A liquid-phase feeding preparation process for electronic-grade sulfuric acid

Abstract

The present invention relates to a liquid-phase feeding preparation process for electronic-grade sulfuric acid. First, the present invention purifies and refines SO3. Using industrial-grade liquid SO3 as the raw material, impurities of light components and heavy components are removed by means of low-temperature rectification and membrane filtration, streamlining the process flow of the subsequent main reaction section, reducing equipment investment, lowering production energy consumption, and eliminating the need to add and use the production auxiliary material high-purity H2O2 to remove SO2 reductants, which can greatly save the total equipment investment and production operation costs. Then, liquid-phase feeding is adopted, making the volume scale of the equipment relatively small. Compared with the "absorption method", for a production device with the same production capacity scale, the reactor specification is only about 1 / 3 of that of the "absorption method". At the same time, since the reaction absorption is carried out twice in total from the lower part to the upper part of the reactor and then to the upper absorption tower, the total absorption rate of the reaction reaches 99.999%.

Description

Technical Field

[0001] The present invention relates to the technical field of sulfuric acid production processes, and in particular, to a liquid-phase feeding preparation process for electronic-grade sulfuric acid. Background Art

[0002] At present, the quality standards of ultra-pure sulfuric acid used in domestic and international electronic semiconductor manufacturing generally follow the standards of the Semiconductor Equipment and Materials International (SEMI). According to different impurity contents, it is divided into 5 grades from Grade1 - Grade5 (i.e., G1 - G5), with the lowest grade being G1 and the best grade being G5. Among them, the metal impurity content of G5-level electronic-grade sulfuric acid is ≤0.010 g / L, corresponding to a semiconductor line width of ≤0.090 μm.

[0003] The national standard of "Electronic-grade Sulfuric Acid" (GB / T41881 - 2022) in China was also released on October 12, 2022, and implemented since May 1, 2023. "Electronic-grade Sulfuric Acid" (GB / T41881 - 2022) is divided into 5 grades from E5 - E1 according to different impurity contents. Among them, the E5-level indicators are basically the same as SEMI-G1, and the E1-level indicators are basically the same as SEMI-G5.

[0004] With the development of China's semiconductor industry, in recent years, the domestic wet electronic chemicals manufacturing industry has also developed relatively fast, including the manufacturing technology of electronic-grade sulfuric acid, which has also been developing synchronously.

[0005] Currently, the mainstream domestic manufacturing technologies for electronic-grade sulfuric acid are distillation method and absorption method.

[0006] The distillation method draws on the traditional purification technology of reagent sulfuric acid. Due to its simple process and low investment, it is still used in the manufacture of low-grade ultrapure sulfuric acid products in China. However, the purity of the electronic-grade sulfuric acid products produced by the distillation method can only reach the G1 (E5) and G2 (E4) grades. The distillation method generally uses industrial sulfuric acid or reagent sulfuric acid with w(H2SO4) of 95%-98% as raw materials and heats and distills them for purification in a quartz glass device, which is a physical purification process. The heat sources used in the distillation method are mainly electricity or gas. The biggest drawback of this process is its high energy consumption and low product quality. According to production practice statistics, when using analytical reagent sulfuric acid as the production raw material to distill 1t of electronic-grade G1 (E5) sulfuric acid, the power consumption is 400-500 kWh, and when producing 1t of electronic-grade G2 sulfuric acid, the power consumption is 700-800 kWh. If industrial sulfuric acid is used as the production raw material, not only does the industrial sulfuric acid need to be pretreated, but the corresponding energy consumption doubles. Due to the limitations of the purification process and equipment, it is also very difficult for the quality indicators of the electronic-grade sulfuric acid manufactured by the distillation method to break through the SEMI-G3 level. In addition, the processing capacity of a single set of equipment is small, and the maximum annual production capacity of a single set is only 10,000 tons / year.

[0007] In recent years, the absorption method process introduced is based on high-concentration SO3 as the raw material, uses electronic-grade sulfuric acid with w(H2SO4) of 95%-98% as the circulating absorption mother liquor, and adds ultrapure water to the system to balance the acid concentration for preparation. The production principle of the absorption method for electronic-grade sulfuric acid is mainly to control the intake of impurities in raw materials, auxiliary materials and the production process. By using process equipment made of high-purity fluoroplastics and through precise process control, the purity of the electronic-grade sulfuric acid products reaches the set target indicators. The quality indicators of the electronic-grade sulfuric acid manufactured by the absorption method have broken through the SEMI-G5 level.

[0008] The production device of the absorption method for electronic-grade sulfuric acid is arranged in a dust-free clean workshop. Its main raw materials are SO3 and ultrapure water. Its key process can be divided into three parts: the gasification of liquid SO3, the absorption of gaseous SO3, and the degassing and fine filtration of semi-finished products. The source of liquid SO3 generally uses fuming sulfuric acid with w(H2SO4) of 107% from an industrial sulfuric acid factory as the mother liquor, and is obtained by heating and evaporating gaseous SO3 and then condensing it (the heat source can generally use steam, electricity or process hot furnace gas), or liquid SO3 can be directly purchased from the market. Ultrapure water generally uses industrial water or domestic tap water as the raw water and is obtained by using equipment made of high-purity materials to remove salts and impurities through multiple stages.

[0009] Gasification of liquid SO3: Generally using steam, electricity or hot furnace gas as the heat source, indirectly exchange heat through a SO3 evaporator to evaporate gaseous SO3.

[0010] Gaseous SO3 absorption: Using a packed absorption tower as the absorption reactor, the gaseous SO3 from the outlet of the SO3 evaporator is introduced into the upper part of the absorption tower, and reacts with the electronic-grade sulfuric acid from the circulating acid tank transported to the upper part of the absorption tower by an acid pump in a downward and co-directional mixing manner in the tower. After absorbing SO3, the temperature and concentration of the electronic-grade sulfuric acid increase, and it flows back to the circulating acid tank by gravity after being cooled by an acid cooler. At the same time, a certain amount of ultrapure water is added to the circulating acid tank to balance the concentration of the circulating absorption acid.

[0011] Degassing and fine filtration: The semi-finished acid is sent to the degassing tower by an acid pump, and at the same time, the liquid level of the circulating acid tank is controlled to be stable by the amount of acid sent out. After passing through the degassing tower and appropriately adding a small amount of electronic-grade H2O2 to remove SO2 reducing substances, the finished acid after fine filtration is produced and sent to the electronic-grade sulfuric acid storage tank, and is canned or loaded in a dust-free workshop and then sold outside.

[0012] The absorption reaction equipment of the absorption process technology is made of imported high-purity fluoroplastic materials from abroad and must be manufactured in a clean and dust-free workshop, resulting in a relatively large increase in equipment investment costs. However, the energy consumption is lower than that of the rectification method, so the product production cost is greatly reduced. Restricted by various factors such as material characteristics, manufacturing conditions, manufacturing capabilities, and subsequent production sites and strict process requirements of electronic-grade sulfuric acid, and the entire production device of the absorption method needs to be installed in a dust-free workshop. Therefore, the maximum production capacity of a single set of the absorption method for electronic-grade sulfuric acid is 30,000 tons / year, and the process diameter of the reactor absorption tower is about 1200 mm. Summary of the Invention

[0013] The purpose of the present invention is to provide a liquid-phase feeding preparation process for electronic-grade sulfuric acid with less investment, low energy consumption, high production capacity, and a smaller reaction tower size.

[0014] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0015] A liquid-phase feeding preparation process for electronic-grade sulfuric acid, the process comprising the following steps:

[0016] Step 1. Refining and purification of industrial-grade liquid SO3

[0017] The industrial-grade liquid SO3 is vaporized by heat exchange with a heat exchanger in the SO3 purification tower. The SO3 gas rises due to heat and reaches the top of the SO3 purification tower, and then enters the SO3 condenser after passing through the mist eliminator at the top of the purification tower;

[0018] The gaseous SO3 entering the SO3 condenser is cooled to a purified liquid SO3 at 30°C to 40°C with a purity of w(SO3) 99.995%;

[0019] Step 2. Secondary absorption of the purified liquid SO3 raw material

[0020] The purified liquid SO3 raw material is transported to the circulation mixing tank at the lower part of the reactor, where it undergoes a mixing reaction with electronic-grade sulfuric acid with w(H2SO4) of 95% - 98%. During the reaction process, ultrapure water is added to the circulation mixing tank; a part of the purified liquid SO3 raw material is vaporized during the reaction, enters the absorption tower at the upper part of the reactor from the lower part of the reactor, and contacts countercurrently with the electronic-grade sulfuric acid with w(H2SO4) of 95% - 98% sprayed from the top to the bottom of the tower to complete the secondary absorption of the purified liquid SO3 raw material.

[0021] Step 3. Preparation of electronic-grade sulfuric acid

[0022] After the mixing reaction in the circulation mixing tank reaches equilibrium, the reaction liquid is discharged from the circulation mixing tank, transported by the electronic-grade sulfuric acid circulation pump to the electronic-grade sulfuric acid cooler for heat exchange cooling and filtration, and then transported to the electronic-grade sulfuric acid storage tank.

[0023] The industrial-grade liquid SO3 raw material in Step 1 relies on the industrial sulfuric acid factory for production or the industrial-grade SO3 raw material purchased from the market. Through the SO3 purification tower made of stainless steel and using the low-temperature distillation process, light component impurities such as SO2 and trace amounts of sulfuric acid, nitrosylsulfuric acid, sulfates, most metal ions and non-metal ions, particulate matter and other heavy component impurities in the raw material are removed respectively. This step of refining and purification is placed in front, which can streamline the subsequent reaction section process flow, reduce equipment investment, lower production energy consumption, and there is no need to add and use the production auxiliary material high-purity H2O2 to remove SO2 reductants, which can greatly save the total equipment investment and production operation costs.

[0024] In Step 2, the purified liquid SO3 raw material is directly sent to the circulation mixing tank at the lower part of the reactor. Most of the liquid SO3 undergoes a liquid-phase mixing reaction with the electronic-grade sulfuric acid in the circulation mixing tank while releasing heat, and ultrapure water is added at the inlet of the circulating acid pipeline in the circulation mixing tank to balance the concentration of sulfuric acid in the circulation mixing tank (the purity of the ultrapure water meets the requirements of Type E-1.2 of the pure water quality for the electronics and semiconductor industries in accordance with ASTM D5127 in the United States, the same below); the remaining small part of the liquid SO3 absorbs the reaction heat and is vaporized, and enters the absorption tower at the upper part of the reactor from the lower part of the reactor for secondary reaction absorption. The total absorption rate of the liquid-phase feeding two-stage reaction reaches 99.999%, and the volume scale of the equipment is small. Compared with the "absorption method", the specification of the reactor of the production device with the same production capacity scale is only about 1 / 3 of that of the "absorption method".

[0025] Preferably, after heat exchange cooling of the electronic-grade sulfuric acid in Step 3, it is sent out in three ways: the first way is transported to the circulation mixing tank at the lower part of the reactor as the electronic-grade sulfuric acid for the mixing reaction; the second way is transported to the upper part of the absorption tower of the reactor as the sprayed electronic-grade sulfuric acid; the third way is to transport the produced finished electronic-grade sulfuric acid to the electronic-grade sulfuric acid storage tank after precision filtration by a precision filter.

[0026] Preferably, for the electronic-grade sulfuric acid used for spraying in the second path, the sulfuric acid flow rate needs to be adjusted to match the spraying density of the tower through a regulating valve first.

[0027] Preferably, in step 1, the industrial-grade liquid SO3 is fed into the SO3 purification tower through a metering pump.

[0028] Preferably, in step 1, the temperature of the heat exchanger is 50°C to 99°C, and the temperature of the vaporized SO3 after heat exchange is controlled in the range of 48 - 50°C.

[0029] Preferably, a reactor mist eliminator is provided at the top of the reactor.

[0030] Preferably, the filtration precision of the mist eliminator at the top of the purification tower and the reactor mist eliminator is 0.003μm.

[0031] Preferably, the process equipment in step 1 is made of S31603 stainless steel and PTFE materials.

[0032] Preferably, the inner lining of the reactor is made of high-purity fluoroplastic material.

[0033] Preferably, clean air is introduced into the top of the reactor to maintain a slightly positive pressure operation throughout the reaction process.

[0034] In summary, in the present invention, SO3 is first refined and purified, which can streamline the process flow of the subsequent main reaction section, reduce the investment in high-purity equipment, lower production energy consumption, eliminate the need to add the production auxiliary material high-purity H2O2 to remove SO2 reductants, and the slightly positive pressure throughout the reaction process enables the device to be installed outdoors in the open air, significantly saving the total investment in clean workshops, equipment and production operation costs; then liquid-phase feeding is adopted, making the volume scale of the equipment smaller. Compared with the "absorption method", for a production device with the same production capacity scale, the specification of its reactor is only about 1 / 3 of that of the "absorption method"; at the same time, since the reaction absorption is carried out twice in total from the lower part to the upper part of the reactor and then into the upper absorption tower, the total absorption rate of the reaction reaches 99.999%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the process flow chart of the present invention;

[0036] Explanation of the reference numerals in the drawings: 1 - SO3 purification tower; 2 - heat exchanger; 3 - mist eliminator at the top of the purification tower; 4 - SO3 condenser; 5 - reactor; 6 - circulation mixing tank; 7 - absorption tower; 8 - reactor mist eliminator; 9 - electronic-grade sulfuric acid circulation pump; 10 - electronic-grade sulfuric acid cooler; 11 - ultra-pure water regulating valve; 12 - ultra-pure water flow meter; 13 - acid concentration meter; 14 - precision filter; 15 - acid production regulating valve; 16 - acid flow meter into the tower; 17 - acid regulating valve into the tower. Detailed implementation manners

[0037] To describe in detail the technical content, achieved object and effect of the present invention, the following is described in conjunction with the implementation manners, but it does not constitute a limitation to the protection scope of the present invention.

[0038] See Figure 1 , the present invention provides a liquid-phase feeding preparation process for electronic-grade sulfuric acid, and the process includes the following steps:

[0039] Step 1. Refining and purification of industrial-grade liquid SO3

[0040] This industrial-grade liquid SO3 is based on fuming sulfuric acid with w(H2SO4) 107.88% from an industrial sulfuric acid plant and is prepared by heating evaporation and condensation, or directly purchased from the market as industrial-grade liquid SO3, and is temporarily stored in a liquid SO3 raw material storage tank. The qualified product of industrial-grade liquid SO3 contains w(SO3) 99.0% and contains trace light component impurities such as SO2 and trace heavy component impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash, which can be effectively removed by low-temperature rectification and membrane filtration methods to achieve the goal of purifying the SO3 raw material.

[0041] To remove the impurities in industrial-grade SO3, the industrial-grade liquid SO3 at about 40°C from the liquid SO3 raw material storage tank is pumped into the middle of the SO3 purification tower 1 by a metering pump and sprayed downward evenly. It is vaporized by indirect heat exchange with the heat exchanger 2 into which hot water at 50°C to 99°C is introduced into the tower, and the amount of hot water entering the heat exchanger 2 is controlled to control the vaporization rate of liquid SO3 and keep the temperature of the gaseous SO3 (containing trace SO2 and slight heavy component impurities) at 48 to 50°C; the gaseous SO3 gas rises to the top of the SO3 purification tower 1, and after being filtered by the membrane demister 3 at the top of the purification tower with a filtration accuracy of 0.0030 m to remove acid mist (the acid mist contains sulfuric acid, nitrosylsulfuric acid, and other trace heavy component impurities), it enters the SO3 condenser 4; the small amount of fuming sulfuric acid with a concentration of w(H2SO4)~109% containing trace sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, ash, etc. heavy component impurities that are not vaporized in the SO3 purification tower 1 is combined with the filtrate from the membrane demister 3 at the top of the purification tower and discharged to the tail liquid treatment tank.

[0042] The gaseous SO3 (containing a trace amount of SO2) entering the SO3 condenser 4 is indirectly heat-exchanged and cooled with circulating cooling water at 30 - 40 °C and 0.3 MPa. Among them, the non-condensable gas (a mixed gas containing a trace amount of SO2 and SO3) at about 45 - 47 °C and 120 kPa is discharged from the upper outlet in the middle of the SO3 condenser 4 to the tail gas treatment tower for treatment; the liquid SO3 product cooled to 30 - 40 °C and with a purity of w(SO3) 99.995% by the SO3 condenser 4 is sent to the reactor 5 through the lower outlet at the tail of the SO3 condenser 4.

[0043] Step 2. Secondary absorption of the purified liquid SO3 raw material

[0044] The reactor 5 has a structure integrating a tower and a tank. A circulating mixing tank 6 is arranged at the lower part of the reactor 5, and an absorption tower 7 is arranged at the upper part of the reactor 5, lined with high-purity fluoroplastic material.

[0045] The purified liquid SO3 raw material after refining and purification is transported through an internally polished stainless steel pipeline to the circulating mixing tank 6 at the lower part of the reactor 5. About 90% of the purified liquid SO3 raw material reacts with the electronic-grade sulfuric acid with w(H2SO4) 95% - 98% in the circulating mixing tank 6, and heat is released simultaneously. At the same time, ultrapure water is continuously added through the ultrapure water flowmeter 11 at the inlet of the circulating sulfuric acid pipeline in the circulating mixing tank 6 to balance the concentration of sulfuric acid in the circulating mixing tank 6 by controlling the ultrapure water flowmeter 12; the remaining about 10% of the purified liquid SO3 raw material is vaporized by the reaction heat and enters the absorption tower 7 at the upper part of the reactor 5 from the lower part of the reactor 5, and countercurrently contacts with the electronic-grade sulfuric acid with w(H2SO4) 95% - 98% sprayed from top to bottom in the upper part of the tower to complete the secondary absorption of SO3 and release heat; a small amount of clean air is introduced into the top outlet of the reactor 5 to maintain a slightly positive pressure inside the reactor 5.

[0046] Step 3. Preparation of electronic-grade sulfuric acid

[0047] The above reaction steps are mainly exothermic reactions. The reaction liquid is transported from the electronic-grade sulfuric acid outlet of the circulating mixing tank 6 at the lower part of the reactor 5 by the electronic-grade sulfuric acid circulation pump 9 to the electronic-grade sulfuric acid cooler 10, and is indirectly heat-exchanged and cooled to 40 - 50 °C with circulating cooling water at 30 - 40 °C and 0.3 MPa, and then sent out in three ways: the first way is transported to the circulating mixing tank 6 at the lower part of the reactor 5 as the sulfuric acid for the mixed reaction; the second way is adjusted to the sulfuric acid flow rate matching the spraying density of the tower through the acid inlet regulating valve 17 and the acid inlet flowmeter 16 and then transported to the absorption tower 7 at the upper part of the reactor 5 as the sulfuric acid for the circulating absorption reaction; the third way is output. While controlling the liquid level of the circulating mixing tank 6 stable through the acid production regulating valve 15, the produced finished electronic-grade sulfuric acid is filtered precisely by the precision filter 14 and then transported to the electronic-grade sulfuric acid storage tank.

[0048] The total absorption rate of the two-stage reaction with liquid-phase feeding reaches 99.999%, and the volume scale of the equipment is relatively small. Compared with the common "absorption method", for a production device with the same production capacity scale, the specification of the reactor 5 is only about 1 / 3 of that of the "absorption method", and the entire reaction process is completed in a slightly positive-pressure closed environment, and the reaction equipment can be arranged outdoors in the open air, greatly reducing the investment in production equipment and clean workshops.

[0049] As a preferred embodiment of the present invention, a condenser mist eliminator 8 is provided at the top of the reactor 5.

[0050] As a preferred embodiment of the present invention, the process equipment in step 1 is all made of S31603 stainless steel and PTFE materials.

[0051] As a preferred embodiment of the present invention, an acid concentration meter 13 is provided before the sulfuric acid that is secondarily transported to the upper part of the reactor 5 to be used as the circulating absorption reaction sulfuric acid and before the finished product electronic-grade sulfuric acid is produced, so as to detect the purity and concentration of the sulfuric acid.

[0052] The following are the engineering design embodiments of the present invention.

[0053] Example 1

[0054] Taking a liquid-phase feeding reaction method electronic-grade sulfuric acid production device with a scale of 100,000 tons / year as an example.

[0055] Based on the fuming sulfuric acid with w(H2SO4) of 107.88% from an industrial sulfuric acid factory as the mother liquor, industrial-grade liquid SO3 is prepared by heating evaporation and condensation and temporarily stored in the liquid SO3 raw material storage tank in the factory. The industrial-grade liquid SO3 qualified product contains w(SO3) of 99.0% and contains trace amounts of light component impurities such as SO2 and trace amounts of heavy component impurities such as sulfuric acid, nitrosyl sulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash, which can be effectively removed by low-temperature rectification and membrane filtration methods to achieve the goal of purifying the SO3 raw material.

[0056] The process is as Figure 1As shown in the figure, to remove impurities from industrial sulfur trioxide, industrial liquid sulfur trioxide at about 40 °C from the factory's liquid SO3 raw material storage tank is pumped into the middle of the SO3 purification tower at a flow rate of about 10.2 t / h by a metering pump, and is evenly sprayed downward through the SO3 nozzles in the tower. It is vaporized by indirect heat exchange with a heat exchanger that passes hot water at 50 °C to 99 °C in the tower. The amount of hot water entering the heat exchanger is controlled to control the vaporization rate of liquid SO3 and maintain the temperature of the gaseous SO3 (containing trace amounts of SO2 and slightly heavier component impurities) at 48 - 50 °C; the gaseous SO3 gas rises to the top of the SO3 purification tower due to heat, and after being filtered and dehumidified by a mist eliminator at the top of the purification tower with a filtration accuracy of 0.0030 m to remove acid mist (the acid mist contains sulfuric acid, nitrosylsulfuric acid, and other trace heavier component impurities), it enters the SO3 condenser; the small amount of fuming sulfuric acid with a concentration of w(H2SO4) ~ 109% containing trace amounts of heavier component impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash that is not vaporized in the SO3 purification tower converges with the filtrate from the mist eliminator at the top of the purification tower and is discharged to the fuming sulfuric acid circulation tank of the main industrial sulfuric acid unit in the factory.

[0057] The gaseous SO3 (containing trace amounts of SO2) entering the SO3 condenser is cooled by indirect heat exchange with circulating cooling water at 30 - 40 °C and 0.3 MPa. Among them, the non-condensable gas (a mixed gas containing trace amounts of SO2 and SO3) at 45 - 47 °C and 120 kPa is discharged through the upper outlet in the middle of the SO3 condenser to the flue gas inlet pipeline of the second absorption tower in the main industrial sulfuric acid unit of the factory for recycling to produce industrial-grade sulfuric acid; the liquid SO3 finished product cooled to 30 - 40 °C and with a purity of w(SO3) 99.995% by the SO3 condenser is sent out through the outlet at the tail of the SO3 condenser.

[0058] For the sulfur trioxide after purification, the light component impurities such as sulfur dioxide (≤0.002 wt%), the heavy component impurities such as sulfuric acid (≤0.0025 wt%), and the sulfur trioxide purity (≥99.995%), and the total purification efficiency reaches 99.5%.

[0059] The high-purity liquid SO3 sent from the SO3 condenser is transported through an internally polished stainless steel pipe to the mixing circulation tank. Approximately 90% of the liquid SO3 is mixed with the 98% electronic-grade sulfuric acid in the tank to complete the (primary) mixing reaction of SO3 and release heat; the remaining approximately 10% of the liquid SO3 is vaporized by the reaction hot gas, enters the absorption tower at the upper part of the reactor from the mixing circulation tank at the lower part of the reactor, and countercurrently contacts the approximately 98% electronic-grade sulfuric acid evenly distributed by the acid distributor and sprayed from top to bottom, to complete the (secondary) absorption reaction of SO3 and release heat; a small amount of clean air is introduced into the outlet at the top of the absorption tower to maintain a slightly positive pressure inside the reactor. The above two-stage reaction process will increase the concentration of the electronic-grade sulfuric acid in the reactor to approximately 98.5%. Therefore, during the reaction process, 2.3 t / h of ultrapure water must be continuously added at the inlet of the circulating sulfuric acid pipe of the mixing circulation tank to maintain a dynamic balance of the electronic-grade sulfuric acid concentration in the tank at approximately 98%.

[0060] The above reaction steps are mainly exothermic reactions. The reaction heat is transported by the electronic-grade sulfuric acid circulation acid pump through the electronic-grade sulfuric acid outlet at the lower part of the reactor circulation mixing tank to the electronic-grade sulfuric acid cooler, and is indirectly heat-exchanged and cooled to 40 - 50 °C with circulating cooling water at 30 - 40 °C and 0.3 MPa, and then sent out in three routes: the first route is transported to the circulating mixing tank at the lower part of the reactor as the sulfuric acid for the mixing reaction; the second route is adjusted to the sulfuric acid flow rate matching the spraying density of the tower through a regulating valve and a flow meter and then transported to the absorption tower at the upper part of the reactor as the sulfuric acid for the circulating absorption reaction; the third route is output outward. While controlling the liquid level of the circulating mixing tank stable through a regulating valve, the produced finished electronic-grade sulfuric acid is transported to the factory electronic-grade sulfuric acid storage tank for storage after filtering out physical particle impurities through an electronic-grade sulfuric acid precision filter with an accuracy of 0.10 m.

[0061] The total absorption rate of SO3 in the above two-stage reaction reaches 99.999%, and the product quality meets the international semiconductor association SEMI-G5 and GB / T41881-2022-E1 standards.

[0062] The equipment before the reactor of the above production device is made of S31603 stainless steel material, and the equipment after the reactor and the reactor are made of steel-lined New-PTFE or ultra-pure PFA material, and the device is arranged outdoors.

[0063] The main process equipment specifications and technical parameters of the liquid-phase feeding reaction method electronic-grade sulfuric acid production device with a scale of 100,000 tons / year are shown in Table 1.

[0064] Table 1 Main process equipment specifications and technical parameters of 100,000 tons / year device

[0065]

[0066]

[0067] The comparison of the key process equipment specifications and technical parameters between the liquid-phase feeding reaction method with a scale of 100,000 tons / year and the "absorption method" with a gas-phase feeding of 30,000 tons / year for the production of electronic-grade sulfuric acid is shown in Table 2.

[0068] Table 2 Comparison of key equipment specifications: Liquid-phase feeding method 100,000 tons / year VS "Absorption method" 30,000 tons / year

[0069]

[0070] Remark: The above S31603 and S304 are domestic materials, and New-PTFE and PFA are imported high-purity materials. Inquiry from domestic equipment manufacturers.

[0071] Conclusion: Through the above comparison, it can be seen that the equipment scale for producing 100,000 tons / year of electronic-grade sulfuric acid by the liquid-phase feeding method is smaller than that for producing 30,000 tons / year of electronic-grade sulfuric acid by the gas-phase feeding "absorption method", that is, while the production capacity is increased, the equipment scale becomes smaller, with less investment and higher efficiency.

[0072] Example 2

[0073] Take the electronic-grade sulfuric acid production device with a liquid-phase feeding reaction method with a scale of 60,000 tons / year as an example.

[0074] Relying on the industrial sulfuric acid factory, the industrial-grade liquid SO3 is prepared by heating, evaporating and condensing the fuming sulfuric acid with w(H2SO4) of 107.88% as the mother liquor, and temporarily stored in the liquid SO3 raw material storage tank in the factory. The industrial-grade liquid SO3 qualified product contains w(SO3) of 99.0% and contains trace light component impurities such as SO2 and trace heavy component impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions and non-metal ions, particulate matter, ash, etc., which can be effectively removed by low-temperature rectification and membrane filtration to achieve the goal of purifying the SO3 raw material.

[0075] The process is as Figure 1As shown in the figure, to remove impurities from industrial-grade sulfur trioxide, industrial-grade liquid sulfur trioxide at approximately 40°C from the factory's liquid SO3 raw material storage tank is pumped into the middle of the SO3 purification tower at a flow rate of approximately 6.12 t / h by a metering pump. It is evenly sprayed downward through the SO3 nozzles in the tower and gasified by indirect heat exchange with a heat exchanger that passes hot water at 50°C to 99°C into the tower. The amount of hot water entering the heat exchanger is controlled to control the gasification rate of liquid SO3 and maintain the temperature of the gaseous SO3 (containing trace amounts of SO2 and slightly heavier components impurities) at 48 to 50°C; the gaseous SO3 gas rises due to heat to the top of the SO3 purification tower, and after being filtered and de-misted by the membrane mist eliminator at the top of the purification tower with a filtration accuracy of 0.0030 m to remove acid mist (the acid mist contains sulfuric acid, nitrosylsulfuric acid, and other trace heavier components impurities), it enters the SO3 condenser; the small amount of fuming sulfuric acid with a concentration of w(H2SO4)~109% containing trace amounts of heavier components impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash that is not gasified in the SO3 purification tower converges with the filtrate from the membrane mist eliminator at the top of the purification tower and is discharged to the fuming sulfuric acid circulation tank of the factory's industrial sulfuric acid main unit.

[0076] The gaseous SO3 (containing trace amounts of SO2) entering the SO3 condenser is cooled by indirect heat exchange with circulating cooling water at 30 to 40°C and 0.3 MPa. Among them, the non-condensable gas (a mixed gas containing trace amounts of SO2 and SO3) at 45 to 47°C and 120 kPa is discharged through the upper outlet in the middle of the SO3 condenser to the flue gas inlet pipeline of the second absorption tower of the factory's industrial sulfuric acid main unit for recycling to produce industrial-grade sulfuric acid; the liquid SO3 finished product cooled to 30 to 40°C and with a purity of w(SO3) 99.995% by the SO3 condenser is sent out through the outlet at the tail of the SO3 condenser.

[0077] The light component impurities such as sulfur dioxide (≤0.002 wt%) and heavy component impurities such as sulfuric acid (≤0.0025 wt%) in the purified sulfur trioxide, and the sulfur trioxide purity (≥99.995%) reach a total purification efficiency of 99.5%.

[0078] The high-purity liquid SO3 sent from the SO3 condenser is transported to the mixing circulation tank through an internally polished stainless-steel pipeline. Approximately 90% of the liquid SO3 is mixed with the 98% electronic-grade sulfuric acid in the tank, completing the (primary) mixing reaction of SO3 and releasing heat; the remaining approximately 10% of the liquid SO3 is vaporized by the reaction hot gas, enters the absorption tower at the upper part of the reactor from the mixing circulation tank at the lower part of the reactor, and countercurrently contacts the electronic-grade sulfuric acid with a concentration of approximately 98% that is evenly distributed by the acid distributor and sprayed from top to bottom in the upper part of the tower, completing the (secondary) absorption reaction of SO3 and releasing heat; a small amount of clean air is introduced into the outlet at the top of the absorption tower to maintain a slightly positive pressure inside the reactor. The above two-stage reaction process will increase the concentration of the electronic-grade sulfuric acid in the reactor to approximately 98.5%. Therefore, during the reaction process, 1.38 t / h of ultrapure water must be continuously injected at the inlet of the circulating sulfuric acid pipeline of the mixing circulation tank to maintain a dynamic balance of the concentration of the electronic-grade sulfuric acid in the tank at approximately 98%.

[0079] The above reaction steps are mainly exothermic reactions. The reaction heat is exported from the outlet of the electronic-grade sulfuric acid at the lower part of the reactor circulation mixing tank, transported to the electronic-grade sulfuric acid cooler by the electronic-grade sulfuric acid circulating acid pump, indirectly exchanged heat with the circulating cooling water at 30 - 40 °C and 0.3 MPa, and cooled to 40 - 50 °C, and then sent out in three ways: The first way is transported to the circulating mixing tank at the lower part of the reactor as the sulfuric acid for the mixing reaction; the second way is adjusted to the sulfuric acid flow rate matching the spraying density of the tower through a regulating valve and a flow meter, and then transported to the absorption tower at the upper part of the reactor as the sulfuric acid for the circulating absorption reaction; the third way is output. While controlling the liquid level of the circulating mixing tank stable through a regulating valve, the produced finished electronic-grade sulfuric acid is filtered through an electronic-grade sulfuric acid precision filter with a precision of 0.10 m to remove physical particle impurities and then transported to the factory electronic-grade sulfuric acid storage tank for storage.

[0080] The total absorption rate of SO3 in the above two-stage reaction reaches 99.999%, and the product quality meets the international semiconductor association SEMI-G5 and GB / T41881-2022-E1 standards.

[0081] The equipment before the reactor of the above production device is made of S31603 stainless-steel material, and the equipment after the reactor and the reactor are made of steel-lined New-PTFE or ultra-pure PFA material. The device is arranged outdoors.

[0082] The main process equipment specifications and technical parameters of the liquid-phase feeding reaction method electronic-grade sulfuric acid production device with a scale of 60,000 tons / year are shown in Table 3.

[0083] Table 3 Main process equipment specifications and technical parameters of 60,000 tons / year device

[0084]

[0085] The comparison of the key process equipment specifications and technical parameters between the liquid-phase feeding reaction method with a scale of 60,000 tons / year and the "absorption method" with a gas-phase feeding of 20,000 tons / year for electronic-grade sulfuric acid production plants is shown in Table 4.

[0086] Table 4 Comparison of key equipment specifications: Liquid-phase feeding method 60,000 tons / year VS "Absorption method" 20,000 tons / year

[0087]

[0088] Remark: The above S31603 and S304 are domestic materials, and New-PTFE and PFA are imported high-purity materials. Inquiry from domestic equipment manufacturers.

[0089] Conclusion: Through the above comparison, it can be seen that the equipment scale for producing 60,000 tons / year of electronic-grade sulfuric acid by the liquid-phase feeding method is smaller than that for producing 20,000 tons / year of electronic-grade sulfuric acid by the gas-phase feeding "absorption method". That is, while the production capacity is increased, the equipment scale becomes smaller, with less investment and higher efficiency.

[0090] Example 3

[0091] Taking the electronic-grade sulfuric acid production plant with a liquid-phase feeding reaction method with a scale of 30,000 tons / year as an example.

[0092] Using the fuming sulfuric acid with w(H2SO4) 107.88% from an industrial sulfuric acid plant as the mother liquor, industrial-grade liquid SO3 is prepared by heating evaporation and condensation and temporarily stored in the liquid SO3 raw material storage tank in the plant. The industrial-grade liquid SO3 qualified product contains w(SO3) 99.0% and contains trace light-component impurities such as SO2 and trace heavy-component impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash. It can be effectively removed by low-temperature rectification and membrane filtration to achieve the goal of purifying the SO3 raw material.

[0093] The process is as Figure 1As shown in the figure, to remove impurities from industrial sulfur trioxide, industrial liquid sulfur trioxide at about 40 °C from the factory's liquid SO3 raw material storage tank is pumped into the middle of the SO3 purification tower at a flow rate of about 3.06 t / h through a metering pump, and is evenly sprayed downward through the SO3 nozzles in the tower. It is vaporized by indirect heat exchange with a heat exchanger that passes hot water at 50 °C to 99 °C into the tower. The amount of hot water entering the heat exchanger is controlled to control the vaporization rate of liquid SO3 and maintain the temperature of the gaseous SO3 (containing trace amounts of SO2 and slightly heavier components impurities) at 48 to 50 °C; the gaseous SO3 gas rises due to heat to the top of the SO3 purification tower, and after being filtered by a demister membrane at the top of the purification tower with a filtration accuracy of 0.0030 m to remove acid mist (the acid mist contains sulfuric acid, nitrosylsulfuric acid, and other trace heavier components impurities), it enters the SO3 condenser; the small amount of fuming sulfuric acid with a concentration of w(H2SO4)~109% containing trace amounts of heavier components impurities such as sulfuric acid, nitrosylsulfuric acid, sulfates, metal ions, non-metal ions, particulate matter, and ash that is not vaporized in the SO3 purification tower converges with the filtrate from the demister membrane at the top of the purification tower and is discharged to the fuming sulfuric acid circulation tank of the main industrial sulfuric acid unit in the factory.

[0094] The gaseous SO3 (containing trace amounts of SO2) entering the SO3 condenser is cooled by indirect heat exchange with circulating cooling water at 30 to 40 °C and 0.3 MPa. Among them, the non-condensable gas (a mixed gas containing trace amounts of SO2 and SO3) at 45 to 47 °C and 120 kPa is discharged from the upper outlet in the middle of the SO3 condenser to the flue gas inlet pipeline of the second absorption tower in the main industrial sulfuric acid unit of the factory for recycling to produce industrial-grade sulfuric acid; the liquid SO3 finished product cooled to 30 to 40 °C and with a purity of w(SO3) 99.995% by the SO3 condenser is sent out through the outlet at the tail of the SO3 condenser.

[0095] For the sulfur trioxide after purification, the light component impurities such as sulfur dioxide (≤0.002 wt%), the heavy component impurities such as sulfuric acid (≤0.0025 wt%), and the sulfur trioxide purity (≥99.995%), and the total purification efficiency reaches 99.5%.

[0096] The high-purity liquid SO3 sent from the SO3 condenser is transported through an internally polished stainless-steel pipeline to the mixing circulation tank. Approximately 90% of the liquid SO3 is mixed with the 98% electronic-grade sulfuric acid in the tank to complete the (primary) mixing reaction of SO3 and release heat; the remaining approximately 10% of the liquid SO3 is vaporized by the reaction hot gas and enters the absorption tower at the upper part of the reactor from the mixing circulation tank at the lower part of the reactor, where it contacts countercurrently with the approximately 98% electronic-grade sulfuric acid evenly distributed by the acid distributor and sprayed from top to bottom, completing the (secondary) absorption reaction of SO3 and releasing heat; a small amount of clean air is introduced into the outlet at the top of the absorption tower to maintain a slightly positive pressure inside the reactor. The above two-stage reaction process will increase the concentration of the electronic-grade sulfuric acid in the reactor to approximately 98.5%. Therefore, during the reaction process, 0.69 t / h of ultrapure water must be continuously added at the inlet of the circulating sulfuric acid pipeline of the mixing circulation tank to maintain a dynamic balance of the concentration of the electronic-grade sulfuric acid in the tank at approximately 98%.

[0097] The above reaction steps are mainly exothermic reactions. The reaction heat is transported by the electronic-grade sulfuric acid circulation acid pump from the outlet of the electronic-grade sulfuric acid at the lower part of the reactor circulation mixing tank to the electronic-grade sulfuric acid cooler, where it is indirectly heat-exchanged and cooled with circulating cooling water at 30 - 40°C and 0.3 MPa to 40 - 50°C, and then sent out in three ways: the first way is transported to the circulating mixing tank at the lower part of the reactor as the sulfuric acid for the mixing reaction; the second way is adjusted to the sulfuric acid flow rate matching the spraying density of the tower through a regulating valve and a flow meter and then transported to the absorption tower at the upper part of the reactor as the sulfuric acid for the circulating absorption reaction; the third way is output externally. While controlling the liquid level of the circulating mixing tank stable through a regulating valve, the produced finished electronic-grade sulfuric acid is filtered through an electronic-grade sulfuric acid precision filter with an accuracy of 0.10 m to remove physical particle impurities and then transported to the factory's electronic-grade sulfuric acid storage tank for storage.

[0098] The total absorption rate of SO3 in the above two-stage reaction reaches 99.999%, and the product quality meets the international semiconductor association SEMI-G5 and GB / T41881-2022-E1 standards.

[0099] The equipment before the reactor of the above production device is made of S31603 stainless-steel material, and the equipment after the reactor and the reactor are made of steel-lined New-PTFE or ultra-pure PFA material. The device is arranged outdoors.

[0100] The main process equipment specifications and technical parameters of the 30,000-ton / year liquid-phase feeding reaction method electronic-grade sulfuric acid production device are shown in Table 5.

[0101] Table 5 Main process equipment specifications and technical parameters of the 30,000-ton / year device

[0102]

[0103] The comparison of the key process equipment specifications and technical parameters between the liquid-phase feeding reaction method with a scale of 30,000 tons / year and the "absorption method" with a gas-phase feeding of 10,000 tons / year for the production device of electronic-grade sulfuric acid is shown in Table 6.

[0104] Table 6 Comparison of key equipment specifications: Liquid-phase feeding method 30,000 tons / year VS "Absorption method" 10,000 tons / year

[0105]

[0106]

[0107] Remarks: The above S31603 and S304 are domestic materials, and New-PTFE and PFA are imported high-purity materials. Inquiry is made to domestic equipment manufacturers.

[0108] Conclusion: Through the above comparison, it can be seen that the equipment scale for producing 30,000 tons / year of electronic-grade sulfuric acid by the liquid-phase feeding method is smaller than that for producing 10,000 tons / year of electronic-grade sulfuric acid by the gas-phase feeding "absorption method", that is, while the production capacity is improved, the equipment scale becomes smaller, with less investment and higher efficiency.

[0109] Consumption quota

[0110] Taking the electronic-grade production device with a scale of 100 kt / a as an example, the consumption quotas of main raw materials and power are shown in Table 7.

[0111] Table 7 Consumption quotas of raw materials and power for the 100 kt / a device (calculated based on w(H2SO4) 100%)

[0112]

[0113] The above embodiments only represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A liquid-phase feeding preparation process for electronic-grade sulfuric acid, characterized in that, The process comprises the following steps: Step 1. Refining and purification of industrial-grade liquid SO3 Industrial-grade liquid SO3 is vaporized in the SO3 purification tower through heat exchange with the heat exchanger. The SO3 gas is heated and rises to the top of the SO3 purification tower. After passing through the membrane demister on the top of the purification tower, it enters the SO3 condenser. The gaseous SO3 entering the SO3 condenser is cooled to the purified liquid SO3 at 30℃~40℃ with a purity of w(SO3)99.995%; Step 2. Secondary absorption of purified liquid SO3 feedstock The purified liquid SO3 raw material is transported to the circulating mixing tank at the bottom of the reactor, where it reacts with electronic-grade sulfuric acid containing 95% to 98% w(H2SO4). Ultrapure water is added to the circulating mixing tank during the reaction. Part of the purified liquid SO3 raw material is vaporized during the reaction and enters the absorption tower at the top of the reactor from the bottom of the reactor. It comes into countercurrent contact with electronic-grade sulfuric acid containing 95% to 98% w(H2SO4) sprayed from the top of the tower, completing the secondary absorption of the purified liquid SO3 raw material. Step 3. Preparation of electronic grade sulfuric acid After the mixing reaction in the circulating mixing tank reaches equilibrium, the reaction liquid is discharged from the circulating mixing tank and transported by the electronic-grade sulfuric acid circulating pump to the electronic-grade sulfuric acid cooler for heat exchange, cooling and filtration, and then transported to the electronic-grade sulfuric acid storage tank.

2. The liquid-phase feeding preparation process of electronic-grade sulfuric acid according to claim 1, characterized in that, In step 3, the electronic grade sulfuric acid is cooled by heat exchange and then sent out in three ways: The first route is transported to the circulating mixing tank at the bottom of the reactor as electronic grade sulfuric acid for the mixing reaction; The second route delivers electronic grade sulfuric acid to the upper part of the reactor absorption tower as spray; The third route transports the finished electronic-grade sulfuric acid produced after filtration by the precision filter to the electronic-grade sulfuric acid storage tank.

3. The liquid-phase feeding preparation process of electronic-grade sulfuric acid according to claim 2, wherein, The electronic grade sulfuric acid used as spray in the second route needs to be adjusted to a sulfuric acid flow rate that matches the spray density of the tower through a regulating valve.

4. A liquid-phase feeding preparation process for electronic-grade sulfuric acid according to any one of claims 1-3, characterized in that, In step 1, the industrial-grade liquid SO3 is transported into the SO3 purification tower via a metering pump.

5. A liquid-phase feeding preparation process for electronic-grade sulfuric acid according to claim 4, characterized in that, In step 1, the temperature of the heat exchanger is 50°C to 99°C, and the temperature of the gasified SO3 after heat exchange is controlled in the range of 48°C to 50°C.

6. The liquid-phase feeding preparation process of electronic-grade sulfuric acid according to claim 4, wherein, A reactor membrane demister is provided on the top of the reactor.

7. A liquid-phase feeding preparation process for electronic-grade sulfuric acid according to claim 6, characterized in that, The filtration accuracy of the purification tower top membrane demister and the reactor membrane demister is 0.003 μm.

8. The liquid-phase feeding preparation process of electronic-grade sulfuric acid according to claim 4, characterized in that, The process equipment in step 1 is made of S31603 stainless steel and PTFE materials.

9. A liquid-phase feeding preparation process for electronic-grade sulfuric acid according to claim 4, characterized in that, The inner lining of the reactor is made of high-purity fluoroplastic material.

10. A liquid-phase feeding preparation process for electronic-grade sulfuric acid according to claim 4, characterized in that, Clean air is introduced into the top of the reactor to maintain a slightly positive pressure operation throughout the reaction process.

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