JP2019104032A - Operation method and controller for screw press type dehydration machine - Google Patents

Abstract

To provide an operation method of a screw press type dehydration machine capable of quickly reaching proper dehydration pressure after start-up and acquiring a dehydration cake having a stabilized moisture content.SOLUTION: There is provided an operation method of a screw press type dehydration machine for dehydrating a slurry comprising: a start step for starting operation at an initial presser pressure which is set higher than a reference value PO and equal to or less than an upper limit value PH, with respect to the reference value PO between an upper limit value PH and a lower limit value PL, the upper limit value PH, the lower limit value PL of a presser pressure P; and an initial presser pressure adjustment step for adjusting a presser pressure P between the upper and lower limit values PH, PL based on an aperture of a back pressure presser after a prescribed time passes since the start step.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method of operating a screw press dehydrator for dewatering a slurry and a control device of the screw press dehydrator.

  A screw press type dewatering machine is used for solid-liquid separation of organic sludge generated in a sewage treatment plant or a food factory. The screw press type dehydrator has a screw disposed inside a cylindrical screen, and a back pressure press (also referred to as a "pressing plate") provided at the outlet of the dewatered cake at the tip of the screw and screw. It is a device that dewaters while pressurizing coagulated sludge introduced inside. The coagulated sludge in which the coagulant is added to the organic sludge in advance becomes a pressed material to be introduced into the screw press type dehydrator.

  In Patent Document 1, in order to stabilize the dewaterability of the sludge discharged from the screw press, the opening ratio of the discharge part is measured in real time, and the discharge of the screw press is adjusted to obtain a predetermined opening ratio. A partial opening ratio constant control method has been proposed.

  In the discharge part opening ratio constant control method, a reference opening ratio and a value for increasing and decreasing the pressing force of the pressing plate are set in advance, and the opening ratio calculated during the screw press operation is compared with the reference opening ratio. When the opening ratio is larger than the reference opening ratio, the pressing force of the pressing plate is increased stepwise, and when the opening ratio is smaller than the reference opening ratio, the pressing force of the pressing plate is decreased stepwise to set the opening ratio to the reference opening ratio It is configured to control.

  According to Patent Document 2, screw press dewatering can be stably performed without solid matter mixing in filtered water at the start of operation or at high load, or abnormal stop of the screw drive device and the sludge pump. The operating method of the aircraft is disclosed,

  The operation method of the screw press dehydrator is configured to move the pressing plate to the open position by the pressing plate automatic opening and closing mechanism at the start of operation of the screw press dewatering machine or at high load, to promote the discharge of sludge cake. There is. The load on the screw press dewatering machine is determined by the water level at the front stage of the screw press dewatering machine or the inflow pressure to the screw press dewatering machine.

JP, 2017-87238, A JP, 2001-38490, A

  The screw press dewatering machine is characterized in that cakes with poor water content are easily discharged at startup, and it takes time to reach an appropriate dewatering pressure, and the back pressure as in the control method disclosed in Patent Document 1 described above In the control to maintain the opening (opening ratio) of the pressurer constant and the control to maintain the pressure constant, it takes a long time to reach the appropriate dehydration pressure, and a large amount of cake with low water content is discharged at startup There was a problem.

  In addition, screw press dewatering machines are poor in the amount of fibrous material and high squeeze hard VTS (Volatile Total Solids) high when it is squeezing hard to squeeze sludge etc. If pressure is applied to the pressing plate more than necessary, conveyance failure will occur. In some cases, the moisture content of the dewatered cake may be further deteriorated. Therefore, when control for maintaining the pressure applied to the back pressure presser constant is adopted, as a result, there is a problem that a pressure more than necessary is applied to the object to be pressed, and transport failure easily occurs.

  Furthermore, the screw press dewatering machine lowers the moisture content more if high pressure is applied to the back pressure presser while squeezing sludge with a large amount of fibrous material and high evaporation residue TS (Total Solids) etc. In addition, even if the water content decreases too much, additional rotation may occur and dewatering may not be possible. Therefore, if constant opening control or constant pressure control is adopted, the moisture content may be lowered more than necessary even if it is not desired to lower the moisture content of the dewatered cake, and in some cases, there may be a problem with turning around and dehydration becoming impossible. The

  In view of the problems described above, an object of the present invention is to provide a method for operating a screw press type dehydrator and a screw press type dehydrator in which an appropriate dewatering pressure is promptly reached after startup and a dewatered cake having a stable water content is obtained. The point is to provide a control device.

  In order to achieve the above-mentioned object, the first characterizing feature of the method of operating a screw press type dehydrator according to the present invention is a screw press for dewatering a slurry as described in claim 1 of the document of the claims. Method of the spin-dryer, wherein the upper limit PH, the lower limit PL, and the standard value PO between the upper limit PH and the lower limit PL set in advance are higher than the standard value PO The presser pressure between the upper limit PH and the lower limit PL based on the start step of starting the operation with the initial presser pressure set to the upper limit PH or less and the opening degree of the back pressure presser after a predetermined time has elapsed from the start step. And an initial presser pressure adjustment step of adjusting P.

  The start-up step started in a state where a high initial pressure pressure lower than the standard value PO and lower than the upper limit PH is applied is performed, and the state is continued for a predetermined time, so that the internal pressure rises. Since the dehydration pressure is appropriate, the amount of cake with a high water content at start-up is effectively suppressed. Then, after a predetermined time, the initial presser pressure adjustment step is performed, and the presser pressure P is adjusted to an appropriate value between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser at that time. Moisture content is properly adjusted without the occurrence of discharge failure.

  As described in claim 2 of the second feature, in addition to the first feature described above, in the initial presser pressure adjusting step, the opening degree L of the back pressure presser after the elapse of the predetermined time is If it is less than the first threshold L1 set in advance, the presser pressure P is adjusted to the lower limit value PL, and if it exceeds the first threshold L1, the pressure P is adjusted to the standard value PO.

  The dewaterability of the dewatered cake is evaluated using the first threshold L1 as an index. If the opening degree L of the back pressure presser is less than the first threshold L1, it is determined that the dewatering property is bad, and the pressure drop P is adjusted to the lower limit value PL, so that the occurrence of the discharge failure can be prevented in advance. If the opening degree L of the back pressure presser exceeds the first threshold L1, it is determined that the dewaterability is not bad, and the presser pressure P is adjusted to the standard value PO so that the water content does not decrease more than necessary.

  According to the third aspect, as described in the third aspect, in addition to the above-described first or second aspect, the presser pressure P is set to the upper limit PH and the lower limit after the initial presser pressure adjusting step. It is in the point provided with the presser opening maintenance step which maintains the opening L of a back pressure presser in predetermined value or a predetermined range by adjusting between PL.

  After the initial presser pressure adjusting step, the presser pressure maintaining step is performed to maintain the pressure L of the back pressure presser at a predetermined value or a predetermined range, based on the pressure L of the back pressure presser P. Is adjusted between the upper limit value PH and the lower limit value PL. For example, if the opening degree L of the back pressure presser is larger than a predetermined value, the presser pressure P is raised, and if the opening degree L of the back pressure presser is smaller than the predetermined value, the presser pressure P is lowered.

  According to the fourth feature, as described in claim 4, in addition to the above-mentioned third feature, the presser opening maintaining step sets the presser pressure P between the upper limit PH and the lower limit PL. The adjustment is to maintain the opening L of the back pressure presser between the first threshold L1 and the second threshold L2 set to a value larger than the first threshold L1.

  Based on the opening L of the back pressure presser, the presser pressure P is set to the upper limit value PH and the upper limit PH so that the opening L of the back pressure presser is maintained between the first threshold L1 and the second threshold L2 of a larger value. As a result of adjusting between the lower limit value PL, the moisture content of the dewatered cake can be dewatered at an appropriate value.

  According to the fifth feature configuration, as described in the fifth aspect, in addition to the above-mentioned fourth feature configuration, the opening degree L of the back pressure presser exceeds the second threshold L2 in the step of maintaining the presser opening. And the presser pressure P is adjusted to the standard value PO.

  When the opening degree L of the back pressure press exceeds the second threshold L2 due to the good dewaterability of the sludge, the presser pressure P decreases so that the water content of the dewatered cake does not decrease more than necessary. Is adjusted to the standard value PO.

  According to the sixth aspect, as described in the sixth aspect, in addition to the fourth aspect described above, the opening L of the back pressure presser exceeds the second threshold L2 in the step of maintaining the opening of the presser. And, when the screw rotational torque S exceeds the preset threshold value SH, the presser pressure P is adjusted toward the lower limit value PL.

  When the degree of opening L of the back pressure press exceeds the second threshold L2 and the screw rotation torque S exceeds the threshold SH due to the good dewaterability of the sludge, the moisture content of the dewatered cake decreases more than necessary. Furthermore, there is a possibility that the turning of the object to be pressed and the screw may occur. In such a case, by adjusting the presser pressure P toward the lower limit value PL, the occurrence of an inconvenience such as a decrease in the moisture content more than necessary or the occurrence of a turnaround can be avoided in advance.

  The first characteristic configuration of the control device of the screw press type dehydrator according to the present invention is, as described in claim 7, a control device of the screw press type dehydrator for dewatering the slurry, which is set in advance. Operation is started with an initial presser pressure set higher than the standard value PO and below the upper limit PH with respect to the upper limit PH, lower limit PL, and standard value PO between the upper limit PH and the lower limit PL of the presser pressure P And an initial presser pressure adjustment control unit that adjusts the presser pressure P between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser after a predetermined time has elapsed from the start of operation. The point is.

  According to a second feature of the present invention, in addition to the above-mentioned first feature, as described in claim 8, the initial presser pressure adjustment control unit is configured to determine an opening degree L of the back pressure presser after the predetermined time has elapsed. If the pressure is less than the first threshold L1 set in advance, the presser pressure P is adjusted to the lower limit value PL, and if it exceeds the first threshold L1, the pressure P is adjusted to the standard value PO.

  As described in claim 9, in addition to the above-mentioned first or second feature configuration, the third feature configuration also includes a presser pressure P after an initial pressor pressure adjustment control by the initial pressor pressure adjustment control unit. It has a point provided with a presser opening degree maintenance control part which maintains the opening degree L of a back pressure presser in a predetermined value or a predetermined range by adjusting between the upper limit PH and the lower limit PL.

  According to a fourth feature of the present invention, as described in the tenth aspect of the invention, in addition to the above-mentioned third feature, the presser opening degree maintenance control unit sets the presser pressure P between the upper limit PH and the lower limit PL. The point L is to maintain the opening L of the back pressure presser between the first threshold and the second threshold L2 set to a value larger than the first threshold L1.

  According to the fifth feature configuration, as described in claim 11, in addition to the above-mentioned fourth feature configuration, the presser opening degree maintenance control unit is configured such that the opening degree L of the back pressure presser is the second threshold L2. If it is exceeded, the presser pressure P is adjusted to the standard value PO.

  According to the sixth aspect of the present invention, as described in claim 12, in addition to the fourth aspect described above, the presser opening maintenance control unit is configured to set the opening L of the back pressure presser to the second threshold L2. If the screw rotation torque S exceeds the predetermined threshold value SH, the pressure control pressure P is adjusted toward the lower limit value PL.

  As described above, according to the present invention, an operating method of a screw press type dehydrator and a control device of a screw press type dehydrator capable of obtaining an adequate dewatering pressure promptly after startup and obtaining a dewatered cake having a stable water content It became possible to provide.

Explanatory drawing of the structure of the screw press type dehydrator according to the present invention Function explanatory drawing of the principal part of the screw press type dehydrator by this invention Flow chart showing control procedure executed by control device

Hereinafter, embodiments of a method of operating a screw press type dehydrator and a control device of the screw press type dehydrator according to the present invention will be described.
FIG. 1 shows the structure of a screw press type dehydrator 10 in which a part of the outer shell screen 2 is removed. The screw press type dehydrator 10 has an outer shell screen 2 provided on a base 1, two upper and lower screw shafts 3 and 4, a back pressure presser 5, an air cylinder 6, a drive unit 7, and a cleaning unit 8 (see FIG. 2) ), And an aggregation and mixing device 11 etc.

  The outer shell screen 2 is formed of a cylindrical metal filter medium in which the axis is in a horizontal posture between the sludge input end 1a and the sludge discharge end 1b, and a plurality of segments are arranged in the axial direction. It is divided into The segment close to the sludge input end 1a is provided with a metal filter material 2a composed of wedge wires with an interval of about 0.2 to 0.5 mm so as to cope with clogging by high pressure filtration, and the segment on the downstream side The metal filter material 2b comprised by the punching metal whose opening diameter is about 0.5-1.5 mm is distribute | arranged to this.

  Screw blades 3a are set on screw shafts 3 and 4 so that the pitch is gradually shortened from the sludge input end 1a to the sludge discharge end 1b, that is, the volume of the filter chamber per pitch of the blades decreases. , 4a are provided. In addition, you may comprise so that the filtration chamber volume per pitch of a screw blade may decrease by enlarging the shaft diameter of the screw shafts 3 and 4 as the sludge discharge side. The screw shafts 3 and 4 are rotationally driven in opposite directions from each other by the drive device 7 configured by an electric motor or the like provided on the base 1 via the gears 7a and 7b which are drive connection mechanisms.

  Slurry, that is, organic sludge to be pressed, is pumped by pump P to aggregation and mixing device 11, and is stirred and mixed by a stirring blade together with a coagulant introduced to aggregation and mixing device 11 to form a floc, and then sludge input side The end 1 a is pressed into a filter chamber separated by the outer shell screen 2.

  The material to be pressed into the filter chamber is filtered by the outer shell screen 2 in the process of being transported toward the sludge discharge end 1b by the screw blades 3a and 4a as the screw shafts 3 and 4 rotate. While being conveyed to the center by the rotation of the two screw shafts 3 and 4 and receiving a strong consolidation and shear dewatering effect, the consolidation is gradually performed along with the conveyance to the downstream side by the screw blades 3a and 4a whose pitch is set shorter gradually Be

  A back pressure presser 5 is disposed at the sludge discharge end 1 b so as to face the opening of the screen 2. The back pressure presser 5 is disposed so that the tip end side of the screw shafts 3 and 4 penetrates through a bush type slide bearing, and the air cylinder 6 and the press shaft 6a press drive toward the sludge charging side end 1a at a predetermined pressure. Be done.

  The dewatered cake is discharged from the gap formed at the end of the screen 2 formed by the balance between the reaction force received from the compressed sludge and the presser pressure and the outer periphery of the back pressure presser 5.

  As an actuator for pressurizing the back pressure presser 5, it is also possible to use a hydraulic cylinder, an electric cylinder or the like other than the air cylinder 7.

  A control device 20 is provided in the above-described screw press type dewatering machine, and the operation is controlled by the control device 20. The control device 20 is constituted by a computer provided with a CPU, a memory, an input / output circuit and the like, and the control program stored in the memory is executed by the CPU to realize expected operation control.

  Control values of torque sensor 13 for detecting the torque of the electric motor incorporated in driving device 7 and ultrasonic sensor 12 for measuring the gap formed between the end of screen 2 and the outer peripheral portion of back pressure presser 5 are control devices It is input to 20. The ultrasonic sensor 12 is erected on the base 1 and then attached to the frame, and the distance between the rear frame and the back surface of the back pressure presser 5 is determined. The gap formed between the end of the back pressure and the outer periphery of the back pressure presser 5 is calculated.

  Generally, the properties of the sludge which is a pressed material can be grasped by evaporation residue TS (Total Solids), evaporation weight reduction VTS (Volatile Total Solids), and the amount of fibrous material.

  The evaporation residue TS (Total Solids) is an index showing the amount of solids in the sludge, and is represented by the amount of substance (mg / L or mg / kg) remaining after drying the sample at 105 to 110 ° C. The evaporation residue TS is the sum of the ignition loss and the ignition residue, or the sum of SS and the soluble substance.

  Ignition weight loss material VTS (Volatile Total Solids) is an index showing the amount of organic matter in sewage and sludge. The evaporation residue TS is subjected to strong ashing at 600 ° C. for 1 hour to express the amount of the volatilized substance in mg / L or mg / kg. The lower the value of VTS, the better the dewaterability.

  In addition, if the amount of fibrous material contained in the sludge is large, it tends to become a core of floc, and the cohesion upon addition of the coagulant is increased.

  The evaporation residue TS is high, the ignition loss VTS is low, and the sludge with a large amount of fibrous material is easy to be dewatered, and the moisture content of the dewatered cake becomes low. It is necessary to adjust the presser pressure applied to the back pressure presser 5. In addition, sludge with low evaporation residue TS, high loss on ignition VTS, and small amount of fibrous material is not easy to dewater, and the moisture content of the dewatered cake is high, so mixing in the dewatered cake and avoiding drainage failure Therefore, it is necessary to adjust the number of rotations of the screw shafts 3 and 4 and the pressure applied to the back pressure presser 5.

  The control device 20 estimates the properties of the sludge as described above based on the respective detection values of the torque sensor 13 and the ultrasonic sensor 12 so as to obtain a dewatered cake of a target processing amount with a target water content. The control signals are output to the electric motor so that the rotational speeds of the screw shafts 3 and 4 are derived by calculating the rotational speeds of the shafts 3 and 4 and the presser pressure applied to the back pressure presser 5. A control signal is output to the air cylinder 6 so as to be the pressure of the pressure.

FIG. 3 shows a control procedure executed by the controller 20, that is, an operation method.
When the power is turned on, the control device 20 first executes the start step (S0, S1) and the initial presser pressure adjustment step (S2 to S4), and then the presser opening degree maintenance step (S5 to S17). Execute repeatedly.

  Screw shaft so that the moisture content of the dewatered cake becomes the target value, and the dewatering amount (kg-DS / h) becomes the target amount, based on the rough properties of the sludge pressed into the filter chamber. The rotational speeds (rpm) of 3 and 4 are set in advance, and the upper limit PH, the lower limit PL, and the standard value PO between the upper limit PH and the lower limit PL are set in advance.

  In addition, the first threshold L1, the second threshold L2, and the third threshold L3 (L1 <L2 <L3) are also set for the opening degree L of the back pressure presser. The first threshold L1 is a value determined such that kneading does not occur in sludge having poor dewaterability, and the third threshold is a value determined such that sludge having good dewaterability is not excessively dewatered. Further, the maximum torque SH allowed for the electric motor (screw shaft) is set.

  In the start-up step, the electric motor is started so that the number of rotations of the screw shaft becomes a set value (about 0.2 to 0.5 rpm in this embodiment), and the presser pressure is higher than the standard value PO and not more than the upper limit PH. The air cylinder is controlled so that the set initial presser pressure (upper limit PH in this embodiment) is obtained (S0), and the state is a predetermined time T1 (about 30 minutes with a screw shaft of 0.3 rpm in this embodiment) It is maintained (S1).

  In the initial presser pressure adjustment step, the presser pressure P is adjusted between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser after the predetermined time T1 has elapsed. If the opening L of the back pressure presser is less than the first threshold L1 set in advance (S2), the presser pressure P is adjusted to the lower limit PL (S4), and if it exceeds the first threshold L1, the presser pressure P is It is adjusted to the standard value PO (S3).

  That is, the dewaterability of the dewatered cake is evaluated using the first threshold L1 as an index. If the opening degree L of the back pressure presser is less than the first threshold L1, it is judged that the dewatering property is bad, and the presser pressure P is adjusted to the lower limit PL to prevent occurrence of discharge failure and prevent screwing. Is avoided. If the opening degree L of the back pressure presser exceeds the first threshold L1, it is determined that the dewaterability is not bad, and the presser pressure P is adjusted to the standard value PO so that the water content does not decrease more than necessary.

  In the stressor opening maintenance step, after the predetermined time T2 (in the present embodiment, a time of about 5 to 10 minutes in which the screw shaft rotates two or more revolutions) has elapsed after the initial presser pressure adjustment step (S5) By adjusting P between the upper limit PH and the lower limit PL, the opening degree L of the back pressure presser is maintained at a predetermined value or a predetermined range.

  If the opening degree L of the back pressure presser is equal to or less than L1 (S6), the presser pressure P is lowered by a predetermined minute operation amount .DELTA.P until the lower limit value PL is reached (S13), and the process returns to step S5. If the opening L of the back pressure presser exceeds L1 (S6) and is less than or equal to L2 (S7), the presser pressure P is increased by a preset micro operation amount ΔP until the upper limit PH is reached ( S14), return to step S5.

  In addition, when the opening L of the back pressure presser exceeds L2 (S7) and becomes L3 or less (S8), if the presser pressure P exceeds the standard value PO (S15), the presser pressure P is preset. The micro operation amount ΔP is lowered (S17), and the process returns to step S5. If the presser pressure P is less than the standard value PO in step S15, the presser pressure P is raised by a predetermined micro operation amount ΔP (S16). Return to S5.

  Furthermore, when the opening L of the back pressure presser exceeds L3 (S8), if the detected torque S is lower than the allowable maximum value (S9), the presser pressure P is set to the standard value PO (S12), and step S5 Return to

  When the detected torque S is equal to or higher than the allowable maximum value in step S9, if the presser pressure P is equal to or less than the standard value PO (S10), the presser pressure P is decreased by a predetermined minute operation amount ΔP (S11), and the process returns to step S5. If the presser pressure P exceeds the standard value PO (S10), the presser pressure P is set to the standard value PO (S12), and the process returns to step S5.

  That is, in the presser opening degree maintaining step, the opening degree L of the back pressure presser is made larger than the first threshold L1 and the first threshold L1 by adjusting the presser pressure P between the upper limit PH and the lower limit PL. By being configured to be maintained between the set second threshold L 2, the moisture content of the dewatered cake can be dewatered at an appropriate value.

  When the opening L of the back pressure presser exceeds the second threshold L 2, the presser pressure P is adjusted toward the standard value PO, so the water content of the dewatered cake having a high water content and a high water content decreases more than necessary do not do.

  Furthermore, when the opening degree L of the back pressure presser exceeds the third threshold L3 and the screw rotation torque S exceeds the preset threshold SH, the depressurizing ability is adjusted by adjusting the presser pressure P toward the lower limit PL. The moisture content of the dewatered cake having a low moisture content is lowered more than necessary, and the occurrence of inconvenience such as the co-rotation of the press and the screw is avoided in advance.

  As described above, according to the operation method of the screw press type dehydrator according to the present invention, the start step started in the state where the high initial presser pressure higher than the standard value PO and not more than the upper limit PH is applied Since the internal pressure of the machine increases by the continuation of the state for a predetermined time and the dewatering pressure immediately becomes appropriate, the discharge amount of the cake having a high water content at the start is effectively suppressed. Then, after a predetermined time, the initial presser pressure adjustment step is performed, and the presser pressure P is adjusted to an appropriate value between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser at that time. Moisture content is properly adjusted without the occurrence of discharge failure.

  Of the control device 20 described above, the function block that executes the start step (S0, S1) constitutes a start control unit that starts operation with an initial presser pressure set higher than the standard value PO and below the upper limit PH. Adjust the presser pressure P between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser after a predetermined time has elapsed from the start of operation by the function block that executes the presser pressure adjusting step (S2 to S4) An initial presser pressure adjustment control unit is configured.

  Furthermore, the opening degree of the back pressure presser is adjusted by adjusting the presser pressure P between the upper limit value PH and the lower limit value PL by a functional block of the control device 20 that executes the presser opening degree maintaining step (S5 to S17). A presser opening degree maintenance control unit configured to maintain L in a predetermined value or in a predetermined range is configured.

  In the embodiment described above, the present invention has been described by taking the twin screw press type dehydrator as an example, but the application object of the present invention is not limited to the twin screw press type dehydrator, and a multi-axial screw press of two or more screws. It is needless to say that the present invention is also applicable to a mold dewatering machine and a single screw press type dewatering machine.

  The upper limit PH and lower limit PL of the presser pressure P, and the standard value PO between the upper limit PH and the lower limit PL, the number of revolutions of the screw shafts 3 and 4 (rpm), and the opening L of the back pressure presser The specific numerical value of the maximum torque SH allowed for the first threshold L1, the second threshold L2, and the third threshold L3 (L1 <L2 <L3) electric motor (screw shaft) is not particularly limited, and A value appropriately set so that the water content of the dewatered cake becomes the target value and the dewatering amount (kg-DS / h) becomes the target amount based on the rough properties of the sludge to be pressed. It is.

  The specific configuration of each part of the above-described screw press type dewatering machine is not limited to the description of the embodiment, and it is needless to say that it can be appropriately modified and designed within the range of achieving the effects of the present invention.

1: Base 2: Outer shell screen 3, 4: Screw shaft 3a, 4a: Screw blade 5: Back pressure press 6: Air cylinder 7: Drive device 10: Screw press type dewatering machine 20: Control device

Claims (12)

An operation method of a screw press type dehydrator for dewatering a slurry,
The initial presser pressure set higher than the standard value PO and below the upper limit PH with respect to the upper limit PH, the lower limit PL, and the standard value PO between the upper limit PH and the lower limit PL set in advance. Start step to start operation with
An initial presser pressure adjustment step of adjusting the presser pressure P between the upper limit value PH and the lower limit value PL based on the opening degree of the back pressure presser after a predetermined time has elapsed from the start step;
The operation method of screw press type dewatering machine is equipped.   In the initial presser pressure adjusting step, if the opening degree L of the back pressure presser after the elapse of the predetermined time is less than the first threshold L1 set in advance, the presser pressure P is adjusted to the lower limit PL, and the first threshold L1 The operating method of the screw press type dehydrator according to claim 1, wherein the presser pressure P is adjusted to the standard value PO if.   After the initial presser pressure adjusting step, the presser pressure maintaining step is performed to maintain the opening degree L of the back pressure presser at a predetermined value or a predetermined range by adjusting the presser pressure P between the upper limit PH and the lower limit PL. The operating method of the screw press type dehydrator according to claim 1 or 2, comprising.   In the presser opening maintaining step, the opening L of the back pressure presser is set to a value larger than the first threshold L1 and the first threshold L1 by adjusting the presser pressure P between the upper limit PH and the lower limit PL. The operating method of the screw press type dehydrator according to claim 3, wherein the operating pressure is maintained between the second threshold L2 and the second threshold L2.   The operating method of the screw press type dehydrator according to claim 4, wherein, in the step of maintaining the presser opening, the presser pressure P is adjusted toward the standard value PO when the opening L of the back pressure presser exceeds the second threshold L2.   When the opening L of the back pressure presser exceeds the second threshold L2 and the screw rotational torque S exceeds the preset threshold SH in the presser opening maintaining step, the presser pressure P is adjusted toward the lower limit PL The operating method of the screw press type dehydrator according to claim 4. A control device of a screw press type dehydrator for dewatering a slurry,
The initial presser pressure set higher than the standard value PO and below the upper limit PH with respect to the upper limit PH, the lower limit PL, and the standard value PO between the upper limit PH and the lower limit PL set in advance. A start control unit that starts operation with
An initial presser pressure adjustment control unit that adjusts the presser pressure P between the upper limit PH and the lower limit PL based on the opening degree of the back pressure presser after a predetermined time has elapsed from the start of operation;
Control device of screw press type dewatering machine.   The initial presser pressure adjustment control unit adjusts the presser pressure P to the lower limit value PL if the opening degree L of the back pressure presser after the elapse of the predetermined time is less than the first threshold L1 set in advance, and the first threshold The control device of the screw press type dehydrator according to claim 7, wherein the presser pressure P is adjusted to the standard value PO if L1 is exceeded.   After the initial presser pressure adjustment control by the initial presser pressure adjustment control unit, the opening degree L of the back pressure presser is maintained at a predetermined value or a predetermined range by adjusting the presser pressure P between the upper limit PH and the lower limit PL. The control device of a screw press type dehydrator according to claim 8 or 9, further comprising:   The presser opening maintenance control unit sets the opening L of the back pressure presser to a value larger than the first threshold and the first threshold L1 by adjusting the presser pressure P between the upper limit PH and the lower limit PL. The controller of the screw press type dehydrator according to claim 9, wherein the controller is maintained between the second threshold L2 and the second threshold L2.   The control device of a screw press type dehydrator according to claim 10, wherein said presser opening degree maintenance control unit adjusts the presser pressure P toward the standard value PO when the opening degree L of the back pressure presser exceeds the second threshold L2. .   When the opening L of the back pressure presser exceeds the second threshold L2 and the screw rotational torque S exceeds the predetermined threshold SH, the presser pressure maintenance control unit directs the presser pressure P to the lower limit PL. The control device of a screw press type dehydrator according to claim 10, wherein the adjustment is performed.

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