SU1736971A1 - Flameless pyrotechnical heat evolving compound - Google Patents

Abstract

Usage: pyrotechnic devices for low-temperature heating, for example, the human body. The essence of the invention: the composition contains, wt%: aluminum 30.0 - 35.0; sodium nitrate 1,4 - 3,0; calcium oxide 0.7-1.5; water else. The composition is prepared by mixing the dry components in a mixer of any type. Characteristics of the composition: the calculated thermal capacity of 3210-3430 cal / h, heat generation time (in terms of 100 g of composition) 23 - 35 minutes at a reaction temperature of 33 - 48 ° C. 1 tab.

Description

The invention relates to flameless heat generating compositions and can be used in devices for heating people.

The stoichiometric mixture of aluminum powder (12 wt.%) And copper chloride (88 wt.%) And separately stored water is closest to the proposed one.

In their dry form, copper-aluminum compounds are not reactive, but with the addition of water, copper begins to displace aluminum from its salt and form an aluminum salt and metallic copper.

2AI + 3Cu -.A + ZCi

with a satisfactory heat generation rate.

The disadvantage of copper-aluminum compositions is the low efficiency due to the low calorific value of the reaction with water at a satisfactory heat release rate.

The purpose of the invention is to increase efficiency by increasing the calorific value.

ability to react with water while maintaining the rate of heat generation (it is desirable that the reaction temperature be in the range of 30 - 50 ° C).

The goal is achieved by the fact that sodium nitrate and calcium oxide are additionally added to the composition including aluminum and separately stored water in the following ratio of components, wt.%: Aluminum 30.0-35.0

Sodium Nitrate 1.4 - 3.0

Calcium Oxide 0.7-1.5

WaterEverything

The oxidation of aluminum powder with water proceeds faster if it is mixed with some oxidizer that is more reactive than water. Calcium oxide (quicklime) is introduced as the primary initiator, the quenching reaction of which (CaO + NaO (OH) 2) proceeds at high speed with the release of heat, which is an impulse for the oxidation of aluminum.

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In order to sustain the protracted exothermic reaction of the oxidation of aluminum, a secondary initiator, sodium nitrate, is introduced. In the presence of moisture, the oxidation of aluminum is accompanied by the reduction of nitrate:

3NaNOa + 8AI + 18H20 3NaOH + + 8AI (OH) 3 + 3NH3

In mixtures of nitrates with aluminum, the reaction of alumina hydrate with the decomposition products of the oxidizing agent can also occur with the formation of aluminate:

3NaOH + ZA (OH) s SNaAlOa + 6HaO

The reaction of aluminum with sodium nitrate, in which the destruction of the oxide film AlaOs occurs, contributes to the oxidation of aluminum by water, as if accompanying this reaction. The reaction rate of the interaction of aluminum with sodium nitrate is significantly lower than the lime slaking reaction.

The maximum aluminum content (35% by weight) and the minimum content of sodium nitrate (1.4% by weight) are limited by the heat generation rate at which a noticeable temperature increase is achieved in the presence of calcium oxide.

The upper limit of sodium nitrate (3% by weight) is determined by the guarantee that the composition will not ignite.

The proposed content of calcium oxide (0.7–1.5 May.%) Is due to the need for the initial initiation of an exothermic reaction depending on the ratio of aluminum and sodium nitrate.

The water content is determined by stoichiometric coefficients, i.e. needs in an amount of water that would ensure complete oxidation of aluminum and quenching of calcium oxide.

All components of the proposed composition are not scarce, cheap, are used in pyrotechnics.

The composition (mixture of powder components) can be prepared on any type of mixing equipment used in pyrotechnics. To do this, a sample of dry components according to the recipe is loaded into the mixer and stirred for 10-15 minutes.

The calculated characteristics of the compositions and the results of experimental data are given in the table.

From the data in the table it can be seen that the proposed composition, in contrast to the known one, has the best indicators of the calorific value and duration of the exothermic reaction with the provision of a favorable temperature in the range of 30 - 50 ° C.

Thus, the inventive composition can be used in heating devices of any type that prevent negative effects on the human body at low ambient temperatures.

Claims (1)

The Invention Pyrotechnic flameless heat-generating composition mainly for low-temperature heating devices, including aluminum and separately stored water, characterized in that, in order to increase efficiency by increasing the calorific value while maintaining heat generation rate, it additionally contains sodium nitrate and calcium oxide in the following ratio components, wt.%: Aluminum30.0-35.0 Sodium Nitrate 1.4 - 3.0 Calcium Oxide 0.7 - 1.5 Water the rest.