JP6948012B2 - Ultrapure water heating method - Google Patents

Description

The present invention relates to a method for heating ultrapure water, and more particularly to an ultrapure water heating method for heating ultrapure water from a secondary pure water production apparatus with a heat exchanger and supplying it as warm ultrapure water to a point of use.

As shown in FIG. 2, the ultrapure water used as water for cleaning semiconductors includes a pretreatment system 50, a primary pure water production device 60, and a secondary pure water production device (often referred to as a subsystem) 70. It is manufactured by treating raw water (industrial water, city water, well water, etc.) with an ultrapure water production device composed of (Patent Document 1). The roles of each system in FIG. 2 are as follows.

In the pretreatment system 50 including agglomeration, pressure levitation (precipitation), filtration (membrane filtration) equipment (coagulation filtration equipment in this conventional example), suspended solids and colloidal substances in raw water are removed. Further, in this process, it is possible to remove high molecular weight organic substances and hydrophobic organic substances.

Pretreated water tank 61, heat exchanger 65, reverse osmosis membrane treatment device (RO device) 62, ion exchange device (mixed bed type or 4-bed 5-tower type, etc.) 63, tank 63A, ion exchange device 63B, In the primary pure water production apparatus 60 provided with the degassing apparatus 64, ions and organic components in the raw water are removed. Steam is supplied to the primary side of the heat exchanger 65 as a heat source fluid. The reverse osmosis membrane treatment apparatus 62 removes salts and also removes ionic and colloidal TOCs. The ion exchange devices 63 and 63B remove salts and inorganic carbon (IC), and also remove TOC components that are adsorbed or ion-exchanged by the ion exchange resin. The degassing device 64 removes inorganic carbon (IC) and dissolved oxygen.

The primary pure water produced by the primary pure water production apparatus 60 is sent to the secondary pure water production apparatus 70 via the pipe 69. The secondary pure water production device 70 includes a sub tank (sometimes referred to as a pure water tank) 71, a pump 72, a heat exchanger 73, a low-pressure ultraviolet oxidation device (UV device) 74, an ion exchange device 75, and an ultrafiltration device. The outer filtration membrane (UF membrane) separation device 76 is provided. The heat exchanger 73 is for controlling the temperature of the secondary pure water. Generally, the supply temperature of secondary pure water (normal temperature ultrapure water) is 23 to 25 ° C., and a cooler is used as the heat exchanger 73 in order to control the temperature within that temperature range. Cold water is used as the cooling source for the cooler.

In the low-pressure ultraviolet oxidizing device 74, TOC is decomposed into _{organic acids and further to CO 2} by ultraviolet rays of 185 nm emitted from a low-pressure ultraviolet lamp. The organic matter and CO ₂ produced by the decomposition are removed by the ion exchange device 75 in the subsequent stage. In the ultrafiltration membrane separation device 76, fine particles are removed, and outflow particles from the ion exchange resin are also removed.

The treated water of the ion exchange device 75 is ultrapure water (normal temperature ultrapure water) sent from the ultrafiltration membrane separation device 76 to the use point 90 via the pipe 81, and after being heated by the heat exchangers 85 and 86. , Ultrapure water (warm ultrapure water) sent to use point 90 via the ultrafiltration membrane separation device 87 and the pipe 88.

In the latter line, the ultrapure water from the secondary pure water production apparatus 70 is heated to about 65 to 75 ° C. by the front stage side heat exchanger 85 and the rear stage side heat exchanger 86 and supplied to the use point 90. The warming water from the use point 90 is circulated to the heat source side of the front stage side heat exchanger 85 via the pipe 91. The return water that has passed through the heat source side of the front stage side heat exchanger 85 has cooled to about 30 to 40 ° C., and is returned to the sub tank 71 via the pipe 92. The latter stage side heat exchanger 86 uses steam as a heat source.

FIG. 3 is a system diagram showing an example of a conventional ultrapure water heating device.

The primary pure water is introduced into the subsystem 4 via the pipe 1, the sub tank 2, and the pipe 3, and the temperature is adjusted by the heat exchanger in the subsequent stage of the sub tank to produce ultrapure water at about 25 ° C. The produced ultrapure water flows in the order of pipe 5, first heat exchanger 6, pipe 9 and second heat exchanger 10, is heated to about 45 to 70 ° C. by heat exchanger 6, and is heated by the heat exchanger 10. It is heated to about 75 ° C. and sent as warm ultrapure water to the use point through the pipe 11. A UF membrane separation device 11A is installed in the pipe 11 immediately before the use point.

A return temperature ultrapure water (return water) of about 75 ° C. from the point of use is introduced into the heat source fluid flow path of the heat exchanger 6 via the pipe 7. This return temperature ultrapure water exchanges heat with the ultrapure water from the subsystem 4 in the heat exchanger 6 to lower the temperature to about 30 ° C., and then is sent to the sub tank 2 by the pipe 8.

The first medium water (water as a heat transfer medium) heated by the heat pump 20 and the steam heat exchanger 15 is circulated and circulated in the heat source fluid flow path of the heat exchanger 10. That is, the first medium water of about 65 ° C. flowing out of the heat exchanger 10 is heated to about 75 ° C. by the condenser 23 of the heat pump 20 of the first circulation flow path, and then to about 80 ° C. by the steam heat exchanger 15. It is heated and flowed into the heat exchanger 10.

Steam (steam) from a boiler or the like flows through the heat source fluid flow path of the heat exchanger 15.

The heat pump 20 compresses a heat medium such as CFC substitute from the evaporator 21 by the pump 22 and introduces it into the condenser 23, and introduces the heat medium from the condenser 23 into the evaporator 21 via the expansion valve 24. It is configured in.

The first medium water from the heat exchanger 10 is introduced into the condenser 23 of the first circulation flow path (high temperature side flow path) via the pipe 12, and the first medium water heated by the condenser 23 passes through the pipe 14. Water is sent to the heat exchanger 15 via the heat exchanger 15. A part of the first medium water from the heat exchanger 15 is returned to the pipe 12 via the bypass pipe 19. As a result, the water temperature of the first medium water introduced into the condenser 23 becomes about 70 ° C. The bypass pipe 19 is provided with a flow rate control valve (not shown).

A circulation pump (not shown) is provided in the pipe 12.

A flow path composed of a pipe 25 and a pipe 27 is provided in order to allow the second medium water (heat pump heat source water) to pass through the heat source fluid flow path (low temperature side flow path) of the evaporator 21.

Heat pump heat source water at about 30 ° C. is introduced into the heat source fluid flow path of the evaporator 21 and exchanges heat with the heat medium of the heat pump 20 to lower the temperature to about 25 ° C., and then is sent to another process via the pipe 25. ..

As a method of operating the heat pump 20, for example, the input power of the heat pump compressor is adjusted so that the outlet temperature of the first medium water becomes a constant temperature. A plurality of heat pumps may be used and the number of heat pumps may be controlled according to the heat load.

In the ultrapure water heating device of FIG. 3, the amount of the first medium water bypassed from the pipe 14 to the pipe 12 via the bypass pipe 19 is a three-way valve provided at the branch portion from the pipe 14 to the bypass pipe 19 (not shown). ) Can be adjusted. When the amount of bypass water is increased, the amount of heat given to the ultrapure water in the heat exchanger 10 is reduced, and when the amount of bypass water is reduced, the amount of heat given in the heat exchanger 10 is increased. Therefore, when the temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10 fluctuates due to the fluctuation of the water amount of the return temperature ultrapure water from the pipe 7, the amount of the first medium water bypassed to the pipe 19 is controlled. As a result, the temperature of the warm ultrapure water sent from the pipe 11 to the use point is maintained constant (75 ° C. in the above case).

Japanese Patent No. 6149993 Japanese Patent No. 6149992

In FIG. 3, when the amount of water of the ultrapure water returning from the pipe 7 fluctuates greatly and the temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10 fluctuates greatly, the amount of water of the first medium bypassed to the pipe 19 is controlled. It is not possible to follow the temperature fluctuation of ultrapure water by itself, and the temperature of warm ultrapure water sent to the use point may deviate from the target temperature.

That is, the amount of warm ultra-pure water used at the point of use may fluctuate greatly in units of several seconds. When the amount of warm ultra-pure water used at the point of use fluctuates, the flow rate of "returning warm ultra-pure water" in FIG. 3 fluctuates. As a result, the amount of heat recovered in the heat exchanger 6 fluctuates, and the temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10 also fluctuates.

For example, in the case of the system of FIG. 3, if the amount of hot ultrapure water used increases rapidly at the point of use and the amount used is maintained, the temperature of the ultrapure water at the inlet of the heat exchanger 10 will decrease. In this case, in order to maintain the ultrapure water outlet temperature of the heat exchanger 10, the amount of bypass water to the pipe 19 is reduced and the flow rate is increased. However, if the three-way valve is adjusted so that the amount of bypass water to the pipe 19 becomes zero, the amount of water to the heat exchanger 10 cannot be increased any more, and the temperature of the warm ultrapure water sent from the pipe 11 to the point of use Cannot be maintained at the target temperature.

Since the temperature of the hot ultra-pure water at the point of use needs to be controlled within a strict range of plus or minus 1 ° C, the inability to maintain the controlled temperature of the hot ultra-pure water may cause a big problem in the equipment using the hot ultra-pure water at the point of use. There is.

Conventionally, in order to avoid the above problem, the amount of first medium water (high temperature circulating water amount) circulating in the pipe 14, the pipe 12, and the bypass pipe 19 has been set to a sufficient amount. In other words, considering the maximum value of warm ultra-pure water used based on past results, even if the amount of warm ultra-pure water used suddenly increases to such a maximum value, it is possible to control the temperature of hot ultra-pure water sent to the use point. As such, the amount of bypass circulating water was set with sufficient margin.

According to such a method, the temperature of the warm ultrapure water sent to the use point is maintained constant even if the amount of ultrapure water used at the use point is significantly increased. However, under normal conditions (when the amount of warm ultra-pure water used is near the average value), there is a problem that the amount of bypass water is extremely large and the operating cost is high. That is, in the normal state, since there is a large amount of return temperature ultrapure water, the temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10 does not decrease so much, and therefore the required heating amount by the high-temperature circulating water (first medium water) also increases. Since it was not large, the operation was continued with a large flow rate of the first medium water bypassing the pipe 19.

As mentioned above, simply taking measures to reduce the amount of high-temperature circulating water (first medium water) avoids the risk of not being able to maintain the temperature of warm ultra-pure water when the amount of hot ultra-pure water used suddenly increases at the point of use. I couldn't.

The present invention solves such a problem and can reduce the amount of high-temperature circulating water and the bypass flow rate while avoiding the risk of not being able to maintain the temperature of warm ultrapure water due to a rapid increase in the amount of hot ultrapure water used at the point of use. It is an object of the present invention to provide a method for heating pure water.

The ultra-pure water heating method of the present invention uses a first heat exchanger that uses the return water from the point of use as a heat source for heating the ultra-pure water from the ultra-pure water production apparatus, and the first heat exchanger. An ultra-pure water heating device that has a heating means for further heating the heated ultra-pure water and supplies the heated ultra-pure water to a use point. The heating means is heated by the first heat exchanger. A second heat exchanger in which the ultra-pure water is passed through the fluid flow path to be heated, and a circulation flow path in which medium water as a heat transfer medium is circulated and circulated in the heat source fluid flow path of the second heat exchanger. In the method of heating ultra-pure water by a heating device provided with a heater for heating the medium water flowing through the circulation flow path and a pump provided in the circulation flow path, the amount of ultra-pure water used at the point of use. The pump is controlled according to the above.

In one aspect of the present invention, the medium water circulation flow path is provided with a bypass flow path that bypasses the second heat exchanger, and the bypass flow path is connected to the bypass flow path according to the amount of ultrapure water used at the point of use. Control the bypass flow rate.

In one aspect of the present invention, a three-way valve for controlling the bypass flow rate is provided, and the opening degree of the three-way valve is controlled according to the amount of ultrapure water used at the point of use.

In one aspect of the present invention, a three-way valve for controlling the bypass flow rate is provided, and the three-way valve opening degree after 1 to 5 minutes is predicted from the current operation data actual measurement value, and the opening degree prediction value is The amount of high-temperature circulating water is controlled so that it becomes almost constant.

In one aspect of the present invention, a multiple regression model or an artificial intelligence model with the "predicted value of the three-way valve opening" as the objective variable is constructed based on the past operation data, and the current operation data measured value is used in the model. Is input to obtain the "predicted value of the three-way valve opening".

In one aspect of the present invention, the explanatory variables of the multiple regression model or the artificial intelligence model include at least "the current value of the three-way valve opening degree" and "the ultrapure water side outlet temperature of the first heat exchanger".

According to the present invention, by reducing the amount of high temperature circulating water and reducing the bypass flow rate,
(1) The power consumption of the circulating water pump can be reduced;
(2) When there is a heat pump in the circulation process of high-temperature circulating water, the temperature difference between the high-temperature circulating water and the heat pump heat source water decreases as the heat pump inlet temperature of the high-temperature circulating water decreases, so the COP (coefficient of performance) of the heat pump is improved. Can be made;
(3) When there are both a heat pump and a steam heat exchanger in the circulation process of high-temperature circulating water, the amount of steam used in the steam heat exchanger can be reduced, and the heating ratio by the heat pump with a small unit price per amount of heat supplied can be increased. Can be;
The effect is obtained.

It is a block diagram of the heating apparatus which concerns on embodiment of this invention. It is a block diagram of the heating apparatus of the conventional example. It is a block diagram of the heating apparatus of the conventional example.

Hereinafter, embodiments will be described with reference to FIG. Although the water temperature is illustrated in the following description, it is an example and does not limit the present invention.

FIG. 1 is a system diagram showing an ultrapure water heating device according to an embodiment.

The primary pure water is introduced into the subsystem 4 via the pipe 1, the sub tank 2, and the pipe 3, and the temperature is adjusted by the heat exchanger included in the subsystem to produce ultrapure water at about 25 ° C. The produced ultrapure water flows in the order of pipe 5, first heat exchanger 6, pipe 9 and second heat exchanger 10, is heated to about 45 to 70 ° C. by heat exchanger 6, and is heated by the heat exchanger 10. It is heated to about 75 ° C. and sent as warm ultrapure water to the use point through the pipe 11. A UF membrane separation device (not shown) is installed in the pipe 11 immediately before the point of use.

A return temperature ultrapure water (return water) of about 75 ° C. from the point of use is introduced into the heat source fluid flow path of the heat exchanger 6 via the pipe 7. This return temperature ultrapure water exchanges heat with the ultrapure water from the subsystem 4 in the heat exchanger 6 to lower the temperature to about 30 ° C., and then is sent to the sub tank 2 by the pipe 8.

Medium water (water as a heat transfer medium) heated by a heater 40 such as a heat pump or a steam heat exchanger is circulated and circulated in the heat source fluid flow path of the heat exchanger 10. That is, the medium water of about 50 to 70 ° C. flowing out from the heat exchanger 10 is introduced into the heater 40 by the pipe 45, the pump 46, and the pipe 47, heated to about 80 ° C., and then the pipe 42, the three-way valve 43, and the pipe. It flows into the heat exchanger 10 via 44.

A part of the medium water from the heater 40 is returned from the three-way valve 43 to the pipe 45 via the bypass pipe 48.

A temperature sensor 50 is provided in the pipe 11, and the measured temperature is input to the control device 51, and the three-way valve 43 and the pump 46 are controlled by the control device 51. From the three-way valve 43, a signal indicating the current opening degree (opening degree at which medium water flows from the pipe 42 to the pipe 44) is input to the control device 51 to the control device 51.

In this embodiment, the amount of circulating water in the medium water is adjusted so that the opening degree of the three-way valve 43 (the opening degree for flowing the medium water from the pipe 42 to the pipe 44) becomes a constant value. Assuming that the opening degree of the three-way valve 43 is expressed by 0% to 100%, it is preferable to increase or decrease the motor rotation speed of the pump 46 and automatically adjust the amount of circulating water in the medium water so that the opening degree is, for example, 75 to 80%. .. For example, an inverter attached to a pump adjusts the motor rotation speed by increasing or decreasing the voltage and frequency.

A method may also be used in which a signal relating to the current three-way valve opening is input to the control device 51, arithmetic processing is performed by the control device 51, the result is sent to the inverter attached to the pump 46, and the inverter adjusts the voltage and frequency of the motor. .. Alternatively, a method may be used in which a relational expression between the opening degree of the three-way valve 43 and the inverter output value is derived in advance and the inverter output value is adjusted based on the relational expression.

When the amount of warm ultra-pure water used at the use point 90 changes significantly, there is a time delay of several minutes before the effect affects the opening degree of the three-way valve 43. Therefore, it is more desirable to use the future predicted value instead of the current three-way valve 43 opening. Here, the future means 1 to 5 minutes after the present time.

For example, based on the operation data for the past several months, the objective variable is "three-way valve opening after two minutes", "current three-way valve opening", and "ultrapure water flowing from the pipe 9 into the heat exchanger 10". By constructing a multiple regression model with the temperature of the temperature sensor as the explanatory variable and inputting the measured value of the current operation data into the model, the detected ultrapure water temperature of the temperature sensor 50 after 2 minutes is maintained at 75 ° C. Predict the "three-way valve opening after 2 minutes" required to do so. By adjusting the amount of high-temperature circulating water (pump 46 discharge amount) based on the predicted value of "three-way valve opening after 2 minutes", it is possible to respond more quickly to a rapid increase in the amount of hot ultra-pure water used. For example, when the predicted value of the three-way valve opening degree after 2 minutes exceeds 80%, the motor rotation speed of the pump 46 is increased so that the opening degree falls within the range of 75 to 80%.

An artificial intelligence model or the like may be used instead of the multiple regression model.

In this way, the amount of bypass water can be reduced and the production cost of warm ultra-pure water can be reduced while avoiding the risk that the temperature of warm ultra-pure water cannot be maintained due to the rapid increase in the amount of hot ultra-pure water used at the point of use.

When the amount of warm ultrapure water used at the point of use increases, the temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10 decreases, and the opening of the three-way valve 43 begins to increase in response to this. , The amount of circulating water in the medium water can be automatically increased, and the risk of deviation from the control target value of the temperature of warm ultrapure water can be avoided.

Furthermore, by predicting the three-way valve opening after a few minutes from the measured values of the "warm ultrapure water return flow rate" and the "temperature of the ultrapure water flowing from the pipe 9 into the heat exchanger 10" at the present time, the current three-way valve opening is predicted. The amount of high-temperature circulating water can be adjusted even faster than adjusting the amount of high-temperature circulating water only by the valve opening, and the risk of deviation from the control target value of the temperature of warm ultrapure water can be avoided more reliably.

A more specific operation example will be described below.

As the heater 40, both a heat pump using the wastewater of the refrigerator as a heat source and a steam heat exchanger using steam as a heat source are used so that the circulating water flows in the order of pump 47 → heat pump → steam heat exchanger. In the heat pump, the input power is adjusted so that the heat pump outlet temperature is constant. Further, the amount of steam is supplied so that the outlet temperature in the steam heat exchanger (that is, the temperature of the medium water flowing through the pipe 42) becomes constant.

(Heat pump outlet temperature of the present invention) = (heat pump outlet temperature of the comparative example), (steam heat exchanger outlet temperature of the present invention) = (steam heat exchanger outlet temperature of the comparative example).

In this embodiment, the output value of the inverter attached to the pump 46 is adjusted so that the opening degree of the three-way valve 43 is 75 to 80% in normal times (that is, the bypass water amount is 20 to 25%). As a result, the average value of the circulating water amount of the medium water is reduced by about 40% as compared with the conventional case. Along with this, the power consumption of the circulating water pump is reduced, and the heating ratio by the heat pump having a low unit price per calorific value is increased. As a result, the overall operating cost can be reduced by about 15%.

That is, in FIG. 3, the amount of ultrapure water used at the point of use is remarkably increased, the amount of ultrapure water returned from the pipe 7 is remarkably reduced, and the temperature of the ultrapure water flowing into the heat exchanger 10 is considerably low ( For example, even when the temperature reaches 40 to 45 ° C. or lower), a sufficiently large amount of high-temperature medium water is flowed through the heat exchanger 10 so that hot ultrapure water at 75 ° C. can be sent from the pipe 11 to the use point 90. It is necessary to increase the amount of medium water bypassed from the pipe 14 to the pipe 19 in normal times and secure the amount of medium water from the pipe 14 to the heat exchanger 10 when the amount of ultrapure water used at the use point 90 increases significantly. was there. Therefore, even in normal times (when the amount of ultrapure water used at the use point 90 is almost the average amount), the amount of hot water discharged from the heat pump 20 to the pipe 14 (the amount of medium water) is increased, and the amount of bypass medium water is increased. It was necessary to prepare for the increase in the amount of ultrapure water used at the point of use. Then, in order to bypass such a large amount of medium water, the pump power cost and the like have increased.

On the other hand, in the present invention, the amount of bypass medium water is kept as small as 20 to 25% in normal times, and when an increase in the amount of medium water supplied to the heat exchanger 10 is predicted (that is, the opening degree of the three-way valve 43). When a significant increase in the amount of hot water is expected), the amount of hot water discharged from the heater 40 is increased. As a result, the amount of high-temperature medium water supplied (the amount of hot water discharged) from the heater 40 in normal times can be significantly reduced as compared with the conventional case.

The controller 51 controls the opening degree of the three-way valve 43 and the motor rotation speed of the pump 46 so that the temperature of the warm ultrapure water toward the use point 90 via the pipe 11 is always maintained at a constant temperature (75 ° C. in this case). The amount of medium water (the amount of high-temperature circulating water) supplied to the heat exchanger 10 is controlled by control. The three-way valve 43 and the bypass pipe 48 may be omitted as long as the warm ultrapure water can be maintained at a constant temperature only by controlling the amount of medium water to the heat exchanger 10 by controlling the pump 46. However, the control of the amount of water supplied to the heat exchanger 10 by controlling the amount of bypass water by the three-way valve 43 is quick and easy, and it is possible to quickly respond to the load fluctuation of the heat exchanger 10. In this embodiment, since the opening degree of the three-way valve 43 is as high as 75 to 80%, the large load increase in the heat exchanger 10 cannot be dealt with by the three-way valve 43 alone. Therefore, as described above, the control of the pump 46 is also used.

The above embodiment is an example of the present invention, and the present invention may be a form other than the illustration.

2 Subtank 4 Subsystem 6 1st heat exchanger 10 2nd heat exchanger 43 Three-way valve 48 Bypass piping 50 Temperature sensor

Claims (6)

A first heat exchanger that uses the return water from the point of use as a heat source to heat the ultrapure water from the ultrapure water production equipment.
An ultrapure water heating device that has a heating means for further heating the ultrapure water heated by the first heat exchanger and supplies the heated ultrapure water to a use point.
The heating means
A second heat exchanger in which ultrapure water heated by the first heat exchanger is passed through a fluid flow path to be heated, and a second heat exchanger.
A circulation flow path for circulating and circulating medium water as a heat transfer medium through the heat source fluid flow path of the second heat exchanger.
A heater that heats the medium water flowing through the circulation flow path,
In a method of heating ultrapure water by a heating device provided with a pump provided in the circulation flow path,
An ultrapure water heating method characterized in that the pump is controlled according to the amount of ultrapure water used at a use point. A bypass flow path that bypasses the second heat exchanger is provided in the medium water circulation flow path.
The method for heating ultrapure water according to claim 1, wherein the bypass flow rate to the bypass flow path is controlled according to the amount of ultrapure water used at the point of use. The ultrapure water heating according to claim 2, wherein a three-way valve for controlling the bypass flow rate is provided, and the opening degree of the three-way valve is controlled according to the amount of ultrapure water used at the point of use. Method. A three-way valve for controlling the bypass flow rate is provided, and the opening degree of the three-way valve is predicted 1 to 5 minutes after the measured value of the current operation data so that the predicted opening value becomes almost constant. The ultrapure water heating method according to claim 2, wherein the amount of high-temperature circulating water is controlled. By constructing a multiple regression model or artificial intelligence model with the "predicted value of the three-way valve opening" as the objective variable based on the past operation data, and inputting the current operation data actual measurement value into the model, " The method for heating ultrapure water according to claim 4, wherein a "predicted value of a three-way valve opening degree" is obtained. The ultrapure water heating method according to claim 5, wherein at least the "current value of the three-way valve opening" and the "ultrapure water side outlet temperature of the first heat exchanger" are included in the explanatory variables of the multiple regression model or the artificial intelligence model.

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