| 摘要 |
<p>Process and apparatus are described for drying sludge, in which process the sludge in a vessel (1) is conducted from top to bottom by means of a loading device (2, 6, 8) and by means of a discharge device (3, 11) in the form of a sludge column with stable layers and is dried in the course of this in countercurrent by means of drying air entering at the bottom of the vessel through a ventilating base (16) furnished with orifices and leaving from the top of the vessel. The heat contained in latent and sensible form in the drying air conducted away from the vessel is transferred via a heat exchanger (13) to the drying air supplied from outside, so that the heat liberated during the drying on account of the remaining putrefaction process is sufficient to maintain the sludge in the vessel at elevated temperature. Part of the dried sludge removed from the bottom of the vessel (1) is mixed with the externally (2) supplied sludge by means of a mixing device (7), in order to adjust the initial consistency and moisture content. According to a particular embodiment of the invention, a second vessel of essentially the same type is provided, to the bottom of which can be supplied drying air withdrawn from the top of the first container and mixed as required with drying air directly supplied from the surroundings. The sludge to be dried can be initially fed to the first or the second of the two vessels and there subjected to a predrying and then transferred from the bottom of this to the top of the other vessel in each case and there subjected to a final drying. <IMAGE></p> |
