Cleaning and liquid contact with solids – Processes – Including distortion or deformation of work
Patent
1999-08-09
2000-12-05
El-Arini, Zeinab
Cleaning and liquid contact with solids
Processes
Including distortion or deformation of work
134 10, 134 13, 134 251, 134 255, 134 26, 134 32, 134 65, 134 70, B08B 102, B08B 302
Patent
active
061561282
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for washing material retained on trash rakes, which is compacted before it enters the washing chamber with the help of a screw conveyor extending horizontally through a washing chamber, loosened up in the washing chamber and washed with injected washing water, and then discharged under compacting and dehydrating from the washing chamber, from which the washing water with the washed-out contaminations is drained through a screen insert. The invention, furthermore, relates to a device for carrying out the process.
In order to wash out the organic component from the material retained on the trash rake of water treatment plants, it is known (from DE 42 11 657 C1) to compact the material retained in the trash rake with the help of a horizontal screw conveyor before it enters into a washing chamber, because by compacting the material retained in the trash rake with the help of a conveyor screw, especially the feces components are mixed with the other trash materials, and kneaded and ground in this mixing process in such a way that effective breaking up and crushing of the coarse feces components is ensured as a precondition for largely washing said organic substances out in the course of the subsequent washing process. In the washing chamber, the waste material treated in said way, which may be additionally loosened up by loosening wings of the conveyor screw, if need be, is rinsed with injected washing water, whereby it is made sure that the filling level of the water will not completely cover the waste material, so that the washing water directly injected onto part of the waste material, which is circulated by the slowly revolving conveyor screw. Following said two-stage washing zone with different water filling levels, the waste material is then dehydrated, whereby the washed-out organic substances are drained with the washing water via screen inserts and returned to the waste water treatment plant. The washed trash material is then dehydrated, compacted and discarded. In spite of the costly two-stage washing process, the washing result remains unsatisfactory because the discharged, washed trash material still contains a component of organic substances that is not at all negligible.
Therefore, the invention is based on the problem of developing a process for washing materials retained in a trash and waste collecting rake of the type described above, in such a way that the result of the washing process can be substantially improved with simple means.
Said problem is solved by the invention in that by periodically interrupting the feed of washing water into the washing chamber, the water filling level in said washing chamber is periodically lowered from a backup level periodically occurring prior to such interruption depending on the amount of raked-in trash and waste in said washing chamber, at least to a residual level ensuring adequate removal of the trash and waste materials from said chamber.
Extensive tests have shown that the organic components, which amount to a major part of the raked-in trash and waste materials, can be separated reliably from the other solid materials only if the raked-in trash and waste materials are subjected to a suitably long washing process in an adequate amount of washing water. This requires as a precondition that the level of the washing water in the washing chamber is suitably high. However, efficient transport of the raked-in trash and waste materials through the washing chamber is obstructed by such a suitably high washing water filling level because of the comparatively slow rotation of the screw conveyor. The feed of washing water is periodically discontinued for this reason, so that the filling level of washing water is lowered to at least a residual level permitting the raked-in trash and waste materials to be conveyed as required. Backing up of the washing water from the residual level after the feed of washing water has been restarted, furthermore, causes washing water to be sprayed directly onto the raked-in materials until such ma
REFERENCES:
patent: 3544369 (1970-12-01), Keogh, Jr.
patent: 5641360 (1997-06-01), Bischof
ABZ Zierler Ges. m.b.H. & Co. KG
El-Arini Zeinab
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