Preparation process of high-purity sulfuric acid

Abstract

The invention relates to the technical field of sulfuric acid preparation, and particularly discloses a high-purity sulfuric acid preparation process which comprises the following specific steps: removing acid gas, heavy metal oxides and carbides by means of spray cooling, alkaline washing, oxidation washing and water washing by adopting a gas washing and adsorption technology; active carbon and a molecular sieve adsorption material are used for further purifying gas; an oxidation catalysis technology is adopted, and conversion of SO2 to SO3 is promoted by using a vanadium pentoxide catalyst at 400-450 DEG C; a countercurrent absorption tower is adopted, concentrated sulfuric acid with the mass fraction being 98% or above serves as an absorption medium, SO3 is absorbed, pyrosulfuric acid is formed, high-purity sulfuric acid is generated through hydrolysis, the absorption temperature is controlled to range from 40 DEG C to 60 DEG C through a circulating cooling system, and SO3 volatilization is prevented. While the purity of the raw materials is improved, the influence of impurities on the product is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of sulfuric acid preparation, and more specifically, the present invention relates to a process for preparing high-purity sulfuric acid. Background Art

[0002] Sulfuric acid (H 2 SO 4 ) is an important chemical product and is widely used in industries such as chemical fertilizers, petroleum refining, electronics manufacturing, and metallurgy. Traditional sulfuric acid preparation processes mainly include the Contact Process and the Chamber Process.

[0003] In the existing published literature 1 (Research on the Process for Preparing High-Purity Calcium Sulfate from Phosphogypsum, 2023), a process for preparing hemihydrate calcium sulfate whiskers from high-purity gypsum is proposed. The hydrothermal method is used, with high-purity calcium sulfate as the raw material, MgCl 2As an additive, 2.4 g of high-purity calcium sulfate was weighed and placed in a crystallization tank with a polytetrafluoroethylene inner lining. 77.6 g of water or dilute sulfuric acid solution was added. After being dispersed evenly, magnesium chloride was added. It was installed in a homogeneous reactor, heated to the set temperature, and the rotation speed was controlled at 30 rpm. After the reaction ended, it was cooled, filtered, dried, and sampled for observation. The formation of calcium sulfate hemihydrate whiskers involves three steps: dissolution, recrystallization, and growth. Through single-factor experiments, the optimal conditions were obtained as follows: solid content 3%, rotation speed 30 rpm, reaction temperature 120 °C, reaction time 4 h, sulfuric acid mass fraction 1%, magnesium chloride addition amount 0.05%. The average aspect ratio of the whiskers reached 106. On this basis, orthogonal experiments were carried out for optimization, and the best conditions were obtained as reaction temperature 120 °C, reaction time 4.5 h, sulfuric acid concentration 0.5%, and additive dosage 0.025%. The average aspect ratio of the prepared calcium sulfate hemihydrate whiskers reached more than 120, and XRD detection showed that the product had a high degree of crystallization. However, phosphogypsum has a high impurity content and a complex occurrence state. Although pretreatment methods such as gravity classification are adopted, some impurities may still affect the quality and performance of the whiskers, making it difficult to accurately control the morphology and aspect ratio of the whiskers, increasing the difficulty of preparing high-quality whiskers. In the existing public literature 2 (Process Research on the Preparation of High-Purity Aluminum Sulfate from Aluminum Ash, 2021), a process for preparing high-purity aluminum sulfate from aluminum ash was proposed. The process flow is as follows: First, the aluminum ash sample provided by an enterprise was screened and ground to 80 mesh, and then the "sulfuric acid leaching - hydrolysis precipitation - crystallization" process was used to recover aluminum sulfate from the aluminum ash. During the leaching process, under the optimal leaching parameters (the leaching agent is sulfuric acid with a concentration of 15%, leaching temperature 40 °C, leaching time 90 min, leaching stirring intensity 300 r / min, solid-liquid ratio 1:10), aluminum oxide reacts with sulfuric acid to form aluminum sulfate. After the reaction, filtration was carried out, and the filter residue was discarded after treatment. Then, during the hydrolysis precipitation process, an excessive amount (15 ml) of 5% hydrogen peroxide was added to oxidize impurities, and the end point pH value was strictly controlled at 4.3 to remove impurities. Filtration was carried out again, and the filter residue was discarded after treatment. Finally, the filtrate was concentrated and cooled for crystallization to obtain the product aluminum sulfate, and its performance was analyzed. However, in the process of preparing high-purity aluminum sulfate from aluminum ash, multiple parameters need to be accurately regulated, such as sulfuric acid concentration, stirring intensity, leaching temperature, solid-liquid ratio, and leaching time. Any change in a parameter will affect the leaching rate of aluminum, which requires a high degree of accuracy and stability in operation, increasing the operation difficulty and control cost in actual production. When the sulfuric acid concentration exceeds 15%, although the aluminum leaching rate will increase in the early stage, it will cause difficulties in solid-liquid separation filtration because the mineral particle size is too small during the leaching process, resulting in an increase in the loss of aluminum in the leaching residue and affecting the overall recovery rate and product quality.

[0004] Therefore, how to effectively remove impurities in the raw materials during sulfuric acid preparation and reduce energy consumption during sulfuric acid preparation has become an urgent problem to be solved at present. Summary of the Invention

[0005] To overcome the above defects of the prior art, the present invention provides a process for preparing high-purity sulfuric acid. By adopting gas washing and adsorption technologies, impurities such as heavy metal oxides, acidic gases, and carbides in the sulfur source are removed to improve the purity of the raw materials. At the same time, an oxidation catalyst is used to increase the conversion rate of sulfur dioxide to sulfur trioxide. Through a countercurrent absorption tower reacting with high-purity concentrated sulfuric acid and combined with a circulating cooling system, ensure SO 3 efficient absorption and prevent energy loss caused by temperature rise, thereby obtaining high-purity sulfuric acid to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A process for preparing high-purity sulfuric acid, comprising the following steps:

[0008] Step S1, adopting gas washing and adsorption technologies, removing acidic gases, heavy metal oxides, and carbides by means of spray cooling, alkaline washing, oxidation washing, and water washing, and further purifying the gas using activated carbon and molecular sieve adsorption materials;

[0009] Step S2, adopting oxidation catalysis technology, using vanadium pentoxide catalyst to promote the conversion of SO 2 to SO 3 under the condition of 400 - 450 °C;

[0010] Step S3, adopting a countercurrent absorption tower, using concentrated sulfuric acid with a mass fraction of more than 98% as the absorption medium to absorb SO 3 and form pyrosulfuric acid, and then hydrolyzing to generate high-purity sulfuric acid. Controlling the absorption temperature at 40 - 60 °C through a circulating cooling system to prevent SO 3 from volatilizing;

[0011] The water washing means in the step S1 removes the residual impurities in the sulfuric acid gas by spraying and washing with ultrapure water. Based on Newton's second law, a droplet motion equation is established, and the probability distribution of droplet size is described based on the Gamma distribution: Among them, P(r; α, β) is the probability density function of the droplet radius r, α is the shape parameter used to control the shape of the distribution, β is the scale parameter used to control the range of the distribution, and Γ(α) is the Gamma function, and the calculation formula is: t is the independent variable in the Gamma function integral. By adjusting the shape parameter α and scale parameter β of the Gamma distribution, the droplet diameter is distributed between 0.1 - 0.5 mm to maximize the droplet number density.

[0012] As a further solution of the present invention, in step S1, the gas washing and adsorption technology is adopted. Acid gases, heavy metal oxides and carbides are removed by means of spray cooling, alkaline washing, oxidation washing and water washing. Activated carbon and molecular sieve adsorption materials are used to further purify the gas and improve the purity of the raw material gas, including the following specific contents: Pyrite is used as the raw material for sulfuric acid. Since the sulfur raw material contains different impurities, it needs to be purified to remove the impurities in the raw material. The purification treatment uses the gas washing technology to remove impurities such as acid gases, heavy metal oxides and carbides in the raw material gas. The gas washing tower is divided into 4 parts, namely: the pretreatment area, the alkaline washing area, the oxidation washing area and the water washing area. The pretreatment area is used to cool and preliminarily remove dust particles in the high-temperature gas. By means of heat exchange and mechanical separation, the gas temperature is reduced to 80-120 °C, and impurities such as large particle dust, metal oxides and sulfuric acid droplets are removed; the pretreatment area adopts a three-stage pretreatment method of spray cooling + cyclone separation + filtration purification. Before the high-temperature gas enters the washing tower, it first passes through a spray water cooler to quickly cool the gas. At the same time, some dust particles are adsorbed by the cooling water droplets, and then the large particle impurities are removed by a cyclone separator. Finally, it passes through a high-temperature corrosion-resistant filter screen for preliminary filtration to improve the cleanliness of the gas. Among them, the spray cooling uses a corrosion-resistant 316L stainless steel atomizing nozzle to spray deionized water at 50-100 °C, and uses gas-liquid contact for sensible heat exchange to quickly reduce the gas temperature and prevent the precipitation of impurities caused by thermal stress cracks or side reactions due to sudden cooling. The cyclone separator adopts a high-efficiency centrifugal design. Using the centrifugal force generated by the rotating motion of the gas, the dust particles with a larger density sink along the wall of the device and are collected in the ash discharge port to remove particles with a diameter greater than or equal to 5 μm. The filtration purification unit uses a ceramic fiber filter screen to further intercept the remaining small particles in the air flow and remove fine particles with a diameter greater than or equal to 1 μm.

[0013] The alkaline washing area is used to remove acid gases, based on the principle of acid-base neutralization reaction and gas-liquid mass transfer. When the gas flow containing acid gases enters the washing tower, the alkaline solution provides sufficient gas-liquid contact area by spraying or bubbling, so that the acid gases are quickly dissolved and undergo chemical reactions to form stable salt solutions, which are carried away by the washing liquid.

[0014] The oxidation washing area removes H 2 S, SO 2 , CO, NH 3 and other reducing impurities through the action of strong oxidants, avoiding catalyst poisoning and improving the purity of sulfuric acid products.

[0015] The water washing area removes the residual soluble impurities in the sulfuric acid gas through ultra-pure water spray washing. The spray water in the water washing area is distributed in the gas flow area in the form of droplets. The movement of the droplets in the spray tower is affected by gravity, gas resistance, buoyancy, surface tension and turbulent diffusion forces. Its motion equation is established by Newton's second law: where m is the mass of the droplet, v is the velocity of the droplet, and F g is the gravity force acting on the droplet, satisfying r is the radius of the droplet, ρ L is the liquid density, and g is the acceleration due to gravity; F d is the air resistance force acting on the droplet during its descent, satisfying C d is the drag coefficient, ρ g is the gas density, A is the cross-sectional area of the droplet, and A = πr 2 ; F b is the buoyancy force acting on the droplet, satisfying F s is the surface tension force of the droplet, satisfying where represents the droplet shape deformation rate; F t is the force exerted by the gas flow turbulence on the droplet, satisfying F t = C t ρ g ∈ 2 / 3 r 5 / 3 , where C t is the turbulence coefficient and ∈ is the turbulence dissipation rate. At the equilibrium state, the terminal velocity v t of the droplet satisfies: F g - F b = F d , that is Solving for the terminal velocity formula gives:

[0016] The mean μ and standard deviation σ of the Gamma distribution are calculated from the shape parameter α and scale parameter β: In the case of normal distribution approximation, 95% of the data falls within the range [μ - 2σ, μ + 2σ]. Therefore, it is set that: μ - 2σ ≥ 0.1, μ + 2σ ≤ 0.5, that is Let and Simplifying gives: x - 2y ≥ 0.1, x + 2y ≤ 0.5. Solving: 0.1 ≤ x - 2y, x + 2y ≤ 0.5, expressing y as gives: The average diameter of the droplet is selected as μ = 0.3 mm, that is Solving gives: Let Solve to get: Get \(6\leq z\leq3\), that is: \(9\leq\alpha\leq36\).

[0017] To maximize the droplet number density and make the peak of the probability density \(P(r)\) reach the maximum within the target range, the mode of the Gamma distribution is Let \(r\ mode Take the median value of \(0.3\ mm\): Combined with the mean formula Solve to get:

[0018] In the preparation process of high-purity sulfuric acid, the sulfur source contains a large amount of impurities, including heavy metals (such as arsenic, lead, cadmium, mercury), organic sulfides (such as mercaptans, thioethers), carbides (such as carbon black, coke particles), etc. Therefore, after the sulfur source is gasified or burned, an adsorption technology is used to purify the gas and remove the residual impurities. The adsorption technology includes physical adsorption, chemical adsorption, and composite adsorption. Through adsorption materials such as activated carbon, molecular sieves, iron oxide, and modified adsorbents, heavy metals, H 2 S, SO 2 , organic sulfur, and carbides are removed to improve the gas purity.

[0019] As a further solution of the present invention, in step S2, an oxidation catalytic technology is adopted. Under the condition of 400 - 450 °C, vanadium pentoxide catalyst is used to promote the conversion of SO 2 to SO 3 , including the following specific contents: The oxidation catalyst is vanadium pentoxide, which can accelerate the oxidation reaction of SO 2 and oxygen at a lower temperature. To improve the conversion rate of SO 2 and lower the reaction temperature, the reaction temperature is 400 - 450 °C. The conversion rate of SO 2 is gradually increased through a multi-stage catalytic oxidation bed, and the optimal temperature is maintained at different stages: the temperature of the first stage is controlled at 400 - 450 °C to activate the catalyst and improve the initial conversion rate; the temperatures of the second and third stages are reduced to 380 - 420 °C to further improve the oxidation efficiency of SO 2 and reduce the decomposition of SO 3 .

[0020] As a further solution of the present invention, in step S3, a countercurrent absorption tower is adopted. Concentrated sulfuric acid with a mass fraction of more than 98% is used as the absorption medium to absorb SO 3 and form pyrosulfuric acid, and then high-purity sulfuric acid is generated through hydrolysis. The absorption temperature is controlled at 40 - 60 °C through a circulating cooling system to prevent the volatilization of SO 3 and improve the sulfuric acid purity, including the following specific contents: SO 3Enter the tower absorption system. The tower absorption system uses a countercurrent absorption tower to enable efficient contact mass transfer between SO 3 gas and concentrated sulfuric acid to form pyrosulfuric acid. Subsequently, the pyrosulfuric acid further reacts with water molecules to generate high-purity sulfuric acid. Since the absorption of SO 3 is a strongly exothermic process, in order to prevent the volatilization of SO 3 caused by temperature rise and reduce the absorption efficiency of SO 3 , the temperature in the absorption tower is controlled between 40 - 60 °C through a circulating cooling system.

[0021] Advantages of the present invention:

[0022] By optimizing the gas washing and adsorption technologies, the present invention effectively removes impurities such as heavy metal oxides, acidic gases, and carbides in the sulfur source, improving the purity of the raw materials. At the same time, an oxidation catalyst is used to increase the conversion rate of sulfur dioxide (SO 2 ) to sulfur trioxide (SO 3 ), reducing the occurrence of side reactions under the optimized temperature control environment and improving the reaction efficiency. Further, through the reaction of the countercurrent absorption tower with high-purity concentrated sulfuric acid and combined with the circulating cooling system, it ensures the efficient absorption of SO 3 , prevents energy loss caused by temperature rise, and thus obtains high-purity sulfuric acid. While ensuring the product quality, this process improves production stability, reduces the requirement for operation precision, and effectively reduces the impact of impurities on the final product, thereby realizing the economical and efficient preparation of high-purity sulfuric acid. Brief Description of the Drawings

[0023] Figure 1 is the process flow chart of a method for preparing high-purity sulfuric acid according to the present invention.

[0024] Figure 2 is a schematic diagram of a process for preparing hemihydrate calcium sulfate whiskers from high-purity gypsum in the prior art.

[0025] Figure 3 is a schematic diagram of a process for preparing high-purity aluminum sulfate from aluminum ash in the prior art.

[0026] Figure 4 is the structural schematic diagram of the gas washing tower of the present invention.

[0027] Figure 5 is the curve graph showing the influence of droplet diameter on gas removal efficiency in the present invention.

[0028] Figure 6 is the probability distribution curve graph of droplet diameter in the present invention. Detailed Embodiments

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] Embodiment 1

[0031] Referring to Figure 1 the flowchart shown, an embodiment of the present invention provides a high-purity sulfuric acid preparation process, which includes the following steps:

[0032] Step S1: Adopt gas washing and adsorption technology, remove acidic gases, heavy metal oxides and carbides through spray cooling, alkaline washing, oxidation washing and water washing means, and further purify the gas by using activated carbon and molecular sieve adsorption materials to improve the purity of the raw material gas.

[0033] Step S2: Adopt oxidation catalysis technology, and use vanadium pentoxide catalyst to promote the conversion of SO 2 to SO 3 under the condition of 400 - 450 °C.

[0034] Step S3: Adopt a countercurrent absorption tower, use concentrated sulfuric acid with a mass fraction of more than 98% as the absorption medium to absorb SO 3 and form pyrosulfuric acid, and then generate high-purity sulfuric acid through hydrolysis. Control the absorption temperature at 40 - 60 °C through a circulating cooling system to prevent SO 3 from volatilizing and improve the purity of sulfuric acid.

[0035] In this embodiment, referring to Figure 2 the schematic diagram shown, a process for preparing hemihydrate calcium sulfate whiskers from high-purity gypsum proposed in the prior art adopts a hydrothermal method with high-purity calcium sulfate as the raw material, MgCl 2As an additive, 2.4 g of high-purity calcium sulfate was weighed and placed in a crystallization tank with a polytetrafluoroethylene inner lining. 77.6 g of water or dilute sulfuric acid solution was added. After being dispersed evenly, magnesium chloride was added. It was installed in a homogeneous reactor, heated to the set temperature, and the rotation speed was controlled at 30 rpm. After the reaction ended, it was cooled, filtered, dried, and sampled for observation. The formation of calcium sulfate whiskers in hemihydrate form involves three steps: dissolution, recrystallization, and growth. Through single-factor experiments, the optimal conditions were obtained as a solid content of 3%, a rotation speed of 30 rpm, a reaction temperature of 120 °C, a reaction time of 4 h, a sulfuric acid mass fraction of 1%, and a magnesium chloride addition amount of 0.05%. The average aspect ratio of the whiskers reached 106. On this basis, orthogonal experiments were carried out for optimization, and the best conditions were obtained as a reaction temperature of 120 °C, a reaction time of 4.5 h, a sulfuric acid concentration of 0.5%, and an additive dosage of 0.025%. The average aspect ratio of the prepared calcium sulfate whiskers in hemihydrate form reached more than 120, and XRD detection showed that the product had a high degree of crystallization. However, phosphogypsum has a high impurity content and a complex occurrence state. Although pretreatment methods such as gravity classification are adopted, some impurities may still affect the quality and performance of the whiskers, making it difficult to accurately control the morphology and aspect ratio of the whiskers, and increasing the difficulty of preparing high-quality whiskers. Refer to Figure 3 As shown in the schematic diagram, a process for preparing high-purity aluminum sulfate from aluminum ash proposed in the prior art is as follows: First, the aluminum ash sample provided by an enterprise is screened and ground to 80 mesh, and then the "sulfuric acid leaching - hydrolysis precipitation - crystallization" process is used to recover aluminum sulfate from the aluminum ash. During the leaching process, under the optimal leaching parameters (the leaching agent is sulfuric acid with a concentration of 15%, the leaching temperature is 40 °C, the leaching time is 90 min, the leaching stirring intensity is 300 r / min, and the solid-liquid ratio is 1:10), aluminum oxide reacts with sulfuric acid to form aluminum sulfate. After the reaction, filtration is carried out, and the filter residue is discarded after treatment. Then, during the hydrolysis precipitation process, an excessive amount (15 ml) of 5% hydrogen peroxide is added to oxidize impurities, and the end-point pH value is strictly controlled at 4.3 to remove impurities. Filtration is carried out again, and the filter residue is discarded after treatment. Finally, the filtrate is concentrated and cooled for crystallization to obtain the product aluminum sulfate, and its performance is analyzed. However, during the process of preparing high-purity aluminum sulfate from aluminum ash, multiple parameters need to be accurately regulated, such as sulfuric acid concentration, stirring intensity, leaching temperature, solid-liquid ratio, and leaching time. Any change in a parameter will affect the leaching rate of aluminum, which requires a high degree of accuracy and stability in operation, increasing the operation difficulty and control cost in actual production. When the sulfuric acid concentration exceeds 15%, although the aluminum leaching rate will increase in the early stage, it will cause difficulties in solid-liquid separation and filtration because the mineral particle size is too small during the leaching process, resulting in an increase in the loss of aluminum in the leaching residue and affecting the overall recovery rate and product quality.

[0036] In step S1, the gas washing and adsorption technology is adopted. Acid gases, heavy metal oxides and carbides are removed by means of spray cooling, alkaline washing, oxidation washing and water washing. Activated carbon and molecular sieve adsorption materials are used to further purify the gas and improve the purity of the raw material gas, including the following specific contents: Pyrite is used as the raw material for sulfuric acid. Since the sulfur raw material contains different impurities, it needs to be purified to remove the impurities in the raw material. The purification process uses gas washing technology to remove impurities such as acid gases, heavy metal oxides and carbides in the raw material gas. Refer to Figure 4 As shown in the structure diagram, the gas washing tower is divided into four parts, namely: a pretreatment area, an alkaline washing area, an oxidation washing area and a water washing area. The pretreatment area is used to cool and preliminarily remove dust particles in the high-temperature gas. By means of heat exchange and mechanical separation, the gas temperature is reduced to 80-120 °C, and impurities such as large particle dust, metal oxides and sulfuric acid droplets are removed; The pretreatment area adopts a three-stage pretreatment method of spray cooling + cyclone separation + filtration purification. Before the high-temperature gas enters the washing tower, it first passes through a spray water cooler to quickly cool the gas. At the same time, some dust particles are adsorbed by the cooling water droplets, and then large particle impurities are removed by a cyclone separator. Finally, it passes through a high-temperature corrosion-resistant filter screen for preliminary filtration to improve the cleanliness of the gas. Among them, the spray cooling uses corrosion-resistant 316L stainless steel atomizing nozzles to spray deionized water at 50-100 °C, and sensible heat exchange is carried out by gas-liquid contact to quickly reduce the gas temperature and prevent the precipitation of impurities caused by thermal stress cracks or side reactions due to sudden cooling. The cyclone separator adopts a high-efficiency centrifugal design. By using the centrifugal force generated by the rotating motion of the gas, dust particles with a larger density sink along the wall of the device and are collected in the ash discharge port to remove particles with a diameter greater than or equal to 5 μm. The filtration purification unit uses a ceramic fiber filter screen to further intercept residual small particles in the air flow and remove fine particles with a diameter greater than or equal to 1 μm.

[0037] The alkaline washing area is used to remove acid gases, based on the principle of acid-base neutralization reaction and gas-liquid mass transfer. When the gas flow containing acid gases enters the washing tower, the alkaline solution provides sufficient gas-liquid contact area through spraying or bubbling, so that the acid gases are quickly dissolved and chemically react to form a stable salt solution, which is carried away by the washing liquid.

[0038] In the oxidation washing area, through the action of strong oxidants, H 2 S, SO 2 , CO, NH 3 and other reducing impurities are removed to avoid catalyst poisoning and improve the purity of sulfuric acid products.

[0039] The water washing area removes the residual soluble impurities in the sulfuric acid gas through ultra-pure water spraying. The spraying water in the water washing area is distributed in the gas flow area in the form of dripping liquid. The movement of the liquid droplets in the spraying tower is affected by gravity, gas resistance, buoyancy, surface tension and turbulent diffusion force. Its movement equation is established by Newton's second law: where m is the mass of the liquid droplet, v is the velocity of the liquid droplet, and F g is the gravity force acting on the liquid droplet, satisfying r is the radius of the liquid droplet, ρ L is the density of the liquid, and g is the acceleration due to gravity; F d is the air resistance force acting on the liquid droplet during its descent, satisfying C d is the drag coefficient, ρ g is the density of the gas, A is the cross-sectional area of the liquid droplet, and A = πr 2 ; F b is the buoyancy force acting on the liquid droplet, satisfying F s is the surface tension of the liquid droplet, satisfying where represents the rate of deformation of the liquid droplet shape; F t is the force exerted by the gas flow turbulence on the liquid droplet, satisfying F t = C t ρ g ∈ 2 / 3 r 5 / 3 where C t is the turbulence coefficient and ∈ is the turbulence dissipation rate. At the equilibrium state, the terminal velocity v t of the liquid droplet satisfies: F g - F b = F d , that is The solution for the terminal velocity formula is: The terminal velocity v t determines the suspension time t s of the liquid droplet in the washing tower. To verify the influence of the liquid droplet diameter r on the suspension time, gas-liquid contact time and gas purification efficiency, a set of experiments was designed. The experimental device includes: a spraying washing tower, a camera system, a particle size analyzer and a gas analyzer. The height of the spraying washing tower is 5 m; the camera system is used to measure the movement of the liquid droplets; the particle size analyzer is used to measure the diameter of the liquid droplets; the gas analyzer is used to detect the removal rates of SO 2 and H 2 S. The experimental steps are as follows:

[0040] Step Y1, set different spraying parameters so that the liquid droplet diameters are 0.05 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.6 mm respectively.

[0041] Step Y2, record the terminal velocity v of the droplet t , and calculate the suspension time t of the droplet s .

[0042] Step Y3, monitor the gas-liquid contact time t c , and analyze the interaction time between the droplet and the gas

[0043] Step Y4, evaluate the removal rates of SO 2 and H 2 S, and compare the washing effects of different droplet diameters

[0044] The specific experimental data are shown in the following table

[0045] Table 1 Verification of the influence of droplet diameter r on suspension time, gas-liquid contact time, and gas purification efficiency

[0046]

[0047] Droplets with too large a diameter (r > 0.5 mm) have a high terminal velocity and fall rapidly, reducing the gas-liquid contact time. Droplets with too small a diameter (r < 0.1 mm) are easily carried away by the air flow, have a long suspension time but evaporate too quickly, reducing the washing efficiency. Refer to Figure 5 the curve graph shown. When r = 0.3 mm, the droplet falling velocity is moderate, the gas-liquid contact time is the longest, and at this time, the removal rates of SO 2 and H 2 S are also the highest

[0048] Describe the probability distribution of droplet size based on the Gamma distribution where P(r; α, β) is the probability density function of the droplet radius r, α is the shape parameter used to control the shape of the distribution, β is the scale parameter used to control the range of the distribution, Γ(α) is the Gamma function, and the calculation formula is t is the independent variable in the integral of the Gamma function. By adjusting α and β, ensure that the droplet diameter in the spray tower is distributed between 0.1 - 0.5 mm, and at the same time maximize the droplet number density so that it is evenly distributed on the entire tower interface to improve gas purity and reduce the impurity content in the sulfuric acid product

[0049] The mean μ and standard deviation σ of the Gamma distribution are calculated through the shape parameter α and scale parameter β In the case of normal distribution approximation, 95% of the data falls within the range of [μ - 2σ, μ + 2σ]. Therefore, set: μ - 2σ ≥ 0.1, μ + 2σ ≤ 0.5, that is Let and Simplified to: \(x - 2y\geq0.1\), \(x + 2y\leq0.5\), solve: \(0.1\leq x - 2y\), \(x + 2y\leq0.5\), express \(y\) as Obtained: The average diameter of the droplets is selected as \(\mu = 0.3\mathrm{mm}\), that is Solving gives: Let The solution is: Obtained \(6\leq z\leq3\), that is: \(9\leq\alpha\leq36\).

[0050] To maximize the droplet number density and make the peak of the probability density \(P(r)\) reach the maximum within the target range, the mode of the Gamma distribution is Let \(r\) mode Take the median value of \(0.3\mathrm{mm}\): Combined with the mean formula The solution is:

[0051] Verify the optimization of the Gamma distribution parameters \(\alpha\) and \(\beta\) through experiments, so that the diameters of the spray droplets are mainly distributed between \(0.1\mathrm{mm}\) and \(0.5\mathrm{mm}\), while maximizing the droplet number density to improve the washing efficiency and reduce the impurity content in the sulfuric acid product. Refer to Figure 6 The shown curve graph, select seven groups of \(\alpha,\beta\) combinations, and repeat each experiment 10 times, as shown in the following table:

[0052] Table 2 Verifying the droplet diameter distribution under different \(\alpha,\beta\) combinations

[0053]

[0054]

[0055] Experimental group D is the best choice. When \(\alpha = 25\), \(\beta = 83.3\), 95.2% of the droplet diameters are distributed between \(0.1\) and \(0.5\mathrm{mm}\), and the highest droplet density is 750 per \(\mathrm{cm}\) 3

[0056] In the preparation process of high-purity sulfuric acid, the sulfur source contains a large amount of impurities, including heavy metals (such as arsenic, lead, cadmium, mercury), organic sulfides (such as mercaptans, thioethers), carbides (such as carbon black, coke particles), etc. Therefore, after the sulfur source is gasified or burned, an adsorption technology is used to purify the gas and remove the residual impurities. The adsorption technology includes physical adsorption, chemical adsorption, and composite adsorption. Through adsorption materials such as activated carbon, molecular sieves, iron oxide, and modified adsorbents, heavy metals, H 2 S, SO 2 , organic sulfur, and carbides are removed to improve the gas purity.

[0057] Step S2: Using the oxidation catalysis technology, promote the conversion of SO under the condition of 400 - 450 °C by using vanadium pentoxide catalyst, including the following specific contents: The oxidation catalyst is vanadium pentoxide, which can accelerate the oxidation reaction of SO and oxygen at a relatively low temperature. To improve the conversion rate of SO and lower the reaction temperature, the reaction temperature is 400 - 450 °C. Gradually increase the conversion rate of SO through a multi-stage catalytic oxidation bed and maintain the optimal temperature at different stages: The temperature of the first stage is controlled at 400 - 450 °C to activate the catalyst and improve the initial conversion rate; The temperature of the second and third stages is reduced to 380 - 420 °C to further improve the oxidation efficiency of SO and reduce the decomposition of SO. 2 Convert SO 3 The oxidation catalyst is vanadium pentoxide, which can accelerate the oxidation reaction of SO and oxygen at a relatively low temperature. 2 To improve the conversion rate of SO 2 and lower the reaction temperature, the reaction temperature is 400 - 450 °C. Gradually increase the conversion rate of SO through a multi-stage catalytic oxidation bed and maintain the optimal temperature at different stages: The temperature of the first stage is controlled at 400 - 450 °C to activate the catalyst and improve the initial conversion rate; The temperature of the second and third stages is reduced to 380 - 420 °C to further improve the oxidation efficiency of SO 2 and reduce the decomposition of SO. 2 3

[0058] Step S3: Adopt a countercurrent absorption tower, use concentrated sulfuric acid with a mass fraction of more than 98% as the absorption medium to absorb SO and form pyrosulfuric acid, and then generate high-purity sulfuric acid through hydrolysis. Control the absorption temperature at 40 - 60 °C through a circulating cooling system to prevent the volatilization of SO and improve the purity of sulfuric acid, including the following specific contents: SO enters the tower-type absorption system. The tower-type absorption system adopts a countercurrent absorption tower to enable efficient mass transfer contact between SO gas and concentrated sulfuric acid to form pyrosulfuric acid. Subsequently, pyrosulfuric acid further reacts with water molecules to generate high-purity sulfuric acid. Since the absorption of SO is a strong exothermic process, in order to prevent the volatilization of SO caused by temperature rise and reduce the absorption efficiency of SO, control the temperature in the absorption tower at 40 - 60 °C through a circulating cooling system. 3 and form pyrosulfuric acid, and then generate high-purity sulfuric acid through hydrolysis. Control the absorption temperature at 40 - 60 °C through a circulating cooling system to prevent the volatilization of SO 3 and improve the purity of sulfuric acid, including the following specific contents: SO 3 enters the tower-type absorption system. The tower-type absorption system adopts a countercurrent absorption tower to enable efficient mass transfer contact between SO 3 gas and concentrated sulfuric acid to form pyrosulfuric acid. Subsequently, pyrosulfuric acid further reacts with water molecules to generate high-purity sulfuric acid. Since the absorption of SO 3 is a strong exothermic process, in order to prevent the volatilization of SO caused by temperature rise and reduce the absorption efficiency of SO 3 control the temperature in the absorption tower at 40 - 60 °C through a circulating cooling system. 3

[0059] By optimizing the gas washing and adsorption technology, the present invention effectively removes impurities such as heavy metal oxides, acid gases, and carbides in the sulfur source and improves the purity of the raw materials. At the same time, an oxidation catalyst is used to increase the conversion rate of sulfur dioxide (SO 2 ) to sulfur trioxide (SO 3 ), reduce the occurrence of side reactions in an optimized temperature control environment, and improve the reaction efficiency. Further, by reacting with high-purity concentrated sulfuric acid in a countercurrent absorption tower and combining with a circulating cooling system, ensure the efficient absorption of SO 3 , prevent energy loss caused by temperature rise, and thus obtain high-purity sulfuric acid. While ensuring the product quality, this process improves the production stability, reduces the requirement for operation precision, and effectively reduces the impact of impurities on the final product, thereby realizing the economical and efficient preparation of high-purity sulfuric acid. ​​​

[0060] As described above, it is only the specific implementation manner of the present application. However, the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims described.

[0061] Finally: The above description is only the preferred embodiment of the present invention and is not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A process for preparing high-purity sulfuric acid, characterized in that: The steps include: Step S1, using gas washing and adsorption technology, removing acidic gases, heavy metal oxides and carbides through spray cooling, alkaline washing, oxidation washing and water washing, and further purifying the gas using activated carbon and molecular sieve adsorption materials; Step S2, using oxidation catalysis technology, using vanadium pentoxide catalyst at 400-450°C to promote the conversion of SO2 to SO3; Step S3, using a countercurrent absorption tower, using concentrated sulfuric acid with a mass fraction of more than 98% as an absorption medium, absorbing SO3 and forming pyrosulfuric acid, and then generating high-purity sulfuric acid through hydrolysis, and controlling the absorption temperature at 40-60°C through a circulating cooling system to prevent SO3 from volatilizing; The water washing means in step S1 removes the impurities remaining in the sulfuric acid gas by spraying ultrapure water, establishes the droplet motion equation based on Newton's second law, and describes the probability distribution of the droplet size based on the Gamma distribution: Among them, P(r; α, β) is the probability density function of the droplet radius r, α is the shape parameter used to control the shape of the distribution, β is the scale parameter used to control the range of the distribution, Γ(α) is the Gamma function, and the calculation formula is: t is the independent variable in the integral of the Gamma function. By adjusting the shape parameter α and scale parameter β of the Gamma distribution, the droplet diameter is distributed between 0.1 and 0.5 mm, maximizing the droplet number density.

2. A process for preparing high-purity sulfuric acid according to claim 1, characterized in that In step S1, the mean μ and standard deviation σ of the Gamma distribution are calculated by the shape parameter α and the scale parameter β: In the case of normal distribution, 95% of the data fall within the range of [μ-2σ,μ+2σ]. Therefore, we set: μ-2σ≥0.1, μ+2σ≤0.5, that is, make and Simplified to: x-2y ≥ 0.1, x+2y ≤ 0.5, solve: 0.1 ≤ x-2y, x+2y ≤ 0.5, express y as get: The average diameter of the droplets is selected as μ = 0.3 mm, that is, Solved: make The solution is: We get 6≤z≤3, that is: 9≤α≤36.

3. A process for preparing high-purity sulfuric acid according to claim 1, characterized in that In step S1, in order to maximize the droplet number density and make the probability density peak value P(r) reach the maximum value within the target range, the mode of the Gamma distribution is Let r mode Take the median value of 0.3mm: Combined with the mean formula The solution is:

4. A process for preparing high-purity sulfuric acid according to claim 1, characterized in that: In step S1, the calculation formula of the droplet motion equation is: Where m is the mass of the droplet, v is the velocity of the droplet, and F g is the gravity on the droplet, satisfying r is the droplet radius, ρ L is the liquid density, g is the gravitational acceleration; F d is the air resistance encountered by the droplet during its descent, satisfying C d is the resistance coefficient, ρ g is the gas density, A is the cross-sectional area of ​​the droplet, and A=πr 2 ; F b is the buoyancy of the droplet, satisfying F s is the surface tension of the droplet, satisfying in, represents the droplet deformation rate; F t is the force of air turbulence on the droplets, satisfying F t =C t ρ g ∈ 2 / 3 r 5 / 3 , where C t is the turbulence coefficient, ∈ is the turbulence dissipation rate; when the equilibrium state is reached, the terminal velocity v of the droplet t Satisfaction: F g -F b =F d ,Right now The terminal velocity formula is:

5. A process for preparing high-purity sulfuric acid according to claim 1, characterized in that: In step S1, pyrite is used as the raw material of sulfuric acid, and the purification process adopts gas washing technology to remove acidic gas, heavy metal oxides and carbides in the raw gas. The gas washing tower is divided into a pretreatment zone, an alkaline washing zone, an oxidation washing zone and a water washing zone.

6. A process for preparing high-purity sulfuric acid according to claim 5, characterized in that: The pretreatment area adopts a three-stage pretreatment method of spray cooling + cyclone separation + filtration purification. A corrosion-resistant 316L stainless steel atomizing nozzle is used to spray 50-100°C deionized water for spray cooling. A centrifugal cyclone separator is used to remove particles with a diameter greater than or equal to 5μm. A ceramic fiber filter is used to remove fine particles with a diameter greater than or equal to 1μm, and the gas temperature is reduced to 80-120°C.

7. A process for preparing high-purity sulfuric acid according to claim 5, characterized in that: The alkaline washing zone is based on the principles of acid-base neutralization reaction and gas-liquid mass transfer. The alkaline solution is fully contacted with the gas flow containing acidic gas by spraying or bubbling to remove the acidic gas; the oxidative washing zone removes H2S, SO2, CO, and NH3 reducing impurities by strong oxidants; the water washing zone removes soluble impurities remaining in the sulfuric acid gas by water washing using ultrapure water spray.

8. A process for preparing high-purity sulfuric acid according to claim 1, characterized in that: The oxidation catalyst used in step S2 is vanadium pentoxide, the reaction temperature is controlled at 400-450°C, and the conversion rate of SO2 is gradually increased through the catalytic oxidation bed. The temperature of the first stage is controlled at 400-450°C, and the temperature of the second and third stages is reduced to 380-420°C.

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