Nitrogen-generating composition for fire extinguishing and method for producing the same

Abstract

The invention relates to nitrogen-generating compositions for saturation fire-extinguishing and to methods for producing same. The composition comprises: 25.0-45.0% by mass of a heavy metal oxide, 12.0-18.0% by mass of a combustion modifier in the form of aluminium oxide modified with cobalt (II) nitrate (Co(NO3)2), with accelerating additives of nickel oxide and copper oxide, with an alkali metal azide making up the remainder to 100% and 0.07-2.0% by mass of a carboxylic acid ester as moistener (residue after drying) above 100%. The composition is produced by mixing aluminium oxide with cobalt nitrate and with the moistener, allowing the mixture to stand and dry out so as to produce a first mixture, separately mixing the first mixture with the heavy metal oxide and the moistener until a second mixture is produced, separately preparing a mixture of alkali metal azide powder with the moistener until a third mixture is produced and then mixing the second mixture and the third mixture simultaneously with copper oxide and nickel oxide, drying out the produced mass and forming granules.

Claims

1. A nitrogen-generating composition for fire extinguishing, comprising: alkali metal azide, heavy metal oxide as an oxidizing agent and fuel, wherein the composition further comprises a combustion modifier in the form of aluminium oxide modified with cobalt (II) nitrate (Co(NO.sub.3).sub.2), nickel oxide and copper oxide as promoting additives, the mixing ratio in wt. % being as follows: TABLE-US-00004 heavy metal oxide 25.0-45.0, cobalt nitrate 1.0-2.0, aluminium oxide 10.0-16.0, copper oxide 0.1-0.2, nickel oxide 0.2-0.3, alkali metal azide balance to 100.

2. The nitrogen-generating composition of claim 1, wherein the heavy metal oxide is iron(III) oxide or titanium(IV) oxide or molybdenum(VI) oxide or a mixture thereof in any combination.

3. The nitrogen-generating composition of claim 1, wherein the alkali metal azide is sodium azide or potassium azide or a mixture thereof in any combination.

4. A method for producing the nitrogen-generating composition of claim 1, comprising: mixing the aluminium oxide with the cobalt(II) nitrate (Co(NO.sub.3).sub.2) and a wetting agent, allowing to stand and dry to produce a first mixture of uniform color; mixing the first mixture with the heavy metal oxide and the wetting agent until a second mixture of uniform color is produced; mixing the alkali metal azide with the wetting agent until a third mixture is produced; mixing the second and third mixtures with the copper oxide and the nickel oxide and drying to produce a resulting mass; and, forming granules from the resulting mass.

5. The method of claim 4, wherein the granules are formed into tablets.

6. The method of claim 4, wherein the wetting agent is ethyl acetate or butyl acetate.

7. The method of claim 4, wherein the alkali metal azide is sodium azide or potassium azide or a mixture thereof in any combination.

8. The method of claim 4, wherein the heavy metal oxide is iron(III) oxide, or titanium(IV) oxide, or molybdenum(VI) oxide or a mixture thereof in any combination.

9. The method of claim 5, wherein the tablets are formed to have a shape of a cylinder with a passage and with an outer to inner diameter ratio from 5 to 7.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention may be better understood with reference to the accompanying figures and specific examples of producing the nitrogen-generating (nitrogen generant) composition for fire-extinguishing in accordance with the present invention.

(2) List of figures, where:

(3) FIG. 1 shows a photograph of condensed residue of the products of combustion of the claimed composition produced in Example 1 herein.

(4) FIG. 2 shows a photograph of condensed residue of the products of combustion of the composition produced in accordance with prior art (patent RU2484075), ref. to Example 4 herein.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(5) The composition of the present invention is produced using:

(6) sodium azide (CAS 26628-22-8), potassium azide (CAS 20762-60-1) as the nitrogen containing substance;

(7) iron(III) oxide (CAS1309-37-1), or titanium(IV) dioxide (CAS13463-67-7), or molybdenum(VI) oxide (CAS1313-27-5) as the oxidizing agent and fuel;

(8) cobalt(II) nitrate (Co(NO.sub.3).sub.2) (CAS 10026-22-9) as a modifier; aluminium oxide (Al.sub.2O.sub.3) (CAS 1344-28-1) also as a modifier;

(9) copper oxide (CuO) (CAS 1317-38-0) as a promoting additive;

(10) nickel oxide NiO (CAS 1313-99-1) as a combustion catalyst;

(11) ethyl acetate or butyl acetate as a process additive, i.e. a wetting agent for mixing the dry components.

(12) The nitrogen-generating (nitrogen generant) composition of the present invention for fire extinguishing is produced as follows:

(13) Stage 1: aluminium oxide modified with cobalt(II) nitrate (Co(NO).sub.3).sub.2) is prepared, to which end cobalt nitrate Co(NO.sub.3).sub.2 and aluminium oxide Al.sub.2O.sub.3 are mixed and ethyl acetate is added, followed by allowing to stand and drying to produce a mixture of uniform color (a 1st mixture), thus providing for aluminium oxide surface absorption by cobalt nitrate. In a particular embodiment, the mixture was agitated during about 20 minutes and then allowed to stand during about 3 hours and dried at a temperature of about 80° C. to remove the wetting agent.

(14) Stage 2: mixing modified aluminium oxide with iron oxide, or titanium oxide, or molybdenum oxide, adding ethyl acetate, which mixture is agitated until a uniform color is achieved (a 2nd mixture). In a particular embodiment, the mixture was agitated during about 15 minutes.

(15) Stage 3: sodium azide is mixed with a wetting agent, i.e. butyl acetate or ethyl acetate, until a viscosity is achieved which is sufficient for subsequent mixing this mixture (a 3rd mixture) with other components of the composition. In a particular embodiment, sodium azide was used in the form of powder and mixed with the wetting agent used in an amount of about 10% of the sodium azide weight during about 15 minutes at a temperature of about 30° C., until a 3rd mixture with a viscosity sufficient for subsequent mixing thereof with other components of the composition is produced.

(16) Stage 4: in a mixer, the mass produced at Stage 2 is mixed with the sodium azide mass produced at Stage 3 and, simultaneously, with copper oxide; the mixing time is 30-40 minutes.

(17) Stage 5: the mass produced at Stage 4 is dried at a temperature enabling removal of residual solvent to produce the claimed composition.

(18) To use the composition of the present invention in a nitrogen generator (a fire-extinguishing generator), the composition is shaped, densified and sized such as to meet the fire-extinguishing generator's thermodynamic, internal ballistics and gas dynamics parameters and its operational requirements.

(19) To this end, at Stage 6, the mass produced at Stage 5 is formed into granules, for example, by passing the mass through a sieve with a specified mesh size, for example, 1.5-3.0 mm.

(20) Stage 7: articles are formed, for example, by compressing the granules into pellets of specified shape, density and strength contributing to the provision of required operating characteristics and affecting thermodynamic and gas dynamics parameters in the respective fire-extinguishing generator combustion chamber.

(21) The tests were done in a generator designed such as to allow using nitrogen-generating pellets in an amount of up to 1000 g and provided with a cooler unit with a cooler loaded into it, such as, in particular, sphere-shaped elements 5-7 mm in diameter made of CB-6 grade aluminium oxide (manufactured by ZiboZhengsenChemicalCo., Ltd), quartz sand (mesh fraction 10-12 (1-2 mm)), or, alternatively, round steel granules 2.5 mm in diameter in the amount of about 900 g.

(22) In the course of the tests, temperature and pressure were measured in the generator housing and the cubicle, records were taken of the nitrogen, oxygen, carbon dioxide and ammonia concentrations in the cubicle atmosphere, and video recording of the generator operation process was carried out. The pellet density was measured and its form was recorded both before and after testing.

(23) Free sodium content in the combustion product residue (sintered mass) was determined by injecting water into the generator housing upon completion of a test and by assessing the quantity of released hydrogen.

(24) Example 1. The nitrogen-generating (nitrogen generant) composition of the present invention was produced by using 450 g of sodium azide, 315 g of iron oxide, 117 g of aluminium oxide, 14 g of cobalt nitrate, 1.8 g of copper oxide, 1.8 g of nickel oxide, 90 g of ethyl acetate (not included in the balance of composition weight). The total weight of the composition's dry components was 899.6 g. Said components in said quantities were mixed as follows:

(25) First (Stage 1), cobalt nitrate Co(NO.sub.3).sub.2 was mixed with aluminium oxide Al.sub.2O.sub.3 during 20 minutes, adding ethyl acetate, until a mixture of uniform color was produced (a 1st mixture), followed by allowing to stand for 3 hours and drying at the temperature of 80° C.

(26) Then (Stage 2), modified aluminium oxide (1.sup.st mixture) was mixed during 15 minutes with iron oxide, adding ethyl acetate, until a mixture of uniform color was produced (a 2nd mixture).

(27) Separately (Stage 3), sodium azide was prepared in a mixer, to which end sodium azide powder was mixed during 15 minutes at the temperature of 30° C. with 10 g of ethyl acetate until a viscosity sufficient for mixing this mixture (a 3rd mixture) with other components was achieved.

(28) Following that (at Stage 4), the mass produced at Stage 2 was mixed during 20 minutes in a mixer with the sodium azide mass produced at Stage 3 and, simultaneously, with copper and nickel oxides.

(29) Then (Stage 5), the mass produced at Stage 4 was dried at the temperature of 80° C. during 2.5 hours until a residual moisture content in the composition of at most 2 wt. % was achieved, such as to remove wetting agent residues, thus producing the claimed composition. Further (Stage 6), the mass produced at Stage 5 was formed into granules by passing the mass through a mesh size 8 (2.4 mm) sieve. Finally, a mass with the weight of 902 g was produced. Therefore, the residual wetting agent content in the composition was 2.4 g, which amounts to ˜0.27% in addition to the main composition.

(30) Further (Stage 7), pellets were formed by compressing the granules to produce articles of 80 mm in diameter, having a 10-mm passage and the weight of 225 g, at the specific compressing pressure of 700 kg/cm.sup.2.

(31) Combustion products of the nitrogen-generating composition of the present invention were analyzed for toxic gas content, such as carbon oxide CO and ammonia NH3, in FP-500S type fire-extinguishing generators (http://www.firepro.hu/en/products/small-to-medium-units/fp-500s). The generator cooler unit contained 750 g of aluminium oxide granules.

(32) The tests were done on a test bench in a cubicle with a volume of about 1 m.sup.3. Toxic gas concentrations were measured with a Drager Tubes measurement system gas detector, an Accuro pump, and detection tubes 0.3% B (CH 29901) for carbon dioxide and 5/a (CH 20501) for ammonia. Oxygen, carbon dioxide and ammonia concentrations were analyzed with a Drager X-am 7000 instrument using the following sensors: CATEX (catalytic) and EC (electrochemical). Nitrogen concentration was measured with a Teledyne 3000 instrument based on an R-33N sensor. Free sodium content in the combustion product residue was determined by injecting water into the generator housing upon completion of a test and by assessing the quantity of released hydrogen.

(33) Pellet density of 2.55 g/cm.sup.3 and its combustion rate of 1.4 mm/s at atmospheric conditions were determined.

(34) The data obtained from the tests are given under Item 1 in the TABLE showing the toxic gas and free sodium concentrations measured in the nitrogen-generating compositions' combustion products.

(35) The analysis indicated that there was no free metallic sodium in the combustion product residue (sintered mass) which fully, without any deformation, retained the shape of the generator housing inner cavity (FIG. 1). The toxic gas concentration was substantially below the maximum allowable values.

(36) Example 2. The nitrogen-generating composition of the present invention was produced by using 504 g of sodium azide, 270 g of titanium oxide, 108 g of aluminium oxide, 13.5 g of cobalt nitrate, 1.8 g of copper oxide, 2.7 g of nickel oxide. Butyl acetate in the amount of 90 g was used as the wetting agent. Said components were mixed following the same sequence as described in Example 1, except for Stage 2, wherein modified aluminium oxide was mixed with titanium oxide. Finally, a mass was produced having the weight of 905 g, with the residual wetting agent content in the composition of 5 g, which is ˜0.56% in addition to the main composition weight. Toxic gas content resulting from combustion of the claimed composition was analyzed as described in Example 1. The obtained data is given in the TABLE under Item 2. No free sodium was detected in the generator housing; the combustion product residue retains the inner shape of the generator housing. The gas toxicity is substantially below the allowable standard values.

(37) Example 3. The nitrogen-generating composition of the present invention was produced by using 520 g of sodium azide, 260 g of molybdenum oxide, 103 g of aluminium oxide, 11 g of cobalt nitrate, 1 g of copper oxide, 2 g of nickel oxide; said components in said quantities were mixed in a staged manner and produced following the same sequence as described in Example 1, except for Stage 2, wherein modified aluminium oxide was mixed with molybdenum oxide. Finally, a mass was produced having the weight of 910 g, with the residual wetting agent content in the composition of 13 g, which is ˜1.45% in addition to the main composition weight. Free sodium and toxic gas contents resulting from combustion of the claimed composition were analyzed as described in Example 1. The obtained data is given in the TABLE under Item 3. There was no free sodium; the combustion product residue retains the inner shape of the generator housing.

(38) Below are examples of further studies of the free sodium and toxic gas contents resulting from combustion of the prior art and experimental nitrogen-generating compositions. The studies were carried out in the same conditions as described in Example 1.

(39) Example 4. The composition was produced in accordance with the process described in patent RU 2484075.

(40) The nitrogen-generating composition was produced by using 540 g of sodium azide, 360 g of iron oxide, loading them into a planetary mixer, and wetting the composition with water. The components were mixed following the sequence described in patent RU 2484075, except for the granule forming stage, wherein the composition was loaded out onto a 14 mesh mechanical sieve with a screen aperture size of 1.5×1.5 mm and passed through the screen into a vessel to produce the granules. Iron(III) oxide powder for ferrites was used in said amount, which, prior to mixing, was sieved through a 028 (25) screen, while the sodium azide powder was used in the as-delivered condition.

(41) The composition components were mixed during 10 minutes in a 35CB mixer with the maximum load of 13 kg.

(42) Then water was added in the amount of 8 wt. % in addition to 100% of the dry components mixture and mixing was done during 15 minutes, followed by blowing air heated to 50° C. into the mixer at the pressure of 0.3 MPa (3 kgf/cm.sup.2) and further mixing of the wetted composition during 25 minutes. The wetted composition was loaded out onto a 14 mesh sieve with a screen aperture size of 1.5×1.5 mm and passed through the screen into a vessel to produce the granules. The produced granules were placed on pallets in a 3-cm layer. The pallets were placed on racks at the temperature of 40° C. for 40 minutes and then allowed to stand for further 5 hours at the temperature of 60° C. with automatic agitation. Finally, a mass was produced having the weight of 901r. Water content was 0.11 wt. %.

(43) Then, compressing was done to produce articles of 80 mm in diameter, with a 30-mm passage and the weight of 225 g, at the specific compressing pressure of 700 kg/cm.sup.2, as described at Stage 7 in Example 1. The generator cooler unit contained 1300 g of aluminium oxide.

(44) Toxic gas content resulting from combustion of the claimed composition was analyzed as described in Example 1. Pellet density was 1.67 g/cm.sup.3; combustion rate at atmospheric conditions was 1.75 mm/s.

(45) The obtained data is given in the TABLE under Item 4.

(46) Both in the generator housing and in the residue, a substantial quantity of free metallic sodium was detected; the slag residue structure was loose, amorphous, with its sizes substantially changed with respected to the housing inner diameter (FIG. 2).

(47) Example 5. The nitrogen-generating (nitrogen generant) composition was produced by using 540 g of sodium azide, 360 g of iron oxide; the dry components were wetted with water. Said components were mixed in a staged manner following the sequence as described in Example 4.

(48) Finally, a mass was produced having the weight of 901 g. Water content was 0.11 wt. %.

(49) Then, compressing was done to produce articles of 80 mm in diameter, with a 30-mm passage and the weight of 225 g, at the specific compressing pressure of 700 kg/cm.sup.2, as described at Stage 7 in Example 1. Toxic gas content resulting from combustion of the claimed composition was analyzed as described in Example 1, except that the generator cooler unit contained 900 g of steel granules and 400 g of quartz sand.

(50) The obtained data is given in the TABLE under Item 5.

(51) Both in the generator housing and in the residue, a substantial quantity of free metallic sodium was detected; the slag residue structure was loose, amorphous, with its sizes substantially changed with respected to the housing inner diameter.

(52) Example 6. The nitrogen-generating composition of the present invention was produced by using 440 g of potassium azide, 325 g of iron(III) oxide, 120 g of aluminium oxide, 15.0 g of cobalt nitrate, 1.8 g of copper oxide, 1.9 g of nickel oxide. Butyl acetate in the amount of 90 g was used as the wetting agent. Said components were mixed following the same sequence as described in Example 1, except for Stage 3, wherein potassium azide was prepared in a mixer, to which end potassium azide powder was mixed during 15 minutes at the temperature of 20° C. with 10 g of butyl acetate until a viscosity sufficient for subsequent mixing thereof with other components was achieved (a 3rd mixture). At Stage 4, the mass produced at Stage 2 was mixed, in a mixer, with the potassium azide mass produced at Stage 3 and, simultaneously, with copper and nickel oxides during 20 minutes. Finally, a mass was produced having the weight of 905 g with the residual butyl acetate content of 0.14 wt. %. The operations at the next stages were the same as those described in Example 1. Toxic gas content resulting from combustion of the claimed composition was analyzed as described in Example 1. The obtained data is given in the TABLE under Item 6. No free sodium was detected in the generator housing; the combustion product residue retains the inner shape of the generator housing. The gas toxicity is substantially below the allowable standard values.

(53) Combustion products of the nitrogen-generating compositions under Items 7 to 14 in the TABLE were analyzed for toxic gas and free sodium contents. The compositions were produced as described in Example 1, with ethyl acetate or butyl acetate used as the wetting agent as shown in the TABLE. Residual wetting agent content in addition to the main composition weight was as follows: in Composition No. 7-0.2 wt. %; in Composition No. 8-0.18 wt. %; in Composition No. 9-0.17 wt. %; in Composition No. 10-0.21 wt. %; in Composition No. 11-0.14 wt. %; in Composition No. 12-0.14 wt. %; in Composition No. 13-0.3 wt. %; in Composition No. 14-0.26 wt. %. Toxic gas content resulting from combustion of these compositions was analyzed as described in Example 1. The results are shown in the TABLE under Items 7 to 14. In respect of these compositions, it was also found that: no free sodium was detected in the generator housing; the combustion product residue retains the inner shape of the generator housing. The gas toxicity is substantially below the allowable standard values.

INDUSTRIAL APPLICABILITY

(54) The above examples of specific implementations demonstrate that the method for producing a nitrogen-generating composition of the present invention for fire extinguishing may be put into practice in accordance with the specification. The above examples demonstrate the feasibility of the claimed result, i.e. precluding the content of metallic sodium, either in the form of aerosol, or in the condensed phase (residue) of the combustion products, and reducing the ammonia and CO contents in the pure nitrogen jet downstream of the fire-extinguishing generator nozzle exit (outlet opening). The inventors herein accomplish the results of precluding the free sodium content and efficient reduction in the toxic gas concentration through using an ancillary reactant, i.e. aluminium oxide modified with cobalt(II) nitrate, thus changing the combustion process kinetics and reducing the metallic sodium content in combustion zones due to sodium iron(III) oxide and sodium aluminate formation, which chemically bind sodium and, by interacting with each other, produce, as a result, a hard-melting solid product devoid of free metallic sodium and having a melting point equal to or higher than 1350° C., while the efficient reduction in the toxic gas concentration is achieved by intensifying their direct oxidation processes through a combination of cobalt(II) nitrate with accelerating additives, i.e. aluminium, copper and nickel oxides, both directly in the nitrogen-generating composition combustion reaction zone and the region where the fire-extinguishing generator cooler is located.

(55) Accomplishment of the technical result is evidenced by the photograph (FIG. 2) showing the condensed residues of combustion products of the prior art (RU2484075) composition, wherein water was used as the wetting agent, and those of the claimed composition produced according to Example 1 herein (FIG. 1). The difference is obvious: the photograph of FIG. 1 shows a solid structure resembling a real clinker, while the photograph of FIG. 2 shows a decomposed structure of the residue.

(56) TABLE-US-00003 TABLE Measured Data on the Toxic Gas and Free Sodium Contents in Nitrogen-Generating Composition Combustion Products Cooler: Al.sub.2O.sub.3 granules, except for Composition No. 5, where steel grits + quartz sand were used. Symbols in the TABLE: W—Residual Wetting Agent (0.14 . . . 1.42 wt. %): EA—Ethyl Acetate, BA—Butyl Acetate; t—Nitrogen Generation Time; N—Gas Generation Efficiency; P—Generator Pressure. Toxic Components in Combustion Products Test Nitrogen-Generating Composition Components (wt. %) CO NH.sub.3 P Parameters No. NaN.sub.3 Fe.sub.2O.sub.3 TiO.sub.2 MoO.sub.3 Al.sub.2O.sub.3 CuO NiO Co(NO.sub.3).sub.2 KN.sub.3 W Na (ppm) (ppm) (atm) t (s) N (%) 1 2 3 4 5 6 7 8 9 10 11 13 14 15 16 17 18 1 50 35 13 0.2 0.2 1.6 EA no 150 10 2 10 40 2 56 30 12 0.2 0.3 1.5 BA no 230 12 3 9 39 3 58 29 11.5 0.1 0.2 1.2 EA no 208 15 2.5 11 36 4 60 40 water yes 845 21 5 5 40 5 60 40 water yes 765 18 7 5 39 6 36 13 0.2 0.2 1.6 49 BA no 210 13 3 8 40 7 43 45 10 0.2 0.3 1.5 EA no 180 17 2 9 38 8 57 25 16 0.2 0.3 1.5 BA no 230 15 3 8 39 9 50 35 13 0.1 0.2 1.7 EA no 120 15 2.5 7 40 10 50 32 16 0.2 0.2 1.6 EA no 110 13 2.3 7 40 11 52 30 15.6 0.2 0.2 2 EA no 115 12 2.4 7 40 12 49 33 15.5 0.2 0.3 2 BA no 175 16 2 9 40 13 50 34 14.6 0.2 0.2 1 EA no 110 13 2.1 9 39 14 53 35 9.5 0.2 0.3 2 EA no 119 15 2.5 8 40 * Toxic gas concentrations immediately dangerous to life (ppm) 3000 5000 * Vrednye veshchestva v promyshlennosti. Spravochnik dlya khimikov, inzhenerov i vrachey. Tom III. Neorganicheskiye i elementoorganicheskiye soedineniya. (Noxious Substances in Industry. A Reference Book for Chemists, Engineers and Physicians. Volume III. Non-organic and Organoelemental Compounds), Leningrad, “Khimiya” 1997 https://de.wikipedia.org/wiki/Ammoniak