JPS6298408A - Method and device for automatically controlling pressure - Google Patents

Abstract

PURPOSE:To realize a high response speed, and also to execute an exact and stable control without using a pulse motor, by detecting a pressure at a prescribed position, and executing a continuous operation of a motor by a prescribed revolving speed, when its detected value is out of a threshold value area. CONSTITUTION:A fluid being a mixture of H2 and naphtha, etc., which is fed from a raw material supply part 1 passes through a passage 3, reaches a reactor 2 through an automatic pressure control device 4, and executes a reaction in the reactor 2 whose internal capacity is 10cc. In this case, the inside of the reactor 2 is heated to an optimum temperature by a heating zone 21, and also held in an optimum pressure by the automatic pressure control device 4. The automatic pressure control device 4 reads a detected value from a pressure detector 7, executes a prescribed processing in a control device 8, and holds a pressure in the reactor 2, in an optimum pressure by controlling a motor 4 and adjusting a valve opening of a pressure control value 6.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an automatic pressure regulating method and device that can be used in small reactors in chemical plants, etc., and particularly relates to a method and device for automatically regulating a set target pressure. The present invention relates to an automatic pressure adjustment method and device that can maintain the same pressure.

[Background technology and its problems]

Traditionally, in chemical plants, etc., a pressure control valve equipped with a motor that can rotate forward and backward and a pressure detector is used as a method to automatically adjust the pressure of small reactors, etc., and the pressure is detected by this pressure horn detector. The detected value and the reference Fl
A method has been used in which, for example, the magnitude and polarity of the voltage to be applied to the motor are determined based on the results of comparison of target pressures, the motor is controlled, and the valve opening degree is adjusted.

Control methods for such motors include on-off control,
There are intermittent control, proportional control, etc. Among them, on-off control is used, for example, when the detected value is larger than the target pressure,
The motor is operated continuously at a constant rotation speed in the direction of closing the pressure regulating valve, and is stopped when the detected value and the target pressure become equal. However, in this type of on/off control, especially when the motor rotation speed is increased to increase the response speed, there is a problem that overshoot is large when stopping, and hunting occurs even when the target pressure is approached, resulting in instability. Therefore, it was inappropriate to maintain the target pressure accurately.

On the other hand, in intermittent control, the motor operates intermittently at appropriate time intervals, which reduces overshoot when stopping, but does not solve the problem of hunting, resulting in poor stability near the target pressure. was insufficient.

To solve this problem, overshoot I can be absorbed within the dead zone by creating a dead zone with an appropriate width above and below the target pressure and prohibiting the motor from operating within this zone. This makes it possible to prevent hunting. However, increasing the width of the dead zone has the disadvantage that it defeats the purpose of accurately maintaining the target pressure.

While the on-off control operates the motor at a constant rotation speed, the proportional control operates the motor at a rotation speed proportional to the difference between the target pressure and the detected value. Particularly when using a pulse motor, continuous rotation from the maximum rotation speed is possible.
It is possible to control the rotation speed in the range up to 11 pm, and 1) it operates at high speed when the difference from the standard pressure is large, and conversely, when the difference from the standard pressure is small, it operates at low speed and fine control. As a result, the response speed is fast and the standard pressure can be maintained accurately and stably.However, the drawback of pulse motors is that they are expensive; The lower limit of the number is about 1100 rp,
Since the pressure cannot be lowered too much, there is a drawback that even if proportional control is used, sufficient accuracy or stability cannot be achieved in the vicinity of the target pressure.

[Purpose of the invention]

An object of the present invention is to provide an automatic pressure adjustment method and device that has a fast response speed and is capable of accurate and stable control without using a pulse motor.

[Means and effects for solving the problem] In the present invention, the opening degree of a pressure regulating valve provided in a flow path of a predetermined fluid system is controlled by a motor capable of forward and reverse rotation to adjust the pressure of the fluid. a dead zone having a necessary and sufficient width above and below the target pressure at a predetermined position of the fluid system;
A limit value range having a width larger than the width of the dead zone and extending to a range including the dead zone is set above and below the target pressure, and the pressure at the predetermined position is detected, and this detected value is When the detected value is outside the limit value range, the motor is operated continuously at a predetermined rotation speed, and when this detected value is within the limit value range and outside the dead band, the motor is operated intermittently at a constant rotation speed, and further, when this detected value is The motor is not operated when it is within the dead band.

More specifically, the flow path is provided with a pressure regulating valve of a pressure reducing valve type, a back pressure valve type, a needle valve type, a globe valve type, etc., and this pressure regulating valve is equipped with a joint box, a gear that can reduce the speed, etc. A motor that can adjust the valve opening is provided via a box or screw. This motor may be a DC motor or an AC motor whose rotation direction can be changed, such as a reversible variable speed motor whose rotational speed can be controlled by voltage or the like. However, if the motor is operated at a constant rotation speed in the continuous operation, the rotation speed does not need to be variable. Furthermore, a pressure detector is provided at a predetermined position in the flow path in order to detect the detected pressure necessary for controlling the motor, and this pressure detector continuously detects the pressure and outputs an electrical signal according to the pressure. It should be capable of outputting, such as strain gauges, Bourdon tube types, and diaphragm types.

On the other hand, regarding the setting of the dead band width and limit value range, although it depends on the accuracy of the pressure detector, the width of the dead band is usually about 1% of the maximum pressure above and below the target pressure, preferably 0.1%.
%, and the width of the limit value range is usually 1-1% of the target pressure.
It is assumed that the pressure is within about 20% of the target pressure. Regarding the above-mentioned intermittent operation, the time for the motor to rotate and turn and the time for the motor to stop are both 0. ]
The ratio between the two times is, if the response speed of the fluid system is slow, the time in the rotating state is lengthened, and if the response speed is fast, the time in the stopped state is lengthened. , it is usually desirable that the two be equal. Furthermore, regarding the continuous operation, in addition to continuous operation at a constant rotation speed, proportional control may include operation at a rotation speed proportional to the width of the difference between the detected pressure and the target pressure, or, for example, about 50% of the target pressure above and below the target pressure. By setting a speed switching range within this range, it is possible to operate by switching the rotation speed, such as rotating at a low speed within this range and rotating at a high speed outside this range.

According to the present invention, when the detected value is outside the limit value range, the motor can be operated rapidly, thereby increasing the response speed, and when the detected value is within the limit value range, the motor can be operated rapidly. When the pressure is outside the dead zone, the motor is finely operated intermittently to make fine adjustments, making it possible to adjust the pressure with high precision.

Furthermore, since the motor is not operated within the dead zone, overshoot and hunting can be prevented, allowing accurate and stable control. The present invention aims to achieve the above object.

〔Example〕

As one embodiment of the present invention, an automatic pressure regulating device for a small reactor will be described with reference to the drawings.

In FIG. 1, a raw material supply section 1 includes a plurality of valve devices,
H2, which is a reactant, and a reactant such as naphtha can be appropriately mixed and sent out from a storage facility (not shown). The reactor 2 is a small reactor with an internal volume of 10 cc, and is equipped with a heating zone 21 to be able to heat the fluid inside during the reaction. A resistance valve 23 for adjusting back pressure is provided to maintain an appropriate pressure during the reaction.

The flow path 3 connecting the raw material supply section 1 and the reactor 2 is as follows:
It consists of piping with a diameter of 178 inches, and a part of this flow path 3 is provided with an automatic pressure regulator 4 that can automatically adjust the pressure in the reactor 2 and the flow path 3 leading thereto, based on the present invention. ing.

This automatic pressure regulator 4 includes a pressure regulating valve 6 which is provided in the flow path 3 and whose opening degree can be adjusted by a motor 5 which can rotate in forward and reverse directions and rotate at a rotation speed according to the voltage. A pressure detector 7 is provided, which can detect the pressure of the internal fluid, etc., and output it as an electrical signal, and the detected value from this pressure detector 7 can be read, and the motor 5 can be electrically controlled. It consists of a control device 8.

Furthermore, the control device 8 is capable of storing setting values necessary for control. ! 1.1 circuit 81 which is a means, a comparison circuit 82 which is a comparison means capable of comparing the numerical value stored in this storage circuit 81 and the detected value, and the result of the comparison in this comparison circuit 82. A command circuit 83 is an operation command means that can command the operation that the motor 5 should perform according to the operation. The motor controller 84 includes a motor controller 84 that can control the rotational operation of the motor 5 by applying an appropriate voltage to the motor 5.

In this embodiment configured as shown in FIG. Reactor 2 with an internal volume of 10 cc
Perform the reaction inside. At this time, the inside of the reactor 2 is heated to an optimum temperature by a heating zone 21, and is maintained at an optimum pressure by an automatic pressure regulator 4. For example, the optimum temperature is approximately 400°.
C1 is also maintained at an optimum pressure of 150 kg/cnl, which is a suitable condition for promoting the reaction.

The automatic pressure regulator 4 reads the detected value from the pressure detector 7, performs predetermined processing in the control device 8, controls the motor 5, adjusts the opening degree of the pressure regulator valve 6, and controls the reactor 2.
The detailed operation is as follows.

In FIG. 2, the ↑a circuit 81 has various setting values necessary for control recorded 41, the target pressure is the optimum pressure of 150 kg/cJ, and the dead zone is ±0 of the target pressure.
．． 1 kg/crA, limit value range is within 20% of target pressure ±1 kg/ca, speed switching range is 5% of target pressure
Each range is stored as ±5 kg/cJ, which is within 0%. The comparison circuit 82 compares these various set values with the detected value, and based on the results of this comparison, the command circuit 83 determines various signals that are commands to be sent to the motor controller 84.

In other words, if the detected value is within the dead band, the operation/stop signal is turned off, but if the detected value is outside the dead band and within the limit range, it is intermittently turned on, and if the detected value is outside the limit range, it is turned on continuously. do. Further, if the detected value is within the speed switching range, the speed switching signal is set to low speed, and if the detected value is outside the speed switching range, it is set to high speed. In each case, when the direction in which the pressure regulating valve 6 is closed is taken as the positive direction, if the detected value is larger than the target pressure, the rotation direction signal is made positive in order to rotate the motor 5 in the positive direction, and the detected value is If the pressure is smaller than the target pressure, the rotation direction signal is similarly reversed. These various signals are sent to the motor controller 84, converted into appropriate voltages, and applied to the motor 5.

The flowchart in FIG. 3 shows the control procedure at this time. In other words, when the detected value is within the dead band, the motor 5
There is no voltage applied to the motor 5 and the motor 5 is in a stopped state, but when the detected value is outside the dead band and within the limit value range, a positive or negative voltage of 20 V is applied to the motor 5 for 1 second once every 5 seconds. The motor 5 performs intermittent operation at low speed. Further, when the detected value is outside the limit value range but within the speed switching range, a positive or negative voltage of 20 V is applied to the motor 5, and the motor 5 continuously operates at a low speed. Further, when the detected value is outside the speed switching range, a positive or negative voltage of 100 cm is applied to the motor 5, and the motor 5 continuously operates at high speed. Note that the positive or negative polarity of each voltage follows the positive or negative polarity of the rotation direction signal.

FIG. 4 is a diagram showing the relationship between time and pressure when a pressure increase test was conducted from atmospheric pressure to a target pressure of 150 kg/cnl in the apparatus of this embodiment. In the figure, high-speed continuous operation is performed from the start of operation until time T, and when the pressure reaches P, that is, the lower limit of the speed switching range, it is switched to low-speed continuous operation, and then at time T2, the pressure is reduced to P2. In other words, when the lower limit of the limit value range is reached, the operation is switched to low-speed intermittent operation, and approximately 180 seconds after the start of operation, the target pressure of 15 Q kg/ca is ±0,
It stabilized within the range of 5 kg/cJ.

As described above, this embodiment has the advantage that it is possible to perform stable and accurate automatic pressure adjustment without using an expensive pulse smoke or the like, with a fast response speed, and without overshoot or hunting.

In addition, in the above embodiment, during continuous operation when the detected value is outside the limit value range, one speed switching range is provided to switch the rotation speed of the motor 5 between high speed and low speed. This can be a simple continuous operation with a constant rotation speed,
Alternatively, two or more speed switching ranges may be provided to perform speed switching in three or more steps, and further, operation is performed by proportional control that controls the rotation speed of the motor 5 in proportion to the difference between the detected value and the target pressure. You can also use it as In short, the present invention provides an automatic pressure regulating method for regulating the pressure of a fluid system by controlling the opening degree of a pressure regulating valve provided in a flow path of a predetermined fluid system using a motor capable of forward and reverse rotation. A dead band having an appropriate width above and below the target pressure at a predetermined position and a limit value range including this dead band and having an appropriate width above and below the target pressure are set, and the pressure at the predetermined position is set. detect,
When this detected value is outside the limit value range, the motor is operated continuously at a predetermined rotation speed, and when this detected value is within the limit value range and outside the dead band, the motor is operated intermittently at a constant rotation speed. It is.

〔Effect of the invention〕

As described below, according to the automatic pressure adjustment method of the present invention,
The effect is that the response speed is fast and precise and stable automatic pressure adjustment is possible without using a pulse motor.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the signal flow of the main part of the embodiment, and FIG. 3 is a flowchart 1 showing the control in FIG. 2. 4 are diagrams showing the relationship between time and pressure and the relationship between time and voltage applied to the motor in the boost test of the embodiment. 1... Raw material supply section, 2... Reactor, 3... Channel,
4... Automatic pressure regulator, 5... Motor, 6...
Pressure control valve, 7...pressure detector, 8...control device,
21... Heating zone, 22... Outlet side piping, 23...
Resistance valve, 81... Memory circuit, 82... Comparison circuit, 83... Command circuit, 84... Motor controller.

Claims (2)

[Claims] (1) In an automatic pressure adjustment method in which the pressure of a fluid system is adjusted by controlling the valve opening degree of a pressure regulating valve provided in a flow path of a predetermined fluid system using a motor that can rotate in forward and reverse directions, A dead band having an appropriate width above and below the target pressure at the position and a limit value range including this dead band and having an appropriate width above and below the target pressure are set, and the pressure at the predetermined position is detected. However, when this detected value is outside the limit value range, the motor is operated continuously at a predetermined rotation speed, and when this detected value is within the limit value range and outside the dead band, the motor is operated intermittently at a constant rotation speed. An automatic pressure adjustment method characterized by: (2) Automatic pressure control equipped with a pressure control valve whose opening degree can be adjusted by a motor that can rotate forward and backward, a pressure detector, and a control device that can control the motor based on the detected value from the pressure detector. In the regulating device, the control device includes a storage means capable of storing each set value of a predetermined target pressure, a limit value range, a dead zone, etc., a comparison means capable of comparing each of these set values with the detected value; Based on the comparison result by this comparison means, if the detected value is outside the limit value range, a command is issued to operate the motor continuously at a predetermined rotation speed, and if the detected value is within the limit value range and outside the dead band, a command is issued to operate the motor continuously. An automatic motor comprising: an operation command means capable of generating a command to intermittently operate the motor at a predetermined rotation speed; and an operation control means capable of controlling the operation of the motor according to commands from the operation command means. Pressure regulator.