Liquid purification or separation – Filter – Movable medium
Reexamination Certificate
2002-01-15
2004-05-25
Prince, Fred G. (Department: 1724)
Liquid purification or separation
Filter
Movable medium
C210S393000, C210S396000, C210S397000
Reexamination Certificate
active
06739458
ABSTRACT:
The present invention is relative to a device for dehydrating sludge, especially dilute sludges, in accordance with the generic part of claim
1
.
Various sludges such as recycled sludge, digesting sludge or fresh sludge, etc. accumulate in the preparation of waste water, especially in sewage treatment plants. These sludges have at times a very high water content that should be reduced. The reducing of the water content simplifies in particular the managing of the sludge as well as, for example, significantly reduces the disposal costs. In particular, mechanical systems are also used for the concentrating of sludges. Usually a conditioning of the sludge with polyelectrolytes (auxiliary flocculation agents) are employed for a mechanical concentrating of sludges. These polyelectrolytes bring about a flocculation of the sludges treated in this manner so that the separation and filtration of the free supernatant water is better possible. As a rule, a volumetric decrease of approximately 80%-90% is possible with mechanical systems in combination with the conditioning of the sludge. In particular, this also makes it possible to render subsequent method steps in the purification of waste water more economical and more effective.
DE 39 42 561 C1 teaches a device that operates continuously and automatically to dehydrate a sludge laced with an auxiliary flocculation agent (e.g., polyelectrolyte). In this system, that operates with a transport worm, conditioned sludge is conducted into a cylindrical wedge-wire screen and transported there by the transport worm continuously from the inlet of the screen cylinder to the discharge of the screen cylinder. The device is set up at an angle of approximately 30° between the inlet and the discharge, as a result of which the flocculated sludge is continuously raised with the transport worm. In addition to the transport, a rotation of the flocculated sludge also takes place, which amplifies the exit of the filtrate water through the wedge-wire screen. The entrained solids remain in the cylinder and are separated at its end via a chute. The filtration time is regulated via the transport speed of the worm.
Usually, a conditioning of the sludge is also carried out in centrifugal systems for separating water from sludges. The work is performed at high rotation speeds in these systems, as a result of which solids settle on the sieve jacket of the centrifuge. The separated water collects in the center of the sieve jacket and flows via an outlet tube out of the jacket. The solid is transported by the centrifuge rotor via a control dam out of the jacket. In addition, devices with rotating sieve drums are also known. The flocculated sludge is centrally introduced into a sieve drum, during which a rotation of the flocculated sludge takes place by means of the rotation of the sieve drum in combination with so-called transport baffles. The supernatant water passes through the sieve surface of the drum to the outside, during which the solid is concentrated in the drum. The solid is ejected by the rotation of the drum through the mounted baffles, that generate a thrust, at the other end of the drum. These sieve drums are mounted at various inclinations between 0° and 10° of their axis.
Furthermore, band filter systems are known that are also designated as band thickeners or straining bands. They also work with sludge conditioned with polyelectrolytes. The flocculated sludge is placed and distributed on a polyester band cloth. The supernatant water flows through the sieve band by gravitation, during which the solid is deposited on its surface. A concentration of the sludge takes place by the advance of the filter cloth over rollers and, e.g., by means of other mounted components such as, e.g., baffles. The sludge moves along the thickening stretch by virtue of the advance of the band-shaped filter cloth and is dumped into a funnel after it has been concentrated.
The known devices have the disadvantage that they are expensive to construct and have a large space requirement.
DE-A 27 47 506 teaches a method of drying pasty, aqueous sludges in which the sludge is spread out on a horizontally aligned sieve surface and brought in contact with warm waste gases. The sludge is treated during the rotation of the sieve surface with various tools that engage into the sludge surface.
BE-A 564 675 teaches a device for dehydrating sludge in which the sludge is placed on rectangular sieve surfaces arranged in a box that are put in motion by vibrations. The box can be put in an inclined position by supports of varying heights.
The present invention has the problem of designing a device for dehydrating sludge, especially, dilute sludges, in such a manner that a device is created that saves space and is simply designed and assures a good separation between liquids and solids, in particular in the case of conditioned sludges. The invention solves this problem with the features of the device in accordance with claim
1
.
The design of the device for dehydrating sludge in accordance with the invention brings it about in an advantageous manner that it can be compactly and economically constructed. The circular design of the sieve surface makes possible an advantageous utilization of the surface and therewith a low space requirement and at the same time a low expenditure for material. The rotatable design makes it possible to transport the sludge to be dehydrated in the device with only one moved part and at the same time to remove the dehydrated sludge out of the device. In addition, this embodiment simultaneously permits other components that cooperate with the device to be designed in an especially short and space-saving manner.
The design of the sieve surface with its axis inclined relative to a horizontal line brings it about that even water or liquids in general that settled on the surface of the sludge can be separated from the sludge. They flow off as a function of the slope. In an advantageous further development of the invention the device comprises a drive device, as a result of which the rotating of the sieve surface and therewith a transport of the dehydrated sludge is possible in an especially simple manner. It is advantageous if the sieve surface is supported by a shaft arranged vertically to the sieve surface. It is especially favorable if this shaft is arranged in the center of the circular sieve surface. Moreover, this shaft has the advantage that the sieve surface can also be caused to rotate, that is, is driven by the shaft. In another advantageous embodiment of the invention the sieve surface is supported in a rotatable fashion by its edge, e.g., on guides of the housing and can advantageously also be driven by its edge, that is, put in rotation.
The device advantageously comprises a supply line for sludge and also an outlet for separated water. It is likewise especially advantageous to provide a discharge for the dehydrated sludge. This makes it possible for the device to be able to operate continuously. In addition, this also makes it possible that the device can be used in an automatic system. The supply line for the sludge is advantageously arranged above the sieve surface thereby and the outlet for the separated water is arranged below the sieve surface, as a consequence of which natural gravity is utilized for dehydrating the sludge. The arrangement of supply and outlet distributed over the circumference brings it about that a reliable separation between water and solids can take place. To this end the container, in which the sieve surface is advantageously arranged, comprises a perforation. In an advantageous further development of the invention the container comprises a cover, as a result of which the sludge can be treated separated from its environment. This is especially advantageous when the device is used in closed spaces since sludges can also entrain components that are dangerous to health.
In an especially advantageous further development of the invention the drive device is mounted above the cover, which makes a simple and economical design of the de
Dority & Manning
Hans Huber AG
Prince Fred G.
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