JPH025157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for controlling the amount of aeration gas sent to a plurality of aeration tanks using one or more blowers.

[Conventional technology]

A conventional example of a device using this type of control method is shown in FIG. Here, 1A and 1B are aeration tanks, and sewage as water to be treated is sewage inlets 2A and 2B.
Supplied from. 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. . Blower 3A,
Suction valves 5A and 5B for constant blower discharge pressure control are provided on the suction side of 3B. A plurality of (two) branch pipes 6A, 6B branch from the collecting pipe 4 and are connected to the aeration tanks 1A, 1B. Branch pipe 6
A, 6B are provided with flow rate control valves 7A, 7B and air volume meters 8A, 8B as an inlet flow rate control mechanism for controlling the flow rate of inlet gas.

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 a dissolved oxygen meter 13 for detecting the amount of dissolved oxygen in the sewage in the aeration tanks 1A and 1B.
A, 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 1
Change and adjust the flow rate setting values given to 2A and 12B,
Dissolved oxygen amount controller 15A with cascade control,
15B is provided.

In this way, the branch path 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.

[Problem that the invention seeks to solve]

The reason for performing constant pressure control in this way is as follows. 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, so if the opening degree of the flow rate control valve 7B is the same, the branch The flow rate fed into the pipe 6B 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, due to mutual interference, the inlet flow rate control loop is not stabilized, and each of the flow rate control valves 7A and 7B repeats opening operation, resulting in instability.

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 and has the problem of wasting excess blower power.

The purpose of the present invention is to solve the above-mentioned blower problem of the conventional method, and to provide a method for controlling the amount of aeration gas inflow, which eliminates mutual interference between branch pipe systems, performs stable control, and reduces loss of power. It is something to do.

[Means for solving problems]

A first invention includes one or more blowers and a plurality of aeration tanks, the discharge side of the blower is connected to a collecting pipe, and the aeration tank is connected to a branch pipe branched from the collecting pipe. The branch pipe is configured to feed aeration gas into the aeration tank, the branch pipe is provided with a feed flow rate control mechanism for controlling the flow rate of the feed gas, and the blower is provided with a blower flow rate control mechanism. In the method for controlling the amount of aeration gas fed into an aeration device, the amount of water flowing into the aeration tank and/or the amount of dissolved oxygen in the water being treated is measured,
The required air volume for the aeration tank is calculated and determined for each predetermined control cycle, and the value of this required air volume is input to the central control mechanism, and the central control mechanism adjusts the blower flow rate based on the sum of the required air volumes. The set amount of the blower flow rate control element of the control mechanism is determined by calculation, and the set amount of the opening degree of the inlet flow rate control element of the aeration tank's inlet flow rate control mechanism, which indicates the maximum required air volume, is set to the amount equivalent to the fully open state. , set value of the opening degree of the inlet flow rate control element of the inlet flow rate control mechanism of the other aeration tank,
An aeration gas that is determined by calculation based on the air volume ratio, outputs the set amounts calculated based on each input required air volume, and controls the blower flow rate control mechanism and the feed flow rate control mechanism. This is a feeding amount control method.

In the second invention, instead of performing the calculation in the first invention by the central control mechanism, each set amount is obtained by performing the calculation in advance for various required air volumes, and these set amounts are calculated as described above in correspondence with the required air volume. These settings are stored in the central control mechanism and outputted according to the required input air volume.

[Effect]

The present invention was made based on the knowledge obtained through repeated research by the inventors in order to solve the above-mentioned problems.In particular, in this aeration tank air volume control, the air volume supplied to the aeration tank can be precisely controlled. Rather, it was confirmed that even if there were some errors, it was acceptable in practice, and the present invention was developed based on this point.

In other words, in the past, in order to reduce errors in the supply air volume, and to ensure that the absolute air volume supplied to each aeration tank (rather than the relative "air volume ratio") was always accurate, each aeration tank was Independent local continuous feedback control was performed. Therefore, as mentioned in the [Prior Art] section, mutual interference occurs between the branch pipes, so in order to prevent this, it is necessary to maintain a high pressure in the collecting pipe, and it is necessary to maintain a constant local pressure to operate the blower. Control was needed.

However, if the high pressure in the lever collector pipe fluctuates, the state of mutual interference between the branch pipes will change and the continuous feedback control for each aeration tank will be disrupted. Therefore, this constant pressure control is a continuous feedback control that keeps the pressure constant at all times. It was necessary to keep it.

In other words, in the past, in order to ensure accurate airflow, local continuous feedback control was performed for each aeration tank and local continuous feedback control to maintain high pressure in the collecting pipe. It was completely unthinkable to perform sampling control that would be expected to be inaccurate.

Therefore, the inventors conceived the above-mentioned points and came up with the present invention.

The present invention performs sampling control at every predetermined control period and has the requirements as shown in the claims, thereby achieving the following effects and effects.

(i) Rather than continuous, local feedback control, this method uses calculations to set the set values of flow rate control elements (flow control valves, etc.) every sampling control cycle, so the following effects occur: This allows for more stable control.

(a) Settings are made for each control period rather than continuously, so although it is a system with poor responsiveness,
The set value remains constant until the next sampling point, and the flow rate control element does not move throughout the control period, allowing stable control.

(b) Since the set amounts of the control elements for air volume distribution control are constant during the control cycle, there is no mutual interference between the systems that are branched in parallel for each aeration tank, and stable control can be achieved.

(ii) For the reason mentioned in (b) above, there is no need to maintain a high pressure in the collecting pipe section to prevent interference, and there is no need for local continuous feedback control to maintain a constant pressure.

Therefore, without having to separate the control system into two loops: one for controlling the amount of air blown to each aeration tank and the other for controlling the amount of suction as a whole, it can be controlled as a large feedback system that includes both controls, and stable control can be achieved. It can be carried out.

(iii) Since there is no need to increase the pressure in the collecting pipe, the power of the blower can be kept to the minimum necessary and energy can be saved.

(iv) Conventionally, it was necessary to control the absolute air volume of each branch pipe by maintaining the differential pressure with respect to the high pressure of the collecting pipe, so the flow control valve of each branch pipe had a restrictor resistance value to maintain the differential pressure. Due to the necessity, there were restrictions on the aperture opening.

In the present invention, since it is not necessary to maintain the collecting pipe at high pressure, the opening degree of the flow control valve only needs to be determined by the "distribution ratio", and a large opening degree with low throttling resistance can be selected, and the setting can be determined by calculation. control is easy and stable.

(v) Since the control is for each sampling control period, there is no movement of the flow rate elements except at the time of sampling, and for example, the frequency of opening of the flow rate control valve, etc. is reduced, and the structure of the flow rate control valve and its driving mechanism is reduced. Just something simple and cheap. For example, a hydraulic or pneumatic drive system is normally required for minute analog operation, but according to the present invention, an inexpensive electric drive system is sufficient.
Furthermore, the life of the flow rate control valve, its driving machine, blower, etc. is extended.

〔Example〕

Embodiments of the present invention will be described using the drawings. Second
In the figure, parts with the same reference numerals as in FIG. 1 have the same structure and function. In this embodiment, the branch pipe 6
There is no inlet flow rate control loop for each system of A and 6B,
Further, an integrated blower discharge pressure control mechanism for maintaining the internal pressure of the collecting pipe 4 at a constant level is not used. There may be a plurality of collecting pipes 4.

Reference numerals 16A and 16B are set air volume calculators, which detect the detected amount of snow inflow from the sewage flow meters 17A and 17B that detect the amount of sewage inflow, and the dissolved oxygen meters 13A and 1.
Based on one or both of the dissolved oxygen amount (hereinafter referred to as DO value) detected values from 3B, the required air volume Qa and Qb in that state are calculated and output as the set air volume at each predetermined control cycle and aggregated. It is sent to the control device 18.

In the central control device 18, the set amount of the blower flow rate control element of the blower flow rate control mechanism is determined by calculation based on the value of the sum of each required air volume, and the set amount of the blower flow rate control element of the aeration tank that indicates the maximum required air volume is determined by calculation. The opening degree of the inlet flow rate control element is set to a value that corresponds to the fully open (not necessarily mechanically fully open, but means the normal maximum opening degree) state, and the inlet flow rate control mechanism of other aeration tanks is The set amount of the opening degree of the inlet flow rate control element is determined by calculation based on the air volume ratio. Alternatively, these set amounts may be calculated in advance for various required air volumes and stored in the central control device 18.

As the blower flow rate control mechanism, the suction valves 5A, 5
B or blower let vane or differential user vane (opening degree of these as a blower flow rate control element), or rotation control mechanism of blowers 3A, 3B (blower rotation speed as a blower flow rate control element), blower 3A, 3B A control method other than the blower discharge side control, such as a number control mechanism (the number of blowers is the blower flow rate control element), is selected and applied alone or in combination.

As the inlet flow rate control mechanism, the flow rate control valve 7A,
7B (input flow rate control element is valve opening degree), etc. are used.

The contents of the central control mechanism 18 will be explained as follows.
As shown in FIG. 5, the integrated control device 18 includes an overall air volume control system consisting of an air volume sum calculation section 19 and a blower flow rate control section 20, an air volume ratio calculation section 21, and an inlet flow rate control system such as a linearizer. It has an air volume distribution control system consisting of parts 22 and 23.

The set air volume calculation units 16A, 16B provide the required air volume corresponding to the process state as the set air volume Qa, Qb. Setting air volume calculator 16A, 16B
serves as a process regulator, which may be a very commonly used regulator with a sampling function.

The sum of required air volumes (Qa, Qb) is calculated by the air volume sum calculation unit 19 from the above-mentioned Qa and Qb values, and the overall air volume is controlled via the blower flow rate control unit 20 based on this sum value. The overall air volume is controlled by (a) selecting the number of blowers, (b) adjusting the opening degree of the blower intake vanes or blower suction valves 5A and 5B, and (c) adjusting the blower rotation speed.

For air volume distribution control, the flow control valve of the aeration tank with the larger required air volume is fully opened, and at the same time the above-mentioned Qa,
From the Qb value, the air volume ratio calculation unit 21 calculates the air volume ratio Qb/Qa.
The relationship between the air volume ratio and the opening degrees of the flow rate control valves 7A and 7B is calculated using the linearizers of the inlet flow rate control units 22 and 23, and the relationship between the air volume ratio and the opening degrees of the flow rate control valves 7A and 7B is calculated.
This is done by adjusting the opening degree in combination.

In order to simplify the controllability of the flow rate control valves 7A, 7B or the control valve structure, a plurality of them may be arranged in parallel or in series.

The main points of this air volume distribution control are: (a) Linearizer (feed flow rate control section 22, 23)
At 7A or 7B, the opening degree of the flow control valve indicating the larger required air volume is fully opened.

(b) The linearizer has the same function as a normally used function generator, and defines the air volume ratio Qb/Qa and the flow rate control valve opening as shown in Figure 6.

In other words, for the 7A system, the air volume ratio (Qb/Qa).
Until then, the flow control valve opening is 100% (fully open or close to fully open), and when Qb/Qa≧(Qb/Qa) ₀ , the opening is reduced. On the other hand, in the 7B system, QbQa<(Qb/
Qa) At ₀ , the opening is narrowed, and at (Qb/Qa) or higher, the opening is 100%.

The above characteristic curves are based on the resistance of the device, the resistance of the branch pipe,
It is determined by the valve characteristics of the flow control valve.

The relationship between the air volume ratio Qb/Qa and the opening degrees of the flow control valves 7A and 7B is determined by the resistance downstream from the collecting pipe 4 (device resistance, branch pipe resistance, flow rate control It is determined by the valve characteristics, etc.).

The above characteristic curve is calculated in advance and stored in the linearizer.

During operation, dissolved oxygen meters 13A, 13B and sewage flow meters 17A, 17B are installed at appropriate control intervals.
Air volume calculators 16A, 16 detect the air volume and set the set air volume Qa, Qb based on the required air volume in that state.
Calculate and output in B.

In response to this, in the central control device 18, the opening degree of the flow control valve 7A or 7B with the larger set air volume is fully opened, and the other opening degrees are determined according to the air volume ratio Qa, Qb. , Qb is obtained.

Therefore, the required air volume of the branch pipes 6A and 6B can be stably obtained without mutual interference,
Moreover, since the flow rate control valves 7A and 7B are opened as wide as possible, there is little loss of power.

To give an example of the operation of the set air volume calculators 16A and 16B, for example, the deviation between the actual DO value and its set value is added to the value output by proportional + integral operation and the value obtained by multiplying the amount of sewage inflow by a constant. The value is calculated and output as the set air volume. At this time, the calculation may be performed by adding a dead time element to the sewage inflow amount. As another example, a predictive control method may be used based on a model of the reaction process of sewage treatment in the aeration tank based on the current actual DO value, amount of sewage inflow, and air volume.

To give another specific example, the set air volume is determined in stages as shown in Figure 3 in approximately proportion to the amount of sewage inflow, and the air volume is set in stages based on the actual amount of sewage inflow as shown in Figure 3. Determine. Furthermore, the actual DO value and DO
The set values of are compared, and the stage of the set air volume determined from the amount of sewage inflow is corrected according to the deviation of the DO value.

In other words, if the actual DO value is smaller than the DO set value, the set air volume level is adjusted to a higher air volume level, and if the actual DO value is greater than the DO set value, the set air volume level is adjusted to a smaller air volume level. Correct. In the figure, ~ indicates the stage of the set air volume.The number of stages is arbitrary, but 3
The control cycle, which has about 10 steps, is determined so that the next air volume control is performed after a period of time has elapsed until the effect of the air volume control performed at a certain time becomes sufficiently apparent. This control period may be fixed, but if it is made variable according to the rate of change in the set air volume, even better quality treated sewage can be obtained.

The set air volume calculators 16A and 16B are normally provided for each aeration tank 1A and 1B. However, if the calculation of the set air volume of either one can represent the set air volume of the other, a set air volume calculator may be provided in either one.

When the central control mechanism 18 stores the set amounts corresponding to various required air volumes, the stored contents are analog quantities such that the manipulated variables corresponding to each set air volume Qa, Qb are output continuously. However, as shown in FIG. ) and combine them, and for each combination, a pattern is determined by calculating in advance the set values such as the opening of the flow control valves 7A, 7B, the number of blowers 3A, 3B, the opening of the suction valves 5A, 5B, etc. It may be stored in the central control mechanism 18. For example, for a pattern such as Qa = 6 and Qb = 1, the number of blowers is 1, the opening degree of flow rate control valve 7A with the larger required air volume is 100%, and the opening degree of 7B is 50% depending on the air volume ratio. The opening degree of the % suction valve 5A is calculated and determined in advance, such as 95%, depending on the sum of the required air volumes.

This calculation is performed in advance by calculating the set amount of the blower flow rate control element based on the sum of each required air volume for any required air volume of each aeration tank, and then calculating the set amount of the blower flow rate control element based on the sum of each required air volume, and The set amount of the opening degree of the inlet flow rate control element is determined to be the amount corresponding to the fully open state, and the set amount of the inlet flow rate control element of the other aeration tanks at that time is calculated based on the air volume ratio. Each set amount obtained by this calculation in advance is stored in the central control mechanism 18 in correspondence with each required air volume, and each set amount corresponding to the input air volume is output.

In the above explanation, there are two aeration tanks 1A and 1B and two blowers 3A and 3B, but there may be three or more aeration tanks and one or more blowers.
If there are three or more aeration tanks, the flow control valve of the system showing the maximum required air volume at each time point is fully opened, and the opening settings of the other flow control valves are determined by calculation according to the air volume ratio.

The above-mentioned linearizer may have an auto-tuning function, which will be described later. Overall air volume control and air volume distribution control are performed every sampling control cycle. This sampling control period may be fixed or variable. Further, a timer or the like may be added to each control loop so that the overall air volume control and the air volume distribution control are not controlled at the same control cycle but at different control cycles.

As described above, the air volume distribution control is a method in which the opening degrees of the flow rate control valves 7A, 7B are defined and adjusted solely based on the value of the air volume ratio Qb/Qa, so feedback control is not performed within the control cycle. However, since the set air volume calculation units 16A and 16B are provided, feedback control is performed as a whole, and the control system operates so that the process value becomes the set value (process value).

In the conventional example (FIG. 1), the flow rate is controlled independently in each branch pipe. Changing the opening degree of the flow control valve of the branch pipe involves mutual interference. In FIG. 1, each flow control valve is controlled and regulated independently of each other using a feedback control system, and is directly affected by the above-mentioned mutual interference. Therefore, if constant pressure control is not performed, the control is unstable, and even if measures such as changing the response speed of each flow rate control are taken, the frequency of opening of the flow rate control valve is still large.

If an attempt is made to operate the flow control valve opening as large as possible for energy saving, generally speaking, the larger the flow control valve opening, the worse the controllability of the valve becomes, making it more unstable.

Further, in the case of FIG. 1, the above-mentioned mutual interference is avoided by adding a constant pressure control loop, but it has the disadvantage that the power consumption of the blower increases.

In the above-described embodiment of the present invention, the linearizer calculates and determines the flow rate control valve opening degree so that a predetermined air volume distribution is achieved every sampling control period, so stable control can be achieved even if the flow rate control valve opening degree is increased. It will be done.

Although the overall air volume control and the distribution control may be controlled simultaneously, it is desirable to perform one of them in advance and perform the other control after the previous control has stabilized.

The central control device 18 may store several types of programs in which combinations of set air volumes Qa and Qb are specified in a chronological manner.

For example, this program runs every hour of the day.
Specify the air volume settings for Qa and Qb. With this method, the set air volume specified by the program is input to the central control mechanism 18 every hour of the day, and the central control mechanism 18 outputs a pattern that corresponds to the specified set air volume, so that Performs air volume control.

The time unit of the program may be arbitrary, and it is desirable to prepare multiple programs with different contents based on seasonal or yearly changes in resistance due to aging of the piping system and an increase in the amount of sewage inflow.

This programming method is based on the setting air volume calculator 16.
Operation can be performed even without signals from A and 16B, and the dissolved oxygen meter 13
If A, 13B or the sewage flowmeters 17A, 17B are out of order, it is possible to automatically or manually switch to this program method and continue air volume control.
For example, in the case of sewage treatment, a program method can be used because the subsequent pattern can be determined based on the amount of rain.

Conversely, the air volume is usually controlled by a program, or the actual DO value and the DO set value are compared, and if the deviation between the two is large, the set air volume level is corrected to match the DO set value. Furthermore, the actual sewage inflow amount is compared with the sewage inflow amount assumed at the time of program creation, and if the deviation between the two is large, the set air volume level is corrected according to the deviation.

When the set air volume is modified as described above, the air volume is controlled in accordance with a pattern corresponding to the corrected set air volume, rather than the set air volume originally specified in the program.

Further, an auto-tuning method as described later can be applied to the above program.

Using the program method, the detector (in this case
Even in the event of a failure of the DO meter or flow meter, the entire system will not go down and the system will be able to operate according to a predetermined program, increasing reliability.

FIG. 7 shows another embodiment in which the aeration tank is 1A, 1
Three cases, B and 1C, are shown. 24 is a pumping source. 7AB and 7C are flow rate control valves. FIG. 8 shows the relationship between the opening degrees of the flow rate control valves 7AB and 7C and the flow rate ratio Qc/Qab in that case. The system flow control valve that indicates the maximum required air volume is always 100% open.

Figures 9 and 10 show aeration tanks 1A, 1B, 1
The case of different piping systems when C and 1D are four is shown. 7D, 7CD, 7ABC, and 7D are flow control valves. The system flow control valve that indicates the maximum required air volume is always 100% open.

When there are multiple aeration tanks, the air volume sum calculation section 19 calculates the sum of Qa+Qb+..., controls the blower flow rate, and the air volume ratio calculation section 21 calculates the sum of Qa+Qb+...
Ratio of Qa:Qb:Qc:... or as required
The air volume ratio, such as the ratio of two air volumes, such as Qa/Qb and Qab/Qc, is calculated to control the inlet flow rate.

Regarding the auto-tuning function of the linearizer, the opening degree of the flow control valve is set based on a characteristic curve stored in the linearizer. This characteristic curve changes depending on the resistance downstream of the collecting pipe 4 (resistance of the device, resistance of the branch pipe, characteristics of the flow control valve, etc.). Therefore, when these resistances change due to aging or the like, the air volume setting value and the actual air volume will differ. Therefore, it becomes necessary to modify the characteristic curve stored in the linearizer to match the actual state.

A method for automatically correcting the characteristic curve of a linearizer will be described below.

At a certain time t _i , the air volume setting values Qa and Qb are determined, and the opening degrees of 7A and 7B are determined and adjusted from Qb/Qa and the characteristic curve of the existing linearizer as shown in Fig. 11, and the actual air volume is Qa', Let it be Qb′. this
Air volume ratio Qb′/Qa′ of Qa′, Qb′ and 7 at time t _i
Correct using the opening calculation values Xa and Xb of A and 7B. At the next control time t _i+1 , the opening degrees of 7A and 7B are determined using the linearizer characteristic curve modified based on the control result at time t _i , and the linearizer is adjusted in the same manner based on this control result. Modify the characteristic curve of.

In the figure, q is the set value of Qb/Qa q′ is the actual value Qb′/Q
It is a′.

The present invention is not limited to the sewage aeration method as described in the embodiments described above, but the present invention is capable of controlling the flow rate by calculating and storing in advance the relationship of constants unique to the entire device to determine the flow rate required by each device from a pressure source to a plurality of devices. It can be applied to the method of doing. For example, it can be applied to heating furnace combustion air, factory ventilation, building air conditioning, etc.

〔Effect of the invention〕

As described in detail in the [Function] section, the present invention provides the following extremely significant practical effects.

(i) Rather than continuous, local feedback control, this method uses calculations to set the set values of flow rate control elements (flow control valves, etc.) at each sampling control cycle, thereby ensuring stable control. It can be carried out.

(ii) There is no need to maintain a high pressure in the collecting pipe to prevent interference, and there is no need for local continuous feedback control to maintain a constant pressure.

Therefore, without having to separate the control system into two loops: one for controlling the amount of air blown to each aeration tank and the other for controlling the amount of suction as a whole, it can be controlled as a large feedback system that includes both controls, and stable control can be achieved. It can be carried out.

(iii) Since there is no need to increase the pressure in the collecting pipe, the power of the blower can be kept to the minimum necessary and energy can be saved.

(iv) Since there is no need to maintain high pressure in the collecting pipe, the opening degree of the flow control valve only needs to be determined by the "distribution ratio", and a large opening degree with low throttling resistance can be selected, and the setting can be determined by calculation. control is easy and stable.

(v) Since the control is for each sampling control period, there is no movement of the flow rate elements except at the time of sampling, and for example, the frequency of opening of the flow rate control valve, etc. is reduced, and the structure of the flow rate control valve and its driving mechanism is reduced. It is simple and inexpensive, and furthermore, the life of the flow control valve, its driving machine, blower, etc. is extended.

[Brief explanation of drawings]

Fig. 1 is a flowchart of the conventional example, Fig. 2 is a flowchart of the embodiment of the present invention, Fig. 3 is a graph showing the stepwise setting of the set air volume, and Fig. 4 is a graph showing the combination pattern of the two set air volume. Graph, Figure 5 is a flow diagram of the central control device, Figure 6 is a graph showing the relationship between flow rate ratio and valve opening, Figure 7 is a flow diagram of another embodiment, and Figure 8 is a graph showing the relationship between flow rate ratio and valve opening. Graph showing the opening degree of the valve, Figure 9,
FIG. 10 is a flowchart of another embodiment, and FIG. 11 is an explanatory graph of autotuning. 1A, 1B, 1C, 1D...Aeration tank, 2A, 2B
...Sewage inlet, 3A, 3B...Blower, 4...Collecting pipe,
5A, 5B... Suction valve, 6A, 6B... Branch pipe, 7
A, 7B, 7AB, 7C, 7D, 7CD, 7ABC
...Flow rate control valve, 8A, 8B... Air flow meter, 9... Pressure gauge, 10... Pressure setting device, 11... Pressure regulator, 12
A, 12B...Flow rate controller, 13A, 13B...Dissolved oxygen meter, 14A, 14B...Dissolved oxygen amount setting device, 1
5A, 15B...Dissolved oxygen amount controller, 16A, 16
B... Setting air volume calculator, 17A, 17B... Sewage flow meter, 18... Central control device, 19... Air volume sum calculation unit,
20...Blower flow rate control section, 21...Air volume ratio calculation section,
22... Feed flow rate control section, 23... Feed flow rate control section,
24...Pumping source.

Claims (1)

[Scope of Claims] 1. A system comprising one or more blowers and a plurality of aeration tanks, the discharge side of the blower being connected to a collecting pipe, and the aeration tank being connected to a branch pipe branching from the collecting pipe. and is configured to feed aeration gas into the aeration tank, the branch pipe is provided with a feed flow rate control mechanism for controlling the flow rate of the feed gas, and the blower is provided with a blower flow rate control mechanism. In a method for controlling the amount of aeration gas fed into an aeration device, the amount of water flowing into the aeration tank and/or the amount of dissolved oxygen in the water to be treated is measured, and the required air volume for the aeration tank is adjusted to a predetermined value. Calculate and determine the required air volume for each control cycle, input this required air volume value to an integrated control mechanism, and set the blower flow rate control element of the blower flow rate control mechanism in the integrated control mechanism based on the sum value of each required air volume. The amount is determined by calculation, and the opening degree of the inlet flow rate control element of the inlet flow rate control mechanism of the aeration tank that indicates the maximum required air volume is set to the amount equivalent to the fully open state, and the inlet flow rate of other aeration tanks is determined by calculation. A set amount of the opening degree of the inlet flow rate control element of the control mechanism is determined by calculation based on the air volume ratio, and these set amounts calculated based on each input required air volume are outputted, and the blower flow rate control mechanism and the feed rate are 1. A method for controlling an aeration gas supply flow rate, comprising controlling an input flow rate control mechanism. 2.Equipped with one or more blowers and a plurality of aeration tanks, the discharge side of the blower is connected to a collecting pipe, the aeration tank is connected to a branch pipe branched from the collecting pipe, and the aeration tank is connected to a branch pipe branched from the collecting pipe. an aeration device configured to send aeration gas to the branch pipe, the branch pipe being provided with a feed flow rate control mechanism for controlling the flow rate of the feed gas, and the blower being provided with a blower flow rate control mechanism. In the aeration gas feeding rate control method, for any required air volume of each aeration tank, the set amount of the blower flow rate control element of the blower flow rate control mechanism determined based on the sum of each required air volume, and the maximum required air volume. The set amount of opening of the inlet flow rate control element of the inlet flow rate control mechanism of the aeration tank indicating the air volume is set as the amount corresponding to the fully open state, and the inlet flow rate of the inlet flow rate control mechanism of the other aeration tank at that time. A set amount of the opening determined based on the air volume ratio of the control element is calculated in advance, and these set amounts are stored in the central control mechanism in correspondence with the required air volume, and the amount of water to be treated in the aeration tank is and/or the amount of dissolved oxygen in the water to be treated, calculates and determines the required air volume for the aeration tank at each predetermined control cycle, inputs this required air volume value into the central control mechanism, and stores the required air volume in the aeration tank. A method for controlling an aeration gas feed rate, comprising: outputting a set amount corresponding to an input required air volume among the set amounts inputted, and controlling the blower flow rate control mechanism and the feed flow rate control mechanism.