JPS6034407B2 - Separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for the separation of solid/liquid mixtures and mixtures of liquids of different densities, in particular for the removal of settled sludge from clarified liquids during wastewater treatment. Regarding.

In a wastewater treatment process, such as that described in our GB 1473665, an aeration step in which the wastewater is intensively aerated is followed by a clarification step in which the sludge is separated from the clarified liquid. The process is carried out.

From the clarification process, the sludge is returned to the Kejo process. The clarification process is usually carried out in a clarification device, which is a vessel with a bottom that slopes downward toward a central point. The sludge settles towards the lower part of the clarifier and the clarified liquid is above it. The sludge is raked downward toward the central bottom outlet for removal. The following three raking methods are commonly used for raking such sludge.

1. A flat scraper blade (
(plural)

Such a machine is rotated near the bottom of the clarifier, gradually scraping the sludge toward the central bottom outlet. 2. A suction scraper rotatably mounted and having a rectangular cross section, with a djffrentjalhead.
, for example, the use of sludge removal by means of a siphon mechanism.

This method provides faster sludge return than the one method described above. 3. Use of steep bottom cone fining equipment and chain scrapers.

The disadvantages of these three methods are as follows.

1. Slow scraper peripheral speed is required to avoid disturbance of settled sludge.

The return of the sludge is therefore slow, and for large diameter clarifiers the return of the sludge is even slower since the rotational speed must be reduced for the same circumferential speed. 2 Suction provides more exhaustive sludge return than Method 1, but still limits peripheral speed.

Also, the equipment required is more complex. Although it is possible to add more suction scrapers (arms),
This increases the complexity and expense of the device. 3
Providing a steep bottom cone on a large diameter fining device
It costs a lot of money.

The method of our UK Patent No. 1473665 mentioned above works well with rapid sludge return.

According to the invention: 'i} a container in which a mixture of liquids or a mixture of liquids and solid particles is allowed to settle in layers with different densities; and {ii} a layer of greater density. Apparatus for withdrawing material from a container comprising: (a' disposed in a layer of greater density, mounted rotatably about the axis of said container; a separation device comprising at least one hollow wing with at least one retractable opening □; and [b] means for discharging the substance drawn into said hollow wing from said container. In the apparatus: the at least one wing has an aircraft wing-like cross section;
There is thus provided a separation device as described above, which is characterized in that it reduces the disturbance of the container contents caused by the rotation of the blades about the axis.

The device of the invention is highly suitable for use in wastewater treatment for exhaustive sludge return from its clarification step to the pneumatic trenching step. The present invention will be explained below regarding wastewater treatment (
However, the present invention is not limited thereto). 0
In the apparatus of the present invention, a scraper consisting of one or more blades is provided, each blade of which is located sufficiently below the interface between the sludge layer forming in the lower part of the clarification vessel and the clarified water above that layer. It is preferable to rotate it so that it is in this position.

The shape of each blade is appropriately selected so as not to disturb the progress of sludge settling as much as possible. By drawing fluid into the interior of the scraper vane and transporting it to an ejection location (usually located in the center of the clarification vessel) fluid turbulence is suitably reduced or eliminated. In the case of wastewater treatment, the extracted sludge is recycled to the aeration process of the wastewater treatment;
Suitably, the amount of recirculation is greater than or equal to the amount that would otherwise be required to be withdrawn to prevent disturbances caused by the rotating scraper blades without sludge withdrawal by the apparatus of the invention. It is. Preferably, the shape of the scraper blade is such that it counteracts disturbance initiation and the flow regime is such that it forms a laminar boundary layer.

Boundary layer separation can be prevented (and thus disturbances are also reduced or prevented) by a proper combination of vane shape, suction position and suction amount. Preferably, the scraper blade is shaped like an aircraft wing. In some applications, only a portion of the scraper blade may be shaped like an aircraft wing, while the remaining portion (e.g., the low-velocity section in the center of the clarification vessel) may simply be a simple pipe(s) or conduit. By doing so, you can save costs. Therefore, in such cases only a portion of the scraper blade is hydrodynamically designed to prevent boundary layer separation. The openings provided in the scraper blades may be of any suitable shape, for example holes or preferably slots.

When the scraper blade is shaped like an aircraft wing, it is appropriate for the sekiguchi to be located behind the blade in the direction of rotation. The cross-sectional area of the scraper blades is selected such that the internal sludge flow velocity towards the central removal location is between low velocities that cause settling/clogging problems and high velocities that cause excessive pressure drops.

The size of the airfoil inlets (e.g., one or more slots) is such that the pressure drop across the slots is sufficiently high that the flow through the slots is not significantly affected by internal lateral sludge flow. Calculated. The cross-sectional area of the airfoil as defined above is determined by selecting the appropriate height and/or longitudinal dimensions of the airfoil. Their dimensions do not necessarily have to be constant over the entire length of the wing.
Suitably, the mechanical configuration of the scraper is as follows: 'a' All motion torque is provided from the central pivot (or peripheral suspension).

That is, the structural strength is sufficient for this purpose. When the wing is an aircraft airfoil, steel or high strength members may be provided at certain locations within the wing to take up the overall strain. (b
} Part or all of the wing can be molded in the form of a hollow molded part.

Such hollow members can be molded, for example, from high-strength plastic materials, with as few obstructions as possible, such as ribs, to avoid internal blockage problems. 'c} A wheel or slide may be provided to take the weight of the vane and move over the bottom of the clarification vessel.

The wing may be suspended at its outer periphery, but this is less preferred. [d' Closures, for example slots, may be subdivided and multiple incoming sludge streams may be transported separately within the blade.

(e) An appropriate method for automatically cleaning the slot intermittently or continuously can be adopted.

'f} The scraper of the invention can be used in conjunction with a simple device for deflecting and scraping large objects on the bottom of a clarification vessel. The speed at which the scraper blade rotates is 0.3
~3 melon h/min (1-100 ft/min), especially 0.9
Preferably, it is within a range corresponding to a circumferential speed of 3 to 40 feet/minute. The scraper of the invention can additionally be used in rectangular clarification vessels.

The scraper of the invention has the following advantages.

'i} Compared to conventional scrapers, it can rotate faster without unduly disturbing the sludge sediment layer. 'i
i} Even in a large clarification device, only one blade makes it possible to return the sludge to the aeration process very quickly.

{iii) It has a simple configuration.

Ribs Because the apparatus of the present invention uses a simpler mechanical configuration and support mechanism, it is less expensive than conventional scraper arm mechanisms.

[Brief explanation of the drawing]

Figures 1-4 are cross-sectional views of four different scraper blade configurations, each with a flow pattern around the periphery indicated by the arrows. In Figure 4, two openings □ are placed at the same position,
In addition to multiple holes at a particular location, multiple locations are shown to be satisfactorily usable. 1: Hollow scraper blade, 2: Sekiguchi. FIG. 1. FIG.2. FIG. 3. FIG. M.

Claims (1)

[Claims] 1. (i) A container in which a mixture of liquids or a mixture of liquid and solid particles is divided into layers with different densities and allowed to settle; and (ii) a layer with a larger density. a device for drawing material from a container, the device comprising: (a) disposed in a greater density layer and rotatably mounted about an axis of the container; (b) means for discharging material drawn into said hollow wing from said container. Separation device as described above, characterized in that said at least one wing has an aircraft wing-like cross-section, thus reducing disturbances of the container contents caused by rotation of the wing about said axis. 2. Separation device according to claim 1, characterized in that at least one opening in the hollow blade is located aft of the leading edge of the blade. 3. The separation device according to claim 1 or 2, characterized in that the hollow wing is provided with openings at at least two different positions in its aircraft wing-like cross section.