JP3439591B2 - Chemical mixing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical mixing device provided in a lower / wastewater treatment plant or the like, and more specifically, it introduces concentrated sludge concentrated by gravity dehydration or the like and mixes it with a chemical such as a coagulant. The present invention relates to a chemical mixing device that supplies a mixture to a pressure dehydration section of a belt press type dehydrator.

[0002]

2. Description of the Related Art Sludge produced as a residue in a lower wastewater treatment plant is an aggregate of organic and inorganic substances having a complicated structure, and because of its small particle size and strong affinity with water, it is suitable. It is difficult to separate water by a dehydration operation such as filtration or centrifugation without performing pretreatment.

For this reason, conventionally, a floc capable of gravity dehydration and shearing / squeezing is mainly produced by mixing a flocculant such as a polymer flocculant with the raw sludge, and the produced floc-like sludge is subjected to a belt press type dehydrator. It was sent to and dehydrated.

The belt press type dehydrator is as shown in FIG. 3, and comprises a plurality of rolls R and a belt-shaped filter cloth 1 which travels in the directions indicated by arrows a and b in accordance with the rotation of each roll R. , 2 for concentrating the sludge 3 that is agglomerated and supplied onto the filter cloth 1 until it loses fluidity, and the sludge 3 concentrated in the gravity dehydration section A for the filter cloth 1 ，
A pressure dehydration unit B that performs pressure dehydration while sandwiching between the two and a shear compression unit C that further shear-compresses the sludge 3 dehydrated by the pressure dehydration unit B are provided.

However, in the above-mentioned conventional method, the coagulant is added to the raw sludge all at once, and it is not sufficient to improve the dewatering property of the hardly dehydratable sludge which has been increasing in recent years. Previously proposed a novel sludge dewatering method in JP-A-6-343999. In this method, a high molecular weight cationic polymer flocculant is added to the raw sludge to generate coarse flocs, and the generated coarse floc-like sludge is concentrated by gravity dehydration. A flocculant is added to flocculate the flocculate so that it can be easily dehydrated, and the flocculated sludge is dewatered under pressure.

[0006]

However, as described above, the method itself of adding a polymer flocculant to the concentrated sludge so that the sludge can be easily dehydrated is a novel method, and therefore, it is highly effective as a concentrated sludge. At present, there is no suitable mixing machine for mixing with a molecular flocculant.

[0007] For example, a rotating drum type or agitation tank type mixer mixes sludge with a low concentration (about 1 to 2%) and a polymer coagulant, so that the above-mentioned concentrated sludge (5 to 5%) is mixed. It is difficult to sufficiently mix (about 10%) and the polymer flocculant.

Even if these kneaders are intentionally used, since they are a system in which sludge is discharged from one point, the mixture of the concentrated sludge and the polymer flocculant has a high concentration, so that it is uniform on the filter cloth. However, the filter cloth does not meander and wrinkles, resulting in insufficient dehydration. In particular, in a belt press type dehydrator that spreads the mixture to a width of 3 m, it is inevitable that the filter cloth meanders and wrinkles.

The present invention solves the above problems, and provides a chemical mixing apparatus capable of sufficiently mixing chemicals such as a flocculant with concentrated sludge and uniformly supplying the mixture onto the filter cloth. It is intended to be provided.

[0010]

In order to solve the above problems, a chemical mixing apparatus according to claim 1 of the present invention introduces concentrated sludge concentrated by gravity dehydration or the like and mixes it with a chemical such as a flocculant. And a chemical mixing device for supplying the mixture to the pressure dehydration section of the belt press type dehydrator, wherein the mixture is filtered above the belt-shaped filter cloth on the front side of the pressure dehydration section of the belt press type dehydrator. It consists of a mixing tank provided in the width direction of the cloth, and an agitator provided inside the mixing tank. The mixing tank has a shape in which the cross section in the advancing direction of the filter cloth is widened in a semicircular shape from the bottom toward the upper side. The agitator is provided in the width direction of the filter cloth as the axial direction, and is attached to the shaft portion rotating around the shaft center and the outer peripheral surface of the shaft portion.
After rotating around the axis of the shaft part to stir and mix the concentrated sludge introduced into the mixing tank and the chemicals, the plurality of blades sent out on the filter cloth and the concentrated sludge toward the mixing tank invite
Guided by the chute as an inflow part and the chute
With a chemical addition pipe that adds the above chemicals to concentrated sludge
With the above chemicals added from the chemical addition pipe
While sweeping away thickened sludge those were a structure for dropping around the shaft portion <br/>.

According to a second aspect of the present invention, there is provided the chemical mixing device in which the blade portion of the stirrer is curved so as to project to the front side in the rotation direction. The chemical mixing device according to claim 3 is characterized in that the mixing tank has one side edge portion along the width direction of the filter cloth as a discharge portion for allowing the mixture to flow over the filter cloth, and the concentrated sludge is provided above the discharge portion. Of the agitator, and the blade portion of the stirrer is configured to rotate around the axis of the shaft portion in the direction from the discharge portion to the inflow portion.

According to the above-mentioned structure of claim 1, the concentrated sludge concentrated by gravity dehydration or the like is introduced into the mixing tank together with a chemical such as a flocculant, and is rotated around the axis of the shaft portion. It is fed while being agitated and mixed with chemicals by a plurality of blades, and is discharged over the entire width of the filter cloth on the front side of the pressure dehydration section.

According to the second aspect of the present invention, splashing of concentrated sludge and desorbed liquid by the blade portion of the stirrer is small, and slag and the like contained in the concentrated sludge is removed from the blade portion as the blade portion rotates. Since it moves in a direction away from it, no entanglement with the blade part occurs. Further, while the rotation speed increases as the outer peripheral portion of the blade portion farther from the shaft portion, the curved blade portion reduces the area of the blade portion per constant distance in the radial direction of the shaft portion at the outer peripheral portion. The impingement of the blades on the thickened sludge and chemicals occurs almost equally regardless of the location near the shaft and the location far from the shaft, and the variation in the degree of mixing is small. Further, even if a foreign matter is caught between the inner peripheral surface of the mixing tank and the blade portion, the blade portion moves in the escape direction, so that no breakage occurs.

According to the third aspect of the present invention, the concentrated sludge and the chemicals introduced into the mixing tank through the inflow portion pass through the upper portion of the tank by the blade portion and are closer to the other side edge facing the discharge portion. After being sent to the area, it will be sent to the discharge section, during which it is sufficiently agitated and mixed to be conditioned.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the belt press type dewatering machine has the same configuration as the conventional one described with reference to FIG. 3, and therefore only the main parts are shown, and the members having the same functions as those of the conventional one are denoted by the same reference numerals. A description will be given.

The belt press type dehydrator has a plurality of rolls R.
And the belt-shaped filter cloths 1 and 2 that run in the directions indicated by the arrows as the rolls R rotate, and rolls R ′ and R ″ that adjust the thickness of sludge. The pressure dehydration unit B is arranged below.

Below the gravity dehydration section A and under pressure dehydration section B
At a position on the front side away from the concentrated sludge 4 concentrated in the gravity dehydration section A, the high cationic polymer flocculant and the pH.
A chemical mixing device 7 that introduces and mixes a chemical 5 such as a regulator, and supplies the mixture, the tempered sludge 6, to the pressure dehydration section B.
Is provided.

The concentrated sludge 4 is supplied to the filter cloth 1 as coarse floc-like sludge by adding a chemical such as a high molecular weight cationic polymer flocculant to the raw sludge and stirring and mixing at a slow speed. Free water is separated in the gravity dehydration section A, and the solid matter concentration is 4 to 1 at the end of the gravity dehydration section A.
It is 0%.

As shown in FIG. 2, the chemical mixing device 7 includes a mixing tank 8 provided above the filter cloth 2 in the width direction of the filter cloth 2, and a stirrer 9 provided inside the mixing tank 8. Consists of. The mixing tank 8 is formed in a shape in which the cross section in the traveling direction of the filter cloth 2 is widened in a semicircular shape from the bottom toward the upper side, and from the end of the gravity dehydration section A toward the mixing tank 8 upward. Chute 1 as an inflow part for guiding the flow of concentrated sludge 4
0, and one side edge portion along the width direction of the filter cloth 2 is used as a discharge part 8a for overflowing the tempered sludge 6 in the tank, and the tempered sludge 6 is filtered to the discharge part 8a. 2 Guide plate 11 to guide
have. On top of the chute 10, the chute 10
There is provided a chemical addition pipe 12 for adding the chemical 5 such as the high cation polymer flocculant to the concentrated sludge 4 guided by.

The stirrer 9 is provided with the width direction of the filter cloth 2 as the axial center direction, and is attached to the shaft portion 13 that rotates counterclockwise around the shaft center in the figure and the outer peripheral surface of the shaft portion 13. , A plurality of blades 14 rotating counterclockwise around the axis of the shaft 13 from the discharge part 8a to the chute 10.
And a motor 15 for rotating the shaft portion 13 at an appropriate rotation speed according to the amount of the concentrated sludge 4 introduced and the type of the chemical 5.

Each of the blade portions 14 has a curved shape so as to project to the front side in the rotation direction thereof, has a length reaching the vicinity of the inner peripheral surface of the mixing tank 8, and has an outer peripheral surface of the shaft portion 13. The blades 14 are mounted in a substantially tangential direction and at appropriate intervals in the circumferential direction and the axial center direction of the shaft portions 13 of the blade portions 14. The curvature of each blade portion 14 is formed so that the arc radius thereof is 0.5 to 1 times the tank radius of the mixing tank 8.

The operation of the above configuration will be described. When the rolls R, R ′, R ″, the filter cloths 1, 2 and the stirrer 9 are driven and the chemical 5 is supplied into the chemical addition pipe 12, the concentrated sludge 4 shoots from the end of the gravity dehydration section A. 10 is guided by the chute 10 while being swept away by the chemical 5 such as the high cation polymer flocculant added from the chemical addition pipe 12 into the shaft portion 13 in the tank 8.
It falls to a position slightly forward (in the traveling direction of the filter cloth 2).

The concentrated sludge 4 that has fallen passes through the upper part of the tank and is discharged by the blade part 14 which rotates in the tank 8 around the axis of the shaft part 13 from the rear side to the front side in the traveling direction of the filter cloth 2. 8a is once sent to a region near the edge on the other side, and then sent to the discharge part 8a while being stirred and mixed with the chemical 5, while the surface hydrophilic layer is destroyed by the action of the chemical 5 and the hydrophobic It is liquefied and tempered so that it can be easily dehydrated.

Conditioned sludge 6 sent to the discharge part 8a
Of the guide plate 11 overflows from the discharge portion 8a.
Is uniformly supplied over the entire width of the filter cloth 2 while being guided to the roll cloth, is further gravity-dewatered until it reaches the roll R ″, and is then thickness-adjusted by the roll R ″, and pressure-dehydrated in the pressure dehydration section B. It

At this time, in the chemical mixing device 7, the stirrer 9 is used.
Since the blade portion 14 of the blade is curved forward in the rotational direction, splashing of the concentrated sludge 4 and the desorbed liquid thereof by the blade portion 14 is small, and slag residue and the like contained in the concentrated sludge 4 are removed from the blade portion 14. Since it moves in a direction away from the blade portion 14 as it rotates, slag and the like will not stick to the blade portion 14.

Further, as the outer peripheral portion farther from the shaft portion 13 has a higher rotation speed of the blade portion 14, while the blade portion 14 is curved, the blade portion 14 per a certain distance in the radial direction of the shaft portion 13 becomes larger. Since the area is small in the outer peripheral portion, the impingement of the blade portion 14 on the concentrated sludge 4 and the chemical 5 is almost the same regardless of the distance from the shaft portion 13. Therefore, the concentrated sludge 4 and the chemicals 5 are uniformly mixed from a portion near the shaft portion 13 to a portion near the wall surface.

Further, even if foreign matter is caught between the inner peripheral surface of the mixing tank 8 and the blade portion 14, the blade portion 14 moves in the direction of escaping from the foreign matter, so that bending occurs and bending occurs. Hateful.

The concentrated sludge 4 and the chemicals 5 are preferably dropped to a position slightly ahead of the shaft portion 13 in the mixing tank 8 as described above, but they may be dropped to a region on the rear side of the shaft portion 13. Even if the blade 13 is dropped to a position further forward of the shaft portion 13, the short pass does not occur due to the action of the blade portion 14 in the rotation direction.

Further, in the above description, the concentrated sludge 4 concentrated in the gravity dehydration section A which constitutes a part of the belt press dehydrator is introduced into the chemical mixing device 7, but a drum screen, a multiple disc, etc. Similarly, the concentrated sludge concentrated in the concentrator having the filter medium of the form can be mixed with the chemical in the chemical mixing device 7.

As the high cation polymer flocculant, a DAM (methacrylate) or DAA (acrylate) high molecular weight cation polymer flocculant is suitable. Is preferably a polycation-based or polyethyleneimine-based high cationic polymer flocculant, but the above-mentioned device is also useful when other chemicals such as polymer flocculant and inorganic flocculant are added.

[0031]

As described above, according to the present invention, a plurality of chemical mixing devices provided on the front side of the pressure dehydration section of the belt press type dehydrator are provided inside the mixing tank along the width direction of the filter cloth. By configuring with a stirrer having blades, it is possible to sufficiently mix chemicals such as flocculants even with concentrated sludge that has been previously concentrated by gravity dehydration, and to prepare a mixture of concentrated sludge and chemicals. The sludge can be uniformly supplied over the entire width of the filter cloth. As a result, the sludge can be suitably conditioned to have a higher dewatering property than before, and meandering and wrinkling of the filter cloth can be prevented, which also improves the dewatering property.

Further, by curving the blade part of the agitator to the front side in the rotation direction, the concentrated sludge and the chemicals can be mixed without variation from the vicinity of the shaft part to the vicinity of the wall surface in the tank, and the sludge by the blade part can be mixed. Further, splashing of the desorbed liquid and entanglement of slag and the like on the blade portion can be reduced, and the blade portion can be prevented from breaking even when foreign matter is caught in the tank wall surface.

Further, the mixing tank is constructed such that one side edge portion along the width direction of the filter cloth serves as an outlet for the tempered sludge, and an inlet for the concentrated sludge is arranged above the outlet for the mixing sludge. Since the blade part is configured to rotate around the axis of the shaft part in the direction from the discharge part to the inflow part, it is possible to prevent insufficiently adjusted sludge from being supplied onto the filter cloth by a short path. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which a chemical mixing device according to an embodiment of the present invention is arranged in a belt press type dehydrator.

FIG. 2 is a plan view of the chemical mixing apparatus shown in FIG.

FIG. 3 is a schematic overall configuration diagram of the conventional belt press type dehydrator shown in FIG. 1.

[Explanation of symbols]

1 filter cloth 2 filter cloth 4 concentrated sludge 5 chemicals 6 Conditioned sludge 7 Chemical mixing device 8 mixing tanks 9 stirrer 13 Shaft 14 blade A gravity dehydration section B Pressurized dehydration unit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-42312 (JP, A) JP 5-269498 (JP, A) JP 59-228916 (JP, A) JP 7- 195100 (JP, A) Actually open 59-49494 (JP, U) Actually open 60-168509 (JP, U) Actually open 54-137262 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 11/00-11/20 B01D 24/38 B01D 33/04

Claims (3)

(57) [Claims] 1. A chemical mixing apparatus which introduces concentrated sludge concentrated by gravity dehydration or the like, mixes it with a chemical such as a flocculant, and supplies the mixture to the pressure dehydration section of a belt press type dehydrator. A mixing tank provided in the width direction of the filter cloth above the belt-shaped filter cloth on the front side of the pressure dehydration section of the belt press type dehydrator, and an agitator provided inside the mixing tank, The mixing tank is formed in a shape in which the cross section in the advancing direction of the filter cloth is widened in a semicircular shape from the bottom toward the upper side, and the agitator is provided with the width direction of the filter cloth as the axial center direction, and is provided around the axis. A rotating shaft part, which is attached to the outer peripheral surface of this shaft part, rotates around the axis of the shaft part, and after stirring and mixing the concentrated sludge and the chemicals introduced into the mixing tank, it is placed on the filter cloth. For multiple blades to be sent out and for the mixing tank
Chute as an inflow part for guiding the concentrated sludge by
Add the above chemicals to the concentrated sludge guided by the sludge
It has a chemical addition pipe that can be added from the chemical addition pipe
Around the shaft while washing away the concentrated sludge with the above chemicals
A chemical mixing device characterized by being dropped to the bottom. 2. The chemical mixing device according to claim 1, wherein the blade portion of the stirrer is formed so as to be curved so as to project forward in the rotation direction. 3. The mixing tank has one side edge portion along the width direction of the filter cloth as an outlet for overflowing the admixture with respect to the filter cloth, and an inlet for concentrated sludge is arranged above the outlet. to become, blade portions of the agitator according to claim 1 or 2, characterized in that rotates in the direction toward the inlet from the discharge section around the axis of the shaft portion
The chemical mixing device described.