Device and method for preparing electronic-grade sulfuric acid from ultrapure fuming sulfuric acid

Abstract

The invention discloses a device and a method for preparing electronic-grade sulfuric acid from ultra-pure fuming sulfuric acid. The device comprises an ultra-pure fuming sulfuric acid system, a sulfur trioxide evaporation system and an ultra-pure sulfur trioxide absorption system. By adopting the device and the method disclosed by the invention, high-quality sulfuric acid can be produced, the content of single metal ion impurities is less than or equal to 0.1 ppb, and 0.2-micron particles are controlled by filtering through a 0.05-aperture filter.

Description

Technical Field

[0001] The invention relates to sulfuric acid, in particular to a method for producing electronic grade sulfuric acid. Technical Background

[0002] Electronic grade sulfuric acid, also known as high purity sulfuric acid and ultrapure sulfuric acid, is a key basic chemical reagent for ultra-clean products. It is widely used in the assembly and processing of semiconductors and ultra-large-scale integrated circuits. It is mainly used for cleaning and etching silicon wafers, and can effectively remove impurity particles, inorganic residues and carbon deposits on the wafers. The purity and cleanliness of electronic grade sulfuric acid have an important impact on the manufacturing, quality, performance and finished products of electronic components.

[0003] Generally, the preparation methods of electronic grade sulfuric acid are divided into distillation and gas absorption. Distillation is a distillation method that uses reflux to separate liquid mixtures into high purity.

[0004] The gas absorption method is to purify the furnace gas to obtain ultra-pure fuming acid. The purified sulfur trioxide after fuming acid is evaporated and demisted is directly absorbed by ultra-pure water. The purification of sulfur trioxide is the key to product compliance. First, add fuming sulfuric acid to the evaporator and evaporate it at 90-130°C using high-temperature furnace gas or steam. The evaporated sulfur trioxide gas passes through the demister to remove the trace sulfuric acid and nitrosyl sulfuric acid entrained therein, and then highly purified inert gas is introduced. After mixing, it enters the absorption tower and is directly absorbed by electronic grade ultra-pure water or ultra-pure sulfuric acid. After cooling, the ultra-pure sulfuric acid product is obtained.

[0005] At present, some domestic enterprises adopt the direct absorption method of sulfur trioxide gas to produce electronic grade sulfuric acid, but they still face problems such as the purity difference of raw material sulfur trioxide and the difficulty of impurity separation, which makes it difficult to further improve the quality of electronic grade sulfuric acid products. The present invention innovates the production control method of two-stage nicotinic acid washing, ultra-pure sulfur trioxide preparation, and ultra-pure sulfur trioxide absorption, solving the problems of raw material purity difference and impurity separation difficulty. Summary of the invention

[0006] The object of the present invention is to provide a device and method for preparing electronic grade sulfuric acid from ultrapure oleum, the process is reliable, the product quality is stable and can reach UP-SSS grade.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A device for preparing electronic grade sulfuric acid from ultrapure oleum, comprising an ultrapure oleum system, a sulfur trioxide evaporation system, and an ultrapure sulfur trioxide absorption system; the oleum system is a two-stage nicotinic acid tower washing system, the high-concentration nicotinic acid at the outlet of the second-stage nicotinic acid tower washing is transported to the sulfur trioxide evaporation system, and the ultrapure sulfur trioxide at the outlet of the sulfur trioxide evaporation system is transported to the ultrapure sulfur trioxide absorption system.

[0009] In some specific technical solutions: the pure oleum system includes a primary nicotinic acid tower and a secondary nicotinic acid tower, the furnace gas from the economizer is connected to the bottom of the primary nicotinic acid tower, the output end of the top of the primary nicotinic acid tower is connected to the bottom of the secondary nicotinic acid tower, the bottoms of the primary nicotinic acid tower and the secondary nicotinic acid tower are equipped with a nicotinic acid tower circulation tank, the nicotinic acid tower circulation tank is connected to the middle of the nicotinic acid tower through a cooler, and the output end of the nicotinic acid tower circulation tank of the secondary nicotinic acid tower is high-concentration nicotinic acid connected to a sulfur trioxide evaporation system;

[0010] Preferably, the output end at the top of the secondary nicotinic acid tower is connected to the bottom of the absorption tower, an absorption tower circulation tank is provided at the bottom of the absorption tower, the absorption tower circulation tank is connected to the middle of the absorption tower through a cooler, the output end at the top of the absorption tower is connected to the raw sulfuric acid device, and the absorption tower circulation tank is connected to the acid circulation tank of the secondary nicotinic acid tower.

[0011] In some specific technical solutions: high-concentration nicotinic acid from an ultra-pure oleum system is connected sequentially through a high-concentration nicotinic acid tank, a preheater, an evaporator, an SO3 condenser and a gas filter, and the output end of the gas filter is connected to an ultra-pure sulfur trioxide absorption system;

[0012] Preferably: the output end at the bottom of the evaporator is connected to the low-concentration nicotinic acid tank through a preheater, and the low-concentration nicotinic acid tank is connected to the acid circulation tank of the secondary nicotinic acid tower;

[0013] Preferably, the pipeline connecting the SO3 condenser and the gas filter is also connected to the output pipeline of the ultra-pure compressed air.

[0014] In some specific technical solutions: ultrapure sulfur trioxide from the sulfur trioxide evaporation system is sequentially connected through an electronic acid absorption tower, an acid circulation tank, a degassing tower, a finished acid cooler and an acid filter, and the output end of the acid filter is the target product;

[0015] Preferably: the acid circulation tank also has an output end connected to the electronic acid absorption tower; the output end of the bottom of the degassing tower is connected to the upper part of the degassing tower, and the output end of the ultrapure compressed air is connected to the bottom of the degassing tower.

[0016] A method for producing electronic-grade sulfuric acid from ultrapure oleum using the above system is disclosed. The method comprises washing the furnace gas at the economizer outlet with the ultrapure oleum system, then evaporating it with the sulfur trioxide evaporation system, and then treating the ultrapure sulfur trioxide obtained after evaporation with the ultrapure sulfur trioxide absorption system to obtain electronic-grade sulfuric acid.

[0017] In some more specific technical solutions, the method includes the following steps:

[0018] (1) Preparation of ultrapure nicotinic acid by two-stage nicotinic acid washing and absorption:

[0019] A stream of furnace gas is introduced from the economizer outlet of the conversion section of the existing sulfuric acid device into the primary nicotinic acid tower of the electronic grade sulfuric acid system. The primary nicotinic acid tower sprays 50-80°C fuming acid containing 20-35% SO3, and continuously circulates and absorbs to achieve dust removal and purification effects. The purified low-concentration fuming acid balances the acid concentration and then returns to the original sulfuric acid device; the process gas continues to enter the secondary nicotinic acid tower to spray 50-80°C fuming acid containing 20-35% SO3. After the fuming acid of this concentration evaporates SO3, it enters the secondary nicotinic acid tower 2 to adjust the acid concentration or add ultrapure water into the system to balance the acid concentration to ensure the production of ultrapure fuming acid;

[0020] (2) Preparation of ultra-pure sulfur trioxide by evaporation of sulfur trioxide:

[0021] The ultra-pure nicotinic acid from the secondary nicotinic acid tower tank enters the high-concentration nicotinic acid tank, is transported to the evaporator to evaporate sulfur trioxide, and the low-concentration nicotinic acid enters the evaporator 10 after completing heat exchange in the preheater, and evaporates ultra-pure SO3 gas at 90-130°C; the ultra-pure SO3 gas passes through the condenser and gas filter in turn to remove the trace sulfuric acid entrained therein and enters the electronic acid absorption tower.

[0022] (3) Absorption and preparation of electronic grade sulfuric acid

[0023] Ultrapure sulfur trioxide enters from the bottom of the electronic acid absorption tower, and the acid from the lower tower enters the acid circulation tank. After being pressurized by the circulation pump, it returns to the electronic acid absorption tower for continuous circulation and absorption, increasing its concentration by 0.2% to 0.3%. Ultrapure water is added to the system to balance the acid concentration. The excess electronic-grade sulfuric acid is pumped to the degassing tower by the acid production pump. Ultrapure air is used to purge the electronic-grade sulfuric acid to remove trace impurities such as SO2, and further purify it to obtain electronic-grade sulfuric acid. The gas absorbed by the electronic acid absorption tower 15 enters the outlet pipeline of the original sulfuric acid device-absorption tower. Due to the heat release of the acid dilution, in order to control the absorption temperature of the spray acid of the electronic acid absorption tower 15 to ≤70°C, the desalted water of the system is used to perform heat exchange cooling on the circulating acid.

[0024] Further: the process gas purified by the secondary nicotinic acid tower continues to enter the absorption tower, sprayed with 96-98% sulfuric acid at 60-80°C, ultrapure water is added to the bottom of the absorption tower to balance the acid concentration, and the excess sulfuric acid is connected to the secondary nicotinic acid tower.

[0025] Further: electronic grade sulfuric acid enters the finished acid cooler, the acid temperature drops to 35-45°C and enters the finished acid intermediate tank, and the finished acid is sequentially passed through the finished acid pump and the acid filter into the acid storage tank for storage.

[0026] Furthermore, the preheater adopts countercurrent heat exchange between 20-30% low-concentration fuming acid at the liquid phase outlet of the evaporator and 22-35% high-concentration fuming acid at the outlet of the secondary fuming acid tower.

[0027] Furthermore: the process gas at the outlet of the gas filter is sent to an absorption tower for absorption, the absorption liquid is 95% to 98% electronic grade sulfuric acid, and the process make-up water in the absorption tower tank is ultrapure water.

[0028] In the technical aspect of the present invention: the outlet of the secondary nicotinic acid tower tank of the sulfur trioxide evaporation system is connected to the inlet of the high-concentration nicotinic acid tank, the outlet of the high-concentration nicotinic acid tank is connected to the inlet of the high-concentration nicotinic acid pump, the outlet of the high-concentration nicotinic acid pump is connected to the inlet of the preheater, the outlet of the preheater is connected to the inlet of the evaporator, the gas phase outlet of the evaporator is connected to the inlet of the condenser, and the outlet of the condenser is connected to the inlet of the gas filter.

[0029] In the technical method of the present invention: the process gas at the outlet of the gas filter of the ultra-pure sulfur trioxide absorption system is sent to the absorption tower for absorption, the absorption liquid is 95% to 98% electronic grade sulfuric acid, and the process make-up water of the acid circulation tank is ultra-pure water.

[0030] In the technical aspect of the present invention: the ultra-pure sulfur trioxide absorption system includes an electronic acid absorption tower, an acid circulation tank, and an acid circulation pump. The acid inlet of the acid circulation tank is connected to the acid discharge port at the bottom of the absorption tower, the acid discharge port of the acid circulation tank is connected to the acid circulation pump, and the outlet end of the acid circulation pump is connected to the acid separator arranged at the upper part of the electronic acid absorption tower; the acid production port of the acid circulation tank is connected to the acid production pump, and the outlet end of the acid production pump is connected to the acid inlet of the upper part of the degassing tower. After the degassing tower removes SO2, it is sent out as product acid through the finished acid pump and the finished acid cooler in sequence.

[0031] The device and method of the present invention adopt a two-stage pickling process to produce ultrapure fuming acid to ensure the cleanliness of fuming acid; SO3 evaporator evaporates ultrapure SO3, uses product electronic acid as circulating acid absorption, and adds ultrapure water to the system to balance the acid concentration. Electronic grade sulfuric acid is stripped and circulated ultrafiltration is performed to obtain the required ultraclean high-purity sulfuric acid. The entire process mainly controls the intake of raw materials, auxiliary materials and impurities in the production process, and directly produces ultraclean high-purity sulfuric acid through process control.

[0032] Beneficial effects of the present invention:

[0033] The present invention utilizes the existing sulfuric acid device, draws out a part of the process gas at the outlet of the primary reforming gas economizer, adds ultrapure oleum, sulfur trioxide evaporation, ultrapure sulfur trioxide absorption, and ultrapure water units, and selectively produces electronic grade sulfuric acid. The process device realizes the leap of sulfuric acid from the traditional chemical industry to the wet electronics field.

[0034] The innovative features of the present invention include:

[0035] (1) The present invention adopts two-stage nicotinic acid washing, wherein the concentration of the first nicotinic acid tower is relatively low and the concentration of the second nicotinic acid tower is relatively high, thereby achieving the purpose of removing sulfur trioxide impurities and ensuring the quality of nicotinic acid.

[0036] (2) After sulfur trioxide evaporates in the present invention, it passes through a condenser and carries a small amount of droplets which are removed through a gas filter, thereby ensuring the quality of sulfur trioxide entering the absorption tower.

[0037] (3) After absorption of ultra-pure sulfur trioxide, UP-SSS grade electronic grade sulfuric acid can be obtained, in which the content of single metal ion impurities is ≤0.1ppb, and it is filtered through a 0.05 pore size filter to control the particles to 0.2 microns.

[0038] (4) The equipment pipelines used in the present invention are all lined with PFA in stainless steel to completely isolate the acidic medium from the stainless steel, thereby preventing the product quality from being contaminated by micro-corrosion of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a schematic diagram of a two-stage nicotinic acid washing system for an electronic grade sulfuric acid production device.

[0040] Among them, 1. primary nicotinic acid tower; 2. secondary nicotinic acid tower; 3. absorption tower; 4-1. primary nicotinic acid tower acid circulation tank; 5-1. primary nicotinic acid tower acid circulation pump; 6-1. primary nicotinic acid tower acid cooler; 4-2. secondary nicotinic acid tower acid circulation tank; 5-2. secondary nicotinic acid tower acid circulation pump; 6-2. secondary nicotinic acid tower acid cooler; 4-3. absorption tower acid circulation tank; 5-3. absorption tower acid circulation pump; 6-3. absorption tower acid cooler.

[0041] Figure 2 This is a schematic diagram of an ultra-pure sulfur trioxide evaporation system for an electronic grade sulfuric acid production device of the present invention.

[0042] Among them, 7. high-concentration nicotinic acid tank; 8. high-concentration nicotinic acid pump; 9. preheater; 10. evaporator; 11. SO3 condenser; 12. gas filter; 13. low-concentration nicotinic acid tank; 14. low-concentration nicotinic acid pump.

[0043] Figure 3 The present invention is a schematic diagram of an electronic-grade sulfuric acid absorption system for an electronic-grade sulfuric acid production device.

[0044] Among them, 15. electronic acid absorption tower; 16. acid circulation tank; 17. acid circulation pump; 18. acid production pump; 19. degassing tower; 20. degassing tower circulation pump; 21. finished acid cooler; 22. finished acid intermediate tank; 23. finished acid pump; 24. acid filter; 25. acid storage tank. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and methods in the art, which should all be included in the protection scope of the present invention.

[0046] like Figures 1 to 3 A device for preparing electronic grade sulfuric acid from ultra-pure oleum, the device comprising an ultra-pure oleum system, a sulfur trioxide evaporation system, and an ultra-pure sulfur trioxide absorption system; the oleum system is a two-stage nicotinic acid tower washing system, the high-concentration nicotinic acid at the outlet of the second-stage nicotinic acid tower washing is transported to the sulfur trioxide evaporation system, and the ultra-pure sulfur trioxide at the outlet of the sulfur trioxide evaporation system is transported to the ultra-pure sulfur trioxide absorption system.

[0047] The pure oleum system comprises a primary nicotinic acid tower 1 and a secondary nicotinic acid tower 2, wherein the furnace gas from the economizer is connected to the bottom of the primary nicotinic acid tower 1, the output end at the top of the primary nicotinic acid tower 1 is connected to the bottom of the secondary nicotinic acid tower 2, and the bottoms of the primary nicotinic acid tower 1 and the secondary nicotinic acid tower 2 are both equipped with nicotinic acid tower circulation tanks, which are connected to the middle of the nicotinic acid towers through a cooler, and the output end of the nicotinic acid tower circulation tank of the secondary nicotinic acid tower 2 is high-concentration nicotinic acid connected to a sulfur trioxide evaporation system;

[0048] The output end at the top of the secondary nicotinic acid tower 2 is connected to the bottom of the absorption tower 3. The bottom of the absorption tower 3 is provided with an absorption tower circulation tank, which is connected to the middle of the absorption tower through a cooler. The output end at the top of the absorption tower is connected to the original sulfuric acid device, and the absorption tower circulation tank is connected to the secondary nicotinic acid tower acid circulation tank.

[0049] The high-concentration nicotinic acid from the ultra-pure oleum system is connected in sequence through a high-concentration nicotinic acid tank 7, a preheater 9, an evaporator 10, an SO3 condenser 11 and a gas filter 12, and the output end of the gas filter 12 is connected to an ultra-pure sulfur trioxide absorption system;

[0050] The output end at the bottom of the evaporator 10 is connected to the low-concentration nicotinic acid tank 13 through the preheater 9, and the low-concentration nicotinic acid tank 13 is connected to the acid circulation tank of the secondary nicotinic acid tower;

[0051] The pipeline connecting the SO3 condenser 11 and the gas filter 12 is also connected to the output pipeline of the ultra-pure compressed air.

[0052] The ultrapure sulfur trioxide from the sulfur trioxide evaporation system is connected in sequence through the electronic acid absorption tower 15, the acid circulation tank 16, the degassing tower 19, the finished acid cooler 21 and the acid filter 24, and the output end of the acid filter 24 is the target product;

[0053] The acid circulation tank 16 also has an output end connected to the electronic acid absorption tower 15; the output end at the bottom of the degassing tower 19 is connected to the upper part of the degassing tower 19, and the output end of the ultra-pure compressed air is connected to the bottom of the degassing tower 19.

[0054] A process for preparing electronic grade sulfuric acid using ultrapure sulfur trioxide comprises the following steps:

[0055] (1) Preparation of ultrapure nicotinic acid by two-stage nicotinic acid washing and absorption:

[0056] A stream of furnace gas is introduced from the outlet of the economizer of the conversion section of the existing sulfuric acid device into the primary nicotinic acid tower 1 of the electronic grade sulfuric acid system. The primary nicotinic acid tower 1 sprays 80°C fuming acid containing 25% SO3, and continuously circulates and absorbs to achieve dust removal and purification effects. The purified low-concentration fuming acid balances the acid concentration and returns to the original sulfuric acid device. The process gas continues to enter the secondary nicotinic acid tower 2 to spray 40°C fuming acid containing 30% SO3. After the ultra-pure fuming acid containing 30% SO3 evaporates SO3, it enters the secondary nicotinic acid tower 2 to adjust the acid concentration or add ultra-pure water to the system to balance the acid concentration to ensure the production of ultra-pure fuming acid. The purified process gas at the top of the secondary nicotinic acid tower 2 continues to enter the absorption tower 3, sprays 70°C sulfuric acid containing 98%, and ultra-pure water is added to the bottom of the absorption tower to balance the acid concentration. The excess 98% sulfuric acid is connected to the secondary nicotinic acid tower 2. The primary nicotinic acid tower 1, the secondary nicotinic acid tower 2, and the absorption tower 3 are respectively provided with a set of acid circulation system, which is composed of an acid circulation tank 4, an acid circulation pump 5, and an acid cooler 6.

[0057] (2) Preparation of ultra-pure sulfur trioxide by evaporation of sulfur trioxide:

[0058] The ultrapure nicotinic acid from the secondary nicotinic acid tank 4-2 enters the high-concentration nicotinic acid tank 7. The high-concentration nicotinic acid is pumped 8 and the evaporator 10 evaporates sulfur trioxide to form a low-concentration nicotinic acid. After heat exchange in the preheater 9, it enters the evaporator 10 and evaporates ultrapure SO3 gas at 90-130°C. The ultrapure SO3 gas passes through the condenser 11 and the gas filter 12 in sequence to remove the trace sulfuric acid entrained therein and enters the electronic acid absorption tower 15.

[0059] (3) Absorption and preparation of electronic grade sulfuric acid

[0060] Ultrapure sulfur trioxide enters from the bottom of the electronic acid absorption tower 15, and the acid from the lower tower enters the acid circulation tank 16. After being pressurized by the circulation pump 17, it returns to the electronic acid absorption tower 15 for continuous circulation and absorption, increasing its concentration by 0.2% to 0.3%. Ultrapure water is added to the system to balance the acid concentration. The excess electronic grade sulfuric acid is sent to the degassing tower 19 by the acid production pump 18. Ultrapure air is used to purge the electronic grade sulfuric acid to remove trace impurities such as SO2 and further purify the electronic grade sulfuric acid. The electronic grade sulfuric acid enters the finished acid cooler 21, and the acid temperature drops to 40°C before entering the finished acid intermediate tank 22. The finished acid is sequentially passed through the finished acid pump 23 and the acid filter 24 and enters the acid storage tank 25 for storage.

[0061] The gas absorbed by the electronic acid absorption tower 15 enters the outlet pipeline of the original sulfuric acid device. Due to the heat release of the acid dilution, in order to control the absorption temperature of the spray acid of the electronic acid absorption tower 15 to ≤70°C, the desalted water of the system is used to perform heat exchange cooling on the circulating acid.

[0062] The electronic grade sulfuric acid in the acid storage tank 25 is high quality sulfuric acid, wherein the single metal ion impurity content is ≤0.1ppb, and after being filtered by the 0.05 pore size acid filter 24, the particles of 0.2 microns can be controlled, and the product index is qualified.

Claims

1. A device for preparing electronic grade sulfuric acid from ultrapure oleum, characterized in that: The device comprises an ultra-pure oleum system, a sulfur trioxide evaporation system and an ultra-pure sulfur trioxide absorption system; the oleum system is a two-stage nicotinic acid tower washing system, the high-concentration nicotinic acid at the outlet of the second-stage nicotinic acid tower washing is transported to the sulfur trioxide evaporation system, and the ultra-pure sulfur trioxide at the outlet of the sulfur trioxide evaporation system is transported to the ultra-pure sulfur trioxide absorption system.

2. The device for preparing electronic grade sulfuric acid from ultrapure oleum according to claim 1, characterized in that: The pure oleum system comprises a primary nicotinic acid tower (1) and a secondary nicotinic acid tower (2), wherein the furnace gas from the economizer is connected to the bottom of the primary nicotinic acid tower (1), the output end of the top of the primary nicotinic acid tower (1) is connected to the bottom of the secondary nicotinic acid tower (2), the bottoms of the primary nicotinic acid tower (1) and the secondary nicotinic acid tower (2) are both equipped with a nicotinic acid tower circulation tank, the nicotinic acid tower circulation tank is connected to the middle of the nicotinic acid tower through a cooler, and the output end of the nicotinic acid tower circulation tank of the secondary nicotinic acid tower (2) is connected to a sulfur trioxide evaporation system for high-concentration nicotinic acid; Preferably, the output end at the top of the secondary nicotinic acid tower (2) is connected to the bottom of the absorption tower (3), the bottom of the absorption tower (3) is provided with an absorption tower circulation tank, the absorption tower circulation tank is connected to the middle of the absorption tower through a cooler, the output end at the top of the absorption tower is connected to the raw sulfuric acid device, and the absorption tower circulation tank is connected to the acid circulation tank of the secondary nicotinic acid tower.

3. The device for preparing electronic grade sulfuric acid from ultrapure oleum according to claim 1, characterized in that: High-concentration nicotinic acid from the ultra-pure oleum system is connected in sequence through a high-concentration nicotinic acid tank (7), a preheater (9), an evaporator (10), an SO3 condenser (11) and a gas filter (12), and the output end of the gas filter (12) is connected to an ultra-pure sulfur trioxide absorption system; Preferably: the output end at the bottom of the evaporator (10) is connected to the low-concentration nicotinic acid tank (13) through the preheater (9), and the low-concentration nicotinic acid tank (13) is connected to the secondary nicotinic acid tower acid circulation tank; Preferably, the pipeline connecting the SO3 condenser (11) and the gas filter (12) is also connected to an output pipeline of ultrapure compressed air.

4. The device for preparing electronic grade sulfuric acid from ultrapure oleum according to claim 1, characterized in that: Ultrapure sulfur trioxide from the sulfur trioxide evaporation system is sequentially connected through an electronic acid absorption tower (15), an acid circulation tank (16), a degassing tower (19), a finished acid cooler (21) and an acid filter (24), and the output end of the acid filter (24) is the target product; Preferably: the acid circulation tank (16) also has an output end connected to the electronic acid absorption tower (15); the output end at the bottom of the degassing tower (19) is connected to the upper part of the degassing tower (19), and the output end of the ultrapure compressed air is connected to the bottom of the degassing tower (19).

5. A method for producing electronic grade sulfuric acid from ultrapure oleum using the system of claim 1, characterized in that: The method comprises the following steps: washing the furnace gas at the economizer outlet through an ultra-pure fuming sulfuric acid system, then evaporating it through a sulfur trioxide evaporation system, and then treating the ultra-pure sulfur trioxide obtained after evaporation through an ultra-pure sulfur trioxide absorption system to obtain electronic grade sulfuric acid.

6. A method for producing electronic grade sulfuric acid from ultrapure oleum using the system of claim 5, characterized in that: The method comprises the following steps: (1) Preparation of ultrapure nicotinic acid by two-stage nicotinic acid washing and absorption: A stream of furnace gas is introduced from the outlet of the economizer of the conversion section of the existing sulfuric acid device into the primary nicotinic acid tower (1) of the electronic grade sulfuric acid system, and the primary nicotinic acid tower (1) sprays fuming acid containing 20-35% SO3 at 50-80°C, and continuously circulates and absorbs to achieve dust removal and purification effect. The purified low-concentration fuming acid is returned to the original sulfuric acid device after the acid concentration is balanced; the process gas continues to enter the secondary nicotinic acid tower (2) to spray fuming acid containing 20-35% SO3 at 50-80°C, and the fuming acid of this concentration evaporates SO3 and enters the secondary nicotinic acid tower 2 to adjust the acid concentration or add ultrapure water into the system to balance the acid concentration, so as to ensure the production of ultrapure fuming acid; (2) Preparation of ultra-pure sulfur trioxide by evaporation of sulfur trioxide: The ultra-pure nicotinic acid from the secondary nicotinic acid tower tank (4-2) enters the high-concentration nicotinic acid tank (7), is transported to the evaporator (10), and the low-concentration nicotinic acid after evaporating sulfur trioxide enters the evaporator (10) after completing heat exchange in the preheater (9), and evaporates ultra-pure SO3 gas at 90-130°C; the ultra-pure SO3 gas passes through the condenser (11) and the gas filter (12) in turn to remove the trace sulfuric acid entrained therein and enters the electronic acid absorption tower (15). (3) Absorption and preparation of electronic grade sulfuric acid Ultrapure sulfur trioxide enters from the bottom of the electronic acid absorption tower (15), and the acid from the lower tower enters the acid circulation tank (16). After being pressurized by the circulation pump (17), it returns to the electronic acid absorption tower (15) for continuous circulation absorption, so that its concentration increases by 0.2% to 0.3%. Ultrapure water is added to the system to balance the acid concentration. The excess electronic grade sulfuric acid is sent to the degassing tower (19) by the acid production pump (18). The electronic grade sulfuric acid is purged with ultrapure air to remove trace impurities such as SO2, and further purified to obtain electronic grade sulfuric acid. The gas absorbed by the electronic acid absorption tower 15 enters the outlet pipeline of the original sulfuric acid device-absorption tower. Due to the heat release of the acid dilution, in order to control the absorption temperature of the spray acid of the electronic acid absorption tower 15 to ≤70°C, the desalted water of the system is used to perform heat exchange cooling on the circulating acid.

7. The method according to claim 6, characterized in that: The process gas purified by the secondary nicotinic acid tower (2) continues to enter the absorption tower (3) and is sprayed with 96-98% sulfuric acid at 60-80°C. Ultrapure water is added to the bottom of the absorption tower to balance the acid concentration, and the excess sulfuric acid is connected to the secondary nicotinic acid tower (2).

8. The method according to claim 6, characterized in that: Electronic grade sulfuric acid enters the finished acid cooler (21), the acid temperature drops to 35-45°C and enters the finished acid intermediate tank (22), and the finished acid passes through the finished acid pump (23) and the acid filter (24) in sequence and enters the acid storage tank (25) for storage.

9. The method according to claim 6, characterized in that: The preheater adopts countercurrent heat exchange between 20-30% low-concentration fuming acid at the liquid phase outlet of the evaporator and 22-35% high-concentration fuming acid at the outlet of the secondary fuming acid tower.

10. The ultrapure sulfur trioxide absorption system according to claim 1, characterized in that: The process gas at the outlet of the gas filter is sent to the absorption tower for absorption, the absorption liquid is 95% to 98% electronic grade sulfuric acid, and the process supplementary water in the absorption tower tank is ultrapure water.

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