JPH1028899A - Screen bowl decanter centrifugal separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the washing effect of a solid to enhance, for example, the purity of a crystal by providing the separator with a leveling means wherein the pitch of the screw blades in a screen part is smaller than the pitch of the screw blades on one end part side. SOLUTION: The pitch P2 of the screw blade 32A in a screen part is made smaller than the pitch P1 of the screw blade 32 on the side of a joining part 22. By this constitution, the washing soln. from washing soln. sprays 73...73 is necessarily passed through the whole of a cake 10 and, therefore, the washing efficiency of the cake can be enhanced. As a result, the washing effect of a solid is enhanced and, for example, the purity of a crystal can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a screen bowl decanter centrifuge having a screen on a wall portion.

[0002]

2. Description of the Related Art Conventionally, as one type of decanter centrifuge, a screen is provided with a screen to reduce the leakage and loss of solids, to separate smaller crystals, and to wash the cake. Screen bowl decanter centrifuges are known.

The outline of this centrifugal separator will be described with reference to FIG. 5. A cylindrical main body 21 and a cylindrical screen 23 having a screen 24 for filtering solids on a wall surface and having a smaller diameter than the cylindrical main body 21 are formed. A bowl 20 having a frusto-conical connecting portion 22 to be connected, and a screw conveyor 30 having a helical, equal pitch screw blade 32 on the outer surface of a conveyor body 31 in the bowl 20.
The basic structure is that it has a rotating means for rotating the bowl 20 and the screw conveyor 30 in the same direction at a different speed.

The rotating means includes support shafts 25A and 25B at both ends of the bowl 20 and corresponding screw conveyors 30.
The support shafts 33A, 33B at both ends are coaxially mounted on the bearings 2A, 2B.
And the rotational driving force from a drive motor (not shown) is transmitted to the pulley wheel 3, thereby rotating the bowl 20, and reducing the rotational force by the speed reducer 4,
The screw conveyor 30 is rotated at a differential speed with respect to 0.

A slurry S as a liquid to be treated is introduced into the compartment 34 of the conveyor main body 31 through the feed pipe 5 and then passes through a through hole in the wall of the cylindrical main body 2.
1 and between the screw conveyor 30.

Since the bowl S and the screw conveyor 30 are placed in a centrifugal force field, the slurry S
Since the solid matter contained therein is pushed to the inner surface side of the bowl 20 and the screw conveyor 30 is rotating, as shown in the drawing, the cake is scraped up from the connecting portion 22 and transferred to the screen portion 23. In the screen section 23, since the screen 24 is formed, filtration (centrifugal dehydration) is performed here, and the screen filtrate is discharged as illustrated. This screen filtrate is returned to the feed pipe 5 together with the raw slurry S through the return path 6. The solid that has been transported through the screen unit 23 and has been drained is discharged from the solid discharge port 7A and the discharge gutter 7B located at the other end.

On the other hand, the clarified liquid separated from the solid matter is discharged from a clarified liquid discharge port 8A and a discharge gutter 8B formed at one end of the bowl 20 and provided with a weir plate 25.

On the other hand, if necessary, means for washing the cake in the screen section 23 is provided as shown in the figure. In the illustrated example, a cleaning liquid supply pipe 71 is disposed at one end.
Through an outer pipe 72 concentric with the feed pipe 5,
The cleaning liquid W supplied into the conveyor body 31 and pressurized by centrifugal force is sprayed toward the cake from the cleaning liquid sprays 73, 73,. It is like that.

[0009]

In such a screen bowl decanter centrifuge, the screen section 23 is provided.
Since filtration (centrifugal dehydration) is performed in, solid-liquid separation is high, and even small crystals can be easily separated,
Further, by washing the cake, a high-purity solid can be obtained. Further, by circulating the screen filtrate to the feed, there is an advantage that leakage and loss of the solid can be reduced.

However, when a conventional screen bowl decanter centrifuge is used, even if the arrangement of the cleaning liquid spray 73 and the amount of the cleaning liquid are devised, the effect of cleaning the crystal is limited.

Accordingly, an object of the present invention is to provide a structure capable of enhancing the effect of washing solids, for example, increasing the purity of crystals.

[0012]

SUMMARY OF THE INVENTION The present invention, which has solved the above-mentioned problems, has a cylindrical main body and a screen for filtering solids on a wall surface, and connects the cylindrical screen with a smaller diameter than the cylindrical main body. A bowl having a frusto-conical connecting portion, a screw conveyor having screw blades in the bowl, and rotating means for rotating the bowl and the screw conveyor in the same direction at a different speed; The slurry supplied between the section and the screw conveyor is centrifuged, and the clarified liquid is passed through the connecting section and the screen section by the transfer force of the screw blade to transfer the solid content from one end of the bowl to the bowl. In the screen bowl decanter centrifuge which discharges from the other end of the screen, respectively, the following (1) It is a screen bowl centrifuge, wherein the at least one level smoothing means to (3) are provided.

(1) Level leveling means in which the pitch of the screw blades in the section from the connecting portion to the first portion of the screen portion or the pitch of the screw blades in the screen portion is smaller than the pitch of the screw blades on one end side.

(2) The screen portion has no or no screen between the screw blade on the connecting portion side and the adjacent screw blade in the screen portion, but the screen is blind, and the liquid is applied to the surface of the solid material. Level leveling means provided with spraying means. (3) Level leveling means provided on the screw conveyor with a leveling member for regulating and leveling the solid surface level between the screw blade and the adjacent screw blade.

In the present invention, it goes without saying that the means (1) to (3) can be used in combination of two or three kinds.

The present invention is based on the following findings. That is, as shown in FIG. 6, the solid matter contained in the slurry S supplied between the cylindrical main body 21 and the screw conveyor 30 through the through hole in the wall surface of the compartment 34, When the cake 10 is pushed to the inner surface side and sequentially transferred to the screen portion 32 side by the screw blade 32, the cake 10 is transferred as a scrape by the screw blade 32, so that the surface level shape of the cake 10 is as shown in the figure. , And is inclined downward to the left in FIG.

After the cake 10 is transported while maintaining its level shape, the angle of inclination is added at the joint portion 22 so that the level inclination becomes tighter.
It is lifted by the screen unit 23 and transported. In the screen section 23, since the screen 24 is formed, filtration (centrifugal dehydration) is performed here, and the screen filtrate is discharged as illustrated.

However, the cake 1 on the surface of the screen 24
Due to the uneven distribution of 0, a region where the transport front side is free or substantially absent of the cake 10 in the section of the screw blades 32, 32 is generated. When the cleaning liquid is sprayed (including spraying or spraying) in such a state, the cleaning liquid mainly contains the cake 10.
The surface of the screen 24 corresponding to the area where there are no 10 layers of cake flows through the surface along the slope, and a short path is passed through the screen 24.
It is a finding that the cleaning liquid does not pass through the layer No. 0 and the cleaning efficiency cannot be increased.

[0019]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conventional screen bowl decanter centrifuge shown in FIG.
A zero level equalizing means is provided, and other basic configurations are as described above. Therefore,
Hereinafter, the leveling means will be mainly described with reference to the accompanying drawings.

<First Mode: The pitch P3 of the screw blades 32A in the section from the connecting portion 22 to the first portion of the screen portion 23 or the pitch P2 of the screw blades 32A in the screen portion 23 is closer to one end ( Level equalizing means smaller than the pitch P1 of the screw blade 32 on the clarified liquid discharge side). FIG. 1 shows a first embodiment of a screen bowl decanter centrifuge according to the present invention. That is, the connecting portion 2
In contrast to the pitch P1 of the screw blades 32 on the second side, the pitch P of the screw blades 32A in the screen portion 23 is
2 has been reduced.

Conventionally, the two pitches are the same. However, in the present invention, the pitch of the screw blades 32A in the screen portion 23 is relatively small.
This degree of reduction is set mainly under the condition that the layer of the cake 10 is formed in the entire section of the screw blades 32A, 32A in the screen portion 23 and is flattened as much as possible, as shown in FIG. (For example, 95-35%
degree).

It may seem at first glance that it is better to reduce the pitch of all the screw blades. In this case, however, the optimum screw is considered in terms of the throughput with respect to the size of the apparatus and the solid-liquid separation. Since the pitch of the blades still exists, it is necessary to provide the screw blades 32 in the cylindrical main body 21 and the connecting portion 22 at the pitch. On the other hand, in the screen portion 23, such a factor is small, and the pitch of the screw blade 32A can be changed.

The present invention does not exclude an aspect in which the pitches of the screw blades 32, 32 of the cylindrical main body portion 21 and the connecting portion 22 are different from each other. Is limited only in relation to the pitch of the screw blades 32 on the connecting portion 22 side.

Also, as long as the pitch of the screw blades 32A in the screen portion 23 is smaller than the pitch of the screw blades 32 in the connecting portion 22, all the screen portions 2
3, between the screw blades 32A, 32A, 32A,
In addition to reducing the pitch of... Between 32A, the pitch of at least one section may be reduced. Furthermore, the pitch of the screw blades 32A in the screen portion 23 can be changed, and for example, can be gradually reduced toward the other end (the solid matter discharge port 7 side).

On the other hand, the case where the pitch P3 in the section (including the screen portion) from the connecting portion 22 to the first portion of the screen portion 23 is reduced (not shown) is also an aspect of the present invention.

Thus, in the first embodiment, together with the following second and third embodiments, a portion where the surface of the screen 24 without the cake 10 layer is exposed between the screw blades 32 as in the related art is produced. Without
Since the cleaning liquid from the cleaning liquid sprays 73 always passes through the entire cake 10, the cleaning efficiency of the cake can be improved.

<Second Aspect: The screen portion 23 has no screen between the screw blade 32A on the connecting portion 22 side and the adjacent screw blade 32A, but the screen 24 is blind and solid. Level Equalizing Means in which Liquid Spraying Means 73 is Provided on Object Surface> FIG. 2 shows a second mode, in which a screw blade 32A on the connecting portion 22 side of the screen portion 23 is adjacent to the screw blade 32A. The blind member 16 is provided between the gap member 32A.

In this case, the cleaning liquid impervious section in the screen section 23 is formed by the pitch P2 of the screw blade 32A.
(1/5) to 2 pitches, or about 20 to 600 mm. In the example of FIG. 2, approximately 1.5 pitches are defined as the non-permeable section of the cleaning liquid.

In the case of blindness, the components of the connecting portion 22 are directly extended by the corresponding length of the screen portion 23,
This can be covered with a separate member while forming the screen 23.

In the second embodiment, the blind member 16
Are supplied with the cleaning liquid, but no dehydration is performed. Therefore, in this portion, the amount of liquid in the cake 10 increases, and as a result, the fluidity of the cake 10 increases, so that the cake 10 spreads entirely between the screw blades 32A, 32A. The level shape of the cake 10 once averaged is
Since it is maintained even in the process of moving to the other end side (solid matter discharge port 7 side), the washing efficiency of the cake is improved as compared with the conventional one.

<Third embodiment: The member 15 for regulating and leveling the solid surface level between the screw blade 32A and the adjacent screw blade 32A is replaced with the screw conveyor 3.
Level leveling means provided at 0. 3 and 4 show a third embodiment. That is, the screw blade 3A adjacent to the screw blade 32A
A leveling member 15 is provided for the screw conveyor 30 to regulate and level the solid surface level between the screw conveyor 30.

The leveling member 15 may be fixed to the screw conveyor body 31 or may be fixed to the screw blade 32A. In any case, the leading edge in the radial direction of the leveling member 15 is fixed to the inner surface of the screen portion 23 with a predetermined clearance. Leveling member 15
In addition to being parallel to the machine axis direction of the leading end edge in the radial direction as shown in FIG. 3, it may be a straight line or a curve having an appropriate angle. The length of the leveling member 15 in the machine axis direction is the screw blade 3
In addition to the entire length of the section of 2A, 32A, as shown in FIG.

According to the third embodiment, the leveling member 15 rotates together with the rotation of the screw conveyor 30, and the cake 10 on the screen 23 is screwed by the screw blades 32A,
Equalize to a uniform thickness throughout 32A.

(Others) In the second embodiment, the application of the cleaning liquid is essential. In other embodiments, the application of the cleaning liquid is desirable, but the application of the cleaning liquid is not essential. That is, as long as the level of the cake 10 is leveled, there is an effect that the centrifugal dewatering property is enhanced as compared with the case where the level is not leveled. Worse).

[0035]

As described above, according to the present invention, the effect of washing solids can be enhanced, and for example, the purity of crystals can be increased.

By the way, it was confirmed that the washing efficiency was remarkably improved in obtaining crystals of the aromatic dicarboxylic acid.

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view of a main part showing an outline of a first embodiment according to the present invention.

FIG. 2 is an enlarged longitudinal sectional view of a main part showing an outline of a second embodiment according to the present invention.

FIG. 3 is an enlarged longitudinal sectional view of a main part showing an outline of a third embodiment according to the present invention.

FIG. 4 is a cross-sectional view thereof.

FIG. 5 is a longitudinal sectional view of a conventional screen bowl decanter centrifuge.

FIG. 6 is an enlarged longitudinal sectional view of a main part thereof.

[Description of Signs] 1 ... Casing, 4 ... Reduction gear, 5 ... Slurry feed pipe, 10 cake, 15 ... Leveling member, 16 ... Blind member, 2
0: bowl, 21: cylindrical body, 22: joint, 23
... Screen part, 24 ... Screen, 30 ... Screw conveyer, 31 ... Conveyor body, 32, 32A ... Screw blade, 73 ... Cleaning liquid spray.

Claims (1)

[Claims] 1. A bowl having a cylindrical main body and a screen for filtering solids on a wall surface, the bowl having a cylindrical screen having a diameter smaller than that of the cylindrical main body and a frusto-conical connecting portion connecting these. A screw conveyor having screw blades in the bowl, and a rotating unit that rotates the bowl and the screw conveyor in the same direction at a different speed, wherein a slurry supplied between the cylindrical main body and the screw conveyor is provided. A screen bowl decanter for discharging a clarified liquid from one end of the bowl and a solid content from the other end of the bowl through the connecting part and the screen part by a transfer force of the screw blade. In the centrifugal separator, at least one of leveling means (1) to (3) below in the screen section A screen bowl centrifuge comprising: (1) Leveling means in which the pitch of the screw blades in the section extending from the connecting portion to the first portion of the screen portion or the pitch of the screw blades in the screen portion is smaller than the pitch of the screw blades on one end side. (2) Between the screw blade on the connecting portion side and the adjacent screw blade in the screen portion, the screen does not have or has a screen, but the screen is blind, and the means for spraying the liquid to the surface of the solid material is not provided. Level leveling means provided. (3) Level leveling means provided on the screw conveyor with a leveling member for regulating and leveling the solid surface level between the screw blade and the adjacent screw blade.