Boiler water treatment device and treatment method

Abstract

A boiler water treatment device and treatment method are provided that prevent carbon dioxide in the atmosphere from mixing with water in a tank. [Solution] A water supply tank 7 is provided which receives pure water from a pure water tank 2 and condensate from a condensate tank 4, and nitrogen gas is supplied from a nitrogen gas source 8 to the pure water tank 2, the condensate tank 4, and the water supply tank 7. Water from the water supply tank 7 is supplied to a boiler, and is passed through an OH-type anion exchange resin tower 17 or 18 by switching using valves 15a, 16a. Treated water from the OH-type anion exchange resin tower 17 or 18 is returned to the water supply tank 7.

Description

[Technical field]

[0001] The present invention relates to a boiler water treatment device and a treatment method for treating boiler feed water supplied to a steam boiler. [Background technology]

[0002] In boiler facilities, pure water is produced from industrial water and other sources through pretreatment (such as coagulation and solid-liquid separation and desalination), the pure water produced is stored in a feedwater tank, and is supplied from the feedwater tank to the boiler as boiler feedwater. In the boiler, steam is generated by heating this boiler feedwater.

[0003] In addition, the condensate produced by condensing the steam from the boiler is returned to the feedwater tank via a condensate return line and is reused as boiler feedwater.

[0004] Conventionally, the entrainment of silica, chloride ions, sulfate ions, etc. into steam has been strictly controlled to prevent scale and corrosion in steam turbines. To check the state of inhibition of this scale and corrosion, the silica concentration of steam and acid electrical conductivity (CC: Cation Conductivity, the electrical conductivity of water after passing through a cation resin) are defined as the quality of steam (for example, JIS B8223:2021) and are managed at each power plant.

[0005] Ions such as silica ions, chloride ions, and sulfate ions can be removed by treatment with ion exchange resins, but colloidal silica and organic substances have low ionicity and cannot be sufficiently removed by ion exchange resins.

[0006] For this reason, in the past, when raw water for pure water production was pretreated, coagulation and sedimentation was performed to remove colloidal silica and organic matter, but when heavy rains occurred, the quality of the raw water itself fluctuated greatly, the colloidal silica concentration in the boiler feed water increased, and there was a risk that the silica concentration in the boiler water would exceed the water quality control standard value. As a countermeasure, the amount of boiler blowdown water could be increased, but this would increase heat loss.

[0007] In addition, the organic matter concentration in raw water may increase due to eutrophication in the raw water source, or the turbidity concentration in raw water may increase due to heavy rain. Organic matter and turbidity components cannot be sufficiently removed by ion exchange devices. Organic matter is thermally decomposed in the boiler to generate organic acids such as formic acid and acetic acid, which causes the acid electrical conductivity of the feed water and main steam to increase, often making it impossible to meet the management standards.

[0008] In industrial boilers, when process condensate is stored in a tank open to the atmosphere and then collected in a condenser or feedwater tank, or when makeup water is received in a feedwater tank open to the atmosphere, carbon dioxide from the atmosphere dissolves in the condensate. This carbon dioxide cannot be sufficiently removed by a deaerator, so the acid conductivity of the feedwater or steam may not be maintained within the control value.

[0009] Conventionally, condensate has been treated with mixed bed ion exchange resin, but this is intended to deal with issues such as seawater leakage from condenser tubes, and does not take into account the contamination of carbon dioxide in the atmospheric open parts of the feedwater system or the recovery of process condensate.

[0010] Colloidal silica and organic matter can be removed by treating the ion-exchanged water supplied to the water supply tank with an RO membrane or ultrafiltration membrane. However, this method cannot remove organic matter from the process condensate.

[0011] Patent Document 1 describes a boiler water treatment device and treatment method that can stably supply high-quality boiler feedwater to a boiler when the boiler facility is first started operating or when the operation is restarted after being shut down.

[0012] The boiler water treatment method and apparatus of Patent Document 1 treats raw water in a pretreatment device to produce pure water, and supplies the pure water from the pretreatment device to a boiler via a pure water supply line.The boiler water treatment method and apparatus extracts a portion of the pure water from the pure water supply line from an extraction section and treats it to remove impurities using an impurity removal means, and returns the treated water to the extraction section or the pure water supply line upstream of it, and a switching means switches between extracting at least a portion of the pure water from the pure water supply line to the impurity removal line or supplying the entire amount to the boiler.

[0013] Patent Document 1 is primarily intended to prevent the intrusion of carbon dioxide when the boiler is started up, and is not intended to prevent the intrusion of impurities while the boiler is in operation. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] JP 2020-67209 A Summary of the Invention [Problem to be solved by the invention]

[0015] Colloidal silica and organic matter entrained in the make-up water, and organic acids in the process drain are thermally decomposed in the boiler and converted into low molecular weight ionic silica and organic acids (formic acid, acetic acid, etc.). These are volatile and are contained in the condensate and collected in the feedwater tank.

[0016] Low molecular weight ionic silica and organic acids can be removed using a condensate demineralizer consisting of anion exchange resin and cation exchange resin. However, amines and ammonia, which are used to adjust the pH level, are dissolved in the condensate, and if the condensate is treated using a condensate demineralizer consisting of anion exchange resin and cation exchange resin, the useful amines and ammonia are also removed.

[0017] Furthermore, when the condensate is treated in a condensate demineralizer made of anion exchange resin and cation exchange resin in order to remove low molecular weight ionic silica and organic acids, if the amount of carbon dioxide mixed in the condensate is large, the anion load becomes large.

[0018] Furthermore, if the condensate is treated only with anion exchange resin, only the anions of salts such as NaCl are removed, which may make it impossible to detect impurities such as Na, Ca, Mg, etc., from seawater, etc., using an acid conductivity measuring device.

[0019] An object of the present invention is to provide a boiler water treatment device and treatment method that prevent carbon dioxide from the atmosphere from mixing with the water in a tank.

[0020] One aspect of the present invention aims to provide a boiler water treatment device and treatment method that can sufficiently remove low-molecular-weight ionic silica and organic acids, and recover condensate without removing amines, ammonia, etc. in the condensate. [Means for solving the problem]

[0021] The gist of the present invention is as follows.

[0022] [1] A boiler water treatment device having a pure water tank for receiving pure water and a condensate tank for receiving condensate, 1. A boiler water treatment device comprising: a nitrogen gas supply means for supplying nitrogen gas to at least one of the tanks.

[0023] [2] A pure water tank for receiving pure water, a condensate tank for receiving condensate, and a water supply tank for receiving the pure water from the pure water tank and the condensate from the condensate tank, The boiler water treatment device further comprises a nitrogen gas supplying means for supplying nitrogen gas to at least one of the pure water tank, the condensate tank and the feed water tank.

[0024] [3] The boiler water treatment device of [1] or [2], wherein the nitrogen gas supply means supplies nitrogen gas to at least the condensate tank.

[0025] [4] The boiler water treatment device according to [2], wherein the nitrogen gas supply means supplies nitrogen gas to the pure water tank, the condensate tank, and the feedwater tank, respectively.

[0026] [5] The boiler water treatment device of [2], further comprising an OH-type anion exchange resin tower through which water from the water supply tank is passed, and the treated water that has passed through the OH-type anion exchange resin tower is returned to the water supply tank.

[0027] [6] A boiler water treatment device according to [1], further comprising an OH-type anion exchange resin tower through which a portion of the combined water obtained by combining the pure water from the pure water tank and the condensate from the condensate tank is passed, and the treated water that has passed through the OH-type anion exchange resin tower is combined with the remainder of the combined water and supplied to the boiler.

[0028] [7] The boiler water treatment device according to [5] or [6], comprising an acid conductivity meter for measuring the acid conductivity of the treated water from the OH type anion exchange resin tower.

[0029] [8] The boiler water treatment device according to any one of [5] to [7], further comprising a sodium concentration meter for measuring the sodium concentration of the treated water from the OH type anion exchange resin tower.

[0030] [9] A boiler water treatment method using the boiler water treatment device of [7], wherein when the acid electrical conductivity detected by the acid electrical conductivity meter reaches or exceeds a predetermined value, the OH type anion exchange resin tower is replaced or the water is switched to passing through an OH type anion exchange resin tower installed in parallel. Effect of the Invention

[0031] In the present invention, by creating a nitrogen atmosphere inside tanks such as a condensate tank, a pure water tank, and a water supply tank, it is possible to prevent carbon dioxide from the atmosphere from mixing with the water in the tank.

[0032] Incidentally, up until now, there have not been many cases where nitrogen pressure has been applied to tanks such as feedwater tanks in medium and high pressure boilers (especially boiler steam system systems with steam turbines in the system). Nitrogen pressure is sometimes applied to soft water feedwater boilers to prevent corrosion caused by oxygen contamination, but it is not generally used to prevent, detect, or remove impurities from pure water feedwater.

[0033] In one embodiment of the present invention, low molecular weight ionic silica and organic acids are removed from the boiler feed water by treating the condensate and feed water with an OH-type anion exchange resin. In addition, since this OH-type anion exchange resin does not remove amines and ammonia in the water, the amines and ammonia used for pH adjustment in the condensate are supplied to the boiler water and reused.

[0034] In one aspect of the present invention, when Na ion-containing impurities such as seawater, industrial water, cooling water, etc. are mixed into the condensate or feed water, Na ions etc. remain in the treated water treated with the OH-type anion exchange resin. Therefore, the Na concentration of the treated water from the OH-type anion exchange resin is measured with a Na concentration meter, and the mixing of Na ion-containing impurities such as seawater, industrial water, cooling water, etc. can be detected from the measured value.

[0035] In one aspect of the present invention, by detecting the acid electrical conductivity of treated water from an OH-type anion exchange resin, when the acid electrical conductivity reaches or exceeds a predetermined value, it is possible to appropriately replace the OH-type anion exchange resin tower or switch the water supply to an OH-type anion exchange resin tower installed in parallel. [Brief description of the drawings]

[0036] [Figure 1] 1 is a configuration diagram of a boiler water treatment device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, an embodiment will be described with reference to FIG.

[0038] In the boiler water treatment system of this embodiment, pure water from a pure water production system (not shown) is introduced into a pure water tank 2 through a pipe 1, and condensate such as turbine condensate or process condensate is introduced into a condensate tank 4 through a pipe 3. The pure water from the pure water tank 2 and the condensate from the condensate tank 4 are introduced into a feed water tank 7 through pipes 5 and 6, respectively. Although not shown in the figure, the pipes 1, 3, 5, and 6 are each provided with a valve.

[0039] Each of the tanks 2, 4, 7 is a sealed tank with a relief valve (not shown) provided at the top, and nitrogen gas can be supplied to the space above the water surface from a nitrogen gas source 8 via a pipe 8a. By supplying nitrogen gas, the space above the water surface in each of the tanks 2, 4, 7 becomes a nitrogen atmosphere with a pressure equal to or higher than atmospheric pressure and equal to or lower than the opening pressure of the relief valve.

[0040] The water in the water tank 7 is sent to a pipe 11 by a pipe 9 and a water supply pump 10. The pipe 11 branches into pipes 12, 13, and 14, and the pipes 12, 13, and 14 are provided with valves 12a, 13a, and 14a, respectively.

[0041] Pipe 12 is provided to supply water to the boiler. Pipe 13 is a drainage pipe to the outside of the system.

[0042] The secondary side (downstream side) of the valve 14a of the pipe 14 branches into pipes 15 and 16, and each of the pipes 15 and 16 is connected to the top of an OH type anion exchange resin tower 17 and 18. The pipes 15 and 16 are provided with valves 15a and 16a.

[0043] One end of pipes 19, 20 is connected to the treated water outlet at the lower end of each of the OH type anion exchange resin towers 17, 18. The other end of the pipes 19, 20 is connected to one end of a pipe 21.

[0044] The other end of the pipe 21 is connected to the water supply tank 7. A sodium concentration meter 22 is provided in the pipe 21, and the valves 13a and 14a are opened and closed in response to the sodium concentration detected by the sodium concentration meter 22.

[0045] Furthermore, an acid electrical conductivity meter (CC meter) 23 is provided in the pipe 21, and the valves 15a and 16a are opened and closed in response to the acid electrical conductivity detected by this acid electrical conductivity meter 23.

[0046] The nitrogen gas source 8 may be a nitrogen cylinder, a nitrogen generator (PSA (Pressure Swing Adsorption)), or the like, as long as it can supply nitrogen-rich gas with a lower concentration of oxygen and carbon dioxide than the atmosphere. The nitrogen gas source 8 is preferably one with high nitrogen purity.

[0047] In the boiler water treatment device configured as described above, whether the boiler is operating, before starting operation, or is out of operation, the water in the feed water tank 7 is passed through the pipe 9, the pump 10, and the pipes 11 and 14, and then through the pipe 15 or 16 to the OH type anion exchange resin tower 17 or 18, and the treated water from the OH type anion exchange resin tower 17 or 18 is circulated through the pipe 19 or 20 and the pipe 21 to the feed water tank 7. As a result, anion components such as low molecular weight ionic silica and organic acids in the feed water are removed in the OH type anion exchange resin tower 17 or 18.

[0048] When the boiler is operating, the valve 12a is open. When the boiler is stopped, the valve 12a is closed.

[0049] During boiler operation, when the detection value of the Na concentration meter 22 is lower than a predetermined value, the valve 13a is closed, the valve 14a is opened, one of the valves 15a and 16a is opened and the other is closed, and water is passed through one of the OH type anion exchange resin towers 17 or 18. In this case, water is first passed through one of the OH type anion exchange resin towers (for example, the OH type anion exchange resin tower 17). Then, the acid conductivity of the treated water is monitored by the acid conductivity meter 23, and this state is maintained as long as the acid conductivity is equal to or lower than a predetermined value.

[0050] When the OH type anion exchange resin tower 17 breaks through and the acid electrical conductivity detected by the acid electrical conductivity meter 23 exceeds a predetermined value, the valves 15a and 16a are switched between open and closed to pass water through the other OH type anion exchange resin tower 18. The breakthrough OH type anion exchange resin tower 17 is regenerated or replaced with a regenerated OH type anion exchange resin tower.

[0051] During boiler operation, when the Na concentration detection value of Na concentration meter 22 reaches or exceeds a preset reference value, valve 14a is closed, valve 13a is opened, a predetermined amount of feedwater is discharged from feedwater tank 7 to the system via piping 13, pure water is supplied to feedwater tank 7 to reduce the Na concentration in the feedwater, and then valve 13a is closed and valve 14a is opened.

[0052] In this boiler water treatment device, the insides of the tanks 2, 4, and 7 are kept under a positive nitrogen pressure atmosphere, so that carbon dioxide in the air does not dissolve in the water in the tanks.

[0053] In addition, the boiler feedwater is treated with the OH-type anion exchange resin towers 17 or 18, so that low molecular weight ionic silica and organic acids are removed from the feedwater, and the quality of the feedwater is good. Although pH adjusters such as amines and ammonia remain in the condensate, treating the feedwater with the OH-type anion exchange resin towers 17 or 18 does not remove the amines and ammonia in the feedwater, so the amount of additional pH adjusters to be added is reduced, and chemical costs are reduced.

[0054] In this embodiment, the Na concentration of the OH type anion exchange resin tower treated water is detected by a Na concentration meter 22, so that when Na ion-containing impurities such as seawater, industrial water, cooling water, etc. are mixed into the feed water, this can be detected quickly.

[0055] In the above embodiment, the pure water tank 2, the condensate tank 4, and the feed water tank 7 are all in a nitrogen atmosphere, but a tank for supplying nitrogen gas may be selected depending on the dissolution state of carbon dioxide. In addition, when recovering condensate containing ammonia at a high concentration (200 to 400 mg / L or more), nitrogen may be supplied only to the condensate tank 4.

[0056] It is preferable to supply nitrogen gas continuously so that air does not flow into the tank even if the water level in the tank drops. If the water level in the tank fluctuates significantly, the amount of nitrogen gas supplied to the tank increases, so it is preferable to reduce the water level fluctuation in the tank, and it is even more preferable to keep the water level constant.

[0057] However, in the present invention, the pressure inside the tank may be measured, and nitrogen may be supplied when the pressure inside the tank becomes lower than atmospheric pressure.

[0058] Nitrogen gas may be supplied to the gas phase portion of the tank, or may be supplied into the water so that nitrogen gas bubbling is performed.

[0059] If the temperature of the water in the tank is high (for example, 80° C. or higher), the amount of carbon dioxide that dissolves in the water is small, so the supply of nitrogen gas may be stopped.

[0060] In the present invention, the downstream ends of pipes 1, 3, 5, 6, and 21 may be connected to the upper parts of tanks 2, 4, and 7, or may be connected to the lower parts of tanks 2, 4, and 7 so that water from the pipes is introduced into the water in the tanks, or water may be passed from the upper parts to the bottom of the tanks below the water level. In this way, the inflow water is prevented from dropping onto the water surface in the tanks and stirring the water near the water surface.

[0061] In the above embodiment, the OH type anion exchange resin towers 17, 18 are installed in parallel, and the water flow to the OH type anion exchange resin towers 17, 18 is switched by the valves 15a, 16a. However, it is also possible to install only one OH type anion exchange resin tower and replace it with a new OH type anion exchange resin tower when the resin breaks through.

[0062] In the present invention, when the temperature of the water passed through the OH type anion exchange resin tower is high (for example, 40°C or higher), it is preferable to lower the temperature using a heat exchanger before passing the water through the OH type anion exchange resin tower.

[0063] In the above embodiment, the water supply tank 7 is provided, but the water supply tank may be omitted. In this case, the pipes 5 and 6 are connected to the pipe 9, and the downstream end of the pipe 21 is connected to the pipe 12.

[0064] As a result, the pure water from the pipe 5 and the condensate from the pipe 6 are joined in the pipe 9. A part of this joined water is treated in the OH type anion exchange resin towers 17 or 18, and the treated water is joined with the rest of the joined water in the pipe 12 and supplied to the boiler.

[0065] The above-described embodiment is merely an example of the present invention, and the present invention may be embodied in other forms than those described above. [Explanation of symbols]

[0066] 2 Pure water tank 4 Condensate tank 7. Water tank 8. Nitrogen gas source 17,18 OH type anion exchange resin tower 22 Na concentration meter 23 Acid Conductivity Meter

Claims

1. In a boiler water treatment device having a pure water tank for receiving pure water and a condensate tank for receiving condensate, A boiler water treatment device comprising a nitrogen gas supply means for supplying nitrogen gas to at least one of the tanks, a boiler water treatment device comprising an OH type anion exchange resin tower through which a portion of the combined water obtained by combining the pure water from the pure water tank and the condensate from the condensate tank is passed, and a Na concentration meter for measuring the Na concentration of the treated water from the OH type anion exchange resin tower, wherein the treated water that has passed through the OH type anion exchange resin tower and the remainder of the combined water are combined and supplied to a boiler.

2. The system includes a pure water tank for receiving pure water, a condensate tank for receiving condensate, and a water supply tank for receiving the pure water from the pure water tank and the condensate from the condensate tank, The boiler water treatment device includes a nitrogen gas supplying means for supplying nitrogen gas to at least one of the pure water tank, the condensate tank, and the feed water tank, A boiler water treatment device comprising an OH type anion exchange resin tower through which water from the water supply tank is passed, and a Na concentration meter for measuring the Na concentration of the treated water from the OH type anion exchange resin tower, wherein the treated water that has passed through the OH type anion exchange resin tower is returned to the water supply tank.

3. 3. The boiler water treatment apparatus according to claim 1, wherein the nitrogen gas supply means supplies nitrogen gas to at least the condensate tank.

4. 3. The boiler water treatment apparatus according to claim 2, wherein said nitrogen gas supplying means supplies nitrogen gas to each of said pure water tank, said condensate tank and said feed water tank.

5. 3. The boiler water treatment device according to claim 1, further comprising an acid conductivity meter for measuring the acid conductivity of the treated water from the OH type anion exchange resin tower.

6. A boiler water treatment method using the boiler water treatment device of claim 5, wherein when the acid electrical conductivity detected by the acid electrical conductivity meter becomes equal to or greater than a predetermined value, an OH type anion exchange resin tower is replaced or water is switched to passing through an OH type anion exchange resin tower installed in parallel.

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