Dissolved gas removal device, pure water production device using the same, and dissolved gas removal method

Abstract

To provide a dissolved gas removing apparatus provided with a plurality of gas separation devices connected to gas suction devices in which the number of the suction devices to be operated can be varied.SOLUTION: A dissolved gas removing apparatus 100 has a plurality of gas separation devices 3A and 3B, each of which has an internal space 31 to which to-be-treated water containing dissolved gas is supplied. The plurality of gas separators 3A and 3B perform separation of dissolved gas from to-be-treated water supplied to the internal spaces 31. The dissolved gas removing apparatus 100 has a plurality of suction devices 14A to 14C. Each of the plurality of suction devices 14A to 14C can be connected to the plurality of gas separation devices 3A, 3B in order to suction out dissolved gas by reducing the pressure in the internal space 31. The dissolved gas removing apparatus 100 has: pressure gauges 5A and 5B for measuring the degree of vacuum in the internal spaces 31 of the gas separation devices 3A and 3B; and a control device 16 that controls at least one of the number of suction devices 14A to 14C to be operated, and the suction power of the suction devices 14A to 14C, according to the degree of vacuum in the internal spaces 31 of the gas separation devices 3A and 3B measured by the pressure gauges 5A and 5B.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a dissolved gas removal device, a pure water production system using the same, and a dissolved gas removal method. [Background technology]

[0002] There is a type of pure water production system known as the two-bed, three-tower (2B3T) system. In this type of pure water production system, a cation exchanger, a gas separation device, and an anion exchanger are arranged in this order from upstream to downstream along the flow of the water to be treated. The cation exchanger removes cationic components from the water to be treated, the gas separation device removes dissolved gases from the water to be treated, and the anion exchanger removes anionic components. Dissolved gases are themselves impurities, so they are removed in the gas separation device. Carbon dioxide in particular dissolves in water to form weakly acidic carbonated water (H + +HCO3 - ), so by removing carbon dioxide, the load on the anion exchange device can be reduced. Gas separation devices are generally used in combination with a suction device that reduces the pressure in the internal space of the gas separation device to suck and remove the dissolved gases, and in this specification, these devices are collectively referred to as dissolved gas removal devices. Patent Document 1 discloses a vacuum pump as the suction device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-77683 Summary of the Invention [Problem to be solved by the invention]

[0004] A water purification system called 2B3T may have multiple trains. That is, multiple trains, each of which includes one cation exchanger, one gas separator, and one anion exchanger, may be installed in one water purification system. This makes it easy to adjust the processing capacity of the water purification system according to the required amount of treated water. However, since each train is designed to operate independently of each other, a suction device is provided exclusively for each gas separator. Therefore, the installation space and cost of the suction device depend on the number of trains in the water purification system, and are difficult to reduce.

[0005] An object of the present invention is to provide a dissolved gas removal device that includes a plurality of gas separation devices and that enables a reduction in the number of suction devices. [Means for solving the problem]

[0006] The dissolved gas removal apparatus of the present invention has a plurality of gas separation devices each having an internal space to which water to be treated containing dissolved gas is supplied. The plurality of gas separation devices separates dissolved gas from the water to be treated supplied to the internal space. The dissolved gas removal apparatus has a plurality of suction devices. is shared by multiple gas separation units, The internal space is depressurized to remove the dissolved gas by suction. Each gas separation device can be connected to and disconnected from a number of suction devices. Dissolved gas removal equipment Multiple Gas Separation Equipment Each Measure the degree of vacuum in the internal space Multiple A pressure gauge; Multiple Measured by pressure gauge Multiple Gas Separation Equipment Each The vacuum cleaner further includes a control device that controls at least one of the number of suction devices in operation and the suction capacity of the suction devices according to the degree of vacuum in the internal space. Effect of the Invention

[0007] According to the present invention, it is possible to provide a dissolved gas removal device that includes a plurality of gas separation devices and that enables a reduction in the number of suction devices. [Brief description of the drawings]

[0008] [Figure 1]1 is a schematic configuration diagram of a pure water producing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a dissolved gas removal device of the pure water production system shown in FIG. [Diagram 3] FIG. 2 is a conceptual diagram showing the operation of the dissolved gas removal device in step 1. [Figure 4] FIG. 1 is a conceptual diagram showing the operation of the dissolved gas removal device in step 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a dissolved gas removal device 100 of the present invention, a pure water production system 1 using the same, and a dissolved gas removal method will be described with reference to the drawings. Fig. 1 shows a schematic configuration diagram of the pure water production system 1 according to one embodiment of the present invention, and Fig. 2 shows a schematic configuration diagram of the dissolved gas removal device 100 of the pure water production system 1 shown in Fig. 1. The pure water production system 1 is used alone or in combination with other water treatment devices in various plants, ultrapure water production systems, etc.

[0010] The water to be treated is supplied to the pure water production system 1 through an inlet line L1 provided upstream of the pure water production system 1. The pure water production system 1 has two systems (system A and system B). The inlet line L1 branches into a first mother pipe L2A and a second mother pipe L2B. System A has a first gas separation device 3A, a first cation exchange device 2A provided in the front stage of the first gas separation device 3A, and a first anion exchange device 4A provided in the rear stage of the first gas separation device 3A, which are arranged on the first mother pipe L2A. System B has a second gas separation device 3B, a second cation exchange device 2B provided in the front stage of the second gas separation device 3B, and a second anion exchange device 4B provided in the rear stage of the second gas separation device 3B, which are arranged on the second mother pipe L2B. The first and second header pipes L2A and L2B join downstream of the pure water production system 1 to form the outlet line L3. The treated water from the pure water production system 1 is transported downstream through the outlet line L3. Since the A and B series have the same configuration, when there is no need to distinguish between them, the first and second gas separation devices 3A and 3B may be referred to as the gas separation device 3, the first and second cation exchange devices 2A and 2B as the cation exchange device 2, the first and second anion exchange devices 4A and 4B as the anion exchange device 4, and the first and second header pipes L2A and L2B as the header pipes L2.

[0011] The cation exchange device 2 is a tower filled with a cation resin or a cation monolith, and removes cationic components contained in the water to be treated. The gas separation device 3 removes dissolved gases such as oxygen and carbon dioxide (carbon dioxide gas) from the water to be treated. The anion exchange device 4 is a tower filled with anion resin or an anion monolith, and removes anionic components contained in the water to be treated. As mentioned above, the gas separation device 3 removes carbon dioxide, which can reduce the load on the downstream anion exchange device 4.

[0012] The gas separation device 3 has an internal space 31 to which water containing dissolved gas is supplied, and separates the dissolved gas from the water supplied to the internal space 31. A mother pipe L2 is connected to the top and bottom of the gas separation device 3. Inlet valves (first valve V1 and second valve V2) are provided at the inlet of the gas separation device 3. A sprinkler nozzle 32 for sprinkling the water to be treated is provided at the top of the internal space 31. A gas-liquid contact material 33 is provided below the sprinkler nozzle 32. The sprinkler nozzle 32 and the gas-liquid contact material 33 increase the surface area of ​​the water to be treated and increase the efficiency of removing dissolved gas. A first gas discharge line L4A and a second gas discharge line L4B are connected to the top of the first gas separation device 3A and the second gas separation device 3B, i.e., the top of the internal space 31, respectively. The first and second gas discharge lines L4A, L4B are connected to first to third suction devices 14A to 14C described later. The internal space 31 of the gas separation device 3 is made to have a negative pressure by the first to third suction devices 14A to 14C.

[0013] The water to be treated, from which cationic components have been removed by the cation exchange device 2, is supplied to the internal space 31 from the top of the gas separation device 3 through the spray nozzle 32. The water to be treated drips down inside the internal space 31, and as it moves further down inside the gas-liquid contact material 33, the dissolved gases are removed from the water, and the water is discharged from the bottom of the internal space 31. The water to be treated, from which the dissolved gases have been removed, is supplied to the anion exchange device 4.

[0014] The first gas discharge line L4A and the second gas discharge line L4B are provided with a first pressure gauge 5A and a second pressure gauge 5B for measuring the degree of vacuum in the internal space 31 of the first gas separation device 3A and the second gas separation device 3B, respectively. The first pressure gauge 5A and the second pressure gauge 5B are preferably provided as close as possible to the first gas separation device 3A and the second gas separation device 3B. The first pressure gauge 5A and the second pressure gauge 5B can also be provided in the internal space 31 of the first gas separation device 3A and the second gas separation device 3B, respectively.

[0015] The first gas discharge line L4A and the second gas discharge line L4B are provided with a first demister pot 6A and a second demister pot 6B, respectively. The first and second demister pots 6A and 6B have collision separation materials (not shown) with which water droplets contained in the suction gas collide and are separated. The separated water droplets are returned to the first gas separation device 3A and the second gas separation device 3B through the first return pipe L5A and the second return pipe L5B, respectively.

[0016] The first to third suction devices 14A to 14C are provided so as to be connectable to the first gas separation device 3A and the second gas separation device 3B. Connectable means that they can be connected and disconnected. Each of the first to third suction devices 14A to 14C can be connected to each of the first gas separation device 3A and the second gas separation device 3B, and can be disconnected from each of the first gas separation device 3A and the second gas separation device 3B. To realize this function, the first gas discharge line L4A and the second gas discharge line L4B join together to form a common gas discharge line L6, which branches into first to third branch pipes L7A to L7C, and the first to third branch pipes L7A to L7C are connected to the first to third suction devices 14A to 14C, respectively. In addition, a third valve V3 and a fourth valve V4 are provided in the first gas exhaust line L4A and the second gas exhaust line L4B, respectively, and by operating these, it is possible to connect and disconnect the first and second gas separation devices 3A, 3B to the first to third suction devices 14A to 14C.

[0017] The first to third branch pipes L7A to L7C are respectively provided with the first to third liquid separators 11A to 11C, the first to third intake filters 12A to 12C, the first to third mechanical boosters 13A to 13C, and the first to third suction devices 14A to 14C. These devices are respectively provided in the first to third branch pipes L7A to L7C in this order from upstream to downstream along the flow direction of the suction gas. The first to third liquid separators 11A to 11C are filters with a collision separation function, and remove water droplets in the suction gas. The first to third liquid separators 11A to 11C may be omitted. The first to third intake filters 12A to 12C are provided with polyester elements, and remove solids with a particle size of 5 μm or more. The first to third intake filters 12A to 12C are provided to protect the downstream first to third mechanical boosters 13A to 13C and the first to third suction devices 14A to 14C, respectively. The first to third mechanical boosters 13A to 13C are provided to increase the exhaust speed and decrease the ultimate pressure (increase the degree of vacuum). The first to third suction devices 14A to 14C are vacuum pumps in this embodiment, but other types of devices such as steam ejectors can be used as long as they can create a negative pressure in the internal space 31 of the first and second gas separation devices 3A and 3B. The first to third suction devices 14A to 14C reduce the pressure in the internal space 31 of the first and second gas separation devices 3A and 3B to suck and remove dissolved gas. The suction gas that has passed through the first to third suction devices 14A to 14C is exhausted to the outside.

[0018] The control device 16 controls the number of the first to third suction devices 14A to 14C to be operated according to the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A and 3B measured by the first and second pressure gauges 5A and 5B, respectively. The control device 16 also adjusts the suction capacity (the rotation speed of the vacuum pump in this embodiment) of the first to third suction devices 14A to 14C according to the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A and 3B. Specifically, the first to third suction devices 14A to 14C have first to third inverters 15A to 15C connected to the first to third suction devices 14A to 14C (vacuum pumps in this embodiment), respectively. The control device 16 controls the first to third inverters 15A to 15C to adjust the rotation speed of the vacuum pump according to the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A and 3B. The first to third inverters 15A to 15C change the frequency of the AC current to control the rotation speed of the motor of the vacuum pump.

[0019] The first to third liquid separators 11A to 11C, the first to third intake filters 12A to 12C, the first to third mechanical boosters 13A to 13C, the first to third suction devices 14A to 14C, the first to third inverters 15A to 15C, and the control device 16 constitute a negative pressure control device 50 for the first and second gas separation devices 3A and 3B. Since the negative pressure control device 50 can be configured as a single unit, it can be installed as a unit, for example, during remodeling work. The first and second gas separation devices 3A and 3B and the negative pressure control device 50 constitute a dissolved gas removal device 100 in the pure water production system 1.

[0020] Next, a method of operating the dissolved gas removal apparatus 100 will be described. First, a method of operating only the A series of the pure water production apparatus 1 will be described. The internal space 31 of the first and second gas separation apparatuses 3A and 3B is assumed to be at atmospheric pressure. The first valve V1, the second valve V2, and the fourth valve V4 are closed, and the third valve V3 is opened. This operation is performed by a control device (not shown) of the pure water production apparatus 1, but may also be performed by the control device 16 of the dissolved gas removal apparatus 100. Next, the control device 16 operates any two or more, preferably all, of the suction devices 14A to 14C to reduce the pressure in the internal space 31 of the first gas separation apparatus 3A. When the degree of vacuum in the internal space 31 of the first gas separation apparatus 3A reaches a predetermined threshold value, the inlet valve (first valve V1) is opened, and the water to be treated is passed only through the A series. Thereafter, at least one of the number of suction devices 14A-14C in operation and the suction capacity of the suction devices 14A-14C (the rotation speed of the vacuum pump in this embodiment) is controlled according to the degree of vacuum in the internal space 31 of the first gas separation device 3A. The aperture of the first valve V1 is controlled according to the water level in the first gas separation device 3A. That is, when the water level in the first gas separation device 3A is high, the aperture of the first valve V1 is decreased, and when the water level in the first gas separation device 3A is low, the aperture of the first valve V1 is increased.

[0021] In this embodiment, when the internal space 31 of the first gas separation device 3A reaches a predetermined degree of vacuum, the control device 16 starts controlling the number of suction devices 14A to 14C in operation. When two suction devices are operated, the control device 16 stops one suction device and operates the remaining one. When three suction devices are operated, the control device 16 stops two suction devices and operates the remaining one. In this case, only one of the three suction devices may be stopped, and when the degree of vacuum increases, another suction device may be stopped and only the remaining one may be operated. Once the degree of vacuum in the internal space 31 of the first gas separation device 3A increases, excessive suction capacity is not required, so that the degree of vacuum in the internal space 31 of the first gas separation device 3A can be maintained with a small number of suction devices.

[0022] The timing of opening the inlet valve (first valve V1) and the timing of starting the control of the number of suction devices 14A to 14C in operation may be the same, or may be the same. In other words, the predetermined vacuum level and the predetermined threshold value can be set separately. If the vacuum level in the internal space 31 decreases during operation of the first gas separation device 3A, the suction devices that have been stopped are restarted, or the rotation speed of the vacuum pump of the suction device in operation is increased, or both of these are performed. The increase in the rotation speed of the vacuum pump is performed via the control of the inverters 15A to 15C. If the vacuum level in the internal space 31 increases, some of the suction devices are stopped, or the rotation speed of the vacuum pump of the suction device in operation is reduced, or both of these are performed.

[0023] As described above, it is generally preferable to adjust the number of suction devices 14A to 14C in operation when the fluctuation of the vacuum degree in the internal space 31 of the gas separation apparatus 3 is large, and to adjust the suction capacity of the suction devices 14A to 14C (the rotation speed of the vacuum pump in this embodiment) when the fluctuation of the vacuum degree is small, but this is not necessarily limited to this method. For example, when the vacuum pump is operating near the upper limit of the allowable rotation speed, there is a large room for reducing the rotation speed, so the rotation speed of the vacuum pump may be reduced instead of reducing the number of operating vacuum pumps. In addition, the number of operating suction devices 14A to 14C and the rotation speed of the vacuum pump may be adjusted simultaneously. For example, the number of operating suction devices 14A to 14C may be reduced and the rotation speed of the vacuum pump may be increased at the same time, or the number of operating suction devices 14A to 14C may be increased and the rotation speed of the vacuum pump may be reduced at the same time.

[0024] The method of operating the A-line and B-line of the pure water production system 1 when the internal space 31 of the first and second gas separation devices 3A, 3B is at atmospheric pressure is basically the same as the above-mentioned method. That is, when the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A, 3B reaches a certain threshold value, the inlet valves (the first valve V1 and the second valve V2) are opened and the water to be treated is passed through the A-line and the B-line. Since the load on the vacuum pumps is high, it is preferable to operate all the vacuum pumps.

[0025] Next, a method of operating only the A series first (step 1) and then operating the A series and the B series (step 2) will be described. Step 1 is performed as described above. When performing step 2, the operation of the A series is stopped once. That is, the two inlet valves (first valve V1, second valve V2) are closed to isolate the pure water production system 1 from other systems. If the B series is started up while the A series is operating, the degree of vacuum in the internal space 31 of the first gas separation device 3A will drop rapidly, and there is a possibility that the dissolved gas concentration of the treated water will increase. The third valve V3 and the fourth valve V4 are left open.

[0026] Next, the control device 16 operates two or more suction devices, preferably all of the suction devices 14A to 14C, to reduce the pressure in the internal space 31 of the first and second gas separation devices 3A and 3B. This operation is preferably performed while the internal space 31 of the first gas separation device 3A is at negative pressure after the operation of the first gas separation device 3A is stopped. This is because the load on the vacuum pump is reduced. For example, the load on the vacuum pump is 1 when the internal space 31 of the first gas separation device 3A (or the second gas separation device 3B) is at atmospheric pressure. When the internal spaces 31 of the first gas separation device 3A and the second gas separation device 3B are both at atmospheric pressure, the load on the vacuum pump is 2. In contrast, when the pressure in the internal space 31 of the first gas separation device 3A is 0.5 times atmospheric pressure and the internal space 31 of the second gas separation device 3B is at atmospheric pressure, the load on the vacuum pump is 1.5. In other words, since the internal space 31 of the first gas separation device 3A is already in a depressurized state, the load of the vacuum pump is reduced accordingly. When the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A and 3B reaches a predetermined threshold, the inlet valves (the first valve V1 and the second valve V2) are opened, and the water to be treated is passed through the A and B series. Thereafter, the control device 16 controls at least one of the number of suction devices in operation and the suction capacity of the suction device (the rotation speed of the vacuum pump in this embodiment) according to the degree of vacuum in the internal space 31 of the first and second gas separation devices 3A and 3B. The specific method is as described above. As described above, the opening degree of the first valve V1 is controlled according to the water level of the first gas separation device 3A. Similarly, the opening degree of the second valve V2 is controlled according to the water level of the second gas separation device 3B. That is, when the water level in the second gas separation device 3B is high, the opening degree of the second valve V2 is decreased, and when the water level in the second gas separation device 3B is low, the opening degree of the second valve V2 is increased.

[0027] FIG. 3(a) shows a dissolved gas removal apparatus 200 of a comparative example, and FIG. 3(b) shows a dissolved gas removal apparatus 100 of this embodiment. The thick lines indicate the locations where the suction gas flows. The capacity of each suction device is the same in the comparative example and this embodiment. FIG. 3 shows the case where only the A series is operated (step 1). In the comparative example, the gas separation device of each series is combined with a dedicated suction device, and two suction devices 14A, 14B are provided in each series. In this embodiment, three suction devices 14A to 14C shared by the two series are provided. In step 1, in the comparative example, the two suction devices 14A, 14B of the A series are operated, but the suction devices 14A, 14B of the B series are not operated. In contrast, in this embodiment, three suction devices 14A to 14C can be operated. As a result, in this embodiment, the internal space 31 of the first gas separation device 3A can be depressurized more quickly than in the comparative example. Therefore, in this embodiment, the internal space 31 of the first gas separation device 3A can be depressurized more quickly than in the comparative example while the total number of suction devices is less than that of the comparative example. In addition, since the total number of suction devices is reduced, the cost, installation space, and maintenance work of the suction devices can be reduced. Since only one control device 16 is provided, the number of control devices can be reduced compared to the case where a control device is provided for each series. In this embodiment, it is also possible to operate only two suction devices, and in this case, the internal space 31 of the first gas separation device 3A can be depressurized at the same speed as in the comparative example. Furthermore, after the internal space 31 of the first gas separation device 3A reaches a predetermined vacuum degree, the suction capacity of the suction devices 14A to 14C can be reduced, so that the operating cost can also be reduced.

[0028] FIG. 4 is a diagram similar to FIG. 3, showing the case where the A series and the B series are operated (step 2). The internal space 31 of the first gas separation apparatus 3A is lower than the atmospheric pressure, and the internal space 31 of the second gas separation apparatus 3B is equal to the atmospheric pressure. In the comparative example, one or two suction devices 14A, 14B are operated in the A series according to the degree of vacuum in the internal space 31, and two suction devices 14A, 14B are operated in the B series. Therefore, in the comparative example, the time required for decompression is determined by the B series. In this embodiment, three suction devices 14A to 14C are operated. When the pressure in the internal space 31 of the first gas separation apparatus 3A is low (the degree of vacuum is high) at the start of step 2, the decompression process is completed earlier than that of the second gas separation apparatus 3B of the comparative example.

[0029] As described above, in this embodiment, three suction devices 14A to 14C are provided for two gas separation devices 3A and 3B, but the number of these devices is not limited. For example, for three or more gas separation devices, more suction devices than the number of gas separation devices can be provided. More generally, according to the dissolved gas removal method of the present invention, water to be treated containing dissolved gas is supplied to the internal space 31 of at least one gas separation device 3 among the multiple gas separation devices 3, and the internal space 31 of this at least one gas separation device 3 is depressurized by two or more suction devices, and the dissolved gas is sucked and removed from the water to be treated supplied to the internal space 31. Then, at least one of the number of suction devices in operation and the suction capacity of the suction devices is controlled by the control device 16 according to the degree of vacuum in the internal space of the gas separation device. [Explanation of symbols]

[0030] 1 Pure water production equipment 2A, 2B First and second cation exchange devices 3A, 3B First and second gas separation devices 4A, 4B First and second anion exchange devices 5A, 5B First and second pressure gauges 14A to 14C First to third suction devices (vacuum pumps) 15A~15C 1st~3rd inverters 16 Control device 31 Interior Space 100 Dissolved Gas Removal Device

Claims

1. a plurality of gas separation devices each having an internal space to which water to be treated containing dissolved gas is supplied, the gas separation devices separating the dissolved gas from the water to be treated supplied to the internal space; a plurality of suction devices that are shared by the plurality of gas separation apparatuses and reduce the pressure in the internal space to aspirate and remove the dissolved gas, the plurality of suction devices being capable of being connected to and disconnected from each of the gas separation apparatuses; a plurality of pressure gauges for measuring the degree of vacuum in the internal space of each of the plurality of gas separation devices; A control device that controls at least one of the number of suction devices in operation and the suction capacity of the suction devices in accordance with the degree of vacuum in the internal space of each of the plurality of gas separation devices measured by the plurality of pressure gauges; A dissolved gas removal device comprising:

2. Each of the plurality of suction devices includes a vacuum pump; The dissolved gas removal apparatus according to claim 1 , wherein the control device adjusts a rotation speed of the vacuum pump depending on the degree of vacuum in the internal space of the gas separation apparatus.

3. A gas separation device having an internal space to which treated water containing dissolved gas is supplied, the gas separation device separating the dissolved gas from the treated water supplied to the internal space; a plurality of suction devices each connectable to the plurality of gas separation devices and configured to reduce the pressure in the internal space to aspirate and remove the dissolved gas; a pressure gauge for measuring the degree of vacuum in the internal space of the gas separation device; A control device that controls at least one of the number of suction devices in operation and the suction capacity of the suction devices according to the degree of vacuum in the internal space of the gas separation device measured by the pressure gauge; having Each of the plurality of suction devices includes a vacuum pump; The control device adjusts the rotation speed of the vacuum pump in accordance with the degree of vacuum in the internal space of the gas separation device, the plurality of gas separation units includes a first gas separation unit; The control device reduces the pressure of the internal space of the first gas separation device using two or more of the suction devices, and then controls at least one of the number of suction devices in operation and the rotation speed of the vacuum pump according to the degree of vacuum in the internal space of the first gas separation device; the plurality of gas separation units further comprising a second gas separation unit; The control device reduces the pressure in the internal spaces of the first and second gas separation devices using two or more suction devices while the internal space of the first gas separation device is at negative pressure after operation of the first gas separation device is stopped, and then controls at least one of the number of suction devices in operation and the rotation speed of the vacuum pump depending on the degree of vacuum in the internal spaces of the first and second gas separation devices.

4. A gas separation device having an internal space to which treated water containing dissolved gas is supplied, the gas separation device separating the dissolved gas from the treated water supplied to the internal space; a plurality of suction devices each connectable to the plurality of gas separation devices and configured to reduce the pressure in the internal space to aspirate and remove the dissolved gas; a pressure gauge for measuring the degree of vacuum in the internal space of the gas separation device; A control device that controls at least one of the number of suction devices in operation and the suction capacity of the suction devices according to the degree of vacuum in the internal space of the gas separation device measured by the pressure gauge; having Each of the plurality of suction devices includes a vacuum pump; The control device adjusts the rotation speed of the vacuum pump in accordance with the degree of vacuum in the internal space of the gas separation device, the plurality of gas separation units includes a first gas separation unit; The control device reduces the pressure of the internal space of the first gas separation device using two or more of the suction devices, and then controls at least one of the number of suction devices in operation and the rotation speed of the vacuum pump according to the degree of vacuum in the internal space of the first gas separation device; the plurality of gas separation units further comprising a second gas separation unit; The control device reduces the pressure in the internal spaces of the first and second gas separation devices using all of the suction devices while the internal space of the first gas separation device is at negative pressure after operation of the first gas separation device is stopped, and then controls at least one of the number of suction devices in operation and the rotation speed of the vacuum pump depending on the degree of vacuum in the internal spaces of the first and second gas separation devices.

5. Each of the plurality of suction devices has an inverter connected to the vacuum pump, The dissolved gas removal apparatus according to claim 2 , wherein the control device controls the inverter to adjust a rotation speed of the vacuum pump in accordance with the degree of vacuum in the internal space of the gas separation apparatus.

6. the plurality of gas separation units includes a first gas separation unit; The dissolved gas removal apparatus of claim 2, wherein the control device reduces the pressure in the internal space of the first gas separation apparatus using two or more suction devices, and then controls at least one of the number of suction devices in operation and the rotation speed of the vacuum pump depending on the degree of vacuum in the internal space of the first gas separation apparatus.

7. A dissolved gas removal device according to any one of claims 1 to 6, a cation exchange device provided upstream of the gas separation device of the dissolved gas removal device; an anion exchange device provided downstream of the gas separation device of the dissolved gas removal device; A pure water production apparatus having the above structure.

8. Supplying water to be treated containing dissolved gas into an internal space of at least one of the plurality of gas separation devices; a plurality of suction devices shared by the plurality of gas separation devices, the plurality of suction devices being capable of being connected and disconnected from the plurality of suction devices for each of the gas separation devices, by using two or more of the plurality of suction devices to reduce the pressure in the internal space of the at least one gas separation device, and to aspirate and remove the dissolved gas from the water to be treated supplied to the internal space; Controlling at least one of the number of suction devices in operation and the suction capacity of the suction devices according to the degree of vacuum of the at least one gas separation device; The method for removing dissolved gas comprises the steps of:

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