Drying plant filter backwashing process - uses compressed air or superheated steam at given temp., or hot gases from combustion chamber

摘要

Wood chip or refuse drying plant using a gravel bed filter, which is cleaned by passing hot air or a gas or gas mixture through it. This is carried out at a temperature between 20 and 80 deg., preferably 30 and 60 deg.C., above the dew point of the hot gas, which may contain steam. The drier is operated alternately until this temperature is reached. The hot gas from the dryer at the start of the drying process is used. The dust enriched drying gas is used straight from the combustion chamber of the hot gas generator of the dryer without a dust extractor. Each washing cycle uses gas at a pressure of between 300 and 1000 mm of water column. Compressed air can be used, or superheated steam. The filter may have round or square cells not higher than the height of the gravel layer.