Fire and explosion protection in dryers

Self ignition of deposits is a frequent cause of explosions in dryers due to the increased process temperature. Self ignition takes place when the heat generation by the reaction is larger than the heat removal through the dust layer. Critical temperatures therefore depend on the volume and geometrical shape of the deposit. Experimental results have to be discussed with respect to the specific process. Typical ignition sources in spray and flow dryers are discussed and preventive measures are given. The abilities and drawbacks of spark detectors and concentration measurements with respect to the prevention of ignition sources is reviewed critically.