Mixed fire extinguisher

Abstract

To provide a mixed fire extinguisher applicable to fires caused by powdered metals.SOLUTION: A mixed fire extinguisher contains water, a thixotropic agent, and a powdered fire extinguisher, wherein the viscosity of the mixed fire extinguisher, as measured at 20°C, ranges from 500 to 10000 mPa / s, and preferably from 1000 to 4000 mPa / s. The mixed fire extinguisher can be used as a fire extinguisher for fires caused by metal powder, and is applicable to fires caused by magnesium powder. A colloidal hydrated silicate is preferable as the thixotropic agent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a mixed fire extinguishing agent, and more particularly to a mixed fire extinguishing agent containing a powder fire extinguishing agent.

Background Art

[0002] Conventionally, for metal fires caused by the combustion of metals such as magnesium, when the metal heated to a high temperature (surface temperature > 1000 °C) reacts chemically with water (hot water), continuously flammable hydrogen is generated, and the surrounding flame ignites the hydrogen, causing an explosion. Therefore, the damage caused by the fire may expand. For metal fires, a fire extinguishing method of suffocating the fire by spraying a powder fire extinguishing agent is adopted.

[0003] In recent years, a fire extinguishing agent in which vermiculite (also called expanded vermiculite) is suspended in water has been developed (see, for example, Patent Document 1). Vermiculite is a kind of powder fire extinguishing agent used when extinguishing metal fires. By spraying a fire extinguishing agent in which vermiculite is suspended in water on a metal fire, the metal surface can be covered with vermiculite, and it is known that the metal fire can thereby be extinguished.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, although the fire extinguishing agent obtained by suspending vermiculite in water can be expected to have a fire extinguishing effect when the burning metal is in a certain lump, when the metal is in powder form, the fire extinguishing agent will penetrate into the powder. As a result, there is a problem that the moisture contained in the fire extinguishing agent comes into contact with the metal and hydrogen is generated, not only rendering the agent ineffective but also potentially expanding the damage.

[0006] Therefore, in facilities that handle powdered metals or factories where metal cutting is performed, where powdered metals are generated, if a fire breaks out, since the cause of the fire may be the powdered metal, in such facilities, a fire extinguishing agent obtained by suspending vermiculite in water is not suitable for use.

[0007] Thus, an object of the present invention is to provide a mixed fire extinguishing agent applicable to fires of powdered metals.

Means for Solving the Problems

[0008] The present invention is a mixed fire extinguishing agent containing water, a thickening agent, and a powder fire extinguishing agent, and is characterized in that the viscosity measured at 20 °C is 500 to 10,000 mPa / s.

[0009] In addition, in the present invention, the viscosity can be set to 1,000 to 4,000 mPa / s. Also, in the present invention, the mixed fire extinguishing agent can be used as a fire extinguishing agent for fires of metal powder. Also, in the present invention, the metal powder can be magnesium powder. Also, in the present invention, the thickening agent can be a colloidal hydrous silicate.

Effects of the Invention

[0010] The present invention can provide a mixed fire extinguishing agent applicable to fires of powdered metals by setting the viscosity of the mixed fire extinguishing agent containing water, a thickening agent, and a powder fire extinguishing agent to 500 to 10,000 mPa / s as measured at 20 °C.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] The inventor of the present invention has discovered that by increasing the viscosity of the mixed fire extinguishing agent containing the powder fire extinguishing agent, it is possible to prevent the mixed fire extinguishing agent from penetrating into the powdery metal. The present invention is based on this finding.

[0013] Embodiments of the present invention will be described below. The mixed fire extinguishing agent of this embodiment contains water, a thixotropic agent, and a powder fire extinguishing agent, and has thixotropy (rheopexy). Here, thixotropy refers to "the property that a gel changes into a fluid sol simply by stirring or shaking, and returns to a gel again when left standing" (quoted from the 4th edition of the Iwanami Dictionary of Physics and Chemistry, Iwanami Shoten).

[0014] The thixotropic agent is a substance that imparts thixotropy to the mixed fire extinguishing agent and is used to make the viscosity of the mixed fire extinguishing agent the viscosity described later. The thixotropic agent is preferably a mineral containing a colloidal hydrous silicate such as smectite, bentonite or montmorillonite, or a synthetic inorganic polymer compound composed of the silicate.

[0015] The powder fire extinguishing agent is a fire extinguishing agent used for extinguishing metal fires (especially fires caused by Class II dangerous goods, iron powder, metal powder, magnesium, or those containing these as defined by the Fire Protection Law). Preferably, it is a fire extinguishing agent that expands by evaporation of crystal water due to heat, spreads the crystals adhering to the metal surface, and can cover the metal surface by cross-linking between the crystals. Examples include vermiculite (also called expanded vermiculite) and perlite (also called expanded pearlite). In this embodiment, the powder fire extinguishing agent is contained in the range of 10 wt% or more and 30 wt% or less of the mixed fire extinguishing agent.

[0016] The mixed fire extinguishing agent is applicable to extinguish fires caused by powdery metals, for example, magnesium powder, particularly magnesium powder with a particle size of about 20 mesh or more and 80 mesh or less. In the present invention, magnesium is defined to include not only pure magnesium but also magnesium alloys.

[0017] In order to prevent the contact between the contained moisture and the metal, the mixed fire extinguishing agent needs to have a viscosity that does not penetrate the powdery metal. On the other hand, when the thixotropic mixed fire extinguishing agent stands still and gels on the metal, the moisture contained in the mixed fire extinguishing agent evaporates due to the heat of the fire, so that the powdery fire extinguishing agent covers the metal to suffocate the fire and cooling extinguishing by the heat of evaporation can be expected. However, if the viscosity is too high, the performance of the cooling extinguishing will decrease.

[0018] Therefore, the viscosity of the mixed fire extinguishing agent measured at 20 °C and 60 rpm with a B-type viscometer (for example, Brookfield Digital Viscometer LVDV-2+PRO) is preferably 500 mPa / s or more and 10000 mPa / s or less, and more preferably 1000 mPa / s or more and 4000 mPa / s or less. Also, it is particularly preferable that the thickener is a colloidal hydrous silicate because it is possible to make the viscosity fluctuation of the mixed fire extinguishing agent due to heat smaller. When the thickener is smectite, the above viscosity can be achieved by containing the thickener at a concentration of about 1 wt% or more and 2 wt% or less.

[0019] The mixed fire extinguishing agent can be prepared by previously dispersing a thickener in water and mixing a powdery fire extinguishing agent into the dispersion. In this case, it is also possible to adjust the amount of the thickener and the powdery fire extinguishing agent according to the particle size and state of the metal powder. When the particle size and state of the metal powder are set, the mixed fire extinguishing agent may be automatically adjusted at a ratio suitable for extinguishing the fire. It is also possible to adjust by mixing a thickener into a suspension of a powdery fire extinguishing agent in water.

[0020] When the mixed fire extinguishing agent is sprayed onto the burning powdered metal, it adheres as a gel to the surface of the powder pile. Due to its viscosity, the adhered mixed fire extinguishing agent stays on the surface without penetrating the powder. When moisture evaporates from the mixed fire extinguishing agent due to the heat of the fire and the powder fire extinguishing agent expands, the surface of the powder is covered with a layer of the expanded powder fire extinguishing agent, suffocating the metal fire. At the same time, the heat of vaporization of water takes heat away from the metal, and the metal fire is extinguished by cooling. Thereby, the mixed fire extinguishing agent can extinguish the metal fire caused by powdered metal.

[0021] As a fire extinguishing device for spraying the mixed fire extinguishing agent of the present embodiment, for example, the fire extinguishing device described in FIG. 1 can be used. The fire extinguishing device 1 includes a chemical tank 2 filled with a dispersion liquid D in which a thickening agent is dispersed in water, a fire extinguishing agent tank 3 filled with a powder fire extinguishing agent P, a pump 4, a mixer 5, a discharge port 6 such as a sprinkler head, and a disaster prevention panel 7, and is connected to a fire detector 8.

[0022] When the fire detector 8 detects a fire in the protection area S where metal powder exists, it transmits a fire signal to the disaster prevention panel 7. The disaster prevention panel 7 that has received the fire signal activates the pump 4. When the pump 4 is activated, shear stress is applied to the dispersion liquid D in the chemical tank 2, and the solubilized dispersion liquid D is sent to the mixer 5. The powder fire extinguishing agent P sent from the fire extinguishing agent tank 3 to the mixer 5 is mixed with the dispersion liquid D sent to the mixer 5 by the mixer 5, and the mixed fire extinguishing agent is adjusted. The mixed fire extinguishing agent is sent to the discharge port 6 and is sprayed into the protection area S from the discharge port 6.

[0023] At this time, for example, information regarding the metal powder in the protection area S from the disaster prevention panel 7, such as information regarding the particle size and state, is input in advance to the mixer 5, and the mixer 5 determines the amount of the powder fire extinguishing agent P to be mixed into the dispersion liquid D based on the information. Note that the means for inputting the information to the mixer is not limited to the disaster prevention panel 7 and may be prepared separately.

[0024] Therefore, in the fire extinguishing agent of the present embodiment, by setting the viscosity measured by a B-type viscometer at 20 °C and 60 rpm to 500 to 10,000 mPa·s, preferably 1,000 to 4,000 mPa·s, due to its viscosity, it is possible to prevent the fire extinguishing agent from penetrating into metal powders, for example, magnesium powder of about 20 mesh to 80 mesh, and the cooling fire extinguishing due to the evaporation of the moisture contained in the fire extinguishing agent can sufficiently contribute to fire extinguishing. Thus, it is possible to provide a fire extinguishing agent applicable to fires of powdery metals.

[0025] Also, as a secondary advantage of setting the viscosity of the fire extinguishing agent as described above, although there is a limit (usually, about 20 wt% is the upper limit) to the amount of the powder fire extinguishing agent that can be suspended in water, by increasing the viscosity with a thickening agent, it becomes possible to contain a larger amount of the powder fire extinguishing agent.

[0026] And as a secondary effect of using a fire extinguishing agent such as the present invention for extinguishing fires caused by magnesium powder, in factories handling magnesium, sometimes fluxes are applied for fire extinguishing during a fire, but the flux generates corrosive gases (such as halogen gases) by thermal decomposition, and the corrosive gas may corrode metal products such as machinery in the surroundings. However, vermiculite and colloidal hydrated silicates do not generate corrosive gases, so it is possible to prevent the corrosion of metal products such as machinery in the surroundings.

[0027] As described above, the present invention has been described based on the above embodiments, but the present invention is not limited to the above embodiments and can be appropriately changed without changing the gist of the invention.

[0028] (1) The fire extinguishing agent of the above embodiment is assumed to be used as a fire extinguishing agent for metal powder fires, particularly applicable to fires caused by powdery metals. However, the fire extinguishing agent can sufficiently contribute to fire extinguishing even in fires caused by metals that are not powders in a certain lump form.

[0029] (2) In the above-described embodiment, the description has been made assuming a fire caused by magnesium powder. However, the present invention is also applicable to fires caused by other metal powders such as iron powder and aluminum powder. Further, the present invention is also applicable to fires such as electrical fires where extinguishing with water is difficult.

[0030] (3) In the above-described embodiment, the description has been made assuming a sprinkler system as the fire extinguishing device. However, the present invention can be a portable fire extinguishing device such as a fire extinguisher in which a premixed fire extinguishing agent is filled and pressurized in a container, and the mixed fire extinguishing agent is discharged when a lever is grasped.

[0031] (4) In the above-described embodiment, the description has been made assuming that the amount of the powder fire extinguishing agent P is determined and mixed in the dispersion liquid D based on the information on the metal powder in the protection area S. However, based on the information on the metal powder in the protection area S, the amount of water and the thickening agent can be determined to mix the dispersion liquid D to adjust the viscosity of the mixed fire extinguishing agent.

Explanation of Reference Numerals

[0032] 1 Fire extinguishing device 2 Chemical tank 3 Fire extinguishing agent tank 4 Pump 5 Mixer 6 Discharge port 7 Disaster prevention panel 8 Fire detector D Dispersion liquid P Powder fire extinguishing agent S Protection area

Claims

Claim 1 A mixed fire extinguishing agent containing water, a thickening agent, and a powdered fire extinguishing agent, characterized in that the viscosity measured at 20 °C is 500 to 10,000 mPa / s. Claim 2 The mixed fire extinguishing agent according to claim 1, characterized in that the viscosity is 1,000 to 4,000 mPa / s. Claim 3 The mixed fire extinguishing agent according to claim 1 or 2, characterized in that the mixed fire extinguishing agent is for extinguishing a fire of metal powder. Claim 4 The mixed fire extinguishing agent according to claim 3, characterized in that the metal powder is magnesium powder. Claim 5 The mixed fire extinguishing agent according to claim 1 or 2, characterized in that the thickening agent is a colloidal hydrous silicate.

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