Preparation device and preparation method of electronic-grade sulfuric acid

Abstract

The invention discloses a preparation device and a preparation method of electronic-grade sulfuric acid. The device mainly comprises a sulfuric acid storage tank, a wiped-film evaporator, a liquid storage tank, a sulfur trioxide absorption tank, a packing absorption tower, a heat exchanger, a filter and the like. A fuming sulfuric acid storage tank is conveyed to a wiped-film evaporator through a diaphragm pump to evaporate sulfur trioxide, the evaporated sulfur trioxide is subjected to circular absorption reaction to generate sulfuric acid, and electronic-grade sulfuric acid is obtained after filtration. The method is simple in technological process, low in evaporation process temperature, high in efficiency and low in metal residue, and high-quality electronic-grade sulfuric acid is obtained.

Description

Technical Field

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

[0002] Electronic grade sulfuric acid, also known as high purity sulfuric acid or ultrapure sulfuric acid, is an indispensable key basic chemical reagent in the development of microelectronics technology. It is widely used in the assembly and processing of semiconductors and ultra-large-scale integrated circuits. It is the largest electronic chemical used in chip manufacturing processes. It has high quality requirements for products, and the metal ion content must reach 10 -12 Order of magnitude.

[0003] At present, the commonly used preparation processes for electronic grade sulfuric acid are mainly distillation and gas absorption. The vast majority of domestic electronic grade sulfuric acid is produced by distillation. This method can be divided into atmospheric distillation and vacuum distillation. The atmospheric distillation temperature is as high as about 330°C, and the equipment material requirements are relatively high; the vacuum distillation pressure is 1.33~2.67 kPa, and the temperature is 175~190°C. The distillation process has many disadvantages, such as high cost, high energy consumption, and some impurities are difficult to remove. The waste gas and sulfuric acid mist generated during the production process are not conducive to environmental protection and are harmful to the human body. It is only suitable for small-scale production. The product quality of the gas absorption method is relatively stable, the impurity removal is relatively simple, the removal rate is high, and the energy consumption is also greatly reduced compared with the distillation method. Compared with the distillation method, the gas absorption method is more suitable for large-scale industrial production.

[0004] CN116281877A discloses a method for preparing electronic-grade sulfuric acid. The invention adopts distillation and impurity removal technology, ultrapure water absorption technology, distillation and light removal technology, and distillation and heavy removal technology to propose an optimized G1-G5 electronic-grade sulfuric acid preparation method; the SO3 distillation system and the sulfuric acid distillation device of the invention are both thermally coupled, and the ultrapure water or sulfuric acid solution in the SO3 absorption device countercurrently absorbs the high-purity gas phase SO3 to release heat, which is used for coupled heat exchange with the SO3 liquid phase feed to reduce the energy consumption of the device; the SO3 distillation system of the invention adopts a heat pump distillation design, which can save a lot of energy consumption compared with the traditional distillation system and has higher economy.

[0005] CN116281876A discloses a method and production system for preparing electronic grade sulfuric acid, which includes the following steps: sulfur trioxide is sent to a heating tank for heating to generate gaseous sulfur trioxide, which is then sent to an absorption tank for filtration and rectification to generate sulfuric acid; it is sent to a blowing tower for impurity removal; and the finished electronic grade sulfuric acid is obtained and sent to a finished product storage tank for storage. The method of the present invention, which uses sulfur trioxide gasification and ultrapure water to react to finally obtain electronic grade sulfuric acid, has low energy consumption.

[0006] CN115448259 A discloses a method for preparing electronic grade sulfuric acid, which specifically comprises preparing fuming sulfuric acid; preparing gaseous sulfur trioxide; purifying sulfur trioxide, absorbing and mixing to obtain electronic grade sulfuric acid. Summary of the invention

[0007] The purpose of the present invention is to provide a preparation device and a preparation method thereof which have simple process flow, low evaporation process temperature, high efficiency, low metal residue, and can obtain high-quality electronic grade sulfuric acid.

[0008] The main technical scheme of the present invention is: a device for preparing electronic grade sulfuric acid, characterized in that the device comprises a sulfuric acid evaporation unit, an absorption unit and a filtration unit; the sulfuric acid evaporation unit comprises a scraped film evaporator, the absorption unit comprises a sulfur trioxide absorption tank, a packed absorption tower and a heat exchanger, and the filtration unit comprises a filter; the scraped film evaporator is sequentially connected to the sulfur trioxide absorption tank, the packed absorption tower and the filter.

[0009] The present invention also provides a method for preparing electronic-grade sulfuric acid using the above-mentioned preparation device, wherein the preparation raw material is subjected to sulfur trioxide evaporation in a scraped film evaporator, the evaporated sulfur trioxide is absorbed and reacted in a sulfur absorption tank and a packed absorption tower to generate sulfuric acid, and the electronic-grade sulfuric acid is obtained after filtering through a filter.

[0010] Generally, the preparation process of the electronic grade sulfuric acid is as follows: the preparation raw materials in the sulfuric acid storage tank are transported to the scraped film evaporator by a diaphragm pump to evaporate sulfur trioxide, the remaining sulfuric acid is stored in the liquid storage tank, and after a certain liquid level, it is returned to the sulfuric acid storage tank by a diaphragm pump, and the evaporated sulfur trioxide enters the bottom of the sulfur trioxide absorption tank for absorption to prepare sulfuric acid, and the sulfur trioxide gas that is not completely absorbed in the sulfur trioxide absorption tank is reabsorbed in the packed absorption tower using the refluxed sulfuric acid, and then discharged into the tail gas absorption bottle for alkali absorption, the sulfuric acid at the bottom of the sulfur trioxide absorption tank is cooled by a heat exchanger, and the prepared sulfuric acid is transported to the top of the packed absorption tower by a diaphragm pump for reflux when the concentration is unqualified, and is absorbed again with the sulfur trioxide gas, and is transported to the crude electronic grade sulfuric acid receiving tank when the sulfuric acid concentration is qualified, and the crude electronic grade sulfuric acid enters the filter through the diaphragm pump, and the electronic grade sulfuric acid is obtained after filtration.

[0011] Furthermore, the scraped film evaporator uses a circulating heating pump to heat and evaporate sulfur trioxide.

[0012] Furthermore, the scraping film evaporation pressure is 2-5 kPa, and the evaporation temperature is 30-50°C.

[0013] Furthermore, the filter membrane of the filter is made of polytetrafluoroethylene.

[0014] Further preferably, the filter determines the pore size of the filter membrane according to the grade of different electronic grade sulfuric acid. By using polytetrafluoroethylene filter membranes with different pore sizes to remove suspended particles, different grades of electronic grade sulfuric acid can be obtained.

[0015] Furthermore, the preparation raw material is oleum or sulfuric acid, preferably oleum.

[0016] Furthermore, the absorption process is ultrapure water or low-concentration electronic grade sulfuric acid.

[0017] Furthermore, the absorption process is cyclic absorption. Compared with the traditional fuming sulfuric acid evaporation method, the present invention has low temperature and high sulfur trioxide escape efficiency. At the same time, when sulfur trioxide escapes in the scraping film evaporation method, the amount of entrained liquid is small, so the amount of metal ions in sulfuric acid carried out is smaller, and the prepared electronic grade sulfuric acid has higher quality and lower metal ion concentration.

[0018] The process flow of the invention is simple, the evaporation process has low temperature, high efficiency and low metal residue, and high-quality electronic grade sulfuric acid is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a connection diagram of an electronic grade sulfuric acid preparation device according to an embodiment of the present invention.

[0020] Figure 1 In the middle, 1-oleum storage tank; 2, 6, 10, 12-diaphragm pumps; 3-wiped film evaporator; 4-liquid storage tank; 5-circulating heating pump; 7-sulfur trioxide absorption tank; 8-packed absorption tower; 9-heat exchanger; 11-coarse electronic grade sulfuric acid receiving tank; 13-filter; 14-tail gas absorption bottle. Implementation

[0021] The present invention is described in detail below in conjunction with embodiments and drawings. Example 1

[0022] A preparation device for electronic grade sulfuric acid Figure 1 , mainly comprising a sulfuric acid evaporation unit, an absorption unit and a filtration unit; the sulfuric acid evaporation unit comprises a scraped film evaporator (3), the absorption unit comprises a sulfur trioxide absorption tank (7), a packed absorption tower (8) and a heat exchanger (9), and the filtration unit comprises a filter (13); the scraped film evaporator (3) is sequentially connected to the sulfur trioxide absorption tank (7), the packed absorption tower (8) and the filter (13).

[0023] The embodiment also includes a fuming sulfuric acid storage tank (1), a diaphragm pump (2, 6, 10, 12), a liquid storage tank (4), a circulating heating pump (5), a crude electronic grade sulfuric acid receiving tank (11) and a tail gas absorption bottle (14). Example 2

[0024] Reference Figure 1 The process of preparing electronic grade sulfuric acid using the preparation device of the embodiment is as follows: the circulating heating pump (5) is turned on to raise the temperature of the heat transfer oil to 30-50°C, a vacuum system is connected to the outlet of the tail gas absorption bottle (14), and the absolute pressure of the vacuum degree of the system is controlled to be 2-5 kPa. Ultrapure water is placed in the sulfur trioxide absorption tank (7) to a liquid level of one-third, and the diaphragm pump (10) is turned on to spray the ultrapure water from the top of the packed absorption tower (8) for reflux. When the pressure and temperature of the entire system are stable, the fuming sulfuric acid in the sulfuric acid storage tank (1) is metered by the diaphragm pump (2) and transported to the scraped film evaporator (3) to evaporate sulfur trioxide. The remaining sulfuric acid is stored in the liquid storage tank (4). When the liquid level in the liquid storage tank (4) reaches two-thirds, the diaphragm pump (6) is turned on to return the sulfuric acid to the sulfuric acid storage tank (1), and the evaporated sulfur trioxide enters the bottom of the absorption tank (7) for absorption to prepare sulfuric acid. The sulfur trioxide absorption tank (7) does not absorb completely. The sulfur trioxide gas is reabsorbed by the refluxed sulfuric acid in the packing absorption tower (8) and then discharged to the tail gas absorption bottle (14) for alkaline absorption. The sulfuric acid at the bottom of the sulfur trioxide absorption tank (7) is cooled to 3-5°C by the heat exchanger (9). The prepared sulfuric acid is transported to the top of the packing absorption tower (8) by a diaphragm pump (10) for reflux when the concentration is unqualified, and is reabsorbed with the sulfur trioxide gas. When the sulfuric acid concentration is qualified, it is transported to the coarse electronic grade sulfuric acid receiving tank (11). The coarse electronic grade sulfuric acid enters the filter (13) through the diaphragm pump (12). The filter membrane diameters are 50nm, 5nm and 2nm respectively, and electronic grade sulfuric acid of different grades is obtained. The specific preparation process data are shown in Table 1, and the quality of the sulfuric acid product is shown in Table 2.

[0025] Table 1 Process conditions for the preparation of sulfuric acid

[0026] Table 2 Product analysis of sulfuric acid

[0027]

[0028] Comparative Example As in the above embodiment, the wiped film evaporator (3) is replaced with a common vacuum distillation apparatus, and the other operation processes are the same as in the embodiment. The specific preparation process data are shown in Table 3, and the quality of the sulfuric acid product is shown in Table 4.

[0029] Table 3 Sulfuric acid preparation process conditions under comparative conditions

[0030] Table 4 Product analysis of sulfuric acid under comparative conditions

[0031] From the perspective of the sulfuric acid preparation efficiency in the examples and comparative examples, under the same preparation time conditions, it is obvious that the sulfuric acid prepared by the scraped film evaporator has a high concentration and high equipment efficiency. At the same time, from the perspective of the preparation quality of sulfuric acid, the residual amount of sulfuric acid metal ions prepared by the scraped film evaporator is lower, and the quality of sulfuric acid is higher. It is also found from the data of the examples and comparative examples that the amount of particulate matter has basically nothing to do with the sulfuric acid evaporation process in the preparation process, but has a greater relationship with the pore size of the filter membrane.

Claims

1. A device for preparing electronic grade sulfuric acid, characterized in that The device comprises a sulfuric acid evaporation unit, an absorption unit and a filtration unit; the sulfuric acid evaporation unit comprises a scraped film evaporator, the absorption unit comprises a sulfur trioxide absorption tank, a packed absorption tower and a heat exchanger, and the filtration unit comprises a filter; the scraped film evaporator is sequentially connected to the sulfur trioxide absorption tank, the packed absorption tower and the filter.

2. A method for preparing electronic grade sulfuric acid, characterized in that The preparation device according to claim 1 is used to prepare the raw material and evaporate sulfur trioxide through a scraped film evaporator. The evaporated sulfur trioxide is absorbed by a sulfur absorption tank and a packed absorption tower to generate sulfuric acid, which is filtered through a filter to obtain electronic grade sulfuric acid.

3. The preparation method according to claim 2, characterized in that The preparation process is as follows: the preparation raw materials in the sulfuric acid storage tank are transported to the scraped film evaporator through a diaphragm pump to evaporate sulfur trioxide, and the remaining sulfuric acid is stored in a liquid storage tank. After a certain liquid level, it is returned to the sulfuric acid storage tank through a diaphragm pump, and the evaporated sulfur trioxide enters the bottom of the sulfur trioxide absorption tank for absorption to prepare sulfuric acid. The sulfur trioxide gas that is not completely absorbed in the sulfur trioxide absorption tank is reabsorbed in the packed absorption tower using the refluxed sulfuric acid, and then discharged into the tail gas absorption bottle for alkali absorption. The sulfuric acid at the bottom of the sulfur trioxide absorption tank is cooled by a heat exchanger, and the prepared sulfuric acid is transported to the top of the packed absorption tower for reflux when the concentration is unqualified by a diaphragm pump, and is absorbed again with the sulfur trioxide gas. When the sulfuric acid concentration is qualified, it is transported to the coarse electronic grade sulfuric acid receiving tank, and the coarse electronic grade sulfuric acid enters the filter through a diaphragm pump, and electronic grade sulfuric acid is obtained after filtration.

4. The preparation method according to claim 3, characterized in that The wiped film evaporator uses a circulating heat pump to heat and evaporate sulfur trioxide.

5. The preparation method according to claim 3, characterized in that The pressure of scraping film evaporation is 2~5 kPa, and the evaporation temperature is 30~50℃.

6. The preparation method according to claim 3, characterized in that The filter membrane of the filter is made of polytetrafluoroethylene.

7. The preparation method according to claim 6, characterized in that The filter determines the pore size of the filter membrane according to the grade of different electronic grade sulfuric acid.

8. The preparation method according to claim 3, characterized in that The raw material for preparation is oleum or sulfuric acid, preferably oleum.

9. The preparation method according to claim 3, characterized in that The absorption process uses ultrapure water or low concentration electronic grade sulfuric acid.

10. The preparation method according to claim 3, characterized in that The absorption process is cyclic absorption.

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