JP2008043914A - Sludge thickening apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge thickening apparatus which can obtain a high dewatering effect by reducing an M alkali concentration of thickened sludge by washing sludge by washing water during thickening and suppressing the amount of a loaded inorganic flocculant low in subsequent dewatering treatment. <P>SOLUTION: The sludge thickening apparatus comprises containing a filtration cylinder 3 in an external cylinder 2, rotatably containing a spiral screw 4 inside the filtration cylinder 3, passing a moisture contained in the sludge through the filtration surface 3a of the filtration cylinder 3, discharging it from a separated liquid discharge pipe 19 as a separated liquid and thickening the sludge while conveying the sludge introduced from a sludge flocculation tank 11 into the filtration cylinder 3 by rotationally driving the spiral screw 4, and discharging thickened sludge from the inside of the filtration cylinder 3, wherein the sludge in the filtration cylinder 3 is washed by making the rotary shaft 4a of the spiral screw 4 hollow and streaming the washing water from the rotary shaft 4a into the filtration cylinder 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a screw press-type sludge concentrating device that concentrates a sludge introduced from a sludge agglomeration tank into a filter cylinder by rotating a spiral screw in the filter cylinder.

  In order to discard or incinerate various types of sludge, the sludge is dehydrated with a dehydrator. However, it is difficult to efficiently dehydrate sludge only with the processing capacity of the dehydrator. For this reason, prior to the dewatering treatment by the sludge dewatering machine, the sludge is agglomerated with a flocculant to form a floc, and the water is separated from the flocked sludge (aggregated sludge) to concentrate the sludge. Various sludge concentrators for implementing this have been proposed and put to practical use.

  By the way, the sludge concentrating device is roughly classified into a rotary screen type and a screw press type. FIG. 2 shows an example of a screw press type sludge concentrating device (see, for example, Patent Documents 1 and 2).

  That is, FIG. 2 is a schematic diagram showing the basic configuration of a conventional sludge concentrating device. The illustrated sludge concentrating device 1 includes a concentrator 1 and a sludge flocculation tank 11, and sludge to which a flocculant is added is sludge. The flocculated tank 11 is agglomerated and flocked, and the flocculent agglomerated sludge is concentrated by the concentrator 1.

  The concentrator 1 is configured by arranging a cylindrical filter tube 3 in a vertical direction inside a cylindrical tank-shaped outer tube 2 having a hermetically sealed structure, and rotatably accommodating a spiral screw 4 in the filter tube 3. Has been.

  Here, the peripheral surface of the portion of the filtration cylinder 3 facing the outer cylinder 2 constitutes a filtration surface 3a made of a punching plate or a wedge wire, and the concentrated sludge discharge pipe 5 is formed from the lower part of the filtration cylinder 3. Is led out horizontally, and a concentrated sludge pump 6 is provided in the middle thereof.

  Further, from the upper and lower sides of the outer cylinder 2, the separated liquid take-out pipes 7 and 8 are led out horizontally, and these separated liquid take-out pipes 7 and 8 rise vertically to the inverted U-shaped separated liquid discharge pipe 9. It is connected to the upward flow pipe 9a. Here, the separation liquid discharge pipe 9 has a horizontal pipe 9b extending horizontally from the upper end of the upward flow pipe 9a, and a downward flow pipe 9c extending vertically downward from the end of the horizontal pipe 9b.

  The spiral screw 4 is configured by spirally winding a screw blade 4b around a rotating shaft 4a, and a motor 10 as a drive source is connected to the rotating shaft 4a. The outer diameter of the spiral screw 4 is set slightly smaller than the inner diameter of the filtration surface 3a of the filter cylinder 3, and a small gap is formed between the outer peripheral edge of the spiral screw 4 and the filtration surface 3a of the filter cylinder 3. Is formed.

  On the other hand, a raw mud supply pipe 12 is connected to a lower portion of the sludge agglomeration tank 11 having a cylindrical tank shape whose upper surface is open. In the sludge agglomeration tank 11, a stirrer 14 that is rotationally driven by a motor 13 is provided.

  Further, an agglomerated sludge introduction pipe 15 extends substantially horizontally from the upper part of the sludge agglomeration tank 11, and this agglomerated sludge introduction pipe 15 is connected to the upper end of the filter cylinder 3 of the concentrator 1.

  Thus, sludge (raw mud) is supplied from the raw mud supply pipe 12 to the sludge agglomeration tank 11, and a flocculant such as a polymer is added to the sludge flowing through the raw mud supply pipe 12, and the flocculant is added. The sludge thus produced is agitated by the agitator 14 in the sludge agglomeration tank 11, and the solid component contained in the sludge is flocked to become agglomerated sludge.

Here, the sludge liquid level h ₂ in the filter cylinder 3 is set lower than the sludge liquid level h ₁ in the sludge aggregation tank 11 (h ₂ <h ₁ ), and both liquid levels h ₁ and h _{2 are set.} (The head difference) Δh ₁₂ (= h ₁ −h ₂ ), the agglomerated sludge in the sludge agglomeration tank 11 passes through the agglomerated sludge introduction pipe 15 and enters the filter cylinder 3 of the concentrator 1. It is introduced from.

In the concentrator 1, the spiral screw 4 is rotationally driven by the motor 10 at a predetermined speed in the filter cylinder 3, and the condensed sludge introduced into the filter cylinder 3 is moved downward by the rotating spiral screw 4. While being conveyed, the moisture contained therein passes through the filtration surface 3a of the filtration cylinder 3 and is stored in the outer cylinder 2 as a separation liquid. Here, since the water level h ₃ of the separation liquid in the separation liquid discharge pipe 9 is set lower than the liquid level h ₂ in the filter cylinder 3 (h ₃ <h ₂ ), both h ₂ and h ₃ Difference (head difference) Δh ₂₃ (= h ₂ −h ₃ ) as a filtration pressure, moisture separated from the coagulated sludge passes through the filtration surface 3a of the filtration cylinder 3 and is separated into the outer cylinder 2 Housed as a liquid. Further, in this case, since the outer cylinder 2 is disposed below the water level h _{3 of the} separation liquid, the separation liquid accommodated in the outer cylinder 2 is filled in the outer cylinder 2 and is contained in the separation liquid. The filtration surface 3a of the filtration cylinder 3 is buried.

Then, the separation liquid accommodated in the outer cylinder 2 flows into the separation liquid discharge pipe 9 from the separation liquid discharge pipes 7 and 8 connected to the upper and lower sides of the outer cylinder 2, and the upward flow pipe of the separation liquid discharge pipe 9. 9a flows upward, overflows in the horizontal pipe 9b, flows downward in the downward flow pipe 9c, and is discharged to the outside. Further, the coagulated sludge conveyed downward in the filter cylinder 3 by the rotation of the spiral screw 4 is concentrated by separating water in the middle thereof to become concentrated sludge, and this concentrated sludge is converted by the concentrated sludge pump 6. It is discharged to the outside through the concentrated sludge discharge pipe 5 and is subjected to a dehydration process by a dehydrator (not shown).
Japanese Patent No. 3627809 JP 2006-0775675 A

  By the way, it is known that high performance can be obtained by using an inorganic flocculant and a polymer flocculant together in the dehydration of organic sludge concentrated by the sludge concentrator as shown in FIG.

  However, digested sludge obtained by anaerobic treatment of sewage sludge and the like has a high M alkali concentration, so when an inorganic flocculant and a polymer flocculant are used together for dehydration, a large amount of inorganic flocculant is consumed. Therefore, there is a problem that the addition rate becomes enormous.

  Therefore, there is a case in which a polymer is first added to the digested sludge to flocate the sludge, the flocated sludge is concentrated by a sludge concentrator, and then an inorganic flocculant is added to the concentrated sludge. Even in such a method, the addition rate of the inorganic flocculant becomes considerably high.

  The present invention has been made in view of the above problems, and its intended treatment is to reduce the M alkali concentration of the concentrated sludge by washing the sludge with washing water during concentration, and to add an inorganic flocculant in the subsequent dehydration treatment An object of the present invention is to provide a sludge concentrator capable of suppressing the amount low and obtaining a high dehydration effect.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a filter cylinder is accommodated in an outer cylinder, a spiral screw is rotatably accommodated in the filter cylinder, and the spiral screw is driven to rotate. While conveying the sludge introduced into the filter cylinder from the sludge aggregation tank, the water contained in the sludge passes through the filtration surface of the filter cylinder and is discharged from the separation liquid discharge pipe as a separation liquid to concentrate the sludge. In addition, in the sludge concentrating device for discharging the concentrated sludge from the inside of the filter cylinder, the spiral shaft of the spiral screw is made hollow, and the washing water is allowed to flow from the rotary shaft into the filter cylinder. It is characterized by washing.

  According to a second aspect of the present invention, in the first aspect of the invention, a plurality of outlets are formed at one axial end of the rotating shaft of the spiral screw, and high-concentration sludge that has been concentrated in the filter cylinder is formed. The washing is performed with washing water that flows out from the outlet into the filter cylinder.

  Invention of Claim 3 introduce | transduces the sludge from the said sludge coagulation tank into the upper part in the said filter cylinder in invention of Claim 1 or 2, and this sludge is made to go down in the filter cylinder with the said spiral screw. While concentrating while being conveyed, the cleaning water supplied through the rotary joint to the upper end of the rotating shaft of the spiral screw is allowed to flow from a plurality of outlets formed at the lower portion of the rotating shaft, and the concentration proceeds in the filter cylinder. It is characterized by washing high concentration sludge.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the separation liquid discharge pipe has a double pipe structure of an outer pipe and an inner pipe, and a height of an upper end edge of the inner pipe. The height is set lower than the liquid level in the filter cylinder, and the upper end edge of the inner tube is used as an overflow portion so that the separated liquid overflows from the outer tube to the inner tube or from the inner tube to the outer tube. And

  According to the first aspect of the present invention, the washing water is allowed to flow from the hollow rotating shaft of the spiral screw into the filter cylinder to wash the sludge in the filter cylinder. The amount of the inorganic flocculant added in the dehydration treatment is kept low, and a high dehydration effect is obtained.

  According to the second aspect of the present invention, since the high-concentration sludge concentrated in the filter cylinder is intensively washed, the M alkali contained in the concentrated sludge is effectively washed away by the wash water and concentrated. The M alkali concentration in the sludge is further lowered, and the amount of the inorganic flocculant added in the subsequent dehydration process is kept low, so that a high dehydration effect is obtained.

  According to the invention described in claim 3, in the sludge concentrating device for concentrating the sludge introduced from the upper part of the filter cylinder while being conveyed downward by the spiral screw, the rotary joint is provided at the upper end of the rotating shaft of the rotating spiral screw. The high-concentration sludge that has been concentrated in the filter cylinder is washed with the wash water by flowing the wash water supplied through the plurality of outlets formed at the lower part of the rotating shaft, so that the M alkali concentration of the concentrated sludge Is effectively reduced, and the amount of the inorganic flocculant added in the subsequent dehydration treatment is kept low, and a high dehydration effect is obtained.

  According to the fourth aspect of the present invention, the separation liquid flowing from the outer cylinder to the discharge pipe overflows at the upper end edge of the inner cylinder and flows into the inner pipe or the outer pipe. Therefore, the upper end edge of the inner cylinder overflows. The length of the overflow portion becomes the circumferential length of the inner cylinder, and the length becomes longer than the width (overflow width) of the overflow portion of the conventional sludge concentrating device. Therefore, according to the sludge concentrating device according to the present invention, even if the amount of the separation liquid changes, the fluctuation of the water level of the separation liquid in the separation liquid discharge pipe can be suppressed to a small level. Fluctuation in the filtration pressure based on the difference between the separation liquid level and the separation liquid level can be kept small, and the filtration pressure can be kept substantially constant even if the separation liquid amount changes. Leakage and clogging of the filtration surface can be prevented.

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

  FIG. 1 is a schematic diagram showing a basic configuration of a sludge concentrating apparatus according to Embodiment 1 of the present invention. In this figure, the same elements as those shown in FIG. The re-explanation about them is omitted.

  In the sludge concentrating apparatus according to the present invention, the rotating shaft 4a of the spiral screw 4 of the concentrator 1 is made hollow, and washing water is allowed to flow from the rotating shaft 4a into the filter tube 3 to clean the sludge in the filter tube 3. It is characterized by.

  The sludge concentrating apparatus according to the present embodiment concentrates the agglomerated sludge introduced from the sludge agglomeration tank 11 into the upper part of the filter cylinder 3 of the concentrator 1 while being conveyed downward by the spiral screw 4. A washing water supply pipe 17 is connected to the upper end portion of the four hollow rotating shafts 4 a via a rotary joint 16. A plurality of outlets 18 are formed at the lower part of the rotating shaft 4a (the part facing the lower part in the filter cylinder 3 where the concentrated high-concentration sludge stays).

In the present embodiment, the separation liquid discharge pipe 19 of the concentrator 1 has a double pipe structure of the outer pipe 20 and the inner pipe 21, and the height of the upper end edge of the inner pipe 21 is set to the sludge in the filter cylinder 3. The liquid level is set to be lower than the liquid level h ₂ , and the separation liquid overflows from the upper end edge of the inner tube 21 to the inner tube 21. Here, the separation liquid discharge pipes 7 and 8 extending horizontally from the top and bottom of the outer cylinder 2 are connected to the top and bottom of the outer pipe 20 of the separation liquid discharge pipe 19, and the inner pipe 21 disposed inside the outer pipe 20 is connected to the outer pipe 20. It penetrates the bottom of the tube 20 and extends downward.

Thus, as in the conventional sludge concentrating apparatus shown in FIG. 2, the agglomerated sludge flocked in the sludge aggregating tank 11 is the sludge liquid level h ₂ in the filter cylinder 3 of the concentrator 1 and the sludge aggregating tank. 11 by the differential pressure based on the difference (head difference) Δh ₁₂ (= h ₁ −h ₂ ) from the sludge liquid level h ₁ , through the coagulated sludge introduction pipe 15 and into the filter cylinder 3 of the concentrator 1. It is introduced from.

The agglomerated sludge introduced into the filter cylinder 3 is conveyed downward by the rotating spiral screw 4, and moisture contained therein passes through the filtration surface 3 a of the filter cylinder 3 and enters the outer cylinder 2. It is stored as a separation liquid. Here, the water level h ₃ of separated liquid in the separated liquid discharge pipe 19 is lower than the liquid level h ₂ of the filtration cylinder 3 (h ₃ <h _2), the difference therebetween h _2, h ₃ (head difference) Delta] h _{23. Using the} differential pressure based on ₂₃ (= h ₂ −h ₃ ) as the filtration pressure, the water separated from the coagulated sludge passes through the filtration surface 3a of the filtration cylinder 3 and is stored in the outer cylinder 2 as a separation liquid. Further, in this case, since the outer cylinder 2 is disposed below the water level h _{3 of the} separation liquid, the separation liquid accommodated in the outer cylinder 2 is filled in the outer cylinder 2 and is contained in the separation liquid. The filtration surface 3a of the filtration cylinder 3 is buried.

  The separation liquid stored in the outer cylinder 2 flows into the outer pipe 20 of the separation liquid discharge pipe 19 from the separation liquid take-out pipes 7 and 8 connected to the upper and lower sides of the outer cylinder 2, and the outer pipe 20 and the inner pipe 21. And flows upward to flow into the inner tube 21, flows into the inner tube 21, flows downward in the inner tube 21, and is discharged to the outside.

  Further, the coagulated sludge conveyed downward in the filter cylinder 3 by the rotation of the spiral screw 4 is gradually concentrated as the water is separated in the middle thereof to become the concentrated sludge. Wash water is supplied from the upper end to the hollow rotary shaft 4a of the spiral screw 4 through the rotary joint 16, and this wash water is filtered from a plurality of outlets 18 formed at the lower part of the rotary shaft 4a. The sludge flocs are washed in the process of flowing into the gap 3 and passing through the gaps of the high-concentration sludge flocs staying in the lower part of the filter cylinder 3. As a result, the M alkali contained in the concentrated sludge is effectively washed away by the washing water, and the M alkali concentration of the concentrated sludge is lowered.

  Then, the concentrated sludge washed with the washing water is discharged to the outside through the concentrated sludge discharge pipe 5 by the concentrated sludge pump 6 and is subjected to a dehydration process by a dehydrator (not shown).

  As described above, according to the sludge concentrating apparatus according to the present invention, the high-concentration sludge staying in the lower part of the filter cylinder 3 by flowing the wash water from the hollow rotary shaft 4a of the spiral screw 4 into the filter cylinder 3. Therefore, the M alkali concentration of the concentrated sludge is lowered, and the amount of the inorganic flocculant added in the subsequent dehydration process in the dehydrator is kept low, so that a high dehydration effect is obtained. In particular, in the present embodiment, high concentration sludge concentrated in the filter cylinder 3 is intensively washed, so that M alkali contained in the concentrated sludge is washed away by washing water, and the M alkali of the concentrated sludge is washed away. The concentration is effectively lowered.

  In the present embodiment, the separation liquid flowing from the outer cylinder 2 through the separation liquid take-out pipes 7 and 8 into the separation liquid discharge pipe 19 overflows at the upper edge of the inner pipe 21 as described above. 21, the upper end edge of the inner tube 21 becomes an overflow portion, and the length of the overflow portion becomes the circumferential length of the inner tube 21. Therefore, the length of the overflow portion in the sludge concentrating apparatus according to the present embodiment is equal to the width (overflow) of the horizontal pipe 9b of the separated liquid discharge pipe 9 which is the overflow portion of the conventional sludge concentrating apparatus shown in FIG. Longer than the flow width).

For this reason, even if the amount of the separation liquid changes, the change in the water level h ₃ of the separation liquid in the separation liquid take-out pipe 19 can be kept small, and the liquid level h ₂ of the filter cylinder 3 and the water level h of the separation liquid discharge pipe 19 change in the difference _{Δh 23 (= h 2 -h 3} ) to based filtration pressure of ₃ can be suppressed. As a result, even if the amount of the separation liquid changes, the filtration pressure can be kept substantially constant, and leakage of solid components on the filtration surface 3a of the filtration cylinder 3 and clogging of the filtration surface 3a can be prevented. In the present embodiment, the separation liquid discharge pipe 19 employs a configuration in which the separation liquid overflows from the outer pipe 20 to the inner pipe 21, but conversely, the separation liquid overflows from the inner pipe 21 to the outer pipe 20. A configuration may be adopted.

In order to confirm the effect of the present invention, the present inventors tested each of the cases where the following three methods (cases 1, 2 and 3) were adopted under the following conditions.
(1) Test conditions:
-Raw mud: Digested sludge-Concentration 1.5%-M alkali content 5,000mg / L
・ Dehydrator: Belt press type dehydrator ・ Polymer addition rate: 1.8% / TS
(2) Test method:
Case 1: Concentrate and wash sludge using the sludge concentrator according to the present invention shown in FIG. 1 (washing water amount: 2 m ³ / h), then add an inorganic flocculant to the concentrated sludge and dehydrate it with a dehydrator・ Case 2: Method of adding polymer to raw mud and not concentrating, dewatering coagulated sludge as it is ・ Dehydrating machine ・ Case 3: Concentrating (washing) sludge using conventional sludge concentrator as shown in FIG. (3) Test results: Dehydrator supply sludge concentration (%) in each case 1, 2 and 3, dehydrator supply sludge Table 1 shows the M alkali content (mg / L), the inorganic agglomeration addition amount (kg / h), and the moisture content (%) of the dehydrated cake.

表１より明らかなように、汚泥を濃縮しないケース２での脱水機供給汚泥濃度は、ポリマー溶液で希釈されて１．３％となり、汚泥を濃縮するケース１，３での脱水機供給汚泥濃度は、４．５％となった。

As is clear from Table 1, the dewatering machine supply sludge concentration in case 2 where no sludge is concentrated is 1.3% when diluted with the polymer solution, and the dewatering machine supply sludge concentration in cases 1 and 3 where the sludge is concentrated. Was 4.5%.

  Case 1 in which sludge was washed with washing water, whereas the alkali content of the dewatering machine supplied sludge M in the cases 2 and 3 in which the sludge was not washed with washing water was 4,400 mg / L diluted with the polymer solution. The dewatering machine supply sludge M alkali content in was lowered to 1,100 mg / L. As a result, in case 1, the amount of the inorganic flocculant added to the sludge in the dehydrator can be reduced to 18 kg / h, which is half the amount of 36 kg / h added in case 3, and the moisture content of the dehydrated cake is 78%. In case 3, the moisture content of the dehydrated cake was 80%, which was 2% lower.

  As a result, according to the sludge concentration apparatus according to the present invention, the M alkali concentration of the concentrated sludge can be lowered by washing the concentrated sludge with washing water, and the amount of the inorganic flocculant added in the subsequent dehydration treatment can be reduced. It has been experimentally confirmed that a high dehydration effect can be obtained while keeping it low.

It is the schematic which shows the basic composition of the sludge concentration apparatus which concerns on this invention. It is the schematic which shows the basic composition of the conventional sludge concentration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concentrator 2 Outer cylinder 3 Filter cylinder 3a Filtration surface 4 Spiral screw 4a Rotating shaft 4b Screw blade 5 Concentrated sludge discharge pipe 6 Concentrated sludge pump 7, 8 Separation liquid take-out pipe 10 Motor 11 Sludge aggregation tank 12 Raw mud supply pipe 13 Motor 14 Stirrer 15 Coagulated sludge introduction pipe 16 Rotary joint 17 Washing water supply pipe 18 Outlet 19 Separation liquid discharge pipe 20 Outer pipe 21 Inner pipe h ₁ Sludge liquid level in sludge aggregation tank h ₂ Sludge liquid level in filter cylinder h ₍₃₎ Separate liquid level in the separate liquid discharge pipe

Claims (4)

A filter cylinder is accommodated in the outer cylinder, a spiral screw is rotatably accommodated in the filter cylinder, and the sludge introduced into the filter cylinder is conveyed from the sludge agglomeration tank by rotationally driving the spiral screw. While, the moisture contained in the sludge passes through the filtration surface of the filter cylinder and is discharged as a separation liquid from the separation liquid discharge pipe to concentrate the sludge, and the concentrated sludge is discharged from the inside of the filtration cylinder. In the sludge concentrator,
A sludge concentrating apparatus, wherein the spiral screw has a rotating shaft hollow, and washing water is allowed to flow from the rotating shaft into the filter tube to wash the sludge in the filter tube.   A plurality of outlets are formed at one axial end of the rotating shaft of the spiral screw, and the high-concentration sludge that has been concentrated in the filter cylinder is washed with washing water that flows out from the outlet into the filter cylinder. The sludge concentration apparatus according to claim 1, wherein the apparatus is washed.   The sludge from the sludge agglomeration tank is introduced into the upper part of the filter cylinder, and the sludge is concentrated while being conveyed downward in the filter cylinder by the spiral screw, and a rotary joint is installed at the upper end of the rotary shaft of the spiral screw. Washing water supplied via a plurality of outlets formed at the lower part of the rotating shaft is flowed to wash the high-concentration sludge that has been concentrated in the filter cylinder. The sludge concentration apparatus as described.   The separation liquid discharge pipe has a double pipe structure of an outer pipe and an inner pipe, the height of the upper end edge of the inner pipe is set lower than the liquid level in the filter cylinder, and the upper end edge of the inner pipe is The sludge concentrating device according to any one of claims 1 to 3, wherein the separating liquid overflows from the outer tube to the inner tube or from the inner tube to the outer tube.

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