JP2021181049A - Centrifugal separator, centrifugal separator operating method - Google Patents

Abstract

To achieve optimization of chemical feeding position in a centrifugal separator which adopts a line chemical feeding system for clogged chemical feeding of a coagulant, and applies a centrifugal force to a process liquid containing a solid content to perform solid-liquid separation.SOLUTION: A centrifugal separator comprises: a bowl which rotates to perform solid-liquid separation of a process liquid therein; a screw conveyor which transports a solid content, which has been separated into solid and liquid in the bowl, toward an exhaust port; and chemical feeder which adds a coagulant to the process liquid. The chemical feeder comprises: first clogged chemical feeding means which adds a coagulant to a flow channel of the process liquid before feeding thereof to the bowl at a point where a turbulent flow generates in the process liquid; second clogged chemical feeding means which adds the coagulant on an upstream side of the point where the turbulent flow is formed; and third clogged chemical feeding means which adds the coagulant on a downstream side of the point where the turbulent flow is formed, and is capable of switching in addition of the coagulant from any of the first to third clogged chemical feeding means.SELECTED DRAWING: Figure 1

Description

The present invention relates to a centrifugal separator that applies centrifugal force to a treatment liquid containing a solid content to separate the solid and liquid, and more particularly to a technique of supplying a flocculant outside the machine in order to promote the solid and liquid separation of the treatment liquid. ..

As a device for solid-liquid separation of a treatment liquid containing a solid content, a centrifuge device called a decanter is known. FIG. 9 schematically shows the basic structure of the decanter. The horizontal decanter 1 includes a bowl 11 and a screw conveyor 12 that rotate around a horizontal axis. Although not shown, a vertical decanter in which the bowl 11 and the screw conveyor 12 rotate around a vertical axis is also known.

The bowl 11 is formed of a cylindrical body having a conical shape at one end or both ends. The screw conveyor 12 is a rotary conveyor provided with screw blades 12a for transporting the solid content separated in the bowl 11. The inside of the screw conveyor 12 is hollow along the axis of rotation center, and the feed tube 13 which is a supply nozzle for the treatment liquid to be centrifuged is inserted with a slight clearance so as not to come into contact with the screw conveyor 12. .. The processing liquid discharged from the tip of the feed tube 13 is supplied to the processing liquid chamber in the screw conveyor 12, is discharged from the supply hole 14 formed on the outer peripheral surface by the action of centrifugal force, and is supplied into the bowl 11. NS.

In such a configuration, for example, when a treatment liquid derived from sewage called sludge is separated into a dehydrated cake and a separation liquid, the treatment liquid is continuously supplied into the bowl 11 and the bowl 11 is rotated at a predetermined number of revolutions. The treatment liquid is separated into a solid phase and a liquid phase in the bowl 11 by the action of centrifugal force. The centrifugally separated solid content is conveyed toward one end side of the bowl 11 by the screw conveyor 12, separated from the liquid phase at the conical portion, and discharged as a dehydrated cake from the solid content outlet 15. On the other hand, the separation liquid overflows from the separation liquid outlet 16 on the opposite side and is discharged.

In order to obtain a dehydrated cake having a desired water content, the centrifugal force (G) applied to the treatment liquid, the torque of the screw conveyor 12, the differential speed between the rotating bowl 11 and the screw conveyor 12 and the like are adjusted. In addition, there is a chemical injection treatment that supplies a flocculant for promoting solid-liquid separation (see, for example, Patent Documents 1 to 7).

Patent Document 1 discloses a centrifuge device embodied by the present inventor, which can control the flow rate ratio between external drug injection and in-flight drug injection. The present inventor is considering optimizing the extracorporeal drug injection as a further improvement. That is, the out-of-machine drug injection often employs a "line drug injection method" in which the flow path of the coagulant is connected to the flow path of the treatment liquid. However, if the position of the external chemical injection is uniformly designed to be the same, for example, the properties of the sludge to be treated differ depending on the sewage treatment plant to be installed, and the expected separation performance may not be obtained even if the chemical injection amount is increased. .. Moreover, even if the expected separation performance is obtained, the separation performance may not be maintained, for example, when it rains and the properties of the sludge to be treated change.

Japanese Patent No. 6230741 Japanese Patent No. 3202289 Special Fair 8-29268 Gazette Japanese Patent No. 5650999 Japanese Patent No. 5425523 Japanese Patent No. 5490442 Japanese Patent No. 5619965

The present invention has been made based on such circumstances, and an object thereof is to inject an extracorporeal agent of a coagulant in a centrifuge device that applies centrifugal force to a treatment liquid containing a solid content to separate the solid and liquid. Is to optimize.

The gist of the present invention is as follows.
(1) The centrifugal separator of the present invention includes a bowl that rotates to separate the internal treatment liquid into solid and liquid, a screw conveyor that conveys the solid content separated by solid and liquid in the bowl toward the discharge port, and the above. In a centrifuge device provided with a chemical injection device for adding a flocculant to the treatment liquid, the chemical injection device forms a turbulent flow in the treatment liquid with respect to the flow path of the treatment liquid before being supplied to the bowl. The turbulent flow is formed by a first external drug injecting means for adding a flocculant at a certain point and a second external drug injecting means for adding a flocculant on the upstream side of the point where the turbulent flow is formed. A third external drug injecting means for adding the flocculant is provided on the downstream side of the point where the flocculant is added, and it is possible to switch from which of the first to third external drug injecting means to add the flocculant. It is a feature.
(2) The point at which the turbulent flow is formed is a line kimisa arranged in the flow path of the treatment liquid.
(3) The point at which the turbulent flow is formed is either a joint member of a pipe or a valve constituting the flow path of the treatment liquid.
(4) The chemical injection device includes an external chemical injection device that adds a flocculant to the treatment liquid before being supplied into the bowl, and an in-flight chemical injection device that adds a flocculant to the treatment liquid supplied into the bowl. And, while variably controlling the ratio of the in-flight drug injection amount to the in-flight drug injection amount, it is also possible to switch and control which of the first to third external drug injection means is used for the in-flight drug injection. ..
(5) The operation method of the centrifugal separator of the present invention is a bowl that rotates to separate the internal treatment liquid into solid and liquid, and a screw conveyor that conveys the solid content separated by solid and liquid in the bowl toward the discharge port. A method of operating a centrifuge device including a chemical injection device for adding a flocculant to the treatment liquid, and a turbulent flow in the treatment liquid with respect to the flow path of the treatment liquid before being supplied to the bowl. The solid-liquid separation state when the flocculant is added to the formed point, the solid-liquid separation state when the flocculant is added to the upstream side of the point where the turbulent flow is formed, and the turbulent flow are formed. It is characterized by including a step of comparing the solid-liquid separation state when the flocculant is added to the downstream side of the point, and a step of deciding from which to add the flocculant based on the result of the comparison. ..

According to the present invention, a turbulent flow is formed with a first external drug injection means for adding a flocculant at a point where a turbulent flow is formed in the treatment liquid to the flow path of the treatment liquid before being supplied to the bowl. A second external drug injection means for adding a flocculant on the upstream side of the point where turbulence is formed and a third external drug injection means for adding the flocculant on the downstream side of the point where turbulence is formed are provided. By providing a drug injection device that can switch whether to add the flocculant from any of the first to third external drug injection means, it becomes possible to optimize the external drug injection.

It is a block diagram of the centrifuge according to 1st Embodiment of this invention. It is a block diagram of the chemical injection module of the said centrifuge. It is a block diagram of the line mixer arranged in the said chemical injection module. It is a flow which shows the supply optimization method of the polymer-based flocculant of the said centrifuge. It is a block diagram of the centrifuge according to the 2nd Embodiment of this invention. It is a block diagram of the centrifuge according to the 3rd Embodiment of this invention. It is a block diagram of the centrifuge according to 4th Embodiment of this invention. It is a block diagram of the centrifuge according to 5th Embodiment of this invention. It is a figure which shows the structure of the conventional centrifuge device.

Hereinafter, the centrifuge according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the technical scope of the present invention is not limited to any limitation by the embodiments described below.

(First Embodiment)
As shown in FIG. 1, the decanter 2 of the present embodiment is centrifugally separated in a casing 2a having a solid content outlet 20 and a separation liquid outlet 21 on the lower surface side, a bowl 3 arranged in the casing, and a rotating bowl 3. It is provided with a screw conveyor 4 for transporting the solid content and a pipe-shaped feed tube 5 for supplying the treatment liquid for centrifugation into the bowl 3. Both shafts of the bowl 3 are supported by a bearing mechanism 22 such as a bearing arranged outside the casing 2a, for example. Further, both shafts of the screw conveyor 4 are supported by a bearing mechanism 23 such as a conveyor bearing. Reference numeral 24 is a partition wall for partitioning the space in the casing 2a.

Then, when the power of the main motor 25, which is a drive device, is transmitted to the pulley 25b on the bowl 3 side via the rotary belt 25a, the bowl 3 rotates, and the gearbox 26 and the spline shaft 26a, which are differential speed generators, are further rotated. Rotational power is transmitted to the screw conveyor 4 through, whereby the bowl 3 and the screw conveyor 4 rotate with a relative differential speed. It can be appropriately adjusted depending on the type and concentration of the treatment liquid, but as an example of normal operation, the bowl 3 is rotated at a predetermined rotation speed selected within the range of ^{500 to 8000 min -1, and 0.5 with respect to the bowl 3.} Centrifugation is performed by rotating the screw conveyor 4 with a relative differential speed of ~ 50 min ^-1. As an example, when sludge derived from sewage is used as a treatment liquid, it is supplied into the bowl 3 at a flow rate of ^{, for example, 2 to 25 m 3 / Hr.}

A motor called a back drive motor 27 is connected to the gearbox 26 via a rotary belt 27a and a pulley 27b. The back drive motor 27 is for braking the screw conveyor 4 so that it rotates slower than the bowl 3. The regenerative power generated in the back drive motor 27 by applying the brake can be supplied to the main motor 25. However, the back drive motor 27 does not necessarily have to be provided. Reference numeral 28 is a support frame for the decanter 2, and reference numeral 29 is a support member for supporting the feed tube 5.

The bowl 3 has a conical portion 31 on one end side of a cylindrical body portion, and a disk-shaped member called a front hub 32 is provided on the other end side. The body portion of the bowl 3 forms a pool (liquid pool) portion of the treatment liquid supplied into the bowl 3. On the other hand, the conical portion 31 forms a beach portion where the solid content conveyed by the screw conveyor 4 separates from the liquid phase, and the solid content discharge port 33 is provided at the end thereof. The front hub 32 is provided with a separation liquid discharge port 34 through which the separation liquid overflows and is discharged. The separation liquid discharge port 34 is a circular opening hole penetrating the front hub 32.

Screw blades 41 for transporting solid content are spirally provided on the outer peripheral surface of the screw conveyor 4. Further, a processing liquid supply hole 42 is provided on the outer peripheral surface of the screw conveyor 4. The processing liquid supply hole 42 communicates with the processing liquid supply chamber 43 formed inside the screw conveyor 4.

The feed tube 5 approaches or is inserted into the processing liquid supply chamber 43 so as not to come into contact with the rotating bowl 3 and the screw conveyor 4. The treatment liquid supply chamber 43 is provided with an upright wall 44 serving as a liquid barrier for preventing the supplied treatment liquid from flowing out in the circumferential direction. On the other hand, a flow path 51 (for example, a pipe) of a processing liquid from a processing liquid feeding means (not shown) such as a pump is connected to the base end side of the feed tube 5. The treatment liquid sent by the treatment liquid feeding means is discharged from the tip of the feed tube 5 into the treatment liquid supply chamber 43. The treatment liquid supplied into the treatment liquid supply chamber 43 is discharged from the treatment liquid supply hole 42 by the action of the centrifugal force of the rotating screw conveyor 4 and is supplied into the bowl 3.

Subsequently, a chemical injection device for adding a flocculant will be described. The decanter 2 of the present embodiment includes a polymer-based drug injection device 7 for adding a polymer-based flocculant while controlling the ratio of the amount of the external drug injection to the in-flight drug injection. Further, it is provided with an inorganic chemical injection device 6 for supplying an inorganic flocculant. That is, FIG. 1 shows, as an example, a decanter 2 in which each flocculant is added in the order of a polymer-based flocculant for external drug injection, a polymer-based flocculant for in-flight drug injection, and an inorganic flocculant for in-flight drug injection. Shows.

First, an external drug injection of a polymer-based flocculant will be described. As a preferable example, the line drug injection method is adopted for the out-of-machine drug injection. Specifically, the chemical injection module 70 of the polymer-based flocculant is connected in the middle of the flow path 51 (for example, piping) of the treatment liquid, and the polymer-based chemical injection module 70 is connected to the treatment liquid flowing in the flow path 51. Add the coagulant.

FIG. 2 shows a preferred example of the drug injection module 70. As shown in FIG. 2, in the chemical injection module 70, a line mixer 8 is arranged in the middle of the flow path 51 of the processing liquid arranged in the vertical direction to form a turbulent flow (including a vortex flow) in the treatment liquid. And. The flow path 51 then turns laterally and connects to the feed tube 5. The chemical injection module 70 branches the flow path 71 of the polymer-based flocculant into three, and one of them is connected to the line mixer 8. A valve 71A is provided in the flow path 71 connected to the line mixer 8 so that the polymer-based flocculant can be added and stopped by opening and closing the valve 71A. That is, the chemical injection module 70 is provided with a "first external chemical injection means" for adding a polymer-based flocculant to a point where a turbulent flow is formed in the treatment liquid.

One of the three branched flow paths 71 of the polymer-based flocculant is connected to the flow path 51 of the treatment liquid on the upstream side of the line mixer 8. A valve 71B is provided in the flow path 71 connected to the upstream side of the line mixer 8 so that the polymer-based flocculant can be added and stopped by opening and closing the valve 71B. That is, the chemical injection module 70 is provided with a "second external chemical injection means" for adding a polymer-based flocculant on the upstream side of the point where the line mixer 8 forms a turbulent flow in the treatment liquid.

One of the three branched flow paths 71 of the polymer-based flocculant is connected to the flow path 51 of the treatment liquid on the downstream side of the line mixer 8. The connection on the downstream side of the line mixer 8 may be a region where the turbulent flow formed by the line mixer 8 remains, or may be after the turbulent flow formed by the line mixer 8 disappears. Preferably, it is connected to the region where the turbulent flow formed by the line mixer 8 remains. A valve 71C is provided in the flow path 71 connected to the downstream side of the line mixer 8 so that the polymer-based flocculant can be added and stopped by opening and closing the valve 71C. That is, the chemical injection module 70 is provided with a "third external chemical injection means" in which the line mixer 8 adds a polymer-based flocculant on the downstream side of the point where turbulence is formed in the treatment liquid.

The first to third external medicine injecting means can switch from which extraneous medicine injecting means to add the polymer-based coagulant by opening and closing the valves 71A to 71B. The valves 71A to 71B as switching control may be opened and closed automatically or manually. The addition of the polymer-based flocculant is not limited to any one of the first to third external drug injection means, and may be added from a plurality of means. In this case, the ratio of the addition amount may be adjusted. Furthermore, the present invention is not limited to the first to third extracorporeal drug injecting means, and extracorporeal drug injecting means may be added to the upstream side and / or the downstream side. Further, the flow path 71 of the polymer-based flocculant does not have to be constructed with pipes branched into three, for example, one flexible hose or the like is used on the downstream side of the valve 72, and any one of valves 71A to 71B is used. The addition position may be switched by connecting a hose or the like to the upstream side.

The distance L1 (that is, the length of the flow path 51) from the addition position of the second external medicine injection means to the addition position of the first external medicine injection means is, for example, 150 to 500 mm. The interval L2 (that is, the length of the flow path 51) from the addition position of the first external medicine injection means to the addition position of the third external medicine injection means is within the range of the turbulent flow formed by the line mixer 8. However, as an example, it is set to 150 to 500 mm. The intervals L1 and L2 can be used as parameters for securing and adjusting the agglutination reaction time (= length / flow rate).

Various types of line mixers 8 can be adopted. The configuration and shape are not particularly limited. FIG. 3 shows an example of the line mixer 8. The line mixer 8 has a circular tubular main body 81 connected in the middle of the flow path 51, and a turbulence forming member 82 having arcuate convex portions facing each other is fixedly arranged in the main body 81. The discharge port 83 of the polymer-based flocculant is provided so as to face each other above (that is, on the downstream side) of the arcuate convex portion of the turbulence forming member 82. As the line mixer 8 of this type, a static mixer manufactured by JMS Co., Ltd. is suitable.

Returning to FIG. 1, a valve 72 as a flow rate adjusting means is provided in the flow path 71 of the polymer-based flocculant connected to the drug injection module 70, and the external medicine is adjusted by adjusting the opening degree of the valve 72. Adjust the pouring flow rate. Further, a flow meter 73 is provided in the flow path 71 so that the flow rate at which the external medicine is injected can be measured. However, the valve 72 is an example of the flow rate adjusting means, and the valve 72 is not limited to this, and another configuration may be adopted as long as the flow rate can be adjusted. For example, a metering pump in which the flow rate can be set variably can be given as another example.

On the base end side of the flow path 71 of the polymer-based flocculant, a polymer-based flocculant liquid feed pump 74 (hereinafter, simply referred to as “aggregator pump 74”) as a liquid feed means is interposed. The source of the flocculant is linked. FIG. 1 shows a tank 75 in which a solution of a polymer-based flocculant is stored as an example of a supply source. As the polymer-based flocculant, any one of an amphoteric polymer, an anionic polymer or a cationic polymer, or a combination thereof can be used. As a preferable example of the polymer-based flocculant, one or more kinds such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, and polyvinyl amidine can be mentioned. As another example of the source of the polymer-based flocculant, for example, there is a dissolving device for dissolving a solid polymer-based flocculant in a solvent (for example, water) to generate a solution.

Next, the in-flight drug injection of the polymer-based flocculant will be described. In-flight drug injection is performed using the feed tube 5 as an example. The feed tube 5 has a multi-tube structure in which a flow path 52 through which the treatment liquid flows is formed in the center, and a flow path 53 through which the polymer-based flocculant flows so as to surround the outer periphery thereof. Then, a flow path 76 (for example, a pipe) from the flocculant pump 74 is connected to the base end side of the feed tube 5. A valve 77 as a flow rate adjusting means is provided in the middle of the flow path 76 from the coagulant pump 74, and the flow rate is adjusted by adjusting the opening degree of the valve 77. Further, a flow meter 78 is provided in the middle of the flow path 76 so that the flow rate of in-flight drug injection can be measured. However, the valve 77 is an example of the flow rate adjusting means, and the valve 77 is not limited to this, and other configurations may be adopted as long as the flow rate can be adjusted. For example, a metering pump in which the flow rate can be set variably can be given as another example. The polymer-based coagulant for in-flight drug injection and external drug injection may be of the same type or different types with different supply sources.

On the tip end side of the feed tube 5, a discharge port for the polymer-based flocculant is formed separately from the discharge port for the treatment liquid in the center. The discharge port of the polymer-based flocculant shall be a plurality of circular opening holes formed so as to penetrate in the radial direction on the peripheral surface on the tip end side of the feed tube 5. On the other hand, inside the screw conveyor 4, an upright wall 44 serving as a partition wall is interposed to form a coagulant supply chamber 45 adjacent to the treatment liquid supply chamber 43. The coagulant supply chamber 45 is a supply chamber having a groove-like cross section formed on the inner peripheral surface of the cavity of the screw conveyor 4 over the entire circumference, and receives the polymer-based coagulant discharged from the feed tube 5 in the radial direction. be able to. Further, a coagulant discharge port 46 for supplying the polymer-based coagulant received in the supply chamber into the bowl 3 is formed in a portion corresponding to the bottom surface of the coagulant supply chamber 45 having a groove-shaped cross section. The coagulant discharge port 46 is a circular opening hole that penetrates the screw conveyor 4 in the radial direction. That is, the polymer-based flocculant is also configured to be supplied into the bowl 3 by utilizing the action of the centrifugal force of the rotating screw conveyor 4, similarly to the treatment liquid. The polymer-based flocculant may be supplied to the treatment liquid in the bowl 3 or may be mixed with the treatment liquid in the middle of being supplied toward the inside of the bowl 3.

The polymer-based drug injection device 7 further includes a flow rate ratio control unit 79 that controls the supply amounts of the external drug injection and the in-flight drug injection. As an example, the flow rate ratio control unit 79 can be configured by a computer system including a storage device such as a CPU and a memory. The flow rate ratio control unit 79 may be installed in the vicinity of the decanter 2 as an operation panel, or may be configured so that the system installed in the central monitoring room exerts its function. Of course, the flow rate ratio control may be manual control in which the operator manually adjusts the opening degree of the valves 72 and 77 while checking the flow rate meters 73 and 78, instead of the automatic control by the flow rate ratio control unit 79.

The flow rate ratio control unit 79 distributes the total supply amount of the polymer-based flocculant to be supplied to the decanter 2, and executes the out-of-machine drug injection and the in-flight drug injection at a predetermined flow rate ratio. The flow rate ratio control between the external medicine injection and the in-flight medicine injection can be performed, for example, by adjusting the balance of the valve opening. More specifically, first, the opening / closing range of the valves 72 and 77 is determined in advance, the most closed state within the range is set to 0%, and the most open state is assigned to 100%. Then, for example, the valve opening degree can be arbitrarily adjusted between 0 and 100% by using an electric actuator with a position meter. The opening / closing range of the valves 72 and 77 may be a range from fully closed to fully open, or may be a range in which the flow rate can be adjusted accurately due to the configuration of the valves 72 and 77. Then, from the state where the valve opening on the external drug injection side is 100% and the valve opening on the in-flight drug injection side is 0% and the flocculant is supplied, the valve opening of both is passed through the intermediate point of 50%. The valve opening on the external drug injection side is set to 0%, and the valve opening on the in-flight drug injection side is set to 100% so that the state in which the flocculant is supplied can be reciprocated. The valve opening on the external drug injection side may be started from 0% and the valve opening on the in-flight drug injection side may be started from 100%. The flow rate ratio control is not limited to the balance adjustment of the valve opening. As another example, a control model in which the valve openings of the external medicine injection and the in-flight medicine injection are set corresponding to the magnitude of the centrifugal force (G) determined by the rotation speed of the bowl 3 may be adopted.

Next, the in-flight drug injection of the inorganic flocculant will be described. In-flight drug injection is performed using the feed tube 5 as an example. In the feed tube 5, a flow path 52 through which the treatment liquid flows is formed in the center, a flow path 53 through which the polymer-based flocculant flows so as to surround the outer periphery thereof, and an inorganic flocculant further surrounds the outer periphery thereof. It has a multi-tube structure with a flow path 54 formed. Then, a flow path 61 (for example, a pipe) of the inorganic flocculant is connected to the base end side of the feed tube 5. A valve 62 as a flow rate adjusting means is provided in the flow path 61 of the inorganic flocculant, and the flow rate of the flocculant is adjusted by adjusting the opening degree of the valve 62. Further, a flow meter 63 is provided in the middle of the flow path 61 so that the flow rate of the in-flight drug injection can be measured. However, the valve 62 is an example of the flow rate adjusting means, and the valve 62 is not limited to this, and another configuration may be adopted as long as the flow rate can be adjusted. For example, a metering pump in which the flow rate can be set variably can be given as another example.

An inorganic flocculant is supplied to the base end side of the flow path 61 of the inorganic flocculant via an inorganic flocculant liquid feed pump 64 (hereinafter, simply referred to as “aggregator pump 64”) as a liquid feed means. The sources are connected. FIG. 1 illustrates a tank 65 in which a solution of an inorganic flocculant is stored as an example of a supply source. As the inorganic flocculant, for example, one or more selected from ferric sulfate (polyiron), PAC and the like can be used. Among them, polyiron is preferable. Of course, other types of inorganic flocculants may be used. Further, the in-flight drug injection and the out-of-flight drug injection coagulant may be of the same type or may be of different types from different sources.

On the tip end side of the feed tube 5, a discharge port for the inorganic flocculant is formed separately from the discharge port for the central treatment liquid and the discharge port for the polymer-based flocculant. The discharge port of the inorganic flocculant shall be a plurality of circular opening holes formed so as to penetrate in the radial direction on the peripheral surface on the tip end side of the feed tube 5. On the other hand, inside the screw conveyor 4, the polymer-based coagulant supply chamber 45 and the adjacent inorganic coagulant supply chamber 47 are formed with the upright wall 44 interposed therebetween. The coagulant supply chamber 47 is a supply chamber having a groove-like cross section formed on the inner peripheral surface of the cavity of the screw conveyor 4 over the entire circumference, and receives the inorganic coagulant discharged from the feed tube 5 in the radial direction. Can be done. Further, a coagulant discharge port 48 for supplying the inorganic coagulant received in the supply chamber into the bowl 3 is formed in a portion corresponding to the bottom surface of the coagulant supply chamber 47 having a groove-shaped cross section. The coagulant discharge port 48 is a circular opening hole that penetrates the screw conveyor 4 in the radial direction. That is, the inorganic flocculant is also configured to be supplied into the bowl 3 by utilizing the action of the centrifugal force of the rotating screw conveyor 4, like the treatment liquid and the polymer flocculant. However, as a preferable example, the inorganic flocculant is supplied to the solid content in the vicinity of the beach portion where solid-liquid separation has progressed.

Subsequently, as an example of the operation method of the decanter 2, a method for optimizing the chemical injection of the polymer-based flocculant when the decanter 2 performs solid-liquid separation of sludge will be described with reference to FIG. If this supply optimization method is executed during normal operation, it will be possible to deal with daily changes in sludge properties. Further, for example, it may be performed at the time of construction or test run when the decanter 2 is newly installed in the sewage treatment plant.

First, it is selected from which of the first to third extracorporeal drug injection means of the drug injection module 70 is added. As an example, valves 71A to 71C are opened and closed so as to be added from the nth extracorporeal drug injection means (n = 1) (Act 10). When the solid-liquid separation of the decanter 2 becomes stable, the flow rate ratio control is executed (Act 11). As an example of the flow rate ratio control, the flow rate ratio control unit 79 shifts the opening degree of the valves 72 and 77 described above (valve 72; 0% → 100%, valve 77; 100% → 0%), for example, every hour. For example, it is performed at intervals of 25%, and the water content of the dehydrated cake, which is a solid content, and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) are confirmed each time (Act12). Then, if the result tends to improve, the shift of the opening is further advanced, and if the result tends to deteriorate, the shift of the opening is returned. By repeating this round trip, the external drug injection and the in-flight drug injection are converged to the optimum balance.

Subsequently, n = n + 1 (Act13 No, Act14) is set, and the valves 71A to 71C are opened and closed so as to be added from the nth extracorporeal drug injection means (n = 2) (Act10). Further, the flow rate ratio control is executed (Act 11), and the water content of the dehydrated cake and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) is confirmed (Act 12). Similarly, n = n + 1 (Act13 No, Act14), and the valves 71A to 71C are opened and closed so as to be added from the nth extracorporeal drug injection means (n = 3) (Act10). Further, the flow rate ratio control is executed (Act 11), and the water content of the dehydrated cake and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) is confirmed (Act 12).

When the flow rate ratio control is completed in all of the first to third extracorporeal drug injection means (Act13 Yes), the water content of the dehydrated cake, which is the separated solid content, and / or the state of the separated liquid (SS concentration, color, It is determined which number was the best external drug injection means (foam, pH, etc.), and the subsequent operation (for example, all day) is to be added from the best external drug injection means (Act15). It is preferable that the flow rate ratio control is continued even in the subsequent operation. More preferably, when the optimum balance point of the flow rate ratio is found, the total supply amount of the flocculant is lowered, and if the result is maintained in a good state, the total supply amount is further lowered, and the result becomes worse. When it becomes a trend, the total supply will be returned. By repeating this round trip, the external drug injection and the in-flight drug injection can be converged to the optimum balance and the optimum total supply amount.

As described above, according to the decanter 2 of the present embodiment, the line mixer 8 is the first external drug injection means for adding the polymer-based flocculant at the point where the line mixer 8 forms a turbulent flow in the treatment liquid, and the line mixer 8. The second external drug injection means for adding the coagulant on the upstream side of the point where the turbulent flow is formed in the treatment liquid, and the coagulant are added on the downstream side of the point where the line mixer 8 forms the turbulent flow in the treatment liquid. By providing a third external drug injection means and a polymer-based drug injection device 7 capable of switching from which of the first to third external drug injection means the flocculant to be added, the external drug is provided. It is possible to optimize the external drug injection of the polymer-based flocculant while controlling the ratio of the injection amount of the injection and the in-flight drug injection.

(Second Embodiment)
Subsequently, the decanter 2 according to the second embodiment will be described. The decanter 2 of the present embodiment has the same configuration as the decanter 2 of the first embodiment, except that the inorganic flocculant is also configured to control the flow rate ratio of the in-flight drug injection and the external drug injection. Therefore, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 5, the line drug injection method is adopted as a preferable example of the external drug injection of the inorganic flocculant. Specifically, the chemical injection module 9 of the inorganic flocculant is connected in the middle of the flow path 51 (for example, piping) of the treatment liquid, and the inorganic coagulant from the chemical injection module 90 is connected to the treatment liquid flowing in the flow path 51. Is added. The medicinal injection module 9 of the inorganic flocculant is arranged on the upstream side of the medicinal injection module 70 of the polymer-based flocculant, and is added to the treatment liquid before the polymer-based flocculant.

In the chemical injection module 9, a line mixer 90 is arranged in the middle of the flow path 51 of the treatment liquid, and is used as a point for forming a turbulent flow (including a vortex flow) in the treatment liquid. The external medicine injection module 9 branches the flow path 71 of the inorganic flocculant into three, and connects one of them to the line mixer 90. A valve 9A is provided in the flow path 66 connected to the line mixer 90 so that the inorganic flocculant can be added and stopped by opening and closing the valve 9A. That is, the chemical injection module 9 is provided with a "first external chemical injection means" for adding an inorganic flocculant to a point where a turbulent flow is formed in the treatment liquid.

One of the three branches of the inorganic flocculant flow path 66 is connected to the flow path 51 of the treatment liquid on the upstream side of the line mixer 90. A valve 9B is provided in the flow path 66 connected to the upstream side of the line mixer 90, and the valve 9B can be opened and closed so that the inorganic flocculant can be added and stopped. That is, the chemical injection module 9 is provided with a "second external chemical injection means" for adding an inorganic flocculant on the upstream side of the point where the line mixer 90 forms a turbulent flow in the treatment liquid.

One of the three branches of the inorganic flocculant flow path 66 is connected to the flow path 51 of the treatment liquid on the downstream side of the line mixer 90. The connection on the downstream side of the line mixer 90 may be a region where the turbulent flow formed by the line mixer 90 remains, or may be after the turbulent flow formed by the line mixer 90 disappears. Preferably, it is connected to the region where the turbulence formed by the line mixer 90 remains. A valve 9C is provided in the flow path 66 connected to the downstream side of the line mixer 90, and the valve 9C can be opened and closed so that the inorganic flocculant can be added and stopped. That is, the chemical injection module 9 is provided with a "third external chemical injection means" in which the line mixer 90 adds an inorganic flocculant on the downstream side of the point where turbulence is formed in the treatment liquid.

The first to third external medicine injecting means can be switched from which external medicine injecting means to add the inorganic flocculant by opening and closing the valves 9A to 9B. The valves 9A to 9B as switching control may be opened and closed automatically or manually. The addition of the inorganic flocculant is not limited to any one of the first to third external drug injection means, and may be added from a plurality of means. In this case, the ratio of the addition amount may be adjusted. Furthermore, the present invention is not limited to the first to third extracorporeal drug injecting means, and extracorporeal drug injecting means may be added to the upstream side and / or the downstream side. The chemical injection module 9 can have the same configuration as the chemical injection module 70 of the polymer-based flocculant shown in FIGS. 2 and 3.

A valve 67 as a flow rate adjusting means is provided in the flow path 66 of the inorganic flocculant connected to the chemical injection module 9, and the flow rate of external drug injection is adjusted by adjusting the opening degree of the valve 67. Further, a flow meter 68 is provided in the flow path 66 so that the flow rate at which the external medicine is injected can be measured. However, the valve 67 is an example of the flow rate adjusting means, and the valve 67 is not limited to this, and another configuration may be adopted as long as the flow rate can be adjusted. For example, a metering pump in which the flow rate can be set variably can be given as another example.

The inorganic drug injection device 6 further includes a flow rate ratio control unit 69 that controls the supply amounts of the external drug injection and the in-flight drug injection. As an example, the flow rate ratio control unit 69 can be configured by a computer system including a storage device such as a CPU and a memory. The flow rate ratio control unit 69 may be installed in the vicinity of the decanter 2 as an operation panel, or may be configured so that the system installed in the central monitoring room exerts its function. Of course, the flow rate ratio control may be a manual control in which the operator manually adjusts the opening degrees of the valves 62 and 67 while checking the flow meters 63 and 68, instead of the automatic control by the flow rate ratio control unit 69.

By configuring the inorganic drug injection device 6 in this way, it is possible to execute, for example, the drug injection optimization method shown in FIG. 4, similarly to the polymer-based drug injection device 7. Therefore, according to the decanter 2 of the second embodiment, for both the polymer-based coagulant and the inorganic-based coagulant, the extracorporeal drug injection is performed while controlling the ratio of the in-flight drug injection amount to the in-flight drug injection. It is possible to optimize the. It is not always necessary to pass through the two line mixers 90 and 8. For example, a valve and a bypass flow path with a valve are provided at the bases of the line mixer 90 and the line mixer 8, respectively, and one of the line mixers 90 or one can be opened and closed by opening and closing the valve. Only the line mixer 8 may be used.

(Third Embodiment)
Subsequently, the decanter 2 according to the third embodiment will be described. The decanter 2 of the present embodiment has the same configuration as the decanter 2 of the first embodiment, except that the polymer-based flocculant is composed only of external drug injection. Therefore, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The decanter 2 of this embodiment is shown in FIG. Even with such a configuration, optimization of the external drug injection of the polymer-based flocculant while controlling the ratio of the external drug injection and the in-flight drug injection as in the decanter 2 of the first embodiment. It becomes possible to plan.

(Fourth Embodiment)
Subsequently, the decanter 2 according to the fourth embodiment will be described. The decanter 2 of the present embodiment has the same configuration as the decanter 2 of the first embodiment, except that the flocculant is added only to the external drug injection of the polymer-based flocculant. Therefore, the same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The decanter 2 of this embodiment is shown in FIG. Even with such a configuration, it is possible to optimize the external drug injection of the polymer-based flocculant, as in the case of the decanter 2 of the first embodiment. In addition, in-flight drug injection may be omitted in FIG. 7, and only external drug injection of the polymer-based flocculant may be used. That is, the pattern of the combination of the polymer-based flocculant and / or the inorganic-based flocculant in the external drug injection and / or the in-flight drug injection is such that the external drug injection is applied to at least one of the polymer-based flocculant or the inorganic flocculant. It suffices if it is included, and does not exclude patterns of combinations other than those of the first to fourth embodiments.

(Fifth Embodiment)
Subsequently, the decanter 2 according to the fifth embodiment will be described. In the decanter 2 of the present embodiment, instead of the chemical injection module 70 (including the line mixer 8) shown as an example in FIG. 2, for example, a pipe for a treatment liquid (that is, a flow path 51) arranged in a sewage treatment plant or the like. The configuration is the same as that of the decanter 2 of the first to fourth embodiments, except that the drug injection optimization is realized by utilizing the above. Therefore, the same components as those in the first to fourth embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, the size and height of the space in which the decanter 2 is installed and the positional relationship with the incidental equipment (for example, the positional relationship of the coagulant pump 74) are not necessarily the same, and therefore, they are arranged from the coagulant pump 74 to the decanter 2. Piping design is performed such as the piping route of the treatment liquid, the piping joints such as elbows, and the mounting position of the valve. In the present embodiment, the optimization of chemical injection of the polymer flocculant is realized by utilizing the piping shape of the treatment liquid.

FIG. 8 shows, as an example, a piping system when the optimization is actually performed. First, the point where the turbulent flow of the treatment liquid occurs in the arranged pipe is extracted. In the example of FIG. 8, it was confirmed that turbulence was generated due to the reducer R, which is a kind of pipe joint. Therefore, the addition position A, which is the point where turbulence is generated due to the reducer R, is set at the point where turbulence is formed in the treatment liquid, and the polymer-based flocculant pipe (that is, the flow path 71) is connected. .. That is, it is a "first extracorporeal drug injection means" in which a polymer-based flocculant is added to a point where a turbulent flow is formed in the treatment liquid. The addition position A is, for example, 5 m away from the decanter 2. As described above, the pipe length can be used as a parameter for securing and adjusting the agglutination reaction time (= length / flow rate). Therefore, the reducer R may be intentionally set at a position 5 m away.

Next, a polymer-based flocculant pipe (that is, a flow path 71) is connected to the addition position B on the upstream side of the reducer R, and on the upstream side of the point where turbulence is formed in the treatment liquid due to the reducer R. It is referred to as a "second extracorporeal drug injection means" to which a polymer-based flocculant is added. The addition position B is set at a distance of, for example, 10 m from the decanter 2 in order to increase the agglutination reaction time.

Next, a polymer-based flocculant pipe (that is, a flow path 71) is connected to the addition position C on the downstream side of the reducer R, and on the downstream side of the point where turbulence is formed in the treatment liquid due to the reducer R. It is referred to as a "third extracorporeal drug injection means" to which a polymer-based flocculant is added. The addition position C is, for example, 2 m away from the decanter 2. Preferably, it is in a pipe extending from the bottom to the top toward the decanter 2.

Further, a polymer-based flocculant pipe (that is, a flow path 71) is connected to the addition position D on the upstream side of the reducer R, and further upstream of the point where turbulence is formed in the treatment liquid due to the reducer R. It is referred to as a "fourth extracorporeal drug injection means" to which a polymer-based flocculant is added. The addition position D is set at a distance of, for example, 15 m from the decanter 2 in order to prolong the agglutination reaction time. It is preferable that the addition position is not a position more than 15 m away.

The first to fourth extracorporeal drug injecting means can switch from which extracorporeal drug injecting means to add the polymer-based flocculant by opening and closing the valve. The opening and closing of the valve as the switching control may be performed automatically or manually. The addition of the polymer-based flocculant is not limited to any one of the first to fourth external drug injection means, and may be added from a plurality of means. In this case, the ratio of the addition amount may be adjusted. Further, the present invention is not limited to the four first to fourth extracorporeal drug injecting means, and the extracorporeal drug injecting means may be added to the upstream side and / or the downstream side.

By setting the first to fourth extracorporeal drug injection means in this way, it is possible to execute, for example, the drug injection optimization method shown in FIG. First, it is selected from which of the first to third extracorporeal drug injection means to be added. As an example, it is added from the nth extracorporeal drug injection means (n = 1) (Act 10). When the solid-liquid separation of the decanter 2 becomes stable, the flow rate ratio control is executed (Act 11). As an example of the flow rate ratio control, the flow rate ratio control unit 79 shifts the opening degree of the valves 72 and 77 described above (valve 72; 0% → 100%, valve 77; 100% → 0%), for example, every hour. For example, it is performed at intervals of 25%, and the water content of the dehydrated cake, which is a solid content, and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) are confirmed each time (Act12). Then, if the result tends to improve, the shift of the opening is further advanced, and if the result tends to deteriorate, the shift of the opening is returned. By repeating this round trip, the external drug injection and the in-flight drug injection are converged to the optimum balance.

Subsequently, n = n + 1 (Act13 No, Act14) is set, and the mixture is added from the nth extracorporeal drug injection means (n = 2) (Act10). Further, the flow rate ratio control is executed (Act 11), and the water content of the dehydrated cake and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) is confirmed (Act 12). Similarly, n = n + 1 (Act13 No, Act14), and the addition is made from the nth extracorporeal drug injection means (n = 3) (Act10). Further, the flow rate ratio control is executed (Act 11), and the water content of the dehydrated cake and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) is confirmed (Act 12). Similarly, n = n + 1 (Act13 No, Act14), and the addition is made from the nth extracorporeal drug injection means (n = 4) (Act10). Further, the flow rate ratio control is executed (Act 11), and the water content of the dehydrated cake and / or the state of the separated liquid (SS concentration, color, foam, pH, etc.) is confirmed (Act 12).

When the flow rate ratio control is completed in all of the first to fourth extracorporeal drug injection means (Act13 Yes), the water content of the dehydrated cake which is the separated solid content and / or the state of the separated liquid (SS concentration, color, It is determined which number was the best external drug injection means (foam, pH, etc.), and the subsequent operation (for example, all day) is to be added from the best external drug injection means (Act15). It is preferable that the flow rate ratio control is continued even in the subsequent operation.

According to the above-described embodiment, it is possible to optimize the chemical injection of the external chemical injection of the polymer flocculant by utilizing the piping shape of the treatment liquid. By extracting the turbulence formation point in the pipe in this way, determining the addition position theoretically, and preferably determining the optimum addition position along the flow of FIG. 4, the drug for extra-machine injection is efficiently used. Note It is possible to optimize. As a result, it is possible to reduce the number of addition positions and avoid a situation in which the effect is not obtained even though the trial is performed. The point where turbulence is generated due to the reducer R is defined as the point where turbulence is formed in the treatment liquid, but it is not limited to this, and turbulence is caused by other pipe joints such as elbows and valves. It may be set at the point where the flow is generated. That is, it is preferable to select a point where turbulence is actively generated in the actual piping system. Further, although the polymer-based flocculant has been described as a preferable example of the fifth embodiment, it may be applied to the inorganic flocculant.

Although the present invention has been described in detail above in accordance with specific embodiments, the present invention in which various substitutions, modifications, changes, etc. in terms of form and details are defined by the description of the scope of claims. It is clear to those with ordinary knowledge in the art that it can be done without departing from the spirit and scope.

2 Decanter 3 Bowl 4 Screw conveyor 6 Inorganic chemical injection device 7 Polymer chemical injection device 70 Chemical injection module 71A, 71B, 71C Valve 79 Flow rate ratio control unit 8 Line mixer 82 Turbulence forming member

Claims (5)

A bowl that rotates to separate the internal treatment liquid into solid and liquid, a screw conveyor that conveys the solid content separated by solid and liquid in the bowl toward the discharge port, and a chemical injection device that adds a flocculant to the treatment liquid. And in a centrifuge equipped with
The chemical injection device includes a first external chemical injection means for adding a flocculant to the flow path of the treatment liquid before being supplied to the bowl at a point where a turbulent flow is formed in the treatment liquid, and the turbulent flow. A second extracorporeal drug injection means for adding a flocculant on the upstream side of the point where the turbulent flow is formed, and a third extracorporeal drug injection means for adding the flocculant on the downstream side of the point where the turbulent flow is formed. A centrifuge device comprising the above, wherein the flocculant can be added or switched from any of the first to third external drug injection means. The centrifuge according to claim 1, wherein the point at which the turbulent flow is formed is a line kimisa arranged in the flow path of the treatment liquid. The centrifuge device according to claim 1, wherein the point at which the turbulent flow is formed is either a joint member of a pipe or a valve constituting the flow path of the treatment liquid. The chemical injection device includes an external chemical injection device that adds a coagulant to the treatment liquid before being supplied into the bowl, and an in-flight chemical injection device that adds a coagulant to the treatment liquid supplied into the bowl. It is characterized by variably controlling the ratio of the in-flight drug injection amount to the in-flight drug injection amount, and switching and controlling which of the first to third external drug injection means is used for the in-flight drug injection. The centrifuge according to any one of claims 1 to 3. A bowl that rotates to separate the internal treatment liquid into solid and liquid, a screw conveyor that conveys the solid content separated by solid and liquid in the bowl toward the discharge port, and a chemical injection device that adds a flocculant to the treatment liquid. It is a method of operating a centrifuge equipped with
The solid-liquid separation state when the flocculant is added to the point where the turbulent flow is formed in the treatment liquid with respect to the flow path of the treatment liquid before being supplied to the bowl, and the upstream side of the point where the turbulent flow is formed. A step of comparing the solid-liquid separation state when the flocculant is added to the solid-liquid separation state and the solid-liquid separation state when the flocculant is added to the downstream side of the point where the turbulent flow is formed.
A method for operating a centrifuge device, comprising: a step of determining from which to add a flocculant based on the results of the comparison.

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