JP2022013478A - Fire protection facility for detached house building - Google Patents

Abstract

To provide a novel fire protection method using nitrogen for detached house building.SOLUTION: There is provided a dry type fire-extinguishing method using nitrogen instead of an existing fire extinguishing method using water, in preparation for a fire of a low-rise detached house building 3. Specifically, in the event of the fire of the building, temporal three-dimensional type of space part is provided by using an assembled frame 8 and a fire proof cloth 7 around the building, and nitrogen gas obtained via a liquefied nitrogen lorry car 1 is emitted to the space part to lower oxygen concentration in the space part and thereby extinguish the fire.SELECTED DRAWING: Figure 1

Description

Detailed description of the invention

Since the dawn of history, people think of fires as extinguishing them with immediate water. The present invention provides a dry fire extinguishing method using nitrogen instead of the conventional wet fire extinguishing method using water in order to minimize human and property damage in the event of a fire in a low-rise detached house.

The origin of the idea of the present invention is that in recent years, there have been some cases that cannot be dealt with by the conventional wet fire extinguishing method. Behind this is the fact that in the latest construction industry, the buildings targeted for fire extinguishing have become orders of magnitude larger and taller, which cannot be caught up with conventional fire extinguishing technologies. For example, in the fire of ASKUL's super-large distribution warehouse in Miyoshi Town, Saitama Prefecture in 2017, the flame spread in all the warehouses, and it took 12 days from the disaster to the extinguishing of the fire.

In addition, there have been some disasters in which global cultural properties have been lost due to fire. One is the fire at the Notre Dame Dam in Paris in 2019. In this case, the spire, which was a symbol of the temple, was burnt down despite the desperate fire extinguishing activities of the fire brigade in the entire city of Paris. The other is the fire at Shurijo Castle in Okinawa that occurred in the same year. In this case, the fire spread to the main buildings of the castle one after another, and almost all the main buildings including the main hall disappeared. In both cases, the flame could not be extinguished despite the hard fire extinguishing using a large amount of water.

Currently, most of the improvement measures being considered as measures to prevent the recurrence of these disasters are a combination of "disaster information by smoke detection" and "sprinklers that use water". The adoption of the above method is almost decisive when planning the reconstruction of Shurijo Castle. Other wooden castles in Japan have been urgently reviewed in the wake of the fire at Shuri Castle, but at present, no alternatives that are superior to the above fire extinguishing law have been proposed.

On the other hand, regarding the fire extinguishing method, along with the above-mentioned wet fire extinguishing method (= hereinafter abbreviated as wet method), there is a dry fire extinguishing method (= hereinafter abbreviated as dry method) using nitrogen or an inert gas. .. The drywall method has already been implemented for some small buildings. For example, at the Pola Museum of Art in Hakone, a method that uses a halogen-based inert gas as a fire extinguishing agent is adopted in the most valuable display room in the museum. In a rather large facility, a drywall method using nitrogen cylinders is installed in the library room of the National Diet Library in Tokyo. ..
It's done.

As mentioned above, the drywall method is a fire extinguishing method that has already been proven, but there are very few examples not only in Japan but also in the world. However, this method is an indispensable fire extinguishing method for the fire extinguishing equipment in the central control room and high voltage electric room of the latest super-large computers. Furthermore, in recent years, the use of hydrogen instead of hydrocarbons has been attracting attention from the viewpoint of preventing global warming. Of these, the construction of hydrogen infrastructure is the most important issue. Nitrogen is an indispensable substance for safety measures when constructing hydrogen infrastructure, and the help of nitrogen is absolutely necessary for its construction. The drywall method using nitrogen is being reviewed gradually in line with the above environmental changes.

As an example, the following patents have already been published.
JP-A-2018-84042 "Nitrogen Infrastructure System"
This patent proposes the construction of hydrogen infrastructure over a wide area using conduits and at the same time "construction of nitrogen infrastructure using conduits". The patent introduces an example of using nitrogen as a safety measure for hydrogen stations and using nitrogen for fire extinguishing in the event of a disaster in a super-large distribution warehouse with a capacity of tens of thousands of meters.

However, the buildings covered by this patent have a volume of tens of thousands of m3, and buildings with a volume of several hundred m3, such as general detached houses, are excluded. As described above, at present, there are some proposals for special applications regarding the dry method using nitrogen, but the number of objects is extremely limited, and the target is a small general building as in the present invention. The invention is not open to the public, not to mention domestically.

The present invention has been made in view of the above problems. The goal is to introduce a new fire extinguishing method for low-rise single-family homes. That is, a dry fire extinguishing method using nitrogen will be introduced instead of the conventional wet fire extinguishing equipment that uses water as the fire extinguishing equipment.

First, the basic principle of substituting nitrogen for a flammable gas using nitrogen will be described. The fire extinguishing method using nitrogen is a method of eliminating the combustible gas among the "combustibles", "ignition source" and "flammable gas" which are the three elements of combustion. These three elements involved in combustion are logically connected by an "AND circuit". A fire can be completely extinguished by using nitrogen to reduce the oxygen concentration in the flammable gas around the fire to the limit. The dry method can extinguish the flame perfectly regardless of the ignition source as long as the building is closed, so the principle is simpler and the fire extinguishing efficiency is extremely high compared to the wet method.

We have already described how to extinguish a fire by blowing suffocating gas in order to prevent valuable works of art from being damaged by fire extinguishing using water in museums. The gases that have been proven as suffocating gases are halogen-based gases and nitrogen. The dry method is still in strong demand, and in the latest case, Abeno Harukas, which boasts the highest height in Japan and was completed in 2014, has introduced the dry method in the high-voltage electric room and the management room of computer equipment. ..

When nitrogen is used for fire extinguishing in a building, it must be considered from the following two main points of view. The first is to improve the fire extinguishing efficiency, which is the main purpose of extinguishing a fire. The second is the prevention of human damage due to oxygen deficiency, which is a secondary negative effect. This second response is particularly important and will be discussed in more detail later.

When nitrogen is blown into the building, the air inside mixes with nitrogen almost uniformly and is finally released to the atmosphere through the exhaust port. Academically, this mixture is called "complete mixture". The oxygen concentration in the building gradually decreases due to the blowing of nitrogen, reaching a concentration at which combustible gas cannot be burned. The oxygen concentration at this time is called "marginal oxygen concentration". This value has a unique value depending on the flammable gas, and is 5.0% and 5.6% for hydrogen and carbon monoxide, respectively, and 12.1% for methane.

Even if the combustible material is a solid, the solid is decomposed by high temperature to generate combustible gas such as hydrogen and carbon monoxide. Therefore, to stop combustion, the oxygen concentration in the building is the limit of the combustible gas as in the case of gas. Nitrogen may be blown until the oxygen concentration becomes lower than the oxygen concentration. The blown nitrogen mixes with the air inside the building and gradually reduces the oxygen concentration inside the building.

Since the amount of nitrogen that can be normally stored in a cylinder is several m3 / piece _, the capacity of the building to be extinguished is generally limited to several tens of m3 to 100 _m3 . For this reason, the target of the conventional drywall method had to be limited to the most valuable rooms in the building, not the entire building. Therefore, in order to adopt this method for large warehouses with a building capacity of tens of thousands of m3 class, the shortage of nitrogen supply is the first bottleneck, and until now there has been almost no opportunity to consider it. However, the volume of the target building this time is about several hundred m3. With this volume, if a liquefied nitrogen lollipop vehicle is used, the quantity is sufficiently within the range.

Liquefied nitrogen is a liquid with a liquid density of 0.809 kg / L and a boiling point of 77 ° K. A liquefied nitrogen lorry vehicle is a special vehicle that is filled in an insulated container and transported. Hundreds of vehicles of this type are currently in operation in Japan and are mainly used as refrigerants. In the case of a large 7-ton vehicle, the maximum load capacity is approximately 6,000 m ₃ / unit in terms of capacity. If the target of fire extinguishing is an individual detached house, the volume of the building is about several hundred m3 _, and the total volume of the surrounding volume including the building is about 2,000 m3 assuming that the height is 10 m. If the target of fire extinguishing can be kept within the above range, it is possible to prevent fire extinguishing in several detached houses with a liquefied nitrogen lorry chassis.

Next, the basic technique for reducing the oxygen gas concentration in the building using nitrogen will be described. Assuming that the combustibles are hydrogen or carbon monoxide, the oxygen concentration must be maintained at 5% or higher for the combustion. From the opposite perspective, if the air inside the building is replaced with nitrogen and the oxygen concentration in the air is reduced to 5% or less, hydrogen and carbon monoxide will be completely extinguished. In the present invention, the oxygen concentration in the combustion gas around the building is reduced to this level (= 5.0%) by blowing nitrogen.

A building with a volume (Am ₃ ) is blown with a volume (Vm ₃ ) of nitrogen to release the same amount of gas inside the building, and the oxygen concentration inside the building is changed from the normal concentration (a ₁ = 21%) to the target oxygen concentration. When reducing to (a ₂ = 5%), the reduction curve follows the "completely mixed formula" and is shown by the following function. Here, e is a constant called the number of Napier.

例えば建屋容積Ａ＝１，０００ｍ_３、ａ_１＝２１．０、ａ_２＝５．０を代入すれば、窒素量Ｖ＝１，４３０ｍ_３となる。即ち容積Ａｍ_３の建屋内の空気を窒素で置換して燃焼を継続できない酸素濃度まで低減させるには、容量で建屋容量Ａの約１．４３倍の窒素が必要である。From the above equation, the amount of nitrogen V that reduces oxygen _a1 in the air to the limit oxygen concentration _a2 is

For example, by substituting the building volume A = 1,000 m ₃ , a ₁ = 21.0, and a ₂ = 5.0, the nitrogen amount V = 1,430 m ₃ . That is, in order to replace the air in the building with a volume of Am ₃ with nitrogen and reduce the oxygen concentration to an oxygen concentration at which combustion cannot be continued, nitrogen of about 1.43 times the volume of the building capacity A is required.

Next, the specific procedure for implementing the drywall method will be described. The fire extinguishing method of the present invention is a proposal to extinguish a fire by extinguishing oxygen by making the entire surrounding space including the building into a nitrogen atmosphere as it is. The first procedure begins with providing a space surrounding the building around the perimeter of the building. This work is carried out by firefighters. What is prepared to provide the space is a frame and refractory cloth that can be easily assembled on site. The frame will be divided into appropriate lengths in advance, and will be connected locally to serve as a support for stretching fireproof cloth.

Fire-resistant cloth is an abbreviation for cloth made of fibers that can withstand high heat. Several types of fire-resistant cloth have already been put into practical use, and new materials such as aluminum-blended aramid fiber that can withstand high heat of 1,000 ° C or higher are under development. Is. For the refractory cloth, cut the cloth made of this material to an appropriate size, mount it on a fire engine, carry it to the disaster site, and connect it locally to make a refractory membrane. The refractory cloth should be fitted with the necessary fasteners in advance so that it can be easily joined on site.

The shape of the space surrounding the building to be extinguished is usually a rectangular cube. The length and width depend on the size of the building, but most urban areas are rectangular with a side of 10m to 20m. Assuming that the space surrounding the building is a two-story building, the height is about 10 m and the space volume is about 1,500 m3. The image of assembling this space is like putting a protective net around the building as seen when painting the exterior of the building, but unlike the case of the protective net, some ingenuity is applied when assembling.

That is to make the shape of the cube "narrow the upper area compared to the lower area". The gentle shape toward the top prevents the backflow of air into the space and enhances the replacement effect by nitrogen. The extent to which the area of the upper part is narrowed may be gradual. At this time, it may be narrowed in one step, or it may be bent in the middle and bent in two steps. By this device, the nitrogen blown into the space is sufficiently mixed with the air inside without short-passing in the space and released to the atmosphere. [Fig. 2] shows the outline of blowing nitrogen around the building.

Nitrogen required for fire extinguishing is received from a nitrogen supply station near the building using a liquefied nitrogen lorry vehicle. This liquefied nitrogen is converted into medium- and low-pressure nitrogen gas by a vaporizer installed separately at the site. Since liquefied nitrogen is ultra-low temperature, it is easily vaporized by the outside air temperature. It is dangerous to supply excessive liquefied nitrogen to the vaporizer during vaporization because it causes a rapid increase in pressure. In some cases, it is desirable to install a safety valve to avoid a sudden pressure rise.

Nitrogen gas leaving the vaporizer is distributed in two directions and blown into the space. One is through a header for blowing nitrogen gas installed at the bottom of the space, and is blown into the space around the building from multiple blowing nozzles attached to the header. This nitrogen is used to reduce the oxygen concentration in the air outside the building.

The other one is used to reduce the oxygen concentration inside the building body by using a hose or the like. This nitrogen inlet is made using the entrance of the building, ventilation openings, small windows, etc. At this time, secure an exhaust port so that the main body of the building is not overpressed by the nitrogen blown into the building. By the nitrogen blowing operation from the above two places, the building is gradually replaced with nitrogen both inside and outside, and finally reaches the above-mentioned limit oxygen concentration (= 5.0%). All combustibles are completely extinguished in an environment of critical oxygen concentration. The outline of this fire extinguishing equipment is shown in [Fig. 1].

The time required for the fire extinguishing operation of the present invention is estimated to be within one hour from the start of blowing nitrogen. The rationale for this is as follows. The liquefied nitrogen lorry vehicle is equipped with a pump that completes the unloading of liquefied nitrogen (= 6,000 m3 in terms of gas amount) in about one hour. The time to replace the previously described space volume of 2,000 m3 with nitrogen using this pump is calculated to be 20 minutes. This time, unlike normal unloading, unloading is via a vaporizer, but in terms of equipment, the above time is an achievable value. This time is a surprisingly short time compared to the wet method. From the above estimation, it can be seen that the dry method has extremely high fire extinguishing efficiency and that it is the preparatory work that determines the fire extinguishing time, not the time spent on the fire extinguishing work itself.

In order to make the best use of the advantages of drywall, it depends on how the time required for preparatory work can be shortened. Work similar to this preparatory work is often found in daily life. For example, at a new construction site of a building, a protective wall will be installed around it to eliminate damage caused by falling objects. In a small case, the net is laid around when painting the outer layer of the house. At present, the time spent on these tasks is not short. However, assembly skills will definitely improve with improvements in tools and construction methods.

The skills of Japanese firefighters are well documented in this field, and it is fully expected that the on-site assembly work will be completed in a short time in the future. Even if there are obstacles around the building depending on the location, the assembly structure is simple and it is possible to deal with it. In addition, it is effective to shorten the time for this work by eliminating utility poles by burying the utility poles currently underway, mainly in urban areas. The goal is to wrap refractory cloth around the building at once, just like pulling a curtain on the stage of a theater. If this time can be shortened, the present invention can maximize its advantages.

With the introduction of the drywall method, the role of firefighters will change completely. Until now, the work of firefighters has been the fire extinguishing activity itself of "extinguishing the flame using a fire hose." This fire extinguishing work will be greatly reduced in the future. All that is required to extinguish the fire is to open the nitrogen supply valve from the vaporizer. The role of firefighters with the introduction of the dry method is to provide a temporary space around the building using a frame and fireproof cloth prior to fire extinguishing activities, and to use liquefied nitrogen as a vaporizer and nitrogen gas as a space. Move on to the two tasks of blowing.

On the other hand, new important work will be added. It is to evacuate residents from the fire area and protect them from an oxygen deficiency accident. As a result, it is no longer necessary to dispatch a large number of fire engines and firefighters to extinguish the fire in the event of a disaster. It will be possible for a few firefighters to respond sufficiently.

Instead, a space will be created around the building, which will require a new work vehicle to carry dedicated materials and a new operative to assemble it locally. The speed of extinguishing the fire depends on the activities of this unit. Furthermore, the source of nitrogen will be transferred from the local nitrogen supply station to the fire department, and in the near future, the day will come when liquefied nitrogen lorry vehicles with vaporizers will be deployed at the local fire department along with fire engines that use water.

The best mode for carrying out the present invention

Finally, oxygen deficiency, which can be said to be a negative effect associated with the present invention, will be described. This symptom is a dangerous symptom that everyone who handles nitrogen should never forget. The oxygen concentration in the atmosphere is 21%, but if this concentration is about 18%, there is no problem in human behavior. However, when the concentration drops below this concentration, humans become ill.

Although the degree of symptoms varies from person to person, in general, up to an oxygen concentration of about 12%, a person is inconvenient but can manage to act. However, when the oxygen concentration drops below 10%, it falls into a dangerous state. At an oxygen concentration of 8%, the person loses consciousness, and at the concentration targeted by the present invention (= 5.0%), all people die after several breaths.

In the case of a fire in a low-rise single-family house, the number of residents affected by the disaster is limited, and since the residents themselves first confirm the evacuation, the probability of overlooking the evacuation is small. On the other hand, the experience of using nitrogen to extinguish a fire is a completely new experience for the general public. Even if there is a vague feeling that "if you inhale nitrogen gas, you will suffocate," you must be prepared for the fact that it will take a considerable number of years to establish that consciousness.

In order to prevent oxygen deficiency accidents, it is extremely important to reconfirm the firefighters who judge that "there are no residents in the fire extinguishing target". The confirmation by the firefighter is done when the setting of the space part is completed using the frame and the refractory cloth. It is unlikely that there will be any survivors in the building at this stage, but as a peculiar example, this is to deal with cases where a person who has evacuated once moves in to pick up something left behind. Only when this reconfirmation is completed will nitrogen be blown into and out of the building.

The reason for conducting multiple confirmations in this way is to make sure that there are no humans in the space. Firefighters should never allow anyone other than firefighters to enter the space once assembled. This series of work by the fire brigade is carried out in a disciplined manner under the command of the fire brigade commander. At this time, the fire brigade always keeps a respiratory protective device with an oxygen cylinder and an oxygen life-saving device in case of rescue of a person who is late to escape.

The above measures to prevent oxygen deficiency in single-family homes must be implemented. This practice is the best and essential form for practicing the present invention. It is very dangerous to carry out the present invention without this measure. Nitrogen introduced to ensure safety should not be a deadly weapon.

The invention's effect

If the dry method using nitrogen can be applied to fire prevention and extinguishing of low-rise detached houses, the number of targets is extremely large. The greatest advantage of the dry method is that the time required to extinguish the fire can be dramatically reduced compared to the conventional wet method that uses water. Furthermore, with the dry method, there is no concern that the interior and furniture inside the building will get wet. In the fire of ASKUL introduced in the previous section, about 10 billion yen of products in stock in the warehouse were wiped out by getting wet due to water discharge.

On the other hand, the rapid introduction of nitrogen into detached buildings directly leads to the serious problem of oxygen deficiency, which is life-threatening for humans. "If you blow nitrogen into a building, you will suffocate." This persistent concern has long been the main reason that has hindered the introduction of nitrogen-based dryfire extinguishing methods. This concern is still correct at this point. Nitrogen is tasteless and odorless, and if used improperly, it becomes a "silent killer gas".

As we enter the new hydrogen era in the 21st century, it is said that the backup by nitrogen will determine the success or failure of its development. Whether nitrogen will be a "safety gas to prevent disasters" or a "homicidal gas that causes suffocation" is required to be decided in this century. In particular, when introducing it into a general house such as a detached house, steady enlightenment activities are required.

To reiterate, the "safety confirmation for oxygen deficiency accident" accompanying the present invention is an indispensable measure that cannot be avoided. The keyword for promoting the present invention is nitrogen. In the 20th century, hydrocarbons were the protagonists of energy, and all industries enjoyed their benefits. On the other hand, it is inviting the global warming phenomenon caused by the by-produced carbon dioxide gas. Environmentally clean hydrogen is attracting attention as an alternative energy source.

However, hydrogen is easy to ignite and is too dangerous to be widely used in the general market as a single gas. The arrival of a hydrogen-based society absolutely requires the help of nitrogen. Currently, in preparation for the advent of a hydrogen-based society, the construction of a hydrogen infrastructure that supplies hydrogen as a mixed gas of hydrogen and nitrogen instead of alone is being considered as one of the risk prevention measures. When this new infrastructure is completed, it will be possible to supply a large amount of nitrogen along with hydrogen, and at the same time, new demand for nitrogen will be stimulated.

With the advent of the hydrogen era, the 21st century will enter an era of change in which nitrogen, which has been a supporting role until now, will play a leading role. In Japan, where the effective site is small and wooden detached houses are densely packed, the dry method using nitrogen has great potential for development. On the other hand, it may take some time for the general public to be aware of the potential dangers of nitrogen. I would like to quietly watch over the present invention playing a part in it.

It is a schematic diagram which shows the whole structure of the dry-type fire extinguishing equipment using nitrogen. It is a schematic diagram in which nitrogen is blown into the inside of a detached house and its surroundings.

1 Liquefied nitrogen lorry car 2 Liquefied nitrogen vaporizer 3 Detached building 4 Nitrogen gas blow hose 5 Exhaust port 6 Nitrogen gas blowout nozzle 7 Fireproof cloth 8 Frame

Liquefied nitrogen is a liquid with a liquid density of 0.809 kg / L and a boiling point of 77 ° K. A liquefied nitrogen lorry vehicle is a special vehicle that is filled in an insulated container and transported. Hundreds of vehicles of this type are currently in operation in Japan and are mainly used as refrigerants. In the case of a large 7-ton vehicle, the maximum load capacity is approximately 6,000 m ³ / unit in terms of capacity. If the target of fire extinguishing is a detached house, the volume of the building is about several hundred m3 ^, and the total volume of the surrounding volume including the building is about 2,000 m3, assuming that the height is ¹⁰ m. If the target of fire extinguishing can be kept within the above range, it is possible to prevent fire extinguishing in several detached houses with one liquefied nitrogen lollipop vehicle.

With the advent of the hydrogen era, the 21st century will enter an era of change in which nitrogen, which has been a supporting role until now, will play a leading role. In Japan, where the effective site is small and wooden detached houses are densely packed, the dry method using nitrogen has great potential for development. On the other hand, it may take some time for the general public to be aware of the potential dangers of nitrogen. I would like to quietly watch over the present invention playing a part in it.

Claims (4)

A fire extinguishing facility used when a detached building encounters a fire. If a fire breaks out in the above building, they will be transported to the site, a temporary space with an open area will be provided around the building, and nitrogen gas prepared separately will be used in the space and inside the building. A dry fire extinguishing facility that has the function of extinguishing or preventing a fire by releasing it to the fire and lowering the oxygen concentration around the building and inside the building to the oxygen concentration required for combustion of combustible gas. The dry fire extinguishing equipment is a mobile type that can be easily transported by a fire engine, and after being assembled in any shape on site, a plurality of injection nozzles for discharging nitrogen gas into the space around the building are provided. The dry fire extinguishing equipment according to claim 1, further comprising a discharge port having a discharge port and a discharge port by a hose for blowing nitrogen into the building. The frame and fireproof cloth used to provide a temporary space on the outer circumference of the detached building have a structure that can be laid in a three-dimensional shape so that a space can be created in the upper part according to the shape of the space to be laid, and the upper part of the three-dimensional type. The dry fire extinguishing equipment according to claim 1, wherein a frame and a fireproof cloth are used so that the area is smaller than the lower area. Regarding the method of supplying nitrogen for the dry fire extinguishing equipment of the detached building, liquefied nitrogen is transported from the nitrogen supply station in the area where the building is located to the building using a liquefied nitrogen lollipop vehicle, and this is used as a vaporizer. The dry fire extinguishing equipment according to claim 1, wherein the nitrogen gas is used and discharged toward the above-mentioned space and the building.

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