JPS61157397A - Apparatus for controlling concentration of dissolved oxygen - Google Patents

Abstract

PURPOSE:To reduce cost, by connecting an aeration tank to the emitting side of a blower through a regulation valve and mounting a pipeline characteristic measuring apparatus for calculating the resistance coefficient of the blow pipe to the aeration tank and the static water head pressure of the aeration tank. CONSTITUTION:The DO values of aeration tanks 1, 2 are detected by DO meters 3, 4 and supplied to system 1 and system 2 demand air amount calculation apparatuses 33, 34 to calculate the demand air amounts Q1, Q2 of the aeration tanks 1, 2. An operation region calculation apparatus 41 operates operation regions E1-E5 prior to control to store the same in an operation region table 42. A demand point calculation apparatus 43 calculates min. emitting pressure P satisfying the demand air amount Q1 from the demand air-amounts Q1, Q2 and temps. T1, T0 to determine a demand point (Q1+Q2, P). A blower selection apparatus 44 selects a blower satisfying a demand from the demand point and the operation regions E1-E5 stored in the operation region table 42.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dissolved oxygen concentration control device suitable for use in a sewage treatment system using an activated sludge method.

[Traditional technique river]

The quality of treated water in sewage treatment systems such as sewage treatment systems is determined by the dissolved oxygen concentration (
(hereinafter abbreviated as Do), it is necessary to maintain pO at an optimal value.

FIG. 8 shows the configuration of a conventional device having two series of aeration tanks (hereinafter abbreviated as air tanks) 1 and 2. DO in the air tank 1.2 is detected by DO meters 3 and 4, and the DO It is supplied as an electrical signal to the controller 5.6. The Do controller 5.6 calculates the air volume necessary to maintain DO at a predetermined value, controls the opening degrees of the control valves 9 and 1O via the air volume controllers 7 and 8, and controls the air tank 1. Supply the necessary air volume to 2. In this case, the above air volume is the air flow meter 11.1
2 and supplied to air volume controllers 7 and 8.

The above control valve 9. Blower 15-1 (i = 1, 2-n) supplies air to the inlet side of lO, and each blower 1
The suction side of 5-1 is equipped with an airflow meter 16-1 and a suction valve 17-1, and the sucked air is unified by a pipe 18 and branched into each n joint 9°10. It's become a trap. Then, the pressure gauge 19 provided in the pipe line 18 measures the discharge pressure P of the blower 15, and the pressure controller 21 controls the discharge pressure P so that it matches the value set by the pressure setting device 20. . That is, the pressure controller 21 controls the discharge pressure P by controlling the air volume controller 22-1 that controls the opening degree of each suction valve 17-1. Also, at this time, the amount of air flowing into each suction valve 17-1 is detected by the airflow meter 16-1, and the total sum is sent to the number controller 24 via the adder 23, and the operation pattern of the blower 15 is determined and selected. The blower is now in operation.

[Problem that the invention seeks to solve]

By the way, in the conventional device described above, each control valve 9
．． 10, the discharge pressure P of the blower 15 is set high, and the required air volume of each air tongue 1.2 is achieved by narrowing the opening of the control valves 9 and 10. are doing. Therefore, the control valve 9. Although the necessary air volume control can be performed by changing the opening degree of IO, the problem is that the discharge pressure P of the blower 15 must be set high in advance, and the power of the blower 15 becomes large. There was a thunderstorm.

Additionally, in order to add another air tongue to an existing device with one air tongue to create the configuration shown in Figure 8, there was a problem in that the existing device had to be significantly modified. . That is, in this case, it is necessary to add the control valve 9 and the air flow meter 11 between the pipe line 18 and the air tank l (if there is only one air tank, the pipe line 18 and the air tank l need to be installed).
(because they are directly connected), there was a problem of high construction costs.

On the other hand, as shown in FIG. 2 of the construction drawing, a control valve 30 and an air flow meter 31 are installed between the pipe 18 and the added air tank 2, while keeping the pipe 18 and the air tank 1 directly connected. Although the construction work is easier when the airflow is inserted, there is a problem in that it becomes extremely difficult to control the air volume.

That is, since there is no control valve between the discharge side of the blower 15 and the air tongue 1, the amount of air supplied to the air tongue 1 is equal to the discharge pressure P.
In addition to depending on the amount of air, it also changes depending on the amount of air flowing into the air tongue 2, and these amounts of air may interfere with each other.

For example, in order to increase the air volume to the air tongue 2 while keeping the air volume to the air tongue l constant, it is possible to first increase the opening of the control valve SO, but this alone will not increase the discharge pressure P.
will drop, and the amount of air flowing into the air tongue will decrease.

Therefore, if the amount of air flowing into the air tongue 1 is controlled by increasing the opening degree of the suction valve 17, the amount of air flowing into the air tongue 2 will increase.

In this way, since the opening degrees of the control valve 30 and the suction valve 17 both affect the air volume of the air tanks 1 and 2, it becomes extremely difficult to adjust the air volume side M (however, unlike the conventional control valve 9.lO
Since there is no extra pressure loss at the pump, the discharge pressure P can be small and the blower power can also be small).

The present invention attempts to overcome such control difficulties in the system configuration shown in FIG.

[Means for solving problems]

In order to solve the above problems, the present invention provides an aeration tank (1) directly connected to the discharge side of the al blower, and an aeration tank (1) connected to the discharge side of the blower via a control valve (30). Tank (2), (c) Air pipe resistance coefficient of each xlv-ship pyp (1), (2) described in fv1, and each aeration tank (1), (2) described in ^11
A pipe line characteristic measuring device (55) for determining the hydrostatic head pressure of ldl, a blower characteristic curve when each suction valve opening is maximized and minimum, and a blower characteristic curve when the control valve opening is maximized and minimum. an operating range calculating device 1i (41) that calculates an operating range corresponding to the operating pattern of each blower from the resistance curve of the above-mentioned resistance curve;
A required point calculating device (4
3); (f) a blower selection device (44) that determines an optimal operating pattern for the blower from the required point and the operating range; Operating point calculation device (4
5).

[Effect]

According to the above configuration, since the pipe line 18 and the air tank 1 remain directly connected, the air tank 2 can be used without modifying the conventional device.
can be expanded. Further, by the following procedure, the required air volume can be supplied to each air tongue 1.2 while maintaining the discharge pressure P at the minimum pressure. The processing for this will be explained below.

(1) Measurement of pipe characteristics.

The air volume supplied to the air tongues t and 2 in Figs. 1 and 2 (volume air volume at discharge pressure P) are Qt-, Qz- (m"/h),
When the discharge pressure is P (mAq), the following equation holds true.

p=r, Qta+H, ・・・・・・・・・・・・・・・
(1) 2=(′・+r)Q″・+8・”””t21
+.

■、; Hydrostatic side pressure of air tank l (A(1)" lj Air tank/2 hydrostatic side pressure (aq)) Here, the resistance coefficient r is a quantity that depends on the opening degree of the control valve 30, and p4 clause When fully open
= Q, when fully closed, r = country. Therefore, when the control valve 30 is fully opened, the equation (2) becomes p=r, Q, 1a + Hl"."".(2a).

On the other hand, the above-mentioned discharge air volumes Q1-, Qya and the corresponding suction air volumes Qr, Q, t (volume air volume at atmospheric pressure PI!L; Nze/h) are calculated according to the Boyle-Share equation. [They are related as follows.

However, Pl: Atmospheric pressure (A(L)) τ6: Constant for converting ℃ to °K τ1: Suction temperature ('C) To: Discharge temperature (℃) Here, atmospheric pressure P and constant T0 are constant. Since it is a number,
Temperature jlT1 p To , discharge pressure P, suction air volume Q (=
Qt + Q, t ) -Q
t Hl can be determined.

Embodiment drawing FIG. 5 is a diagram showing the above measurement method, and shows the control valve 3.
0 is fully open, and the operating pattern of the air pump 15 and the opening degree of the suction valve 17 are changed appropriately (that is, by changing the discharge pressure P and the suction air volume q), and when the suction air tct becomes stable, the suction temperature is T1, suction air volume q, discharge pressure P, discharge temperature To, and discharge air volume Qxa are measured. Then, by substituting these into equation (4) to find the suction air volume Qt, the suction air volume q, becomes Qt
=Q-Qt, and the discharge air volume Q+a can be determined by equation (3).

Therefore, if the above measurements are made at several points to several tens of points, and the value P @ Q (a + Qza is applied to equations (11 and (2)) and the least squares method is applied, the pipe characteristic parameter rl + HIt
r2. Hy can be calculated. The pipe characteristic measuring device 35 performs this work, and is composed of a data collection section 35a that collects data and a pipe characteristic calculation section 55t+ that performs the above calculation.

(2) Determining the operating range Next, the operating pattern is changed by changing the combination of operating blowers, and in each operating pattern, the openings of the suction valve 17 and the control valve 30 are changed. Find the area (operating area) on the Q,-P plane where the calculation is possible.

First, the blower characteristics when changing the opening degree η (%) of the suction valve 17 will be considered.

A certain blower (for example, blower 15-1) is operated, the suction valve 17 is fully opened (η=100%), and the discharge valve 51 in FIG.
, 52. By measuring the discharge pressure P and suction air TCT when the opening degree of the control valve 30 is varied, a basic blower characteristic curve M shown in FIG. 4 is obtained. The formula for this curve M is: P=aQ, +1) and L+(!...
(5) However, a, b, and c are expressed as blower characteristic constants.

Next, when resistance is applied by changing the opening degree I7 (ch) of the suction valve 17, the pressure loss ΔP (tomo A (1)) due to this resistance is: ! ΔP=k (η)・q...・・・・・・
(6) However, k(η); resistance coefficient when valve opening degree η is (
**Aq/(m”/h)), which corresponds to the pressure loss curve N shown in Fig. 4.Then, the blower characteristic curve M1 when the opening degree of the suction valve 17 is q% is as follows. (Details of this method are described, for example, in Fluid Machinery (published by Morikita Publishing Co., Ltd., 1980) by Mitsukiyo Murakami et al., pages 185-186)
,.

(2) Draw a perpendicular line from point sl (coordinates Q, IF) on curve M to the q-axis, and set the intersection point Ei2 (Q, O).

Draw a straight line It passing through the 0 point S2 and the point (0, -Poo), and find the intersection point ft11M1l,). 3 (Qx
, -aa) Set to 1. Note that the above point (0,
-P. ) is the point of absolute zero pressure.

A straight line l that passes through the 0 point S1 and the point (0, -Poo),
The intersection with the perpendicular line passing through point 3 is 84 (Qx tax)
shall be.

(2) If point 81 is moved on curve M and point B4 is obtained by the same operation as above, this becomes blower characteristic curve M.

If we express the above operation in a formula, we first get the straight line It.

The expression becomes , from the expression. Also, a straight line! Since the formula of , becomes, pffllH't at point S4 is...
・・・・・・・・・・・・ Ql. In this way, the blower characteristic -iIi1M corresponding to the opening degree η of the suction valve 17 is determined, and the blower characteristic curve Ml corresponding to the maximum opening degree ηmaK and the minimum opening degree 1m.

M2 is 18i on the Q-F plane as shown in FIG. will be shown.

('b) Next, consider the resistance curve when the opening degree of the control valve 30 is changed.

Now, since the effective water depths of Air Tan 1.2 are equal,
Hydrostatic head pressure H1 and H! of equations (1) and (2). It almost matches. If we put this as ■, the resistance curve of the entire ventilation system is P”R (Qja + Qga) + H・””...
...”' Qυ However, R is the resistance coefficient of the entire ventilation system (xAq/(m”/h)). From this equation and equations (1) and (2), the resistance coefficient R can be calculated as follows:
If +oo, then 1=r1,Q,,==Q, and (
Equation 12 (corresponds to Equation 11, and the resistance curves I, l
is as shown in Figure 5. On the other hand, if the control valve 30 is fully opened and the resistance coefficient r→0, then the resistance curve at this time is as follows, and the fifth
The curve L2 shown in the figure corresponds to this.

In this way, on the Q-P plane, resistance curves Ll and L2 are drawn that have a weight of 6 to equation (1) and equation 04, and these curves are respectively expressed when the control valve 30 is fully closed and fully opened. handle.

The area between the curves bl l L2 is the control valve 50
It shows the range that can be achieved by changing the opening degree of

Therefore, the blower characteristics 1 MIIM2 determined by the above (al)
The area E surrounded by the resistance curves Ll and I+2 obtained in (b) is the operating area that can be realized by controlling the openings of the suction valve 17 and the control valve 50, and each point of this operating area σ (operating point), the opening degree η of the suction valve 17 and the resistance coefficient r of the control valve 30 are uniquely determined.

Next, when the blowers are operated in parallel, the characteristic curves of the operating blowers are synthesized, and the operating region as shown in Figure 6 is obtained! ! ii to z5 are obtained. These operating ranges, each operating point within the range, the opening degree η of the suction valve 17 and the resistance coefficient r of the control valve 30 corresponding to each operating point are calculated in advance and stored in the memory.

(3) Calculation of required points.

Next, the air volume that should be blown to the air tongue 1.2 (required air volume) Q
When t and Qt (volume air volume at atmospheric pressure) are given, the corresponding point on the Q-P plane (qrtpr
) (hereinafter, this point will be referred to as the required point).

First, when the required air volume is qi, the corresponding
t1 discharge air volume: Q, +a can be found from equation (3),
Substituting this into equation (1), we get: Here, is a value determined by the discharge temperature To and the suction temperature T1, and P
, is the atmospheric pressure (constant), so Q! By modifying Equation 19, a 203rd order equation for discharge pressure can be obtained.

That is, P + (2F, -H,)P +Pa (Pa-2H,)P
Pa (Hl + rHK Q, 1) = 0”
(17) Then, by solving the fin equation, the point (ctt+:p) can be found, and this discharge pressure P is the blower required to blow the above air volume Q+,l;Lt. Discharge pressure. Also, the air volume Qt can be calculated using the formula GL! from the suction air volume Q and the air volume Q1. = Q, Ql. Note that the above point (Q, III') is (1
), it is a point on the resistance curve bl in FIGS. 5 and 6.

(4) Arrowhead of blower selection and operating point.

Next, the blower is selected and the operating point is determined by comparing the required point and the operating range.

(al　l! If it is within the required point operation area.

For example, as shown in FIG.
*? ) is within the operating range, this point A
is the operating point, and correspondingly, the resistance coefficient r of the control valve 50 and the opening degree η of the suction valve 17 are determined.

(When the bl request point is between curves I, 1 and I12 and not in the operating region.

For example, as shown in FIG. 7, the required point A (Q, r++
'Qrz I p & ) is the driving area]! ! If the device is placed between l and 2, the curve passing through point A and satisfying formula I and each area]! ! 1. I! i2, ll1
The intersection with the boundary line of 3 (closer to point A) is AI, A2. A
S, the required point A, each point AI, A2 . Select the operating range with the smallest difference in air volume from A3. In this case, the operating region E2 is selected, the point A2 becomes the operating point, and the corresponding resistance coefficient r of the control valve 30 and opening degree η of the suction valve 17 are determined.

(If the chi sought point is below song 41jL2.

For example, as shown in FIG. 7, the required point B (Qrm+
Qr4, pB) is below songs #I, 2,
At the discharge pressure FB determined from the air volume Qrm to the air tongue l,
Even if the control valve 60 is fully opened, the air volume Q and r4 to the air tongue 2 cannot be achieved.

In such a case, the control valve 50 is fully opened (that is, on the song wL2), and the discharge pressure P that can supply the air volume Qr< is determined from equations (2a) and (4), and this is set as Pia. Then, the operating point B when the discharge pressure is Pica is determined, and the corresponding resistance coefficient r of the control valve 30 and opening angle η of the suction valve 17 are determined.

In this way, in any of the above cases (al to tel), operation is performed at the minimum discharge pressure that satisfies the required air volume.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment for realizing the above-described effects. In this figure, Airta/
The Do value of each air tongue 1.2 is detected by the Do total 3.4, and this is supplied to the required air volume calculating device 33, 34, which calculates the required air volume Q, i, q! of each air tongue 1.2. is required. In addition, 35 is a pipe characteristic parameter rl t Hl s
Pipeline characteristic measuring device for determining rf + Hl, 56.
57 is the suction temperature T! , a thermometer that measures the discharge temperature T0. Each of these values is supplied to the air volume distribution control device 40, and each calculation described in the [Operation] column is performed.

First, prior to control, the operating region calculation device 41 performs [
tlL! mentioned in (2) of [Effect]! The motion ranges 11jl to IC5 are calculated using iE, and these are stored in the drive range table 4.
Store in 2. Further, the required point calculating device 43 calculates the minimum discharge pressure P that satisfies the required air volume Q from the required air volume Qz-Q and the temperature T1+TO, and calculates the minimum discharge pressure P that satisfies the required air volume Q, and calculates the required point (Q+ + Qt
＋? ) to determine. The blower selection device 44 selects the required point (Q+ + Qt t P ) and the operating area tape/
From each operating range Ml to E5 stored in L/42,
Select the blower that best meets your requirements5t
.

The number control device 24 is informed of the blower to be operated by the blower selection device [44], and controls the operation of the blower 17. The operating point calculation device 45 determines the optimal operating point from the required point and the blower to be operated, calculates the suction air volume and the air volume of the air tongue 2, and controls the suction valve opening 4° control device 38 and the splinter valve control device 39, respectively. send commands to.

In such a configuration, by carrying out the operation described in the above [Operation] section, it becomes possible to send the necessary fire to the air tongue 1.2 with a small discharge pressure R.

〔Effect of the invention〕

As explained above, the present invention connects the air tongue to be added to the existing pipe line via the control valve, and satisfies the required air volume with the minimum discharge pressure from the predetermined operating range of the blower. By extracting the operating point where the operation is possible, and determining the opening degrees of the control valve and blower suction valve and the blower to be operated based on this operating point, the following effects can be achieved. .

(1) When adding an air tongue, there is no need to change the existing ventilation system, so construction costs are low.

(2) Since the required air volume can be sent with the minimum discharge pressure, less blower power is required, resulting in energy savings.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the ventilation system of the same embodiment, and FIG.
The figure is a block diagram for explaining the method for measuring pipe characteristic parameters, Figure 4 is a graph showing the method for determining the blower characteristic -11Ma from the blower basic characteristic curve M, and Figure 5 is the method for determining the operating region E. The graph in FIG. 6 shows the operating range 11-1!15 during blower parallel operation, and the graph in FIG. 7 shows the required point A. FIG. 8 is a graph for explaining the method of determining operating points AI and B from B, and FIG. 8 is a block diagram showing the configuration of a conventional dissolved oxygen fineness control device. 1.2...Air tongue (aeration/tank), 15
... blower, 17 ... suction valve, 50 ... control valve,
55... Pipeline characteristic measuring device, 41... Operating point calculating device, 43... Request point calculating device, 44... Blower selection device, 45... Operating point calculating device.

Claims (1)

[Scope of Claims] Dissolved oxygen concentration in which the amount of air supplied to an aeration tank is controlled by controlling the operating pattern of a plurality of blowers and the opening degree of a suction valve provided on the suction side of each of the blowers. In the control device, (a) an aeration tank directly connected to the discharge side of the blower, (b) an aeration tank connected to the discharge side of the blower via a control valve, and (c) an aeration tank connected to each of the aeration tanks. (d) a pipe characteristic measuring device for determining the blast pipe resistance coefficient and the hydrostatic head pressure of each of the aeration tanks; (e) an operating range calculation device that calculates an operating range corresponding to the operating pattern of each of the blowers from a resistance curve when the air flow rate is maximized and minimized; (f) a blower selection device that calculates an optimal operating pattern of the blower from the required point and the operating range; A dissolved oxygen concentration control device comprising: an operating point calculation device that calculates the opening degrees of the control valve and the suction valve from an operating pattern.