JP7270490B2 - Water supply equipment and water supply method for cooling towers - Google Patents

Description

The present invention relates to a water supply system and method for cooling towers.

A method is known in which waste water is recovered and reused as circulating water for a cooling tower, make-up water, or the like. Cooling towers are usually installed outdoors, and the amount of circulating water scattered from the cooling tower is susceptible to the temperature, humidity, etc. of the surrounding environment, and the required amount of make-up water fluctuates.

By the way, waste water is collected by a membrane filtration system that combines membrane filtration using microfiltration membrane (MF membrane) or ultrafiltration membrane (UF membrane) and reverse osmosis membrane treatment using reverse osmosis membrane (RO membrane). It is known that the water is reused as make-up water for cooling towers, etc. (see, for example, Patent Document 1). In such a membrane filtration system, when the membrane fouls, the amount of permeated water decreases, so the membrane is washed.

As a method for cleaning microfiltration membranes and ultrafiltration membranes, backwash water is passed from the secondary side to the primary side of the membrane to wash deposits on the membrane surface, and gas is supplied to the primary side of the membrane. When physical cleaning such as air scrubbing or physical cleaning such as backwashing is difficult to remove, chemical-added water containing chemicals such as oxidizing agents, alkaline agents, and acid agents is circulated in the membrane, or the membrane is treated with chemical-added water. Chemical cleaning such as chemical cleaning such as immersion in water is a common method. As a method for cleaning a reverse osmosis membrane, chemical cleaning in which chemical-added water is circulated is generally used.

However, chemical cleaning usually takes several hours to tens of hours, and the operating rate of the membrane filtration system drops significantly. be.

In addition, for microfiltration membranes and ultrafiltration membranes, there is a cleaning method called chemical-enhanced backwash (CEB) in which chemicals are added to the backwash water, but increasing the number of chemical-enhanced backwashes improves the cleaning effect. However, since the operating rate of the system decreases, it becomes difficult to obtain the necessary amount of recovered water, just as with chemical cleaning.

In order to avoid such a decrease in the operation rate of membrane filtration systems, a spare membrane filtration line that can be operated even during chemical washing and chemical backwashing is sometimes installed, but this increases the installation area of the equipment and costs lead to an increase in

JP 2011-156483 A

An object of the present invention is to provide a water supply device and a water supply method for cooling towers, in which the amount of water supplied to the cooling tower using water recovered by a membrane filtration system combining membrane filtration treatment and reverse osmosis membrane treatment is stabilized. to do.

The present invention is for cooling towers, in which water to be treated is treated by membrane filtration using a turbidity removal membrane and reverse osmosis membrane treatment using a reverse osmosis membrane, and at least part of the resulting treated water is supplied to a cooling tower. A water supply device, comprising: a membrane filtration device that performs the membrane filtration process on the water to be treated; a reverse osmosis membrane treatment device that performs the reverse osmosis membrane process on the membrane filtration treated water obtained by the membrane filtration process; a water supply amount prediction unit that predicts the future water supply amount of the cooling tower based on at least one of temperature and humidity; a membrane cleaning prediction unit for predicting a cleaning timing for cleaning at least one of the turbidity removal membrane and the reverse osmosis membrane; and a control means having a cleaning timing determination unit that searches for a cleaning timing at which the required amount of water supply is not insufficient and determines a new cleaning timing when the required amount of water supply is insufficient in the cooling tower. It is a water supply device.

In the cooling tower water supply device, it is preferable that the control means controls cleaning of at least one of the turbidity removal membrane and the reverse osmosis membrane at a new cleaning timing determined by the cleaning timing determining section.

Preferably, the cooling tower water supply apparatus further includes a display section for displaying the new cleaning timing determined by the cleaning timing determination section.

In the cooling tower water supply device, the cleaning of the turbidity removal membrane is performed by at least one of chemical cleaning and chemical-enhanced backwashing, and the cleaning of the reverse osmosis membrane includes chemical cleaning, pure water flushing, and intermittent acid injection. , intermittent injection of alkali, intermittent injection of oxidizing agent, and intermittent injection of slime control agent.

The present invention is for cooling towers, in which water to be treated is treated by membrane filtration using a turbidity removal membrane and reverse osmosis membrane treatment using a reverse osmosis membrane, and at least part of the resulting treated water is supplied to a cooling tower. A water supply method, comprising: a membrane filtration step of performing the membrane filtration treatment on the water to be treated; a reverse osmosis membrane treatment step of performing the reverse osmosis membrane treatment on the membrane filtration treated water obtained by the membrane filtration treatment; A water supply amount prediction step of predicting the future water supply amount of the cooling tower based on at least one of temperature and humidity; a membrane cleaning prediction step of predicting a cleaning timing for cleaning at least one of the turbidity removal membrane and the reverse osmosis membrane; and a cleaning timing determining step of searching for a cleaning timing at which the required amount of water supply does not run short, and determining a new cleaning timing, when the required amount of water supply is insufficient.

In the cooling tower water supply method, it is preferable to control cleaning of at least one of the turbidity removal membrane and the reverse osmosis membrane at a new cleaning timing determined by the cleaning timing determination step.

In the cooling tower water supply method, it is preferable to display the new cleaning timing determined by the cleaning timing determining step.

In the water supply method for a cooling tower, the cleaning of the turbidity removal membrane is performed by at least one of chemical cleaning and chemical-enhanced backwashing, and the cleaning of the reverse osmosis membrane includes chemical cleaning, pure water flushing, and intermittent acid injection. , intermittent injection of alkali, intermittent injection of oxidizing agent, and intermittent injection of slime control agent.

To provide a water supply apparatus and a water supply method for a cooling tower, in which the amount of water supplied to the cooling tower using water recovered by a membrane filtration system that combines membrane filtration treatment and reverse osmosis membrane treatment is stabilized by the present invention. can be done.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows an example of the water supply apparatus for cooling towers which concerns on embodiment of this invention.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

An outline of an example of a water supply system for cooling towers according to an embodiment of the present invention is shown in FIG. 1, and the configuration thereof will be described.

The water supply apparatus 1 for cooling towers in FIG. It is a device that supplies to The cooling tower water supply device 1 includes a membrane filtration device 12 that performs a membrane filtration process on the water to be treated using a turbidity removal membrane, and a reverse osmosis membrane on the membrane filtration treated water obtained by the membrane filtration process. and a reverse osmosis membrane processing device 16 for processing. The water supply apparatus 1 for cooling towers may include a water tank 10 to be treated that stores water to be treated, and a membrane filtration treated water tank 14 that stores membrane filtration treated water.

In the water supply apparatus 1 for cooling towers of FIG. The outlet of the water tank 10 to be treated and the inlet of the membrane filtration device 12 are connected by a water pipe 22 to be treated via a pump 38 . The outlet of the membrane filtration device 12 and the inlet of the membrane filtration treated water tank 14 are connected by a membrane filtration treated water pipe 24 . A membrane filtration treated water outlet of the membrane filtration treated water tank 14 and an inlet of the reverse osmosis membrane treatment device 16 are connected by a membrane filtration treated water pipe 28 . A permeated water outlet of the reverse osmosis membrane treatment device 16 and an inlet of the cooling tower 18 are connected by a permeated water pipe 32 . A concentrated water pipe 34 is connected to a concentrated water outlet of the reverse osmosis membrane treatment device 16 . The outlet of the cooling tower 18 and the water pipe 20 to be treated may be connected by a pipe 36 . A backwash water outlet of the membrane filtration treated water tank 14 and the middle of the membrane filtration treated water pipe 24 are connected by a backwash water pipe 30 via a backwash pump 40 . A backwashing drainage pipe 26 is connected to a backwashing drainage outlet on the primary side of the membrane filtration device 12 . The cooling tower water supply apparatus 1 includes a control unit 42 as control means, and the pump 38, the backwash pump 40, and the control unit 42 are connected by electrical connection or the like.

The operation of the cooling tower water supply method and the cooling tower water supply apparatus 1 according to the present embodiment will be described.

The to-be-treated water is sent to the to-be-treated water tank 10 through the to-be-treated water pipe 20 as necessary, and after being stored, is sent to the membrane filtration device 12 through the to-be-treated water pipe 22 by the pump 38 . In the membrane filtration device 12, the water to be treated is subjected to membrane filtration using a turbidity removing membrane (membrane filtration step). The water to be treated is passed from the primary side to the secondary side of the turbidity removal membrane, and suspended solids and the like contained in the water to be treated are filtered. The membrane filtration treated water that has been subjected to the membrane filtration treatment is sent to the membrane filtration treated water tank 14 through the membrane filtration treated water pipe 24 as needed and stored therein.

Part of the membrane filtration treated water is sent from the membrane filtration treated water tank 14 to the reverse osmosis membrane treatment device 16 through the membrane filtration treated water pipe 28 . In the reverse osmosis membrane treatment device 16, reverse osmosis membrane treatment is performed on the membrane filtration treated water (reverse osmosis membrane treatment step). At least part of the permeated water obtained by the reverse osmosis membrane treatment is sent as treated water to the cooling tower 18 through the permeated water pipe 32 and supplied as circulating water, make-up water, and the like. Concentrated water obtained by reverse osmosis membrane treatment is discharged through a concentrated water pipe 34 .

As the membrane filtration process progresses, suspended solids and the like accumulate on the surface of the turbidity removing membrane, and filtration resistance may occur. When the turbidity removing membrane of the membrane filtration device 12 needs to be washed, the turbidity removing membrane is washed. For example, a chemical is added to the water to be treated or the like in the water tank 10 to be treated or the water to be treated pipe 22, and the chemical-added water to which the chemical is added is brought into contact with the turbidity removal film, or the turbidity removal film is immersed in the chemical-added water. Chemical cleaning of the turbidity removing membrane of the membrane filtration device 12 is performed by washing. Alternatively, for example, at least part of the membrane filtration treated water is passed from the membrane filtration treated water tank 14 to the secondary membrane filtration device 12 through the backwash water pipe 30 and the membrane filtration treated water pipe 24 by the backwash pump 40 as backwash water. It is introduced from the side and discharged from the primary side to backwash the turbidity removing membrane of the membrane filtration device 12 (backwashing step). At this time, a chemical may be added to the backwash water in the membrane filtration treatment water tank 14 or the backwash water pipe 30 to perform chemical enhanced backwash (CEB) of the turbidity removal membrane. The backwashing drainage is discharged through the backwashing drainage pipe 26 from the backwashing drainage outlet. In this case, the backwash pump 40, the backwash water pipe 30, the treated water pipe 24, etc. function as washing means (backwash means).

When the reverse osmosis membrane of the reverse osmosis membrane treatment device 16 needs to be washed, for example, a chemical is added to the membrane filtration treated water or the like in the membrane filtration treated water tank 14 or the membrane filtration treated water pipe 28, and the chemical is added. The chemical cleaning of the reverse osmosis membrane of the reverse osmosis membrane processing device 16 is performed by bringing the chemical-added water thus prepared into contact with the reverse osmosis membrane. Alternatively, for example, a reverse osmosis membrane treatment device can be obtained by flushing pure water through pure water, intermittent injection of acid into membrane filtration treated water, intermittent injection of alkali, intermittent injection of oxidizing agent, intermittent injection of slime control agent, etc. Washing of 16 reverse osmosis membranes may be performed.

In the cooling tower water supply method and cooling tower water supply apparatus 1 according to the present embodiment, the future water supply amount of the cooling tower 18 is predicted based on at least one information of temperature and humidity based on weather forecasts, etc. At least one of the turbidity removal membrane and the reverse osmosis membrane is cleaned at a cleaning timing when the water supply to the cooling tower 18 is not insufficient, that is, at a cleaning timing when the amount of water supplied to the cooling tower 18 is small. As a result, the amount of feed water supplied to the cooling tower using the water recovered by the membrane filtration system combining the membrane filtration treatment and the reverse osmosis membrane treatment is stabilized.

The control unit 42 includes, for example, a water supply amount prediction unit that predicts the future water supply amount of the cooling tower 18 based on at least one of temperature and humidity, and at least one of the differential pressure and flow rate of the turbidity removal membrane and the reverse osmosis membrane. Based on the tendency, the membrane cleaning prediction unit that predicts the cleaning timing for cleaning at least one of the turbidity removal membrane and the reverse osmosis membrane, and the prediction of the water supply amount prediction unit and the prediction of the membrane cleaning prediction unit are compared, and a cleaning timing determination unit that searches for a cleaning timing at which the required amount of water supply does not run short and determines a new cleaning timing when the necessary amount of water supply is insufficient at the cleaning timing. The control unit 42 controls the pump 38 and the backwash pump 40 according to the new cleaning timing determined by the cleaning timing determination unit, and cleans at least one of the turbidity removal membrane and the reverse osmosis membrane. By washing at least one of the turbidity removal membrane and the reverse osmosis membrane at the new washing timing determined by the washing timing determination unit, the water recovered by the membrane filtration system combining the membrane filtration process and the reverse osmosis membrane process is recovered. The supply of feed water to the used cooling tower is stabilized.

<Embodiment 1: Determining the cleaning timing of the turbidity removal film based on temperature and humidity such as weather forecast>
The water supply amount prediction unit of the control unit 42 acquires information on future temperature and humidity from a weather forecast or the like, and predicts the scattering amount of the circulating water in the cooling tower 18 based on at least one of the acquired temperature and humidity. , predicts the future water supply rate of the cooling tower 18 .

For prediction of the future water supply amount of the cooling tower 18, for example, future temperature and humidity information obtained from a weather forecast or the like, past temperature, humidity, water supply amount data, and the like may be used.

The membrane cleaning prediction unit of the control unit 42 acquires data such as the differential pressure and flow rate of membrane filtration by the turbidity removing membrane, predicts the future differential pressure based on the tendency of differential pressure increase, and cleans the turbidity removing membrane. Predict cleaning timing.

Linear approximation, exponential approximation, or the like may be used to predict the cleaning timing for cleaning the turbidity-removing film, or prediction may be made from past differential pressure vs. water flow data.

The cleaning timing determination unit of the control unit 42 calculates in advance the decrease in the recovery amount due to the decrease in operating rate when chemical cleaning of the turbidity-removing film or chemical-enhanced backwashing is performed. By comparing the prediction by the water supply amount prediction unit and the prediction by the membrane cleaning prediction unit, if the necessary water supply amount is insufficient at the cleaning timing predicted by the membrane cleaning prediction unit, the cleaning timing at which the necessary water supply amount is not insufficient. and determine a new cleaning timing. For example, when the differential pressure of the turbidity removal membrane reaches a predetermined differential pressure (e.g., 100 kPa), it is expected that the air temperature will be high and the amount of circulating water in the cooling tower will increase. If the required amount of water supply is large, for example, the chemical cleaning of the turbidity removal membrane may be performed during the latest time period when the temperature is the lowest.

The same is true when performing chemical-strengthened backwashing instead of chemical cleaning. The timing predicted by the membrane cleaning prediction unit that the turbidity removal membrane tends to be clogged and the need to increase the number of times of chemical-strengthened backwashing to eliminate the clogging of the turbidity removal membrane, and the timing predicted by the water supply amount prediction unit If the timing of increasing the replenishment amount to the cooling tower overlaps, for example, the number of times of chemical-strengthened backwash may be increased at the timing before that to reduce clogging of the turbidity removal membrane.

<Embodiment 2: Determining the cleaning timing of the reverse osmosis membrane based on temperature and humidity such as weather forecast>
The water supply amount prediction unit of the control unit 42 acquires information on future temperature and humidity from a weather forecast or the like, and predicts the scattering amount of the circulating water in the cooling tower 18 based on at least one of the acquired temperature and humidity. , predicts the future water supply rate of the cooling tower 18 .

The membrane cleaning prediction unit of the control unit 42 acquires data such as the differential pressure and flow rate of the reverse osmosis membrane treatment by the reverse osmosis membrane, predicts the future differential pressure based on the tendency of the differential pressure increase, and Predict the cleaning timing for cleaning.

The cleaning timing determination unit of the control unit 42 calculates in advance the decrease in the recovery amount due to the decrease in operating rate when the reverse osmosis membrane is chemically cleaned or the like. By comparing the prediction by the water supply amount prediction unit and the prediction by the membrane cleaning prediction unit, if the necessary water supply amount is insufficient at the cleaning timing predicted by the membrane cleaning prediction unit, the cleaning timing at which the necessary water supply amount is not insufficient. and determine a new cleaning timing. For example, when the permeability coefficient (m/d/MPa) of the reverse osmosis membrane reaches 80 to 70% of the initial value, it is expected that the air temperature will be high and the amount of circulating water in the cooling tower will increase. If the required amount of water supply is greater than the collected amount, the chemical cleaning of the reverse osmosis membrane may be performed, for example, during the most recent time period when the temperature is the lowest.

Cleaning of the reverse osmosis membrane can be carried out together with chemical cleaning or separately from chemical cleaning, including pure water flushing in which pure water is passed through the reverse osmosis membrane, intermittent injection of acid into membrane filtration treated water, intermittent injection of alkali, and oxidizing agent. Intermittent injection of the agent, intermittent injection of the slime control agent, etc. may be performed.

For chemical cleaning, for example, chemical-added water in which chemicals such as an oxidizing agent, an alkaline agent, and an acid agent are added to the membrane may be circulated, or the membrane may be immersed in chemical-added water.

The chemical is not particularly limited as long as it can enhance the cleaning effect of the membrane. Examples include acid agents such as oxalic acid, citric acid, hydrochloric acid, sulfuric acid and nitric acid, and alkalis such as aqueous sodium hydroxide solution. agents and the like.

Examples of the oxidizing agent include chlorine-based oxidizing agents such as hypochlorous acid or salts thereof, bromine-based oxidizing agents such as hypobromous acid, and stabilized hypochlorous acid compositions containing a chlorine-based oxidizing agent and a sulfamic acid compound. stabilized hypobromous acid composition containing a bromine-based oxidizing agent such as bromine and a sulfamic acid compound, ozone, etc., and from the viewpoint of the deterioration effect of reverse osmosis membranes and the effect of suppressing biofouling, etc., stabilization Hypochlorous acid compositions or stabilized hypobromite compositions are preferred.

Examples of slime control agents include chlorine-based oxidizing agents such as hypochlorous acid or salts thereof, bromine-based oxidizing agents such as hypobromous acid, chlorine-based oxidizing agents such as hypochlorous acid or salts thereof, and sulfaamines such as sulfamic acid. a stabilized hypochlorous acid composition containing an acid compound, a stabilized hypobromous acid composition containing a bromine-based oxidizing agent such as bromine and a sulfamic acid compound such as sulfamic acid, and the like, and deterioration of the reverse osmosis membrane. A stabilized hypochlorous acid composition or a stabilized hypobromite composition is preferable from the viewpoint of influence, biofouling inhibitory effect, and the like.

<Embodiment 3: Tool for Proposing Timing of Cleaning of Membrane>
When applying the cooling tower water supply method and the cooling tower water supply system to an existing site, it may be necessary to significantly modify the control and piping. The cooling tower water supply method according to the present embodiment may be applied as a tool for proposing the timing of membrane cleaning to the user. For example, the cleaning of the membrane may be performed manually rather than automatically under the control of the controller.

The cooling tower water supply apparatus 1 may have, for example, display means for displaying the new cleaning timing determined by the cleaning timing determining section of the control section 42, and the new cleaning timing may be displayed on the display means.

The display means includes, for example, a monitor such as a liquid crystal display, and presents information to the user.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

<Examples and Comparative Examples>
Using the water supply equipment for cooling towers shown in Figure 1, information on future temperatures is obtained from weather forecasts, and based on the obtained temperatures, the amount of circulating water in the cooling towers is predicted, and the future water supply amount of the cooling towers is calculated. predicted. In addition, based on the differential pressure of the turbidity-removing membrane and the tendency of the flow rate, the cleaning timing of the chemical-strengthened backwashing of the turbidity-removing membrane was predicted. In the example, when the air temperature was low and it was predicted that the amount of circulating water in the cooling tower would be small, chemical-enhanced backwashing of the turbidity removal membrane was carried out. In the comparative example, when the differential pressure of the turbidity-removing membrane exceeded a specified value, chemical-strengthened backwashing of the turbidity-removing membrane was performed. In the example, the amount of feed water supplied to the cooling tower was more stable than in the comparative example.

1 water supply device for cooling tower, 10 water tank to be treated, 12 membrane filtration device, 14 membrane filtration treatment water tank, 16 reverse osmosis membrane treatment device, 18 cooling tower, 20, 22 water to be treated pipe, 24, 28 membrane filtration treated water pipe , 26 backwash drain pipe, 30 backwash water pipe, 32 permeated water pipe, 34 concentrated water pipe, 36 pipe, 38 pump, 40 backwash pump, 42 control unit.

Claims (8)

A water supply device for a cooling tower, which treats water to be treated by a membrane filtration process using a turbidity removal membrane and a reverse osmosis membrane process using a reverse osmosis membrane, and supplies at least part of the obtained treated water to the cooling tower. hand,
a membrane filtration device that performs the membrane filtration process on the water to be treated;
a reverse osmosis membrane treatment device for performing the reverse osmosis membrane treatment on the membrane filtration treated water obtained in the membrane filtration treatment;
A water supply amount prediction unit that predicts the future water supply amount of the cooling tower based on at least one of temperature and humidity, and at least one of the turbidity removal membrane and the reverse osmosis membrane. Based on the trend of differential pressure and flow rate, a membrane cleaning prediction unit for predicting a cleaning timing for cleaning at least one of the turbidity removal membrane and the reverse osmosis membrane; a control means having a cleaning timing determination unit that searches for a cleaning timing at which the required amount of water supply does not run short and determines a new cleaning timing when the required amount of water supply is insufficient at the timing;
A water supply device for a cooling tower, characterized by comprising: The cooling tower water supply device according to claim 1,
The water supply device for a cooling tower, wherein the control means controls cleaning of at least one of the turbidity removal membrane and the reverse osmosis membrane at a new cleaning timing determined by the cleaning timing determining section. The cooling tower water supply device according to claim 1 or 2,
A water supply system for a cooling tower, comprising display means for displaying a new cleaning timing determined by the cleaning timing determining section. The cooling tower water supply device according to any one of claims 1 to 3,
Cleaning of the turbidity removal membrane is performed by at least one of chemical cleaning and chemical-strengthened backwashing,
Cleaning of the reverse osmosis membrane is performed by at least one of chemical cleaning, pure water flushing, intermittent acid injection, intermittent alkali injection, intermittent injection of oxidizing agent, and intermittent injection of slime control agent, Water supply equipment for cooling towers. A water supply method for a cooling tower, in which water to be treated is treated by membrane filtration using a turbidity removal membrane and reverse osmosis membrane treatment using a reverse osmosis membrane, and at least part of the obtained treated water is supplied to the cooling tower. hand,
a membrane filtration step of performing the membrane filtration treatment on the water to be treated;
A reverse osmosis membrane treatment step of performing the reverse osmosis membrane treatment on the membrane filtration treated water obtained in the membrane filtration treatment;
a water supply amount prediction step of predicting a future water supply amount of the cooling tower based on at least one of temperature and humidity;
a membrane cleaning prediction step of predicting a cleaning timing for cleaning at least one of the turbidity removal membrane and the reverse osmosis membrane based on the tendency of the differential pressure and flow rate of at least one of the turbidity removal membrane and the reverse osmosis membrane;
By comparing the prediction of the water supply amount prediction process and the prediction of the membrane cleaning prediction process, if the necessary water supply amount is insufficient at the cleaning timing, a cleaning timing that does not cause the necessary water supply amount to be insufficient is searched for, and a new cleaning timing is obtained. a cleaning timing determination step of determining a suitable cleaning timing;
A water supply method for a cooling tower, characterized by comprising: A water supply method for a cooling tower according to claim 5,
A water supply method for a cooling tower, characterized in that cleaning of at least one of the turbidity removal membrane and the reverse osmosis membrane is controlled at a new cleaning timing determined by the cleaning timing determination step. The cooling tower water supply method according to claim 5 or 6,
A water supply method for a cooling tower, characterized in that the new cleaning timing determined by the cleaning timing determining step is displayed. The cooling tower water supply method according to any one of claims 5 to 7,
Cleaning of the turbidity removal membrane is performed by at least one of chemical cleaning and chemical-strengthened backwashing,
Cleaning of the reverse osmosis membrane is performed by at least one of chemical cleaning, pure water flushing, intermittent acid injection, intermittent alkali injection, intermittent injection of oxidizing agent, and intermittent injection of slime control agent, Water supply method for cooling towers.

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