What is the dust  explosion-proof, that is, dust in the limits of the explosion, encountered heat  (fire or temperature), the flame instantly spread throughout the mixed  dust space, chemical reaction speed, While  the release of a lot of heat, the formation of a high temperature and  great pressure, the system energy into mechanical work and light and  heat radiation, with a strong destructive power.

Basic definition

The following are the same as the any solid matter that is in fine powder state is called dust. The dust that can burn and explode is called combustible dust; the dust that floats in the air is called suspended dust;On the dust called the deposition of dust. It has been found that the following seven types of dust are  explosive: metals (such as magnesium powder, aluminum powder); coal;  grain (eg wheat, starch); feed such  as cotton powder, fish meal); agricultural products (such as cotton,  tobacco); forest products (such as paper powder, wood flour); synthetic  materials (such as plastics, dyes). Some factories and mines in the production process of  the dust, in particular, some of the organic matter generated in the  dust, in some specific conditions will occur explosion burning accident.  Domestic and foreign research results show that these conditions are generally there Three kinds: (1) flammable dust to the appropriate concentration in  the air suspension, the formation of people often say dust clouds; (2)  have plenty of air and oxidants; (3) a fire or strong Vibration and friction. It  is generally believed that the explosive dust as long as the conditions  (1) and conditions (2), it means that there may be signs of accidents.

Explosion process

Dust  explosion can be seen as the development of the following three steps:  the first step is the suspension of dust in the heat under the role of  rapid dry distillation or gasification to produce combustible gas; the  second step is  Combustible gas mixed with air  and burning; the third step is the heat emitted by the combustion of  dust, heat conduction and flame radiation way to the nearby suspended or  blowing up the dust, which the dust is heat and vaporized to allow the combustion cycle to proceed. With  each cycle of the successive, the reaction rate gradually accelerated,  through the intense combustion, and finally the formation of an  explosion. This Explosive reaction  and explosive flame speed, blast wave velocity, explosion pressure will  continue to accelerate and rise, and was leaping development.

Explosion characteristics

The following are the same as the "
(1) multiple explosions are the biggest feature of dust explosion;

(2) dust explosion required for the minimum ignition energy is higher, generally more than a few dozen joules or more.

(3)  Compared with the flammable gas explosion, the dust explosion pressure  increased slowly, the higher the pressure lasted for a long time, the  release of energy, destructive.

Main hazard

  (1) has a very destructive. Dust  explosion involves a wide range of coal, chemical, pharmaceutical  processing, wood processing, food and feed processing and other  departments have occurred. Such as1952  - 1979, Japan, all kinds of dust explosion accidents 209, a total of  546 casualties, of which the crushing and milling engineering and dust  separation project is more prominent, each 46. federal Germany  1965 - 1980 all kinds of dust explosion accidents occurred 768, of  which the more serious is the wood powder and wood products dust and  food feed explosion, accounting for 32% and 25% respectively. recent years,  The frequency of dust explosion in China each year: local explosion  150-300 times the system exploded 1-3 times, and showed an increasing  trend. China's dust explosion occurred in particular the system burst Fried, caused a serious loss, only in 1987 Harbin linen factory flax  dust explosion, killed 58 people, seriously injured 177 people, direct  economic losses of 8.82 million yuan.

  (2) prone to secondary explosion. The first explosion of air waves to the deposition of equipment or the  ground on the dust blowing up in the explosion after a short period of  time the center of the explosion will form a negative pressure,The surrounding fresh air will be filled from outside to inside, the  formation of the so-called "return to the wind", mixed with the dust, in  the first explosion of ignited the ignition caused a second explosion.The  second explosion, the dust concentration is generally much higher than  an explosion, so the second explosion power is much larger than the  first time. For example, a sulfur powder factory, grinding machine internal explosion,The explosion wave spreads along the gas pipe from the attritor to the  cyclone, and the second explosion occurred in the cyclone. The  explosion wave propagated through the cyclone in the cyclone To the workshop, raised the settlement in the building and process equipment on the sulfur dust, and an explosion occurred. (3) can produce toxic gases. One is carbon monoxide; the other is exploding A toxic gas that decomposes itself (such as plastic). The production of gas often caused a large number of people after the explosion poisoning, must pay full attention