Ignition studies of selected explosive mixtures of gases and dusts emitted from cement kilns

The gas compositions and the dust loadings of two cement plants were investigated. The samples were taken at the inlet and the outlet of the electrostatic precipitators and then analyzed on a gas chromatograph. The measured gas concentrations were used as a basis for flammability tests in order to verify or correct existing safe operation limits for the precipitators. Two sets of flammability tests were conducted using a modified version of the 20 litre chamber designed by the US Bureau of Mines. In the first set, the lean limits of different clean gas mixtures assumed to be present under upset operating conditions were determined. In the second set, the amount of cement dust necessary to render an explosive clean gas mixture inert was examined. The results of the flammability tests show that the measured exhaust gas composition is well in the safe range. Under upset conditions, however, the gas composition could be explosive, and in most cases the amount of dust present in the precipitator exhaust gas would not be sufficient to prevent an ignition of the gas.<>