Acid recovery method and acid recovery apparatus
The use of a nanofiltration membrane and separate evaporation steps efficiently separates and recovers inorganic acids and metal salts from mixed solutions, addressing inefficiencies and costs in conventional methods by reducing energy consumption and equipment load.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- SASAKURA ENG CO LTD
- Filing Date
- 2024-11-13
- Publication Date
- 2026-05-25
AI Technical Summary
Existing methods for recovering inorganic acids from mixed solutions containing metal salts, such as those generated in aluminum electrolytic capacitor manufacturing, are inefficient and costly due to high energy consumption and equipment load, as they fail to separate and recover the acids and salts effectively.
A method and apparatus utilizing a nanofiltration membrane to separate a mixed solution into an aqueous inorganic acid solution and a concentrated metal salt solution, followed by separate evaporation steps to reduce the volume and concentration of each, thereby reducing energy costs and equipment load.
The proposed method significantly reduces energy costs and equipment load by separating metal salts from inorganic acids, allowing for more efficient recovery and concentration of both components, achieving a 62% reduction in evaporation rates compared to conventional methods.
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Figure 2026085340000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an acid recovery method and an acid recovery apparatus for recovering an inorganic acid from a mixed solution containing an inorganic acid and a metal salt of the inorganic acid.
Background Art
[0002] For example, in the manufacturing process of an aluminum electrolytic capacitor, a waste liquid (mixed solution) in which aluminum chloride is mixed with hydrochloric acid is generated. A treatment method for reusing this mixed solution has been conventionally studied. Conventionally, a method (evaporation method) has been proposed in which the mixed solution is heated and evaporated in an evaporation apparatus to generate vapor containing an inorganic acid, and the inorganic acid such as hydrochloric acid is recovered on the vapor side. Note that metal salts such as aluminum chloride remain on the liquid side and are recovered as a concentrated solution of the metal salt.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
[0008] Furthermore, the acid recovery method of this disclosure includes the acid recovery method described in Section 2 below as a preferred embodiment of the acid recovery method described in Section 1 above.
[0009] Item 2. The acid recovery method according to Item 1, further comprising a second evaporation step of evaporating the permeate water to produce a concentrated solution of the inorganic acid.
[0010] Furthermore, the acid recovery method of this disclosure includes the acid recovery method described in item 3 below as a preferred embodiment of the acid recovery method described in item 1 or 2 above.
[0011] Item 3. The acid recovery method according to Item 1 or 2, wherein the inorganic acid is hydrochloric acid.
[0012] Furthermore, the acid recovery method of this disclosure includes the acid recovery method described in item 4 below as a preferred embodiment of the acid recovery method described in item 3 above.
[0013] Item 4. The acid recovery method according to Item 3, wherein the metal salt is aluminum chloride.
[0014] To solve the above problems, the acid recovery apparatus of this disclosure is based on the acid recovery apparatus described in Section 5 below.
[0015] Item 5. An acid recovery apparatus for recovering an inorganic acid from a mixed solution containing an inorganic acid containing a monovalent anion and a metal salt of the inorganic acid containing a divalent or greater metal ion, A membrane separation apparatus comprising a nanofiltration membrane, configured to separate the mixed solution into permeate containing an aqueous solution of the inorganic acid and a concentrated solution of the metal salt by passing water through the nanofiltration membrane, A first evaporator for evaporating and concentrating the concentrated metal salt solution, An acid recovery device equipped with the following features.
[0016] Furthermore, the acid recovery apparatus of this disclosure includes, as a preferred embodiment of the acid recovery apparatus described in item 5 above, the acid recovery apparatus described in item 6 below.
[0017] Item 6. The acid recovery apparatus according to item 5, further comprising a second evaporator that evaporates the permeate water to produce a concentrated solution of the inorganic acid. [Effects of the Invention]
[0018] According to the acid recovery method and acid recovery apparatus of this disclosure, by passing a mixed solution of inorganic acid and metal salt through a nanofiltration membrane, the metal salt can be removed from the mixed solution, separating it into an aqueous solution of inorganic acid and a concentrated solution of metal salt. Therefore, in the first evaporation step in the first evaporator, the volume of the concentrated solution of metal salt is reduced compared to the conventional technology. Thus, in the first evaporation step in the first evaporator, the energy cost for evaporating the concentrated solution of metal salt can be reduced, and the load on the evaporator and running costs can be reduced. Furthermore, the aqueous solution of inorganic acid may be recovered as is, depending on the concentration of the inorganic acid, or it may be recovered with a higher concentration of inorganic acid by evaporating it in the second evaporation step in the second evaporator. In this case, since the metal salt of the inorganic acid is not mixed in the aqueous solution of inorganic acid, unlike the conventional technology, the inorganic acid can be recovered on the liquid side. Thus, in the second evaporation step in the second evaporator, the energy cost for evaporating the aqueous solution of inorganic acid can be reduced, and the load on the evaporator and running costs can be reduced. [Brief explanation of the drawing]
[0019] [Figure 1] Figure 1 is a schematic diagram of the first embodiment of the acid recovery apparatus. [Figure 2] Figure 2 is a schematic configuration diagram of a second embodiment of the acid recovery device.
Embodiments for Carrying Out the Invention
[0020] Hereinafter, embodiments of the acid recovery method of the present disclosure will be described with reference to the accompanying drawings. Figure 1 is a schematic configuration diagram of an acid recovery device used in the acid recovery method according to an embodiment of the present invention.
[0021] As shown in Figure 1, the acid recovery device 1 includes a membrane separation device 2 connected by a raw solution tank 10 and a pipe 11. A mixed solution containing an inorganic acid containing a monovalent anion and a metal salt of an inorganic acid containing a metal ion of divalent or more is stored in the raw solution tank 10. In the present embodiment, a mixed solution containing hydrochloric acid containing chloride ions and aluminum chloride which is a metal salt (chloride salt) of hydrochloric acid and contains aluminum ions is stored in the raw solution tank 10. The mixed solution may contain chloride salts other than aluminum chloride. The membrane separation device 2 is configured to perform membrane separation on the mixed solution supplied from the raw solution tank 10.
[0022] The inside of the casing 20 of the membrane separation device 2 is partitioned by a nanofiltration membrane 21 to form a primary chamber 22 and a secondary chamber 23. The mixed solution supplied to the primary chamber 22 of the membrane separation device 2 by the operation of a pump (not shown) from the raw solution tank 10 is separated into permeated water that permeates through the nanofiltration membrane 21 and flows into the secondary chamber 23 and non-permeated water that does not permeate through the nanofiltration membrane 21, and then discharged to the outside of the membrane separation device 2 through pipes 12 and 13, respectively.
[0023] The nanofiltration membrane 21 generally has a relatively high permeability of monovalent ions compared to the permeability of divalent or higher ions (polyvalent ions), thus limiting (or blocking) the permeation of polyvalent ions while allowing the permeation of monovalent ions. The nanofiltration membrane 21 selectively removes divalent or higher ions from the mixed solution. Therefore, if the mixed solution contains a metal salt containing divalent or higher ions, the nanofiltration membrane 21 separates the mixed solution into a concentrated solution of the metal salt containing divalent or higher ions (non-permeable water) and an aqueous solution of the inorganic acid (permeable water).
[0024] The nanofiltration membrane 21 can be a semipermeable membrane made of conventionally known materials such as cellulose acetate, polyamide, polysulfone, or aquaporin (protein). The nanofiltration membrane 21 can be made of conventionally known shapes such as a flat membrane or a hollow fiber membrane.
[0025] As shown in Figure 1, the acid recovery device 1 includes an evaporator 3 (second evaporator) that evaporates the aqueous solution of inorganic acid supplied from the membrane separation device 2. The evaporator 3 is configured to concentrate the aqueous solution of inorganic acid by evaporating it, for example, by heating.
[0026] The evaporator 3 can be a known flash-type evaporative concentrate, for example, which heats an aqueous solution of an inorganic acid in a heater to a supersaturated state and then sprays it into an evaporator under reduced pressure to evaporate it. The evaporator 3 is not particularly limited in its method of evaporation, as long as it can evaporate an aqueous solution of an inorganic acid to produce a concentrated solution of the inorganic acid.
[0027] The concentrated inorganic acid solution produced in the evaporator 3 is discharged outside the evaporator 3 through the piping 14. This allows for the recovery of a highly concentrated aqueous solution of inorganic acid.
[0028] As shown in Figure 1, the acid recovery device 1 includes an evaporator 4 (first evaporator) that evaporates the concentrated metal salt solution supplied from the membrane separation device 2. The evaporator 4 is configured to concentrate the concentrated metal salt solution by evaporating it, for example, by heating.
[0029] The evaporator 4 can be a known flash-type evaporator / concentrator, for example, which heats a concentrated metal salt solution in a heater to a supersaturated state, and then sprays it into an evaporator under reduced pressure to evaporate it. The evaporator 4 is not particularly limited in its method of evaporation, as long as it can evaporate and concentrate the concentrated metal salt solution.
[0030] The concentrated metal salt solution, concentrated in the evaporator 4, is discharged outside the evaporator 4 through the piping 15. This allows the concentrated metal salt solution to be recovered in a reduced volume.
[0031] In the acid recovery method using the acid recovery apparatus 1 described above, first, a mixed solution of hydrochloric acid and aluminum chloride, generated, for example, in the manufacturing process of aluminum electrolytic capacitors, is supplied under pressure from the stock tank 10 to the membrane separation apparatus 2. In the membrane separation apparatus 2, the mixed solution is passed through the nanofiltration membrane 21. Metal salts containing divalent or higher ions do not permeate the nanofiltration membrane 21, while hydrochloric acid does. Therefore, in the primary chamber 22 of the membrane separation apparatus 2, most of the metal salts do not permeate the nanofiltration membrane 21 and are discharged from the membrane separation apparatus 2 as a concentrated solution of metal salts. In contrast, most of the hydrochloric acid contained in the mixed solution permeates the nanofiltration membrane 21 as an aqueous solution of hydrochloric acid and moves to the second chamber 23, where it is discharged from the membrane separation apparatus 2 with a significantly reduced concentration of metal salts. The concentration of the aqueous solution of hydrochloric acid discharged from the membrane separation apparatus 2 may be higher than the concentration of hydrochloric acid in the mixed solution.
[0032] As described above, according to the acid recovery method and acid recovery apparatus of this embodiment, the membrane separation apparatus 2 removes the metal salt from the mixed solution of inorganic acid and metal salt, separating the mixed solution into an aqueous solution of inorganic acid and a concentrated solution of metal salt, which can then be supplied to the evaporator 3 and evaporator 4, respectively. Therefore, in the evaporator 3, since the metal salt of the inorganic acid is not mixed in the supplied aqueous solution of inorganic acid, unlike the conventional technology, the inorganic acid can be recovered on the liquid side. Thus, the energy cost for evaporating the aqueous solution of inorganic acid in the evaporator 3 can be reduced, and the load and running costs on the evaporator 3 can be reduced. Furthermore, in the evaporator 4, the volume of the supplied concentrated solution of metal salt is reduced compared to the conventional technology. Thus, the energy cost for evaporating the concentrated solution of metal salt in the evaporator 4 can be reduced, and the load and running costs on the evaporator 4 can be reduced.
[0033] An example of the evaporation rate in the evaporator of this embodiment is as follows: By supplying a mixed solution containing 7.5% hydrochloric acid and 2.9% aluminum chloride, respectively, to the membrane separation device 2 at a rate of 231 t / day, the membrane separation device 2 obtains 180 t / day of aqueous hydrochloric acid solution and 51 t / day of concentrated metal salt solution. When the 180 t / day of aqueous hydrochloric acid solution is evaporated and concentrated in the evaporator 3, 51 t / day of vapor and 129 t / day of concentrated hydrochloric acid solution are obtained. Furthermore, when the 51 t / day of concentrated metal salt solution is evaporated and concentrated in the evaporator 4, 29 t / day of vapor and 22 t / day of concentrated metal salt solution are obtained. On the other hand, if the same mixed solution is supplied to the evaporator at a rate of 231 t / day and evaporated, as in the conventional technology, 209 t / day of vapor containing hydrochloric acid and 22 t / day of concentrated metal salt solution are obtained. In the acid recovery method and acid recovery apparatus of this embodiment, two evaporators 3 and 4 are used. The evaporation rate of the two evaporators 3 and 4 is 80 t / day, which is approximately 62% less than that of conventional technology, and significantly reduces the load on the evaporators and running costs.
[0034] While embodiments of the acid recovery method and acid recovery apparatus described herein have been explained above, the acid recovery method and acid recovery apparatus described herein are not limited to the embodiments described above, and various modifications are possible as long as they do not depart from the spirit of this disclosure.
[0035] In the above embodiment, the concentration of the aqueous solution of inorganic acid discharged from the membrane separation device 2 after passing through the nanofiltration membrane 21 of the membrane separation device 2 is higher than the concentration of the inorganic acid in the mixed solution. Therefore, if the concentration of the aqueous solution of inorganic acid discharged from the membrane separation device 2 exceeds the desired concentration, the aqueous solution of inorganic acid discharged from the membrane separation device 2 may be recovered without evaporation and concentration in the evaporator 3, as shown in Figure 2.
[0036] In the above embodiment, the metal salt of hydrochloric acid is aluminum chloride, but the metal salt of hydrochloric acid is not limited to aluminum chloride, and may be chlorides of various other metals such as cobalt, nickel, copper, zinc, and iron. Furthermore, the metal salt may include chlorides of monovalent metal ions such as lithium.
[0037] In the above embodiment, the inorganic acid is hydrochloric acid, but the inorganic acid is not limited to hydrochloric acid as long as it contains a monovalent anion. The inorganic acid may be, for example, sulfuric acid, nitric acid, hydrofluoric acid, or phosphoric acid. When the inorganic acid is sulfuric acid, nitric acid, hydrofluoric acid, or phosphoric acid, the metal salts of sulfuric acid, nitric acid, hydrofluoric acid, or phosphoric acid can be, but are not limited to, metal salts of aluminum, cobalt, nickel, copper, zinc, iron, lithium, etc. [Explanation of Symbols]
[0038] 1. Acid recovery device 2 Membrane separation device 3. Evaporator (Second Evaporator) 4. Evaporator (First Evaporator) 21 nanofiltration membrane
Claims
1. An acid recovery method for recovering an inorganic acid from a mixed solution containing an inorganic acid containing a monovalent anion and a metal salt of the inorganic acid containing a divalent or higher metal ion, A membrane separation step involves passing the mixed solution through a nanofiltration membrane to separate it into permeate containing an aqueous solution of the inorganic acid and a concentrated solution of the metal salt. A first evaporation step involves evaporating and concentrating the concentrated solution of the metal salt, An acid recovery method having the following characteristics.
2. The acid recovery method according to claim 1, further comprising a second evaporation step of evaporating the permeate water to produce a concentrated solution of the inorganic acid.
3. The acid recovery method according to claim 1 or 2, wherein the inorganic acid is hydrochloric acid.
4. The acid recovery method according to claim 3, wherein the metal salt is aluminum chloride.
5. An acid recovery apparatus for recovering an inorganic acid from a mixed solution containing an inorganic acid containing a monovalent anion and a metal salt of the inorganic acid containing a divalent or greater metal ion, A membrane separation apparatus comprising a nanofiltration membrane, configured to separate the mixed solution into permeate containing an aqueous solution of the inorganic acid and a concentrated solution of the metal salt by passing water through the nanofiltration membrane, A first evaporator for evaporating and concentrating the concentrated metal salt solution, An acid recovery device equipped with the following features.
6. The acid recovery apparatus according to claim 5, further comprising a second evaporation device that evaporates the permeate to produce a concentrated solution of the inorganic acid.