RU2455043C1 - Low-temperature flameless aerosol-forming fire-extinguishing composition - Google Patents

Abstract

FIELD: fire-prevention facilities.

SUBSTANCE: low-temperature flameless aerosol-forming fire-extinguishing composition includes a potassium nitrate and a cellulose and fibre mass is characterised by the fact that as a flammable binder it contains starch and starch paste, and as a burning modifier - a calcium nitrate, at the following ratio of components, wt %: potassium nitrate - 30…70; calcium nitrate - 5…35; cellulose-fibre mass -5…35, starch paste - 5…25, starch - 5…25. The technical result is development of a composition, in which a flammable binder has low combustion heat and relatively high content of oxygen in a molecular link, which makes it possible to change composition burning into a low-temperature flameless mode with preservation of acceptable parameters of fire-extinguishing efficiency and content of carbon monoxide.

EFFECT: expansion of methods for further treatment of an aerosol-forming composition mass due to application of a starch paste.

9 cl, 2 tbl

Description

The invention relates to the field of fire fighting equipment, in particular to means for extinguishing fires with a fire extinguishing aerosol, widely used to protect industrial and transport facilities, such as warehouses, industrial premises, electrical equipment, engine compartments of vehicles, etc.

A fire extinguishing aerosol is formed during the combustion of special compositions containing potassium nitrates and / or potassium perchlorates as an oxidizing agent, and plasticized or unplasticized polymers capable of passing into a viscous-fluid or plastic state under the influence of thermal and / or mechanical effects as a fuel-binding agent. Such polymers include phenol-formaldehyde and epoxy resins, polyvinyl butyral, cellulose ethers, rubbers and others.

The active part of the extinguishing aerosol is made up of the smallest (0.5 ... 5 microns) particles of potassium compounds, which are formed as a result of chemical reactions between the oxidizing agent and fuel and are dispersed into the environment by the gaseous products of these reactions.

The extinguishing efficiency of the aerosol is higher, the greater the number and smaller the particle size of potassium compounds, and these indicators depend on the temperature and completeness of chemical reactions between the oxidizing agent and the fuel. In turn, the combustion temperature of the composition, ceteris paribus, directly depends on the calorific value of the fuel-binder.

The results of calculating the specific heat of combustion and oxygen balance for a number of combustible and combustible binders are given in Table 1.

The heat of combustion of the combustible binder determines the temperature of the resulting aerosol, which from the point of view of practical application cannot exceed some critical values that determine the safety of the fire extinguisher for the environment.

Reducing the temperature of the extinguishing aerosol in existing developments is achieved either by introducing coolers from the series: dicyandiamide, melem, melamine, etc. (patent RU 2095104, C1, 10.11.1997), or by using special cooling elements in the design of the extinguishing aerosol generator in the form granules, tubes, monoblocks, etc. (patent RU 2064305, C1, 07.27.1996), or a combination of both methods.

Both methods reduce fire extinguishing efficiency in comparison with the efficiency of uncooled aerosol by 2 or more times, while worsening the toxicological parameters of the aerosol due to the increase in carbon monoxide, which in a cooled aerosol is not subject to oxidation by atmospheric oxygen.

A similar directivity is the aerosol-forming composition for extinguishing fires (patent RU 2160619, class A62D 1/06, dated 20.12.2000), containing potassium nitrate 65-75%, fuel-binder 0-5%, dicyandiamide 10-20% and additionally combustible (the rest), capable of burning paired with potassium nitrate. Starch, hydroquinone, phenolphthalein, salicylic acid amide and other substances are proposed as additional fuel.

In fact, an attempt was made to replace the traditional combustible-binder (phenol-formaldehyde resin or iditol) with other combustibles (starch, hydroquinone, phenolphthalein, salicylic acid amide, etc.) under the pretext of combating incandescent particles, which limit the applicability of this fire extinguishing method to the high temperature of the aerosol .

The closest analogue is a composition containing potassium nitrate and pulp as a combustible binder and a method for its preparation, based on the impregnation of pulp and pulp in a hot saturated solution of potassium nitrate, followed by extraction, drying and molding of products (patent application No. 2009119565 dated 05.25.2009).

The main disadvantages of this composition are unstable combustion at a potassium nitrate content increased to 70% and insufficient plasticity of the composition when forming charges for fire extinguishing devices, which necessitates molding at relatively high temperatures of 80 ... 105 ° C and pressures of 30 ... 150 MPa. The main disadvantages of the manufacturing method of the composition are the low productivity and the periodic nature of the technology of "deaf" pressing, rolling and rolling, as well as the limited geometric shapes and sizes of the resulting products.

Table 1 shows the results of calculating the specific heat of combustion and the oxygen balance of the combustible binders known from the prior art;

Table 2 - the results of the assessment of the complex of the main properties of the claimed composition.

The objective of the invention was to find such a composition that, on the one hand, would provide a low-temperature and stable combustion regime while maintaining high fire extinguishing efficiency of the resulting aerosol, and on the other hand, would allow the formation of articles of various shapes and sizes safely and efficiently.

The technical result is the creation of a composition in which the fuel-binder has a low calorific value and a relatively high oxygen content in the molecular unit (high oxygen balance α), which allows the combustion of the composition to be switched to a low-temperature flameless mode while maintaining acceptable fire extinguishing efficiency and carbon monoxide content . Also, the technical result achieved by using the proposed composition is the expansion of methods for further processing the mass of the aerosol forming composition, by imparting a certain plasticity to the mass, which allows forming charges for fire extinguishing devices at low temperature and low pressure, which significantly increases the safety of creating and processing the mass of the aerosol forming composition.

The solution of the problem and the achievement of technical results is carried out by the claimed new low-temperature flameless aerosol-forming fire extinguishing composition.

The proposed low-temperature flameless aerosol-forming extinguishing composition, including potassium nitrate and pulp, is characterized by the fact that it contains starch and starch paste as a combustible binder, and calcium nitrate as a combustion modifier, in the following ratio, wt.%:

potassium nitrate - 30 ... 70 calcium nitrate - 5 ... 35 pulp - 5 ... 35 starch paste - 5 ... 25 (in terms of starch) starch - 5 ... 25

Preferably, the composition comprises, as pulp, chopped paper or cut cotton thread.

Preferably, the composition contains, as a combustible binder, starch and starch paste from various types of plant materials: potatoes, corn, rice and wheat, both individually and in mixture.

Preferably, the composition contains 0.1 ... 1.0% industrial or liquid paraffin as a processing aid, and 0.1 ... 1.0% charcoal or soot as a combustion stabilizer.

Preferably, the resulting composition is molded into articles of the required size and geometry.

Preferably, the resulting composition is formed by compression or extrusion through dies of a given geometric shape and size, followed by drying to a moisture content of 1-2% by blowing with hot air.

Preferably, the resulting composition is molded on smooth or corrugated rollers by means of a set of “stocking”, followed by cutting, removing from the work roll and drying by blowing with hot air.

Preferably, the resulting composition is formed by dosing the plastic composition into a special form or directly into the body of the fire extinguisher, followed by drying by heating the mold or body and / or blowing it with hot air.

In the combustion process of the claimed composition, the thermal destruction of cellulose and starch occurs with the formation of a soot skeleton, which activates the decomposition of potassium nitrate. Since the thermal costs of thermal degradation of cellulose and starch are quite large, and their heat of combustion is quite small, the combustion process of the composition occurs in flameless mode without significant heating of the combustion products. This opens up wide prospects for significantly facilitating and simplifying the design of fire extinguishing aerosol generators by eliminating the heavy and bulky aerosol cooling units.

The presence in the macromolecules of cellulose and starch up to 50 wt.% Oxygen can significantly increase the oxygen balance of the composition to α values of 0.7 ... 0.9, which reduces the content of toxic carbon monoxide in the combustion products to acceptable values. At high values of α, corresponding to the content of up to 70% potassium nitrate, the mass of the soot frame formed during the destruction of the fuel-binder is insufficient to activate the decomposition of potassium nitrate, which is reflected in the appearance of fused slags and in the instability of the composition burning. To eliminate this phenomenon, a combustion stabilizer is additionally introduced into the composition, the role of which is charcoal or soot in the amount of 0.1 ... 1.0%. In order to regulate the burning rate, calcium nitrate was introduced into the composition, which, with a content of 5 to 17%, allows to increase the burning rate from 1.3-1.8 to 2.2-3.3 mm / s.

The quality of the products obtained by the extrusion method substantially depends on the technological properties of the composition, such as adhesion to the surface of the forming die, causing the effect of adhesion and distortion of the surface of the obtained products, up to a change in the required shape, size and solidity. To reduce the adhesive properties, a technological additive was introduced into the composition - industrial or liquid paraffin in the amount of 0.1 ... 1.0%.

Evaluation of the fire extinguishing effectiveness of products from the claimed composition was carried out in a transparent and sealed container of 9 liters.

For this purpose, an alcohol lamp filled with gasoline was first set on fire inside the tank, and then a “tablet” or a canvas of the claimed composition of a certain mass. The free-burning time of the spirit lamp in a closed volume before spontaneous extinction was a little more than 3 minutes. The result of the experiment was considered positive if the extinguishing of the spirit lamp occurred 40 ... 60 seconds after the composition was burned. Fire extinguishing concentration was determined as the result of dividing the initial mass of the tablet or web by the volume of the container.

The temperature on the combustion surface of the sample of the claimed composition was determined using a thermocouple. The carbon monoxide content in the extinguishing aerosol was determined in a 9-liter tank using an aspirator and Dragger tubes. The results of the assessment of the complex of the main properties of the claimed composition are presented in table.2.

As mentioned above, the extinguishing effectiveness of an aerosol is determined by both the temperature and the completeness of chemical reactions during combustion of the compositions. The degree of contamination of the aerosol with hot coal particles and the content of toxic carbon monoxide in it also depend on the completeness of the reactions. The completeness of chemical reactions in mixtures of solids is determined by the contact surface between these substances, i.e. the smaller the size of the particles reacting with each other and the more uniformly they are mixed in the volume of the mixture, the higher the completeness of the reaction, ceteris paribus. This is an important technological aspect of the production of aerosol forming compositions.

In the proposed method for producing the composition, the mixing of pulp and starch with potassium nitrate is carried out in a hot saturated solution of the latter, which contributes to the uniform distribution of components as a result of sorption of potassium nitrate from cellulose and starch from the solution and ensures the safety of the mixture production process.

The process of swelling of cellulose-fibrous material and starch in a hot saturated solution of potassium nitrate has a duration of 8 ... 10 minutes and ends with the formation of a plastic mass.

Further, the process of processing the mass goes along the path of molding products with subsequent drying to a moisture content of 1 ... 2%, for example, by blowing with hot air with a temperature of 95 ... 105 ° C.

An additional technical result achieved by the proposed method is the expansion of methods for further processing the mass of the aerosol forming composition through the use of gelatinization of starch, namely, the use of extrusion, rolling and molding technologies.

This became possible because during the gelatinization of starch, as well as for the gelatinization of flour, which is widely used in the production of pasta, a plastic mass or dough is formed that can easily deform and flow under mechanical stress.

The pressing of the plastic mass was carried out on a screw press with dies. The diameter and humidity of the pressed cords were 5 ... 11 mm and 25 ... 35 wt.%, Respectively. Further, the cords were subjected to cutting and drying to a moisture content of 1 ... 2 wt.% By blowing with hot air.

Rolling of the plastic mass was carried out on smooth and corrugated (corrugation along the axis of the rolls) rollers, at room temperature. After dialing the “stocking” on the work roll, the rollers were stopped, the “stocking” was cut and removed, followed by cutting the web into pieces of the required size and drying on a heated metal surface.

The plastic mass was molded into the mold using a syringe dispenser manually, followed by drying of the filled mold on a heated metal surface.

The final finish of products from the composition may consist in hydrophobization of their surface by applying a special varnish with a dry film thickness of 50 ... 80 microns.

Table 1 Calculation results of specific heat of combustion and oxygen balance of combustible and combustible binders Name of fuel Content Elements wt.% Q, Kcal / kg Acid balance α C H O coal one hundred 0 0 8100 0 phenol formalde. resin (iditol) 74,4 5.8 19.8 6938 0,081 epoxy resin ED-20 71.0 7.9 21.1 7146 0,083 polyvinyl butyral 67.6 9.9 22.5 7326 0,087 phenolphthalein 75,5 4.4 20.1 6675 0,085 hydroquinone 65,4 5.5 29.1 5894 0.133 salicylic acid 60.9 4.3 34.8 5086 0.176 starch 44,4 6.2 49.4 3837 0.294 cellulose 44,4 6.2 49.4 3837 0.294

Table 2. The results of the assessment of the complex of basic properties of the claimed composition Name of displays Indicator Values for Samples No. 1 Number 2 Number 3 Number 4 Number 5 Number 6 Number 7 Number 8 Number 9 Chemical composition,% Potassium nitrate 30,0 54.7 54,4 60.0 60.5 63.6 52.8 34.8 70.0 Calcium nitrate 5,0 5,0 5,0 5,0 5,0 5,0 17.0 35.0 7.0 Cellulose paper / thread 35.0 9.6 24.9 5,0 23.8 5,0 17.7 17.7 11.9 Starch 5,0 25.0 5,0 5,0 5,0 5,0 6.8 6.8 5,0 Paste 23.9 5,0 10.0 24.3 5,0 20.6 5,0 5,0 5,0 Coal / Soot 0.1 0.6 0.6 0.6 0.6 0.7 0.6 0.6 1,0 Oil ind./ Vaseline. 1,0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Acid balance, α 0.40 0.65 0.65 0.74 0.76 0.81 0.85 0.90 1.00 Density, g / cc 1.15 1,2 1,2 1,2 1,2 1,2 1,0 1,0 0.96 Burning rate, mm / s 0.45 1.83 0.95 1.44 1.75 1.34 3.3 0.9 2.2 Combustion surface temperature, ° C 550-600 600-650 600-650 600-650 650-700 650-700 650-700 650-700 950-1000 Character of burning (steady / unstable) no Yes Yes Yes Yes Yes Yes Yes Yes Flame / Individual Languages no no no no no no no no Yes Fire extinguisher. con-tion, g / cu. m 78 60 53 40 35 thirty fifty 79 74 The content of CO, vol.% 1.20 0.60 0.65 0.50 0.30 0.20 0.15 0.2 0.3

Claims (9)

1. Low-temperature flameless aerosol-forming fire extinguishing composition, including potassium nitrate and pulp, characterized in that it contains starch and starch paste as a combustible binder, and calcium nitrate as a combustion modifier in the following ratio of components, wt.%:
potassium nitrate 30 ... 70 calcium nitrate 5 ... 35 pulp 5 ... 35 starch paste 5 ... 25 starch 5 ... 25 2. The composition according to claim 1, characterized in that it contains cut paper as a pulp. 3. The composition according to claim 1, characterized in that as the pulp and pulp it contains cut cotton thread. 4. The composition according to any one of claims 1 to 3, characterized in that it contains starch and starch paste from various types of plant materials: potatoes, corn, rice, wheat, both individually and in the form of a mixture. 5. The composition according to claim 4, characterized in that it additionally contains 0.1-1.0% industrial or liquid paraffin as a technological additive, and 0.1-1.0% of charcoal or soot as a combustion stabilizer . 6. The composition according to any one of claims 1, 5, characterized in that it is molded into products of the required size and geometry. 7. The composition according to claim 6, characterized in that the molding of the products is carried out by pressing or extrusion through dies of a given size and geometry, followed by drying to a moisture content of 1-2% by blowing with hot air. 8. The composition according to claim 6, characterized in that the molding of products is carried out on smooth or grooved rollers by means of a set of "stocking" with its subsequent cutting, removal from the work roll and drying by blowing with hot air. 9. The composition according to claim 6, characterized in that the molding of the products is carried out by dispensing the plastic composition into a special form or directly into the body of the fire extinguisher, followed by drying by heating the mold or body and / or blowing with hot air.