Ultrapure water production apparatus

Abstract

To provide an ultrapure water production apparatus in which an operation of a subsystem can be continued even if a sequence circuit for controlling a pump breaks down.SOLUTION: An ultrapure water production apparatus includes: a sub-tank 11; a water treatment device that treats water from the sub-tank 11 to produce ultrapure water; a sub-pump 12 that delivers water from the sub-tank 11 to the water treatment device; a water supply pipe 21 for supplying the ultrapure water treated by the water treatment device to a use point 22; a return pipe 23 for supplying unused ultrapure water not used at the use point 22 to the sub-tank as return water; a sub-pump relay 31 for switching between supplying and not supplying power to the sub-pump 12; a sequence circuit that provides a contact closure signal to the sub-pump relay 31 during operation of the ultrapure water production apparatus; and a spare relay 32 that is provided in parallel with the sub-pump relay 31. The spare relay 32 has its contacts closed while the water treatment device is in a water-passing state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ultrapure water production system, and more particularly to an improvement in a switch circuit for a pump or the like of an ultrapure water production system. [Background technology]

[0002] Ultrapure water used in semiconductor manufacturing processes and the like is produced by treating raw water (industrial water, city water, well water, etc.) in an ultrapure water production system consisting of a pretreatment system 1, a primary pure water system 3, and a subsystem 10, as shown in Figure 2.

[0003] In the pretreatment system 1, which is composed of a coagulation, pressure flotation (sedimentation), filtration device, etc., suspended solids and colloidal substances in the raw water are removed. The treated water from the pretreatment system is supplied to the primary pure water system 3 via the primary pure water raw water tank 2.

[0004] The primary pure water system 3 is equipped with a reverse osmosis (RO) membrane separation device, a degassing device, and an ion exchange device (mixed bed type, 2-bed 3-tower type, or 4-bed 5-tower type) and removes ions and organic components from the raw water.

[0005] The primary pure water from the primary pure water system 3 is delivered to the sub-tank 11 via a pipe 4. A valve 4a is provided in the middle of the pipe 4. A pipe 5 branches off from the pipe 4 upstream of the valve 4a, and a valve 5a is provided on the pipe 5. The amount of primary pure water supplied to the sub-tank 11 is adjusted by adjusting the opening of the valves 4a and 5a with a valve controller (not shown).

[0006] The primary pure water in the sub-tank 11 is passed by a sub-pump 12 successively through water treatment devices, such as a cooling heat exchanger 13, a degassing membrane device 14, and a low-pressure ultraviolet (UV) oxidation device 16. The pressure in the secondary side (gas chamber) of the gas separation membrane of the degassing membrane device 14 is reduced by a vacuum pump 15.

[0007] The water flowing out from the low-pressure ultraviolet oxidation device 16 is further pressurized by a booster pump 17 and passed through a deionization device 18 and a UF device 19 in that order, and the obtained ultrapure water is sent to a use point 22 via a pipe 21. Note that the booster pump 17 may also be placed between the deionization device 18 and the UF device 19.

[0008] In the low-pressure ultraviolet oxidation device 16, UV rays having a wavelength of about 185 nm, which is usually used in ultrapure water production devices, are irradiated to decompose TOC in the primary pure water into organic acids. These organic acids are removed together with other ions in the deionization device 18. Note that an electric deionization device or a mixed-bed ion exchange device is used as the deionization device 18.

[0009] The UF (ultrafiltration membrane) device 19 is for removing fine particles in the water. The water that does not pass through the UF membrane (concentrated water) is returned to the primary pure water raw water tank 2 through a pipe 20.

[0010] A flow meter 11a is provided in the piping 11 that conveys water from the UF device 10 to the point of use 12, and the sub-pump 12 and booster pump 17 are controlled by an inverter-controlled pump controller (not shown) so that the flow rate detected by the flow meter 11a becomes a predetermined value.

[0011] Unused ultrapure water that has not been used at the point of use 22 is returned to the subtank 11 via the return pipe 23 and the flow rate control valve 25. The flow rate control valve 25 is controlled by a valve controller (not shown) so that the pressure in the return pipe 13 detected by the pressure sensor 23a becomes a predetermined value.

[0012] The operation management device of the subsystem is equipped with a sequence circuit (PLC: Programmable Logic Controller) that starts and stops the sub-pump 12 and the booster pump 17. When an operation start signal is sent from the operation management device to the sequence circuit by an operator's switch-on operation, the sub-pump relay interposed between the sub-pump 12 and the power supply, and the booster pump relay interposed between the booster pump 17 and the power supply are both closed. The sequence circuit constantly sends a contact closure signal (pump operation command) to the sub-pump relay and the booster pump relay while the subsystem is operating.

[0013] Similarly, the control circuit for the vacuum pump 15 also includes a vacuum pump relay to which a contact closure signal is given from the sequence circuit while the subsystem is in operation. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] JP 2020-37088 A Summary of the Invention [Problem to be solved by the invention]

[0015] In the above-mentioned conventional ultrapure water production system, if the sequence circuit fails during operation of the subsystem and a contact closure signal is no longer applied to the pump relay, each pump will stop and operation of the subsystem will cease.

[0016] An object of the present invention is to provide an ultrapure water production system in which the operation of the subsystems continues even if a sequence circuit for controlling a pump breaks down. [Means for solving the problem]

[0017] [1] A sub-tank for storing primary pure water from the primary pure water system and water not used at the point of use; a water treatment device for treating the water from the sub-tank to produce ultrapure water; a sub-pump for supplying water from the sub-tank to the water treatment device; a water supply pipe for supplying the ultrapure water treated by the water treatment device to a use point; a return pipe for supplying unused ultrapure water not used at the use point to the sub-tank as return water; a sub-pump relay for switching between supplying and not supplying power to the sub-pump; a sequence circuit for supplying a contact closure signal to the sub-pump relay during operation of the ultrapure water production apparatus; a spare relay provided in parallel with the sub-pump relay; Equipped with The ultrapure water producing apparatus is characterized in that the contact of the standby relay is in a closed state while the water treatment apparatus is in a water-passing state.

[0018] [2] The water treatment device has a booster pump for boosting the pressure of water flowing through the water treatment device, the ultrapure water production apparatus includes a booster pump relay that switches between on and off of power supply to the booster pump, and a backup booster pump relay that is provided in parallel with the booster pump relay; the sequence circuit applies a contact closure signal to the booster pump relay during an operation period of the ultrapure water production apparatus; The ultrapure water production system according to [1], wherein the backup relay for the booster pump has its contacts in a closed state while the water treatment system is in a water-passing state.

[0019] [3] The water treatment device has a degassing membrane device connected to a vacuum pump, the ultrapure water production apparatus includes a vacuum pump relay that switches between supplying power to the vacuum pump and not supplying power to the vacuum pump, and a vacuum pump standby relay that is provided in parallel with the vacuum pump relay; the sequence circuit applies a contact closure signal to the vacuum pump relay during an operation period of the ultrapure water production apparatus; The ultrapure water production system according to [1] or [2], wherein the vacuum pump standby relay has a contact closed state while the water treatment system is in a water flow state. Effect of the Invention

[0020] According to the present invention, even if the sequence circuit fails and a contact closure signal cannot be applied to the pump relay, the standby relay continues to supply power to the pump, allowing the subsystem to continue operating. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 illustrates a pump control circuit according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a configuration diagram of an ultrapure water production apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram of a pump control circuit according to this embodiment. The pump control circuit switches between supplying power to a pump installed in a water treatment device, and is provided, for example, between a power source 40 and a sub-pump 12 of an ultrapure water production device shown in Fig. 2, and switches between supplying power to the sub-pump 12 and not supplying power.

[0023] The pump control circuit has a sub-pump relay 31 and a standby relay 32. The sub-pump relay 31 and the standby relay 32 are so-called relay switches each having a contact and a coil for opening and closing the contact, and the contact closes when the coil is energized and opens when the energization to the coil is cut off.

[0024] The subordinate pump relay 31 is connected between the power source 40 and the subordinate pump 12, and switches between supplying power from the power source 40 to the subordinate pump 12 by opening and closing. The standby relay 32 is connected in parallel with the subordinate pump relay 31 between the power source 40 and the subordinate pump 12, and switches between supplying power from the power source 40 to the subordinate pump 12 by opening and closing.

[0025] The operation management device of the subsystem 10 has a sequence circuit (PLC: Programmable Logic Controller) that starts and stops the subordinate pump 12. The sequence circuit switches the subordinate pump relay 31 between open and closed states.

[0026] When an operator turns on the switch and an operation start signal is sent from the operation management device to the sequence circuit, the sequence circuit sends a contact closure signal (pump operation command) to the sub-pump relay 31. The contact closure signal energizes the coil of the sub-pump relay 31, closing the contacts and operating the sub-pump 12.

[0027] The sequence circuit constantly provides a contact closure signal to the sub-pump relay 31 while the subsystem is operating, and the sub-pump 12 continues to operate.

[0028] When the sub-pump 12 operates and the water treatment device downstream of the sub-tank 11 is in a water-passing state, a contact close signal is sent to the standby relay 32. For example, the operation management device of the subsystem 10 determines that the water-passing state has been reached when the "water passing" step is reached in the startup operation program of the sequence circuit, and sends a contact close signal to the standby relay 32. The contact close signal energizes the coil of the standby relay 32, closing the contacts.

[0029] When an operator turns off the switch and an operation stop signal is sent from the operation management device to the sequence circuit, the sequence circuit stops outputting a contact closure signal to the sub-pump relay 31. This cuts off the current to the coil of the sub-pump relay 31, and the contact opens.

[0030] Furthermore, when the operator turns off the switch, the operation management device stops outputting a contact closure signal to the standby relay 32. This cuts off the current to the coil of the standby relay 32, and the contacts open. When the contacts of the sub-pump relay 31 and the standby relay 32 open, the power supply to the sub-pump 12 is cut off, and the sub-pump 12 stops.

[0031] If the sequence circuit fails while the subsystem is operating, the sequence circuit stops outputting a contact closure signal to the sub-pump relay 31, causing the current to flow through the coil of the sub-pump relay 31 to open, thereby cutting off the power to the contacts.

[0032] In this embodiment, even if the sequence circuit fails, the output of the contact closure signal to the standby relay 32 continues, so the contact of the standby relay 32 is closed. Therefore, power supply to the subordinate pump 12 continues, and the subordinate pump 12 continues to operate, allowing the subsystem 10 to continue operating.

[0033] According to this embodiment, costs can be reduced compared to the case where the risk of failure of the sequence circuit is countered by duplication of the sequence circuit.

[0034] In the above embodiment, the pump control circuit having the sub-pump relay 31 and the spare relay 32 is disposed between the power source 40 and the sub-pump 12, but a pump control circuit of a similar configuration may be disposed between the power source and the booster pump 17. For example, a pump control circuit having a booster pump relay and a spare relay for the booster pump disposed in parallel is disposed between the power source and the booster pump 17. A contact closure signal is applied to the booster pump relay from the sequence circuit. Similar to the spare relay 32, the contact closure signal is applied to the booster pump spare relay while the water treatment device is in a water flowing state, regardless of the state of the sequence circuit.

[0035] Also, the pump control circuit may be disposed between the power source and the vacuum pump 15. For example, a pump control circuit having a vacuum pump relay and a vacuum pump spare relay disposed in parallel is disposed between the power source and the vacuum pump 15. A contact closing signal is applied to the vacuum pump relay from the sequence circuit. Similar to the spare relay 32, the vacuum pump spare relay is applied with a contact closing signal while the water treatment device is in a water flowing state, regardless of the state of the sequence circuit.

[0036] The above-described subsystem 10 is merely an example, and some of the devices may be omitted, some of the devices may be replaced with other devices of the same type, or devices having other functions may be installed. [Explanation of symbols]

[0037] 1 Pretreatment System 3 Primary Pure Water System 10 Subsystems 11 Subtank 12 Sub-pump 13 Heat exchanger 14 Deaeration membrane device 16 Low-pressure UV oxidation equipment 17 Booster Pump 18 Deionizer 19 UF equipment 23a Pressure Sensor 25 Flow Control Valve 31 Sub-pump relay 32 Spare Relay 40 Power supply

Claims

1. a sub-tank for storing primary pure water from the primary pure water device and water not used at the point of use; a water treatment device for treating the water from the sub-tank to produce ultrapure water; a sub-pump for supplying water from the sub-tank to the water treatment device; a water supply pipe for supplying the ultrapure water treated by the water treatment device to a use point; a return pipe for supplying unused ultrapure water not used at the use point to the sub-tank as return water; a sub-pump relay for switching between supplying and not supplying power to the sub-pump; a sequence circuit for supplying a contact closure signal to the sub-pump relay during operation of the ultrapure water production apparatus; a spare relay provided in parallel with the sub-pump relay; Equipped with The ultrapure water producing apparatus is characterized in that the contact of the standby relay is in a closed state while the water treatment apparatus is in a water-passing state.

2. The water treatment device has a booster pump for increasing the pressure of water flowing through the water treatment device, the ultrapure water production apparatus includes a booster pump relay that switches between on and off of power supply to the booster pump, and a backup booster pump relay that is provided in parallel with the booster pump relay; the sequence circuit applies a contact closure signal to the booster pump relay during an operation period of the ultrapure water production apparatus; 2. The ultrapure water producing system according to claim 1, wherein the booster pump standby relay has a contact closed state while the water treatment system is in a water-passing state.

3. The water treatment device has a degassing membrane device connected to a vacuum pump, the ultrapure water production apparatus includes a vacuum pump relay that switches between supplying power to the vacuum pump and not supplying power to the vacuum pump, and a vacuum pump standby relay that is provided in parallel with the vacuum pump relay; the sequence circuit applies a contact closure signal to the vacuum pump relay during an operation period of the ultrapure water production apparatus; 3. The ultrapure water producing system according to claim 1, wherein said vacuum pump standby relay has a contact closed state while said water treatment system is in a water-passing state.

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