Pure water production system and method for operating the pure water production system

Abstract

A pure water production system is provided that can optimize energy for temperature adjustment when treating water to be treated and supplying the temperature-adjusted pure water. SOLUTION: The pure water production system 1 comprises a tank 2 for storing pretreated water W, a water supply pipe 3 connected to the tank 2, and a pure water production section 4 connected to the water supply pipe 3. Primary pure water W2 produced in the pure water production section 4 is supplied to a sub-tank 5, and the excess flows back to the tank 2 as circulating water W3 via a circulating water channel 6, making it possible to recycle and reuse the water. The system has a heating means 7 as a temperature adjustment means for heating the pretreated water W. Furthermore, a recovered water flow path 10 is connected to the sub-tank 5. And, downstream of the heating means 7, temperature sensors and flow meters 11, 12, 13, 14 are capable of transmitting information to a control means (not shown), and the control means controls the heating means 7 based on the information.

Description

[Technical field]

[0001] The present invention relates to a pure water production system and an operating method thereof, and more particularly to a pure water production system and an operating method thereof that stores recovered water and circulating water together with raw water to be treated in a tank, treats the water to be treated, and supplies the pure water that has been temperature-adjusted. [Background technology]

[0002] Conventionally, a pure water production system for producing pure water from raw water such as city water, groundwater, or industrial water is basically composed of a pretreatment device and a primary pure water system. Of these, the pretreatment device is composed of, for example, a heat exchanger, a coagulation device, a pressurized floatation device, a filtration device, etc. For example, as shown in FIG. 5, a primary pure water system 21 includes a tank 22 for storing pretreated water W as raw water to be treated, a water supply pipe 23 connected to the tank 22, a Hoan filter 24 sequentially provided on the water supply pipe 23, a reverse osmosis membrane 25, a membrane degassing device 26, a UV oxidation device 27, and a regenerative mixed bed ion exchange device 28. The downstream side of the mixed bed ion exchange device 28 is connected to a sub tank 30 for producing ultrapure water and a use point, while a circulation flow path is formed by a return pipe 29 connected to the tank 22.

[0003] The pretreated water W is mixed with unused circulating water W3 to produce treated water W1, which is then treated in the above-mentioned pure water production system 21 to produce pure water (primary pure water) W2. This pure water (primary pure water) W2 is fed to a subtank 28 and further treated in a downstream system, such as a secondary pure water system composed of a low-pressure ultraviolet oxidation device, a mixed-bed ion exchange device, and an ultrafiltration membrane device, or is used at the point of use.

[0004] In this pure water production system 21, heating and cooling are often performed at various points to control the temperature of the water to be treated, such as heating in a pretreatment device upstream of the tank 22, or cooling in a subsystem provided downstream of the primary pure water production system 21. From the viewpoint of water conservation, it is becoming more common to merge recovered industrial wastewater into the tank 22 and supply it to the pure water production system 21 as the water to be treated W1.

[0005] In this case, the temperature of the recovered water is often not controlled, and when this water is used as the water to be treated W1 in the pure water production system 21, the amount of heat for heating or cooling may be excessive or insufficient compared to when the recovered water is not used. Similarly, when the circulating water W3 of the pure water production system 21 is merged into the tank 22, the amount of heat for heating or cooling may be excessive or insufficient compared to when the circulating water W3 is not used.

[0006] As an example of a pure water production system 21 that reuses such recovered water, Patent Document 1 discloses a wastewater recovery method that uses a sub-pure water production system equivalent to the pure water production system and switches the flow path of the pure water production system depending on the TOC value of the system, without deteriorating the quality of the produced pure water. Patent Document 2 discloses that in a pure water production system that circulates pure water, the rotation speed of a pump is switched based on the result of detecting a change in the flow rate of the pure water, thereby controlling the temperature rise caused by circulating the pure water. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-107294 A [Patent Document 2] Patent Publication No. 2023-8823 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the pure water production system described in Patent Document 1 focuses only on the quality of the recovered water, and does not consider how to handle the heat quantity (water temperature and water volume) that takes into account the heat balance of the entire water treatment device due to the use of recovered water.In addition, the pure water production system described in Patent Document 2 considers the rise in water temperature due to the circulation of pure water, but does not consider temperature adjustment of the makeup water (raw water to be treated) and the recovered water, resulting in a problem that only partial optimization is achieved.

[0009] In other words, in the past, there was no pure water production system that enabled energy optimization in which recovered water and circulating water were stored in a tank together with the raw water to be treated, and the pure water that had been treated and temperature-adjusted was then sent out as the water to be treated.

[0010] The present invention has been made in view of the above problems, and has an object to provide a pure water producing system that can optimize the energy used for temperature adjustment when storing recovered water and circulating water together with raw water to be treated in a tank and supplying pure water that has been treated and temperature-adjusted as the water to be treated. Another object of the present invention is to provide a method for operating such a pure water producing system. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, firstly, the present invention provides a pure water manufacturing system which supplies and treats water to be treated from a storage tank into which raw water to be treated, recovered water and circulating water flow in, and supplies pure water at a predetermined temperature, the pure water manufacturing system having a water temperature adjustment means for the raw water to be treated, a water temperature measuring means for measuring the temperature of the raw water to be treated before the temperature adjustment, and a water temperature measuring means for measuring the temperature of the raw water to be treated after the temperature adjustment, a water temperature measuring means and a water volume measuring means for the recovered water, a water temperature measuring means and a water volume measuring means for the circulating water, measurement values ​​of the water temperature measuring means and water volume measuring means for the recovered water, a water temperature measuring means and a water volume measuring means for the circulating water, and a control means for calculating the volume and water temperature of the raw water to be treated after temperature adjustment from the water volume and water temperature delivered by the pure water manufacturing system, and for controlling the temperature adjustment means based on the calculation result and the measurement value of the water temperature measuring means before the temperature adjustment (Invention 1). In this invention, the term "pure water producing system" is not limited to a primary pure water apparatus that treats pretreated water to produce pure water (primary pure water), but also includes an ultrapure water producing system consisting of a secondary pure water apparatus (subsystem) that further treats this primary pure water to produce ultrapure water.

[0012] In the above invention (Invention 1), it is preferable that the control means calculates the amount of the raw water to be treated and the water temperature after temperature adjustment from the measured values ​​of the water temperature measuring means and water volume measuring means for the recovered water, the water temperature measuring means and water volume measuring means for the circulating water, and the water volume and temperature of the pure water production system, using the following relational expressions (1) and (2), and controls the temperature adjustment means based on the calculation result and the measured value of the water temperature measuring means before the temperature adjustment (Invention 2). Amount of raw water treated = Amount of water used - Amount of recovered water - Amount of circulated water (1) Raw water temperature = (used water temperature × used water volume – recovered water temperature × recovered water volume – circulated water temperature × circulated water volume) / raw water volume × safety factor (2) (In the formula, the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling.)

[0013] According to such inventions (Inventions 1 and 2), the temperature and volume of the raw water to be treated, recovered water, and circulating water flowing into the tank of the pure water production system, which is the water to be treated, and the temperature and volume of the pure water supplied from the pure water production system (including a portion of the water flowing out) are measured, and a set value required for heating or cooling the incoming raw water to be treated so as to achieve the required temperature of the pure water is calculated, and the water temperature adjustment means is controlled based on this, making it possible to change the set temperature of the raw water to be treated in real time and operate the system.

[0014] In the above inventions (Inventions 1 and 2), the temperature adjustment means is preferably one or more of a heat exchanger with a heat source such as steam, hot water, or cold water, or with wastewater (Invention 3).

[0015] According to this invention (Invention 3), the temperature of the raw water to be treated can be adjusted with high accuracy using a general-purpose means.

[0016] Secondly, the present invention provides a method for operating a pure water production system which supplies and treats water to be treated from a storage tank into which raw water to be treated, recovered water, and circulating water flow, and supplies pure water at a predetermined temperature, wherein the method measures the temperature of the raw water to be treated before temperature adjustment, the temperature and volume of the recovered water, and the temperature and volume of the circulating water, calculates the volume of the raw water to be treated and the water temperature after temperature adjustment from these measured values ​​and the volume and temperature of the water supplied by the pure water production system, and adjusts the temperature of the raw water to be treated based on the calculation result and the measured value of the water temperature before the temperature adjustment (Invention 4).

[0017] In the above invention (Invention 4), it is preferable to calculate the amount of the raw water to be treated and the water temperature after temperature adjustment according to the following relational expressions (1) and (2) (Invention 5). Amount of raw water treated + amount of recovered water + amount of circulated water = amount of water used (1) Raw water temperature = (used water temperature × used water volume – recovered water temperature × recovered water volume – circulated water temperature × circulated water volume) / raw water volume × safety factor (2) (In the formula, the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling.)

[0018] According to such inventions (Inventions 4 and 5), the temperature and volume of the raw water to be treated, recovered water and circulating water flowing into the tank of the pure water production system, and the temperature and volume of the pure water delivered from the pure water production system (including a portion of the water flowing out), are measured, and a set value required for heating or cooling the incoming raw water to be treated so as to achieve the required temperature of the pure water is calculated, and the water temperature adjustment means is controlled based on this, making it possible to change the set temperature of the raw water to be treated in real time and operate the system.

[0019] In the above inventions (Inventions 4 and 5), it is preferable to set upper and lower limits on the calculated value of the temperature of the raw water to be treated, and when the calculated value deviates from the upper and lower limits, to adjust the temperature by setting the temperature of the raw water to a fixed value (Invention 6).

[0020] According to this invention (Invention 6), by adjusting the temperature at a later stage without performing excessive temperature adjustment on the raw water to be treated during operation of the pure water production system, the energy consumption required for temperature adjustment can be distributed during operation. Effect of the Invention

[0021] The present invention is a pure water production system equipped with a water storage tank into which raw water to be treated, recovered water, and circulating water flow in. The system measures the temperature and amount of raw water to be treated, recovered water, and circulating water flowing into the tank as water to be treated, and the temperature and amount of pure water sent from the pure water production system (including a part of the outflow), calculates a set value required for heating or cooling the raw water to be treated so that the pure water has a required temperature, and controls the water temperature adjustment means based on this. Therefore, the set temperature of the raw water to be treated can be changed in real time for operation. This reduces the amount of steam and hot water required for heating, or the amount of cold water required for cooling, and greatly reduces the energy consumption of the entire water treatment device. Furthermore, since the pure water production system can be operated under controlled temperature conditions, it becomes possible to prevent sudden water quality abnormalities and problems in the water treatment device. [Brief description of the drawings]

[0022] [Figure 1]1 is a schematic diagram showing a pure water production system according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a state during flow rate fluctuation in the operation method of the pure water producing system of the first embodiment. [Diagram 3] 1 is a schematic diagram showing a state during flow rate fluctuation in the operation method of the pure water producing system of Comparative Example 1. FIG. [Figure 4] FIG. 11 is a schematic diagram showing a state during flow rate fluctuation in the operation method of the pure water producing system of the second embodiment. [Diagram 5] FIG. 1 is a schematic diagram showing a conventional pure water production system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The ultrapure water producing system of the present invention and its operating method will be described in detail below.

[0024] <Pure water production system> 1 shows a pure water production system according to one embodiment of the present invention. In this embodiment, the pure water production system 1 comprises a tank 2 for storing pretreated water W as raw water treated in a pretreatment device, a water supply pipe 3 connected to the tank 2, and a pure water production section 4 equipped with a reverse osmosis membrane, a membrane degassing device, a UV oxidation device, a regenerative mixed bed ion exchange device, and the like, which are connected to the water supply pipe 3. Primary pure water W2 produced in the pure water production section 4 is supplied to a sub-tank 5, and the surplus is returned to the tank 2 via a circulation water channel 6, making it possible to reuse it as circulating water W3.

[0025] In the pure water production system 1 as described above, a secondary pure water production device (subsystem) 8 is provided with a heating means 7 as a temperature adjustment means for heating the pretreated water W, and a cooling means 9 as a temperature adjustment means at the rear of the sub-tank 5. Furthermore, a recovered water flow path 10 for the recovered water W4 recovered from various facilities and use points is connected to the tank 5. A temperature sensor and flow meter 11 for monitoring the temperature and flow rate of the pretreated water W after heating is provided downstream of the heating means 7, and a temperature sensor and flow meter 12 for monitoring the temperature and flow rate of the circulating water W3 is provided in the circulating water path 6. Furthermore, a temperature sensor and flow meter 13 for monitoring the temperature and flow rate of the recovered water W4 is provided in the recovered water flow path 10, and a temperature sensor and flow meter 14 for monitoring the temperature and flow rate of the primary pure water W2 is provided at the rear of the sub-tank 5 and the front of the cooling means 9. The heating means 7 is provided with a temperature sensor (not shown) for monitoring the temperature of the pretreated water W before heating. These temperature sensors and flow meters 11, 12, 13, 14 are capable of transmitting information to a control means such as a PLC (not shown), and this control means controls the heating means 7 based on this information.

[0026] <How to operate the pure water production system> Next, a method of operating the above-described pure water producing system 1 will be described.

[0027] First, the pretreated water W as raw water to be treated, which is obtained by treating raw water in a pretreatment device (not shown), is temporarily stored in the tank 2. The circulating water W3 and the recovered water W4 are also stored in the tank 2. The pretreated water W, the circulating water W3, and the recovered water W4 stored in the tank 2 are treated as the water to be treated W1 in the pure water production section 4 to obtain primary pure water (pure water) W2. The primary pure water W2 is sent to a sub-tank 5 in an amount corresponding to the amount of water used, and then treated in a secondary pure water production device (subsystem). The unused primary pure water W2 is returned to the tank 2 from the circulation water channel 6 as the circulating water W3. In the operation method of the pure water production system 1 as described above, the pretreated water W is heated to a predetermined temperature by the heating means 7. Furthermore, the primary pure water W2 is cooled to a required temperature, for example, to about 25° C. by the cooling means 9 in the secondary pure water production device 8 as necessary. Furthermore, the circulating water W3 and the recovered water W4 each have a predetermined temperature.

[0028] Therefore, the temperature (T1) and flow rate (Q1) of the circulating water W3 are measured by the temperature sensor and flow meter 12, the temperature (T2) and flow rate (Q2) of the recovered water W4 are also measured by the temperature sensor and flow meter 12, and the temperature (feed water temperature: T3) and flow rate (feed water volume: Q3) of the primary pure water W2 are measured by the temperature sensor and flow meter 14. Then, from the values ​​of these temperature sensors and flow meters 12, 13, and 14, the control means calculates the required amount (Q) of pretreated water W by the following calculation formula (1). Here, the feed water temperature (T3) is the required temperature in the secondary pure water production system 8. Q = Q3 - Q1 - Q2 (1)

[0029] The following relationship roughly holds between the calculated required amount (Q) of pretreated water W and the required temperature (T) of the pretreated water W after heating, the temperature (T1) and flow rate (Q1) of the circulating water W3, the temperature (T2) and flow rate (Q2) of the recovered water W4, and the temperature (water supply temperature: T3) and flow rate (water supply rate: Q3) of the primary pure water W2. T3×Q3=(T×Q+T1×Q1+T2×Q2) Therefore, the required temperature (T) for pretreatment W after heating can be calculated using the following formula (2). T=(T3×Q3-T1×Q1-T2×Q2) / Q×S (2) (In the formula, S is a safety factor, which is preferably about 1.0 to 1.2.)

[0030] The control means controls the heating means 7 so that the temperature of the pretreated water (raw water for treatment) W becomes T (℃) based on the temperature of the pretreated water (raw water for treatment) W before heating. This makes it possible to optimize the energy consumption in the heating means 7. Furthermore, the pure water production unit 4 can deliver the primary pure water W2 at the required temperature (T3) of the secondary pure water production device 8, so there is no need to cool the primary pure water W2 with the cooling means 9, and this also makes it possible to optimize the energy consumption. It is preferable to set an upper limit and a lower limit for the calculated value of the water temperature T (℃) of the pretreated water (raw water for treatment) W, and set a standard temperature (e.g., 20 to 25℃), and when the calculated value deviates from the upper limit and the lower limit, to control the water temperature of the pretreated water (raw water for treatment) W to the standard temperature. This makes it possible to operate the system by dispersing the energy consumption required for temperature adjustment by adjusting the temperature at a later stage without performing excessive temperature adjustment at the stage of temperature adjustment of the pretreated water (raw water for treatment) W.

[0031] Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment and various modifications are possible. For example, the above embodiment is a case where the pretreated water W is heated by the heating means 7, but the present invention can be similarly applied to a case where the pretreated water W is cooled by a cooling means. In this case, however, it is preferable that the safety factor (S) is about 0.8 to 1.0. Furthermore, as the temperature adjustment means such as the heating means and the cooling means, general-purpose means such as a heat source such as steam, hot water, cold water, or a heat exchanger with wastewater can be used. Furthermore, the pure water production section 4 and the secondary pure water production device 8 can be applied to those with various configurations. EXAMPLES

[0032] The present invention will now be described in more detail with reference to the following specific examples.

[0033] [Example 1] In the pure water production system 1 shown in FIG. 2, the required water temperature of the secondary pure water production device 8 is 25° C. and the required water volume is 80 m 3 / h, so the flow rate of the primary pure water W2 was 100 m 3 / h, the amount of circulating water W3 is 20m 3 / h. The temperature of the recovered water W4 was 30°C and the amount of water was 40 m 3 / h, so the amount of pretreated water (raw water) W was 40 m 3 / h. The pretreated water (raw water to be treated) W under these conditions was set to 20°C and controlled by the heating means 7 to operate the pure water production system 1. As a result, the primary pure water W2 at 25°C could be sent to the secondary pure water production apparatus 8, and the secondary pure water production apparatus 8 could be operated without the need for cooling by the cooling means 9. [Comparative Example 1]

[0034] After the operation of Example 1, the amount of recovered water W4 was 50 m 3 / h, the amount of pretreated water (raw water) W was increased to 30 m 3 / h and operation was continued as it was (conventional example). 3 / h, recovered water W4 is 50m at 30℃ 3 / h, the primary pure water W2 and the circulating water W3 were at 26.25° C. As a result, it became necessary to cool the primary pure water W2 to 25° C. by the cooling means 9 of the secondary pure water production system 8.

[0035] [Example 2] After the operation of Example 1, the amount of recovered water W4 was 50 m 3 / h, the amount of pretreated water (raw water) W was increased to 30 m 3 The temperature of the pretreated water (raw water for treatment) W after heating was calculated as / h based on formula (2). T = (T3 x Q3 - T1 x Q1 - T2 x Q2) / Q x S =(25×100-25×20-30×50) / 30 ≒16.7(℃)

[0036] Therefore, the pretreated water (raw water) W was set to 16.7°C and controlled by the heating means 7 to operate the pure water production system 1. The primary pure water W2 at 25°C could be sent to the secondary pure water production apparatus 8, and the secondary pure water production apparatus 8 could be operated without the need for cooling by the cooling means 9.

[0037] As is clear from the above Comparative Example 1 and Example 2, according to the operation method of the pure water producing system 1 of Example 2, by lowering the heating set value in the heating means 7 to 16.7°C, it was possible to reduce the energy required for cooling by 1.25°C in the secondary pure water producing apparatus 8. Furthermore, the operation method of the pure water producing system 1 of Comparative Example 1 also resulted in excessive heating, and it was possible to reduce the energy in the heating means 7 associated with heating by Δ=20-16.7=3.3°C. [Explanation of symbols]

[0038] 1 Pure water production system 2 Tank 3 Water pipe 4 Pure water production department 5 Subtank 6 Circulation waterway 7 Heating means (temperature adjustment means) 8 Secondary water purification system (subsystem) 9 Cooling means (temperature adjustment means) 10 Recovered water flow path 11 Temperature sensor and flow meter (water temperature measuring means and water volume measuring means) 12 Temperature sensor and flow meter (water temperature measuring means and water volume measuring means) 13 Temperature sensor and flow meter (water temperature measuring means and water volume measuring means) 14 Temperature sensor and flow meter (water temperature measuring means and water volume measuring means) W Pretreated water (raw water for treatment) W1 Water to be treated W2 Primary pure water W3 Circulating water W4 Reclaimed water

Claims

1. A pure water production system that supplies and treats water to be treated from a water storage tank into which raw water to be treated, recovered water, and circulating water flow, and delivers pure water at a predetermined temperature, A means for adjusting the temperature of the raw water to be treated, a means for measuring the temperature of the raw water to be treated before the temperature adjustment, and a means for measuring the temperature of the raw water to be treated after the temperature adjustment; A water temperature measuring means and a water volume measuring means for the recovered water; A water temperature measuring means and a water volume measuring means for the circulating water; a control means for calculating the amount of the raw water to be treated and the water temperature after temperature adjustment from the measured values ​​of the water temperature measuring means and the water volume measuring means of the recovered water, the water temperature measuring means and the water volume measuring means of the circulating water, and the water volume and temperature of the pure water producing system, and for controlling the temperature adjustment means based on the calculation result and the measured value of the water temperature measuring means before the temperature adjustment; A pure water production system having the above structure.

2. 2. The pure water producing system according to claim 1, wherein the control means calculates the amount of the raw water to be treated and the temperature of the raw water after temperature adjustment from the measured values ​​of the water temperature measuring means and the water volume measuring means of the recovered water, the water temperature measuring means and the water volume measuring means of the circulating water, and the water volume and temperature of the pure water producing system, according to the following relational expressions (1) and (2), and controls the temperature adjustment means based on the calculated result and the measured value of the water temperature measuring means before the temperature adjustment. Amount of raw water treated = Amount of water used - Amount of recovered water - Amount of circulated water ... (1) Raw water temperature = (used water temperature x used water volume - recovered water temperature x recovered water volume - circulated water temperature x circulated water volume) / raw water volume x safety factor ... (2) (In the formula, the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling.)

3. A method for operating a pure water production system, which supplies and treats water to be treated from a water storage tank into which raw water to be treated, recovered water, and circulating water flow, and delivers pure water at a predetermined temperature, comprising the steps of: Measure the temperature of the raw water before temperature adjustment, the temperature and amount of the recovered water, and the temperature and amount of the circulating water; A method for operating a pure water production system, in which the volume of the raw water to be treated and the water temperature after temperature adjustment are calculated from these measurement values ​​and the water supply volume and water supply temperature of the pure water production system, and the temperature of the raw water to be treated is adjusted based on the calculation result and the measurement value of the water temperature before the temperature adjustment.

4. 4. The method for operating a pure water producing system according to claim 3, wherein the amount of the raw water to be treated and the temperature of the treated raw water after temperature adjustment are calculated according to the following relational expressions (1) and (2). Amount of raw water treated + amount of recovered water + amount of circulated water = amount of water used ... (1) Raw water temperature = (used water temperature x used water volume - recovered water temperature x recovered water volume - circulated water temperature x circulated water volume) / raw water volume x safety factor ... (2) (In the formula, the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling.)

5. 5. A method for operating a pure water production system as described in claim 3 or 4, further comprising setting upper and lower limits on the calculated value of the temperature of the raw water to be treated, and when the calculated value deviates from the upper and lower limits, adjusting the temperature of the raw water to a fixed value.

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