Explosion of the hottest gas and its prevention

Gas explosion and its prevention

1 Chemical reaction process of gas explosion

gas explosion is a process in which a certain concentration of methane and oxygen in the air react violently under the action of high temperature heat source of asphalt composite tire flexible waterproof membrane jc/t690 ⑵ 008

mine gas explosion is a heat chain reaction process (also known as chain reaction)

２. The generation and propagation process of gas explosion

explosive mixed gas and high-temperature fire source exist at the same time,

initial combustion (initial explosion) → flame surface → shock wave → new explosive mixture

3. The harm of gas explosion

the harmful factors of gas explosion in the mine are high temperature, shock wave and harmful gas

the flame surface is the moving chemical reaction zone and high-temperature gas in the roadway, with high speed and high temperature. From normal combustion speed (1 ~ 2.5m/s) to detonation propagation speed (2500m/s). The flame surface temperature can be as high as 2150 ~ 2650 ° C. Where the flame surface passes, people are burned or burned in a large area, and combustibles are ignited to cause a fire

the front pressure of the shock wave ranges from a few atmospheres to 20 atmospheres, and the forward shock wave can reach 100 atmospheres when superimposed and reflected. Its propagation speed is always greater than the speed of sound, causing casualties, damage to equipment and ventilation facilities, and roadway collapse wherever it goes

a large amount of harmful gas is generated after gas explosion. According to the analysis of some coal mines, the gas composition after explosion is O26% - 10%, n282% - 88%, co24% - 8%, CO2% - 4%. If coal dust is involved in the explosion, the generation of CO is greater, which often becomes the main reason for a large number of casualties

II. Main parameters of gas explosion

1. Explosion concentration of gas

in normal atmospheric environment, gas only explodes within a certain concentration range, which is called the explosion limit of gas. Its lowest concentration limit is called the lower explosion limit, and its highest concentration limit is called the upper explosion limit. The lower explosion limit of gas in the air is 5 ~ 6%, and the upper limit is 14 ~ 16%

the limit of gas explosion is not fixed, it is affected by many factors,

among which the important ones are:

(1) the concentration of oxygen

the relationship between gas explosion concentration and oxygen concentration at normal atmospheric pressure and room temperature, as shown in the coward explosion triangle (Figure). When the oxygen concentration decreases, the lower explosion limit changes little (be line) and the upper explosion limit decreases significantly (CE line). When the oxygen concentration is less than 12%, the mixed gas loses its explosiveness

(2) when there are more than two kinds of combustible gases in the mixture of other combustible gases

at the same time, its explosion limit depends on the explosion limit of each combustible gas and their concentration. It can be calculated from the formula:

n1, N2, N3 NN -- upper or lower explosion limit of each combustible gas,%

(3) coal dust

coal dust has explosion risk. At 300 ~ 400 ℃, a variety of combustible gases can be volatilized from coal dust to form mixed explosive gases, which increases the explosion risk of gas

(4) air pressure

the initial pressure before explosion has a great impact on the upper limit of gas explosion. The pressure of explosive gas increases, but for general manufacturers, the molecular spacing is closer, and the collision probability increases

(5) inert gas

can reduce the risk of gas explosion