CA2040771A1

CA2040771A1 - Process for fighting and extinguishing fires and an apparatus for carrying out this process

Info

Publication number: CA2040771A1
Application number: CA002040771A
Authority: CA
Inventors: Zbigniew Bogulawski
Original assignee: Individual
Current assignee: AQUAMOT AG
Priority date: 1990-04-19
Filing date: 1991-04-18
Publication date: 1991-10-20
Also published as: IL97893A0; DE4012549A1

Abstract

ABSTRACT

The present invention describes a new fire-extinguishing and fire-prevention process in which calcium precipitates and/or specially activated calcium carbonate, i.e., specially finely ground or finely divided calcium carbonate that is environmentally friendly and not injurious to health, is used.
This seals the burning surface immediately and breaks the reaction chain. The toxic gases and injurious substances that are released by the thermal decomposition of plastics react with the calcium carbonate and are bound so that no dioxins, including toxic chlorinated and/or fluorinated hydrocarbons, are formed.

Description

204077~

The present invention relates to a process for fiqhting and extinguishing fires, in which water that contains a fire-retarding substance is distributed over the area of the fire.

Losses to the national economy occasioned by fire damage reach a considerable figure every year for example, in Switzerland and in the Federal Republic of Germany, more than five billion Swiss Francs. New construction materials and production processes, the increase of ground, air, and water transportation, the movement of dangerous goods, and the use of chemical substances, corrosive and/or toxic liquids, gases and vapours, and plastics, constitute risks in the event of fires that were not previously assessed correctly and which one can counteract only by using special agents and apparata. For this reason, developments in all areas of technology and the economy, which are taking place continuously, are compelling fire-fighting forces and resources to ad~ust to this new situation.

Modern fire-fighting methods require fire-fighting forces that have outstanding equipment to prevent losses (fire, environmental protection, water) and to render assistance in the event of misadventure (assistance at accidents) and public emergencies, when assistance rendered in the case of injuries caused by the escape or formation of combustible or explosive and/or toxic liquids, gases, or vapours plays an increasingly greater role.
For these reasons, preventing the occurrence of such hazardous 204~771 situations or the rapid elimination of such situations is becoming increasingly important when f ires are being fought.

Fire brigades are provided with various types of fire-fighting vehicles to fight fires and to render the types of assistance outlined abova; these vehicles are, for example, large tank-type fire trucks, auxiliary fire trucks, dry chemical fire-fighting vehicles, and multi-purpose vehicles. As a rule, the fire trucks are fitted with a centrifugal pump that incorporates a high-pressure stage that operates in the normal pressure range of 40 bar. Depending on requirements, a professional (full-time) fire brigade with five transporter vehicles has access to an extensive interchangeable charge or load system with up to 24 charges or bodies for all possible types of operation. They also carry extinguishing agents such as water and foam agents or extinguishing powder. In the private sector, hand fire extinguishers that operate in a similar manner (by a pressurizing medium) are used.

In the known wet extinguishing method, additives, in particular (water-soluble) salts, are used, and these are added to the water that is used to fight fires; such additives serve to lower the freezing point in order to prevent the water from freezing as a consequence of the temperature drop that occurs when it is ejected under pressure. The use of such substances does not, however, bring about any improvement in the extinguishing effect, --`` 2040771 for which reason mainly dry or foam extinguishing agents are used in had fire extinguishers; these have a good extinguishing effect although, depending on the type of fire that is to be put out, they frequently react to cause environmentally harmful or even toxic substances which are released to the atmosphere or to some other part of the environment.

It is the task of the present invention to create a procedure for fighting and extinguishing fires, with the help of which it is possible to achieve an improved extinguishing effect and at the same time reduce environmental damage caused by the extinguishing process which, in this case, is based on the wet method.

This task has been solved by the procedure described in patent claim 1.

Unexpectedly and most surprisingly it has been found that ~trth allcal~ oxides or hydroxides, in particular such substances that are based on lime ~ magnesium, assume properties which permit them to be u-ced for fighting fires as a part of the wet extinguishing method if they are activated to form a fine-grain ~ r bul~
powder with a large specific surface area or a low piled~density.
On the basis of experience, this effect can be attributed, on the one hand, to the fact that the activated material is deposited as a film on the surface of the burning material and so seals its surface as to prevent it giving off combustible gases as a basis for further combustion, or at least reduces this to a decisive extent. ~urthermore, the activated material acts as an energy absorbing agent ~StosEpartncrA~in the sense that it deactivates the reactionable particles (radicals) with the result that the chain reaction by which the fire spreads is interrupted.
Finally, a large part of the resulting gases or volatile injurious substances that are carried in the gases are absorbed so that, as a result of the process according to the present invention, there is also a significant reduction in environmental damage and personal risk that occur during fires.

Calcined lime or lime dissolved in a mixture of water and alcohol or ground to a fine-grain powder and which has lattice imperfections in its structure as a result of being ground can be used as the activated product. These calcium compounds and precipitates, which are marketed under the names of "Wulfrasorp"
or "Neutralith" are particularly fine with regard to their grain size, and are environmentally benign and non-injurious to health;
in addition to their particularly small grain size they are also characterized by a particularly large surface area and an extremely low piled density, and by a through-flow speed of 25,000-30,000 Blain. However, equally good results can be obtained by using a precipitate of lime (CaC03) formed from an aqueous solution by chemical reaction and precipitated in this way; like the substances named above, this also displays the following new effect when used as a fire-extinguishing agent:

20~0771 1. They neutralize and react with the injurious substances that are given off and/or result during present-day types of fire~ as a result of the thermal decomposition or low-temperature carbonization of plastics, so that chlorinated and/or fluorinated hydrocarbons or their reaction products such as dioxins, furan~s, and the like are not formed. This greatly increases the chances of survival for people within burning buildings. Fifty years ago, a person in a burning corridor could, accordinq to statistics, function or run for approximately 16 m before being rendered unconscious because of an oxygen deficit and as a result of the formation of carbon monoxide; based on statistical comparisons, in the case of fires in corridors that are carpeted and which contain plastics, this figure is only 8 m today.

~ r The use of calcium precipitates ~ specially activated calcium carbonate reduces the formation and the spread of toxic gases.

ar~d~v~

2. Calcium precipitates ~ carbonates, in the form of powder, in solution, or mixed with foam agents, seal the surface of burning objects and thereby immediately prevent the continued formation of flame and the supply of oxygen that is necessary for the fire to develop; the reaction chain is broken.

-`-` 2040771 3. The coating of extinguishing agent that remains after the fire has been extinguished can be easily washed away or vacuumed up.

Thus, using the process according to the present invention, fires can be localized and fought more effectively than was formerly the case, i.e., this can be done more rapidly and with the use of smaller quantities of water. In addition, environmental damage, which could scarcely be avoided up to now, such as the escape of different types of injurious or toxic liquids from storage tanks, tanker trucks of all kinds, and bulk carriers, (for example, for chlorine, ammonia, phosgene, and radioactive liquids) can be localized which is to say they can be prevented from spreading.
It is a further important advantage that by using the procedure according to the present invention large area fires, in particular forest fires, can be localized and fought effectively.
A major advantage of the present process is that it can, in the main, be effected with existing equipment such as is used by a modern fire brigade and in that it constitutes no risk to the environment and the surroundings. The extinguishing agent that is used is non-injurious for humans, animals, plants (for example, grass), structures, and other useful objects, and is non-toxic.

The extinguishing agents that are used are of fine-grain and flow o~ s~c~
easily and have a large active surfaceLwhich, at approximately 40 m2/g, as measured according to BET, is approximately twice as great as other comparable products. They can also be used advantageously as a suspension of lime that has been previously slaked in a quenching operation. However, because its formation is exothermic, in the case of a fire, calcium hydroxide has the advantage that it develops no exothermic hydration reactions:
CaO + H2O ===== Ca (OH)2 HR (25C) = -15.7 kcal/mol HR (580C) = -24.2 kcal/mol In a particularly advantageous embodiment of the present invention, calcium carbonate is used as the activated product, which, because it is ground to a fine-grain powder, has lattice defects in its structure, in which connection one or more tenside ors~lrfacfo~ ntS
additives~in particular a wetting agent, have been added either during or after the grinding process. In this connection it is expedient to produce the particles so that they are as spherical as possible, which will ensure an even flow when the dry powder or slurry is sprayed out of the nozzle.

The new process for extinguishing fires is based on the principle that the surface of a burning material, e.g., wood, textiles, and/or plastics, or liquid fuels (such as various mineral oil products) is allowed to decompose thermally, by spraying the seat of the fire with a very finely divided spray using a substance that has limited fire resistance at a high temperature (approximately 600C) and a great adhesive force at existing temperatures, during the continuous thermal action of the heat during the absorption of the heat with water separation (reversal of the reaction described above), in which connection the temperature of the burning portion and of the flames is greatly reduced (see point 4 in the diagram). The decomposition products (CaO and H2O) are removed in the updraft of the fire and carried into the cooler zone above the flame cone. Ultimately, during these processes, the following effects, which are decisive for the extinguishing process, will occur:

1. Because of the fact that for all practical purposes the burning surface is coated almost continuously, the fire is cut off immediately and evenly from the active zone and from a supply of fresh air, which would maintain the fire. As a result of this, the fire is extinguished immediately in those areas so sprayed.

2. The product of the decomposition that takes place (CaO and H20) rises and moves into the cooler zone above the flame cone, where the moisture content of the combustion gases reaches saturation point (which is to say at a higher moisture content than at the dew point temperature). This results in a dense fog phase and the so-called rehydration of the decomposition products (CaO and H2O = Ca(OH) 2) begins; this is followed by a momentary and marked 2~4077~

agglomeration of the particles that have reacted and the particles that are carrying the moisture fall back into the fire. In this way, 25-35%-wt of the combustion water that i8 formed in the fire returns to the fire itself and is thus part of the extinguishing cycle (of a reversible process).

The material that is used for this extinguishing process is non-toxic to humans, animals and plants (e.g. grass) and, furthermore, does not damage buildings or other objects. The coating formed of the residue from the extinguishing agent which remains after the fire has been extinguished can be removed from the surfaces on which it has been deposited very rapidly by rinsing with water.

Additional embodiments and advantages of the present invention are set out in the following description in which the invention is explained on the basis of the drawings of embodiments that are appended hereto. These drawings show the following:

igure 1: a diagrammatic cross section of a hand fire extinguisher according to the present invention;
Figure 2: a diagrammatic partial cross section through figure 1;
Figure 3: a partial diagrammatic cross section through another embodiment of a hand fire extinguisher.

The hand fire extinguisher shown in the drawings consists of a container 3 that comprises two compartments 1, 2, of which one chamber 1 serves to hold water and is fitted with a stirring mechanism 4, whereas the other chamber 2 is used to hold a fine-grain powder with a low specific piled density or a large relative surface, respectively, which is of an activated lime or magnesium-based product. The extinguishing agent is delivered from the container by means of a pump 6 that is driven by a motor 5, and passes through the line 7, when, at the same time, the motor 5 is used to activate the stirrer 4 that is immersed in the extinguishing agent. The two chambers 1, 2 are connected to each other through a manually operated lock.

In the embodiment shown in figures 1 and 2, the container 1 that is used to hold the water is in the form of a container that is open at the top and which is fitted on its up edge with a locking mechanism that comprises a clip edge 8 and a number of hooks 9 that are used to hold the container 2, which holds the powdered extinguishing agent, and which is formed as a top section; on its side that is proximate to the water container 1 the container 2 incorporates a bottom 10 that incorporates a tear-out seal. In order to create the tear-out seal the flexible wall 10, which is, for example, of soft plastic, sheet metal, or the like, is provided with a peripheral perforation and within the perforation a tear tab 13. Within the water container 1 there is a rotatable shaft 14 with an exterior operating lever 15 and a gripper 16 that fits into the eyelet of the tear tab 13 such that when the outer operating lever 15 is rotated, the perforation is torn and thus the extinguishing agent powder is emptied into the water.

In contrast to this, in the embodiment of a hand fire extinguisher that is shown in figure 3, the chambers that are used to hold the water and to hold the powdered extinguishing agent are enclosed within a common housing 18; within the upper section of the container, which is used to hold the powdered extinguishing agent, there is a flap l9 that opens to the side and a holder to accommodate a bag 20 that is filled with extinguishing agent. In addition, on a pull rod 29 that extends outwards through the wall of the container and which is supported so as to be able to slide in the wall, there is a blade 22 that extends into the vicinity of the bag 20, with the help of which the bag 20 can be slit open when required so that the contents are emptied into the water. The bag can be supported in this part of the container in any desired manner although it is done advantageously as shown in figure 3, in such a way that the bag is provided with two eyelets or tabs that extend in the longitudinal direction of the bag, a in that within the container there are two rods, attached at one end, onto which the bag can be slid and held by means of the tabs (not shown herein).

204~771 It is preferred that the bag consist of water-resistant material that is also impermeable to water and be closed in any manner so as to make it water-tight.

EXA~PLES
In the process that forms the basis for the present invention prepared calcium hydroxide, i.e., Ca(H0)2 either as a powder alone or with other additives that increase the piled density such as calcium carbonate, dolomite, water, as well as in the form of a concentrated aqueous calcium hydroxide suspension, is used as the extinguishing substance. The latter can be produced as calcium hydroxide or, alternatively, as lime. Of great importance is the fact that the powdered calcium hydroxide has a arge absorptive force for relative water moisture, i.e., a or-sU~ace a~ea specific surface~of approximately 40 m2/g.

he extinguishing substance is applied to the fire as follows:

- the calcium hydroxide powder is spread evenly over the fire and falls freely onto this such that on the way down it absorbs the relative moisture from the combustion gas. In the event that the piled density of the extinguishing substance is not great enough to overcome the force of the rising gases, the extinguishing substance is mixed, as described above, with up to 5-75%-wt of additives that will increase the piled density. The additives ~ r~mYfr~be~
s~ou Id ~ also possess fire-extinguishing properties.

- the calcium hydroxide suspension in water (20-25%-wt of solids) is applied to the burning area of the conflagration, divided as finely as possible, using fire-extinguishing eguipment.

- the calcium hydroxide suspension in water (15-20%-wt of solids) is sprayed over the conflagration so as to form a fog with droplets that are smaller than 100 microns, when it agglomerates and then falls back onto the fire. Fogging equipment can be used in order to intensify this process.

The results as based on thermal calculations and tests that were carried out indicate that the portion of a fire affected by direct fire-fighting methods could be extinguished in a few seconds (5-20 seconds), in which connection the estimated use of water (for adjusting the piled density, and for producing the suspension) amounts to only a fraction, i.e. less than 10-15%, of the quantity of water used in the normal course of events during standard extinguishing procedures. Given that a fine distribution of 250 microns is imparted to the extinguishing suspension when putting out fires, the use of the extinguishing agent, in respect to a safety coefficient of 2.5, amounts to the following:

- 7.8 x 10 4 k/m2 = 7.8 x 10 1 k/1000 m2 (100% extinguishing substance) - 3.9 k/1000 m2 (20% extinguishing aqueous suspension~

Thus, in theory, in order to extinguish a burning surface of 1000 m2, one uses 3.125 k of extinguishing water.

Example 1 Extinguishing a burning house.
Extinguishing agent: 20~ aqueous suspension.
The house measures 20 x 10 x 40 m and has an effective area of 65,000 m2 calculated on the basis of fire-fighting requirements.
Given that during the extinguishing process, the coating procedure would have to be carried out three times, the use of extinguishing agent would amount to the following:

- V(L) = 3 x 65,000 m> .10 -3 x 3.9 k : 1.25 k/L = 608.4 litres - W(ater) = 608.4 L x 1.25 k/L x 0.80 = 608.4 litres Working pressure: 40 bar A calcium hydrate suspension is produced directly through a suitable binary nozzle at the side of the fire. The above-cited quantity of extinguishing agent contains no agents to prevent the fire spreading to neighbouring residences.

Example 2 Extinguishing a forest fire.

Alternative l: Extinguishing agent: a powder mixture of 60%-wt of calcium hydrate with approximately 40 m2/g specific surface +
25%-wt CaC03 + 25%-wt water. The extinguishing agent is spread by mechanical means (e.g., from a helicopter flying directly over the fire, at approximately 25 to 30 m above the flame cone. This alternative can be used in the case of a high-density forest.
The estimated use of extinguishing agent amounts to the following:
- G(k) = 150 x 150 m x 0.00025 m x 2.5 x 1.25 = 17.6 t Alternative 2: A sparse area of forest, the fire has burned itself out, and fire-prevention measures have been taken to prevent the fire from spreading. In this case, two variations can be used to fight the fire. One variation is based on spraying the trees that are beyond the area of burning forest and which have not as yet been touched by fire, with a suspension as set out in Example 1, or by applying the mixture set out in Alternative 1 on the fire breaks in the forest, in which case only water is added to form the mixture, this being done at 25-50%-wt (the second variation). In this connection it is advantageous to lay mats impregnated with the extinguishing agent and which include only a very small portion of combustible packing, to the fire breaks in the forest.

Example 3 Counter-measures to be adopted in the case of leakage from a liquid-chlorine container.
Quantity sf chlorine escaping from the container: 100 k/h.
A layer of fog phase 10 m in diameter and 5 m high is formed around the defective container. Other factors are as described above. At the same time, the contents are pumped out of the container. The use of the active agent is as follows:
- G = 3.14 x 102 x 5 x 0.05 x 0.025 x 1.25 = 2.45 t Calculation: 2.45 t x 0.20 = 0.490 tonnes Ca(OH) = 265 k Ca++
Purifying reaction (simplified representation):
Ca++ + = CACl2 (40.08)g + (71.0)g = (111.08)g (56.45)k + (100.0)k = (156.45)k 265 k Ca++ are available for carrying out the reaction. The elimination of the chlorine can be safely assumed.

Note: other inorganic compounds can be used as absorbent for the escaping environmentally benign substances, which are soluble in water and chemically reactive.

Example 4 Surrounding buildings endangered by a fire.
The outsides of these buildings are carefully sprayed with an extinguishing agent suspension.

If Use: as described above. Once the fire has been put out the extinguishing agent is washed off with water.

Exam~le 5 The structural elements are produced from combustible material, e.g., styropor and/or wood. The elements that are endangered by fire are rendered independently fire-proof by applying extinguishing agent powder by vacuum technology or by wetting, or by single or multiple layers of extinguishing agent powder.

Claims

1. A process for fighting and extinguishing fires involving Class A, B, or C materials, in which a flame-retarding substance is distributed over the fire, characterized in that an alkaline earth oxide or hydroxide on activated lime or magnesium-based product processed to form a fine-grain powder with a low specific piled density or a large relative surface is distributed evenly in the area of the fire.

2. A process as defined in claim 1, characterized in that the fine-grain powder is distributed on the fire as a suspension formed in water.

3. A process as defined in claim 1, characterized in that the fine-grain powder is distributed on the fire in the form of a suspension formed in water.

4. A process as defined in claim 1 to claim 3, characterized in that calcium hydroxide is used as the activated product, this being produced by calcining and slaking lime (CaCO3) with a mixture of water and alcohol.

5. A process as defined in one of the claims 1 to 3, characterized in that calcium carbonate that contains lattice defects in its structure as a result of being ground to a fine-grain powder is used as the activated product.

6. A process as defined in claim 5, characterized in that fire-fighting is effected with an activated product to which one or more tenside additives, in particular a wetting agent, have been added during or after the grinding process.

7. A process as defined in claim 5 or claim 6, characterized in that the activated product is formed from spherical particles.

8. A process as defined in one of the claims 1 to 3, characterized in that a lime precipitate (CaCO3) formed by chemical reaction and precipitated in this manner and in aqueous solution is used as the activated product.

9. A process as defined in one of the claims 1 to 7, characterized in that activated magnesium oxide alone or together with an activated lime-based product is used as the activated product.

10. A process as defined in one of the claims 1 to 9, characterized in that the activated product is contained in the suspension in a quantity between 5-25%-wt, and preferably approximately 10%-wt.

11. A process as defined in one of the claims 1 to 10, characterized in that a tenside additive, in a quantity of up to n10%-wt relative to the total quantity of the suspension is added to the suspension in order to improve its homogeneity and the wetting characteristics of the extinguishing agent as applied to the combustible material.

12. A process as defined in one of the claims 1 to 10, characterized in that additives, preferably additives with fire-extinguishing properties, are added to the carrier liquid in order to increase its specific weight and thus the homogeneity of the suspension.

13. A process as defined in one of the claims 1 to 12, characterized in that one provides or installs mats that are coated or filled with a fine-grain powder of an activated lime or magnesium-based product with a low specific piled density or a large relative surface in combustible structures or structures that are endangered by fire, for example, buildings, ships, tanker vehicles, rail cars, containers, or aircraft.

14. A process as defined in one of the claims 1 to 12, characterized in that the installed layers or mats are encased by an easily ignited covering that is destroyed by heat and/or flame so that the extinguishing agent is released, this then spreading on the surrounding surfaces that are threatened by fire.

15. A process as defined in one of the claims 1 to 12, characterized in that the extinguishing agent is spread or dispersed within the framework of fire precautions or fighting methods used in buildings and in traffic areas of all sorts, by way of sprinkler systems and all existing distribution systems.

16. A process as defined in one of the claims 1 to 15, characterized in that an active fog is formed by spraying a suspension of fire extinguishing agent that is divided as finely as possible in order to extinguish fires in buildings that contain environmentally hazardous, explosive, or radioactive substances, said fog releasing in part the product that is based on lime or magnesium as it sinks/disperses--as a function of the drying effect of the fire or explosion--the product then falling on the remaining combustible areas and preventing the fire from spreading.

17. A process as defined in one of the claims 1 to 16, characterized in that the suspension that is used to generate the fog contains additional inorganic, alkaline absorption means such as caustic soda, caustic potash, soda solution.

18. A process as defined in one of the claims 1 to 17, characterized in that in industrial fires with a gas front that builds up behind the first flame front the extinguishing agent is used in a binary process such that the lime or magnesium-based product is used in the form a dry powder or as an emulsion on the flame front and in the form of a sprayed fog in order to combat the heavy gases that move along the ground in the form of a cloud and the light gases that rise immediately into the air.

19. A process as defined in one of the claims 1 to 18, characterized in that the solid and liquid components of the suspension that is to be sprayed are stored separately in the required quantities in containers that are specific to the application, the solid components being emptied into the liquid immediately prior to use and then mixed to form a homogenous mixture by means of a stirring mechanism.

20. An apparatus for carrying out the process according to one of the claims 1 to 19, characterized in that a container (3) that incorporates two chambers (1,2), of which one chamber (1) that is used to contain the water is fitted with a stirring mechanism (4), and the other chamber (6) is used to contain a fine-grain powder with a low specific piled density or a large relative surface, that is of an activated lime or magnesium-based product, the chambers (1,2) being connected to each other by means of a lock that can be opened by hand.

21. An apparatus as defined in claim 20, characterized in that the water container is provided with a pump (6) that is driven by means of a motor (5) in order to spray out the suspension, the motor (5) simultaneously operating the stirring mechanism (4) that is immersed in the suspension.

22. An apparatus as defined in one of the claims 20 to 21, characterized in that the container (1) that is used to hold the water is in the form of a container that is open at the top and has at its upper end a lock (8,9) to hold the container that is formed as an attachment and which holds the powdered extinguishing agent, this being provided on the side that is proximate to the water container (1) with a wall (10) that is flexible and incorporates a tear-type closure.

23. An apparatus as defined in claim 22, characterized in that the flexible wall (10) incorporates a peripheral perforation and is provided within the perforation with a tear tab (13) there being a rotatable shaft (14) in the water container (1), said shaft incorporating an external lever (15) and a gripper (16) that engages in the tab (13) such that rotation of the outer lever (15) tears the perforation so that the extinguishing powder is emptied into the water.

24. An apparatus as defined in claim 19 or claim 21, characterized in that the container (18) that holds the water and the container that is used to hold the powdered extinguishing agent are connected to each other and the container section that holds the powdered extinguishing agent is provided with a flap (19) that opens to the side and a holder for supporting a bag (20) that contains the extinguishing agent, there being in the container wall a blade (21) that extends into the area of the bag (20) and is operated from the outside, with the help of which the bag (20) is slit open so as to allow the contents to empty into the water as required.

25. An apparatus as defined in claim 24, characterized in that the bag incorporates two tags that extend in the longitudinal direction and the container incorporates two carrier rods that are secured at one end and which are used to support the bag by means of its tags.

26. An apparatus as defined in claim 24 or 25, characterized in that the bag is of water-resistant material that is impermeable to water and is sealed so as to be water-tight.