JPH024321B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is a method of flocculation for flocculating colloid particles by adding an inorganic flocculant and an organic polymer flocculant to a suspension, and then separating the colloid particles by sedimentation. This relates to a precipitation device.

[Prior art] In general, a coagulation-sedimentation device is composed of a flocculant mixing section, a floc growth section, and a solid-liquid separation section, and can be used in various devices, including those in which each part is independent or integrated. has been commercialized. Among these, what is called a granulation and sedimentation device has the advantage of being able to achieve a sedimentation separation rate 5 to 10 times that of other devices, and as a result, its installation area is significantly smaller.

Granulation and precipitation equipment usually consists of a flocculant mixing tank and a solid-liquid separation tank.Inorganic flocculants and organic polymer flocculants are added in the flocculant mixing tank, and then transferred as fine flocs to the solid-liquid separation tank. floc growth and solid-liquid separation are performed simultaneously. In this case, according to granulation theory, the stirring blades provide an appropriate stirring action under the upward flow, so that the flocs become denser and the denser flocs come together, resulting in pelletization (granulation) and sedimentation. It is explained that the separation speed increases.

The solid-liquid separation tank of a conventional granulation and precipitation apparatus is as shown in FIG. 1, in which a liquid to be treated 1 is introduced from the bottom of the tank and is separated into solid and liquid while forming an upward flow.
The pellet group remains in the tank and forms a pellet blanket layer, and the pellet group is discharged from an outflow pipe 8 provided at the upper end of the pellet blanket layer by a timer, an interface detector (not shown), etc. This is done intermittently.

In Fig. 1, numeral clarifier, pellet generator, 2 inflow pipe for liquid to be treated, 3 draft tube, 4 rotating shaft, 5 stirring blade, 7 scraper,
Reference numeral 9 indicates a pellet group, 10 indicates a clear water outflow pipe, 11 indicates clear water, and 12 indicates a motor with a speed reducer.

However, in the solid-liquid separation tank in conventional granulation and precipitation equipment, sufficient consideration has not been given to the concentration process of the pellet group, and it is necessary to install a separate concentration tank for concentration, and furthermore, the raw water SS When the amount exceeds 1000mg/, the concentration tank may have a larger capacity than the solid-liquid separation tank.
The advantage of the granulation and sedimentation equipment, which is that the installation area is small, has often been lost. In addition, if good flocculation conditions cannot be obtained due to extreme fluctuations in raw water quality or the failure of the flocculant injection pump due to an accident, contaminants (colloids in the raw water) Not only does the mixture of particles and hydroxide produced by injecting an inorganic flocculant get mixed into the treated water, but also, as is the fate of the blanket type, the pellets that have been formed (blanket layer) also flow out. There were some shortcomings.

[Purpose of the invention]

An object of the present invention is to eliminate these conventional drawbacks, expand the range of application of the granulation and precipitation apparatus, and provide a solid-liquid separation apparatus that can be easily maintained and managed.

[Structure of the invention]

In the present invention, a draft tube that communicates with a raw water inflow pipe is fixedly provided near the center of the upper part of the tank, which has a treated water outflow section at the top and a sludge discharge section at the bottom, and horizontally rotatable stirring is provided in the draft tube. Wing A
are arranged in multiple stages, and stirring blades B having a diameter longer than the diameter of the tube are arranged in multiple stages directly below the draft tube so as to be rotatable in the horizontal direction, and furthermore, a blocking plate is arranged in the horizontal direction below the draft tube. This is a solid-liquid separation device.

The most important consideration in the present invention is to organically combine the pelletizing function of the floc and the concentrating function of the pellet based on granulation theory. In other words, an inorganic flocculant and an organic polymer flocculant are added in a flocculant mixing tank to form fine flocs, and the treated liquid is pelletized in a solid-liquid separation tank, and the characteristics of the resulting pellets are utilized. It is a matter of rational concentration. In addition to this, the present invention is designed to enable pellet generation without forming a blanket layer.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS. 2 and 3. In the upper part, there is treated water, ie, clear water 31.
An outflow pipe 30 for thickened sludge 37 at the bottom, an outflow pipe 36 for thickened sludge 37 at the bottom
A draft tube 23 that communicates with the inflow pipe 22 for the raw water, that is, the liquid to be treated 21, is fixedly arranged in the vertical direction near the center of the upper part of the tank 38 having a tank 38.
A rotating shaft 24 is provided passing through the draft tube 23 and along its center line.
A stirring blade 25 as the stirring blade A, a stirring blade 26 as the stirring blade B, a blocking plate 34, a picket fence 35, and a scraper 27 are disposed on the rotating shaft 24 in order from above to below, and a motor with a speed reducer 32 allows for integral rotation in the horizontal direction.

The stirring blades 25 have a flat plate shape or other shape having a granulating action, and are provided in the draft tube 23 in multiple stages in the vertical direction. The stirring blade 2
The shape and function of the stirring blades 6 are substantially the same as those of the stirring blades 25, but the diameter of each blade is longer than the diameter of the draft tube 23, and they are provided directly below the draft tube 23 in multiple stages in the vertical direction.

Each of the stirring blades 26 is provided with an annular member 33 ₁ in the shape of a truncated inverted cone according to the mounting procedure shown in FIG.
Although the annular members 33 ₂ and 33 ₃ are arranged so as to surround the rotating shaft 24 and concentrically with the rotating shaft 24, only the annular member 33 ₁ located at the innermost position may be provided.
In any case, the opening area of the upper end opening of this annular member 33 ₁ is made larger than the opening area of the lower end opening of the draft tube 23 so that the liquid flowing out from the draft tube 23 can smoothly descend inside the annular member 33 ₁ . It is preferable to make it moist.

The blocking plate 34 is a circular plate having an area larger than the opening area of the lower end opening of the draft tube 23, and is provided in the horizontal direction.
It is more preferable that the opening area be larger than the opening area of the lower end opening of the annular member 33 ₃ located at the outermost position. Note that a plurality of strip plates may be arranged radially and horizontally. That is, the blocking plate 34 may be of any type as long as it is capable of blocking at least a portion, preferably substantially the entire amount, of the liquid to be processed flowing out of the draft tube 23 and converting the flow direction into an upward flow. It may be fixed to the side wall of the tank 38 so that it cannot rotate.

Furthermore, the stirring blades 25 and 26 may be provided on separate rotating shafts and rotated at different rotational speeds, or both stirring blades and the picket fence may be provided on separate rotating shafts so that the rotational speeds of the three are different from each other. You can also do that.

In FIG. 2, numerals and numerals indicate the same elements as in the conventional example of FIG. 1, and numerals indicate a concentrating section, respectively.

Next, the operation of this embodiment will be explained. The liquid to be treated 21 in which fine flocs have been generated passes through the inflow pipe 22 and reaches the draft tube 23. A stirring blade 25 is rotating slowly inside the draft tube 23.
The inflow energy of the liquid to be treated flowing in from the inflow pipe 22 is made uniform, and while the liquid to be treated descends in the draft tube 23, a uniform downward flow velocity is given to the liquid to be treated. That is, it is important that the stirring blade 25 rotates slowly, and although it changes depending on the shape of the stirring blade, it is generally appropriate to set the circumferential speed to 1 m/s or less. On the other hand, if the rotational speed of the stirring blades 25 is high, not only will a swirl flow occur in the draft tube 23, but it will also inhibit pelletization, which is not preferable.

The liquid to be treated, which has been given a uniform downward flow velocity in this way, passes through the stirring blades 26 and the annular member 33, and
It collides with the blocking plate 34 while maintaining a uniform downward flow velocity. The blocking plate 34 converts the downward flow into an upward flow and forms a boundary with the concentration section. Therefore, it is preferable to make the cross-sectional area larger than the draft tube 23 so as not to cause turbulence in the water flow to the concentration section. Furthermore, it is desirable to provide a rotational speed difference between the blocking plate 34 and the stirring blades 26 to prevent pellets from accumulating on the blocking plate 34, but in order to do this, the blocking plate 34 should not be rotated. Alternatively, the blocking plate 34 may be attached to a rotating shaft different from the rotating shaft 24.

Now, the liquid to be treated that has been converted into an upward flow by the blocking plate 34 flows onto the outer peripheral surface of the annular member ₃₃₁ .
₂ , 33 ₃ rises toward the outer periphery along the inner peripheral surface or outer peripheral surface of 3. At this time, since the stirring blades 26 are rotating, a shearing force acts on the upward flow, making it possible to equalize the uneven flow.

That is, the flow of the liquid to be treated, which was a downward flow in the draft tube 23, is changed to
The components of the annular member and the stirring blades 26 result in a uniform upward flow velocity in the clarifying section.

By the way, the stirring blades 26 play another important role in addition to making the uneven flow uniform. It is the pelletization of agglomerated flocs. Pelletization, which promotes floc densification and association between flocs, occurs approximately as follows.

When the flow is changed upward by the blocking plate 34 and the annular member, the flow velocity is significantly lower than when the flow is downward. In other words, the stirring force within the fluid decreases rapidly, resulting in a change from what is generally called rapid stirring to slow stirring. Therefore, flocs begin to grow rapidly, but at that time,
Since moderate stirring by the stirring blades 26 is carried out in an upward flow, as the flocs grow, the flocs frequently meet with each other, becoming densified and becoming pellets. Furthermore, since the generated pellets have strong adhesion, they combine with the growing flocs and eventually become pellets with a sedimentation rate of about 500 to 1000 mm/min, which defies the upward flow rate and travels from the pellet generation section to the concentration section. . On the other hand, the clarified liquid to be treated passes through the clarification section and flows out as clear water 31 from the outflow pipe 30 at the upper end. Note that the peripheral speed of the stirring blade 26 is preferably 0.05 to 1.0 m/s. At 0.05 m/s or less, pellets are difficult to form, and at 1.0 m/s, a swirling flow occurs.

On the other hand, since the pellet group that has reached the concentrating section has almost no upward flow velocity, it will settle at the sedimentation speed of the pellet group itself. In conventional granulation and sedimentation equipment, when trying to concentrate a group of pellets, the pellets are often destroyed during the transfer process to the concentration tank, and even if pellets with excellent sedimentation properties are produced, they cannot be concentrated. It was not possible to take advantage of the advantages of pellets in the process.

However, by arranging the concentration section in this way, it becomes possible to utilize the excellent sedimentation properties of the pellets also in the concentration step. It is particularly preferable that a picket fence 35 and a scraper 27 are disposed on the rotating shaft 24 in the lower part of the thickening section to promote thickening and prevent sludge accumulation, and the circumferential speed of the picket fence 35 is 2.
~3 m/min (0.03-0.05 m/s) is suitable.

The thus concentrated sludge is discharged from the system as thickened sludge 37 through the outflow pipe 36.

In addition, in this embodiment, since the raw water inflow pipe is located at the upper part and is open, there is an advantage that maintenance and management are easy.

As described above, the present invention has a completely different concept from the solid-liquid separation tank of the conventional granulation and precipitation apparatus. In other words, in response to the problem of how to perform pellet generation and pellet concentration almost simultaneously in the same tank, the present invention goes back to granulation theory, without being bound by conventional methods, and focuses only on its function. It was born.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) Ultra-high-speed solid-liquid separation is easy because pellets are produced at a sedimentation separation rate of 500 to 1000 mm/min (small installation area).

(2) Highly concentrated sludge can be obtained in a short time because it can be concentrated as pellets (no thickening tank required, small footprint).

(3) Because the discharged sludge is highly concentrated, raw water SS
can be applied even if the amount is 1000 mg/or more (expanded scope of application).

(4) Since there is no blanket layer, even if there is a sudden change in water quantity or water quality and the coagulation state deteriorates, the water quality will not deteriorate significantly (high stability, easy maintenance).

(5) Even though the concentration section is increased, there is no blanket section, so the height of the tank remains the same as the conventional device (compact).

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional example, FIG. 2 is a sectional view of an embodiment of the present invention, and FIG. 3 is a perspective view showing how to attach an annular member. ... Clarifying section, ... Pellet generation section, ...
Concentration section, ... pellet blanket layer, 1, 2
1...Liquid to be treated, 2, 22...Inflow pipe, 3, 23
... Draft tube, 4, 24 ... Rotating shaft,
5,25... Stirring blade, 26... Stirring blade, 7,27
... Scraper, 8 ... Outflow pipe, 9 ... Pellet group, 10, 30 ... Outflow pipe, 11, 31 ... Clear water, 12, 32 ... Motor with speed reducer, 33 ₁ ,
33 ₂ , 33 ₃ ... annular member, 34 ... blocking plate, 3
5... Picket fence, 36... Outflow pipe, 37
...Thickened sludge, 38...tank.

Claims (1)

[Scope of Claims] 1. A draft tube that communicates with the raw water inflow pipe is fixedly provided near the center of the upper part of the tank, which has a treated water outflow section at the top and a sludge discharge section at the bottom, and a draft tube that rotates horizontally within the draft tube. At the same time, stirring blades A are arranged in multiple stages, and stirring blades B having a diameter longer than the diameter of the tube are arranged in multiple stages directly under the draft tube so as to be rotatable in the horizontal direction. A solid-liquid separation device characterized by being equipped. 2. The device according to claim 1, wherein the blocking plate has an area larger than the cross-sectional area of the lower end opening of the draft tube. 3. The device according to claim 1 or 2, wherein the stirring blade B is provided with one or more annular members. 4. Claim 1, wherein a picket fence and a scraper are rotatably arranged below the blocking plate.
2. The device according to item 2, item 3, or item 3.