AU659291B2 - A method for fire extinguishing - Google Patents

Description

659291 S F Ref: 235371

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

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*t I Name and Addres Name and Address of Applicant: Actual Inventor(s): Ljuberetskoe Nauchno-Proizvodstvennoe Obiedinenie "Sojuz" Moskovskaya oblast Dzerzhinsky ulitsa Sovetskaya, 6 SOVIET UNION Anatoly Nikolaevich Baratov, Vyacheslav Vladimirovich Belokon, Vyacheslav Ivanovich Deruzhinsky, Leonid Vasilievich Zabelin, Eduard Ljudvigovich Kazarian, Anatoly Vasilievich Marchenko, Jury Alexandrovich Militsyn, Boris Ivanovich Mironov, Zinovy Petrovich Pak, Boris Petrovich Perepechenko, Vitaly Grigorievich Tamurka, Eduard Grigorievich Tkachev, Vladimir Vasilievich Sharshkov, Galina Grigorievna Shakhrai and Tatyana Pavlovna Korobenina ir ilyl Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia A Method for Fire Extinguishing Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845/3 i I II A IETHOD FOR FIRE EXTINGUISHING The present invention relates to fire prevention equipment and, more specifically, it relates to a method for fire extinguishing.

Most efficiently the present invention can be applied in extinguishing fire catching the enclosed space, e.g.the industrial and civil premises, means of transport etc.

At present frequency of fire incidents increases in proportion to extensive growth of industrial potential. Particularly affected are chemical and gas-and-oil processing industries where accidental blowouts or escapes of the easily inflammable or combustible fluids and-gases threaten to explode. Just asiworrisome is the fire-threat to timber and coal industriesi 15 'For centuries fires have been most ravaging at sea.

j Almost '30 7 of all marine accidents are the result of

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i i .devastatingfire. Effective fire fighting has become an urgent: problem of safety in navigation.

j The prior art method for fire extinguishing relies on supply'or delivery into the combustion zone of the gaseous, galoid compounds (Halon) which by their fire extinguishing and operational characteristics belong to the group of toxic and ozone-destructing chemicals.

By 2000, their use will'have to be totally banned or phased out in accordance with landmark Montreal Protocol (1987) for 'the protection of the earth's stratospheric: ozone layer.

Hence it is necessary to provide an ecologically pure method for fire extinguishing that does not wipe out ozone, and avoids the toxic effects in living beings.

Partly, ,this problem is solved by the known fire extinguishing method which is ecologically pure i N. Baratov, E. N. Ivanov,"Pozharotushenie na predpriatiyakh khimicheskoi i neftepererabatyvayuschei promyshlennosti", 1979,Khimiya, [Moscow],p. 347),comprising supply or delivery into the combustible zone of the gaseous substances or i' agents that are inert in relation to chemical reactions in the combustion zone, and reduce oxygen content in the air, and also bring down,by consuming a certain amount of heat, the flame temperature below the critical level at which the combustion process discontinues. These agents are represented by carbon dioxide.0C02,water vapor H2O,nitrogen

N

2 and noble gases described as thermal ballasts. The mechanism of their.. fire extinguishing action is practically the sai, while their quantities,required for fire extinguishing depend' on their thermal and 'physical aspects based on different values of thermal capadity and conductivity.

Nitroge'n, for instance, is used to suppress burning of materials which react with Halons -and water with' o 15 explosion. Carbon dioxide and water vapor are used when halons are economically disadvantageous.

0 Given the inert relation of the agents to chemical reactions in the combustion zone, their relevant fire extinguishing mass concentration is considerably higher than that of 'Halons, which explains why the use of such fire extinguishing compounds has become limited in its applicability.

Few years later, widely employed among the known techniques was the method for volumetric extinguishing of fire based on the fire extin uishing powders (A.N.BaratoV, L.P.Bogman, "Ognetushasohie poroshkovye sostavy", 1982, Stroizdat [Moscow], pp.60-62).

What is implied by the volumetric fire extinguishing is the creation in a limited volume', e.g. a room,a hold, a shop etc. (hereafter referred to as "the protected volume") of a medium that does not feed fire' This is secured by supplyihg 'the gaseous agents or aerosols into the protected volume, and their.uniform dispersion therein in quantities providing such level of concentratidn at which both combustion and explosion are impossible. By the zone of combustion 's meant a portion or division of space i Iji occupied by the visible flame, wherein there happens the chemical process, namely, the interplay or engagement of gaseous agents, i.e. the products of decomposition by fire of the primary materials, with environmental oxygen.

The known method is obtained by supplying into the combustion zone of a medium in the form of powder conveyed by gas under pressure. The compressed powder once ejected, constitutes aerosol that enwraps or encompasses and ultimately suppresses the flame, which is achieved by way of inhibiting the chemical reaction of burning with the help of powder fractions. According to contemporary perceptions, the mechansim of fire extinguishing operation performed by aerosol, contemplates annihilation of the "active centres" that are responsible for the combustion process generation at conflagaration site, on the surface of solid fractures of aerosol. Those "aidve centres" are represented by atomic particles or molecular fragments (radicals) having free valence, in which case there unfold the branched chain reactions, typical of the combustion process. However, this Smethod for fire extinguishing has limited application due to relatively low dispersiveness S 15 of powders. For this reason, it becomes difficult to provide uniform dispersion and continued suspension of the powder aerosol fractions in the protected volume.

Since the powders ar, manufactured beforehand and are kept for a long time under the compressed gas pressure, they are subject to lumping and coagulation which stand in the way to formation of highly dispersive aerosol to be supplied into the combustion zone.

Coarse-grained dispersive powder reveals insufficient fire extinguishing capacity, S: compared to that of "Halon".

It is an object of this invention to provide a method for fire extinguishing based on Ssuppression of the chemical reaction of burning through re-alignment or re-combination of 2the flame "active centres" by means of the heterogeneous aerosol particles.

25 There is disclosed a method of extinguishing fire, comprising supplying into the S' combustion zone an aerosol which when applied to a flame causes localization and suppression of said flame, wherein said aerosol is produced by burning a synthetic solid oxygen-containing fuel and comprises condensates of particles of metal oxides, carbonates, sulfides or phosphates or mixtures thereof in a gas containing oxygen, nitrogen, carbon dioxide and water vapours.

N:\LIBAA00O220:VGS -4- The .concept of this inventioh is accomplished by that supplied into the combustion zone is a medium which interaction or engagement with the flame causes its localization and suppression,said medium being in the form of an aerosol created by burning a synthetic solid fuel whichcontains oxygen.

Execution of the proposed fire extinguishing method provides suppression of chemical reactions taking place in the combustion zone. A distinguishing feature of aerosol produced by fuel combustion is in its high dispersiveness with particle size of less than 2. p, which secures large surface of their engagement with the "active centres".

As is known, the "active centres" are represented by atomic particles or radicals 'having free valence, enabling, development of the branched chain reactions, typical for homogeneous combustion. When 'the "active centres" strike the particles, they are adsorbed by the latter on their surface. In the course of engagement of the particle matter with an "a6tive centre" the latter re-aligns and turns inert. Energy released during, this re-alignment or recombinatiod of the' "active centres", is assimilated by the S particles prohibiting dissociation of;molecules formed as a result of the "active centres" re-combination. And this' helps suppress the combustio process.

S 25 Aerosol which is produced by fuel combustion is.

finely dispersive. Hence,the number of particles per cubic measure of medium increases, thus raising the frequency of.

particles striking the "active centres".

STo determine the mass of synthetic fuel with oxygen content the following formula is useful: M K x V, where V- volume of the combustion zone in cubic meters, K concentration of aerosol in the combustion zone, K 0.010 0.2 kg/cu. mn The relationship was obtained on the basis of test records.

I II i i II-~ K value depends on qualities 'of material set on fire, and also it 'depends on architecture and hermetic sealing, of the protected volume,e.g. n office,a store,a workshop, an aircraft, a vehicle etc. With K 0.01 kg/cu. m, fire extinguishing is not. guaranteed because the summation surface of aerosol/particles' is inadequate to remove the "active centres". With K 0.01 2 kg/cu.m,these' "active centres" are removed from the flame by aerosolparticles.

With K 0.2 kg/cu.m,solid fuel expenditure is essentially; inefficient.

It 'is necessary that aerosol contains oxides or' carbonates or phosphates of metals or their inixtures. It has been established by experiment that the said compounds' are remarkably "akin" to the "active centres", which means that frequency of the "active centres" re-alignment in relation to the said compounds is high. In other words,the chain reactions of combustion are interrupted more often.

Hence, to suppress the combustion process, smaller amount of aerosol will be required.

It is preferred that the metals are selected from group I of the periodic system '(law) because 'their compounds are less toxic, "abundantly present .in nature, comparatively cheap,. and, as stated, remarkably ."akin" to the "active centres".

Highly dispersive aerosol needs cooling before it is supplied to the combustion, zone.' At lower temperatures aerosol'requires less time to suppress fire because in this case the process of balancihg or equalizing the irregularity of aerosol concentration in relation to a height of the protected volume, is accelerated, said irregularity being caused by elevating power existing by virtue of aerosol -and environment temperature difference.

Aerosol: is cooled down to below critical temperature of conflagration or blasting of the explosive gas mixtures.

It is recommended to perform cooling at a rate of at least 400 degrees per second. I.

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g 0 ro 0o 0 oo 1 0 0c 9 40 00 0 0 0 0 0 a on ftI* o IL o When the-'cooling of aerosol -is done at a rate 400 degrees per second, it remains highly dispersive for several tens of minutes due to suppression of coagulation, which results in greater efficiency of fire suppression.

It is preferred that introduced into aerosol .should be such gaseous, medium that is inert in relation to the.

combustion process, selected from 'the group of CO N 2 He, Ar,, or their mixtures ih proportion to mass of at least 1:30.

As a result, owing to the fact that oxygen content in the combustion zone is brought down as the inert medium is supplied into the said zone, the synthetic fuel mass with oxygen content, which is used to suppress fire, reduces.

The object of the present inveition will become more 15 fully apparent from the following description, of its particular embodiments and accompanying drawing, wherein: Fig. 1 is a schematic longitudinal section of the' chamber in, which diesel oil combustion and fire extinguishing process take place according to the invention; Fig. 2 is a diagrammatic representation of timemeasured temperature curve of diesel oil combustion, and similar representation df time-measured temperature curve related to combustion of solid fuel with oxygen 25 content, having mass of 1.230 kg; Fig. 3 is a diagrammatic representation of timemeasured temperature curve of diesel oil combustion, and similar representation of time-measured temperature, curve related' to combustion of solid fuel with oxygen content, having mass of 2.370 kg; Fig. 4 is a diagrammatic representation of timemeasured temperature curve of diesel oil combustion, and similar representation of time-measured temperature curve related to combustion of solid fuel with oxygen content, having mass 2.370kg.

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-7- EMBODIMENT I A meth6d ,,for fire extinguishing according .to the invention was accomplished in a special chamber 1 (Fig.1) having volume of 60 cu. m, which is representative of conventional premises intended for fire protection. Inside chamber 1, there is a drip cup or pan 2 filled with diesel oil, having combustion surfacp of 1 sq.m, and placed on -support 3. Incandescent filambnt 4 serves to ignite' diesel oil. Inside chamber 1 hold,placed on slip (stapel) 5 there is an aerosol generator which comprises a dylindrical body 7'with orifice 8, containing solid fuel with oxygen content, for instance,in the form of cylinder. Incandescent filament' 10 provides ignition of solid fuel 9. Walls 11 of' chamber 1 are made of reinforced 'concrete. To imitate V 15 deficiency of hermetic sealing, there is a metal gate 12.

which can be moved in the longitudinal,direction in order l to ensure .variable entrance area of the ventilating clearance 13. Temperature levels in zone 14-of diesel oil combustion .are controlled with the help of:thermocouples (not shown in diagram), .said thermocouples being used also to control aerosole temperatures (not shown in diagram).

To determine .the requied aerosole concenRtration in the given volume in order to ensure fire extinguishing at' the combustion site, the solid,fuel mass quantities were varied. Voltage applied to incandescent filament producd conflagration and burning of diesel oil placed in drip pan 2. Once the combustion process becomes steady, say in seconds, voltage is applied to incandescent filament 10 to ignite solid fuel 9 having .mass of 1.230 kg on the physical scale. Aerosol generated by fuel 9 combustion is mixed with air and fills up the whole volume of chamber 1.

Upon termination of the generator 6 operational period,the suppression of flame in zone 14 oi diesel oil combustion could not be achieved, as is evident from diagrams and (Fig. 2):both representing a curve that crosses axis (t) of abscissae at two points. Points ai,a2 correspond to the S' i

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i j -8- 8 beginning and the end of diesel, oil combustion, while points'bl, b2'reflect the beginning and the end of burning, the solid fuel with oxygen; content. Time consumed till termination of diesel fuel combustion '(point a2) essentially exceeds/.that of solid fuel burning (b2) which corresponds; to the/period of its complete burn-down. In this case, ,aerosole concehtration equals 0.'020 kg/cu. m., .which is inadequate to extinguish fire because the; summation surface of its particles' have turnedout to be; incapable of removing the "active centres". Then the solid' fuel mass was increased. With 2.370 kg mass of solid fuel, the flame in zone 14 of diesel oil combustion was localized &id suppressed.Point a2 and b2 on abscissae axis coincided (Fig.3) reflecting the termination of diesel S 15 oil and solid fuel combustion. Aerosole combustion in this o case reached 0.040 kg/cu.m o 0In consequence of the above examination it may stated.

S0 that this concentration of aerosol is adequate for fire 0 extinguishing- Aerosol which ,filled the measure of chamber i (Fig.1) has the following composition: gaseou: oxygen (02),nitrogen (N 2 ),carbon dioxide (CO 2 ),water vapor (H 2 0), and condensed particles of sodium chloride (NaCl) and sodium carbonate (Na 2 CO0), said partioles not exceeding.2 mm. The "active centres", namely atoms and radicals'0, H, S: 25 H, CO responsible for combustion process development, descend on the surface of the said condensed particles and interact or engage with them; in which case there are created molecular particles that are incapacitated for the work function of the combustion "active centres".

Further concentration .of aerosol in chamber I affords faster suppression of fire in the combustion zone.

As is shown in diagrams and (Fig.4),point a2 which represents the time of termination of diesel oil combustion, is placed on abscissae, axis nearer to the point of reference than b2 Ihich corresponds'to the time of termination of solid fuell burning.. This indicates that t 7' higher concentration of aerosol 0.040 kg/cu, m results in excessive expenditure of solid fuel with oxygen content.

EMBODIMENT II A method according to the invention is applied in view of -fire,' for 'instance, in the machine-room of a watercraft due to oil conflagration. In its enclosed volume, synthetic solid fuel is burnt,' to generate aerosol filling" the measure of the machine-room. The solid fuel' is in the form of,pots placed in the machine-room, their mass being calculated on'the basis of formula: M K x,V, where V volume of the combustion zone, e.g. 1300 cu.m; K aerosol concentration, e.g. 0.040 kg/cu. m.

Fuel is inflamed either with ignition device placed in each shop with pots, or from the fire source itself.

Aerosol which filled the measure of the machine-room i i has the following composition: gaseous oxygen (02),nitrogen

(N

2 carbon dioxide (C02), water .vapor (H20), and S" condensed particles of potassium chloride (KC1), sodium chloride (NaCl), sodium .carbonate .(Na 2

CO

3 potassium sulphate (K 2 S0 4 The "active centres", namely atoms and radicals 0, H, OH, CO responsible for combustion process development, descend on the surface of the said condensed particles and interact or engage with them; in which case there are created molecular particles incapacitated for the work function of the "active bentres". Energy released during the re-alignment or re-combination of the "active centres", is assimilated by the particles prohibiting dissociation of molecules fofmed.

The above process affords suppression of fire in the machine-room. In this case, oxygen content which is filled up with aeropole, practically does not diminish, and so there is no impact against respiration.

I 4 S- 10 EMBODIMENT III Another embodiment of the invention is obtained by; cooling aerosol bef6re it is supplied to chamber 1, say down to 900 K, by means of its ingression/passage through the familiar heat exchanger. 'The volume of chamber 1, the dimensions of drip pan 2 with diesel oil contained .therein, the quantity of solid fuel 9 with oxygen content (2.370 kg) as well as the procedure foll'bwed to inflame diesel oil and extinguish fire are similar to those in embodiment I.

The distinguishing feature lies in the fact that during the supply of cooled aerosol having greater, density of gas run (phase) into the,said chamber 1, the process of balancing or equalizing the aerosole concentration in relation to; a height of the said chamber is accelerated. As a result,' the flame in the combustion zone 14 is getting suppressed 9 seconds earlier than in embodiment I (Fig. 3.

EMBODIMENT IV A method, for fire extinguishing is accomplished, according to this invention in chamber 1 (Fig.1) equipped with a supply system which is inert in relation to the.

process of gaseous medium combustion, e. g. the burning of' nitrogen. The procedure of aerosol delivery is same as in embodiment I. The distinguishing feature is afforded by the medium set on fire which is represented by isopropylalcohol having mass of up ,to 32 kg. Time required for complete burn-down is 20 minutes. To extinguish the same only by nitrogen N 2 20 kg of nitrogen will have to be supplied to chamber 1. In order to extinguish the burning isopropylalcohol in chamber 1 by aerosol only, said aerosol should be generated by combustion in chamber of' solid fuel with oxygen content, 'having mass of 2.5 kg., Within 5 minutes of alcohol ignition, when .the flame becomes steady, first the highly dispersive aerosol generated by combustion of solid fuel with oxygen content, is supplied, then, in 10 seconds, gaseous nitrogen N 2 11 kg for 1. 5 'seconds. Owing to'nitrogen N 2 delivery,, the concentration, of oxygen 0 2 1n chamber i has comle down., As a result alcohol combustion ;'has termiinated 22 seconds earlier than' if, the/f ire extin'guishing .were to he'carried.

out only by, aerosol. The l-eqired quantity'of saud fuel has reduc~dto 1. 26 kg, Accordingly, the 'Fire extinguishing efficiency has grown two- fold, ii 1

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Claims (8)

1. A method of extinguishing fire, comprising supplying into the combustion zone an aerosol which when applied to a flame causes localization and suppression of said flame, wherein said aerosol is produced by burning a synthetic solid oxygen-containing fuel and comprises condensates of particles of metal oxides, carbonates, sulfides or phosphates or mixtures thereof in a gas containing oxygen, nitrogen, carbon dioxide and water vapours.

2. A method according to claim 1, characterised in that the mass of said fuel is determined by the formula: M K.V, wherein V is the volume of said combustion zone in cubic metres and K is the concentration of said aerosol in said combustion zone and is 0.010 to 0.2 kg.m- 3

3. A method according to claim 1 or claim 2, characterised in that said metals belong to group I of the periodic system.

4, A method according to any one of claims 1 to 3, characterised in that said S 15 aerosol is cooled before it is supplied to the combustion zone.

5. A method according to claim 4, characterised in that said aerosol is cooled down below the critical temperature of inflammation or blasting of explosive gas mixtures.

6. A method according to claim 4, characterised in that said aerosol is cooled down at a rate of at least 400 degrees per second. '0 0 a

7. A method according to any one of claims 1 to 6, characterised in that a gaseous medium, (which is inert relative to the combustion process, being at least one of carbon dioxide, nitrogen, water vapour, helium or argon in a ratio to mass of at least 1:30) is introduced into said aerosol. 25

8. A method of extinguishing fire, substantially as hereinbefore described with reference to any one of the Examples. Dated 23 December, 1994 Ljuberetskoe Nauchno-Proizvodstvenue Obiedinenie "Sojuz" Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON N C I N:\LIBAA100220;VGS