JP7017399B2 - Operation method of screw press type dehydrator and control device of screw press type dehydrator - Google Patents

Description

The present invention relates to an operation method of a screw press type dehydrator for dehydrating a slurry and a control device of the screw press type dehydrator.

A screw press type dehydrator is used to separate organic sludge generated in sewage treatment plants and food factories into solid and liquid. In a screw press type dehydrator, a screw is placed inside a cylindrical screen, and a back pressure presser (also referred to as a "pressing plate") provided at the screw and the outlet of the dehydrated cake at the tip of the screw allows the screen to be pressed. It is a device that dehydrates the coagulated sludge introduced inside while pressurizing it. The coagulated sludge to which the coagulant is added to the organic sludge in advance becomes the pressed product to be introduced into the screw press type dehydrator.

In Patent Document 1, the upper limit value and the lower limit value are set for the drive torque of the screw, paying attention to the correlation between the rotation speed of the screw and the water content of the dehydrated cake, and the drive torque exceeds the upper limit value for a certain period of time. A control method is proposed in which the water content is increased by increasing the number of revolutions, and the water content is lowered by decreasing the number of revolutions when the drive torque falls below the lower limit for a certain period of time, and the same control is repeated after a certain period of time. Has been done.

In Patent Document 2, a moisture meter for measuring the water content of the dehydrated sludge discharged from the dehydrated sludge discharge port of the screw press dehydrator and the measured value of the moisture meter are input at predetermined time intervals and based on the measured value. The pressing pressure of the back pressure plate provided at the dehydrated sludge discharge port in the screw press dehydrator and the number of rotations of the screw are adjusted so that the water content of the dehydrated sludge discharged from the dehydrated sludge discharge port becomes a certain value or less. A sludge treatment system equipped with a control device that can be controlled as a control target has been proposed.

Japanese Unexamined Patent Publication No. S58-54999 Japanese Patent Application Laid-Open No. 2015-120161

However, in the method of controlling the rotation speed of the screw based on the fluctuation of the drive torque as described in Patent Document 1, not only it takes time to obtain the dehydrated cake having the desired water content, but also the rotation of the screw. As a result of adjusting the number, there is a problem that the processing amount per unit time fluctuates.

When the water content of the dehydrated cake is the desired value while the screw rotation speed is low, it is difficult to restore the treated amount to the target treated amount while maintaining the water content. There was also a problem.

Further, as described in Patent Document 2, in the method of controlling the pressing pressure of the back pressure plate and the rotation speed of the screw based on the measured value of the moisture content of the dehydrated cake, the moisture content of the cake is not necessarily adjusted to the desired value. In some cases, even if the pressing pressure of the back pressure plate reaches the upper limit, the water content cannot be adjusted to the desired value, which may cause an inconvenient situation in which the operator must be warned.

For example, when the sludge to be pressed is sewage-treated sludge, the sludge that is first obtained in the settling pond and is easy to squeeze and contains a large amount of inorganic matter and the sludge that is obtained in the final settling pond and is difficult to squeeze and contains a large amount of organic matter. The mixed sludge is press-fitted into the screw press type dehydrator, but due to the convenience of treatment, the mixing ratio of the sludge frequently fluctuates greatly, so that the above-mentioned inconvenient situation frequently occurs.

In view of the above-mentioned problems, an object of the present invention is a screw capable of obtaining the desired water content while suppressing fluctuations in the treatment amount even when the properties of the slurry to be pressed fluctuate greatly. It is a point of providing an operation method of a press type dehydrator and a control device of a screw press type dehydrator.

In order to achieve the above object, the first characteristic configuration of the operation method of the screw press type dehydrator according to the present invention is the operation method of the screw press type dehydrator for dehydrating the slurry , and the predetermined pressure control. Supply pressure Pi of the slurry with the standard value Pi0 set, screw rotation speed N for squeezing and transporting the slurry with the predetermined rotation speed control standard value N0, and the slurry with the predetermined chemical amount control standard value K0 set in advance. At least two of the injection amounts K of the coagulant to be injected are selected as control targets, and each control is performed so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. The drive torque control step is configured to include a drive torque control step for setting a control value of the target, and the drive torque control step includes a control value of each control target and each control standard value when the drive torque S exceeds the first threshold value SH. As a result of the comparison by the comparison step and the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is rotated. When the number control standard value is less than N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the initialization step of setting the control value of each control target to each control standard value, and the initialization step. Is in the point of including.

After the screw press type dehydrator is started, the drive torque control step is executed, and the control target is such that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Is controlled. Here, at least two of the supply pressure Pi of the slurry, the screw rotation speed N, and the chemical injection amount K are selected as control targets. Then, when the drive torque S exceeds the first threshold value SH, the comparison step is executed, and all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi 0, and the screw rotation speed N. If the control value is less than the rotation speed control standard value N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, it is judged that recovery cannot be achieved by continuous control up to that point. The control value of each control target is set to each control standard value, and the control state changes at once so that the drive torque can be quickly adjusted to obtain the desired water content.

The second characteristic configuration is an operation method of a screw press type dehydrator for dehydrating a slurry , in which a predetermined pressure control standard value Pi0 is set, a supply pressure Pi of the slurry, and a predetermined rotation speed control standard. At least two of the screw rotation speed N for squeezing and transporting the slurry with the value N0 and the chemical injection amount K of the coagulant to be pre-injected into the slurry with the predetermined chemical amount control standard value K0 are selected as control targets. , A drive torque control step for setting a control value of each controlled object so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. When the drive torque S becomes less than the second threshold value SL, the drive torque control step is a comparison step for comparing the control value of each control target with each control standard value, and all selected as a result of comparison by the comparison step. The control target is the state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, the state where the control value of the screw rotation speed N exceeds the rotation speed control standard value N0, and the control value of the chemical injection amount K is the chemical amount. When it corresponds to the state of less than the control standard value K0, it includes an initialization step of setting the control value of each control target to each control standard value.

After the screw press type dehydrator is started, the drive torque control step is executed, and the control target is such that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Is controlled. Here, at least two of the supply pressure Pi of the slurry, the screw rotation speed N, and the chemical injection amount K are selected as control targets. Then, when the drive torque S becomes less than the second threshold value SL, the comparison step is executed, and all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi 0, and the screw rotation speed N is controlled. If the value exceeds the rotation speed control standard value N0 or the control value of the drug injection amount K is less than the drug solution amount control standard value K0, it is judged that recovery cannot be achieved by continuous control up to that point, and each is determined. The control value to be controlled is set to each control standard value, and the control state changes at once so that the desired water content can be quickly adjusted to the driving torque.

In the third feature configuration, in addition to the first feature configuration described above, as a result of comparison by the comparison step, one of the selected control targets has a pressure control standard value Pi 0 as the control value of the supply pressure Pi. The control value of each control target when the state exceeds, the control value of the screw rotation speed N is less than the rotation speed control standard value N0, or the drug injection amount K does not exceed the drug injection amount control standard value K0. On the other hand, a control value update step for executing any setting process of lowering the supply pressure Pi, increasing the screw rotation speed N, and lowering the drug injection amount K is further included.

As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is less than the rotation speed control standard value N0. When the state and the drug injection amount K do not correspond to the state where the drug injection amount control standard value K0 is exceeded, the drive torque S is gradually controlled to be equal to or less than the first threshold value SH by continuous control up to that point. To.

In the fourth feature configuration, in addition to the second feature configuration described above , the control value of the supply pressure Pi is the pressure control standard value Pi0 for any of the selected control targets as a result of the comparison by the comparison step. Each control target when less than, the state where the set value of the screw rotation speed N exceeds the rotation speed control standard value N0, and the state where the set value of the drug injection amount K does not correspond to the state of less than the drug injection amount control standard value K0. A control value update step for executing any of the setting processes of the supply pressure Pi increase setting, the screw rotation speed N decrease setting, and the drug injection amount K increase setting with respect to the control value of
There is a point to include further.

As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the set value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the state and the set value of the drug injection amount K do not correspond to the state of less than the drug injection amount control standard value K0, the drive torque S is gradually set to be equal to or higher than the second threshold SL by continuous control up to that point. Be controlled.

The fifth characteristic configuration is an operation method of a screw press type dehydrator for dehydrating a slurry , in which a predetermined pressure control standard value Pi0 is set, a supply pressure Pi of the slurry, and a predetermined rotation speed control standard. At least two of the screw rotation speed N for squeezing and transporting the slurry with the value N0 and the chemical injection amount K of the coagulant to be pre-injected into the slurry with the predetermined chemical amount control standard value K0 are selected as control targets. , A drive torque control step for setting a control value of each controlled object so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. The drive torque control step is a comparison step in which when the drive torque S exceeds the first threshold value SH or the drive torque S becomes less than the second threshold value SL, the control value of each control target and each control standard value are compared. When the drive torque S exceeds the first threshold value SH, the control value of the supply pressure Pi exceeds the pressure control standard value Pi0 for all the selected control targets as a result of the comparison by the comparison step. , When the control value of the screw rotation speed N is less than the rotation speed control standard value N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the control value of each control target is controlled. When the drive torque S is set to a standard value and the drive torque S is less than the second threshold value SL, the control value of the supply pressure Pi is the pressure control standard for all the control targets selected as a result of the comparison by the comparison step. When the value is less than Pi 0, the control value of the screw rotation speed N exceeds the rotation speed control standard value N0, and the control value of the drug injection amount K is less than the drug solution amount control standard value K0, each control target An initialization step for setting a control value to each control standard value, and a standby step for holding a set value for each control target when the drive torque S is less than the first threshold value SH and exceeds the second threshold value SL. And, in the point including.

When the drive torque S exceeds the first threshold SH or becomes less than the second threshold SL, the comparison step is executed. In the former case, all the selected control targets have the control value of the supply pressure Pi as the pressure control standard. When the value Pi0 is exceeded, the control value of the screw rotation speed N is less than the rotation speed control standard value N0, or the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, each control target The control value of is set to each control standard value, and in the latter case, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi 0, and the control value of the screw rotation speed N is When the rotation speed control standard value N0 is exceeded and the control value of the drug injection amount K is less than the drug solution amount control standard value K0, the control value of each control target is set to each control standard value and the control state is set. Will change at once and will be quickly adjusted to the drive torque to obtain the desired water content. When the drive torque S is less than the first threshold value SH and exceeds the second threshold value SL, the set value of each control target is held so that the drive torque becomes stable.

In the sixth characteristic configuration, in addition to any of the above -mentioned first to fifth characteristic configurations, the supply pressure Pi, the screw rotation speed N, and the drug injection amount K are selected as the control targets. At the point.

It is preferable that the supply pressure Pi, the screw rotation speed N, and the drug injection amount K are selected as control targets in terms of increasing the degree of freedom of control.

In addition to the fifth or sixth feature configuration described above , the seventh feature configuration includes control standards for cases where the drive torque S exceeds the first threshold value SH and cases where the drive torque S is less than the second threshold value SL. The point is that the values are set to different values.

By making each control standard value for initialization different between the case where the drive torque S is on the high side and the case where the drive torque S is on the low side, more appropriate control becomes possible.

The first characteristic configuration of the control device of the screw press type dehydrator according to the present invention is the control device of the screw press type dehydrator for dehydrating the slurry , and the slurry is set with a predetermined pressure control standard value Pi0. Supply pressure Pi, screw rotation speed N for squeezing and transporting a slurry set with a predetermined rotation speed control standard value N0, and chemical injection amount of a flocculant to be pre-injected into a slurry set with a predetermined chemical liquid volume control standard value K0. At least two of K are selected as control targets, and the control value of each control target is set so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. The drive torque control unit is configured to include a drive torque control unit that executes a torque control step, and when the drive torque S exceeds the first threshold value SH, the drive torque control unit obtains a control value of each control target and each control standard value. As a result of the comparison between the comparison processing unit that executes the comparison step to be compared and the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi 0, and the screw rotation speed N. When the control value of is less than the rotation speed control standard value N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the control value of each control target is set to each control standard value. It includes an initialization processing unit that executes an initialization step.

The second characteristic configuration is a control device of a screw press type dehydrator for dehydrating the slurry, and the supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, and the predetermined rotation speed control standard. At least two of the screw rotation speed N for squeezing and transporting the slurry with the value N0 and the chemical injection amount K of the coagulant to be pre-injected into the slurry with the predetermined chemical amount control standard value K0 are selected as control targets. , A drive torque control unit that executes a drive torque control step that sets a control value for each control target so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. When the drive torque S becomes less than the second threshold value SL, the drive torque control unit includes a comparison processing unit that executes a comparison step of comparing the control value of each control target with each control standard value. As a result of comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the control value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the control value of the drug injection amount K is less than the drug solution amount control standard value K0, the initialization processing unit that executes the initialization step to set the control value of each control target to each control standard value, and the initialization processing unit. Is in the point of including.

In the third feature configuration, in addition to the first feature configuration described above , the control value of the supply pressure Pi is the pressure control standard value Pi0 for any of the selected control targets as a result of the comparison by the comparison step. Control of each control target when the control value of the screw rotation speed N is less than the rotation speed control standard value N0, or when the drug injection amount K does not exceed the drug injection amount control standard value K0. It further includes a control value update unit that executes any setting process of a decrease setting of the supply pressure Pi, an increase setting of the screw rotation speed N, and a decrease setting of the drug injection amount K with respect to the value.

In the fourth feature configuration, in addition to the second feature configuration described above , the control value of the supply pressure Pi is the pressure control standard value Pi0 for any of the selected control targets as a result of the comparison by the comparison step. Each control target when less than, the state where the set value of the screw rotation speed N exceeds the rotation speed control standard value N0, and the state where the set value of the drug injection amount K does not correspond to the state of less than the drug injection amount control standard value K0. It further includes a control value update unit that executes any setting process of the supply pressure Pi increase setting, the screw rotation speed N decrease setting, and the drug injection amount K increase setting with respect to the control value of.

The fifth characteristic configuration is a control device for a screw press type dehydrator for dehydrating the slurry, and the supply pressure Pi of the slurry in which a predetermined pressure control standard value Pi0 is set and a predetermined rotation speed control standard. At least two of the screw rotation speed N for squeezing and transporting the slurry with the value N0 and the chemical injection amount K of the coagulant to be pre-injected into the slurry with the predetermined chemical amount control standard value K0 are selected as control targets. , A drive torque control unit that executes a drive torque control step that sets a control value for each control target so that the drive torque S of the screw falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. When the drive torque S exceeds the first threshold value SH or the drive torque S becomes less than the second threshold value SL, the drive torque control unit comprises a control value for each control target and each control standard. When the drive torque S exceeds the first threshold value SH, the comparison processing unit that executes the comparison step for comparing the values, and as a result of the comparison by the comparison step, all the control targets selected are the supply pressure Pi. The control value of the pressure control exceeds the pressure control standard value Pi0, the control value of the screw rotation speed N is less than the rotation speed control standard value N0, and the control value of the drug injection amount K exceeds the chemical solution amount control standard value K0. If the above is true, the control value of each control target is set to each control standard value, and when the drive torque S is less than the second threshold value SL, all the controls selected as a result of comparison by the comparison step. The target is a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, a state where the control value of the screw rotation speed N exceeds the rotation speed control standard value N0, and the control value of the chemical injection amount K is the chemical amount control standard. When the value is less than K0, the initialization processing unit that executes the initialization step of setting the control value of each control target to each control standard value, and the drive torque S of less than the first threshold value SH and the first 2 The point includes a standby processing unit that executes a standby step for holding a set value of each control target when the threshold value exceeds SL.

In the sixth characteristic configuration, in addition to any of the above -mentioned first to fifth characteristic configurations, the supply pressure Pi, the screw rotation speed N, and the drug injection amount K are selected as the control targets. At the point.

In the seventh feature configuration, in addition to the first or second feature configuration described above , each control standard is used when the drive torque S exceeds the first threshold value SH and when it is less than the second threshold value SL. The point is that the values are set to different values.

As described above, according to the present invention, even when the properties of the slurry to be pressed fluctuate greatly, the screw press type can obtain the desired water content while suppressing the fluctuation of the treated amount. It has become possible to provide a method for operating a dehydrator and a control device for a screw press type dehydrator.

Explanatory drawing of structure of screw press type dehydrator by this invention Functional explanatory view of the main part of the screw press type dehydrator by this invention Flow chart showing the control procedure executed by the control device A flowchart showing another embodiment and showing a control procedure executed by the control device. A flowchart showing another embodiment and showing a control procedure executed by the control device. A flowchart showing another embodiment and showing a control procedure executed by the control device. Explanatory diagram of the relationship between drive torque S and water content

Hereinafter, an operation method of the screw press type dehydrator and an embodiment of the control device of the screw press type dehydrator according to the present invention will be described.
FIG. 1 shows the structure of the screw press type dehydrator 10 from which a part of the outer body screen 2 is removed. The screw press type dehydrator 10 includes an outer body screen 2 provided on the base 1, two upper and lower screw shafts 3, 4, a back pressure presser 5, an air cylinder 6, a drive device 7, and a cleaning device 8 (see FIG. 2). ), The coagulation / mixing device 11 and the like are provided.

The outer body screen 2 is composed of a cylindrical metal filter medium arranged so that the axis is in a horizontal posture between the sludge input side end 1a and the sludge discharge side end 1b, and has a plurality of segments in the axis direction. It is divided into. A metal filter medium 2a composed of wedge wires with an interval of about 0.2 mm is arranged in a segment close to the sludge input side end 1a, which is a filtration zone, in order to cope with clogging due to high-pressure filtration, and dehydration on the downstream side thereof. A metal filter medium 2b made of punching metal having an opening diameter of about 0.6 to 1.0 mm is arranged in a segment serving as a zone.

The screw blades 3a of the screw shafts 3 and 4 are set so that the pitch is gradually shortened from the sludge input side end portion 1a to the sludge discharge side end portion 1b, that is, the filter chamber volume per blade pitch is reduced. , 4a are provided. A screw is composed of screw shafts 3 and 4 and screw blades 3a and 4a. By increasing the diameter of the screw shafts 3 and 4 toward the sludge discharge side, the filter chamber volume per pitch of the screw blades may be reduced. The screw shafts 3 and 4 are rotationally driven in opposite directions by a drive device 7 composed of an electric motor or the like provided on the base 1 via gears 7a and 7b which are drive connection mechanisms.

The slurry, that is, the organic sludge to be pressed, is pumped to the coagulation / mixing device 11 by the pump P, and is stirred and mixed with the coagulant made of polomer charged into the coagulation / mixing device 11 with a stirring blade to form a floc. It is press-fitted from the sludge charging side end portion 1a into the filter chamber partitioned by the outer body screen 2.

The consolidated material pressed into the filter chamber is filtered by the outer cylinder screen 2 in the process of being conveyed toward the sludge discharge side end 1b by the screw blades 3a and 4a as the screw shafts 3 and 4 rotate. While being caught in the central part by the rotation of the two screw shafts 3 and 4 and undergoing a strong consolidation / shear dehydration effect, the screw blades 3a and 4a whose pitch is set to be gradually shortened gradually compacted as the screw blades 3a and 4a were conveyed to the downstream side. Will be converted.

A back pressure presser 5 is arranged at the sludge discharge side end portion 1b so as to face the opening of the screen 2. The back pressure presser 5 is arranged so that the tip side of the screw shafts 3 and 4 penetrates through the bush type slide bearing, and is pressed and driven toward the sludge charging side end portion 1a by a predetermined pressure by the air cylinder 6 and the pressing shaft 6a. Will be done.

The dehydrated cake is discharged from the gap formed between the end portion of the screen 2 formed by the balance between the reaction force received from the pressed sludge and the presser pressure and the outer peripheral portion of the back pressure presser 5.

As an actuator for pressurizing the back pressure presser 5, a hydraulic cylinder, an electric cylinder, or the like can be used in addition to the air cylinder 7.

The screw press type dehydrator described above is provided with a control device 20, and the operation is controlled by the control device 20. The control device 20 is composed of a computer including 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 the desired operation control.

The torque sensor 13 that detects the torque of the electric motor incorporated in the drive device 7, the pressure sensor 14 that detects the supply pressure of the slurry, and the gap formed between the end portion of the screen 2 and the outer peripheral portion of the back pressure presser 5 are measured. Each detection value of the ultrasonic sensor 12 is input to the control device 20. The ultrasonic sensor 12 is attached to a rear frame erected on the base 1, a distance between the rear frame and the back surface of the back pressure presser 5 is obtained, and the screen 2 is controlled by the control device 20 based on the distance. It is configured to calculate the gap formed between the end portion of the back pressure presser 5 and the outer peripheral portion of the back pressure presser 5.

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

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

Ignition weight loss VTS (Volatile Total Solids) is an index showing the amount of organic matter in sewage and sludge. The amount of substance volatilized by igniting the evaporation residue TS at 600 ° C. for 1 hour is expressed in mg / L or mg / kg. The smaller the VTS value, the better the dehydration.

Further, if the amount of fibrous substance contained in the sludge is large, it tends to become a core of frock, and the cohesiveness when a flocculant is added increases.

Sludge with a high evaporation residue TS, a low ignition loss VTS, and a large amount of fibrous material is easy to dehydrate, and the water content of the dehydrated cake is low. It is necessary to adjust the presser pressure applied to the back pressure presser 5. In addition, sludge with a low evaporation residue TS, a high ignition loss VTS, and a small amount of fibrous material is not easy to dehydrate, and the water content of the dehydrated cake is high. Therefore, it is necessary to adjust the number of rotations of the screw shafts 3 and 4 and the presser pressure applied to the back pressure presser 5.

As shown in FIG. 7, when the screw press type dehydrator is started and started up, a certain correlation is seen between the drive torque S of the screw and the water content of the dehydrated cake, and the drive torque S is high. As it rises, the water content decreases.

In the control device 20 according to the present invention, for example, the water content of the dehydrated cake is 75 ± α% in a state where the screw press type dehydrator is up (this value is a value appropriately set according to the slurry to be dehydrated). The supply pressure Pi of the slurry, the screw rotation speed N for squeezing and transporting the slurry, and the chemical injection of the coagulant to be pre-injected into the slurry so that the drive torque S is maintained between the minimum value SL and the maximum value SM. It is configured to select at least two quantities K as the control target and set the control value of the selected control target.

The supply pressure Pi is controlled by adjusting the rotation speed of the pump P that pumps the slurry to the coagulation / mixing device 11, and the screw rotation speed N is controlled by adjusting the rotation speed of the electric motor provided in the drive device 7. The drug injection amount K is controlled by adjusting the amount of the polymer to be injected into the coagulation / mixing device 11.

By adjusting the supply pressure Pi of the slurry, the filtration rate can be controlled appropriately in the filtration zone, and a stable cake can be sent to the dehydration zone. By adjusting the chemical injection amount K within a predetermined range, the size of the frock suitable for filtration can be controlled. However, the preferable adjustment range of the chemical injection amount K is limited, and the water content deteriorates regardless of which side deviates from the adjustment range. Increasing the screw rotation speed N increases the treatment amount, but the water content tends to deteriorate. Therefore, the adjustment of the chemical injection amount K and the screw rotation speed N is an auxiliary position, and the significance of adjusting the screw rotation speed N when the processing amount changes as a result of adjusting the supply pressure Pi and the chemical injection amount K. There is.

During the above control, the pressure of the back pressure presser 5 may be adjusted in order to bring the water content of the dehydrated cake closer to the target value.

Hereinafter, the operation procedure executed by the control device 20 will be described in detail.
The control device 20 sets the chemical injection amount K, the rotation speed N of the screw shafts 3 and 4, the supply pressure Pi of the slurry, and the presser pressure Po applied to the back pressure presser 5 at the time of startup as set values at the time of startup, and is described above. The start-up control step is to press the slurry into the filter chamber of the twin-screw press type dehydrator, perform filtration treatment in the filtration zone and dehydration treatment in the dehydration zone, and start up so that the drive torque S falls within a predetermined range. Will be executed. The start-up control step takes approximately 30 to 60 minutes.

In the case of a uniaxial screw press type dehydrator, the slurry is press-fitted into the filter chamber with the screw shaft stopped, and after the slurry is filled in the filter chamber, the rotation speed N of the screw shaft, the supply pressure Pi of the slurry, and the back pressure presser 5 The presser pressure Po applied to is set to the set value at the time of start-up and is started up. The predetermined range of the drive torque S at the time of startup may be the same value as the first threshold value SH, which is an index in the drive torque control step, and the second threshold value SL, which is smaller than the first threshold value SH, or is wider than that. It may be a range or a narrow range. The control procedure of the start-up control step is not limited to the above-mentioned procedure, and the procedure is not particularly limited as long as the drive torque S can be started up within a predetermined range.

The flowcharts of FIGS. 3 to 6 described below are drive torque control steps executed after the start-up control step.
As shown in FIG. 3, the drive torque control step is repeatedly executed at the predetermined interval T3 (SA1), the supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, and the predetermined rotation speed control standard value N0. The screw rotation speed N for squeezing and transporting the slurry in which is set, and the chemical injection amount K of the coagulant to be pre-injected into the slurry in which the predetermined chemical amount control standard value K0 is set are all selected as control targets, and the screw is driven. The control value of each control target is set so that the torque S falls within the range of the first threshold value SH and the second threshold value SL smaller than the first threshold value SH (SA2 to SA21).

Hereinafter, the drive torque control step will be described in detail with reference to FIG.
In the drive torque control step, when the drive torque S is less than the second threshold SL (SA2, Y) or the drive torque S exceeds the first threshold SH (SA2, Y), but the torque is not abnormally high. (SA4, N), a comparison step of comparing the control value of each control target with each control standard value is executed (SA5, SA12).

When the drive torque S exceeds the second threshold value SL (SA2, N) and is less than the first threshold value SH (SA3, N), a standby step (SA2, SA3, SA1) for holding the set value of each control target. ) Is executed. In the standby step, the drive torque S is controlled to an appropriate range, and the water content of the dehydrated cake is adjusted to an appropriate range.

In the comparison step SA5 executed when the drive torque S exceeds the first threshold value SH, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi 0, and the screw rotation speed. It is compared whether or not the control value of N corresponds to the state where the rotation speed control standard value N0 is less than the state, and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0. The value is set to each control standard value (SA9). Even if the control value is adjusted in these states, it is determined that it is difficult for the drive torque S to converge to the first threshold value SH or less, and the value is returned to the standard value.

In the comparison step SA12 executed when the drive torque S becomes less than the second threshold value SL, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi 0, and the screw rotation speed. It is compared whether or not the control value of N corresponds to the state where the rotation speed control standard value N0 is exceeded and the control value of the drug injection amount K is less than the drug solution amount control standard value K0. The value is set to each control standard value (SA16). Even if the control value is adjusted in these states, it is determined that it is difficult for the drive torque S to converge to the second threshold value SL or higher, and the value is returned to the standard value. The above-mentioned steps SA5, SA9, SA12, and SA16 are initialization steps. The initialization step changes the control state at once so that the desired water content can be quickly adjusted to the driving torque.

When any of the control targets that do not satisfy the conditions exists in the comparison step SA5 (SA5, N), the control values of the supply pressure Pi, the drug injection amount K, and the screw rotation speed N are updated, respectively. First, if the supply pressure Pi is not the minimum pressure PiL (SA6, N), the correction amount ΔPi set in advance is reduced and corrected (SA10). Next, if the drug injection amount (drug injection rate) K is not the minimum drug injection rate KL (SA7, N), the correction amount ΔK set in advance is reduced and corrected (SA11). Further, if the screw rotation speed N is not the preset maximum value NH, the screw rotation speed N is increased and corrected by the preset correction amount ΔN (SA8). When each control value reaches a preset limit value PiL, KL, NH, that value is maintained.

When any of the control targets that do not satisfy the conditions exists in the comparison step SA12 (SA12, N), the control values of the supply pressure Pi, the drug injection amount K, and the screw rotation speed N are updated, respectively. First, if the supply pressure Pi is not the maximum pressure PiH (SA13, N), the correction amount ΔPi set in advance is increased and corrected (SA17). Next, if the drug injection amount (drug injection rate) K is not the maximum drug injection rate KH (SA14, N), the correction amount ΔK set in advance is increased and corrected (SA18). Further, if the screw rotation speed N is not the preset minimum value NL, the screw rotation speed N is reduced and corrected by the preset correction amount ΔN (SA15). When each control value reaches a preset limit value PiH, KH, NL, that value is maintained.

The limit values PiL, PiH, KL, KH, NL, NH, and the correction values ΔPi, ΔK, ΔN in the controllable range of each control target are values that are appropriately set in advance based on the device characteristics and the slurry properties. .. Further, the pressure control standard value Pi0 is set in the range of PiL <Pi0 <PiH, the rotation speed control standard value N0 is set in the range of NL <N0 <NH, and the drug solution amount control standard value K0 is KL <K0 <KH. Set to range.

The control standard values Pi0, N0, and K0 may be set to different values depending on whether the drive torque S exceeds the first threshold value SH or is less than the second threshold value SL. By making each control standard value for initialization different between the case where the drive torque S is on the high side and the case where the drive torque S is on the low side, more rapid and appropriate control becomes possible.

In order to reduce the maintenance cost, K0 should be set to a value as small as possible, and Pi0 and N0 should be set to an average value at which a desired sludge treatment amount can be obtained.

If the drive torque S is abnormally high torque in step SA4, it is determined that the cake water content has dropped too much, an alarm is issued, and the supply pressure Pi is set to a value PiLL sufficiently smaller than the lower limit value PiL (PiLL <. It is set to <PiL) (SA19), torque is reduced, and after waiting for a predetermined time T4 (about 5 minutes in this embodiment) (SA20), the lower limit value is returned to PiL. When the supply pressure Pi is greatly reduced, the slurry is conveyed by a screw without being sufficiently filtered, and as a result, the average water content of the slurry in the machine becomes high, and the torque can be reduced in an emergency evacuation.

In the present invention, at least two of the supply pressure Pi of the slurry, the screw rotation speed N for squeezing and transporting the slurry, and the chemical injection amount K of the coagulant to be pre-injected into the slurry are selected as control targets, and the driving torque S of the screw is the second. The control value of each control target may be set by the following procedure so as to fall within the range of the first threshold value SH and the second threshold value SL smaller than the first threshold value SH.

The procedure for selecting the supply pressure Pi and the drug injection amount K is shown in FIG. 4, the procedure for selecting the supply pressure Pi and the screw rotation speed N is shown in FIG. 5, and the chemical injection amount K and the screw rotation speed N are selected. The procedure is shown in FIG.

In any example, when the drive torque S exceeds the first threshold value SH, the control value of the supply pressure Pi exceeds the pressure control standard value Pi0 for all the selected control targets as a result of the comparison by the comparison step. When the state, the state where the control value of the screw rotation speed N is less than the rotation speed control standard value N0, and the state where the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the control value of each control target is set. When the drive torque S is set to the control standard value and the drive torque S is less than the second threshold SL, the control value of the supply pressure Pi is the pressure control standard value for all the selected control targets as a result of the comparison by the comparison step. When the control value of the screw rotation speed N exceeds the rotation speed control standard value N0, or the control value of the drug injection amount K corresponds to the state of less than the drug solution amount control standard value K0, the control of each control target is performed. It is configured to perform an initialization step that sets the value to each control standard value.

Further, as a result of comparison in the comparison step SA5, one of the selected control targets is in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is the rotation speed control standard value. When the state of less than N0 and the state where the drug injection amount K does not exceed the drug injection amount control standard value K0, the supply pressure Pi is set to decrease and the screw rotation speed N is increased for each control target control value. A control value update step for executing any setting process of setting or lowering the drug injection amount K is included. The drive torque S is gradually controlled to be equal to or less than the first threshold value SH by continuous control up to that point.

As a result of comparison by the comparison step SA12, one of the selected control targets is in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the set value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the set value of the drug injection amount K does not correspond to the state of less than the drug injection amount control standard value K0, the supply pressure Pi is set to increase and the screw rotation speed N is decreased for each control target control value. A control value update step is included to execute a setting process of either the setting or the increase setting of the drug injection amount K. The drive torque S is gradually controlled to be equal to or higher than the second threshold value SL by continuous control up to that point.

As described above, the control device of the screw press type dehydrator according to the present invention executes a start-up control step of squeezing the slurry supplied inside and starting up so that the drive torque S of the screw falls within a predetermined range. The start-up control unit and the slurry that is repeatedly executed after the start-up control step and has the supply pressure Pi of the slurry set to the predetermined pressure control standard value Pi0 and the slurry set to the predetermined rotation speed control standard value N0 are squeezed and conveyed. At least two of the chemical injection amount K of the coagulant to be pre-injected into the slurry in which the screw rotation speed N and the predetermined chemical amount control standard value K0 are set are selected as control targets, and the screw drive torque S is the first threshold value SH. And a drive torque control unit that executes a drive torque control step that sets a control value of each control target so as to fall within the range of the second threshold SL smaller than the first threshold SH.

Then, when the drive torque S exceeds the first threshold value SH or the drive torque S becomes less than the second threshold value SL, the drive torque control unit compares the control value of each control target with each control standard value. When the drive torque S exceeds the first threshold value SH, the control value of the supply pressure Pi is the pressure control standard value Pi0 for all the selected control targets as a result of the comparison by the comparison step. When the control value of the screw rotation speed N is less than the rotation speed control standard value N0, or the control value of the drug injection amount K exceeds the chemical solution amount control standard value K0, the control of each control target is controlled. When the value is set to each control standard value and the drive torque S is less than the second threshold value SL, as a result of comparison by the comparison step, all the selected control targets have the control value of the supply pressure Pi as the pressure. Each control corresponds to a state where the control standard value is less than Pi0, a state where the control value of the screw rotation number N exceeds the rotation number control standard value N0, and a state where the control value of the drug injection amount K is less than the chemical solution amount control standard value K0. Each control has an initialization processing unit that executes an initialization step that sets a target control value to each control standard value, and when the drive torque S is less than the first threshold value SH and exceeds the second threshold value SL. It is configured to include a wait processing unit that executes a wait step that holds a target set value.

It goes without saying that the specific configuration of each part of the screw press type dehydrator described above is not limited to the description of the embodiment, and can be appropriately modified and designed within the range in which the action and effect according to the present invention are exhibited.

1: Base 2: Outer body screens 3, 4: Screw shafts 3a, 4a: Screw blades 5: Back pressure presser 6: Air cylinder 7: Drive 10: Screw press type dehydrator 13: Torque sensor 14: Pressure sensor 20 :Control device

Claims (14)

A method of operating a screw press type dehydrator for dehydrating a slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation number N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control step, which sets the control value of each control target so as
Is configured with
The drive torque control step is
When the drive torque S exceeds the first threshold value SH, a comparison step of comparing the control value of each control target with each control standard value, and
As a result of comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is less than the rotation speed control standard value N0. When the control value of the state and the drug injection amount K exceeds the drug solution amount control standard value K0, the initialization step of setting the control value of each control target to each control standard value, and
A method of operating a screw press type dehydrator, which comprises. A method of operating a screw press type dehydrator for dehydrating a slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation number N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control step, which sets the control value of each control target so as
Is configured with
The drive torque control step is
When the drive torque S becomes less than the second threshold value SL, a comparison step of comparing the control value of each control target with each control standard value, and
As a result of comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the control value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the control value of the state and the drug injection amount K corresponds to the state of less than the drug solution amount control standard value K0, the initialization step of setting the control value of each control target to each control standard value, and
A method of operating a screw press type dehydrator, which comprises. As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is less than the rotation speed control standard value N0. When the drug injection amount K does not exceed the drug injection amount control standard value K0, the supply pressure Pi is set to decrease, the screw rotation speed N is set to increase, for each control target control value. A control value update step for executing one of the setting processes of the decrease setting of the drug injection amount K,
The method for operating a screw press type dehydrator according to claim 1 , further comprising. As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the set value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the set value of the drug injection amount K does not correspond to the state of less than the drug injection amount control standard value K0, the supply pressure Pi is set to increase and the screw rotation speed N is decreased for each control target control value. The control value update step for executing the setting process of either the setting or the increase setting of the drug injection amount K,
The method for operating a screw press type dehydrator according to claim 2 , further comprising. A method of operating a screw press type dehydrator for dehydrating a slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation number N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control step, which sets the control value of each control target so as
Is configured with
The drive torque control step is
When the drive torque S exceeds the first threshold value SH or becomes less than the second threshold value SL, a comparison step of comparing the control value of each control target with each control standard value is used.
When the drive torque S exceeds the first threshold value SH, as a result of the comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi 0, and the screw. When the control value of the rotation speed N is less than the rotation speed control standard value N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the control value of each control target is set to each control standard value. As well as setting to
When the drive torque S is less than the second threshold SL, as a result of the comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi 0, and the screw. When the control value of the rotation speed N exceeds the rotation speed control standard value N0 and the control value of the drug injection amount K corresponds to the state of less than the drug solution amount control standard value K0, the control value of each control target is set to each control standard value. Initialization step to set to, and
A standby step for holding a set value of each control target when the drive torque S is less than the first threshold value SH and exceeds the second threshold value SL.
A method of operating a screw press type dehydrator, which comprises. The operation method of the screw press type dehydrator according to any one of claims 1 to 5 , wherein the supply pressure Pi, the screw rotation speed N, and the chemical injection amount K are selected as the control targets. The screw according to claim 5 or 6 , wherein each control standard value is set to a different value depending on whether the drive torque S exceeds the first threshold value SH or becomes less than the second threshold value SL. How to operate the press type dehydrator. A control device for a screw press type dehydrator for dehydrating slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation speed N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control unit that executes the drive torque control step to set the control value of each control target.
Is configured with
The drive torque control unit is
When the drive torque S exceeds the first threshold value SH, a comparison processing unit that executes a comparison step of comparing the control value of each control target with each control standard value, and the comparison processing unit.
As a result of comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is less than the rotation speed control standard value N0. When the control value of the state and the drug injection amount K exceeds the drug solution amount control standard value K0, the initialization processing unit that executes the initialization step of setting the control value of each control target to each control standard value, and the initialization processing unit.
A control device for a screw press type dehydrator, characterized in that it contains. A control device for a screw press type dehydrator for dehydrating slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation speed N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control unit that executes the drive torque control step to set the control value of each control target.
Is configured with
The drive torque control unit is
When the drive torque S becomes less than the second threshold value SL, a comparison processing unit that executes a comparison step of comparing the control value of each control target with each control standard value, and the comparison processing unit.
As a result of comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the control value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the control value of the state and the drug injection amount K corresponds to the state of less than the drug solution amount control standard value K0, the initialization processing unit that executes the initialization step of setting the control value of each control target to each control standard value, and the initialization processing unit.
A control device for a screw press type dehydrator, characterized in that it contains. As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi0, and the control value of the screw rotation speed N is less than the rotation speed control standard value N0. When the drug injection amount K does not exceed the drug injection amount control standard value K0, the supply pressure Pi is set to decrease, the screw rotation speed N is set to increase, for the control value of each controlled object. The control device for a screw press type dehydrator according to claim 8 , further comprising a control value updating unit that executes any setting process of the reduction setting of the drug injection amount K. As a result of comparison by the comparison step, one of the selected control targets is in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi0, and the set value of the screw rotation speed N exceeds the rotation speed control standard value N0. When the set value of the drug injection amount K does not correspond to the state of less than the drug injection amount control standard value K0, the supply pressure Pi is set to increase and the screw rotation speed N is decreased for each control target control value. The control device for a screw press type dehydrator according to claim 9 , further comprising a control value updating unit that executes any setting process of setting or raising the drug injection amount K. A control device for a screw press type dehydrator for dehydrating slurry.
The supply pressure Pi of the slurry in which the predetermined pressure control standard value Pi0 is set, the screw rotation speed N for squeezing and transporting the slurry in which the predetermined rotation speed control standard value N0 is set, and the predetermined chemical amount control standard value K0 are set. At least two of the coagulant injection amounts K to be pre-injected into the slurry are selected as control targets, and the screw drive torque S falls within the range of the first threshold SH and the second threshold SL smaller than the first threshold SH. Drive torque control unit that executes the drive torque control step to set the control value of each control target.
Is configured with
The drive torque control unit is
When the drive torque S exceeds the first threshold value SH or becomes less than the second threshold value SL, a comparison processing unit that executes a comparison step of comparing the control value of each control target with each control standard value. When,
When the drive torque S exceeds the first threshold value SH, as a result of the comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi exceeds the pressure control standard value Pi 0, and the screw. When the control value of the rotation speed N is less than the rotation speed control standard value N0 and the control value of the drug injection amount K exceeds the drug solution amount control standard value K0, the control value of each control target is set to each control standard value. As well as setting to
When the drive torque S is less than the second threshold SL, as a result of the comparison by the comparison step, all the selected control targets are in a state where the control value of the supply pressure Pi is less than the pressure control standard value Pi 0, and the screw. When the control value of the rotation speed N exceeds the rotation speed control standard value N0 and the control value of the drug injection amount K corresponds to the state of less than the drug solution amount control standard value K0, the control value of each control target is set to each control standard value. The initialization processing unit that executes the initialization step set to
When the drive torque S is less than the first threshold value SH and exceeds the second threshold value SL, a standby processing unit that executes a standby step for holding a set value of each control target, and a standby processing unit.
A control device for a screw press type dehydrator, characterized in that it contains. The control device for a screw press type dehydrator according to any one of claims 8 to 12 , wherein a supply pressure Pi, a screw rotation speed N, and a chemical injection amount K are selected as each control target. The screw according to claim 8 or 9 , wherein each control standard value is set to a different value depending on whether the drive torque S exceeds the first threshold value SH or becomes less than the second threshold value SL. Control device for press type dehydrator.

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