JP2001087799A - Operation method of centrifuge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method of a centrifuge which is capable of stably keeping the actual revolving speed of a bowl to be a target revolving speed with respect to variation of the quantity of a charged solid material. SOLUTION: The actual revolving speed of the bowl 1 measured by a bensor 15 of revolving speed is sampled at every control period and is taken into a sequencer 14, a deviation between the target revolving speed and the actual revolving speed is calculated by the sequencer 14, the deviation which exceeds a prescribed allowable value is added to the present command value of revolving speed or is subtracted from the same and the temporary command value of revolving speed is calculated. The calculated temporary command value of revolving speed is instructed to an inverter 13 of an electric motor 6, thereafter, the rate of change of revolving speed at a prescribed observing time is calculated, a modifying constant corresponding to the calculated rate of change of revolving speed is selected from among modifying constants which are preliminarily determined at every rate of constant of revolving speed based on rule of thumb and the new command value of revolving speed which is calculated by multiplying the selected modifying constant to the temporary command value of revolving speed is instructed to the inverter 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for operating a centrifugal separator used as a centrifugal dehydrator or a centrifugal concentrator in a sewage treatment plant or the like.

[0002]

2. Description of the Related Art A conventional centrifugal dehydrator and a centrifugal concentrator are, for example, as shown in FIG. 3, in which a bowl 1 has a cylindrical straight body 2a and a cone 2b having a tapered diameter. The screw conveyor 3 is arranged concentrically inside the bowl 1. A cake outlet 4 is provided at the tip of the cone 2b, and a separated liquid outlet 5 is provided at the base of the straight body 2a.

[0003] An electric motor 6 is connected to the bowl 1 via a belt (not shown), a hydraulic motor 7 is connected to the screw conveyor 3, and a hydraulic drive unit 8 is connected to the hydraulic motor 7. A sludge supply pipe 9 is arranged concentrically inside the screw conveyor 3, and a chemical solution supply pipe 10 is provided in communication with the sludge supply pipe 9 in the middle. In this configuration, the bowl 1 driven to rotate by the electric motor 6 and the screw conveyor 3 driven to rotate by the hydraulic motor 7
Rotates at a high speed with a slight differential speed. The polymer flocculant is introduced into the sludge supply pipe 9 through the chemical supply pipe 10, and the polymer flocculant and raw sludge are continuously fed into the bowl 1 through the sludge supply pipe 9.

[0004] Inside the bowl 1, sludge particles in the raw sludge form flocculated floc by the action of a polymer flocculant, and the raw sludge is separated into a cake 11 and a separated liquid 12 by centrifugal force. The cake 11 accumulates on the inner peripheral surface of the bowl 1, and the separated liquid 12 stays inside the cake 11. The screw conveyor 3 with a slight speed difference from the bowl 1 is the cake 1
1 is conveyed from the straight body portion 2a to the cone portion 2b, and the dehydrated cake is discharged from the cake discharge port 4 to the outside of the bowl 1. On the other hand, the separated liquid is discharged from the separated liquid discharge port 5 to the outside of the bowl 1.

[0005]

In the above-mentioned conventional configuration, the rotation speed of the bowl 1 is controlled by controlling the electric motor 6 by an inverter, so that the bowl 1 rotates at a target rotation speed (fixed value). The number of rotations of the electric motor 6 in the design required for the above is given to the inverter as a rotation number command value.

The amount of solids charged in the bowl 1 (concentration of sludge × flow rate) fluctuates according to a change in the set value of sludge input flow rate and a change in sludge concentration. Act as a change. For this reason,
The slip amount of the electric motor 6 and the belt for transmitting power fluctuates, and a difference occurs between the actual rotation speed of the bowl 1 and the target rotation speed, so that there is a problem that a specified centrifugal effect cannot be obtained.

[0007] It is difficult to measure the amount of solids charged in real time, and it is not possible to control the rotation speed using the amount of solids charged directly as a control index. On the other hand, when feedback control is performed by giving a rotation speed command value to the inverter using the actual rotation speed as a control index, during the time required for the actual rotation speed to return to the target rotation speed, the amount of input solid matter, which is the motor load, is reduced. Is changed, the rotation speed command value given to the inverter becomes an inappropriate value, and as a result, the actual rotation speed becomes excessive or too low with respect to the target rotation speed, and control may be diverged.

The present invention solves the above-mentioned problems, and provides a method of operating a centrifuge capable of stably maintaining the actual number of rotations of a bowl at a target number of rotations with respect to a change in the amount of solids charged. With the goal.

[0009]

In order to solve the above-mentioned problems, a method of operating a centrifuge according to the present invention according to claim 1 comprises:
The bowl into which the raw sludge flows is rotated by a driving device, and the centrifugal separator, which controls the actual rotation speed of the bowl to the target rotation speed by instructing the rotation speed command value from the sequencer to the driving device, controls the bowl in real time. The actual rotation speed is sampled at each control cycle, taken into the sequencer, the deviation between the target rotation speed and the actual rotation speed is calculated by the sequencer, and the deviation exceeding the predetermined allowable value is added to or subtracted from the current rotation speed command value, and the provisional rotation speed is calculated. The command value is calculated, the calculated provisional rotation speed command value is instructed to the drive device, and then the rotation speed change rate during a predetermined observation time is calculated. From the above, a correction constant corresponding to the calculated rotation speed change rate is selected, and a new rotation speed command value calculated by multiplying the provisional rotation speed command value by the selected correction constant is instructed to the drive device. .

According to a second aspect of the present invention, there is provided a method for operating a centrifuge according to the present invention, wherein a control cycle corresponding to a calculated rotational speed change rate is selected from control cycles previously determined for each rotational speed change rate by empirical rules. Then, the next actual rotation speed is sampled in this control cycle.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The centrifugal separator according to the present embodiment has the same basic structure as that described above with reference to FIG. In FIG. 1 and FIG.
Is connected to an electric motor 6 for controlling the rotation of the electric motor 6 via a belt (not shown), and the inverter 13 is connected to a sequencer 14 for controlling the operation of the centrifuge. . A rotation speed sensor 15 for measuring the rotation speed of the bowl 1 in real time is connected to the sequencer 14. A functional circuit for operation control is set in the sequencer 14, and the functional circuit has a correction constant N
And a control cycle t for each value of the rotational speed change rate ρ are stored as control data.

The operation of the above configuration will be described below. During operation, the polymer flocculant and raw sludge are continuously introduced into the bowl 1 through the sludge supply pipe 9, and the bowl 1 driven by the electric motor 6 and the screw conveyor 3 driven by the hydraulic motor 7 are slightly moved. High speed rotation with differential speed. The rotation speed control of the bowl 1 is performed by instructing the rotation speed command value from the sequencer 14 to the inverter 13 to adjust the actual rotation speed to the target rotation speed. For this,
The actual rotation speed of the bowl 1 is measured in real time by the rotation speed sensor 15, and the measured value is sampled every control cycle and taken into the sequencer 14.

As shown in FIG. 2, the sequencer 14 calculates a deviation between the target rotation speed SV and the actual rotation speed PV,
The absolute value of the deviation is compared with a predetermined allowable value X. And
If the deviation exceeds a predetermined allowable value X, the deviation is added to or subtracted from the current rotational speed command value MV to provide a provisional rotational speed command value MV.
Calculate ₁ . The calculated rotational speed command value MV ₁ provisional instructs the inverter 13 to control to bring the actual rotational speed PV of the bowl 1 to the target rotational speed SV.

After the provisional rotation speed command value MV ₁ is instructed to the inverter 13, a predetermined observation time T is measured by a timer, and after the predetermined observation time T has elapsed, the rotation speed change rate ρ is calculated. The rotational speed change rate ρ is obtained by dividing the absolute value of the difference between the previously measured actual rotational speed PV and the actual rotational speed PV ₁ after the lapse of the predetermined observation time T by the predetermined observation time T.

A correction constant N corresponding to the calculated rotational speed change rate ρ, a correction constant N previously determined for each value of the rotational speed change rate ρ by an empirical rule, and the selected correction constant N is provisionally determined. Is multiplied by the rotation speed command value MV ₁ to calculate a new rotation speed command value MV, instructing the rotation speed command value MV to the inverter 13 and bringing the actual rotation speed PV of the bowl 1 closer to the target rotation speed SV. Do.

Further, a control cycle t corresponding to the calculated rotational speed change rate ρ is selected from control cycles t determined in advance for each value of the rotational speed change rate ρ by an empirical rule, and this control cycle t is determined. Control cycle t for sampling the next actual rotational speed PV
And

[0017]

As described above, according to the present invention, when feedback control of the rotation speed of the bowl is performed using the actual rotation speed as a control index, the load fluctuation that increases or decreases due to the change in the amount of solids charged is observed as the rotation speed change rate. Since the correction constant according to the rotation speed change rate is obtained in advance as an empirical rule, and the provisional rotation speed command value is corrected with the correction constant, the rotation speed command value to be given to the inverter depends on the input solids amount. The value becomes an appropriate value, the actual rotation speed converges to the target rotation speed, and the actual rotation speed of the bowl can be stably maintained at the target rotation speed. Further, by changing the control cycle according to the rotation speed change rate, the actual rotation speed can be quickly restored to the target rotation speed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a centrifuge according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of a sequencer in the embodiment.

FIG. 3 is a schematic diagram showing a configuration of a conventional centrifuge.

[Explanation of symbols]

 Reference Signs List 1 bowl 2a straight body part 2b cone part 3 screw conveyor 4 cake discharge port 5 separated liquid discharge port 6 electric motor 7 hydraulic motor 8 hydraulic drive unit 9 sludge supply pipe 10 chemical supply pipe 11 cake 12 separation liquid 13 inverter 14 sequencer 15 rotation Number sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D057 AA10 AB01 AC01 AC06 AD01 AE03 AE12 AF05 BA04 BB02 BB03 BC16 CA07 CB05 4D059 AA03 BE38 BE56 CB06 CB07 EA20 EB20

Claims (2)

[Claims] 1. A centrifugal separator in which a bowl into which raw sludge flows is rotationally driven by a driving device, a rotation speed command value is instructed from the sequencer to the driving device, and the actual rotation speed of the bowl is controlled to a target rotation speed. The actual rotation speed of the bowl to be measured is sampled at each control cycle and taken into the sequencer.The sequencer calculates the deviation between the target rotation speed and the actual rotation speed, and calculates the deviation exceeding the predetermined allowable value as the current rotation speed command value. A provisional rotation speed command value is calculated by addition and subtraction, and the calculated provisional rotation speed command value is instructed to the drive device. A correction constant corresponding to the calculated rotation speed change rate is selected from the determined correction constants, and a new rotation speed command value calculated by multiplying the provisional rotation speed command value by the selected correction constant is specified to the drive device. A method for operating a centrifuge, comprising: 2. A control cycle corresponding to the calculated rotation rate change rate is selected from control cycles determined in advance for each rotation rate change rate by an empirical rule, and the next actual rotation rate is sampled in this control cycle. The method for operating a centrifuge according to claim 1, wherein: