JP6587996B2 - Screw press and operating method of screw press - Google Patents

Description

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

  Conventionally, a screw press has been used as a device for squeezing sludge (liquid-containing material) discharged from liquid treatment facilities such as water and sewage treatment plants and human waste treatment plants and separating water from the sludge (ie, dehydrating). Are known. This screw press includes a filter cylinder formed from a screen (perforated plate) and a screw arranged inside the filter cylinder. 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. By rotating the screw blades by a rotating mechanism connected to the screw shaft, the sludge put into the filter cylinder is squeezed and dehydrated. At the downstream opening end of the filtration cylinder, a back pressure plate that dams sludge is arranged. With this back pressure plate, cake (dehydrated sludge) sent by rotating screw blades is retained, and a plug made of cake ( Plug). This plug applies back pressure to the cake fed later, and further squeezes the cake, thereby reducing the moisture content of the sludge in the filter cylinder.

  No screw blade is provided at the position where the plug is formed, and only the screw shaft is present. The cake forming the plug (hereinafter referred to as “plug cake”) is pressed against the back pressure plate by the cake fed later, and is gradually discharged from the downstream opening end of the filter cylinder. The size of the back pressure applied to the cake in the filter cylinder is determined the position of the back plate against the downstream side opening end of the filtration tube (i.e., the size of the outlet plug cake is discharged) and by the amount of plug Cake The amount of plug cake is determined by the plug length. The plug length is a 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 varies depending on the properties (eg, viscosity, moisture content, etc.) of the sludge charged into the filter cylinder. 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 is lowered with the plug length being increased, the cylindrical plug cake may be hardened, and the plug cake that hits the back pressure plate may not be smoothly discharged from the filter cylinder. In addition, the plug cake and the screw shaft may rotate together, and the plug cake may not be discharged from the filter cylinder. In order to solve these problems, the dehydrating press described in Patent Document 1 includes a moving device that moves the screw shaft in the axial direction. By moving the screw shaft with respect to the filter cylinder by the moving device, the plug cake having a low water content can be pushed out (that is, discharged) from the filter cylinder. Furthermore, it is possible to apply further pressure to the cake in the filtration cylinder by moving the screw shaft in the axial direction.

Japanese Patent Laid-Open No. 11-347796 JP 2012-532 A JP 61-162298 A JP 58-32599 A JP 59-191593 A

However, the screw press provided with the moving device for moving the screw shaft in the axial direction has the following problems.
(I) Since the moving device receives a reaction force when compressing the cake in the filtration cylinder while simultaneously moving the screw shaft, which is a heavy object, and the rotating device connected to the screw shaft, a large thrust is required. To do. For this reason, a high-output moving device is required, which leads to an increase in the size and manufacturing cost of the entire screw press.
(Ii) Since the screw shaft that is moved by the moving device penetrates the wall at the end of the filtration cylinder, a bearing that has water-stopping properties and that simultaneously receives the rotational movement and straight movement of the screw shaft is disposed on the wall of the filtration cylinder. There is a need. Such a bearing has a special structure and is expensive.
(Iii) The screw blade and the filter cylinder are arranged through a minute gap between them. Therefore, when the screw shaft is moved by the moving device, it is necessary to manufacture the moving device with high accuracy so that the screw blades do not contact the filtration cylinder.
(Iv) When the screw shaft is moved toward the discharge side of the filtration cylinder, there is no screw blade in the sludge inlet, so the sludge introduced into the filtration cylinder cannot be transferred and the sludge dewatering efficiency decreases. To do.
(V) During sludge filtration, a concentrated sludge layer is formed on the inner surface of the filter cylinder, and this sludge layer is transferred while being scraped off by screw blades. However, when there is no screw blade in the sludge inlet, the sludge layer is not scraped off by the screw blade, and the 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 overall size of the screw press is increased.
(Vii) When a high back pressure is applied to the cake in the filter cylinder in order to increase the dewatering efficiency, the cake and the screw are rotated, and the operation of the screw press cannot be continued. The appropriate back pressure to be applied to the cake in the filter cylinder is often not constant because it is affected by the properties (eg, viscosity, moisture content, etc.) of the sludge charged into the filter cylinder. Therefore, in order to apply an appropriate back pressure to the cake in the filtration cylinder, it is necessary to finely adjust the back pressure plate. However, since the back pressure plate is only allowed to move linearly and is disposed at a position away from the sludge inlet, the back pressure plate and the screw are added to the cake in the filtration cylinder. It is difficult to finely adjust the back pressure.

  Patent Documents 2 and 3, in order to adjust the back pressure applied to the cake in the filter tube, a first screw that is disposed to the insertion portion side of the filtration tube, in the transport direction of the sludge, the first screw The apparatus provided with the 2nd screw arrange | positioned in the downstream of is described.

  In the dehydrating apparatus described in Patent Document 2, the amount of cake discharged from the casing (corresponding to the filtration cylinder) can be adjusted by adjusting the rotation speed of the second screw. Further, in this dewatering device, the length of a pressure adjusting guide provided at the downstream end of the casing is adjusted to press against a resistor (corresponding to the back pressure plate) that can move forward and backward with respect to the second screw. The back pressure applied to the dehydrated cake 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 operation. Therefore, it is difficult to adjust the back pressure applied to the cake in the casing in a timely manner according to the properties of the sludge put into the casing. Furthermore, since the number of turns of the blades of the second screw is large, if the dehydrating sludge having a high viscosity is the cake is attached to the second screw, and the cake and second screw ends up rotating together.

  The screw press described in Patent Document 3, an output signal of the pressure detector for detecting the pressure of cake was squeezed by the first stage screw, the output signal of the flow rate detector for detecting the flow rate of the discharged filtrate from the filtration tube Based on the above, the back pressure applied to the cake in the filter cylinder is adjusted. Therefore, the resistor described in Patent Document 2 is not necessary for this screw press. However, the screw press, like the dehydration device described in Patent Document 2, since the number of turns of the blade provided in the second stage screw is large, a screw press, in the case of performing the dehydration treatment of the sludge with a high viscosity , The cake and the second stage screw will go around. Moreover, in the screw press of patent document 3, when high back pressure is added to the cake in a filter cylinder, in order to avoid rotation, it is comprised so that a cake may be discharged from a filter cylinder. Is difficult to add to the cake in the filter cylinder, and the dewatering efficiency cannot be increased.

  The screw press type dehydrator described in Patent Literature 4 and Patent Literature 5 also includes two screw shafts. However, the screw shaft on the discharge side has a truncated cone shape whose shaft diameter increases toward the discharge port of the outer cylinder (corresponding to the filtration cylinder). Therefore, when the cake in the filtration cylinder and the screw shaft are rotated, 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 that can increase the efficiency of separating a liquid from a liquid-containing material and can discharge a plug cake from the filter cylinder without moving the screw relative to the filter cylinder. For the purpose. Furthermore, this invention aims at providing the operating method of this screw press.

One reference example of the present invention includes a filter cylinder into which a liquid-containing material is charged, and a first screw that is arranged concentrically with the filter cylinder in the filter tube and transfers the liquid-containing material in a predetermined transfer direction. And a second screw, a first rotating mechanism that rotates the first screw, and a second rotating mechanism that rotates the second screw independently of the first screw, the second screw, The first screw is disposed downstream of the first screw in the transfer direction, and the first screw has a frustum-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, and the second rotating mechanism is configured to move the second screw to the second screw shaft. 1 screw and is capable of rotating at different rotational speeds, the number of turns of the second screw blade is a screw press, characterized in that less than 3 vol.

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

One aspect of the present invention includes a filter cylinder into which a liquid-containing material is charged, a first screw that is disposed concentrically with the filter cylinder in the filter tube, and that 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; 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, and the second rotating mechanism moves the second screw to the second screw shaft. It is possible to rotate at different rotational speeds and screw, the winding direction of the second screw blade, said the winding direction of the first screw blade is screw press, which is a reversed.

In a preferred aspect of the present invention, the pitch of the second screw blades is smaller than the pitch of the first screw blades.
One reference example 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 aspect of the present invention, the second rotation mechanism is configured such that the rotation direction of the second screw can be switched in the same direction or the reverse direction with respect to the rotation direction of the first screw. Features.
In a preferred aspect of the present invention, the second rotation mechanism includes a drive machine for rotating the second screw, and a detector capable of detecting current and / or torque of the drive machine, The rotation direction of the second screw may be switched based on the current and / or torque of the driving machine.

Another aspect of the present invention is the above-described method of operating the screw press, wherein the liquid-containing material in the filter cylinder is removed by rotating the first screw without rotating the second screw. 2 The screw is transferred to the screw to form a plug cake around the second screw shaft, and after the plug cake is formed, the second screw is rotated to discharge the plug cake from the filter cylinder. Is a driving method characterized by

One reference example of the present invention is characterized in that the discharge amount of the plug cake is adjusted by changing a rotation speed of the second screw.
One reference example of the present invention is to adjust the back pressure applied to the liquid-containing material squeezed by the first screw by performing intermittent operation that alternately repeats rotation and stop of the second screw. Features.
One reference example of the present invention is characterized in that a back pressure applied to the liquid-containing material squeezed by the first screw is adjusted by changing a rotation direction of the second screw.
One reference example of the present invention is characterized in that the rotational direction of the second screw is changed based on a current and / or torque of a drive unit of the second drive mechanism.

According to the present invention, the back pressure applied to the liquid-containing material in the filter cylinder can be adjusted by controlling the rotation speed of the second screw that can rotate independently of the first screw. While increasing the efficiency of separating the liquid from the inclusions, it is possible to prevent the cake and the second screw from rotating. Furthermore, the plug cake can be smoothly discharged from the filter cylinder by rotating the second screw independently of the first screw. Therefore, the plug cake can be discharged from the filtration cylinder without moving the first screw and the second screw with respect to the filtration cylinder. Furthermore, since the first screw and the second screw do not move with respect to the filter cylinder, the first screw blade and the second screw blade can always face the entire screen surface of the filter cylinder. As a result, it becomes possible to separate the liquid from the liquid-containing material using the entire screen surface of the filtration cylinder, and the efficiency of separating the liquid from the liquid-containing material can be improved.
Furthermore, 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 filter cylinder in a short time. Therefore, even when the liquid-containing material from which the liquid is separated by the screw press has a high viscosity, the plug cake can be discharged from the filter cylinder before the plug cake is brought together 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 opposite direction to the first screw in order to discharge the plug cake from the filter cylinder. It is 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 reverse rotation direction, it is possible to prevent the plug cake and the second screw from rotating. . As a result, the screw press can be operated while applying a high back pressure to the liquid-containing material, so that the efficiency of separating the liquid from the liquid-containing material can be increased.

It is a mimetic diagram showing a screw press concerning one embodiment. It is a schematic sectional drawing of the 2nd screw shown by FIG. It is a schematic diagram for demonstrating the winding number of a 2nd screw blade | wing. It is a schematic diagram which shows the screw press which concerns on other embodiment. It is a schematic sectional drawing of the 2nd screw shown by FIG. It is a figure explaining operation | movement of the screw press shown by FIG. It is a figure explaining operation | movement of the screw press shown by FIG. It is a figure explaining operation | movement of the screw press shown by FIG. It is the 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 other embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram illustrating a screw press according to an embodiment. A screw press shown in FIG. 1 has a cylindrical screen casing (filter cylinder) 1 and is arranged concentrically with the screen casing 1 in the screen casing 1 to transfer sludge (liquid-containing material) in a predetermined transfer direction D. The first screw 3 and the second screw 4 to be transferred to the first rotation mechanism 7, the first rotation mechanism 7 that rotates the first screw 3, the second rotation mechanism 20 that rotates the second screw 4 independently of the first screw 3, It has. The screen casing 1 is formed from 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 introduced into the screen casing 1 from the introduction port 2 is transferred in a predetermined transfer direction D within the screen casing 1 by the rotating first screw 3 and second screw 4. Furthermore, the screw press has a control unit 6 that controls the operations of the first rotating mechanism 7 and the second rotating mechanism 20.

  The second screw 4 is connected to the first screw 3 so as to be able to 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. A plug cake described later is discharged from the screen casing 1 into the discharge chamber 33. The length of the second screw 4 in the axial direction is shorter than the length of the first screw in the axial direction. First screw 3, a first screw shaft 3A frustoconical its diameter gradually increases toward the downstream side in the transport direction D of the sludge (tapered), which is fixed to the outer surface of the first screw shaft 3A And 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 blocking wall 8. One end of the first screw shaft 3A (upstream end in the transfer direction D) extends through the blocking wall 8. The closing wall 8 is provided with a water sealing device 10 that seals a gap between the closing wall 8 and the first screw shaft 3A. The upstream end of the first screw shaft 3A extending through the blocking wall 8 is rotatably supported by bearings 11 and 12 installed on a 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 3 </ b> A is connected to a first rotation mechanism 7 for rotating the first screw 3. In the present embodiment, the first rotating mechanism 7 includes a first driving machine (for example, an electric motor) 14, a sprocket 15 fixed to the rotating shaft of the first driving machine 14, and a sprocket fixed to the first screw shaft 3A. 16 and a chain 17 wound around these sprockets 15 and 16. The sprocket 16 is located between the bearings 11 and 12. When the first drive unit 14 of the first rotation mechanism 7 is driven, the sprocket 15 fixed to the rotation shaft of the first drive unit 14 rotates, and the sprocket 16 fixed to the first screw shaft 3A via the chain 17. 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 (downstream end in the transfer direction D) of the first screw shaft 3A, a reduced diameter portion 3C 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 a cylindrical second screw shaft 4A and is rotatably supported by 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, the upstream end of the second screw shaft 4 </ b> A is connected to the first screw shaft 3 </ b> A with the reduced diameter portion 3 </ b> C of the first screw shaft 3 </ b> A inserted into the second screw shaft 4. 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 seal structure to prevent passing through the gap between the sludge sliding bearing 30 and the reduced diameter portion 3C of the screen casing 1 (e.g., a labyrinth structure), and slide bearing 30 and / or the reduced diameter portion 3C May be provided.

  As shown in FIGS. 1 and 2, the second screw shaft 4A of the second screw 4 is disposed 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 4 </ b> A extends through the wall 33 </ b> A 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). ) Is supported by the bearings 22 and 23 installed in a freely rotating manner 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 rotating mechanism 20 includes a second driving machine (for example, an electric motor) 24, a sprocket 25 fixed to the rotating shaft of the second driving machine 24, and a sprocket fixed to the second screw shaft 4A. 26 and a chain 27 wound around the sprockets 25 and 26. The sprocket 26 is located between the bearings 22 and 23. When the second drive unit 24 of the second rotation mechanism 20 is driven, the sprocket 25 fixed to the rotation shaft of the second drive unit 24 rotates, and the sprocket 26 fixed to the second screw shaft 4A via the chain 27. Rotate. As a result, the second screw 4 is rotated by the second rotation mechanism 20.

  The second driver 24 is connected to the control unit 6. The second drive machine 24 includes an 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 driving machine 24 via the inverter. The second driving machine 24 can rotate the second screw 4 independently of the first screw 3. In addition, it is preferable that the said 1st drive machine 14 also incorporates the inverter which can change the rotational speed and rotation direction of this 1st drive machine 14. FIG.

  Although not shown, the rotation shaft of the second drive unit 24 may be connected to the second screw shaft 4A via a speed reducer. Alternatively, the rotation shaft of the second driving 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 extends spirally 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 length in the axial direction of the screen casing 1. Identical or long.

  A minute gap is formed between the inner surface of the screen casing 1 and the first screw blade 3 </ b> B, and the first screw blade 3 </ b> B 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 4 </ b> B, and the second screw blade 4 </ b> B can rotate without contacting the screen casing 1. ing. The sludge introduced into the screen casing 1 from the inlet 2 formed at the upstream end of the screen casing 1 is moved toward the discharge chamber 33 by the rotating first screw blade 3B and the second screw blade 4B (that is, transferred). In the direction D).

  In the present embodiment, the winding direction (that is, the spiral direction) of the second screw blade 4B is opposite to the winding direction of the first screw blade 3B. Therefore, when the sludge input from the input port 2 is sent out to the discharge chamber 33, the second screw 4 is rotated in the opposite direction to 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 input from the input 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). Furthermore, the number of turns of the second screw blade 4B is less than 3. FIG. 3 is a schematic diagram 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 4 </ b> B extending in a spiral shape is 1 when the second screw blade 4 </ b> B advances 360 ° around the first screw shaft 4 </ b> A from the start point S <b> 1 to the point S <b> 2. Count with winding. 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 dewatering region 1A in which the first screw 3 is disposed and a plug forming region 1B in which the second screw 4 is disposed. A space in which the sludge is transferred in the dewatering region 1A is formed by the inner surface of the screen casing 1, the first screw blade 3B, and the first screw shaft 3A. The cross-sectional area of the transfer space gradually decreases along the sludge transfer direction D, as shown in FIG. Therefore, as the sludge introduced from the inlet 2 is transferred through the 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 a filtrate receiver 38 disposed below the screen casing 1. A drain 39 is connected to the filtrate receiver 38, and the filtrate recovered by the filtrate receiver 38 is discharged from the screw press through the drain 39.

  A space in which the sludge is transferred in the plug formation 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-sectional area of this transfer space is constant. In the plug formation region 1B, a plug cake is formed by the sludge (ie, cake) dehydrated in the dewatering region 1A. A method for 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. The configuration of the present embodiment not specifically described is the same as the configuration of the embodiment shown in FIG. The screw press shown in FIG. 4 is different from the screw press shown in FIG. 1 in that the first rotating mechanism 7 is connected not to the upstream end of the first screw 3 but to the downstream end.

  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. Yes. The bearings 11 and 12 of the first rotating 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 3 </ b> C is disposed between the bearings 11 and 12. An upstream end of the first screw shaft 3 extending through the blocking wall 8 is rotatably supported by a 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 embodiment described above does not have a moving mechanism that moves 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, compared with the conventional screw press provided with a moving mechanism, the whole screw press can be comprised compactly. Further, since the first screw 3 and the second screw 4 is not moved in the axial direction relative to the screen casing 1, making it possible to always face the entire screen surface of the screen housing 1 a first screw blade 3B and the second screw blade 4B it can. As a result, since the sludge can be dehydrated using the entire screen casing 1, the dewatering efficiency of the sludge (that is, the efficiency of separating the liquid from the liquid-containing material) can be improved.

  Next, an operation method of the screw press shown in FIG. 1 will be described with reference to FIGS. 6 to 8 are views for explaining the operation of the screw press shown in FIG. In the following, the operation method of the screw press shown in FIG. 1 will be described, 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 rotates the first screw 3 by driving the first rotating mechanism 7 in a state where the second screw 4 is stopped. Next, sludge (liquid-containing material) is charged into the screen casing 1 from the charging port 2. As described above, since the position of the first screw 3 in the axial direction with respect to the screen casing 1 is fixed, the first screw blade 3 </ b> B always exists below the inlet 2. Accordingly, the sludge introduced from the inlet 2 is transferred toward the second screw 4 (that is, in the transfer direction D) by the rotating first screw blade 3B without stagnation on the spot.

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

  While the sludge is transferred through the dewatering area 1A of the screen casing 1, the sludge is dehydrated to become a cake, and is sent to the plug forming area 1B where the second screw 4 is disposed. As shown in FIG. 6, since the second screw 4 is not rotating at the beginning of operation (that is, stopped), the cake in the plug formation region 1B is not discharged into the discharge chamber 33, and the plug is formed. Stay in 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 dewatering region 1A to the plug forming region 1B. The cake in the plug forming region 1B is squeezed by being prevented from moving by the second screw blade 4B, and becomes a cake having a low water content. This low moisture content cake forms a plug cake that hinders subsequent cake movement. By the plug cake formed around the second screw shaft 4A, back pressure is applied to the subsequent cake, 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 through the drain 39.

  As the operation of the screw press continues, 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 moisture content of the subsequent cake is high, the subsequent cake can be reliably dammed up by the plug cake formed in the plug forming region 1B, so that a single flow of the subsequent cake can be prevented. This “single flow” means that the subsequent cake having a moisture content higher than that of the plug cake passes through the plug forming region 1B as it is and is discharged into the discharge chamber 33.

  As shown in FIG. 7, after the plug cake is formed, the control unit 6, a second screw 4 to the rotating direction of the first screw 3 is rotated in the reverse direction, the plug cake by the second screw blade 4B It is sent out to the discharge chamber 33 little by little (that is, discharged). As described above, since the formation of the plug cake and the discharge of the plug cake are continuously performed, the screw press can be operated with the plug cake always present in the plug formation region 1B.

  The plug cake on the second screw 4 is discharged into the discharge chamber 33 by the second screw blade 4B of the second screw 4 rotated by the second rotating mechanism 20 while applying back pressure to the subsequent cake. The controller 6 can adjust the amount of plug cake discharged to the discharge chamber 33 by changing the rotation speed of the second screw 4. More specifically, when the control unit 6 decreases 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, Emissions increase. When the discharge amount of the plug cake decreases, the subsequent cake stays in the dewatering region 1A, and the back pressure applied to the subsequent cake increases. Therefore, the controller 6 can reduce the water content of the subsequent cake by reducing the rotation speed of the second screw 4. In one embodiment, the back pressure applied to the subsequent cake may be adjusted by performing an intermittent operation in which the rotation and 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. In addition, the plug cake having a low water content can be removed from the screen casing 1. As a result, the same effect as that obtained when the screw shaft is moved toward the opening end of the screen casing by the moving device provided in the conventional screw press can be obtained. Furthermore, according to 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. Furthermore, since a back pressure plate and a back pressure plate operating mechanism are unnecessary, a 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). Thus, if the pitch P1 of the second screw blade 4B is smaller than the pitch P2 of the first screw blade 3B, the transfer distance of the plug cake is discharged to the discharge chamber 33 while the second screw 4 is rotated 1 short Therefore, the back pressure applied to the cake in the dewatering region 1A can be adjusted more finely.

  In the conventional screw press, if the plug cake squeezed into a cylindrical shape becomes too hard, the hardened plug cake closes the screen casing and cannot be discharged from the screen casing. Furthermore, this hardened plug cake will be used 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 formation region 1B is discharged into 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 rotating in the direction opposite to 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 in the plug formation region 1B and the second screw 4 and / or the rotation of the cake in the dewatering region 1A and the first screw 3 is prevented, so that high back pressure is applied to 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. When the plug cake has a high viscosity, the plug cake may be rotated 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 is pushed out to the discharge chamber 33 by the subsequent cake, and there is a possibility that the back pressure cannot be effectively applied to the subsequent cake. Therefore, the number of turns of the second screw blade 4B is preferably 2 turns 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. Rotation of the second screw 4 to the first screw 3 in the same direction, the plug cake formed in the plug-forming region 1B is pushed towards the dewatering region 1A, it is made greater back pressure by cake dewatering region 1A it can. As a result, the sludge dewatering efficiency 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 dewatering region 1 </ b> A may be rotated with the first screw 3. Therefore, after rotating the second screw 4 in the same direction as the first screw 3 for a certain amount of time, the rotation direction of the second screw 4 is returned to the opposite direction to the rotation direction of the first screw 3 (FIG. 7). reference). Since the screw press of this 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 to the discharge chamber 33 like a screw conveyor. can do. Thus, the control part 6 can adjust the back pressure applied to the sludge squeezed by the first screw 3 in the dewatering region 1A by changing the rotation direction of the second screw 4. In order to reliably discharge the plug cake to the discharge chamber 33, the rear end of the second screw blade 4 </ b> B of the second screw 4 may be configured to protrude slightly from the opening end of the screen casing 1.

  When the control unit 6 changes the rotation speed and the rotation direction of the second screw 4, the sludge can be dehydrated 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 second screw 4 is rotated in the forward direction (the direction opposite to the direction of rotation of the first screw 3) to discharge the plug cake to the discharge chamber 33, while pressing the sludge in the screen casing 1 to perform the dehydration process. Do. During dehydration of the sludge, the second screw 4 is rotated in the reverse direction (the same direction as the rotation direction of the first screw 3), and dehydrated to a further low water content cake in dewatering region 1A, then the The plug screw having a low water content may be discharged into the discharge chamber 33 by rotating the two screws 4 in the forward direction. Such an operation of changing the rotation direction of the second screw 4 is preferably performed periodically at intervals according to the properties of the sludge.

  As shown in FIGS. 6 to 8, the second drive unit 24 of the second rotation mechanism 20 may include a detector 28 that can detect the current value and / or torque of the second drive unit 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 driving machine 24 has a correlation with the load applied to the second driving machine 24 in order to rotate the second screw 4. Therefore, the control unit 6 changes the rotation direction of the second screw 4 based on the current value and / or torque output signal sent from the detector 28, so that the second according to the load applied to the second driver 24. The rotation direction of the screw 4 can be switched. As described above, the rotation direction of the second screw 4 may be changed based on the current value and / or torque of the second drive unit 24.

  FIG. 9 is a schematic view showing the second screw 4 according to another embodiment. The pitch of the second screw blades 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 ''). Thus, 'the pitch P1 of the downstream' pitch P1 on the upstream side when larger than ', the transfer cake to plug formation region 1B from dehydration region 1A by the rotation of the first screw 3, the plug-forming region 1B It can be gradually retained. As a result, since the back pressure applied to the cake in the dewatering region 1A does not increase rapidly, it is possible to effectively prevent the cake in the dewatering region 1A from rotating with the first screw 3.

  FIG. 10 is a schematic view showing a screw press according to still another embodiment. The configuration of the present embodiment not specifically described is the same as the configuration of the embodiment shown in FIG. 10 is that the winding direction of the second screw blade 4B of the second screw 4 (that is, the spiral direction) is the same as the winding direction of the first screw blade 3B of the first screw 3. 1 is different from the screw press shown in FIG.

  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 input from the input port 2 is sent 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 discharge 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 3. Furthermore, the number of turns of the second screw blade 4B is preferably 2 turns 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 rotates the first screw 3 by driving the first rotating mechanism 7 with the second screw 4 stopped. Then, the sludge (liquid inclusions) were charged into a screen casing 1 from inlet 2, the sludge, the first screw blade 3B to rotate toward the second screw 4 (i.e., in the transport direction D) to transfer .

  As described above, while the dewatering area 1A in which the first screw 3 is disposed is transferred, the sludge is dehydrated to become a cake and is sent to the plug forming area 1B in which the second screw 4 is disposed. At the beginning of operation, the second screw 4 is not rotating (that is, stopped), so the cake in the plug formation region 1B is not discharged into the discharge chamber 33 but stays in the plug formation region 1B. As a result, a plug cake that prevents the subsequent cake from moving is formed in the plug forming region 1B. The back cake 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 sends the plug cake to the discharge chamber 33 little by little by the second screw blade 4B (that is, ,Discharge). As described above, since the formation of the plug cake and the discharge of the plug cake are continuously performed, the screw press can be operated with the plug cake always present in the plug formation region 1B.

  The plug cake on the second screw 4 is discharged into the discharge chamber 33 by the second screw blade 4B of the second screw 4 rotated by the second rotating mechanism 20 while applying back pressure to the subsequent cake. Also in the screw press shown in FIG. 10, the control unit 6 can adjust the amount of the 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 decreases 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, Emissions increase. When the discharge amount of the plug cake decreases, the subsequent cake stays in the dewatering region 1A, and the back pressure applied to the subsequent cake increases. Therefore, the controller 6 can reduce the water content of the subsequent cake by reducing the rotation speed of the second screw 4. In one embodiment, the back pressure applied to the subsequent cake may be adjusted by performing an intermittent operation in which the rotation and 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 that obtained when the screw shaft is moved toward the opening end of the screen casing by the moving device provided in the conventional screw press can be obtained. Furthermore, 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. Furthermore, since a back pressure plate and a back pressure plate operating mechanism are unnecessary, a screw press can be manufactured at low cost.

  The second screw 4 may be rotated in the opposite direction to the first screw 3. Rotation of the second screw 4 in the opposite direction as the first screw 3, the plug cake formed in the plug-forming region 1B is pushed towards the dewatering region 1A, be made greater back pressure by cake dewatering region 1A it can. As a result, the sludge dewatering efficiency can be improved.

  Further, when the second screw 4 is rotated in the opposite direction to the first screw 3, the plug cake in the plug forming region 1B rotated by the second screw 4 and the dewatering region 1A rotated by the first screw 3 are obtained. The cakes are pressed against each other in the reverse direction. Big Consequently, while preventing the co-rotation of the cake and the first screw 3 rotating together, and dehydration region 1A of the plug cake and second screw 4 in the plug-forming region 1B, the cake in the dehydration region 1A 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 dewatering 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 a direction opposite to the first screw 3 for a certain amount 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. Thus, the control part 6 can adjust the back pressure applied to the sludge squeezed by the first screw 3 in the dewatering region 1A by changing the rotation direction of the second screw 4. In order to reliably discharge the plug cake to the discharge chamber 33, the rear end of the second screw blade 4 </ b> B of the second screw 4 may be configured to protrude slightly from the opening end of the screen casing 1.

  Similar to the screw press shown in FIG. 1, the control unit 6 changes the rotation speed and direction of the second screw 4 to dewater sludge to a low water content that cannot be achieved by the conventional screw press. be able to. The operation of changing the rotation direction of the second screw 4 is preferably performed periodically at intervals according to the properties of the sludge. Alternatively, the rotation direction of the second screw 4 may be changed based on the current value and / or torque of the second driving 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 blades 4B is preferably smaller than the pitch of the first screw blades 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 like the screw press described with reference to FIGS. 4 and 5. Also good.

  The screw press of the embodiment described above is used to separate water, which is a liquid, from sludge, which is an example of a liquid-containing material. In order to separate the liquid from a liquid-containing material other than sludge, this screw press is used. It may be used. For example, the screw press which concerns on the above-mentioned embodiment can be used also for processing of foodstuffs, such as fruit and oil, and processing of industrial products, such as a recycling process of used paper. In food processing, a screw press is used to squeeze raw materials (liquid-containing materials) such as fruits and seeds and separate liquids such as fruit juice and oil from the raw materials. In the recycling of used paper, the used paper is mixed with water and chemicals to loosen the used paper into fibrous materials. A screw press is used to squeeze a fibrous material and liquid mixture (liquid containing material) to separate the fibrous material from the mixture.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement 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. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

1 Screen casing (filter cylinder)
DESCRIPTION OF SYMBOLS 1A Dehydration | dehydration area | region 1B Plug formation area | region 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 part 7 1st Rotation mechanism 8 Blocking wall 10 Water seal device 11, 12 Bearing 14 First drive unit 15, 16 Sprocket 17 Chain 20 Second rotation mechanism 22, 23 Bearing 24 Second drive unit 25, 26 Sprocket 27 Chain 28 Detector 30, 31 Slide bearing 33 Discharge chamber 36 Bearing 38 Filtrate receiver 39 Drain

Claims (5)

A filter cylinder into which the liquid-containing material is charged;
A first screw and a second screw that are arranged concentrically with the filtration cylinder in the filtration cylinder and transfer the liquid-containing material in a predetermined transfer direction;
A first rotation mechanism for rotating the first screw;
A second rotating mechanism for rotating the second screw independently of the first screw,
The second screw is disposed downstream of the first screw in the transfer direction;
The first screw has a frustoconical 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.
The screw press characterized in that the winding direction of the second screw blade is opposite to the winding direction of the first screw blade. The pitch of the second screw blade, screw press according to claim 1, characterized in that less than the pitch of the first screw blade. The said 2nd rotation mechanism is comprised so that the rotation direction of the said 2nd screw can be switched to the same direction or the reverse direction with respect to the rotation direction of the said 1st screw, or 1st or more. The screw press according to 2 . The second rotation mechanism includes a drive machine for rotating the second screw, and a detector capable of detecting current and / or torque of the drive machine,
The screw press according to claim 3 , wherein a rotation direction of the second screw is switched based on a current and / or torque of the driving machine. It is the operating method of the screw press as described in any one of Claims 1 thru | or 4 , Comprising:
By rotating the first screw without rotating the second screw, the liquid-containing material in the filtration cylinder is transferred to the second screw, and a plug cake is formed around the second screw shaft. Forming,
After the plug cake is formed, the second screw is rotated to discharge the plug cake from the filter cylinder.

Images