Analysis of Coal Dust Ignition Deposited in a Layer at Constant and Variable Temperature of Heating Panel

The present work analyses the tendency of ignition of the “Barbara” coal dust from a heated surface. Minimum coal dust layer ignition temperature was measured at a fixed temperature of heating plate (standard method) and at temperature of the heating plate increasing at constant rate. Dust layers of thickness ranging from 5 to 50 mm were tested. Permissible temperature of surfaces of electrical equipment were determined on the basis of PN-EN 60079-14 standard requirements concerning the method of lowering the permissible equipment surface temperature along with the increasing thickness of the layer from 5 mm to 50 mm in order to maintain an adequately high safety margin. Based on the results, significant differences were found for both methods of determination. For a 5 mm dust layer, the permissible temperature of equipment differed by ca. 140 °C and they decreased as the layer thickness rose, down to ca. 40 °C for a 50 mm dust layer.