Method and system for producing oleum from waste sulfuric acid

Abstract

so as to obtain a second sulfuric acid solution; Step (S4): the second sulfuric acid solution is heated to decompose the sulfuric acid to obtain a mixture comprising SO 3and water; and Step (S5): the SO 3and the water in the mixture are separated, and the SO 3is subjected to an absorption process to obtain an oleum with high concentration. The preparation system sequentially comprises: a waste sulfuric acid storage unit, a reaction unit comprising a sulfur dioxide supply module and a reaction tank, a heating assembly including a first heating tank and a second heating tank, a water separation module, and a SO 3absorption unit.

Description

[Technical Field]

[0001] This invention relates to a method for treating waste sulfuric acid solution, and more particularly to a method for preparing fuming sulfuric acid from waste sulfuric acid solution. [Previous Technology]

[0002] Sulfuric acid can be used in agriculture, automotive, and electronics industries. The sulfuric acid market size was US$13.68 billion in 2023 and is expected to continue growing for at least the next 10 years. Electronic-grade sulfuric acid is a high-purity form of sulfuric acid, primarily used in the semiconductor industry for substrate cleaning, etching silicon wafers, and as a reagent in various chemical reactions. Due to the expansion of emerging technologies such as consumer electronics, automotive electronics, and 5G and IoT devices, the electronics industry is developing rapidly. Coupled with increased investment in semiconductor manufacturing and rising demands for precision and miniaturization of electronic components, large quantities of electronic-grade sulfuric acid are often used in the manufacturing process, resulting in a large amount of waste sulfuric acid solution that needs to be discharged. Taking the RCA wet chemical cleaning process in semiconductor manufacturing as an example, caro acid (H2SO4), composed of electronic-grade sulfuric acid and hydrogen peroxide (H₂O₂), is used to remove residual photoresist and organic contaminants from the wafer surface, making it the largest source of process waste liquid.

[0003] In order to meet the international trend of sustainable business development and the challenges of strict environmental regulations governing the production and disposal of chemicals, operating costs may increase. Effectively utilizing these waste sulfuric acid solutions can meet the trend and reduce costs. However, since waste sulfuric acid solutions contain hydrogen peroxide, which is less stable than fresh sulfuric acid, removing the hydrogen peroxide contained in carboxylic acid is the primary issue if recycling and reuse are required.

[0004] To address this, numerous methods have been developed to treat hydrogen peroxide in waste sulfuric acid solutions. These include adding reagents (such as hydrochloric acid, nitric acid, vanadium, etc.) to decompose hydrogen peroxide, using ultraviolet irradiation to decompose it, or treating the waste sulfuric acid solution at high temperatures to thermally decompose the hydrogen peroxide into oxygen and water. However, these methods require the purchase of additional reagents or equipment, and must avoid the explosion hazards of high-temperature oxygen release or the problem of acid corrosion on equipment. This increases the overall complexity and cost of the process and may also generate more safety risks that require attention. Therefore, how to effectively treat waste sulfuric acid solutions still requires further research and development by relevant technical personnel.

[0005] Fumigating sulfuric acid is a sulfuric acid solution of sulfur trioxide (SO3). High-concentration fuming sulfuric acid is highly volatile. If sulfur trioxide escapes into the environment, it will cause serious pollution, posing a significant threat to human health, plant and animal growth, and related equipment. In recent years, with the rapid increase in demand for fuming sulfuric acid, environmental issues related to its storage process have attracted attention. If the fuming sulfuric acid production process can be easily connected to an electronic-grade sulfuric acid manufacturing system, it will not only save energy but also improve process safety. [Summary of the Invention]

[0006] In view of the technical defects of the above-mentioned waste sulfuric acid solution treatment method, the purpose of this invention is to provide a method that can simultaneously treat waste sulfuric acid solution and prepare fuming sulfuric acid, which can not only simplify the process and equipment and save energy, but also has high safety, thus reducing the overall operating cost.

[0007] Another objective of this invention is to provide a method for simultaneously treating waste sulfuric acid solution and preparing fuming sulfuric acid, which not only reduces the amount of chemical reagents used, but also reduces derivative waste, thus being environmentally friendly and in line with the trend of sustainable development.

[0008] To achieve the aforementioned objective, this invention provides a method for producing fuming sulfuric acid from waste sulfuric acid, which includes the following steps (S1) to (S5). Step (S1): Collect waste sulfuric acid solution containing hydrogen peroxide; Step (S2): Provide sulfur dioxide and the waste sulfuric acid solution to a reaction tank, allowing the hydrogen peroxide and sulfur dioxide to undergo a redox reaction to obtain a first sulfuric acid solution; wherein the reaction temperature of the redox reaction is 80°C to 110°C; Step (S3): Introduce the first sulfuric acid solution into a first heating tank to obtain a second sulfuric acid solution; wherein the first heating temperature of the first heating tank is 100°C to 220°C; Step (S4): Introduce the second sulfuric acid solution into a second heating tank to decompose the sulfuric acid in the second sulfuric acid solution to obtain a mixture containing sulfur trioxide and water; wherein the second heating temperature of the second heating tank is greater than the first heating temperature but not higher than the azeotropic point of sulfuric acid and water; and Step (S5): After a separation process of sulfur trioxide and water in the mixture, the sulfur trioxide undergoes an absorption process to obtain high-concentration fuming sulfuric acid; the concentration of the high-concentration fuming sulfuric acid is 36% by weight (wt%) or more.

[0009] This invention first involves a redox reaction (SO2 + H2O2 → H2SO4) between SO2 and H₂O₂ in a waste sulfuric acid solution to consume the highly reducing H₂O₂. Then, the waste sulfuric acid solution is heated at a temperature not exceeding the azeotropic point of sulfuric acid and water to decompose the sulfuric acid into a mixture of SO3 and water. The SO3 and water are then separated, collected, and absorbed, ultimately yielding a high-concentration fuming sulfuric acid. Since no byproducts are generated during the first-stage redox reaction, there are no new product residues, improving atom utilization and facilitating subsequent fuming sulfuric acid production. Furthermore, compared to directly burning sulfuric acid to produce SO2 and then oxidizing it to SO3, the second stage of this invention uses a relatively lower heating temperature to extract SO3, thus simplifying energy use, reducing the load on manufacturing equipment, and minimizing the generation of harmful substances.

[0010] According to this invention, the waste sulfuric acid solution only needs to contain sulfuric acid and H2O2, and its source is not limited. In some embodiments, the waste sulfuric acid solution may be waste liquid generated from cleaning machines, semi-finished products, or etching processes in technology plants (such as semiconductor plants, panel plants, or PCB plants), but is not limited to these.

[0011] In some embodiments, the waste sulfuric acid solution in step (S1) may contain sulfuric acid, H2O2 and water; based on the total weight of the waste sulfuric acid solution, the content of sulfuric acid is 60 wt% to 70 wt% and the content of H2O2 is 0.2 wt% to 5.0 wt%.

[0012] Preferably, the sidewall of the reaction tank in step (S2) has a sandwich structure, which can be circulated with cooling water, thus facilitating temperature regulation, but is not limited thereto.

[0013] According to this invention, the source of SO2 in step (S2) is not particularly limited. Since SO2 is a byproduct generated during the production of high-purity sulfuric acid and must undergo pollution control treatment before being emitted, its direct utilization would have environmental and energy-saving advantages. Therefore, in some embodiments, the SO2 in step (S2) may include sulfur dioxide byproducts generated during the sulfuric acid production process; preferably, it is sulfur dioxide byproducts generated during the electronic-grade sulfuric acid production process. In other embodiments, the SO2 in step (S2) may include purchased chemical SO2. In still other embodiments, the SO2 in step (S2) may simultaneously include sulfur dioxide byproducts generated during the sulfuric acid production process and purchased chemical SO2, but is not limited to these.

[0014] In addition, when step (S2) is in progress or completed, the compressed dry air (CDA) in the waste sulfuric acid solution can be discharged from the reaction tank.

[0015] According to this invention, step (S3) is to remove unreacted SO2 from the first sulfuric acid solution, increase the concentration of sulfuric acid, and, in order to make the waste sulfuric acid solution after the subsequent redox reaction more capable of decomposing sulfur trioxide and water, step (S3) mainly provides a preheating effect. Accordingly, the first heating temperature is preferably 120°C to 200°C, but is not limited to this.

[0016] Preferably, the material of the first heating tank may include a glass liner, but is not limited thereto.

[0017] According to this invention, step (S4) is to decompose the sulfuric acid in the second sulfuric acid solution into a mixture containing SO3 and water. On the one hand, since the second heating temperature is higher than the general boiling point of water, most of the water can be discharged from the top in the form of water vapor; on the other hand, SO3-rich gas is drawn out from the middle height of the second heating tank. However, even though the drawn-out gas is rich in SO3, it will still contain water vapor, so the drawn-out gas is still the mixture containing sulfur trioxide and water.

[0018] Preferably, the second heating temperature may be greater than 200°C and less than or equal to 320°C, but is not limited thereto.

[0019] Preferably, the separation process can be carried out in step (S5) using a water separation module; wherein the material of the water separation membrane contained in the water separation module includes zeolite, ceramic, carbon nanotubes or combinations thereof, but is not limited thereto.

[0020] In order to keep SO3 in a gaseous state as much as possible and reduce the amount of water vapor absorbed and reverted to form sulfuric acid, preferably, during the process of guiding the mixture in step (S4) from the second heating tank to the water separation module, the temperature of the process is kept at least 300°C, for example, the temperature of the process can be 300°C to 500°C, but is not limited thereto.

[0021] In some embodiments, step (S5) may include steps (S5-a) and (S5-b). Step (S5-a): The sulfur trioxide and water in the mixture are subjected to the separation process to obtain the sulfur trioxide; Step (S5-b): The sulfur trioxide is sequentially subjected to a condensation process and an absorption process to obtain the high-concentration fuming sulfuric acid.

[0022] Preferably, under normal pressure, the condensation temperature of the condensation process can be below 45°C; for example, the condensation temperature can be from 40°C to 18°C, but is not limited thereto. Specifically, the condensation temperature can be 20°C, 25°C, 28°C, 30°C, or 35°C.

[0023] This invention also provides a preparation system for producing fuming sulfuric acid from waste sulfuric acid, which is a preparation system constructed based on the above-mentioned method for producing fuming sulfuric acid from waste sulfuric acid. The preparation system for producing fuming sulfuric acid from waste sulfuric acid includes: a waste sulfuric acid solution storage unit having a waste sulfuric acid solution storage tank and a waste sulfuric acid delivery pipe connected in series; a reaction unit having a reaction tank, a sulfur dioxide supply group, and a first sulfuric acid solution delivery pipe; a heating assembly including a first heating tank, a heating tank delivery pipe, a second heating tank, and a mixture output pipe connected in sequence; a water separation module including a water separation membrane device, a sulfur trioxide gas output pipe, and a separated water output pipe; and a sulfur trioxide absorption unit connected to the sulfur trioxide gas output pipe for absorbing sulfur trioxide to obtain the fuming sulfuric acid. The waste sulfuric acid solution storage tank is used to contain the waste sulfuric acid solution, which contains hydrogen peroxide. The waste sulfuric acid delivery pipe is connected to the reaction tank to introduce the waste sulfuric acid solution; the sulfur dioxide supply group supplies sulfur dioxide to the reaction tank; the hydrogen peroxide and sulfur dioxide in the waste sulfuric acid solution undergo a redox reaction in the reaction tank to obtain a first sulfuric acid solution; the first sulfuric acid solution delivery pipe is connected to the reaction tank to discharge the first sulfuric acid solution. The first sulfuric acid solution delivery pipe is also connected to a first heating tank; the first heating tank heats the first sulfuric acid solution to a first heating temperature to obtain a second sulfuric acid solution; the first heating temperature is between 100°C and 220°C; a heating tank distribution pipe introduces the second sulfuric acid solution into the second heating tank; the second heating tank heats the second sulfuric acid solution to a second heating temperature to obtain a mixture containing sulfur trioxide and water; the second heating temperature is higher than the first heating temperature but not higher than the azeotropic point of sulfuric acid and water; the mixture output pipe discharges the mixture. The water separation membrane device is connected to the mixture output pipe, the sulfur trioxide gas output pipe, and the separated water output pipe, respectively. The water separation membrane device includes a water separation membrane, and the material of the water separation membrane includes zeolite, ceramic, carbon nanotubes, or a combination thereof. The sulfur trioxide gas output pipe is used to discharge the sulfur trioxide gas obtained after treatment by the water separation membrane device. The separated water output pipe is used to discharge the water obtained after treatment by the water separation membrane device.

[0024] Preferably, the sulfur dioxide supply group may include sulfur dioxide cylinders and sulfur dioxide piping; the sulfur dioxide cylinders are used to contain sulfur dioxide; the sulfur dioxide piping is used to introduce sulfur dioxide generated during the sulfuric acid manufacturing process.

[0025] Preferably, the heating tank delivery pipe is connected to the upper part of the second heating tank, so that the second sulfuric acid solution is introduced from the upper part of the second heating tank; the second sulfuric acid solution is gradually heated during its passage through the second heating tank. Preferably, the second heating tank can monitor the sulfuric acid concentration in the second sulfuric acid solution.

[0026] Preferably, the material of the second heating tank may include acid-resistant bricks, stainless steel, low-carbon steel, or combinations thereof, but is not limited thereto. Specifically, the acid-resistant bricks are made of high-silica raw materials, such as quartz, feldspar, clay, or combinations thereof, but are not limited thereto. The carbon content of the carbon steel may be from 0.03 wt% to 0.2 wt%, but is not limited thereto.

[0027] Preferably, the preparation system may further include a water condensation device, which includes a water condensation tank, a vacuum pump, a delivery pump, and a recovery water pipeline; the water condensation tank is connected to the vacuum pump; the delivery pump is connected to the recovery water pipeline; the water condensation tank is connected to the recovery water pipeline, and the aqueous solution collected in the water condensation tank is transported to the first heating tank via the recovery water pipeline. The operation of the vacuum pump can facilitate the extraction of sulfur trioxide gas from the second heating tank.

[0028] Preferably, the preparation system may further include a sulfur trioxide cooling device, which is disposed downstream of the water separation module and upstream of the sulfur trioxide absorption unit; wherein, the sulfur trioxide cooling device includes a sulfur trioxide condensation tank and a liquid sulfur trioxide output pipe connected in series; the sulfur trioxide gas output pipe is connected to the sulfur trioxide condensation tank; the temperature of the sulfur trioxide condensation tank is 18°C ​​to 40°C; the sulfur trioxide absorption unit includes a sulfur trioxide absorption tower and a fuming sulfuric acid discharge pipe connected in series; the sulfur trioxide absorption tower contains more than 98 wt% sulfuric acid. Preferably, the sulfur trioxide condensation tank may be equipped with room temperature sulfuric acid as a coolant, but is not limited thereto. Specifically, the temperature of the sulfur trioxide condensation tank may be 20°C, 25°C, 28°C, 30°C, or 35°C, but is not limited thereto.

[0029] Preferably, the preparation system may further include a waste treatment unit that is connected to the reaction tank in the reaction unit, which can be used to discharge compressed dry air (CDA) from the waste sulfuric acid solution into the reaction tank; or, in some embodiments, the waste treatment unit may be connected to the first heating tank, which can be used to treat unreacted sulfur dioxide and / or water.

[0030] Preferably, the preparation system can be connected to an electronic-grade sulfuric acid manufacturing system via a high-concentration fuming sulfuric acid delivery pipeline. In some embodiments, the high-concentration fuming sulfuric acid delivery pipeline may include one or more control valves, through which the fuming sulfuric acid can be delivered from the preparation system to the electronic-grade sulfuric acid manufacturing system for use.

[0031] Preferably, the preparation system and the electronic-grade sulfuric acid manufacturing system have a temporary storage tank, which is connected to both the preparation system and the electronic-grade sulfuric acid manufacturing system. In some embodiments, the upstream and downstream of the temporary storage tank can be connected to control valves; when the electronic-grade sulfuric acid manufacturing system consumes some fuming sulfuric acid, causing its original concentration to decrease, the lower concentration fuming sulfuric acid can be left in the temporary storage tank, and the lower concentration fuming sulfuric acid can flow into the sulfur trioxide absorption tower through the connected pipeline by opening or closing the control valve, so as to regenerate the high concentration fuming sulfuric acid.

[0032] In this specification, the range represented by "small value to large value" means, unless otherwise specified, that the range is greater than or equal to the small value and less than or equal to the large value. For example: the first heating temperature is 100°C to 220°C, which means that the range of the first heating temperature is "greater than or equal to 100°C and less than or equal to 220°C".

[0033] In the description of this specification, it should be noted that if the orientation or positional relationship indicated by terms such as "center", "up", "down", "top", "bottom", "inner", "outer" is based on the orientation or positional relationship shown in the diagram, it is only for the convenience of describing this creation, and is not intended or implied that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, a specific orientation should not be understood as a limitation on this creation.

Implementation Method

[0034] Hereinafter, specific implementation methods of this invention will be described with reference to the following embodiments and accompanying drawings. Those skilled in the art can easily understand the advantages and effects achieved by this invention through the content of this specification, and can make various modifications and changes without departing from the spirit of this invention to implement or apply the content of this invention. Repeated reference symbols and / or words may be used in various embodiments. These repeated symbols or words are for simplification and clarity purposes and are not intended to limit the relationship between the various embodiments and / or the structures described. In addition, the graphics in the drawings are not drawn according to dimensions, and these graphics are used for illustrative purposes.

[0035] Example 1: Method and preparation system for producing fuming sulfuric acid from waste sulfuric acid

[0036] Hereinafter, fuming sulfuric acid will be produced from waste sulfuric acid using the method flowchart shown in Figure 1 and the preparation system for producing fuming sulfuric acid from waste sulfuric acid shown in Figure 2.

[0037] As shown in Figure 2, the preparation system 1 for producing fuming sulfuric acid from waste sulfuric acid of this invention includes: a waste sulfuric acid solution storage unit 10, a reaction unit 20, a heating component 30, a water separation module 40, and a sulfur trioxide absorption unit 50.

[0038] The waste sulfuric acid solution storage unit 10 has a waste sulfuric acid solution storage tank 11 and a waste sulfuric acid conveying pipe 12 connected to each other; the waste sulfuric acid solution storage tank 11 is used to contain the waste sulfuric acid solution, which contains H2O2. On the other hand, in step (S1), the waste sulfuric acid solution is collected by the waste sulfuric acid solution storage unit 10; wherein, based on the total weight of the waste sulfuric acid solution, the content of H2O2 is approximately 5.0 wt%.

[0039] The reaction unit 20 includes a reaction tank 21, a sulfur dioxide supply group 22, and a first sulfuric acid solution conveying pipe 23; the waste sulfuric acid conveying pipe 12 is connected to the reaction tank 21, and the waste sulfuric acid conveying pipe 12 introduces the waste sulfuric acid solution from the waste sulfuric acid solution storage tank 11 into the reaction tank 21; the sulfur dioxide supply group 22 supplies SO2 to the reaction tank 21; the first sulfuric acid solution conveying pipe 23 is connected to the reaction tank 21, and the first sulfuric acid solution conveying pipe 23 is used to discharge the reacted waste sulfuric acid solution (i.e., the first sulfuric acid solution) from the reaction tank 21. On the other hand, in step (S2), SO2 and the aforementioned waste sulfuric acid solution are provided in the reaction tank 21, so that H2O2 and SO2 undergo a redox reaction to obtain the first sulfuric acid solution; wherein, the reaction temperature of the redox reaction is 80°C to 110°C, so that H2O2 and SO2 can react more fully.

[0040] The heating assembly 30 includes a first heating tank 31, a heating tank delivery pipe 32, a second heating tank 33, and a mixture output pipe 34, which are sequentially connected. The first sulfuric acid solution delivery pipe 23 is connected to the first heating tank 31; and, as in step (S3), the first sulfuric acid solution is introduced into the first heating tank 31 and heated to a first heating temperature of the first heating tank 31 to obtain a second sulfuric acid solution; wherein, the first heating temperature is 100°C to 220°C. Next, as in step (S4), the heating tank delivery pipe 32 introduces the second sulfuric acid solution from the first heating tank 31 into the second heating tank 33; the second heating tank 33 heats the second sulfuric acid solution to a second heating temperature of the second heating tank 33, causing the sulfuric acid in the second sulfuric acid solution to decompose to obtain a mixture containing SO3 and water; wherein, the second heating temperature is greater than the first heating temperature and not higher than the azeotropic point of sulfuric acid and water. Finally, the mixture output pipe 34 discharges the mixture out of the second heating tank 33.

[0041] In step (S5), after the sulfur trioxide and water in the mixture are separated, the sulfur trioxide is absorbed to obtain the fuming sulfuric acid. On the other hand, the water separation module 40 includes a water separation membrane device 41, a sulfur trioxide gas output pipe 42, and a separated water output pipe 43; wherein, the water separation membrane device 41 is connected to the mixture output pipe 34, the sulfur trioxide gas output pipe 42, and the separated water output pipe 43 respectively; the water separation membrane device 41 includes a water separation membrane, the material of which includes zeolite, ceramic, carbon nanotubes, or a combination thereof. The sulfur trioxide gas output pipe 42 is used to discharge the SO3 gas obtained after treatment by the water separation membrane device 41; the separated water output pipe 43 is used to discharge the water obtained after treatment by the water separation membrane device 41. The sulfur trioxide absorption unit 50 is connected to the sulfur trioxide gas output pipe 42 to absorb sulfur trioxide to obtain the fuming sulfuric acid.

[0042] Example 2: Method and preparation system for producing fuming sulfuric acid from waste sulfuric acid

[0043] The method for producing fuming sulfuric acid from waste sulfuric acid used in this embodiment is the same as that in Embodiment 1, except that the preparation system 1 for producing fuming sulfuric acid from waste sulfuric acid is slightly different. For details of the preparation system 1 for producing fuming sulfuric acid from waste sulfuric acid in this embodiment, please refer to Figure 3. The preparation system 1 for producing fuming sulfuric acid from waste sulfuric acid includes: a waste sulfuric acid solution storage unit 10, a reaction unit 20, a heating component 30, a water separation module 40, a sulfur trioxide cooling device 60, a sulfur trioxide absorption unit 50, a waste treatment unit 70, and a high-concentration fuming sulfuric acid conveying pipeline 80.

[0044] The waste sulfuric acid solution storage unit 10 has a waste sulfuric acid solution storage tank 11 and a waste sulfuric acid conveying pipe 12 connected to each other; the waste sulfuric acid solution storage tank 11 is used to contain and collect waste sulfuric acid solution, which contains H2O2. The content of H2O2 is approximately 5.0 wt% based on the total weight of the waste sulfuric acid solution.

[0045] The reaction unit 20 includes a reaction tank 21, a sulfur dioxide supply group 22, and a first sulfuric acid solution delivery pipe 23. The waste sulfuric acid delivery pipe 12 is connected to the reaction tank 21, and the waste sulfuric acid solution is introduced into the reaction tank 21 from the waste sulfuric acid solution storage tank 11 through the waste sulfuric acid delivery pipe 12. Furthermore, a delivery pump P can be installed on the waste sulfuric acid delivery pipe 12 to facilitate the delivery of the waste sulfuric acid solution. To ensure a more complete reaction between H2O2 and SO2, a heating jacket 211 can be installed outside the reaction tank 21, and the temperature can be set to approximately 100°C. The sulfur dioxide supply group 22 includes a sulfur dioxide cylinder 221, a cylinder piping 222, and a sulfur dioxide piping 223. The sulfur dioxide cylinder 221 contains fresh SO2 (i.e., purchased chemical SO2), and SO2 gas is introduced into the reaction tank 21 from the sulfur dioxide cylinder 221 through the cylinder piping 222, which is connected to the reaction tank 21. In addition, the sulfur dioxide piping 223 is connected to the electronic-grade sulfuric acid manufacturing system 2, which can supply SO2 gas generated during the sulfuric acid manufacturing process of the electronic-grade sulfuric acid manufacturing system 2 to the reaction tank 21. In some cases, this embodiment may optionally install control valves V on both the sulfur dioxide piping 223 and the gas cylinder piping 222. Therefore, the operator can choose to prioritize the use of SO2 gas through the sulfur dioxide piping 223. If the SO2 gas supplied by the sulfur dioxide piping 223 is insufficient, the operator can then open the control valve V on the gas cylinder piping 222. Thus, the SO2 gas, a byproduct that needs to be controlled during the sulfuric acid manufacturing process, can be consumed first, and the amount of SO2 gas that needs to be purchased can be reduced, resulting in the advantage of reduced raw material costs.

[0046] Furthermore, the first sulfuric acid solution delivery pipe 23 is connected to the reaction tank 21 and the first heating tank 31. A delivery pump P can be installed on the first sulfuric acid solution delivery pipe 23 to facilitate the transfer of the waste sulfuric acid solution (i.e., the first sulfuric acid solution) after the reaction from the reaction tank 21 to the first heating tank 31. In some embodiments, the first sulfuric acid solution delivery pipe 23 can be equipped with a delivery pump P and can form a loop with the reaction tank 21. A control valve V is provided on the aforementioned loop to force the waste sulfuric acid solution and / or the first sulfuric acid solution to circulate in order to accelerate the reaction of H2O2 and SO2. After it is determined that the waste sulfuric acid solution in the reaction tank 21 no longer contains H2O2, the control valve V on the aforementioned loop is closed and the control valve V connecting to the first heating tank 31 is opened to deliver the first sulfuric acid solution to the first heating tank 31.

[0047] In addition, the reaction tank 21 is connected to the waste discharge treatment unit 70, which can be used to discharge CDA or unreacted SO2 gas in the waste sulfuric acid solution from the reaction tank 21, and pollution prevention and control treatment is carried out by the waste discharge treatment unit 70.

[0048] The heating assembly 30 includes a first heating tank 31, a heating tank delivery pipe 32, a second heating tank 33, and a mixture output pipe 34, which are connected in sequence. The first heating tank 31 is filled with a filler 311 (mainly made of stainless steel 316) in its upper region, and a heating pipe 312 is provided in the middle section of the first heating tank 31. The first heating tank 31 heats the first sulfuric acid solution to a first heating temperature (100°C to 200°C) to obtain a second sulfuric acid solution. Furthermore, the first heating tank 31 can also be connected to a waste treatment unit 70; when there is unreacted SO2 and / or water vapor in the first heating tank 31, it can be sent to the waste treatment unit 70 after further separation and treatment.

[0049] Next, the heating tank delivery pipe 32 introduces the second sulfuric acid solution from the top of the first heating tank 31 into the second heating tank 33; wherein, the middle area of ​​the second heating tank 33 is provided with a filler 331 (the main material of which is ceramic and borosilicate glass), and the material of the second heating tank 33 includes an acid-resistant brick lining; the second heating tank 33 is equipped with a heating jacket 332, and the second sulfuric acid solution is heated to a second heating temperature (about 300°C), so that the sulfuric acid in the second sulfuric acid solution is first concentrated due to the evaporation of water, and then further forms SO3 gas and water vapor due to the increase in sulfuric acid concentration, so as to obtain a mixture containing SO3 and water. Subsequently, the mixture is guided from the second heating tank 33 to the water separation module 40 by the mixture output pipe 34. Furthermore, since SO3 is easily redissolved in water, the temperature of the mixture output pipe 34 is maintained at about 300°C to 500°C. In some embodiments, the second heating tank 33 may be equipped with a sulfuric acid concentration monitoring device (not shown). Alternatively, a steam recovery pipe can be installed on the top of the second heating tank 33 to prevent water vapor from continuously accumulating in the second heating tank 33.

[0050] The water separation module 40 includes a water separation membrane device 41, a sulfur trioxide gas output pipe 42, and a separated water output pipe 43; wherein the water separation membrane device 41 is connected to the mixture output pipe 34, the sulfur trioxide gas output pipe 42, and the separated water output pipe 43 respectively; the water separation membrane device 41 includes a water separation membrane, the material of which includes zeolite, ceramic, carbon nanotubes, or a combination thereof; and, in order to maintain the temperature of the water separation membrane device 41, a heating jacket 411 may be provided outside the water separation membrane device 41.

[0051] The water separated by the water separation membrane device 41 is guided from the separated water output pipe 43 to the water condensation device 44. The water condensation device 44 includes a water condensation tank 441 (containing a water condensation pipe 4411), a transfer pump P, and a vacuum pump 442; the vacuum pump 442 is connected to the water condensation tank 441, which helps to effectively extract SO3 gas from the second heating tank 33. The water condensation tank 441 is also connected to the transfer pump P, which can be installed on the pipeline connecting the water condensation tank 441 and the first heating tank 31, to return the collected aqueous solution containing sulfuric acid to the first heating tank 31, becoming part of the first sulfuric acid solution in the first heating tank 31.

[0052] On the other hand, the SO3 gas separated by the water separation membrane device 41 is transported to the sulfur trioxide cooling device 60 through the sulfur trioxide gas output pipe 42. The sulfur trioxide cooling device 60 is located downstream of the water separation module 40 and upstream of the sulfur trioxide absorption unit 50. The sulfur trioxide cooling device 60 includes a sulfur trioxide condensation tank 61 and a liquid sulfur trioxide output pipe 62 connected to each other; wherein, a condenser pipe 611 is provided in the sulfur trioxide condensation tank 61, and sulfuric acid at room temperature is introduced into the condenser pipe as a coolant, so that the high concentration of SO3 gas condenses at 45°C to form liquid SO3.

[0053] Liquid SO3 is guided from the liquid sulfur trioxide output pipe 62 to the sulfur trioxide absorption unit 50. The sulfur trioxide absorption unit 50 includes a connected sulfur trioxide absorption tower 51 and a fuming sulfuric acid discharge pipe 52; the middle area of ​​the sulfur trioxide absorption tower 51 may be filled with a packing material 511 (the main material of which is stainless steel 316); the sulfur trioxide absorption tower 51 contains more than 98 wt% sulfuric acid, therefore, high-concentration liquid SO3 can be absorbed by the concentrated sulfuric acid in the sulfur trioxide absorption tower 51. In addition, in some embodiments, the fuming sulfuric acid discharge pipe 52 may be connected to a loop returning to the sulfur trioxide absorption tower 51, and a transfer pump P and a control valve V are installed on this loop, so that the fuming sulfuric acid can circulate in this loop connected in series with the sulfur trioxide absorption tower 51 until the concentration of SO3 reaches a level suitable for manufacturing electronic-grade sulfuric acid, and then the control valve V on the aforementioned loop is closed, and the required fuming sulfuric acid is transported through the fuming sulfuric acid discharge pipe 52 to the electronic-grade sulfuric acid manufacturing system 2 for use as a raw material for the production of electronic-grade sulfuric acid. When the concentration of fuming sulfuric acid in the electronic-grade sulfuric acid manufacturing system 2 decreases due to SO3 consumption during the sulfuric acid production process, the lower concentration of fuming sulfuric acid can be transferred to the temporary storage tank 90. ​​The temporary storage tank 90 is connected to both the sulfur trioxide absorption tower 51 and the electronic-grade sulfuric acid manufacturing system 2. In some embodiments, a transfer pump P and a control valve V can be installed on the pipeline from the temporary storage tank 90 to the sulfur trioxide absorption tower 51, thereby allowing for better control of different flow paths as needed.

[0054] In summary, this invention, through the coordinated steps (S1) to (S5) of producing fuming sulfuric acid from waste sulfuric acid, specifically by first consuming the highly reducing H2O2 through the reaction of SO2 with H₂O₂ in the waste sulfuric acid solution to form sulfuric acid (H₂SO₄), and then by heating the waste sulfuric acid solution at a temperature not exceeding the azeotropic point of sulfuric acid and water to decompose the sulfuric acid into a mixture of SO₃ and water. This effectively regenerates the waste sulfuric acid solution into a raw material applicable to electronic-grade sulfuric acid processes. Therefore, this invention not only effectively reduces acidic waste but also offers advantages such as energy efficiency and reduced equipment load, achieving environmental friendliness and compliance with sustainable development goals. [Simplified Explanation of the Diagram]

[0055] Figure 1 is a schematic flowchart of the method for producing fuming sulfuric acid from waste sulfuric acid according to this invention. Figure 2 is a schematic diagram of the preparation system for producing fuming sulfuric acid from waste sulfuric acid in Example 1 of this invention. Figure 3 is a schematic diagram of the preparation system for producing fuming sulfuric acid from waste sulfuric acid in Example 2 of this invention. [Biomaterial Storage]

[0057] None

Claims

1. A method for producing fuming sulfuric acid from waste sulfuric acid, comprising the following steps: Step (S1): Collect waste sulfuric acid solution containing hydrogen peroxide; Step (S2): Provide sulfur dioxide and the waste sulfuric acid solution to a reaction tank, allowing the hydrogen peroxide and sulfur dioxide to undergo a redox reaction to obtain a first sulfuric acid solution; wherein the reaction temperature of the redox reaction is 80°C to 110°C; Step (S3): Introduce the first sulfuric acid solution into a first heating tank to obtain a second sulfuric acid solution; wherein the first heating temperature of the first heating tank is 100°C to 220°C; Step (S4): Introduce the second sulfuric acid solution into a second heating tank to decompose the sulfuric acid in the second sulfuric acid solution to obtain a mixture containing sulfur trioxide and water; wherein the second heating temperature of the second heating tank is greater than the first heating temperature but not higher than the azeotropic point of sulfuric acid and water; and Step (S5): After a separation process of sulfur trioxide and water in the mixture, the sulfur trioxide undergoes an absorption process to obtain high-concentration fuming sulfuric acid; the concentration of the high-concentration fuming sulfuric acid is 36% by weight or more.

2. The method as described in claim 1, wherein, The sulfur dioxide in this step (S2) includes sulfur dioxide produced during the sulfuric acid manufacturing process.

3. The method as described in claim 1, wherein, In this step (S5), a water separation module is used to perform the separation process; wherein the water separation membrane contained in the water separation module is made of zeolite, ceramic, carbon nanotubes or a combination thereof.

4. The method as described in claim 3, wherein, During the process of guiding the mixture from the second heating tank to the water separation module, the temperature of the process is maintained at 300°C to 500°C.

5. The method as described in any one of claims 1 to 4, wherein, Step (S5) includes: Step (S5-a): subjecting the sulfur trioxide and water in the mixture to the separation process to obtain the sulfur trioxide; Step (S5-b): subjecting the sulfur trioxide to a condensation process and an absorption process in sequence to obtain the high-concentration fuming sulfuric acid.

6. A preparation system for producing fuming sulfuric acid from waste sulfuric acid, comprising: A waste sulfuric acid solution storage unit, which has a waste sulfuric acid solution storage tank and a waste sulfuric acid conveying pipe connected to each other; The waste sulfuric acid solution storage tank is used to contain waste sulfuric acid solution, which includes hydrogen peroxide; a reaction unit has a reaction tank, a sulfur dioxide supply group, and a first sulfuric acid solution delivery pipe; wherein, the waste sulfuric acid delivery pipe is connected to the reaction tank to introduce the waste sulfuric acid solution; the sulfur dioxide supply group supplies sulfur dioxide to the reaction tank; the hydrogen peroxide and sulfur dioxide in the waste sulfuric acid solution undergo a redox reaction in the reaction tank to obtain the first sulfuric acid solution; the first sulfuric acid solution delivery pipe is connected to the reaction tank to discharge the first sulfuric acid solution; a heating assembly includes a first heating tank, a heating tank delivery pipe, a second heating tank, and a mixture output pipe connected in sequence; wherein, the first sulfuric acid solution delivery pipe is connected to the first heating tank; the first heating tank heats the first sulfuric acid solution to a first heating temperature to obtain a second sulfuric acid solution; wherein, the first heating temperature is 100°C to 220°C; the heating tank delivery pipe introduces the second sulfuric acid solution into the second heating tank; The second heating tank heats the second sulfuric acid solution to a second heating temperature to obtain a mixture containing sulfur trioxide and water; wherein the second heating temperature is higher than the first heating temperature and not higher than the azeotropic point of sulfuric acid and water; the mixture output pipe is used to discharge the mixture; a water separation module includes a water separation membrane device, a sulfur trioxide gas output pipe, and a separated water output pipe; wherein the water separation membrane device is connected to the mixture output pipe, the sulfur trioxide gas output pipe, and the separated water output pipe respectively; the water separation membrane device includes a water separation membrane, the material of which includes zeolite, ceramic, carbon nanotubes, or a combination thereof; the sulfur trioxide gas output pipe is used to discharge the sulfur trioxide gas obtained after treatment by the water separation membrane device; the separated water output pipe is used to discharge the water obtained after treatment by the water separation membrane device; and a sulfur trioxide absorption unit is connected to the sulfur trioxide gas output pipe to absorb sulfur trioxide to obtain the fuming sulfuric acid.

7. The preparation system as described in claim 6, wherein, The sulfur dioxide supply unit includes sulfur dioxide cylinders and sulfur dioxide piping; the sulfur dioxide cylinders are used to contain sulfur dioxide; and the sulfur dioxide piping is used to introduce sulfur dioxide produced during the sulfuric acid manufacturing process.

8. The preparation system as described in claim 6, wherein, The preparation system further includes a water condensation device, which includes a water condensation tank, a vacuum pump, a delivery pump, and a recovery water pipeline; the water condensation tank is connected to the vacuum pump; the delivery pump is connected to the recovery water pipeline; the water condensation tank is connected to the recovery water pipeline, and the aqueous solution collected in the water condensation tank is transported to the first heating tank through the recovery water pipeline.

9. The preparation system as described in any one of claims 6 to 8, wherein, The preparation system further includes a sulfur trioxide cooling device, which is located downstream of the water separation module and upstream of the sulfur trioxide absorption unit. The sulfur trioxide cooling device comprises a sulfur trioxide condensation tank and a liquid sulfur trioxide output pipe connected together. The sulfur trioxide gas output pipe is connected to the sulfur trioxide condensation tank. The temperature of the sulfur trioxide condensation tank is 18°C ​​to 40°C. The sulfur trioxide absorption unit comprises a sulfur trioxide absorption tower and a fuming sulfuric acid discharge pipe connected together. The liquid sulfur trioxide output pipe is connected to the sulfur trioxide absorption tower. The sulfur trioxide absorption tower contains more than 98% by weight of sulfuric acid.

10. The preparation system as described in any one of claims 6 to 8, wherein, The material of the second heating tank includes acid-resistant bricks, stainless steel, low-carbon steel, or a combination thereof.

11. The preparation system as described in claim 10, wherein, The preparation system is connected to the electronic-grade sulfuric acid manufacturing system through a high-concentration fuming sulfuric acid delivery pipeline.

12. The preparation system as described in claim 11, wherein, The preparation system and the electronic-grade sulfuric acid manufacturing system have a temporary storage tank, which is connected to both the preparation system and the electronic-grade sulfuric acid manufacturing system.

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