What Is Minimum Ignition Energy?

Minimum Ignition Energy refers to the minimum spark energy that can cause the dust cloud (or combustible gas and air mixture) to burn (or explode). Also called minimum spark ignition energy or critical ignition energy.

The minimum ignition energy is also called ignition energy, minimum spark ignition energy, or critical ignition energy. It refers to the critical energy value necessary to ignite a mixture of combustible gas and air.

The concentration of the mixed gas has a greater impact on the ignition energy. Generally, when the concentration of the combustible gas is higher than the stoichiometric concentration, the required ignition energy is the smallest. Or the energy of the ignition source is less than the minimum energy, the combustibles cannot catch fire. Therefore, the minimum ignition energy is also an important parameter for measuring the flammability of combustible gases, vapors, and dust. For impact friction sparks and static sparks that release a small amount of energy, is their energy greater than the minimum ignition energy? It is an important condition to determine whether it can be used as a fire source to cause a fire and explosion accident. ^[1]

When the energy of the ignition source is lower than this critical value, the combustible hybrid system is generally not ignited. The minimum ignition energy can be determined by the electric spark method, that is, a capacitor of a certain capacity is connected in parallel on the discharge electrode, and its capacitance is set to C (F). When the spark voltage on the electrode is U (V), the discharge energy E (J) can be calculated by the following formula:

E = 0.5C · U ²

What really has practical guiding significance for safe production is the minimum ignition energy of the medium, that is, the limit sensitivity of the substance's electrostatic spark.

On the most

Minimal ignition energy dust hazard

Dust floating in the air often causes huge harm to human life and property. One of its hazards is to pollute the atmosphere and affect human health. Dust flowing in the atmosphere often contains many toxic components, such as chromium, manganese, cadmium, lead, mercury, arsenic, etc. When the human body inhales dust, particles smaller than 5 m can easily penetrate the lungs, cause toxic pneumonia or silicosis, and sometimes cause lung cancer. Once the pollutants deposited in the lungs are dissolved, they will directly invade the blood and cause blood poisoning. Undissolved pollutants may also be absorbed by the cells, leading to the destruction of the cell structure. In addition, dust can contaminate buildings and cause valuable ancient buildings to suffer corrosion. Dust falling on the leaves of plants will hinder photosynthesis and inhibit its growth.

The second hazard of dust is explosion. According to legend, as early as the windmill and water mill era, there have been a series of mill dust explosions. In the 20th century, with the development of industry, dust explosion accidents are more common and the types of explosion dust are increasing. According to statistics, from 1913 to 1973, there were 72 serious dust explosion accidents in the United States alone in industry and agriculture. In 1919, a dust explosion occurred in a starch plant in Ohio, which almost destroyed the plant and killed 43 people. There were 177 major dust explosions in Japan from 1952 to 1975, with a total of 75 deaths and 410 injuries.

In 1977, a modern grain depot in Louisiana, the United States, exploded, causing more than half of the grain silos to be destroyed. Even office buildings were not spared. 36 people died and the direct economic loss amounted to US $ 30 million. The United Kingdom and Canada have also experienced excessive dust explosions in the chemical and papermaking industries, with 243 deaths and 204 casualties in the UK alone. ^[3]

Avoidance of minimal ignition hazards

Although dust may explode, it can be avoided if reliable measures are taken. The precautionary measures should focus on the conditions of the explosion: control the dust concentration; prevent the ignition point; reduce the oxygen concentration in the air; take effective dust reduction measures; establish forecasts System; set explosion pressure relief port, etc. In addition, it is necessary to establish necessary rules and regulations in management and implement management measures.