JPS628208A - Rate controller - Google Patents

Abstract

PURPOSE:To correct the mixing rate of a mixer to a target rate speedily even when the supply amount of a primary-side raw material is small by supplying a secondary-side raw material regardless of the size of the primary-side raw material if the mixing rate of the mixer deviates from the target ratio. CONSTITUTION:If water quality detected by a water quality gauge 38 deviates from target water quality for some reason, the 2nd water quality controller 44 performs P operation on the basis of the deviation between the detected water quality and target water quality to calculate the correction quantity of a chemical injection flow rate corresponding to the deviation. The adder 52 of a chemical injection flow rate adjusting part 46 adds the correction quantity of the chemical injection flow rate to the injection flow rate of chemicals proportional to the flow rate of raw water and outputs a target chemical injection flow rate to a flow rate controller 47, thereby controlling the flow rate of chemicals. The 1st water quality controller 42, on the other hand, performs P operation on the basis of the deviation between the detected water quality and target water quality and vary the correction quantity of an injection rate which is constant so far.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is applied to a gas proportional mixing system i [1, etc.] for controlling the proportional injection of chemicals and controlling the calorie content of fuel gas in water purification plants, etc. A ratio i that controls and adds another variable Y in proportion to a certain variable X to obtain the target vIZ! 131Y is attached to the llIn device.

[Technical background of the invention and its problems]

The conventional chemical injection control system is based on the relational expression: chemical injection flow rate = injection rate x raw water basin, and for example, as shown in FIG. The injection rate is multiplied by 12 to determine the target chemical injection flow rate, and the flow rate controller 14
Then, the control valve 18 is operated to increase or decrease the flow rate of the chemical injected from the chemical flow meter 16 so that the flow rate of the chemical is added to the mixing tank 20 so that it becomes equal to the target chemical injection flow rate.

By the way, in order to correct the discrepancy between the water quality of the mixing tank 20 and the preset target water quality, a chemical injection control device has conventionally been used. ! 11
A water quality controller 22 is installed in the water quality controller 22, and the injection rate correction interval is determined from the deviation between the water quality after chemical injection obtained in the water quality IT 24 and the target water quality, and this is added to the preset basic injection rate using the adder 2.
A method is adopted in which the injection rate is increased/decreased until there is no difference between the target water quality and the water quality after chemical injection, such as by adding 6 times.

However, with the innovative conventional technology, the following problems have arisen due to fluctuations in the flow rate of raw water.

In other words, in order to eliminate the deviation between the water quality of the mixed water already flowing into the mixing tank and the target water quality, it is necessary to inject an extra amount of chemicals equivalent to the shortage rate x the volume of the mixing tank, but if the same amount If the raw water flow rate is small for injecting chemicals, the chemical injection flow rate proportional to this will also be small and it will take a long time.

In other words, the control response speed for maintaining the water quality for chemical injection at the target water quality depends on the magnitude of the raw water flow rate, and if the raw water flow rate is small, the response becomes extremely slow and the deviation continues for a long time.

In particular, when the raw water flow rate becomes zero, the deviation remains forever.

In addition to adjusting the water that has already flowed into the mixing tank 20 to the target water quality, it is also necessary to perform a correction operation to optimize the injection rate so that the water quality after chemical injection at the subsequent raw water inflow valve will reach the target water quality. However, since the control response is slow when the raw water flow rate is small, it inherently takes time to converge the injection rate to the optimal value, and there is a deviation between the water quality of the mixing tank after chemical injection and the target water quality. One question is whether to further increase the injection rate by the amount that corrects the inflow portion to the mixing tank, or It has been difficult to quickly obtain the optimum injection rate due to the unreasonable requirement that the injection rate should be reduced. Therefore, the injection rate for the new inflow portion of raw water deviates from the optimum injection rate for a long time, which causes a new deviation between the water quality after injection and the target water quality, which causes the problem of poor control characteristics. there were.

[Purpose of the invention]

The present invention was made in view of the drawbacks of the prior art described above, and when there is a deviation between the ratio of the primary raw material and the secondary raw material after mixing and the target ratio, regardless of the size of the primary raw material and the secondary raw material, By adding an element to supply secondary raw materials, we have created a ratio control device that can control the ratio quality after mixing and improve control response even when the supply amount of primary raw materials is zero. The purpose is to obtain.

[Summary of the invention]

In the ratio control device according to the present invention, there is provided a means for detecting a mixing ratio of a primary raw material and a secondary raw material after mixing, a means for determining a ratio correction amount from a deviation between this mixing ratio and a target ratio, and means for determining a secondary side raw material supply amount correction amount from a deviation of the target ratio; a preset basic ratio is corrected by the ratio correction layer to obtain a correction ratio; the correction ratio is multiplied by the primary side raw material supply amount; The apparatus further includes means for adding the secondary side raw material supply amount correction amount to obtain a target supply amount of the secondary side raw material, and means for controlling the supply of the secondary side raw material in response to the target supply amount.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the first embodiment.

FIG. 1 is a block diagram showing a drug injection system according to the present invention. In the figure, raw water is mixed via a raw water flow meter 30, and chemicals are mixed via a chemical flow meter 32 and a control valve 34)
It is designed to be supplied to J36.

A water quality meter 38 is provided on the outlet side of the mixing tank 36 to measure the water quality after the chemical is injected.

Raw water flow rate 30. The chemical flow meter 32 and the water quality meter 38 are connected to the input side of the chemical injection control device M40, and the control valve 34 is connected to the output side of the chemical injection control device M40.

The chemical injection control device 40 basically controls the supply of chemicals in proportion to the raw water flow rate, but the injection rate is adjusted so that the water quality in the mixing tank 36 after chemical injection maintains the target water quality. In addition to being variable, the chemical supply m<flow port) can be variably controlled independently of the raw water flow R.

This chemical injection control device 40 includes a first water quality controller 42 that calculates the deviation between the water quality after chemical injection obtained as detection data from the water quality meter 38 and a preset target water quality and calculates an injection rate correction amount by sample PI operation or the like; A second water quality controller 44 calculates the deviation between the water quality after chemical injection and the target water quality obtained from the water quality meter 38 and calculates the chemical injection flow rate correction amount by sample P operation, etc., and a preset basic injection rate and the injection rate correction amount. and a drug injection flow rate correction amount, a target injection flow rate adjustment unit 46 that calculates a target drug injection flow rate from the raw water flow rate obtained as detection data from the raw water flow meter 30, and a drug flow rate obtained as detection data from the drug flow meter 32 as the target drug flow rate. A flow rate controller 4 that controls the regulating valve 34 to match the
It consists of 7.

If a discrepancy occurs between the water quality in the mixing tank 36 and the target water quality,
It is thought that the chemical injection rate to raw water is inappropriate.

The first water quality controller 42 has a function of correcting the chemical injection rate and injecting the chemical into the raw water that will flow in from now on at the optimum injection rate.

On the other hand, the second water quality controller 44 has a function of adding a chemical injection flow rate in addition to the raw water proportional amount in order to bring the mixed water of raw water and chemicals that has already entered the mixing tank 36 to the target water quality. .

The adjustment unit 46 calculates the corrected injection rate by adding the injection rate correction period sent from the first water quality controller 42 to the preset basic injection rate, and the adjustment unit 46 calculates the corrected injection rate. li) Calculator 50 that calculates the raw water proportional portion of the chemical injection flow rate by multiplying the raw water flow port obtained as detection data from the raw water flow meter 30 and using the calculation formula: chemical injection flow rate = correction ratio × raw water flow ω; It consists of an adder 52 that adds the chemical injection flow rate correction amount sent from the second water quality controller 44 to the injection flow rate to determine whether it is the target chemical injection flow.

The flow rate controller 47 has a II function that determines the deviation from the chemical flow rate obtained from the chemical flow meter 32 in accordance with the target chemical injection flow rate, and controls the chemical flow rate by controlling the opening degree of the control valve 34 in a direction to eliminate the deviation. are doing.

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

Here, it is assumed that the first water quality controller 42 and the second water quality controller 44 perform a PI operation and a P operation, respectively.

First, chemicals are injected into raw water at a certain injection rate.
In a steady state where the mixing tank 20 maintains the target water quality,
Since there is no deviation between the detected value of the water quality meter 38 and the target water quality, the output of the second water quality controller 44 is zero due to P operation. Therefore, no chemicals are added to the mixed water of raw water and chemicals that has already entered the mixing tank 20.

Furthermore, since there is no deviation between the detected value and the target water quality, the first water quality controller 42 outputs a certain injection rate correction amount for PI operation, and this is the basic value that is determined by the adder 48 of the target chemical injection flow rate adjustment section 46. A corrected injection rate is calculated as the optimum injection rate by adding it to the 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, the optimum injection rate is multiplied by the raw water flow rate in the multiplier 50 to obtain the chemical injection flow rate for the raw water inflow flow rate at that time, and since the chemical injection flow rate correction amount is zero, it is directly sent to the flow rate controller 47 as the target chemical injection flow rate. Output.

The flow layer controller 47 controls the control valve 18 so that the chemical flow rate becomes the target chemical injection flow rate.

As a result, chemicals are injected into the raw water that subsequently flows in at an optimal injection rate. Even if the raw water flow rate changes, since the chemical flow rate changes in proportion to the raw water flow rate, the mixed water quality in the mixing tank 36 maintains the target water quality.

If the water quality detected by the water quality meter 38 deviates from the target water quality for some reason in this state, the second water quality controller 44 performs the P operation based on the deviation between the detected water quality and the target water quality.
Find the chemical injection flow rate correction amount corresponding to the difference and adjust the chemical injection flow 1
It is output to the adjustment section 46.

The chemical injection flow rate m correction amount is added to the raw water flow rate and the proportional chemical injection flow rate by an adder 52, and is outputted to the flow rate controller 47 as a target chemical injection flow rate to control the chemical flow rate. however,
When the target chemical injection flow rate is negative, it is treated as zero.

In this way, the second water quality controller 44 corrects the chemical flow rate in response to the water quality deviation, regardless of the size of the raw water being diverted, and corrects the water quality of the mixed water that has already flown into the mixing tank 36. Control responsiveness is not affected by the raw water flow rate, and correction is quickly performed even when the raw water flow rate is small. Even if the raw water flow becomes zero, if the chemical injection flow 8 correction maximum is positive, the mixed water of the already inflow will surely reach the target water quality within the specified time.

On the other hand, if the water quality of the mixing tank 36 detected by the water quality meter 38 deviates from the target water quality, the first water quality controller 42 performs the PI operation based on the &i difference between the detected water quality and the target water quality, and the injection that was constant until then Change the rate correction amount.

1st. Among the control operations of the water quality controller 42, the operating section (1) integrates the deviation between the detected water quality and the target water quality over time, and plays the role of correcting an injection rate that deviates from the optimum value for some reason in the direction of optimization. . Even if the raw water flow rate is small, the deviation between the water quality of the mixed water already flowing into the mixing tank 36 and the target water quality is quickly corrected by the chemical injection flow 8 correction base output of the second water quality controller 44, so that the injection rate can be optimized. The changes will be made promptly.

On the other hand, in the P operation part of the adjustment operation of the first water quality controller 42, the mixing tank 3
6 has the role of correcting the deviation between the water quality of the already inflow mixed water and the target water quality according to the subsequent inflow of raw water.

The output value of the first water quality controller 42 is sent as an injection rate correction amount to an adder 48 of the target injection flow ω adjustment section 46 and added to the basic injection rate to obtain a corrected injection rate. Then, the corrected injection rate is multiplied by the raw water flow rate in a multiplier 50 to obtain the raw water flow rate and the chemical injection flow rate of the proportional valve.

Is this raw water flow rate proportional chemical injection? The Jl amount is added to the chemical injection flow 8 correction output from the second water quality controller 44 in an adder 52, and is output as a target value to the flow rate controller 47 to control the chemical flow rate.

As a result, the water quality of the water that has already flowed into the mixing tank 36 is corrected separately from the chemical injection flow 8 correction, and when the raw water flow rate is large, the correction is made even more intense, and as a result, optimization is quickly achieved. Chemicals can be injected into subsequent inflow raw water at a certain injection rate, and the new inflow portion will quickly reach the target water quality. Therefore, the mixing tank 36
This hardly prevents the inflow valve from correcting deviations in water quality, and the control response becomes faster.

In this way, as the water quality in the mixing tank 36 approaches the target water quality, the corrected injection rate output by the adder 48 also approaches the optimum value, and when the target water quality is obtained, the optimum injection rate is reached.

Thereafter, when a certain amount of raw water flows into the mixing tank 36, which has the target water quality, chemicals are also injected at the optimum injection rate in proportion to the amount of raw water, so that the water quality in the mixing tank 36 maintains the target water quality.

Note that the first water quality controller 42 may perform only one operation based on the deviation between the target water quality and the detected water quality and wait for the injection rate correction amount. In addition, input the raw water flow rate from the raw water flow meter 30 and the chemical flow rate from the chemical flow meter 32, integrate each for a certain time, and determine the target water quality from the relationship between the ratio of the raw water flow rate integrated value and the chemical flow rate integrated value and the detected water quality. An optimum injection rate correction amount may be obtained to achieve this.

On the other hand, the second water quality controller 44 outputs a constant value of the chemical injection flow 8 correction amount when there is a deviation between the target water quality and the detected water quality, or outputs a chemical injection flow port correction amount that is proportional to the square of the deviation. It's okay.

Separately, when changing the target water quality, it is necessary to change the basic injection rate as well and reduce the injection rate correction level to improve controllability. Improved operability is achieved by providing a converter 54 that inputs a target water quality into the control device 60 and converts it into a basic injection rate based on a relationship such as a linear equation determined in advance through experiments, etc. and outputs it to the adder 48. be able to.

Further, when the target water quality is changed, the control responsiveness can be further improved by adjusting the coefficients of the PI operation, P operation, etc. of the first or second water quality controller 42 or 44 according to the magnitude of the target water quality.

Furthermore, the adder for adding the basic injection rate and the injection rate correction amount in FIG. 1 may be replaced with an S calculator to obtain the corrected injection rate. In this case, the first water quality controller may be operated to output 1 when there is no need to correct the injection rate.

(Effects of the Invention) As explained above, according to the present invention, if a deviation occurs between the mixing ratio after mixing and the target ratio, the secondary raw material is supplied regardless of the size of the primary raw material. As a result, even when the supply amount of primary raw materials is small, it is possible to quickly adjust the target ratio. Since ratio correction can be performed in parallel, control responsiveness is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a chemical proportional injection device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing a conventional chemical proportional injection device, and FIG. 3 is a schematic configuration diagram showing a conventional chemical proportional injection device. FIG. 1 is a schematic configuration diagram showing such a chemical proportional injection device. 30... Raw water flow meter 32... Chemical flow meter 3
6...Mixing tank 38...Water quality meter ・4
0... Chemical injection control device 42... First water quality controller 44... Second water quality controller 46... Flow ω adjustment section 47... Flow rate controller 60... Chemical injection control device Fig. 1 Figure 2

Claims (1)

[Claims] In a ratio control device that detects the supply amount of the primary side raw material and controls the supply rate of the secondary side raw material in proportion to the supply rate of the primary side raw material, the mixing ratio after mixing the primary side raw material and the secondary side raw material is means for detecting the ratio correction amount from the deviation between the mixing ratio and the target ratio, means for obtaining the secondary side raw material supply amount correction amount from the deviation between the mixing ratio and the target ratio, The ratio is corrected by the ratio correction amount to obtain a correction ratio, this correction ratio is multiplied by the primary side raw material supply amount, and the secondary side raw material supply amount correction amount is added to obtain the target supply amount of the secondary side raw material. 1. A ratio control device comprising: means for determining the target supply amount; and means for controlling the supply of secondary side raw materials in response to the target supply amount.