JP6761092B2 - Screw press and how to operate the screw press - Google Patents

Description

The present invention relates to a screw press that presses a liquid-containing material such as sludge to separate the liquid from the liquid-containing material. Furthermore, the present invention relates to a method of operating a screw press.

Conventionally, a screw press has been used as a device for separating (that is, dehydrating) water from sludge (liquid-containing matter) discharged from a liquid treatment facility such as a water and sewage treatment plant or a urine treatment plant by pressing the sludge. Are known. The screw press includes a filter tube formed of a screen (perforated plate) and a screw arranged inside the filter tube. The screw has a screw shaft arranged concentrically with the filtration cylinder and a screw blade fixed to the outer surface of the screw shaft. The sludge charged into the filtration tube is squeezed and dehydrated by rotating the screw blades by a rotating mechanism connected to the screw shaft. A back pressure plate that dams up sludge is placed at the downstream opening end of the filtration tube, and the back pressure plate allows the cake (dehydrated sludge) sent by the rotating screw blades to stay and plugs made of cake (dehydrated sludge). A stopper) is formed. Back pressure is applied to the cake to which this plug is sent later to further squeeze the cake, thereby reducing the water content of the sludge in the filter tube.

No screw blades are provided at the position where the plug is formed, only the screw shaft exists. The cake forming the plug (hereinafter referred to as “plug cake”) is pressed against the back pressure plate by the cake sent later, and is gradually discharged from the downstream opening end of the filtration tube. The amount of back pressure applied to the cake in the filter tube is determined by the position of the back pressure plate with respect to the downstream opening end of the filter tube (that is, the size of the discharge port from which the plug cake is discharged) and the amount of the plug cake. The amount of plug cake is determined by the plug length. The plug length is the distance from the end of the screw blade to the back pressure plate, and is synonymous with the length of the plug cake. The appropriate plug length depends on the properties of the sludge charged into the filter tube (eg, viscosity, moisture content, etc.). Therefore, as disclosed in Patent Document 1, a mechanism for adjusting the plug length has been conventionally proposed.

If the water content of the plug cake decreases while the plug length is increased, the cylindrical plug cake may harden and the plug cake that hits the back pressure plate may not be smoothly discharged from the filter tube. In addition, the plug cake and the screw shaft may rotate together, making it impossible to discharge the plug cake from the filter tube. In order to solve these problems, the dehydration press described in Patent Document 1 is provided with a moving device for moving the screw shaft in the axial direction thereof. By moving the screw shaft with respect to the filter tube with the moving device, the plug cake having a low water content can be pushed out (that is, discharged) from the filter tube. Further, by moving the screw shaft in the axial direction, it is possible to apply further pressure to the cake in the filtration tube.

Japanese Unexamined Patent Publication No. 11-347996 Japanese Unexamined Patent Publication No. 2012-532 Japanese Unexamined Patent Publication No. 61-162298 Japanese Unexamined Patent Publication No. 58-32599 Japanese Unexamined Patent Publication No. 59-191593

However, the screw press provided with the moving device for moving the screw shaft in the axial direction has the following problems.
(I) The moving device requires a large thrust because it receives a reaction force when compressing the cake in the filtration tube while simultaneously moving the heavy screw shaft and the rotating device connected to the screw shaft. To do. For this reason, a high-power moving device is required, which leads to an increase in the size of the entire screw press and an increase in manufacturing cost.
(Ii) Since the screw shaft moved by the moving device penetrates the wall at the end of the filtration cylinder, a bearing that has water-stopping property and simultaneously receives the rotational movement and the linear movement of the screw shaft is arranged on the wall of the filtration cylinder. There is a need. Such bearings have a special structure and are expensive.
(Iii) The screw blades and the filtration tube are arranged with a minute gap between them. Therefore, it is necessary to manufacture the moving device with high accuracy so that the screw blades do not come into contact with the filter cylinder when the screw shaft is moved by the moving device.
(Iv) When the screw shaft is moved toward the discharge side of the filter cylinder, the sludge charged into the filter cylinder cannot be transferred because the screw blades disappear from the sludge input portion, and the sludge dewatering efficiency decreases. To do.
(V) During sludge filtration, a concentrated sludge layer is formed on the inner surface of the filtration cylinder, and this sludge layer is transferred while being scraped off by screw blades. However, when the sludge input portion has no screw blades, the sludge layer is not scraped off by the screw blades, and that portion does not function as a filtration surface.
(Vi) Since the screw shaft slides, space for the stroke of the screw shaft is required. As a result, the size of the entire screw press is increased.
(Vii) If a high back pressure is applied to the cake in the filter tube in order to increase the dehydration efficiency, the cake and the screw will rotate together, and the operation of the screw press cannot be continued. The proper back pressure to be applied to the cake in the filter tube is often not constant because it is affected by the properties of the sludge charged into the filter tube (eg, viscosity, moisture content, etc.). Therefore, in order to apply an appropriate back pressure to the cake in the filtration tube, it is necessary to finely adjust the back pressure plate. However, since the back pressure plate is only allowed to move linearly and is located away from the sludge inlet, this rotation of the back pressure plate and screw adds it to the cake in the filter tube. It is difficult to make fine adjustments to the back pressure.

Patent Document 2 and Patent Document 3 describe a first screw arranged on the input portion side of the filter cylinder and the first screw in the sludge transfer direction in order to adjust the back pressure applied to the cake in the filter cylinder. Describes a device with a second screw located downstream of the.

In the dehydrator described in Patent Document 2, the amount of cake discharged from the casing (corresponding to the above-mentioned filtration tube) can be adjusted by adjusting the rotation speed of the second screw. Further, in this dehydrator, by adjusting the length of the pressure adjustment guide provided at the downstream end of the casing, the second screw is pressed against a resistor (corresponding to the above back pressure plate) that can move forward and backward. The back pressure applied to the dehydrated cake to be made can be adjusted. However, in order to change the length of the pressure adjustment guide, it is necessary to stop the dehydrator and perform a large-scale work. Therefore, it is difficult to timely adjust the back pressure applied to the cake in the casing according to the properties of the sludge charged into the casing. Further, since the number of turns of the blades of the second screw is large, when the sludge having high viscosity is dehydrated, the cake adheres to the second screw, and the cake and the second screw rotate together.

In the screw press described in Patent Document 3, the output signal of the pressure detector that detects the pressure of the cake squeezed by the first stage screw and the output signal of the flow detector that detects the flow rate of the filtrate discharged from the filter tube. Based on, the back pressure applied to the cake in the filter tube is adjusted. Therefore, this screw press does not require the resistor described in Patent Document 2. However, since this screw press has a large number of turns of blades provided on the second stage screw like the dehydrator described in Patent Document 2, when the screw press is used to dehydrate sludge having high viscosity. , The cake and the second stage screw rotate together. Further, in the screw press described in Patent Document 3, when a high back pressure is applied to the cake in the filter cylinder, the cake is discharged from the filter cylinder in order to avoid rotation, so that the back pressure is high. Is difficult to add to the cake in the filter tube, and the dehydration efficiency cannot be increased.

The screw press type dehydrator described in Patent Document 4 and Patent Document 5 also has two screw shafts. However, the screw shaft on the discharge side has a truncated cone shape in which the shaft diameter expands toward the discharge port of the outer cylinder (corresponding to the above-mentioned filtration cylinder). Therefore, when the cake in the filtration cylinder and the screw shaft rotate together, the back pressure cannot be reduced and the cake cannot be forcibly discharged from the outer cylinder.

Therefore, the present invention provides a screw press capable of increasing the efficiency of separating the liquid from the liquid-containing material and discharging the plug cake from the filter cylinder without moving the screw with respect to the filter cylinder. The purpose is. Furthermore, it is an object of the present invention to provide a method of operating this screw press.

One aspect of the present invention includes a filter cylinder into which a liquid-containing material is charged, a first screw which is arranged concentrically with the filter cylinder in the filter cylinder and transfers the liquid-containing material in a predetermined transfer direction. A second screw, a first rotation mechanism for rotating the first screw, and a second rotation mechanism for rotating the second screw independently of the first screw are provided, and the second screw is the transfer. Arranged on the downstream side of the first screw in the direction, the first screw has a conical first screw shaft and a first screw blade fixed to the outer surface of the first screw shaft. The second screw has a cylindrical second screw shaft and a second screw blade fixed to the outer surface of the second screw shaft, and the second rotation mechanism attaches the second screw to the second screw. It is possible to rotate at a rotation speed different from that of the 1 screw, and the rotation direction of the 2nd screw can be switched in the same direction or in the opposite direction to the rotation direction of the 1st screw. The screw press is characterized in that the number of turns of the blade is less than three.

One reference example of the present invention is characterized in that the number of turns of the second screw blade is two or more.

A reference example of the present invention is a filter cylinder into which a liquid-containing material is charged, and a first screw which is arranged concentrically with the filter cylinder in the filter cylinder and transfers the liquid-containing material in a predetermined transfer direction. A second screw, a first rotating mechanism for rotating the first screw, and a second rotating mechanism for rotating the second screw independently of the first screw are provided, and the second screw is the same. It is arranged on the downstream side of the first screw in the transfer direction, and the first screw has a conical first screw shaft and a first screw blade fixed to the outer surface of the first screw shaft. The second screw has a cylindrical second screw shaft and a second screw blade fixed to the outer surface of the second screw shaft, and the second rotation mechanism has the second screw. The screw press is capable of rotating at a rotation speed different from that of the first screw, and the winding direction of the second screw blade is opposite to the winding direction of the first screw blade.

A reference example of the present invention is characterized in that the pitch of the second screw blade is smaller than the pitch of the first screw blade.
A preferred embodiment of the present invention is characterized in that the pitch of the second screw blades on the upstream side of the second screw is larger than the pitch of the second screw blades on the downstream side of the second screw.
In a preferred embodiment of the present invention, the second rotation mechanism has a drive for rotating the second screw and a detector capable of detecting the current and / or torque of the drive. The rotation direction of the second screw is switched based on the current and / or torque of the drive machine.

Another aspect of the present invention is the method of operating the screw press, in which the liquid-containing material in the filtration tube is subjected to the first screw by rotating the first screw without rotating the second screw. Transfer to 2 screws to form a plug cake around the 2nd screw shaft, and after the plug cake is formed, rotate the 2nd screw to discharge the plug cake from the filter tube. It is a driving method characterized by.

A preferred embodiment of the present invention is characterized in that the discharge amount of the plug cake is adjusted by changing the rotation speed of the second screw.
A preferred embodiment of the present invention is characterized in that the back pressure applied to the liquid-containing material squeezed by the first screw is adjusted by performing an intermittent operation in which rotation and stop of the second screw are alternately repeated. And.
A preferred embodiment of the present invention is characterized in that the back pressure applied to the liquid-containing material squeezed by the first screw is adjusted by changing the rotation direction of the second screw.
A preferred embodiment of the present invention is characterized in that the rotation direction of the second screw is changed based on the current and / or torque of the drive of the second rotation mechanism.

According to the present invention, the back pressure applied to the liquid content in the filtration tube can be adjusted by controlling the rotation speed of the second screw, which can rotate independently of the first screw, and thus the liquid. It is possible to prevent the cake from rotating with the second screw while increasing the efficiency of separating the liquid from the inclusions. Further, by rotating the second screw independently of the first screw, the plug cake can be smoothly discharged from the filtration tube. Therefore, the plug cake can be discharged from the filter tube without moving the first screw and the second screw with respect to the filter tube. Further, since the first screw and the second screw do not move with respect to the filtration cylinder, the first screw blade and the second screw blade can always face the entire screen surface of the filtration cylinder. As a result, the entire screen surface of the filter tube can be used to separate the liquid from the liquid content, and the efficiency of separating the liquid from the liquid content can be improved.
Further, according to the configuration in which the number of turns of the second screw blade is less than 3, the plug cake can be discharged from the filtration tube in a short time. Therefore, even when the liquid content from which the liquid is separated by the screw press has a high viscosity, the plug cake can be discharged from the filter tube before the plug cake rotates with the second screw.
Further, according to the configuration in which the winding direction of the second screw blade is different from the winding direction of the first screw blade, the second screw is rotated in the direction opposite to that of the first screw in order to discharge the plug cake from the filtration tube. Be done. Therefore, since the liquid content squeezed by the rotation of the first screw and the plug cake rotated by the second screw are pressed against each other in the opposite rotation direction, the rotation of the plug cake and the second screw can be prevented. .. As a result, the screw press can be operated while applying a high back pressure to the liquid content, so that the efficiency of separating the liquid from the liquid content can be improved.

It is a schematic diagram which shows the screw press which concerns on one Embodiment. It is the schematic sectional drawing of the 2nd screw shown in FIG. It is a schematic diagram for demonstrating the number of turns of a 2nd screw blade. It is a schematic diagram which shows the screw press which concerns on other embodiment. It is the schematic sectional drawing of the 2nd screw shown in FIG. It is a figure explaining the operation of the screw press shown in FIG. It is a figure explaining the operation of the screw press shown in FIG. It is a figure explaining the operation of the screw press shown in FIG. It is a schematic diagram which showed the 2nd screw which concerns on other embodiment. It is a schematic diagram which shows the screw press which concerns on still another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a screw press according to an embodiment. The screw press shown in FIG. 1 is arranged concentrically with the cylindrical screen casing (filtration cylinder) 1 and the screen casing 1 in the screen casing 1, and sludge (liquid content) is transferred in a predetermined transfer direction D. The first screw 3 and the second screw 4 to be transferred to the casing, the first rotation mechanism 7 for rotating the first screw 3, and the second rotation mechanism 20 for rotating the second screw 4 independently of the first screw 3. It has. The screen casing 1 is formed of a screen (perforated plate) such as punching metal. A sludge inlet 2 is formed at the upstream end of the screen casing 1. The sludge charged into the screen casing 1 from the charging port 2 is transferred in the screen casing 1 in a predetermined transfer direction D by the rotating first screw 3 and the second screw 4. Further, the screw press has a control unit 6 that controls the operation of the first rotation mechanism 7 and the second rotation mechanism 20.

The second screw 4 is connected to the first screw 3 so that it can rotate independently of the first screw 3. The first screw 3 and the second screw 4 extend through the screen casing 1 and the discharge chamber 33, respectively. The discharge chamber 33 is connected to the screen casing 1. The plug cake described later is discharged from the screen casing 1 into the discharge chamber 33. The axial length of the second screw 4 is shorter than the axial length of the first screw. The first screw 3 is fixed to the outer surfaces of the truncated cone-shaped (tapered) first screw shaft 3A and the first screw shaft 3A whose diameter gradually increases toward the downstream side in the sludge transfer direction D. It has a first screw blade 3B. The second screw 4 has a cylindrical second screw shaft 4A and a second screw blade 4B fixed to the outer surface of the second screw shaft 4A.

The upstream end of the screen casing 1 is sealed by a closing wall 8. One end of the first screw shaft 3A (upstream end in the transfer direction D) extends through the closing wall 8. A water sealing device 10 that seals the gap between the closing wall 8 and the first screw shaft 3A is installed on the closing wall 8. The upstream end of the first screw shaft 3A extending through the closing wall 8 is rotatably supported by bearings 11 and 12 installed on the base (not shown) while restraining axial movement. .. One of the bearings 11 and 12 can be omitted.

The upstream end of the first screw shaft 3A is connected to a first rotation mechanism 7 for rotating the first screw 3. In the present embodiment, the first rotation mechanism 7 includes a first drive (for example, an electric motor) 14, a sprocket 15 fixed to the rotation shaft of the first drive 14, and a sprocket fixed to the first screw shaft 3A. A 16 and a chain 17 wound around the sprockets 15 and 16 are provided. The sprocket 16 is located between the bearings 11 and 12. When the first drive machine 14 of the first rotation mechanism 7 is driven, the sprocket 15 fixed to the rotation shaft of the first drive machine 14 rotates, and the sprocket 16 fixed to the first screw shaft 3A via the chain 17 To rotate. As a result, the first screw 3 is rotated by the first rotation mechanism 7. The first drive unit 14 is connected to the control unit 6, and the control unit 6 is configured to be able to control the operation of the first drive unit 14.

Although not shown, the rotating shaft of the first driving machine 14 may be connected to the first screw shaft 3A via a speed reducer. Alternatively, the rotating shaft of the first driving machine 14 may be directly connected to the first screw shaft 3A.

FIG. 2 is a schematic cross-sectional view of the second screw 4 shown in FIG. As shown in FIG. 2, the second screw shaft 4A has a hollow structure. At the other end of the first screw shaft 3A (downstream end in the transfer direction D), a reduced diameter portion 3C to be inserted into the cylindrical second screw shaft 4A is formed. By forming the reduced diameter portion 3C on the first screw shaft 3A, a wall surface 3D perpendicular to the axial direction is formed on the first screw shaft 3A. The reduced diameter portion 3C is inserted into the cylindrical second screw shaft 4A and is rotatably supported by the slide bearings 30 and 31 fixed to the inner wall 4C of the second screw shaft 4A. With such a configuration, the first screw 3 is rotatably connected to the second screw 4.

As shown in FIG. 2, with the reduced diameter portion 3C of the first screw shaft 3A inserted inside the second screw shaft 4, the upstream end of the second screw shaft 4A is the first screw shaft 3A. It is in contact with the wall surface 3D. In one embodiment, a slight gap may be formed between the upstream end of the second screw shaft 4A and the wall surface 3D of the first screw shaft 3A. In this case, the sliding bearing 30 and / or the reduced diameter portion 3C is provided with a seal structure (for example, a labyrinth structure) that prevents sludge in the screen casing 1 from passing through the gap between the sliding bearing 30 and the reduced diameter portion 3C. It may be provided in.

As shown in FIGS. 1 and 2, the second screw shaft 4A of the second screw 4 is arranged concentrically with the first screw shaft 3A. The outer diameter of the second screw shaft 4A is the same as the maximum diameter of the first screw shaft 3A. The second screw shaft 4A extends through the wall 33A of the discharge chamber 33. The upstream end of the second screw shaft 4A is rotatably supported by the first screw shaft 3A via the slide bearings 30 and 31, and the downstream end of the second screw shaft 4A is a base (not shown). ), The bearings 22 and 23 are rotatably supported while restraining the movement in the axial direction. The bearing 23 can be omitted.

The downstream end of the second screw shaft 4A is connected to a second rotation mechanism 20 for rotating the second screw 4. In the present embodiment, the second rotation mechanism 20 includes a second drive (for example, an electric motor) 24, a sprocket 25 fixed to the rotation shaft of the second drive 24, and a sprocket fixed to the second screw shaft 4A. 26 and a chain 27 wound around these sprockets 25 and 26 are provided. The sprocket 26 is located between the bearings 22 and 23. When the second drive machine 24 of the second rotation mechanism 20 is driven, the sprocket 25 fixed to the rotation shaft of the second drive machine 24 rotates, and the sprocket 26 fixed to the second screw shaft 4A via the chain 27. To rotate. As a result, the second screw 4 is rotated by the second rotation mechanism 20.

The second drive machine 24 is connected to the control unit 6. The second drive machine 24 has a built-in inverter (not shown), and the control unit 6 is configured to be able to control the operation of the second drive machine 24 via the inverter. That is, the control unit 6 can control the rotation speed and the rotation direction of the second drive machine 24 via the inverter. The second drive machine 24 can rotate the second screw 4 independently of the first screw 3. It is preferable that the first drive machine 14 also has an inverter capable of changing the rotation speed and the rotation direction of the first drive machine 14.

Although not shown, the rotating shaft of the second drive machine 24 may be connected to the second screw shaft 4A via a speed reducer. Alternatively, the rotating shaft of the second drive machine 24 may be directly connected to the second screw shaft 4A.

The first screw blade 3B extends spirally along the axial direction of the first screw shaft 3A, and the second screw blade 4B spirally extends along the axial direction of the second screw shaft 4A. The total length of the portion of the first screw 3 to which the first screw blade 3B is fixed and the portion of the second screw 4 to which the second screw blade 4B is fixed is the axial length of the screen casing 1. Same or longer.

A minute gap is formed between the inner surface of the screen casing 1 and the first screw blade 3B so that the first screw blade 3B can rotate without contacting the screen casing 1. Similarly, a minute gap is formed between the inner surface of the screen casing 1 and the second screw blade 4B, so that the second screw blade 4B can rotate without contacting the screen casing 1. ing. The sludge charged into the screen casing 1 from the inlet 2 formed at the upstream end of the screen casing 1 is transferred toward the discharge chamber 33 by the rotating first screw blades 3B and the second screw blades 4B (that is, transferred). Can be transferred (in direction D).

In the present embodiment, the winding direction of the second screw blade 4B (that is, the spiral direction) is opposite to the winding direction of the first screw blade 3B. Therefore, when the sludge charged from the charging port 2 is sent out to the discharge chamber 33, the second screw 4 is rotated in the direction opposite to that of the first screw 3 as shown in FIG.

The winding direction of the second screw blade 4B may be the same as the winding direction of the first screw blade 3B. In this case, when the sludge charged from the charging port 2 is sent out to the discharge chamber 33, the second screw 4 is rotated in the same direction as the first screw 3. An embodiment in which the winding direction of the second screw blade 4B is the same as the winding direction of the first screw blade 3B will be described later.

As shown in FIG. 2, the pitch P1 of the second screw blade 4B is smaller than the pitch P2 of the first screw blade 3B (that is, P1 <P2). Further, the number of turns of the second screw blade 4B is less than three. FIG. 3 is a schematic view for explaining the number of turns of the second screw blade 4B. As shown in FIG. 3, the number of turns of the second screw blade 4B extending spirally is 1 when the second screw blade 4B advances 360 ° around the first screw shaft 4A from the start point S1 to the point S2. Count as a roll. In the second screw 4 shown in FIG. 3, the number of turns of the second screw blade 4B is two.

As shown in FIG. 1, the screen casing 1 is divided into a dehydration region 1A in which the first screw 3 is arranged and a plug forming region 1B in which the second screw 4 is arranged. The space to which sludge is transferred in the dehydration region 1A is formed by the inner surface of the screen casing 1, the first screw blade 3B, and the first screw shaft 3A. As shown in FIG. 1, the cross-sectional area of this transfer space gradually decreases along the sludge transfer direction D. Therefore, as the sludge charged from the charging port 2 is transferred through this transfer space by the first screw blade 3B, the sludge is squeezed and dehydrated. The filtrate that has passed through the screen (perforated plate) of the screen casing 1 is collected by the filtrate receiver 38 arranged below the screen casing 1. A drain 39 is connected to the filtrate receiver 38, and the filtrate collected by the filtrate receiver 38 is discharged from the screw press via the drain 39.

The space to which sludge is transferred in the plug forming region 1B is formed by the inner surface of the screen casing 1, the second screw blade 4B, and the second screw shaft 4A. As shown in FIG. 1, the cross section of this transfer space is constant. In the plug forming region 1B, a plug cake is formed by the sludge (that is, cake) dehydrated in the dehydrated region 1A. The method of forming the plug cake will be described later.

FIG. 4 is a schematic view showing a screw press according to another embodiment. FIG. 5 is a schematic cross-sectional view of the second screw 4 shown in FIG. Since the configuration of the present embodiment not particularly described is the same as the configuration of the embodiment shown in FIG. 1, the duplicate description thereof will be omitted. The screw press shown in FIG. 4 differs from the screw press shown in FIG. 1 in that the first rotation mechanism 7 is connected to the downstream end portion of the first screw 3 instead of the upstream end portion.

As shown in FIGS. 4 and 5, the reduced diameter portion 3C of the first screw shaft 3A extends through the cylindrical second screw shaft 4A and protrudes from the rear end of the second screw shaft 4A. There is. The bearings 11 and 12 of the first rotation mechanism 7 rotatably support the reduced diameter portion 3C protruding from the rear end of the second screw shaft 4A. The sprocket 16 fixed to the reduced diameter portion 3C is arranged between the bearings 11 and 12. The upstream end of the first screw shaft 3 extending through the closing wall 8 is rotatably supported by the bearing 36. With such a configuration, the second rotation mechanism 20 can rotate the second screw 4 independently of the first screw rotated by the first rotation mechanism 7.

The screw press of the above-described embodiment does not have a moving mechanism for moving the first screw 3 and the second screw 4 in the axial direction with respect to the screen casing 1. That is, the relative positions of the screen casing 1 and the first screw 3 and the second screw 4 are fixed. Therefore, the entire screw press can be configured more compactly as compared with the conventional screw press provided with the moving mechanism. Further, since the first screw 3 and the second screw 4 do not move in the axial direction with respect to the screen casing 1, the first screw blade 3B and the second screw blade 4B can always face the entire screen surface of the screen casing 1. it can. As a result, the sludge can be dewatered using the entire screen casing 1, so that the sludge dewatering efficiency (that is, the efficiency of separating the liquid from the liquid content) can be improved.

Next, the operation method of the screw press shown in FIG. 1 will be described with reference to FIGS. 6 to 8. 6 to 8 are diagrams for explaining the operation of the screw press shown in FIG. The operation method of the screw press shown in FIG. 1 will be described below, but the screw press shown in FIG. 4 can be operated by the same operation method.

As shown in FIG. 6, the control unit 6 drives the first rotation mechanism 7 to rotate the first screw 3 with the second screw 4 stopped. Next, sludge (liquid-containing material) is charged into the screen casing 1 from the charging port 2. As described above, since the axial position of the first screw 3 with respect to the screen casing 1 is fixed, the first screw blade 3B is always present under the inlet 2. Therefore, the sludge charged from the charging port 2 is transferred toward the second screw 4 (that is, in the transfer direction D) by the rotating first screw blade 3B without staying in place.

In the dehydration region 1A where the first screw 3 is arranged, the cross-sectional area of the space where the sludge is transferred gradually decreases along the transfer direction D. Therefore, the sludge is squeezed as it is transferred through the dehydration region 1A, and the water contained in the sludge is filtered by the screen casing 1. Since the sludge layer accumulated on the inner surface of the screen casing 1 is scraped off by the rotating first screw blade 3B, the inner surface (filtration surface) of the screen casing 1 in the dehydration region 1A is always maintained in a good state.

While the sludge is transferred through the dehydration region 1A of the screen casing 1, the sludge is dehydrated into a cake and sent to the plug forming region 1B where the second screw 4 is arranged. As shown in FIG. 6, since the second screw 4 is not rotating (that is, stopped) at the beginning of operation, the cake in the plug forming region 1B is not discharged to the discharge chamber 33, and the plug is formed. It stays in the region 1B. The cake is gradually accumulated on the second screw 4 and pressed against the second screw blade 4B by sludge (hereinafter referred to as “subsequent cake”) transferred from the dehydration region 1A to the plug forming region 1B. The cake in the plug forming region 1B is squeezed by being hindered from moving by the second screw blade 4B, resulting in a cake having a low water content. This low moisture content cake forms a plug cake that impedes subsequent cake movement. Back pressure is applied to the subsequent cake by the plug cake formed around the second screw shaft 4A, and the subsequent cake is further squeezed. The water separated from the plug cake in the plug forming region 1B is collected by the filtrate receiver 38 and discharged from the screw press via the drain 39.

As the operation of the screw press is continued, the plug cake is uniformly formed over the entire circumference of the second screw shaft 4A. As a result, as shown in FIG. 6, a plug cake that reliably dams the subsequent cake is formed around the second screw shaft 4A. Therefore, even when the water content of the subsequent cake is high, the plug cake formed in the plug forming region 1B can reliably block the subsequent cake, so that one-sided flow of the subsequent cake can be prevented. This "one-sided flow" means that a subsequent cake having a higher water content than the plug cake passes through the plug forming region 1B as it is and is discharged to the discharge chamber 33.

As shown in FIG. 7, after the plug cake is formed, the control unit 6 rotates the second screw 4 in the direction opposite to the rotation direction of the first screw 3, and the second screw blade 4B makes the plug cake. It is gradually sent out to the discharge chamber 33 (that is, discharged). In this way, since the plug cake is formed and the plug cake is discharged continuously, the screw press can be operated with the plug cake always present in the plug forming region 1B.

The plug cake on the second screw 4 is discharged to the discharge chamber 33 by the second screw blade 4B of the second screw 4 rotated by the second rotation mechanism 20 while applying back pressure to the subsequent cake. The control unit 6 can adjust the amount of plug cake discharged into the discharge chamber 33 by changing the rotation speed of the second screw 4. More specifically, when the control unit 6 reduces the rotation speed of the second screw 4, the discharge amount of the plug cake decreases, and when the control unit 6 increases the rotation speed of the second screw 4, the plug cake Emissions increase. When the discharge amount of the plug cake decreases, the subsequent cake stays in the dehydration region 1A, and the back pressure applied to the subsequent cake increases. Therefore, the control unit 6 can reduce the rotation speed of the second screw 4 to reduce the water content of the subsequent cake. In one embodiment, the back pressure applied to the subsequent cake may be adjusted by performing an intermittent operation in which the rotation and the stop of the second screw 4 are alternately repeated.

As described above, in the present embodiment, the first screw 3 and the second screw 4 are moved with respect to the screen casing 1 by rotating the second screw 4 in the direction opposite to the rotation direction of the first screw 3. Instead, the plug cake with low water content can be removed from the screen casing 1. As a result, the same effect as when the screw shaft is moved toward the open end of the screen casing by the moving device provided in the conventional screw press can be obtained. Further, according to the present embodiment, it is not necessary to provide a resistor such as a back pressure plate at the discharge side end of the screen casing 1. Therefore, the plug cake can be smoothly discharged from the screen casing 1 to the discharge chamber 33. Further, since the back pressure plate and the operation mechanism of the back pressure plate are not required, the screw press can be manufactured at low cost.

The pitch P1 (see FIG. 2) of the second screw blade 4B of the second screw 4 is smaller than the pitch P2 of the first screw blade 3B of the first screw 3 (that is, P1 <P2). When the pitch P1 of the second screw blade 4B is made smaller than the pitch P2 of the first screw blade 3B in this way, the transfer distance of the plug cake discharged to the discharge chamber 33 during one rotation of the second screw 4 is short. Therefore, the back pressure applied to the cake in the dehydrated region 1A can be finely adjusted.

In a conventional screw press, if the cylindrically squeezed plug cake becomes too hard, the hardened plug cake occludes the screen casing and cannot be discharged from the screen casing. Furthermore, this hardened plug cake goes around with the screw. As a result, the operation of the screw press cannot be continued. In the screw press of the present embodiment, the winding direction of the second screw blade 4B of the second screw 4 is opposite to the winding direction of the first screw blade 3B of the first screw 3. Therefore, when the plug cake formed in the plug forming region 1B is discharged to the discharge chamber 33, the second screw 4 is rotated in the direction opposite to the rotation direction of the first screw 3, as shown in FIG. When the cake is pressed against the plug cake by the first screw 3 that rotates in the direction opposite to that of the second screw 4, a force in the direction opposite to the rotation direction of the second screw 4 is applied to the plug cake. As a result, the rotation of the plug cake and the second screw 4 in the plug forming region 1B and / or the rotation of the cake and the first screw 3 in the dehydration region 1A are prevented, so that the back pressure is high against sludge. It becomes possible to operate the screw press while adding.

When the number of turns of the second screw blade 4B is 3 or more, the time for transferring the plug cake formed in the plug forming region 1B to the discharge chamber 33 becomes long. If the plug cake has a high viscosity, the plug cake may rotate with the second screw 4. In the present embodiment, since the number of turns of the second screw blade 4B is less than 3, the plug cake can be discharged from the screen casing 1 in a short time. Therefore, even when the sludge dehydrated by the screw press has a high viscosity, the plug cake can be discharged from the screen casing 1 before the plug cake rotates together with the second screw 4. When the number of turns of the second screw blade 4B is one, the plug cake may be pushed out to the discharge chamber 33 by the subsequent cake, and back pressure may not be effectively applied to the subsequent cake. Therefore, the number of turns of the second screw blade 4B is preferably 2 or more and less than 3 turns.

As shown in FIG. 8, the second screw 4 may be rotated in the same direction as the first screw 3. When the second screw 4 is rotated in the same direction as the first screw 3, the plug cake formed in the plug forming region 1B is pushed out toward the dehydration region 1A, and a larger back pressure can be applied to the cake in the dehydration region 1A. it can. As a result, the dewatering efficiency of sludge can be improved.

If the second screw 4 is rotated in the same direction as the first screw 3 for a long time, the cake in the dehydration region 1A may rotate with the first screw 3. Therefore, after rotating the second screw 4 in the same direction as the first screw 3 for a certain period of time, the rotation direction of the second screw 4 is returned to the direction opposite to the rotation direction of the first screw 3 (FIG. 7). reference). Since the screw press of the present embodiment does not have a resistor such as a back pressure plate that prevents the plug cake from being discharged, the second screw 4 smoothly discharges the plug cake into the discharge chamber 33 like a screw conveyor. can do. By changing the rotation direction of the second screw 4 in this way, the control unit 6 can adjust the back pressure applied to the sludge squeezed by the first screw 3 in the dehydration region 1A. In order to reliably discharge the plug cake into the discharge chamber 33, the rear end of the second screw blade 4B of the second screw 4 may be configured to slightly protrude from the open end of the screen casing 1.

By changing the rotation speed and rotation direction of the second screw 4, the control unit 6 can dehydrate the sludge to a low water content that cannot be achieved by a conventional screw press. That is, with the second screw 4 stopped, the first screw 3 is rotated to form a plug cake around the second screw shaft 4A. Next, the sludge in the screen casing 1 is squeezed and dehydrated while the second screw 4 is rotated in the forward direction (the direction opposite to the rotation direction of the first screw 3) to discharge the plug cake into the discharge chamber 33. Do. During the dewatering treatment of the sludge, the second screw 4 is rotated in the opposite direction (the same direction as the rotation direction of the first screw 3) to dehydrate the cake in the dehydration region 1A to a lower water content, and then the first screw. 2 The screw 4 may be rotated in the forward direction to discharge the plug cake having a low water content into the discharge chamber 33. It is preferable that the operation of changing the rotation direction of the second screw 4 is performed periodically at intervals according to the properties of the sludge.

As shown in FIGS. 6 to 8, even if the second drive machine 24 of the second rotation mechanism 20 has a detector 28 capable of detecting the current value and / or torque of the second drive machine 24. Good. The detector 28 is connected to the control unit 6 via a signal line (not shown). The current value and / or torque of the second drive machine 24 correlates with the load applied to the second drive machine 24 to rotate the second screw 4. Therefore, the control unit 6 changes the rotation direction of the second screw 4 based on the output signal of the current value and / or the torque sent from the detector 28, so that the second screw 4 is second according to the load applied to the second drive 24. The rotation direction of the screw 4 can be switched. In this way, the rotation direction of the second screw 4 may be changed based on the current value and / or torque of the second drive machine 24.

FIG. 9 is a schematic view showing the second screw 4 according to another embodiment. The pitch of the second screw blade 4B of the second screw 4 shown in FIG. 9 is different between the upstream side and the downstream side in the sludge transfer direction D. More specifically, the pitch P1 ″ on the upstream side of the second screw blade 4B is larger than the pitch P1 ″ on the downstream side of the second screw blade 4B (that is, P1 ″> P1 ″). When the pitch P1'on the upstream side is made larger than the pitch P1'on the downstream side in this way, the cake transferred from the dehydration region 1A to the plug forming region 1B by the rotation of the first screw 3 is transferred to the plug forming region 1B. It can be gradually retained. As a result, the back pressure applied to the cake in the dehydration region 1A does not rise sharply, so that it is possible to effectively prevent the cake in the dehydration region 1A from rotating with the first screw 3.

FIG. 10 is a schematic view showing a screw press according to still another embodiment. Since the configuration of the present embodiment not particularly described is the same as the configuration of the embodiment shown in FIG. 1, the duplicate description thereof will be omitted. In the screw press shown in FIG. 10, the winding direction (that is, the spiral direction) of the second screw blade 4B of the second screw 4 is the same as the winding direction of the first screw blade 3B of the first screw 3. It is different from the screw press shown in 1.

In the present embodiment, the winding direction of the second screw blade 4B is the same as the winding direction of the first screw blade 3B. Therefore, when the sludge charged from the charging port 2 is sent out to the discharge chamber 33, the second screw 4 is rotated in the same direction as the first screw 3 as shown in FIG. In order to eject the plug cake from the screen casing 1 in a short time, the number of turns of the second screw blade 4B is less than three. Further, the number of turns of the second screw blade 4B is preferably two or more in order to effectively apply back pressure to the subsequent cake. The number of turns of the second screw blade 4B shown in FIG. 10 is two.

Next, the operation method of the screw press shown in FIG. 10 will be described. First, the control unit 6 drives the first rotation mechanism 7 to rotate the first screw 3 with the second screw 4 stopped. Next, sludge (liquid-containing material) is charged into the screen casing 1 from the charging port 2, and the sludge is transferred toward the second screw 4 (that is, in the transfer direction D) by the rotating first screw blade 3B. ..

As described above, while the sludge is transferred to the dehydration region 1A where the first screw 3 is arranged, the sludge is dehydrated into a cake and sent to the plug forming region 1B where the second screw 4 is arranged. At the beginning of operation, since the second screw 4 is not rotating (that is, stopped), the cake in the plug forming region 1B is not discharged to the discharge chamber 33, but stays in the plug forming region 1B. As a result, a plug cake that hinders the subsequent movement of the cake is formed in the plug forming region 1B. Back pressure is applied to the subsequent cake by the plug cake formed around the second screw shaft 4A, so that the subsequent cake can be further squeezed.

After the plug cake is formed, the control unit 6 rotates the second screw 4 in the same direction as the rotation direction of the first screw 3, and gradually sends the plug cake to the discharge chamber 33 by the second screw blade 4B (that is,). ,Discharge). In this way, since the plug cake is formed and the plug cake is discharged continuously, the screw press can be operated with the plug cake always present in the plug forming region 1B.

The plug cake on the second screw 4 is discharged to the discharge chamber 33 by the second screw blade 4B of the second screw 4 rotated by the second rotation mechanism 20 while applying back pressure to the subsequent cake. In the screw press shown in FIG. 10, the control unit 6 can adjust the amount of plug cake discharged into the discharge chamber 33 by changing the rotation speed of the second screw 4. More specifically, when the control unit 6 reduces the rotation speed of the second screw 4, the discharge amount of the plug cake decreases, and when the control unit 6 increases the rotation speed of the second screw 4, the plug cake Emissions increase. When the discharge amount of the plug cake decreases, the subsequent cake stays in the dehydration region 1A, and the back pressure applied to the subsequent cake increases. Therefore, the control unit 6 can reduce the rotation speed of the second screw 4 to reduce the water content of the subsequent cake. In one embodiment, the back pressure applied to the subsequent cake may be adjusted by performing an intermittent operation in which the rotation and the stop of the second screw 4 are alternately repeated.

Also in this embodiment, the plug cake having a low water content can be removed from the screen casing 1 without moving the first screw 3 and the second screw 4 with respect to the screen casing 1. As a result, the same effect as when the screw shaft is moved toward the open end of the screen casing by the moving device provided in the conventional screw press can be obtained. Further, also in this embodiment, it is not necessary to provide a resistor such as a back pressure plate at the discharge side end of the screen casing 1. Therefore, the plug cake can be smoothly discharged from the screen casing 1 to the discharge chamber 33. Further, since the back pressure plate and the operation mechanism of the back pressure plate are not required, the screw press can be manufactured at low cost.

The second screw 4 may be rotated in the direction opposite to that of the first screw 3. When the second screw 4 is rotated in the direction opposite to that of the first screw 3, the plug cake formed in the plug forming region 1B is pushed toward the dehydration region 1A, and a larger back pressure can be applied to the cake in the dehydration region 1A. it can. As a result, the dewatering efficiency of sludge can be improved.

Further, when the second screw 4 is rotated in the direction opposite to that of the first screw 3, the plug cake in the plug forming region 1B rotated by the second screw 4 and the dehydration region 1A rotated by the first screw 3 The cakes are pressed against each other in the opposite direction of rotation. As a result, the cake in the dehydration region 1A is large while preventing the plug cake in the plug forming region 1B and the second screw 4 from rotating and the cake in the dehydration region 1A and the first screw 3 from rotating. Since back pressure can be applied, sludge can be dehydrated to a low water content. However, if the back pressure applied to the cake in the dehydration region 1A is too high, the cake may leak from the screen (perforated plate) of the screen casing 1. Therefore, after rotating the second screw 4 in the direction opposite to that of the first screw 3 for a certain period of time, the rotation direction of the second screw 4 is returned to the same direction as the rotation direction of the first screw 3. By changing the rotation direction of the second screw 4 in this way, the control unit 6 can adjust the back pressure applied to the sludge squeezed by the first screw 3 in the dehydration region 1A. In order to reliably discharge the plug cake into the discharge chamber 33, the rear end of the second screw blade 4B of the second screw 4 may be configured to slightly protrude from the open end of the screen casing 1.

Similar to the screw press shown in FIG. 1, the control unit 6 changes the rotation speed and rotation direction of the second screw 4 to dehydrate sludge to a low water content that cannot be achieved by a conventional screw press. be able to. It is preferable that the operation of changing the rotation direction of the second screw 4 is performed periodically at intervals according to the properties of sludge. Alternatively, the rotation direction of the second screw 4 may be changed based on the current value and / or torque of the second drive machine 24 sent from the detector 28 to the control unit 6.

As described with reference to FIG. 2, the pitch of the second screw blade 4B is preferably smaller than the pitch of the first screw blade 3B. As described with reference to FIG. 9, the pitch on the upstream side of the second screw blade 4B may be larger than the pitch on the downstream side of the second screw blade 4B. Although not shown, the first rotation mechanism 7 of the screw press shown in FIG. 10 is connected to the downstream end of the first screw 3 as in the screw press described with reference to FIGS. 4 and 5. May be good.

The screw press of the above-described embodiment is used to separate liquid water from sludge, which is an example of a liquid content, but this screw press is used to separate a liquid from a liquid content other than sludge. You may use it. For example, the screw press according to the above embodiment can also be used for processing foods such as fruits and oils, and processing industrial products such as recycled waste paper. In the processing of foods, a screw press is used to squeeze raw materials (liquid-containing substances) such as fruits and seeds and separate liquids such as fruit juice and oil from the raw materials. In the recycling process of used paper, the used paper is mixed with water and liquids such as chemicals to loosen the used paper into fibrous substances. A screw press is used to squeeze a mixture of fibrous material and liquid (liquid content) to separate the fibrous material from the mixture.

The above-described embodiment is described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to carry out the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is construed in the broadest range according to the technical idea defined by the claims.

1 Screen casing (filter tube)
1A Dehydration area 1B Plug formation area 2 Input port 3 1st screw 3A 1st screw shaft 3B 1st screw blade 3C Reduced diameter part 3D wall surface 4 2nd screw 4A 2nd screw shaft 4B 2nd screw blade 6 Control unit 7 1st Rotating mechanism 8 Blocking wall 10 Water sealing device 11, 12 Bearing 14 First drive machine 15, 16 Sprocket 17 Chain 20 Second rotation mechanism 22, 23 Bearing 24 Second drive machine 25, 26 Sprocket 27 Chain 28 Detector 30, 31 Plain bearing 33 Drain chamber 36 Bearing 38 Strain receiver 39 Drain

Claims (8)

The filter tube into which the liquid content is charged and
In the filter tube, the first screw and the second screw, which are arranged concentrically with the filter tube and transfer the liquid content in a predetermined transfer direction,
The first rotation mechanism for rotating the first screw and
A second rotation mechanism for rotating the second screw independently of the first screw is provided.
The second screw is arranged on the downstream side of the first screw in the transfer direction.
The first screw has a truncated cone-shaped first screw shaft and a first screw blade fixed to the outer surface of the first screw shaft.
The second screw has a cylindrical second screw shaft and a second screw blade fixed to the outer surface of the second screw shaft.
The second rotation mechanism can rotate the second screw at a rotation speed different from that of the first screw, and the rotation direction of the second screw is the same as that of the first screw. Can be switched in the direction or the opposite direction,
A screw press characterized in that the number of turns of the second screw blade is less than three. The screw press according to claim 1, wherein the pitch of the second screw blades on the upstream side of the second screw is larger than the pitch of the second screw blades on the downstream side of the second screw. The second rotation mechanism includes a drive for rotating the second screw and a detector capable of detecting the current and / or torque of the drive.
The screw press according to claim 1 or 2, wherein the rotation direction of the second screw is switched based on the current and / or torque of the driving machine. The method for operating a screw press according to any one of claims 1 to 3.
By rotating the first screw without rotating the second screw, the liquid-containing material in the filtration tube is transferred to the second screw, and a plug cake is placed around the second screw shaft. Form and
An operation method characterized in that after the plug cake is formed, the second screw is rotated to discharge the plug cake from the filter tube. The operation method according to claim 4, wherein the discharge amount of the plug cake is adjusted by changing the rotation speed of the second screw. 4. The fourth aspect of the present invention is characterized in that the back pressure applied to the liquid-containing material squeezed by the first screw is adjusted by performing an intermittent operation in which rotation and stop of the second screw are alternately repeated. How to drive. The operation method according to claim 4, wherein the back pressure applied to the liquid-containing material squeezed by the first screw is adjusted by changing the rotation direction of the second screw. The operation method according to claim 7, wherein the rotation direction of the second screw is changed based on the current and / or torque of the drive machine of the second rotation mechanism.

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