TW201609567A - Wastewater processing tank for wastewater containing sodium aluminate and wastewater processing method - Google Patents

Abstract

Provided is a single-tank integrated wastewater processing tank that is used in the processing of wastewater containing sodium aluminate discharged during an aluminum member surface processing or molding/machining step, and in particular, reduces as much as possible the amount of clinker generation of aluminum hydroxide at the inner wall surface of a separation unit and is thus able to prevent problems stemming from clinker adhesion. Also provided is a wastewater processing method that uses the tank to process wastewater containing sodium aluminate and recovers a sodium hydroxide solution and aluminum hydroxide. The single-tank integrated wastewater processing tank that is for wastewater containing sodium aluminate and in which a precipitation unit and a separation unit are configured integrally is characterized by a cooling means being provided to the precipitation unit positioned below the tank main body, and a heating means being provided to the separation unit positioned above the tank main body.

Description

Waste liquid treatment tank containing waste liquid of sodium aluminate and waste liquid treatment method

The present invention relates to a waste liquid treatment tank containing a waste liquid of sodium aluminate and a waste liquid treatment method using the same, and particularly relates to a hydrolysis of sodium aluminate to a precipitate located under the tank body, and which will be separated above the tank body In the waste liquid processing tank in which the precipitation portion and the separation portion which are formed by the solid-liquid separation of the aluminum hydroxide produced by the partial hydrolysis are formed, the content of the clinker which is generated on the groove wall surface and adheres to the aluminum hydroxide can be effectively suppressed. A waste liquid treatment tank for sodium aluminate waste liquid and a waste liquid treatment method using the same.

Aluminum made of aluminum or aluminum alloy has been widely used in various parts such as ships, vehicles, machinery, or construction materials such as window frames, other electrical products, business supplies, household goods, etc. At this time, aluminum processing In a specific shape, various surface treatments are carried out for the purpose of purifying the surface, imparting corrosion resistance, design improvement, etc., and using it as a desired aluminum product.

Further, when such an aluminum material is used as an actual aluminum product, the aluminum material is subjected to various forming processes for forming a desired shape, or improvement of corrosion resistance or wear resistance, addition of decoration and other functions, and the like. In the various surface treatments performed, when the aluminum material is processed or surface treated, the aluminum-containing waste liquid is inevitably generated along with the processing or surface treatment, and it is necessary to carry out the aluminum-containing waste liquid. Processing.

That is, the forming process of the aluminum material is, for example, extruding the aluminum material into a specific cross-sectional shape using a die mouth, and performing die-die extrusion molding for manufacturing the aluminum mold material, but the extrusion nozzle is formed at the end of the extrusion operation. Thereafter, the aluminum material remaining in the pores of the nozzle was dissolved and removed by using a high-concentration sodium hydroxide aqueous solution as a cleaning liquid. Further, when the cleaning liquid of the nozzle is repeatedly used, aluminum is dissolved in the cleaning liquid, and gradually accumulates as sodium aluminate, and accordingly, the solubility of the cleaning liquid to aluminum is lowered, so After a certain amount of washing treatment or a washing liquid after a certain period of washing treatment, it is necessary to be treated as a waste liquid of the aged washing liquid.

Further, as the surface treatment of the aluminum material, anodizing treatment for imparting corrosion resistance or abrasion resistance to the surface of the aluminum material using an aqueous solution of sulfuric acid, or electrochemical treatment of the surface of the aluminum material using an aqueous solution of nitric acid or hydrochloric acid has been widely performed. Roughening of the roughening, or etching treatment of the surface of the aluminum material by using an aqueous solution of sodium hydroxide, and the above anodizing treatment or roughening treatment is generally performed by etching with a sodium hydroxide solution. Pre- or post-processing. Further, in the surface treatment of the aluminum material, aluminum is dissolved in the sodium hydroxide aqueous solution of the treatment liquid, and gradually accumulates as sodium aluminate, so that the solubility for aluminum is lowered, so that the surface treatment is performed for a specific amount or after a certain period of time. The aqueous sodium hydroxide solution is discharged as a waste liquid of the aged treatment liquid.

A cleaning solution or treatment formed from the aqueous sodium hydroxide solution In the liquid aging waste liquid, the aluminum component derived from aluminum is accumulated in a large amount as sodium aluminate, and such a large amount of sodium aluminate-containing waste liquid containing sodium aluminate is used to recover the sodium component present in the waste liquid or A variety of attempts have been made so far for the valuable substances such as aluminum components and their effective use.

For example, in Patent Document 1, it is proposed to etch the aluminum material with an aqueous solution of sodium hydroxide, and then perform anodizing treatment with an aqueous solution of sulfuric acid, neutralize the waste sulfuric acid discharged from the anodizing treatment step with a base, and separate the gel formed at this time. Aluminium hydroxide, which reacts with sodium hydroxide to form a sodium aluminate solution, and mixes the sodium aluminate solution with the spent sodium hydroxide solution discharged from the etching step and adds aluminum hydroxide as a seed in the mixture. A method in which the aluminum component in the mixed solution is precipitated as crystalline aluminum hydroxide and the aqueous sodium hydroxide solution of the mother liquid is used as an etching solution.

Further, in Patent Document 2, it is proposed to separate aluminum ions from the system from a portion of the treatment liquid containing the sodium aluminate solution and recover the sodium hydroxide solution, and to mix the recovered sodium hydroxide solution with the treatment liquid to make the aluminum ions in the treatment liquid. The concentration is maintained at a specific concentration, and when the surface of the aluminum plate is etched, the aluminum slurry generated from the neutralization of the waste acid and the spent alkali discharged from the surface treatment step of the aluminum plate is mixed in one of the treatment liquids, and the treatment is performed. One of the liquids is partially adjusted to a supersaturated sodium aluminate solution, and the crystalline aluminum hydroxide is crystallized and a sodium hydroxide solution is recovered.

Further, in Patent Document 3, when the treatment of the nozzle waste liquid generated when the aluminum remaining in the pores of the nozzle is dissolved is proposed, the release agent contained in the nozzle waste liquid is removed in advance by the adsorbent, and hydrogen is introduced. Alumina is added to the die waste liquid (supersaturated sodium aluminate solution) after removing the release agent, and precipitated The crystalline aluminum hydroxide is simultaneously reused as a die solution by using a caustic soda aqueous solution.

That is, in the surface treatment or forming process of such an aluminum material, it is generally carried out by adding crystals to the sodium aluminate-containing waste liquid having high supersaturation discharged from the surface treatment or the forming process. Aluminum hydroxide is used as a seed, and the supersaturation is further increased by lowering the temperature of the solution by lowering the temperature of the solution, thereby hydrolyzing the sodium aluminate in the waste liquid and precipitating the crystalline aluminum hydroxide, followed by solid-liquid separation and hydrolysis. Then, the treated liquid having a low degree of supersaturation recovers the crystalline crystalline alumina as a valuable substance, and solid-liquid separation of the particulate aluminum hydroxide contained in the filtrate by a clarifier for the filtrate, and recycling to the surface In the step of the treatment or the forming process, the supersaturation is further lowered by heating, and reused as a treatment liquid or a washing liquid. Here, the "supersaturation" is a value expressed by "aluminum concentration / saturated aluminum concentration" in a sodium aluminate solution.

Further, when the sodium aluminate waste liquid containing the high supersaturation is treated in a large amount, a so-called multi-tank separation type waste liquid treatment apparatus using a crystalline aluminum hydroxide is used. a precipitation tank which is added to a waste liquid containing sodium aluminate and hydrolyzed, and precipitates crystalline aluminum hydroxide, and is purified by solid-liquid separation of crystalline aluminum hydroxide in the liquid treated in the precipitation tank. The device is composed of individual slots and is connected in series. In contrast, when the amount of processing is small, the operation is simple and the installation area is small, and the initial cost is relatively low, and the precipitation unit is usually used. (Precipitation tank) A so-called single-tank-integrated waste liquid treatment tank integrally formed with a separation unit (purifier).

However, in the single-tank-integrated waste liquid treatment tank, the supersaturation of the sodium aluminate is hydrolyzed and the precipitated portion of the crystalline aluminum hydroxide precipitates in the presence of the seed, although the supersaturation is lowered, but the supersaturation is lowered. The liquid treated after precipitation of crystalline aluminum hydroxide is still supersaturated. Therefore, when the temperature of the solution is lowered to precipitate crystalline aluminum hydroxide, it is known that the solubility of saturated aluminum usually takes 30 to 40 days, since it is generally 1 in the industry. Since it is rapidly precipitated in ~2 days, the treated liquid after the hydrolysis treatment in which the self-precipitating portion moves toward the separation portion precipitates aluminum hydroxide due to the low supersaturation, and since the precipitated aluminum hydroxide is different from the precipitation portion, Since there is no seed, the slag is attached to the inner wall surface of the separation portion, etc., and since the adhered slag exerts the effect of the seed, the precipitation of aluminum hydroxide is accelerated, and the separation portion is gradually made. The problem of volume reduction, etc. According to the investigation by the inventors of the present invention, the adhesion of such a slag to the inner wall surface of the separation portion is on average about 15 to 20% of the volume of the separation portion per year.

Therefore, in the past, in order to prevent problems caused by the slag sticking to the inner wall surface of the single-slot integrated type separation portion, the operation was stopped at a frequency of about once/year, and the liquid in the tank was extracted, and the rock was used. The crushing slag is crushed, and the slag removing step (desilting operation) in the cleaning tank is performed. According to the investigation by the inventors, the slag removal operation requires an average of 15 labors per year (worker × working days) Further, it is necessary to temporarily accommodate another generation tank having a volume larger than the capacity of the waste liquid treatment tank of the solution extracted from the tank, which is economically burdensome to the operator.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. Sho 52-043, No. 184

[Patent Document 2] Japanese Patent Publication No. 04-323, No. 386

[Patent Document 3] WO 01/040123

Therefore, when the inventors of the present invention treat a waste liquid containing sodium aluminate having a high degree of supersaturation in a single-tank-integrated waste liquid treatment tank, the generation of the aluminum hydroxide slag adhering to the inner wall surface of the separation portion or the like is minimized as much as possible. As a result of actively discussing the method, it was found that a cooling means is provided at the deposition portion below the tank body, and a heating means is provided at the separation portion positioned above the tank body, thereby reducing the presence of the aluminum hydroxide seed in the precipitation portion. The temperature of the solution of the high supersaturation waste liquid is such that the sodium aluminate in the waste liquid is hydrolyzed to precipitate the crystalline aluminum hydroxide to form a sodium aluminate solution having a low supersaturation, and the treated liquid after the hydrolysis is moved from the precipitation portion. Going to the separation portion, increasing the temperature of the treated liquid in the separation portion to a specific temperature range higher than the temperature of the solution of the waste liquid, and maintaining the treated liquid in the vicinity of the saturated aluminum solubility in the separation portion, or In the following, it is possible to effectively suppress the generation of slags on the inner wall surface of the separation portion, etc., and thus the present invention has been completed.

Accordingly, an object of the present invention is to provide a waste liquid treatment tank containing a waste liquid of sodium aluminate, which is used for the treatment of a waste liquid containing sodium aluminate discharged in the step of surface treatment or forming processing of aluminum material. Slot integrated In the waste liquid treatment tank, in particular, the amount of the aluminum hydroxide slag generated on the inner wall surface of the separation portion can be reduced as much as possible to prevent the problem caused by the adhesion of the slag.

In addition, the object of the present invention is to provide a waste liquid treatment method for a waste liquid containing sodium aluminate, which is used for treating a waste liquid containing sodium aluminate using the waste liquid treatment tank, and recovering sodium hydroxide solution and aluminum hydroxide. .

That is, the present invention is a waste liquid treatment tank containing a waste liquid of sodium aluminate, which comprises: adding a seed of aluminum hydroxide to a waste liquid containing sodium aluminate with high supersaturation, and making the waste liquid a precipitation portion in which aluminum aluminate is hydrolyzed to precipitate aluminum hydroxide; and a separation portion that performs solid-liquid separation of the aluminum hydroxide precipitated in the treated liquid obtained by hydrolyzing the sodium aluminate in the waste liquid; a waste liquid treatment tank containing a waste liquid containing sodium aluminate, wherein the deposition portion is below the tank body and the separation portion is above the tank body, and the separation portion and the separation portion are mutually connected to each other. A cooling means for cooling the waste liquid is provided in the precipitation portion, and a heating means for heating the treated liquid is provided in the separation portion.

Further, the present invention relates to a waste liquid treatment method for a waste liquid containing sodium aluminate, which comprises treating a waste liquid containing sodium aluminate containing sodium aluminate using a waste liquid treatment tank containing the above-mentioned waste liquid containing sodium aluminate. A waste liquid treatment method for waste liquid, characterized in that a high supersaturation sodium sulphate-containing waste liquid is introduced into a precipitation portion located below the tank body of the waste liquid treatment tank, and a seed of aluminum hydroxide is added, and the precipitation is performed. In the middle part of the waste liquid under stirring The sodium aluminate is hydrolyzed, and then, when the hydrolyzed liquid is subjected to solid-liquid separation in the separation portion above the tank body to recover the sodium hydroxide solution and the aluminum hydroxide, the cooling means provided in the precipitation portion is used to The temperature of the waste liquid in the precipitation portion is maintained within a range of 40 to 65 ° C, and the temperature of the treated liquid in the separation portion is maintained at a temperature 10 to 50 ° C higher than the temperature of the waste liquid by a heating means provided in the separation portion. The temperature within the range.

In the present invention, the waste liquid treatment tank for treating the waste liquid containing sodium aluminate is provided with a precipitation portion at a position below the tank body, and a separation portion is integrally provided at a position above the tank body and the precipitation portion, and such a precipitation portion The separation unit can be configured to communicate with each other. Further, the waste liquid introduced into the precipitation portion is cooled in the precipitation portion in the presence of the aluminum hydroxide seed, whereby the sodium aluminate in the waste liquid is hydrolyzed to precipitate aluminum hydroxide as crystals, and the sodium aluminate is hydrolyzed. The subsequently treated liquid is slowly and solidly separated into the formed aluminum hydroxide crystal and the sodium hydroxide solution while being slowly flowing, and rises to the separation portion as a low supersaturation into the precipitation portion. The solution containing sodium aluminate is discharged from the upper portion of the separation portion to the outside of the waste liquid treatment tank.

Further, in the present invention, a cooling means is provided in the precipitation portion to cause aluminum hydroxide in the presence of an aluminum hydroxide seed at a solution temperature of a sodium aluminate-containing waste liquid having a high degree of supersaturation introduced into the precipitation portion. The crystals precipitated and reduced to a low supersaturation of the sodium aluminate-containing waste liquid, resulting in a lower supersaturation of the sodium aluminate-containing waste liquid. The cooling means can be exemplified by a cooling sleeve, a cooling coil, a plate heat exchanger, etc., and if it is possible to cool the waste liquid, it may be provided inside the precipitation portion or may be provided outside the precipitation portion. (outer wall surface), in order to facilitate the maintenance of the slag block, etc., it is preferably disposed on the outer wall surface of the precipitation portion so as to surround the outer wall surface, and is formed between the upper portion and the lower portion in the groove body. The temperature gradient is preferably set at a lower portion than the center of the side surface of the groove body. The temperature at which the waste liquid containing sodium aluminate is cooled by the cooling means varies depending on the type of the waste liquid introduced into the precipitation portion, but is usually 40 to 65 °C.

In the present invention, in the separation unit, the crystal of aluminum hydroxide formed by hydrolysis of sodium aluminate and the sodium hydroxide solution are finally subjected to solid-liquid separation, and the crystal of aluminum hydroxide is further deposited from the separation portion through the precipitation portion. In the lower portion, the sodium hydroxide solution, for example, a V-shaped slit formed on the outer peripheral portion of the upper end portion of the peripheral wall portion of the separation portion, overflows toward the surround and is discharged to the outside of the groove body. Further, in order to effectively exhibit the function as a purifier, the separation portion preferably has an inverted conical trapezoidal shape having a peripheral wall portion that expands upward, thereby not only elongating the time for sedimentation of the crystal of aluminum hydroxide. The precipitated aluminum hydroxide crystals may be guided along the peripheral wall portion to the lower deposition portion. The inclination angle of the inner surface of the peripheral wall of the peripheral wall portion of the inverted conical trapeze shape with respect to the horizontal plane is 60° or more and 80° or less, preferably 65° or more and 75° or less. When the inclination angle is less than 60°, the sliding property of the aluminum hydroxide is poor. It is easy to accumulate, and there is a problem that it eventually becomes a slag block, and when it is more than 80°, there is a problem that the water area (the horizontal area of the upper portion of the groove) cannot be obtained widely.

In the present invention, a heating means for heating the treated liquid is provided in the separation portion, and a cooling means for cooling the waste liquid provided in the deposition portion is supplemented, and the separation portion is provided At The temperature of the liquid to be treated is maintained at a temperature higher than the temperature of the waste liquid in the precipitation portion by 10 ° C or more and 50 ° C or less, preferably 15 ° C or more and 40 ° C or less. Further, the heating means can be exemplified by, for example, a heating sleeve, a heating coil, a plate heat exchanger, etc., and the heating means can be mounted at a position as long as it can heat the treated liquid in the separation portion to a specific temperature. The restriction may be, for example, a peripheral wall portion of the separation portion or a separation of the separation portion into 2 to 8 compartments in the circumferential direction for the purpose of preventing the liquid in the separation portion from rotating and allowing the treated liquid to stand still. The partition wall is attached to the partition wall or the like.

The waste liquid treatment tank containing the sodium aluminate-based waste liquid according to the present invention can effectively suppress the inside of the tank body to which the treated liquid after the hydrolysis is contacted in the waste liquid treatment tank integrally formed by the separation portion and the separation portion. The wall surface, in particular, the slag of aluminum hydroxide is generated and adhered to the inner wall surface of the separation portion functioning as a purifier.

Further, according to the waste liquid treatment method using the waste liquid treatment tank of the present invention, it is possible to suppress the generation of the slag in the separation portion while discharging the waste liquid containing sodium aluminate in the die extrusion molding or the anodizing treatment. The treatment is carried out, and the sodium hydroxide solution and aluminum hydroxide can be recovered.

1‧‧‧ slot body

1a‧‧‧ bottom

2‧‧‧Department

3‧‧‧Separation Department

3a‧‧‧Walls

4‧‧‧ upper cylinder

4a‧‧‧Import

4b‧‧‧skirt

5‧‧‧drain tube

6‧‧‧Agitator

6a‧‧‧Agitating wing

6b‧‧‧Agitator shaft

7‧‧‧Separating sleeve (dividing wall)

7a‧‧‧ divider

7b‧‧‧ Compartment

7c‧‧‧Connected holes

7d‧‧‧Connected holes

8‧‧‧Cooling sleeve

8a‧‧‧Inlet of the refrigerant

8b‧‧‧Discharge of refrigerant

9‧‧‧heating sleeve

9a‧‧‧Import of heat medium

9b‧‧‧Hot media export

10‧‧‧Support

11‧‧‧Rolling pieces

12‧‧‧V incision

13‧‧‧Liquid discharge

L ₁ ‧‧‧Pre-treatment waste

L ₂ ‧‧‧treated liquid

D‧‧‧ Waste treatment tank

C‧‧‧ Centrifugal Separator

A‧‧‧crystalline aluminum hydroxide

T‧‧‧ sodium hydroxide solution recovery tank

E‧‧‧ etching step

1 is a waste liquid containing sodium aluminate for explaining an embodiment of the present invention. Conceptual view of the section of the waste treatment tank.

Fig. 2 is a plan view showing the plane along the line A-A of Fig. 1.

Fig. 3 is a cross-sectional conceptual view taken along line B-B of Fig. 2.

Fig. 4 is a cross-sectional conceptual view taken along line C-C of Fig. 2.

Fig. 5 is a flow chart showing a method of treating the waste liquid of the etching waste liquid of Investigation Example 1 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described based on the embodiments shown in the drawings.

1 to 4 show a waste liquid treatment tank containing a waste liquid of sodium aluminate according to an embodiment of the present invention. In Fig. 1 to Fig. 4, the entire shape of the tank body 1 of the waste liquid processing tank is formed into a cylindrical shape having an open upper end, and an alumina acid containing high supersaturation before introduction of hydrolysis is provided at the lower portion of the tank body 1. a portion 2 of the sodium waste liquid (pre-treatment waste liquid L ₁ ), and a separation portion 3 for allowing the liquid L _{2 having a} low degree of supersaturation after hydrolysis to be subjected to solid-liquid separation at the upper portion, and further The upper portion of the separating portion 3 is formed with an inverted conical trapezoidal peripheral wall portion 3a which is expanded upward and has an inclined angle of 70° with respect to the horizontal plane of the inner surface of the peripheral wall.

In this embodiment, the groove portion of the body 1 is the central line of the separating portion 3 from which downward through the upper, and the upper end of a front waste water treatment prior to introduction of _a hydrolyzable L 4a, while the lower end having a flared downward protection of a skirt portion 4b, the lower end of the skirt portion 4b is disposed to reach the upper cylinder 4 of the precipitation portion 2, and a draught tube 5 is disposed at a position below the upper cylinder 4. The upper end portion is in the skirt portion 4b of the upper cylinder 4, and the lower end portion extends to the vicinity of the bottom portion 1a of the groove body 1, and further, the stirring device 6 is disposed in the upper cylinder 4 and the draft tube 5, The agitating blade 6a is positioned in the above-described draft tube 5, and the agitating shaft 6b penetrates from the agitating blade 6a into the upper cylinder 4 and extends above the upper cylinder 4. Further, in this embodiment, in the groove body 1, the concept is that the portion lower than the lower end position of the skirt portion 4b of the upper cylinder 4 is the precipitation portion 2, and the concept is that it is larger than the skirt portion 4b. more lower end position only upper part of the treated liquid L ₂ of the separating section 3.

Further, in this embodiment, the separating portion 3 is provided with four partition walls 7, one end of which is fixed to the peripheral wall portion 3a, and the other end of which is fixed to the upper cylinder 4, and the region surrounded by the peripheral wall portion 3a faces the same The circumferential direction is divided into four compartments. Those based on the partition wall 7 by rotation of the stirring blades 5 6a of the draft tube, while rotating toward the downward flow of waste water treatment prior to ₁ L of the same time as the side with the rotation directly treated liquid L ₂ directly rises during rotation, are prevented from continuously rotating within the separation unit 3 and the separation-based treatment liquid L ₂ portion still within the person through 3.

In this embodiment, the heating means for heating the treated liquid L ₂ in the separating portion 3 is formed such that the heating sleeve 9 is provided on the outer surface of the peripheral wall of the separating portion 3, and the partition wall 7 itself functions as a heating sleeve. (The partition wall is hereinafter referred to as a "separating sleeve"), and the partitioning sleeve (dividing wall) 7 is such that the inside thereof is divided into four compartments 7b in the vertical direction by the three partition plates 7a, and above. The partitioning plate 7a and the lower partitioning plate 7a are formed on the upper cylinder 4 side with a communication hole 7c for allowing the upper and lower compartments to communicate with each other, and the partitioning plate 7a in the middle is formed on the side of the peripheral wall portion 3a. A communication hole 7c is formed between the upper and lower compartments 7b and the heating sleeve 9, and a communication hole 7d is formed between the upper and lower compartments 7b. Further, the separation portion 3 is provided with a heat medium introduction port 9a passing through the upper portion of the heating sleeve 9 on the outer surface of the peripheral wall and the uppermost partition 7b of the partition sleeve 7, and the heating sleeve 9 outside the peripheral wall Below the position, there is a discharge port 9b for the heat medium.

And, in this embodiment, in the outer peripheral wall of the deposition unit 2 is provided with 8 L ₁ cooling means to cool the cooling sleeve so as to precipitate the pre-processed portion of the waste liquid 2, the cooling sleeve 8 is provided at a position below the refrigerant The inlet 8a is guided, and a discharge port 8b for refrigerant is provided at an upper position.

In addition, in Fig. 1, reference numeral 10 supports the upper cylinder 4 and the support portion of the stirring device 6 provided at the upper end portion of the groove body 1, and the reference numeral 11 is collected from the upper end of the peripheral wall portion 3a of the separation portion 3. Surrounding piece of the treated liquid (sodium hydroxide solution) after the separation, and the symbol 12 will be treated by the static separation of the liquid from the upper end of the peripheral wall portion 3a (sodium hydroxide solution) The V slit is guided into the surrounding member 11. Further, the symbol 13 is such that the treated liquid (sodium hydroxide solution) in the surrounding member 11 is evacuated to the liquid discharge port outside the tank body 1. Further, the draft tube 5 is supported in the tank body 1 by means of a supporting metal member or the like as illustrated.

Accordingly, in this embodiment, the pre-treatment waste liquid L ₁ cooled to a higher supersaturation of 40 to 65 ° C is usually introduced into the upper cylinder 4 from the introduction port 4a provided at the upper end of the cylinder 4, and It flows downward by the rotation of the stirring blade 6a of the stirring device 6 [refer to the double arrow of Fig. 1 ( )], through the inside of the draft tube 5, into the lower portion of the precipitation portion 2 in which the aluminum hydroxide seed is present, and in the deposition portion 2, the cooling sleeve 8 provided on the outer surface of the peripheral wall is further cooled to 40 to 65 ° C. It becomes a supersaturated solution of sodium aluminate and is hydrolyzed to become a crystal of the treated liquid L ₂ and precipitate aluminum hydroxide.

Further, the liquid L ₂ treated after the hydrolysis in the deposition unit 2 raises the outer side of the catheter 5 (see the double arrows of FIGS. 1, 3, and 4). Skirt portion)], through the upper part 4b of the cylinder 4 and the gap between the upper end of the draft tube 5 and into the upper portion of the cylinder 4, the front of the waste liquid treatment within the upper portion of the cylinder 4 L ₁ The liquid flow merges, and the inside of the draft tube 5 is again lowered, and the other portion enters the skirt portion 4b of the upper cylinder 4 and the separation portion 3 positioned above the precipitation portion 2. Further, the treated liquid L ₂ that has entered the separation portion 3 is stopped by the respective partition sleeves 7 in the separation portion 3 in the rotational direction, and is in the region surrounded by the peripheral wall portion 3a in the shape of the inverted conical trapezoid. The rising liquid flow is more slowly, and as far as possible, the crystal of the aluminum hydroxide in the treated liquid L ₂ is allowed to stand apart and settle downward. Further, the treated liquid (sodium hydroxide solution) L ₂ after separating the crystals of aluminum hydroxide is taken out from the liquid discharge port 13 through the surround member 11 through the V slit 12 formed at the upper end of the peripheral wall portion 3a of the separation portion 3 to Outside the tank body 1, and if necessary, the aluminum concentration is again lowered and used as a sodium hydroxide solution.

Here, the treated liquid L ₂ entering the separation portion 3 is divided into four partitions by a heating sleeve 9 provided on the outer peripheral wall of the separating portion 3 and a region surrounded by the peripheral wall portion 3a of the separating portion 3. and four separate play between the sleeve 7 is formed in such manner as a function of the heating sleeve is heated to a temperature higher than the temperature within the waste water treatment prior to deposition of _a portion 2 L high range of 10 ~ 50 ℃. Here, in the embodiment, in the cooling sleeve 8, the refrigerant introduction port 8a is provided below the cooling sleeve 8, and the refrigerant discharge port 8b is provided at the upper position so that the refrigerant self-cooling sleeve 8 The lower side flows upward (refer to the arrow (→) of FIG. 1), and the heating sleeve 9 is provided with the heat medium discharge port 9b at the lower position, and the heat medium introduction port 9a is provided at the upper position, and is set. The heat medium introduction port 9a of the partition 7b of the uppermost partitioning sleeve 7 is disposed so that the heat medium flows downward from the upper side of the heating sleeve 9 and the partition sleeves 7 (refer to FIG. The arrow (→) of FIG. 3 and FIG. 4 is set so that the temperature gradually rises from the lower end side of the deposition part 2 in the tank main body 1 toward the upper end side of the separation part 3.

In this embodiment, lower portion within the separator 3 through the treatment of over-saturation of the liquid L becomes ₂ because the front of the waste liquid temperature of ₁ L 2 than the inner portion of the deposition process is high, it becomes the lower the degree of supersaturation or saturation, so The ability to precipitate aluminum hydroxide crystals (crystallization precipitation force) is lowered, and the occurrence of slag in the separation portion 3 can be suppressed as much as possible.

Here, when discussing the solubility of aluminum in aqueous sodium hydroxide solution, for example, having a total sodium hydroxide (total-NaOH) concentration: 100.0 g/L, free sodium hydroxide (free-NaOH) concentration: 73.3 g/L , aluminum concentration: 18.0g / L, and the proportion of aluminum in the total sodium hydroxide (total - NaOH) (weight ratio: wr): 0.180 composition of the solution (including There is a waste liquid of sodium aluminate), the temperature of the solution (45 ° C), the solubility of aluminum (10.7 g / L), and the residual amount of precipitation [the amount of precipitation is the amount of aluminum dissolved in the sodium hydroxide solution, and The relationship between the aluminum concentration in the solution (18 g/L) and the aluminum solubility (10.7 g/L) (7.3 g/L) is as shown in Table 1, since the solubility of aluminum increases with temperature, and Since the aluminum concentration of the precipitate is reduced (the degree of supersaturation is reduced), the rate of precipitation is reduced. According to this, the value obtained by dividing the precipitation residual amount by the solubility of aluminum is a value indicating the strength of precipitation ability, and an index as a crystallization deposition force can be used.

[Exploration Example 1]

The waste liquid treatment tank containing the sodium aluminate waste liquid of the embodiment of the present invention shown in FIGS. 1 to 4 is used in the anodizing treatment plant according to the flow shown in FIG. The etching liquid thus formed is used to treat the etching waste liquid (the waste liquid containing sodium aluminate) discharged from the etching step of the aluminum material, and the case of recovering the sodium hydroxide solution will be described.

In FIG. 5, the etching step E is performed by immersing the aluminum material in an etching solution made of a sodium hydroxide solution having a concentration of 100 g/L at 45 to 55 ° C, and discharging the aluminum from the etching step E to dissolve the aluminum in the hydrogen. Etching waste liquid in a sodium oxide solution (a waste liquid containing sodium aluminate). The etching waste liquid is transferred to the waste liquid treatment tank D, and the temperature of the solution is lowered to 50 ° C during the transfer, and the etching waste liquid L ₁ (the waste liquid containing sodium aluminate dissolved in aluminum hydroxide with high supersaturation degree is obtained; The pre-treatment waste liquid) is placed in a deposition portion at the lower portion of the tank main body of the waste liquid treatment tank, and further cooled to 45 ° C in the presence of the aluminum hydroxide seed in the precipitation portion, and a part of the sodium aluminate is hydrolyzed to become aluminum hydroxide. Crystallization with sodium hydroxide (sodium hydroxide solution). Then, the liquid L _{2 which has} been treated by hydrolysis in the precipitation portion is gradually separated into a crystal of aluminum hydroxide and a sodium hydroxide solution, and the sodium hydroxide solution is raised in the separation portion of the upper portion of the tank main body maintained at 70 ° C. Finally, the upper end of the peripheral wall portion of the separation portion is discharged to the outside of the tank through the discharge groove at the peripheral portion thereof, and the crystal of aluminum hydroxide gradually increases in concentration in the lower portion of the precipitation portion, and is extracted from the lower portion of the tank body of the waste liquid treatment tank. . Thus, the crystal of aluminum hydroxide extracted from the lower portion of the tank body is filtered by the centrifugal separator C to be used as the valuable crystalline aluminum hydroxide A, and the sodium hydroxide solution discharged to the outside of the tank is temporarily transferred to the recovery tank S. The composition is adjusted therein and reused as an etching solution in the etching step E.

Here, the composition of the waste liquid L ₁ before the treatment which is discharged from the etching treatment step E and enters into the precipitation portion of the waste liquid treatment tank D is, for example, the total sodium hydroxide (total-NaOH) concentration: 100 g/L, Aluminum concentration: 25g/L, and the ratio of aluminum in total sodium hydroxide (total-NaOH) (wr): 0.25, the pre-treatment waste liquid L _{1 is} in the precipitation part of the lower part of the tank body of the waste liquid treatment tank. Cooling to 45 ° C in the presence of alumina seeds, in which sodium aluminate is hydrolyzed to a total sodium hydroxide (total - NaOH) concentration: 100 g / L, aluminum concentration: 18 g / L, and total sodium hydroxide ( The proportion of aluminum in total - NaOH) (weight ratio: wr): 0.18. The treated aluminum concentration of liquid L ₂ (18 g / L) is higher than the aluminum solubility (10.7 g / L) at 45 ° C, still supersaturated, but heated to 70 ° C when rising into the separation part, its aluminum When the solubility is increased to 18 g/L or more, precipitation of aluminum hydroxide in the separation portion is prevented, and it is possible to prevent the slag from adhering to the inner wall surface of the separation portion.

[Exploration Example 2]

For the waste liquid treatment tank using the sodium aluminate-containing waste liquid of the embodiment of the present invention shown in FIGS. 1 to 4, in the aluminum mold manufacturing factory, the nozzle which is made of the sodium hydroxide solution is washed. The cleaning solution is used to clean the nozzle waste liquid (the waste liquid containing sodium aluminate) discharged from the nozzle cleaning step of the used nozzle, and to recover the sodium hydroxide solution.

From the nozzle cleaning step, discharging a ratio of, for example, total sodium hydroxide (total-NaOH) concentration: 200 g/L, aluminum concentration: 70 g/L, and total sodium hydroxide (total-NaOH) (weight ratio) :wr): a nozzle waste liquid of a composition of 0.35, and a nozzle liquid of 100 ° C (a waste liquid containing sodium aluminate in a saturated state; a waste liquid before treatment) is introduced into the precipitation portion in a waste liquid treatment tank. Then, it is cooled to 50 ° C in the presence of aluminum hydroxide seeds, and the treated liquid of sodium aluminate is hydrolyzed to become total sodium hydroxide (total - NaOH). Degree: 200 g/L, aluminum concentration: 50 g/L, proportion of aluminum in total sodium hydroxide (total-NaOH) (weight ratio: wr): 0.25. The treated aluminum concentration of the liquid (50 g/L) is higher than the aluminum solubility (31.3 g/L) at 50 ° C, and is still in a supersaturated state, but is heated to 75 ° C when it is raised to the separation portion, so that The aluminum saturated solubility is increased to 52.4 g/L, so that it is an unsaturated solution, and precipitation of aluminum hydroxide in the separation portion can be prevented, and the slag block can be prevented from adhering to the inner wall surface of the separation portion.

1‧‧‧ slot body

1a‧‧‧ bottom

2‧‧‧Department

3‧‧‧Separation Department

3a‧‧‧Walls

4‧‧‧ upper cylinder

4a‧‧‧Import

4b‧‧‧ hem

5‧‧‧ catheter

6‧‧‧Agitator

6a‧‧‧Agitating wing

6b‧‧‧Agitator shaft

7‧‧‧Isolation sleeve (partition wall)

7a‧‧‧Isolation board

7b‧‧‧Area

7c‧‧‧Connected holes

7d‧‧‧Connected holes

8‧‧‧Cooling sleeve

8a‧‧‧Inlet of the refrigerant

8b‧‧‧Discharge of refrigerant

9‧‧‧heating sleeve

9a‧‧‧Import of heat medium

9b‧‧‧Hot media export

10‧‧‧Support

11‧‧‧Rolling pieces

12‧‧‧V incision

13‧‧‧Liquid discharge

A‧‧‧crystalline aluminum hydroxide

L ₁ ‧‧‧Pre-treatment waste

L ₂ ‧‧‧treated liquid

D‧‧‧ Waste treatment tank

Claims (5)

A waste liquid treatment tank containing a waste liquid of sodium aluminate, which comprises: adding a seed of aluminum hydroxide to a waste liquid containing sodium aluminate with high supersaturation, and hydrolyzing the sodium aluminate in the waste liquid to precipitate a precipitation portion of aluminum hydroxide; and a separation portion for solid-liquid separation of the aluminum hydroxide precipitated in the treated liquid obtained by hydrolyzing the sodium aluminate in the waste liquid; and the precipitation portion is below the groove body And the waste liquid treatment tank containing the waste liquid of sodium aluminate which is formed by integrally forming the separation portion and the separation portion so as to be connected to the separation portion, and is characterized in that the separation portion is provided in the deposition portion. The cooling means for cooling the waste liquid, and the heating means for heating the treated liquid in the separation portion. The waste liquid processing tank of the waste liquid containing sodium aluminate according to claim 1, wherein the separation portion is formed in an inverted conical trapezoidal shape having a peripheral wall portion that is expanded upward, and the heating means is provided in the peripheral wall portion. The waste liquid processing tank of the waste liquid containing sodium aluminate of claim 2, wherein the inclination angle of the peripheral wall portion is 60 or more and 80 or less with respect to the horizontal. The waste liquid processing tank containing the waste liquid of sodium aluminate according to any one of claims 1 to 3, wherein the tank main body is provided with a central portion penetrating from the upper side toward the lower side through the separation portion, and the lower end reaches the precipitation portion In the upper cylinder, a partition wall that divides the inside of the partition portion partitioning the peripheral wall portion and the upper cylinder portion into a plurality of regions in the circumferential direction is provided between the peripheral wall portion of the separation portion and the upper cylinder And the heating means is provided on the partition wall. A waste liquid treatment method for a waste liquid containing sodium aluminate, which comprises treating a waste liquid containing sodium aluminate using a waste liquid treatment tank containing a waste liquid of sodium aluminate according to any one of claims 1 to 4. A waste liquid treatment method for a waste liquid of sodium aluminate, characterized in that a high supersaturation of a waste liquid containing sodium aluminate and a seed of aluminum hydroxide are introduced into a precipitation portion located below the tank body of the waste liquid treatment tank. The sodium aluminate in the waste liquid is hydrolyzed in the precipitation portion by stirring, and then the hydrolyzed liquid is subjected to solid-liquid separation in the separation portion above the tank body to recover the sodium hydroxide solution and hydrogen. In the case of alumina, the temperature of the waste liquid in the deposition unit is maintained within a range of 40 to 65 ° C by a cooling means provided in the deposition portion, and the treated liquid in the separation portion is heated by a heating means provided in the separation portion The temperature is maintained at a temperature within a range of 10 to 50 ° C higher than the temperature of the aforementioned waste liquid.