RU2290240C1 - Fire-extinguishing composition - Google Patents

Abstract

FIELD: fire fighting, particularly aqueous fire-extinguishing foams based on surfactants and adapted to extinguish combustible materials and flammable liquids in open and closed spaces.

SUBSTANCE: fire-extinguishing composition comprises magnesium chloride hydrate taken as aqueous solution and water-based film-forming foam. Above components are taken in the following amounts (% by composition volume): magnesium chloride hydrate solution - 85-88%, water-based film-forming foam - remainder. Magnesium chloride content in the composition is 15-25% by composition weight.

EFFECT: increased efficiency fire extinguishment with low-expansion foam and reduced time of suppression of fires seated on horizontal and vertical planes, possibility of composition storage under low temperatures.

3 cl, 3 tbl, 3 ex

Description

The invention relates to aqueous solutions of foaming agents based on surface-active substances (SAS) and is intended for extinguishing combustible materials and flammable liquids both in open space and in conditions of volumetric foci of ignition in rooms during storage of the solution at low temperatures (up to minus 35 ° FROM).

Currently, various types of fire extinguishing compositions are known. So, for example, from the copyright certificate SU 865303 (IPC-3: A 62 D 1/02, publ. 09/23/1981), the composition of the foaming agent is known, including an anionic surfactant, water and an additive - a mixture of calcium chloride and magnesium chloride, - in the following ratio of components in weight%: surfactant - 0.75 ÷ 2.2 wt.%; calcium chloride - 0.02 ÷ 0.12 wt.%; magnesium chloride - 0.005 ÷ 0.04 wt.%; water is the rest. As a result of adding calcium chloride and magnesium chloride to the mixture, the fire fighting time is reduced, the cost of the extinguishing composition is minimized, which generally increases the extinguishing efficiency of the composition.

From the description of the copyright certificate SU 1780774 (IPC-5: A 62 D 1/00, publ. 15.12.1992), a composition for extinguishing fires containing hydrated magnesium chloride is known. The increase in fire extinguishing efficiency in the known solution is achieved through the use of water-soluble polar liquids (alcohols, esters, glycols, amines) to dissolve bischofite (a natural crystalline salt containing 88-99% MgCl ₂ · 6H ₂ O).

This composition has a high fire extinguishing efficiency, but it can not be used to extinguish fires in storage at low temperatures. In addition, due to the formation of an extremely unstable film, the oxidant enters from the environment to the combustion surface. As a result of this, repeated ignition is possible.

From the patent RU 2157710 C1 (IPC-7: A 62 D 1/02, publ. 20.10.2000) a fire extinguishing composition is known containing a surfactant - 12 ÷ 24 wt.%, Higher fatty alcohol (C ₆ -C ₁₂ ) - 1.5 ÷ 3.0 wt.% And water. In order to increase frost resistance and reduce corrosion activity, ammonium acetate in an amount of 10 ÷ 52 wt.% Is introduced into the foaming agent.

It should be noted that with an increase in the content in the known composition of ammonium acetate, which affects the frost resistance and corrosion activity of the fire extinguishing composition, the foam stability decreases and, accordingly, the fire extinguishing efficiency of the generated foam decreases.

A foaming agent is also known (copyright certificate SU 1790421, IPC-5: A 62 D 1/00, publ. 23.01.1993), containing a surfactant - 6.5 ÷ 7.0 wt.%, Basic aluminum chloride 14.0 ÷ 14.6 wt.%, Ammonium acetate 30.0 ÷ 36.5 wt.%, And water (the rest). To extinguish fires, an aqueous solution is used, consisting of 2–3% of a foaming agent and 20% of magnesium chloride. In this case, the fire extinguishing properties of the composition are maintained during prolonged storage of the composition at low temperatures - up to -32 ° C. However, due to the inclusion of aluminum chloride in the composition, this extinguishing composition is corrosive, which leads to a reduction in the life of fire-fighting equipment.

It should be noted that the known fire extinguishing compositions do not form a stable water film on the entire combustion surface, which should prevent the flow of oxygen to the combustible material and the evaporation of volatile substances from the combustion surface. As a result, fire fighting is not effective enough and the possibility of re-ignition and atmospheric pollution of toxic substances released during combustion is not ruled out.

The closest analogue of the patented invention is a fire extinguishing composition described in international application WO 0147604 (IPC-7 A 62 D 1/02, publ. 05.07.2001). The known composition is prepared on the basis of an aqueous film-forming foaming agent, in which a 50 ÷ 60% aqueous solution of potassium acetate and ethylene glycol or propylene glycol are added in an amount of 15 ÷ 20 wt.% To reduce the freezing point of the solution. The composition does not freeze to -50 ° C. However, film formation on the ignition surface is possible only at temperatures up to -1 ° C. At lower temperatures, a film does not form on the ignition surface.

As a result, when extinguishing fires, the evaporation of volatile organic vapors into the atmosphere occurs, which cause environmental pollution by toxic substances, and the flow of oxygen to the burning surface increases the extinction time, i.e. to reduce the fire extinguishing effectiveness of the composition.

The problem solved by the patented invention is the formation on the combustion surface of a stable heat-insulating water film that prevents the flow of oxygen from the atmosphere to the ignition site and the evaporation of volatile substances from the burning surface into the surrounding space. In this case, the fire extinguishing composition must be stored and operated without reducing the fire extinguishing efficiency in a wide range of low temperatures - up to -35 ° С. In addition, the invention is aimed at eliminating the possibility of precipitation of salts in a fire extinguishing composition when using untreated tap water during the preparation of the solution.

The technical result achieved by using the patented invention is to increase the efficiency of extinguishing fires with low-foam foam and reduce the time to extinguish fires during storage of the foaming composition at low temperatures (up to -35 ° C) both on horizontal and vertical surfaces due to the formation of cooling heat-insulating water film and increase the hydrostatic resistance of the foam.

This technical result is achieved through the use of a fire extinguishing composition consisting of a film-forming foaming agent based on water and an additive that reduces the freezing temperature of the solution. According to the present invention, magnesium chloride hydrate is used as an additive in the form of an aqueous solution in the following ratio of components in volume percentages of the total volume of the extinguishing agent:

- an aqueous solution of magnesium chloride hydrate - 85 ÷ 88%,

- water-based film-forming foaming agent - the rest.

The content of magnesium chloride in the extinguishing composition is 15 ÷ 25 wt.% Of the total amount of the extinguishing composition.

As a film-forming foaming agent based on water, organofluoric acid-based foaming agents can be used, for example, PO-6A3F, Light Water, Sthamex-AFFF and other similar foaming agents.

When extinguishing fires using the patented composition, the foam from the fire extinguisher is fed to the source of ignition and, flowing down, forms a water film on the burning surface, topped with a foam emulsion. A film formed on a burning surface prevents the evaporation of fuel vapor and stops the flow of oxidant to the surface of the burning liquid. In addition, this film helps to cool the surface of the fire. As a result, the process of extinguishing the flame is intensified and, accordingly, the time to extinguish the fire is reduced.

A film-forming foaming agent with an aqueous solution of magnesium chloride hydrate at a given percentage of components allows you to effectively suppress ignition sources due to the stable film formation on the combustion surface during storage of the composition at low temperatures.

, а затем гидрат хлорида магния (например, шестиводный хлорид магния MgCl₂·6H₂O). При этом количество подаваемого гидрата хлорида магния и воды берут примерно в равных частях:To obtain a fire extinguishing composition, it is necessary to first prepare an aqueous solution of magnesium chloride hydrate with a density of 1.21 ± 0.01 g / cm ³ and a volume of not more than 300 l. The salt solution is mixed in a capacitive mixer equipped with a stirrer. Before preparing the aqueous solution, untreated tap water and magnesium chloride hydrate are supplied to the mixer. First, water is supplied to the mixer in an amount

and then magnesium chloride hydrate (for example, hexahydrate magnesium chloride MgCl ₂ · 6H ₂ O). The amount of hydrated magnesium chloride and water is taken in approximately equal parts:

- масса подаваемого гидрата хлорида магния, кг;Where

- the mass of the supplied hydrate of magnesium chloride, kg;

- масса воды, подаваемой в смеситель, кг.

- mass of water supplied to the mixer, kg

The required ratio of components in the solution is provided by weight dosing. The volume of the prepared aqueous solution of magnesium chloride hydrate is calculated by the formula:

where ρ = 1.21 g / cm ³ = 1.21 kg / l is the specified density of an aqueous solution of magnesium chloride hydrate;

- масса подаваемого гидрата хлорида магния, кг;

- the mass of the supplied hydrate of magnesium chloride, kg;

- масса воды, подаваемой в смеситель, кг.

- mass of water supplied to the mixer, kg

(V - полный объем получаемого раствора). Затем подается гидрат хлорида магния до достижения полного объема V раствора. Однако этот метод требует точного поддержания температуры воды и гидрата хлорида магния в диапазоне 18±2°С.When preparing an aqueous solution of magnesium chloride hydrate, it is also possible to use the volumetric method for dispensing components. In this case, water is first supplied with a volume of

(V is the total volume of the resulting solution). Then, magnesium chloride hydrate is supplied until the full volume of the V solution is reached. However, this method requires accurate maintenance of the temperature of water and hydrate of magnesium chloride in the range of 18 ± 2 ° C.

Verification of the component composition of the solution of magnesium chloride hydrate was carried out by determining the density of the resulting solution using a hydrometer. The average density of the solution is determined by the results of three measurements. Moreover, the measurement error should be ± 0.01 g / cm ³ , that is, the density of the obtained aqueous solution of magnesium chloride hydrate should be in the range (1.2 ÷ 1.22) g / cm ³ .

After obtaining the required amount of an aqueous solution of magnesium chloride hydrate, fire extinguishing agents are refilled, which can be used as extinguishers, fire extinguishing backpacks, mobile fire extinguishing installations, etc. To do this, first add 85 ÷ 88 vol.% Solution of magnesium chloride hydrate to the refueling tank (of the total composition), and then add 12 ÷ 15 vol.% Of the finished water-based foaming agent, respectively. This sequence of supply of the mixed components allows to reduce foaming of the solution in the capacity of the fire extinguisher. The content of magnesium chloride in the extinguishing composition is maintained in the range (15 ÷ 25) wt.% Of the total amount of the extinguishing composition.

Various well-known foaming agents can be used as film-forming water-based foaming agents, for example: “Sthamex-AFFF 3%” (manufacturer - German company “Dr. Sthamer-Hamburg”), “PO-6A3F”, which can be used in three versions “ PO-6A3F (1.5%) ”,“ PO-6A3F (3%) ”and“ PO-6A3F (6%) ”(manufacturer - CJSC Aegis-PTV), Light Water (manufacturer - American company "3M") and other similar film-forming foaming agents.

Before use, the fire extinguishing composition was stored for 30 days at a temperature of -35 ° C. The effectiveness of extinguishing fires when using a fire extinguishing composition is confirmed by the following examples.

Example No. 1

To refuel a 6-liter fire extinguisher, 0.8 L (6 L × 0.133) film-forming foaming agent and 5.2 L (6 L × 0.867) aqueous solution of magnesium chloride hydrate were used. To obtain 5.2 l of an aqueous solution of magnesium chloride hydrate, 3.25 kg of untreated tap water and 3.042 kg of magnesium chloride hydrate (MgCl ₂ · 6H ₂ O) were first supplied to the mixer. The required ratio of components in the solution is provided by weight dosing. The correctness of obtaining an aqueous solution of magnesium chloride hydrate with the required concentration of components was checked by measuring the density of the resulting solution using a hydrometer. The density of the resulting solution was 1.21 g / cm ³ .

Then 5.2 l of an aqueous solution of magnesium chloride hydrate was poured into a fire extinguisher (86.7% of the total volume of the fire extinguisher) and 0.8 l of a water-based foaming agent was added. In this example, we used a synthetic fluorine-containing film-forming foaming agent of Russian production “PO-6A3F (3%)” (CJSC Egida-PTV) in accordance with TU 24 1279-002-49888 190-98.

This foaming agent is characterized as a non-combustible, non-explosive, moderately hazardous substance of hazard class 3 according to GOST 12.1.007. There is no flash point in the open crucible. Auto-ignition temperature is absent to the boiling point.

"PO6A3F" (3%) "has the following properties:

1) appearance - a homogeneous liquid without sediment and separation;

2) density at 20 ° С - 1000 ÷ 1200 kg / m ³ ;

3) kinematic viscosity at 20 ° C - not more than 200 mm ² / s;

4) pH = 6.5 ÷ 10.0;

5) the multiplicity of the foam of low multiplicity using water is not more than 20;

6) the hydrostatic resistance of the foam with low multiplicity using water - not less than 60 s;

7) the time of extinguishing n-heptane with a low multiplicity foam with the intensity of the working solution supply (0.059 ± 0.002) l / (m ² · s) - not more than 120 s

The resulting fire extinguishing composition had the following characteristics:

- the content of magnesium chloride in the fire extinguishing composition is 20.6% by weight of the total amount of the composition;

- the multiplicity of the foam is 10;

- hydrostatic resistance of the foam - 23 min;

- the quenching time of n-heptane at a flow rate of the working solution (0.059 ± 0.002) l / (m ² · s) - 35 s;

- the storage temperature of the extinguishing agent is -35 ° C.

As can be seen from the above characteristics, when using the patented composition, the quenching time of n-heptane is reduced in comparison with the pure foaming agent of the grade “PO-6A3F (3%)” at the same intensity of the working solution supply (0.059 ± 0.002) l / (m ² · from).

To prepare an aqueous solution of magnesium chloride hydrate, hexahydrate magnesium chloride MgCl ₂ · 6H ₂ O was used. No precipitation of salts was observed in the extinguishing composition. The comparison was carried out with the initial solution of the foaming agent brand "PO-6A3F (3%)" without additives.

Foam for each experiment was prepared by whipping 100 ml of the prepared solution in a steel cylindrical container for 20 s. The resulting foam was supplied by compressed air through a pipeline from a container to the surface of a burning liquid (n-heptane). Foam consumption was varied by a change in air flow.

Since the density of the working solution of the foaming agent is practically no different from the density of water, in the course of research it was assumed that the volume of solution in liters is numerically equal to its mass in kilograms. The mass of the consumed solution was determined by weighing the container together with the foam before and after each experiment.

Comparison of a foaming agent solution containing an aqueous solution of magnesium chloride hydrate and the finished PO-6A3F (3%) foaming solution was carried out according to the following criteria.

1. The foam ratio is the ratio of the resulting foam volume to the total volume of the solution. The foam multiplicity in the considered examples was determined as the ratio of the height of the foam layer in the tank to the thickness of the layer of foaming agent in the tank until the foam is obtained.

2. Hydrostatic stability. Evaluation of resistance was carried out by the time of allocation of 50% of the liquid from the foam.

3. The critical intensity of the solution. The assessment was carried out according to the intensity of the destruction of the foam under extinguishing.

The intensity value was determined by the formula characterizing the dependence of the quenching time of n-heptane in the tank on the intensity of the supply of the extinguishing agent.

The feed rate of solutions J was calculated by the formula:

where m ₀ and m ₁ - the mass of the container with foam before and after extinguishing the source of fire, kg;

S _p - tank area, m ² ;

τ _T - quenching time, s.

In this case, the quenching time τ _T depends on the ratio of the feed rate and the hydrostatic resistance of the foam.

4. Extinguishing efficiency. The assessment was made according to the ratio of time and unit costs of the extinguishing agent to stop burning a unit of the area of the fire source.

For evaluation, we used the P _ET indicator of the efficiency of extinguishing a fire source:

where q _beats is the specific consumption of the solution, l / m ² ,

τ _T - quenching time at the selected feed rate, s.

The results are presented in table No. 1.

Table number 1 No. Criteria for evaluation Composition based on PO-6A3F (3%) Composition containing "PO-6A3F (3%)" and MgCl ₂ · 6H ₂ O one. Foam ratio 10 10 2. Hydrostatic resistance of foam, min 2,3 23 3. Quenching time of n-heptane at a solution feed rate of 0.059 ± 0.002 l / (m ² · s), s 85 35 four. Fire extinguishing efficiency, m ² / (l · s) 0.002 0.0135

Example No. 2

A 6-liter fire extinguisher was charged with a fire-extinguishing composition consisting of 5.28 L (6 L × 0.88) of an aqueous solution of magnesium chloride hydrate and 0.72 L (6 L × 0.867) of the film-forming synthetic fluorine-containing foaming agent Sthamex-AFFF (3% ) ”, Produced by the German company“ Dr. Sthamer-Hamburg. " Frother “Shtamex-AFFF (3%)” is based on a surfactant - tenside. Sthamex-AFFF is used to extinguish Class A and B fires by creating a gas-tight film on a burning surface. This blowing agent is stable and stable in relation to the thermal radiation of combustible substances with a high content of polar additives, such as alcohol.

Depending on the required quality, the foaming concentrate was mixed with untreated tap water in volumes from 3 to 6%.

The foaming solution had the following characteristics:

1) appearance - a homogeneous liquid without sediment and separation;

2) hydrostatic resistance of the foam - 310 s;

3) density at 20 ° С - 1045 kg / m ³ ;

4) pH = 6.5 ÷ 8.5;

5) the multiplicity of the foam is 10;

6) frost resistance - up to -15 ° C;

7) the quenching time of n-heptane with a flow rate of the working solution (0.059 ± 0.002) l / (m ² · s) - 79 s.

The preparation of an aqueous solution of magnesium chloride hydrate was carried out analogously to example No. 1. The resulting fire extinguishing composition had the following characteristics:

- the content of magnesium chloride is 25 wt.% of the total amount of the extinguishing agent;

- the density of the resulting solution is 1.22 g / cm ³ ;

- the multiplicity of the foam is 10;

- hydrostatic resistance - 25 min;

- the quenching time of n-heptane at a flow rate of the working solution (0.059 ± 0.002) l / (m ² · s) - 35 s.

The storage temperature of the resulting fire extinguishing composition, at which the composition retained these properties for a long time, was -35 ° C.

The resulting solution containing 25 wt.% Magnesium chloride of the total amount of fire extinguishing composition was compared with the initial aqueous solution of the film-forming foaming agent "Shtamex-AFFF (3%)". The preparation conditions of the compared solutions and evaluation criteria were consistent with example No. 1. The results are presented in table No. 2.

Table number 2 No. Criteria for evaluation Composition based on "Shtamex-AFFF (3%)" Composition containing "Shtamex-AFFF (3%)" and MgCl ₂ · 6H ₂ O one Foam ratio 10 10 2 Hydrostatic resistance of foam, min 5.2 25 3 Extinguishing time of n-heptane at the rate of solution supply 0,059 ± 0,002 l / (m ² · s), s 79 35 four. Fire extinguishing efficiency, m ^{2 /} (l · s) 0.003 0.0135

Example No. 3

5.1 L (6 L × 0.85) of an aqueous solution of magnesium chloride hydrate and 0.9 L (6 L × 0.15) of a foaming agent based on organofluoric acids of the Easy Water brand, produced, were charged into a 6-liter fire extinguisher American company 3M (Minnesota Mining and Manufacturing Co).

The Easy Water brand foaming agent is an aqueous solution of a surfactant liquid concentrate based on fluorine compounds, which forms a stable foam layer on the surface of burning liquids that insulates the burning surface.

The foaming agent without the addition of magnesium chloride hydrate has the following characteristics:

1) hydrostatic resistance of the foam - 4 ÷ 5 min;

2) density at 20 ° С - (1.01 ÷ 1.16) · 10 ³ kg / m ³ ;

3) kinematic viscosity at 20 ° С - not more than 30 ÷ 35 mm ² / s;

4) pH = 6.5 ÷ 8.5;

5) the concentration of the working solution is 3 ÷ 6 vol.%;

6) surface tension - 17.5 mN / m;

7) the foam ratio is 6 ÷ 10;

8) the hydrostatic resistance of the foam - 5 min;

9) the quenching time of n-heptane at a flow rate of the working solution (0.059 ± 0.002) l / (m ² · s) - 150 s.

The resulting fire extinguishing composition containing magnesium chloride hydrate, had the following characteristics:

- the content of magnesium chloride - 15 wt.% of the total amount of extinguishing agent;

- the multiplicity of the foam is 10;

- hydrostatic resistance - 25 minutes

The storage temperature of the obtained extinguishing composition, at which the composition for a long time retained the extinguishing properties, was -35 ° C.

A comparative analysis of the resulting solution containing 25 wt.% Magnesium chloride of the total amount of the extinguishing agent was carried out with the initial water solution of the Easy Water blowing agent without additives. The results of the comparative analysis are presented in table No. 3.

Table number 3 No. Criteria for evaluation Light Water Based Composition Composition containing "Light water" and MgCl ₂ · 6H ₂ O one Foam ratio 8 10 2 Hydrostatic resistance of foam, min 5 23 3 Extinguishing time of n-heptane at the rate of solution supply (0,059 ± 0,002) l / (m ² · s), s 150 35 four. Fire extinguishing efficiency, m ² / (l · s) 0,0007 0.0135

As can be seen from the presented comparative analysis (see tables No. 1-3), the introduction of magnesium chloride hydrate (MgCl ₂ · 6H ₂ O) into the foaming agent did not affect the foaming ability of the solution. The multiplicity of the foam obtained under the same conditions has not changed.

Studies have shown that a low-level foam based on an aqueous solution of magnesium chloride hydrate, ceteris paribus, has a higher hydrostatic stability compared to the initial foaming solution. It was also found that a fire extinguishing composition containing a water-based film-forming foaming agent and magnesium chloride hydrate provides higher fire extinguishing efficiency, characterized by a shorter extinguishing time of n-heptane.

In the course of comparative tests, it was found that the maximum foam extinguishing efficiency when using the initial aqueous solution of the film-forming foaming agent “PO-6A3F”, “Sthamex-AFFF”, “Light Water”, etc. without additives is achieved at a significantly higher feed rate than with the use of a fire extinguishing composition containing a foaming agent and an aqueous solution of magnesium chloride hydrate. The required feed rate of the initial blowing agent solution is approximately two times higher than the feed rate of the composition containing the blowing agent solution and magnesium chloride hydrate. In addition, it was found that when using untreated tap water for the preparation of a fire extinguishing composition under conditions of long-term storage of the composition in a fire extinguisher at low temperatures, salt deposition does not occur.

From the obtained experimental data it also follows that the patented fire extinguishing composition has high fire extinguishing efficiency during prolonged storage at low temperatures (up to -35 ° C) and can be used in fire extinguishing means for various purposes to extinguish ignitions of flammable liquids and other combustible materials in various climatic conditions .

Claims (3)

1. A fire extinguishing composition containing a water-based film-forming foaming agent and an additive that lowers the freezing point of the fire extinguishing composition, characterized in that magnesium chloride hydrate in the form of an aqueous solution is used as an additive in the following ratio of components,% of the total volume of the fire extinguishing composition: An aqueous solution of magnesium chloride hydrate 85 ÷ 88 Water Based Foaming Agent Rest the content of magnesium chloride in the extinguishing composition is 15 ÷ 25% of the total amount of the extinguishing composition. 2. The fire extinguishing composition according to claim 1, characterized in that as a foaming agent based on water, an organofluoric acid based foaming agent is used. 3. Fire extinguishing composition according to claim 2, characterized in that the foaming agent “PO-6A3F (3%)” is used as a film-forming foaming agent based on organofluorine acids.