JP3446621B2 - Sludge coagulation granulator and sludge dewatering method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge aggregating and granulating apparatus and a sludge dewatering method, and more particularly to a sludge aggregating and granulating apparatus capable of aggregating and granulating sludge into strong and coarse flocs, and , Using an inorganic coagulant and an amphoteric organic polymer coagulant (hereinafter referred to as "amphoteric polymer") to coagulate sludge,
The present invention relates to a method for obtaining a dehydrated cake having a low water content with high treatment efficiency by performing dehydration treatment.

[0002]

2. Description of the Related Art Conventionally, as a method for dehydrating anaerobic digested sludge generated in a treatment process of sewage, night soil or organic industrial wastewater, a cationic polymer is added to the sludge in an amount of about 1.5 to 2% by weight (SS). In general, a method of reacting and aggregating and then dehydrating with a dehydrator is used. As this dehydrator, a centrifugal dehydrator, a belt press dehydrator, a screw press dehydrator,
A vacuum dehydrator and a filter press dehydrator are mainly used. In order to improve the dehydration property of sludge, a liquid containing flocculated sludge is introduced into a stirring tank and gently stirred by a stirrer to grow the flocs.

[0003]

In recent years, the properties of anaerobic digested sludge generated in various treatment processes have tended to deteriorate more and more, and the dehydration property thereof is becoming worse year by year.

On the other hand, in the conventional sludge dewatering method using a cationic polymer, it is necessary to add a considerably large amount of the cationic polymer, and the dehydrated cake obtained has a high water content, which is a tolerable limit of 85. In some cases, it could be about%. In such a dehydrated cake having a high water content, the transportation cost is hindered and the disposal cost increases.

The present invention solves the above-mentioned problems of the prior art and agglomerates and granulates anaerobic digested sludge to form strong and coarse flocs with excellent dehydration properties,
Another object of the present invention is to provide a sludge dewatering method capable of efficiently aggregating, concentrating, and dehydrating anaerobic digested sludge to obtain a dehydrated cake having a sufficiently reduced water content.

[0006]

A sludge flocculation and granulation apparatus of the present invention is provided with a tank body into which a sludge to be treated is introduced in a lower portion and the granulated sludge is discharged from an upper portion, and a lower portion of the tank body. Axial flow type stirring blade, a first radial flow type stirring blade provided above the axial flow type stirring blade, and a second radial flow provided above the first radial flow type stirring blade Type stirring blades, a drive device having a rotating shaft for rotating these stirring blades, and a partition plate provided at a height between the first radial flow type stirring blades and the second radial flow type stirring blades And there is an opening in the center
Is provided, and the rotary shaft is inserted through this opening,
It is characterized by including a partition plate through which sludge moves upward in the tank through this opening .

In this sludge agglomeration granulator, sludge is effectively agglomerated and granulated by agitating blades provided in three stages in the vertical direction to form strong and coarse flocs excellent in dewatering property. Obtainable. In addition, since a partition plate is provided between the first radial flow type stirring blade and the second radial flow type stirring blade, the middle stage in the stirring region by the second radial flow type stirring blade in the upper stage The flocs can be effectively aged without being affected by the stirring region by the first radial flow type stirring blades. Also, at the bottom of this partition plate,
Since the first radial-flow type stirring blade and the axial- flow type stirring blade are provided in two stages, it is possible to perform strong stirring to promote aggregation and granulation of sludge. On the other hand, since the second radial flow type stirring blade is provided in one stage on the upper part of the partition plate, the flocs can be satisfactorily aged with relatively weak stirring.

In the sludge dewatering method of the present invention, an inorganic flocculant and an amphoteric organic polymer flocculant are added to and mixed with sludge to form flocs, and water is separated and concentrated. The method is characterized in that after the organic polymer coagulant is added and mixed, it is granulated by a coagulation granulator and the granulated sludge is dehydrated by a dehydrator.

In the sludge dewatering method of the present invention,
By adopting the conditions of 1), a highly concentrated granulated sludge that is strong and has remarkably good dewatering property can be obtained, and by dehydrating this granulated sludge efficiently, a dehydrated cake with a significantly reduced water content can be obtained. .

An inorganic flocculant effective for improving the cohesiveness of sludge and lowering the water content is used in combination with an amphoteric polymer effective for improving the cohesiveness of sludge. By performing the two-stage flocculation, the reaction between the sludge and the inorganic flocculant and the reaction between the sludge and the amphoteric polymer are effectively performed. The coagulated sludge is concentrated in order to improve the dewatering property. The concentrated sludge is granulated to further improve the dehydration property. In the sludge dewatering method of the present invention, it is particularly preferable to use the agglomeration granulation apparatus of claim 1 as the agglomeration granulation apparatus.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 (a) is a longitudinal sectional view showing an embodiment of the sludge flocculation / granulation apparatus of the present invention, and FIG. 1 (b) is FIG. 1 (a).
It is sectional drawing which follows the BB line of FIG. FIG. 2 is a system diagram showing an embodiment of a sludge dewatering method of the present invention, and FIG. 3 is a sectional view showing an embodiment of a coagulating / concentrating tank according to the present invention.

First, with reference to FIG. 1, a sludge agglomerating and granulating apparatus of the present invention will be described.

In FIG. 1, 10 is an agglomeration granulation tank, which is connected at its lower part with a pipe 1 for introducing sludge to be treated (concentrated sludge to which an amphoteric polymer is added in this embodiment), and at the upper part of the sludge for granulation. The discharge pipe 2 is connected. This agglomeration granulator 1
In FIG. 0, from the bottom, an axial flow type stirring blade (in the present embodiment, a turbine blade having a twisted flat blade) 3, a first radial flow type stirring blade (in this embodiment, a battledore blade) 4, and a first A radial flow type stirring blade 2 (a flat blade in this embodiment) 5 is provided. These stirring blades 3, 4, 5 have a common rotary shaft 6
And is rotated by a drive device (not shown). A partition plate 7 is provided at a height position between the first radial flow type stirring blade 4 and the second radial flow type stirring blade 5. 7A is an opening provided in the center of the partition plate 7, and the rotary shaft 6 is inserted through the opening 7A.
The granulated sludge flows upward in the tank through the opening 7A.

The axial-flow type stirring blade 3 is intended to generate a liquid flow mainly in the axial direction by rotation, and is provided with an angled fan turbine (a turbine in which blades made of flat plates are obliquely crossed with respect to a horizontal rotating surface), A propeller is used.

The radial flow type stirring blades 4 and 5 mainly generate a liquid flow in a radial direction by rotation, and the blade surface is substantially vertical to the horizontal rotation surface.

As shown in FIG. 1, the first radial flow type stirring blade 4 arranged in the middle stage has a mounting shaft 4A extending in the radial direction,
It is preferable that the flat plate 4B is provided on the tip side of the mounting shaft 4A, and the flat plate 4B has a slight receding angle θ with respect to the rotation direction. It is preferable to provide about 2 to 4 blades 4 at equal intervals in the circumferential direction. Sweep angle θ is 15
It is preferably about 20 ° to 20 °.

As the second radial flow type stirring blade 5 arranged in the upper stage, one having a mounting shaft 5A and a flat plate 5B is similarly used. The plate width of the second radial flow type stirring blade 5 is smaller than that of the first radial flow type stirring blade 4 (for example, 30 to 40).
%), And those having a large length (for example, 120 to 130%) are preferable. It is preferable that two to four second radial flow type stirring blades 5 are provided at equal intervals in the circumferential direction.

Of the stirring blades provided in the upper and lower three stages in the agglomerating and granulating tank 10, the lower axial flow stirring blade 3 is from the bottom of the agglomerating and granulating tank 10 to 1/20 of the effective tank height. 1/2
At the height position of about 5, the first radial flow type stirring blade 4 in the middle stage
Is 1/3 to 1 of the effective tank height from the bottom of the coagulation and granulation tank 10.
At a height position of about /3.5, the upper second radial flow type stirring blade 5 is 1/1 of the effective tank height from the tank bottom of the agglomeration granulation tank 10.
It is preferable that they are respectively provided at height positions of about 1.4 to 1 / 1.5.

The partition plate 7 provided between the first radial flow type stirring blade 4 and the second radial flow type stirring blade 5 has an effective tank height from the bottom of the granulating and concentrating tank 10. It is preferably located at a height of ½, and the area of the opening 7A provided in the partition plate 7 is preferably set to be equal to or slightly larger than the cross-sectional area of the introduction pipe 2 for the sludge to be treated.

In the agglomeration and granulation tank 10 as described above, the sludge to be treated introduced from the lower part of the tank is first agglomerated and flocculated by stirring by the axial flow type stirring blade 3 in the lower stage, and then the first sludge in the middle stage. After the flocs are further coarsened by the stirring by the radial flow type stirring blade 4, the flocs rise through the opening 7A of the partition plate 7, and the flocs are matured by the stirring by the second radial flow type stirring blade 5 in the upper stage. Thus, strong and coarse granulated particles can be obtained.

Next, an embodiment of the sludge dewatering method of the present invention will be described in detail with reference to FIG.

In the method shown in FIG. 2, first, the raw mud (sludge to be treated) in the raw mud tank 11 is introduced into the coagulation / concentration tank 12 via the pipe 21 by the pump P ₁ . In this introduction pipe 21,
An inorganic coagulant injection pipe 22 is provided, the inorganic coagulant is added, and the coagulated sludge that has undergone the coagulation reaction during transportation in the pipe 21 is introduced into the coagulation concentration tank 12.

As the inorganic coagulant, ferric chloride, aluminum sulfate, aluminum chloride, polyaluminum chloride (PAC), polyiron sulfate, etc. can be used.
The amount of the inorganic flocculant added to the raw mud depends on the type of compound used and the properties of the raw mud, but is preferably 30 to 40% by weight based on the sludge SS (dry weight of sludge).

As shown in FIG. 2, the inorganic coagulant is added to the sludge introduced into the coagulation / concentration tank 12 in advance to cause the coagulation reaction, and then the coagulation reaction with the amphoteric polymer in the coagulation / concentration tank 12 is more effective. It is possible to carry out various agglutination reactions. The aggregation reaction time with this inorganic aggregating agent, that is,
The transfer time of the sludge in the pipe 21 from the addition of the inorganic coagulant to the sludge to the introduction into the coagulation concentration tank 12 is 20 to 20.
It is preferable that the time is about 30 seconds.

The coagulated sludge coagulated with the inorganic coagulant undergoes a coagulation reaction with the amphoteric polymer introduced from the pipe 23 in the coagulation / concentration tank 12, flocs are coarsened and concentrated, and the concentrated sludge and separated water are respectively piped. It is taken out from 24 and 25.

FIG. 3 shows a coagulation / concentration tank suitable for the present invention. A coagulation sludge introduction pipe 21 and an amphoteric polymer introduction pipe 23 are connected to the lower part of the coagulation / concentration tank 12, and radiation is provided in the tank. Flow type stirring blades (flat blades in this embodiment) 31,
32 and 33 are provided in three stages in the vertical direction. These stirring blades 31, 32, 33 are attached to a common rotating shaft 34, and are rotated by a driving device (not shown). The radial flow type stirring blades 31, 32, 33 are mounted on the mounting shafts 31A, 32A, 33A and the flat plates 31B, 32B, 3 respectively.
3B, and 2 to 4 sheets (two sheets in this embodiment) are provided in the circumferential direction.

A concentric circular draining screen 35 is provided immediately above the upper stirring blade 31, the concentrated sludge discharge pipe 24 is below the screen 35, and the separated water drain pipe 25 is this. It is attached to the top of the screen 35. The scraper 3 for cleaning the screen 35 is provided above the stirring blade 31.
6 is attached.

As described above, in the coagulation / concentration tank 12 having the stirring blades provided in multiple stages, the flocculation can be coarsened by efficiently promoting the coagulation reaction of sludge rising in the tank. The water can be separated by the screen 35 to concentrate the coagulated sludge.

In this embodiment, such a flocculating and concentrating tank 12 is used.
The above flocculated sludge and amphoteric polymer are introduced into the lower part of the tank through pipes 21 and 23, respectively, to make the flocs coarse.

As the amphoteric polymer to be used, the colloid equivalent value (a value) obtained by colloid titration at pH 3 showing a cationic constitutional unit (cationic group) amount (hereinafter referred to as "cation amount") is 1.0 to 3. 7 meq / g, anionic constitutional unit (anion group) amount (hereinafter referred to as "anion amount")
Colloid equivalent value (b value) determined by colloid titration at pH 7 which indicates the difference between the amount of cationic constitutional unit and -0.1 to 0.7 me
It is preferably q / g and the value of (ab) / a showing the ratio of the amount of anions / the amount of cations is in the range of 0.8 to 1.8.

Examples of such amphoteric polymers include copolymers of anionic monomer components and cationic monomer components, copolymers of anionic monomer components, cationic monomer components and nonionic monomer components. Alternatively, a Mannich modified product or a Hoffmann degradation product of a copolymer of an anionic monomer component and a nonionic monomer component can be used.

Examples of the anionic monomer component include acrylic acid (AA), sodium acrylate (NaA), methacrylic acid and sodium methacrylate. Examples of the cationic monomer component include dimethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate (DAM),
Examples thereof include dimethylaminopropyl (meth) acrylate, and their quaternized products. Specific examples of the quaternary compound include dimethylaminoethyl acrylate quaternary compound (DAA). Also,
Dimethylaminopropyl acrylamide hydrochloride (DA
PAAm) may be used. Examples of the nonionic monomer component include acrylamide (AAm), methacrylamide, and N, N′-dimethyl (meth) acrylamide. As the copolymer of these compounds, specifically, a DAA / AA / AAm copolymer, a DAM / AA / AAm copolymer, a DAPAAm /
AA / AAm copolymer, DAA / AA copolymer, or N
Examples thereof include Mannich modified products of aA / AAm copolymer. Moreover, what hydrolyzed the copolymer of vinylformamide or vinylacetamide and (meth) acrylic acid can also be used.

The amount of the above-mentioned amphoteric polymer added to the flocculating and concentrating tank 12 is preferably 0.5 to 1.0% by weight based on the sludge SS.

In the flocculating / concentrating tank 12, coarse flocs of about 5 to 10 mm can be formed by further flocculating the flocculated sludge with the inorganic flocculant with the amphoteric polymer.

In this coagulation / concentration tank 12, the amount of concentrated sludge that flows out is subtracted from the amount of coagulated sludge that flows in (this amount corresponds to the discharge amount of the sludge extraction pump P ₂ of the coagulation / granulation tank 13 in the subsequent stage). A large amount of separated water is discharged from the pipe 25, and the sludge is concentrated by an amount commensurate with the separated water. The concentration ratio of this sludge is preferably about 1.5 to 2.0 times.

The concentrated sludge from the coagulation / concentration tank 12 is supplied to the pipe 2
After the amphoteric polymer is added from No. 6, it is introduced into the coagulation and granulation tank 13. As the agglomeration granulation tank 13, the agglomeration granulation tank 10 shown in FIG. 1 in which the stirring blades 3, 4, and 5 are arranged in three stages and provided with a partition plate 7 is used.

The same amphoteric polymer as that used in the coagulation / concentration tank 12 can be added to this thickened sludge, and the addition amount thereof is 0.1 to 0.3% by weight based on the sludge SS. preferable.

Here, the amphoteric polymer is used in the coagulation / granulation tank 13
However, as shown in the figure, by adding the sludge to the introducing pipe 24 of the concentrated sludge to start the agglomeration early before being introduced into the agglomeration granulation tank 13, the agglomeration efficiency is further enhanced. be able to.

The sludge transfer time in the pipe 24 from the addition of the amphoteric polymer to the introduction into the coagulation and granulation tank 13 is preferably about 3 to 4 seconds.

When the amphoteric polymer is directly added to the coagulation / granulation tank 13, the amphoteric polymer is added below the partition plate (partition plate 7 in FIG. 1) of the coagulation / granulation tank 13, preferably at the lower part of the flocculation / granulation tank. Do not add it to the upper part of the partition plate that will be the aging area.

In the flocculation and granulation tank 13, as in the previous stage, the flocs that were slightly destroyed while being transferred from the flocculation and concentration tank 12 were agitated by the stirring blades in the lower stage (axial flow type stirring blade 3 in FIG. 1). Aggregation is performed, and then the flocs are coarsened by stirring with the stirring blades in the middle stage (first radial flow type stirring blades 4 in FIG. 1), and the flocs grow into coarse particles having a particle size of about 10 mm. Further, the grown flock passes through the opening of the partition plate (opening 7A of the partition plate 7 in FIG. 1) and rises,
It is aged by stirring with the upper stirring blade (second radial flow type stirring blade 5 in FIG. 1). The reaction time in the agglomeration and granulation tank 13 is preferably about 2 to 5 minutes.

The granulated sludge in which strong and coarse flocs are formed by stirring with the stirring blades provided in three stages as described above is the sludge drawing pump P ₂ from the upper part of the flocculation and granulation tank 13.
Is pulled out through the pipe 27 and sent to the dehydrator,
It is dehydrated. As this dehydrator, a belt press dehydrator, a centrifugal dehydrator, a screw press dehydrator or the like can be used.

According to the present invention, since the two-stage flocculation in which the inorganic flocculant and the amphoteric polymer are used in combination, a granulated sludge having a remarkably excellent dehydration property can be obtained. A dehydrated cake having a low water content of about 68 to 82% can be obtained.

[0045]

EXAMPLES The present invention will be described in more detail with reference to the following examples.

Example 1 Sewage anaerobic digestion sludge was dehydrated by the method for dehydrating sludge of the present invention shown in FIG.

After adding an inorganic coagulant to the raw mud (concentration: 1%), it was introduced into the coagulating and concentrating tank 12, and the amphoteric polymer was mixed and coagulated and concentrated twice. Then, after adding the amphoteric polymer to the concentrated sludge, it is introduced into the coagulation and granulation tank 13 for granulation,
The granulated sludge was dehydrated.

Polyiron sulfate was used as the inorganic coagulant, and 40% by weight of a product having a pure content of 38% was added as the product weight to the sludge SS, and the reaction time in the pipe after adding the inorganic coagulant was 20 seconds. And Further, as the amphoteric polymer,
Colloid equivalent (a) value at pH 3 is 2.6 meq /
g, pH 7 colloid equivalent (b) value is 0 meq /
Using a DAA / AA / AAm copolymer having a value of (ab) / a of 1 in g, 0.8% by weight was added to sludge SS in the coagulation / concentration tank 12, and the reaction time was 2 minutes. did. On the inlet side of the coagulation / granulation tank 13, 0.1% by weight was added to the sludge SS, the reaction time in the pipe was 3 seconds, and the residence time in the coagulation / granulation tank 13 was 5 minutes.

As the coagulating / concentrating tank 12, an effective height of 2 m
Then, 0.5m height from the bottom of the tank, 1m height, 1.5m
A stirring blade equipped with two flat blades was provided at each height. Each of the stirring blades has a blade area (area of flat plate portion) of 40 cm × 10 cm.

As shown in FIG. 1, the coagulation and granulation tank 13 has an effective height of 1.8 m, a turbine blade at a height of 0.1 m from the bottom of the tank, and a battledore blade at a height of 0.6 m. ,
A flat blade was provided at a height of 1.7 m, and a partition plate was provided at a height of 0.9 m from the bottom of the tank. The area of the opening of this partition plate is almost the same as the sectional area of the pipe for introducing the concentrated sludge. Two turbine blades with a length of 20 cm in the diameter direction of the tank were attached, and the battledore blade had an attachment shaft length of 15 cm, a flat plate portion of about 30 cm x 25 cm, and a receding angle θ of 15 °. Two things are attached.
The flat blade has a mounting axis length of 5 cm and a flat plate portion of about 40 cm.
Two sheets with a size of × 10 cm are attached.

A belt press dehydrator was used for dehydration of the granulated sludge, and dehydration was performed at a filtration rate of 130 kg / m · hr (130 kg per 1 m of filter cloth width was treated per hour).

The water content of the obtained dehydrated cake was 79%, and a dehydrated cake having a remarkably low water content could be obtained.

[0053]

As described above in detail, according to the sludge aggregating and granulating apparatus and the sludge dewatering method of the present invention, the sludge is efficiently agglomerated, concentrated and dehydrated to sufficiently reduce the water content. You can get a dehydrated cake.

[Brief description of drawings]

FIG. 1 (a) is a vertical cross-sectional view showing an embodiment of a sludge aggregating and granulating apparatus of the present invention, and FIG. 1 (b) is B of FIG. 1 (a).
It is sectional drawing which follows the -B line.

FIG. 2 is a system diagram showing an embodiment of a sludge dewatering method of the present invention.

FIG. 3 is a cross-sectional view showing an embodiment of a coagulating / concentrating tank according to the present invention.

[Explanation of symbols]

3 Axial flow type stirring blade 4 First radial flow type stirring blade 5 Second radial flow type stirring blade 7 dividers 10 Agglomeration granulator 11 raw mud tank 12 Aggregation concentration tank (first aggregation reaction tank) 13 Aggregation granulation tank (second aggregation reaction tank)

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Claims (3)

(57) [Claims] 1. A tank body into which sludge to be treated is introduced in the lower part and granulated sludge is discharged from the upper part, an axial-flow type stirring blade provided in the lower part of the tank body, and an axial-flow type stirring blade A first radial flow type stirring blade provided above, a second radial flow type stirring blade provided above the first radial flow type stirring blade, and a rotary shaft for rotating these stirring blades. A partition plate provided at a height between the driving device and the first radial flow type stirring blade and the second radial flow type stirring blade, the partition plate being opened in the center thereof.
A mouth is provided, and when the rotary shaft is inserted through this mouth,
And a partition plate for moving sludge upward in the tank through this opening . 2. An inorganic flocculant and an amphoteric organic polymer flocculant are added to and mixed with sludge to form flocs, and water is separated and concentrated, and an amphoteric organic polymer flocculant is further added to the concentrated sludge. A method for dehydrating sludge, which comprises mixing and then granulating with a coagulation granulator, and dehydrating the granulated sludge with a dehydrator. 3. The method for dewatering sludge according to claim 2, wherein the agglomeration granulation apparatus according to claim 1 is used as an agglomeration granulation apparatus.