JPH0223923Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a mixture of substances in a liquid that controls the concentration of a substance that is mixed into a liquid in a container and is concentrated by reduction due to evaporation of the liquid so that it does not exceed a predetermined value. The present invention relates to a concentration control device, and particularly to a concentration control device for a mixed substance in liquid suitable for a boiler blow device.

For example, in a boiler, various impurities are contained in the water supply, and these impurities gradually accumulate (concentrate) as a result of repeated water supply as a result of the use of steam, causing scales to form in the piping. This results in a decrease in boiler efficiency and corrosion of pipes. Therefore, in the boiler, it is necessary to remove the impurities as appropriate and keep their concentration below a predetermined value. Since these impurities do not evaporate, they cannot be removed in the evaporation system of the boiler, but must be removed in the water system. Therefore, the water system of the boiler is equipped with a drainage channel and a blow valve to adjust the amount of water drained at appropriate locations, and the impurities are discharged to the outside along with the water, thereby reducing the concentration of impurities.

Drainage by the above-mentioned blow valve is performed according to the amount of water supplied and the concentration of the supplied water, that is, the concentration of impurities contained in the supplied water. good. but,
In reality, the amount of water supplied fluctuates, and the concentration of the supplied water cannot necessarily be said to be exactly constant, so if a fixed amount of water is discharged from the blow valve, the impurity concentration will gradually change. . However, the speed of this change is extremely slow, and in terms of time, the change is in units of hours, not minutes. in general,
This density change is expressed by the following equation.

P=W/wp ₀ −(W/wp ₀ −p ₁ )e ^{-w/V t} ……(1) Here, P: Concentration after time t p ₀ : Concentration of feed water p ₁ : Initial can Concentration of water W: Water supply amount w: Blow amount V: Water retention amount t: Elapsed time In other words, when the water supply amount W increases from a state of equilibrium at a certain concentration, the concentration also increases, but as mentioned above, the concentration change is It is extremely gradual.

In order to control the impurity concentration of boiler canned water, which exhibits such gradual concentration changes, conventional control devices have used a normal PID controller, but stable control has not been achieved. That is, when the impurity concentration exceeds a certain set value, the PID controller detects this and outputs an instruction signal to open the blow valve, and the blow valve opens in response to this signal to drain water. However, as mentioned above, since the concentration changes slowly, the concentration does not decrease in a short period of time. Therefore, the PID controller further outputs an instruction signal to open the blow valve, and as a result, the blow valve quickly becomes fully open. When this fully open state continues for a while, the impurity concentration decreases and eventually becomes lower than the set value. Therefore, the PID controller operates and outputs an instruction signal to close the blow valve.
Although the blow valve moves from a fully open state to a closed state, the concentration does not increase because the concentration change is gradual. Therefore, the PID controller further outputs an instruction signal to close the blow valve, and as a result, the blow valve is quickly fully opened. As a result of the above-described repetition, the blow valve repeatedly goes into a fully open state and a fully closed state, resulting in so-called hunting, which makes it impossible to perform stable control.

An object of the present invention is to provide a concentration control device for a mixed substance in a liquid, which eliminates the above-mentioned conventional drawbacks and can stably control the concentration of a substance mixed in the liquid.

In order to achieve the above object, the present invention includes a container,
A substance mixed in the liquid in the container, which includes a supply passage for supplying liquid to the container, a discharge passage for discharging the liquid in the container, and a discharge valve provided in the discharge passage. A detection means for detecting the concentration of The present invention is characterized by being provided with a calculation means that continuously outputs the value calculated within a predetermined preceding time period, and a discharge valve driving means that drives the discharge valve based on the output of the calculation means. do. With the above configuration, the value outputted from the calculation means to the discharge valve driving means is a constant value at least within the predetermined time, so that stable control without hunting can be performed.

Hereinafter, the present invention will be explained based on the illustrated embodiments.

FIG. 1 is a schematic system diagram of a steam system, a water system, and a control system of a boiler can water impurity concentration control device according to a first embodiment of the present invention.

In the figure, 1 is the steam barrel of the boiler, 2 is canned water in the steam barrel 1, and 3 is steam in the steam barrel 1. Reference numeral 4 designates a steam pipe that guides steam separated within the steam barrel 1, 5 a water supply pipe that supplies canned water, and 6 a water supply control valve that is interposed in the middle of the water supply pipe 5 to adjust the amount of water supplied. 7 is a drain pipe for discharging the canned water 2 in the steam barrel 1, and 8 is a blow valve interposed in the middle of the drain pipe 7 to adjust the discharge amount of the canned water 2.

Reference numeral 11 denotes a blow valve driving device that controls opening and closing of the blow valve 8. 12 is a concentration detector that measures the impurity concentration of the canned water 2 and outputs a signal according to the measured value. Reference numeral 13 denotes an average value calculator which inputs the signal from the concentration detector 12 and calculates the average value thereof. The average value calculator 13 sets a certain time interval, and calculates the average value of the signal corresponding to the concentration input from the concentration detector 12 within this time interval. Note that, if the above-mentioned time interval is one unit time, the above-mentioned average value will be equal to the integrated value. A signal corresponding to the average value calculated by the average value calculator 13 is input to the blow valve driving device 11 to drive it.

Here, the operation of this embodiment will be explained. In the steam barrel 1, the amount of canned water 2 decreases due to evaporation and drainage from the blow valve 8. Therefore, the water supply control valve 6 supplies water corresponding to the amount of evaporation and blowing, and keeps the level of the canned water 2 constant. on the other hand,
The impurity concentration of the canned water detected by the concentration detector 12 is input to the average value calculator 13, where the average value within a fixed time interval is calculated. and,
The average value calculator 13 outputs a signal corresponding to this average value at the next fixed time interval, and also inputs the signal from the concentration detector 12 to perform the next average value calculation operation. The blow valve driving device 11 drives the blow valve 8 to an opening degree according to the output signal from the average value calculator 13. In this case, since the output from the average value calculator 13 is a constant value within the fixed time interval, the opening degree of the blow valve 8 is also held constant. Then, at the next fixed time interval, a signal corresponding to the new average value is received from the average value calculator 13, and the opening degree is changed.

In this way, in this embodiment, an average value calculator is provided to calculate the average value of the impurity concentration of canned water at a certain fixed time interval, and to adjust the blow valve according to this average value at the next fixed time interval. Since the opening degree is kept constant, hunting does not occur.
Stable control can be performed.

FIG. 2 is a schematic diagram of the steam system, water system, and control system of the boiler can water impurity concentration control device according to the second embodiment of the present invention.

In FIG. 2, parts that are the same as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. 14 is a calculation device that inputs the signal from the concentration detector 12 and performs calculation based on a predetermined formula, and a signal corresponding to the calculation result is output to the blow valve driving device 11.
The blow valve 8 is maintained at the opening degree according to the signal for a certain time interval. This embodiment differs from the embodiment shown in FIG. 1 in that an arithmetic unit 14 is provided in place of the average value arithmetic unit 13. The mathematical formula that is the basis of the calculation in the calculation device 14 is determined by the following idea.
In other words, when the amount of water supplied changes, the impurity concentration also changes, but assuming that the same amount of water supplied continues in the next time interval, the next time interval is calculated from the impurity concentration at the beginning and end of the previous time interval and the blow amount at that time. In order to return the impurity concentration to the set value at intervals, the blow amount may be determined as shown in the following equation.

w ₁ = p ₁ + p ₂ / p ₂ + p _s w+2 (2p ₂ − _{p 1} − P _s ) / p ₂ + p _s V where, w ₁ : Blow amount in the next time interval w : Blow in the previous time interval Quantity p ₁ : Initial impurity concentration in the previous time interval p ₂ : Last impurity concentration in the previous time interval p _s : Set value concentration V : Amount of water held Since the change in impurity concentration is gradual as mentioned above, this Omitting the second term in the equation has little effect, so w ₁ =p ₁ +p ₂ /p ₂ +p _s w . By the way, this formula is used when it is assumed that the change in concentration is approximately linear, but since the change in concentration is not linear over a long time, It is preferable to perform the calculation using the following equation.

w ₁ =p ₂ −p ₁ e ^{-w/V t} /p _s −p ₂ e ^{-w1/V t} w1−e ^{-w1/V t}
/1-e ^{-w/V t} where t indicates the time interval.

The time interval t is constant, and the amount of retained water V and the amount of blowing w, w ₁ do not change much, so e ^{-w/V t} ≒ e ^{-w1/V t} If t is replaced by a constant K, w ₁ = p ₂ +p ₁ K/p _s −p ₂ Kw.

As described above, in this embodiment, the amount to be blown from the blow valve is calculated based on a predetermined formula using a concentration detector and a calculation device, and the opening degree of the blow valve is calculated at regular intervals based on the calculation result. Since the control is performed, stable control can be performed accurately without causing hunting.

FIG. 3 is a schematic diagram of the steam system, water system, and control system of a boiler can water impurity concentration control device according to a third embodiment of the present invention.

In the figure, the same parts as those shown in FIG. 1 are given the same reference numerals, and the explanation will be omitted. Reference numeral 15 denotes an arithmetic device, which performs arithmetic operations based on a different formula from that of the arithmetic device 14 in the second embodiment. Reference numeral 16 denotes a flow rate detection device provided in the water supply pipe 5 upstream of the water supply control valve 6, which detects the amount of canned water supplied and outputs a signal in accordance with this. Arithmetic device 15 of this embodiment
inputs the detection signal of the flow rate detector 16 as well as the detection signal of the concentration detector 12, and performs calculations based on the following formula. In other words, the formula used in the second embodiment attempts to control the next time interval based on the result that appears as a change in concentration, regardless of changes in the amount of water supplied, and the change is gradual. Therefore, satisfactory control can be achieved using this equation as well. However, in order to perform more accurate control, it is necessary to use a mathematical formula that takes into account the amount of water supplied. The formula is listed below. The blow amount w is determined from the above equation (1): w=Wp ₀ (1−e ^{-w/V t} )/ _ps −p ₁ e ^{-w/V tHere} , the blow amount w and the approximate time interval to be set are If the value is determined, e ^{-w/V t} will be a certain value K ₁ . Therefore, if _K1 is _a constant, the next blow amount w is w= _Wp0 (1- _K1 )/ _ps - _p1K1 .

In this way, in this embodiment, the amount to be blown from the blow valve is calculated based on a predetermined formula using a concentration detector, a flow rate detector, and a calculation device, and the amount to be blown from the blow valve is calculated based on the calculation result at regular time intervals. Since the opening degree of the valve is controlled, stable control can be performed more accurately without causing hunting.

In addition, in the above-mentioned example, the impurity concentration of boiler can water was illustrated, but it is not limited to this, and the substance in the liquid is concentrated, and it is necessary to maintain the concentration constant. This can be applied to any given system.

As described above, in the present invention, the concentration of a substance mixed in a liquid in a container is detected, and based on that value, calculations are performed to bring the concentration closer to a predetermined concentration within a predetermined time. Since the value calculated for the preceding predetermined time period is output within a predetermined time period and the discharge valve is controlled using this value, the value to be controlled is constant at least within the above predetermined time period, thereby preventing hunting. It is possible to perform stable concentration control.

[Brief explanation of the drawing]

1, 2 and 3 respectively show the steam system, water system and It is a schematic system diagram of a control system. 1... Boiler steam barrel, 2... Boiler canned water, 5
... Water supply pipe, 7 ... Drain pipe, 8 ... Blow valve, 1
1... Blow valve drive device, 12... Concentration detector,
13... Average value calculator, 14, 15... Arithmetic device, 16... Flow rate detector.

Claims (1)

[Claims for Utility Model Registration] 1. A container, a supply passage for supplying liquid to the container, and a discharge passage for discharging the liquid in the container;
A discharge valve provided in the discharge passage includes a detection means for detecting the concentration of a substance mixed in the liquid in the container, and a control time divided into predetermined time intervals and detected by the detection means. calculation means for performing a calculation for bringing the concentration closer to a predetermined concentration within the predetermined time based on the calculated value, and continuously outputting the value calculated in the preceding predetermined time within the predetermined time; and a discharge valve drive means for driving the discharge valve based on the output of the arithmetic means. 2 Utility Model Registration Scope of Claims Paragraph 1, wherein the calculation means outputs a signal based on the difference between the average concentration value within the predetermined time period and the predetermined concentration value within the next predetermined time period. Features: Concentration control device for mixed substances in liquid. 3. Claims for Utility Model Registration Paragraph 1 provides that the calculation means outputs the calculation result obtained within the predetermined time period by calculation according to a predetermined mathematical formula within the next predetermined time period. A concentration control device for a mixed substance in a liquid, characterized by: