Multi-stage evaporation and purification combined electronic-grade sulfuric acid production process

Abstract

The invention discloses a multi-stage evaporation and purification combined electronic-grade sulfuric acid production process. The process comprises the following steps: step 1, raw material pretreatment; step 2, first-stage evaporation; step 3, secondary evaporation; step 4, preparing sulfur trioxide; step 5, purifying sulfur trioxide; step 6, absorption with ultra-pure sulfuric acid; step 7, heating and degassing; step 8, performing precise filtration; and step 9, product sub-packaging. According to the multi-stage evaporation and purification combined electronic-grade sulfuric acid production process provided by the invention, efficient preparation of electronic-grade sulfuric acid is realized through the synergistic effect of the multi-stage evaporation and purification steps; the process has the remarkable advantages of low energy consumption, high impurity removal rate, stable product quality and the like, the purity of the prepared electronic-grade sulfuric acid can reach an extremely high level, and metal ions and particulate matters can meet strict standards of the high-end electronic industry; meanwhile, the process is easy and convenient to operate, industrial production is easy to achieve, and remarkable economic benefits and social benefits are achieved.

Description

Technical Field

[0001] This invention belongs to the field of electronic sulfuric acid production technology, specifically a multi-stage evaporation and purification process for producing electronic-grade sulfuric acid. Background Technology

[0002] Electronic-grade sulfuric acid, a key fundamental chemical reagent in the development of microelectronics technology, has extremely stringent purity requirements, necessitating strict control over the content of impurities such as metal ions, particulate matter, and reducing agents. Traditional processes, such as distillation, are energy-intensive and have limited effectiveness in impurity removal; some gas absorption methods are complex, with stringent requirements on equipment materials and operating conditions, resulting in high production costs and inconsistent product quality. Therefore, developing a highly efficient, low-energy-consumption process for producing electronic-grade sulfuric acid with a high impurity removal rate is of significant practical importance.

[0003] Based on this, a multi-stage evaporation and purification process for producing electronic-grade sulfuric acid was designed. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the prior art, the present invention provides an electronic-grade sulfuric acid production process that combines multi-stage evaporation and purification, effectively solving the problems mentioned in the background.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a multi-stage evaporation and purification process for producing electronic-grade sulfuric acid, comprising the following steps:

[0006] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into a pretreatment tank and add a potassium permanganate solution with a mass fraction of 8%-12%. The amount of potassium permanganate solution added is 0.3%-0.7% of the mass of industrial-grade sulfuric acid.

[0007] Turn on the stirring device and stir at a speed of 80-120 rpm for 25-35 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid and oxidize them into harmless substances.

[0008] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.2-0.4 MPa, an evaporation temperature of 140-160℃, and an evaporation pressure of 0.04-0.06 MPa.

[0009] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0010] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator. The heating medium is saturated steam, with a steam pressure range of 0.3-0.5 MPa, an evaporation temperature of 170-190℃, and an evaporation pressure of 0.07-0.09 MPa.

[0011] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0012] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to the pyrolysis reactor. Dry air is introduced into the reactor; the air must be precisely filtered to remove impurities, with a particulate matter content ≤0.01μm. Simultaneously, the reactor temperature is raised to 750-850℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0013] ;

[0014] The mixed gas (SO3, H2O, and air) produced by the reaction first enters the condenser heat exchanger, where it is condensed at 120-130℃ to remove most of the water vapor. The remaining gas containing SO3 is temporarily stored in a gas buffer tank.

[0015] Step 5, Sulfur trioxide purification: The SO3-containing gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%. The adsorber adsorbs the trace amounts of moisture and sulfuric acid droplets remaining in the gas at 80-90℃.

[0016] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 90-110℃. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0017] Then, highly purified nitrogen gas with a purity of not less than 99.999% is introduced at a flow rate of 8-12 L / min. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0018] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, ultrapure sulfuric acid with a mass fraction of 95%-98% is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0019] The absorption temperature is 40-50℃ and the absorption pressure is 0.12-0.18MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0020] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transferred to the heating and degassing tank. The solution temperature is raised to 55-65℃ by steam heating and maintained for 25-35 minutes to remove dissolved gases from the solution.

[0021] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.01-0.1μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.15-0.25MPa, and the filtration speed is 4-6L / min.

[0022] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done with ultrapure water, and the drying temperature is 110-130℃ for 1.5-2.5 hours.

[0023] Preferably, in step one, the raw material pretreatment, the stirring temperature is 25-35℃.

[0024] Preferably, in step four, the preparation of sulfur trioxide, the pyrolysis reaction temperature is controlled at 750-850℃ and the condensation temperature is 120-130℃ to ensure that sulfuric acid is fully pyrolyzed and to prevent SO3 from combining with water to form sulfuric acid.

[0025] Preferably, in step five, sulfur trioxide purification, the operating pressure of the demister is 0.08-0.12 MPa to ensure the demister effect; the silica gel in the adsorber needs to be regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0026] Preferably, in step seven, heating and degassing, the heating process is carried out by a slow heating method, with a heating rate of 4-6℃ / min, in order to avoid local overheating of the solution and precipitation of impurities due to excessively rapid temperature changes.

[0027] Preferably, in step eight, precision filtration, the filter membrane is backwashed periodically during the filtration process. The backwashing pressure is 0.25-0.35 MPa and the backwashing time is 8-12 minutes to ensure the filtration performance and service life of the filter membrane.

[0028] Preferably, in step nine, product packaging, the cleanliness of the ultra-clean workbench reaches the Class 100 standard, and the ambient temperature and humidity are strictly controlled during the packaging process, with the temperature at 23-27℃ and the humidity at 40-60%, to avoid product contamination.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The electronic-grade sulfuric acid production process provided by this invention, which combines multi-stage evaporation and purification, achieves efficient preparation of electronic-grade sulfuric acid through the synergistic effect of multi-stage evaporation and purification steps. This process has significant advantages such as low energy consumption, high impurity removal rate, and stable product quality. The purity of the prepared electronic-grade sulfuric acid can reach extremely high levels, and both metal ions and particulate matter can meet the stringent standards of the high-end electronics industry. At the same time, the process is simple to operate and easy to implement for industrial production, resulting in significant economic and social benefits. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0032] In the attached diagram:

[0033] Figure 1 A flowchart illustrating an exemplary embodiment of the present invention is shown; Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides a multi-stage evaporation and purification process for producing electronic-grade sulfuric acid, comprising the following steps:

[0036] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into a pretreatment tank and add a potassium permanganate solution with a mass fraction of 8%-12%. The amount of potassium permanganate solution added is 0.3%-0.7% of the mass of industrial-grade sulfuric acid.

[0037] Turn on the stirring device and stir at a speed of 80-120 rpm for 25-35 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid and oxidize them into harmless substances.

[0038] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.2-0.4 MPa, an evaporation temperature of 140-160℃, and an evaporation pressure of 0.04-0.06 MPa.

[0039] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0040] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator. The heating medium is saturated steam, with a steam pressure range of 0.3-0.5 MPa, an evaporation temperature of 170-190℃, and an evaporation pressure of 0.07-0.09 MPa.

[0041] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0042] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to the pyrolysis reactor. Dry air is introduced into the reactor; the air must be precisely filtered to remove impurities, with a particulate matter content ≤0.01μm. Simultaneously, the reactor temperature is raised to 750-850℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0043] ;

[0044] The mixed gases SO3, H2O and air produced by the reaction first enter the condenser heat exchanger, where they are condensed at 120-130℃ to remove most of the water vapor. The remaining SO3-containing gas is temporarily stored in the gas buffer tank.

[0045] Step 5, Sulfur trioxide purification: The SO3-containing gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%. The adsorber adsorbs the trace amounts of moisture and sulfuric acid droplets remaining in the gas at 80-90℃.

[0046] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 90-110℃. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0047] Then, highly purified nitrogen gas with a purity of not less than 99.999% is introduced at a flow rate of 8-12 L / min. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0048] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, ultrapure sulfuric acid with a mass fraction of 95%-98% is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0049] The absorption temperature is 40-50℃ and the absorption pressure is 0.12-0.18MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0050] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transferred to the heating and degassing tank. The solution temperature is raised to 55-65℃ by steam heating and maintained for 25-35 minutes to remove dissolved gases from the solution.

[0051] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.01-0.1μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.15-0.25MPa, and the filtration speed is 4-6L / min.

[0052] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done with ultrapure water, and the drying temperature is 110-130℃ for 1.5-2.5 hours.

[0053] In step one of this embodiment, the raw material pretreatment is carried out at a stirring temperature of 25-35℃.

[0054] In step four of this embodiment, the preparation of sulfur trioxide involves controlling the pyrolysis reaction temperature at 750-850℃ and the condensation temperature at 120-130℃ to ensure that sulfuric acid is fully pyrolyzed and to prevent SO3 from combining with water to form sulfuric acid.

[0055] In step five of this embodiment, sulfur trioxide purification, the operating pressure of the demister is 0.08-0.12 MPa to ensure the demister effect; the silica gel in the adsorber needs to be regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0056] In step seven of this embodiment, heating and degassing are carried out by slowly increasing the temperature at a rate of 4-6°C / min to avoid local overheating of the solution and precipitation of impurities due to rapid temperature changes.

[0057] Step eight of this embodiment is precision filtration. During the filtration process, the filter membrane is backwashed periodically. The backwashing pressure is 0.25-0.35 MPa and the backwashing time is 8-12 minutes to ensure the filtration performance and service life of the filter membrane.

[0058] In step nine of this embodiment, product packaging, the cleanliness level of the ultra-clean workbench reaches Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled, with the temperature at 23-27℃ and the humidity at 40-60%, to avoid product contamination.

[0059] Example 1:

[0060] A multi-stage evaporation and purification process for producing electronic-grade sulfuric acid includes the following steps:

[0061] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into the pretreatment tank and add an 8% (w / w) potassium permanganate solution. The amount of potassium permanganate solution added is 0.3% of the mass of the industrial-grade sulfuric acid.

[0062] Turn on the stirring device, set the stirring speed to 80 rpm, and stir for 25 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid, oxidizing them into harmless substances;

[0063] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.2 MPa, an evaporation temperature of 140℃, and an evaporation pressure of 0.04 MPa.

[0064] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0065] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator, the heating medium is saturated steam, the steam pressure range is 0.3 MPa, the evaporation temperature is 170℃, and the evaporation pressure is 0.07 MPa.

[0066] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0067] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to a pyrolysis reactor. Dry air is introduced into the reactor and filtered precisely until the particulate matter content is ≤0.01μm. The reactor temperature is then raised to 750℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0068]

[0069] The mixed gas produced by the reaction enters the condenser heat exchanger, where it is condensed and dehydrated at 120°C. The remaining gas containing SO3 enters the gas buffer tank.

[0070] Step 5, Sulfur trioxide purification: The gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%, and adsorbs trace amounts of moisture and sulfuric acid droplets at 80℃.

[0071] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 90°C. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0072] Then, highly purified nitrogen gas with a purity of not less than 99.999% and a flow rate of 8 L / min is introduced. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0073] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, 96.5% ultrapure sulfuric acid is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0074] The absorption temperature is 40℃ and the absorption pressure is 0.12MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0075] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transported to the heating and degassing tank. The solution temperature is raised to 55°C by steam heating and maintained for 25 minutes to remove the dissolved gas from the solution.

[0076] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.03 μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.15 MPa and the filtration speed is 4 L / min.

[0077] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done by rinsing with ultrapure water, and the drying temperature is 110℃ for 1.5 hours.

[0078] In step one of this embodiment, the raw material pretreatment is carried out at a stirring temperature of 25°C.

[0079] In step four of this embodiment, the preparation of sulfur trioxide involves a pyrolysis reaction at a temperature of 750°C and a condensation temperature of 120°C.

[0080] In step five of this embodiment, sulfur trioxide purification, the operating pressure of the demister is 0.08 MPa to ensure the demister effect; the silica gel in the adsorber is regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0081] In step seven of this embodiment, heating and degassing are carried out by slowly increasing the temperature at a rate of 4°C / min to avoid local overheating of the solution and precipitation of impurities due to rapid temperature changes.

[0082] Step eight of this embodiment is precision filtration. During the filtration process, the filter membrane is backwashed periodically. The backwashing pressure is 0.25 MPa and the backwashing time is 8 minutes to ensure the filtration performance and service life of the filter membrane.

[0083] In step nine of this embodiment, product packaging, the cleanliness level of the ultra-clean workbench reaches Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled at 23°C and 45% to avoid product contamination.

[0084] Example 2:

[0085] A multi-stage evaporation and purification process for producing electronic-grade sulfuric acid includes the following steps:

[0086] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into the pretreatment tank and add a 12% (w / w) potassium permanganate solution. The amount of potassium permanganate solution added is 0.7% of the mass of the industrial-grade sulfuric acid.

[0087] Turn on the stirring device, set the stirring speed to 120 rpm, and stir for 35 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid, oxidizing them into harmless substances;

[0088] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.4 MPa, an evaporation temperature of 160℃, and an evaporation pressure of 0.06 MPa.

[0089] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0090] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator with saturated steam as the heating medium. The steam pressure range is 0.5 MPa, the evaporation temperature is 190℃, and the evaporation pressure is 0.09 MPa.

[0091] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0092] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to the pyrolysis reactor. Dry air is introduced into the reactor and filtered precisely until the particulate matter content is ≤0.01μm. The reactor temperature is raised to 850℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0093]

[0094] The mixed gas produced by the reaction enters the condenser heat exchanger, where it is condensed and dehydrated at 130°C. The remaining gas containing SO3 enters the gas buffer tank.

[0095] Step 5, Sulfur trioxide purification: The gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999% to adsorb trace amounts of moisture and sulfuric acid droplets at 90℃.

[0096] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 110°C. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0097] Then, highly purified nitrogen gas with a purity of not less than 99.999% and a flow rate of 12 L / min is introduced. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0098] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, 97% ultrapure sulfuric acid is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0099] The absorption temperature is 50℃ and the absorption pressure is 0.18MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0100] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transported to the heating and degassing tank. The solution temperature is raised to 65°C by steam heating and maintained for 35 minutes to remove the dissolved gas from the solution.

[0101] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.07 μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.25 MPa and the filtration speed is 6 L / min.

[0102] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done by rinsing with ultrapure water, and the drying temperature is 130℃ for 2.5 hours.

[0103] In step one of this embodiment, the raw material pretreatment is carried out at a stirring temperature of 35°C.

[0104] In step four of this embodiment, the preparation of sulfur trioxide involves a pyrolysis reaction at 850°C and a condensation temperature of 130°C.

[0105] In step five of this embodiment, sulfur trioxide purification, the operating pressure of the demister is 0.12 MPa to ensure the demister effect; the silica gel in the adsorber is regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0106] In step seven of this embodiment, heating and degassing are carried out by slowly increasing the temperature at a rate of 6°C / min to avoid local overheating of the solution and precipitation of impurities due to rapid temperature changes.

[0107] Step eight of this embodiment is precision filtration. During the filtration process, the filter membrane is backwashed periodically. The backwashing pressure is 0.35 MPa and the backwashing time is 12 minutes to ensure the filtration performance and service life of the filter membrane.

[0108] In step nine of this embodiment, product packaging, the cleanliness level of the ultra-clean workbench reaches Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled at 27°C and 50% to avoid product contamination.

[0109] Example 3:

[0110] A multi-stage evaporation and purification process for producing electronic-grade sulfuric acid includes the following steps:

[0111] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into the pretreatment tank and add a 10% (w / w) potassium permanganate solution. The amount of potassium permanganate solution added is 0.5% of the mass of the industrial-grade sulfuric acid.

[0112] Turn on the stirring device, set the stirring speed to 100 rpm, and stir for 30 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid, oxidizing them into harmless substances;

[0113] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.3 MPa, an evaporation temperature of 150℃, and an evaporation pressure of 0.05 MPa.

[0114] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0115] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator with saturated steam as the heating medium. The steam pressure range is 0.4 MPa, the evaporation temperature is 180℃, and the evaporation pressure is 0.08 MPa.

[0116] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0117] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to a pyrolysis reactor. Dry air is introduced into the reactor and filtered precisely until the particulate matter content is ≤0.01μm. The reactor temperature is then raised to 800℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0118]

[0119] The mixed gas produced by the reaction enters the condenser heat exchanger, where it is condensed and dehydrated at 125°C. The remaining gas containing SO3 enters the gas buffer tank.

[0120] Step 5, Sulfur trioxide purification: The gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%, and adsorbs trace amounts of moisture and sulfuric acid droplets at 85℃.

[0121] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 100°C. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0122] Then, highly purified nitrogen gas with a purity of not less than 99.999% and a flow rate of 10 L / min is introduced. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0123] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, 95% ultrapure sulfuric acid is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0124] The absorption temperature is 45℃ and the absorption pressure is 0.15MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0125] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transported to the heating and degassing tank. The solution temperature is raised to 60°C by steam heating and maintained for 30 minutes to remove the dissolved gas from the solution.

[0126] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.05 μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.2 MPa and the filtration speed is 5 L / min.

[0127] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done by rinsing with ultrapure water, and the drying temperature is 120℃ for 2 hours.

[0128] In step one of this embodiment, the raw material pretreatment is carried out at a stirring temperature of 30°C.

[0129] In step four of this embodiment, the preparation of sulfur trioxide involves a pyrolysis reaction at 800°C and a condensation temperature of 125°C.

[0130] In step five of this embodiment, sulfur trioxide purification, the operating pressure of the demister is 0.10 MPa to ensure the demister effect; the silica gel in the adsorber needs to be regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0131] In step seven of this embodiment, heating and degassing are carried out by slowly increasing the temperature at a rate of 5°C / min to avoid local overheating of the solution and precipitation of impurities due to rapid temperature changes.

[0132] Step eight of this embodiment is precision filtration. During the filtration process, the filter membrane is backwashed periodically. The backwashing pressure is 0.3 MPa and the backwashing time is 10 minutes to ensure the filtration performance and service life of the filter membrane.

[0133] In step nine of this embodiment, product packaging, the cleanliness level of the ultra-clean workbench reaches Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled at 25°C and 55% to avoid product contamination.

[0134] Example 4:

[0135] A multi-stage evaporation and purification process for producing electronic-grade sulfuric acid includes the following steps:

[0136] Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into the pretreatment tank and add a potassium permanganate solution with a mass fraction of 8%-12%. The amount of potassium permanganate solution added is 0.4% of the mass of the industrial-grade sulfuric acid.

[0137] Turn on the stirring device, set the stirring speed to 85 rpm, and stir for 27 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid, oxidizing them into harmless substances;

[0138] Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.25 MPa, an evaporation temperature of 145℃, and an evaporation pressure of 0.05 MPa.

[0139] Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution.

[0140] Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator with saturated steam as the heating medium. The steam pressure range is 0.35 MPa, the evaporation temperature is 175℃, and the evaporation pressure is 0.08 MPa.

[0141] The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution.

[0142] Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to a pyrolysis reactor. Dry air is introduced into the reactor and filtered precisely until the particulate matter content is ≤0.01μm. The reactor temperature is then raised to 780℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid.

[0143]

[0144] The mixed gas produced by the reaction enters the condenser heat exchanger, where it is condensed and dehydrated at 122°C. The remaining gas containing SO3 enters the gas buffer tank.

[0145] Step 5, Sulfur trioxide purification: The gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%, and adsorbs trace amounts of moisture and sulfuric acid droplets at 82℃.

[0146] Fuming sulfuric acid is added to a falling film evaporator and evaporated at 95°C. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it.

[0147] Then, highly purified nitrogen gas with a purity of not less than 99.999% and a flow rate of 9 L / min is introduced. After mixing with sulfur trioxide gas, the mixture enters the absorption tower.

[0148] Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, 98% ultrapure sulfuric acid is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution.

[0149] The absorption temperature is 42℃ and the absorption pressure is 0.13MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency.

[0150] Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transferred to the heating and degassing tank. The solution temperature is raised to 57°C by steam heating and maintained for 28 minutes to remove dissolved gases from the solution.

[0151] Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.04 μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.18 MPa and the filtration speed is 5 L / min.

[0152] Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done by rinsing with ultrapure water, and the drying temperature is 115℃ for 1.8 hours.

[0153] In step one of this embodiment, the raw material pretreatment is carried out at a stirring temperature of 28°C.

[0154] In step four of this embodiment, the preparation of sulfur trioxide involves a pyrolysis reaction temperature of 780°C and a condensation temperature of 122°C.

[0155] In step five of this embodiment, sulfur trioxide purification, the operating pressure of the demister is 0.09 MPa to ensure the demister effect; the silica gel in the adsorber needs to be regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

[0156] In step seven of this embodiment, heating and degassing are carried out by slowly increasing the temperature at a rate of 5°C / min to avoid local overheating of the solution and precipitation of impurities due to rapid temperature changes.

[0157] Step eight of this embodiment is precision filtration. During the filtration process, the filter membrane is backwashed periodically. The backwashing pressure is 0.28 MPa and the backwashing time is 9 minutes to ensure the filtration performance and service life of the filter membrane.

[0158] In step nine of this embodiment, product packaging, the cleanliness level of the ultra-clean workbench reaches Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled at 24°C and 52% to avoid product contamination.

[0159] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0160] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-stage evaporation and purification process for producing electronic-grade sulfuric acid, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: Introduce industrial-grade sulfuric acid into a pretreatment tank and add a potassium permanganate solution with a mass fraction of 8%-12%. The amount of potassium permanganate solution added is 0.3%-0.7% of the mass of industrial-grade sulfuric acid. Turn on the stirring device and stir at a speed of 80-120 rpm for 25-35 minutes to promote the full reaction of potassium permanganate with the reducing impurities in sulfuric acid and oxidize them into harmless substances. Step 2, Primary Evaporation: The pretreated sulfuric acid solution is transported to the primary evaporator. The primary evaporator is a falling film evaporator. The heating medium is saturated steam with a steam pressure of 0.2-0.4 MPa, an evaporation temperature of 140-160℃, and an evaporation pressure of 0.04-0.06 MPa. Sulfuric acid solution enters from the top of the evaporator and forms a uniform liquid film along the inner wall of the heating tube. Under the action of heating, the water in the sulfuric acid solution begins to vaporize, forming sulfuric acid vapor and concentrated sulfuric acid solution. Step 3, Secondary Evaporation: The concentrated sulfuric acid solution obtained from the primary evaporation enters the secondary evaporator. The secondary evaporator is a forced circulation evaporator. The heating medium is saturated steam, with a steam pressure range of 0.3-0.5 MPa, an evaporation temperature of 170-190℃, and an evaporation pressure of 0.07-0.09 MPa. The concentrated sulfuric acid solution circulates at high speed in the heating tube under the action of the circulating pump, and at the same time continuously absorbs heat, causing the water in the solution to further vaporize, resulting in a higher concentration of sulfuric acid solution. Step 4, Sulfur Trioxide Preparation: The high-concentration sulfuric acid solution obtained from the secondary evaporation is transferred to the pyrolysis reactor. Dry air is introduced into the reactor; the air must be precisely filtered to remove impurities, with a particulate matter content ≤0.01μm. Simultaneously, the reactor temperature is raised to 750-850℃ to induce the pyrolysis reaction of the high-concentration sulfuric acid. ； The mixed gases SO3, H2O and air produced by the reaction first enter the condenser heat exchanger, where they are condensed at 120-130℃ to remove most of the water vapor. The remaining SO3-containing gas is temporarily stored in the gas buffer tank. Step 5, Sulfur trioxide purification: The SO3-containing gas in the gas buffer tank is introduced into the falling film adsorber, which is filled with high-purity silica gel with a purity ≥99.999%. The adsorber adsorbs the trace amounts of moisture and sulfuric acid droplets remaining in the gas at 80-90℃. Fuming sulfuric acid is added to a falling film evaporator and evaporated at 90-110℃. The evaporated sulfur trioxide gas passes through a demister, which is a wire mesh demister, which can effectively remove trace amounts of sulfuric acid and nitrosyl sulfuric acid entrained in it. Then, highly purified nitrogen gas with a purity of not less than 99.999% is introduced at a flow rate of 8-12 L / min. After mixing with sulfur trioxide gas, the mixture enters the absorption tower. Step 6, Absorption of Ultrapure Sulfuric Acid: In the absorption tower, ultrapure sulfuric acid with a mass fraction of 95%-98% is used as the mother acid and sprayed down from the top of the absorption tower. It comes into countercurrent contact with the purified sulfur trioxide gas entering from the bottom of the absorption tower, and an absorption reaction occurs to generate an electronic grade sulfuric acid solution. The absorption temperature is 40-50℃ and the absorption pressure is 0.12-0.18MPa. The absorption tower is equipped with multi-stage packing material, which is made of high-purity fluoroplastic to increase the gas-liquid contact area and improve the absorption efficiency. Step 7, Heating and Degassing: The electronic-grade sulfuric acid solution obtained from the absorption tower is transferred to the heating and degassing tank. The solution temperature is raised to 55-65℃ by steam heating and maintained for 25-35 minutes to remove dissolved gases from the solution. Step 8, Precision Filtration: The heated and degassed electronic-grade sulfuric acid solution is filtered through a filter membrane with a pore size of 0.01-0.10 μm. The filter membrane adopts a pleated filter element structure to increase the filtration area and improve the filtration efficiency; the filtration pressure is 0.15-0.25 MPa, and the filtration speed is 4-6 L / min. Step 9, Product Packaging: The filtered electronic-grade sulfuric acid solution is transported to the ultra-clean packaging workshop and packaged in an ultra-clean workbench. Before packaging, the packaging containers are thoroughly cleaned and dried. The cleaning is done with ultrapure water, and the drying temperature is 110-130℃ for 1.5-2.5 hours.

2. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, Step one, raw material pretreatment, involves stirring at a temperature of 25-35℃.

3. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, In step four, the preparation of sulfur trioxide, the pyrolysis reaction temperature is controlled at 750-850℃ and the condensation temperature is 120-130℃ to ensure that sulfuric acid is fully pyrolyzed and to avoid SO3 from combining with water to form sulfuric acid.

4. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, In step five, sulfur trioxide purification, the operating pressure of the demister is 0.08-0.12 MPa to ensure the demister effect; the silica gel in the adsorber needs to be regenerated regularly to avoid adsorption saturation leading to a decrease in purification effect.

5. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, In step seven, heating and degassing, a slow heating method is used during the heating process, with a heating rate of 4-6℃ / min, to avoid local overheating of the solution and precipitation of impurities due to excessively rapid temperature changes.

6. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, Step eight, precision filtration, involves periodically backwashing the filter membrane during the filtration process. The backwashing pressure is 0.25-0.35 MPa, and the backwashing time is 8-12 minutes to ensure the filtration performance and service life of the filter membrane.

7. The electronic-grade sulfuric acid production process using multi-stage evaporation and purification as described in claim 1, characterized in that, In step nine, product packaging, the cleanliness of the ultra-clean workbench reaches the Class 100 standard. During the packaging process, the ambient temperature and humidity are strictly controlled, with the temperature at 23-27℃ and the humidity at 40-60%, to avoid product contamination.

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