JP2000254549A - Centrifugal separation apparatus provided with chemical injection means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal separation apparatus provided with a chemical injection means capable of decreasing the chemical injection ratio. SOLUTION: This centrifugal separation apparatus 1 separates raw sludge into a dewatered cake and a separated liquid by stagnating the sludge between an outer shell bowl 2 and an inner shell screw 4 by utilizing the rotation difference of them. The raw sludge is supplied to a sludge supply chamber 6 of an inner shell screw 4 through a sludge supply pipe 7 and at the same time, a chemical such as a flocculant is to be injected to the raw sludge in the sludge supply chamber 6 from chemical releasing holes 20 of a chemical injection pipe 8. The tip end of the chemical injection pipe 8 is closed and a plurality of the chemical releasing holes 20 are formed in the outer circumferential part in the periphery of the tip end part of the chemical injection pipe 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the injection of a chemical such as a flocculant used for efficiently recovering solids in solid-liquid separation of raw sludge at a sewage treatment plant or a sewage treatment plant. And a centrifuge provided with the chemical injection device.

[0002]

2. Description of the Related Art FIG. 3A is a schematic front view showing a main part of a conventional centrifugal separator in a cross-sectional view.
FIG. 3B is an enlarged view of an AA arrow showing an opening of the composite pipe in the centrifuge shown in FIG. In the figure, reference numeral 1 denotes a centrifuge. The centrifugal separator 1 includes a rotatable outer bowl 2, a main motor (M / M) 3 for rotating the outer bowl 2 around the axis, and the outer bowl 2.
Inner screw 4 arranged coaxially in the inside, and forward and reverse rotation of the inner screw 4 around the axis (directions of arrows B and C)
Back drive motor (B / M) 5 for providing the sludge, a sludge supply chamber 6 provided in the inner screw 4 for receiving raw sludge, and a sludge supply for supplying raw sludge into the sludge supply chamber 6 A pipe 7; a chemical injection pipe 8 arranged coaxially around the outer periphery of the sludge supply pipe 7 for injecting a chemical such as a flocculant for facilitating solid-liquid separation from the raw sludge; And a plurality of communication ports 9 formed on the wall surface of the sludge supply chamber 6 to communicate the sludge supply chamber 6 with the outer trunk bowl 2. That is, the centrifugal separator 1 internally includes a drug injection device having a drug injection tube 8.

[0003] The outer shell bowl 2 is a substantially cylindrical member having a larger diameter at the front (right side in FIG. 3A) than at the rear (left side in FIG. 3A). A pool 2a for sedimenting and separating raw sludge is formed on the inner surface side of the section. This pool 2a is a separation tank for separating and separating raw sludge supplied from the inside of the sludge supply chamber 6 through the communication port 9, and utilizes the centrifugal force generated by rotation of the outer bowl 2 to make the pool 2a. Is moved to the bottom surface of the outer bowl 2, that is, to the inner surface side of the outer bowl 2, and the supernatant liquid is discharged as a separated liquid from a discharge port 10 provided in front of the outer bowl 2.

[0004] The solids that have moved to the bottom side of the pool 2a are dewatered from a discharge port 11 provided behind the outer bowl 2 by a screw 4a spirally provided on the outer peripheral surface of the inner barrel screw 4. Discharged as a cake.

A large-diameter chemical injection pipe 8 is coaxially arranged on and integrated with the outer peripheral portion of the sludge supply pipe 7.
This composite pipe constitutes a double pipe feed pipe. One end (end) of the composite pipe is inserted into the sludge supply chamber 6, and the other end of the sludge supply pipe 7 is connected to a sludge supply pump (not shown) and a sludge storage tank (not shown), The chemical injection pipe 8 is connected to a chemical storage tank (not shown). The supply port 7a of the sludge supply pipe 7 and the injection port 8 of the chemical injection pipe 8 constituting the composite pipe thus configured.
3a is concentric as shown in FIG. 3 (b), and the raw sludge and the chemical are respectively discharged substantially in the axial direction of the pipe.

Reference numeral 12 denotes a gear box interposed between the outer body bowl 2 and the inner body screw 4 and the back drive motor 5 for changing the rotation direction and the rotation speed of the inner body screw 4. . When the rotation speed of the outer shell bowl 2 is kept constant, the speed difference between the two can be appropriately adjusted by changing the rotation speed of the inner screw 4 with the gear box 12.

Next, the operation will be described. When the sludge dewatering process is started, the raw sludge stored in the sludge storage tank (not shown) is supplied to the sludge supply pipe 7 by a supply pump (not shown).
Is supplied to the sludge supply chamber 6 in the inner screw 4 of the centrifugal separator 1 of the centrifugal separator 1 and a chemical for coagulating the raw sludge is coaxial with the sludge supply pipe 7 from a chemical storage tank (not shown). The sludge is discharged toward the raw sludge via the chemical injection pipe 8 provided. The mixture of the raw sludge and the chemicals is retained in the pool 2a and separated into solids (SS) and water that have been agglomerated by the chemicals. At this time, sedimentation of solids in the mixture is promoted by centrifugal force generated by the rotational force of the outer bowl 2. The separated liquid is discharged from the discharge port 10, and the solid content is separated and dewatered, and is discharged from the discharge port 11 as a dewatered cake.

In such a centrifugal separator 1, the smaller the difference between the rotation speeds of the outer shell bowl 2 and the inner shell screw 4, the longer the sludge residence time, the lower the water content of the dewatered cake. However, the SS recovery rate deteriorates. On the other hand, as the differential speed increases, the residence time of the sludge decreases, and conversely, the SS recovery rate improves, but the water content of the dewatered cake increases.

[0009]

The performance of such a centrifugal separator 1 depends on the state of sludge and the amount of chemical injection, and the cost of chemicals such as flocculants is particularly high.
At present, it occupies a large weight of about 70 to 80% of the running cost. For this reason, in the field of sludge treatment technology, there is a strong demand for technology development for reducing the chemical injection rate. This chemical cost can be reduced by efficient mixing (reaction) of the raw sludge and the chemical, and there is a need for further mixing efficiency.

Under these circumstances, the conventional centrifugal separator 1 shown in FIGS. 3 (a) and 3 (b) will be examined again. The pipe 8 is integrated and integrated, and the supply port 7a of the sludge supply pipe 7
The injection port 8a of the chemical injection tube 8 is concentric.
Therefore, the chemical is released along the substantially axial direction of the chemical injection pipe 8 in the same manner as the raw sludge. In the above configuration, the sludge supply chamber 6 rotates with the rotation of the inner body screw 4 to increase the contact chance. However, there is a problem that the chemical cannot sufficiently contact the raw sludge in the sludge supply chamber 6.

FIGS. 4A and 4B show another example of a conventional composite pipe described in, for example, Japanese Patent Application Laid-Open No. 10-5627. FIG.
(B) is an enlarged view taken along the line AA of (a). In the composite pipe of this example, a small-diameter chemical injection pipe 8 is arranged coaxially in a sludge supply pipe 7, contrary to the conventional composite pipe shown in FIGS. 3 (a) and 3 (b). The direction of release of the chemical to the raw sludge is substantially along the axial direction of the chemical injection pipe 8 as in the conventional composite pipe. Therefore, in the case of this composite pipe, similarly to the composite pipe shown in FIGS. 3A and 3B, there is a problem that the chemical can be brought into contact with only a part of the raw sludge in the sludge supply chamber 6. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is applicable to the above-described centrifugal separator, and has a centrifugal separator provided with a chemical injection means capable of reducing a chemical injection rate. The purpose is to get the machine.

[0013]

According to the present invention, there is provided a centrifugal separator provided with a chemical injection means, comprising: a rotatable outer shell bowl;
An inner screw rotatably disposed coaxially in the outer bowl; a pool formed between the inner screw and the outer bowl; and a pool provided in the inner screw. It has a sludge supply chamber, a sludge supply pipe for supplying raw sludge to the sludge supply chamber, a communication port communicating the sludge supply chamber with the pool, and a chemical injection means for injecting a chemical into the sludge supply chamber. In a centrifuge provided with a chemical injection means, the chemical injection means is provided with a chemical injection pipe disposed in the sludge supply chamber, and is provided on a circumference of the chemical injection pipe and discharges the chemical into the sludge supply chamber. And a plurality of drug release holes.

Further, the sludge supply pipe may be provided inside the chemical injection pipe, and the chemical discharge hole may be provided on the outer periphery near the tip of the chemical injection pipe.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. 1 (a), 1 (b) and 1 (c) are views showing a configuration of a centrifuge according to Embodiment 1 of the present invention, wherein (a) is a front view and (b) is a sludge supply. It is a front view showing composition of a compound pipe which consists of a pipe and a medicine injection pipe, and (c) is an AA arrow view of (b). In addition,
In the components of the first embodiment, the same reference numerals are given to the same components as those of the conventional centrifuge or the chemical injection device shown in FIGS. 3 and 4, and the description of the components is omitted. I do.

The first embodiment is characterized in that a tip end of a chemical injection pipe 8 arranged on an outer peripheral portion of a sludge supply pipe 7 is closed, and a plurality of chemical discharge holes 20 are formed in an outer peripheral portion near the distal end portion. Are formed at equal intervals.

The inside diameter of the sludge supply pipe 7 is in the range of about 15 to 80 mm, and the inside diameter of the chemical injection pipe 8 coaxially arranged on the outer periphery of the sludge supply pipe 7 is in the range of about 20 to 100 mm. It is preferable to use SUS304, which is excellent in corrosion resistance, as a material for forming both tubes. The number of the drug release holes 20 is in a range of about 2 to 8, and the shape may be any of a circle, a rectangle, and the like. The diameter of the drug release hole 20 is appropriately determined in consideration of physical properties such as the viscosity of the drug, the amount of sludge supplied, the sludge treatment performance of the centrifugal separator 1, and the like, and is in a range of about 2 to 10 mm. Further, the chemical release hole 20 has a range of about 5 to 200 mm from the opening end of the sludge supply pipe 7. The dewatering performance of the centrifuge 1 is 0.8 to 100.
m ³ / hour. The sludge concentration of the raw sludge supplied to such a centrifuge 1 is 0.8 to 3.0% (8000 to 30%).
000 mg / L), and the concentration of the polymer flocculant as a chemical to be injected into the raw sludge is usually 0.1 to 0.3%, and the injection amount is 0.04 to ³⁰ m ³ / hour. is there.
The chemical injection ratio, which is the injection ratio of the chemical to the raw sludge, is 0.1%.
4 to 3.0%. Although the chemical injection pipe 8 is provided coaxially with the sludge supply pipe 7, both pipes do not necessarily need to be provided coaxially.

Next, the operation will be described. As shown in FIG. 1A, raw sludge is supplied into a sludge supply chamber 6 via a sludge supply pipe 7, and chemicals are supplied to a plurality of chemical injection pipes 8 provided on an outer peripheral portion of the sludge supply pipe 7. The radially outward of the chemical injection pipe 8 from the chemical discharge hole 20 is radially discharged toward the raw sludge in the sludge supply chamber 6. That is, the distal end of the chemical injection tube 8 is closed, and instead, a plurality of small-diameter chemical discharge holes are provided on the outer peripheral surface. Often,
It is released in multiple directions. This greatly increases the chance of contact of the chemical with the raw sludge and sufficiently mixes the raw sludge and the chemical, thereby promoting solid-liquid separation of the raw sludge. The supernatant liquid overflows from the pool 2a of the outer bowl 2, and is efficiently discharged as a separated liquid from the discharge port 10,
The dewatered cake is discharged from the discharge port 11 by the screw 4a of the inner screw 4.

By providing the above-described drug release hole 20 in the drug injection pipe 8 as described above, the drug is supplied to the drug injection pipe 8.
Can be released in a direction that intersects (orthogonal in this case) the axis of the wastewater, and the chemicals can be efficiently diffused into the raw sludge. The rate level can be maintained.

Embodiment 2 In the above embodiment, FIG.
As shown in (b), a configuration in which the sludge supply pipe 7 and the chemical injection pipe 8 are combined and integrated is adopted.
In this case, the sludge supply pipe 7 and the chemical injection pipe 8 may be provided separately, and both ends may be inserted into the same sludge supply chamber 6. In this case, the inner diameter of the chemical injection pipe 8 is 5
The range is about 50 mm, preferably 10 mm.

Embodiment 3 The chemical injection tube 8 can be configured to be able to move forward and backward along the axial direction. By using such a chemical injection pipe 8 which can move forward and backward, it becomes possible to uniformly inject the chemical into the raw sludge supplied into the sludge supply chamber 6, and further reduce the chemical injection rate. Can be planned. The forward / backward movement may use hydraulic pressure, pneumatic pressure, or the like, or may employ an electric type. In addition, a reaction force of drug release may be used by using an elastic material.

Embodiment 1 FIG. Solid-liquid separation of raw sludge was performed using the centrifuge 1 having the structure shown in FIGS. 1 (a) to 1 (c).
In the centrifuge 1, the inner diameter of the sludge supply pipe 7 is set to 20 mm.
And the inner diameter of the chemical injection tube 8 is 30 mm, and the inner diameter is 3 mm
10 mm from the opening end of the sludge supply pipe 7
Four were formed at the position of. The dewatering performance of the centrifuge 1 was 1 m ³ / hour. The sludge concentration of the raw sludge supplied to such a centrifuge 1 is 1.0% (1000%).
0 mg / L). 0.1% polymer flocculant concentration
And the injection rate was 0.04 to 0.12 m ³ / hour. Chemical injection rates ranged from 0.4 to 1.2%.

On the other hand, in the conventional centrifugal separator shown in FIGS. 3A and 3B, the sludge supply pipe 7 has an inner diameter of 20 m.
m and the inner diameter of the drug injection tube 8 is set to 30 mm, and the drug is released along the substantially axial direction of the drug injection tube 8 in FIG.
It was the same as the centrifuge of the present invention shown in (a) and (b).

The SS recovery rate and the water content of the dehydrated cake were measured, and the results are shown in FIG. FIG. 2 is a characteristic diagram of the centrifugal separator 1 in which the ordinate represents the SS recovery rate (%) and the water content (%) of the dehydrated cake, and the abscissa represents the chemical injection rate (%). In FIG. 2, a line including a white circle indicates the result of the present embodiment, and a line including a black circle indicates the result of the conventional example.

As is apparent from FIG. 2, when achieving the same SS recovery and water content of the dewatered cake, the case of this embodiment requires less than the conventional example, and specifically, about 10%.
% Reduction can be achieved.

[0026]

As described above, according to the present invention, by providing the chemical injection hole in the chemical injection pipe of the chemical injection means, the raw sludge in the sludge supply chamber is vigorously and vigorously multi-directionally applied to the sludge supply chamber. Since the chemical is injected, the chemical and the raw sludge can be efficiently mixed. Further, since the chemical and the raw sludge react sufficiently, there is an effect that the conventional SS recovery rate and the conventional moisture content of the dewatered cake can be maintained even with a small chemical injection rate. Therefore, the cost of chemicals, which accounted for most of the running cost of the centrifuge, can be reduced, and sludge treatment can be performed at low cost. Further, according to the present invention, since the chemical injection pipe and the sludge supply pipe are combined and integrated, the space of the apparatus can be saved.

[Brief description of the drawings]

1 (a), 1 (b) and 1 (c) are diagrams showing a configuration of a centrifuge according to Embodiment 1 of the present invention,
(A) is a schematic front view in which a part is viewed in cross section, (b) is a front view showing a configuration of a composite pipe including a sludge supply pipe and a chemical injection pipe, and (c) is an A in (b). FIG.

FIG. 2 is a characteristic diagram of a centrifuge in which the ordinate represents the SS recovery rate (%) and the water content (%) of the dehydrated cake, and the abscissa represents the chemical injection rate (%).

FIG. 3A is a schematic front view in which a part of the configuration of a conventional centrifuge is shown in cross section, and FIG. 3B is an opening of a composite pipe in the centrifuge shown in FIG. A indicating the part
FIG.

4A and 4B show another example of a conventional composite pipe, where FIG. 4A is a front view, and FIG. 4B is an enlarged view of A in FIG. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Centrifuge 2 Outer bowl 2a Pool 3 Main motor 4 Inner screw 4a Screw 5 Back drive motor 6 Sludge supply chamber 7 Sludge supply pipe 7a Supply port (sludge supply pipe) 8 Chemical injection pipe 8a Inlet (chemical injection pipe) 9) Communication port 10, 11 Outlet port 12 Gear box 20 Chemical release port

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D037 AA12 BA28 BB09 CA08 4D057 AA11 AB01 AC01 AC06 AD01 AE03 AF05 BC07 4D059 AA03 BE38 BE53 BE54 BE56

Claims (2)

[Claims] A rotatable outer bowl, and an inner barrel screw rotatably disposed coaxially within the outer bowl;
A pool formed between the inner body screw and the outer body bowl, a sludge supply chamber provided in the inner body screw, a sludge supply pipe for supplying raw sludge to the sludge supply chamber, In a centrifugal separator provided with a communication port for communicating a sludge supply chamber with the pool and a chemical injection means for injecting a chemical into the sludge supply chamber, the chemical injection means includes: Centrifugal provided with a chemical injecting means, comprising: a chemical injecting pipe disposed in the pipe; and a plurality of chemical discharging holes provided on a circumference of the chemical injecting pipe and discharging the chemical into the sludge supply chamber. Separator. 2. The method according to claim 1, wherein a sludge supply pipe is provided inside the chemical injection pipe, and a chemical discharge hole is provided on an outer periphery near a tip end of the chemical injection pipe. A centrifuge equipped with a chemical injection means.