When it comes to dust, everyone has different understandings and understandings. In fact, there are many ways to call dust, such as floating sinks, metal powders, and flour. Although they are called different types of dust, they are collectively referred to as dust. What is dust? How did it explode?

Here, SINOVAC Xiao Bian has introduced the dust from the bottom line.

What is dust?

Dust refers to solid particles suspended in the air. Traditionally there are many names for dust, such as dust, dust, smoke, dust, dust, powder, etc. These terms have no obvious boundaries. According to the International Organization for Standardization, a solid suspended particle with a particle size of less than 75 μm is defined as dust.

How did dust explode?

Dust explosions are caused by the high pressure created by the burning of combustible dust suspended in the air. Dust is a fine particle of a solid substance, and its surface area is much larger than that of a block material of the same weight, so it is easy to catch fire. If it is suspended in air and reaches a certain concentration, an explosive mixture is formed.

Dust explosion is very dangerous, because when the heat source (open flame or temperature) is encountered, the flame spreads instantaneously throughout the mixed dust space, the chemical reaction speed is extremely fast, and at the same time, a large amount of heat is released to form a very high temperature and a large pressure. The energy is transformed into mechanical work as well as light and heat radiation, which has a strong destructive power.

Currently, seven types of substances are known to have explosive dust: metals (such as magnesium powder, aluminum powder); coal; food (such as wheat, starch); feed (such as blood meal, fish meal); agricultural and sideline products (such as cotton, tobacco); forest products (such as paper powder, wood flour); synthetic materials (such as plastics, dyes). Dust fire and explosion accidents occur in coal mines, flour mills, sugar mills, textile mills, sulfur plants, feed, plastics, metal processing plants, and grain warehouses. This is related to the conditions required for dust explosions. Dust explosion itself is a special kind of combustion phenomenon. It also needs three conditions: combustibles, combustion aids and ignition sources.

Research results at home and abroad show that there are generally three conditions that are prone to dust explosions: (1) Flammable dust is suspended in the air at an appropriate concentration to form a dust cloud; (2) There is sufficient air and Oxidizer; (3), with fire or strong vibration and friction.

It is generally believed that as long as the explosive dust meets condition (1) and condition (2), it means that there is a sign that an accident may occur.

In addition, after the first explosion, at the explosion point of dust, due to the thermal expansion of the air, the density becomes smaller, the counter-current of the explosion point (commonly referred to as “return wind”) is rapidly formed, and in case of dust clouds and thermal energy, a second explosion will occur. Therefore, the timely use of vacuum equipment to do dust control measures is necessary.