Cement Manufacturers Association (CMA)

Various conditions play a role in the development of violence, when an connected vessels, of which the possible vessels is only one. The most important and dangerous conditions in the VRM-to-DC riser duct the following: - The explosion in the mill leads to - If an explosion was ignited in the mill, the O percentage of the process air in the system must have been >13 % at the moment of the ignition and this O level will also be available for the support of combustion in the riser duct. - The concentration of coal dust-in-air in the duct will be something like 500 g/m , which is in the most supportive section of the total range of dust-in-air explosivity (roughly 50 … 2,000 g/m ). - All this will support the transition of the it will consume the available coal particles and O , developing heat/pressure and propagation speed. - The propagation speed development is a function of the length of the propagation path. More precisely, a function of the L/D (length/diameter) rate of the duct. The velocity of the process air in the duct is usually roughly 19 m/s. With the duct will easily accelerate to a value like 200 m/s. This equals 720 km/h. It is not hard to imagine that anything in the way of a burning pressurised air mass that moves through a duct at this speed will be exposed to violence. How to deal with this? - Don’t allow high pressure to build up where the propagation starts. - propagation starts. - Use a self reclosing explosion vent for this that closes immediately upon having vented. and by putting it ‘somewhere’. The vent has to be positioned correctly and the geometry of the duct and the explosion vent have to ensure diversion of the volume into the atmosphere. This requires specialist design. The explosion vent has to have a very low must not be a problem, since the duct is operated under negative pressure. The consideration that has to be prioritised optimal conditions for the diversion be hindered by considerations like the desire to simplify the installation or to protect people, such considerations have to rank lower and solutions have to be found. The order for the protection of the system to be real. In the industry, in many cases such a diverter vent is not in place, of the wrong type, incorrectly positioned, or left without the necessary regular maintenance. Often, the recoil force that is caused by explosion venting is not included in the design strength of the supporting structure. - For HBM systems only The separator is an enclosure with a volume of several m . This enclosure has 3 (from below), separator-to-DC riser duct the transport of the separated coarse coal particles (downward & lateral). Page 36