RU2257930C1 - Solid nitrogen source composition for obtaining breathing gas - Google Patents

Abstract

FIELD: individual respiratory apparatuses, particularly composition of chemical substances for respiratory apparatuses.

SUBSTANCE: composition comprises sodium azide in amount of 50-70% by weight and chrysotile asbestos in amount of 30-50% by weight.

EFFECT: improved fire safety along with increased nitrogen emission.

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Description

The invention relates to solid nitrogen sources and can be used for individual breathing apparatus. Equipping individual breathing apparatus with such a nitrogen source will increase the effectiveness of breathing protection by diluting the oxygen medium with nitrogen, i.e. thus prevent the toxic effects of pure oxygen under high pressure and prolonged use.

Solid sources of nitrogen are known that emit nitrogen for the rapid filling of gas pads during automobile collisions, for example, a composition containing alkali metal azide 65-74%, iron oxide (III) 10-28%, sodium nitrate 5-16% and hydrophobic colloidal silica 0 , 1-2% according to US patent No. 4836255, IPC С 06 В 35/00, 1989. However, when these compositions are burned, a high (almost explosive) rate of nitrogen evolution and, as a rule, the presence of a significant amount of harmful impurities in the gas are characteristic. Thus, the use of nitrogen of such compositions for respiratory mixtures is excluded.

It should be noted that almost all compositions of solid nitrogen sources for respiratory mixtures include sodium azide, since the composition should have a high nitrogen output per unit mass.

In addition to sodium azide as a nitrogen-containing substance and as a combustible component, the composition of a solid nitrogen source includes substances that actually play the role of an oxidizing agent. In order to have a high nitrogen yield, the azide content (due to the oxidizing agent) must be extremely high. However, an increase in the composition of the azide content is accompanied by a simultaneous increase in the linear combustion rate, combustion temperature, and the release of metallic sodium into the gas phase. Thus, the composition becomes flammable, and the nitrogen released is unsuitable for breathing. For normal operation, the composition of the solid nitrogen source must have a minimum linear burning rate and a solid residue that binds sodium metal. The contradiction between the specific nitrogen output, fire safety and the absence of harmful impurities in the respiratory mixture in a solid nitrogen source is allowed by the selection of the optimal oxidizing agent, which ensures the minimum burning rate of the composition.

As a prototype, the applicant selected US patent 3996079, IPC C 06 B 35/00, 1976, offering a gas generating composition based on alkali or alkaline earth metal azide and iron oxide or nickel oxide. This is the most fire-safe composition of the known, because when it is burned, a strong combustion residue is formed that preserves the initial shape of the briquette.

However, the combustion temperature of this composition is still quite high, which is unacceptable when using nitrogen-forming compounds in individual breathing apparatus.

The content of nickel and iron oxides in these compositions corresponds to stoichiometric nitrogen formation reactions, i.e. nickel oxide - 28.3% and iron oxide - 29%. By increasing the content of nickel oxide to 74.2% and iron oxide to 70.3%, it is possible to ensure fire safety of the compositions (the combustion temperature of the composition is below 550 ° C). However, the specific nitrogen yield sharply decreases.

The objective of the invention is to increase the fire safety of the composition while maintaining a high yield of nitrogen per unit mass.

The problem is solved in that the composition of the solid nitrogen source based on sodium azide additionally contains chrysotile asbestos in the following ratio of components (wt.%):

sodium azide 50-70 chrysotile asbestos 30-50

This composition is more fireproof due to the lower burning rate (about 2 times) and lower combustion temperature (about 90-100 °). At the same time, this composition allows you to maintain the shape of the residue and maintain a high specific nitrogen yield.

A method of manufacturing a solid nitrogen source of the claimed composition consists in grinding, mixing and wetting the starting components, followed by traditional molding the mixture into briquettes of various configurations (blocks, tablets), depending on the need.

Examples of the claimed composition of a solid nitrogen source are shown in table 1.

Table 1 Example Number The content of components,% Note Sodium azide Asbestos chrysotile Example 1 70 thirty The composition with the highest nitrogen output Example 2 60 40 Example 3 fifty fifty

Tests of the molded compositions (diameter 45 mm) of solid nitrogen sources were carried out in a sealed chamber equipped with an electric initiating device, an aerosol filter (filter - material grade FMT-G) and a nitrogen outlet. The combustion temperature of the compositions was recorded using a thermocouple, and the volume and rate of nitrogen evolution were determined using a rotameter and gas meter GSB-400.

The chamber was pre-filled with nitrogen.

The density of the tablets with a diameter of 45 mm was 1.74-1.90 g / cm ³ .

For comparison, a solid nitrogen source was tested under the same conditions in US Pat. No. 3,996,079.

The test results are shown in table 2.

table 2 Solid nitrogen source Combustion temperature, ° С Burning rate
mm / s Fire safety assessment The output of nitrogen, l / kg Note The inventive composition according to example 1 530 0.3 Is safe 360 The inventive composition according to example 2 490 0.29 Is safe 310 The inventive composition according to example 3 460 0.25 Is safe 258 Known composition with an iron oxide content of 29.9% 660-735 0.5 Fire hazard 300 Use in breathing apparatus is not permitted. Known composition with an iron oxide content of 31.1% 660-735 0.5 Fire hazard 300 - ″ -

As can be seen from the data presented, the inventive composition is relatively fireproof, as it has a lower combustion temperature and lower burning rate, providing a quiet nature of the evolution of nitrogen. In this case, the specific nitrogen yield of the proposed composition remains quite high.

As a result, it is possible to use solid nitrogen sources for personal respiratory protection.

Claims (1)

A solid nitrogen source for breathing mixtures based on sodium azide, characterized in that it additionally contains chrysotile asbestos in the following ratio of components, wt.%: Sodium azide 50-70 Asbestos chrysotile 30-50