JPH031077Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a screw decanter type centrifuge for dewatering organic sludge generated in sewage, human waste, and various industrial wastewater treatment processes. [Prior Art] An example of a screw decanter type centrifuge conventionally used for dewatering organic sludge generated in sewage, human waste, and various industrial wastewater treatment processes is explained with reference to Figure 2. On the outside of a, an outer shell b is provided concentrically with the inner shell a, and the outer shell b is supported by a bearing c so as to rotate at high speed. A screw d is attached to the outer periphery of the inner shell a, and a feed pipe e is provided on the central axis of the inner shell a. From the right end of the feed pipe e in Figure 2, flocs produced by adding a cationic organic polymer condensing agent to the sludge slurry are sent and fall into the chamber f of the inner shell a. .
The flocs that have fallen into the chamber f enter the outer shell b from the chamber f through the discharge port g, and are separated into sludge deposits h and separated liquid i by the centrifugal force caused by the high speed rotation of the outer shell b. . After the sludge deposit h is scraped up from the separated liquid i by the screw d, it is discharged to the outside of the outer shell b from the discharge port j, and the separated liquid i is passed through the orifice k.
is discharged from the outer shell b. In the screw decanter type centrifugal separator shown in Fig. 2 described above, the sludge deposit h scraped up from the separated liquid i by the screw d is concentrated on the particle surface or in the interparticle voids due to the compaction effect caused by the centrifugal force. Although a certain amount of moisture is removed, the waste is discharged with a fairly high moisture content, which has the disadvantage of increasing the cost of subsequent landfilling, drying, and incineration. Therefore, in the past, a screw decanter type centrifugal separator as shown in FIG. 3 was developed to reduce the water content of the sludge deposit. In the conventional screw decanter type centrifuge shown in FIG. 3, notches l are made here and there in the inner diameter of a large diameter screw d. In addition to the screw d, a small-diameter auxiliary screw m is attached to the outer periphery of the inner shell a. The auxiliary screw m passes through the cutout hole l of the large-diameter screw d, and forms a spiral wound in the opposite direction to that of the screw d. The other parts have the same structure as shown in FIG. 2, and the same parts as in FIG. 2 are given the same reference numerals. In the conventional screw decanter type centrifugal separator shown in FIG. 3, the sludge deposit h is dehydrated by consolidation while being sent to the right side in FIG. 3 inside the outer shell b by the screw d. Since the water in the sludge deposit h leaks into the surface layer n inside the sludge deposit h, the moisture content becomes higher toward the inside. This inner surface layer n is connected to a discharge port j by an auxiliary screw m.
The outer peripheral part o with low moisture content is sent in the opposite direction.
Since only the sludge deposit is sent to the discharge port j by the screw d and discharged from the outer shell b, it is possible to obtain a sludge deposit with a low water content. The sludge deposits in the surface layer n scraped off by the auxiliary screw m are dehydrated while staying in the outer shell b, enter the outer peripheral part o in a sufficiently dehydrated state, and are passed through the discharge port by the screw d. j, and is discharged from the outer shell b. [Problems that the invention aims to solve] The screw decanter centrifuge shown in Figure 3 also uses a pre-addition method in which an organic polymer flocculant is added to the sludge and the sludge deposits are dehydrated. However, with this method, residual water remains trapped, so it was still not possible to dehydrate sufficiently. The present invention aims to significantly reduce the water content of sludge deposits discharged from a screw decanter centrifuge, thereby reducing sludge treatment costs. [Means for solving the problem] The present invention consists of an outer shell that is provided concentrically on the outside of the inner shell and has a discharge port on one end and rotates at high speed, an inner pipe that sends sludge into the outer shell, and an inner pipe that rotates at high speed. A large-diameter screw is attached to the outer circumference of the shell to scrape up the sludge deposits that have settled and separated inside the outer shell from the separated sludge liquid and send it toward the discharge port, and a large-diameter screw is installed concentrically on the outside of the inner pipe to scrape up the sludge deposits that have settled and separated inside the outer shell from the separated liquid. The outer tube adds an inorganic flocculant to the sludge deposits, and a large-diameter screw is attached to the outer periphery of the inner cylinder as a reversely wound spiral. This is a screw decanter type centrifuge equipped with a small-diameter auxiliary screw that sends in the opposite direction. [Operation] An inorganic flocculant is added to the sludge deposits scraped up from the separated liquid, and due to the mixing action of the screw, it fully reacts with the sludge deposits to remove residual moisture trapped in the sludge deposits and separate them. The water is pushed out to the surface layer, and this surface layer is scraped off by an auxiliary screw and sent in the opposite direction to the discharge port, from which sludge deposits with a low moisture content are discharged. [Example] Hereinafter, an example of the present invention will be described based on the drawings. In Fig. 1, reference numeral 1 denotes an outer shell, which is supported by a bearing 2 and rotates at high speed, and the right end side in Fig. 1 has a reduced diameter and a discharge port 3 is provided at the end. An orifice 4 is provided at the left end of the outer shell 1 in FIG. Outer body 1
An inner shell 5 is provided concentrically inside the body, and a large-diameter screw 6 is attached to the outer periphery of the inner shell 5. The screw 6 is provided with notch holes 7 in some places, and the screw 6 is inserted through these notch holes 7.
A small-diameter auxiliary screw 8, which is spirally wound in the opposite direction, is also attached to the outer periphery of the inner shell 5.
Chambers 9 and 10 are formed inside the inner shell 5,
The chambers 9 and 10 are communicated with the inside of the outer shell 1 through discharge ports 11 and 12, respectively. The discharge port 11 faces the large diameter portion of the outer shell 1, and the discharge port 12 faces the discharge port 3.
It faces the reduced diameter part of the outer shell 1 that is close to . An inner tube 13 is provided on the central axis of the inner shell 5 and faces the chamber 9. From the right end of this inner tube 13 in FIG. 1, a flocculation floc 14 produced by adding a cationic organic polymer flocculant to the sludge slurry is sent. Inner tube 13
An outer tube 15 is provided concentrically with the inner tube 13, and near the left end of the outer tube 15 in FIG.
It communicates with the chamber 10 by an outlet 16 . An inorganic flocculant 18 is supplied to the outer pipe 15 via a branch pipe 17. Iron salts are mainly suitable as the inorganic flocculant 18, and polyferrous sulfate, ferric chloride, ferrous sulfate, ferric sulfate, and the like are used. In the screw decanter type centrifugal separator shown in FIG. It falls into the inside of body 1. The centrifugal force caused by the high speed rotation of the outer shell 1 separates the liquid into a separated liquid 19 and a sludge deposit 20. The separated liquid 19 is then discharged from the orifice 4 to the outside of the outer shell 1, and the sludge deposits 20 are scraped up from the separated liquid 19 by the screw 6, and
The inside is sent toward the discharge port 3. The inorganic flocculant 18 supplied into the outer tube 15 via the branch pipe 17 enters the chamber 10 through the outlet 16,
Furthermore, it is added to the sludge deposit 20 scraped up from the separated liquid 19 through the discharge port 12 . The sludge deposit 20 scraped up from the separated liquid 19 has already had some moisture removed, and an inorganic flocculant 18 is added to it and mixed by the screw 6 while being sent to the discharge port 3. It will be done. As a result, the sludge deposit 20 is further dehydrated by the chemical action of the inorganic flocculant 18 to remove residual water and the compaction action by centrifugal force, and the water is transferred to the inner surface layer 21 of the sludge deposit 20. Because of the exudation, the surface layer 21 side has a high water content, and the outer peripheral part 22 has a low water content. The sludge deposit 20 in the outer peripheral portion 22 having a low moisture content is sent toward the discharge port 3 by the screw 6 and is discharged from the outer shell 1 as a sludge deposit having a low moisture content.
The sludge deposit 20 on the surface layer 21 side with a high water content is sent in the direction opposite to the discharge port 3 by the auxiliary screw 8, and is dehydrated while remaining in the outer shell 1, and finally is sufficiently dehydrated. The liquid enters the outer circumferential portion 22 in a state in which the liquid is absorbed, and is discharged from the outer shell 1. The water content of sludge deposits obtained by the conventional apparatus shown in FIGS. 2 and 3 and the apparatus of the present invention shown in FIG. 1 is as shown in the following table.

[Effect of idea]

This invention uses an inorganic flocculant to remove residual moisture in sludge deposits, and uses an auxiliary screw to send the sludge deposits in the surface layer, which has a high moisture content, in the opposite direction from the discharge port of the outer shell. extremely low sludge deposits can be obtained.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of one embodiment of the present invention;
3 are longitudinal sectional views of the conventional device. In the figure, 1 is an outer shell, 3 is a discharge port, 5 is an inner shell, 6 is a screw, 8 is an auxiliary screw, 13 is an inner pipe,
15 is an outer tube, 18 is an inorganic flocculant, 19 is a separation liquid,
20 is the sludge deposit, 21 is the surface layer, and 22 is the outer periphery.

Claims (1)

[Scope of utility model registration request] An outer shell that is provided concentrically on the outside of the inner shell and has a discharge port on one end and rotates at high speed; an inner pipe that sends sludge into the outer shell; and an inner pipe that is attached to the outer circumference of the inner shell and performs sedimentation and separation inside the outer shell. a large-diameter screw that scrapes up the sludge deposits from the sludge separation liquid and sends them in the direction of the discharge port; A small diameter screw is attached to the outer periphery of the inner shell as a spiral winding in the opposite direction to the large diameter screw and sends the surface layer of the sludge deposits scraped up from the separated liquid in the opposite direction to the discharge port. A screw decanter type centrifuge characterized by being equipped with an auxiliary screw.