JPH09653A - Sodium flame extinguishing method - Google Patents

Abstract

PURPOSE: To facilitate the fire extinguishing process by inhibiting the generation of aerosol and white smoke by allowing stable and harmless compounds, such as sodium oxide, sodium peroxide, and sodium hydroxide, to be produced through reactions between air and solid sodium or with liquid sodium vaporized into the air. CONSTITUTION: Upon detection of the leakage of Na 2, a metal Na sump 1 on a truck 6 is dispatched to the point of leakage of Na 2 for Na 2 collection. In view of the quantity of Na collected and the spread of flame, a shovel, small fire-extinguisher, or flexible compressor tube 5 is used to cover airtight the Na surface or flame with an extinguishant 3, 3'. In this process, chemically stable m-sodium silicate (Na2 SiO2 ) 4 is generated along the contact surface between Na 2 and the extinguishant 3' for the suspension of combustion and then for complete extinguishment due to interrupted oxygen supply.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for extinguishing a sodium flame.

[0002]

2. Description of the Related Art Metallic sodium used in FBR and various FBR testing devices is very active and easily reacts with various constituent elements. Therefore, it is usually a closed loop device or a free liquid surface. In the case of a device, a tank container, or the like in which is present, it is used by being covered with an inert gas such as argon (Ar) to block air and moisture.

For example, in an FBR and a test device, Na
Is used at a temperature of 120 to 600 ° C., and if this high temperature Na leaks from a pipe, a device or the like, a rapid oxidation reaction occurs as shown in Chemical formula 1, Chemical formula 2 and Chemical formula 3. Transiently black sodium peroxide (Na ₂ O ₂ )
And white sodium oxide (Na ₂ O) are mixed and generated,
It is considered that this unstable ignition of sodium peroxide causes a fire. The ignition temperature of Na is 3
Although it is around 00 ° C, the combustion flame is almost 500-700 ° C.
To rise.

[0004]

[Chemical formula 1] 2Na + 1 / 2O ₂ = Na ₂ O (Chemical formula 1)

[0005]

Embedded image Na ₂ O + 1 / 2O ₂ = Na ₂ O ₂ (Chemical formula 2)

[0006]

[Formula 3] 2Na + O ₂ = Na ₂ O ₂ (Formula 3) Note that the combustion of Na begins and Na ₂ O and Na ₂ are present in the combustion section.
Once sodium oxide such as O ₂ is produced, since this product is porous, Na is supplied to the surface of the product and burns due to the surface tension of Na and the chimney effect due to the Na flame. The form of lava rises. Therefore, irregularities of approximately several cm are generated on the burning surface.

The length of the flame in the Na fire is at most 2 to 3 cm, which is relatively short, and the burning velocity (.about.0.1 mm ² / sec) is about one digit smaller than that of the petroleum fire. Although the spread of the fire is slow in this way, the amount of white smoke that is highly irritating is large, so it is necessary to be careful enough to overestimate the fire and confuse it, or to be suffocated by smoke. This Na
Most of smoke generated by the combustion, scattered as aerosols Na ₂ O type.

FIG. 3 shows the relationship between oxygen concentration and Na temperature at the ignition limit of Na. As can be seen from the figure, combustion occurs at an oxygen concentration of 5% or more on the upper right side of the ignition temperature limit curve where the Na temperature is about 200 ° C or higher, and conversely, on the lower side of the ignition curve, only oxidation occurs and fire occurs in the air. It is considered to be an area that cannot be.

However, in practice, even with solid Na, depending on the humidity in the atmosphere, it is often experienced that the moisture reacts with Na to produce hydrogen gas (H ₂ ) as shown in Chemical formula 4 and ignites. ing.

[0010]

[Chemical formula 4] Na + H ₂ O = NaOH + 1 / 2H ₂ (Chemical formula 4) Generally, for a Na fire in a Na handling facility, it is better to extinguish it mainly by using sodium bicarbonate (NaHCO ₃ ) or dry sand. In addition, the present Fire Defense Law stipulates that sodium bicarbonate, dry sand, expanded vermiculite, etc. should be applied as extinguishing agents.

The types of commercially available Na fire extinguishing agents and their advantages and disadvantages are described below.

(1) Fire Extinguisher A A powder fire extinguisher containing sodium chloride (NaCl) as a main component, which is a substance which is half melted to form crust for extinguishing by suffocation. It is effective above 300 ° C, but complete digestion is difficult because the crust cracks and reignites at low temperatures below 300 ° C. Further, there is a problem such as corrosion due to Cl.

(2) Extinguishing agent B A powder extinguishing agent containing anhydrous sodium carbonate (Na ₂ CO ₃ ) as a main component, which is superior in extinguishing property to extinguishing agent A and can be easily post-treated. However, although a choking effect can only be expected and it is effective on the low temperature side, complete digestion is difficult on the high temperature side of 300 ° C or higher. Even a small amount of Na fire requires a large amount of fire extinguishing agent.

(3) Fire Extinguisher C A powder fire extinguisher containing sodium bicarbonate (NaHCO ₃ ) as a main component, but the fire extinguishing power is inferior to that of the extinguishing agents A and B. Also,
Since it decomposes to produce water, the secondary reaction becomes a problem.

(4) Dry Sand A large amount of dry sand is effective for a small amount of Na fire because it has a large heat capacity. However, since it has a high density and sinks in molten Na, Na spills from the Na levee and the container for leaking Na, and because it is difficult to seal the cover, it is difficult to suffocate and the Na temperature does not drop easily. There's a problem. In addition, it should be noted that it may react with moisture contained in dry sand or water of crystallization to raise the temperature temporarily and the reaction may become violent.

(5) Others In foreign countries such as the United States and the United Kingdom, graphite powder type pellets (expanded about 100 times at 180 to 250 ° C.) are used as a fire extinguisher for pool fires. Although it is said that it can be applied to, it can only be expected to have a choking effect.

As described above, the extinguishing agent is a method in which a substance having a large heat capacity is used to cover the flame portion to suffocate and lower the temperature to extinguish the fire. Therefore, when the spread of the Na fire is large or when the amount of Na in the Na receiving container is large, it is difficult to completely extinguish the fire.
Even when it is desired to solidify a, it is difficult to lower the temperature because it uses an extinguishing agent with large physical capacity and conflicting physical properties, and it is difficult to re-burn and suppress emission of white smoke accompanied by highly irritating aerosol, and it takes time to extinguish the fire. There's a problem.

[0018]

The prior art was not developed by fully understanding the characteristics of Na fire. That is, since the molten Na burns, it is covered by a fire extinguisher, which is only a so-called suffocation effect. Even if the air is temporarily shut off, if the temperature does not drop and Na solidifies, the coating cracks and re-burns. To do this and to extinguish a fire requires a large amount of extinguishing agent, which needs to be resolved.

The object of the present invention is to use only silica (SiO ₂ ) fine powder which is inexpensive and easily available as a Na fire extinguishing agent, or
A mixture of this with Na ₂ CO ₃ is added to Ag ₂ CO ₃ ,
ZnCO _3, PbCO ₃ and one of MgCO _3, or two or more, used in the fire extinguishing agent with the addition of about a few% to 40% so as to cover the flame portion, N in Na wetted surface
(EN) It is intended to provide a Na fire extinguishing agent, a fire extinguishing method, and a device thereof which can easily extinguish a fire by reacting with a to form a stable compound and suppressing generation of aerosol or white smoke.

[0020]

In order to achieve the above object, the present invention uses a fine powder of SiO ₂ as a Na fire extinguishing agent alone, and SiO ₂ and Na ₂ CO ₃ in a ratio of 1: 1 or 2: 1. Ag ₂ CO ₃ , ZnCO ₃ , PbCO ₃
A fire extinguishing agent containing one or a plurality of carbonates such as MgCO ₃ and approximately several to 40% is used. At the time of extinguishing fire, the flame portion is covered with these extinguishing agents, and Na and the extinguishing agent react with each other on the Na-wetted surface to generate a chemically stable substance, thereby forming a chemically stable layer to extinguish the fire. Further N
Completely block air contact with the liquid surface and extinguish by suffocation. Further, the generated aerosol is reacted with CO ₂ gas generated by thermal decomposition of carbonate to collect Na ₂ CO ₃ .

[0021]

The Na fire extinguishing agent of the present invention is used as a fine powder of SiO ₂ alone, or a mixture of SiO ₂ and Na ₂ CO ₃ in a ratio of 1: 1 or 2: 1 so as to cover the burned portion of Na. These react with Na to form chemically stable Na ₂ SiO ₃ and Na ₂ Si is formed in the liquid contact part between the extinguishing agent and the molten sodium.
A stable layer of O ₃ is formed to extinguish the fire. In addition, since it covers the entire fire area, it can be extinguished completely by suffocation.

Since the Na burning surface has irregularities,
In order to completely cover this, free-flowing SiO ₂
Than only, this was mixed well with SiO ₂ by the addition of Na ₂ CO _3, by attaching a Na ₂ CO ₃ on SiO ₂ surfaces, and easily cover the convex portion of the fire extinguishing agent, further choking effect Improve.

In addition, when Na is burned, a large amount of aerosol with strong irritating odor is generated as white smoke. Most of this aerosol is scattered as Na ₂ O, but Ag ₂ C
O _3, ZnCO _3, PbCO ₃ and one carbonate such as MgCO _3, or by using a plurality of types extinguishing agent was added, reacts with CO ₂ to produce by pyrolysis, the aerosol in a stable compound ( Can be collected as Na ₂ CO ₃ ),
Environmental pollution can be prevented, and one of the thermally decomposed ZnO,
Since Ag ₂ O, PbO, MgO, etc. are reduced to metallic sodium and then alloy with Na, there is an advantage that a synergistic effect of lowering the activity of Na can be expected.

[0024]

Embodiments of the present invention will be described below.

First, if Na leaks,
As a basic measure, it is important not only to isolate the substance that easily reacts with Na but also to extinguish the fire as in the case of a general fire. Therefore, if Na leaks from the piping or tank container of the FBR or Na tester, do not rush to know the situation sufficiently, and then use a steel pan or the like to receive Na into It is important to carry out fire extinguishing work after suppressing the spread and preventing the spread of fire.

From the knowledge obtained so far, it can be considered that a large accident such as a guillotine rupture generally occurs in a Na pipe or the like, and a large amount of sodium is unlikely to leak instantly, and an FBR or Na test is performed. When a trouble occurs in the device, it is a system that urgently drains Na in the system to the Na storage tank, so it can be considered that a large amount of Na will not leak into the air at one time.

In the unlikely event that such a serious accident occurs, it is difficult to immediately carry out fire fighting activities.
It is excluded from the scope of the present invention because it is possible to protect the human body and prevent burning, and take measures after taking sufficient time for study.

Therefore, in the present invention, it will be described below as being applied to a fire of Na of several tens of liters or less, or a small leak.

Table 1 shows the physical properties of the conventional commercial digestive agent and the proposed digestive agent in comparison.

[0030]

[Table 1]

As can be seen from the table, the apparent density of SiO ₂ 150 to 200 mesh, which is the extinguishing agent of the present invention, is approximately 0.45, and the density of liquid sodium (0.8 to 0.8).
It is as small as about 1/2 of 0.95). For this reason, it is possible to cover the flame portion and easily seal and suffocate it without settling in the liquid sodium in the flame portion of the Na fire.

As mentioned above, although the apparent density of the fire extinguishing agent of the present proposal is small and hardly settles, it is considered that the fire extinguishing agent enters the liquid sodium. Since this increases the chances of contact with sodium near the liquid surface, it promotes the formation of a reaction layer, so that some diffusion or sedimentation is a preferable phenomenon for quenching.

Further, as a fire extinguishing agent, Ag ₂ CO ₃ , Zn
When one kind or plural kinds of carbonates such as CO ₃ , PbCO ₃ and MgCO ₃ is added in an amount of several to 40%, these carbonates are thermally decomposed by the combustion heat of Na (decomposition temperature: 200 to 350). ° C.) cause, in order to generate CO ₂ gas, it can be expected choking effect this and N
A large amount of white smoke with a strong pungent odor due to combustion of a (main component is Na
₂ O aerosol) and the reaction was stable compound (Na ₂ C
Since it can be collected as O ₃ ), environmental pollution can be prevented.
Of the additives, the case of using PbCO ₃ will be described in detail below as an example. At 315 ° C., PbCO ₃ is thermally decomposed to generate CO ₂ gas as shown in Chemical formula 5. This CO ₂ reacts with highly irritating Na ₂ O, Na ₂ O _{2 and the} like emitted as white smoke and can be collected as stable and harmless Na ₂ CO ₃ as shown in Chemical formula 6. Further, one of the thermally decomposed PbO is reduced to metallic sodium and converted into metallic lead, and then Na and Na ₁₅ P are added.
Since intermetallic compounds such as b ₄ , Na ₅ Pb and Na ₄ Pb are produced, a synergistic effect of lowering the activity of metallic sodium can be expected. By the way, Pb is about 40w in Na at 250 ° C.
Although t% is dissolved, if it is added in a large amount, the total density of the fire extinguishing agent is increased, so about 10% or less is desirable.

[0034]

[Chemical formula 5] PbCO ₃ → PbO + CO ₂ (Chemical formula 5)

[0035]

[Chemical formula 6] Na ₂ O + CO ₂ = Na ₂ CO ₃ (Chemical formula 6) Fig. 1 shows an example of extinguishing Na by leaking Na from the piping of the experimental apparatus and collecting it in a steel pan. FIG. 1 is a steel Na receiving container, 2 is leakage Na collected in the receiving container, 3 is an extinguishing agent, 3'is an extinguishing agent spray-coated on the collected Na, 4 is a reaction product of the extinguishing agent and Na, 5 is a flexible tube for spraying a digestive agent, 6 is a dolly for carrying a Na receiving container, and 14 is a solenoid valve.

For example, if the leakage of Na is detected or found in a part of the pipe, as shown in FIG. 1, a metal Na receiving container which has been dried and stored in advance is mounted on a trolley to the leakage location of Na. Carry it and collect Na in it. Then, the amount of Na collected or the shovel spreads depending on the spread of the flame.
A small fire extinguisher, a pressure-feeding flexible tube, or the like is used to cover the Na surface or flame portion with an extinguishing agent and seal it.

At this time, chemically stable sodium metasilicate (m
-Sodium silicate: Na ₂ SiO ₃ ) is produced, and a chemically stable layer is formed, so that combustion is stopped, and further, the supply of oxygen is cut off, and the fire is completely extinguished.

[0038]

Embedded image 2Na + SiO ₂ + 1 / 2O ₂ = Na ₂ SiO ₃ (Formula 7) FIG. 2 shows an automatic or semi-automatic digester in a reactor plant or a Na handling facility. 3 is a digestive agent,
5 is a flexible tube, 10 is a digestive hopper, 11
Is a heater for drying the stored extinguisher, 12 is a vacuum pump for degassing the system and vacuum drying the extinguishing agent in the hopper, and 13 is for pumping the degassing and extinguishing agent in the hopper. Pressurized gas conduit, 14-1 to 14-4 are solenoid valves,
Reference numeral 15 is a pressure reducing valve for a gas cylinder, 16 is an inert gas cylinder for pressurization for pressure-feeding a digestive agent, 17 is a Na handling facility or a test device, 18 is a Na leak detector, 19 is a signal line,
Reference numeral 20 is a relay, 21 is a switch for manually activating the fire extinguisher, 22 is a stop valve, 23 is a refueling port for the extinguishing agent, and 24 is a buzzer for notifying the leakage of Na.

In the above structure, when Na leaks in the Na handling facility, the test apparatus 17, etc., the Na leak detector 18 detects it and the buzzer 24
Sounds to inform about the leakage of Na. The signal from the detector opens the solenoid valve 14-4 via the relay 20, pressurizes the inside of the hopper and simultaneously opens the solenoid valve 14-2, so that the extinguishing agent 3 is sprayed from the flexible tube 5 to extinguish the fire. It has become.

After the flame portion is covered with the extinguishant to a thickness of several cm, the change switch 21 is manually operated to temporarily stop the spray of the extinguishant. As mentioned above, if the fire extinguishing agent is coated on the Na flame portion to a thickness of several cm, the Na fire will be extinguished, but it will be confirmed whether or not the flame portion could be completely covered with the fire extinguishing agent, or whether it will not reignite. In case of exposed parts or reignition, move the flexible tube and use a manual switch to spray extinguishing media to extinguish the fire completely.

The amount of spray of the extinguishant may be determined in advance, and the solenoid valve may be closed by a timer or the like, or the spray level may be detected by using a photoelectric tube to extinguish the fire automatically. It is possible.

The Na fire extinguishing agent, the fire extinguishing method, and the apparatus therefor can be applied not only to FBR-related facilities and apparatuses, but also to various products using metallic sodium and test apparatuses.

As described above, AgCO _{3 is} used only as a fine powder of silica (SiO ₂ ) which is inexpensive and easily available as a Na fire extinguisher, or a mixture of this with sodium carbonate (Na ₂ CO ₃ ) as appropriate. , ZnCO _3, PbCO ₃ and Mg
A few% to 40% of one or more types of CO ₃
When added and mixed well to cover the flame part, it reacts with Na on the Na-wetted surface to form a stable compound and forms a chemically stable layer to extinguish the fire. In addition, it is possible to prevent aerosols and white smoke from being polluted as stable compounds and suppress their generation and release to prevent environmental pollution.

[0044]

According to the present invention, a fine powder of SiO ₂ alone, a mixture of SiO ₂ and Na ₂ CO ₃ in a ratio of 1: 1 or 2: 1 is added to AgCO ₃ , ZnCO ₃ , PbCO ₃ and A few% to 40% of one or more kinds of MgCO ₃
%, And when mixed well and used so as to cover the combustion part of Na, this reacts with Na to form chemically stable Na ₂ SiO ₃ and the wetted part of the extinguishant and molten sodium In addition, a stable layer of Na ₂ SiO ₃ is formed, which covers the entire fire area and suppresses the supply of oxygen.

Further, when Na is burned, a large amount of aerosol having a strong irritating odor is generated as white smoke. Most of this aerosol is scattered as Na ₂ O, but by using the fire extinguisher of the present invention, the carbonate causes thermal decomposition and CO ₂
Since gas is generated and this reacts with the aerosol to collect as a stable and harmless compound, environmental pollution can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of collecting and extinguishing leaking sodium according to an embodiment of the present invention.

FIG. 2 is a sectional view of an automatic fire extinguishing system for leaking sodium according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the relationship between the ignition limit of molten sodium and the amount of oxygen.

[Explanation of symbols]

1 ... Na receiving container, 2 ... Na, 3,3 '... Extinguishing agent, 4 ...
Reaction product, 5 ... Flexible tube, 6 ... Truck, 1
4 ... Solenoid valve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuo Kawasaki 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Electric Co., Ltd.

Claims (6)

[Claims] 1. When high-temperature sodium leaks from piping or equipment and a sodium fire occurs, liquid sodium and sodium leaked into the air and sodium oxide produced by reacting with components in the air. , A method of extinguishing a sodium flame, which is characterized by generating stable and harmless compounds such as sodium peroxide and sodium hydroxide to extinguish the fire. 2. The digestive agent according to claim 1, which is a fine powder of silica having an apparent density lower than that of sodium, so that the digestive agent and sodium are not precipitated in molten sodium at a liquid contact interface with sodium. Reacts to produce stable and harmless sodium silicate, covers and seals the flame part, and extinguishes the sodium flame. 3. The method according to claim 1, wherein the silica content is 150 to 20.
As fine powder of 0 mesh, silica alone or well mixed with sodium carbonate to adhere to the silica surface,
A sodium flame extinguisher that extinguishes a Na fire by using an automatic spraying device for extinguishing agents that makes it easy to cover the surface of the combustion part where irregularities occur in the flame part, or a manual small spray type extinguisher. 4. The silica fire powder according to claim 1, wherein silica fine powder alone or a mixture of silica and sodium carbonate in a ratio of sodium carbonate to a flame portion of a sodium fire is used with respect to the amount of sodium having a thickness of several flame surface layers. A method of extinguishing a sodium flame in which the sodium is extinguished by covering the whole so that there is no exposed portion of sodium and sealing the flame portion to suffocate the sodium fire. 5. The sodium fire extinguisher according to claim 1, wherein Ag
_{2 CO 3, ZnCO 3, PbCO} 3 and one carbonate such as MgCO ₃ or a plurality of these species, approximately several% to 4
By adding and mixing 0%, these are Na
The combustion heat of the carbon causes thermal decomposition to generate CO ₂ gas, and the CO ₂ gas has a choking effect and the generated Na.
By reacting with smoke, that is, sodium aerosol and collecting as stable and harmless Na ₂ CO ₃ , environmental pollution is prevented, and one of thermally decomposed ZnO, Ag
₂ O, PbO ₂ and MgO are reduced to Na,
A method of extinguishing a sodium flame that forms an alloy with sodium metal. 6. The fire extinguishing agent hopper capable of detecting and leaking sodium from an FBR or a sodium plant such as a large laboratory, and using a flexible tube or the like from the fire extinguishing agent hopper according to claim 1. A method of extinguishing a sodium flame that extinguishes a sodium fire by automatically extinguishing a fire extinguisher.