JP2004139235A - Method for stable operation at the start of fluid process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stable operation at the start of a fluid process which can stabilize the start-up control of the fluid process at its operation start. <P>SOLUTION: The method for stable operation is constituted such that the computation output value of a PID computation part 18 during the last stable operation before the operation start of a filtration process is stored in a PID computation output value storage part 22 at any time, the latest computation output value is fixed and applied for a predetermined time as a computation output value at the operation start of an upcoming filtration process, and then, the operation is switched to a PID automatic control operation. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stable operation method when starting operation of a fluid process such as a liquid or a gas, and more particularly to a stable operation method suitable for starting operation of a filtration process of a filtration device including a control interference system. is there.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in automatic control of a fluid process such as liquid or gas, an on / off operation, a proportional operation (hereinafter, simply referred to as “P operation”), and an integral operation (Integral; , Simply referred to as "I operation"), a differential operation (hereinafter, simply referred to as "D operation"), and a PI operation or a proportional operation / integration operation in which a proportional operation / integral operation is simultaneously performed. A control is performed in which the measured value is made to coincide with the target value in a short time and stably using a PID operation or the like in which all the differential operations are performed at the same time, and a deviation generated by disturbance is eliminated as soon as possible.
[0003]
Also, a multi-PID operation has been proposed in which a plurality of PID constants (proportional band PB, integration time T _I , differentiation time T _D ) are switched according to a measured value or a target set value, and a combination of a plurality of target values and a PID constant is proposed. May be stored in the controller and recalled and used as needed (for example, see Non-Patent Document 1).
[0004]
In addition, in the cross-flow type microfiltration or ultrafiltration processing method in which the filtration is performed while circulating the undiluted solution, the input pressure of the undiluted solution to the filtration membrane is changed at the time of backwashing, air bubbling, or switching from the stopped state to the filtration processing start. There has also been proposed one that performs low-pressure operation for a predetermined time to protect the filtration membrane and perform stable operation (for example, see Patent Document 1).
[0005]
[Non-patent document 1]
Published by The Energy Conservation Center, Publishing Division, published February 5, 1992, Hiroshi Matsuyama, "Automatic control that anyone can understand", p. 85
[Patent Document 1]
JP-A-10-33957
[Problems to be solved by the invention]
However, in the above-described conventional example, when there are a plurality of control points to be controlled in the fluid process and interfere with each other, the control becomes unstable when the individual PID control is started up. There has been a problem that operation becomes impossible due to an abnormality.
[0007]
An object of the present invention is to solve the above-described problem, and an object of the present invention is to provide a stable operation method at the start of a fluid process that can stabilize start-up control at the start of operation of a fluid process. is there.
[0008]
[Means for Solving the Problems]
The stable operation method at the start of the fluid process according to the present invention for achieving the above object is a stable operation method at the start of the operation of the fluid process, and is performed when the stable operation is performed immediately before the start of the operation of the fluid process. The operation output value of the controlled object is stored as needed, the latest operation output value is fixed for a predetermined time as the operation output value at the start of the next operation of the fluid process, and then switched to a predetermined automatic control operation. And
[0009]
Since the present invention is configured as described above, the calculated output value during the previous stable operation is stored as needed, and the latest calculated output value is used as the calculated output value at the start of the next operation of the fluid process for a predetermined time. By fixing, the start-up control at the start of the operation of the fluid process can be stabilized, and by switching to a predetermined automatic control operation such as PID control at the stage of stabilization, the PID control can be performed from a fixed state close to the stable operation. , Etc., can be stably switched in a state where the deviation when switching to the predetermined automatic control operation is small, and the stable operation can be continued.
[0010]
Further, the stable operation method at the start of the fluid process can be effectively applied to a filtration process of a filtration device including a control interference system in which a plurality of control points to be controlled interfere with each other.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in the drawing, as an example of a stable operation method at the start of a fluid process according to the present invention, a fluid process is applied to a filtration process of a filtration device including a control interference system in which a plurality of control points to be controlled interfere with each other. One embodiment of the case will be specifically described.
[0012]
FIG. 1 is a diagram showing an example of the configuration of a filtration device to which a stable operation method at the start of a fluid process according to the present invention is applied, and FIG. 2 is control for implementing the stable operation method at the start of a fluid process according to the present invention. It is a block diagram of a system.
[0013]
FIG. 3 is a diagram showing control characteristics of a stock solution, a filtrate, and a stock solution that are control interference systems in a filtration device to which the stable operation method at the start of a fluid process according to the present invention is applied. FIG. It is a figure explaining an example of the filtration process in the filtration device shown.
[0014]
The filtration device shown in FIG. 1 is configured as a cross-flow type precision or ultrafiltration device that performs filtration while circulating undiluted liquid such as river water, lake water, groundwater, or seawater. A control interference system is constituted by automatically controlling the undiluted solution, the filtrate and the undiluted solution of the circulating system by the respective PID controls.
[0015]
In FIG. 1, reference numeral 1 denotes a stock solution tank, and reference numeral 2 denotes a stock solution supply pump for sending stock solution 1 a stored in the stock solution tank 1 to a filtration membrane module 4 via a stock solution pipe 3.
[0016]
An undiluted solution supply motor-operated valve 5 is provided in the undiluted solution pipe 3 from the undiluted solution supply pump 2 to the filtration membrane module 4 so that the opening area of the flow path can be continuously changed and controlled. A pressure sensor 6 serving as a detection unit is disposed downstream of the flow path.
[0017]
Reference numeral 7 denotes a calculation control unit that calculates an operation signal based on a pressure signal of the stock solution 1 a flowing through the stock solution pipe 3 detected by the pressure sensor 6 and controls the stock solution supply motor-operated valve 5.
[0018]
Reference numeral 4 denotes a filtration membrane module, in which a hollow fiber-shaped filtration membrane is accommodated in a case, and a plurality of filtration membrane modules 4 are actually connected in parallel to constitute a filtration membrane unit.
[0019]
When the undiluted solution 1a is supplied from the undiluted solution pipe 3 to the filtration membrane module 4, it is permeated from the outside to the inside of the hollow fiber membrane provided in the filtration membrane module 4 or permeated from the inside to the outside and filtered. The filtrate 9a is led to the filtrate pipe 8 and stored in the filtrate tank 9.
[0020]
In the filtrate pipe 8 from the filtration membrane module 4 to the filtrate tank 9, there is provided a filter motorized valve 10 capable of continuously changing and controlling the opening area of the flow path. An electromagnetic flowmeter 11 serving as a detection unit is disposed on the upstream side of the flow path.
[0021]
Reference numeral 12 denotes a calculation control unit that calculates an operation signal based on a flow signal of the filtrate 9 a flowing through the filtrate pipe 8 detected by the electromagnetic flow meter 11, and controls the motorized filtration valve 10.
[0022]
On the other hand, a part of the stock solution 1 a supplied from the stock solution pipe 3 to the filtration membrane module 4 flows through the outside or inside of the hollow fiber membrane of the filtration membrane module 4 as a circulating stock solution, and is led to the stock solution return pipe 13, and the stock solution tank It returns to 1.
[0023]
The undiluted liquid return valve 13 that can be controlled by continuously changing the opening area of the flow path is provided in the undiluted liquid return pipe 13 from the filtration membrane module 4 to the undiluted liquid tank 1. An electromagnetic flowmeter 15 serving as a detection unit is disposed on the upstream side of the flow path.
[0024]
Reference numeral 16 denotes a calculation control unit that calculates an operation signal based on a flow signal of the circulating return stock solution flowing through the stock solution return pipe 13 detected by the electromagnetic flow meter 15, and controls the stock solution return electric valve 14.
[0025]
Next, a configuration of a control system for implementing a stable operation method at the start of a filtration process will be described as an example of a fluid process according to the present invention with reference to FIG. In FIG. 2, each of the arithmetic control units 7, 12, and 16 is provided with a target value setting unit 17 that constitutes an input unit such as a touch panel. In the target value setting unit 17, for example, “0 to 4000” , "0-8000", and "0-12000".
[0026]
Reference numeral 18 denotes a PID calculation unit in which PID constants (proportional band PB, integration time T _I , differentiation time T _D ) are set in advance according to the target set value. As an example of the PID constant, P = 0.2, I = 0.1, D = 0.05 and the like are set.
[0027]
For these PID constants, the PID constant at the time of stable operation immediately before the start of the operation of the fluid process is stored, and the PID constant may be adopted as the PID constant at the start of the next operation of the fluid process. I can do it.
[0028]
The PID calculation unit 18 calculates the digital value input by the target value setting unit 17 according to the proportional operation / integral operation / differential operation, for example, “0-4000”, “0-8000”, “0” A predetermined digital value in the range of "12000" is output.
[0029]
The digital value output from the PID operation unit 18 is converted to an analog value by a D / A (digital / analog) conversion unit 19.
[0030]
For example, when controlling the current value as an analog value in the range of “4 mA to 20 mA”, digital values in the range of “0 to 4000”, “0 to 8000”, and “0 to 12000” are equally divided. When the current value and the digital value are associated with each other, and the voltage is controlled as an analog value in a range of “1 V to 5 V”, each of the ranges of “0 to 4000”, “0 to 8000”, and “0 to 12000” The digital value can be equally divided to associate the voltage value with the digital value.
[0031]
Then, an operation signal consisting of an analog value such as a current value or a voltage value output from the D / A conversion unit 19 is transmitted to the undiluted liquid supply electric valve 5, the filtration electric valve 10, the undiluted liquid return electric valve 14, the undiluted liquid supply, and the like. The flow is transmitted to a control unit such as a frequency adjuster of an inverter that controls the pump 2 to control the flows of the stock solution 1a, the filtrate 9a, and the returned stock solution, respectively.
[0032]
On the other hand, the pressure sensor 6 provided in each of the stock solution pipes 3, the filtrate solution pipe 8, and the stock solution return pipe 13, and the pressure of the stock solution 1 a flowing through the stock solution pipe 3 in the detection unit including the electromagnetic flowmeters 11 and 15, The flow rate of the filtrate 9a flowing through the undiluted liquid return pipe 13 and the undiluted liquid is detected as a measured value composed of an analog value such as a current value or a voltage value.
[0033]
The measured analog value is detected in, for example, a current value range of “4 mA to 20 mA” or a voltage value range of “1 V to 5 V”, and a digital value is detected by an A / D (analog / digital) conversion unit 20. Is converted to
[0034]
For example, when the current value is detected as an analog value in the range of “4 mA to 20 mA”, the digital value in the range of “0 to 4000”, “0 to 8000”, and “0 to 12000” is equally divided. When a current value and a digital value are associated with each other, and a voltage value is detected as an analog value in a range of “1 V to 5 V”, each of “0 to 4000”, “0 to 8000”, and “0 to 12000” The digital value of the range can be equally divided to associate the voltage value with the digital value.
[0035]
The digital value output from the A / D conversion unit 20 is compared in the comparator 21 with the digital value output from the target value setting unit 17 and input to the PID calculation unit 18 so that the deviation becomes “0”. The digital value to be input is appropriately modified. The above is the routine when the PID is automatically controlled.
[0036]
Reference numeral 22 denotes a PID calculation output value storage unit that stores a digital value serving as a calculation output value output from the PID calculation unit 18 as needed. The PID calculation output value stored as needed is input to the D / A conversion unit 19. It is configured to be able to.
[0037]
That is, as an example of the fluid process, when starting the operation of the filtration process of the filtration device shown in FIG. 1, the undiluted solution flowing through the undiluted solution pipe 3 to be controlled at the time of stable operation immediately before the start of the operation of the filtration process 1a, the latest calculation in the PID calculation output value storage unit 22 which stores the calculation output values of the PID calculation unit 18 for controlling the flow of the filtrate 9a flowing through the filtrate pipe 8 and the return stock solution flowing through the stock solution return pipe 13 as needed. The output value is fixed as a calculated output value at the start of the operation of the next filtration process for a predetermined time T, and thereafter, is switched to a PID automatic control operation which is a predetermined automatic control operation.
[0038]
Then, when the operation of the filtration process of the filtration device shown in FIG. 1 is started, the latest operation output value stored in the PID operation output value storage unit 22 when the stable operation was performed immediately before the operation of the filtration process was started. Is input to the D / A converter 19, and is fixed to the digital value for a predetermined time T.
[0039]
During this time, the digital value output from the PID operation unit 18 is stored in the PID operation output value storage unit 22 at any time, but is not input to the D / A conversion unit 19, and the D / A conversion unit 19 A fixed digital value that is the latest calculation output value when the stable operation was performed last time is input from the calculation output value storage unit 22.
[0040]
After a predetermined time T elapses, the fixed digital value output from the PID calculation output value storage unit 22, which is the latest calculation output value at the last stable operation, is cut off, and the PID The digital value output from the operation unit 18 is input to the D / A conversion unit 19, and the operation is switched to the PID automatic control operation.
[0041]
3A is a diagram showing the control characteristics of the filtrate 9a, FIG. 3B is a diagram showing the control characteristics of the undiluted solution, and FIG. 3C is a diagram showing the control characteristics of the undiluted solution 1a. First, in accordance with a preset filtrate discharge target value S ₁ , a stock solution return target value S _{2, and a} stock solution supply target value S ₃ , the D / A converter 19 stores a stable operation last time from the PID calculation output value storage unit 22. A fixed digital value, which is the latest calculation output value at the time of this, is input, and the filtrate 9a, the undiluted solution and the undiluted solution 1a are manually controlled by PID.
[0042]
In this embodiment, PID manual control of filtrate 9a, as shown in FIG. 3 (a), the time T ₁ by the D / A converter 19 from the PID calculation output value storing unit 22 at the time of stable operation in the previous Recently is input the operation output value become fixed digital value, PID manual control of the return stock, as shown in FIG. 3 (b), _{T 2} hours _(T 2> T ₁₎ by the D / a converter 19 Is input from the PID calculation output value storage unit 22 as the latest calculation output value at the time of the last stable operation, and the PID manual control of the stock solution 1a is performed as shown in FIG. _{For 3} hours (T ₃ > T ₂ ), a fixed digital value which is the latest calculation output value at the time of the last stable operation is input from the PID calculation output value storage unit 22 to the D / A conversion unit 19.
[0043]
In the meantime, the digital value serving as the calculation output value output from the PID calculation unit 18 is appropriately corrected, and the control of the filtrate 9a, the undiluted solution and the undiluted solution 1a is assumed assuming that the PID is automatically controlled based on the digital value. The characteristics change relatively slowly as shown by the two-dot chain line in FIGS.
[0044]
Then, switching the filtrate 9a after _{T 1} from the start of operation from the PID manual control to PID automatic control, the further switched to the PID automatic control of the stock solution back after _{T 2} from the PID manual control, further PID manual control of the stock solution 1a after _{T 3} Switch to PID automatic control.
[0045]
Accordingly, stable operation can be started in a short time even in the filtration process of the filtration device including the interference control system.
[0046]
FIG. 4 is a view for explaining an example of a specific filtration process in the filtration device shown in FIG. 1. In FIG. 4, in the process from the air release step to the air release circulation step, the filtration motor-operated valve 10 is set at the initial opening. The undiluted liquid return electric valve 14 is fixed at the initial opening degree for 1 minute and 30 seconds, and the undiluted liquid supply electric valve 5 is fixed at the initial opening degree for 2 minutes for 1 minute.
[0047]
Thereafter, in the filtration step, PID manual control for inputting a fixed digital value which is the latest computation output value when the stable operation was performed last time from the PID computation output value storage unit 22 to the D / A conversion unit 19 of the filtration electric valve 10 in the filtration process , The stock solution return electric valve 14 is fixed by PID manual control for 1 minute and 30 seconds, and the stock solution supply electric valve 5 is also fixed by PID manual control for 2 minutes.
[0048]
One minute after the start of the filtration step, the filtrate 9a is switched from the PID manual control to the PID automatic control. Further, one minute and 30 seconds after the start of the filtration step, the filtrate is returned from the PID manual control to the PID automatic control, and the filtration step is started. After 2 minutes, the stock solution 1a is switched from PID manual control to PID automatic control.
[0049]
After performing the filtration step for 20 minutes, the filtration operation is stopped, and a backwashing step of cleaning the filtration membrane module 4 is performed for 20 seconds.
[0050]
Then, after the backwash operation is stopped, the digital value which is stored in the PID calculation output value storage unit 22 as needed and is the latest calculation output value output from the PID calculation unit 18 when the stable operation is performed in the previous filtration process is fixed. Is input to the D / A converter 19, and the process proceeds to the filtration step.
[0051]
The control target of the fluid process can be applied to pressure, flow rate, temperature, steam, humidity, concentration, and the like. If the pressure and flow rate are control targets, a solenoid valve, an electric valve, an air valve, a control valve is used as a control unit. Alternatively, a pump or a frequency adjuster of an inverter for driving and controlling the pump can be used as the control unit. If the temperature is to be controlled, a heater or the like can be used as the control unit. Further, a pressure sensor, a flow rate sensor, a temperature sensor, a concentration sensor, a humidity sensor, or the like can be used as the detection unit.
[0052]
Also, in the present embodiment, an example of controlling three of the undiluted liquid supply electric valve 5, the filtration electric valve 10, and the undiluted liquid return electric valve 14, which is a control interference system, has been described. The present invention can be applied to a case where one of the valve 10 and the undiluted liquid return electric valve 14 is controlled alone, or a case where any two of them are controlled, and is also applicable to three or more controls.
[0053]
Also, as an example of the automatic control operation, a case has been described in which PID control in which all of the proportional operation, the integral operation, and the differential operation are simultaneously performed is applied, but in the automatic control of a fluid process such as a liquid or a gas, the measured value is set to a target value. Applicable on / off operation control, proportional operation (P operation) control, integration operation (I operation) control, differential operation (D operation) control, etc., which can be used for matching, may be used as appropriate. -PI control or the like that simultaneously performs the integration operation may be used.
[0054]
Further, the present invention may be applied to automatic control operations such as a PID operation with a gap, a gain scheduling control, a multi-PID operation, a two-degree-of-freedom PID operation, and a sample PID operation.
[0055]
【The invention's effect】
Since the present invention has the above-described configuration and operation, the calculated output value during the previous stable operation is stored as needed, and the latest calculated output value is calculated as the calculated output value at the start of the next fluid process operation. The start-up control at the start of the fluid process operation can be stabilized by fixing for a predetermined time, and by switching to a predetermined automatic control operation such as PID control at the stage of stabilization, fixed operation close to stable operation The state is switched stably with a small deviation when switching from the state to a predetermined automatic control operation such as PID control, and stable operation can be continued.
[0056]
Further, the stable operation method at the start of the fluid process can be effectively applied to a filtration process of a filtration device including a control interference system in which a plurality of control points to be controlled interfere with each other.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a configuration of a filtration device to which a stable operation method at the start of a fluid process according to the present invention is applied.
FIG. 2 is a block diagram of a control system for implementing a stable operation method at the start of a fluid process according to the present invention.
FIG. 3 is a diagram showing control characteristics of a stock solution, a filtrate, and a stock solution that are control interference systems in a filtration device to which a stable operation method at the start of a fluid process according to the present invention is applied.
FIG. 4 is a diagram illustrating an example of a filtration process in the filtration device shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Undiluted solution tank 1a ... Undiluted solution 2 ... Undiluted solution supply pump 3 ... Undiluted solution piping 4 ... Filtration membrane module 5 ... Undiluted solution supply electric valve 6 ... Pressure sensor 7 ... Calculation control unit 8 ... Filtrate piping 9 ... Filtrate tank 9a ... Filtrate DESCRIPTION OF SYMBOLS 10 ... Filtration electric valve 11 ... Electromagnetic flow meter 12 ... Operation control part 13 ... Undiluted liquid return piping 14 ... Undiluted liquid return electric valve 15 ... Electromagnetic flow meter 16 ... Operation control part 17 ... Target value setting part 18 ... PID operation part 19 ... D / A converter 20 A / D converter 21 comparator 22 PID operation output value storage

Claims (2)

This is a stable operation method when starting the operation of the fluid process.The operation output value of the control target when the stable operation was performed immediately before the start of the operation of the fluid process is stored as needed, and the latest operation output value is stored in the next fluid operation. A stable operation method at the start of a fluid process, characterized in that the operation output value at the start of the process is fixed for a predetermined time and then switched to a predetermined automatic control operation. The method according to claim 1, wherein the fluid process is a filtration process of a filtration device including a control interference system.

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