TWI585035B - A waste acid recycling process - Google Patents

Description

Process for recycling waste acid liquid

This invention relates to a process for recovering and reconstituting a spent acid acid from the semiconductor industry into a usable semiconductor grade sulfuric acid.

Sulfuric acid (H ₂ SO ₄ ) is a highly corrosive strong mineral acid that is corrosive to metals, biological tissues and rocks.

Sulfuric acid is produced by burning sulfur in air to produce sulfur dioxide (SO ₂ ) gas. After purification and impurity removal, sulfur dioxide and oxygen are oxidized in a high temperature environment using vanadium pentoxide (V ₂ O ₅ ) as a catalyst. Sulfur trioxide (SO ₃ ), followed by absorption of sulfur trioxide with concentrated sulfuric acid to form fuming sulfuric acid (H ₂ S ₂ O ₇ , also known as H ₂ SO ₄ ‧ SO ₃ ), and finally dilute the fuming sulfuric acid with water Forming 98% sulfuric acid.

In today's semiconductor industry, such as wafer surface treatment, a large amount of semiconductor grade sulfuric acid is used, which produces a large amount of waste sulfuric acid solution. However, these waste sulfuric acid liquids still contain more than 50% sulfuric acid, metals and other impurities. Direct discharge into the environment after treatment not only causes damage to water, soil and environmental ecology, but also creates waste of resources.

The treatment methods of the conventional waste sulfuric acid solution are as follows: 1. Neutralization treatment: the waste sulfuric acid solution is discharged as waste water after neutralization by acid and alkali, 2. Recycling and reuse: the waste sulfuric acid liquid is concentrated into industrial grade sulfuric acid, 3. Derivatization: The waste sulfuric acid solution is made into fertilizer or pesticide, such as ammonium sulfate and copper sulfate.

Although the above treatment method can solve the problem of partial waste sulfuric acid solution, the semiconductor industry The demand for semiconductor grade sulfuric acid is huge and the source is endless. Therefore, the huge waste sulfuric acid solution will continue to be generated. With the global environmental awareness and the limited global resources, the recycling economy has become a trend in the world. How to effectively use resources and recycle resources, recycling and recycling waste to solve the problem of resource shortage and environmental pollution, and to achieve sustainable resources and economic benefits, is an important issue to be solved today.

The object of the present invention is to provide a process for recycling waste acid liquid, which is obtained by recycling a large amount of waste acid liquid produced by the semiconductor industry to obtain a semiconductor grade sulfuric acid, which can be directly recycled to a semiconductor process, such as The processing of the wafer surface can reduce the industry's huge demand for semiconductor grade sulfuric acid, as well as the cost of processing the spent acid solution, and also reduce the environmental damage caused by the waste acid solution.

The spent acid solution is selected from the group consisting of waste sulfuric acid, hydrogen sulfide, sulfur-containing combustible gas or waste organic solvent.

For the above purposes, the technical means of the present invention consists in introducing the spent acid solution into a decomposition furnace, heating to produce SO ₂ , followed by cooling and purification to produce pure SO ₂ gas, and passing pure SO ₂ gas through a conversion. a tower, the conversion tower is filled with a catalyst to convert pure SO ₂ gas into SO ₃ gas; then the SO ₃ gas is introduced into an absorption tower, which is absorbed by the existing sulfuric acid and water in the absorption tower, that is, a cigarette is obtained. Sulfuric acid, the fuming sulfuric acid is introduced into a thin film distiller to obtain a metal-free high-purity SO ₃ gas, and the high-purity SO ₃ gas is removed by a demister to remove liquid sulfuric acid and solid impurities, and then diluted with an inert gas. Metallic high purity SO ₃ gas, this dilution helps to reduce the SO ₂ gas remaining in the SO ₃ gas, and also reduces the possibility of SO ₂ gas being absorbed by the high purity dilute sulfuric acid solution in the subsequent process, and then this SO ₃ The gas is introduced into the high-purity dilute sulfuric acid. When the SO ₃ gas is absorbed by the high-purity dilute sulfuric acid, a high-purity sulfuric acid is generated, and the high-purity sulfuric acid is filtered and the residual solid impurities are removed to remove the impurities. which is Sulfuric acid as a semiconductor grade, a semiconductor grade sulfuric acid was added and the product was introduced into a column through a column of high purity to the product of deionized water to adjust the concentration of the semiconductor grade sulfuric acid, the concentration is adjusted to meet the desired drive system of the semiconductor industry.

S1~S8‧‧‧Steps

1‧‧‧ Waste acid solution

2‧‧‧Decomposition furnace

3‧‧‧ Conversion Tower

4‧‧‧ Catalyst

5‧‧‧ absorption tower

6‧‧‧ water

7‧‧‧Fume sulfuric acid

8‧‧‧Inert gas

9‧‧‧film distiller

91‧‧‧ defogger

10‧‧‧ filter

11‧‧‧ catheter

12‧‧‧High purity deionized water

13‧‧‧High purity sulfuric acid

14‧‧‧Reaction tower

15‧‧‧Filter tube

151‧‧‧Filter membrane

16‧‧‧Product Tower

17‧‧‧Semiconductor grade sulfuric acid

Figure 1 is a block flow diagram of the present invention.

Figure 2 is a schematic view of the apparatus of the present invention.

Figure 3 is a schematic enlarged view of a portion of the apparatus of the present invention.

In order to facilitate the review committee to have a better understanding and understanding of the technical means and operation process of the present invention, the embodiments are combined with the drawings, and the details are as follows.

Referring to Figures 1 to 3, the process for recycling waste acid liquid provided by the present invention is carried out according to the following steps:

First, a waste acid solution 1 is introduced into a decomposition furnace 2, and step S1 is performed to heat the waste acid solution 1 to a temperature between 600 ° C and 700 ° C. At this time, the spent acid solution 1 generates SO ₂ gas and oxygen. (O ₂ ) and water vapor (H ₂ O), etc.; then proceeding to step S2, cooling the SO ₂ gas generated in step S1 to between 250 ° C and 350 ° C, and removing ash particles and trace amounts of SO ₃ through a purification process Purified pure SO ₂ gas; then proceeding to step S3, passing pure SO ₂ gas through a conversion column 4, which is filled with a catalyst 8 which is converted when the pure SO ₂ gas passes through the conversion tower 4 to SO ₃ gas; followed by step S4, in step S3 arising moved to a SO ₃ gas absorption tower 5, the SO ₃ gas is absorbed in the absorbing column 5 of both sulfuric acid, fuming sulfuric acid to produce out of 7 (Oleum); then proceeding to step S5, introducing the fuming sulfuric acid 7 into a thin film distiller 9, regenerating SO ₃ gas at a temperature of 60 ° C to 140 ° C by thin film distillation, and removing solid impurities, and passing through the thin film distillation method Producing a metal-free high-purity SO ₃ gas; then performing the step S6 to introduce the SO ₃ gas into a filter 10, the removal of the liquid sulfuric acid residue; followed by step S8, the SO ₃ gas is introduced into a reaction column 14 through a conduit 11, is introduced into the reaction column 14 is in the SO ₃ gas in both the high purity of the reaction column 14 Absorbed by dilute sulfuric acid, that is, a high-purity sulfuric acid 13 is generated. When the SO ₃ gas flows through the conduit 11, 1% to 50% of the inert gas 8 is added to the conduit 11 (step S7), and the inert gas 8 is sO ₃ gas will dilute trace of sO ₂ gas, thus reduce the possibility of sO ₂ gas to be absorbed in subsequent processes high-purity sulfuric acid solution; then the high purity sulfuric acid in step S8 13 through a filter 15 into tube In the product tower 16, a filter membrane 151 is disposed in the filter tube 15. When the high-purity sulfuric acid 13 is introduced into the product tower 16 through the filtration membrane 151, the solid impurities remaining in the high-purity sulfuric acid 13 are filtered to remove impurities. The high-purity sulfuric acid 13 becomes a semiconductor grade sulfuric acid 17.

Through the above steps, the waste acid solution 1 can be made into the semiconductor grade sulfuric acid 17 and can be reused in the semiconductor process, so as to achieve the purpose of recycling the semiconductor grade sulfuric acid 17 for recycling. The specifications of the semiconductor grade sulfuric acid 17 are detailed in the annex.

Referring to FIG. 3 again, the semiconductor grade sulfuric acid 17 can be adjusted by adding 1% to 50% of high purity deionized water 12 to the product column 16 to adjust the concentration of the semiconductor grade sulfuric acid 17 to meet The needs of the semiconductor industry process.

The waste acid solution 1 is selected from the group consisting of waste sulfuric acid, hydrogen sulfide, sulfur-containing combustible gas or waste organic solvent.

The catalyst 4 added in the step S3 may be vanadium pentoxide (V ₂ O ₅ ).

Step S5, the fuming sulfuric acid 7 produced in step S4 is introduced into the thin film distiller 9 having a demister 91, and the SO ₃ gas is taken from the temperature at a temperature of 60 ° C to 140 ° C by a thin film distillation method. The fuming sulfuric acid 7 is separated to obtain a metal-free high-purity SO ₃ gas, and then in step S6, SO ₃ gas is introduced into the filter 10 to remove residual liquid sulfuric acid and solid impurities.

The inert gas 8 added in the above step S7 may be replaced by high purity nitrogen or air.

The high-purity sulfuric acid 13 produced in the step S8 is introduced into the product tower 16 through the filter tube 15, and the filter membrane 151 disposed in the filter tube 15 has a pore diameter of less than 1 μm, and the material thereof can be all A fluoroalkoxy vinyl ether copolymer (PFA) or a fluorinated polyolefin or the like.

The invention utilizes a large amount of the waste acid solution 1 produced by the semiconductor industry to be recovered and processed to obtain the semiconductor grade sulfuric acid 17. The process not only establishes a new circular economy model, but also regenerates and reuses the waste acid solution 1 so that the resources can be forever Continued use, also practiced the production of green environmental protection, and also created a new environmental protection industry. Moreover, the semiconductor grade sulfuric acid 17 remanufactured by the present invention can be directly recycled in the semiconductor industry process, in addition to reducing the industry-grade sulfuric acid. The demand of 17 and the cost of processing the spent acid solution 1 can also reduce the environmental damage caused by the waste acid 1 discharge and the energy consumption.

The detailed description of the preferred embodiments of the present invention is not intended to limit the scope of the present invention, and the equivalent implementations or modifications of the present invention should be included in the present invention. In the scope of patents.

S1-S8‧‧‧ steps

Claims (9)

A process for recycling waste acid liquid, the process comprising: introducing a waste acid liquid into a decomposition furnace, heating the waste acid liquid to generate SO ₂ gas, oxygen and water vapor, and then cooling the SO ₂ gas to produce pure SO ₂ gas; passing pure SO ₂ gas through a conversion tower filled with a catalyst to convert pure SO ₂ gas into SO ₃ gas; introducing SO ₃ gas into an absorption tower, the SO ₃ gas will be The sulfuric acid and water contained in the absorption tower are absorbed to generate a fuming sulfuric acid; the fuming sulfuric acid is introduced into a thin film distiller having a mist eliminator, and the SO ₃ gas is again generated by thin film distillation, and the SO is further generated. ₃ gas is introduced into a filter to produce a high-purity and metal-free SO ₃ gas; the SO ₃ gas is introduced into a reaction tower through a conduit, and is absorbed by the high-purity dilute sulfuric acid in the reaction tower, that is, a high Purity sulfuric acid, and adding an inert gas to the conduit; and filtering the high-purity sulfuric acid through a filter tube to obtain a semiconductor grade sulfuric acid. The process for recycling waste acid liquid as described in claim 1, wherein the waste acid liquid is selected from the group consisting of waste sulfuric acid, hydrogen sulfide, and sulfur-containing combustible gas. For the recycling process of the waste acid solution described in claim 1, wherein 1% to 50% of high-purity deionized water may be added to a product tower to adjust the concentration of the semiconductor-grade sulfuric acid to meet The needs of the semiconductor industry process. The process for recycling waste acid liquid as described in claim 1, wherein the waste acid liquid is heated at a temperature ranging from 600 ° C to 700 ° C. The process for recycling waste acid liquid as described in claim 1 wherein the temperature at which SO _{2 is} cooled is in the range of 250 ° C to 350 ° C. The process for recycling waste acid liquid as described in claim 1 wherein the temperature of the thin film distillation reaction is in the range of 60 ° C to 140 ° C. The process for recycling waste acid liquid as described in claim 1 wherein the inert gas is high purity nitrogen or air and is added in an amount of from 1% to 50%. The process for recycling waste acid liquid as described in claim 1, wherein the filter tube is provided with a filter membrane having a pore diameter of less than 1 μm. The process for recycling waste acid liquid as described in claim 9 wherein the filter film is made of a perfluoroalkoxy vinyl ether copolymer (PFA) and a fluorinated polyolefin.