JPH10272372A - Method for recovery of regenerated salt for water softening apparatus, and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably the regenerating salt to be supplied to a salt water tank and lighten the man power necessary to throw a salt to the tank, by selectively recovering a portion containing an unused regenerated salt from wastewater at the time of regenerating a cation-exchange resin and reusing the recovered salt as a regenerated salt. SOLUTION: In the water softening apparatus 1 comprising a resin cylinder 2 filled with a cation exchange resin and a salt water tank 3, after a prescribed amount of raw water (hard water) is converted into soft water by the function of a cation exchange resin, the cation exchange resin is regenerated by carrying out processes of back washing, regenerating with salt water, washing with water, etc. At that time, the discharged salt concentration in the wastewater (containing unused salt for regeneration) flowing in a water discharging line 6 is detected by an electric conductivity meter 9 and at the time when the discharged salt concentration reaches a prescribed concentration, an automatic valve 10 is closed and an automatic valve 12 is opened to store the wastewater in a regenerating wastewater tank 13. After that, the wastewater is separated into unused salt water for regeneration and dewatered salt by an electrodialyser 14 and the separated unused salt water for regeneration is turned back to the treatment tank from a regenerating and recovering tank 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water softener, and more particularly, to a method of recovering unused regenerated salt from wastewater at the time of regenerating a cation exchange resin, and reusing the recovered salt as a regenerated salt. The present invention relates to a method and an apparatus for recovering salt.

[0002]

2. Description of the Related Art Conventionally, in supplying water to a boiler or the like, a hard component in raw water is removed in order to prevent scale adhesion in a can body which causes a decrease in thermal efficiency, expansion and rupture of a water pipe, and soft water. Supplying as has been done.
Such a water softening treatment is usually performed by a water softener filled with a cation exchange resin.

According to a conventional water softener, when raw water containing a hardness component such as calcium ions is allowed to flow through a filled cation exchange resin, the hardness component is removed by ion exchange to become soft water. However, in the conventional water softener, it is not possible to remove a hardness component higher than the exchange capacity that the cation exchange resin originally has. Therefore, in order to restore the ability of the cation exchange resin, an operation of regenerating using a salt as a regenerating agent is required. In this regeneration operation, in the water softener for supplying water to the boiler, the salt for regeneration is replenished every 2 to 7 days. The amount of the salt needs to be about 2 to 5 times equivalent to the adsorbed hardness component. Further, in a water softener for a boiler, in order to avoid a trouble of a hardness leak, the original replacement capacity is 50 to 80 times. The fact is that the use of% has shifted to the regeneration process. For this reason,
Since a conventional water softener requires a large amount of salt, a large amount of salt is replenished each time. Particularly in a large-capacity water softener, human labor is extremely large in supplying salt.

[0004]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a method and an apparatus for recovering a regenerated salt in a water softener capable of recovering and reusing unused salt in a water softener regeneration step. It is intended to provide.

[0005]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the invention according to the first aspect is characterized in that unused effluent from wastewater at the time of regeneration of a cation exchange resin is used. A portion containing a regenerated salt is selectively recovered, and the recovered salt is reused as a regenerated salt. The invention according to claim 2, wherein a salt concentration in the wastewater is detected and a predetermined concentration is detected. The recovery operation of the unused regenerated salt from the wastewater is started when the water concentration reaches a predetermined value, and the recovery operation is stopped when the salt concentration falls below a predetermined concentration. Wherein the recovery operation is started after a predetermined time has elapsed after the predetermined concentration has been reached or after a predetermined amount of wastewater has been discharged, and the invention according to claim 4, wherein the resin filled with a cation exchange resin is used. Equipped with a cylinder and a saltwater tank In a water softener, an electrodialysis device is connected to a drain line for discharging wastewater during regeneration of the cation exchange resin, and the electrodialysis device and the salt water tank are connected via a recovery line, and The invention according to claim 5 is characterized in that an electric conductivity meter,
A first automatic valve is provided, and a second automatic valve is provided in a second drain line. The invention according to claim 6 further comprises a flow meter or a timer control means provided in the drain line. It is characterized by.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. The apparatus for recovering regenerated salt and the method for recovering the same according to the present invention are as follows. This is realized in a system for supplying soft water. The regenerated salt recovery apparatus according to the present invention connects an electrodialysis apparatus to a drainage line for discharging wastewater during regeneration of a cation exchange resin in a water softener having a resin cylinder filled with a cation exchange resin and a salt water tank. In addition, an electric conductivity meter, a first automatic valve and a second automatic valve are connected to the drain line, and the electrodialyzer and the salt water tank are connected via a recovery line. Further, a flow meter and a timer control means (a configuration in which the first automatic valve has a timer control function) are provided in the drain line.

In the electrodialysis apparatus, a plurality of cation exchange membranes and a plurality of anion exchange membranes are alternately arranged, and a treatment tank is formed by an anode plate and a cathode plate arranged on both outer sides of the alternate arrangement. The wastewater (including unused regenerated salt) discharged during regeneration of the cation exchange resin is introduced into the treatment tank, and a direct current is applied between the anode plate and the cathode plate to form a positive electrode. It is configured to separate unused regenerated brine and demineralized water (hard water) through the ion exchange membrane and the anion exchange membrane.

[0008] According to the recovery method of the regenerated salt recovery apparatus,
The water softener softens a predetermined amount of general city water (hard water) by the action of the cation exchange resin, and then regenerates the cation exchange resin. In this regeneration step, each step such as back washing, salt water regeneration, and water washing is usually performed to regenerate the cation exchange resin. In the backwashing and rinsing steps, the general city water is introduced into the resin cylinder, and in the saltwater regenerating step, saltwater is introduced from the saltwater tank. Then, the wastewater after the treatment in each step flows into the drainage line. For the wastewater flowing into this drainage line, the electric conductivity meter detects the discharged salt concentration (including unused regenerated salt) in the wastewater, and selects only a wastewater portion having a preset high salt concentration to the electrodialysis device. Collected and supplied. That is, wastewater having a low salt concentration such as the backwashing and washing steps is closed by closing a second automatic valve (supply valve to the electrodialyzer) provided in the drainage line and opening the first automatic valve. The electric conductivity meter detects a portion with high salt concentration in the wastewater in the regeneration step, and based on the detected value, closes the first automatic valve and opens the second automatic valve to open the salt concentration. High wastewater to the electrodialysis device. The wastewater supplied to the electrodialysis device is separated into unused regenerated brine and demineralized water by the action of the electrodialysis device, and the unused regenerated brine is concentrated and recovered, and the brine is recovered through the recovery line. Reflux to tank. On the other hand, the desalted water is discarded outside the system as wastewater.

Further, in the wastewater in the regeneration step, the concentration of the hardness (CaCl ₂ , MgCl _2, etc.) is relatively high in the initial flow portion, and the concentration of the salt to be recovered is low, so that the initial flow portion may be discarded. . In this case, a flow meter is provided in the drain line, the integrated flow rate of the initial flow portion is measured by the flow meter, and when a predetermined flow rate is reached, waste water is supplied to the electrodialysis device. Further, the integrated flow rate can be controlled by timer control means instead of the flow meter.

As described above, unused regenerated salt is selectively recovered from wastewater at the time of regenerating a cation exchange resin,
Since this recovered salt was reused as regenerated salt,
As in the prior art, the amount of salt for regeneration to be supplied to the salt water tank can be significantly reduced, and human labor can be reduced.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and is an explanatory view schematically showing the configuration of a regenerated salt recovery device for a water softener. FIG. 2 is a conceptual view of a treatment tank of the electrodialysis device of FIG. FIG.

FIG. 1 shows a water softener 1 according to the present invention.
As a basic configuration, a resin cylinder 2 filled with a cation exchange resin, a salt water tank 3, a raw water line 4 to the resin cylinder 2, a soft water line 5 from the resin cylinder 2, and a And a control valve 8 for switching a salt water line 7 between the resin tube 2 and the salt water tank 3 for each processing step.

In the water recovery device 1 according to the present invention, the electric conductivity meter 9 is connected to the drain line 6 in the water softener 1.
And a first automatic valve 10, and a second drain line 11 branched between the electric conductivity meter 9 and the first automatic valve 10 in order to recover the regenerated salt. This second drain line 11 has a second automatic valve 12 and a recycled wastewater tank 13.
Are provided. This reclaimed wastewater tank 13 is connected to the electrodialysis device 14 via a wastewater supply line 30 provided with a pump 19 for supplying reclaimed wastewater. A drain line 36 is connected to the recycled wastewater tank 13.

The electrodialyzer 14 is connected to the salt water tank 3 via a recovery line 15,
The recovery line 15 is provided with a regeneration / recovery tank 16 and a pump 17. The recycle tank 16 is provided with a makeup water line 31, and further connected to a circulation line 29 with the electrodialyzer 14. The electrodialyzer 14 is provided with a desalinated water line 18 for discharging the desalinated water (hard water) selectively separated here, and the desalinated water line 18 is connected to the regeneration wastewater tank 13. .

In the above configuration, the control valve 8, the electrodialyzer 14, the electric conductivity meter 9, the automatic valves 10, 11 and the pumps 17, 19 are connected to a controller (not shown) via a signal line (not shown). (Omitted).

The electrodialyzer 14 is shown in FIG.
As shown in FIG.
1 and the cathode plate 22 are arranged in a state where an appropriate interval is maintained. Within the space between the anode plate 21 and the cathode plate 22, a plurality of cation exchange membranes 23 that transmit only cations and a plurality of anion exchange membranes 24 that transmit only anions are alternately arranged. . The cation exchange membrane 23,
It is important to use a monovalent ion selective permeation membrane which does not easily transmit multivalent ions such as Ca ²⁺ and Mg ²⁺ and easily transmits monovalent ions such as Na ⁺ . Such both exchange membranes 23, 24
Are alternately arranged via a suitable spacer (not shown) so as to form a small room between them. As described above, since the cation exchange membranes 23 and the anion exchange membranes 24 are alternately arranged, a small chamber for taking in ions (hereinafter, referred to as “cell”)
, And small chambers (hereinafter, referred to as “desalting chambers”) 26, 26,... For removing ions are formed alternately. Therefore, when a liquid is passed through each of the small chambers and a direct current is passed, both the negative and positive ions are taken into the liquid in each of the concentrating chambers 25 from the desalting chambers 26 adjacent to each other. Happens. On the other hand, from the liquid in each of the desalting chambers 26, the two ions are separated from the enrichment chamber 2 on both sides.
5, respectively, so that desalination will occur.
Further, on both sides of these membrane groups, an anode plate 21 and a cathode plate 22 for passing a direct current are arranged while maintaining an appropriate gap between the ion exchange membranes 23 and 24 located on both sides. Thus, an anode chamber 27 and a cathode chamber 28 are respectively formed.

In the processing tank 20, the anode plate 21 and the cathode plate 22 disposed on both outer sides of the alternate arrangement by the ion exchange membranes 23 and 24 have a DC power supply 32 and a switch 33. They are connected by an electric circuit 34.

According to the recovery method of the regenerated salt recovery apparatus having the above structure, the water softener 1 softens a predetermined amount of raw water (hard water) by the action of the cation exchange resin, and then regenerates the cation exchange resin. . In this regeneration step, each step such as back washing, salt water regeneration, and water washing is usually performed to regenerate the cation exchange resin. In the backwashing and rinsing steps, raw water is introduced into the resin cylinder 2 from the raw water line 4 via the control valve 8, and in the saltwater regenerating step, the saltwater is supplied from the saltwater tank 3 through the brine line 7 and the control valve 8. It is introduced into the resin cylinder 2. Then, the wastewater after the treatment in each step is caused to flow into the drainage line 6 via the control valve 8.

In the wastewater (including unused regenerated salt) flowing into the drainage line 6, the concentration of discharged salt (concentration of unused regenerated salt) in the wastewater is detected by an electric conductivity meter 9.
If the detected value is less than the preset salt concentration, the wastewater opens the first automatic valve 10 of the drain line 6 (at this time, the second automatic valve 12 of the second drain line 11 is closed). )) And is discarded outside the system. The wastewater whose discharged salt concentration has reached a predetermined concentration is stored in the reclaimed wastewater tank 13 by closing the first automatic valve 10 and opening the second automatic valve 12. The wastewater stored in the recycled wastewater tank 13 is
The pump 19 is driven to supply the wastewater to the treatment tank 20 of the electrodialysis device 14 via the wastewater supply line 30. This treatment tank 2
The wastewater supplied into the chamber 0 is separated into unused regenerated brine and demineralized water by the action of the electrodialysis device 14. The unused regenerated salt water separated here is concentrated and collected, flows into the reclaim tank 16 through the collection line 15, and returns to the treatment tank 20 through the circulation line 29. In this reflux process, the unused regenerated salt water is re-concentrated and stored in the reclaim tank 16. Unused regenerated salt water stored in the reclaim tank 16 is supplied to the pump 1
7 is supplied to the salt water tank 3 via the recovery line 15 by appropriately driving.

On the other hand, the desalinated water separated from the wastewater flows into the reclaimed wastewater tank 13 via a desalinated water line 18 and is further circulated in the treatment tank 20 to separate unused regenerated salt. Then, the water is desirably discharged as desalinated water from the reclaimed wastewater tank 13 through the drain line 36 outside the system.

Here, the separation of the wastewater in the processing tank 20 will be described. The wastewater supplied into the processing tank 20 flows into each desalting chamber 26. In this way, with the wastewater flowing into the treatment tank 20, the switch 33 is operated to supply a direct current between the anode plate 21 and the cathode plate 22, thereby causing the cation exchange membrane 23 and the anion exchange membrane 23 to pass through. When a direct current is passed through the wastewater in each desalting chamber 26 partitioned by 24, cations (eg, Na ⁺ , Ca ²⁺ ) in the wastewater
Migrates toward the cathode, while anions (eg, C
l ^-) is, migrate towards the anode. At this time, Na ⁺
Is passed through the cation exchange membrane 23 and passes through the next concentration chamber 25.
However, since the cation exchange membrane 23 has a property that the multivalent ions are hardly permeated, Ca ²⁺ can hardly move to the respective enrichment chambers 25. Similarly, Cl ^- is transmitted through the anion exchange membrane 24 can move to each concentrating compartment 25. Further, Na ⁺ and Cl ⁻ moved to the respective concentration chambers 25 are blocked by the ion exchange membranes 23 and 24 respectively, and are again returned to the respective desalting chambers 26.
Can not move to Therefore, it is possible to selectively recover NaCl in each of the enrichment chambers 25, and it is also possible to increase the concentration of NaCl after recovery by selecting an appropriate current density, an energizing time, and an amount of water on the recovery side.

Next, a second embodiment, which replaces the first embodiment, will be described with reference to FIG. In the second embodiment, the wastewater in the regeneration step of the cation exchange resin has a relatively high concentration of hardness (CaCl ₂ , MgCl _2, etc.) in the initial flow portion and a low concentration of salt to be recovered because the concentration is low. Parts may be discarded. In this case, a flow meter 35 is provided downstream of the electric conductivity meter 9 to measure an integrated flow rate from the initial flow portion, and when the flow rate reaches a preset flow rate, wastewater is supplied to the electrodialysis device 14. . Then, when the salt concentration in the wastewater falls below a predetermined value, the supply of the wastewater to the electrodialysis device 14 is stopped as in the first embodiment. Further, a timer control means (a configuration in which the first automatic valve 10 has a timer control function) may be provided instead of the flow meter 35. The configuration other than the above is the same as that of the first embodiment, and a description thereof will be omitted.

[0023]

As described above, according to the present invention, unused regenerated salt is selectively recovered from wastewater at the time of regenerating a cation exchange resin, and the recovered salt is reused as regenerated salt. As a result, the amount of salt for regeneration to be supplied to the salt water tank can be significantly reduced. Therefore,
It is possible to reduce human labor for inputting salt.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a configuration of a first embodiment of a regenerated salt recovery device for a water softener embodying the present invention.

FIG. 2 is a conceptual diagram of a processing tank of the electrodialysis apparatus of FIG.

FIG. 3 is an explanatory view schematically showing a configuration of a second embodiment of the regenerated salt recovery apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water softener 2 Resin cylinder 3 Salt water tank 6 Drain line 9 Electric conductivity meter 10 First automatic valve 11 Second drain line 12 Second automatic valve 13 Regeneration wastewater tank 14 Electrodialyzer 15 Collection line 16 Regeneration tank 35 Flow meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Floating Hole 7 in Horie-cho, Matsuyama-shi, Ehime, Japan Miura Research Institute, Inc. Inventor Takekazu Ogura 7, Horie-cho, Matsuyama-shi, Ehime Prefecture, Miura Research Institute (72) Inventor Atsushi Mihara 7, Horie-cho, Matsuyama-shi, Ehime Prefecture, Miura Research Institute, Inc.

Claims (6)

[Claims] 1. Regeneration of a water softener characterized by selectively recovering a portion containing unused regenerated salt from wastewater at the time of regenerating a cation exchange resin, and reusing the recovered salt as a regenerated salt. Salt recovery method. 2. detecting the salt concentration in the wastewater, starting a recovery operation of unused regenerated salt from the wastewater when the concentration reaches a predetermined concentration, and starting the recovery operation when the salt concentration falls below a predetermined concentration. The method according to claim 1, wherein the salt is stopped. 3. The method for recovering regenerated salt from a water softener according to claim 2, wherein the recovery operation is started after a predetermined time has elapsed after the predetermined concentration has been reached or after a predetermined amount of wastewater has been discharged. 4. An electrodialyzer 14 is connected to a drain line 6 for discharging waste water during regeneration of a cation exchange resin in a water softener 1 having a resin tube 2 filled with a cation exchange resin and a salt water tank 3. A regenerated salt recovery device for a water softener, wherein the electrodialysis device 14 and the salt water tank 3 are connected via a recovery line 15. 5. The drainage line 6 according to claim 4, wherein an electric conductivity meter 9 and a first automatic valve 10 are provided, and a second automatic valve 12 is provided in the second drainage line 11. Regenerated salt recovery equipment for water softeners. 6. The reclaimed salt recovery device for a water softener according to claim 5, wherein a flow meter or timer control means is provided in the drain line 6.