RU2277003C2 - Fire-extinguishing composition - Google Patents

Abstract

FIELD: fire-fighting, particularly explosion-protective and fire-extinguishing equipment.

SUBSTANCE: powder composition comprises active fire-extinguishing components, namely water-insoluble inorganic salt crystalline hydrate or crystalline hydrate mixture taken in amount of 90.0-97.8% by weight and additive taken in amount of 2.2-10.0% by weight. The additive is adapted to change fire-extinguishing powder service properties. Bound water content in crystalline hydrate is 25-62% by weight.

EFFECT: increased fire-extinguishing ability and extended range of materials suitable to be used as active fire-extinguishing powder components.

3 cl, 2 dwg, 2 tbl, 12 ex

Description

The proposed technical solution relates to the field of fire extinguishing agents and can be used to equip automatic explosion protection (AVZ) and other equipment - powder vehicles, stationary powder plants, mobile and manual fire extinguishers.

Known extinguishing powder composition (US patent No. 4149976, Comissariat Energie Atomigue), adopted as the closest analogue of the claimed technical solution as a prototype. This composition to increase the fire extinguishing properties of the powder as an active component contains sodium carbonate crystalline hydrate Na ₂ CO ₃ * H ₂ O in an amount of 47.4 wt.% (Example 1) to 61.4 wt.% (Example 2) with a crystallization content water from 1 to 16 wt.%. The rest of the extinguishing powder is made up of additives that provide the correction of its operational properties.

The disadvantages of the extinguishing powder composition according to US Pat. US No. 4169976 are as follows.

Firstly, the composition is characterized by a low content of crystallization water. This reduces its heat-absorbing ability of the powder, makes it unstable in time and ultimately negatively affects the fire extinguishing ability of the powder composition.

Another disadvantage of the extinguishing powder composition is its high hygroscopicity. Crystalline hydrate Na ₂ CO ₃ * H ₂ O, like its original salt, Na ₂ CO _{3 is} readily soluble in water. At 20 ° C, the solubility of sodium carbonate is 21.8 g in 100 g of water (see Properties of inorganic compounds. Reference - Efimov A.I. et al. - L .: Chemistry, 1983, p. 165). Compositions containing hygroscopic inorganic salts as active quenching components are prone to caking due to variable ambient humidity that occurs when the temperature changes even in sealed containers. This leads to a deterioration in fluidity, therefore, to a deterioration in the extinguishing properties of the powders. Such extinguishing powders require the inclusion of a large number of additives in them that protect them from caking and increase their stability during storage, as well as additives that increase the fluidity of the powders (all these are so-called additives that provide correction of the operational properties of the extinguishing powder).

However, the introduction of additives into the composition of the extinguishing powder reduces the relative content of the active component in it, and therefore the fire extinguishing ability of the powder. In addition, the preparation of additives, their grinding, classification, dosage, mixing with the active component complicate the process of preparing a mixture of extinguishing powder and, therefore, increase the cost of its production and increase the cost of the powder.

The purpose of the invention is to increase the extinguishing efficiency of both the active component and the extinguishing powder composition by increasing the stabilization of the heat-absorbing ability close to the heat of vaporization of the water, as well as by reducing the number of additives providing correction of the powder's operational properties and increasing the content of the active component while maintaining the fire extinguishing powder properties (in particular, heat-absorbing ability) for a long time (including during storage).

In addition, an additional objective of the invention is to expand the range of active components of fire extinguishing powders.

The invention consists in the following.

A fire extinguishing powder composition is proposed, which includes the active component and additives providing correction of the operational properties of the fire extinguishing powder.

The composition of the extinguishing powder is characterized in that it contains the water-insoluble inorganic salt crystalline hydride or a mixture of such crystalline hydrates as the active component. The powder composition is also characterized in that the content of bound water in the composition of crystalline hydrates of the inorganic salt is 25-62 wt.%. The ratio of the components in the extinguishing powder composition is, wt.%:

water insoluble crystalline hydrate

or a mixture of such crystalline hydrates 90.0-97.8 correction additive fire extinguisher performance powder 2.2-10.0

The extinguishing powder composition is also characterized in that, as a water-insoluble crystalline hydrate of an inorganic salt, it is preferable to use the compounds:

MgCl ₂ * 5Mg (OH) ₂ * 7H ₂ O,

MgNH ₄ PO ₄ * 6H ₂ O,

Mg ₃ (PO ₄ ) ₂ * 22H ₂ O,

MgCO ₃ * Mg (OH) ₂ * 3H ₂ O

CaCl ₂ * 3Ca (OH) ₂ * 12H ₂ O,

Al ₂ (SO ₄ ) ₃ * 6Ca (OH) ₂ * 26H ₂ O,

Al ₂ O ₃ * SO ₃ * 9H ₂ O

Fire extinguishing powder is also characterized in that as an active extinguishing component it contains a mixture of crystalline hydrates with the addition of another type of active extinguishing component.

This allows you to get the following technical effect:

- increase the fire extinguishing efficiency of the powder by increasing the heat-absorbing ability to a value that is practically no different from the heat of evaporation of water, and by optimizing the temperature range of heat absorption;

- to increase the fire extinguishing ability of the powder by reducing the concentration of oxygen in the combustion zone with water vapor formed during thermal decomposition of crystalline hydrates. The volume of water vapor, referred to normal conditions, can reach, for example, Mg ₃ (PO ₄ ) ₂ * 22H ₂ O 700 l per 1 kg of fire extinguishing powder;

- to increase the fire extinguishing efficiency of the powder by ensuring the non-hygroscopicity of the active component due to its low solubility (not more than tenths of a percent), as a result of which to ensure the stability of the quality of the extinguishing powder over time (including during long-term storage);

- increase the extinguishing ability of the extinguishing powder composition by increasing the proportion of active extinguishing component and reducing the number of additives that provide correction of the operational properties of the powder; the latter allows you to reduce the costs associated with the preparation of additives, simplify the process, reduce the cost of the production process and reduce the cost of powder;

- an additional reduction in the cost of fire extinguishing powders is achieved by including in their composition the cheapest and most affordable reagent - water;

- expand the range of substances used as an active component to obtain fire extinguishing powders.

The invention is illustrated by drawings, which depict:

Figure 1 is a derivatogram of a water-insoluble crystalline hydrate MgNH ₄ PO ₄ * 6H ₂ O;

Figure 2 - derivatogram traditionally used as the active component of a fire extinguishing powder ammophos.

A fire extinguishing powder composition is proposed that includes an active component and additives providing correction of the operational properties of the fire extinguishing powder.

As an active component, the composition contains a water-insoluble crystalline hydrate of an inorganic salt or a mixture of such crystalline hydrates. In this case, insoluble crystalline hydrates are characterized in that the content of bound (crystallization) water in them is 25-62 wt.%. The upper limit of the content of crystallization water in crystalline hydrates is due to the lack of information in the literature and practical data on the existence of water-insoluble crystalline hydrates with a greater than 62% content of crystallization water.

The optimal ratio of components in the proposed fire extinguishing powder composition is, wt.%:

Water-insoluble inorganic crystalline hydrate

salts or a mixture of such crystalline hydrates 90.0-97.8 Correction additives extinguishing powder properties 2.2-10.0

As water-insoluble crystalline hydrate of the inorganic salt, it is preferable to use the compounds:

MgCl ₂ * 5Mg (OH) ₂ * 7H ₂ O,

MgNH ₄ PO ₄ * 6H ₂ O,

Mg ₃ (PO ₄ ) ₂ * 22H ₂ O,

MgCO ₃ * Mg (OH) ₂ * 3H ₂ O

CaCl ₂ * 3Ca (OH) ₂ * 12H ₂ O,

Al ₂ (SO ₄ ) ₃ * 6Ca (OH) ₂ * 26H ₂ O,

Al ₂ O ₃ * SO ₃ * 9H ₂ O

and etc.

A study of the literature showed that at least 40 compounds of this class are known. However, additional research is required to determine their properties.

As an additive that ensures the correction of the operational properties of the extinguishing powder, neutral traditionally used hydrophobizing, anti-caking substances, substances that increase fluidity, etc. are implied.

As an anti-caking additive, you can use a mixture of Aerosil with highly dispersed hydrophobic substances. Water-repellent additives are used to preserve the extinguishing properties of the powders during their long-term storage. As hydrophobizing additives, organic substances, insoluble salts of fatty acids, for example, calcium stearate, organosilicon compounds, are used. Fine additives having good chemical and mechanical resistance, for example, mica, kaolin, aluminosilicate, alumina, can be used as additives to increase fluidity.

It is possible to use both a crystalline hydrate and a mixture of crystalline hydrates or a mixture of crystalline hydrates with the target addition of another type of active quenching components, for example ammophos, potassium chloride, as an active quenching component. They can be added to quenching powders based on crystalline hydrates of salts to give them special properties. For example, ammonium phosphates (ammophos) form a film on the surface of burning solid bodies that impedes the access of oxygen to the burning surface, thereby contributing to quenching and preventing re-ignition (smoldering).

The methods for producing water-insoluble crystalline hydrates of inorganic salts are different, but, as a rule, they involve mixing solutions of the starting components with the subsequent formation of a precipitate.

Example 1

When a magnesium salt solution is added to a neutral or slightly alkaline alkali metal phosphate solution, an amorphous precipitate of magnesium phosphate is formed, which then becomes crystalline and at the same time acquires the composition Mg ₃ (PO ₄ ) ₂ * 22H ₂ O (see page of G. Remy's monograph Inorganic Chemistry, T. 1. M.: Mir, 1972, 827 p.).

Example 2

The crystalline hydrate composition MgCl ₂ * 5Mg (OH) ₂ * 7H ₂ O is formed during the mixing of the so-called magnesia cement (Sorel cement). The process proceeds according to the following reaction:

5MgO + MgCl ₂ + 12H ₂ O = MgCl ₂ * 5Mg (OH) ₂ * 7H ₂ O

(see p. 226 books by V. Schulze, V. Tischer, V. P. Ettel Mortars and concrete on cementless binders. M: Stroyizdat, 1990, 240 pp.).

Example 3

The crystalline hydrate Al ₂ O ₃ * SO ₃ * 9H ₂ O, another spelling of the formula (AlO) ₂ SO ₄ * 9H ₂ O, is found in nature in the crystalline state in the form of the websterite mineral (see page 359 of the monograph by G. Remi Inorganic chemistry course , Moscow: Mir, 1972, 824 p.).

The required physical properties of crystalline hydrates (particle size, bulk density, specific surface area) can be obtained - some may be used in the synthesis, others may require preliminary preparation in the process of obtaining fire extinguishing powder composition, which consists in drying, grinding, etc.

To prepare a fire extinguishing powder composition from non-hygroscopic water-insoluble crystalline hydrates of inorganic salts, any of the currently existing methods for preparing fire extinguishing powders using drying, crushing, mixing, excluding chemical interaction, as in a.c. SU 1787456 A.

The following are examples of methods for preparing fire extinguishing powder compositions based on water-insoluble crystalline hydrates of inorganic salts (examples 4-9).

Example 4 (similar to A.S. SU 1692598 A1)

The active component (crystalline hydrate) is dried at a temperature of 90-95 ° C to a constant temperature. After that, it is ground to a fineness of 10 ⁵ -10 ⁸ cm ^-1 . Then it is mixed with Aerosil in the following ratio, wt.%

Main component 98 Aerosil 2

Example 5

The active component (crystalline hydrate) is dried at a temperature of 90-95 ° C to a constant temperature. White carbon black is dried at a temperature of 120-125 ° C to a residual moisture content of not more than 0.5%. White carbon black is mixed with a silicone hydrophobizing liquid and all components are mixed until a homogeneous mixture is obtained with a uniformity coefficient of not more than 10%.

The ratio of components is the following, wt.%

Active component 97.5% -97.8 White soot 2 Organosilicon liquid 0.2-0.5

Example 6

The active component (crystalline hydrate) is dried at a temperature of 90-95 ° C to a constant temperature and is ground in a mill to particles with a diameter of not more than 100 microns. The active component of another class (ammophos, potassium chloride, ammonium sulfate, cryolite, sodium bicarbonate, etc.) is also dried and ground to particles of the same size or smaller. Further, all components are mixed in the following ratio, wt.%.

Insoluble crystalline hydrate 30-70 Active component of another class 25-68 Water-repellent organosilicon liquid 0.2-0.3 White carbon black with a specific surface area of at least 100 m ² / g 1.0-2.0; Aluminosilicate or silica 3.0-10.0

Example 7 (similar to A.S. SU 1333348 A1)

The composition is prepared by mixing, grinding and sieving the components in the following ratio, wt.%:

Anti-caking additives 1.0-5.0 Flow Additives 0.5-7.0 Active ingredient (crystalline hydrate) rest

Example 8

The active component is dried at 90 ± 5 ° C until the moisture content is not more than 0.5%. Then it is ground to a fraction of 0.1-0.05 mm. The resulting product is mixed with additives that adjust its properties to a homogeneous mixture in the following ratio, wt.%

Active ingredient (crystalline hydrate) 91 Additives for fluidity, for example fireclay powder 7.5 Aerosil 1,5

Example 9 (similar to A.S. SU 1460331 A1)

Extinguishing powder is obtained by grinding the dried components in a ball mill for 5 minutes in the following ratio, wt.%.

Crystal hydrate 95.0-99.1 Aerosil 0.9-5.0

The fire extinguishing mechanism using crystalline hydrates insoluble in water as an active component is as follows.

Thermal destruction of these compounds occurs by spontaneous destruction of them at high temperatures with the formation of water vapor and gaseous ammonia or carbon dioxide.

Example 10

MgNH ₄ PO ₄ * 6H ₂ O → MgHPO ₄ + 6H ₂ O _(steam) + NH _{43 (gas)}

Example 11

MgCO ₃ * Mg (OH) ₂ * 3H ₂ O → 2MgO + 3Н ₂ O _(steam) + СО _{2 (gas)}

Example 12

Mg ₃ (PO ₄ ) ₂ * 22H ₂ O → Mg ₃ (PO ₄ ) ₂ + 22H ₂ O _(steam)

During thermal decomposition of crystalline hydrates, heat absorption occurs, for some compounds exceeding 2100 kJ / kg of crystalline hydrate. This leads to a decrease in temperature in the combustion zone and the formation of a large volume of gaseous products that block the access of oxygen to this zone.

The active quenching component, consisting of water-insoluble crystalline hydrates, absorbs heat in the temperature range of 90-300 ° C, with up to 770 liters of steam and gaseous products (reduced to normal conditions) being released. All this provides high quenching efficiency.

The six-water magnesium ammonium phosphate MgNH ₄ PO ₄ * 6H ₂ O synthesized by the author was investigated. . This temperature range is considered the most favorable for fighting fire. The mass loss was 54%, which is higher than estimated (50.8%). Probably, the water adsorbed on the surface of the powder affected it. The results of derivatographic analysis coincide with the data presented in the book by R.G. Lepilina and N.M.Smirnova Thermograms of inorganic phosphate compounds. Directory. L .: Nauka, 1984, 334 p.

At the same derivatograph, an analysis of ammophos, traditionally used as an active quenching powder, was performed. The results of the derivatographic analysis of ammophos are shown in figure 2. The decomposition energy of ammophos, calculated from the peak area on the differential temperature curve, is about 8 times lower than that of six-water magnesium ammonium phosphate, and decomposition begins at a higher temperature.

The thermal decomposition energy was calculated from the area of DTA peaks in the derivatograms. In the figures, these peaks are shaded. A quantitative assessment made by comparing the peak areas of the studied compounds and the reference substance, benzoic acid, gave the total heat of decomposition of six-water magnesium ammonium phosphate 1990 kJ / kg, which satisfactorily coincided with the data of thermochemical calculation - 2140 kJ / kg.

The results of laboratory studies of the powders given in the examples of the description of the invention are shown in table 1.

Table 1 Fire Extinguishing Powders for Class B Fire Powder grade Extinguishing concentration, kg / m ² Pirant 0.70 PSB-3 0.66 P-1A 1.06 Example 4, Crystal hydrate MgNH ₄ PO ₄ * 6H ₂ O - 98 wt.%,
Aerosil - 2 wt.%
The content of bound water in the powder is 43.2 wt.% 0.48 Example 5, Crystal hydrate Mg ₃ (PO ₄ ) ₂ * 22H ₂ O - 97.5 wt.%
White carbon black - 2 wt.%
Silicone fluid PES-5 - 0.5 wt.%
The content of bound water in the powder is 58.7 wt.% 0.41 Example 6, Crystal hydrate MgNH ₄ PO ₄ * 6H ₂ O 70 wt.%,
A component of another class - (NH ₄ ) ₂ SO ₄ - 25.8 wt.%,
Organosilicon liquid - 0.2 wt.%
White carbon black - 1.0 wt.%
Silica (kieselguhr) - 3 wt.%
The content of bound water in the powder is 30.9 wt.% 0.59 Example 7, Anti-caking additive (Aerosil) - 1.0
Additives for fluidity (silica) - 2.0 wt.%
Crystalline hydrate Al ₂ O ₃ * SO ₃ • 9H ₂ O - 97 wt.%
The content of bound water in the powder is 45.7 wt.% 0.55 Example 8, Crystal hydrate Mg ₃ (PO ₄ ) ₂ * 22H ₂ O - 91 wt.%
Fireclay powder - 7.5 wt.%
Aerosil - 1.5 wt.%
The content of bound water in the powder is 54.8 wt.% 0.43 Example 9, Crystal hydrate MgNH ₄ PO ₄ * 6H ₂ O - 99.0 wt.%
Aerosil - 1.0 wt.%
The content of bound water in the powder is 43.6 wt.% 0.46 A separate example not included in the description
Crystalline hydrate CaSO ₄ * 2Н ₂ O - 98 wt.%
Aerosil - 2 wt.%
The content of bound water in the powder is 20.5 wt.% 0.99

The amount of additives that adjust the operational properties of the extinguishing powder affect their fire extinguishing ability. Table 2 shows the results of extinguishing a model fire site with an area of 0.1 m ² . The minimum amount of powder required to extinguish a flame is shown. Fire extinguishing ability of powders for a model fire center of class “B”

table 2 Sample Name Minimum mass for extinguishing the source, g Inert powder (silica sand) More than 3.0 PSB-3 0.5 Pirant 1,5 Sodium Bicarbonate Powder (Japan) 1,0 Test Powder + 1% Calcium Stearate 0.4 Test Powder + 3% Calcium Stearate 0.6 Test Powder + 5% Calcium Stearate 1,0 Test Powder + 3% Calcium Lauryl Sulfate 1,5

It can be seen that an increase in the amount of water-repellent additive (calcium stearate) worsens the quenching properties of the powders.

Low, not more than 0.3 g / l, the solubility of crystalline hydrates in water plays an important role in the storage of fire extinguishing powder compositions. The adsorption of water vapor from the surrounding atmosphere even in sealed containers at lower temperatures and subsequent desorption at higher temperatures is not accompanied by the dissolution of the main component, the crystalline hydrate of the extinguishing powder, and does not lead to the coalescence of small crystals with each other. This splicing is the main reason for caking of powders and other inorganic compounds (for example, mineral fertilizers). This property of water-insoluble compounds, in this case, crystalline hydrates, allows to reduce the amount of additives providing such characteristics of fire extinguishing powder as low caking and high fluidity while ensuring the stability of fire extinguishing properties of the powder over time. For example, six-water magnesium ammonium phosphate has been stored for more than two years in a container protected only from dust, while not caking and has not lost flowability.

Claims (3)

1. Fire extinguishing powder composition, including an active extinguishing component and additives, providing the correction of the operational properties of the fire extinguishing powder, characterized in that it contains water-insoluble inorganic crystalline hydrate or a mixture of such crystalline hydrates, the content of bound water in the composition of inorganic crystalline hydrates is 25-62 wt.%, And the ratio of the components is, wt.%: Water Insoluble Crystalline Hydrate inorganic salt or a mixture of such crystalline hydrates 90.0-97.8 Correction Supplements fire extinguishing powder performance 2.2-10.0 2. Fire extinguishing powder composition according to claim 1, characterized in that, as a water-insoluble crystalline hydrate of an inorganic salt, it is preferable to use the following compounds: MgCl ₂ · 5Mg (OH) ₂ · 7H ₂ O, MgNH ₄ PO ₄ · 6H ₂ O, Mg ₃ (PO ₄ ) ₂ · 22H ₂ O, MgCO ₃ · Mg (OH) ₂ · 3H ₂ O, CaCl ₂ · 3Ca (OH) ₂ · 12H ₂ O, Al ₂ (SO ₄ ) ₃ · 6Ca (OH) ₂ · 26H ₂ O, Al ₂ O ₃ · SO ₃ · 9H ₂ O. 3. Fire extinguishing powder composition according to claims 1 and 2, characterized in that, as an active quenching component, it contains a mixture of water-insoluble crystalline hydrates of inorganic salts with the addition of other active quenching components.

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