JP2973458B2 - Control method of centrifuge - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for controlling a centrifugal separator used in water treatment and various manufacturing processes, which separates solids from a stock solution and continuously discharges the same by a screw. Even when the properties of the stock solution change, the operation can be easily dealt with without interrupting the operation.

[Background Art] There is a screw decanter-type centrifuge capable of continuously discharging separated solids by a screw in one of centrifuges.

In this centrifugal separator, as shown in a schematic cross-sectional structure in FIG. 3, an outer shell bowl 1 that is driven to rotate to apply a centrifugal force to the stock solution A is provided, and a slight rotation difference is provided in the outer shell bowl 1. It is provided with an inner body screw 2 that rotates at a lower rotational speed than the outer body.
Is separated into solids B and liquid C by centrifugal force accompanying rotation of the outer bowl 1, and the solids B deposited on the inner wall of the outer bowl 1 are discharged to the outside by the inner screw 2. Thus, the solid B and the liquid C can be continuously separated.

In such a centrifugal separator, an outer bowl 1 driven by a main motor is provided through a gear box 3 composed of planetary gears to provide a predetermined rotation difference to the inner screw 2 with respect to the outer bowl 1. A differential speed motor is provided so as to connect the inner screw 2 and change the rotation difference of the inner screw 2 when the properties of the stock solution A change.

Also, as a safety device for the centrifuge, it detects the current value of the differential speed motor and stops the centrifuge when the rated current value is reached, or detects the current value and torque of the differential speed motor. Control of the rotation speed and torque of the inner screw is performed.

[Problems to be Solved by the Invention] In such a centrifuge, when the safety device operates and stops, the operation may be continued unless the device is disassembled and cleaning such as removing solids is performed. There is a problem that can not be done.

In addition, when the properties of the undiluted solution to be centrifuged change, the current value and torque of the differential speed motor are detected and only the rotation speed of the inner screw is changed. However, there is a problem that the scraping becomes defective depending on the properties of the processing solution, and the centrifuge is overloaded, the operation is not performed smoothly and the operation becomes unstable.

The present invention has been made in view of the problems of the related art, and has as its object to provide a control method of a centrifuge that can cope with a change in the properties of a stock solution without interrupting the operation.

[Means for Solving the Problems] In order to solve the above problems, a control method of a centrifuge according to the present invention includes an outer shell bowl for applying a centrifugal force to a rotation-driven stock solution, and an outer shell bowl provided in the outer shell bowl. When controlling a centrifugal separator having an internal screw that discharges solids separated by a rotation difference, the load on the internal screw is detected to control the current set value or torque set value of the safety device. When the set value becomes lower than the upper limit, the supply of the undiluted solution is stopped, and the rotation speed of the outer shell bowl is reduced, or the rotation speed of the outer shell bowl is reduced, and at the same time, the rotation of the outer shell bowl and the inner shell screw is reduced. The method is characterized in that the rotation difference is increased to discharge the residual solids with the inner screw, and thereafter, when the inner screw becomes a steady load, control is performed so as to return to the original steady operation.

[Operation] According to such a control method of the centrifuge, the load on the inner screw is detected, and when the set value becomes smaller than the upper limit of the current set value or the torque set value of the safety device, the undiluted solution is removed. And the centrifugal force is reduced by lowering the rotation of the outer shell bowl, or the rotation difference of the inner shell screw is increased in the outer shell bowl in this state, and the rotation is left by the inner shell screw. The solids are discharged to the outside, and the operation is returned to the original steady operation after the load is reduced, so that it is possible to cope with an increase in the load without interrupting the operation.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2 relate to an embodiment of a control method of a centrifuge according to the present invention. FIG. 1 is a schematic configuration diagram of a control system, and FIG. 2 is a flowchart for explaining the control contents.

In this screw decanter type centrifugal separator, an outer shell bowl 1 that is driven to rotate to apply a centrifugal force to the stock solution A, and a slight rotation difference is given to the outer shell bowl 1 so that the number of rotations is smaller than that of the outer shell bowl. An inverter motor 4 is provided as a variable-speed motor for driving the outer body bowl 1, and the power is transmitted via a belt 5. A differential speed motor 6 constituted by an inverter motor as a variable speed motor is connected to a pinion pulley 10 via a belt 7 to the inner body screw 2 so that a rotation difference from the outer body bowl 1 can be changed. The speed is changed by the box 3 to transmit the power. .

As a control system of such a centrifuge, the inverter motor 4 and the differential speed motor 6 are provided with inverters 4a and 6a, respectively, so that the rotation speed can be changed by a rotation speed command from the control device 8. Has become.

Further, a current relay 9 is provided between the control device 8 and the differential speed motor 6 to detect a load on the inner body screw 2, and is connected to the control device 8.

The control by the control system of such a centrifuge is performed as follows.

(1) When the undiluted solution A is supplied and the operation of the centrifuge is performed, the solids B and the liquid C are separated by centrifugation, and at the same time, the load current I of the inner screw 2 is detected by the current relay 9. You.

In this current relay 9, a maximum upper limit value Dmax is set corresponding to the rated current of the differential speed motor 6, and a lower current value is set as a set value D. As the set value D, For example, a value that is higher by 2 to 4 Amps than the current value at the time of steady operation is used, and two levels are set.

Then, in the steady state of the centrifuge, the solid matter B deposited on the inner wall of the outer body bowl 1 is discharged to the outside by the inner body screw 2, but the properties of the stock solution A do not change or the solid matter is not scraped out. In this case, when the amount of solid matter B deposited on the inner wall of the outer bowl 1 increases, the load on the inner screw 2 increases.

(2) The load on the inner body screw 2 increases, and the load current I
Becomes larger, the set value D and the upper limit value Dmax are compared, and until the set value D is reached, steady operation is performed.

(3) If the load current I of the inner screw 2 exceeds the set value D and further increases to the maximum upper limit value Dmax or more, the operation of the centrifuge becomes dangerous, and the operation is stopped via the safety device. Is done.

(4) The control for load reduction is performed in a range where the load current I of the inner screw 2 is larger than the set value D and smaller than the maximum upper limit value Dmax, the stock solution pump is stopped, and the stock solution A is transferred to the centrifuge. At the same time as the feeding is stopped, a low-speed rotation command is output to the inverter motor 4 that drives the outer bowl 1 to reduce the rotation speed of the outer bowl 1 and reduce the centrifugal force acting on the stock solution A inside. .

(5) In this state, the solids B accumulated on the inner wall of the outer bowl 1 are discharged.

If the load current value is still high even when the rotation speed of the outer body bowl is reduced, a command to increase the speed difference is output from the control device 8 to the speed difference motor 6, and the rotation of the inner body screw 2 is steadily operated. The rotation speed is reduced to the rotation speed equal to or lower than the rotation speed at the time, and the solid matter B is discharged outside.

(6) The outer bowl 1 of the centrifuge is set to the low speed state to discharge the solid matter B therein. During this time, the load current I of the inner screw 2 is detected and compared with the set value D. When the load current I becomes lower than the set value D, a speed increase command is output to the inverter motor 4 to return the rotation of the outer shell bowl 1 to the steady circuit, and an operation command is output to the stock solution pump. The operation is resumed, the stock solution A is supplied to the centrifuge, and the operation is returned to the steady operation. When the speed of the differential speed motor is changed, the rotation speed of the screw is returned to the normal rotation speed.

(7) Even after returning to the normal operation, the load current I of the inner body screw 2 is detected, and the same control is performed during the operation of the centrifuge.

When the outer bowl 1 and the like are returned to the normal operation after the discharge of the residual solid matter B by the inner body screw 2, the required time is set by a timer without detecting the load current I of the inner body screw 2. After the lapse of the set time, for example, after 3 to 5 minutes, the operation can be returned to the steady operation.

Further, after outputting the speed increasing command to return the outer bowl 1 to the steady operation, the time until the outer bowl 1 becomes the steady rotation is set by a timer. Supply can be started.

According to such a control method of the centrifugal separator, when the properties of the stock solution A change and the load on the inner screw 2 increases, the load current I of the inner screw 2 is minimized as in the related art. Without the upper limit value Dmax and the centrifuge being stopped, at the stage where the previous load current I became the set value D,
The solids B remaining in the outer shell bowl 1 can be discharged while the operation of the centrifuge is continued, and there is no need for decomposition or the like.

Further, the load of the inner screw 2 is detected by the current relay 9 and can be easily controlled by the control device 8 only by setting two values of the maximum upper limit value Dmax and the set value D. Is also easy to apply.

Further, when the solid matter B remaining in the outer body bowl 1 is discharged, the supply of the undiluted solution A is stopped without increasing only the rotation difference between the outer body bowl and the inner body screw 2, and the outer body bowl 1 Since the rotation is reduced, the operating state of the centrifuge does not become unstable.

Therefore, it is possible to increase the amount of remaining solids without interrupting the operation of the centrifuge due to the change in the properties of the stock solution A, and the flexibility of the centrifuge increases.

In the above embodiment, the internal screw load detection is performed by the current relay. However, a load detector such as a torque detector may be provided, and the load may be controlled in two stages according to the value.

In addition, although an inverter motor is used as a variable-speed prime mover for applying a centrifugal force to the outer-body bowl and a variable-speed prime mover for changing the rotation difference between the outer-body bowl and the inner-body screw, the present invention is not limited to this. Is fine.

Furthermore, changes may be made to each component without departing from the spirit of the present invention.

[Effects of the Invention] As described above in detail with the embodiment, according to the centrifuge control method of the present invention, the load on the inner body screw is detected, and the set value is smaller than the upper limit. Sometimes the feed of the undiluted solution is stopped, and the rotation of the outer shell bowl is slowed to reduce the centrifugal force, or the rotation difference of the inner screw is increased in this state and the inner screw remains by the inner screw. Since the solids are discharged to the outside, it is not necessary to interrupt the operation of the centrifuge, and it is possible to easily cope with an increase in the load.

In addition, by improving the scraping property, the centrifuge can be prevented from being overloaded, and the solid matter accumulated in the outer bowl can be scraped off relatively easily without being decomposed.

Further, since the control system is simply composed of the control device and the load detector of the inner screw, the reliability is high and the application to existing devices is easy.

[Brief description of the drawings]

1 and 2 relate to an embodiment of a control method of a centrifuge according to the present invention. FIG. 1 is a schematic configuration diagram of a control system.
The figure is a flowchart for explaining the control contents. FIG. 3 is a schematic sectional view of a screw decanter-type centrifuge according to an example of the controlled object of the present invention. 1: outer body bowl, 2: inner body screw, 3: gear box, 4:
Inverter motor (for outer bowl drive), 5: belt, 6:
Differential speed motor (for internal screw rotation), 7: Belt, 8: Control device, 9: Current relay (load detector), 10: Pinion pulley, D: Set value, Dmax: Maximum value, I: Load current .

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B04B 1/20 B04B 13/00

Claims (2)

(57) [Claims] 1. A centrifugal separator comprising: an outer body bowl which is driven to rotate to apply a centrifugal force to a stock solution; and an inner body screw provided in the outer body bowl and provided with a rotation difference to discharge separated solids. In controlling the machine, the load on the inner screw is detected, and when the load is greater than the steady-state value and reaches a predetermined set value lower than the upper limit of the current set value or torque set value of the safety device, the supply of undiluted liquid is performed. At the same time, the centrifugal force of the outer bowl is reduced by reducing the rotation speed of the outer bowl, and the remaining solids are discharged by the inner screw. A method for controlling a centrifugal separator, characterized in that the centrifugal separator is controlled to return to a normal operation. 2. The method for controlling a centrifuge according to claim 1, wherein the rotation speed of the outer shell bowl is reduced and the rotation difference between the outer shell bowl and the inner shell screw is increased.