Drying procedure for wet materials such as effluent sludge uses gas containing nitrogen or CO2 to render material inert

摘要

The procedure, involving the use of a gas for drying a wet or damp material, has at least 90 per cent of the drying gas made up of an inert gas such as nitrogen or carbon dioxide. The gas is put into contact with the material being dried during its storage and drying processes, and is injected at a rate that gives an oxygen concentration in the atmospherenot above 0.7 times the maximum oxygen content (MOC). The drying procedure employs a heater with a series of channels mounted in series and/or in parallel and into which nitrogen or CO2 are injected. The injection system includes a neutralising gas feed (3) to an injection surface (2) on the wall of a hopper (1). One end (31) of the gas feed pipe is connected to the source of a neutralising gas, the other end (32) directed towards the injection surface is closed but has radial outlets (33) delivering the gas into a homogenisation chamber (4).