JPS6348563B2 - - Google Patents

Description

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

[Conventional technology]

Conventionally, various flocculation/sedimentation devices have been used to separate fine particles in this type of suspension.

[Problem that the invention seeks to solve]

However, in the conventional method, there were problems in that coagulation and precipitation took time, the density of the produced flocs was small, and the equipment was large.

The present invention aims to make the flocculation/sedimentation device more compact by coagulating fine particles in a liquid with high efficiency, and in the case of solid particles, the density of the generated flocs is increased to advantageous for the dewatering operation at the rear end. The purpose of the present invention is to provide a method for separating fine particles in

[Means for Solving the Problems] The present invention provides a method for moving a suspension containing a flocculant and a plurality of columnar objects arranged in parallel to each other in a direction perpendicular to the columnar objects. This is a method for separating fine particles in a suspension, which is characterized in that the columnar object is moved to generate a Karman vortex in the suspension behind the columnar object, thereby agglomerating the suspended fine particles.

[Effect]

In order to achieve the above-mentioned object, 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 the Reynolds number is in the range of approximately 60 to 5000, when a flow hits a columnar object A (grab body) such as a cylinder, two regular rows of Karmans are formed behind the object as shown in Figure 1. A vortex train of vortices C is formed, and the vortex generation cycle N is N≒0.2V/D (V is the relative velocity of the object and fluid, D is the equivalent diameter of the cylinder),
Exciting a fluid.

(2) Because 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, coagulate, and at the same time are pressed together.

Regarding these phenomena (1) and (2), the Reynolds number is Re=DV/ν (ν is the dynamic viscosity coefficient of the fluid)
Therefore, by appropriately selecting the equivalent diameter D of the columnar object and the relative velocity V between the liquid and the object, it is easy to control so as to create conditions in which the Karman vortex C is easily generated stably.

The Karman vortices C that occur one after another behind the columnar object A 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, due to the synergistic effect of the rapid growth of particles and the increase in their density, the sedimentation speed of the flocs is significantly increased, so that not only the flocculating device but also the settling device can be downsized.

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

Furthermore, since particles are vibrated by the excitation effect of the fluid by the Karman vortex, aggregation of particles outside the vortex is also slightly promoted.

The present invention utilizes the effect of the Karman vortex, where suction is performed by the pressure drop at the center of the vortex, rapidly agglomerating, growing, and compressing fine particles, and the effect of exciting the fluid through the generation cycle of the Karman vortex. In particular, the generation and maintenance of Karman vortices, which are the driving force behind these actions, are
Playback is now stable.

That is, in the present invention, since the liquid is moved in a direction perpendicular to the columnar object, the Karman vortex can be stably generated.
Additionally, once a Karman vortex is generated and moves downstream (downstream in the flow relative to the columnar object), the central axis of the vortex moves in a direction parallel to the columnar object, but the main axis In the invention, other columnar objects are also parallel to each other, that is, parallel to the axis of the generated Karman vortex, so the axis of the vortex is disturbed in different directions to maintain the Karman vortex without disappearing, and, The axes of the Karman vortices reproduced in the columnar object on the downstream side are all parallel, so Karman vortices with axes in different directions collide, interfere with each other, and disappear, resulting in turbulent flow. Therefore, the generation, maintenance, and reproduction of Karman vortices are always performed stably as vortices with the axis in the same direction.

In this way, the Karman vortex is always maintained in the same direction everywhere in the flow path, so the particles held at the center of the vortex are not actively dissipated and are held at the center of the Karman vortex for a long time. The low pressure in the center of the vortex continues to promote agglomeration and growth, and the solid particles continue to be pressed together, increasing the density of the resulting floc.

Since the arrangement of a columnar object (grab body) that moves relative to the fluid is simple, according to the present invention, fine particles in a 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 miniaturization of coagulation/sedimentation equipment and advantageous dewatering operations at the rear end in the case of solid particles.

〔Example〕

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

FIG. 2 shows an embodiment of the baffle plate system, in which a is a plan sectional view and b is a XX sectional view of a. Raw water is inlet 1
Accordingly, a flocculant (for example, a polymer) is added from the nozzle 2 near the inlet. In the flow path formed by the baffle plate 3, a plurality of columnar objects 4 are provided parallel to each other and perpendicularly so as to be substantially perpendicular to the flow within the flow path. In preparation for the attenuation of the Karman vortices, the columnar objects 4 are set at appropriate intervals so as to repeatedly generate Karman vortices, and are set parallel and perpendicular to each other so as not to disturb the direction of the axis of the generated Karman vortices. be. While the fluid passes through the flow path, the flocs are coagulated and consolidated according to the above-mentioned principle, rapidly precipitate, and are discharged from the sludge outlet 6 at the bottom, and are discharged from the fluid outlet 5.
Treated water (clear water) is obtained from

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'. Similar to the above, a plurality of columnar objects 4' are supported substantially horizontally in parallel to each other and at right angles to the flow, and are provided at appropriate intervals in parallel flow paths partitioned by inclined plates 3'. While the fluid ascends through the flow path, the Karman vortices repeatedly generated by each columnar object 4' promote agglomeration, growth, and compression of fine particles, and as before, the flocs rapidly settle and slide on the upper surface of the inclined plate 3'. The sludge is 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, where a is a side sectional view;
b shows a YY 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 the inlet 1'', adds flocculant through the nozzle 2'', and is surrounded by an inner cylinder 3'' and guided to the flow aggregation chamber.In the aggregation chamber, a plurality of columns arranged vertically in parallel on concentric circles are introduced into the aggregation chamber. The objects 4'' are rotated by the drive machine 7, and the raw water moves relative to each columnar object 4'' in a direction perpendicular to it. In this case,
Since the velocity V changes in proportion to the installation radius r of the columnar object 4'', the diameter D of the columnar object 4'' is r It is preferable to change the frequency N≒0.2V/D and keep it constant (see Figure 4b). In the flocculation chamber, the flocs are flocculated and consolidated according to the above principle by the Karman vortex generated behind the columnar object 4'', and rapidly settle, and are discharged from the sludge outlet 6'' at the bottom of the outer tank 8. Ru. 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 the location of solid particles in a liquid. However, as an example of liquid-liquid separation, for example, in the case of oil separation from oil-containing wastewater, it is possible to coagulate oil in water using the above-mentioned principle. can. In this case, the flocs of coagulated oil are lighter than water, so they are floated and removed.

[Effects of the Invention] According to the present invention, Karman vortices are stably generated by the liquid flowing at right angles to the columnar objects, and Karman vortices are generated because the columnar objects are arranged parallel to each other. The axes of the vortices are all parallel,
The different directions of the axes do not interfere with each other and cause turbulence, which causes the Karman vortex to disappear.The Karman vortex is stably maintained and reproduced, and the particles are retained in the Karman vortex for a long time. A suspension that promotes agglomeration, growth, and compression, highly efficient agglomeration of fine particles in liquid, miniaturizes equipment, and increases the density of produced flocs for solid particles, reducing the burden on rear equipment. The present invention provides a method for separating fine particles in the air, which is extremely effective in practice.

[Brief explanation of the drawing]

Figure 1 is a principle diagram explaining the principle of the present invention, Figure 2 is a diagram explaining the principle of the present invention.
The figures show an example of the baffle plate system, where a is a plan sectional view, b is a XX sectional view, Figure 3 is a side sectional view showing an example of the inclined plate system, and Figure 4 is an example of the stirring system. A is a side sectional view, and b is a YY sectional view. 1, 1', 1"...Inlet, 2, 2', 2"...Nozzle, 3...Break plate, 3'...Slanted plate, 3"...Inner cylinder, 4, 4', 4" ...Columnar object, 5, 5', 5''...
...Fluid outlet, 6, 6', 6''...extraction port.

Claims (1)

[Claims] 1. A suspension to which a flocculant has been added and a plurality of columnar objects arranged in parallel to each other are relatively moved in a direction perpendicular to the columnar objects, so that the suspension liquid behind the columnar objects is moved. A method for separating fine particles in a suspension, which is characterized by generating a Karman vortex therein to agglomerate suspended fine particles.