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

Abstract

In a pure water production system 1, a pretreatment device 2 has a raw water tank 21, a heating means 22, a coagulation tank 23, a pressurized flotation device 24, and a filtration membrane 25. A primary pure water device 3 has a tank 31, an activated carbon tower 32, a membrane degassing device 33 as a decarbonation device, a relay tank 34, a reverse osmosis membrane device 35, an ultraviolet oxidation device 36, and a regenerable ion exchange device 37. A first temperature measuring means is provided to the raw water tank 21, and a second temperature measuring means is provided immediately after the heating means 22. A dew point temperature measuring means is further provided. These temperature measuring means are configured so at to be able to transmit data to a control means, and the control means is configured so as to be able to control the heating means 22 on the basis of the data from the first temperature measuring means and the second temperature measuring means. In this way, a pure water production system is achieved in which the purpose is to preserve equipment by suppressing the occurrence of condensation in the pure water production system, and thus preventing erroneous detection in various types of sensors as well as condensation-associated corrosion of devices.

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 for the pure water production system, which are intended for facility maintenance, by suppressing the occurrence of condensation in the pure water production system and preventing erroneous detection by various sensors and corrosion of devices due to condensation.

[0002] Conventionally, pure water production systems that produce pure water from raw water such as city water, groundwater, or industrial water basically consist of a pretreatment device and a primary water purification system. The pretreatment device is composed of, for example, a heat exchanger, a coagulation device, a flotation device, and a filtration device. The primary water purification system is composed of, for example, activated carbon, a decarbonation device, one or two reverse osmosis membrane devices, and a mixed-bed ion exchange device. The pure water (primary pure water) produced by this pure water production system consisting of the pretreatment device and primary water purification system is supplied to downstream systems, such as a secondary water purification system composed of, for example, a low-pressure ultraviolet oxidation device, a mixed-bed ion exchange device, and an ultrafiltration membrane device, or to a point of use.

[0003] In this pure water production system, the pretreatment device often performs temperature control as follows depending on the temperature of the raw water (industrial water, river water, etc.). For example, if the raw water temperature is lower than 20 to 23°C, steam, hot water, or heat recovery means are used to minimally heat the water to 20 to 23°C, depending on the required water temperature at the point of use. On the other hand, if the raw water temperature exceeds 20 to 23°C, the raw water temperature is cooled to around 20 to 23°C using cold water, or the water is treated as is, and the temperature is adjusted later in the pure water production system.

[0004] In this way, it is common to heat or cool the raw water to around 20-23°C and then process it in a pure water production system. However, depending on the ambient temperature, when the temperature-adjusted water to be treated (raw water) is processed in the pure water production system, condensation may occur in the tanks, piping, or various components, which may cause false alarms from water leak sensors and, in the long term, may lead to concerns about corrosion of the equipment.

[0005] To address this issue, if the pure water production system is installed indoors, air conditioning equipment may be operated in the building to prevent condensation, or the pure water production system itself may be kept warm while it is operated; however, in either case, there is the problem of excessive energy consumption.

[0006] Furthermore, Patent Document 1 describes a method for operating a pure water production system that includes a reverse osmosis membrane device and a degassing device, and that heats raw water to 40 to 45° C. Furthermore, Patent Document 2 discloses a method for operating a pure water production system that heats water to be treated that is passed through a degassing device, a reverse osmosis membrane device, and an ion exchange device to 35 to 80° C.

[0007] Japanese Patent Laid-Open No. 10-309575 Japanese Patent Laid-Open No. 2000-51845

[0008] However, both Patent Documents 1 and 2 are technologies that pursue improvements in the removal efficiency of target substances by a pure water production system, and are not pure water production systems that take into consideration long-term equipment maintenance and are capable of achieving both stable operation of water treatment equipment and efficient operating energy.

[0009] The present invention has been made in consideration of the above-mentioned problems, and has as its object to provide a pure water production system and an operating method for the pure water production system, which are intended for facility maintenance, by suppressing the occurrence of condensation in the pure water production system and preventing erroneous detection by various sensors and corrosion of equipment due to condensation.

[0010] In order to achieve the above-mentioned object, the present invention first provides a pure water production system comprising a pretreatment device, a primary pure water device, a heating means for the water to be treated in the pretreatment device, a control means for the heating means of the pretreatment device, a temperature measuring means for the water to be treated in the pretreatment device, and a temperature measuring means for the water to be treated heated by the heating means, wherein the control means controls the heating means so that the water to be treated heated by the heating means reaches a temperature higher than the dew point temperature in the atmosphere (Invention 1).

[0011] According to this invention (Invention 1), by heating the water to be treated in the pretreatment device so that its temperature is higher than the dew point, condensation can be prevented in the tanks, piping, and various components of the pretreatment device and primary pure water device, and deterioration due to corrosion of the equipment and erroneous detection by various sensors such as water leak sensors can be prevented. Furthermore, since the viscosity of the water to be treated decreases as the temperature increases, operating the pure water production system at a temperature higher than the dew point temperature can be expected to reduce the viscosity of the water to be treated, thereby reducing the pumping power required, increasing the amount of permeated water in the reverse osmosis membrane device, and improving the efficiency of the degassing device.

[0012] In the above invention (Invention 1), it is preferable that the control means controls the temperature of the water to be treated heated by the heating means to be at least 2° C. higher than the dew point temperature (Invention 2).

[0013] According to this invention (Invention 2), the probability that the water to be treated in the primary pure water treatment system downstream of the pretreatment system will also be able to flow at a temperature higher than the dew point temperature increases, thereby reliably preventing condensation in the tanks and components of the primary pure water treatment system, and preventing deterioration due to corrosion of the equipment and false detection by various sensors such as water leak sensors.

[0014] In the above invention (Invention 1), it is preferable that the primary pure water system comprises one or more water treatment elements selected from the group consisting of a reverse osmosis membrane device, an ion exchange device, a membrane degassing device, and an ultrafiltration membrane, and that these water treatment elements have been pretreated with pure water at 26 to 40°C to reduce leachable substances (Invention 3).

[0015] According to this invention (Invention 3), even if the water to be treated is at a temperature higher than the dew point, leaching from the water treatment elements of the primary pure water device can be suppressed, and the quality of the pure water as treated water can be maintained.

[0016] Secondly, the present invention provides a method for operating a pure water production system comprising a pretreatment device, a primary pure water system, and a means for heating the water to be treated in the primary pure water system, in which the water to be treated in the pretreatment device is heated so that the temperature of the water to be treated in the pretreatment device is higher than the dew point temperature of the atmosphere (Invention 4).

[0017] According to this invention (Invention 4), by heating the water to be treated in the pretreatment device so that its temperature is higher than the dew point, condensation can be prevented in the tanks, piping, and various components of the pretreatment device and primary pure water device, and deterioration due to corrosion of the equipment and erroneous detection by various sensors such as water leak sensors can be prevented. Furthermore, since the viscosity of the water to be treated decreases as the temperature increases, operating the pure water production system at a temperature higher than the dew point temperature can be expected to reduce the pumping power required as the viscosity of the water to be treated decreases, increase the amount of permeate in the reverse osmosis membrane device, and improve the efficiency of the degassing device.

[0018] In the above invention (invention 4), it is preferable to heat the water to be treated in the pretreatment device to a temperature that is 2° C. or more higher than the dew point temperature (invention 5).

[0019] According to this invention (Invention 5), the probability that the water to be treated in the primary pure water system downstream of the pretreatment system will also be able to flow at a temperature higher than the dew point temperature is increased, thereby reliably preventing condensation in the tanks and components of the primary pure water system, and preventing deterioration due to corrosion of the equipment and false detection by various sensors such as water leak sensors.

[0020] In the above invention (invention 4), it is preferable to feed the treated water from the primary water purification system directly to the subsequent stage (invention 6).

[0021] According to this invention (Invention 6), it is possible to reduce the energy consumption involved in the operation of the pure water production system.

[0022] In the above invention (Invention 6), it is preferable that the temperature of the treated water from the primary water purification system is adjusted in a subsequent stage (Invention 7).

[0023] According to this invention (Invention 7), the temperature of the pure water can be adjusted to a temperature suitable for a treatment device such as a secondary pure water treatment device provided downstream of the primary pure water treatment device or for a point of use.

[0024] The pure water production system of the present invention prevents condensation in the tanks and components of the pretreatment device and primary pure water system by heating the temperature of the water to be treated in the pretreatment device so that it is higher than the dew point temperature, and can prevent deterioration due to corrosion of the equipment and false detection by various sensors such as water leak sensors.

[0025] It is a schematic diagram showing the result of a water flow test of the pure water producing system of Example 1. It is a schematic diagram showing the result of a water flow test of the pure water producing system of Comparative Example 1.

[0026] The ultrapure water producing system of the present invention will be described in detail below.

[0027] 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 pretreatment device 2 and a primary pure water system 3. The pretreatment device 2 includes a raw water tank 21 for storing raw water W, a heating means 22, a flocculation tank 23, a pressurized flotation device 24, and a filtration membrane 25 such as a turbidity removal UF filter. The primary pure water system 3 includes a tank 31, an activated carbon tower 32, a membrane degassing device 33 as a decarbonation device, a relay tank 34, a reverse osmosis membrane device 35, an ultraviolet oxidation device 36, a regenerative ion exchange device 37, and, if necessary, an ultrafiltration membrane.

[0028] Here, the heating means 22 is preferably installed at the front end of the pretreatment device 2, but is not limited to this. The heating means 22 is preferably a waste heat recovery system using a heat exchanger or heat pump for industrial wastewater, or a device for mixing recovered water at a higher temperature than the water to be treated, but may also be a device using steam or hot water. Furthermore, the components of the pretreatment device 2 and the primary pure water device 3 are preferably made of materials that can withstand water temperatures above the dew point (approximately 26 to 40°C). Furthermore, the membrane degassing device 33, reverse osmosis membrane device 35, regenerative ion exchange device 37, and ultrafiltration membrane are preferably pretreated with pure water at 26 to 40°C to reduce leachable materials.

[0029] In the pure water production system 1 described above, the raw water tank 21 is provided with a first temperature measurement means (not shown) for measuring the initial temperature of the raw water W (the water to be treated), and a second temperature measurement means (not shown) for measuring the temperature of the heated raw water W is provided immediately after the heating means 22. Furthermore, in this embodiment, the pure water production system 1 also includes a dew point temperature measurement means (not shown) for measuring the dew point around the system. This dew point temperature measurement means can be a measuring instrument that measures the ambient temperature and humidity and calculates the dew point temperature, or a dew point thermometer. Alternatively, instead of directly measuring the dew point temperature, the dew point temperature can be estimated by referring to dew point temperatures in past weather data. These temperature measurement means can transmit data to a control means (not shown), such as a personal computer, which can control the heating means 22 based on the data from the first and second temperature measurement means. In this embodiment, the tank 31 is also provided with a third temperature measuring means (not shown) for measuring the temperature of the pretreated water W1, and the third temperature measuring means is also capable of transmitting data to the control means, so that the heating means 22 can be controlled taking into consideration the data from this third temperature measuring means.

[0030] <Operation Method of Pure Water Production System> Next, an operation method of the above-described pure water production system 1 will be described.

[0031] First, raw water W is stored in a raw water tank 21 of the pretreatment device 2. The raw water W is supplied from the raw water tank 21 by a pump (not shown) and heated by a heating means 22. Subsequently, impurities are coagulated from the heated raw water W in a coagulation tank 23 of the pretreatment device 2, and then low-specific-gravity coagulated flocs are removed by a pressure flotation device 24. Then, turbidity is removed by a filtration membrane 25, and pretreated water W1 is obtained. Next, the pretreated water W1 is stored in a tank 31, and the primary pure water system 3 includes an activated carbon tower 32, a membrane degasser 33, a reverse osmosis membrane device 35, an ultraviolet oxidation device 36, a regenerative ion exchanger 37, and, if necessary, an ultrafiltration membrane, which removes most of the electrolytes, fine particles, live bacteria, etc. from the pretreated water W1 and decomposes organic matter, thereby obtaining primary pure water (pure water) W2.

[0032] In the process of producing such primary pure water (pure water) W2, the temperature of the raw water W in the raw water tank 21 of the pretreatment device 2 is measured by a first temperature measuring means, while the dew point temperature in the atmosphere is measured by a dew point temperature measuring means. Then, the raw water W is supplied by a pump (not shown). Based on the amount of raw water W supplied per unit time, the measurement value of the first temperature measuring means, and the measurement value of the dew point temperature measuring means, the raw water W is heated by the heating means 22 so that the temperature of the raw water W is equal to or higher than the dew point temperature, particularly 2°C or higher than the dew point temperature. Condensation may occur if the raw water W is below the dew point temperature. However, even if the temperature is equal to or higher than the dew point temperature but less than 2°C, the likelihood of condensation occurring increases depending on the installation locations of the elements constituting the pretreatment device 2 and the primary pure water device 3. The set temperature for heating the raw water W may be set to a temperature 2°C or more higher than the maximum dew point temperature in accordance with the trend in dew point temperature in the region where the pure water production system 1 is installed, and the system may operate steadily at that set temperature, or may be set to a temperature 2°C or more higher than the maximum dew point temperature for each season, such as winter or summer, in accordance with the trend in dew point temperature during those periods, and the system may operate steadily at that set temperature. There is no particular limit to the upper limit of the temperature of the raw water W when heated, but heating to a temperature above 40°C is not preferred because excessive energy is required for heating.

[0033] The temperature of the heated raw water W is confirmed by the second temperature measuring means, and based on this measurement value, the heating by the heating means 22 is controlled. Furthermore, in the heating of the raw water W as described above, it is preferable to measure the temperature of the pretreated water W1 stored in the tank 31 of the primary pure water system 3 by the third temperature measuring means, and control the heating by the heating means 22 so that this temperature is equal to or higher than the dew point temperature, particularly 2°C higher than the dew point temperature.

[0034] By heating the raw water W to a temperature higher than the dew point temperature, particularly a temperature at least 2°C higher than the dew point temperature, and producing primary pure water (pure water) W2 using the pure water production system 1, condensation can be prevented in the various components and piping of the pretreatment device 2 and the primary pure water production system 3, and deterioration due to corrosion of the equipment and erroneous detection by various sensors such as water leak sensors can be prevented. Furthermore, since the viscosity of the water to be treated decreases as the temperature increases, operating the pure water production system 1 at a temperature higher than the dew point temperature for the raw water W or pretreated water W1 can reduce the viscosity of the water to be treated, thereby reducing the pumping power required, increasing the amount of permeate in the reverse osmosis membrane device 35, and improving the decarbonation efficiency in the membrane degassing device 33. Note that if the temperature of the raw water W is higher than the dew point temperature without heating, particularly if it is higher than the dew point temperature by 2°C or more, the raw water W can be treated directly in the pure water production system 1.

[0035] The primary pure water (pure water) W2 produced by the pure water production system 1 can be supplied directly to downstream equipment or use points without cooling. For example, in the case of an ultrapure water production system, it can be supplied to a secondary pure water production system (subsystem). This reduces the energy consumption associated with the operation of the pure water production system 1. The temperature of the primary pure water (pure water) W2 can then be adjusted as needed in these secondary pure water production systems (subsystems) or use points.

[0036] Although 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, the pure water production system 1 is not limited to that shown in FIG. 1 and can be variously modified as long as it includes the pretreatment device 2 and the primary pure water system 3. The downstream treatment is not limited to an ultrapure water production system, and various devices or points of use may be used. Furthermore, a heating means may be provided on the primary pure water system 3 side and controlled in the same manner.

[0037] The present invention will be described in more detail based on the following specific examples.

[0038] Example 1 In the pure water production system 1 shown in Figure 1, well water at 17°C was used as raw water W. Since the dew point temperature in Tokyo rises to a maximum of approximately 28°C in the summer, the raw water W was heated to 30°C by the heating means 22, and the pure water production system 1 was operated from May to October in the summer. As a result, condensation S was prevented throughout the pure water production apparatus 1, as shown in Figure 2.

[0039] Comparative Example 1 In the pure water production system 1 shown in Figure 1, well water at 17°C was used as raw water W and heated to 20°C by the heating means 22. The pure water production system 1 was operated from May to October in the summer. As a result, there were periods when the temperature of the raw water W was below the dew point temperature, and condensation S occurred in the tank 31 and piping of the pure water production system 1, as shown in Figure 3. For this reason, it became necessary to operate conditioning equipment in the installation space of the pure water production system 1 to prevent condensation, or to keep the entire pure water production system 1 at a temperature above the dew point temperature.

[0040] REFERENCE SIGNS LIST 1 Pure water production system 2 Pretreatment device 21 Raw water tank 22 Heating means 23 Coagulation tank 24 Pressure flotation device 25 Filtration membrane 3 Primary pure water device 31 Tank 32 Activated carbon tower 33 Membrane degassing device (decarbonation device) 34 Relay tank 35 Reverse osmosis membrane device 36 Ultraviolet oxidation device 37 Ion exchange device W Raw water (water to be treated) W1 Pretreated water W2 Primary pure water (pure water) S Condensation

Claims

1. A pure water production system comprising a pretreatment device, a primary pure water device, a means for heating the water to be treated in the pretreatment device, a control means for the heating means of the pretreatment device, a means for measuring the temperature of the water to be treated in the pretreatment device, and a means for measuring the temperature of the water to be treated heated by the heating means, wherein the control means controls the heating means so that the water to be treated heated by the heating means reaches a temperature higher than the dew point temperature in the atmosphere.

2. The pure water producing system according to claim 1, wherein the control means controls the temperature of the water heated by the heating means to be at least 2° C. higher than the dew point temperature.

3. A pure water production system as described in claim 1 or 2, wherein the primary pure water device is equipped with one or more water treatment elements selected from the group consisting of a reverse osmosis membrane device, an ion exchange device, a membrane degassing device, and an ultrafiltration membrane, and these water treatment elements have been pretreated with pure water at 26 to 40°C to reduce leachable substances.

4. A method for operating a pure water production system comprising a pretreatment device, a primary pure water device, and a means for heating the water to be treated in the primary pure water device, wherein the water to be treated in the pretreatment device is heated so that the temperature of the water to be treated in the pretreatment device is higher than the dew point temperature in the atmosphere.

5. The method for operating a pure water production system according to claim 4, wherein the water to be treated in the pretreatment device is heated to a temperature at least 2°C higher than the dew point temperature.

6. The method for operating a pure water production system according to claim 4, wherein the treated water from the primary pure water system is directly supplied to a subsequent stage.

7. The method for operating a pure water production system according to claim 6, wherein the temperature of the treated water from the primary pure water system is adjusted in a subsequent stage.

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