Plant for drying sludge

The invention relates to a plant for drying Sludges, in particular sewage sludge.

Sludges fall in different ways, for example, in municipal wastewater treatment plants, on. The disposal of such Sludge is a significant problem.

It is known to recycle sewage sludge by drying, whereby its mass be greatly diminished can. The product obtained by the drying may then, for example, spread on fields as fertilizer will.

Objections to such use of dried sewage sludge however is when these infectious are charged nuclei. It is therefore to ensure that during drying a reliable sterilization takes place.

The invention is therefore based on the object, a plant to provide for drying of sludges, in which a reliable sterilization to be recovered Sludges occurs.

This object is achieved by a system for drying sludge, in particular sewage sludge, with a thin sludge feed, a mechanical Predewatering, a storage container, a feed pump, a by having a plurality provided superimposed screw conveyors Cascade dryer a cascade dryer heated Heating system, a vapor washer, of which with one of Cascade dryer upcoming vapor line, a hot water inlet, a water return and a Exhaust Filters leading exhaust duct is provided, and a discharge conveyor, wherein the pre-dewatered paste-like slurry by the feed pump at the level of the top of the screw conveyor in the cascade dryer and introduced at the level of the bottom of the Screw conveyor as a dry substance of this on the Discharge conveyor is removed, continue with a Means for generating a negative pressure in the Cascade dryer.

The means for generating a negative pressure is preferably as one in which the filter leading exhaust duct of introduced fan formed.

The cascade drier is a with the exhaust air duct be provided associated shaft, which in on the Cascade dryer introduced perforations with the communicated by the screw conveyors swept areas.

The invention is described below with reference to drawings explained. The single FIGURE shows a schematic Representation of such a system.

The drying of sludges, in particular sewage sludge serving conditioning ( "mud" used in this application can eligible waste of any kind with there is a relatively high moisture content to be) from a thin sludge feed 1, a mechanical predewatering 2, a reservoir 3, a feed pump 4, a cascade dryer 5, a Heating system 6, a vapor washer 7, an exhaust filter 8, a discharge conveyor 9 and a fan 11th

The cascade drier is provided with a plurality - in the embodiment shown three - arranged one above another Screw conveyors 5a, 5b, 5c provided. The Heating 6 heating the jacket of the cascade dryer 3 and the single screw conveyor 5a, 5b, 5c. The at Application of heat escaping vapors occur over a shaft 5d introduced into the cascade dryer Perforations with the screw conveyors 5a, 5b, 5c swept areas communicates, into the vapor 7a in the vapor washer 7 a. In the vapor washer 7 via a hot water inlet 7b condensed which is introduced hot water and washes the Vapors, the wash water then exits the water return 7c again. The Ahluft is an exhaust duct 7d out in an exhaust filter. 8

The from the feed pump 4 from the reservoir 3 in the area of ​​the top of the screw conveyor 5a introduced Sludge passes through the cascade dryer 5 through, he exits as of dry, crumb-like product sem end portion of the bottom of the auger 5c the conveyor 5 and is in the illustrated Embodiment then in a Trockengutstapelbehälter 10 temporarily stored until it is executed.

causing the evaporation of the water in the cascade dryer 5 the pressure build-up in this and an outlet of secondary air through bushes and the like. The flow of air and water vapor in the Cascade dryer 5 is therefore no ko ntrolliert. This may have the result that germs relatively quickly by the cascade dryer 5 through rush and insufficient be sterilized.

To such a non wünschtes taking those germs avoid, is in the exhaust duct 7d a fan 11 provided that the vapors through the vapor washer 7 through pulling, so that in the cascade dryer 5 Pressure prevails which is lower than the ambient pressure. This ensures that bacteria do not faster than the dried material rush through the cascade dryer 5 can, so that a complete sterilization of the ensure material to be dried.