JPS63178306A - Injection control device - Google Patents

Abstract

PURPOSE:To obtain high responsiveness prevented from the influence of the feeding flow rate of a raw material by finding out a correcting injection volume from a deviation or an injection correcting value, converting the correcting injection volume into a correcting injection flow rate and then adding the correcting injection flow rate to an objective injection flow rate to correct the objective injection flow rate. CONSTITUTION:When a detected water quality from a water quality meter 4 is shifted from an objective water quality, a correcting medicine volume corresponding to a deviation between the detected water quality and the objective water quality is found out by mimic process parts 6, 7 and a correcting medicine flow rate is found out through a converting circuit 9. On the other hand, a converter 8 finds out an injection rate correcting value from the correcting medicine volume and adds the flow rate to a reference injection rate to find out a corrected injection rate and a multiplier 11 multiplies the corrected injection rate by a raw water flow rate to find out the medicine injecting flow rate proportional to the raw water flow rate. The correcting medicine flow rate is added to the medicine injection flow rate proportional to the raw water flow rate and the added value is outputted to a controller 5 as an objective medicine injection flow rate to control the medicine flow rate. Thus, the medicine flow rate can be rapidly corrected even if the raw water flow rate is low.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an injection control device suitable for chemical injection I control used in water purification plants and the like.

(Prior Art) FIG. 8 shows the configuration of a conventional chemical injection υ control device.

In the figure, 1 is a raw water flow meter, 2 is a chemical flow m meter, 3 is a control valve, 4 is a water quality meter, 5 is a controller, 20 is a target chemical injection flow m calculating section, and 30 is a mixing tank.

The target chemical injection flow f is obtained by multiplying the raw water flow M obtained by the raw water flow meter 1 and the injection rate obtained by the target chemical injection flow m calculation unit 20.
f1 (=raw water flow direction x injection rate) is determined, and the valve opening degree of the control valve 3 is reduced and mixed so that the chemical injection flow rate obtained by the chemical flow meter 2 is equal to the target chemical injection flow rate using the controller 5. A chemical is injected into the tank 30.

Further, in this conventional example, the target chemical injection flow rate calculation unit 20 calculates the injection rate correction amount from the deviation between the water quality after chemical injection obtained by the water quality meter 4 and the target water quality.

The target chemical injection flow rate calculation unit 20 includes a reciprocal part (KO, hereinafter referred to as the static characteristic reciprocal part) 6 of a simulated process static characteristic part, and a simulated process dynamic characteristic part (Gc (S), hereinafter referred to as the dynamic characteristic part) 7. The chemical injection water quality is controlled to the target water quality using complementary feedback as follows.

That is, the injection rate correction amount is calculated from the deviation between the water quality after chemical injection obtained by the water quality meter 4 and the preset target water quality,
This injection rate correction amount is added to a preset basic injection rate to obtain a corrected injection rate, and this corrected injection rate is multiplied by the raw water flow rate to obtain a target injection rate.

Here, the static characteristic part (static gain) of the process transfer function
If Kp is the dynamic characteristic part (kinetic gain) and Gp (S) is the dynamic characteristic part (dynamic gain), then if Kc = KI) and GO (S) = Gl) (S), then the above-mentioned injection rate correction amount Although the chemical injection water quality changes and the deviation decreases, the output of the dynamic characteristic section 7 increases by the amount corresponding to the decrease, and the injection rate correction amount is kept unchanged. Therefore, as an injection rate correction amount, responsiveness similar to open circuit control can be obtained, and it is an effective means for things such as drug injection control that have a large dead time element.

However, the conventional chemical injection control device described above has the following problems. In other words, as the raw water flow rate changes, the dynamic gain Gp(S) also changes, so when the simulated dynamic gain GO(S) is fixed, Gc
(S)=Gp (S) is no longer satisfied, and control responsiveness deteriorates.

Therefore, when the raw water flow rate becomes zero, the deviation remains forever, and the corrected injection rate diverges to infinity.

Further, in the conventional example described above, the deviation is corrected based on the flow rate of raw water, but the correction based on the flow rate of raw water cannot cover the amount remaining in the mixture 120, resulting in poor i-controllability.

(Problems to be Solved by the Invention) As described above, in the above-mentioned conventional chemical injection control device,
There was a problem in that the control response was poor and it was impossible to control when the raw water flow rate was zero or to correct the residual amount in the mixing tank.

The present invention has been made based on the above-mentioned problems, and its purpose is to provide an injection control system with high control responsiveness that is not affected by the raw material supply basin.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention detects the mixing ratio after mixing the raw material and the injected material, and detects the deviation between the mixing ratio and the target ratio. The injection rate correction m of the injectable material is determined based on the injection rate, the injection rate correction m is added to the preset basic injection rate to obtain the corrected injection rate, and the corrected injection rate is multiplied by the feed addition of the raw material. In a device that controls the injectable material mixed into the raw material based on the target injectable flow rate, the corrected injectable amount is determined from the above deviation or injection rate correction amount,
The present invention is characterized in that the corrected injection volume is converted into a corrected injection volume, and the corrected injection volume is added to the target injection volume for correction.

(Function) In the present invention, the corrected injection flow rate m is determined from the deviation between the mixing ratio and the target ratio or the injection rate correction amount obtained from this deviation, and this corrected injection volume is converted into the corrected injection volume. The target injection flow rate is corrected by adding it to the target injection flow rate.

(Embodiment) FIG. 1 shows the configuration of an embodiment of the apparatus according to the present invention.

As shown, mix I! Raw water is supplied to 30 via a raw water flow meter 1, and chemicals are injected via a chemical flow meter 2 and a control valve 3. Furthermore, a water quality meter 4 is provided on the outflow side of the mixing tank 30 to measure the water quality after the chemicals are injected. The detected raw water flow rate and measured water quality (chemical injection contact water quality) are supplied to the target chemical injection flow rate calculation section 20. Further, the detected chemical flow is supplied to the controller 5.

The target chemical injection flow rate calculation unit 20 is configured to control the mixing tank 3 after chemical injection.
In addition to variably controlling the injection rate so that the water quality at zero is equal to the target water quality, chemicals are The supply amount can be controlled variably.

For this purpose, the target chemical injection flow rate calculation unit 20 calculates the deviation between the measured water quality (chemical injection contact water quality) and the target water quality, and calculates the corrected chemical amount from this deviation by the simulated process static characteristic reciprocal unit 6.
and a simulated process dynamic characteristics section 7, a converter 8 which inputs the corrected chemical amount obtained, converts it into an injection rate corrected amount, and outputs it, and also inputs the corrected chemical amount, converts it into a corrected chemical flow rate, and outputs it. A conversion circuit 9 is provided.

The simulated process static characteristic reciprocal part 6 and the simulated process dynamic characteristic part 7 are parts for simulating setting of the process characteristic function including the injection equipment, and are used to set the target water quality and chemical injection water quality by sample P operation, etc. The corrected chemical amount is determined so that the deviation becomes zero.

This correction chemical m is added to the mixing tank 3 before the target water quality is changed.
It is determined based on the amount of chemicals required to make the retained amount of the mixture of raw water and chemicals flowing into the tank 0 to the target water quality after the change. In other words, only this corrected amount of chemicals is added to the mixing tank 30.
By injecting the water into the mixing tank 30, the water quality of the water remaining in the mixing tank 30 can be made to the target water quality even if the raw water flow rate is zero. This corrected chemical amount is converted into a corrected chemical flow rate via the conversion circuit 9 and supplied.

FIG. 2 shows an example of the conversion circuit 9.

The three examples shown in FIG. 2 (Δ) to (C) are the same structure but expressed in different ways. In addition, the same figure (D) shows the flow fflx
The configuration is such that a program of time = darkness is set in the memory, and the flow R (output) is obtained from the capacitance (input) by program control. Furthermore, the diagram (E) is constructed by feeding back the actual flow rate to the input, so that a more accurate corrected chemical flow rate value can be obtained.

The injection rate correction amount is added to a preset basic injection rate to obtain a corrected injection rate, and this corrected injection rate is added to a preset basic injection rate.
1 is multiplied by the detected raw water flow rate.

The output of this multiplier 11 is a proportional valve for the chemical injection stream,
In this embodiment, the target chemical injection flow rate is determined by adding the corrected chemical flow rate to the raw water flow m proportional valve of the chemical injection flow port.

The determined target chemical injection flow rate is supplied to the controller 5. Then, the controller 5 calculates the deviation between the target chemical injection flow rate and the chemical injection flow rate detected by the chemical flow meter 2.
The control valve 3 is controlled so that the valve opening is proportional to this deviation.

Next, the operation of the above embodiment will be explained.

First, chemicals are injected into raw water at a certain injection rate.
In a steady state where the mixing tank 30 maintains the target water quality,
Since there is no deviation between the detected value of the water quality meter 4 and the target water quality, no chemicals are added to the mixed water of raw water and chemicals that has already flowed into the mixing tank 30.

Also, at this time, a constant injection rate correction m is obtained,
This is added to the basic injection rate to obtain a corrected injection rate as the optimum injection rate. However, if the target water quality is obtained while injecting chemicals into raw water at the basic injection rate, the injection rate correction amount is zero.

Then, this optimum injection rate is multiplied by the raw water flow rate in the multiplier 11 to obtain the chemical injection flow rate for the raw water flow rate at that time, and since the corrected chemical flow rate is zero, it is directly output to the controller 5 as the target chemical injection flow rate. As a result, the [1 valve 3] is controlled so that the chemical flow mountain becomes the target chemical injection flow I.

Therefore, chemicals are injected into the raw water flowing into the sliding door at an optimal injection rate. Even if the raw water flow rate changes, the chemical flow rate changes in proportion to the change, so that the mixed water quality in the mixing tank 30 maintains the target water quality.

In this state, if the water quality detected by the water quality meter 4 deviates from the target water quality for some reason, the simulation process section 6.7 calculates a corrected chemical amount corresponding to the deviation between the detected water quality and the target water quality. Then, the corrected chemical flow rate is determined via the conversion circuit 9.

On the other hand, in the converter 8, an injection rate correction amount is obtained from the correction chemical, and is added to the basic injection rate to obtain a corrected injection rate.

Then, a multiplier 11 multiplies the corrected injection rate by the raw water flow rate to obtain the chemical injection flow rate of the raw water flow rate proportional valve.

The above-mentioned corrected chemical flow rate is added to the chemical injection flow m of the raw water flow rate proportional valve and outputted to the controller 5 as the target chemical injection flow m,
Drug ytm is controlled. However, when the target injection flow rate is negative, it is treated as zero.

In this way, the amount of chemicals corresponding to the water quality deviation is calculated based on the relationship s with the raw water flow rate, and the corrected chemical flow rate is calculated from this corrected chemical amount and mixed. Therefore, the responsiveness of water quality control is not affected by the flow rate of raw water, and correction is performed quickly even when the flow rate of raw water is small. Therefore, even if the raw water flow m becomes zero, if the chemical flow rate correction layer is positive, the mixed water that has already flown in will surely reach the target water quality within a certain time.

In addition, the water quality of the water already flowing into the mixing tank 30 is quickly corrected to the target water quality by the chemical injection flow rate correction amount.
As a result, chemicals can be injected into subsequent inflow raw water at an injection rate that is quickly optimized, and the new inflow section quickly reaches the target water quality. Therefore,
This hardly interferes with the deviation correction operation for the quality of the water already flowing into the mixing tank 30, and the control response becomes faster.

In this way, when the water quality of the mixing tank 30 approaches the target water quality, the corrected injection rate also approaches the optimum value, and when the target water quality is obtained, the optimum injection rate is reached.

Thereafter, when raw water of a certain level flows into the mixing tank 30, which has the target water quality, chemicals are also injected at the optimum injection rate in proportion to the flow, so that the water quality of the mixing tank 30 maintains the target water quality.

FIG. 3 shows the configuration of a second embodiment of the present invention.

In this embodiment, the injection rate correction amount is first determined by the simulation process units 6 and 7 from the deviation between the target water quality and the water quality after chemical injection, and is added to the basic injection rate. The corrected chemical amount is determined via 8. This corrected chemical m is converted into a corrected chemical flow rate via the conversion circuit 9, and is added to the raw water flow ω proportional valve of the chemical injection 51m to obtain the target chemical injection flow rate.

Even with this configuration, the same effects as those of the first embodiment can be obtained.

FIG. 4 shows the configuration of a third embodiment of the present invention.

In this embodiment, the extraction point of the simulated process dynamic characteristic section 7 is changed and the output of the conversion circuit 9 is used as the extraction point, and the corrected chemical flow,
After the quantity is integrated via the integrator 10, it is supplied to the simulated process dynamic characteristics section 7.

With this configuration, in addition to the effects of the first embodiment, the simulated process dynamic characteristic section 7 can be configured without taking into account the characteristics of the conversion circuit 9, so the configuration of the dynamic characteristic section 7 is simplified. It has the effect of being

FIG. 5 shows the configuration of a fourth embodiment of the present invention.

This embodiment adopts and organizes the configuration example shown in FIG. 2(E) as the conversion circuit 9 of the third embodiment in FIG.
Since the device configuration is simplified and the actual 8i amount is fed back, a more accurate corrected chemical flow M can be determined.

FIG. 6 shows the configuration of a fifth embodiment of the present invention.

This embodiment is configured to integrate the output of the simulated process static characteristic reciprocal unit 6 via an integrator 13 to obtain a corrected chemical amount, and exhibits the same effect as the first embodiment.

FIG. 7 shows the configuration of a sixth embodiment of the present invention.

This embodiment takes into consideration controllability in cases where the deviation between the target water quality and the measured water quality is too large, such as when the water in the mixing tank 30 is raw water without chemical injection at the start of chemical injection control, etc. Therefore, in such a state, the injection rate correction valve is set to zero, and the basic injection rate is not corrected.

For this reason, in this embodiment, a changeover switch 15 is provided, and when the deviation between the target water quality and the measured water quality is too large and the determined injection rate correction valve is equal to or higher than a predetermined value, the changeover switch 15 is switched to control the injection rate correction valve. is set to zero.

As a result, in each of the embodiments described above, transient overcorrection at the start of control can be prevented.

In this embodiment, the changeover switch 15 may be configured to set the used injection rate correction to zero.

Further, in each of the above embodiments, controllability can be further improved if feedforward control is used in combination to correct the injection rate by taking various factors such as raw water quality into consideration.

[Effects of the Invention] As explained above, according to the present invention, the injection material is supplied regardless of the raw material supply flow rate, so injection with good responsiveness can be achieved without being affected by changes in the raw material supply flow rate. Control equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, and FIG. 2 (A
) to (E) are block diagrams showing an example of a conversion circuit used in the present invention, FIGS. 3 to 7 are block diagrams showing other embodiments of the present invention, and FIG. 8 is a structure of a conventional example. It is a diagram. 1... Raw water flow meter 2... Chemical flow meter 3... Control valve 4... Water quality meter 5... Controller 6... Simulated process static characteristic reciprocal part 7... Simulated process Dynamic characteristic section 8...Converter 9...Conversion circuit 20...Target chemical injection flow rate calculation section 30...Mixing tank

Claims (1)

[Claims] (1) Detect the mixing ratio after mixing the raw material and the injectable, calculate the injection rate correction amount for the injectable based on the deviation between the mixing ratio and the target ratio, and adjust the injection rate correction amount to the preset basic injection. In a device that controls the injected material mixed into the raw material by adding it to the injection rate to obtain the corrected injection rate, and multiplying the corrected injection rate and the feed flow rate of the raw material to obtain the target injection flow rate. , After determining the corrected injection volume from the above deviation or injection rate correction amount and converting the corrected injection volume into a corrected injection volume,
An injection control device characterized by adding a correction injection flow rate to the target injection flow rate to correct the target injection flow rate.