JP2021115536A - Ozone water production equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ozone water production apparatus capable of quickly converging an ozone concentration to a target concentration. A control unit (80) executes stop control when the ozone concentration C becomes higher than the first threshold value C1 through a downward inflection point lower than the target concentration Cset after switching from stop control to supply control. .. The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset, which is obtained based on the target concentration Cset and the minimum value Cmin which is the ozone concentration corresponding to the descending inflection point. [Selection diagram] Fig. 3

Description

The present disclosure relates to an ozone water production apparatus.

There is known an ozone water production apparatus that generates ozone water and supplies the generated ozone water to a predetermined target.

The ozone water production apparatus disclosed in Patent Document 1 includes an ozone generator, an ejector, and a tank. The ozone gas generated by the ozone generator is mixed with the water flowing through the liquid flow path in the ejector. In the ejector, ozone gas dissolves in water to generate ozone water. Ozone water is stored in the tank. The ozone water in the tank is supplied to a predetermined target via the supply path.

Japanese Unexamined Patent Publication No. 2018-153727

An ozone water producing apparatus as described in Patent Document 1 regulates the ozone concentration of ozone water supplied to a target. Specifically, an on-off valve is provided in the gas flow path of the ozone generator. An ozone concentration sensor is provided in the supply path. The control unit controls the on-off valve so that the ozone concentration detected by the ozone concentration sensor converges to a predetermined target concentration.

However, such control has a problem that the ozone concentration does not easily converge to the target concentration. This point will be described in detail with reference to FIG. In FIG. 9, the horizontal axis is time and the vertical axis is ozone concentration C detected by the ozone concentration sensor. The white circles in FIG. 9 mean the start of supply control, and the cross marks mean the start of stop control.

When the operation of the ozone generator starts, supply control is executed at point p1. In supply control, the on-off valve is opened and ozone gas is supplied to the supply path. When the supply control starts, the ozone concentration C gradually increases. When the ozone concentration C reaches the target concentration Cset at point p2, the stop control is executed. In the stop control, the on-off valve is closed and the supply of ozone gas to the supply path is stopped. However, there is a time delay between the time when the stop control is started and the time when the ozone concentration C decreases. Therefore, the ozone concentration C greatly exceeds the target concentration Cset, and the range of overshoot of the ozone concentration C becomes large.

After that, when the ozone concentration C decreases and the ozone concentration C reaches the target concentration Cset at point p3, the supply control is executed again. However, there is a time delay between the start of supply control and the rise in ozone concentration. In addition, ozone in ozone water is consumed by a so-called autolysis reaction. The self-decomposition reaction is a reaction in which ozone reacts with, for example, OH radicals and superoxide radicals and is decomposed in a chain reaction. Therefore, even if the stop control is executed at the point p3, the ozone concentration C is much lower than the target concentration Cset, and the width of the undershoot of the ozone concentration C becomes large.

As described above, in the control of the comparative example shown in FIG. 9, the width of the undershoot and overshoot of the ozone concentration C becomes relatively large. Therefore, there is a problem that the ozone concentration C does not easily converge to the target concentration Cset, and the fluctuation with respect to the desired ozone concentration is large.

The present disclosure has been made in view of such a point, and an object thereof is to provide an ozone water production apparatus capable of quickly converging an ozone concentration to a target concentration.

In order to solve the above-mentioned problems, the control unit (80) of the present disclosure sets the ozone concentration C between the minimum value Cmin and the target concentration Cset after switching from the stop control to the supply control. When it becomes higher than the threshold value C1, stop control is performed. In the present disclosure, stop control is performed when the ozone concentration C exceeds the first threshold value C1 which is lower than the target concentration Cset. Therefore, since the stop control can be executed at an earlier timing than the above-mentioned comparative example, the width of the overshoot of the ozone concentration C can be reduced.

In order to solve the above problem, the control unit (80) of the present disclosure switches the ozone concentration C between the maximum value Cmax and the target concentration Cset after switching from the supply control to the stop control. Supply control is performed when the value becomes lower than the threshold value C2. In the present disclosure, supply control is performed when the ozone concentration C falls below the second threshold value C2, which is higher than the target concentration Cset. Therefore, since the supply control can be executed at an earlier timing than the above-mentioned comparative example, the width of the undershoot of the ozone concentration C can be reduced.

The first threshold value C1 is preferably expressed by the relational expression of C1 = Cset− (Cset−Cmin) × α (0 <α <1). By this relational expression, the first threshold value C1 can be set to a value lower than the target concentration Cset.

The second threshold value C2 is preferably expressed by the relational expression of C2 = Cset + (Cmax−Cset) × β (0 <β <1). By this relational expression, the second threshold value C2 can be set to a value higher than the target concentration Cset.

The β may be smaller than the α. The rate of the ozone gas autolysis reaction tends to be slower than the rate at which ozone gas is supplied from the ozone generator to the supply path. Therefore, if β is too large, the ozone concentration C may not reach the target concentration Cset after the supply control is started. On the other hand, when β is lower than α, the second threshold value becomes relatively low. Therefore, it is possible to prevent the ozone concentration C from reaching the target concentration Cset.

According to the present disclosure, since the first threshold value C1 for executing the stop control is lower than the target concentration Cset, the stop control can be executed at a relatively early timing. Therefore, the width of the ozone concentration overshoot can be reduced, and the ozone concentration C can be quickly converged to the target concentration Cset. The first threshold value C1 is determined based on the minimum value Cmin corresponding to the downward inflection point of the ozone concentration C and the target concentration Cset. Therefore, it is possible to prevent the first threshold value C1 from becoming excessively low or excessively high.

According to the present disclosure, since the second threshold value C2 for executing the supply control is higher than the target concentration Cset, the supply control can be executed at a relatively early timing. Therefore, the width of the ozone concentration undershoot can be reduced, and the ozone concentration C can be quickly converged to the target concentration Cset. The second threshold value C2 is determined based on the maximum value Cmax corresponding to the rising inflection point of the ozone concentration C and the target concentration Cset. Therefore, it is possible to prevent the second threshold value C2 from becoming excessively low or excessively high.

FIG. 1 is a piping system diagram showing a schematic configuration of an ozone water production apparatus according to an embodiment. FIG. 2 is an overall flowchart of ozone concentration control according to the embodiment. FIG. 3 is a graph showing the relationship between ozone concentration and time in the ozone concentration control according to the embodiment. FIG. 4 is a flowchart of supply control according to the embodiment. FIG. 5 is a flowchart of stop control according to the embodiment. FIG. 6 is a graph corresponding to FIG. 3 for explaining control when the ozone concentration continues to rise. FIG. 7 is a graph corresponding to FIG. 3 for explaining control when the ozone concentration continues to decrease. FIG. 8 is a piping system diagram showing a schematic configuration of the ozone water production apparatus according to the second modification. FIG. 9 is a graph showing the relationship between ozone concentration and time in ozone concentration control according to a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

<< Embodiment >>
The ozone water production apparatus (1) according to the embodiment generates ozone water and supplies the generated ozone water to a predetermined target. The predetermined target is, for example, a semiconductor manufacturing factory. As shown in FIG. 1, the ozone water production apparatus (1) is a liquid having a gas flow path (10) having an ozone generator (20), a tank (44), an ejector (35), and a pump (45). It is provided with a flow path (30).

<Gas flow path>
An ozone generator (20) is provided in the gas flow path (10). The ozone generator (20) is a discharge type ozonizer. The ozone generator (20) uses oxygen as a raw material and generates ozone gas by generating an electric discharge in the oxygen.

The gas flow path (10) includes a gas supply path (11) and a gas discharge path (12). The inflow end of the gas supply path (11) is connected to the ozone generator (20). The outflow end of the gas supply path (11) is connected to the gas suction section (35c) of the ejector (35). The gas discharge path (12) branches off from the gas supply path (11).

A first gas on-off valve (13) is provided in the gas supply path (11). The first gas on-off valve (13) is provided on the downstream side of the branch portion of the gas discharge path (12) in the gas supply path (11). The first gas on-off valve (13) opens and closes the gas supply path (11).

A second gas on-off valve (14) is provided in the gas discharge path (12). The second gas on-off valve (14) opens and closes the gas discharge path (12). The ozone gas discharged from the gas discharge path (12) is processed by, for example, an ozone decomposition device (not shown).

<Overall configuration of liquid flow path>
The liquid flow path (30) has a water supply channel (31), a supply channel (40), a first return flow path (60), and a second return flow path (70). The water supply channel (31) is a flow path for supplying raw water to the liquid flow path (30). The raw water may be a liquid containing other components (for example, carbonated water) as long as it contains water as a main component. The supply path (40) is a flow path for supplying ozone water to the target. The first return flow path (60) is a flow path for returning the ozone water in the supply path (40) to the upstream side of the ejector (35). The second return flow path (70) is a flow path for returning ozone water to the tank (44).

<Water supply channel>
The inflow end of the water supply channel (31) connects to the source of raw water. The outflow end of the water supply channel (31) is connected to the liquid inflow portion (35a) of the ejector (35). The water supply channel (31) is provided with a water supply side on-off valve (32) and a first flow rate sensor (33) in this order from the upstream side to the downstream side. The water supply side on-off valve (32) opens and closes the water supply channel (31). The water supply side on-off valve (32) is composed of, for example, an air operated valve. The first flow rate sensor (33) measures the flow rate of water flowing through the water supply channel (31). In addition, "water" described in the following description may also mean water containing ozone.

<Ejector>
The ejector (35) has a liquid inflow part (35a), a liquid outflow part (35b), and a gas suction part (35c). The outflow end of the water supply channel (31) is connected to the liquid inflow section (35a). The liquid inflow section (35a) is connected to the inflow end of the supply path (40). The outflow end of the gas supply path (11) is connected to the gas suction section (35c). Inside the ejector (35), a nozzle portion, a mixing portion, and a diffuser portion (not shown) are provided. In the ejector (35), when the water flowing in from the liquid inflow portion (35a) flows through the nozzle portion, the flow velocity of the water is accelerated. At the nozzle portion, water is depressurized by the throttle portion at the tip thereof. At the nozzle portion, ozone gas is sucked from the gas suction portion to the mixing portion due to the differential pressure of water before and after the nozzle portion. The sucked ozone gas mixes with water in the mixing section. In the mixing portion, ozone gas is dissolved in water to generate ozone water having a predetermined concentration. Ozone water flows through the diffuser section where the cross section of the flow path is gradually expanded, is boosted, and then flows out from the liquid outflow section (35b) to the supply path (40).

<Supply channel>
The supply channel (40) includes a first pipe (41), a second pipe (42), and a third pipe (43). The inflow end of the first pipe (41) is connected to the liquid outflow portion (35b) of the ejector (35). The outflow end of the first pipe (41) is connected to the tank (44). The inflow end of the second pipe (42) is connected to the tank (44). The outflow end of the second pipe (42) is connected to the inflow end of the first return flow path (60), the inflow end of the second return flow path (70), and the inflow end of the third pipe (43). The outflow end of the third pipe (43) leads to a predetermined target. The second pipe (42) is provided with a pump (45), an ozone concentration sensor (46), and a pressure sensor (47) in this order from the upstream end to the downstream side. The third pipe (43) is provided with a second flow rate sensor (48) and a supply side on-off valve (49) in this order from the upstream side to the downstream side.

The tank (44) is a hollow container. The tank (44) temporarily stores water. The ozone gas remaining in the tank (44) is discharged to the outside of the tank (44) as exhaust ozone. The discharged ozone is processed by, for example, an ozone decomposition device (not shown).

The tank (44) is provided with a level sensor (50) that detects the water level in the tank (44). The level sensor (50) is configured to be capable of detecting at least two levels of water levels, L and H. The level sensor (50) corresponds to the water level detector.

The pump (45) carries the water in the supply path (40).

The ozone concentration sensor (46) detects the ozone concentration of the water (ozone water) in the supply path (40). The ozone concentration sensor (46) corresponds to the detector. The signal indicating the ozone concentration detected by the ozone concentration sensor (46) is output to the control unit (80).

The pressure sensor (47) detects the pressure of water in the supply path (40) (strictly speaking, the second pipe (42)).

The second flow rate sensor (48) detects the flow rate of water in the supply path (40) (strictly speaking, the third pipe (43)).

The supply-side on-off valve (49) opens and closes the supply path (40) (strictly speaking, the third pipe (43)). The supply side on-off valve (49) is composed of, for example, an air operated valve.

<First return flow path>
The inflow end of the first return flow path (60) is connected to the outflow end of the second pipe (42). The outflow end of the first return flow path (60) is connected to the water supply channel (31). A flow rate control valve (61) is provided in the first return flow path (60). The flow rate control valve (61) regulates the flow rate of water flowing through the first return flow path (60). Here, the flow rate of water regulated by the flow rate control valve (61) includes zero. In this case, the flow rate control valve (61) is fully closed.

<Second return flow path>
The inflow end of the second return flow path (70) is connected to the outflow end of the second pipe (42). The outflow end of the second return flow path (70) is connected to the tank (44). A first back pressure valve (71) is provided in the second return flow path (70). The first back pressure valve (71) is a pressure control valve that constantly adjusts the water pressure in the second return flow path (70) or the supply path (40).

<Control unit>
As schematically shown in FIG. 1, the ozone water production apparatus (1) includes a control unit (80). The control unit (80) has a microcomputer and a memory device (specifically, a semiconductor memory) for storing software for operating the microcomputer. The control unit (80) has an input unit for inputting a detection signal or the like and an output unit for outputting the control signal or the like.

Although not shown in FIG. 1, the water level (L and H) detected by the level sensor (50) is input to the input unit of the control unit (80). The control unit (80) controls the water supply side on-off valve (32) according to the detected water level of the level sensor (50). Specifically, when the detected water level of the level sensor (50) reaches L, the control unit (80) opens the water supply side on-off valve (32). When the water supply side on-off valve (32) is opened, raw water is replenished in the tank (44). After that, when the detected water level of the level sensor (50) reaches H, the control unit (80) closes the water supply side on-off valve (32). When the water supply side on-off valve (32) is closed, the supply of raw water to the tank (44) is stopped.

Although not shown in FIG. 1, the control unit (80) switches between operation and stop of the ozone generator (20). In addition, the control unit (80) switches the open / closed state of the supply side on-off valve (49).

The ozone concentration C detected by the ozone concentration sensor (46) is input to the input unit of the control unit (80). The control unit (80) controls at least the first gas on-off valve (13) so that the ozone concentration C detected by the ozone concentration sensor (46) converges to the target concentration Cset. The control unit (80) alternately switches between supply control and stop control. The supply control is a control for supplying ozone gas from the ozone generator (20) to the supply path (40). The stop control is a control for stopping the supply of ozone gas from the ozone generator (20) to the supply path (40).

The control unit (80) has a storage unit. The storage unit stores the target concentration Cset, the Lower threshold value C1, the Upper threshold value C2, the minimum value Cmin, and the maximum value Cmax. In the storage unit, these parameters are updated as appropriate. The target concentration Cset is the target value of the ozone concentration C supplied to the target. The Lower threshold value C1 is a determination value for determining switching from supply control to stop control. The Lower threshold C1 corresponds to the first threshold. The Upper threshold value C2 is a determination value for determining switching from stop control to supply control. The Upper threshold C2 corresponds to the second threshold. The minimum value Cmin is the ozone concentration C corresponding to the inflection point in the range lower than the target concentration Cset during supply control. The maximum value Cmax is the ozone concentration C corresponding to the ascending inflection point in a range higher than the target concentration Cset during stop control.

After switching from the stop control to the supply control, when the ozone concentration C becomes higher than the first threshold value C1, the control unit (80) executes the stop control. The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset. The calculation unit of the control unit (80) obtains the first threshold value C1 by the following equation (1).

C1 = Cset- (Cset-Cmin) x α (0 <α <1) ... (1)

α may be greater than 0 and less than 1. Preferably, α is greater than 0.2 and less than 0.8. More preferably, α is greater than 0.3 and less than 0.7. More preferably, α is greater than 0.4 and less than 0.8. Most preferably, α is 0.5. The control unit (80) has a setting unit for appropriately changing α. The initial setting value of α is 0.5.

After switching from the supply control to the stop control, when the ozone concentration C becomes lower than the second threshold value C2, the control unit (80) executes the supply control. The second threshold value C2 is a value between the maximum value Cmax and the target concentration Cset. The calculation unit of the control unit (80) obtains the second threshold value C2 by the following equation (2).

C2 = Cset + (Cmax-Cset) x β (0 <β <1) ... (2)

β may be greater than 0 and less than 1. Preferably β is greater than 0.2 and less than 0.8. More preferably, β is greater than 0.3 and less than 0.7. More preferably, β is greater than 0.4 and less than 0.8. Most preferably, β is 0.5. The control unit (80) has a setting unit for appropriately changing β. The initial setting value of β is 0.5.

-Driving operation-
The operating operation of the ozone water production apparatus (1) will be described with reference to FIG.

When the ozone water production apparatus (1) is operated, the control unit (80) operates the ozone generator (20). In the ozone generator (20), silent discharge is performed between the electrode pairs. The control unit (80) opens the supply side on-off valve (49). The pump (45) is in operation.

When silent discharge is performed by the ozone generator (20), ozone gas having a predetermined concentration is generated. The ozone gas generated by the ozone generator (20) flows through the gas supply path (11) and is sent to the gas suction unit (35c) of the ejector (35). When the pump (45) is operated, the water in the first return flow path (60) is sent to the liquid inflow section (35a) of the ejector (35) via the water supply channel (31). In the ejector (35), the ozone gas sucked by the gas suction part (35c) and the water flowing into the liquid inflow part (35a) are mixed, and the ozone gas is dissolved in the water. The ozone water in the ejector (35) is sent to the tank (44) via the first pipe (41) and temporarily stored in the tank (44).

The ozone water in the tank (44) flows through the second pipe (42) and the third pipe (43) in this order and is sent to the target. A part of the ozone water in the second pipe (42) is returned to the water supply channel (31) via the first return flow path (60). The total amount of water supplied to the target and the amount of water flowing through the first return flow path (60) may be larger than the amount of water flowing through the second pipe (42). In this case, the excess ozone water in the second pipe (42) is returned to the tank (44) via the second return flow path (70).

<Control of ozone concentration>
During the operation of the ozone generator (20) described above, the control unit (80) controls the ozone concentration C to converge to the target concentration Cset (hereinafter referred to as ozone concentration control). Ozone concentration control will be described with reference to FIGS. 2 to 7.

<Basic flow of ozone concentration control>
As shown in FIG. 2, when the operation of the ozone water production apparatus (1) is started, the ozone concentration control is executed. In step ST1, the control unit (80) sets the Lower threshold C1, Upper threshold C2, minimum value Cmin, and maximum value Cmax to the target concentration Cset (for example, 20 ppm).

In step ST2, the control unit (80) determines whether or not there is a command to end the operation of the ozone water production apparatus (1). When the operation end command is input to the input unit of the control unit (80), the control unit (80) ends the ozone concentration control. If not, step ST3 is performed.

In step ST3, the control unit (80) executes supply control. In supply control, the control unit (80) opens the first gas on-off valve (13). In addition, the control unit (80) closes the second gas on-off valve (14). In this state, ozone gas generated from the ozone generator (20) is supplied to the supply path (40).

In step ST4, the control unit (80) executes stop control. In stop control, the control unit (80) closes the first gas on-off valve (13). In addition, the control unit (80) opens the second gas on-off valve (14). In this state, the supply of ozone gas from the ozone generator (20) to the supply path (40) is stopped. The excess ozone gas generated from the ozone generator (20) flows through the gas discharge path (12) and is decomposed by, for example, an ozone decomposition device.

When step ST4 ends, step ST2 is executed again. As described above, the control unit (80) alternately repeats the supply control (step ST3) and the stop control (step ST4) until the operation end command is input.

<Initial supply control>
Immediately after the operation of the ozone water production apparatus (1) starts, the initial supply control is executed. As shown in FIG. 4, when the supply control is started, the control unit (80) opens the first gas on-off valve (13) in step ST31. In step ST31, the control unit (80) closes the second gas on-off valve (14). As a result, the ozone gas generated from the ozone generator (20) is supplied to the supply path (40).

As shown in FIG. 3, in the initial supply control, the ozone concentration C gradually increases from the state of the point a1 (ozone concentration C = 0). The ozone concentration C is lower than the target concentration Cset until the ozone concentration C reaches the point a2 (target concentration Cset). Therefore, in step ST32, the control unit (80) determines that the ozone concentration C is lower than the target concentration Cset. In this case, step ST34 is executed. In step ST34, the control unit (80) sets the maximum value Cmax and the Lower threshold value C1 to the target concentration Cset (for example, 20 ppm).

In step ST35, the control unit (80) determines whether or not the ozone concentration C is higher than the Lower threshold value C1. The Lower threshold C1 was set to the target concentration Cset (eg 20 ppm) in step ST1. Therefore, when the ozone concentration becomes higher than the point a2, the condition of step ST35 is satisfied and the supply control ends.

<Stop control after the first supply control>
When the initial supply control is completed, the stop control is executed. As shown in FIG. 5, when the stop control is started, the control unit (80) closes the first gas on-off valve (13) in step ST41. In step ST41, the control unit (80) opens the second gas on-off valve (14). As a result, the ozone gas generated from the ozone generator (20) is not supplied to the supply path (40).

In step ST42, the control unit (80) determines whether the ozone concentration C is higher than the target concentration Cset. When the first gas on-off valve (13) is closed, the supply of ozone gas to the supply path (40) is stopped. However, there is a time delay between when the supply of ozone gas is stopped and when the ozone concentration C decreases. Due to this time delay, the ozone concentration C further rises immediately after the supply of ozone gas is stopped at point a2. As a result, the condition of step ST42 is satisfied, and step ST44 is executed.

In step ST44, the control unit (80) sets the minimum value Cmin and the Upper threshold C1 to the target concentration Cset (for example, 20 ppm).

In step ST45, the control unit (80) determines whether the ozone concentration C is lower than the Upper threshold C2. In the previous supply control step ST34, the Upper threshold C2 was set to the target concentration (eg 20 ppm). Therefore, when the ozone concentration C is higher than the target concentration Cset at point a2, the condition of step ST45 is not satisfied and step ST46 is executed.

In step ST46, the control unit (80) determines whether the ozone concentration C is higher than the maximum value Cmax. In step ST34 of the supply control immediately before, the maximum value Cmax was set to the target concentration Cset (for example, 20 ppm). Therefore, when the ozone concentration C is higher than the target concentration Cset at point a2, the condition of step ST46 is satisfied and step ST47 is executed.

In step ST47, the control unit (80) updates the maximum value Cmax to the current ozone concentration C. Next, in step ST48, the control unit (80) calculates the Upper threshold C2 based on the above equation (2). Then, the process returns to step ST45.

Steps ST46 and ST47 are repeated until the ozone concentration C reaches the rising inflection point.

After a certain period of time has passed since the first gas on-off valve (13) was closed, the ozone concentration C reached the ascending inflection point at point a3, and then the ozone concentration C decreased. During the period when the ozone concentration C is between the points a2 and a3, the condition of step ST45 is not satisfied.

When the ozone concentration C becomes lower than the rising inflection point (maximum value Cmax) at point a3, the condition of step ST46 is not satisfied. Therefore, steps ST47 and ST48 are skipped and step ST45 is executed. In other words, the maximum value Cmax and the Upper threshold C2 are not updated or calculated after the ozone concentration C has passed the rising inflection point (point a3).

After that, when the ozone concentration C becomes lower than the point a4 which is the Upper threshold C2, the condition of step ST45 is satisfied. As a result, the stop control is terminated and the supply control is executed again.

<Supply control from the second time onward>
When the first stop control is completed, the second supply control is executed, and ozone gas is supplied to the supply path (40) again in step ST31. However, there is a time delay between the start of ozone gas supply and the rise of ozone concentration C. In addition, the ozone concentration C of the ozone water supplied to the supply channel (40) rapidly decreases due to the so-called autolysis reaction. Therefore, immediately after the supply of ozone gas starts at point a4, the ozone concentration C further decreases.

During the period when the ozone concentration C is between the points a4 and a5 (target concentration Cset), the condition of step ST32 is not satisfied and step T33 is executed. In step ST33, the control unit (80) determines whether or not the ozone concentration C is higher than the maximum value Cmax. The ozone concentration C between points a4 and a5 is lower than the maximum value Cmax. The maximum value Cmax referred to here corresponds to the maximum value (point a3) obtained in the previous stop control. Therefore, the condition of step ST33 is not satisfied, and step ST32 is executed again.

After that, when the ozone concentration C becomes lower than the target concentration Cset at point a5, the condition of step ST32 is satisfied, and step ST34 is executed. In step ST34, the control unit (80) sets the maximum value Cmax and the Upper threshold C2 to the target concentration Cset (for example, 20 ppm).

In step ST35, the control unit (80) determines whether or not the ozone concentration C is higher than the Lower threshold value C1. In the previous stop control step ST44, the Lower threshold C1 was set to the target concentration (for example, 20 ppm). Therefore, when the ozone concentration C is lower than the target concentration Cset at point a5, the condition of step ST35 is not satisfied and step ST36 is executed.

In step ST36, the control unit (80) determines whether the ozone concentration C is lower than the minimum value Cmin. In step ST44 of the immediately preceding stop control, the minimum value Cmin was set to the target concentration Cset (for example, 20 ppm). Therefore, when the ozone concentration is lower than the target concentration Cset at point a5, the condition of step ST36 is satisfied and step ST37 is executed.

In step ST37, the control unit (80) updates the minimum Cmin to the current ozone concentration C. Next, in step ST38, the control unit (80) calculates the Lower threshold value C1 based on the above equation (1). Then, the process returns to step ST35.

Steps ST36 and ST37 are repeated until the ozone concentration C reaches the descending inflection point.

After a certain period of time has passed since the first gas on-off valve (13) was opened, the ozone concentration C reached the downward inflection point at point a6, and then the ozone concentration C increased. During the period when the ozone concentration C is between points a5 and a6, the condition of step ST35 is not satisfied.

When the ozone concentration C becomes lower than the downward inflection point (minimum value Cmin) at point a6, the condition of step ST36 is not satisfied. Therefore, steps ST37 and ST38 are skipped and step ST35 is executed. In other words, the minimum Cmin and Lower threshold C1 are not updated or calculated after the ozone concentration C has passed the descending inflection point (point a6).

After that, when the ozone concentration C becomes higher than the point a7 which is the Lower threshold value C1, the condition of step ST35 is satisfied. As a result, the supply control ends and the stop control is executed again. Subsequent stop control and supply control are as described above. The control unit (80) alternately repeats the stop control and the supply control until the command for ending the operation in step ST2 of FIG. 2 is input. As a result, as shown in FIG. 3, the ozone concentration C quickly converges to the target concentration Cset.

<Control example when the ozone concentration does not converge to the target concentration in supply control>
As described above, after switching from the supply control to the stop control, when the ozone concentration C passes through the rising inflection point and becomes lower than the Upper threshold value C2, the control unit (80) executes the supply control. However, depending on the operating conditions or the set value of β, the ozone concentration C may not be so low in the supply control, and the target concentration Cset may not be reached. Therefore, in such a case, the control unit (80) ends the supply control and executes the stop control. This control will be described with reference to FIGS. 4 and 6.

When the ozone concentration C becomes lower than the Upper threshold C2 at point b1 in FIG. 6, supply control is executed. Due to the effect of the time delay, the ozone concentration C further decreases. In this case, the condition of step ST32 is not satisfied, and step ST33 is executed. As shown in FIG. 6, when the downward inflection point (point b2) of the ozone concentration C becomes higher than the target concentration Cset, the condition of step ST32 is not satisfied and the processing after step ST34 is not performed.

In this case, the ozone concentration C further rises and becomes higher than the maximum value Cmax. Here, the maximum value Cmax is a value obtained in the previous stop control. In this case, the condition of step ST33 is satisfied, and the supply control ends. Then, stop control is executed.

As described above, when the ozone concentration C becomes higher than the maximum value Cmax of the previous stop control after switching from the stop control to the supply control, the control unit (80) ends the supply control and executes the stop control. .. By this control, it is possible to surely suppress that the ozone concentration C does not converge to the target concentration Cset and continues to rise.

<Control example when the ozone concentration does not converge to the target concentration in stop control>
As described above, after switching from the stop control to the supply control, when the ozone concentration C passes through the descending inflection point and becomes higher than the Lower threshold value C1, the control unit (80) executes the stop control. However, depending on the operating conditions or the set value of α, the ozone concentration C may not be so high under the stop control, and the target concentration Cset may not be reached. Therefore, in such a case, the control unit (80) ends the stop control and executes the supply control. This control will be described with reference to FIGS. 5 and 7.

When the ozone concentration C becomes higher than the Lower threshold value C1 at the point d1 in FIG. 7, the stop control is executed. Due to the effect of the time delay, the ozone concentration C rises further. In this case, the condition of step ST42 is not satisfied, and step ST43 is executed. As shown in FIG. 7, when the rising inflection point (point d2) of the ozone concentration C becomes lower than the target concentration Cset, the condition of step ST43 is not satisfied and the processing after step ST44 is not performed.

In this case, the ozone concentration C further decreases and becomes lower than the minimum value Cmin. Here, the minimum value Cmin is a value obtained in the previous supply control. In this case, the condition of step ST43 is satisfied, and the stop control ends. Then supply control is executed.

As described above, when the ozone concentration C becomes lower than the minimum value Cmin of the previous stop control after switching from the supply control to the stop control, the control unit (80) ends the stop control and executes the supply control. .. By this control, it is possible to surely suppress that the ozone concentration C does not converge to the target concentration Cset and continues to decrease.

-Effect of embodiment-
In the stop control, the Upper threshold value C2 for determining the execution of the supply control is obtained based on the maximum value Cmax and the target concentration Cset. The Upper threshold C2 is a value between the maximum value Cmax and the target concentration Cset. Since the Upper threshold C2 is higher than the target concentration Cset, supply control can be executed quickly. Since the Upper threshold C2 is lower than the maximum value Cmax, it is possible to avoid the problem that the ozone concentration C does not reach the target concentration Cset. As a result, the width of the undershoot of the ozone concentration C can be reduced as compared with the comparative example shown in FIG. 9, and the ozone concentration C can be quickly converged to the target concentration Cset.

In particular, by setting β to 0.5, the Upper threshold C2 becomes an intermediate value between the maximum value Cmax and the target concentration Cset. Therefore, it can be suppressed that the width of the undershoot cannot be sufficiently reduced because the Upper threshold C2 becomes excessively low. By making the Upper threshold C2 excessively high, it is possible to reliably avoid the problem that the ozone concentration C does not reach the target concentration Cset.

In the supply control, the Lower threshold value C1 for determining the execution of the stop control is obtained based on the minimum value Cmin and the target concentration Cset. The Lower threshold C1 is a value between the minimum value Cmin and the target concentration Cset. Since the Lower threshold C1 is lower than the target concentration Cset, stop control can be executed quickly. Since the Lower threshold value C1 is higher than the minimum value Cmin, it is possible to avoid the problem that the ozone concentration C does not reach the target concentration Cset. As a result, the width of the undershoot of the ozone concentration C can be reduced as compared with the comparative example shown in FIG. 9, and the ozone concentration C can be quickly converged to the target concentration Cset.

In particular, by setting β to 0.5, the Lower threshold value C1 becomes an intermediate value between the minimum value Cmin and the target concentration Cset. Therefore, it is possible to prevent the overshoot width from being insufficiently reduced due to the Lower threshold value C1 becoming excessively high. By making the Lower threshold C1 excessively low, it is possible to reliably avoid the problem that the ozone concentration C does not reach the target concentration Cset.

-Modified example of the embodiment-
In the above-described embodiment, the configuration of the following modification may be used.

<Modification example 1>
The β of the above equation (2) may be smaller than the α of the above equation (1). The rate of the ozone gas autolysis reaction tends to be slower than the rate of supplying ozone gas from the ozone generator (20) to the supply path (40). Therefore, if β is too large, the ozone concentration C may not reach the target concentration Cset after the supply control is started. On the other hand, by making β smaller than α, the Upper threshold C2, which is the second threshold, becomes relatively low. Therefore, it is possible to prevent the ozone concentration C from reaching the target concentration Cset.

<Modification 2>
The ozone water production apparatus (1) of the second modification shown in FIG. 8 differs from the above embodiment in the relationship between the tank (44) and the ejector (35). In the liquid flow path (30) of the second modification, the tank (44) is arranged on the upstream side of the ejector (35). The outflow end of the water supply channel (31) connects to the tank (44). A relay path (75) is connected between the tank (44) and the liquid inflow portion (35a) of the ejector (35). A pump (45) and a first flow rate sensor (33) are provided in the relay path (75). A supply channel (40) is provided between the liquid outflow part (35b) of the ejector (35) and the target.

The liquid flow path (30) of the second modification has the first return flow path (60) as in the embodiment, but does not have the second return flow path (70). The first return flow path (60) is provided with a second back pressure valve (72) in place of the flow control valve (61) of the embodiment. In the supply path (40) of the second modification, a gas-liquid separator may be provided on the downstream side of the ejector (35). The gas-liquid separator separates ozone gas in ozone water.

Also in the second modification, the ozone concentration control similar to that of the above embodiment is performed so that the ozone concentration C converges to the target concentration Cset. In the second modification, since the tank (44) is not provided in the supply path (40), the ozone concentration C tends to fluctuate due to the supply control and the stop control. On the other hand, by performing the same ozone concentration control as in the above embodiment, the width of the overshoot of the ozone concentration C can be reduced. Similarly, the width of the undershoot of ozone concentration C can be reduced.

<< Other Embodiments >>
In the above embodiment, in the supply control, the ozone gas generated by the ozone generator (20) is supplied to the supply path (40) by opening the first gas on-off valve (13). However, in the supply control, ozone gas may be supplied to the supply path (40) by operating the stopped ozone generator (20).

In the above embodiment, in the stop control, the supply of ozone gas to the supply path (40) is stopped by closing the first gas on-off valve (13). However, in the stop control, the supply of ozone gas to the supply path (40) may be stopped by stopping the operating ozone generator (20).

In the ozone concentration control of the above embodiment, the control unit (80) makes the following determinations of both A and B according to the present disclosure. A: The control unit (80) determines the execution of the stop control based on the first threshold value C1 in the supply control. B: The control unit (80) determines the execution of the supply control based on the second threshold value C2 in the stop control. However, the control unit (80) may make only one of A and B determinations.

The first threshold value C1 does not necessarily have to be based on the above equation (1). The first threshold value C1 may be obtained based on the target concentration Cset and the minimum value Cmin, and may be a value between the minimum value Cmin and the target concentration Cset.

The second threshold value C2 does not necessarily have to be based on the above equation (2). The second threshold value C2 may be obtained based on the target concentration Cset and the maximum value Cmax, and may be a value between the maximum value Cmax and the target concentration Cset.

After switching from the supply control to the stop control, the control unit (80) of the embodiment ends the stop control and executes the supply control when the ozone concentration C becomes lower than the minimum value Cmin of the previous stop control. However, the control unit (80) may end the stop control and execute the supply control when the ozone concentration C becomes lower than the predetermined third threshold value after switching from the supply control to the stop control. Here, the third threshold value may be a value lower than the target concentration Cset. Further, the control unit (80) may end the stop control and execute the supply control when a predetermined time elapses after switching from the supply control to the stop control.

The control unit (80) of the embodiment ends the supply control and executes the stop control when the ozone concentration C becomes higher than the maximum value Cmax of the previous supply control after switching from the stop control to the supply control. However, the control unit (80) may end the supply control and execute the stop control when the ozone concentration C becomes higher than the predetermined fourth threshold value after switching from the stop control to the supply control. Here, the fourth threshold value may be a value higher than the target concentration Cset. Further, the control unit (80) may end the supply control and execute the stop control when a predetermined time elapses after switching from the stop control to the supply control.

The ozone generator (20) of the embodiment is a discharge type ozonizer. However, the ozone generator (20) may be of another type such as an electrolysis type or an ultraviolet type.

In addition, each component such as the above-described embodiment, modification, and other examples may be replaced or changed within a range that can be combined.

As described above, the present disclosure is useful for ozone water production equipment.

1 Ozone water production equipment
20 Ozone generator
40 Supply channel
46 Detector
80 Control unit

Claims (6)

Ozone generator (20) that generates ozone gas and
A supply path (40) through which ozone water containing ozone gas supplied from the ozone generator (20) flows, and
A detection unit (46) that detects the ozone concentration C of the ozone water in the supply path (40), and
Supply control for supplying ozone gas from the ozone generator (20) to the supply path (40) so that the ozone concentration C detected by the detection unit (46) converges to the target concentration Cset, and the ozone generator ( It is provided with a control unit (80) that alternately switches between stop control for stopping the supply of ozone gas from 20) to the supply path (40).
After switching from the stop control to the supply control, the control unit (80) executes the stop control when the ozone concentration C becomes higher than the first threshold value C1 through a downward inflection point lower than the target concentration Cset. death,
The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset, which is obtained based on the target concentration Cset and the minimum value Cmin which is the ozone concentration corresponding to the descending inflection point. Ozone water production equipment characterized by being. Ozone generator (20) that generates ozone gas and
A supply path (40) through which ozone water containing ozone gas supplied from the ozone generator (20) flows, and
A detection unit (46) that detects the ozone concentration C of the ozone water in the supply path (40), and
Supply control for supplying ozone gas from the ozone generator (20) to the supply path (40) so that the ozone concentration C detected by the detection unit (46) converges to the target concentration Cset, and the ozone generator ( It is provided with a control unit (80) that alternately switches between stop control for stopping the supply of ozone gas from 20) to the supply path (40).
After switching from the supply control to the stop control, the control unit (80) executes the supply control when the ozone concentration C becomes lower than the second threshold value C2 through an inflection point higher than the target concentration Cset. death,
The second threshold value C2 is a value between the maximum value Cmax and the target concentration Cset, which is obtained based on the target concentration Cset and the maximum value Cmax which is the ozone concentration corresponding to the rising inflection point. Ozone water production equipment characterized by being. In claim 2,
After switching from the stop control to the supply control, the control unit (80) executes the stop control when the ozone concentration C becomes higher than the first threshold value C1 through a downward inflection point lower than the target concentration Cset. death,
The first threshold value C1 is a value between the minimum value Cmin and the target concentration Cset, which is obtained based on the target concentration Cset and the minimum value Cmin which is the ozone concentration corresponding to the descending inflection point. Ozone water production equipment characterized by being. In claim 1 or 3,
The first threshold value C1 is
An ozone water production apparatus characterized by being represented by the relational expression of C1 = Cset− (Cset−Cmin) × α (0 <α <1). In claim 2 or 3,
The second threshold value C2 is
An ozone water production apparatus characterized by being represented by the relational expression of C2 = Cset + (Cmax−Cset) × β (0 <β <1). In claim 3,
The first threshold value C1 is
It is expressed by the relational expression of C1 = Cset- (Cset-Cmin) x α (0 <α <1).
The second threshold value C2 is
It is expressed by the relational expression of C2 = Cset + (Cmax−Cset) × β (0 <β <1).
An ozone water production apparatus in which the β is smaller than the α.

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