JP6581856B2 - Blower control device - Google Patents

Description

  The present invention relates to an apparatus for controlling the number of blowers for controlling the quality of treated water in a sewage treatment plant, for example.

  Now that environmental issues and cost reductions have become essential, sewage treatment plants are also required to improve the quality of treated water discharged into public water areas, further energy savings, and improvement in maintainability using ICT. .

  In sewage treatment plants, organic matter, nitrogen, etc. in sewage are removed with a microbial suspension called activated sludge. A biological reaction tank in which air is blown into activated sludge by a blower is called an aerobic tank. In the aerobic tank, organic substances are ingested / consumed and removed by an assimilation / catabolic reaction by microorganisms. In addition, ammonia nitrogen, which is the main nitrogen component in the inflowing sewage, is oxidized in the aerobic tank to become nitrate nitrogen. Nitrate nitrogen is reduced to nitrogen in the subsequent oxygen-free tank and released into the atmosphere.

  In these water treatment processes, a blower that blows air into activated sludge consumes a large amount of power. Therefore, in order to reduce the power consumption of the blower, for example, by controlling the blower appropriately by DO constant control that makes the concentration of dissolved oxygen (DO) installed at the end of the aerobic tank constant, the required air volume is controlled by the aerobic tank. To send.

  Here, there is a certain degree of correlation between the amount of air sent from the blower to the biological reaction tank and the power consumed by the blower, but it is not a proportional relationship. For example, when controlling the blower air flow by turning ON / OFF multiple blowers, the number of blowers is increased or decreased with a certain value of the calculated required air flow as a threshold, and the excess air flow is discharged into the atmosphere from the air discharge valve. To do. Since the number of blowers and power consumption are proportional, the air volume sent from the blower (calculated required air volume) and the power consumption are stepped. In general, in order to prevent frequent increase / decrease in the number of blowers, for example, the threshold of airflow when reducing the number of blowers from two to one is smaller than the threshold of airflow when increasing the number of blowers from one to two. . Therefore, there are cases where the number of blowers is different for the same air volume, that is, the power consumption is different. In other words, the graph of the power consumption with respect to the air volume has a step-like relationship that partly overlaps.

  In the case of a blower that controls the air volume by means of an inverter or an inlet vane, there is a certain degree of correlation between the air volume and power consumption (Non-Patent Document 1), but generally the efficiency is highest at the maximum air volume point of the blower. In controlling a plurality of blowers, if the number of blowers is increased, the air flow per unit is reduced even with the same air flow, and the efficiency is lowered. Therefore, the graph of the power consumption against the air volume has a relationship in which a part of the monotonically increasing step overlaps.

  In order to properly control the number of blowers and reduce power consumption, the amount of air flow that can be achieved with this overlap, that is, with a small number of blowers, should be minimized as much as possible. It ’s fine.

  Patent Document 1 relates to a device for controlling the number of blower devices that controls the amount of aeration air to be blown into an aeration tank of a sewage treatment plant using an activated sludge method, and in particular, an appropriate dissolved oxygen amount (hereinafter, DO) of an aeration tank. It is an invention relating to a device for controlling the number of operating blower devices for blowing an aeration air amount for securing a value). If the DO value does not tend to decrease when the DO value is changed, that is, if the incoming water quality load tends to decrease, the increase in the number of blowers is suppressed by suppressing the increase in the number of blowers. To do.

  Patent Document 2 corrects the air volume calculated in the clear weather mode in the rainy weather mode, because the inflow flow pollution load is different between clear weather and rainy weather. By providing, automatic control is to be realized in all states, and a unit control unit that determines the number of units for the obtained air volume is provided.

Japanese Patent Laid-Open No. 06-149301 Japanese Patent Laid-Open No. 04-071691

Hiroshi Enomoto, Tadaaki Sakamoto, Shizukazu Shindo: Energy evaluation method for blower equipment at sewage treatment plants, Journal “EICA”, Vol.11 No.2 / 3, pp.115-118 (2006)

  Japanese Patent Laid-Open No. 2004-228561 is a countermeasure for changing the set value of the DO value in DO control. In general, DO control is operated at a constant value for a long period of time, and the DO is caused to follow the target value by PI control. In that case, the DO value frequently increases or decreases near the target value. In addition, even when the incoming water quality load increases, for example, the required air volume momentarily exceeds the threshold for increasing the number of blowers, and the number of blowers increases, but after that, only the air volume of the overlap portion may be required thereafter. .

  In Patent Document 2, the necessary air volume is efficiently calculated not only in fine weather but also in rain by providing a rainy weather mode. However, the efficiency of the number of blowers is not mentioned, and the calculated necessary air volume is not mentioned. However, it is difficult to increase the number of blowers.

  In order to solve such a problem of the conventional configuration, an object of the present invention is to provide a blower control device capable of appropriately controlling the water quality of sewage treatment and suppressing power consumption by the blower. There is.

In order to achieve the above object, a blower control device of the present invention includes inflow water that is treated water, a flow meter that measures the flow rate of the inflow water, an aerobic tank that oxidizes the inflow water, and the preferred A plurality of blowers for sending air to the air tank, an air flow meter for measuring the air volume of the air sent to the aerobic tank, a required air volume calculating unit for calculating the air volume required for the aerobic tank, and the plurality of blowers And a blower control unit that controls the flow rate and the number of units of air, and the flow rate variation pattern of the inflowing water and the flow rate variation pattern of the air that is sent to the aerobic tank It is determined that the flow rate measured by the flow meter at a certain time and the air flow measured by the air flow meter at a certain time are within a normal range, and the predicted air flow is calculated from the air flow variation pattern. Wind forecast Comprising an arithmetic unit, wherein the blower control unit is characterized in performing the threshold determination of the number increase or decrease of the blower in the predicted air volume and air volume the indispensable air volume calculation unit has calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the power consumption by a blower can be suppressed, controlling the water quality of a sewage process appropriately by controlling the number of blowers appropriately.

The block diagram of the blower control apparatus of Example 1. FIG. Relationship between blower air volume and blower power consumption. Control flow for conventional blower unit control (conventional mode). Control flow (prediction mode) for controlling the number of blowers when one blower is operating. Daily fluctuation pattern of air volume and flow rate. Control flow (prediction mode) for controlling the number of blowers when operating two blowers. The block diagram of the blower control apparatus of Example 2. FIG. Mode discrimination flow. Control flow for controlling the number of blowers when a single blower is operating (rain prediction mode). Relationship between flow rate and air volume during rainfall. Control flow for controlling the number of blowers when operating two blowers (rain prediction mode).

  Embodiments of the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a configuration diagram of Embodiment 1 of the present invention.

  This embodiment is an example in which a blower number control device is applied to a sewage treatment plant using activated sludge. Sewage 100 flows into the biological reaction tank 1 and flows out as treated water 101. A diffuser tube 2 is immersed in the biological reaction tank 1, and two blowers, a first blower 11 and a second blower 12, communicate with each other. The flow rate of the inflowing sewage 100 is measured by the flow meter 21. In the biological reaction tank 1, the part that feeds air through the air diffuser 2 is an aerobic tank, and the dissolved oxygen concentration at the end is measured by a dissolved oxygen concentration meter 22. The amount of air sent is measured by an air flow meter 23.

  Information on the flow meter 21, the dissolved oxygen concentration meter 22, and the air flow meter 23 is sent to the required air flow calculating unit 31, and the required air flow is calculated. The calculated necessary air volume is sent to the predicted air volume calculator 32. The predicted air volume calculating unit 32 calculates the predicted air volume based on the daily air volume fluctuation pattern, the flow rate fluctuation pattern and the calculated required air volume from the daily fluctuation pattern database 33, and the blower control unit 34 calculates the required air volume and the calculated air volume. Based on the predicted air volume, the flow rate of the blower and the threshold value for increase / decrease in the number of units are determined, and the first blower 11 and the second blower 12 are controlled.

  A conventional method for controlling the number of blowers will be described.

  FIG. 2 shows the relationship between the blower air volume and the blower power consumption when the conventional blower number control is performed using two blowers equipped with inlet vanes. The power consumption increases as the blower air volume increases. Two blowers can generate more air volume than one blower, but some overlap.

FIG. 3 is a control flow (conventional mode) of conventional blower unit control. The required air volume calculation unit 31 controls the required air volume QBr (t) [m3 / hr] at time t using, for example, PID control so that the dissolved oxygen concentration is constant, and then the single blower is operated. In the case (S1), the required air volume QBr (t) at the time t is compared with the threshold Th1 [m3 / hr] (S2), and if the required blower air volume QBr (t) [m3 / hr] is less than the threshold Th1, the blower One unit operation is continued (S1). When it becomes larger, one blower is activated and two blowers are operated (S3). In this case, compared indispensable air volume at time t QBR (t) and the threshold value Th2 [m3 / hr] (S4 ), the threshold Th2 when the small I必 main blower air amount QB than (<Th1) stop one blower Then, one blower is operated (S1). From FIG. 2, it can be seen that if the air volume between the threshold values Th1 and Th2 is operated by two blowers, the power consumption of the blower may be reduced.

As a method therefor, FIG. 4 shows a control flow (prediction mode) for controlling the number of blowers according to the first embodiment. This is the case of operating one blower (S1). The required air volume Q _Br (t) at time t is compared with the threshold Th ₁ (S2). If the required air volume Q _Br (t) at time t is greater than the threshold Th ₁ , the sewage flow rate Q (t over the past n hours ) [m ³ / hr] and the blower air volume Q _B (t) [m ³ / hr] are compared with their daily fluctuation patterns (S3).

FIG. 5 shows an example of the daily fluctuation pattern of the air volume and the flow rate. The solid line is the daily fluctuation pattern. The dotted line is the value of the daily fluctuation pattern ± 10%. In the comparison (S3) in FIG. 4, for example, if the current time is 12:00 and n = 24 hours, if the air volume and flow rate values until 12:00 yesterday are outside the range of this dotted line, determining (S4), and two blower operation based on the required blower air volume Q _Br (t) exceeds the threshold value Th ₁ (S8). On the other hand, if both the flow rate and the air volume are within the range, the predicted air volume Q _Bp (t + Δt) after time Δt (for example, 15 minutes) is derived from the daily fluctuation pattern database (S5). The predicted air volume Q _Bp (t + Δt) is compared with the threshold value Th ₁ (S6). If this also exceeds the threshold value Th ₁ , it is determined that the air volume of the blower needs to be increased now and in the future, and the blower 2 A stand-alone operation is performed (S8). If the threshold is less than Th _1, the request to increase the number of blowers is instantaneous. After Δt (for example, after 15 minutes), it is determined that the required air volume can be provided by the current number of blowers, and the operation of one blower is continued. (S1). However, if the required blower air volume Q _Br (t) continuously exceeds the threshold value Th ₁ during the past mΔt (for example, m = 4, mΔt = 60 minutes) (S7), Regardless of the predicted air volume, two blowers are operated.

FIG. 6 shows a control flow (prediction mode) for controlling the number of blowers in the case of two blowers (S1) in the first embodiment. In order to reduce power consumption, if the threshold value is lower than Th ₁ , the number of blowers should be set to one as much as possible. Therefore, as described above, when the required blower air volume Q _Br (t) at time t is smaller than the threshold Th ₁ (S2), the sewage flow rate Q (t) and the blower air volume Q _B (t) over the past n hours and those Are compared (S3). If the air volume and flow rate are out of range (S4), it is determined that the condition is different from the normal condition. As in the conventional mode, if the required blower air volume Q _Br (t) falls below the threshold Th ₂ (S6), the blower 1 It is assumed to be a stand-alone operation. On the other hand, if both the flow rate and the air volume are within the range (S4), the predicted air volume Q _Bp (t + Δt) after time Δt (for example, 15 minutes) is derived from the normal daily fluctuation pattern database (S5). If this also falls below the threshold Th ₁ (S7), it is determined that the blower air volume can be reduced now and in the future, and one blower is operated (S9). If the threshold value is Th ₁ or more, the request to reduce the number of blowers is instantaneous, and after Δt (for example, after 15 minutes), it is determined that it is necessary to cover the required air volume with the current number of blowers. The operation is continued (S1). However, if the required blower air volume Q _Br (t) continuously falls below the threshold value Th ₁ during the past mΔt (for example, m = 4 and mΔt = 60 minutes) (S8), Regardless of the predicted air volume, a single blower is operated (S9).

  By the method of the present embodiment, the time period for calculating the necessary air volume by reducing the number of blowers is excessive, and the power consumption can be suppressed.

  In this embodiment, a blower provided with an inlet vane is used. However, a blower provided with an inverter may be used, or a blower having only ON / OFF may be used. In this case, for example, it is conceivable to control the air flow into the biological reaction tank by discharging a surplus air flow into the atmosphere using a discharge valve.

  In the present embodiment, the dissolved oxygen concentration constant control is used for the calculation of the required air volume in the required air volume calculating unit 31. However, as long as the required air volume is given, nitrification using, for example, air magnification control or an ammonia meter is used. Control, control derived from a database based on actual values, or the like may be used.

  In this embodiment, the daily fluctuation pattern is set to one for the flow rate and the air volume, but may be changed according to the time (for example, the month, the rainy season, the season) and the event (for example, summer vacation, year-end and New Year holidays). Further, the current daily fluctuation pattern may be created based on, for example, an average value at normal times based on the actual values of the flow rate and the air volume. Furthermore, it is possible to provide a rainfall flow rate and air volume fluctuation pattern according to the rainfall amount and the rainfall time, and change the daily fluctuation pattern according to the rainfall amount and the rainfall time. Moreover, you may use an air magnification instead of an air volume so that it may describe below.

  In this embodiment, using the flow rate and the air volume as the daily fluctuation pattern, it is determined whether the current flow rate and the air volume are within the range, but for the air volume, using the air magnification made dimensionless by the flow rate, It may be determined whether the flow rate and air magnification at the current time are within the range.

  Although this embodiment has been described as a blower control device in sewage treatment, any device that calculates the necessary air volume of a blower and controls a plurality of blowers can be applied without being limited to sewage treatment.

(Example 2)
FIG. 7 is a configuration diagram of Embodiment 2 of the present invention. The rainfall information acquisition unit 41 and the rain forecast air volume correction unit 42 are added to the configuration of the first embodiment, and signals are sent to the rain information acquisition unit 41, the rain forecast air volume correction unit 42, and the forecast air volume calculator 32. The case where two blowers are used as in the first embodiment will be described.

  The rainfall information acquisition unit 41 acquires the rainfall information (for example, the area, the amount of rainfall, the time, etc.) of the area related to the target area. There are three modes for controlling the number of blowers. The first is the conventional mode shown in FIG. The second is the prediction mode shown in FIGS. 4 and 6 of the first embodiment. The third is a rain prediction mode that corrects the predicted air volume during rain as shown below. As described in the first embodiment, the method using the daily fluctuation pattern database at the time of rainfall belongs to the prediction mode.

FIG. 8 shows a mode discrimination flow. When rainfall is not detected by the rainfall information acquisition unit 41 (S1), the prediction mode is set (S2). When rain is detected, the sewage flow rate Q (t) and the blower air volume Q _B (t) over n hours before the rain and their daily fluctuation patterns are compared as in the first embodiment (S3). For example, in the case of n = 24, if the air volume and the flow rate are within the range over the past 24 hours, the process proceeds to the rain prediction mode (S5). If it is outside the range, it is raining in a state different from the normal time, so the prediction method in the present invention is not used, and the number of blowers is determined in the conventional mode according to the conventional method (S6).

FIG. 9 shows an example of the control flow in the rain prediction mode when a single blower is operating. When the required blower air volume Q _Br (t) at time t is larger than the threshold Th ₁ (S2), the predicted air volume Q _Bp (t + Δt) after time Δt (for example, 15 minutes) is derived from the normal daily fluctuation pattern database. After (S3), based on the relationship between the flow rate and the air volume at the time of rain, a predicted air volume correction calculation at the time of rain (S4) is performed.

FIG. 10 shows an example of the relationship between the flow rate and the air volume during rainfall. This function represents that the required air volume decreases with a delay when the sewage flow rate increases due to rainfall. This is a phenomenon that occurs as a result of the inflow sewage diluted by rainfall flowing down into the biological reaction tank from the upstream side. The flow rate increment ΔQ (t) [m ³ / hr] is the increment relative to the normal sewage flow rate Q (t), and the predicted air flow increment ΔQ _Bp (t + Δt _x ) is the normal amount of air required after Δt _x hours. This is the predicted increment from the daily fluctuation pattern. It can be derived from past air volume and flow rate and rainfall information, for example, Δt _x is 5 hours.

Using this rainfall-time air volume relationship, a predicted air volume Q _Bp (t + Δt) after time Δt is derived. First, ΔQ (t− (Δt _x −Δt)), which is the flow rate increment before time Δt _x -Δt, is derived (FIG. 9 (S5)), and the flow rate is calculated from the relationship between the flow rate and the air volume during rainfall (FIG. 10). An air flow increment ΔQ (t + Δt) with respect to the increment ΔQ (t− (Δt _x −Δt)) is derived (S6). Next, the predicted air volume Q _Bp (t + Δt) after time Δt is derived by adding the air volume increment ΔQ (t + Δt) to the air volume Q (t + Δt) at time t + Δt in the daily fluctuation pattern database ( S7). If the threshold value is Th ₁ or more, the request to reduce the number of blowers is instantaneous, and after Δt (for example, after 15 minutes), it is determined that it is necessary to cover the required air volume with the current number of blowers. The operation is continued (S10). When the lower threshold value Th _1, the air volume of the blower now be determined that it can be reduced in the future, and one blower operation (S1). However, if the required blower air volume Q _Br (t) continuously exceeds the threshold Th ₁ during the past mΔt (eg, m = 4, mΔt = 60 minutes), it is determined that the daily fluctuation pattern remains. The two blowers are operated (S10).

FIG. 11 shows an example of the control flow in the rain prediction mode when operating two blowers. When the required blower air volume Q _Br (t) at time t is larger than the threshold Th ₁ (S2), the predicted air volume Q _Bp (t + Δt) after time Δt (for example, 15 minutes) is derived from the normal daily fluctuation pattern database. After (S3), based on the relationship between the flow rate and the air volume at the time of rain, a predicted air volume correction calculation at the time of rain (S4) is performed. The contents of the implementation are the same as in the above-described operation of one blower.

Corrected predicted air volume predicted air volume Q _Bp (t + Δt) If this also falls below the threshold Th ₁ (S8), it is determined that the air volume of the blower can be reduced now and in the future, and one blower is operated (S10). ). If the threshold value is Th ₁ or more, the request to reduce the number of blowers is instantaneous, and after Δt (for example, after 15 minutes), it is determined that it is necessary to cover the required air volume with the current number of blowers. The operation is continued (S1). However, if the required blower air volume Q _Br (t) continuously falls below the threshold Th ₁ during the past mΔt (eg, m = 4, mΔt = 60 minutes) (S9), Regardless of the predicted air volume, a single blower is operated (S10).

  By the method of the present embodiment, the time period for calculating the necessary air volume by reducing the number of blowers is excessive, and the power consumption can be suppressed.

  In this embodiment, a blower provided with an inlet vane is used. However, a blower provided with an inverter may be used, or a blower having only ON / OFF may be used. In this case, for example, it is conceivable to control the air flow into the biological reaction tank by discharging a surplus air flow into the atmosphere using a discharge valve.

  In the present embodiment, the dissolved oxygen concentration constant control is used for the calculation of the required air volume in the required air volume calculating unit 31. However, as long as the required air volume is given, nitrification using, for example, air magnification control or an ammonia meter is used. Control, control derived from a database based on actual values, or the like may be used.

  In this embodiment, the daily fluctuation pattern is set to one for the flow rate and the air volume, but may be changed according to the time (for example, the month, the rainy season, the season) and the event (for example, summer vacation, year-end and New Year holidays). Further, the current daily fluctuation pattern may be created based on, for example, an average value at normal times based on the actual values of the flow rate and the air volume. Moreover, you may use an air magnification instead of an air volume so that it may describe below.

  In this embodiment, using the flow rate and the air volume as the daily fluctuation pattern, it is determined whether the current flow rate and the air volume are within the range, but for the air volume, using the air magnification made dimensionless by the flow rate, It may be determined whether the flow rate and air magnification at the current time are within the range.

  Although this embodiment has been described as a blower control device in sewage treatment, any device that calculates the necessary air volume of a blower and controls a plurality of blowers can be applied without being limited to sewage treatment.

1 Biological reaction tank
2 Air diffuser
11 First blower
12 Second blower
21 Flow meter
22 dissolved oxygen concentration meter
23 Air flow meter
31 Required air volume calculator
32 Predicted air volume calculator
33-day fluctuation pattern database
34 Blower control unit
41 Rainfall information acquisition unit
42 Predicted air volume correction during rain
100 sewage
101 Water to be treated

Claims (5)

Inflow water to be treated,
A flow meter for measuring the flow rate of the influent water;
An aerobic tank for oxidizing the inflow water;
A plurality of blowers for sending air to the aerobic tank;
An air flow meter for measuring the air flow of the air sent to the aerobic tank;
A required air volume calculating unit for calculating the air volume required for the aerobic tank;
A blower control unit for controlling the air volume and the number of the plurality of blowers;
In a blower control device comprising
A daily fluctuation pattern database for storing a flow fluctuation pattern of the inflowing water throughout the day and an air flow fluctuation pattern of the daily flow of air sent to the aerobic tank;
Determining that the flow rate measured by the flow meter at a certain time and the air volume measured by the anemometer at a certain time are within a normal range;
A predicted air volume calculation unit for calculating a predicted air volume from the air volume fluctuation pattern;
With
The blower control device, wherein the blower control unit determines a threshold value for increasing / decreasing the number of blowers based on the air volume calculated by the necessary air volume calculating unit and the predicted air volume. In the predicted air volume calculation unit, determining whether the flow rate measured by the flow meter at a certain time is within an allowable flow rate range derived based on the flow rate according to the flow rate variation pattern;
Determining whether the airflow measured by the airflow meter at a certain time is within an allowable airflow range derived based on the airflow according to the airflow fluctuation pattern;
The blower control device according to claim 1, wherein the blower control device is a predicted air volume calculation unit that calculates a predicted air volume from the air volume fluctuation pattern. Furthermore, a rain information acquisition unit and a rain forecast air volume correction unit are provided,
The blower control device according to claim 1 or 2, wherein the predicted air volume calculated by the predicted air volume calculating unit is corrected based on the rain predicted air volume correcting unit. When the predicted air volume correction method calculated by the predicted air volume calculating unit in the rain predicted air volume correcting unit is a function that expresses the relationship between the flow rate and the air volume during rainfall, the required air volume is 4. A blower control device according to claim 3, wherein a function representing decreasing is used. 5. The blower control device according to claim 4, wherein the function representing the relationship between the flow rate and the air volume at the time of raining uses a function representing that the required air volume decreases with a delay when the sewage flow rate increases due to rain. .

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