There are many types of combustibles used in industrial production, and the amount of combustibles is huge. Moreover, the production process is complicated. Therefore, various protective measures must be taken according to different conditions. From the point of view of the destructive power of the explosion, the explosion generally requires five conditions:
Basic principles of explosion protection (1) Flammable substances that provide energy (sources of release);
(2) Auxiliary combustion oxidizer (oxidant);
(3) Uniform mixing of flammable substances and combustion aids;
(4) The mixture is placed in a relatively closed space (surrounding body);
(5) Ignition sources with sufficient energy.
The ignition source, combustible material and combustion improver in the above conditions are the three elements of combustion explosion. Explosion protection technology is based on these explosion conditions and adopts corresponding technical measures and management measures to achieve the purpose of preventing accidents.
The suppression of the concentration of combustibles is closely related to the explosive concentration of the explosive mixture. The relationship between the explosion intensity and the change in concentration is similar to the sine curve of the cycle. If the concentration state is low or too high, no explosion occurs. These two points are called explosions. Lower limit concentration and upper explosive concentration. Below the lower explosive concentration, the mixture cannot be ignited because the calorific value of the flammable material is so low that it cannot maintain the minimum temperature required for the flame to propagate through the mixture; if the concentration increases gradually beyond the upper explosive concentration, the combustible material Increased, but the oxygen concentration of the combustion support is lower than the stoichiometric value, it can not meet the need of complete combustion of the mixture, and it will not explode.
Therefore, the occurrence of an explosion accident can be prevented through the control of the concentration of combustibles, or the destructive power that can be caused by an explosion accident can be minimized.
Control of oxygen concentration When an inerting medium is added to an explosive atmosphere, on the one hand, the oxygen component of the explosive atmosphere can be diluted, reducing the chance of the action of molecules and oxygen molecules of combustible substances, and also separating the combustible components from the oxygen molecules. A barrier that does not burn is formed between them; when activated molecules collide with inertizing medium particles, the activated molecules lose their activation energy and cannot react. On the other hand, if the combustion reaction has taken place, the resulting radicals will interact with the inertizing medium particles, causing them to lose their activity, leading to interruption of the combustion chain reaction; at the same time, the inerting medium will also absorb a large amount of heat released by the combustion reaction, making The heat cannot accumulate, and the combustion reaction does not spread to other combustible components, which suppresses the combustion reaction.
Therefore, by adding an inerting medium to the combustible/air explosive atmosphere, the explosive range of the combustible component is reduced. When the inertizing medium is increased to a sufficient concentration, the upper and lower explosion limits can be coincided with each other, and then the inerting medium concentration can be increased. Combustion air mixture will no longer burn.
The influence of the control temperature of the ignition source on the chemical reaction speed is particularly significant. For the general reaction, if the initial concentration is equal, the reaction speed is accelerated by approximately 2 to 4 times for each 10°C increase in temperature. Therefore, the temperature (that is, the ignition source generally referred to) makes it possible to speed up the reaction and cause the initial factor of an explosion accident. One of the important measures to prevent the explosion accident is to control the ignition source.
One of the important features of weakening explosion pressure and shock wave explosion is that when the explosive material explodes, the high-temperature and high-pressure gas produced will expand at a very high speed, causing the pressure in the enclosure to increase rapidly, which will cause the enclosure to burst, form a shock wave, and cause damage. . In order to prevent or reduce the sudden increase of the pressure in the surrounding body due to explosion, the surrounding body should not be relatively closed as much as possible.
Basic principles of explosion protection (1) Flammable substances that provide energy (sources of release);
(2) Auxiliary combustion oxidizer (oxidant);
(3) Uniform mixing of flammable substances and combustion aids;
(4) The mixture is placed in a relatively closed space (surrounding body);
(5) Ignition sources with sufficient energy.
The ignition source, combustible material and combustion improver in the above conditions are the three elements of combustion explosion. Explosion protection technology is based on these explosion conditions and adopts corresponding technical measures and management measures to achieve the purpose of preventing accidents.
The suppression of the concentration of combustibles is closely related to the explosive concentration of the explosive mixture. The relationship between the explosion intensity and the change in concentration is similar to the sine curve of the cycle. If the concentration state is low or too high, no explosion occurs. These two points are called explosions. Lower limit concentration and upper explosive concentration. Below the lower explosive concentration, the mixture cannot be ignited because the calorific value of the flammable material is so low that it cannot maintain the minimum temperature required for the flame to propagate through the mixture; if the concentration increases gradually beyond the upper explosive concentration, the combustible material Increased, but the oxygen concentration of the combustion support is lower than the stoichiometric value, it can not meet the need of complete combustion of the mixture, and it will not explode.
Therefore, the occurrence of an explosion accident can be prevented through the control of the concentration of combustibles, or the destructive power that can be caused by an explosion accident can be minimized.
Control of oxygen concentration When an inerting medium is added to an explosive atmosphere, on the one hand, the oxygen component of the explosive atmosphere can be diluted, reducing the chance of the action of molecules and oxygen molecules of combustible substances, and also separating the combustible components from the oxygen molecules. A barrier that does not burn is formed between them; when activated molecules collide with inertizing medium particles, the activated molecules lose their activation energy and cannot react. On the other hand, if the combustion reaction has taken place, the resulting radicals will interact with the inertizing medium particles, causing them to lose their activity, leading to interruption of the combustion chain reaction; at the same time, the inerting medium will also absorb a large amount of heat released by the combustion reaction, making The heat cannot accumulate, and the combustion reaction does not spread to other combustible components, which suppresses the combustion reaction.
Therefore, by adding an inerting medium to the combustible/air explosive atmosphere, the explosive range of the combustible component is reduced. When the inertizing medium is increased to a sufficient concentration, the upper and lower explosion limits can be coincided with each other, and then the inerting medium concentration can be increased. Combustion air mixture will no longer burn.
The influence of the control temperature of the ignition source on the chemical reaction speed is particularly significant. For the general reaction, if the initial concentration is equal, the reaction speed is accelerated by approximately 2 to 4 times for each 10°C increase in temperature. Therefore, the temperature (that is, the ignition source generally referred to) makes it possible to speed up the reaction and cause the initial factor of an explosion accident. One of the important measures to prevent the explosion accident is to control the ignition source.
One of the important features of weakening explosion pressure and shock wave explosion is that when the explosive material explodes, the high-temperature and high-pressure gas produced will expand at a very high speed, causing the pressure in the enclosure to increase rapidly, which will cause the enclosure to burst, form a shock wave, and cause damage. . In order to prevent or reduce the sudden increase of the pressure in the surrounding body due to explosion, the surrounding body should not be relatively closed as much as possible.
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