Minimum ignition temperature of a dust cloud (ignition temperature)

Definition

Lowest temperature of a hot surface at which the most flammable mixture of dust and air ignites under specified test conditions.

Determination

To determine the ignition temperature according to Godbert-Greenwald a small quantity of dust (0.1 g to 3.5 g) is blown down into an electrically heated, vertically arranged tube 36 mm in diameter and 400 mm long by means of a variable air blast (V = 50 cm³ to 300 cm³, p = 1.1 bar to 1.6 bar).

In the so-called BAM-oven, the dust to be tested is blown against a vertical impact surface, the hottest point inside the horizontal oven. The concentration of the dust/air mixture is varied within certain limits through the input of different quantities of dust and the lowest temperature, at which ignition occurs, is determined.
The aim of these tests is therefore to determine the ignition behaviour of a dust cloud in transient contact with a hot surface in a closed temperature field. The lowest temperature at which the dust/air mixture tested in the described equipment burns with a closed flame, is referred to as the ignition temperature.

In the case of sedimentation of the dust caused by the horizontal arrangement of the BAM-oven, smouldering gases may arise, so that the values determined in this equipment may be lower than those determined with the Godbert-Greenwald equipment.

Remark

The values specified in brackets for the Godbert-Greenwald apparatus (G-G) refer to an older test equipment with a slightly longer tube. They are lower than the values determined with the 400 mm tube. The abbreviation "n.i.u. ..." means: no ignition up to ... °C.

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