| 摘要 |
For the purpose of dewatering sewage sludge, the sludge pretreated with a flocculant is subjected, prior to pressing, to preliminary dewatering by means of drag classifiers arranged in decks above one another, the sludge predewatered to approximately 20% DM (dry matter) being transferred, without the use of pumps and therefore gently, by gravity into a sludge silo from which the predewatered sludge intermittently flows into at least one filter press, which can be charged from above, where it is dewatered to at least 50% DM. Consequently, the sludge cake is so hard that after size reduction it is present as chunks which retain their shape even when heaped up and do not clump together, so that the surface area of the sludge cake pieces, in a subsequent secondary drying process in the open air by means of drying belts, does not change, and secondary drying up to approximately from 90 to 95% DM can be achieved.
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