JP2000160490A - Method and apparatus for controlling operation of concentration control type head box of paper machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a high-concentration raw material not to flow backward to the flow rate control valve side of a low-concentration raw material in starting and shut-down and to independently control a total head and a flow rate ratio in an operation using a concentration control type head box. SOLUTION: In starting an operation, an auxiliary pump 21 and a main pump 2 are driven in this order. After the flow rate ratio of the high- concentration raw material 5 to the low-concentration raw material 5a reaches a set value of operation, a total head control is carried out and simultaneously a flow rate ratio is controlled so as to maintain the set value of operation of the flow rate ratio. When the operation is shut down, the main pump 2 and the auxiliary pump 21 are stopped in this order. In an ordinary control, the total head and the flow rate ratio are separated and controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation control method and apparatus capable of independently controlling a flow ratio and a total head of a density control type head box of a paper machine.

[0002]

2. Description of the Related Art As shown schematically in FIG. 3, an example of a wet section of a paper machine has a mesh section (WP) and a press section (not shown) downstream thereof. WP), the upstream side of the raw material supply pipe 3 in which the main pump (fan pump) 2 is installed in the middle is connected to the raw material silo 4 and the downstream side is connected to the main header 8, and the raw material is supplied by the operation of the main pump 2. The raw material 5 in the silo 4 is sucked and discharged, and the discharged raw material 5 is supplied from the main header 8 to the head box 1 and the head box 1
It is made to flow out as a film-like water flow (jet).

[0003] The head box 1 is provided with a slice 12 at a front upper portion of a mixing chamber 9 through a dispersion branch pipe 11 for dispersing the fibers in the raw material 5 so as not to aggregate.
And the mixing chamber 9
The main header 8 is connected to the lower end of the main body 8 via a number of coarse branch pipes 10 arranged in the width direction. The raw material 5 supplied from the main header 8 to the head box 1 passes through the distribution branch pipe 11, and then is sliced. 12 so that it can be allowed to flow onto the grate 6.

[0004] In the above-mentioned crossing part (WP),
A total head detector 13 installed at the width end of the slice 12 for detecting the pressure (total head) in the head box 1 and a setting device 1 for determining a target value of the total head
And a 4, comprising a differential pressure gauge 15 for determining the pressure difference by comparing the said total head setting value set in the total head detection value TH ₁ and setter 14 from total head detector 13 (pneumatic) TH ₀ Further, a bypass line 16 provided with a sub-valve 17 as a total head control valve is provided midway between the upstream and downstream portions of the main pump 2 of the raw material supply pipe 3 so that the differential pressure obtained by the differential pressure gauge 15 is reduced. A controller 7 for sending an opening adjustment command to the sub-valve 17 based on the
, The discharge flow rate of the raw material 5 to be supplied from the main pump 2 to the main header 8 is finely adjusted by adjusting the flow rate of the raw material 5 to bypass the bypass line 16. ,
The total head of the raw material 5 in the head box 1 is controlled so as to be always at a set value. Conventionally, the total valve for controlling the sub-valve 17 for the purpose of finely adjusting the discharge pressure by one main pump 2 is conventionally used. Only the head control is performed automatically.

In recent years, in the head box 1 in which the total head is controlled as described above, the concentration of the raw material 5, that is, the basis weight can be adjusted without adversely affecting the fiber orientation. Is being developed.

FIG. 4 shows an example of this. In a configuration similar to that shown in FIG. 3, a subheader 18 is connected to the rear side of each coarse branch pipe 10 of the head box 1 via a distribution pipe 19. Then, a flow control valve 20 is attached to each distribution pipe 19, and a downstream end of a low-concentration raw material supply pipe 22 in which a sub-pump (fan pump) 21 is installed is connected to the sub-header 18. Concentration raw material supply pipe 2
2 is connected to a low-concentration raw material silo 23 for storing a low-concentration raw material 5a such as white water, and the high-concentration raw material 5 from the main header 8 is passed through each coarse branch pipe 10 into the mixing chamber 9. And the low-concentration raw material 5a from the sub-header 18 is introduced into the coarse branch pipe 10 through the distribution pipe 19, whereby the coarse branch pipe 10
The high-concentration raw material 5 and the low-concentration raw material 5a are mixed therein, and the concentration is adjusted.
At this time, the concentration of the raw material 5 ', that is, the basis weight, can be controlled by changing the mixing amount of the low-concentration raw material 5a by adjusting the flow control valve 20.

[0007]

However, when the concentration control type head box 1 as shown in FIG. 4 is used, the operations of the main pump 2 and the sub pump 21 interfere with each other.
Not only is it impossible to perform the total head control as shown in FIG. 3 automatically, but also when the operation is started up or shut down, the high-concentration raw material 5 flows back to the flow control valve 20 side. This may cause a problem that fiber chips adhere to the flow control valve 20 and cause clogging.

Accordingly, the present invention enables the flow rate ratio between the high-concentration raw material and the low-concentration raw material and the control of the total head to be stably performed using the concentration control type head box, An object of the present invention is to provide a method and apparatus for controlling the operation of a concentration control type head box of a paper machine in which a high-concentration raw material does not flow back to a flow control valve provided on a sub-header side during lowering.

[0009]

According to the present invention, in order to solve the above-mentioned problems, a raw material discharged from a main pump is supplied from a main header to a head box, and a low-concentration raw material discharged from a sub-pump is supplied to a sub-header. In the method and apparatus for controlling the operation of a concentration control type head box of a paper machine, the raw material is supplied to the head box through a plurality of distribution pipes with a flow control valve to adjust the raw material concentration, and to be discharged from the slice of the head box. The rotation speeds of the main pump and the sub-pump are adjusted during the operation start-up control, the normal control, and the operation shutdown control. Drive the pump to increase the rotation speed, and the flow rate ratio between the high-concentration raw material from the main pump and the low-concentration raw material from the sub-pump is a predetermined value. Flow rate control is performed by adjusting the rotation speeds of both pumps so that the total head of the head box is detected during normal control, and control is performed by obtaining the differential pressure between the detected value and the set value using a differential pressure gauge. The total head control and the flow rate ratio control are performed separately, and the drive of the main pump is stopped before the drive of the sub-pump is stopped during the operation shutdown control. Here, the low-concentration raw material includes not only white water but also water alone. Hereinafter, the low-concentration raw material is used in the present invention in this sense.

The control of the start and the end of the operation, in which the main pump is driven later when the operation is started and the main pump is stopped first when the operation is stopped, is separated from the normal control for controlling the total head. Thereby, stable operation can be performed without causing a backflow of the raw material to the flow control valve side.

During normal control, when the flow ratio from the main pump and the sub-pump is within the allowable range and the total head is out of the allowable range, the main pump and the sub-pump are maintained with the operation set value of the flow ratio maintained. The total head coarse adjustment control that adjusts the rotation speed and roughly adjusts the discharge pressure is performed, or during normal control, the flow rate ratio of the high-concentration raw material to the low-concentration raw material is within the allowable range when the total head is within the allowable range. If the flow rate is out of the allowable range, the main pump and the sub-pump are adjusted to rotate at different speeds to adjust the flow rate. The total head control valve is fine-tuned by adjusting the total head control valve based on the differential pressure value obtained by the differential pressure gauge. By the, it is possible to stably control the total head and flow rate ratio.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a method and an apparatus for controlling the operation of a density control type head box of a paper machine according to the present invention. As shown in FIG. In the configuration in which the sub-valve 17 is controlled to perform total head control for the purpose of fine adjustment of ', motors 24 and 25 each having a rotation speed adjusting function are connected to the main pump 2 and the sub-pump 21, respectively. Further, a flow meter 26 is provided in the middle of the raw material supply pipe 3 connecting the main pump 2 and the main header 8, and a flow meter 27 is provided in the middle of the low concentration raw material supply pipe 22 connecting the sub pump 21 and the sub header 18. Further, comparing the detection values of the flow meters 26 and 27, the high-concentration raw material 5 discharged from the main pump 2 and the low-concentration raw material 5a discharged from the sub-pump 21 are compared. And a comparator 30 for comparing the flow ratio calculated by the flow ratio calculator 28 with the flow ratio operation set value set by the flow ratio setter 29. The controller 7 has a function of transmitting a drive command to the motor 24 of the main pump 2 and the motor 25 of the sub-pump 21 based on the value obtained by the comparator 30.

Next, the operation of the head box 1 will be described with reference to FIG.
This will be described with reference to (a), (b), and (c). Note that FIG.
In (a), RM is the rotation speed of the main pump 2, RS
2 (b), QM indicates the discharge flow rate of the high-concentration raw material 5 from the main pump 2, QS indicates the discharge flow rate of the low-concentration raw material 5a from the sub-pump 21, and FIG. In (c), TH is slice 12
5 shows the total head of the raw material 5 'flowing out of the apparatus.
2A, 2B and 2C, A is a start-up control range including a first process section I, a second process section II, a third process section III, and a fourth process section IV. A normal control (total head control) range including five process parts V, and C indicates a fall control range including the sixth process part VI and the seventh process part VII.

First, in the start-up control range A, first, the sub-pump 21 is driven to start up to a required rotational speed (first process section I). When the sub-pump 21 reaches a certain rotation speed, the main pump 2 is driven to increase the rotation speed of the main pump 2 so that the flow rate from the sub-pump 21 and the main pump 2 becomes the initial startup set value x. Yes (second
Process Division II). Subsequently, the rotation speed of the main pump 2 is gradually increased, and the rotation speed of the sub-pump 21 is gradually reduced so that the flow rate becomes the intermediate startup set value y (third process section III). When the flow rate ratio between the main pump 2 and the sub-pump 21 reaches the set value y, the control is switched to flow rate control by the main pump 2 and the sub-pump 21 so that the flow rate becomes the operation set value z (fourth process unit I).
V).

Next, as described above, the control is switched to the normal control when the flow rate ratio reaches the operation set value z.
In this case, in the normal control range B, the flow rate QM of the high-concentration raw material 5 discharged from the main pump 2 is detected by the flow meter 26, and the flow rate QS of the low-concentration raw material 5a discharged from the sub-pump 21 is detected by the flow meter 27. These values are input to the flow ratio calculator 28 to calculate the flow ratio. The calculated value is compared with the operation set value z set by the flow ratio setter 29. Is exceeded, the drive command is sent to the motors 24 and 25 by the command from the controller 7, the rotation speeds of the main pump 2 and the sub pump 21 are controlled, and the flow ratio control is performed. When the total head is out of the condition and the total head is out of the condition, a command is given to the motors 24 and 25 by a command from the controller 7 so that the rotation speeds of the main pump 2 and the sub pump 21 are increased and decreased, and the discharge pressure is reduced. Coarse total head coarse adjustment control for (discharge pressure increase, decrease control) of and controls the sub-valve 17 by total head control for fine adjustment of the discharge pressure is carried out (step 5 section V).

As described above, in the normal control range B, the flow rate ratio control and the total head coarse adjustment control for coarsely adjusting the discharge pressure and the total head control for finely adjusting the discharge pressure are performed. Is required to perform case-by-case control.

More specifically, first, when both the total head and the flow rate ratio are within the set conditions, the differential pressure gauge 1 is used while keeping the rotation speeds of the main pump 2 and the sub pump 21 as they are.
5, the sub-valve 17 is controlled by a command from the controller 7 to perform total head control.

Next, when the total head is within the set conditions and the flow rate ratio deviates from the operation set value z and falls outside the allowable conditions, the rotational speeds of the main pump 2 and the sub pump 21 are individually increased or decreased. , The flow ratio is controlled so that the flow ratio is within the conditions.

Furthermore, there is the flow rate ratio is the condition, if the total head is out conditions, i.e., in FIG. 2 (c), the upper limit value TH _u and a lower limit greatly deviated total head TH from the set value TH ₀ If it exceeds any value TH _d, the coarse adjustment of the discharge pressure both increase or decrease the rotational speed of the main pump 2 and the subordinate fuel pump 21, the total head coarse adjustment as add total head TH in condition Control is performed.

If the total head and the flow rate ratio are out of the conditions, the flow rate control is performed.

On the other hand, when ending the normal control as described above, a shutdown is performed. In the fall control range C, first, the drive of the main pump 2 is stopped to reduce the rotation speed to zero (sixth process section VI). After a certain time elapses after the rotation speed of the main pump 2 becomes zero, the sub pump 2
1 to stop the rotation speed to zero (the seventh
Process part VII).

As described above, according to the present invention, the drive of the main pump 2 and the sub-pump 21 at the time of start-up and shut-down of the operation is separated from the normal control.
Backflow to the flow control valve 20 side can be prevented,
In addition, since the total head control and the flow ratio control are divided into cases during normal control, stable operation can be performed.

[0024]

As described above, according to the method and apparatus for controlling the operation of the head box section of a paper machine according to the present invention, the raw material discharged from the main pump is supplied from the main header to the head box and discharged from the sub pump. A low-concentration raw material is supplied from the sub-header to the head box through a plurality of distribution pipes with a flow control valve to adjust the concentration of the raw material, and is discharged from a slice of the head box. In the operation control method and apparatus, the rotation speeds of the main pump and the sub-pump are adjusted during operation start-up control, during normal control, and during operation shutdown control, and during the start-up control, the sub-pump is driven to be constant. Drive the main pump to increase the number of revolutions.The high-concentration material from the main pump and the low-concentration The flow ratio control is performed by adjusting the rotation speeds of both pumps so that the flow ratio with the raw material becomes a predetermined value.In normal control, the total head of the head box is detected and the difference between the detected value and the set value is detected. The total head control for obtaining and controlling the pressure with a differential pressure gauge and the flow rate control are performed separately, and the operation of the main pump is stopped and then the operation of the sub-pump is stopped during the operation shutdown control. Therefore, when starting up or shutting down the operation, the high-concentration raw material does not flow backward to the flow control valve side, and it is possible to prevent clogging due to the adhesion of fiber waste, and at the time of normal control, When the flow ratio from the main pump and the sub pump is within the allowable range and the total head is out of the allowable range, the rotation speed of the main pump and the sub pump is adjusted while maintaining the operation set value of the flow ratio. The total head coarse adjustment control to make coarse adjustment of the discharge pressure is performed by using the total head within the allowable range during normal control. When it is off, adjust the rotation speed of the main pump and sub-pump to perform flow ratio control to correct the flow ratio.
When both the flow rate ratios are within the allowable range, the total head control valve is adjusted based on the differential pressure value obtained by the differential pressure gauge to perform the total head control for finely adjusting the discharge pressure, so that the main pump can be used. Automatic control of the total head can be performed while controlling the flow ratio of the high-concentration raw material discharged and the low-concentration raw material discharged from the sub-pump, whereby stable operation can be performed.
Demonstrate excellent effects such as.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of an operation control device for a density control type head box of a paper machine according to the present invention.

FIG. 2 shows the operation status of a concentration control type head box of a paper machine, in which (a) shows a change in the number of rotations of a pump,
(B) is a diagram showing the transition of the raw material flow rate, and (c) is a diagram showing the transition of the total head.

FIG. 3 is a schematic view showing an example of a conventional screen making machine.

FIG. 4 is a schematic diagram showing another example of the conventional papermaking machine screen net.

[Explanation of symbols]

 Reference Signs List 1 head box 2 main pump 3 raw material supply pipe 5 raw material (high-concentration raw material) 5a low-concentration raw material 5 'raw material 7 controller 8 main header 9 mixing chamber 11 dispersion branch pipe 12 slice 13 total head detector 14 total head setting device 15 Differential pressure gauge 17 Sub valve (total head control valve) 18 Sub header 19 minute pipe 20 Flow control valve 21 Sub pump 26,27 Flow meter 28 Flow ratio calculator 29 Flow ratio setting device 30 Comparator

Claims (5)

[Claims] 1. A material discharged from a main pump is supplied from a main header to a head box, and a low-concentration material discharged from a sub pump is supplied from the sub header to the head box through a plurality of distribution pipes with a flow control valve. In the operation control method of the concentration control type head box of the paper machine in which the concentration of the raw material is adjusted to flow out of the slice of the head box, the rotation speeds of the main pump and the sub pump are set at the time of the operation start-up control and the normal operation. During the start-up control, the sub-pump is driven to a certain number of revolutions, and then the main pump is driven to increase the number of revolutions. The flow rate ratio control is performed by adjusting the rotation speed of both pumps so that the flow rate ratio between the raw material and the low-concentration raw material from the sub-pump becomes a predetermined value. At the time of control, the total head control that detects the total head of the head box and obtains and controls the differential pressure between the detected value and the set value with a differential pressure gauge, and the flow rate ratio control are performed separately. An operation control method for a density control type head box of a paper machine, wherein the operation of the main pump is stopped before the operation of the sub-pump is stopped during the operation shutdown control. 2. In normal control, when the flow ratio from the main pump and the sub-pump is within the allowable range and the total head is out of the allowable range, the main pump and the sub-pump are maintained with the operation set value of the flow ratio maintained. 2. The operation control method for a density control type head box of a paper machine according to claim 1, wherein a total head coarse adjustment control for adjusting a discharge speed by adjusting a rotation speed is performed. 3. During normal control, when the total head is within the allowable range and the flow ratio of the high-concentration raw material to the low-concentration raw material is out of the allowable range of the operation set value, the rotational speeds of the main pump and the sub-pump are adjusted. 2. The operation control method for a density control type headbox of a paper machine according to claim 1, wherein the flow rate control for correcting the flow rate ratio is performed by performing the control. 4. A total head control for finely adjusting a discharge pressure by adjusting a total head control valve based on a differential pressure value obtained by a differential pressure gauge when both a total head and a flow rate ratio are within allowable ranges during normal control. The operation control method for a density control type head box of a paper machine according to claim 1, wherein the operation is performed. 5. A total head detector provided at a width end of said slice of a head box for supplying a raw material discharged from a main pump through a main header and a plurality of coarse branch pipes and causing the raw material to flow out of the slice. A differential pressure gauge for comparing a total head detection value by the total head detector with a total head set value, and an opening degree to a total head control valve provided in a bypass line of the main pump based on a value obtained by the differential pressure gauge. And a controller for sending an adjustment command, and a subheader connected to the subpump is connected to each of the coarse branch pipes via a distribution pipe, and a flow control valve is attached to each of the distribution pipes, and A flow ratio calculator for calculating the flow ratio between the high-concentration raw material discharged and the low-concentration raw material discharged from the sub-pump, and the value and the flow ratio of the flow ratio calculator A comparator for comparing the operation set value with the operation set value; and further, the controller has a function of sending a command to adjust the rotation speed of the main pump and the sub pump based on the value obtained by the comparator. An operation control device for a density control type head box of a paper machine, characterized by having a configuration.