Liquid seal pump operation method, membrane degassing device, pure water production system and pure water production method

Abstract

In the operation method of the liquid-seal vacuum pump, liquid is discharged from the vacuum pipe 30 connected to the liquid-seal vacuum pump 28; the sealing liquid is pressurized and supplied to fill the liquid-seal vacuum pump 28 with a specified amount, and the liquid-seal vacuum pump 28 is driven until the pressure of the vacuum pipe 30 is reduced to a specified pressure; and when the pressure of the vacuum pipe 30 is reduced to a specified pressure, the supply of pressurized sealing liquid to the liquid-seal vacuum pump 28 is stopped, so that the sealing liquid circulates from the liquid-seal vacuum pump 28 in the circulation flow path 40, and the state in which a specified amount of sealing liquid exists in the liquid-seal vacuum pump 28 is maintained.

Description

Technical Field

[0001] The invention relates to an operating method of a liquid seal pump, a membrane degassing device, a pure water manufacturing system and a pure water manufacturing method. Background Art

[0002] In a membrane degassing device that constitutes a part of a pure water production device, etc., condensed water is generated on the gas phase side of the membrane degassing device. This condensed water can be a major cause of poor condition of the membrane degassing device. This condensed water may cause, for example, poor operation of a vacuum pump or a decrease in the membrane area through which gas passes during degassing, thereby causing performance degradation.

[0003] To solve this problem, Japanese Patent Application Laid-Open No. 2000-185203 describes a method for operating a membrane degassing device, which includes supplying an inert gas into the hollow fiber membrane to eliminate the vacuum after stopping the water degassing step, thereby maintaining the hollow fiber membrane in a normal state. Summary of the invention

[0004] Problems to be solved by the invention

[0005] However, a liquid seal vacuum pump such as a suction membrane degasser has a structure that circulates a seal liquid through a circulation flow path.

[0006] Here, for example, when the membrane degasser is stopped and then restarted, liquid may remain in the vacuum piping from the membrane degasser to the liquid seal vacuum pump, causing the vacuum degree to decrease, and the vacuum degree may also decrease inside the liquid seal vacuum pump. Alternatively, after the membrane degasser is stopped, the vacuum piping may return to normal pressure.

[0007] The inside of the liquid seal vacuum pump operates in a predetermined vacuum state, and a certain degree of vacuum is required to discharge the sealing liquid. Therefore, if the vacuum degree is low as described above, the sealing liquid cannot circulate in the circulation flow path, and the liquid seal vacuum pump cannot be driven.

[0008] However, there is no technology that can drive the liquid seal vacuum pump even when the vacuum degree of the vacuum piping is in a state of being reduced. For example, in the above-mentioned Japanese Patent Publication No. 2000-185203, the following problem is not considered: due to the generation of condensed water on the gas phase side of the membrane degassing device, the vacuum degree of the vacuum piping is reduced, which may make it impossible to drive the liquid seal vacuum pump.

[0009] In addition, in order for the liquid seal vacuum pump to be properly driven, the amount of sealing liquid in the liquid seal vacuum pump must be appropriate. For example, if the liquid seal vacuum pump is full of sealing liquid or insufficient sealing liquid, the liquid seal vacuum pump cannot be driven and stops.

[0010] The purpose of the present disclosure is to obtain a method for operating a liquid-sealed vacuum pump, a membrane degassing device, a pure water manufacturing system equipped with the membrane degassing device, and a pure water manufacturing method using the pure water manufacturing system, wherein the liquid-sealed vacuum pump can be driven even when the vacuum degree of the vacuum piping is in a lowered state, and since the membrane degassing device is equipped with such a liquid-sealed vacuum pump, it can reliably degas the treated liquid even when the vacuum degree of the vacuum piping is in a lowered state.

[0011] Means of solving problems

[0012] In the first mode of operating the liquid-seal vacuum pump, liquid is discharged from a vacuum pipe connected to the liquid-seal vacuum pump; sealing liquid is pressurized and supplied to fill the liquid-seal vacuum pump with a specified amount, and the liquid-seal vacuum pump is driven until the pressure in the vacuum pipe is reduced to a specified pressure; and when the pressure in the vacuum pipe is reduced to a specified pressure, the supply of the pressurized sealing liquid to the liquid-seal vacuum pump is stopped, so that the sealing liquid circulates in a circulation flow path from the liquid-seal vacuum pump to maintain a state in which a specified amount of sealing liquid exists in the liquid-seal vacuum pump.

[0013] That is, in the first method of operating the liquid-sealed vacuum pump, even if there is liquid in the vacuum pipe when the liquid-sealed vacuum pump is started, the liquid is discharged. Therefore, it is possible to avoid the following situation: the liquid in the vacuum pipe fills the vacuum pump, causing the liquid-sealed vacuum pump to become undriveable.

[0014] Then, the sealing liquid is supplied under pressure to fill the liquid seal vacuum pump with a predetermined amount. Thus, the amount of sealing liquid in the liquid seal vacuum pump can be set to an amount suitable for driving the liquid seal vacuum pump. In addition, since the liquid seal vacuum pump is driven while the sealing liquid is supplied under pressure until the pressure of the vacuum piping is reduced to a predetermined pressure, the liquid seal vacuum pump can continue to operate without stopping, and the vacuum degree of the vacuum piping can reach a predetermined range.

[0015] When the pressure of the vacuum pipe is reduced to a predetermined pressure, the supply of sealing liquid to the liquid seal vacuum pump is stopped. Then, the sealing liquid is circulated in the circulation flow path from the liquid seal vacuum pump to maintain a predetermined amount of sealing liquid in the liquid seal vacuum pump. Thus, the operating state of the liquid seal vacuum pump can be maintained by using the sealing liquid circulating in the circulation flow path.

[0016] As described above, in the method of operating the liquid seal vacuum pump according to the first aspect, the liquid seal vacuum pump can be driven even when the vacuum degree of the vacuum pipe is in a state of being reduced.

[0017] In the second aspect, the liquid is discharged from the vacuum pipe by supplying pressurized gas to the vacuum pipe.

[0018] Since the pressurized gas is supplied to the vacuum pipe, the liquid can be easily discharged from the vacuum pipe.

[0019] In the third aspect, the liquid in the vacuum pipe is sent to the liquid seal vacuum pump by supplying pressurized gas to the vacuum pipe.

[0020] There is no need for a step of discharging the liquid in the vacuum pipe to a member other than the liquid seal vacuum pump, and the liquid can be easily discharged from the vacuum pipe.

[0021] In a fourth aspect, the pressurized sealing liquid is supplied to the liquid seal vacuum pump from the middle of the circulation flow path.

[0022] Since the circulation flow path is used as a part of the flow path for supplying the pressurized sealing liquid to the liquid seal vacuum pump, the sealing liquid can be easily supplied.

[0023] In the fifth aspect, the pressurized sealing liquid is introduced from the circulation flow path between the gas-liquid separation tank in the middle of the circulation flow path and the liquid seal vacuum pump.

[0024] Therefore, the pressurized sealing liquid can be supplied to the liquid seal vacuum pump without sending the pressurized sealing liquid to the gas-liquid separation tank.

[0025] In the sixth aspect, excess sealing liquid of the liquid seal vacuum pump is discharged through the circulation flow path.

[0026] Since the excess sealing liquid of the liquid seal vacuum pump can be circulated through the circulation flow path, the sealing liquid is not wasted compared to a structure in which the exhaust liquid of the liquid seal vacuum pump is directly discarded.

[0027] In the seventh embodiment of the membrane degassing device, there are: a liquid-seal vacuum pump; a membrane degassing component, the interior of the membrane degassing component is sucked through a vacuum pipe connected to the liquid-seal vacuum pump; a discharge unit, the discharge unit discharges liquid from the vacuum pipe; a circulation flow path, the circulation flow path is connected to the liquid-seal vacuum pump and circulates the sealing liquid; and a supply component, the supply component supplies the pressurized sealing liquid to the liquid-seal vacuum pump.

[0028] In this membrane degassing device, since there is a discharge unit, even if there is liquid in the vacuum piping when the liquid seal vacuum pump is started, the liquid will be discharged through the discharge unit, thereby making it possible to keep the vacuum degree of the vacuum piping at a higher state and the vacuum degree of the liquid seal vacuum pump at a higher state.

[0029] Furthermore, by supplying pressurized sealing liquid to the liquid seal vacuum pump through the supply member, the sealing liquid amount of the liquid seal vacuum pump can be set to an amount suitable for driving. By driving the liquid seal vacuum pump until the pressure of the vacuum piping reaches a specified pressure, the vacuum degree of the vacuum piping can be within a specified range.

[0030] When the pressure of the vacuum pipe reaches a predetermined pressure, the supply of sealing liquid to the liquid seal vacuum pump through the supply member is stopped, so that the sealing liquid circulates in the circulation flow path. That is, the operating state of the liquid seal vacuum pump can be maintained by the sealing liquid circulating in the circulation flow path, and degassing can be performed by the membrane degassing member. Even if the vacuum degree of the vacuum pipe is in a lowered state due to the stop of the membrane degassing device, the liquid seal vacuum pump can be reliably driven and degassing can be performed by the membrane degassing member.

[0031] In the eighth embodiment of the pure water production system, there are: a pure water production device, which produces pure water from raw water by removing impurities; and a membrane degassing device of the seventh embodiment, which constitutes a part of the pure water production device and removes gas from treated water in the pure water production process or the pure water produced.

[0032] In this pure water manufacturing system, since the membrane degassing device of the seventh embodiment is provided, even if the vacuum degree of the vacuum pipe is in a low state due to the stop of the membrane degassing device, the liquid seal vacuum pump can be reliably driven to perform degassing by the membrane degassing member. Furthermore, the membrane degassing member can remove gas from the treated water in the process of pure water manufacturing or the produced pure water.

[0033] In the ninth mode of the pure water manufacturing method, the pure water manufacturing method manufactures pure water through a pure water manufacturing system, and the pure water manufacturing system comprises: a pure water manufacturing device, which manufactures pure water from raw water after removing impurities; and a membrane degassing device, which constitutes a part of the pure water manufacturing device and removes gas from treated water in the process of manufacturing the pure water or the manufactured pure water; in the pure water manufacturing method, liquid is discharged from the vacuum pipe connecting the membrane degassing device and the liquid seal vacuum pump, and the sealing liquid is pressurized and supplied to fill the liquid seal vacuum pump with a specified amount, and the liquid seal vacuum pump is driven until the pressure of the vacuum pipe is reduced to a specified pressure. When the pressure of the vacuum pipe is reduced to a specified pressure, the supply of the pressurized sealing liquid to the liquid seal vacuum pump is stopped, so that the sealing liquid circulates from the liquid seal vacuum pump in the circulation flow path to maintain the state in which a specified amount of the sealing liquid exists in the liquid seal vacuum pump.

[0034] In the pure water production method, when the pure water production system produces pure water, gas can be removed from the treated water in the pure water production process or the produced pure water by the membrane degassing device. The inside of the membrane degassing device uses a liquid seal vacuum pump and suction through a vacuum pipe.

[0035] Even if there is liquid in the vacuum pipe when the liquid seal vacuum pump is started, the liquid is discharged, thereby preventing the vacuum pump from being filled with liquid in the vacuum pipe and becoming unable to drive the liquid seal vacuum pump.

[0036] Then, the sealing liquid is supplied under pressure to fill the liquid seal vacuum pump with a predetermined amount. Thus, the amount of sealing liquid in the liquid seal vacuum pump can be adjusted to an amount suitable for driving. In addition, since the liquid seal vacuum pump is driven while the sealing liquid is supplied under pressure until the pressure of the vacuum piping is reduced to a predetermined pressure, the liquid seal vacuum pump can continue to operate without stopping, and the vacuum degree of the vacuum piping can reach a predetermined range.

[0037] When the pressure of the vacuum pipe is reduced to a predetermined pressure, the supply of sealing liquid to the liquid seal vacuum pump is stopped. Then, the sealing liquid is circulated in the circulation flow path to maintain a predetermined amount of sealing liquid in the liquid seal vacuum pump. Thus, the operating state of the liquid seal vacuum pump can be maintained by using the sealing liquid circulating in the circulation flow path.

[0038] Thus, in the method for producing pure water according to the ninth aspect, even if the vacuum degree of the vacuum pipe is in a low state, the liquid seal vacuum pump can be driven, and the inside of the membrane degassing device can be sucked by operating the liquid seal vacuum pump.

[0039] Effects of the Invention

[0040] In the present disclosure, even when the vacuum degree of the vacuum pipe is in a state where it is reduced, the liquid seal vacuum pump can be driven. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a configuration diagram of a pure water production system including the membrane degassing device according to the first embodiment.

[0042] Figure 2 It is a structural diagram showing a membrane degassing device according to the first embodiment.

[0043] Figure 3 This is a structural diagram showing a state in which the membrane degassing device according to the first embodiment is being driven.

[0044] Figure 4 This is a structural diagram showing a state in which the membrane degassing device according to the first embodiment is being driven.

[0045] Figure 5This is a structural diagram showing a state in which the membrane degassing device according to the first embodiment is being driven.

[0046] Figure 6 This is a structural diagram showing a state in which the membrane degassing device according to the first embodiment is being driven. DETAILED DESCRIPTION

[0047] Hereinafter, a membrane degassing device according to a first embodiment, in which the interior of the membrane degassing device is sucked by a liquid seal vacuum pump, and a pure water production system including the membrane degassing device will be described with reference to the drawings.

[0048] The pure water production system 12 of the first embodiment includes a pure water production device 62, which produces pure water from raw water after removing impurities. The pure water production device 62 includes a pretreatment device 14, a primary pure water device 16, a pure water tank 18, a secondary pure water device 20, and a use point 22. In addition, a membrane degassing device 24 described later constitutes a part of the pure water production device 62.

[0049] Raw water is supplied to the pre-treatment device 14. Examples of the raw water include industrial water, tap water, groundwater, and river water.

[0050] The pretreatment device 14 performs turbidity removal and other treatments to obtain pretreated water from which part of the suspended matter and organic matter in the raw water have been removed. It should be noted that the pretreatment device 14 may be omitted depending on the quality of the raw water.

[0051] In the primary pure water device 16, an adsorbent such as activated carbon is used to adsorb particles remaining in the pre-treated water, and a membrane filtration device such as a reverse osmosis membrane device is used to remove inorganic ions, organic matter, particles, etc. In addition, the primary pure water device 16 may also be equipped with an ion exchange device or an ultraviolet irradiation device. The ion exchange device removes residual ions, etc. from the pre-treated water.

[0052] In the first embodiment, the primary pure water device 16 further uses a membrane degassing device 24 (see Figure 2 ) to remove dissolved gases such as dissolved oxygen from the pretreated water.

[0053] The positions of the above-mentioned various devices in the primary pure water device 16, that is, the order in the flow direction of the pre-treated water, are set in an order suitable for each treatment, and are not limited to a specific order.

[0054] In the primary pure water device 16, as described below, the pretreated water obtained by the pretreatment device 14 is purified as needed to remove impurities and obtain primary pure water.

[0055] The primary pure water obtained by the primary pure water device 16 is sent to the pure water tank 18. The pure water tank 18 is a container for temporarily storing the primary pure water obtained by the primary pure water device 16.

[0056] The primary pure water stored in the pure water tank 18 is sent to the secondary pure water device 20 .

[0057] The secondary pure water device 20 has, for example, an ultraviolet irradiation device. The ultraviolet irradiation device decomposes organic matter in the primary pure water or performs a killing treatment (sterilization) of live bacteria by irradiating the primary pure water with ultraviolet rays. The secondary pure water device 20 may also have a structure for removing impurity ions such as organic acids generated by the ultraviolet irradiation device through an ion exchange device. In addition, in the secondary pure water device 20, it may also be configured to remove gases, especially dissolved oxygen, from the primary pure water through a membrane degassing device, as in the primary pure water device 16.

[0058] Furthermore, the secondary pure water device 20 of the present embodiment includes a membrane filtration device (UF). The membrane filtration device (UF) removes particles from the primary pure water to obtain ultrapure water.

[0059] The ultrapure water obtained by the secondary pure water device 20 is sent to the use point 22 as a use location. Among the sent ultrapure water, the unused ultrapure water is circulated to the primary pure water device 16 or the pure water tank 18 as it is.

[0060] Figure 2 The membrane degassing device 24 used in the primary pure water device 16 is shown. The membrane degassing device 24 is provided in the primary pure water flow path through which the treated liquid, i.e., the primary pure water, flows, and the membrane degassing device 24 has a membrane degassing member 26. A hollow fiber membrane is arranged inside the membrane degassing member 26 as an example, and the hollow fiber membrane is used to divide the membrane into a gas phase and a liquid phase.

[0061] The liquid to be degassed, in the technology disclosed herein, is supplied to the liquid phase of the membrane degassing member 26. Then, the gas phase is depressurized by the liquid seal vacuum pump 28 described later, so that the gas in the primary pure water passes through the hollow fiber membrane and moves to the gas phase. Thus, the dissolved gas is removed from the primary pure water.

[0062] The membrane degassing member 26 is connected to the liquid seal vacuum pump 28 via a vacuum pipe 30. In addition, in the present embodiment, a gas supply pipe 32 is connected to the gas phase portion of the membrane degassing member 26. A gas supply valve 34 is provided on the gas supply pipe 32. By driving a gas supply pump (not shown) and opening the gas supply valve 34, a predetermined gas (e.g., N2 gas) can be supplied to the gas phase portion of the membrane degassing member 26.

[0063] The vacuum pipe 30 is provided with a gas pressure sensor 36 for detecting the internal pressure and a vacuum opening and closing valve 38 for opening and closing the vacuum pipe 30 .

[0064] The liquid seal vacuum pump 28 is connected to a circulation flow path 40. The circulation flow path 40 includes a gas-liquid separation tank 42 and a heat exchanger 44. The circulation flow path 40 is configured such that the sealing liquid circulates from the liquid seal vacuum pump 28 to the liquid seal vacuum pump 28 via the gas-liquid separation tank 42 and the heat exchanger 44 through a plurality of circulation pipes 46A, 46B, and 46C. By circulating the sealing liquid in this way, the sealing liquid discharged from the liquid seal vacuum pump 28 can be returned to the liquid seal vacuum pump 28 and reused.

[0065] The sealing liquid discharged from the liquid seal vacuum pump 28 may contain gas. The sealing liquid is separated into gas and liquid in the gas-liquid separation tank 42. Then, the sealing liquid from which the gas is removed in the gas-liquid separation tank 42 flows to the circulation pipe 46B and reaches the heat exchanger 44.

[0066] In the heat exchanger 44, the sealing liquid sent from the gas-liquid separation tank 42 to the liquid seal vacuum pump 28 exchanges heat with a heat medium (not shown) to keep the liquid temperature of the sealing liquid within a predetermined range. The sealing liquid whose temperature is adjusted by the heat exchanger 44 flows to the circulation pipe 46C.

[0067] The circulation pipe 46C is provided with a circulation on-off valve 48 and a flow meter 50. The sealing liquid can be circulated in the circulation flow path 40 by opening the circulation on-off valve 48.

[0068] The flow meter 50 detects the circulation amount of the sealing liquid in the circulation flow path 40 (the amount of the sealing liquid flowing per unit time). The data of the detected circulation amount is sent to a control device (not shown). The control device performs the following control: when the circulation amount of the sealing liquid is within a specified range, the liquid seal vacuum pump 28 is in a driving state, and when the circulation amount of the sealing liquid is not within the specified range, the liquid seal vacuum pump 28 is in a stopped state.

[0069] A sealing liquid supply pipe 52 and a sealing liquid discharge pipe 54 are connected to the gas-liquid separation tank 42. A sealing liquid supply valve 56 is provided on the sealing liquid supply pipe 52. A pressure pump (not shown) is also provided on the sealing liquid supply pipe 52. By driving the pressure pump and opening the sealing liquid supply valve 56, sealing liquid can be supplied to the gas-liquid separation tank 42. The sealing liquid overflowing from the gas-liquid separation tank 42 is discharged from the sealing liquid discharge pipe 54.

[0070] From the upstream side ( Figure 2 A branch pipe 58 is branched from the sealing liquid supply pipe 52. The branch pipe 58 merges with the circulation pipe 46C between the circulation on-off valve 48 and the combining flow meter 50.

[0071] The branch pipe 58 is provided with a branch opening and closing valve 60 . By closing the sealing liquid supply valve 56 and opening the branch opening and closing valve 60 , the pressurized sealing liquid can be sent to the liquid seal vacuum pump 28 without passing through the gas-liquid separation tank 42 .

[0072] Next, the function of this embodiment and the operation method of the liquid seal vacuum pump are described. Figure 3 to Figure 6 In each valve, the closed state is shown in blank, and the open state is shown in black. In addition, in each pipe, the state with fluid flowing is shown with thick lines, and the state without fluid flowing is shown with thin lines.

[0073] Here, the case where the membrane degassing device 24 is in a stopped state and then restarts operation is taken as an example. In this case, in the vacuum piping 30, there is sometimes condensed water (an example of liquid in the vacuum piping 30), for example, generated on the gas phase side of the membrane degassing device 24. Moreover, sometimes the vacuum degree of the vacuum piping 30 becomes low due to the condensed water, and the vacuum degree inside the liquid-sealed vacuum pump 28 may also become low. It should be noted that, as described above, the state in which the vacuum degree of the vacuum piping 30 is low and the vacuum degree inside the liquid-sealed vacuum pump 28 is also low may also occur in the following situations: for example, when a new membrane degassing device 24 starts to operate, or when a part of the elements in the existing membrane degassing device 24 are replaced (as an example, the liquid-sealed vacuum pump 28 is replaced), or when the membrane degassing device 24 is stopped urgently for some reason.

[0074] However, the liquid seal vacuum pump 28 is a pump that is driven when the internal vacuum degree is set to a predetermined value. Furthermore, when the vacuum degree of the liquid seal vacuum pump 28 is low, the sealing liquid cannot be circulated in the circulation flow path 40. In this case, since the flow meter 50 detects that the circulation amount of the sealing liquid in the circulation flow path 40 is not within the predetermined range, the control device (not shown) stops the driving of the liquid seal vacuum pump 28 even when the liquid seal vacuum pump 28 is being driven.

[0075] In this regard, in the operating method of the liquid-sealed vacuum pump disclosed in the present application, first, Figure 3As shown, condensed water is discharged from the vacuum pipe 30 without driving the liquid seal vacuum pump 28. In the membrane degassing device 24 of the present embodiment, since a gas supply pipe 32 is connected to the membrane degassing component 26, for example, the gas supply valve 34 and the vacuum opening and closing valve 38 are both in an open state, and the gas flows from the gas supply pipe 32 to the vacuum pipe 30 via the membrane degassing device 24. As a result, the liquid in the vacuum pipe 30 can be sent to the liquid seal vacuum pump 28 together with the supplied gas, so that the condensed water is discharged from the vacuum pipe 30. In this case, the pressure of the supply gas is sufficient as long as the condensed water in the vacuum pipe 30 can be discharged, so high pressure is not required. For example, the supply pressure is preferably 0.01MPa to 0.4MPa, and more preferably 0.04MPa to 1.5MPa. As the gas, for example, an inert gas such as nitrogen, argon, or air can be used.

[0076] Here, the sealing liquid discharged from the liquid seal vacuum pump 28 flows to the gas-liquid separation tank 42 via the circulation pipe 46A. In addition, the sealing liquid overflowing from the gas-liquid separation tank 42 is discharged from the sealing liquid discharge pipe 54 to the outside.

[0077] It should be noted that, in this stage, the circulation on-off valve 48 and the branch on-off valve 60 are in a closed state so that the sealing liquid does not flow from the circulation flow path 40 into the liquid seal vacuum pump 28. In addition, by setting the sealing liquid supply valve 56 to an open state, the pressurized sealing liquid can be supplied to the gas-liquid separation tank 42 in advance.

[0078] Then, if Figure 4 As shown, the sealing liquid supply valve 56 is in a closed state, and the branch opening and closing valve 60 is in an open state. Thus, the pressurized sealing liquid is sent to the liquid seal vacuum pump 28 via the branch pipe 58 and a part of the circulation pipe 46C (the part closer to the downstream side than the confluence of the branch pipe 58). Even in this state, the sealing liquid discharged from the liquid seal vacuum pump 28 flows to the gas-liquid separation tank 42 via the circulation pipe 46A. However, the circulation opening and closing valve 48 maintains a closed state, and the sealing liquid does not flow from the gas-liquid separation tank 42 to the liquid seal vacuum pump 28. The pressurized sealing liquid is preferably water. Raw water such as city water, industrial water, pure water, ultrapure water, distilled water, etc., and intermediate treatment water when making them can be used. From the perspective of keeping the membrane degassing device 24, especially the membrane degassing component 26 clean, the sealing water is more preferably pure water, ultrapure water, distilled water, etc., and intermediate treatment water when making them, and is further more preferably pure water and ultrapure water. The supply pressure of the sealing liquid is preferably 0.05 MPa to 0.4 MPa, more preferably 0.1 MPa to 0.2 MPa.

[0079] Then, if Figure 5As shown, the liquid seal vacuum pump 28 is driven by a control device (not shown) to suck gas from the vacuum pipe 30. As a result, the vacuum degree of the vacuum pipe 30 increases. In addition, the vacuum degree of the liquid seal vacuum pump 28 also increases. Since the pressure of the vacuum pipe 30 is detected by the gas pressure sensor 36, the liquid seal vacuum pump 28 is continuously driven until the vacuum degree of the vacuum pipe 30 reaches a predetermined range (decreases to a predetermined pressure).

[0080] When the vacuum degree of the vacuum pipe 30 reaches the specified range, Figure 6 As shown in FIG. 1 , the branch on-off valve 60 is closed, and the circulation on-off valve 48 is opened. Thus, the sealing liquid is sent to the liquid seal vacuum pump 28 through the sealing liquid circulating in the circulation flow path 40. That is, the liquid seal vacuum pump 28 is maintained in a state where a predetermined amount of sealing liquid exists, and the liquid seal vacuum pump 28 continues to operate.

[0081] As is apparent from the above description, in the present embodiment, even if liquid exists in the vacuum pipe 30 and the degree of vacuum in the vacuum pipe 30 is in a low state, the liquid seal vacuum pump 28 can be driven.

[0082] In this embodiment, the membrane degassing device 24 having the liquid seal vacuum pump 28 is incorporated in the primary pure water device 16. That is, during the process of producing primary pure water by the primary pure water device 16, the membrane degassing device 24 can be reliably driven from the stopped state to degas the treated water (pretreated water).

[0083] Thus, in the above content, an example is given in which the membrane degassing device 24 is assembled in the primary pure water device 16, but the membrane degassing device 24 may be assembled in the secondary pure water device 20 to replace the primary pure water device 16, or assembled in both the primary pure water device 16 and the secondary pure water device 20. In short, the membrane degassing device 24 constitutes a part of the pure water manufacturing device 62, and can be assembled in a part of the pure water manufacturing system 12.

[0084] In addition, the pure water manufacturing system involved in the technology disclosed in the present invention is not limited to a structure having a secondary pure water device 20, and may also be a structure that delivers pure water manufactured by a primary pure water device 16 to a use point 22. In the structure having a secondary pure water device 20, the pure water obtained by the secondary pure water device 20 has impurities further removed compared to the primary pure water obtained by the primary pure water device 16, and is sometimes referred to as ultrapure water. That is, the pure water manufacturing system involved in the technology disclosed in the present invention also includes an ultrapure water manufacturing system that can substantially manufacture ultrapure water.

[0085] In addition, in the pure water production system according to the technology disclosed in the present invention, depending on the type of raw water, the pre-treatment device 14 may be omitted. In other words, even a configuration without the pre-treatment device 14 is included in the pure water production system according to the technology disclosed in the present application.

[0086] In the above example, as an example of a discharge unit for discharging liquid from the vacuum pipe 30, a structure in which the liquid is sent to the liquid seal vacuum pump 28 by the gas pressure supplied from the gas supply pipe 32 is cited, but the structure of the discharge unit for discharging liquid from the vacuum pipe 30 is not limited thereto. For example, the following structure may be adopted, in which the liquid in the vacuum pipe 30 is discharged to the liquid seal vacuum pump 28 due to gravity by locating the liquid seal vacuum pump 28 at the lowest part in the vertical direction of the vacuum pipe 30. By providing a structure in which pressurized gas is supplied to the vacuum pipe 30 as in the above embodiment, the liquid in the vacuum pipe 30 can be discharged more reliably and in a shorter time.

[0087] In addition, the discharge destination of the liquid in the vacuum piping 30 is not limited to the liquid-sealed vacuum pump 28. For example, it may be configured as follows: a discharge piping with an open front end is branched from the lowest part of the vacuum piping 30 in the vertical direction, and an on-off valve is provided to open and close the discharge piping. In this structure, when discharging liquid from the vacuum piping 30, it is sufficient to open the on-off valve. In the first embodiment of the present disclosure, since the liquid in the vacuum piping 30 moves toward the liquid-sealed vacuum pump 28, the branch piping and on-off valve branching from the vacuum piping 30 described above are not required. In addition, there is no need to open and close the on-off valve, and the liquid can be easily discharged from the vacuum piping 30.

[0088] In addition, in the above example, as an example of a supply member for supplying pressurized sealing liquid to the liquid seal vacuum pump 28, the following structure is listed: the branch pipe 58 is branched from the sealing liquid supply pipe 52 and merged with the circulation flow path 40 (circulation pipe 46C). The branch pipe 58 can also be provided independently of the sealing liquid supply pipe 52 or the circulation flow path 40. In the structure in which a pipe is provided that branches from the sealing liquid supply pipe 52 and merges with the circulation flow path 40 as the above-mentioned branch pipe 58, since the sealing liquid supply pipe 52 and the circulation flow path 40 also serve as a part of the flow path for conveying pressurized sealing liquid to the liquid seal vacuum pump 28, the structure can be simplified.

[0089] The branch pipe 58 merges with the circulation flow path 40 at a position downstream of the gas-liquid separation tank 42. Therefore, the pressurized sealing liquid can be supplied to the liquid seal vacuum pump 28 without being sent to the gas-liquid separation tank 42.

[0090] In the above content, the sealing liquid discharged during the process of supplying the pressurized sealing liquid to the liquid seal vacuum pump 28 is discharged to the gas-liquid separation tank 42 through the circulation flow path 40. The sealing liquid discharged from the liquid seal vacuum pump 28 flows through the circulation flow path 40 and returns to the liquid seal vacuum pump 28 again, so that no waste of sealing liquid is generated.

[0091] The entire contents disclosed in Japanese Patent Application No. 2021-164278 filed on October 5, 2021 are incorporated into this specification by reference.

[0092] All documents, patent applications and technical standards described in this specification are incorporated into this specification by reference, the same as if the individual documents, patent applications and technical standards were specifically and individually described.

Claims

1. A method for operating a liquid seal vacuum pump, wherein: Discharge the liquid from the vacuum pipe connected to the liquid seal vacuum pump; Supplying the sealing liquid under pressure so that the liquid-sealed vacuum pump is filled with a predetermined amount, and driving the liquid-sealed vacuum pump until the pressure of the vacuum pipe is reduced to a predetermined pressure; and When the pressure of the vacuum pipe decreases to a specified pressure, the supply of the pressurized sealing liquid to the liquid seal vacuum pump is stopped, so that the sealing liquid circulates from the liquid seal vacuum pump to the circulation flow path, and a specified amount of the sealing liquid is maintained in the liquid seal vacuum pump.

2. The method for operating a liquid seal vacuum pump according to claim 1, wherein: The liquid is discharged from the vacuum pipe by supplying pressurized gas to the vacuum pipe.

3. The method for operating a liquid seal vacuum pump according to claim 2, wherein: By supplying pressurized gas to the vacuum pipe, the liquid in the vacuum pipe is sent to the liquid seal vacuum pump.

4. The method for operating a liquid seal vacuum pump according to any one of claims 1 to 3, wherein: The pressurized sealing liquid is supplied to the liquid seal vacuum pump from midway in the circulation flow path.

5. The method for operating a liquid seal vacuum pump according to claim 4, wherein: The pressurized sealing liquid is sent to the circulation flow path between the gas-liquid separation tank in the circulation flow path and the liquid seal vacuum pump.

6. The method for operating a liquid seal vacuum pump according to any one of claims 1 to 3 and 5, wherein: Excess sealing liquid of the liquid seal vacuum pump is discharged through the circulation flow path.

7. A membrane degassing device, wherein: have: Liquid seal vacuum pump; a membrane degassing member, the interior of which is sucked through a vacuum pipe connected to the liquid seal vacuum pump; a discharge unit configured to discharge liquid from the vacuum pipe; a circulation flow path connected to the liquid seal vacuum pump and circulates the sealing liquid, the circulation flow path having a gas-liquid separation tank, a sealing liquid supply pipe and a sealing liquid discharge pipe connected to the gas-liquid separation tank, and a sealing liquid supply valve and a pressure pump provided on the sealing liquid supply pipe; and A supply member supplies the pressurized sealing liquid to the liquid seal vacuum pump.

8. A pure water production system, wherein: have: A pure water production device, wherein the pure water production device produces pure water from raw water after removing impurities; as well as The membrane degassing device according to claim 7 constitutes a part of the pure water production device and removes gas from the treated water in the process of producing the pure water or the produced pure water.

9. A method for producing pure water, wherein: The pure water production method produces pure water by a pure water production system. The pure water production system comprises: A pure water production device for producing pure water from raw water by removing impurities; and a membrane degassing device which constitutes a part of the pure water manufacturing device and removes gas from treated water in the pure water manufacturing process or the manufactured pure water; In the pure water production method, discharging liquid from a vacuum pipe connecting the membrane degasser and a liquid seal vacuum pump; Supplying the sealing liquid under pressure so that the liquid-sealed vacuum pump is filled with a predetermined amount, and driving the liquid-sealed vacuum pump until the pressure of the vacuum pipe is reduced to a predetermined pressure; and When the pressure of the vacuum pipe decreases to a specified pressure, the supply of the pressurized sealing liquid to the liquid seal vacuum pump is stopped, so that the sealing liquid circulates from the liquid seal vacuum pump to the circulation flow path, and a specified amount of the sealing liquid is maintained in the liquid seal vacuum pump.

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