SELF-IGNITION-TEMPERATURE

 

[VDI 2263, Part 1]

 

The test substance (sample) is filled into a wire basket and then put into a heating chamber with fresh air inlet (2 l/min), where it is exposed to a constant temperature.

 

The temperature difference between the sample and the air in the chamber (i.e., the DT-signal) is recorded and plotted against time.

 

If during the test a positive DT-signal is observed this indicates an exothermic decomposition, most probably due to oxidation.

 

In some cases the exothermic reaction occurs only after a certain induction time.

 

Such reactions are called "autocatalytic" - independent of the true reaction mechanism.

 

The highest temperature (rounded to multiples of 10 C) at which the DT-Signal does not exceed +5 C is determined (called basket limit temperature "KGT").

 

By extrapolation of these values, the self-ignition temperature of large bulk volumes can be calculated.

 

This value can be used to determine safe drying temperatures for convection dryers (e.g., fluidized bed dryers, spray dryers).

 

Depending on the dryer type, the maximum temperature to which the dry material may be exposed is KGT or KGT minus 10 C.