Method and apparatus for reusing hydrofluoric acid wastewater

Abstract

The present invention provides a method for reusing hydrofluoric acid waste liquid and an apparatus for reusing hydrofluoric acid waste liquid, which uses only hydrofluoric acid waste liquid as a source of hydrofluoric acid to produce a product containing hydrofluoric acid at a predetermined concentration. [Solution] The method for reusing hydrofluoric acid waste liquid comprises the steps of: preparing a hydrofluoric acid waste liquid containing 0.1% to 35% by mass of hydrogen fluoride, 1000 ppm or less of silicon, 1000 ppm or less of nitric acid, and a total of 1% or less of metal elements and inorganic acids; a first distillation step of distilling the hydrofluoric acid waste liquid to obtain a first concentrated liquid containing 30% to 40% by mass of hydrogen fluoride; and a second distillation step of distilling the first concentrated liquid to obtain a first product consisting of a distillate and a second product consisting of a second concentrated liquid, wherein the first product contains 30% to 40% by mass of hydrogen fluoride, and the second product contains 30% to 40% by mass of hydrogen fluoride, 1% or less of silicon, 1% or less of nitric acid, and a total of 5% or less of metal elements and inorganic acids.

Description

Technical Field

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[0001] The present disclosure relates to a method for recycling hydrofluoric acid waste liquid and a recycling apparatus for hydrofluoric acid waste liquid.

Background Art

[0002] Patent Document 1 discloses a method for cleaning stainless steel using hydrofluoric acid waste liquid as an acid cleaning solution for stainless steel.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a method for recycling hydrofluoric acid waste liquid and a recycling apparatus for hydrofluoric acid waste liquid, which can produce a product containing hydrogen fluoride at a predetermined concentration using only hydrofluoric acid waste liquid as a hydrogen fluoride source. \>

Means for Solving the Problems

[0005] The present disclosure includes the following configurations.

[0006] Step of preparing a hydrofluoric acid waste liquid-containing liquid containing 0.1% or more and 35% or less of hydrogen fluoride, 1000 ppm or less of silicon, 1000 ppm or less of nitric acid, and a total of 1% or less of metal elements and inorganic acids on a mass basis; A first distillation step of distilling the hydrofluoric acid waste liquid-containing liquid to obtain a first concentrated liquid containing 30% or more and 40% or less of hydrogen fluoride on a mass basis; A second distillation step of distilling the first concentrated liquid to obtain a first product composed of a distillate and a second product composed of a second concentrated liquid; The first product contains 30% or more and 40% or less of hydrogen fluoride on a mass basis. The second product is a method for reusing hydrofluoric acid waste liquid, comprising, by mass, 30% to 40% of the hydrogen fluoride, 1% or less of the silicon, 1% or less of the nitric acid, and a total of 5% or less of the metal element and the inorganic acid.

[0007] Item 2. The hydrofluoric acid wastewater-containing liquid is prepared without adding a solid additive to hydrofluoric acid wastewater discharged in the semiconductor manufacturing process, as described in Item 1 above, for the method of reusing hydrofluoric acid wastewater.

[0008] Item 3. The method for reusing hydrofluoric acid waste liquid as described in Item 2 above, wherein the solid additive comprises at least one selected from the group consisting of potassium fluoride, sodium fluoride, potassium chloride, sodium chloride, magnesium fluoride, lithium fluoride, lithium nitrate, potassium nitrate, sodium nitrate, calcium nitrate, barium nitrate, and phosphoric acid.

[0009] Item 4. The hydrofluoric acid wastewater-containing liquid is prepared without adding sulfuric acid to hydrofluoric acid wastewater discharged in a semiconductor manufacturing process, according to any one of the above items 1 to 3.

[0010] Item 5. The hydrofluoric acid wastewater-containing liquid is hydrofluoric acid wastewater discharged in the semiconductor manufacturing process, as described in any of Items 1 to 4 above, for the purpose of reusing hydrofluoric acid wastewater.

[0011] Item 6. The hydrofluoric acid wastewater-containing liquid is prepared by adding pure water to hydrofluoric acid wastewater discharged in the semiconductor manufacturing process, the method for reusing hydrofluoric acid wastewater according to any one of Items 1 to 4 above.

[0012] Item 7. The first product is an etching solution raw material, and the method for reusing hydrofluoric acid waste liquid as described in any of Items 1 to 6 above.

[0013] Item 8. A method for reusing hydrofluoric acid waste liquid according to any one of Items 1 to 7 above, wherein the second product is a raw material for metal cleaning solutions, a raw material for the chemical synthesis of inorganic fluorine compounds, a raw material for etching solutions, or a raw material for glass matting agents.

[0014] Item 9. A method for reusing hydrofluoric acid wastewater according to any one of Items 1 to 8 above, wherein the method for reusing hydrofluoric acid wastewater does not include a step for removing silicon, nitric acid, metal elements, and inorganic acids.

[0015] Item 10. The method for reusing hydrofluoric acid waste liquid according to any one of items 1 to 9, wherein the metal element comprises at least one selected from the group consisting of Ag, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, and As.

[0016] Item 11. The method for reusing hydrofluoric acid waste liquid according to any one of items 1 to 10, wherein the inorganic acid comprises at least one selected from the group consisting of H2SO4, H3PO4, HCl, and HNO3.

[0017] Item 12. The method for reusing hydrofluoric acid waste liquid according to any one of Items 1 to 11 above, wherein the second product contains, by mass, the metal element and the inorganic acid in total amount of 0% or more and 5% or less.

[0018] Item 13. A first distillation column for performing distillation on a hydrofluoric acid waste liquid, A second distillation column is used to perform distillation on the first concentrate concentrated in the first distillation column, A first product storage tank for storing the first product consisting of the distillate distilled from the second distillation column, A hydrofluoric acid wastewater recycling apparatus comprising: a second product storage tank for storing a second product consisting of a second concentrated liquid concentrated in the second distillation column; and

[0019] Item 14. The hydrofluoric acid waste liquid contained, by mass, contained 0.1% to 35% hydrogen fluoride, 1000 ppm or less silicon, 1000 ppm or less nitric acid, and a total of 1% or less metal elements and inorganic acids. The aforementioned first concentrated liquid contains 30% to 40% hydrogen fluoride by mass. The aforementioned first product contains 30% to 40% hydrogen fluoride by mass. The second product is a reuse device for hydrofluoric acid waste liquid according to item 13 above, containing 30% or more and 40% or less hydrogen fluoride, 1% or less silicon, 1% or less nitric acid, and a total of 5% or less metal elements and inorganic acids by mass standard.

[0020] Item 15. The inner walls of the first distillation column, the second distillation column, the first product storage tank, and the second product storage tank are lined with fluororesin, and it is a reuse device for hydrofluoric acid waste liquid according to item 13 or item 14 above.

Effect of the Invention

[0021] According to the present disclosure, it is possible to provide a method for reusing hydrofluoric acid waste liquid and a reuse device for hydrofluoric acid waste liquid that can produce a product containing hydrogen fluoride at a predetermined concentration using only hydrofluoric acid waste liquid as a hydrogen fluoride source.

Brief Description of the Drawings

[0022] [Figure 1] It is a flowchart showing the method for reusing hydrofluoric acid waste liquid of the present disclosure. [Figure 2] It is a schematic diagram for explaining the method for reusing hydrofluoric acid waste liquid and the reuse device for hydrofluoric acid waste liquid of the present disclosure.

Embodiments for Carrying Out the Invention

[0023] In this specification, when a numerical range is indicated as "A~B", it means A or more and B or less. When there is no unit description for A and there is a unit description only for B, the units of A and B are the same.

[0024] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0025] In this disclosure, unless otherwise specified, pressure refers to absolute pressure.

[0026] The following describes specific embodiments of this disclosure in detail, but this disclosure is not limited to the embodiments described below.

[0027] Patent Document 1 describes adding unused hydrofluoric acid to hydrofluoric acid wastewater in order to reduce the concentration of impurities (Si, B, P, Cl) in the hydrofluoric acid wastewater.

[0028] In recent years, the demand for hydrofluoric acid, used for etching and cleaning products, has been steadily increasing, particularly in the semiconductor industry. Consequently, the price of hydrofluoric acid has also risen. Therefore, there is a need for a method of reusing hydrofluoric acid wastewater that can produce products containing hydrogen fluoride at a specified concentration using only hydrofluoric acid wastewater, without using unused hydrofluoric acid as a source of hydrogen fluoride.

[0029] As a result of diligent research, the inventors have completed a method for reusing hydrofluoric acid waste liquid and a hydrofluoric acid waste liquid recycling apparatus that can produce a product containing hydrogen fluoride at a predetermined concentration using only hydrofluoric acid waste liquid, without using unused hydrofluoric acid, by preparing a hydrofluoric acid waste liquid containing impurities at a predetermined concentration and performing distillation on the hydrofluoric acid waste liquid as described below.

[0030] [Embodiment 1: Method for reusing hydrofluoric acid waste liquid] As shown in Figure 1, a method for reusing hydrofluoric acid wastewater according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") comprises: Step S1 of preparing a hydrofluoric acid wastewater-containing liquid containing, by mass, 0.1% to 35% hydrogen fluoride, 1000 ppm or less silicon, 1000 ppm or less nitric acid, and a total of 1% or less metal elements and inorganic acids; Step S2 of distilling the hydrofluoric acid wastewater-containing liquid to obtain a first concentrated liquid containing, by mass, 30% to 40% hydrogen fluoride; and Step S3 of distilling the first concentrated liquid to obtain a first product consisting of a distillate and a second product consisting of a second concentrated liquid. The first product contains, by mass, 30% to 40% hydrogen fluoride. The second product contains, by mass, 30% to 40% hydrogen fluoride, 1% or less silicon, 1% or less nitric acid, and a total of 5% or less metal elements and inorganic acids.

[0031] <Process for preparing a hydrofluoric acid waste liquid> In the process of preparing the hydrofluoric acid wastewater-containing solution, the solution is prepared containing, by mass, 0.1% to 35% hydrogen fluoride, 1000 ppm or less silicon, 1000 ppm or less nitric acid, and a total of 1% or less of metal elements and inorganic acids.

[0032] The mass-based hydrogen fluoride content of the hydrofluoric acid wastewater-containing solution is 0.1% to 35%, preferably 10% to 35%, or more preferably 20% to 35%, from the viewpoint of making it easier to achieve a hydrogen fluoride content of 30% to 40% in the second concentrate in the second step. The mass-based hydrogen fluoride content of the hydrofluoric acid wastewater-containing solution is measured by titration. The mass-based hydrogen fluoride content of the first concentrate, the first product, and the second product is also measured by the same method.

[0033] The silicon content by mass in the hydrofluoric acid wastewater-containing solution is 1000 ppm or less, preferably 500 ppm or less, or more preferably 100 ppm or less, from the viewpoint of making it easier to reduce the silicon content of the second product to 1% or less. There is no particular lower limit to the silicon content by mass in the hydrofluoric acid wastewater-containing solution, but from the viewpoint of the silicon content contained in hydrofluoric acid wastewater discharged in the semiconductor manufacturing process, it can be 0 ppm or more. The silicon content by mass in the hydrofluoric acid wastewater-containing solution is measured by ICP-MS. The silicon content by mass in the first concentrate, the first product, and the second product is also measured by the same method.

[0034] The mass-based nitric acid content of the hydrofluoric acid wastewater-containing solution is 1000 ppm or less, preferably 500 ppm or less, or more preferably 100 ppm or less, from the viewpoint of making it easier to reduce the nitric acid content of the second product to 1% or less. There is no particular lower limit to the mass-based nitric acid content of the hydrofluoric acid wastewater-containing solution, but from the viewpoint of the nitric acid content contained in hydrofluoric acid wastewater discharged in semiconductor manufacturing processes, it can be 0 ppm or more. The mass-based nitric acid content of the hydrofluoric acid wastewater-containing solution is measured by ion chromatography. The mass-based nitric acid content of the first concentrate, the first product, and the second product is also measured by the same method.

[0035] The total mass-based content of metal elements and inorganic acids in the hydrofluoric acid wastewater solution is 1% or less, preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of making it easier to reduce the total mass-based content of metal elements and inorganic acids in the second product to 5% or less. There is no particular lower limit to the total mass-based content of metal elements and inorganic acids in the hydrofluoric acid wastewater solution, but from the viewpoint of the content of metal elements and inorganic acids contained in hydrofluoric acid wastewater discharged in semiconductor manufacturing processes, it can be 0% or more. The mass-based content of metal elements in the hydrofluoric acid wastewater solution is measured by ICP-MS. The inorganic acid content in the hydrofluoric acid wastewater solution is measured by ion chromatography. The mass-based content of metal elements and inorganic acids in the first concentrate, the first product, and the second product are also measured by the same method.

[0036] The mass-based content of metal elements in hydrofluoric acid wastewater is preferably 0.1% or less, or more preferably 0.01% or less. There is no particular lower limit to the mass-based content of metal elements in hydrofluoric acid wastewater, but from the viewpoint of the metal element content in hydrofluoric acid wastewater discharged in semiconductor manufacturing processes, it can be 0% or more.

[0037] The metallic element may consist of at least one selected from the group consisting of Ag, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, and As.

[0038] The mass-based content of inorganic acids in hydrofluoric acid wastewater is preferably 0.1% or less, or more preferably 0.01% or less. There is no particular lower limit to the mass-based content of inorganic acids in hydrofluoric acid wastewater, but from the viewpoint of the inorganic acid content contained in hydrofluoric acid wastewater discharged in semiconductor manufacturing processes, it can be 0% or more.

[0039] The inorganic acid may consist of at least one selected from the group consisting of H2SO4, H3PO4, HCl, and HNO3.

[0040] The hydrofluoric acid waste liquid is preferably prepared by adding solid additives to the hydrofluoric acid waste liquid discharged during the semiconductor manufacturing process. This prevents the first and second products from being contaminated with components derived from solid additives, thus enabling the production of higher-purity first and second products.

[0041] The solid additive may include at least one selected from the group consisting of potassium fluoride, sodium fluoride, potassium chloride, sodium chloride, magnesium fluoride, lithium fluoride, lithium nitrate, potassium nitrate, sodium nitrate, calcium nitrate, barium nitrate, and phosphoric acid. These solid additives can suppress the precipitation of metal elements contained in the hydrofluoric acid waste liquid. The hydrofluoric acid waste liquid used in Embodiment 1 has a low metal element content, so precipitation of metal elements is unlikely to occur during the manufacturing process. Therefore, in the hydrofluoric acid waste liquid reuse method of Embodiment 1, it is not necessary to add these solid additives when preparing the hydrofluoric acid waste liquid.

[0042] It is preferable that the hydrofluoric acid waste liquid is prepared without adding sulfuric acid to the hydrofluoric acid waste liquid discharged in the semiconductor manufacturing process. This prevents sulfuric acid-derived components from being mixed into the first and second products, thus enabling the production of higher-purity first and second products. Sulfuric acid can suppress the precipitation of metal elements contained in the hydrofluoric acid waste liquid. The hydrofluoric acid waste liquid used in Embodiment 1 has a low metal element content, so precipitation of metal elements is unlikely to occur in the manufacturing process. Therefore, in the hydrofluoric acid waste liquid reuse method of Embodiment 1, it is not necessary to add sulfuric acid when preparing the hydrofluoric acid waste liquid.

[0043] The hydrofluoric acid waste liquid is preferably hydrofluoric acid waste liquid discharged from the semiconductor manufacturing process. This simplifies the manufacturing process because the hydrofluoric acid waste liquid can be used as a raw material without adding pure water or additives.

[0044] The hydrofluoric acid wastewater-containing solution is preferably prepared by adding pure water to the hydrofluoric acid wastewater discharged in the semiconductor manufacturing process. This allows the content of hydrogen fluoride, silicon, nitric acid, and metal elements and inorganic acids in the hydrofluoric acid wastewater-containing solution to be adjusted to a desired range.

[0045] The hydrofluoric acid waste liquid may contain hydrofluoric acid, silicon, nitric acid, metal elements, inorganic acids, and unavoidable impurities. The hydrofluoric acid waste liquid may consist of hydrofluoric acid, silicon, nitric acid, metal elements, inorganic acids, and unavoidable impurities. The types of metal elements and inorganic acids are as described above. Examples of unavoidable impurities include alcohols such as isopropyl alcohol.

[0046] <First Distillation Process> In the first distillation step, the hydrofluoric acid waste liquid is distilled to obtain a first concentrated liquid containing 30% to 40% hydrogen fluoride by mass. In the first distillation step, a distillation column with multiple theoretical stages can be used, and either continuous distillation or batch distillation may be employed.

[0047] From the viewpoint of processing efficiency, the lower limit of the temperature in the first distillation process is preferably 80°C or higher, or more preferably 100°C or higher. From the viewpoint of equipment protection, the upper limit of the temperature in the first distillation process is preferably 130°C or lower, or more preferably 120°C or lower.

[0048] From the viewpoint of equipment protection, the lower limit of the pressure in the first distillation process is preferably 101 kPa or higher, or more preferably 110 kPa or higher. From the viewpoint of operating temperature control, the upper limit of the pressure in the first distillation process is preferably 150 kPa or lower, or more preferably 130 kPa or lower.

[0049] In the first distillation step, nothing is added to the hydrofluoric acid waste liquid, and the hydrofluoric acid waste liquid is distilled as is. In the first distillation step, no solid additives or sulfuric acid are added to the hydrofluoric acid waste liquid. The explanation of the solid additive is the same as the explanation for the process of preparing the hydrofluoric acid waste liquid.

[0050] The first concentrate contains 30% to 40% hydrogen fluoride by mass. This allows the hydrofluoric acid in the first concentrate to have an azeotropic point at specific temperatures and pressures. Having an azeotropic point in the hydrofluoric acid in the first concentrate facilitates temperature and pressure control during the second distillation process. From an operational control standpoint, the mass content of hydrogen fluoride in the first concentrate is preferably 30% to 40%, or 35% to 39%.

[0051] The mass-based content of silicon, nitric acid, metal elements, and inorganic acids in the first concentrated solution maintains the mass-based content of silicon, nitric acid, metal elements, and inorganic acids in the hydrofluoric acid wastewater-containing solution.

[0052] The mass-based content of silicon, nitric acid, metal elements, and inorganic acids in the first concentrated solution is greater than the mass-based content of silicon, nitric acid, metal elements, and inorganic acids in the hydrofluoric acid wastewater-containing solution.

[0053] The first concentrated solution may not contain solid additives or sulfuric acid.

[0054] In the first distillation step, the first distillate is obtained along with the first concentrate. The first distillate is recovered water that contains no impurities other than unavoidable ones. The recovered first distillate can be added to the hydrofluoric acid wastewater in the process of preparing the hydrofluoric acid wastewater-containing liquid. This allows for adjustment of the content of each component in the hydrofluoric acid wastewater-containing liquid.

[0055] <Second Distillation Process> In the second distillation process, the first concentrate is distilled to obtain a first product consisting of the distillate and a second product consisting of the second concentrate.

[0056] The temperature and pressure in the second distillation step are not particularly limited, as long as they are sufficient to give the hydrofluoric acid in the first concentrate an azeotrope.

[0057] In the second distillation step, nothing is added to the first concentrate, and the first concentrate is distilled as is. In the second distillation step, no solid additives or sulfuric acid are added to the first concentrate. The explanation of the solid additive is the same as the explanation in the step for preparing the hydrofluoric acid waste liquid.

[0058] The first product consists of a distillate containing 30% to 40% hydrogen fluoride by mass. The content of silicon, nitric acid, metal elements, and inorganic acids in the first product may be below the detection limit (0.1 ppm or less).

[0059] The first product preferably consists of hydrofluoric acid and unavoidable impurities. Examples of unavoidable impurities include isopropyl alcohol. The first product may not contain solid additives or sulfuric acid.

[0060] The use of the first product is not particularly limited. For example, the first product can be used as a raw material for etching solutions used in semiconductor manufacturing processes.

[0061] The second product consists of a second concentrated liquid containing, by mass, 30% to 40% hydrogen fluoride, 1% or less silicon, 1% or less nitric acid, and a total of 5% or less metal elements and inorganic acids. The types of metal elements and inorganic acids are the same as those described in the process for preparing the hydrofluoric acid waste liquid.

[0062] The upper limit of the silicon content by mass in the second product is 1% or less, preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of the second product's application and performance. The lower limit of the silicon content by mass in the second product is not particularly limited, but it can be 0% or more from the viewpoint of the silicon content of the hydrofluoric acid waste liquid.

[0063] The upper limit of the mass-based nitric acid content in the second product is 1% or less, preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of the second product's usability. The lower limit of the mass-based nitric acid content in the second product is not particularly limited, but it can be 0% or more from the viewpoint of the nitric acid content in the hydrofluoric acid waste liquid.

[0064] The upper limit of the total mass content of metal elements and inorganic acids in the second product is 5% or less, preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of the second product's application performance. The lower limit of the total mass content of metal elements and inorganic acids in the second product is not particularly limited, but it can be 0% or more from the viewpoint of the total content of metal elements and inorganic acids in the hydrofluoric acid waste liquid.

[0065] The upper limit of the mass-based content of metal elements in the second product is preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of the second product's application and performance. The lower limit of the mass-based content of metal elements in the second product is not particularly limited, but it can be 0% or more from the viewpoint of the mass-based content of metal elements in the hydrofluoric acid waste liquid.

[0066] The upper limit of the mass-based inorganic acid content in the second product is preferably 0.1% or less, or more preferably 0.01% or less, from the viewpoint of the second product's application and performance. The lower limit of the mass-based inorganic acid content in the second product is not particularly limited, but it can be 0% or more from the viewpoint of the mass-based inorganic acid content in the hydrofluoric acid waste liquid.

[0067] The second product may contain hydrofluoric acid contained in the hydrofluoric acid waste liquid, as well as all other components (silicon, nitric acid, metal elements, and inorganic acids) except for unavoidable impurities.

[0068] The second product preferably consists of hydrofluoric acid, silicon, nitric acid, a metal element, an inorganic acid, and unavoidable impurities. The second product preferably consists of hydrofluoric acid and unavoidable impurities. Examples of unavoidable impurities include isopropyl alcohol. The second product does not contain solid additives or sulfuric acid.

[0069] The uses of the second product are not particularly limited. For example, the second product can be used as a raw material for metal cleaning solutions, a raw material for the chemical synthesis of inorganic fluorine compounds, a raw material for etching solutions, or a raw material for glass matting agents.

[0070] The hydrofluoric acid wastewater recycling method of Embodiment 1 does not require the removal of silicon, nitric acid, metal elements, and inorganic acids. According to this, the hydrofluoric acid wastewater recycling method of Embodiment 1 can produce the first and second products without generating wastewater and waste containing at least one of silicon, nitric acid, metal elements, and inorganic acids. Furthermore, the wastewater and waste generated by removing silicon, nitric acid, metal elements, and inorganic acids contain hydrofluoric acid. Since the hydrofluoric acid wastewater recycling method of Embodiment 1 does not require the removal of silicon, nitric acid, metal elements, and inorganic acids, the recycling rate of hydrofluoric acid can be improved.

[0071] The hydrofluoric acid wastewater reuse method of Embodiment 1 preferably does not use solid additives and sulfuric acid. This prevents the first and second products from being contaminated with components derived from solid additives and sulfuric acid, thus allowing for the production of higher-purity first and second products.

[0072] [Embodiment 2: Apparatus for reusing hydrofluoric acid waste liquid] As shown in Figure 2, a hydrofluoric acid wastewater recycling apparatus according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") comprises a first distillation column 1 for performing distillation on a hydrofluoric acid wastewater-containing liquid, a second distillation column 2 for performing distillation on a first concentrated liquid concentrated in the first distillation column 1, a first product storage tank 3 for storing a first product consisting of the distillate distilled from the second distillation column 2, and a second product storage tank 4 for storing a second product consisting of a second concentrated liquid concentrated in the second distillation column. The first distillation column 1 and the second distillation column 2 may be connected via a first concentrated liquid flow path 12. The second distillation column 2 and the first product storage tank 3 may be connected via a first product flow path 14. The second distillation column 2 and the second product storage tank 4 may be connected via a second product flow path 15.

[0073] The first distillation column 1 performs distillation on the hydrofluoric acid waste liquid, separating it into a first distillate containing almost nothing other than hydrofluoric acid and unavoidable impurities, and a concentrated first concentrate. The first distillation column 1 can be a conventionally known distillation column with a number of theoretical stages.

[0074] The first distillation column 1 may be connected to a hydrofluoric acid wastewater-containing liquid channel 11 into which hydrofluoric acid wastewater-containing liquid is introduced. The top of the first distillation column 1 may be connected to a first distillate channel 13 for extracting the first distillate separated by distillation. The first distillate channel 13 may be connected to a cooling condenser (not shown) for cooling and condensing the first distillate.

[0075] The bottom of the first distillation column 1 may be connected to a first concentrate channel 12 for extracting the concentrated first concentrate. The end of the first concentrate channel 12 opposite to the side connected to the first distillation column 1 may be connected to a second distillation column 2.

[0076] The second distillation column 2 performs distillation on the first concentrate, separating it into a first product consisting of the distillate and a second product consisting of the second concentrate. The second distillation column 2 can be a conventionally known distillation column with a multi-stage theoretical number of stages.

[0077] The top of the second distillation column 2 may be connected to a first product channel 14 for extracting the first product separated by distillation. The end of the first product channel 14 opposite to the side connected to the second distillation column 2 may be connected to a first product storage tank 3. The first product channel 14 may be connected to a cooling condenser (not shown) for cooling and condensing the first product, and the first product cooled and condensed in the cooling condenser may be stored in the first product storage tank 3.

[0078] The bottom of the second distillation column 2 may be connected to a second product channel 15 for extracting the second product. The end of the second product channel 15 opposite to the side connected to the second distillation column 2 may be connected to a second product storage tank 4. The second product channel 15 may also be connected to a cooling condenser (not shown) for cooling and condensing the second product, and the second product cooled and condensed in the cooling condenser may be stored in the second product storage tank 4.

[0079] The descriptions of the hydrofluoric acid waste liquid-containing liquid, the first concentrated liquid, the first product, and the second product in Embodiment 2 are the same as those in Embodiment 1.

[0080] It is preferable that the inner walls of the first distillation column, the second distillation column, the first product storage tank, and the second product storage tank are lined with fluororesin. This allows for the production of higher purity first and second products. Furthermore, it is preferable that the inner walls of the hydrofluoric acid waste liquid-containing liquid channel, the first concentrated liquid channel, the first distillate liquid channel, and the first product channel are lined with fluororesin.

[0081] While embodiments of this disclosure have been described above, various modifications to the form and details are possible without departing from the spirit and scope of the claims. [Examples]

[0082] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0083] [Example 1] A method for reusing hydrofluoric acid wastewater was implemented using the hydrofluoric acid wastewater recycling apparatus shown in Figure 2.

[0084] <Process for preparing a hydrofluoric acid waste liquid> A hydrofluoric acid wastewater solution was prepared containing, by mass, 3% hydrogen fluoride, 100 ppm silicon, 100 ppm nitric acid, a total of 0.1% metallic elements, and a total of 0.1% inorganic acids. The metallic elements consisted of Ag, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, and As. The inorganic acids consisted of H2SO4, H3PO4, HCl, and HNO3.

[0085] <First Distillation Process> Using the first distillation column 1 shown in Figure 2, the hydrofluoric acid waste liquid was distilled to obtain a first concentrate containing 35% hydrogen fluoride by mass. The temperature of the first distillation process was 90°C and the pressure was 103 kPa. Nothing was added to the hydrofluoric acid waste liquid during the first distillation process; the hydrofluoric acid waste liquid was distilled as is. In the first distillation process, a first distillate was obtained along with the first concentrate. The first distillate was recovered water that contained no impurities other than unavoidable ones.

[0086] <Second Distillation Process> Using the second distillation column 2 shown in Figure 2, the first concentrate was distilled to obtain a first product consisting of the distillate and a second product consisting of the second concentrate. The temperature during the second distillation process was 90°C and the pressure was 103 kPa. Nothing was added to the first concentrate during the second distillation process; the first concentrate was distilled as is. The first product was stored in the first product storage tank 3, and the second product was stored in the second product storage tank 4.

[0087] The first product contained 35% hydrogen fluoride by mass. The content of silicon, nitric acid, metal elements, and inorganic acids in the first product was below the detection limit (0.1 ppm or less).

[0088] The second product contained 35% hydrogen fluoride by mass. The second product contained hydrofluoric acid that was present in the hydrofluoric acid waste liquid, as well as all other components (silicon, nitric acid, metal elements, and inorganic acids) except for unavoidable impurities.

[0089] [Example 2] A method for reusing hydrofluoric acid wastewater was implemented using the hydrofluoric acid wastewater recycling apparatus shown in Figure 2.

[0090] <Process for preparing a hydrofluoric acid waste liquid> A hydrofluoric acid wastewater solution was prepared containing, by mass, 35% hydrogen fluoride, 1000 ppm silicon, 1000 ppm nitric acid, a total of 0.5% metallic elements, and a total of 0.5% inorganic acids. The metallic elements consisted of Ag, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, and As. The inorganic acids consisted of H2SO4, H3PO4, HCl, and HNO3.

[0091] <First Distillation Process> Using the first distillation column 1 shown in Figure 2, the hydrofluoric acid waste liquid was distilled to obtain a first concentrate containing 36% hydrogen fluoride by mass. The temperature of the first distillation process was 90°C and the pressure was 103 kPa. Nothing was added to the hydrofluoric acid waste liquid during the first distillation process; the hydrofluoric acid waste liquid was distilled as is. In the first distillation process, a first distillate was obtained along with the first concentrate. The first distillate was recovered water that contained no impurities other than unavoidable ones.

[0092] <Second Distillation Process> Using the second distillation column 2 shown in Figure 2, the first concentrate was distilled to obtain a first product consisting of the distillate and a second product consisting of the second concentrate. The temperature during the second distillation process was 90°C and the pressure was 103 kPa. Nothing was added to the first concentrate during the second distillation process; the first concentrate was distilled as is. The first product was stored in the first product storage tank 3, and the second product was stored in the second product storage tank 4.

[0093] The first product contained 36% hydrogen fluoride by mass. The content of silicon, nitric acid, metal elements, and inorganic acids in the first product was below the detection limit (0.1 ppm or less).

[0094] The second product contained 36% hydrogen fluoride by mass. The second product contained hydrofluoric acid contained in the hydrofluoric acid waste liquid, as well as all components other than unavoidable impurities (silicon, nitric acid, metal elements, and inorganic acids).

[0095] [Consideration] The hydrofluoric acid wastewater recycling methods of Examples 1 and 2 could be made without the removal of silicon, nitric acid, metal elements, and inorganic acids. The hydrofluoric acid wastewater recycling methods of Examples 1 and 2 could be made without generating wastewater and waste containing at least one of silicon, nitric acid, metal elements, and inorganic acids, thereby obtaining the first and second products. Furthermore, the wastewater and waste generated by removing silicon, nitric acid, metal elements, and inorganic acids contains hydrofluoric acid. Because the hydrofluoric acid wastewater recycling methods of Examples 1 and 2 can be made without the removal of silicon, nitric acid, metal elements, and inorganic acids, the recycling rate of hydrofluoric acid could be improved.

[0096] The hydrofluoric acid wastewater reuse methods in Examples 1 and 2 did not use solid additives or sulfuric acid. As a result, since components from solid additives and sulfuric acid were not mixed into the first and second products, it was possible to obtain first and second products of higher purity. [Explanation of Symbols]

[0097] 1. First distillation column 2. Second distillation column 3. First product storage tank 4. Second product storage tank 11. Flow path containing hydrofluoric acid wastewater 12 First concentrated liquid channel 13 First distillate flow path 14. First product flow path 15 Second product flow path

Claims

1. The process involves preparing a hydrofluoric acid wastewater-containing liquid that, by mass, contains 0.1% to 35% hydrogen fluoride, 1000 ppm or less silicon, 1000 ppm or less nitric acid, and a total of 1% or less metal elements and inorganic acids. A first distillation step involves distilling the hydrofluoric acid waste liquid to obtain a first concentrated liquid containing 30% or more and 40% or less of the hydrogen fluoride by mass, The system includes a second distillation step in which the first concentrate is distilled to obtain a first product consisting of a distillate and a second product consisting of a second concentrate. The aforementioned first product contains 30% to 40% of the hydrogen fluoride by mass. The second product is a method for reusing hydrofluoric acid waste liquid, comprising, by mass, 30% to 40% of hydrogen fluoride, 1% or less of silicon, 1% or less of nitric acid, and a total of 5% or less of the metal element and the inorganic acid.

2. The hydrofluoric acid waste liquid-containing liquid is prepared without adding a solid additive to hydrofluoric acid waste liquid discharged in a semiconductor manufacturing process, as described in claim 1, for the method of reusing hydrofluoric acid waste liquid.

3. The method for reusing hydrofluoric acid waste liquid according to claim 2, wherein the solid additive comprises at least one selected from the group consisting of potassium fluoride, sodium fluoride, potassium chloride, sodium chloride, magnesium fluoride, lithium fluoride, lithium nitrate, potassium nitrate, sodium nitrate, calcium nitrate, barium nitrate, and phosphoric acid.

4. The hydrofluoric acid waste liquid-containing liquid is prepared without adding sulfuric acid to hydrofluoric acid waste liquid discharged in a semiconductor manufacturing process, as described in claim 1 or claim 2, for the method of reusing hydrofluoric acid waste liquid.

5. The method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2, wherein the hydrofluoric acid waste liquid-containing liquid is hydrofluoric acid waste liquid discharged in a semiconductor manufacturing process.

6. The hydrofluoric acid waste liquid-containing liquid is prepared by adding pure water to hydrofluoric acid waste liquid discharged in a semiconductor manufacturing process, as described in claim 1 or claim 2, for the method of reusing hydrofluoric acid waste liquid.

7. The first product is an etching solution raw material, and the method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2.

8. The method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2, wherein the second product is a raw material for a metal cleaning solution, a raw material for the chemical synthesis of inorganic fluorine compounds, a raw material for an etching solution, or a raw material for a glass matting agent.

9. The method for reusing hydrofluoric acid wastewater according to claim 1 or claim 2, wherein the method for reusing hydrofluoric acid wastewater does not include a step for removing silicon, nitric acid, metal elements, and inorganic acids.

10. The method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2, wherein the metal element comprises at least one selected from the group consisting of Ag, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, and As.

11. The aforementioned inorganic acid is H ２ SO ４ , H ３ PO ４ HCl and HNO ３ A method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2, comprising at least one selected from the group consisting of the following.

12. The method for reusing hydrofluoric acid waste liquid according to claim 1 or claim 2, wherein the second product contains, by mass, 0% or more of the metal element and the inorganic acid in total of 5% or less.

13. A first distillation column for performing distillation on a hydrofluoric acid waste liquid, A second distillation column is used to perform distillation on the first concentrate concentrated in the first distillation column, A first product storage tank for storing the first product consisting of the distillate distilled from the second distillation column, A hydrofluoric acid wastewater recycling apparatus comprising: a second product storage tank for storing a second product consisting of a second concentrated liquid concentrated in the second distillation column; and

14. The aforementioned hydrofluoric acid waste liquid contains, by mass, 0.1% to 35% hydrogen fluoride, 1000 ppm or less silicon, 1000 ppm or less nitric acid, and a total of 1% or less of metal elements and inorganic acids. The aforementioned first concentrated liquid contains 30% to 40% hydrogen fluoride by mass. The aforementioned first product contains 30% to 40% hydrogen fluoride by mass. The hydrofluoric acid wastewater recycling apparatus according to claim 13, wherein the second product contains, by mass, 30% to 40% of hydrogen fluoride, 1% or less of silicon, 1% or less of nitric acid, and a total of 5% or less of metal elements and inorganic acids.

15. The hydrofluoric acid wastewater recycling apparatus according to claim 13 or claim 14, wherein the inner walls of the first distillation column, the inner walls of the second distillation column, the inner walls of the first product storage tank, and the inner walls of the second product storage tank are lined with fluororesin.

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