JPS5827692A - Airflow controller for aeration vessel - Google Patents

Abstract

PURPOSE:To eliminate ineffective power consumption, by adding objective airflow values for aeration vessels to obtain a gross airflow value, and controlling a suction valve with a value, obtained by adding an in-pipe loss in response to the gross airflow value at the end of an air blow pipe in the aeration vessel, as a target value. CONSTITUTION:When required airflow amounts for aeration vessels 10 are large, a gross airflow Q obtained by adding an objective airflow value for each aertion vessel becomes large, an objective value of injection pressure calculated by corrector 13 becomes large, a pressure controller 14 carries out control operation to open a suction valve 4, and the injection pressure of a blower 1 increases so that the necessary airflow is performed to the aeration vessels 10. When the required airflow amount for the aeration vessels 10 are reduced, the target airflow value to be inputted to an aeration airflow controller 9 becomes small, so that the aertion airflow controller 9 suqueezes an aeration airflow control valve 8 to reduce an actual airflow amount to a level corresponding to the objective airflow amount.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air volume control device for an aeration tank in a sewage or wastewater treatment plant.

Activated sludge is widely used to treat sewage and industrial wastewater, and in order to activate the sludge in the aeration tank, an air flow rate several times the inflow of the water to be treated is required. Several blowers will be installed. Furthermore, constant air pressure control is adopted to prevent variations in piping resistance leading to each aeration tank and to prevent surging of the air blower. A block diagram of a conventional air volume control device is shown in FIG. 11) in the figure is a blower, and the capacity of the blower is normally determined by the amount of air blown to the aeration tank (3 to 7 times the amount of inflow water) and the amount of air blown to the preliminary aeration tank (1 time the amount of inflow water). , multiple (several) blowers are used because large capacity is required. (2) is an intake hole, which is equipped with a filter for purifying the air. (31 is a suction air flow meter that uses an orifice etc. to measure the suction air volume. <4J is a suction valve, (53 is a discharge pressure needle installed in one pipe that collects the discharge side pipes of the blower, (6) is a pressure regulator, which compares the discharge pressure measurement value from the discharge pressure gauge (5) with a predetermined set pressure and controls the opening degree of the suction valve (4) so as to reduce the deviation to zero. A constant pressure control is performed.Each blast pipe branched at the downstream position of the discharge pressure gauge (5) is connected to each aeration tank a1 via an aeration air volume needle (7) such as an orifice and an aeration air volume control valve (8). The output of the 1ilI airflow meter (7) is inputted to each aeration airflow rate controller (9), and is compared with the 0.000m airflow rate determined by the amount of inflow water, etc., so that the deviation is zero. The wind is blown towards the mouse.

Aeration air volume alS control valve in single air volume control device (8)
The WJz diagram shows the characteristics of control by Curve R8- in the figure
R is a pressure-airflow curve when the control valve (8) is fully open, and the discharge pressure is a constant value P. , then point A of pressure P0 on the curve R-R0. The flow rate Q0 is the air flow rate when the control valve (8) is fully open, that is, the discharge pressure is P. This is the maximum air flow rate when At this time, the pressure pB and the pressure P0 at the intersection of the curve R8-Ro with the vertical axis, that is, when the air volume is zero,
The difference (Po Pg) is the pipe line loss of the piping when the air volume Q0 is Toshi, and the pressure PH is the terminal pressure at the end of the blast pipe in each aeration tank C1 (i).

Now, without changing the discharge pressure P, the air volume is Qs (Ql
The pressure-airflow curve when the control valve (8) is throttled down so that <Qo) is plotted on the horizontal axis from point A on curve R1-R, and pressure P on curve R8-R1. If the intersection of the perpendicular AIQ+ and the curves -R, -R is C1, then the pressures P and P at point C1.

(Ps Ps ) This is the valve loss caused by throttling the Fi control valve (8). Also, CPr Pm)
#i is the pipe line loss of the piping when the air volume is Q1. Toe 9,
In this case, the air volume Ql is obtained by throttling the control valve (8) while keeping the discharge pressure at a constant value P, so a valve loss greater than the pipe resistance at that time occurs9, which is wasteful. be.

The discharge pressure required to obtain the air volume Q1 is P, and if the discharge pressure is set to Pl, the air volume can be set to Q without throttling the control valve (8), reducing unnecessary valve loss to zero. be able to.

On the other hand, the control characteristics of the suction valve (4) of the blower 111 are as shown in FIG. In the figure, the curve B0 is the pressure-air volume curve when the suction valve (4) is not throttled, and when the suction valve (4J) is throttled, it changes to the pressure car air volume-1Iil#i curve (B1).The curve R8-Ro is This is the pressure-air volume curve when the air volume control valve (8) is fully open, which is the same as the companion shown in Figure 2.
If you narrow down to 1, the driving point is a song! ! From the intersection A0 of Be and the song @R, -Ro to the intersection A of the curve B1 and Ran @R, -Ro,
The power required by the blower (1) at that time curves from the curve L0.

, and the power decreases. Therefore, by setting and controlling the blower discharge pressure to Pl when the required air flow rate to the aeration tank is Ql, the blower power can be reduced by the difference between the curve passing to the air flow rate Q and the song 1IILI.

As is clear from the above explanation, the conventional air flow control device shown in Fig. 1 keeps the discharge pressure of the blower constant regardless of the amount of air blown to the aeration tank, and the The amount of air blown is controlled by changing the opening degree of the aeration air amount control valve (8).

When the required air flow rate increases, the required power of the blower also increases in order to obtain the required discharge pressure, and even when the required air flow rate decreases, the aeration air flow control valve (8) is throttled in the operating state 11. Since the feed rate is reduced due to the valve loss, power is wasted.

The present invention was made in order to eliminate the waste of power in conventional air volume control devices, and in order to make the discharge pressure of the fan necessary and sufficient to ensure the necessary amount of air blown to the aeration tank, The actual air volume value to the aeration tank is determined by adding the target air volume values for each aeration tank, and the discharge pressure is calculated by adding the pipe line loss corresponding to that air volume to the required end pressure at the end of the air pipe in the aeration tank. The purpose of the present invention is to provide an aeration tank air volume control device that achieves a reduction in valve loss in an aeration air volume control valve and a reduction in power for feeding mm by controlling a suction valve based on a target value of .

Embodiments of the present invention will be described below with reference to the drawings. An embodiment of the aeration tank air volume control device according to the present invention + j Valve, (51If
i discharge pressure gauge, (7) aeration air volume needle, (8) aeration air volume control valve, (9) aeration air volume control meter, αG#i aeration cypress aeration These are constructed in the same manner as shown in FIG. aυ is an adder, into which a signal indicating the zero air volume value of each aeration tank is inputted, and outputs a linear velocity air volume value Q obtained by adding these signals.

A3 is the pressure setting device, and the aeration tank (1 (end pressure P at the end of the blower pipe in the aeration tank obtained by adding an appropriate pressure to the head of water at the end of the blower pipe in l)! be done.

03 is a correction device, into which the set pressure pg from the pressure setting device αa and the linear velocity air volume value Q from the addition 5all are input, and the piping loss pressure proportional to approximately the square of the linear velocity air volume value 9 is calculated. Discharge pressure target value P obtained by adding set pressure pB
Outputs 1. That is, p, −pl! +(af(Q
) 10b) -・-tt+Here P,: Discharge pressure target value PE: Set pressure a, b: Constant af (Q) ``The piping loss term 04), which is approximately proportional to the square of the sewing air volume, is the pressure adjustment With a needle, the discharge pressure target value P1 from the correction device α4 and the output of the discharge pressure gauge (5), that is, the actual discharge pressure Pb
and the suction valve (4) so that the deviation becomes zero.
Controls the opening degree.

In the aeration tank air volume control device according to the present invention configured as described above, when the required air volume of the aeration tank αq becomes large, the linear velocity air volume value Q, which is the sum of the target air volume values of the respective aeration tanks, becomes large. In the above case, the discharge pressure target values P and L calculated by the correction device α turbidity according to equation 1 become large, and therefore the discharge pressure of the pressure regulator (141 performs a control operation to open the suction valve (4) and blow all the air). increases, and the required air volume is blown to the aeration tank Q(l). When the required air volume of the aeration tank (11) decreases, the 0 2 air volume value input to the aeration air volume controller (9) becomes smaller. Therefore, the aeration air volume controller (9) throttles the aeration air volume control valve (8) and reduces the actual air volume to match the air volume of 1 camphor.In addition, the nominal air volume of each aeration tank is input to the adder 0υ. Since the value becomes smaller, the linear velocity air volume value Q decreases, so the discharge pressure target value P is calculated and output by the correction device αJ.
, decreases, so the control signal of the pressure regulator α is throttled down to the suction valve (4) and the blower is turned off. 1) The discharge pressure decreases.

At the same time, the power of the blower fil is also reduced. As the discharge pressure of the blower (1) decreases, the output of the aeration air volume needle (7) decreases, and the aeration air volume adjustment needle (9) performs a control action to open the aeration air volume control valve (8) to match the air volume target value. Then, the aeration air volume is set so that the required aeration air volume is blown while the valve loss of the aeration air volume control valve (8) is reduced.

As detailed above, according to the aeration tank air volume control device according to the present invention, the discharge pressure of the blower is controlled to a pressure necessary and sufficient to blow the required air volume, depending on the size of the required air volume of the aeration tank. As a result, the discharge pressure of the blower is controlled to be constant so as to maintain the high discharge pressure required when the air flow is large.Compared to conventional air volume control devices, the power of the blower is reduced and This eliminates the waste of adjusting the air cover to match the required air volume by adjusting the aeration air volume control valve (8) when the required air volume of the aeration tank is small, and it is possible to realize an energy-efficient aeration tank blower device. . 1

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional aeration tank air volume control device, Fig. 2 is a graph showing the characteristics of the aeration air volume control valve control, Fig. 3 is a graph showing the characteristics of the suction valve control, and Fig. 4 is a graph showing the characteristics of the suction valve control. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of an embodiment of an air tank style IT control device according to the present invention. l...Blower 2...Intake hole 3...Suction flow meter 4...Suction valve 5...Discharge pressure gauge 7...Aeration air flow meter 8...Aeration air flow control valve 9.Aeration air flow control meter 10...Aeration tank
11...Adder 12°゛・Pressure setting device 13
...Correction device 14...Pressure regulator agent Patent attorney Inoue - Male → Wind cover (29t IJσ Figure 3 Figure 4

Claims (1)

[Claims] a plurality of air blowers each having a suction valve;
A discharge pressure gauge is inserted and connected to a single pipe where the discharge side pipes of these blowers are collected, and a plurality of pipes are branched at the bale flow position of this discharge pressure needle through an aeration air flow meter and an aeration air flow control valve. A plurality of blower pipes are connected one-to-one to the aeration tank, and an autonomous air volume value and the aeration air volume are provided for each of these pipes and are determined in accordance with the amount of water to be treated that flows into each aeration tank. This was accomplished by adding an aeration air volume controller that controls the opening degree of the aeration air volume control valve so that the deviation from the air volume measurement value from the meter is zt2, and the nine air volume values of each of the aeration tanks. an adder that calculates and outputs an air volume value; and a pressure setting device that sets the end pressure of the blast pipe obtained by adding an appropriate pressure to the water head applied to the blast pipe end in the aeration tank and outputs this set pressure. , the set pressure from this pressure setting device and the achieved air volume value from the adder are input, and the pipe loss pressure which is approximately proportional to the square of the achieved air volume value is calculated, and the set pressure is added to this pipe loss pressure to obtain the result. a correction device that outputs the discharge pressure target value that has been calculated, and compares the discharge pressure target value from the correction device with the pressure creation value from the discharge pressure gauge and opens the suction valve so that the deviation becomes zero. An aeration tank air volume control device that is equipped with a pressure adjustment needle that controls the flow rate of the aeration tank.