JPS6044006A - Separation of fine particle in suspension - Google Patents

Abstract

PURPOSE:To attain to miniaturize a flocculative precipitation apparatus, by relatively moving a suspension and columnar matter to generate a Karman vortex in the suspension behind the columnar body, and performing flocculation of fine particles in the suspension by a simple addition apparatus. CONSTITUTION:A flocculant (e.g., a high-molecular flocculant) is added to raw water entering through an inlet 1 from a nozzle 2 and columnar matters 4 are set in a flowline formed by flow inhibiting plates 3 at appropriate intervals so as to prepare for the attenuation of a Karman vortex C and to be capable of repeatedly generating the Karman vortex. In this state, flocs are flocculated in the vortex C, densely compacted and rapidly precipitated during the passage of a fluid A through the flowline and the formed sludge is discharged from the sludge withdrawing port 6 provided to the lower part while supernatant treated water is obtained from a fluid outlet 5. When fine particles in raw water are solid particles, the density of formed flocs becomes high and the succeeding dehydrating operation is made favorable.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating fine particles in suspensions, such as sludge separation and oil separation in water, sewage and industrial waste liquids.

Conventionally, various flocculation/sedimentation devices have been used to separate fine particles in this type of suspension, but coagulation and sedimentation takes time, the density of the flocs produced is small, and equipment is required. It had the disadvantage of being large.

The present invention aims to downsize the flocculation/sedimentation apparatus by making it possible to flocculate submerged fine particles with high efficiency using a simple additional device. The purpose of this invention is to make the dehydration operation more advantageous.

In order to achieve this objective, the inventors conducted repeated research, and based on the findings obtained at that time, the present invention was made.

That is, first, the present invention was made by paying attention to the following phenomenon.

(1) When a flow hits a columnar object A (bluff body) such as a cylinder in the Reynolds number range of about 60 to 5000, a regular phenomenon called Karman vortex 0 occurs behind the object as shown in Figure 1. A certain two-row partial sequence is formed, and the vortex generation cycle N is 0.2 V/D (V is the relative velocity of the object and the fluid, D
is the equivalent diameter of the cylinder) and excite the fluid.

(2) Since the center of the vortex causes a rapid pressure drop, the fine particles in the liquid are attracted to the center of the vortex due to the pressure difference and are pressed together at the same time.

Since Reynolds number: Re-DV/ν (ν is the dynamic viscosity coefficient of the fluid), the equivalent diameter of the columnar object and the relative velocity between the liquid and the object are appropriately selected to obtain the above-mentioned Karman vortex 0. It is easy to match the occurrence conditions.

The Karman vortices 0 that occur one after another behind the columnar object and the person gradually attenuate while moving at a slower speed than the fluid, but during this time, the fine particles in the liquid are attracted to the low-pressure vortex center and rapidly aggregate. At the same time as they grow, the solid particles are pressed together by the acceleration caused by the rapid pressure drop at the vortex core, so the density of the generated floc increases.

That is, the synergistic effect of the rapid growth of the particles and the increase in their density significantly increases the sedimentation speed of the flocs, so that not only the flocculating device but also the settling device can be downsized.

Furthermore, the increased density of the produced flocs has the advantage that the dewatering operation at the rear end is also advantageous.

Furthermore, the particles vibrate due to the excitation effect of the fluid due to the Karman vortex, so the #! Nests are also slightly promoted.

Since the arrangement of columnar objects (bluff bodies) that move relative to the fluid is simple, according to the present invention, fine particles in suspension can be agglomerated with high efficiency using a simple additional device as described above. It has a wide range of applications in wastewater treatment and other liquid treatment industries, such as making it possible to make a coagulation/sedimentation device into a shed and, in the case of solid particles, also advantageous for dewatering at the rear end.

In the present invention, a suspension liquid and a columnar object are moved relative to each other, a Karman vortex is generated in the suspension liquid behind the columnar object, and suspended fine particles are agglomerated! This is a method for separating fine particles in a suspension.

Embodiments of the present invention will be described with reference to the drawings.

Figure 2 shows an example of the baffle plate system, where (a) is a plan cross-sectional view;
(b) shows the XX sectional view of (a). Raw water enters from inlet 1, and a flocculant (for example, polymer) is added from nozzle 2 near the inlet. Column-shaped objects 4 are provided in the flow path formed by the baffle plate 3, and are set at appropriate intervals to prepare for attenuation of the Karman vortex and to repeatedly generate Karman vortices. While the fluid passes through the flow path, the flocs are aggregated and consolidated according to the above-mentioned principle, rapidly precipitate, and are discharged from the sludge outlet 6 at the bottom, and treated water (clear water) is released from the fluid outlet 5.
is obtained.

FIG. 3 shows a side sectional view of an embodiment of the inclined plate system. Raw water enters through inlet 1' and flocculant is added through nozzle 2'. Similarly to the above, columnar objects 4' are provided at appropriate intervals in parallel flow paths partitioned by inclined plates 3'. While the fluid moves up the flow path, the flocs rapidly settle as described above, slide on the upper surface of the inclined plate 6' and are discharged from the lower sludge outlet 6', and the treated water is taken out from the fluid outlet 5'.

Figure 4 shows an example of the stirring method, (a) is a side sectional view, (b)
) shows a y-y cross-sectional view of (a). In the case of the stirring method, a columnar object is moved to generate a relative velocity with the fluid. Raw water enters through an inlet 1'', a flocculant is added through a nozzle 2'', and the raw water is led to a flocculation chamber surrounded by an inner cylinder 6''.

Inside the coagulation chamber, columnar units 4'' arranged concentrically are rotated by a drive machine 7.

In this case, the speed ■ is proportional to the installation radius r of the columnar object 4''.
changes, so we aim to match the frequency of the Karman vortices and also aim for the external particle aggregation effect due to the excitation action.
It is best to keep the vibration frequency N and 0.2V/D constant (Figure 4 (
b)). In the flocculation chamber, the flocs are flocculated and consolidated according to the above-mentioned principle by the Karman vortices generated behind the columnar objects 4'', and rapidly settle, and are discharged from the sludge outlet 6'' at the bottom of the outer tank 8. The treated water overflows from the upper edge of the outer cylindrical tank 8 and is taken out from the fluid outlet 5''.

An example of sewage treatment has been described above as an example of separation of solid particles in a liquid, but oil in water can also be agglomerated according to the above principle in the case of separation of oil from oil-containing wastewater as an example of liquid-liquid separation.

In this case, the flocs of coagulated oil are lighter than water, so they are floated and removed.

According to the present invention, fine particles in a liquid can be agglomerated with high efficiency,
It is possible to provide a method for separating fine particles in a suspension, which reduces the size of the apparatus and increases the density of generated flocs for solid particles, thereby reducing the burden on rear equipment, which is extremely effective in practice.

[Brief explanation of the drawing]

-7- Figure 1 is a detailed explanation of the principle of the present invention, Figure 2 is an embodiment of the baffle plate system, (a) is a plan sectional view, and (b) is
A cross-sectional view, FIG. 3 is a side cross-sectional view showing an example of the inclined plate method,
Figure 4 shows an example of the stirring method, (a) is a side sectional view, (b)
is a YY sectional view. 1.1', 1"...inlet, 2.2', 2"...nozzle, 6... baffle plate, 6'... inclined plate, 6"... inner cylinder, 4. 4', 4"...columnar object, 5.5', 5"
...Fluid outlet, 6, 6', 6"...extraction port. Patent applicant: Ebara Corporation Representative Patent Attorney: Tadashi Takagi; Patent Attorney: 1,111) Twisting Patent Attorney: Takao Maruyama, JP-A GO-44006 (3)

Claims (1)

[Claims] t. Fine particles in a suspension, which is characterized in that the suspension and a columnar object are relatively moved to generate a Karman vortex in the suspension behind the columnar object to aggregate the suspended particles. Separation method.