JPH0157804B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a system for branching and feeding fluid from one or more fluid machines such as pumps or blowers to two series of treatment process devices such as aeration tanks through collecting pipes. The present invention relates to a flow rate control method for a fluid piping system.

As an example of a conventional system, FIG. 1 shows a system using a blower as the fluid machine and an aeration tank as the treatment process device.

Here, 1A and 1B are aeration tanks, and sewage as water to be treated is supplied from sewage inlets 2A and 2B. In order to supply aeration gas (oxygen or air) to the aeration tanks 1A, 1B, a plurality of (two in the figure) blowers 3A, 3B are connected at their discharge sides to a single collecting pipe 4. . On the suction side of the blowers 3A and 3B, there is a suction valve 5A for constant control of the blower discharge pressure.
5B is provided. A plurality of (two) branch pipes 6A and 6B branch from the collecting pipe 4, and the aeration tank 1
Connected to A and 1B. The branch pipes 6A, 6B include flow rate control valves 7A, 7B as an inlet flow rate control mechanism for controlling the flow rate of inlet gas, and air flow meters 8A,
8B is provided.

Regarding control, the blower flow rate control mechanism compares the set value from the pressure gauge 9 and pressure setting device 10 that detects the pressure in the collecting pipe 4 with the detected value from the pressure gauge 9, and adjusts the blower flow rate based on the deviation. A pressure regulator 11 is provided that controls the flow rate of the blower by adjusting the opening degrees of suction valves 5A and 5B, which are control elements, to keep the pressure of the collecting pipe 4 constant. Regarding the inlet flow rate control mechanism, the detected values of the airflow meters 8A and 8B are compared with the set value, and the opening degrees of the flow rate control valves 7A and 7B, which are inlet flow rate control elements, are adjusted based on the deviation to control the inlet flow rate. Flow rate controller 12A to maintain the set value,
12B, and dissolved oxygen meters 13A, which detect the amount of dissolved oxygen in the sewage in the aeration tanks 1A and 1B.
13B, the set values from the dissolved oxygen amount setters 14A, 14B and the detected values from the dissolved oxygen meters 13A, 13B are compared, and based on the deviation, the flow rate controller 12
A dissolved oxygen amount controller 15A, 1 that changes and adjusts the flow rate set value given to A, 12B and performs cascade control.
5B is provided.

In this way, the branch pipe 6A of each aeration tank 1A, 1B,
An inlet flow rate control loop is provided for each aeration tank 6B, and control is performed by these control loops so that the required air volume is obtained for each aeration tank 1A, 1B. On the other hand, the pressure in the collecting pipe 4 is controlled at a constant level to maintain a slightly higher pressure so that each inlet flow rate control group can independently control the flow rate without mutual interference.

If this constant pressure control is not performed, the pressure inside the collecting pipe 4 will change depending on the opening degree of the flow control valve 7A of the branch pipe 6A system. The inlet flow rate of the system will change. Therefore, when the flow rate control valve 7B is adjusted, the flow rate fed into the branch pipe 6A system changes due to a similar phenomenon. In this way, the inlet flow rate control loop is not stabilized due to mutual interference, and each flow rate control valve 7A, 7
B has the drawback of repeating the opening operation and becoming unstable.

Therefore, in order to stabilize the control, the internal pressure of the collecting pipe 4 must be maintained at a constant high pressure during operation. As a result, in order to obtain the required air volume, it is necessary to throttle the flow rate using the flow rate control valves 7A and 7B. When viewed from the blowers 3A and 3B, this throttle becomes a discharge-side throttle, which has the disadvantage of wasting excess blower power.

The present invention eliminates the above-mentioned drawbacks of the conventional method, eliminates mutual interference between branch pipe systems, and performs stable control.
Moreover, it is an object of the present invention to provide a method for controlling the amount of aeration gas flowing in with less loss of power.

In the present invention, the discharge side of one or more fluid machines operated in parallel is connected to a single collecting pipe, and the fluid is sent to two lines of processing equipment connected to branch pipes branching from the collecting pipe. In the flow rate control method for a fluid piping system configured as follows, the branch pipe is provided with an inlet flow rate control mechanism for controlling the flow rate of the inlet fluid, and the fluid machine is provided with a fluid machine flow rate control mechanism, The system includes an integrated control mechanism that controls the flow rate of the fluid piping system, detects the process state in each of the processing process devices, calculates the amount of fluid to be fed to the processing device based on the detected value, and controls the flow rate of the fluid piping system. The inlet flow rate set values Q _a ^* and Q _b ^* are inputted to the central control mechanism, and the actual inlet flow rates are detected in each of the branch pipes and inputted to the central control mechanism as the detected inlet flow rates Q _a and Q _b . In the integrated control mechanism, overall flow rate control that controls the total flow rate of the entire feed flow rate, and flow rate distribution control that controls the flow rate distribution to the two processing processing devices, are performed, and the overall flow rate control is performed. is the inlet flow rate set value Q _a ^*
and Q _b ^* , and the flow rate distribution control is performed by controlling the fluid mechanism flow rate control mechanism based on the sum of ΔR _i /Δ R _j =-(Q _j /Q _i ) ^3where , i, j: Symbols indicating any two of the three series, the two treatment process equipment series and the fluid machine series △R: The symbol of a certain series Amount of resistance correction in a piping system Q: A method for controlling the flow rate of a fluid piping system, which is characterized by adjusting the amount based on the relationship between the air flow rate of a certain series.

Embodiments of the present invention will be described using the drawings.

Figure 2 shows two blowers 3A and 3 as fluid machines.
B is used, suction valves 5A and 5B are used as the fluid mechanical flow rate control mechanism, and flow rate control valves 7A and 7B are used as the inlet flow rate control mechanism.

As will be described later, reference numeral 25 is an integrated control mechanism that controls the flow rate by controlling the fluid piping system as a whole, and includes an overall flow rate adjustment unit 26 that controls the total flow rate of the entire incoming flow rate, and a two-line processing process unit 25. device 27A,
A flow rate distribution adjustment section 28 is provided to control the distribution of the flow rate fed into the flow rate 27B.

29A and 29B are process detectors 30A and 30B that detect process state quantities in the treatment process equipment, such as the amount of dissolved oxygen and the amount of sewage inflow;
is a process setting device that determines the set value of the process state quantity, and compares the detected value and set value of the process state quantity with 30A, 30B, and sends the fluid necessary for the process state quantity to become the process set value. A process controller 31 that calculates the inflow flow rate and sends the inflow flow rate set values Q _a ^* and Q _b ^* to the central control mechanism 25
A and 31B are provided. Air flow meter 8A, 8B
The actual feed flow rate detection values Q _a and Q _b detected at are also sent to the central control mechanism 25 .

The system related to the branch pipe 6A is called the A system, the system related to the branch pipe 6B is called the B system, and the pumping source system related to the blowers 3A and 3B is called the C system.

Calculation of the feed flow rate set values Q _a ^* and Q _b ^* shall be performed at appropriate sampling intervals. In principle, the sampling period should be longer than the time it takes for the flow rate control to operate and stabilize, and the sampling period can be varied as necessary. Furthermore, the operation of the process controller should be tailored to the characteristics of the equipment.

In the overall flow rate adjustment section 26, the above-mentioned Q _a ^* ,
Calculate the total Q _c ^* (Q _c ^* = Q _a ^* + Q _b ^* ) from Q _b ^* ,
The overall air volume is controlled so that the actual total Q _c becomes Q _c ^* . On the other hand, the air volume distribution control is performed so that the air volume of system A becomes Q _a ^* , and the air volume of system B becomes Q _b ^* . Although it is desirable to control one of the two in advance and to control the other after the control is stabilized, it is also possible to control both at the same time.

FIG. 3 shows an example of a method in which overall air volume control is performed first, and after this control has stabilized, the overall air volume is kept constant and only the air volume distribution is controlled to be the set air volume distribution. In this case, the overall air volume control can be performed by operating any of the flow control valves 7A, 7B and the suction valve 5A if the overall air volume is to be increased, but if more than one of the three is being operated, the opening/closing direction may be changed. It is desirable that they all be in the same direction. On the other hand, when reducing the overall air volume, it is preferable to operate the suction valve 5A. When the flow control valves 7A and 7B are throttled, they act as discharge throttles when viewed from the blower 3A side, and the blower 3A requires extra power.

As the fluid mechanical flow control mechanism, the suction valve 5A,
5B, a blower let vane, a differential user vane, a rotation speed control mechanism, a number control mechanism, etc. of the blowers 3A and 3B can be used.

The operation of the flow rate controller 32 is as shown in FIG.
Inlet flow rate set value Q _a ^* (or Q _b ^* or Q _b ^* /Q _a ^* )
Find the deviation E _r between the input flow rate detection value Q _a (or Q _b or Q _b /Q _a ), and perform normal proportional + integral operations, or perform more advanced calculations if necessary. Outputs the manipulated variable △M _v .

To explain the operation of the device shown in FIG. 4, as mentioned above, it calculates and outputs the required manipulated variable △M _v based on the inlet flow rate set value Q _a ^* , etc., and outputs the required manipulated variable ΔM _v
Based on this, one of the flow rate control valves 7A, 7B and the suction valve 5A are adjusted in combination as follows so as to eliminate mutual interference between the flow rate control valves 7A and 7B.

The selector 33 selects which of the flow control valves 7A and 7B of the branch pipes 6A and 6B is to be adjusted. The selection is as follows. That is, 7
Among A and 7B, select the valve whose opening degree is adjusted in the opening direction. If one of the two valves is fully open (or at the maximum setting), select the other valve,
If both are fully open (or at the maximum setting), select one of them.

Which of 7A and 7B is in the opening direction is determined by which branch pipe the air volume is to be increased. That is, for example, when increasing the air volume of the A system, the flow rate control valve of the A system is adjusted in the opening direction. At this time, the air volume distribution can also be adjusted by adjusting 7B of the B system in the closed direction, but if it is throttled down, it will become a state of throttle on the discharge side when viewed from the blower side, so open 7A.

Examples of the selector 33 mentioned above are shown in FIGS. 5 and 6.

In the figure, X is the opening degree of the flow control valves 7A and 7B,
Xmax is its maximum setting opening.

After the valves to be adjusted are determined in this manner, 7A and 5A (or 7B and 5A) are adjusted in combination in the following manner. For example, when adjusting 7A and 5A, the ratio of the correction amount of pumping source resistance to the correction amount of A system branch pipe resistance (△R _c /
△R _a ) is made proportional to the cube of the air volume ratio (Q _a /Q _c ). However, the signs are opposite. If V _a is in the open direction, V _c is in the closing direction; if V _a is in the closing direction, V _c is
is the opening direction.

Generally, when the flow in a pipe is turbulent, the pressure loss P _L in the pipe is proportional to the square of the flow rate Q in the pipe. (P _L = RQ ² ) In the case where ΔR can be expressed by the above relationship,
The amount of change is shown.

When adjusting 7B and 5A, use the same method to adjust the amount of correction for each resistance using the following relationship: △R _c / △R _b = -1/(Q _c / Q _b ) ³ = - (Q _b / Q _c ) ³ decide.

The computing unit 34A in FIG. 3 computes the relationship ΔR _c /ΔR _a , and the computing unit 34B computes the relationship ΔR _c /ΔR _b .

In the computing units 34A and 34B, △R _a = △R _b = △
If M _v and the only difference is Q _a and Q _b , they can be the same.

Next, using the converters 35A, 35B, and 35C, the amount of opening change to be adjusted is determined from the amount of correction of each resistance obtained by the above method.

Generally, the resistance of a piping system including valves has nonlinearity as shown in FIG.

The converters 35A, 35B, and 35C compensate for the relationship shown in FIG. 8 for each piping system. For example, in the same figure, the initial state is P, and the amount of resistance correction is △R.
When this is the case, the amount of change in the opening degree of the valve is ΔX, and the opening degree is adjusted to Q.

In addition, if the range of change in the set air volume is small, the amount of change in the opening of the flow control valves 7A, 7B is small, and the nonlinearity of resistance and valve opening can be ignored, converters 35A, 35 are used.
B and 35C are no longer needed. There is also a method of compensating for the above-mentioned nonlinearity by devising the shape of the valve.

Further, when the relationship between the resistance and the valve opening degree is almost the same, the converters 35A, 35B, and 35C can be used in common.

FIG. 9 shows another embodiment of the integrated control mechanism 25, in which the selector 33 first makes a selection and then inputs the signal to the A circuit 36A or the B circuit 36B.

In the embodiments described above, the overall air volume control is performed first, and after the control is stabilized, the air volume distribution control is performed, but conversely, the air volume distribution control may be performed first. In the air volume distribution control in this case,
When controlling the air volume distribution while keeping the overall air volume constant, the air volume distribution may be controlled using the method described above.

In the embodiments described above, the flow rate control valve and the suction valve, that is, 7A and 5A or 7B and 5A, were controlled in combination in air volume distribution control.
As shown in the figure, two flow control valves 7A and 7B may be combined.

The flow controller 32 is the same as in the previous example.

The selector 33 is a selector that adjusts the valve with the smaller opening of the flow rate control valves 7A and 7B in the opening direction.

When changing the air volume distribution, for example, when increasing the air volume of the A-system branch pipe, it is sufficient to operate 7A in the opening direction or 7B in the closing direction.

In this embodiment, in order to make both valves open as large as possible, the valve with the smaller opening is adjusted in the opening direction.

Specifically, a method can be considered in which the sign (positive, negative) of ΔM _v is switched.

The characteristic of the arithmetic unit 34B is △R _a /△R _b =−(Q _b /Q _a ) ³ .

Converters 35A and 35B are similar to the previous example.

A plurality of flow control valves 7A and 7B may be arranged in parallel or in series to simplify controllability or control valve structure.

The present invention can be applied not only to sewage aeration methods, but also to methods of controlling flow rates from a pressure source to multiple devices by calculating and storing in advance the relationship between constants unique to the entire device to determine the flow rate required by each device. . For example, it can be applied to heating furnace combustion air, factory ventilation, building air conditioning, etc.

ADVANTAGE OF THE INVENTION According to the present invention, there is provided a method for controlling the amount of aeration gas that is capable of stably supplying the required air volume without causing each branch system to interfere with each other, and that can prevent loss of power. This can produce extremely great practical effects.

[Brief explanation of drawings]

Figure 1 is a flow diagram of a conventional example, Figures 2 to 10 are related to an embodiment of the present invention, Figures 2 and 3 are flow diagrams of an embodiment of the present invention, and Figure 4 is a flow diagram of a flow rate controller. Figures 5 and 6 are flow sheets showing the operation of the selector, and Figure 7 _is a flow sheet showing _{the operation} of the selector _.
) ³ , FIG. 8 is a graph showing the function of the converter, and FIGS. 9 and 10 are flowcharts of different embodiments of the central control mechanism. 1A, 1B...Aeration tank, 2A, 2B...Sewage inlet, 3A, 3B...Blower, 4...Collecting pipe, 5
A, 5B... Suction valve, 6A, 6B... Branch pipe, 7
A, 7B...Flow rate control valve, 8A, 8B...Air flow meter, 9...Pressure gauge, 10...Pressure setting device, 11...
...Pressure regulator, 12A, 12B...Flow rate regulator, 13A, 13B...Dissolved oxygen meter, 14A, 1
4B...Dissolved oxygen amount setting device, 15A, 15B...
Dissolved oxygen amount controller, 25...Integrated control mechanism, 26
...Overall flow rate adjustment section, 27A, 27B...Treatment process device, 28...Flow rate distribution adjustment section, 29A,
29B... Process detector, 30A, 30B...
Process setting device, 31A, 31B... Process controller, 32, 32A, 32B... Flow rate controller, 3
3... Selector, 34A, 34B... Arithmetic unit, 35
A, 35B, 35C...Converter, 36A...A circuit, 36B...B circuit.

Claims (1)

[Claims] 1. The discharge side of one or more fluid machines operated in parallel is connected to a single collecting pipe, and the fluid is delivered to two lines of treatment process equipment connected to branch pipes branching from the collecting pipe. Flow rate control of a fluid piping system configured to supply fluid, wherein the branch pipe is provided with an inlet flow rate control mechanism for controlling the flow rate of the injected fluid, and the fluid machine is provided with a fluid mechanical flow rate control mechanism. The method includes an integrated control mechanism that controls the flow rate of the fluid piping system, detects the state of the process in each of the treatment process devices, and calculates the amount of fluid to be fed to the treatment process device based on the detected value. The inlet flow rate set values Q _a ^* and Q _b ^* are then input to the central control mechanism, and the actual inlet flow rates are detected in each of the branch pipes and the detected inlet flow rates Q _a and Q _b are used for the central control mechanism. The integrated control mechanism performs overall flow rate control that controls the total flow rate of the entire feed amount, and flow rate distribution control that controls the flow rate distribution to the two processing process devices, and the above-mentioned The overall flow rate control is based on the above-mentioned inlet flow rate set value Q _a ^*
and Q _b ^* , and the flow rate distribution control is performed by controlling the fluid mechanism flow rate control mechanism based on the sum of ΔR _i /Δ R _j =-(Q _j /Q _i ) ^3where , i, j: Symbols indicating any two of the three series, the two treatment process equipment series and the fluid machine series △R: The symbol of a certain series Amount of resistance correction in a piping system Q: A method for controlling the flow rate of a fluid piping system, which is characterized by adjusting the amount based on the relationship between the air flow rate of a certain series.