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

Abstract

This pure water production system 1 comprises a tank 2 for storing pretreated water W, a water pipe 3 connected to the tank 2, and a pure water production part 4 communicating with the water pipe 3. Primary pure water W2 produced by the pure water production part 4 can be circulated and used by being supplied to a sub-tank 5 and circulating the excess to the tank 2 as circulated water W3 through a circulating water passage 6. A heating means 7 serving as a temperature adjusting means for heating the pretreated water W is provided. Further, a recovered water flow passage 10 is connected to the sub-tank 5. In addition, downstream of the heating means 7, a temperature sensor and flowmeters 11, 12, 13, 14 can transmit information to a control means (not shown), and the control means controls the heating means 7 on the basis of the information. According to this pure water production system, when supplying pure water, obtained by treating water to be treated and adjusting the temperature thereof, the energy of the temperature adjustment can be optimized.

Description

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

[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 in which recovered water and circulating water are stored in a tank together with raw water to be treated, and the system treats the water to be treated and supplies the temperature-adjusted pure water.

[0002] Conventionally, pure water production systems for producing pure water from raw water such as city water, groundwater, or industrial water basically consist of a pretreatment device and a primary pure water system. The pretreatment device is, for example, composed of a heat exchanger, a flocculation device, a flotation 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 (the raw water to be treated), a water supply pipe 23 connected to the tank 22, a Hoan filter 24 sequentially installed in 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 or 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 water to be treated W1, which is then treated in the above-described pure water production system 21 to produce pure water (primary pure water) W2. This pure water (primary pure water) W2 is sent to a sub-tank 28 and further treated in a downstream system such as a secondary pure water system comprising 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 locations to control the temperature of the water to be treated, such as by heating in a pretreatment device located upstream of the tank 22 or by cooling in a subsystem located downstream of the primary pure water production system 21. From the perspective of water conservation, it is becoming more common for recovered water from industrial wastewater to be combined with the tank 22 and supplied to the pure water production system 21 as 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 from 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 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 also discloses a pure water production system that circulates pure water, in which the temperature rise caused by circulating the pure water is controlled by switching the pump rotation speed based on the results of detecting changes in the flow rate of the pure water.

[0007] JP 2016-107294 A JP 2023-8823 A

[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 deal with the heat quantity (water temperature and water volume) that takes into account the heat balance of the entire water treatment system due to the use of recovered water.Furthermore, the pure water production system described in Patent Document 2 takes into account the rise in water temperature due to the circulation of pure water, but does not consider temperature adjustment of the make-up water (raw water to be treated) and the recovered water, resulting in the 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 raw water to be treated, and the pure water that was 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-mentioned problems, and aims to provide a pure water production system 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 purified water that has been temperature-adjusted, while optimizing the energy used for temperature adjustment. Another aim of the present invention is to provide a method for operating such a pure water production system.

[0011] In order to achieve the above-mentioned object, the present invention first provides a pure water production system that 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 delivers pure water at a predetermined temperature, the pure water production system comprising: 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; a means for measuring the temperature of the raw water to be treated after the temperature adjustment; a means for measuring the temperature of the recovered water; a means for measuring the water volume of the circulating water; a means for measuring the water temperature of the recovered water and the water volume of the circulating water; and a control means for calculating the water volume and temperature of the raw water to be treated after temperature adjustment from the water volume and temperature delivered by the pure water production 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 production system" is not limited to a primary water purification system that treats pretreated water to produce pure water (primary pure water), but also includes an ultrapure water production system that includes a secondary water purification system (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 raw water to be treated and the temperature of the raw water after temperature adjustment using the following relational expressions (1) and (2) from the measured values ​​of the recovered water temperature measuring means and water volume measuring means, the circulating water temperature measuring means and water volume and feed water temperature of the pure water manufacturing system, and controls the temperature adjustment means based on the calculation result and the measured value of the water temperature measuring means before temperature adjustment (Invention 2). Raw water amount to be treated=amount of water used-amount of recovered water-amount of circulating water (1) Raw water temperature to be treated=(amount of water used-amount of recovered water-temperature of recovered water-circulating water-temperature of circulating water-circulating water volume) / amount of raw water to be treated×safety factor (2) (where the safety factor is 1 to 1.2 when heating, and 0.8 to 1.0 when cooling)

[0013] According to these 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, as well as the temperature and volume of the pure water delivered from the pure water production system (including a portion of the outflow), are measured, and the set value required for heating or cooling the incoming raw water to achieve the required temperature of the pure water is calculated, and the water temperature adjustment means is controlled based on this, thereby 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 adjusting 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] In a second aspect, the present invention provides a method for operating a pure water production system that 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 delivers pure water at a predetermined temperature, wherein 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 are measured, and the volume and temperature of the raw water to be treated after temperature adjustment are calculated from these measurements and the volume and temperature of the water delivered by the pure water production system, and the temperature of the raw water to be treated is adjusted based on the calculation result and the measured value of the water temperature before temperature adjustment (Invention 4).

[0017] In the above invention (Invention 4), it is preferable to calculate the amount of raw water to be treated and the temperature of the water after temperature adjustment using the following relational expressions (1) and (2) (Invention 5): Amount of raw water to be treated + Amount of recovered water + Amount of circulated water = Amount of water used (1) Temperature of raw water to be treated = (Temperature of water used x Amount of water used - Temperature of recovered water x Amount of recovered water - Temperature of circulated water x Amount of circulated water) / Amount of raw water to be treated x Safety factor (2) (In the formulas, 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, as well as the temperature and volume of the pure water delivered from the pure water production system (including a portion of the outflow), are measured, and the set value required for heating or cooling the incoming raw water to achieve the required temperature of the pure water is calculated, and the water temperature adjustment means is controlled based on this, thereby 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 water 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 water temperature of the raw water to a fixed value (Invention 6).

[0020] According to this invention (Invention 6), when the pure water production system is operated, the temperature of the raw water to be treated is not adjusted excessively, but rather the temperature is adjusted at a later stage, thereby distributing the energy consumption required for temperature adjustment.

[0021] The present invention relates to a pure water production system equipped with a storage tank for receiving raw water, recovered water, and circulated water. The system measures the temperature and volume of the raw water, recovered water, and circulated water flowing into the tank as the water to be treated, as well as the temperature and volume of the pure water delivered from the pure water production system (including a portion of the water flowing out). The system calculates the setpoints for heating or cooling the incoming raw water to achieve the required temperature, and controls the water temperature control means based on these calculations. This allows the system to operate with the setpoint temperature of the raw water changed in real time. This reduces the amount of steam and hot water required for heating, and the amount of cold water required for cooling, significantly reducing the overall energy consumption of the water treatment system. Furthermore, because the pure water production system can be operated under controlled temperature conditions, it is possible to prevent unexpected water quality abnormalities and other problems in the water treatment system.

[0022] Fig. 1 is a schematic diagram showing a pure water producing system according to one embodiment of the present invention; Fig. 2 is a schematic diagram showing a state when a flow rate fluctuates in the operating method of the pure water producing system of Example 1; Fig. 3 is a schematic diagram showing a state when a flow rate fluctuates in the operating method of the pure water producing system of Comparative Example 1; Fig. 4 is a schematic diagram showing a state when a flow rate fluctuates in the operating method of the pure water producing system of Example 2; Fig. 5 is a schematic diagram showing a conventional pure water producing system;

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

[0024] 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 (raw water treated in a pretreatment device), a water supply pipe 3 connected to the tank 2, and a pure water production section 4 connected to the water supply pipe 3 and equipped with a reverse osmosis membrane, a membrane degasser, a UV oxidation device, a regenerative mixed-bed ion exchanger, etc. Primary pure water W2 produced in the pure water production section 4 is supplied to a sub-tank 5, with the surplus returning to the tank 2 via a circulation water channel 6 for reuse as circulating water W3.

[0025] The pure water production system 1 as described above includes a secondary pure water production apparatus (subsystem) 8 having a heating means 7 as a temperature control means for heating the pretreated water W, and a cooling means 9 as a temperature control means, downstream of the subtank 5. Furthermore, the tank 5 is connected to a recovered water flow path 10 for recovered water W4 recovered from various facilities and use points. A temperature sensor and flow meter 11 is provided downstream of the heating means 7 to monitor the temperature and flow rate of the pretreated water W after heating, and a temperature sensor and flow meter 12 is provided in the circulation water path 6 to monitor the temperature and flow rate of the circulating water W3. Furthermore, a temperature sensor and flow meter 13 is provided in the recovered water flow path 10 to monitor the temperature and flow rate of the recovered water W4, and a temperature sensor and flow meter 14 is provided downstream of the subtank 5 and upstream of the cooling means 9 to monitor the temperature and flow rate of the primary pure water W2. The heating means 7 is also provided with a temperature sensor (not shown) to monitor the temperature of the pretreated water W before heating. These temperature sensors and flow meters 11, 12, 13, and 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] <Method of Operating the Pure Water Production System> Next, a method of operating the pure water production system 1 as described above will be described.

[0027] First, raw water is treated in a pretreatment device (not shown) to produce pretreated water W, which is then temporarily stored in tank 2. Circulating water W3 and recovered water W4 are also stored in tank 2. The pretreated water W, circulating water W3, and recovered water W4 stored in tank 2 are treated as water to be treated W1 in the pure water production section 4 to obtain primary pure water (pure water) W2. An amount of primary pure water W2 used is sent to a sub-tank 5, where it is treated in a secondary pure water production system (subsystem). Unused primary pure water W2 is returned to tank 2 through a circulation water channel 6 as circulating water W3. In the operation method of the pure water production system 1 described above, pretreated water W is heated to a predetermined temperature by heating means 7. Furthermore, in the secondary pure water production system 8, the primary pure water W2 is cooled as needed to a required temperature, for example, to about 25°C by cooling means 9. Furthermore, the circulating water W3 and 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 amount: 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 using 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 generally 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 (feed temperature: T3) and flow rate (feed rate: Q3) of the primary pure water W2: T3×Q3=(T×Q+T1×Q1+T2×Q2) Therefore, the required temperature (T) of the pretreated water W after heating can be calculated using the following calculation formula (2): T=(T3×Q3-T1×Q1-T2×Q2) / Q×S (2) (where S is a safety factor, and is preferably set to about 1.0 to 1.2.)

[0030] The control means controls the heating means 7 based on the temperature of the pretreated water (raw water) W before heating so that the temperature of the pretreated water (raw water) W becomes T (°C). This allows optimization of energy consumption by 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, eliminating the need to cool the primary pure water W2 using the cooling means 9. This also allows optimization of energy consumption. It is preferable to set upper and lower limits for the calculated value of the water temperature T (°C) of the pretreated water (raw water) W and to set a standard temperature (e.g., 20 to 25°C). If the calculated value deviates from the upper and lower limits, the temperature of the pretreated water (raw water) W is controlled to the standard temperature. This allows operation to be performed without excessive temperature adjustment during the temperature adjustment stage of the pretreated water (raw water) W, by adjusting the temperature at a later stage, thereby distributing the energy consumption required for temperature adjustment.

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

[0032] The present invention will be described in more detail based on the following specific examples.

[0033] [Example 1] In the pure water production system 1 shown in Figure 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 water supply rate of the primary pure water W2 was 100 m ３ / h, the amount of circulating water W3 is 20 m ３ 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, and the pure water production system 1 was operated. As a result, primary pure water W2 at 25°C could be supplied to the secondary pure water production system 8, and the secondary pure water production system 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 to be treated) W was increased to 30 m ３ / h and continued operation as it was (conventional example). ３ / h, recovered water W4 is 50m at 30°C ３ / h, the primary pure water W2 and circulating water W3 reached 26.25° C. As a result, it became necessary to cool the primary pure water W2 to 25° C. using 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 to be treated) W was increased to 30 m ３ / h, and the temperature of the pretreated water (raw water to be treated) W after heating was calculated based on formula (2): T = (T3 x Q3 - T1 x Q1 - T2 x Q2) / Q x S = (25 x 100 - 25 x 20 - 30 x 50) / 30 ≈ 16.7 (°C)

[0036] Therefore, the temperature of the pretreated water (raw water) W was set to 16.7°C and controlled by the heating means 7, and the pure water production system 1 was operated. The primary pure water W2 at 25°C could be supplied to the secondary pure water production system 8, and the secondary pure water production system 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 operating method of the pure water production system 1 of Example 2, by lowering the heating setpoint 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 production apparatus 8. Furthermore, the operating method of the pure water production system 1 of Comparative Example 1 also resulted in excessive heating, and it was possible to reduce the energy required in the heating means 7 for heating by Δ=20-16.7=3.3°C.

[0038] REFERENCE SIGNS LIST 1 Pure water production system 2 Tank 3 Water supply pipe 4 Pure water production section 5 Sub-tank 6 Circulating water channel 7 Heating means (temperature adjustment means) 8 Secondary pure water production device (subsystem) 9 Cooling means (temperature adjustment means) 10 Recovered water flow path 11 Temperature sensor and flow meter (water temperature measurement means and water volume measurement means) 12 Temperature sensor and flow meter (water temperature measurement means and water volume measurement means) 13 Temperature sensor and flow meter (water temperature measurement means and water volume measurement means) 14 Temperature sensor and flow meter (water temperature measurement means and water volume measurement means) W Pretreated water (raw water to be treated) W1 Water to be treated W2 Primary pure water W3 Circulating water W4 Recovered water

Claims

1. A pure water production system that 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 delivers pure water at a predetermined temperature, comprising: 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 means for measuring the temperature and volume of the recovered water; a means for measuring the temperature and volume of the circulating water; and a control means for calculating the volume and temperature of the raw water to be treated after temperature adjustment from the measured values ​​of the water temperature and volume measuring means for the recovered water, the water temperature and volume measuring means for the circulating water, and the water volume and temperature delivered by the pure water production system, and for controlling the temperature adjustment means based on the calculation result and the measured value of the water temperature measuring means before temperature adjustment.

2. The pure water manufacturing system according to claim 1, wherein the control means calculates the amount of raw water to be treated and the temperature of the raw water after temperature adjustment using the following relational expressions (1) and (2) based on the measured values ​​of the recovered water temperature measuring means and water volume measuring means, the circulating water temperature measuring means and water volume measuring means, and the water supply amount and water temperature of the pure water manufacturing system, and controls the temperature adjustment means based on the calculation result and the measured value of the water temperature measuring means before temperature adjustment: Raw water amount to be treated = Water volume used - Recovered water volume - Circulating water volume ... (1) Raw water temperature to be treated = (Water temperature used x Water volume used - Recovered water temperature x Recovered water volume - Circulating water temperature x Circulating water volume) / Raw water amount to be treated x Safety factor ... (2) (where the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling) 3. A pure water production system according to claim 1 or 2, wherein the temperature adjusting means is one or more of a heat source such as steam, hot water, or cold water, or a heat exchanger with wastewater.

4. A method for operating a pure water production system that 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 delivers pure water at a predetermined temperature, comprising measuring 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, calculating the volume and temperature of the raw water to be treated after temperature adjustment from these measured values ​​and the volume and temperature of the water delivered by the pure water production system, and adjusting the temperature of the raw water to be treated based on the calculation result and the measured value of the water temperature before temperature adjustment.

5. The method for operating a pure water production system according to claim 4, wherein the amount of raw water to be treated and the temperature of the water after temperature adjustment are calculated using the following relational expressions (1) and (2): Amount of raw water to be treated + Amount of recovered water + Amount of circulated water = Amount of water used (1) Temperature of raw water to be treated = (Temperature of water used x Amount of water used - Temperature of recovered water x Amount of recovered water - Temperature of circulated water x Amount of circulated water) / Amount of raw water to be treated x Safety factor (2) (where the safety factor is 1 to 1.2 when heating and 0.8 to 1.0 when cooling) 6. A method for operating a pure water production system as described in claim 4 or 5, in which an upper and lower limit are set for 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, the temperature of the raw water to be treated is adjusted to a fixed value.