Study of the Prediction Method of the Dust Explosion Characteristic of the Combustible Powder By the Analysis of the Combustible Gas

When we perform the safety assessment of powder process, we evaluate or survey the minimum ignition energy (MIE) of powder. Based on the MIE of the powder and the estimated energy of the ignition source in the process, we carry out the safety measures, such as electrostatic measures and nitrogen inerting, to prevent the dust explosion hazard in powder process. However, the test standard of the evaluation of the MIE requires us to prepare several hundred gram of powders, which pass through 200mesh sieve (the opening of the sieve is 75μm). We labor to prepare the sample for the dust explosion test. So it is considered that the development of the evaluation and the prediction method of the dust explosion characteristic (MIE) by a small quantity of the sample is very useful.

In general, the following scheme is proposed as mechanism of dust explosion,

1st Step: The ignition energy causes the volatilization, the vaporization or the decomposition of powders floating in the air. And the combustible gases are released from the powders..

2nd Step: The mixture of the combustible gases and the air ignites.

3rd Step: The heat which is generated by the flame causes the volatilization, the vaporization or the decomposition of powders. As the result, the flame spreads.

The 1st step of the dust explosion phenomenon is the gasification of the powder by the ignition energy. It is considered that the dust explosion characteristics have a correlation with the behavior of the combustible gas generation. The objective of this study is to develop the prediction method of the dust explosion characteristic (the level of MIE) by a small quantity of the sample. We are analyzing the amount of the combustible gas generated form powder by using TG (Thermogravimetry) analysis. And we are trying to investigate the relationship between the dust explosion characteristics (the level of MIE) and the amount of the combustible gases generated by the thermal decomposition. In this presentation, I will report the current status of this study.

Keywords: dust explosion, minimum ignition energy, MIE , TG,, thermogravimetry analysis