Cement Manufacturers Association (CMA)

If there are indications that in a given location, under given climate conditions oxidation must be expected to happen, it will be necessary to include the raw coal storage in the raw coal silo(s) in the monitoring and emergency inerting concept of the coal grinding plant. This means that CO and O monitoring have to be installed and that the capacity of the emergency inerting system is chosen large enough to also cover the volume of raw coal silo(s). It makes sense to combine the CO monitoring with O monitoring. The 2 gas analysers can both be in line with one single air pre-treating system and the availability of O indication gives real time information on the progress of the emergency inerting process. Emergency inerting aims at a quick reduction of O in the atmosphere of the relevant enclosure. - Raw coal mill in-feed which a coal dust explosion can take place. This means that anything with an open connection with the grinding chamber will apart from the process air in-feed, 2 in-feeds for coal. Unlike VRM systems, where the separator normally is integrated system is a separate enclosure. particles that stems from this It is normal (with very few exceptions) that the necessary explosion isolation, or at least explosion de-coupling, that should be in place at mills’ raw coal inlet is not in place, or not correctly designed. EPSR. About the necessary degree of EPSR confusion exists. Some mill suppliers are speaking of EPSR good for 6 or 8 bar g, which clearly is unrealistic. The USAmerican code NFPA 85 demands EPSR good for 50 psi g (3.45 bar g), but an NFPA-internal investigation into the source of this requirement some years ago went without result. Serious calculations have resulted in the explosion pressure in the mill chamber of for this is that air-swept mills have a relatively large air inlet and relatively large air-ground fuel outlet, through which explosion pressure will dissipate into the larger volume of the system. - Mill’s air inlet In some cases, explosion venting will be installed on the air inlet of a mill. This only makes sense when the distance between the mill and an upstream booster fan or air heater is so short that such equipment could be damaged by the possible explosion pressure in the mill. It will normally not be a problem to realise the necessary EPSR in the air duct. that are felt in the air duct upstream of the mill is explosion pressure and possibly a to ignite fuel and extinguish quickly, since available. Apart from protecting a booster fan or air heater, explosion vents on the air inlet side protection of the system. Page 34