JP5219674B2 - Screw press and its operating method - Google Patents

Description

  The present invention relates to a screw press that depressurizes and dehydrates an object to be squeezed such as sewage sludge, human waste, septic tank sludge, and industrial wastewater sludge, and an operation method thereof.

  Conventionally, as this type of screw press, for example, as shown in FIG. 16, a rotatable screw shaft 62 is provided in a filter cylinder 61, and the screw shaft 62 is supplied from the supply port 71 into the filter cylinder 61 on the outer periphery. A spiral screw blade 64 is provided to send the pressed object to the discharge port 63.

  The discharge port 63 of the filter cylinder 61 is provided with a back pressure plate 65 that acts as a back pressure on the direction opposite to the feeding direction of the object to be compressed and opens and closes the discharge port 63. Further, a rotation driving device 66 for rotating the screw shaft 62 and a hydraulic cylinder 67 for moving the back pressure plate 65 in the opening / closing directions O and S are provided.

  Further, the screw shaft 62 is movable back and forth in the axial direction A, and a hydraulic cylinder 68 for moving the screw shaft 62 in the axial direction A is provided. The rotational drive device 66 is provided on a movable base 69 that is movable in the axial direction A. The movable base 69 is provided with a bearing device 70 that rotatably holds the screw shaft 62.

  According to this, during the dehydrating operation, as shown in FIG. 16A, the rotational drive device 66 is driven to rotate the screw shaft 62, and the hydraulic cylinder 67 is driven to close the back pressure plate 65 with a predetermined force. Press to S. The to-be-squeezed object 72 supplied into the filter cylinder 61 from the supply port 71 is compressed while being sent from the supply port 71 side to the discharge port 63 side by a screw blade 64 that rotates integrally with the screw shaft 62, and becomes a dehydrated cake. While pressing the back pressure plate 65 in the opening direction O, the back pressure plate 65 is discharged from between the discharge port 63 (the discharge side end of the filter tube 61) and the back pressure plate 65. At this time, the back pressure plate 65 stays at a position where the pressing force in the closing direction S applied by the hydraulic cylinder 67 and the pressing force in the opening direction O applied by the discharged compressed material are balanced (stopped).

  When the dehydration operation is continued for a certain period of time in this state, a compacted zone (plug zone) comprising the squeezed material 72 that has been squeezed and reduced to the target moisture content is provided immediately before the discharge port 63 in the filter cylinder 61. ) Is formed. By forming such a compaction band, the compressed object 72 having a higher moisture content located on the supply port 71 side than the compaction band is discharged from the discharge port 63 before being compressed to the target moisture content. Can be prevented. Thereby, since the to-be-squeezed object 72 sent continuously from the supply port 71 side to the discharge port 63 side falls to a target moisture content one by one in a compaction zone, the stable dehydration operation can be performed.

  Moreover, when the moisture content of the to-be-compressed object 72 in the discharge port 63 in the filter cylinder 61 falls too much rather than the target moisture content, the to-be-compressed object 72 falls into a blockage state, and becomes difficult to be discharged | emitted. At this time, as shown in FIG. 16B, the piston rod of the hydraulic cylinder 68 is extended to advance the screw shaft 62 in the axial direction A, so that the screw blades 64 are integrated with the screw shaft 62 in the axial direction. It advances to A and the to-be-compressed object 72 is pushed by the said screw blade | wing 64 which advances, and is discharged | emitted from the discharge port 63 forcibly. Thereby, it can prevent that the to-be-compressed material 72 obstruct | occludes in the discharge port 63. FIG.

  Thereafter, as shown in FIG. 16A, the piston rod of the hydraulic cylinder 68 is shortened and the screw shaft 62 is moved backward in the axial direction A, whereby the screw blades 64 are integrated with the screw shaft 62 in the axial direction A. Go back to the original position.

The screw press having the configuration for moving the screw shaft 62 in the axial direction A as described above is described in, for example, Patent Document 1 below.
Japanese Patent No. 3373432

  In the conventional type, the screw shaft 62 is moved in the axial direction A in order to prevent the water content from being excessively reduced and the compressed material 72 from being blocked by the discharge port 63, and the compressed material 72 is moved to the axial direction A. Although it is forcibly discharged from the discharge port 63, in order to move the screw shaft 62 in the axial direction A, a dedicated hydraulic cylinder 68, a movable base 69, etc. are required, and the configuration of the screw press 60 is complicated. In addition, there is a problem of increasing the size.

  An object of this invention is to provide the screw press which can prevent that a to-be-squeezed material obstruct | occludes by a discharge port with a simple structure, and its operating method.

In order to achieve the above object, according to the first aspect of the present invention, a screw shaft capable of rotating forward and backward is provided in a filter cylinder,
Screw blades are provided on the outer periphery of the screw shaft to send the object to be squeezed supplied into the filter cylinder to the discharge port.
In the discharge port of the filter cylinder, it is a screw press operation method provided with a back pressure plate that acts as a back pressure on the direction opposite to the feed direction of the object to be compressed and opens and closes the discharge port,
A normal operation process in which the screw shaft is rotated forward while pressing the back pressure plate in a closing direction with a predetermined force, and the squeezed object is discharged from the outlet of the filter cylinder;
After the normal operation process, the back pressure plate is forcibly moved from the position at the time of the normal operation process in the opening direction, and the discharge promotion process for discharging the squeezed material from the discharge port of the filter cylinder for a predetermined time, and
After the discharge promotion process, a back pressure plate closing process is performed in which the screw shaft is rotated in the reverse direction while moving the back pressure plate in the closing direction .
Thereafter, the back pressure plate closing process returns to the normal operation process again .

  According to this, in the normal operation process, the screw shaft rotates forward and the back pressure plate is pressed in the closing direction with a predetermined force. The object to be squeezed supplied into the filter cylinder is squeezed while being sent to the discharge port side by screw blades that rotate positively integrally with the screw shaft to form a dehydrated cake, and while pressing the back pressure plate in the opening direction, It is discharged from between the pressure plates. At this time, the back pressure plate remains in a position where the pressing force in the closing direction balances the pressing force in the opening direction that is acted on by the pressed object to be discharged.

  In this state, when the normal operation process is continued for a certain period of time, a compacted zone (plug zone) made of a material to be squeezed and reduced to the target moisture content is immediately compressed at the portion immediately before the outlet in the filter cylinder. It is formed. By forming such a compacted zone, the material to be squeezed with a high water content located upstream (consolidated material supply side) of the compacted zone is discharged from the outlet before being compressed to the target moisture content. Can be prevented. Thereby, since the to-be-squeezed material continuously sent to the discharge port side falls to a target moisture content one by one in a consolidation zone, stable dehydration operation can be performed.

  In addition, if the moisture content of the object to be compressed in the vicinity of the discharge port in the filter cylinder is excessively lower than the target moisture content, the object to be compressed will not be discharged due to a closed state. Switch to the process.

  As a result, the back pressure plate is forcibly moved in the opening direction from the position during the normal operation process, and the interval between the discharge port and the back pressure plate is increased as compared with the normal operation process. For this reason, the to-be-compressed object is reliably discharged | emitted from between a discharge port and a back pressure plate, and it can prevent that a to-be-compressed object obstruct | occludes to a discharge port. At this time, the compacted band whose water content has decreased excessively disappears and disappears.

  When a predetermined time elapses after the discharge promotion process is started, the discharge promotion process is switched to the back pressure plate closing process. As a result, the screw shaft is reversely rotated while the back pressure plate is forcibly moved in the closing direction from the open position at the time of the discharge promotion step, and the screw blade in the filter cylinder is reversely rotated integrally with the screw shaft. The thing is slightly returned from the discharge port side to the upstream side (supply side), and the object to be squeezed in the discharge port is not discharged but is retained in the discharge port.

  As a result, the back pressure plate is not pressed in the opening direction by the object to be squeezed, and the back pressure plate moves reliably and smoothly in the closing direction to close the discharge port, so that the moisture content is reduced until just before the compaction band is formed. The pressed object is retained in the filter cylinder without being discharged from the outlet as it is.

  Thereafter, the back pressure plate closing process is switched to the normal operation process again. As a result, the screw blades rotate forward integrally with the screw shaft, and the object to be squeezed is compressed while being sent to the discharge port side by the screw blades, while pressing the back pressure plate in the opening direction, between the discharge port and the back pressure plate. Discharged from. At this time, the back pressure plate remains at a position where the pressing force in the closing direction balances the pressing force in the opening direction that is acted on by the pressed object to be discharged.

  In the operation method of the screw press as described above, the material to be squeezed is blocked at the discharge port with a simple structure in which the screw shaft is fixed in the axial direction without moving the screw shaft in the axial direction as in the prior art. It is possible to prevent this.

  Furthermore, in the back pressure plate closing process, the pressed object whose moisture content has been reduced until just before forming the compacted band is retained in the filter cylinder without being discharged from the outlet as it is. , The compaction zone is formed in a short time, and the dehydration operation is stabilized.

The screw press operating method according to the second aspect of the present invention is such that, in the back pressure plate closing process, when the back pressure plate is moved in the closing direction and a predetermined time has elapsed, the screw shaft is rotated in the reverse direction while the back pressure plate is continuously moved in the closing direction. Is.

According to this, when switching from the discharge promotion process to the back pressure plate closing process, first, the back pressure plate is forcibly moved in the closing direction from the open position at the time of the discharge promotion process, and when a predetermined time elapses in this state, The screw shaft rotates backward while the back pressure plate continues to move in the closing direction.

The operation method of the screw press according to the third aspect of the present invention is switched from the normal operation step to the discharge promotion step when the pressure in the filter cylinder rises above the specified pressure,
The back pressure plate closing process is performed after the discharge promotion process is performed for a predetermined time.

  According to this, when performing the normal operation process and dewatering, if the moisture content of the compressed material near the outlet in the filter cylinder is excessively lower than the target moisture content, the compressed material falls into a closed state. As a result, the pressure in the filter cylinder rises. For this reason, when the pressure in the filter cylinder rises above the specified pressure, the object to be squeezed is reliably discharged from between the discharge port and the back pressure plate by switching from the normal operation process to the discharge promotion process. It is possible to prevent the compressed product from being blocked at the discharge port.

The operation method of the screw press according to the fourth aspect of the present invention switches from the normal operation process to the discharge promotion process when the drive current of the electric motor that rotates the screw shaft rises above the specified current.
The back pressure plate closing process is performed after the discharge promotion process is performed for a predetermined time.

  According to this, when performing the normal operation process and dewatering, if the moisture content of the compressed material near the outlet in the filter cylinder is excessively lower than the target moisture content, the compressed material falls into a closed state. As a result, the load on the electric motor increases and the drive current increases. For this reason, when the drive current of the electric motor rises above the specified current, the pressed object is surely discharged from between the discharge port and the back pressure plate by switching from the normal operation process to the discharge promotion process. It is possible to prevent an object from being blocked at the discharge port.

The operation method of the screw press according to the fifth aspect of the present invention is to switch from the normal operation process to the discharge promotion process after performing the normal operation process for a certain period of time.
The back pressure plate closing process is performed after the discharge promotion process is performed for a predetermined time.

According to this, for the squeezed product with stable properties and little fluctuation, the moisture content of the squeezed product decreases excessively from the target moisture content after starting the normal operation process based on tests and experiences. Therefore, it is possible to generally specify the occurrence time of the closed state until the pressed object is hardly discharged. Therefore, by setting the predetermined time according to the occurrence time of the closed state, after a predetermined time has elapsed since the start of the normal operation process, the pressed object is reliably obtained by switching from the normal operation process to the discharge promotion process. It is discharged from between the discharge port and the back pressure plate to prevent the object to be squeezed from being blocked by the discharge port.
In the operation method of the screw press according to the sixth aspect of the present invention, in the back pressure plate closing process, the object to be squeezed whose moisture content has decreased until just before forming the compacted band made of the object to be squeezed with the target moisture content is retained in the filter cylinder. Is.

The screw press according to the seventh aspect of the present invention is provided with a screw shaft that can freely rotate in the forward and reverse directions in the filter cylinder.
Screw blades are provided on the outer periphery of the screw shaft to send the object to be squeezed supplied into the filter cylinder to the discharge port.
In the discharge port of the filtration cylinder, a back pressure plate is provided that acts as a back pressure in the direction opposite to the feed direction of the squeezed object and opens and closes the discharge port,
A rotation driving device for rotating the screw shaft, an opening / closing device for moving the back pressure plate in the opening / closing direction, and a control device for controlling the rotation driving device and the opening / closing device;
The control device controls the opening / closing device so that the back pressure plate is pressed in the closing direction with a predetermined force, and controls the rotation drive device so that the screw shaft rotates forward, and the back pressure plate is forced A second control for controlling the opening / closing device to move in the opening direction, and the opening / closing device to control the opening / closing device so that the back pressure plate moves in the closing direction. There third row and a control for controlling, from the first control proceeds to a second control, after performing the second control performs the third control, again a first control from the third control It is something to return to.

  According to this, at the start of operation, the control device first performs the first control. As a result, the screw shaft rotates in the forward direction, the back pressure plate is pressed in the closing direction with a predetermined force, and the normal operation process is started. In the normal operation process, the object to be squeezed supplied into the filter cylinder is squeezed while being sent to the discharge port side by a screw blade that rotates positively integrally with the screw shaft to form a dehydrated cake, and presses the back pressure plate in the opening direction. However, it is discharged from between the discharge port and the back pressure plate. At this time, the back pressure plate remains in a position where the pressing force in the closing direction balances the pressing force in the opening direction that is acted on by the pressed object to be discharged.

  When the normal operation process is continued for a certain period of time in this state, a compaction band is formed in the portion immediately before the discharge port in the filter cylinder. By forming such a compaction zone, the object to be squeezed with a high water content located upstream from the compaction zone is prevented from being discharged from the outlet before being compressed to the target moisture content. be able to. Thereby, since the to-be-squeezed material continuously sent to the discharge port side falls to a target moisture content one by one in a consolidation zone, stable dehydration operation can be performed.

  In addition, when the moisture content of the object to be compressed in the vicinity of the discharge port in the filter cylinder is excessively lower than the target moisture content, the object to be compressed becomes difficult to be discharged due to a closed state. Switch from control to second control. As a result, the back pressure plate is forcibly moved in the opening direction from the position during the normal operation process, and the discharge promotion process is started. In the discharge promotion process, since the interval between the discharge port and the back pressure plate is expanded as compared with the normal operation step in the first control, the squeezed object is reliably discharged from between the discharge port and the back pressure plate, It can prevent that the to-be-compressed object obstruct | occludes at a discharge port. At this time, the compacted band whose water content has decreased excessively disappears and disappears.

  When a predetermined time has elapsed since the start of the second control, the control device switches from the second control to the third control. Thereby, the screw shaft rotates in the reverse direction while the back pressure plate is forcibly moved in the closing direction from the open position in the discharge promotion step, and the back pressure plate closing step is started. In the back pressure plate closing process, the screw blades rotate in reverse with the screw shaft, so that the material to be squeezed in the filter cylinder is slightly returned from the discharge port side to the upstream side (supply side), and the squeezed product in the discharge port Things are retained in the outlet without being discharged.

  As a result, the back pressure plate is not pressed in the opening direction by the object to be squeezed, and the back pressure plate moves reliably and smoothly in the closing direction to close the discharge port, so that the moisture content is reduced until just before the compaction band is formed. The pressed object is retained in the filter cylinder without being discharged from the outlet as it is.

  Thereafter, the control device switches from the third control to the first control again. As a result, the normal operation process is started again, the screw blades rotate forward integrally with the screw shaft, and the object to be squeezed is squeezed while being sent to the discharge port side by the screw blades, pressing the back pressure plate in the opening direction. However, it is discharged from between the discharge port and the back pressure plate. At this time, the back pressure plate remains at a position where the pressing force in the closing direction balances the pressing force in the opening direction that is acted on by the pressed object to be discharged.

  In the operation method of the screw press as described above, the material to be squeezed is blocked at the discharge port with a simple structure in which the screw shaft is fixed in the axial direction without moving the screw shaft in the axial direction as in the prior art. It is possible to prevent this.

  Furthermore, in the back pressure plate closing step executed by the third control, the object to be squeezed whose moisture content has been reduced until immediately before forming the compacted band is retained in the filter cylinder without being discharged from the discharge port. Therefore, after that, in the normal operation process executed by the first control, the compaction zone is formed in a short time, and the dehydration operation is stabilized.

The screw press in the eighth invention is provided with a pressure detection device for detecting the pressure in the filtration cylinder,
When the pressure detected by the pressure detection device rises above the specified pressure, the control device switches from the first control to the second control, performs the second control for a predetermined time, and then performs the second control to the third control. Switching to control.

  According to this, dehydration is performed in the normal operation process by the control device performing the first control. At this time, if the moisture content of the object to be compressed in the vicinity of the discharge port in the filter cylinder is excessively lower than the target moisture content, the object to be compressed falls into a closed state and is difficult to be discharged. To rise. For this reason, when the pressure in the filter cylinder rises above the specified pressure, the control device switches from the first control to the second control. Thereby, it transfers to a discharge | emission acceleration | stimulation process from a normal driving | operation process, and to-be-compressed material can be reliably discharged | emitted from between a discharge port and a back pressure plate, and it can prevent that a to-be-compressed product obstruct | occludes to a discharge port.

In the screw press according to the ninth aspect of the present invention, the rotational drive device comprises an electric motor,
An ammeter that detects the drive current of the electric motor is provided,
When the drive current detected by the ammeter rises above the specified current, the control device switches from the first control to the second control, performs the second control for a predetermined time, and then performs the second control to the third control. Switching to control.

  According to this, dehydration is performed in the normal operation process by the control device performing the first control. At this time, if the moisture content of the object to be compressed in the vicinity of the discharge port in the filter cylinder is excessively reduced below the target moisture content, the object to be compressed is difficult to be discharged due to a closed state, which increases the load on the motor. The drive current increases. For this reason, when the drive current of the electric motor rises above the specified current, the control device switches from the first control to the second control. Thereby, it transfers to a discharge | emission acceleration | stimulation process from a normal driving | operation process, and to-be-compressed material can be reliably discharged | emitted from between a discharge port and a back pressure plate, and it can prevent that a to-be-compressed product obstruct | occludes to a discharge port.

The screw press in the tenth invention is provided with a timer for detecting time,
When the time detected by the timer reaches a certain time after starting the first control, the control device switches from the first control to the second control, and after performing the second control for a predetermined time, The second control is switched to the third control.

According to this, for the squeezed product with stable properties and little fluctuation, the moisture content of the squeezed product is excessively lower than the target moisture content after starting the first control based on tests and experiences. Thus, it is possible to generally specify the occurrence time of the closed state until the pressed object is hardly discharged. Therefore, by setting the certain time according to the blocking state occurrence time, by switching from the first control to the second control after a certain time has elapsed since the control device started the first control, It is possible to prevent the object to be compressed from being discharged from between the discharge port and the back pressure plate, and to block the object to be compressed from the discharge port.
In the screw press according to the eleventh aspect of the present invention, when the control device performs the third control, the squeezed product whose moisture content has decreased until just before forming the compacted band made of the squeezed product having the target moisture content is the filter cylinder. It is to be kept inside.

  As described above, according to the present invention, the object to be squeezed is blocked at the discharge port with a simple structure in which the screw shaft is fixed in the axial direction without moving the screw shaft in the axial direction as in the prior art. Can be prevented.

  Furthermore, in the back pressure plate closing step, the pressed object whose water content has been reduced until just before forming the compacted band is retained in the filter cylinder without being discharged from the outlet as it is, and in the subsequent normal operation step The compacted band is formed in a short time, and the dehydration operation is stabilized.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1-3, 11 is a screw press which squeezes and dewaters the object 10 to be squeezed, such as sewage sludge, human waste, septic tank sludge and industrial wastewater sludge, and is a cylindrical filter arranged in a horizontal direction. A screw shaft 13 that can freely rotate forward and backward is inserted concentrically into the tube 12. The filtration cylinder 12 is made of a punching metal having a large number of holes (or a wedge having a large number of slits, etc.), and a supply port 14 for supplying the material 10 to be compressed into the filtration cylinder 12 is formed at one end of the filtration cylinder 12. The other end is formed with a discharge port 15 for discharging the dewatered object 10 to the outside.

  The screw shaft 13 is formed in a tapered shape having a small diameter on one end supply side and a large diameter on the other end discharge side, and is fixed in the axial direction A. A spiral screw blade 16 is provided on the outer periphery of the screw shaft 13 to send the object 10 to be squeezed supplied from the supply port 14 into the filter cylinder 12 to the discharge port 15. In addition, the space | interval of the inner peripheral surface of the filtration cylinder 12 in the radial direction and the outer peripheral surface of the screw shaft 13 is gradually reduced toward the other end discharge side.

  The supply port 14 is provided with a hopper 17 for feeding the material 10 to be squeezed. In addition, a rotational drive device 18 that rotationally drives the screw shaft 13 is provided in front of the screw shaft 13. The rotation drive device 18 includes a rotation drive shaft 19 provided on the screw shaft 13, an electric motor 20, and a speed reduction device 21 that decelerates and transmits the rotation drive force of the electric motor 20 to the rotation drive shaft 19.

  Behind the discharge port 15 of the filter cylinder 12 is provided a back pressure plate 22 that acts as a back pressure on the direction opposite to the feeding direction of the compressed object 10 and opens and closes the discharge port 15. The back pressure plate 22 has a tapered surface facing the discharge port 15, the more the back pressure plate 22 moves in the closing direction S, the smaller the opening area of the discharge port 15, and the more the back pressure plate 22 moves in the opening direction O, The opening area of the discharge port 15 increases.

  An opening / closing device 23 that moves the back pressure plate 22 in the opening / closing directions O and S is provided behind the back pressure plate 22. The opening / closing device 23 includes a hydraulic cylinder device 24, a hydraulic pump 26 that supplies hydraulic oil in the oil tank 25 to the hydraulic cylinder device 24, and an electromagnetic switching valve 27 that switches the piston rod 24 a of the hydraulic cylinder device 24 to be withdrawn and retracted. And have. When the switching valve 27 is switched to one switching position 27a, the piston rod 24a protrudes to move the back pressure plate 22 in the closing direction S, and when the switching valve 27 is switched to the other switching position 27b, The rod 24a retracts and moves the back pressure plate 22 in the opening direction O.

  A pressure detection device 29 that detects the pressure in the filter cylinder 12 is provided at the end (consolidation zone forming portion) on the discharge port 15 side in the filter cylinder 12. In addition, the screw press 11 is provided with a control device 30 that controls the electric motor 20 of the rotary drive device 18, the hydraulic pump 26 of the opening / closing device 23, and the switching valve 27 to perform the first to third controls.

  In the first control, the switching valve 27 is switched to one switching position 27a so that the back pressure plate 22 is pressed in the closing direction S with a predetermined force, and the electric motor 20 is rotated so that the screw shaft 13 rotates forward. Is to control. The second control is to switch the switching valve 27 to the other switching position 27b so that the back pressure plate 22 is forced to move in the opening direction O. In the third control, first, the switching valve 27 is switched to one switching position 27a so that the back pressure plate 22 is forcibly moved in the closing direction S, and further, the screw shaft is delayed by a predetermined delay time. The electric motor 20 is controlled so that 13 reversely rotates. The control device 30 includes a timer 30a that measures time.

Next, an operation method of the screw press 11 will be described with reference to a flowchart shown in FIG. 4 and a time chart shown in FIG.
At the start of operation, control device 30 first performs first control (step-1). As a result, the screw shaft 13 rotates forward, the switching valve 27 is switched to one switching position 27a, the piston rod 24a of the hydraulic cylinder device 24 protrudes, and the back pressure plate 22 is pressed in the closing direction S with a predetermined force. Then, the normal operation process is started (step-2).

  Then, as shown in FIG. 1, the object 10 to be squeezed supplied from the hopper 17 into the filter cylinder 12 is sent from the supply port 14 side to the discharge port 15 side by the screw blade 16 that rotates positively integrally with the screw shaft 13. While being pressed, it becomes a dehydrated cake and is discharged from between the discharge port 15 (the discharge side end of the filter tube 12) and the back pressure plate 22 while pressing the back pressure plate 22 in the opening direction O. At this time, the back pressure plate 22 remains in a position where the pressing force in the closing direction S applied by the hydraulic cylinder device 24 balances the pressing force in the opening direction O applied by the discharged compressed material 10 (stops). The pressure in the filter cylinder 12 is detected by the pressure detection device 29.

  When the normal operation process is continued for a certain period of time in this state, the compacted zone B (comprising the object 10 to be squeezed and reduced to the target moisture content is compressed immediately before the outlet 15 in the filter cylinder 12. Plug zone) is formed. By forming such a compaction band B, the object 10 having a higher moisture content located closer to the supply port 14 than the compaction band B is discharged from the discharge port 15 before being compressed to the target moisture content. Can be prevented. Thereby, since the to-be-squeezed object 10 sent continuously from the supply port 14 side to the discharge port 15 side falls to the target moisture content one by one in the compaction zone B, the stable dehydration operation can be performed.

  Moreover, when the moisture content of the to-be-compressed thing 10 in the discharge port 15 in the filtration cylinder 12 falls too much rather than a target moisture content, since the to-be-compressed object 10 falls into an obstruction | occlusion state and becomes difficult to discharge, the filtration cylinder 12 The pressure inside rises. For this reason, when the detected pressure detected by the pressure detection device 29 rises above a specified pressure (for example, 500 to 800 kPa) (step-3), the control device 30 determines that the object 10 to be compressed is as described above. It is determined that the vehicle is in the closed state, and the first control is switched to the second control (step-4).

  Thereby, the switching valve 27 is switched to the other switching position 27b, the piston rod 24a of the hydraulic cylinder device 24 is retracted as shown in FIG. 6, and the back pressure plate 22 is moved from the open position when the normal operation process is performed. The discharge is forcibly moved to the maximum open position (full open position) in the opening direction O, and the discharge promotion process is started (step-5). In the discharge promotion process, the interval between the discharge port 15 and the back pressure plate 22 is larger than that in the normal operation process, so that the pressed object 10 in the closed state is reliably between the discharge port 15 and the back pressure plate 22. Is discharged, the closed state of the object to be compressed 10 is eliminated, and the pressure in the filter cylinder 12 is reduced. As a result, the compaction band B disappears once and disappears.

  When a predetermined time (for example, 1 to 5 seconds) elapses after the discharge promotion process is started (step-6), the control device 30 switches from the second control to the third control (step-7). Thereby, first, the switching valve 27 is switched to one switching position 27a, and the piston rod 24a of the hydraulic cylinder device 24 protrudes, and as shown in FIG. 7, the back pressure plate 22 is more than the open position in the discharge promotion process. Forcibly moving in the closing direction S, the back pressure plate closing process is started (step -8).

  When a predetermined delay time (for example, 1 to 5 seconds) elapses from the start of the back pressure plate closing process (step-9), the screw shaft 13 is moved for a specified time (for example, 5 to 20) while the back pressure plate 22 is continuously moved in the closing direction S. Rotate backwards for (second) (step -10). As a result, the screw blade 16 reversely rotates integrally with the screw shaft 13 while the back pressure plate 22 moves in the closing direction S, and the pressed object 10 in the filter cylinder 12 is discharged into the discharge port 15 by the reversely rotating screw blade 16. The product 10 is slightly returned from the side to the supply port 14 side, and the squeezed object 10 in the discharge port 15 is retained in the discharge port 15 for a specified time without being discharged.

  As a result, the back pressure plate 22 can be reliably and smoothly moved in the closing direction S and the discharge port 15 can be closed without being pressed in the opening direction O by the pressed object 10. Thereby, the to-be-compressed object 10 in which the moisture content fell until just before forming the compacted belt | band | zone B is retained in the filter cylinder 12, without being discharged | emitted from the discharge port 15 as it is.

  As described above, after the screw blade 16 is reversely rotated for a specified time (step-11), the control device 30 switches from the third control to the first control again (step-1). As a result, the normal operation process is started again (step-2), and the screw blade 16 rotates forward integrally with the screw shaft 13, and as shown in FIG. It is squeezed while being sent from the side to the discharge port 15 side, and discharged from between the discharge port 15 and the back pressure plate 22 while pressing the back pressure plate 22 in the opening direction O. At this time, the back pressure plate 22 remains in a position where the pressing force in the closing direction S applied by the hydraulic cylinder device 24 and the pressing force in the opening direction O applied by the pressed object 10 to be discharged are balanced.

  In the operation method of the screw press 11 as described above, the object to be squeezed 10 has a simple structure in which the screw shaft 13 is fixed in the axial direction A without moving the screw shaft 13 in the axial direction A as in the prior art. Can be prevented from being blocked by the discharge port 15.

  In addition, in the back pressure plate closing process executed by the third control, the object to be compressed 10 whose water content has decreased until just before the compaction band B is formed is not discharged from the discharge port 15 as it is. Therefore, in the normal operation process executed by the first control, the compaction zone B is formed in a short time and the dehydration operation is stabilized.

  In addition, the graph of FIG. 8 has shown the relationship between the pressure by the side of the discharge port 15 in the filter cylinder 12 in the normal driving | operation process, and the moisture content of the dewatering cake (to-be-pressed object 10) discharged | emitted from the discharge port 15, In the range where the pressure is P1 to P2 (for example, 500 to 800 kPa), the consolidation zone B is normally formed. When the pressure detection device 29 detects a pressure higher than the pressure P2 (corresponding to the specified pressure), the control device 30 determines that the water content is excessively reduced and the squeezed object 10 is in a closed state, Switch from the first control to the second control.

  In the first embodiment, as shown in FIGS. 1 and 3, the pressure in the filter cylinder 12 is detected by the pressure detection device 29. However, in the second embodiment described below, FIG. As shown in FIG. 10, an ammeter 32 is provided instead of the pressure detection device 29, and the drive current of the electric motor 20 is detected by the ammeter 32.

  That is, according to the flowchart shown in FIG. 11 and the time chart shown in FIG. 12, when the normal operation process is performed, the moisture content of the object 10 to be compressed at the outlet 15 in the filter cylinder 12 is more than the target moisture content. When the pressure decreases, the compressed object 10 falls into a closed state and becomes difficult to be discharged. Therefore, the load of the electric motor 20 increases and the drive current increases. For this reason, when the drive current detected by the ammeter 32 is higher than a specified current (for example, 20 to 50% of the rated current of the electric motor 20) (step -3), the control device 30 Thus, it determines that the to-be-compressed material 10 has fallen into the obstruction | occlusion state, and switches from 1st control to 2nd control (step -4).

  Thereby, a discharge promotion process is started (step-5), the obstruction | occlusion state of the to-be-compressed article 10 is eliminated, and the drive current of the electric motor 20 falls. At this time, the compacted band B whose water content has decreased excessively disappears once.

  When a predetermined time (for example, 1 to 5 seconds) elapses after the discharge promotion process is started (step-6), the control device 30 switches from the second control to the third control (step-7). As a result, the back pressure plate 22 is forcibly moved in the closing direction S from the open position during the discharge promoting step, and the back pressure plate closing step is started (step -8).

  When a predetermined delay time elapses from the start of the back pressure plate closing process (step-9), the screw shaft 13 is reversely rotated for a specified time while the back pressure plate 22 is continuously moved in the closing direction S (step -10). As a result, the screw blade 16 reversely rotates integrally with the screw shaft 13 while the back pressure plate 22 moves in the closing direction S, and the pressed object 10 in the filter cylinder 12 is discharged into the discharge port 15 by the reversely rotating screw blade 16. The product 10 is slightly returned from the side to the supply port 14 side, and the squeezed object 10 in the discharge port 15 is retained in the discharge port 15 for a specified time without being discharged.

  Thereby, the back pressure plate 22 can be reliably and smoothly moved in the closing direction S and the discharge port 15 can be closed. Therefore, the squeezed product 10 whose water content has decreased until just before the compaction band B is formed, Without being discharged from the discharge port 15 as it is, it is retained in the filter tube 12.

  As described above, after the screw blade 16 is reversely rotated for a specified time (for example, 5 to 20 seconds) (step-11), the control device 30 switches from the third control to the first control again (step-1). Thereby, the normal operation process is started again (step-2).

  In the operation method of the screw press 11 as described above, the object to be squeezed 10 has a simple structure in which the screw shaft 13 is fixed in the axial direction A without moving the screw shaft 13 in the axial direction A as in the prior art. Can be prevented from being blocked by the discharge port 15.

  In addition, in the back pressure plate closing process executed by the third control, the object to be compressed 10 whose water content has decreased until just before the compaction band B is formed is not discharged from the discharge port 15 as it is. Therefore, in the normal operation process executed by the first control, the compaction zone B is formed in a short time and the dehydration operation is stabilized.

  The graph of FIG. 13 shows the relationship between the drive current of the electric motor 20 in the normal operation process and the moisture content of the dehydrated cake (the pressed product 10) discharged from the discharge port 15, and the drive current is K1 to K2. In the range of (for example, 20 to 50% of the rated current of the electric motor 20), the consolidation band B is normally formed. When the ammeter 32 detects a current larger than the drive current K2 (corresponding to the specified current), the control device 30 determines that the moisture content is excessively reduced and the squeezed object 10 is in a closed state, Switch from the first control to the second control.

  In the first and second embodiments, the first control is performed using the pressure value in the filter cylinder 12 detected by the pressure detection device 29 or the drive current value of the motor 20 detected by the ammeter 32 as an index. In the third embodiment described below, the timer 30a provided in the control device 30 is used without using the pressure detection device 29 or the ammeter 32. The control is switched from the first control to the second control using time as an index.

  That is, according to the flowchart shown in FIG. 14 and the time chart shown in FIG. 15, the control device 30 reaches a certain time (for example, 2 to 4 hours) from the time when the time detected by the timer 30 a starts the first control. Then (step-3), the first control is switched to the second control (step-4). As a result, the normal operation process is performed for a predetermined time, and then the normal operation process is switched to the discharge promotion process (step-5).

  In addition, about the to-be-compressed object 10 with a stable property and little fluctuation | variation, based on a test, experience, etc., after the normal operation process is started, the to-be-compressed object 10 falls into an obstruction | occlusion state and becomes difficult to be discharged | emitted. The generation time can be roughly specified. Therefore, by setting the certain time according to the occurrence time of the closed state, the first control is performed from the first control as described above when the squeezed object 10 enters the closed state (or immediately before the compressed object 10 enters the closed state). 2 is switched to the control of No. 2 to start the discharge promotion process (Step-5), and the blocked state of the object to be squeezed 10 is eliminated. At this time, the compacted band B whose water content has decreased excessively disappears and disappears.

  When the timer 30a detects that a predetermined time (for example, 1 to 5 seconds) has elapsed since the start of the discharge promotion process (step -6), the control device 30 switches from the second control to the third control (step -7) Thereby, the back pressure plate closing process is started (step -8), and the back pressure plate 22 is forcibly moved in the closing direction S as in the first and second embodiments. The shaft 13 rotates reversely for a specified time (steps -9 to 11). Thereby, the back pressure plate 22 can be reliably and smoothly moved in the closing direction S and the discharge port 15 can be closed. Therefore, the squeezed product 10 whose water content has decreased until just before the compaction band B is formed, Without being discharged from the discharge port 15 as it is, it is retained in the filter tube 12.

  As described above, after the screw blade 16 is reversely rotated for a specified time (for example, 5 to 20 seconds) (step-11), the control device 30 switches from the third control to the first control again (step-1). Thereby, the normal operation process is started again (step-2).

  In the operation method of the screw press 11 as described above, the object to be squeezed 10 has a simple structure in which the screw shaft 13 is fixed in the axial direction A without moving the screw shaft 13 in the axial direction A as in the prior art. Can be prevented from being blocked by the discharge port 15.

  In addition, in the back pressure plate closing process executed by the third control, the object to be compressed 10 whose water content has decreased until just before the compaction band B is formed is not discharged from the discharge port 15 as it is. Therefore, in the normal operation process executed by the first control, the compaction zone B is formed in a short time and the dehydration operation is stabilized.

In each of the above-described embodiments, the first to third controls are automatically performed by the control device 30, but may be performed by a person instead of the control device 30.
In each of the embodiments, as shown in FIGS. 1 and 9, the screw shaft 13 is formed in a taper shape, and the distance between the inner peripheral surface of the filter tube 12 and the outer peripheral surface of the screw shaft 13 in the radial direction is the other end. Although it is reduced as it goes to the discharge side, the screw shaft 13 may be formed in a straight shape instead of a taper shape, and the pitch of the screw blades 16 may be reduced toward the other end discharge side.

  In each of the above embodiments, as shown in the time charts of FIGS. 5, 12, and 15, in the back pressure plate closing step, first, the back pressure plate 22 is forcibly moved in the closing direction S, and in this state, When the delay time elapses, the screw shaft 13 is rotated in the reverse direction while continuously moving the back pressure plate 22 in the closing direction S. However, the back pressure plate 22 is forcibly moved in the closing direction S without the predetermined delay time. The screw shaft 13 may be reversely rotated simultaneously with the movement. First, the screw shaft 13 is reversely rotated, and when a predetermined delay time elapses in this state, the back pressure plate 22 may be forcibly moved in the closing direction S while the screw shaft 13 is reversely rotated.

  In the first embodiment, when the detected pressure detected by the pressure detection device 29 rises above the specified pressure, the discharge promotion process is started by switching to the second control, and in the second embodiment, When the driving current detected by the ammeter 32 rises above the specified current, the discharge promotion process is started by switching to the second control. However, the present invention is not limited to this, for example, the discharge is discharged from the discharge port 15. When the moisture content of the pressed object 10 to be measured is measured and the measured moisture content falls to 65 to 75% or less, the discharge promotion process may be started by switching to the second control.

It is a figure of the screw press in the 1st Embodiment of this invention, and shows a normal driving | operation process. It is a figure of the opening / closing apparatus which moves the back pressure plate of a screw press. It is a block diagram of a control system of the screw press. It is a flowchart which shows the operating method of a screw press same as the above. It is a time chart which shows the operating method of a screw press similarly. It is a figure of a screw press and shows a discharge promotion process. It is a figure of a screw press and shows a back pressure plate closing process. It is a graph which shows the relationship between the pressure by the side of the discharge port in the filter cylinder of a screw press, and the moisture content of a dewatering cake. It is a figure of the screw press in the 2nd Embodiment of this invention, and shows a normal driving | operation process. It is a block diagram of a control system of the screw press. It is a flowchart which shows the operating method of a screw press same as the above. It is a time chart which shows the operating method of a screw press similarly. It is a graph which shows the relationship between the drive current of the electric motor of a screw press, and the moisture content of a dewatering cake. It is a flowchart which shows the operating method of the screw press in the 3rd Embodiment of this invention. It is a time chart which shows the operating method of a screw press similarly. It is a figure of the conventional screw press.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Compressed object 11 Screw press 12 Filter cylinder 13 Screw shaft 15 Discharge port 16 Screw blade 18 Rotation drive device 20 Electric motor 22 Back pressure plate 23 Opening and closing device 29 Pressure detection device 30 Control device 30a Timer 32 Ammeter O Opening direction S Closing direction

Claims (11)

A screw shaft that can rotate forward and backward is provided in the filter cylinder,
Screw blades are provided on the outer periphery of the screw shaft to send the object to be squeezed supplied into the filter cylinder to the discharge port.
In the discharge port of the filter cylinder, it is a screw press operation method provided with a back pressure plate that acts as a back pressure on the direction opposite to the feed direction of the object to be compressed and opens and closes the discharge port,
A normal operation process in which the screw shaft is rotated forward while pressing the back pressure plate in a closing direction with a predetermined force, and the squeezed object is discharged from the outlet of the filter cylinder;
After the normal operation process, the back pressure plate is forcibly moved from the position at the time of the normal operation process in the opening direction, and the discharge promotion process for discharging the squeezed material from the discharge port of the filter cylinder for a predetermined time, and
After the discharge promotion process, a back pressure plate closing process is performed in which the screw shaft is rotated in the reverse direction while moving the back pressure plate in the closing direction .
Then, the operating method of the screw press characterized by returning to the normal operation process again from the back pressure plate closing process . 2. The screw press according to claim 1, wherein, in the back pressure plate closing step, when the back pressure plate is moved in the closing direction and a predetermined time elapses, the screw shaft is reversely rotated while the back pressure plate is continuously moved in the closing direction. Driving method. When the pressure in the filter cylinder rises above the specified pressure, switch from the normal operation process to the discharge promotion process,
The operating method of the screw press according to claim 1 or 2, wherein the back pressure plate closing step is performed after the discharge promotion step is performed for a predetermined time. When the drive current of the motor that rotates the screw shaft rises above the specified current, switch from the normal operation process to the discharge promotion process,
The operating method of the screw press according to claim 1 or 2, wherein the back pressure plate closing step is performed after the discharge promotion step is performed for a predetermined time. After performing the normal operation process for a certain time, switch from the normal operation process to the emission promotion process,
The operating method of the screw press according to claim 1 or 2, wherein the back pressure plate closing step is performed after the discharge promotion step is performed for a predetermined time. In the back pressure plate closing step, the object to be squeezed whose moisture content has decreased until just before forming a compacted band composed of the object to be squeezed with a target moisture content is retained in the filter cylinder. The operation method of the screw press of any one of these. A screw shaft that can rotate forward and backward is provided in the filter cylinder,
Screw blades are provided on the outer periphery of the screw shaft to send the object to be squeezed supplied into the filter cylinder to the discharge port.
In the discharge port of the filtration cylinder, a back pressure plate is provided that acts as a back pressure in the direction opposite to the feed direction of the squeezed object and opens and closes the discharge port,
A rotation driving device for rotating the screw shaft, an opening / closing device for moving the back pressure plate in the opening / closing direction, and a control device for controlling the rotation driving device and the opening / closing device;
The control device controls the opening / closing device so that the back pressure plate is pressed in the closing direction with a predetermined force, and controls the rotation drive device so that the screw shaft rotates forward, and the back pressure plate is forced A second control for controlling the opening / closing device to move in the opening direction, and the opening / closing device to control the opening / closing device so that the back pressure plate moves in the closing direction. The third control is performed to control the control, the first control is shifted to the second control, the second control is performed, the third control is performed, and the third control is changed to the first control again. Screw press characterized by returning. A pressure detecting device for detecting the pressure in the filter cylinder is provided;
When the pressure detected by the pressure detection device rises above the specified pressure, the control device switches from the first control to the second control, performs the second control for a predetermined time, and then performs the second control to the third control. The screw press according to claim 7, wherein the screw press is switched to control. The rotary drive device consists of an electric motor,
An ammeter that detects the drive current of the electric motor is provided,
When the drive current detected by the ammeter rises above the specified current, the control device switches from the first control to the second control, performs the second control for a predetermined time, and then performs the second control to the third control. The screw press according to claim 7, wherein the screw press is switched to control. A timer to detect time is provided,
When the time detected by the timer reaches a certain time after starting the first control, the control device switches from the first control to the second control, and after performing the second control for a predetermined time, The screw press according to claim 7, wherein the control is switched from the second control to the third control. When the control device performs the third control, the squeezed product whose moisture content has decreased until just before forming the compacted band made of the squeezed product with the target moisture content is retained in the filter cylinder. The screw press according to any one of claims 7 to 10.

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