JP2002331292A - Fluoric acid-containing wastewater treatment method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To treat fluoric acid-containing wastewater for recovering both fluoric acid and water for recycle at a low operation cost with least waste generated. SOLUTION: The fluoric acid-containing wastewater treatment apparatus is constituted of a fluoric acid wastewater supply system 1, an alkali supply system 2 for supplying KOH or the like for neutralizing fluoric acid-containing wastewater, an evaporation/concentration device 3 for concentrating a neutralized liquid to about 50 time while recovering distilled water, an ion exchange device 5 receiving the supply of a concentrated liquid and the supply of pure water from a pure water supply system 6 and generating hydrogen ions and hydroxyl ions from both liquids to separate and discharge highly concentrated fluoric acid and alkali, or the like. Fluoric acid wastewater can be treated so as to recover distilled water of high purity and highly concentrated fluoric acid in a reutilizable form without almost generating waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrofluoric acid wastewater treatment apparatus for treating hydrofluoric acid wastewater containing dilute hydrofluoric acid, and more particularly to a hydrofluoric acid wastewater treatment apparatus used for cleaning during a manufacturing process of electronic parts such as semiconductors. It is conveniently used as a processing technology.

[0002]

2. Description of the Related Art Usually, hydrofluoric acid wastewater is treated by a method of neutralizing hydrofluoric acid with slaked lime to form calcium fluoride, and separating and separating the calcium fluoride. However, in this method,
There is a problem in that a large amount of waste consisting of calcium fluoride sludge is generated. In addition, according to such a treatment method, a precipitation operation and a dehydration operation are required to separate calcium fluoride from the suspension water containing calcium fluoride, and thus large facilities that occupy a large space are required. There was also the problem of becoming.

[0003] In contrast to such a conventional treatment method, there is a method of treating a hydrofluoric acid-containing wastewater in which neutralized hydrofluoric acid wastewater is diluted with an alkaline aqueous solution such as an aqueous solution of caustic soda or potassium hydroxide, and then concentrated by evaporation to recover distilled water. It has been proposed (see JP-A-9-271785). According to this method,
Since hydrofluoric acid wastewater becomes concentrated water and is greatly reduced in weight, it is said that by adding a chemical equivalent of slaked lime to this, post-treatment can be carried out efficiently.

However, in such a processing method,
The problem of generating a large amount of calcium fluoride waste has not been solved. On the other hand, the nitric hydrofluoric acid waste liquid is passed through the deoxidizing chamber of the first electrodialyzer, and potassium hydroxide (caustic potash) is added to neutralize the hydrofluoric acid in the pH adjusting chamber, and the desalting chamber of the second electrodialyzer is used. Through which sodium hydroxide and hydrofluoric acid are respectively taken out of the alkali line and the acid line under the action of the ion exchange membrane, and the former is reused in this system, and the latter is recovered. And a method for separating and recovering nitric acid and hydrofluoric acid from nitric hydrofluoric acid waste liquid in which nitric acid is separated therefrom has been proposed (JP-A-9-10).
557).

In this method and apparatus, a third electrodialysis chamber is further provided, and a nitric hydrofluoric acid waste liquid after the pH adjustment is put into and passed through the concentrating chamber, and the nitric hydrofluoric acid after passing through the second electrodialysis apparatus is passed. There has also been proposed a method and an apparatus in which an acid waste liquid is passed through a desalting chamber of a third electrodialysis chamber, and potassium salt as a salt therein is moved to a concentration chamber side.

However, in this method, since hydrogen ions for generating hydrofluoric acid are generated by ionizing water in an alkali line and an acid line using a bipolar membrane, a high concentration of, for example, 4 mol / l is obtained. The salt has a low current efficiency of 89%, the bipolar membrane also allows impurities to permeate, and the impurities are mixed into the recovered hydrofluoric acid for reuse, and the water in the waste liquid cannot be recovered. There are various problems. That is, this method relates to the reuse of nitric hydrofluoric acid waste liquid used for pickling stainless steel sheets and the like, and to a process that enables reuse of hydrofluoric acid for cleaning electronic components in which impurities are strictly regulated. It is not an applicable technology.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, reduces the operating cost, generates little waste, and converts both hydrofluoric acid and water in hydrofluoric acid-containing wastewater into electronic components. An object of the present invention is to provide a method and an apparatus for treating hydrofluoric acid wastewater, which can be recovered with high purity to such an extent that they can be reused for washing and the like and can be effectively reused, and are optimal for environmental conservation.

[0008]

According to the present invention, there is provided a hydrofluoric acid wastewater treatment method for treating hydrofluoric acid wastewater containing dilute hydrofluoric acid.
A neutralization step of adding an alkali that forms a highly water-soluble salt when added to the hydrofluoric acid wastewater to the hydrofluoric acid wastewater to make the hydrofluoric acid wastewater a neutralizing solution, and evaporating the neutralized solution with an evaporator A concentration step of concentrating the solution to a high concentration below the solubility of the salt to obtain a concentrated solution, and supplying pure water to at least a side where hydrogen ions are generated in an ion exchange operation, and electrolyzing the pure water to obtain a solid. The concentrated solution is separated into hydrofluoric acid-containing water, alkali-containing water, and the remaining demineralized water by an ion exchange operation including an operation of generating the hydrogen ions by permeating the polymer electrolyte membrane, and respectively separating the hydrofluoric acid-containing water system and the alkali. A separation step for allowing discharge to a water-containing system and a return system for returning to the evaporative concentration apparatus.

According to a second aspect of the present invention, in addition to the above, a concentration detecting step for detecting the concentration of the concentrated solution, and when the detected concentration becomes the high concentration, the concentrated solution is allowed to stand still in the concentrated solution storage section. A standing step of separating the upper liquid and a lower impurity-containing liquid, an upper liquid extracting step of extracting the upper liquid to be subjected to the ion exchange operation, and a draining step of discharging the impurity-containing liquid And the following.

In this case, the step of allowing the concentrated liquid to stand still in the concentrated liquid storage section usually involves removing the concentrated liquid from the concentrated liquid storage section of the evaporating and concentrating apparatus, placing it in another storage section, and allowing it to stand still. This may be performed, but may be performed by a method of allowing the concentrated liquid to stand still in the concentrated liquid reservoir itself.

A third aspect of the present invention is a hydrofluoric acid wastewater treatment apparatus for treating hydrofluoric acid wastewater containing diluted hydrofluoric acid.
A hydrofluoric acid wastewater supply system capable of supplying the hydrofluoric acid wastewater, and an alkali that generates a highly water-soluble salt when added to the hydrofluoric acid wastewater and added to the hydrofluoric acid wastewater to neutralize the hydrofluoric acid wastewater An alkali supply system capable of supplying alkali to be liquefied, and an evaporative concentration device that takes in the neutralized solution, evaporates and concentrates to a high concentration below the solubility of the salt to form a concentrated solution,
Pure water is supplied while the concentrated liquid is supplied.Pure water is supplied to at least the side where hydrogen ions are generated in an ion exchange operation, and the pure water is electrolyzed and permeated through the solid polymer electrolyte membrane. The concentrated solution is separated into hydrofluoric acid-containing water, alkali-containing water, and the remaining demineralized water by an ion exchange operation including an operation of generating the hydrogen ions, and the concentrated liquid is separated into a hydrofluoric acid-containing water system, an alkali-containing water system, and the evaporative concentration device, respectively. It is characterized by having an ion exchange device capable of discharging to a return system and a pure water supply system capable of supplying the pure water.

According to a fourth aspect of the present invention, in addition to the above, a concentration detecting means for detecting the concentration of the concentrated liquid, a concentrated liquid storing means for storing the concentrated liquid, and a concentrated liquid stored by the concentrated liquid storing means. An upper liquid supply system for supplying the upper liquid to the ion exchange device, an impurity liquid discharge system for discharging the lower liquid of the stored concentrated liquid, and an ion exchange device operating means for operating the ion exchange device. When the concentration detection means detects the high concentration, the storage means is operated to store the concentrated liquid, and after a lapse of a predetermined time, the upper liquid supply system supplies the upper liquid to the ion exchange device, and And a control means for controlling the operating means to operate the ion exchange device after the liquid is discharged and the liquid is discharged from the lower part and supplied.

In this case, as the concentrated liquid storage means, a concentrated liquid storage section such as a suitable tank is usually provided outside the evaporative concentration apparatus, and the concentrated liquid is supplied from the concentrated liquid storage section of the concentrated evaporator to the external concentrated liquid. The apparatus is provided with a suitable concentrated liquid transfer device for transferring the concentrated liquid to the storage section, but provided with a concentration stopping means for stopping concentration by the evaporative concentration apparatus while the concentrated liquid is allowed to stand still, and the concentrated liquid reservoir itself of the evaporative concentration apparatus is provided. May be used as a concentrated liquid storage unit. In this case, another equipment for storing the concentrated liquid is not required, so that the equipment cost can be reduced, and the space for installing the equipment is not required. However, as described above, a standing time for separating the upper liquid and the lower liquid in the evaporative concentration apparatus is required, and the concentration operation cannot be performed during this time, so that the operation rate of the evaporative concentration apparatus decreases. Therefore, this means is adopted when this point is not a problem in the facility planning.

[0014]

FIG. 1 shows an example of the overall configuration of a hydrofluoric acid wastewater treatment apparatus to which the present invention is applied. The present apparatus is a hydrofluoric acid wastewater containing a dilute concentration of hydrofluoric acid, for example, a hydrofluoric acid wastewater after being used for cleaning in a manufacturing process of an electronic component. A hydrofluoric acid wastewater supply system 1, an alkali supply system 2, an evaporative concentrator 3, which is capable of supplying hydrofluoric acid wastewater.
It comprises an ion exchange device 5 and the like.

The hydrofluoric acid wastewater supply system 1 usually stores hydrofluoric acid wastewater after washing electronic components and the like in an intermediate tank, and then continuously or with a pump (not shown) so as to be compatible with the treatment in the present apparatus. It is configured to supply water intermittently and is connected to the lower part of the body part 31 of the evaporative concentration device 3.

The alkali supply system 2 comprises potassium hydroxide (K
OH) or sodium hydroxide (NaOH) to supply an alkali that generates potassium fluoride (KF) as a highly water-soluble salt when added to hydrofluoric acid wastewater. It is composed of a system. Such alkali is added to hydrofluoric acid wastewater to make it a neutralizing solution. The alkali supply system 2 is usually connected to the hydrofluoric acid drainage supply system 1 as shown in the figure, but may be directly connected to the body of the evaporative concentration device 3.

The evaporating and concentrating device 3 is a device which takes in the neutralized solution and evaporates it, for example, concentrates it into a concentrated solution at a concentration of about 50 times less than the solubility of the salt KF to obtain a concentrated solution. Heating steam chamber 32, heating pipe 33, condensed water chamber 3
4, a heated steam system 35, a concentrated liquid reservoir 36 for storing the concentrated liquid,
In this embodiment, the condenser 37, which is a separate component, the vacuum pump 38, the distilled water pump 39, the cooling water system 40, the heated steam drain system 41, and the concentrated liquid circulation system 4 including the concentrated liquid circulation pump 42
3, a concentrated liquid discharging system 44, a concentrated liquid discharging pump 45, and the like. Although the evaporative concentrator 3 of this example is a single-effect vapor heating type device with a reduced-pressure horizontal tube, a high-efficiency evaporative concentrator such as a multi-effect type or a vapor compression type can also be used.

The ion exchange device 5 receives the concentrated liquid from the concentrated liquid discharge system 44 and the pure water from the pure water supply system 6 capable of supplying pure water. As hydrofluoric acid-containing water, for example, about 2% hydrofluoric acid water and as alkali-containing water, for example, 6% KOH
This is a device for separating and discharging an aqueous solution and the remaining demineralized water, and a liquid chamber 5 to be treated, through which a concentrated liquid to be treated flows.
A pair of anion exchange membranes 5 arranged to form
2 and a cation exchange membrane 53, a cation-type solid polymer electrolyte membrane 54 and an anion-type solid polymer electrolyte membrane which are disposed opposite to these membranes, respectively, and are supplied with pure water in contact with an anode and a cathode (not shown). 55 are provided.

The remaining electrolyzed demineralized water is supplied to a return system 5
The liquid is discharged to the concentrated liquid reservoir 36 through the pipe 6 and returned. The hydrofluoric acid water and the alkali-containing water are respectively a hydrofluoric acid recovery system 57 which is a hydrofluoric acid-containing water system and a KOH which is an alkali-containing water system.
It is discharged to the recovery system 58. The generated oxygen and hydrogen are released to the atmosphere directly or via a piping system. Although FIG. 1 shows only one ion exchange device 5, a plurality of such devices are usually provided. In the above-described ion exchange operation, pure water may be supplied to at least a side where hydrogen ions are generated, and the pure water may be electrolyzed and permeated through the solid polymer electrolyte membrane to generate the hydrogen ions. In the example, H + and OH are used as described later by the cationic and anionic solid polymer electrolyte membranes 55 as described above.
-Is occurring.

Although not shown in detail in FIG. 1, ordinary equipment such as an electric system, equipment including a manual valve and an automatic valve, and an operation device are provided as necessary. The present device is configured to perform a driving operation suitable for the purpose of use, such as automatic driving or manual driving.

FIG. 2 shows an example of a hydrofluoric acid wastewater treatment method to which the present invention is applied. The hydrofluoric acid wastewater treatment method is a method of treating hydrofluoric acid wastewater containing a dilute concentration of hydrofluoric acid using an apparatus as shown in FIG. 1, and basically comprises a neutralization step A, a concentration step B, and an ion exchange operation. And a separation step C.

In the neutralization step A, for example, KOH as the alkali is added to the hydrofluoric acid wastewater, and the hydrofluoric acid wastewater is added to, for example, PH.
Make up to about 10 neutralization solution. Potassium fluoride KF, a salt of the neutralizing solution, is well soluble in water and has a saturation solubility of 30%.
% Or more. By thus neutralizing the hydrofluoric acid in the hydrofluoric acid wastewater, it is possible to prevent the hydrofluoric acid from evaporating and entering the distilled water in the next concentration step B. as a result,
High-purity distilled water is obtained, which can be reused as washing water, and the material used for the part of the steam concentrator that comes into contact with the condensed water is not corroded by hydrofluoric acid. Cost material can be adopted.

In the concentration step B, the neutralized liquid is evaporated to a high concentration by an evaporator. That is, the concentration of the KF is set to a concentration of 30% or less, and in this example, the concentration is increased to a high concentration of about 6%, which is a sufficient margin. The concentration magnification at this time is 50 times. In this case, hydrofluoric acid is neutralized as described above,
The transition to the distilled water side and the associated problems have been solved. Note that the concentrated liquid at the bottom of the concentrated liquid reservoir 36 is discharged little by little at appropriate intervals so that impurities do not accumulate more than a certain amount.

[0024] If the KF is concentrated and sufficiently reduced in this way, it becomes relatively easy to treat the concentrate with slaked lime as in the prior art. However, in that case, the same amount of sludge is still generated and the turbid liquid remains, though reduced in amount, and it is necessary to dispose of these.
Therefore, in the present invention, as described below, a unique treatment method of further treating a highly concentrated liquid by an ion exchange operation is employed.

In the separation step C, pure water is supplied, and the concentrated liquid is separated into hydrofluoric acid-containing water and alkali-containing water by an ion exchange operation to be discharged. That is, the solid polymer electrolyte membranes 54 and 55 are formed by the ion exchange device as shown in FIG.
While supplying pure water to the portion, the concentrated liquid is supplied so as to pass through the liquid chamber to be treated 51 surrounded by the anion exchange membrane 52 and the cation exchange membrane 53.

As a result, as shown in FIG. 3, pure water is electrolyzed to generate hydrogen ions H + and hydroxyl ions OH−, which are concentrated but neutralized to form ionic bonds of potassium hydrofluoride. F− and K + of KF pass through the anion exchange membrane 52 and the cation exchange membrane 53 and bind to H + and OH−, respectively.
H is generated, and water containing these is discharged. In this case, since pure water is electrolyzed using the solid polymer electrolyte membrane, H +
And OH- to be supplied, and the HF and KOH to be produced can be of high purity.

Since high-purity HF is required for reuse in cleaning electronic parts and the like, the cation-type solid polymer electrolyte membrane 54 is used to generate H + as described above. Although it is provided, it is also possible to adopt a method of electrolyzing a normal electrode solution without using the anion-type solid polymer electrolyte membrane 55 on the OH-generating side.

These water contents are HF and KO, respectively.
Since H is contained at a high concentration, each can be reused. As a result, according to the hydrofluoric acid wastewater treatment method of the present invention, hydrofluoric acid wastewater can be treated with almost no waste.

The inventors conducted an experiment for treating hydrofluoric acid wastewater using the above hydrofluoric acid wastewater treatment apparatus and method, and obtained the following results: hydrofluoric acid wastewater treatment amount: 1000 L / h concentration : 0.1% Alkali used: KOH aqueous solution Used amount: 20 L / h Concentration: 14% Neutralization value: PH9.5 Concentration ratio: 50 times Salt (KF) concentration in concentrated solution: 6% (1 mol / L) Fluorine ion concentration in the generated distilled water: 1 ppm or less Evaporation temperature at the time of concentration evaporation: about 70 ° C. Ion exchange device Membrane area: 800 cm ² × 10 cells Current × voltage: 3 V × 120 A × 10 cells Current efficiency: 98% pure Water supply Anode chamber: 0.4 L / h × 10 cells Cathode chamber: 0.15 L / h × 10 cells Separated hydrofluoric acid content water: 44 L / h Hydrofluoric acid concentration: 2% Potassium as an impurity: 1 ppm Bottom Separated potassium hydroxide-containing water content: 20 L / h Potassium hydroxide concentration: 14% According to the above experimental results, a sufficiently high concentration of hydrofluoric acid-containing water can be recovered from hydrofluoric acid wastewater to clean electronic components and the like. It can be reused as a hydrofluoric acid solution having a concentration of about 0.5%. Also, potassium hydroxide could be recovered at a sufficiently high concentration of about 14% of the concentration when used as an alkali for neutralization, and could be reused as described above.
Further, since the solid polymer electrolyte membrane was used, a high current efficiency of 98% was obtained when the concentration of the salt (KF) in the concentrated solution was as high as 6% (1 mol / L).

On the other hand, in the ion exchange apparatus, the highly concentrated solution was subjected to the ion exchange treatment. However, no problems such as clogging of the membrane occurred, and sufficient separation performance could be secured. Further, the evaporation temperature was set to 70 ° C., and the concentrated liquid was passed through the ion exchange apparatus without cooling, but no abnormality was found in the membrane.

As described above, according to the hydrofluoric acid wastewater treatment apparatus and method of the present invention using both the concentration treatment and the ion exchange treatment accompanied by the supply of pure water, the separation performance and durability of the ion exchange membrane are affected. Instead, the hydrofluoric acid wastewater can be treated so that it can be reused. Therefore, the present invention saves raw materials such as hydrofluoric acid and alkali in cleaning electronic parts and the like, and eliminates generation of waste.
It can contribute to the public benefit of resource saving and environmental conservation.

FIG. 4 shows another example of a hydrofluoric acid wastewater treatment apparatus to which the present invention is applied. The apparatus of the present embodiment includes, in addition to the apparatus of FIG. 1, a specific gravity sensor 7 as a concentration detecting means for detecting the concentration of the concentrated liquid, the concentrated liquid storage section 36 as a concentrated liquid storing means for storing the concentrated liquid, and an evaporative concentration apparatus. Automatic opening / closing valves 10, 11, and 12 provided in the hydrofluoric acid drainage supply system 1, the alkali supply system 2, and the heating steam supply system 35, which serve as concentration stop means capable of stopping concentration by 3 and the concentrated liquid circulation, respectively. The stored upper liquid such as a pump 42 is transferred to the ion exchange device 5.
Inlet 81 opened at an appropriate height to supply
An upper liquid supply system 8 having the concentrated liquid discharge pump 45; an automatic blow valve 91 as an impurity liquid discharge system branched from the concentrated liquid circulation system 43 so as to discharge liquid below the concentrated liquid reservoir 36; A blow line 9 provided with a circulating system automatic valve 92, an automatic opening / closing valve 13 provided in the pure water supply system 6 as an operating means for operating the ion exchange device, an operation control panel 14 as a control means, and the like are provided. .

Reference numerals 15 and 16 denote a PH meter for detecting the pH of the concentrated solution and an automatic adjusting valve provided in the alkali supply system 2.
Control the flow rate of OH.

FIG. 5 can be implemented by an apparatus as described above.
The basic steps of the hydrofluoric acid wastewater treatment method are shown. In this example,
Concentration detection method that detects the concentration of the concentrated solution
About B₁When the detected concentration reaches a predetermined constant concentration
After stopping the concentration step, the concentrated liquid is allowed to stand still in the concentrated liquid reservoir 31.
Stationary process for separating the upper liquid and the lower impurity-containing liquid
B _TwoThe upper liquid so that it can be subjected to ion exchange operations.
Upper liquid removal process B_ThreeAnd liquid containing impurities
Outgoing drainage process B_FourHas been added. According to the device of FIG.
If these steps are performed, the operation control panel
Implemented.

That is, when the specific gravity sensor 7 detects a specific gravity of 1.03 g / cm ³ corresponding to, for example, a concentration of 6% as the target high concentration, the concentration stopping means stops the concentration, and the control unit 14 starts the concentration. The upper liquid supply system 8 supplies the upper liquid to the ion exchanger 5, for example, 30 minutes after the elapse of time until the impurities in the concentrated liquid are substantially settled down, and the blow valve 91 of the blow line 9 is opened. The liquid in which impurities are precipitated in the lower part of the concentrated liquid reservoir 36 is discharged, and then the ion exchange device 5 is controlled to operate.

The stop of the concentration by the evaporative concentration device 3 is usually performed by closing the automatic on-off valves 10, 11, and 12 and stopping the concentrate circulation pump 42 and the concentrate discharge pump 45. When the concentration is resumed, these valves are opened and the pumps are operated. The time during which the concentration is stopped and the concentrated liquid is allowed to stand is usually set by a timer according to the actual operation state, but may be set by another appropriate method that can determine the degree of sedimentation of impurities.

When the impurities are blown, the blow valve 91 is opened as described above.
3, the automatic valve 92 is provided in this system.
This valve is closed and the circulation pump 42 is operated for a short time. The supply of pure water to the ion exchange device 5 is performed before and after the supply of the concentrated liquid.

According to the apparatus of this embodiment, when a certain amount of impurities is contained in the hydrofluoric acid wastewater, the impurities are blown down in correspondence with the concentration operation, so that the impurities accumulate in the concentrated liquid and remain. When supplying the concentrated liquid to the ion exchange apparatus, it is possible to prevent the introduction of a problematic amount of impurities. As a result, the operation state of the ion exchange device can be maintained in good condition, operations such as cleaning of the membrane can be greatly reduced, and the durability of the membrane can be increased. In addition, it is possible to solve the problem such as sticking of the scale to the relevant portions of the evaporative concentration device 3 and the ion exchange device 5.

FIG. 6 shows still another example of the hydrofluoric acid wastewater treatment apparatus to which the present invention is applied. The apparatus of this example is different from the apparatus of FIG. 4 in that a separate storage tank 17 is provided as one of the concentrated liquid storage means. The storage tank 17 is an atmospheric pressure tank and is open to the atmosphere as shown in the figure. Also, automatic opening / closing valves 10, 11, and 12 provided in the hydrofluoric acid wastewater supply system 1, the alkali supply system 2, and the heating steam supply system 35, and the automatic operation for switching the concentrate circulation pump 42 and the concentrate circulation system 43 are performed. The devices such as the valves 92 and 93 serving as temporary concentration interrupting means also constitute the concentrated liquid storing means. The blow line 9 is provided with a blow valve 91. Since the storage tank 17 is of the atmospheric pressure type, the liquid at the bottom where impurities are precipitated is discharged by gravity.

The process of treating hydrofluoric acid wastewater by the apparatus of this embodiment is basically performed in the step of FIG. 5 similarly to the apparatus of FIG. In this case, the left step B _2, it reaches a certain concentration concentration detected by the specific gravity meter 7 is predetermined, automatic opening and closing valve hydrofluoric acid waste water supply system 1 10 and the automatic valve of the concentrate circulating system 43 9
By closing the second valve and the like and opening the automatic valve 93, the concentration step is temporarily interrupted and the liquid in the concentrated liquid reservoir 36 is discharged into the storage tank 17. This discharge is performed in a very short time, and when the discharge is completed, the valve 93 is closed and the valves 92, 10 and the like are opened, and the concentration step is immediately restarted.

On the other hand, the storage tank 17, a separate independent stand Step B ₂ It is made from the concentration operation, Step B ₂ following the step of FIG. Like the device of FIG. 4 is performed. According to such a device, the storage tank 17 and the automatic valve 93 are added, but it is not necessary to stop the evaporating and concentrating device while the concentrated liquid is allowed to stand still, so that the operation rate of the entire equipment is improved. Can be.

FIG. 7 shows a hydrofluoric acid wastewater treatment apparatus to which the present invention is applied.
5 shows another example of a concentrating system. The evaporating and concentrating apparatus 3 of this example is
It is a heavy duty type device and has two fuselage parts 31₁, 3
1_Two, First heating steam system 35₁, Torso part 31₁Evaporation from
Second heating steam system 35 _TwoThe first body part 31₁Is
The partially concentrated semi-concentrated liquid is supplied to the second body part 31._TwoLiquid leading to
Transfer system 1_Two, First and second heated steam drain system 41₁, 4
1_Two, First and second vacuum pumps 38₁, 38_Two, Etc.
I have.

In the apparatus of this embodiment, the first and second body parts 3
1 _1, 31 ₂ of the evaporation temperature are about 70 ° C. and 40 °
° C. Therefore, as the cooling water, ordinary industrial water,
Any water such as cooling water for a cooling tower, groundwater, river water, etc. can be used. According to the apparatus of this example, since the temperature of the concentrated water sent to the ion exchange operation can be lowered, the separation performance is somewhat disadvantageous and the operation operation is somewhat complicated, but the steam consumption is significantly reduced. In addition, the evaporation temperature can be necessarily lowered without providing a cooler or the like, and the durability of the membrane of the ion exchange device can be improved.

In the apparatus shown in FIG.
The degree of vacuum according to 8 may be increased and the evaporation temperature may be set to 40 ° C to 50 ° C. Also in that case, the durability of the ion exchange membrane can be improved. Further, if necessary based on operation results, etc., a cooler can be additionally provided in the concentrated liquid discharge system 44 of the apparatus shown in FIG.

[0045]

As described above, according to the present invention, in the invention of claim 1, the method for treating hydrofluoric acid wastewater includes a neutralization step, a concentration step, and a separation step having a predetermined structure.
Addition of an alkali that forms a highly water-soluble salt when added to hydrofluoric acid wastewater in the neutralization process to hydrofluoric acid wastewater to make it a neutralized solution, so that hydrofluoric acid is mixed into distilled water evaporated in the concentration process And this can be made reusable water. Also, in the concentration step, the neutralized solution is evaporated and concentrated to a high concentration below the solubility of the salt to form a concentrated solution, so the hydrofluoric acid and alkali contained in the ionic bond as salts are concentrated and recovered. Can be made reusable when done. In the separation step, pure water is supplied to at least a side where hydrogen ions are generated, and the pure water is concentrated by an ion exchange operation including an operation of electrolyzing the pure water and permeating the solid polymer electrolyte membrane to generate the hydrogen ions. Since the liquid is separated into hydrofluoric acid-containing water and alkali-containing water and can be discharged, by performing this operation, high-concentration hydrofluoric acid and alkali can be separately recovered. The remaining demineralized water, which may contain impurities, is returned to the evaporating and concentrating device and treated, for example, by the usual method of intermittent small-volume blow drainage at the bottom of the concentrated water reservoir.

As a result, hydrofluoric acid wastewater was additionally supplied as distilled water, hydrofluoric acid, and a processing material without generating sludge or turbid liquid as in the case of the slaked lime treatment of the prior art, that is, generating almost no waste. It can be completely separated from alkali. In this case, since the separated hydrofluoric acid and alkali have a high concentration, the entire amount can be reused. In addition, since pure water is electrolyzed using a solid polymer electrolyte membrane to generate hydrogen ions for hydrofluoric acid generation, impurities are prevented from being mixed into hydrofluoric acid, and the high purity necessary for cleaning electronic components and the like is prevented. Can be regenerated as hydrofluoric acid. Further, current efficiency at this time can be improved, and power consumption can be reduced.

As a result, according to the first aspect of the present invention, it is possible to reduce the operating cost in the cleaning step using hydrofluoric acid and to contribute to the public benefit of resource saving and prevention of generation of waste.

According to the third aspect of the present invention, the hydrofluoric acid wastewater treatment apparatus includes a hydrofluoric acid wastewater supply system, an alkali supply system, an evaporative concentration device, an ion exchange device, and a pure water supply system having a predetermined structure. The hydrofluoric acid wastewater to be treated is supplied, and an alkali that forms a highly water-soluble salt when added to the hydrofluoric acid wastewater is added to the hydrofluoric acid wastewater to make it a neutralized solution, which is taken into an evaporator and evaporated to evaporate. The solution is concentrated to a high concentration below the solubility of the salt to form a concentrated solution, and this solution is supplied to an ion exchange device and pure water is supplied to separate the concentrated solution into hydrofluoric acid-containing water and alkali-containing water by an ion exchange operation. Can be discharged. As a result, the same function and effect as the first aspect can be obtained.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the method for treating hydrofluoric acid wastewater includes a concentration detecting step having a predetermined structure, a standing step, an upper liquid removing step, and a draining step. Therefore, the concentration of the concentrated solution is detected during the concentration step, and the concentration step is interrupted or stopped when the detected concentration reaches a predetermined target high concentration in the stationary step, and the concentrated solution is evaporated and concentrated. Is separated from the upper liquid and the lower impurity-containing liquid by leaving the liquid in the concentrated liquid storage part or the concentrated liquid storage part of the evaporative concentration apparatus itself, and in the removal step, the upper part to be subjected to ion exchange operation The liquid containing impurities is taken out and supplied to the ion exchange operation, and the impurity-containing liquid is discharged in the discharging step. When the hydrofluoric acid wastewater contains some impurities, this is discharged in accordance with the concentration operation, and the concentrated liquid is discharged. Accumulation of impurities inside and no stagnation Without, the ion exchange operation to supply concentrate free of impurities, it is possible to separately discharge the impurities.

As a result, the introduction of impurities when performing the ion exchange operation is prevented, the operation state of the apparatus used for the ion exchange operation is improved, and operations such as cleaning of the membrane are greatly reduced. In addition, the durability of the film can be increased. In addition, it is possible to prevent the scale from sticking to a device for evaporative concentration or a related portion of the ion exchange device.

According to a fourth aspect of the present invention, in addition to the third aspect of the present invention, the hydrofluoric acid wastewater treatment apparatus further comprises a concentration detecting means having a predetermined structure, a concentrated liquid storing means, an upper liquid supply system, and an impurity discharging system. And the ion exchange device operating means and the control means. When the concentration detecting means detects a predetermined high concentration by the control means, the concentrated liquid storing means is operated to store the concentrated liquid, and after a predetermined time elapses, the upper part is turned on. The liquid supply system supplies the upper liquid of the stored concentrated liquid to the ion exchange device, and the impurity liquid discharge system discharges the lower liquid in which the impurities are precipitated, and after the supply, the operating means operates the ion exchange device. By controlling so as to cause the same effect as in the second aspect of the invention. Further, since the method of claim 2 can be automatically carried out, the treatment of hydrofluoric acid wastewater which hardly generates waste can be automatically carried out to save labor.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of the entire configuration of a hydrofluoric acid wastewater treatment apparatus to which the present invention is applied.

FIG. 2 is an explanatory diagram showing a basic configuration of a hydrofluoric acid wastewater treatment method to which the present invention is applied.

FIG. 3 is an explanatory view of an ion exchange operation in the apparatus and method.

FIG. 4 is an explanatory view showing another example of the entire configuration of the hydrofluoric acid wastewater treatment apparatus to which the present invention is applied.

FIG. 5 is an explanatory view showing another example of the basic configuration of the hydrofluoric acid wastewater treatment method to which the present invention is applied.

FIG. 6 is an explanatory view showing still another example of the entire configuration of the hydrofluoric acid wastewater treatment apparatus to which the present invention is applied.

FIG. 7 is an explanatory view showing another example of the concentrating device portion of the hydrofluoric acid wastewater treatment device to which the present invention is applied.

[Explanation of symbols]

Reference Signs List 1 hydrofluoric acid drainage supply system 2 alkali supply system 3 evaporative concentrator 5 ion exchanger 6 pure water supply system 7 specific gravity sensor (concentration detection means) 8 upper liquid supply system 10, 11, 12 automatic open / close valve (concentrate storage means) 13 Automatic open / close valve (Ion exchange device operating means) 14 Operation control panel (Control means) 17 Concentrated liquid storage tank (Concentrated liquid storing means) 36 Concentrated liquid storage section (Concentrated liquid storing means) 42 Circulation pump (Concentrated liquid storing means) 45 Concentrated liquid discharge pump (upper liquid supply system, concentrated liquid storage means) 57 Hydrofluoric acid recovery system (hydrofluoric acid-containing water system) 58 KOH recovery system (alkali-containing water system) 91 Automatic blow valve (impurity liquid discharge system) 92 Automatic circulation system The valve (impurity liquid discharge system, concentrate storage means) 93 automatic valve (impurity liquid discharge system, concentrate storage means) A neutralization step B concentration step C separation step B ₁ concentration detecting step B ₂ standing step B ₃ top Extraction Step B ₄ draining step

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C02F 1/46 ZAB C02F 1/46 103 F-term (Reference) 4D006 GA17 HA02 JA02 KA01 KB18 MA03 MA13 MA14 MA40 MB07 PA04 PB08 PB27 PB28 PC01 4D034 AA27 BA01 CA12 CA21 4D061 DA08 DB18 EA09 EB01 EB04 EB13 EB39 ED20 FA02 GC05

Claims (4)

[Claims] 1. A hydrofluoric acid wastewater treatment method for treating a hydrofluoric acid wastewater containing a dilute concentration of hydrofluoric acid, wherein an alkali which generates a highly water-soluble salt when added to the hydrofluoric acid wastewater is added to the hydrofluoric acid wastewater. A neutralization step of converting the hydrofluoric acid wastewater into a neutralized solution, a concentration step of evaporating the neutralized solution with an evaporator and concentrating the solution to a high concentration below the solubility of the salt to obtain a concentrated solution, and an ion exchange operation. The concentrated liquid is supplied by an ion exchange operation including an operation of supplying pure water to at least a side where hydrogen ions are generated, electrolyzing the pure water and permeating the solid polymer electrolyte membrane to generate the hydrogen ions. A separation step of separating the hydrofluoric acid-containing water, the alkali-containing water and the remaining demineralized water into a hydrofluoric acid-containing water system, an alkali-containing water system, and a return system for returning to the evaporating and concentrating apparatus. Characteristic Hydrofluoric acid wastewater treatment method of. 2. A concentration detecting step for detecting a concentration of the concentrated solution, and when the detected concentration becomes the high concentration, the concentrated solution is allowed to stand still in a concentrated solution storing section, and an upper liquid and a lower impurity-containing liquid are separated from each other. And a draining step of draining the impurity-containing liquid. Item 4. The hydrofluoric acid wastewater treatment method according to Item 1. 3. A hydrofluoric acid wastewater treatment apparatus for treating hydrofluoric acid wastewater containing dilute hydrofluoric acid, comprising: a hydrofluoric acid wastewater supply system capable of supplying the hydrofluoric acid wastewater; An alkali supply system capable of supplying an alkali which is a salt that produces a high salt and is added to the hydrofluoric acid wastewater to convert the hydrofluoric acid wastewater into a neutralizing solution; and An evaporative concentration device that concentrates to a high concentration below the solubility to make a concentrated solution,
Pure water is supplied while the concentrated liquid is supplied.Pure water is supplied to at least the side where hydrogen ions are generated in an ion exchange operation, and the pure water is electrolyzed and permeated through the solid polymer electrolyte membrane. The concentrated solution is separated into hydrofluoric acid-containing water, alkali-containing water, and the remaining demineralized water by an ion exchange operation including an operation of generating the hydrogen ions, and the separated liquid is separated into a hydrofluoric acid-containing water system, an alkali-containing water system, and the evaporative concentrator. A hydrofluoric acid wastewater treatment apparatus, comprising: an ion exchange device capable of discharging to a return system; and a pure water supply system capable of supplying the pure water. 4. A concentration detecting means for detecting the concentration of the concentrated liquid, a concentrated liquid storing means for storing the concentrated liquid, and a liquid above the concentrated liquid stored by the concentrated liquid storing means is supplied to the ion exchange device. An upper liquid supply system for supplying, an impurity liquid discharge system for discharging a liquid below the stored concentrated liquid, an ion exchange device operating means for operating the ion exchange device, and the concentration detecting means for detecting the high concentration. Upon detection, the storage means is operated to store the concentrated liquid, and after a lapse of a predetermined time, the upper liquid supply system supplies the upper liquid to the ion exchange device, and the impurity liquid discharge system discharges the lower liquid. The hydrofluoric acid wastewater treatment apparatus according to claim 3, further comprising control means for controlling the operation means to operate the ion exchange device after the supply.