JP5024658B2 - Operation control method for multiple screw press - Google Patents

Description

  The present invention relates to an operation control method for a plurality of rows of screw presses that perform solid-liquid separation of agglomerated slurry while rotating an outer cylinder and a screw shaft at a differential speed, and in particular, between a starting end side of an outer cylinder with a screen stretched and a screw shaft. The present invention relates to an operation control method for a multiple screw press that controls the flow rate of a stock solution to be constant in order to control the press-fitting pressure of a processing stock solution such as sludge supplied therebetween.

  A conventional screw press is provided with a cylindrical screen and a screw shaft that is rotatable inside thereof, and is separated into solid and liquid while conveying the coagulated sludge by driving rotation of the screw shaft. And a pressure detector for detecting the press-fitting pressure of the raw solution supplied to the screw press. As an operation control method of the screw press, the supply flow rate of the stock solution supply pump is controlled so that the press-fit pressure detected by the pressure detector becomes substantially constant. That is, the discharge amount of the stock solution supply pump is decreased in the direction in which the detection pressure increases, and the discharge amount of the stock solution supply pump is increased in the direction in which the detection pressure decreases.

As such a screw press operation control method, for example, Patent Document 1 discloses. In this patent document 1, in addition to the above method, a cleaning device capable of cleaning the cylindrical screen from the outer peripheral side is provided, and the supply flow rate in the sludge supply system corresponding to the stock solution supply pump is the set amount for starting cleaning. In the following, by operating the cleaning device by the cleaning control means, the clogging of the cylindrical screen is eliminated, the supply flow rate to the screw press is recovered early, and the processing efficiency is improved. Also, the screw press is provided with a supply pressure detection means, a screw torque detection means, and a screw rotation speed control means, and the rotation speed of the screw is controlled based on the detection result of the supply pressure and torque so that the water content of the dewatered cake A screw press that makes the rate constant is described in Patent Document 2.
JP 2004-90049 A Japanese Patent No. 3542970

  In a conventional screw press operation control method, the supply flow rate of the stock solution supply pump is controlled to control the supply flow rate of the stock solution supplied to the screw press in order to control the press-fitting pressure of the stock solution supplied to the screw press to a constant level. To do. In practice, however, the amount of processing varies depending on the concentration of the stock solution and the dehydration. For example, the supply flow rate increases when the stock solution concentration is low, and the supply flow rate decreases when the stock solution concentration is high. Therefore, there is a problem that the supply flow rate fluctuates. In addition, in a screw press that controls the moisture content and torque of the dewatered cake by detecting the sludge concentration and supply amount, the supply sludge amount and sludge concentration constantly vary, and the rotational torque applied to the screw shaft and outer cylinder screen also varies. However, there is also a problem that it is difficult to make the water content of the dehydrated cake uniform.

  In order to achieve the problem to be solved by the above invention, an operation control method for a multiple-type screw press according to the present invention connects a plurality of rows of screw presses to a plurality of branch supply pipes branched from a slurry supply pipe of a processing stock solution. Then, a screw shaft is installed in a rotatable outer cylinder with a screen stretched, and the processing stock solution supplied to the starting end side of the outer cylinder is rotated at a differential speed to the rear end side of the outer cylinder. When separating the filtrate from the screen of the outer cylinder while transporting and removing the cake from the outlet on the rear end side of the outer cylinder, the pressure of the processing stock solution supplied to the starting end side of the outer cylinder is kept constant. In order to control, in the operation control method of the screw press for controlling the stock solution flow rate of the processing stock solution, the stock solution flow rate of the processing stock solution is measured, and the measured stock solution flow rate is out of the preset reference stock solution flow rate range. When the said plurality of rows of by controlling the rotational frequency of the screw shaft, is characterized in that to control the reference value by returning the stock flow of the processing stock solution within the range of the reference stock solution flow.

  The operation control method for a multiple screw press according to the present invention is the operation control method for the screw press, wherein when the flocculant is added to the processing stock solution, the stock solution concentration range is set in several stages in advance. Measure the stock concentration of the treatment stock solution, and gradually increase or decrease the coagulant injection rate based on the measured stock solution concentration so that the standard dosing rate of the coagulant corresponds to the stock solution concentration at each stage. It is what you do.

  The operation control method of the multiple screw press according to the present invention is such that a plurality of screw presses are connected to a plurality of branch supply pipes branched from a slurry supply pipe of a processing raw solution, and a screw is attached to a rotatable outer cylinder having a screen stretched. The process stock solution supplied to the start end side of the outer cylinder is separated from the screen of the outer cylinder while the screw shaft is rotated at a differential speed and conveyed to the rear end side of the outer cylinder. When the cake is taken out from the outlet on the rear end side of the outer cylinder, the stock solution flow rate of the processing stock solution is controlled in order to control the press-fitting pressure of the processing stock solution supplied to the starting end side of the outer cylinder to be constant. In the operation control method of the screw press, the cake moisture content is measured with a moisture meter disposed in the dewatered cake discharge portion of each screw press, and the average cake moisture content is calculated, and a preset standard When out of range of a rk moisture content, and it is characterized in that increase or decrease the dosing rate of the flocculant to control the cake moisture content to a reference value.

  Further, the operation control method of the multiple screw press according to the present invention is the operation control method of the screw press, wherein the average cake moisture content is compared with the cake moisture content of each screw press, and the rotational speed of the outer cylinder is compared. Are controlled individually to adjust to the average cake moisture content.

  Further, the operation control method of the multiple screw press according to the present invention is the operation control method of the screw press, wherein when the cake moisture content is controlled to a reference value by increasing or decreasing the chemical injection rate of the flocculant, the chemical injection is performed. An upper and lower limit value is set for the rate, and when the drug injection rate reaches the upper and lower limit value, an alarm is issued while maintaining the upper and lower limit values of the drug injection rate.

  As described in the means for solving the above-mentioned problems, the operation control method for the multiple screw press according to the present invention provides the processing stock solution for controlling the press-fitting pressure of the processing stock solution supplied to the screw press to be constant. When the measured flow rate of the processing stock solution deviates from the preset reference flow rate range, the number of rotations of the screw shaft is increased / decreased, the stock solution flow rate is controlled to be constant, and several steps are performed in advance. The dosage of flocculant has been increased or decreased step by step so as to correspond to the concentration of the stock solution set, so that the amount of chemical used can be reduced, and the optimal flocculent sludge can be obtained. Stable operation can be performed.

  Further, according to the present invention, the moisture content of the dehydrated cake discharged from the plurality of rows of screw presses is measured to calculate the average cake moisture content. When the moisture content is outside the preset standard cake moisture content range, the flocculant In addition to maintaining the average cake moisture content at the reference value by increasing and decreasing the chemical injection rate of each of the multiple rows of screws, the individual cake moisture content of the multi-row screw press is also controlled by individually controlling the rotation speed of the outer cylinder. Therefore, the moisture content of the dehydrated cake discharged from each screw press can be maintained at a uniform and optimal value, and a stable dehydrated cake can be obtained, making it easy to manage post-dehydration treatment processes such as landfill and incineration. Thus, the running cost can be reduced.

  Hereinafter, an operation control method of a multiple screw press according to the present invention will be described with reference to the drawings. First, FIG. 1 is a longitudinal sectional view of a screw press used in the present invention. The screw press 1 is supported on the front and rear frames 8 and 14 and is placed inside an outer cylinder 2 with a screen stretched around its periphery. A screw shaft 3 around which a screw blade 4 is wound is provided. The shaft diameter of the screw shaft 3 increases from the slurry supply side to the dewatered cake discharge side, and the filtration chamber 5 between the outer cylinder 2 and the screw shaft 3 extends from the supply side to the discharge side. It is shrinking. A screw drive shaft 15 connected to the screw shaft 3 is pivotally supported by a bearing 22 disposed on a frame 21 of the frame 14. A sprocket 23 is fitted on the screw drive shaft 15 and is linked to a screw drive machine 24 mounted on the frame 14.

  FIG. 2 is an enlarged view of the supply side of the screw press. A flange 6 is connected to the starting end side of the outer cylinder 2, and a sprocket 7 is fitted to the end face of the flange 6. The sprocket 7 is mounted on a frame 8. The outer cylinder 2 is connected to the outer cylinder drive unit 9 that can be rotated in the forward and reverse directions, so that the outer cylinder 2 can be rotated forward or backward. A supply pipe 10 is connected to the start end of the screw shaft 3, and the aggregated slurry supplied from the supply pipe 10 passes through a supply hole 11 a that opens from the supply path 11 to the start end of the screw shaft 3. To be supplied.

  FIG. 3 is an enlarged view of the discharge side of the screw press. A rotating plate 12 is connected to the rear end side of the outer cylinder 2, and the rotating plate 12 can freely rotate on a rotating plate bearing 13 fixed to the frame 14. Has been supported. A screw drive shaft 15 is connected to the rear end portion of the screw shaft 3, and a sprocket 23 is fitted on the screw drive shaft 15 as shown in FIG. 24 are linked to each other. The terminal portion of the screw drive shaft 15 is pivotally supported by a bearing 22 placed on a mount 21. The dewatered cake discharge portion 17 on the terminal end side of the outer cylinder 2 is provided with a discharge port 16, and a presser 18 is provided in the discharge port 16, and the presser 18 is slidable on the moving shaft 19. The opening of the discharge port 16 is adjusted while applying back pressure to the cake with an air cylinder 20 that is suspended and connected to the rear end of the presser 18.

  Refer to FIG. 1 again. The outer cylinder driver 9 and the screw driver 24 are actuated to rotate the outer cylinder 2 and the screw shaft 3 in the reverse direction in the reverse direction so as to agglomerate from the supply path 11 of the screw shaft 3 to the filtration chamber 5 at the start end of the outer cylinder 2. Supply slurry. This agglomerated slurry is transferred to the rear end portion of the outer cylinder 2 by a screw blade 4 wound around the outer peripheral portion of the screw shaft 3. At this time, the filtrate is separated from a screen (not shown) stretched on the outer cylinder 2, accumulated in a filtrate trough 26 provided below the outer cylinder 2, and discharged outside. While the agglomerated slurry in the filtration chamber 5 is transferred to the rear end side of the outer cylinder 2, pressure is gradually applied due to the gradual reduction of the volume of the filtration chamber 5, and dehydration further proceeds. The back pressure acting on the dewatered cake is adjusted by adjusting the opening amount of the discharge port 16 with the presser 18 provided opposite to the discharge port 16 on the terminal end side of the outer cylinder 2, and the dewatering property of the dehydrated cake is adjusted. The moisture content of the dehydrated cake can be adjusted by adjusting the pressure. The back pressure acting on the dehydrated cake is adjusted by controlling the fluid pressure supplied to the air cylinder 20 described above. And the dewatering cake discharged | emitted from the discharge port 16 accumulates in the sludge receiving tank 27 provided in the downward direction of the dewatering cake discharge part 17, and is discharged | emitted outside.

  FIG. 4 is a conceptual diagram in which a dewatered cake moisture content meter 38 is disposed in the dewatered cake discharge portion of the screw press so that the moisture content of the dewatered cake discharged from the discharge port 16 of the screw press 1 can be continuously measured. I have to. A connecting pipe 39 that can be attached and detached is connected to the end portion of the outer cylinder 2 through the flange. The connecting pipe 39 is provided with a moisture content meter 38 for measuring the moisture content of the dehydrated cake discharged from the dehydrated cake discharge portion 17. The moisture meter 38 used in the present invention utilizes microwaves and measures the moisture content of the cake using the phase difference generated between transmission and reception of microwaves, The moisture content meter 38 to be used is not limited to one using microwaves. Using the moisture content of the dehydrated cake measured by the moisture content meter 38, as described later, the chemical injection rate of the flocculant added to the stock solution was increased and decreased, and the moisture content of the measured cake was initially set at the start of operation. Control is performed so that the moisture content of the standard cake is obtained.

  FIG. 5 is a schematic configuration diagram of an operation control method for a multiple screw press according to the present invention, and the operation control system will be described. The processing stock solution stored in the sludge storage tank 28 is supplied to the agglomeration mixing tank 33 through the stock solution supply pipe 29 at a stock solution flow rate QS by a constant flow type stock solution supply pump SP. In the middle of the stock solution supply pipe 29, a concentration meter D for measuring the stock solution concentration CS of the processing stock solution and a stock solution flow meter F for measuring the stock solution flow rate QS of the processing stock solution are aggregated with the stock solution supply pump SP. It is provided between the mixing tank 33.

  Further, in the middle of the stock solution supply pipe 29 between the stock solution flow meter F and the coagulation mixing tank 33, the polymer flocculant stored in the polymer dissolution tank 30 is fed by a chemical solution supply pump PP capable of adjusting the flow rate. A chemical solution supply pipe 31 that is supplied at a chemical solution flow rate QP is connected. In the middle of the chemical liquid supply pipe 31, a chemical liquid flow meter FP for measuring the chemical liquid flow rate QP is provided between the chemical liquid supply pump PP and the raw liquid supply pipe 29. As shown in FIG. 5, the end of the stock solution supply pipe 29 is connected to the bottom of a closed type agglomeration mixing tank 33, and sludge to which a polymer flocculant is added is pressed from the bottom of the agglomeration mixing tank 33 and stirred. Aggregate flocs are produced by mixing and stirring at 34. A slurry supply pipe 35 is connected to the upper part of the agglomeration mixing tank 33, and a plurality of branch supply pipes 36a and 36b branched from the slurry supply pipe 35 are connected to the screw presses 1a and 1b, respectively. The agglomerated slurry is press-fitted into the supply pipe 10 of the screw press 1 shown in FIG. In the embodiment according to the present invention, two screw presses 1a and 1b are installed, but the number can be increased as necessary.

  Further, referring to FIG. 5, a concentration meter D and a stock solution flow meter F arranged in the stock solution supply pipe 29 and a chemical solution flow meter FP arranged in the chemical solution supply pipe 31 are connected to the chemical solution injection controller 32. Then, a detection signal of the detected stock solution concentration CS of the processing stock solution is transmitted to the chemical solution injection controller 32 to adjust the chemical solution flow rate QP supplied from the chemical solution supply pump PP and correspond to the stock solution concentration CS set in advance in several stages. The dosing rate is controlled so that the dosing rate of the flocculant is reached. The stock solution flow meter F is connected to a flow rate controller 37 that transmits a detection signal of the stock solution flow rate QS, and proportionally controls the chemical solution flow rate QP and the stock solution flow rate QS. The slurry supply pipe 35 is provided with a pressure gauge P, and measures the press-fitting pressure PS of the agglomerated slurry supplied to the screw press 1. The pressure injection pressure PS measured by the pressure gauge P is compared with a preset reference pressure injection pressure P0, and a command is given to the stock solution supply pump SP so that the reference pressure injection pressure P0 is reached, and the stock solution flow rate QS is increased or decreased. Thus, the press-fit pressure constant control operation is performed. Actually, the detection signal measured by the pressure gauge P is transmitted to the pressure controller 42, and a command is given from the pressure controller 42 to the stock solution supply pump SP.

  On the other hand, a comparison is made between the stock solution flow rate QS transmitted to the flow rate controller 37 and a preset reference stock solution flow rate Q0, and a command is given to the screw driver 24 of the screw press 1 so that the reference stock solution flow rate Q0 is obtained. The rotational speed M of the screw shaft 3 is increased / decreased, and the stock solution flow rate constant control operation is performed.

  Further, the moisture content meters 38a and 38b provided in the screw presses 1a and 1b shown in FIG. 5 are connected to a moisture content controller 40. The moisture content controller 40 is connected to the indicators 41a and 41b, and the chemical solution injection control. Connected to the vessel 32. The indicators 41a and 41b are connected to the outer cylinder drivers 9a and 9b of the screw presses 1a and 1b. Detection signals of the cake moisture content Wa and Wb of the dehydrated cake measured by the moisture meter 38a and 38b are transmitted to the moisture content controller 40, and the average cake moisture content W of the cake moisture content Wa and Wb is calculated. The average cake moisture content W is compared with the preset reference cake moisture content W0, and a command is given to the chemical injection controller 32 so as to obtain the reference cake moisture content W0. . Then, each cake moisture content Wa, Wb and the average cake moisture content W are compared and judged, and an instruction is given from the indicators 41a, 41b to the outer cylinder drive units 9a, 9b so as to obtain the average cake moisture content W. The cake moisture contents Wa and Wb are controlled by increasing or decreasing the rotational speeds Na and Nb of the outer cylinder.

  Next, based on the flowchart of FIG. 6, the operation control method of the multiple screw press according to the present invention will be described. In order to operate the screw press 1 in a stable manner, the press-fitting pressure PS of the processing stock solution supplied to the screw press 1 is basically controlled to be constant. Therefore, in order to control the press-fitting pressure PS to be constant, the rotational speed of the stock solution supply pump SP is controlled to control the stock solution flow rate QS of the processing stock solution supplied to the screw press 1. In parallel with the constant control operation of the press-fitting pressure PS, the cake moisture contents Wa and Wb of the dewatered cake discharged from a plurality of screw presses 1a and 1b (two in the embodiment according to the present invention) are measured. Then, the average cake moisture content W is calculated, and the number of revolutions of the chemical supply pump PP is set so as to increase or decrease the chemical injection rate A of the polymer flocculant so that the average cake moisture content W becomes the reference cake moisture content W0. It is something to control.

Furthermore, it demonstrates in detail based on FIG. First, driving of the screw presses 1a and 1b is started, and the outer cylinders 2a and 2b and the screw shafts 3a and 3b are rotated at a differential speed. Then, initial settings are made for the following items.
1: Reference press-fit pressure P0
2: Standard stock solution flow rate Q0
3: Standard injection rate A0
4: Upper limit drug injection rate Amax
5: Lower limit drug injection rate Amin
6: Standard cake moisture content W0

  Subsequently, the stock solution concentration CS of the processing stock solution supplied by the stock solution supply pump SP is measured by the densitometer D, and this measured value is a stock solution concentration CS1, CS2,. Compare to which range it belongs. And the chemical injection rate A is set in advance to the chemical injection rates A1, A2,... Corresponding to the stock solution concentrations CS1, CS2,. Therefore, the standard dosing rate A0 is set so that the initial setting of the standard dosing rate A0 is switched from the dosing rate A corresponding to the measured stock solution concentration CS and the appropriate flocculant is added. To change. Monitoring of the stock solution concentration CS and the reference drug injection rate A0 is usually performed automatically when a predetermined time arrives, or may be manually performed at an arbitrary time.

  When the operation is started, the press-fitting pressure PS of the processing stock solution supplied to the screw press 1 is detected by the pressure gauge P, and this detection signal is transmitted to the pressure controller 42. The pressure controller 42 compares the transmitted press-fit pressure PS with a preset reference press-fit pressure P0. When the press-fitting pressure PS of the agglomerated slurry is larger than the reference press-fitting pressure P0 (PS> P0), a command is given from the pressure controller 42 to the stock solution supply pump SP to reduce the rotation speed of the stock solution supply pump SP, and the stock solution flow rate. Reduce QS. On the other hand, when the press-fit pressure PS is smaller than the reference press-fit pressure P0 (PS <P0), a command is given from the pressure controller 42 to the stock solution supply pump SP to increase the rotation speed of the stock solution supply pump SP, and the stock solution flow rate QS is set. increase. As described above, the press-fitting pressure is controlled, and the press-fitting pressure Ps is substantially maintained at the reference press-fitting pressure P0.

  In order to control the press-fitting pressure PS of the processing stock solution supplied to the screw press 1 at a constant level, flow control is performed using the stock solution flow rate QS of the processing stock solution as a parameter. The stock solution flow rate QS of the stock solution supply pump SP is measured by the flow meter F, and the measured stock solution flow rate QS is compared with a preset reference stock solution flow rate Q0. When the stock solution flow rate QS deviates from the difference α from the reference stock solution flow rate Q0, the rotational speed M of the screw shaft is increased or decreased to control the flow rate so that the stock solution flow rate QS becomes equal to the reference stock solution flow rate Q0.

  The flow rate control will be described in detail. The measured value of the stock solution flow rate QS measured by the flow meter F is transmitted to the flow rate controller 37. The stock solution flow rate QS transmitted by the flow rate controller 37 is compared with a preset reference stock solution flow rate Q0. When the stock solution flow rate QS is larger than the reference stock solution flow rate Q0 (QS-Q0> α), a command is given from the flow controller 37 to the screw driver 24 to reduce the stock solution flow rate QS, and the rotational speed M of the screw shaft is set. Decrease. On the other hand, when the stock solution flow rate QS is smaller than the reference stock solution flow rate Q0 (Q0−QS> α), a command is given from the flow controller 37 to the screw driver 24 to increase the stock solution flow rate QS, and the rotational speed M of the screw shaft is set. increase. As described above, the stock solution flow rate is controlled by increasing / decreasing the rotational speed of the screw shaft, and the stock solution flow rate QS is substantially maintained at the reference stock solution flow rate Q0.

  In the embodiment of the present invention, the control is performed so that the cake moisture content of the dewatered cake is set to the set value in parallel with the constant press-fitting pressure control and the constant flow control. Based on FIG. 6, the control method of a cake moisture content is explained in full detail. After setting the reference chemical injection rate A0, the moisture content meters 38a and 38b attached to the screw presses 1a and 1b are used to measure the cake moisture content Wa and Wb of the dehydrated cake discharged from the screw presses 1a and 1b. The measured value is transmitted to the moisture content controller 40. An average cake moisture content W {W = (Wa + Wb) / 2} of the cake moisture content Wa and Wb transmitted by the moisture content controller 40 is calculated. When the average cake moisture content W is higher than the preset reference cake moisture content W0 {W−W0> β (β: tolerance of the reference cake moisture content W0)}, the average cake moisture content W should be reduced. Then, a command is given from the moisture content controller 40 to the chemical supply pump PP via the chemical injection controller 32 to increase the chemical injection rate A. On the other hand, when the average cake moisture content W is lower than the reference cake moisture content W0 (W0−W> β), the chemical solution is supplied from the moisture content controller 40 via the chemical solution injection controller 32 to increase the average cake moisture content W. A command is given to the supply pump PP, and the chemical injection rate A is decreased. As described above, the chemical injection rate A is controlled so that the average cake moisture content W is substantially maintained at the reference cake moisture content W0. In addition, in order to maintain the cake moisture content constant control operation, the range of the chemical injection rate A that is increased or decreased is limited to ± 20% to ± 30% of the reference chemical injection rate A0.

  When the range of the chemical injection rate A to be increased to decrease the average cake water content W exceeds the upper limit of + 20% to + 30% of the reference chemical injection rate A0, when the preset upper limit value Amax is reached While giving an alarm, the operation of the screw press 1 is continued while maintaining the upper limit value Amax. On the other hand, when the range of the dose rate A to be decreased exceeds the lower limit of −20% to −30% of the reference dose rate A0, an alarm is issued when the preset lower limit value Amin is reached, and this lower limit is set. The operation of the screw press 1 is continued while maintaining the value Amin. Then, the alarm is manually stopped and the stock solution concentration CS and the reference drug injection rate A0 are manually monitored again, and if the reference drug injection rate A0 is switched, the operation is returned to the beginning of the operation process and the press-fitting pressure is constant. Restart from control operation. If there is no switching of the reference drug injection rate A0, the current operation is continued without changing the operation process.

  When the average cake moisture content W becomes substantially equal to or less than the reference cake moisture content W0, the average cake moisture content W is compared with the cake moisture content Wa of the dehydrated cake discharged from the screw press 1a. When the cake moisture content Wa is higher than the average cake moisture content W {Wa-W> δ (δ: tolerance of the average cake moisture content W)}, the rotational speed of the outer cylinder drive 9a to reduce the cake moisture content Wa And the speed difference with the screw shaft 3a is gradually reduced. Even if the rotational speed of the outer cylinder driving device 9a becomes 0 and the outer cylinder 2a is stopped, if the cake moisture content Wa is higher than the average cake moisture content W, the outer cylinder driving device 9a is reversely rotated. The outer cylinder 2a is rotated in the same direction as the rotation direction of the screw shaft 3a, and the differential speed is gradually reduced. On the other hand, when the cake moisture content Wa is lower than the average cake moisture content W (W−Wa> δ), the rotational speed of the outer cylinder drive 9a is increased to increase the cake moisture content Wa, and the difference from the screw shaft 3a. Increase speed gradually. Also, the water content Wb of the dehydrated cake discharged from the screw press 1b is controlled in the same manner as the screw press 1a, and the water content of the cake of the dehydrated cake discharged from the plurality of rows of screw presses 1a, 1b. The rates Wa, Wb... Are individually controlled so as to be approximately equal to the average cake moisture content W.

  As described above, if the differential speed between the outer cylinders 2a and 2b and the screw shafts 3a and 3b is increased, the same effect as that obtained by increasing the rotational speed of the screw shafts 3a and 3b can be obtained. The residence time in the cylinders 2a and 2b is shortened, the dehydration time is shortened, and the cake moisture contents Wa and Wb of the dehydrated cake discharged from the screw presses 1a and 1b are increased. Conversely, if the differential speed between the outer cylinders 2a, 2b and the screw shafts 3a, 3b is reduced, the same effect as that obtained by reducing the rotational speed of the screw shafts 3a, 3b can be obtained. The residence time in 2a, 2b becomes longer, the dehydration time is extended, and the cake moisture content Wa, Wb of the dehydrated cake discharged from the screw press 1a, 1b is lowered.

  The operation control method of the multiple screw press according to the present invention supplies the coagulated slurry to the screw press while performing an operation for controlling the press-fitting pressure to a constant level, and controls the rotational speed of the screw shaft to control the stock solution supply flow rate. The moisture content of the dewatered cake discharged from each screw press is measured while the operation is maintained at a constant level, and the flocculant drug injection rate corresponding to the sludge concentration set in advance at the start of operation is slightly changed. Thus, the moisture content of the dehydrated cake can be kept uniform and constant. And the rotation speed of each outer cylinder can be controlled individually, and the water | moisture-content difference of the dewatering cake discharged | emitted from several screw press can also be eliminated. By such an operation control method, the moisture content of the dewatered cake can be kept constant corresponding to the change in the sludge properties, and the amount of the flocculant used can be reduced. In addition, since the properties of the dewatered cake are stable, it is easy to manage the treatment process after dewatering, and multiple rows of screw presses are controlled simultaneously, so that mass treatment of sewage mixed raw sludge, sewage digested sludge, activated surplus sludge, etc. It can be used as a screw press that is optimal for the required treatment plant.

It is a partial longitudinal cross-sectional side view of the screw press used for the operation control method of the multiple screw press which concerns on this invention. Similarly, it is an enlarged view of the stock solution supply side of the screw press. Similarly, it is an enlarged view of the cake discharge side of the screw press. Similarly, it is the schematic of the screw press which attached the moisture meter. It is a schematic block diagram of the operation control method of the multiple screw press which concerns on this invention. It is a flowchart of the operation control method of the multiple screw press which concerns on this invention.

Explanation of symbols

1, 1a, 1b Screw press 2 Outer cylinder 3 Screw shaft 16 Discharge port 17 Dehydrated cake discharge part 35 Slurry supply pipe 36a, 36b Branch supply pipe 38 Moisture content meter A0 Reference chemical injection rate A Chemical injection rate Amax Upper limit Amin Lower limit CS, CS1, CS2 Stock solution concentration PS Press-in pressure Q0 Standard stock solution flow rate QS Stock solution flow rate W0 Standard cake water content W Average cake water content Wa, Wb Cake water content

Claims (3)

A plurality of screw presses (1a, 1b,...) Connected to a plurality of branch supply pipes (36a, 36b,...) Branched from the processing solution slurry supply pipe (35), and a screen is stretched. A screw shaft (3) is installed in the outer cylinder (2), and the processing stock solution supplied to the starting end side of the outer cylinder (2) is rotated at a differential speed to rotate the screw shaft (3). ) While separating the filtrate from the screen of the outer cylinder (2) while transporting it to the rear end side and taking out the cake from the outlet (16) on the rear end side of the outer cylinder (2), the outer cylinder In the operation control method of the screw press for controlling the stock solution flow rate (QS) of the processing stock solution in order to control the press-fitting pressure (PS) of the processing stock solution supplied to the starting end side of (2), the processing stock solution The stock solution flow rate (QS) is measured, and this measured stock solution flow rate (QS) Is out of the range of the preset reference stock solution flow rate (Q0), the rotational speed (M) of the plurality of rows of screw shafts (3) is controlled to control the stock solution flow rate (QS) of the processing stock solution. At the same time as returning to the range of the stock solution flow rate (Q0) and controlling to the reference value, the moisture content meter (38a, disposed in the dewatered cake discharge section (17) of each screw press (1a, 1b...) 38b...), The cake moisture content (Wa, Wb...) Is measured, the average cake moisture content (W) is calculated, and it is out of the preset standard cake moisture content (W0) range. In addition, the average cake moisture content (W) and the individual screw presses (1a, 1b,...) Are controlled by increasing / decreasing the chemical injection rate (A) of the flocculant to control the average cake moisture content (W).・) Compare the moisture content of the cake (Wa, Wb ...) And the rotational speed (Na, Nb · · ·) of the outer cylinder (2) to individually control the average multiple communication type screw press operation control method characterized by adjusting the cake moisture content (W) .   When the flocculant is added to the processing stock solution, the stock solution concentration range is set in advance in several stages, and the stock solution concentration (CS) of the processing stock solution is measured. Based on the measured stock solution concentration (CS) , Characterized in that the flocculant drug injection rate (A) is increased or decreased step by step so that the flocculant standard drug injection rate (A0) corresponding to the stock solution concentration (CS1, CS2,...) At each stage is obtained. An operation control method for a multiple screw screw press according to claim 1. When controlling the average cake water content (W) to a reference value by increasing or decreasing the chemical injection rate (A) of the flocculant, upper and lower limit values (Amax, Amin) are set to the chemical injection rate (A), Note ratio (a) is the upper limit value (Amax, Amin) when it is, the upper and lower limits of the Kusurichuritsu (a) (Amax, Amin) in claim 1, characterized in that alert while maintaining An operation control method of the multiple screw press described.

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