Labile bromine fire suppressants

Abstract

A class of fire suppressant compounds which have labile bromine atoms bound to atoms other than carbon have been discovered to be more effective at suppressing fires than Halon 1211 and Halon 1301. Moreover, this class of fire suppressant compounds hydrolyze or oxidize rapidly in the troposphere and as a consequence thereof, they have minimal ozone depletion potential.

Description

Thus lower average bond energies indicate the possibility of labile bonds in a group of materials, but further experimentation with specific materials is required to establish the lability of the bond compared with Halons.

	TABLE I
	Composition	Phase	% Br	Comments
	PBr3	liquid	88	brominating agent
	POBr3	liquid	83	brominating agent
	SOBr2	liquid	77	brominating agent
	BrF3	liquid	58	reactive solvent
	BrF5	liquid	46	reactive solvent
	PBr5	solid	92	brominating agent
	TiBr4	solid	87	reacts with water
	SiBr4	liquid	92	reacts with water
	IBr	solid	39	decomposes at 116° C.
	CuBr	solid	29	brominating agent
	NOBr	gas	73	brominating agent
	BrF	gas	81	boils at −20° C.
	C4H4O2NBr	solid	44.9	decomposes at 170° C.
	BBr3	liquid	96	boils at 90° C.
	BrCl	gas	70	decomposes at 10° C.

In one embodiment of the invention liquid SOBr₂ is introduced as an air-pressurized mist into a 500,000 Btu/hr fire resulting from kerosene flowing at a rate of 4 grams per second through a nozzle with cross-flowing compressed air to atomize the liquid into a fine mist. The fire is contained in a flame holder whose volume is approximately 8 liters and is further blown by an atmospheric cross-wind of 40 miles per hour. The fire is reproducibly and irreversibly extinguished with less than one gram of SOBr₂ in less than 0.2 seconds as confirmed by videotape records of the experiments. The same fire is not reproducibly suppressed with aliquots of 25 grams of CF₃Br added to the same location.

In another embodiment of the invention 0.2 cubic centimeters of PBr₃ is mixed with 0.7 cubic centimeters of liquid carbon dioxide. The liquid CO₂ propels the PBr₃ through a valve and into the flame zone, generated as herein above described, as it is opened, irreversibly and completely extinguishing the flame in the presence of flowing fuel, air, and hot surfaces.

Extinguishment of a similar fire, with a hydrocarbon fuel burn rate of 12 grams per second, by Halon 1301 is taught by Alvarez in chapter 3 of Gann (ibid.) to require between 90 and 130 grams per second of CF₃Br for suppression. Another example of a gasoline fire with similar heat output is taught by Ford in chapter 1 of Gann (ibid.) to require between 500 and 1500 grams of Halon 1301 for suppression. Another fire, in which 10 grams per second of jet fuel are burned in fast-flowing air at the Air Force Flight Dynamics Laboratory Engine Nacelle test facility (Wright-Patterson AFB, OH) requires between one and three kilograms of Halon 1301 for reproducible suppression. In each of these examples the quantity of Halon 1301 required to suppress a similar fire is between 100 and 1000 times greater than that required of the compositions of matter described herein above, of which SOBr₂ and PBr₃ are specific embodiments.

The labile bromine atoms and high proportion of bromine in the composition of matter listed in Table I provide a more efficient fire suppression formulation than the Halons, which typically have less bromine by weight (Halon 1301 and 1211 are 54% and 48% Br, respectively) and lesser proclivity for liberating bromine atoms when thermally or chemically activated in a combustion environment.

Methods for dispersing gas, liquid, or solid suppressants require designs based upon such factors as specific geometry of the locus of the fire, flow properties of the fire suppressants, and flame conditions of the fire. For example, fine mists of liquid are transported by fluid-dynamical drag forces along flow streamlines in the nacelle of an aircraft engine. The mists vaporize in hot zones, liberating bromine atoms by pyrolysis in precisely the regions where the heat released by combustion is most intense. Inasmuch as the drag coefficient is inversely proportional to the droplet diameter, as is known to people practiced in the art of fluid dynamics, there is a range of aerosol size distributions which most effectively deliver specific suppressants to specific fires. Another such factor for a gaseous composition is the mixing of suppressant flow with turbulent flames in a well-ventilated fire, which is affected by the delivery pressure, the nozzle contour and orientation, the mass-flow rate of the suppressant, and the fluid dynamical properties of the fire. Dispersing methods designed for suppressing fire in the nacelle of a jet engine differ from dispersing methods designed for suppressing fire in the engine compartment of a motor vehicle, the flu of a chimney, or the gas-handling manifold of a semiconductor processing clean-room.

Methods for preventing and extinguishing fires of jet fuel using a composition of matter class which is highly efficient and environmentally friendly is also disclosed by the present inventors in Final Technical Report FR-4021 (US Air Force Phase I SBIR Contract F33615-94-C-5005, November 1994).

Although preferred embodiments of the invention have been described, it will be understood that within the scope of this invention various changes may be made in the amount of fire suppressant, the composition of a fire suppressant mixture, and the method for dispersing fire suppressants which is generally stated consist of a class of fire suppressants and methods of dispersing such fire suppressants capable of carrying out the objects set forth as disclosed in the appended claims.

Claims

1. A fire suppressant composition consisting essentially of at least one brominated, non-carbon compound selected from the group consisting of PBr₃, POBr₃, SOBr₂, BrF₃, BrF₅, PBr₅, TiBr₄, SiBr₄, IBr, CuBr, NOBr, BrF, and BBr₃, which is combined with a propellant such that the ozone depletion potential of the composition is less than 0.1.

2. The fire suppressant composition of claim 1 wherein ozone depletion potential is defined on a scale where the ozone depletion caused by CFI₃ is 1.0.

3. A fire suppressant composition consisting of at least one labile brominated compound selected from the group consisting of PBr₃, POBr₃, SOBr₂, BrF₃, BrF₅, TiBr₄, SiBr₄, IBr, CuBr, NOBr, BrF, BBr₃, and BrCl, which is combined with a propellant selected from the group consisting of CO₂, N₂, compressed air, and HCFC-123 (CF₃CCl₂H).

4. The fire suppressant composition of claim 3 wherein ozone depletion potential of the propellant equals 0.016.

5. A fire suppressant composition consisting essentially of: at least one brominated, non-carbon compound in a liquid state selected from the group consisting of TiBr₄ and SiBr₄; and a propellant combined with the compound for propelling the composition such that sufficient bromine atoms are liberated from the composition to suppress a fire, wherein the composition has no ozone depletion potential.

6. The composition of claim 5, wherein the propellant is selected from the group consisting of CO₂, N₂, and compressed air.

7. The composition of claim 5 wherein said brominated compound is TiBr₄.

8. The composition of claim 5 wherein said brominated compound is SiBr₄.

9. The composition of claim 5 wherein said brominated compound is TiBr₄ and the propellant is nonflammable.

10. The composition of claim 5 wherein said brominated compound is SiBr₄ and the propellant is nonflammable.

11. The composition of claim 7 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of oxygen.

12. The composition of claim 11 wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

13. The composition of claim 7 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of heat.

14. The composition of claim 13 wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

15. The composition of claim 7 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of water.

16. The composition of claim 15 wherein said wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

17. The composition of claim 8 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of oxygen.

18. The composition of claim 17 wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

19. The composition of claim 8 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of heat.

20. The composition of claim 19 wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

21. The composition of claim 8 wherein said brominated compound is not stable in, and said sufficient bromine atoms are liberated in, the presence of water.

22. The composition of claim 21 wherein said wherein said liberated bromine atoms are sufficient to catalytically suppress the fire.

23. The composition of claim 7 wherein the propellant is selected from the group consisting of a non-flammable, pressurized gas; a deflagrating, solid, gas-generating cartridge; and a pressurized liquid.

24. The composition of claim 8 wherein the propellant is selected from the group consisting of a non-flammable, pressurized gas; a deflagrating, solid, gas-generating cartridge; and a pressurized liquid.

25. A fire suppressant composition consisting essentially of TiBr₄ in a liquid state and a propellant combined with the TiBr₄ for propelling the composition to catalytically suppress a fire, wherein the composition has no ozone depletion potential.

26. The composition of claim 25, wherein the propellant is selected from the group consisting of CO₂, N₂, and compressed air.

27. The composition of claim 25 wherein the propellant is nonflammable.

28. The composition of claim 25 wherein the TiBr₄ is not stable in the presence of at least one of oxygen, heat, and water.

29. The composition of claim 25 wherein the propellant is selected from the group consisting of a non-flammable, pressurized gas; a deflagrating, solid, gas-generating cartridge; and a pressurized liquid.

30. A fire suppressant composition consisting essentially of SiBr₄ in a liquid state and a propellant combined with the SiBr₄ for propelling the composition to catalytically suppress a fire, wherein the composition has no ozone depletion potential.

31. The composition of claim 30, wherein the propellant is selected from the group consisting of CO₂, N₂, and compressed air.

32. The composition of claim 30 wherein the propellant is nonflammable.

33. The composition of claim 30 wherein the SiBr₄ is not stable in the presence of at least one of oxygen, heat, and water.

34. The composition of claim 30 wherein the propellant is selected from the group consisting of a non-flammable, pressurized gas; a deflagrating, solid, gas-generating cartridge; and a pressurized liquid.