Minimum Ignition Temperature of dust
Physical meaning and use in risk assessment of powder MIT
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Solids Handling Safety
# Dust explosion physical properties # MIT - Minimum Ignition Temperature of dust
1. Definition of MIT
If a dust cloud enters in contact with a hot surface, it may auto-ignite and explode. The Minimum Ignition Temperature is the minimum temperature for which a hot surface will ignite a dust cloud [Laurent].
2. Experimental determination of MIT
The MIT is measured experimentally. The experiment consists in putting in suspension dust of the material to be tested in a cloud that has a concentration in between the minimum explosion concentration and maximum explosion concentration (determining this concentration may need additional experiments) and submitting the dust cloud to a hot surface in an oven.
The MIT is the smallest temperature of the oven observed that triggers an explosion at the concentration tested.
To be representative, such experiences must be carried out following a clear protocol (example : ASTM E1491 in US, EN 50281-2-1 in Europe). The test machine mentioned in the norm is also important as values may be slightly different from one apparatus to another. Norms and literature are mentioning the Godbert Greenwald furnace and the BAM furnaces as apparatuses to perform the tests.
Those protocols should not be confused with the minimum ignition temperature of dust layers which corresponds to other conditions and physical meanings.
3. MIT typical range
MIT values are generally in between 150 and 700 degrees celsius, of course dependent of the nature of the material.
Each processor must carry out a dust explosion risk analysis in order to assess the risk related to a specific material in a specific process and take necessary precaution and mitigation measures.
4. Use in risk assessment
|Grain dust||430 [Mills]|
|Lemon balm||480 [Polka]|
|Rice flakes||430 [Polka]|
|Senna fruit||520 [Polka]|
460 for corn starch [Polka]
|Sunflower hulls||460 [Polka]|
|Wheat Flour||380 [Mills]|
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