Classifications

• • A—HUMAN NECESSITIES
  • A62—LIFE-SAVING; FIRE-FIGHTING
  • A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
  • A62D1/00—Fire-extinguishing compositions; Use of chemical substances in extinguishing fires
  • A62D1/0028—Liquid extinguishing substances
  • A62D1/0035—Aqueous solutions

Definitions

• This invention relates to fire extinguishing solutions for use against dry fires and fires particularly difiicult to extinguish such as those of hydrocarbons or inflammable chemicals and mixed fires, that is to say, fires of combustible solid substances (wood, paper, rags, etc.) soaked for example with hydrocarbons or chemicals.
• potassium salts have interesting fire extinguishing properties and may be used either in the form of powder or in the form of aqueous solutions to fight fires.
• aqueous solutions of potassium acetate optionally mixed with other alkali metal salts and/or products such as wetting agents and other surface active agents which make the spraying easier.
• These solutions containing a relatively small quantity of potassium acetate are suitable to fight dry fires or fires generally easy to extinguish but they are not highly effective against fires of very inflammable substances such as gasoline for instance.
• An object of this invention is to provide novel and more effective fire extinguishing solutions based on potassium acetate.
• Another object is to provide a method of extinguishing fires with the solutions of this invention.
• solutions containing from about 300 to about 600 g./l. of potassium acetate will very quickly extinguish fires of hydrocarbons or inflammable chemicals (excepting, however, particularly rebellious fires of sulfur compounds such as carbon disulfide and percaptans). Nevertheless, within the above-mentioned limits, it is advisable to choose the concentration of the solution according to the nature of the fires to be dealt with: for fires of high boiling hydrocarbons and those of a large number of chemicals such as alcohol, aldehydes, amines, petroleum ether, ethyl ether, etc-., solutions containing from 300 to 400 g./l. of potassium acetate give the best results. But for fires of low boiling hydrocarbons such as gasoline, solutions containing from about 500 to 600 g./l. are more effective to obtain complete extinction.
• wetting agents do not better the specific extinguishing properties of the solutions disclosed in the present invention, such products added in small quantities, by reducing the surface tension of the liquid, will improve the dispersion of the droplets whereby the spraying operation is made easier. Therefore, the use of a wetting agent is mainly dependent upon the type of spraying apparatus chosen. Obviously, the wetting agent must be compatible with the dissolved salts: for example, to the solution disclosed in the present invention it is possible to add a wetting agent of oxyethylenic alkylphenol type or a phosphate ester of non-ionic compounds, preferably in quantity not exceeding 2% by weight of solution. Specific examples of such wetting agents are compounds of formula Where n is 6 to 15, R is H or CH and R an alkyl residue having 8 or 9 carbon atoms.
• tetrapotassium pyrophosphate to potassium acetate solutions does not appreciably alter the freezing points.
• the freezing point of a solution containing 400 g./l. of acetate and 100 g./l. of pyrophosphate is close to 40 C.
• the fire extinguishing solutions disclosed in the present invention can thus be stored without any danger of freezing, those having a freezing point equal or lower to -40 C. being of course selected when climatic conditions are particularly severe.
• the extinguishing properties of these solutions are not altered at low temperature and they remain fiuid enough to allow an effective spraying operation with a suitable device.
• the fire extinguishing solutions herein set forth can be produced by any known method but a particularly simple method has been found to prepare them at low cost.
• potassium acetate solutions are prepared by the action of acetic acid on a mixture of potassium carbonate and hydroxide.
• neutralization is reached much more quickly and more easily than by the already known and generally used processes.
• the known processes comprise reacting acetic acid with either potassium carbonate or potassium hydroxide, both known methods having serious drawbacks; in the first case the mixture must be heated and stirred vigorously in order to facilitate the evolution of carbon dioxide; and in the second case, a strong cooling is necessary to eliminate the heat caused by neutralization of potassium hydroxide.
• the method of the present invention overcomes these various drawbacks and allows manufacture of potassium acetate without any external heating or cooling.
• This method consists in gradually adding a quantity of acetic acid sufficient to obtain neutralization to an aqueous solution of potassium hydroxide containing potassium car bonate, the molar ratio K CO /KOH of the mixture being in the range of 0.5:1 to 1.25:1, preferably 0.6:1 to 0.8:1.
• the gradual addition of acetic acid means that the whole amount of acetic acid is not added all at once to the aqueous solution of potassium hydroxide containing potassium carbonate as it would cause a too sudden evolving of carbon dioxide.
• the addition of acetic acid is made either step by step or continuously at a rate sufficient to obtain a steady degasifying.
• the temperature of the reaction mixture adjusts itself at a suitable value which is from about 95 to about 60 C., preferably close to 80-85 C. when the molar ratio K CO /KOH is comprised between 0.6:1 and 0821. Additionally, carbon dioxide evolves spontaneously without requiring any vigorous agitation for degasifying. Only .a slight stirring of the mixture is enough to obtain a slurry of potassium carbonate and to prevent it from collecting at the bottom of the reaction vessel.
• fire extinguishing solutions can be prepared directly at the desired concentration ready for spraying onto fires. But, should the site of utilization be situated far from the manufacturing unit, it is possible to prepare highly concentrated solutions fairly close to saturation point, for instance solutions containing 800 to 1000 g./l. of potassium acetate, in order to reduce transportation costs. These solutions can also include the tetr-apotassium phosphate and/or wetting agent in the appropriate proportions, taking into account that the solutions will be eventually diluted to concentrations of less than about 600 g./l. of KAc. Besides saving transport costs, these highly concentrated solutions also have the advantage of being much less corrosive than the more dilute ones and can hence be stored and transported without any damage to the containers.
• extinguishing solutions disclosed in the present invention can be employed in any usual type of apparatus for projecting or spraying water under gas pressure.
• Example 1 A highly concentrated solution of potassium acetate was prepared as follows:
• the solution thus obtained was used to prepare a series of more dilute solutions at pH 7.5, containing respectively 300, 400, 500 and 600 g./l. of potassium acetate with which were carried out different field tests with hydrocarbon fires under the conditions hereafter described.
• Example 3 10 liters of gasoline, some old rags and pieces of wood were placed in a round pan measuring 0.80 m. diameter and 0.20 m. high. These substances were ignited and left to burn for two minutes, the result being that the whole stake was burning fiercely.
• a solution containing 300 g./l. of potassium acetate, g./l. of tetrapotassium pyrophosphate and 2% by weight of a wetting agent commonly sold under the trade-name of GAFAC RE 610 was then sprayed onto the blazing fire. It took only one second to extinguish it completely in all cases, i.e., the first ignition and the following reignitions. In fact, after the first re-ignition the wood does not catch fire again owing to the fireproof properties of tetrapotassium pyrophosphate. Moreover, no spontaneous flames reappear after the first extinguishing operation.
• a method of extinguishing a fire which method comprises the step of contacting the source of the fire with an aqueous solution containing about 300-600 grams/liter of potassium acetate and in addition a sufficient quantity of tetrapotassium pyrophosphate to increase the extinguishing eflect of said potassium acetate, said solution having a pH higher than 7.
• a method of extinguishing fires in climatic temperatures of below 40 C. which method comprises the step of, at said temperatures, contacting the source of the fire with an aqueous solution containing about 400 grams/liter of potassium acetate and about 100 grams/ liter tetrapotassium pyrophosphate, said solution having a pH higher than 7.
• a fire extinguishing composition comprising, on the basis of a liter of aqueous solution, about 300 to about 600 grams/ liter of potassium acetate, a sufficient amount of tetrapotassium pyrophosphate to increase the extinguishing effect of said potassium acetate, and suificient water to make a liter of solution, said solution having a pH above 7.
• a fire extinguishing composition suitable for climatic conditions below 40 C. comprising, on the basis of a liter of aqueous solution, about 400 grams/liter of potassium acetate, about 100 grams/ liter of tetrapotassium pyrophosphate, and sufficient water to make a liter of solution, said solution having a pH above 7.
• a fire extinguishing composition comprising, on the basis of a liter of aqueous solution, about 300 to about 400 grams/liter of potassium acetate, about 100 to about 200 grams/liter of tetrapotassium pyrophosphate, a wetting agent compatible with the dissolved salts in a concentration of less than 2% by Weight of the solution, and sutficient Water to make a liter of solution, said solution having a pH above 7.
• a process for the preparation of an aqueous potas sium acetate fire extinguishing solution comprises gradually adding acetic acid to an aqueous mixture of potassium carbonate and potassium hydroxide, the molar ratio K CO /KOH of the mixture being about 0.5 :1 to about 1.25:1, the quantity of acetic acid being sufficient to neutralize said mixture, said solution having a pH above 7.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Fire-Extinguishing Compositions (AREA)
• Fireproofing Substances (AREA)

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Cited By (18)

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Citations (4)

• 0
  • BE BE634504D patent/BE634504A/xx unknown
• 1962
  • 1962-08-03 FR FR905979A patent/FR1338454A/fr not_active Expired
• 1963
  • 1963-07-11 GB GB27501/63A patent/GB1016590A/en not_active Expired
  • 1963-07-15 US US295213A patent/US3274105A/en not_active Expired - Lifetime
  • 1963-07-16 CH CH888463A patent/CH430462A/fr unknown
  • 1963-07-19 LU LU44095D patent/LU44095A1/xx unknown
  • 1963-07-24 DE DES86344A patent/DE1196080B/de active Pending

Patent Citations (4)

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