas-liquid equilibrium mode, and the length of the pipeline through the foam conveying pipeline. Control the state of the foam and how to properly adapt the design according to the existing foam fire extinguishing system settings. 3 Conclusions The fixed-type compressed air foam system is technically feasible to use the liquid-spraying method, especially in the foaming agent reserve amount, which is lower than the existing aspirating foam system. A higher foam supply strength results in a better fire extinguishing effect, with 5 L/(min such as 2) approaching the critical supply strength of the liquid jet compressed air foam. The foaming liquid with added fluorosurfactant has better fire control performance than the non-fluorinated surfactant. In the varieties with fluorosurfactant added, the "film forming" foam fire extinguishing agent is superior to the "non-film forming". Type "foam fire extinguishing agent. For the fire extinguishing time, also follow the "film forming type" Foam fire extinguishing agents are superior to the "non-film forming" foam fire extinguishing agent.
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