JP2874295B2 - Multi-layer paper machine controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a control device for an apparatus for making paper by manufacturing.
In particular, the present invention relates to an improvement suitable for use in producing multilayer paper.

<Prior Art> The present applicant manufactures a control device of a paper machine for producing a single layer of paper known in, for example, Japanese Patent Publication No. 63-43513. Such a single-layer paper machine is capable of producing a large amount of paper at high speed, and is therefore used in large-scale paper mills. As another type of paper machine, there is a machine that produces paper by making multiple layers. Such a multi-layer paper machine uses low-cost pulp such as waste paper for the middle layer (called "anko") using high-quality pulp for the surface, and manufactures paper at a low raw material cost. Because of its relatively slow paper making speed, it is used in small and medium-sized paper mills.

FIG. 6 is a block diagram of a conventional multilayer paper machine, in which eight white water circulators (i) to (Viii) are arranged in series. In the figure, a seed box 1 contains seeds (raw materials) sent from a machine chest, and seed boxes 1a and 1c respectively contain white water circulators (i), (ii) and (Vii), (V
iii) is connected to take charge of the production of the surface layer, and the seed box 1b is connected to the white water circulators (iii) to (Vi) to take charge of the production of the bean paste. The seed valve 2 is a valve for taking out the raw material from the seed box 1, and sends the raw material liquid to the silo 4 via the air vent 3. The fan pump 5 sends the raw material liquid from the silo 4 to the nozzle 6. Here, the wire 7 is in a roll shape, and the pulp component of the raw material ejected from the nozzle 6 adheres, and the remaining portion is accommodated in the head 8. The felt 9 is a portion where the raw material attached to the wire 7 is stuck, and passes through the white water circulators (i) to (Viii) to form eight layers of base paper.
Then, the paper is compressed by a press part (not shown) to a predetermined paper thickness, dried through a dry part, glossed on the surface of the paper by a calendar, and wound around a reel.

In the apparatus configured as described above, the liquid amount supplied from the seed port valve 2 is controlled by the liquid level ΔP in the seed box 1. Therefore, there is a platform that the paper thickness of the layer in charge of each white water circulator tends to be non-uniform and the controllability is extremely poor.

FIG. 7 is an explanatory view of another conventional apparatus. Seed box 1b contains
The flow meter 11 and the flow valve 12 are inserted in place of the seed port valve 2, and the flow controller 10 makes the basis weight of the paper manufactured based on the basis weight signal detected by the basis weight meter (not shown) constant. Thus, each flow controller sends a valve opening control signal to the flow valve 11.

In the device configured as described above, the flow controller 10 controls the grammage of the bean based on the detection signal of the grammage meter. As a modified embodiment, there is a method of controlling the seed port valve 2 without using the flow valve 12, and a method of controlling the basis weight of the surface layer and the back layer instead of the bean paste.

<Problems to be Solved by the Invention> FIG. 8 is a perspective view showing the structure of paper manufactured by the above-mentioned conventional apparatus, and FIG. 9 is a sectional view. The basis weight of paper manufactured by a multilayer paper machine is 250 to 350 g / m ² , and the variation in basis weight is about 3% for a good machine and about 10% for a bad machine. Therefore, in order to secure a constant basis weight even in poor quality paper,
There is a first problem in that the amount of raw material used inevitably increases and the raw material cost increases.

The second problem relates to improvement in controllability of the basis weight. In the white water circulation system, the fiber (pulp) concentration in the seed box may change suddenly. At this time, according to the simple flow rate control, since the fiber concentration is simulated as being constant, the basis weight temporarily changes. In the conventional apparatus shown in FIG. 7, this change in grammage is detected by the grammage meter after a certain time constant, and the set value of the flow rate is changed again to control the target grammage. Therefore, it has been desired to improve controllability with respect to a change in the fiber concentration in the seed box.

A first object of the present invention is to provide a multi-layer paper machine control device with stable quality and low production cost by keeping the basis weight ratio of each layer constant. It is another object of the present invention to provide a paper machine control device in which a change in the basis weight is small even if the pulp concentration in the seed box changes.

<Means for Solving the Problems> FIG. 1 is a block diagram showing the configuration of the present invention for achieving the second object, and shows a case of a single layer for simplicity of explanation.
In the figure, the white water circulator runs from the seed box (1) to the pipeline (14).
The raw material is sent to the silo (4) through the sieve, and the white water contained in the silo is sent to the wire (7) through the fan pump (5).
To make the fibers adhere to the base paper attaching section (9). A paper machine has one or more white water circulators.

The paper machine control device includes a basis weight sensor (20) for measuring the amount of fibers attached to the base paper attachment portion, and a sensor for scanning the basis weight sensor in the width direction of the base paper being manufactured and collecting measured values. The control unit (30) calculates the fiber amount (MD) of the white water circulator from the flow rate (Q) of the white water flowing through the pipeline and the pulp concentration (C) of the white water, and the calculation cycle is determined by the white water. This deviation is satisfied from a deviation (ΔMD) between the basis weight detection value sent from the sensor control unit and a predetermined target value, and a fiber amount calculation unit (40) that takes about the time required to pass through the pipeline. A flow control unit (50) for calculating a white water flow rate necessary for the above based on the calculation result of the fiber amount calculation unit, and outputting a signal for controlling a flow rate flowing into the pipeline based on the calculation result. It is characterized by.

In the multi-layer paper machine control device, in order to keep the ratio of each layer constant, a fiber amount calculation unit (42) provided one-to-one with a control target of the white water circulator, and a fiber amount calculation unit And a contribution rate calculation unit (44) for calculating the contribution rate (Ki) of each target white water circulator from the total fiber amount borne by the white water circulators of the entire control target from the calculated fiber amount. .

<Operation> Each component of the present invention performs the following operation. The raw material flowing through the pipeline is self-equilibrium, and as the fiber concentration decreases (increases), the pipeline loss decreases (increases) and the flow rate increases (decreases), and thus flows substantially into the white water circulator. The amount of fiber will not change as much as the change in concentration in the seed box. But,
Since the conduit is relatively long and the flow rate is limited, a time delay occurs in the self-equilibrium. Therefore, the fiber amount calculation unit performs the calculation in batches at intervals of about the time required for the white water to pass through the pipeline, and the flow control unit also controls the valve opening in the pipeline in batches. The control cycle of the paper machine was substantially lengthened to prevent the overshoot of the grammage from becoming excessive, thereby improving the controllability of the grammage.

Since the contribution rate calculation unit 44 calculates the contribution rate Ki to the actual basis weight of each white water circulator, the flow rate control unit 50 controls the flow rate of the pipeline in accordance with the deviation from the target contribution rate and the control mode. By doing so, each layer is controlled to a constant ratio of the target contribution rate,
Variation in basis weight is reduced.

<Example> Hereinafter, the present invention will be described with reference to the drawings.

FIG. 2 is a configuration block diagram showing one embodiment of the present invention. In the figure, the white water circulator sends the raw material from the seed box 1 to the silo 4 via the pipe 14, sends the white water contained in this silo to the wire 7 via the fan pump 5, and feeds the base paper attachment portion (felt). The fibers are attached to the felt 9 and the fibers are sequentially attached to the felt 9. The pipe 14 has, for example, about 25 m, and the time required for the flow to be 25 seconds when the flow velocity is 1 m / s. The remaining white water containing the fiber that did not adhere to the wire 7 is collected in the bed 8 and returned to the silo 4. The grammage sensor 20 measures the amount of fibers adhering to the felt 9, and is installed at, for example, an outlet of a white water circulator at the last stage, or provided immediately before a reel. The sensor control unit 30 is a grammage sensor.
20 is to scan the width of the base paper being manufactured and collect the measured values. Scanning is performed in a cycle of about 30 seconds, and data processing is performed in units of this scanning.

The fiber amount calculation unit 42 determines the flow rate Qi (i:
It calculates the absolute dry fiber amount MDi of the white water circulator from the pulp concentration Ci of the white water and the pulp concentration Ci of the white water, and is given by the following equation.

MDi = Qi · Ci (1) Since this calculation cycle is about the time required for white water to pass through the pipe 14, the scanning cycle of the grammage sensor 20 is about the same as the white water pipe passing time. The timing is obtained from the scan signal of the sensor control unit 30. The fiber amount calculation unit 42 is provided one-to-one for each of the white water circulators to be controlled. The pulp concentration Ci may be simulated and set in the various boxes 1 to be constant, or may be measured using a densitometer. The flow rate Qi may be measured by the flow meter 15 provided in the pipe. The contribution rate calculation unit 44 calculates the contribution rate Ki of each target white water circulator from the total fiber amount borne by the white water circulator of the entire control target from the fiber amount 42 calculated by each fiber amount calculation unit, Calculate by the following formula.

Ki = BDi / ΣBDi (2) From the deviation ΔMD between the basis weight detection value sent from the sensor control unit 30 and the predetermined target value, the flow rate control unit 50 determines the white water flow rate necessary to satisfy this deviation by the contribution rate. The calculation is performed based on the calculation result of the calculation unit 44. The total control amount is a deviation ΔMD of the total basis weight, and a target contribution rate is specified in advance for each layer.
The total control amount is distributed to the respective white water circulators using the divergence direction or the divergence amount with respect to the contribution ratio Ki calculated in (1). From this calculation result, a signal for controlling the flow rate flowing through the pipeline of each white water circulator is output. For example, a valve opening signal is sent to a valve 16 provided in the pipeline 14. Here, the control mode selection unit 51 selects one of three types from a simple apportioning mode 52, a weighted apportioning mode 53, and an acceleration apportioning mode 54.

Next, each control mode will be described. FIG. 3 is an explanatory diagram of the simple apportioning mode. In this case, the middle three layers are to be controlled (AUT), and the remaining one surface layer and one back layer are manual operation (MAN). The equation used here is
It is given by the following equation.

数 Number of layers / k｝ · ΔMD (3) Here, 数 the number of layers is the total number of white water circulators connected in series to the felt 9, and h is the total number of white water circulators controlled by the flow controller 50, preferably When all the white water circulators are controlled, the basis weight of each layer becomes a constant ratio, which is convenient. In this example, the number of layers is 5 and k is 3. Only the layers in the AUT are controlled at the same ratio, and the total control amount is the control amount of the entire grammage.

FIG. 4 is an explanatory view of the weighted apportionment mode, in which the ratio of the amount of the absolutely dry fiber is calculated, and only the layers separated in the same direction from the target contribution are controlled by the same control amount. If it deviates in the reverse direction, control is performed in the reverse direction. The reason why the control amount is made stepwise is that good responsiveness can be obtained empirically, and is to cope with the nonlinearity of the system. The arithmetic expression is given by the following expression.

Ki · {number of layers / k} · ΔMD (4) The flow rate is set in advance from the target contribution rate Ki of each layer, and the flow rate control unit 50 controls the flow rate so as to reach the set flow rate. The control amount in each white water circulator is uniform.

FIG. 5 is an explanatory diagram of the accelerated apportionment mode, in which the ratio of the absolutely dry fiber amount is calculated and controlled by a control amount corresponding to the deviation amount deviating from the target contribution ratio. The operation expression is given by the following expression.

Ki · {number of layers / k} · ΔMD · G (5) The flow rate is set in advance from the target contribution rate Ki of each layer, and the flow rate control unit 50 controls the flow rate so as to reach the set flow rate. The control amount in each white water circulator changes the gain G according to the deviation.

When the grammage control is stable, the weighted apportioning mode is used, and when the disturbance is large, the accelerated apportioning mode is used. FIG. 10 is a cross-sectional view of the paper in a stable control state, in which the basis weight is specified in advance for each layer.

Next, self-equilibrium will be described. Returning to FIG. 1, assume that the liquid level difference H between the seed box 1 and the silo 4 is 4 m. In the line 14, the loss head due to the line resistance is 1.5 m when the fiber concentration C is 3.0%. Then, the effective head ΔP becomes 2.5 m. If the flow rate Q at this time is 20 m ³ / H, the total fiber amount is 0.
6000T / H. Now, it is assumed that the CV values have the following relationship.

Here, the CV value is an equation for calculating the valve diameter, and the diameter φ
Is 1 inch and gives a flow rate when ΔP is 1 pound (= 0.07 m).

Here, it is assumed that the fiber concentration C decreases by 0.10% to 2.90%. Then, the loss head due to pipeline resistance is reduced by 7.24% to 1.5 / 1.0724 = 1.40m. Then, ΔP is next to 2.60m, the flow rate Q is a 20.4 ³ / H, total fiber amount is 0.5916T / H. Therefore, even if the fiber concentration is reduced by 3.33% from the original concentration to 2.90%, the fiber amount is reduced only by 1.40%. Conversely, suppose that the fiber concentration C increases by 0.10% to 3.10%. Then, the loss head due to pipeline resistance increases by 7.24% to 1.5 × 1.0724 = 1.61 m. Then ΔP is 2.39
m, the flow rate Q becomes 19.6 ³ / H, and the total fiber amount is 0.6064.
T / H. Therefore, the fiber concentration is 3.3
A 3% increase to 2.90% would only increase fiber content by 1.40%. When the flow rate control is performed as shown in FIG. 7, it is understood that the basis weight changes later by the amount of change in the fiber concentration, and the stability of the basis weight is inferior.

<Effect of the Invention> As described above, according to the present invention, the fiber amount calculation unit 4
Since 0 and 42 are calculated in batches using the scan cycle of the grammage sensor, the change in fiber concentration in the seed box is alleviated by utilizing the self-equilibrium of white water, and the stability of grammage is improved. In addition, since the calculation is performed in batches, the fiber amount calculation units 40, 4
The calculation load of 2 and the calculation load of the flow control unit 50 can be reduced.

When a plurality of white water circulators are provided, the contribution ratio calculator 44 calculates the actual contribution ratio Ki to the basis weight of each white water circulator, and the flow rate controller 50 calculates the deviation from the target contribution ratio. And the flow rate of the pipe line 14 according to the control mode is controlled, so that each layer is controlled to a constant ratio of the target contribution rate, the variation in the basis weight is reduced (for example, about 1% of the total basis weight), and the manufacturing cost is reduced. descend.

[Brief description of the drawings]

FIGS. 1 and 2 are block diagrams showing the construction of the present invention, FIGS. 3 to 5 are explanatory views of the control mode of the flow control unit 50, FIGS. 6 and 7 are explanatory views of a conventional apparatus, and FIGS. FIG. 10 to FIG. 10 are explanatory views of the cross section of the multilayer paper. 1 ... seed box, 4 ... silo, 5 ... fan pump, 7 ...
... wire, 9 ... felt (base paper adhesion part). 20 ... Basic weight sensor, 30 ... Sensor control unit, 40,42 ... Fiber amount calculation unit, 44 ... Contribution ratio calculation unit, 50 ... Flow control unit.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) D21F 7/06 D21F 1/74 D21F 11/08

Claims (1)

(57) [Claims] A raw material is sent from a seed box (1) to a silo (4) via a pipe (14), and white water contained in the silo is sent to a wire (7) via a fan pump (5). An apparatus for controlling a paper machine in which a plurality of white water circulators for adhering fibers to a base paper adhering section (9) are arranged in series, wherein a basis weight sensor (20) for measuring the amount of fibers adhering to the base paper adhering section; A sensor controller (30) that scans the basis weight sensor in the width direction of the base paper being manufactured and collects measurement values; a flow rate (Qi) of white water flowing through the pipeline; and a pulp concentration of the white water. From (Ci), the fiber amount (MDi) of the white water circulator is calculated, and this calculation cycle is set to about the time required for white water to pass through the pipeline, and the control target of the white water circulator is determined. The fiber amount calculation unit (4
2) and a contribution rate calculation unit that calculates the contribution rate (Ki) of each target white water circulator from the total fiber amount borne by the white water circulator of the entire control target from the fiber amount calculated by each fiber amount calculation unit. (44) and, based on a deviation (ΔMD) between the basis weight detection value sent from the sensor control unit and a predetermined target value, a white water flow rate required to satisfy this deviation is calculated by the contribution ratio calculation unit. A flow control unit (50) for calculating a flow rate based on the calculation result and outputting a signal for controlling a flow rate flowing through the pipeline of each of the white water circulators.