Preparation method of electronic grade sulfuric acid and device for preparing electronic grade sulfuric acid

Abstract

The invention relates to the field of preparation of chemical products, and discloses a preparation method of electronic-grade sulfuric acid and a device for preparing the electronic-grade sulfuric acid. The preparation method comprises the following steps: S1, carrying out reaction and twice conversion and twice absorption on liquid sulfur and air to obtain fuming sulfuric acid and first tail gas; s2, evaporating the fuming sulfuric acid to obtain SO3-containing gas and evaporated fuming sulfuric acid, purifying the SO3-containing gas, performing third absorption on the obtained purified SO3-containing gas by using ultrapure water, and performing SO2 removal and filtration on the obtained high-purity sulfuric acid to obtain electronic-grade sulfuric acid; and S3, returning the evaporated fuming sulfuric acid to the step S1, and carrying out two-time conversion and two-time absorption. According to the invention, fuming sulfuric acid and electronic-grade sulfuric acid production systems are combined, recycling of three wastes is realized, and the method is suitable for large-scale industrial production of electronic-grade sulfuric acid.

Description

Technical Field

[0001] The invention relates to the field of chemical product preparation, and in particular to a method for preparing electronic-grade sulfuric acid and a device for preparing electronic-grade sulfuric acid. Background Art

[0002] Wet electronic chemicals are one of the essential and key basic chemical materials in the production process of VLSI, liquid crystal display panels, solar cells, etc. Electronic grade sulfuric acid is the most important product of wet electronic chemicals. It is also called high-purity sulfuric acid and ultra-pure sulfuric acid. It is an ultra-clean and high-purity reagent and an essential key basic chemical reagent in the development of microelectronics technology. It is widely used in the assembly and processing of semiconductors and VLSI. It is mainly used for cleaning and etching of silicon wafers, and can effectively remove impurity particles, inorganic residues and carbon deposits on the wafers.

[0003] The production processes of electronic grade sulfuric acid include distillation and gas absorption.

[0004] The distillation process mainly includes four parts: chemical pretreatment system, continuous distillation system, ultra-clean multi-stage filtration system and ultra-clean canning system. In order to obtain high-purity products, electric heating is now mostly used, that is, the electric heating wire converts electrical energy into thermal energy, and then transfers the heat to the raw sulfuric acid in the kettle through the glass or quartz tube wall, so that it is heated, boiled and vaporized, and the purpose of purification is achieved through distillation. Therefore, there are problems of high energy consumption and high production costs. In addition, the temperature of the finished product is very high, and it is not economical to cool it with water, which is easy to cause waste of energy and water resources.

[0005] The gas absorption method is the mainstream technology for large-scale industrial production of electronic-grade sulfuric acid at home and abroad. This method mostly uses industrial-grade sulfur trioxide as raw material, and produces electronic-grade sulfuric acid by evaporation (vaporization), impurity removal, absorption, filtration, etc., such as CN103407972A, CN104925759A and CN110255506A. In the process of air stripping and product filling, the acidic waste gas generated cannot be directly discharged at high altitude, and a new tail gas absorption device must be built. After multi-stage absorption of SO2 and acid mist in the waste gas, it can meet the emission standards, such as CN104843653A, CN111994879A. In addition, when cleaning tank trucks and filling equipment with ultrapure water, a certain amount of acid-containing wastewater will be generated, which cannot be directly discharged after collection, and a new wastewater treatment system must be built or outsourced for treatment. Due to the existence of environmental protection issues such as the difficulty in treating the "three wastes", the large-scale industrial production of electronic-grade sulfuric acid is limited.

[0006] Therefore, there is an urgent need for a process that can recycle wastewater and tail gas in production, reduce production energy consumption, and obtain high-quality electronic-grade sulfuric acid. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem that waste water and tail gas in the production of electronic grade sulfuric acid in the prior art are difficult to treat, and to provide a method for preparing electronic grade sulfuric acid and a device for preparing electronic grade sulfuric acid. The preparation method can recycle waste water and tail gas in production, reduce production energy consumption, and obtain high-quality electronic grade sulfuric acid.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for preparing electronic grade sulfuric acid, wherein the preparation method comprises:

[0009] S1, reacting liquid sulfur and air and performing two-turn and two-absorption to obtain oleum and the first tail gas;

[0010] S2, evaporating the oleum to obtain a SO3-containing gas and evaporated oleum, wherein the SO3-containing gas is purified, the purified SO3-containing gas is subjected to a third absorption with ultrapure water, and the obtained high-purity sulfuric acid is de-SO2-ed and filtered to obtain electronic grade sulfuric acid;

[0011] S3, returning the evaporated fuming sulfuric acid to S1 for the two-turn and two-absorption process.

[0012] The second aspect of the present invention provides a device for preparing electronic grade sulfuric acid, wherein the device comprises: a fuming sulfuric acid system and an electronic grade sulfuric acid system connected; wherein,

[0013] The oleum system comprises: a sulfur incinerator and a two-rotation and two-absorption unit connected in sequence;

[0014] The electronic grade sulfuric acid system comprises: an evaporator, a purification system, a third absorption tower, a stripping tower and a filter which are connected in sequence;

[0015] The liquid phase outlet of the evaporator is in communication with the two-turn and two-absorption unit, and is used to return the evaporated oleum to the oleum system to continue producing the oleum.

[0016] Through the above technical solution, the beneficial effects of the present invention are:

[0017] The electronic-grade sulfuric acid system of the present invention uses oleum as a raw material, evaporates part of SO3 from the oleum raw material, and then returns the evaporated oleum to the oleum system, which can effectively reduce the evaporation temperature of oleum and reduce the energy consumption of the electronic-grade sulfuric acid system. The present invention adopts a set of production equipment to co-produce oleum and electronic-grade sulfuric acid, and can flexibly allocate products according to market conditions and better cope with market risks.

[0018] In a preferred embodiment of the present invention, by selecting the appropriate type of co-catalyst, the conditions of the first absorption and the second absorption, the evaporation temperature of 104%-108% oleum, and the conditions of the third absorption, oleum and electronic-grade sulfuric acid of higher quality are obtained, so that the oleum product meets the superior product standard, and the electronic-grade sulfuric acid product meets the SEMI G4 standard.

[0019] In addition, the present invention adopts oleum (104%-108% oleum) with a free SO3 content of 17-36wt% as a raw material, and organically combines two production systems of oleum and electronic grade sulfuric acid. The waste gas generated by the electronic grade sulfuric acid system during air stripping and product filling can be sent to the drying section of the oleum system for supplementary air; the acid-containing waste water generated by the electronic grade sulfuric acid system during cleaning and filling equipment can be sent to the two-transformation and two-absorption (including the first conversion reaction, the first absorption, the second conversion reaction and the second absorption) section of the oleum system for absorption and water replenishment. In this way, on the one hand, the recycling of waste gas and waste water of the electronic grade sulfuric acid system is realized, that is, the "zero" emission of the electronic grade sulfuric acid system has better environmental benefits; on the other hand, the air and absorption water consumption of the oleum system can be reduced, and energy saving and consumption reduction of the oleum system are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a flow chart of a process for preparing electronic grade sulfuric acid in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] A first aspect of the present invention provides a method for preparing electronic grade sulfuric acid, wherein the preparation method comprises:

[0023] S1, reacting liquid sulfur and air and performing two-turn and two-absorption to obtain oleum and the first tail gas;

[0024] S2, evaporating the oleum to obtain a SO3-containing gas and evaporated oleum, wherein the SO3-containing gas is purified, the purified SO3-containing gas is subjected to a third absorption with ultrapure water, and the obtained high-purity sulfuric acid is de-SO2-ed and filtered to obtain electronic grade sulfuric acid;

[0025] S3, returning the evaporated fuming sulfuric acid to S1 for the two-turn and two-absorption process.

[0026] The present invention has no particular restrictions on the conditions for the reaction of liquid sulfur and air, and the conventional method and conditions for preparing sulfur dioxide by the reaction of liquid sulfur and air in the art can be adopted. For example, liquid sulfur and dried air can be reacted at a mass flow ratio of 1:(2-4) at 1000-1050°C.

[0027] According to the present invention, preferably, the content of free SO3 in the oleum is 17-36wt% (104%-108% oleum), preferably 20-25wt%. Oleum that meets this condition can be used as the raw material for preparing electronic grade sulfuric acid, and the evaporation temperature of oleum can be controlled within a reasonable range, reducing the corrosion to equipment. For example, free SO3 can be selected to be oleum (i.e. 105% oleum) with a content of 22wt%, and 105% oleum is a commercially available common specification and can be used as a product for flexible deployment.

[0028] According to the present invention, preferably, the two-conversion and two-absorption process includes: subjecting the SO2-containing gas obtained by the reaction to a first conversion reaction, and then subjecting the obtained gas after the first conversion reaction to a first absorption with an absorbent to obtain fuming sulfuric acid and a first gaseous product after the first absorption, and then subjecting the first gaseous product to a second conversion reaction, and then subjecting the obtained second gaseous product to a second absorption with the fuming sulfuric acid after the first absorption.

[0029] According to the present invention, preferably, the process of the first conversion reaction comprises: subjecting the SO2-containing gas to a first-stage conversion reaction, a second-stage conversion reaction and a third-stage conversion reaction in sequence.

[0030] According to the present invention, preferably, the temperatures of the first-stage conversion reaction, the second-stage conversion reaction and the third-stage conversion reaction are 380-430° C., 410-460° C. and 400-450° C. respectively. The temperatures of the first-stage, second-stage and third-stage conversion reactions respectively meet this range, which can improve the efficiency of converting SO2 to SO3.

[0031] According to the present invention, preferably, the process of the second conversion reaction comprises: subjecting the first gas phase product to a four-stage conversion reaction and a five-stage conversion reaction in sequence.

[0032] According to the present invention, preferably, the temperature of the four-stage conversion reaction and the five-stage conversion reaction are 390-440° C. and 400-450° C. respectively. The temperature of the four-stage conversion reaction and the five-stage conversion reaction meets this range, which can improve the efficiency of converting SO2 to SO3.

[0033] According to the present invention, preferably, the first-stage conversion reaction, the second-stage conversion reaction, the third-stage conversion reaction, the fourth-stage conversion reaction and the fifth-stage conversion reaction are each independently carried out in the presence of a catalyst and a co-catalyst.

[0034] According to the present invention, preferably, the catalyst is selected from vanadium-based catalysts, preferably V2O5.

[0035] According to the present invention, preferably, the promoter is selected from alkali metal sulfates, preferably K2SO4 and / or Na2SO4, preferably K2SO4.

[0036] According to the present invention, preferably, in the one-stage conversion reaction, the two-stage conversion reaction, the three-stage conversion reaction, the four-stage conversion reaction and the five-stage conversion reaction, based on the weight of the liquid sulfur, the amount of the catalyst used is independently 6-9wt%, and the amount of the co-catalyst used is independently 0.5-1wt%.

[0037] According to the present invention, preferably, after the three-stage conversion reaction, the obtained first conversion reaction gas is cooled to below 200°C, and then the first absorption is performed with an absorbent. The first conversion reaction gas is cooled to below 200°C, which can improve the absorption efficiency of SO3.

[0038] According to the present invention, preferably, after the second conversion reaction, the obtained second gas phase product is cooled to below 190° C., and then the second absorption is performed, so that SO 3 can be almost completely absorbed.

[0039] After evaporation, the oleum is returned to the two-transformation and two-absorption section as a SO3 absorbent. The first absorption and the second absorption make the SO3 obtained by the first conversion reaction and the second conversion reaction react continuously with the absorbent to continuously increase the concentration of the oleum. It is a cyclic absorption process. The acid circulation amount (the amount of oleum after evaporation returned to S1 for two-transformation and two-absorption) is controlled by adjusting the acid pump current and controlling the pump outlet pressure. The acid pump outlet pressure is controlled to be 0.3-0.55MPa.

[0040] According to the present invention, preferably, in S2, the evaporation temperature is 108-147° C., preferably 131-141° C. The evaporation temperature satisfies this range, which can maintain a high evaporation efficiency and control the temperature within a reasonable range, thereby reducing corrosion to the equipment.

[0041] According to the present invention, preferably, S2 further comprises: cooling the SO3-containing gas to 50-60°C before performing the purification.

[0042] In S2 of the present invention, the purification is performed by filtering to remove trace sulfuric acid and other impurities carried in the SO3-containing gas. Preferably, the purification is performed by two-stage filtration, the filtration accuracy of the first stage filtration is 0.15-0.25 μm, the filtration accuracy of the second stage filter is 0.05-0.15 μm, and the pressure is 0.2-0.4 MPa. In a specific embodiment of the present invention, the shell of the two-stage filter is made of 304 stainless steel, and the filter element is made of polytetrafluoroethylene (PTFE).

[0043] According to the present invention, preferably, free SO3 in the oleum after the evaporation has a content of 8-27wt% (i.e. 102%-106% oleum). Free SO3 in the oleum after the evaporation has a content that satisfies this range. If too much SO3 is evaporated, i.e. free SO3 in the oleum after the evaporation has a content that is low, the evaporation temperature needs to be increased, which can aggravate the corrosion of equipment.

[0044] Furthermore, the content of free SO3 in the fuming sulfuric acid after evaporation is 10-15wt%.

[0045] According to the present invention, preferably, the mass flow ratio of the evaporated oleum to the oleum returned to S1 is 1:(1.1-1.3), that is, the mass flow ratio of the evaporated oleum returned to S1 to the oleum entering the evaporator is 1:(1.1-1.3). The oleum is evaporated to obtain SO3-containing gas and evaporated oleum; wherein the SO3-containing gas is purified and subjected to a third absorption with ultrapure water to prepare electronic grade sulfuric acid; and the evaporated oleum is returned to S1 to participate in the absorption of the gas after the first conversion reaction.

[0046] According to the present invention, preferably, in S2, the content of sulfuric acid in the high-purity sulfuric acid is 95-97 wt %.

[0047] According to the present invention, preferably, the third absorption process comprises: contacting the purified SO3-containing gas with the ultrapure water, cyclically absorbing the purified SO3-containing gas with the obtained acid solution to obtain the high-purity sulfuric acid. In the present invention, the purified SO3-containing gas is contacted with ultrapure water, the ultrapure water absorbs SO3 in the SO3-containing gas to obtain the acid solution, and the acid solution is cyclically absorbed with SO3 until the desired concentration (sulfuric acid content is 95-97wt%) of high-purity sulfuric acid is obtained.

[0048] According to the present invention, preferably, the conditions for the third absorption include: a temperature of 30-60°C, preferably 30-45°C; and a pressure of 0.1-0.3 MPa, preferably 0.1-0.2 MPa.

[0049] In S2, the resistivity of the ultrapure water at 25° C. is greater than or equal to 18 MΩ·cm. Ultrapure water products commonly found in the market all meet this specification.

[0050] According to the present invention, preferably, in the third absorption, the mass flow ratio of the purified SO3-containing gas to the ultrapure water is (3-4):1.

[0051] According to the present invention, preferably, in the third absorption, the mass flow ratio of the circulating acid solution, the high-purity sulfuric acid and the ultrapure water is (80-90): (4-5): 1. The SO3-containing gas entering the absorption tower contacts the ultrapure water in a reverse contact form, the ultrapure water absorbs SO3 in the SO3-containing gas, and the obtained acid solution returns to the absorption tower to circulate and absorb SO3. The flow ratio of the circulating acid solution, the high-purity sulfuric acid and the ultrapure water refers to the ratio of the flow rate of the acid solution returning to the absorption tower, the flow rate of the high-purity sulfuric acid flowing out of the absorption tower after obtaining the high-purity sulfuric acid of the required concentration, and the flow rate of the ultrapure water entering the absorption tower.

[0052] According to the present invention, preferably, in S2, the method for removing SO2 comprises: stripping the high-purity sulfuric acid with ultra-pure air; wherein the mass flow ratio of the ultra-pure air to the high-purity sulfuric acid is (420-470):1.

[0053] According to the present invention, preferably, in S2, the filtration is performed using a filter of grade G4 or above to remove microparticles in the high-purity sulfuric acid.

[0054] According to the present invention, preferably, the preparation method further comprises: after the high-purity sulfuric acid is de-SO2ed and filtered, it is also bottled to obtain electronic grade sulfuric acid, second tail gas and waste water; wherein,

[0055] The second tail gas is returned to S1 to mix with air and react with liquid sulfur; the waste water is returned to S1 to mix with the absorbent to perform the first absorption on the gas after the first conversion reaction.

[0056] In the present invention, the second tail gas includes: the exhaust gas from the outlet of the third absorption tower, the exhaust gas generated when the SO2 is blown off with ultrapure air, and the exhaust gas generated during the canning process of the electronic grade sulfuric acid product. The second tail gas is sent to the drying section of the oleum system for supplementary air. The acid-containing wastewater generated by the electronic grade sulfuric acid system during the cleaning and filling of the equipment can be sent to the two-conversion and two-absorption (including the first conversion reaction, the first absorption, the second conversion reaction and the second absorption) section of the oleum system for absorption and water replenishment.

[0057] According to the present invention, preferably, the preparation method further comprises: absorbing and washing the first tail gas in sequence; wherein the absorption liquid is a mixed liquid containing Na2SO4, Na2SO3 and NaHSO3. The first tail gas (mainly SO2, containing a small amount of SO3) first enters the tail gas absorption tower, and contacts with the sprayed Na2SO4-Na2SO3-NaHSO3 absorption liquid in reverse to remove most of the SO2 and SO3 therein; then enters the water washing tower to further wash away the SO2 and SO3 in the tail gas, as well as the entrained NaHSO3, etc. wherein the ratio of Na2SO4, Na2SO3 and NaHSO3 in the absorption liquid is not particularly limited, as long as it can effectively absorb SO2 and SO3. For example, Na2SO4, Na2SO3 and NaHSO3 can be mixed with water to prepare a density of 1040-1060kg / m 3 of aqueous solution.

[0058] The second aspect of the present invention provides a device for preparing electronic grade sulfuric acid, wherein the device comprises: a fuming sulfuric acid system and an electronic grade sulfuric acid system connected; wherein,

[0059] The oleum system comprises: a sulfur incinerator and a two-rotation and two-absorption unit connected in sequence;

[0060] The electronic grade sulfuric acid system comprises: an evaporator, a purification system, a third absorption tower, a stripping tower and a filter which are connected in sequence;

[0061] The liquid phase outlet of the evaporator is in communication with the two-turn and two-absorption unit, and is used to return the evaporated oleum to the oleum system to continue producing the oleum.

[0062] According to the present invention, preferably, the two-conversion and two-absorption unit comprises: a first conversion system, a first absorption tower, a second conversion system and a second absorption tower.

[0063] According to the present invention, preferably, the first conversion system comprises: a first converter, a first superheater, a second converter, a first heat exchanger, a third converter and a second heat exchanger which are connected in sequence. The first superheater, the first heat exchanger and the second heat exchanger are used to cool or heat the first converter outlet gas, the second converter outlet gas and the third converter outlet gas respectively.

[0064] According to the present invention, preferably, the second conversion system comprises: a fourth converter, a second superheater, a fifth converter and a third superheater connected in sequence. The second superheater is used to cool or heat the furnace gas at the outlet of the fourth converter; the third superheater is used to cool the furnace gas at the outlet of the fifth converter.

[0065] According to the present invention, preferably, a third heat exchanger is further provided between the first absorption tower and the second conversion system for heating the furnace gas at the outlet of the first absorption tower.

[0066] According to the present invention, preferably, the oleum system further comprises: a dryer and a cooler; wherein,

[0067] The dryer is connected to the inlet of the sulfur incinerator and is used to dry the air. The dried air enters the sulfur incinerator to react with liquid sulfur.

[0068] The cooler is arranged between the sulfur incinerator and the first conversion system.

[0069] According to the present invention, preferably, the device further comprises a filling system.

[0070] According to the present invention, preferably, the gas phase outlets of the filling system and the stripping tower are respectively connected to the inlet of the dryer, so as to send the waste gas flowing out of the filling system and the stripping tower into the dryer in the oleum system for use as supplementary air.

[0071] According to the present invention, the acid-containing wastewater generated by the electronic-grade sulfuric acid system during the cleaning and filling of equipment can be sent to the two-transfer and two-absorption sections of the oleum system for absorption and water replenishment.

[0072] According to the present invention, preferably, the device further comprises a tail gas treatment system for treating the tail gas generated by the oleum system; the tail gas treatment system comprises a tail gas absorption tower, a water scrubber and an electric demister; wherein,

[0073] The tail gas absorption tower is used to remove SO2 and SO3 in the tail gas generated by the oleum system; the water scrubber is used to further remove SO2 and SO3 in the tail gas, as well as the entrained NaHSO3; the electric demister is used to remove residual acid mist.

[0074] According to a specific embodiment of the present invention, Figure 1 As shown, the method for preparing electronic grade sulfuric acid in the device provided by the present invention comprises:

[0075] Liquid sulfur and dried air are introduced into the sulfur incinerator for high-temperature incineration. The outlet gas (containing SO2 gas) is cooled by the fire tube boiler and then enters the first converter for a first-stage conversion reaction; the outlet gas of the first stage enters the second converter for a second-stage conversion reaction; the outlet gas of the second stage enters the third converter for a third-stage conversion reaction. The outlet gas of the third stage is cooled by the cold-hot heat exchanger and the economizer in turn, and then enters the first absorption tower to obtain oleum after the first absorption and the first gas phase product. The gas (first gas phase product) coming out of the first absorption tower is heated by the cold-hot heat exchanger and the hot-hot heat exchanger, and then enters the fourth converter for a fourth-stage conversion reaction; the outlet gas of the fourth stage enters the fifth converter for a fifth-stage conversion reaction. The gas after the reaction (second gas phase product) is cooled by the superheater and the economizer in turn, and then enters the second absorption tower, and the oleum after the first absorption is used for a second absorption to obtain oleum and the first tail gas (the outlet tail gas of the second absorption tower). The first exhaust gas enters the absorption tower, water washing tower and electrostatic demister in sequence. After absorption, water washing and two-stage electrostatic demister, the first exhaust gas meets the emission standards.

[0076] The prepared oleum is passed into an evaporator to obtain SO3-containing gas and evaporated oleum. The evaporated oleum enters the first absorption tower of the oleum system, and continues to produce oleum after absorbing SO3. After the evaporated SO3-containing gas is cooled and purified by gas, the purified SO3-containing gas enters the top of the third absorption tower, and ultrapure water is passed into the bottom of the tower. The purified SO3-containing gas is subjected to the third absorption with ultrapure water, and the sulfuric acid obtained by absorbing SO3 is returned to the third absorption tower for circulation absorption until the sulfuric acid concentration reaches 95-97wt% and then begins to be discharged from the tower. The 95-97wt% high-purity sulfuric acid obtained in the third absorption tower enters the stripping tower, and the residual SO2 gas in the high-purity sulfuric acid is removed by ultrapure air. The high-purity sulfuric acid after stripping enters the G4 grade filter, and after micro-particle filtration, it is filled to obtain electronic grade high-purity sulfuric acid. Among them, the tail gas generated in the absorption tower, stripping tower and canning process is sent to the drying section of the oleum system for supplementary air. The wastewater generated by the cleaning and filling system is sent to the two-transformation and two-absorption (including the first conversion reaction, the first absorption, the second conversion reaction and the second absorption) section of the oleum system to be used as water replenishment for the first absorption tower and the second absorption tower.

[0077] The present invention will be described in detail below through examples and comparative examples. In the following examples, unless otherwise specified, all methods are conventional methods; and the reagents and materials used, unless otherwise specified, can be obtained from commercial sources.

[0078] The various indicators of fuming sulfuric acid are measured with reference to GB / T534-2014 "Industrial Sulfuric Acid", and the various indicators of electronic grade sulfuric acid are measured with reference to SEMI C44-0708 "Sulfuric Acid Specifications and Guidelines".

[0079] The following examples are based on Figure 1 Flow chart illustrating the preparation of electronic grade sulfuric acid.

[0080] Example 1

[0081] The oleum raw material is prepared according to the following steps: liquid sulfur and dried air are introduced into the sulfur incinerator for high temperature (1020°C) incineration, the mass flow ratio of liquid sulfur to dried air is 1:3.3, the furnace gas at the outlet of about 1000°C is cooled by the fire tube boiler, the temperature is reduced to 400°C, and then enters the first stage of the converter to react at a temperature of 400°C. The gas at the outlet of the first stage enters the second stage of the converter to react at a temperature of 455°C. The gas at the outlet of the second stage is cooled by the hot-hot heat exchanger, the temperature is reduced to 440°C, and enters the third stage of the converter to react at a temperature of 440°C. The gas at the outlet of the third stage is cooled to 190°C by the cold-hot heat exchanger and the economizer in turn, and enters the first absorption tower to obtain oleum and the first gas phase product after the first absorption. The furnace gas (first gas phase product) coming out of the first absorption tower is heated to 420°C by the cold-hot heat exchanger and the hot-hot heat exchanger, and enters the fourth stage of the converter to react at a temperature of 420°C. After the gas at the outlet of the fourth stage is cooled to 420°C by the superheater, it enters the fifth stage of the converter to react at a temperature of 420°C. The reacted gas is cooled to 180°C by the superheater and the economizer in turn, and enters the second absorption tower to obtain fuming sulfuric acid product. Based on the weight of liquid sulfur, the amount of catalyst V2O5 used in each converter is 8wt%, and the amount of co-catalyst K2SO4 is 0.8wt%. The outlet tail gas of the second absorption tower enters the tail gas treatment process, and is absorbed (the absorbent is an aqueous solution of Na2SO4-Na2SO3-NaHSO3 with a density of 1050kg / m 3 ) and water washing, two-stage electrostatic demisting, the SO2 concentration in the tail gas is ≤180ppm, and the acid mist is ≤5ppm, meeting the emission standards.

[0082] Electronic grade sulfuric acid is prepared according to the following steps: the oleum product is passed into the evaporator, and the SO3-containing gas is evaporated at 134°C. The remaining 103% oleum after evaporation enters the first absorption tower of the oleum system (the oleum after evaporation is introduced into the first absorption tower by the acid pump, and the outlet pressure of the acid pump is controlled to be 0.35MPa by adjusting the acid pump current), and 105% oleum is continuously produced after absorbing SO3. The mass flow ratio of 105% oleum entering the evaporator to 103% oleum returning after evaporation is 1.13:1. After the evaporated SO3-containing gas is cooled to 55°C, it is purified by gas purification (two-stage filtration is adopted, the shell material of the two-stage filter is 304 stainless steel, the filter element material is PTFE, the filtration accuracy of the first stage filtration is 0.2μm, the filtration accuracy of the second stage filter is 0.1μm, and the pressure is 0.3MPa) and the purified SO3-containing gas enters the top of the third absorption tower, and ultrapure water is introduced into the bottom of the tower. The sulfuric acid obtained by absorbing SO3 returns to the tower for cyclic absorption until the sulfuric acid concentration reaches 96wt% and then begins to exit the tower. The operating temperature of the third absorption tower is 35°C, the operating pressure is 0.12MPa, and the resistivity of ultrapure water is 18MΩ·cm (25°C); the mass flow ratio of the purified SO3-containing gas and ultrapure water in the third absorption tower is 3.6:1; the mass flow ratio of the sulfuric acid for circulating absorption, the sulfuric acid exiting the tower after absorption, and the ultrapure water is 84:4.6:1. The 96wt% high-purity sulfuric acid produced in the third absorption tower enters the stripping tower, and the residual SO2 gas in the high-purity sulfuric acid is removed by ultra-pure air. The mass flow ratio of ultra-pure air to the high-purity sulfuric acid entering the tower is 440:1. The high-purity sulfuric acid after stripping enters the G4 filter, and after micro-particle filtration, it is filled to obtain electronic-grade high-purity sulfuric acid. The tail gas generated in the absorption tower, stripping tower and canning process is sent to the drying section of the oleum system for supplementary air. The wastewater generated by the cleaning and filling system is sent to the two-turn and two-absorption section of the oleum system for water replenishment in the absorption tower.

[0083] Example 2

[0084] The oleum raw material is prepared according to the following steps: liquid sulfur and dried air are introduced into a sulfur incinerator for high temperature (1020°C) combustion, the mass flow ratio of liquid sulfur to dried air is 1:3.3, the furnace gas at the outlet of about 1050°C is cooled by a fire tube boiler, the temperature drops to 420°C, and then enters the first stage of the converter to react at a temperature of 420°C. The gas at the outlet of the first stage enters the second stage of the converter to react at a temperature of 420°C. The gas at the outlet of the second stage enters the third stage of the converter to react at a temperature of 420°C. The gas at the outlet of the third stage is cooled to 175°C by a cold heat exchanger and a coal economizer in turn, and enters the first absorption tower to obtain oleum and the first gas phase product after the first absorption. The furnace gas (first gas phase product) coming out of the first absorption tower is heated to 420°C by a cold heat exchanger and a hot heat exchanger, and enters the fourth stage of the converter to react at a temperature of 420°C. The gas at the outlet of the fourth stage enters the fifth stage of the converter to react at a temperature of 420°C. The reacted gas is cooled to 160°C through a superheater and a coal economizer in turn, and enters a second absorption tower to obtain a fuming sulfuric acid product. Based on the weight of liquid sulfur, the amount of catalyst V2O5 in each converter is 6wt%, and the amount of co-catalyst K2SO4 is 0.5wt%. The outlet tail gas of the second absorption tower enters the tail gas treatment process, and after absorption (the absorbent is the same as in Example 1) and washing, and two-stage electric demisting, the SO2 concentration in the tail gas is ≤180ppm, and the acid mist is ≤5ppm, which is up to the emission standard.

[0085] Electronic grade sulfuric acid is prepared according to the following steps: the oleum product is passed into an evaporator, and the SO3-containing gas is evaporated at 135°C. The remaining 103% oleum after evaporation enters the first absorption tower of the oleum system (oleum is introduced into the first absorption tower by an acid pump after evaporation, and the acid pump outlet pressure is controlled to be 0.35MPa by adjusting the acid pump current), and 105% oleum is continuously produced after absorbing SO3. The mass flow ratio of the 105% oleum entering the evaporator and the 103% oleum returned after evaporation is 1.18:1. After the evaporated SO3-containing gas is cooled to 55°C, the purified SO3-containing gas obtained after gas purification (purification method is the same as in Example 1) enters the top of the third absorption tower, and ultrapure water is passed into the bottom of the tower, and the sulfuric acid obtained by absorbing SO3 returns to the tower for circulation absorption, until the sulfuric acid concentration reaches 96wt% and then begins to discharge the tower. The operating temperature of the third absorption tower is 38°C, the operating pressure is 0.14MPa, and the resistivity of ultrapure water is 18MΩ·cm (25°C); the mass flow ratio of the purified SO3 gas and ultrapure water in the third absorption tower is 3.2:1; the mass flow ratio of sulfuric acid for circulating absorption, sulfuric acid out of the tower after absorption, and ultrapure water is 82:4.5:1. The 96wt% high-purity sulfuric acid produced in the third absorption tower enters the stripping tower, and the residual SO2 gas in the high-purity sulfuric acid is removed by ultrapure air. The mass flow ratio of ultrapure air to the high-purity sulfuric acid entering the tower is 450:1. The high-purity sulfuric acid after stripping enters the G4 grade filter, and after micro-particle filtration, electronic grade high-purity sulfuric acid is obtained by filling. The tail gas generated in the absorption tower, stripping tower and canning process is sent to the drying section of the oleum system for supplementary air. The wastewater generated by the cleaning and filling system is sent to the two-turn and two-absorption section of the oleum system for water replenishment in the absorption tower.

[0086] Example 3

[0087] The oleum raw material is prepared according to the following steps: liquid sulfur and dried air are introduced into the sulfur incinerator for high temperature (1020°C) incineration, the mass flow ratio of liquid sulfur to dried air is 1:3.3, the furnace gas at the outlet of about 1000°C is cooled by the fire tube boiler, the temperature drops to 405°C, and then enters the first stage of the converter to react at a temperature of 405°C. The gas at the outlet of the first stage enters the second stage of the converter to react at a temperature of 430°C. The gas at the outlet of the second stage is cooled by the hot-hot heat exchanger, the temperature drops to 425°C, and enters the third stage of the converter to react at a temperature of 425°C. The gas at the outlet of the third stage is cooled to 180°C by the cold-hot heat exchanger and the economizer in turn, and enters the first absorption tower to obtain oleum and the first gas phase product after the first absorption. The furnace gas (first gas phase product) coming out of the first absorption tower is heated to 415°C by the cold-hot heat exchanger and the hot-hot heat exchanger, and enters the fourth stage of the converter to react at a temperature of 415°C. The four-stage outlet gas enters the five-stage converter and reacts at a temperature of 415°C. The reacted gas is cooled to 170°C through a superheater and a coal economizer in turn, and enters the second absorption tower to obtain a fuming sulfuric acid product. Based on the weight of liquid sulfur, the amount of catalyst V2O5 in each converter is 9wt%, and the amount of co-catalyst K2SO4 is 1wt%. The outlet tail gas of the second absorption tower enters the tail gas treatment process, and after absorption (the absorbent is the same as in Example 1) and water washing, two-stage electric demisting, the SO2 concentration in the tail gas is ≤180ppm, and the acid mist is ≤5ppm, which meets the emission standards.

[0088] Electronic grade sulfuric acid is prepared according to the following steps: the oleum product is passed into an evaporator, and the SO3 gas is evaporated at 137°C. The remaining 103% oleum after evaporation enters the first absorption tower of the oleum system (oleum is introduced into the first absorption tower by an acid pump after evaporation, and the acid pump outlet pressure is controlled to be 0.35MPa by adjusting the acid pump current), and 105% oleum is continuously produced after absorbing SO3. The mass flow ratio of the 105% oleum entering the evaporator and the 103% oleum returned after evaporation is 1.2:1. After the evaporated SO3 gas is cooled to 55°C, the purified SO3 gas obtained after gas purification (purification method is the same as in Example 1) enters the top of the third absorption tower, and ultrapure water is passed into the bottom of the tower, and the sulfuric acid obtained by absorbing SO3 returns to the tower for circulation absorption, until the sulfuric acid concentration reaches 96wt% and then begins to discharge the tower. The operating temperature of the third absorption tower is 40℃, the operating pressure is 0.16MPa, and the resistivity of ultrapure water is 18MΩ·cm (25℃); the mass flow ratio of the purified SO3 gas and ultrapure water in the third absorption tower is 3.5:1; the mass flow ratio of sulfuric acid for circulating absorption, sulfuric acid out of the tower after absorption, and ultrapure water is 85:4.8:1. The 96wt% high-purity sulfuric acid produced in the third absorption tower enters the stripping tower, and the residual SO2 gas in the high-purity sulfuric acid is removed by ultrapure air. The mass flow ratio of ultrapure air to the high-purity sulfuric acid entering the tower is 460:1. The high-purity sulfuric acid after stripping enters the G4 grade filter, and after micro-particle filtration, electronic grade high-purity sulfuric acid is obtained by filling. The tail gas generated in the absorption tower, stripping tower and canning process is sent to the drying section of the oleum system for supplementary air. The wastewater generated by the cleaning and filling system is sent to the two-transfer and two-absorption section of the oleum system for water replenishment in the absorption tower.

[0089] Example 4

[0090] The oleum raw material is prepared according to the following steps: liquid sulfur and dried air are introduced into the sulfur incinerator for high temperature (1020°C) combustion, the mass flow ratio of liquid sulfur to dried air is 1:3.3, the furnace gas at the outlet of about 1050°C is cooled by the fire tube boiler, the temperature drops to 410°C, and then enters the first stage of the converter to react at a temperature of 410°C. The gas at the outlet of the first stage is cooled by the heat exchanger and enters the second stage of the converter to react at a temperature of 435°C. The gas at the outlet of the second stage is cooled by the hot-hot heat exchanger and the temperature drops to 430°C, and enters the third stage of the converter to react at a temperature of 430°C. The gas at the outlet of the third stage is cooled to 185°C by the cold-hot heat exchanger and the economizer in turn, and enters the first absorption tower to obtain oleum and the first gas phase product after the first absorption. The furnace gas (first gas phase product) coming out of the first absorption tower is heated to 430°C by the cold-hot heat exchanger and the hot-hot heat exchanger, and enters the fourth stage of the converter to react at a temperature of 430°C. The four-stage outlet gas enters the five-stage converter and reacts at a temperature of 430°C. The reacted gas is cooled to 175°C through a superheater and a coal economizer in turn, and enters the second absorption tower to obtain a fuming sulfuric acid product. Based on the weight of liquid sulfur, the amount of catalyst V2O5 in each converter is 7wt%, and the amount of co-catalyst K2SO4 is 0.7wt%. The outlet tail gas of the second absorption tower enters the tail gas treatment process, and after absorption (the absorbent is the same as in Example 1) and water washing, two-stage electric demisting, the SO2 concentration in the tail gas is ≤180ppm, and the acid mist is ≤5ppm, which meets the emission standards.

[0091] Electronic grade sulfuric acid is prepared according to the following steps: the oleum product is passed into an evaporator, and the SO3-containing gas is evaporated at 136°C. The remaining 103% oleum after evaporation enters the first absorption tower of the oleum system (oleum is introduced into the first absorption tower by an acid pump after evaporation, and the acid pump outlet pressure is controlled to be 0.35MPa by adjusting the acid pump current), and 105% oleum is continuously produced after absorbing SO3. The mass flow ratio of the 105% oleum entering the evaporator and the 103% oleum returned after evaporation is 1.22:1. After the evaporated SO3-containing gas is cooled to 55°C, the purified SO3-containing gas obtained after gas purification (purification method is the same as in Example 1) enters the top of the third absorption tower, and ultrapure water is passed into the bottom of the tower, and the sulfuric acid obtained by absorbing SO3 returns to the tower for circulation absorption, until the sulfuric acid concentration reaches 96wt% and then begins to discharge the tower. The operating temperature of the third absorption tower is 37°C, the operating pressure is 0.14MPa, and the resistivity of ultrapure water is 18MΩ·cm (25°C); the mass flow ratio of the purified SO3 gas and ultrapure water in the third absorption tower is 3.8:1; the mass flow ratio of the sulfuric acid for circulating absorption, the sulfuric acid out of the tower after absorption, and the ultrapure water is 90:5:1. The 96wt% high-purity sulfuric acid produced in the third absorption tower enters the stripping tower, and the residual SO2 gas in the high-purity sulfuric acid is removed by ultrapure air. The mass flow ratio of ultrapure air to the high-purity sulfuric acid entering the tower is 465:1. The high-purity sulfuric acid after stripping enters the G4 grade filter, and after micro-particle filtration, electronic grade high-purity sulfuric acid is obtained by filling. The tail gas generated in the absorption tower, stripping tower and canning process is sent to the drying section of the oleum system for supplementary air. The wastewater generated by the cleaning and filling system is sent to the two-turn and two-absorption section of the oleum system for water replenishment in the absorption tower.

[0092] Example 5

[0093] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that when preparing oleum, the types of co-catalysts were different, namely K2SO4 and Na2SO4. Specifically, "the amount of co-catalyst K2SO4 was 0.4wt% and the amount of Na2SO4 was 0.4wt%" was used to replace "the amount of co-catalyst K2SO4 was 0.8wt%". Oleum product was obtained, and then electronic grade high purity sulfuric acid was obtained.

[0094] Example 6

[0095] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that the type of the promoter was different when preparing oleum, and the promoter was Na2SO4. Specifically, "the amount of the promoter Na2SO4 was 0.8wt%" was replaced with "the amount of the promoter K2SO4 was 0.8wt%". The oleum product was obtained, and then the electronic grade high purity sulfuric acid was obtained.

[0096] Example 7

[0097] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that the evaporation temperature of 105% fuming sulfuric acid was different when preparing electronic grade sulfuric acid. Specifically, "evaporating SO3-containing gas at 147°C" was used to replace "evaporating SO3-containing gas at 134°C". Electronic grade high purity sulfuric acid was obtained.

[0098] Example 8

[0099] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that, when preparing electronic grade sulfuric acid, the evaporation temperature of 105% oleum and the temperature of the third absorption tower were different. Specifically, "evaporating SO3-containing gas at 147°C; the operating temperature of the third absorption tower was 60°C" was used to replace "evaporating SO3-containing gas at 134°C; the operating temperature of the third absorption tower was 35°C". Electronic grade high purity sulfuric acid was obtained.

[0100] Example 9

[0101] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that the evaporation temperature of 105% oleum and the pressure of the third absorption tower were different when preparing electronic grade sulfuric acid. Specifically, "evaporating SO3-containing gas at 147°C; the operating pressure of the third absorption tower was 0.3MPa" was used to replace "evaporating SO3-containing gas at 134°C; the operating pressure of the third absorption tower was 0.12MPa". Electronic grade high purity sulfuric acid was obtained.

[0102] Example 10

[0103] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that the temperatures of the first absorption and the second absorption were different when preparing oleum. Specifically, "the three-stage outlet gas was cooled to 210°C through the cold and hot heat exchanger and the economizer in turn, and entered the first absorption tower; the reacted gas was cooled to 200°C through the superheater and the economizer in turn, and entered the second absorption tower" was used to replace "the three-stage outlet gas was cooled to 190°C through the cold and hot heat exchanger and the economizer in turn, and entered the first absorption tower; the reacted gas was cooled to 180°C through the superheater and the economizer in turn, and entered the second absorption tower". The oleum product obtained only meets the first-class product index requirements of oleum.

[0104] Comparative Example 1

[0105] Electronic grade sulfuric acid was prepared according to the method of Example 1, except that oleum was not prepared, but liquid SO3 was used as raw material to prepare electronic grade sulfuric acid, and the liquid SO3 was evaporated at 60°C to produce gas containing SO3. The steps after evaporating the SO3 gas were the same as those in Example 1, and the electronic grade sulfuric acid product obtained did not meet the SEMI G4 standard requirements. In addition, the tail gas generated in the absorption tower, the stripping tower and the canning process contained SO2 and sulfuric acid mist, and the cleaning and filling system produced acidic wastewater, which could not meet GB26132-2010 "Emission Requirements for Pollutants in Sulfuric Acid Industry", and it was necessary to build a new waste gas treatment device and a wastewater treatment device, or collect the waste gas and wastewater and entrust a qualified enterprise to carry out centralized treatment.

[0106] Test Case

[0107] The contents of free SO3, ash, iron, arsenic and lead in the oleum product obtained in each embodiment were measured respectively. The results are shown in Table 1.

[0108] Table 1

[0109]

[0110] The metal cation content, anion content and the amount of particulate matter in the finished electronic-grade sulfuric acid products obtained in each embodiment and comparative example were measured respectively, and the results are shown in Table 2.

[0111] Table 2

[0112]

[0113] It can be seen from the results of Table 1 and Table 2 that the quality of oleum and electronic-grade sulfuric acid prepared by the method of the present invention in Examples 1-4 is relatively high. Moreover, the organic combination of the two production systems of oleum and electronic-grade sulfuric acid can not only realize the recycling of waste water and waste gas of the electronic-grade sulfuric acid system, but also reduce the air and absorption water consumption of the oleum system, and has better environmental protection and economic benefits compared with a single production system. Comparative Example 1 does not prepare oleum, but prepares electronic-grade sulfuric acid with liquid SO3 as raw material. The prepared electronic-grade sulfuric acid does not meet the SEMI G4 standard requirements, and the tail gas generated in the absorption tower, stripping tower and canning process contains SO2 and sulfuric acid mist, and the cleaning and filling system will produce acidic wastewater, which cannot meet GB26132-2010 "Requirements for Pollutant Emissions in Sulfuric Acid Industry".

[0114] In addition, the types of co-catalysts were changed in Examples 5 and 6. Although the oleum products obtained also met the standards of superior products, the ash content, iron content and lead content in the oleum products, as well as the metal cation content, anion content and the number of particles in the electronic-grade sulfuric acid products obtained were increased compared with Example 1. Example 10 increased the temperatures of the first absorption and the second absorption, and the oleum products obtained only met the first-class index requirements of oleum, and the metal cation content, anion content and the number of particles in the electronic-grade sulfuric acid products obtained were increased. In addition, Example 7 changed the evaporation temperature of 105% oleum when preparing electronic-grade sulfuric acid, Example 8 changed the evaporation temperature of 105% oleum and the temperature of the third absorption when preparing electronic-grade sulfuric acid, and Example 9 changed the evaporation temperature of 105% oleum and the pressure of the third absorption when preparing electronic-grade sulfuric acid. Although the electronic-grade sulfuric acid products obtained all met the SEMI G4 standard, compared with Example 1, the metal cation content, anion content and the number of particles in the electronic-grade sulfuric acid products obtained were increased. This shows that only when the type of co-catalyst, the conditions of the first absorption and the second absorption, the evaporation temperature of 105% oleum, and the conditions of the third absorption all meet a certain range can high-quality oleum and electronic-grade sulfuric acid be obtained.

[0115] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing electronic grade sulfuric acid, characterized in that: The preparation method comprises: S1, reacting liquid sulfur and air and performing two-turn and two-absorption to obtain oleum and the first tail gas; S2, evaporating the oleum to obtain a SO3-containing gas and evaporated oleum, wherein the SO3-containing gas is purified, the purified SO3-containing gas is subjected to a third absorption with ultrapure water, and the obtained high-purity sulfuric acid is de-SO2-ed and filtered to obtain electronic grade sulfuric acid; S3, returning the evaporated fuming sulfuric acid to S1 for the two-turn and two-absorption process.

2. The preparation method according to claim 1, characterized in that: The content of free SO3 in the oleum is 17-36wt%, preferably 20-25wt%.

3. The preparation method according to claim 1 or 2, characterized in that: The two-conversion and two-absorption process comprises: subjecting the SO2-containing gas obtained by the reaction to a first conversion reaction, subjecting the obtained gas after the first conversion reaction to a first absorption with an absorbent, obtaining oleum and a first gas phase product after the first absorption, subjecting the first gas phase product to a second conversion reaction, and subjecting the obtained second gas phase product to a second absorption with the oleum after the first absorption; Preferably, the process of the first conversion reaction comprises: subjecting the SO2-containing gas to a first-stage conversion reaction, a second-stage conversion reaction and a third-stage conversion reaction in sequence; Preferably, the temperatures of the first-stage conversion reaction, the second-stage conversion reaction and the third-stage conversion reaction are 380-430° C., 410-460° C. and 400-450° C. respectively; Preferably, the process of the second conversion reaction comprises: subjecting the first gas phase product to a four-stage conversion reaction and a five-stage conversion reaction in sequence; Preferably, the temperatures of the four-stage conversion reaction and the five-stage conversion reaction are 390-440° C. and 400-450° C., respectively; Preferably, the first-stage conversion reaction, the second-stage conversion reaction, the third-stage conversion reaction, the fourth-stage conversion reaction and the fifth-stage conversion reaction are each independently carried out in the presence of a catalyst and a co-catalyst; Preferably, the catalyst is selected from vanadium-based catalysts, preferably V2O5; Preferably, the promoter is selected from alkali metal sulfates, preferably K2SO4 and / or Na2SO4, preferably K2SO4; Preferably, in the one-stage conversion reaction, the two-stage conversion reaction, the three-stage conversion reaction, the four-stage conversion reaction and the five-stage conversion reaction, based on the weight of the liquid sulfur, the amount of the catalyst used is independently 6-9wt%, and the amount of the co-catalyst used is independently 0.5-1wt%.

4. The preparation method according to claim 3, characterized in that: The first absorption temperature is less than or equal to 200° C. Preferably, the second absorption temperature is less than or equal to 190°C.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In S2, the evaporation temperature is 108-147°C, preferably 131-141°C; Preferably, the content of free SO3 in the fuming sulfuric acid after evaporation is 8-27wt%, preferably 10-15wt%; Preferably, the mass flow ratio of the evaporated oleum returned to S1 to the oleum is 1:(1.1-1.3).

6. The preparation method according to any one of claims 1 to 5, characterized in that: In S2, the content of sulfuric acid in the high-purity sulfuric acid is 95-97wt%; Preferably, the third absorption process comprises: contacting the purified SO3-containing gas with the ultrapure water, and cyclically absorbing the purified SO3-containing gas with the obtained acid solution to obtain the high-purity sulfuric acid; Preferably, the conditions of the third absorption include: temperature of 30-60°C, preferably 30-45°C; pressure of 0.1-0.3MPa, preferably 0.1-0.2MPa; Preferably, in the third absorption, the mass flow ratio of the purified SO3-containing gas to the ultrapure water is (3-4): 1; Preferably, in the third absorption, the mass flow ratio of the circulating acid solution, the high-purity sulfuric acid and the ultrapure water is (80-90):(4-5):

1.

7. The preparation method according to any one of claims 1 to 6, characterized in that: In S2, the method for removing SO2 includes: stripping the high-purity sulfuric acid with ultra-pure air; wherein the mass flow ratio of the ultra-pure air to the high-purity sulfuric acid is (420-470):

1.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The preparation method further comprises: after the high-purity sulfuric acid is de-SO2ed and filtered, it is also bottled to obtain electronic-grade sulfuric acid, second tail gas and waste water; wherein, The second tail gas is returned to S1 to mix with air and react with liquid sulfur; the waste water is returned to S1 to mix with the absorbent to perform the first absorption on the gas after the first conversion reaction. Preferably, the preparation method further comprises: absorbing and washing the first tail gas in sequence; wherein the absorption liquid is a mixed liquid containing Na2SO4, Na2SO3 and NaHSO3.

9. A device for preparing electronic grade sulfuric acid, characterized in that: The device comprises: a fuming sulfuric acid system and an electronic grade sulfuric acid system connected to each other; wherein, The oleum system comprises: a sulfur incinerator and a two-rotation and two-absorption unit connected in sequence; The electronic grade sulfuric acid system comprises: an evaporator, a purification system, a third absorption tower, a stripping tower and a filter which are connected in sequence; The liquid phase outlet of the evaporator is in communication with the two-turn and two-absorption unit, and is used to return the evaporated oleum to the oleum system to continue producing the oleum.

10. The device according to claim 9, characterized in that The two-conversion and two-absorption unit comprises: a first conversion system, a first absorption tower, a second conversion system and a second absorption tower; Preferably, the first conversion system comprises: a first converter, a first superheater, a second converter, a first heat exchanger, a third converter and a second heat exchanger connected in sequence; Preferably, the second conversion system comprises: a fourth converter, a second superheater, a fifth converter and a third superheater connected in sequence; Preferably, a third heat exchanger is further provided between the first absorption tower and the second conversion system; Preferably, the oleum system further comprises: a dryer and a cooler; wherein, The dryer is connected to the inlet of the sulfur incinerator and is used to dry the air. The dried air enters the sulfur incinerator to react with liquid sulfur. The cooler is arranged between the sulfur incinerator and the first conversion system.

11. The device according to claim 9 or 10, characterized in that The device also includes a filling system; Preferably, the gas phase outlets of the filling system and the stripping tower are respectively connected to the inlet of the dryer, so as to send the waste gas flowing out of the filling system and the stripping tower into the dryer in the oleum system for use as supplementary air.

12. The device according to any one of claims 9 to 11, characterized in that: The device also includes a tail gas treatment system for treating the tail gas generated by the oleum system; the tail gas treatment system includes a tail gas absorption tower, a water washing tower and an electric demister; wherein, The tail gas absorption tower is used to remove SO2 and SO3 in the tail gas generated by the oleum system; the water scrubber is used to further remove SO2 and SO3 in the tail gas, as well as the entrained NaHSO3; the electric demister is used to remove residual acid mist.

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