Preparation process of high-purity sulfuric acid

Abstract

This invention discloses a process for preparing high-purity sulfuric acid, relating to the field of sulfuric acid preparation technology. The process involves: crushing and screening pyrite, then mixing it with pretreated pyrite to obtain roasting raw material, which is then fed into a fluidized bed furnace for roasting; the resulting high-temperature furnace gas undergoes waste heat recovery, dust removal and purification, cooling and impurity removal, two-stage electrostatic precipitation, and drying; under the action of a catalyst for SO2 conversion, sulfur dioxide is catalytically converted to sulfur trioxide, and finally, the sulfur trioxide is absorbed in stages by a multi-stage absorption tower to obtain high-purity sulfuric acid. This invention's preparation process, through the synergistic effect of pretreated pyrite for impurity removal and modification, two-stage electrostatic precipitation for deep purification, a highly stable catalytic system, and multi-stage absorption tower for staged absorption, can effectively remove harmful impurities from the raw materials and process system, inhibit catalytic poisoning and side reactions, and improve the purity and quality of the finished sulfuric acid.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid preparation technology, and more specifically to a process for preparing high-purity sulfuric acid. Background Technology

[0002] Sulfuric acid is one of the most important basic chemicals in modern industry, widely used in chemistry, metallurgy, petroleum refining, battery manufacturing, and other fields. Currently, sulfuric acid is mainly produced through the contact process. Its core process involves roasting pyrite or sulfur in a fluidized bed furnace to generate high-temperature furnace gas containing SO2. This gas undergoes dust removal, washing, and drying to remove impurities such as dust, arsenic, fluorine, and acid mist. Under the action of a catalyst, SO2 is converted to SO3, which is then absorbed by concentrated sulfuric acid to produce sulfuric acid. Traditional production processes have long relied on high-grade pyrite or purchased sulfur. With resource depletion and increasingly stringent environmental regulations, the production cost of sulfuric acid is rising. Gold sulfide, while rich in sulfur, also contains impurities such as arsenic and fluorine, and is considered hazardous waste. Furthermore, large stockpiles of gold sulfide occupy land and pose a risk of leachate pollution.

[0003] Vanadium-based catalysts for sulfur dioxide conversion are usually prepared by impregnation. After calcination, V2O5 tends to aggregate on the surface to form crystals with poor dispersibility, resulting in a reduction of active sites and a decrease in catalytic efficiency. Local overheating can trigger side reactions, affecting SO2 conversion rate. Furthermore, the thermal expansion coefficients of V2O5 and γ-alumina are mismatched, which can easily lead to cracks and spalling during high-temperature cycling, causing loss of active components.

[0004] Therefore, how to use sulfur gold sand in the preparation of sulfuric acid and improve the performance of vanadium-based catalysts for sulfur dioxide conversion are urgent problems to be solved in the current sulfuric acid preparation process. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a process for preparing high-purity sulfuric acid.

[0006] The objective of this invention can be achieved through the following technical solutions: A process for preparing high-purity sulfuric acid includes the following steps: Step (1): Crush and sieve the pyrite to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace and introduce air for roasting; the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing; the furnace gas from the dynamic scrubbing tower passes through a primary electrostatic precipitator and a secondary electrostatic precipitator to remove acid mist, and then enters a drying tower for drying to obtain dried furnace gas; Step (2): The dried furnace gas is preheated and then enters a converter containing a catalyst for SO2 conversion to carry out the conversion reaction, resulting in high-temperature furnace gas after conversion. After the high-temperature furnace gas is cooled down, it is then sequentially absorbed by the nicotinic acid absorption tower and the first absorption tower. After absorption by the first absorption tower, it is further cooled down and then absorbed by the second absorption tower to obtain high-purity sulfuric acid.

[0007] A process for preparing high-purity sulfuric acid includes the following specific steps: Step (1): Crush and sieve the pyrite to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace, use an air blower to send air into the fluidized bed furnace, heat to 850-950℃ for fluidized bed roasting for 2-2.5 hours, the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing and impurity removal, cool to 65-70℃, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; Furthermore, the ratio of crushed pyrite to pretreated pyrite sand is 7-8g:2-3g; the ratio of air to roasting raw materials is 3.5-4.5 Nm³ / kg.

[0008] Furthermore, the inlet gas temperature of the waste heat boiler is controlled at 850-950℃, the outlet gas temperature is controlled at 340-380℃, and the working steam pressure is 1.2-1.6MPa; the inlet flow velocity of the furnace gas entering the cyclone separator is 16-22m / s, and the equipment pressure drop is 0.8-1.5kPa; the operating furnace gas temperature in the electrostatic precipitator is controlled at 320-360℃, the secondary DC voltage is 45-55kV, the working current is 80-160mA, the furnace gas velocity is 0.6-1.0m / s, and the residence time of the furnace gas in the electrostatic precipitator is not less than 4.5s.

[0009] Furthermore, the primary electrostatic precipitator controls the inlet temperature to ≤38℃, the secondary voltage to ≥50kV, and the outlet acid mist concentration to ≤30mg / Nm³; the secondary electrostatic precipitator controls the inlet temperature to ≤38℃, the secondary voltage to 55-60kV, and the outlet acid mist concentration to ≤5mg / Nm³.

[0010] Furthermore, sulfuric acid with a mass fraction of 93-95% is used as the spray acid in the drying tower, and the temperature of the spray acid is 25-35℃. The furnace gas flows from bottom to top, and the spray acid flows from top to bottom, with a furnace gas to spray acid ratio of 1m³ / min. 3The gas flow rate is 8-12 L, the gas velocity is 0.6-0.9 m / s, the residence time of the gas in the drying tower is 12-18 s, and the pressure in the drying tower is -10 kPa to -7 kPa.

[0011] Step (2): The dried furnace gas is preheated to 390-420℃ by a preheater and then enters a converter containing a catalyst for SO2 conversion. After the conversion reaction is carried out at 390-420℃ for 2.0-3.0 hours, high-temperature furnace gas after conversion is obtained. The high-temperature furnace gas after conversion is cooled to 170-190℃ by a preheater and then enters the nicotinic acid absorption tower and the first absorption tower in sequence. After absorption in the first absorption tower, it is further cooled to 150-160℃ by a postheater and then enters the second absorption tower to obtain high-purity sulfuric acid.

[0012] Furthermore, the nicotine absorption tower uses nicotine at 60-80℃ for absorption, and controls the liquid-to-gas ratio to be 12-16 L / Nm³. 3 Both the first and second absorption towers use sulfuric acid at 70-80℃ and a mass fraction of 98% for absorption. The liquid-to-gas ratio in the first absorption tower is controlled at 10-14 L / Nm³. 3 The liquid-to-gas ratio in the second absorption tower is controlled at 8-12 L / Nm³. 3 The volumetric flow rate of the dried furnace gas and the proportion of the catalyst loading volume for SO2 conversion are 700-900 Nm³. 3 / h:1m 3 .

[0013] In step (ii), the high-temperature furnace gas after absorption and conversion by the nicotinic acid absorption tower produces nicotinic acid; the high-temperature furnace gas after absorption and conversion by the first and second absorption towers produces high-purity sulfuric acid.

[0014] Furthermore, the preparation method of pretreated sulfur gold sand includes the following steps: Step (1): Crush and sieve the sulfur gold sand to obtain fine sulfur gold sand particles, then mix it with water, add ball milling media, and ball mill to obtain ball milling slurry; Step (2): Mix the ball mill slurry and sodium carbonate solution, heat and stir, filter to obtain filter cake; add the filter cake to solution s, stir, filter, perform three-stage countercurrent washing, control the pH of the washing liquid, filter under pressure, dry to obtain pretreated sulfur gold sand.

[0015] Furthermore, the preparation method of pretreated sulfur gold sand includes the following specific steps: Step (1): Mechanically crush and sieve the sulfur gold sand to obtain fine sulfur gold sand particles, then mix it with water, add ball milling media, ball mill for 35-40 minutes, and discharge the material to obtain ball mill slurry; Furthermore, the ratio of fine sulfur gold sand particles to water is 1g:1-1.5mL; the ball milling media is obtained by mixing zirconia balls with diameters of 25mm, 15mm and 8mm in a mass ratio of 1:2:2; the total mass ratio of fine sulfur gold sand particles to water and the mass ratio of ball milling media is 1-1.5:2.

[0016] Step (2): Mix the ball mill slurry and sodium carbonate solution, heat to 45-55℃, stir for 2.5-3h, filter to obtain filter cake; add the filter cake to solution s, stir for 2-2.5h, filter, and then perform three-stage countercurrent washing until the pH of the washing liquid is 6.5-7.5, filter by pressure, dry to obtain pretreated sulfur gold sand.

[0017] Furthermore, the ratio of ball milling slurry to sodium carbonate solution is 1g:2.5-3.0mL; the mass fraction of sodium carbonate solution is 3-5%; the ratio of filter cake to solution S is 1g:2.5-3.5mL; solution S is a mixture of 0.8mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 65.5-66.5:1.

[0018] Furthermore, in the three-stage countercurrent washing process, the washing water and the material form a countercurrent washing flow; the stirring speed is controlled at 400 r / min during each stage of washing, and the duration of a single stirring and washing cycle is set to 5 min.

[0019] Furthermore, the preparation method of the catalyst for SO2 conversion includes the following steps: Step A1: Place γ-alumina in a protective gas atmosphere, heat and hold it at that temperature, then cool it with the furnace, and transfer it to a reaction vessel. After introducing a protective gas, seal the reaction vessel, continue heating, then introduce steam, control the pressure inside the reaction vessel, hold it at that temperature, stop introducing steam, cool it, remove it and wash it, and finally dry it to obtain activated γ-alumina. Step A2: Mix ureapropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine with an aqueous ethanol solution, stir, adjust the pH of the system to obtain a hydrolysate; mix activated γ-alumina with the hydrolysate, heat and stir, let stand, dry, raise the temperature and keep warm to obtain a modified carrier; Step A3: Add the modified support to the mixed solution, stir, filter, and dry to obtain a dry filter cake; mix the dry filter cake and ammonium metavanadate solution, heat, add aluminum sol, stir, filter, dry, then calcine at a higher temperature, and cool with the furnace to obtain a catalyst for SO2 conversion.

[0020] Furthermore, the preparation method of the catalyst for SO2 conversion includes the following specific steps: Step A1: Place γ-alumina in a protective gas atmosphere, heat to 480-490℃, hold for 4-4.2h, cool with the furnace, then transfer to a reactor, introduce protective gas for 5-10min, seal the reactor, continue heating to 300-310℃, then introduce steam, control the pressure inside the reactor to 0.5-1.0MPa, hold for 3-3.5h, stop introducing steam, cool, remove and wash, and finally dry to obtain activated γ-alumina; In step A1, γ-alumina is sequentially subjected to high-temperature inert calcination and hydrothermal vaporization treatment to increase the content of active hydroxyl groups on the surface of γ-alumina, thereby obtaining activated γ-alumina.

[0021] Step A2: Mix ureapropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine with an aqueous ethanol solution, stir for 10-15 min, adjust the pH of the system to 4.6-5.0 to obtain a hydrolysate; mix activated γ-alumina with the hydrolysate, heat to 55-60℃, stir for 2-2.5 h, let stand for 5-10 min, dry, raise the temperature to 320-330℃, and keep warm for 2-2.5 h to obtain the modified support; Furthermore, the ratio of ureapropyltriethoxysilane to N-[3-(trimethoxysilyl)propyl]ethylenediamine is 13.5-14.5 g: 4-5 g; the ratio of the total mass of ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to the volume of the ethanol-water solution is 3-3.5 g: 100 mL; the ethanol-water solution is obtained by mixing ethanol and water in a volume ratio of 8-9: 1-2, and the volume fraction of ethanol is 95%.

[0022] Furthermore, the ratio of activated γ-alumina to hydrolysate is 1-2 g: 5-10 mL.

[0023] In step A2, ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine are hydrolyzed in an aqueous ethanol solution to form silanols. The silanols condense with the active hydroxyl groups on the surface of activated γ-alumina to form covalent bonds, introducing amino and urea groups onto the surface of γ-alumina to obtain a modified support.

[0024] Step A3: Add the modified support to the mixed solution, stir for 1.5-2 hours, filter, and dry the filter cake at 80°C for 2-2.5 hours to obtain a dry filter cake; mix the dry filter cake and ammonium metavanadate solution, heat to 50-55°C, add aluminum sol, stir for 2.0-2.5 hours, filter, and dry the obtained filter cake at 85-90°C for 2-2.5 hours, then dry at 105-110°C for 3.5-4 hours, followed by calcination and furnace cooling to obtain the catalyst for SO2 conversion.

[0025] Furthermore, the ratio of the modified carrier to the mixed solution is 1g:8-10mL; the mixed solution is obtained by mixing cerium nitrate, lanthanum nitrate, and water in a ratio of 0.05-0.1mol:0.02-0.04mol:1L and stirring for 10-15min; the ratio of the dried filter cake, ammonium metavanadate solution, and aluminum sol is 1g:7-9mL:0.5-1.0mL; the molar concentration of the ammonium metavanadate solution is 0.25-0.35mol / L.

[0026] Furthermore, the heating and calcination process is as follows: the temperature is increased to 220-230℃ at a rate of 2-2.5℃ / min, held for 1.5-2h, and then increased to 380-400℃ and held for 3-3.5h.

[0027] In step A3, the modified support is sequentially impregnated in a mixed solution (cerium nitrate and lanthanum nitrate dissolved in water) and an ammonium metavanadate solution to obtain a precursor for SO2 conversion catalyst loaded with V-Ce-La composite active components. After subsequent drying and calcination, it is finally converted into a catalyst with SO2 conversion activity, namely γ-Al2O3 loaded with V2O5-CeO2-La2O3, which is the catalyst for SO2 conversion.

[0028] The beneficial effects of this invention are: This invention discloses a process for preparing high-purity sulfuric acid. The process involves: crushing and screening pyrite, then mixing it with pretreated pyrite sand to obtain roasting raw material, which is then fed into a fluidized bed furnace and roasted at high temperature. The resulting high-temperature furnace gas is first cooled and its waste heat recovered by a waste heat boiler, and then passed through a cyclone separator and an electrostatic precipitator to remove dust, resulting in pre-purified furnace gas. The pre-purified furnace gas is then sent to a dynamic wave scrubbing tower for washing and impurity removal, followed by two stages of electrostatic precipitators to remove acid mist, and then passed into a drying tower to remove moisture, resulting in dried furnace gas. The dried furnace gas is then further processed by a heat exchanger... After being preheated to the reaction temperature by the heater, the gas is sent to the converter, where it undergoes catalytic conversion under the action of a catalyst for SO2 conversion, converting sulfur dioxide into sulfur trioxide and obtaining high-temperature furnace gas. The high-temperature furnace gas is then cooled by heat exchange and then sequentially fed into a nicotinic acid absorption tower and a first absorption tower for absorption. The furnace gas discharged from the first absorption tower is cooled by heat exchange again and then enters the second absorption tower for deep absorption. Nicotinic acid is used as the absorption medium in the nicotinic acid absorption tower, and sulfuric acid with a mass fraction of 98% is used as the absorption medium in both the first and second absorption towers. The temperature and liquid-gas ratio of the corresponding absorption media are controlled to finally produce high-purity sulfuric acid.

[0029] This invention is not limited to the conventional use of pyrite to prepare sulfuric acid, but rather utilizes sulfur gold sand solid waste in a resource-efficient manner, which is beneficial for reducing production costs. Nicotinic acid has a strong affinity and solubility for high concentrations of sulfur trioxide, exhibits a mild gas-liquid reaction, can stably absorb high concentrations of SO3, inhibits the formation of acid mist and aerosols, and avoids the entrainment of impurities, thus providing a prerequisite for the preparation of high-purity sulfuric acid.

[0030] The pretreated sulfide gold sand used in this invention is obtained by sequentially crushing and ball milling sulfide gold sand, treating it with sodium carbonate solution, treating it with solution S (a mixture of 0.8 mol / L sulfuric acid solution and 30% hydrogen peroxide), three-stage countercurrent washing, pressure filtration, and drying. First, the sulfide gold sand is treated with calcium carbonate solution. This utilizes the weakly alkaline environment to neutralize the acidic substances on the surface of the sulfide gold sand, simultaneously removing free silicates and clay gangue impurities. It also preliminarily solidifies some volatile harmful components, gently modifies the mineral surface properties, avoids excessive damage to effective sulfide components by strong alkali, and retains the sulfur element required for acid production to the greatest extent. Next, treatment with solution S is used. The acidic system of solution S can dissolve highly toxic and harmful impurities such as arsenic and fluorine in the ore. Hydrogen peroxide, as a mild oxidant, can oxidize and decompose low-valence reducing impurities in the sulfide gold sand, removing toxic substances that affect catalyst activity. The material surface is then washed with a three-stage countercurrent wash to remove residual leaching agents and soluble salt impurities. The pH of the material is adjusted to neutral to prevent residual acids and alkalis from being introduced into the roasting system, corroding equipment and interfering with catalytic conversion. This process yields pretreated sulfuric acid with low impurity content. This sulfuric acid preparation process, combining pretreated sulfuric acid, two-stage electrostatic precipitator, and multi-stage absorption tower for graded absorption, can effectively improve the purity of sulfuric acid.

[0031] The SO2 conversion catalyst used in this invention is first obtained by sequentially treating γ-alumina with high-temperature inert calcination and hydrothermal vaporization to obtain activated γ-alumina; then, the surface of the activated γ-alumina is modified with ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to introduce amino and urea groups into the surface of the γ-alumina to obtain a modified support; then, the modified support is sequentially impregnated with a mixed solution (obtained by dissolving cerium nitrate and lanthanum nitrate in water) and an ammonium metavanadate solution to obtain a precursor for SO2 conversion catalyst loaded with V-Ce-La composite active components. After subsequent drying and calcination, it is finally converted into a catalyst with SO2 conversion activity, namely γ-Al2O3 loaded with V2O5-CeO2-La2O3, i.e., SO2 conversion catalyst. Introducing amino and urea groups onto the surface of γ-alumina allows them to form coordination bonds with cerium and lanthanum metal ions, anchoring the active components. Coordination with urea groups improves high-temperature resistance, inhibits migration, loss, and aggregation of active components under high-temperature conditions, and enhances the interfacial bonding between CeO2, La2O3, and γ-alumina obtained through subsequent sintering. During the impregnation process with ammonium metavanadate solution, the added aluminum sol exhibits high lattice compatibility with the support, significantly reducing interfacial thermal expansion mismatch. Ammonium metavanadate dissolves in water and undergoes hydrolysis to generate oxyvanadate anions. Positively charged aluminum sol particles adsorb these oxyvanadate anions due to electrostatic interactions. Electron-deficient aluminum centers in the aluminum sol can coordinate and complex with the amino and urea groups on the γ-alumina surface, thereby enhancing the interfacial bonding between V2O5 and γ-alumina obtained through subsequent sintering. Finally, a catalyst for SO2 conversion with high stability under high-temperature conditions is obtained. This SO2 conversion catalyst uses V2O5 as the main active component. It relies on the excellent oxygen storage and release capacity and valence state regulation of CeO2 to improve the reaction rate and resist the poisoning of arsenic and fluorine impurities in the raw material system. It uses La2O3 to strengthen the interfacial bonding strength and high-temperature structural stability of the three phases and inhibit the sintering loss of active components. The three components achieve efficient synergy through electronic regulation, oxygen species transfer and site function complementarity, which significantly improves the catalytic conversion rate of sulfur dioxide, reaction selectivity and long-term operation stability. It is suitable for high impurity furnace gas conditions and ensures the stable production of high-purity sulfuric acid from the catalytic process. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0033] The purity of the high-purity sulfuric acid obtained in Examples 4-6 and Comparative Examples 1-4 of this invention was determined by acid-base titration.

[0034] Example 1 The catalyst for SO2 conversion is prepared by the following steps: Step A1: Place γ-alumina (supplier: Aladdin, item number: A1507041) in a nitrogen atmosphere, heat it to 480℃ at a rate of 10℃ / min, hold it at this temperature for 4 hours, cool it to room temperature in the furnace, then transfer it to a reactor, purge it with nitrogen for 5 minutes, seal the reactor, continue heating to 300℃, then purge it with steam, control the pressure inside the reactor to 0.5MPa, hold it at this temperature for 3 hours, stop purging the steam, cool it to room temperature, remove it and wash it six times with deionized water, and finally dry it at 120℃ for 2 hours to obtain activated γ-alumina; Step A2: Ureapropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, and an aqueous ethanol solution were mixed and stirred at room temperature for 10 min. The pH of the system was adjusted to 4.6 with acetic acid to obtain a hydrolysate. The activated γ-alumina was mixed with the hydrolysate, heated to 55°C, stirred at 400 rpm for 2 h, allowed to stand for 5 min, dried at 110°C for 6 h, and then heated to 320°C at a rate of 5°C / min and held for 2 h to obtain the modified product. The carrier; the ratio of ureapropyltriethoxysilane to N-[3-(trimethoxysilyl)propyl]ethylenediamine is 13.5 g: 4 g; the ratio of the total mass of ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to the volume of the ethanol-water solution is 3 g: 100 mL; the ethanol-water solution is obtained by mixing ethanol and water in a volume ratio of 8:2, with an ethanol volume fraction of 95%; the ratio of activated γ-alumina to hydrolysate is 1 g: 5 mL.

[0035] Step A3: Add the modified carrier to the mixed solution, stir at 500 rpm for 1.5 h at room temperature, filter, and dry the filter cake at 80℃ for 2 h to obtain a dry filter cake; mix the dry filter cake and ammonium metavanadate solution, heat to 50℃, add aluminum sol (supplier: Jinan Feiyue Chemical Co., Ltd., 25 kg), stir at 500 rpm for 2.0 h, filter, dry the obtained filter cake at 85℃ for 2 h, then dry at 105℃ for 3.5 h, then calcine, and cool to room temperature in the furnace to obtain SO2 conversion. The catalyst was modified; the ratio of the modified support to the mixed solution was 1 g: 8 mL; the mixed solution was obtained by mixing cerium nitrate, lanthanum nitrate, and water in a ratio of 0.05 mol: 0.02 mol: 1 L and stirring for 10 min; the ratio of the dried filter cake, ammonium metavanadate solution, and alumina sol was 1 g: 7 mL: 0.5 mL; the molar concentration of the ammonium metavanadate solution was 0.25 mol / L; the calcination process was as follows: the temperature was increased to 220 °C at a rate of 2 °C / min, held for 1.5 h, and then increased to 380 °C and held for 3 h.

[0036] Example 2 The catalyst for SO2 conversion is prepared by the following steps: Step A1: Place γ-alumina (supplier: Aladdin, item number: A1507041) in a nitrogen atmosphere, heat it to 485℃ at a rate of 10℃ / min, hold it at that temperature for 4.1h, cool it to room temperature in the furnace, then transfer it to a reactor, purge it with nitrogen for 8min, seal the reactor, continue heating to 305℃, then purge it with steam, control the pressure inside the reactor to 0.8MPa, hold it at that temperature for 3.3h, stop purging the steam, cool it to room temperature, remove it and wash it six times with deionized water, and finally dry it at 120℃ for 2h to obtain activated γ-alumina; Step A2: Ureapromyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine and aqueous ethanol solution were mixed and stirred at room temperature for 13 min. The pH of the system was adjusted to 4.8 with acetic acid to obtain a hydrolysate. The activated γ-alumina and the hydrolysate were mixed, heated to 58℃, stirred at 400 rpm for 2.3 h, allowed to stand for 8 min, dried at 110℃ for 6 h, and heated to 325℃ at a rate of 6℃ / min and held for 2.3 h to obtain the modified support. The ratio of ureapropyltriethoxysilane to N-[3-(trimethoxysilyl)propyl]ethylenediamine was 14.0 g: 4.5 g; the ratio of the total mass of ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to the volume of the ethanol-water solution was 3.3 g: 100 mL; the ethanol-water solution was obtained by mixing ethanol and water in a volume ratio of 8.5:1.5, with an ethanol volume fraction of 95%; the ratio of activated γ-alumina to hydrolysate was 1.5 g: 8 mL.

[0037] Step A3: Add the modified carrier to the mixed solution, stir at 500 rpm for 1.8 h at room temperature, filter, and dry the filter cake at 80℃ for 2.3 h to obtain a dried filter cake; mix the dried filter cake and ammonium metavanadate solution, heat to 53℃, add aluminum sol (supplier: Jinan Feiyue Chemical Co., Ltd., 25 kg), stir at 500 rpm for 2.3 h, filter, dry the obtained filter cake at 88℃ for 2.3 h, then dry at 108℃ for 3.7 h, then calcine, and cool to room temperature in the furnace to obtain SO2 conversion. The catalyst was modified; the ratio of the modified support to the mixed solution was 1 g: 9 mL; the mixed solution was obtained by mixing cerium nitrate, lanthanum nitrate and water in a ratio of 0.08 mol: 0.03 mol: 1 L and stirring for 13 min; the ratio of the dried filter cake, ammonium metavanadate solution and aluminum sol was 1 g: 8 mL: 0.8 mL; the molar concentration of the ammonium metavanadate solution was 0.30 mol / L; the heating and calcination process was as follows: the temperature was increased to 225 °C at a rate of 2.2 °C / min, held for 1.8 h, and then increased to 390 °C and held for 3.3 h.

[0038] Example 3 The catalyst for SO2 conversion is prepared by the following steps: Step A1: Place γ-alumina (supplier: Aladdin, item number: A1507041) in a nitrogen atmosphere, heat it to 490℃ at a rate of 10℃ / min, hold it at that temperature for 4.2h, cool it to room temperature in the furnace, then transfer it to a reactor, purge it with nitrogen for 10min, seal the reactor, continue heating to 310℃, then purge it with steam, control the pressure inside the reactor to 1.0MPa, hold it at that temperature for 3.5h, stop purging the steam, cool it to room temperature, remove it and wash it six times with deionized water, and finally dry it at 120℃ for 2h to obtain activated γ-alumina; Step A2: Ureapropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, and an aqueous ethanol solution were mixed and stirred at room temperature for 15 min. The pH of the system was adjusted to 5.0 with acetic acid to obtain a hydrolysate. Activated γ-alumina was mixed with the hydrolysate, heated to 60°C, stirred at 400 rpm for 2.5 h, allowed to stand for 10 min, dried at 110°C for 6 h, and then heated to 330°C at a rate of 7°C / min and held for 2.5 h to obtain the modified... The carrier; the ratio of ureapropyltriethoxysilane to N-[3-(trimethoxysilyl)propyl]ethylenediamine is 14.5 g: 5 g; the ratio of the total mass of ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to the volume of the ethanol-water solution is 3.5 g: 100 mL; the ethanol-water solution is obtained by mixing ethanol and water in a volume ratio of 9:1, with an ethanol volume fraction of 95%; the ratio of activated γ-alumina to hydrolysate is 2 g: 10 mL.

[0039] Step A3: Add the modified carrier to the mixed solution and stir at 500 rpm for 2 hours at room temperature. Filter and dry the filter cake at 80°C for 2.5 hours to obtain a dried filter cake. Mix the dried filter cake with ammonium metavanadate solution, heat to 55°C, add aluminum sol (supplier: Jinan Feiyue Chemical Co., Ltd., 25 kg), stir at 500 rpm for 2.5 hours, filter, and dry the resulting filter cake at 90°C for 2.5 hours, then at 110°C for 4 hours. Subsequently, calcine the mixture and cool it to room temperature in the furnace to obtain SO2 conversion. The catalyst, modified support, and mixed solution were used in a ratio of 1g:10mL. The mixed solution consisted of cerium nitrate, lanthanum nitrate, and water mixed in a ratio of 0.1mol:0.04mol:1L and stirred for 15min. The dry filter cake, ammonium metavanadate solution, and aluminum sol were used in a ratio of 1g:9mL:1.0mL. The molar concentration of the ammonium metavanadate solution was 0.35mol / L. The calcination process was as follows: the temperature was increased to 230℃ at a rate of 2.5℃ / min, held for 2h, and then increased to 400℃ and held for 3.5h.

[0040] Example 4 A process for preparing high-purity sulfuric acid includes the following steps: Step (1): Crush pyrite (supplier: Hubei Shineng Chemical Technology Co., Ltd., 1 ton) and pass it through a 100-mesh sieve to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace, use an air blower to send air into the fluidized bed furnace, heat to 850℃ for fluidized bed roasting for 2 hours, the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing and impurity removal, cool to 65℃, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; The ratio of crushed pyrite to pretreated sulfur gold sand is 7g:2g, and the ratio of air to roasting raw materials is 3.5 Nm³ / kg. The inlet temperature of the waste heat boiler is controlled at 850℃, the outlet temperature is controlled at 340℃, and the working steam pressure is 1.2MPa. The inlet velocity of the furnace gas entering the cyclone separator is 16m / s, and the equipment pressure drop is 0.8kPa. The furnace gas temperature in the electrostatic precipitator is controlled at 320℃, the secondary DC voltage is 45kV, the working current is 80mA, the furnace gas velocity is 0.6m / s, and the residence time of the furnace gas in the electrostatic precipitator is 5.0s. The inlet temperature of the first-stage electrostatic precipitator is controlled at 38℃, the secondary voltage is 50kV, and the outlet acid mist concentration is 30mg / Nm³. The inlet temperature of the second-stage electrostatic precipitator is controlled at 38℃, the secondary voltage is 55kV, and the outlet acid mist concentration is 5mg / Nm³.

[0041] The drying tower uses 93% sulfuric acid as the spray acid solution at a temperature of 25°C. The furnace gas is drawn from bottom to top, while the spray acid solution is drawn from top to bottom. The ratio of furnace gas to spray acid solution is 1 m³ / s. 3 The gas flow rate is 0.6 m / s, the residence time of the gas in the drying tower is 12 s, and the pressure in the drying tower is -10 kPa.

[0042] Step (II): The dried furnace gas is preheated to 390°C via a preheater and then enters a converter containing the SO2 conversion catalyst obtained in Example 1. After a conversion reaction at 390°C for 2.0 hours, high-temperature furnace gas is obtained. The high-temperature furnace gas is then cooled to 170°C via a preheater and sequentially enters a nicotinic acid absorption tower and a first absorption tower for absorption. After absorption in the first absorption tower, it is further cooled to 150°C via a postheater and then enters a second absorption tower for absorption to obtain high-purity sulfuric acid. Nicotinic acid (99.9% purity) at 60°C is used in the nicotinic acid absorption tower for absorption, and the liquid-to-gas ratio is controlled at 12 L / Nm³. 3 Both the first and second absorption towers use 98% sulfuric acid at 70℃ for absorption. The liquid-to-gas ratio in the first absorption tower is controlled at 10 L / Nm³. 3 The liquid-to-gas ratio in the second absorption tower is controlled at 8 L / Nm³. 3 The volumetric flow rate of the dried furnace gas and the ratio of the loading volume of the SO2 conversion catalyst obtained in Example 1 are 700 Nm³. 3 / h:1m 3 .

[0043] The preparation method of pretreated sulfur gold sand includes the following steps: Step (1): Mechanically crush the sulfide gold sand through a 2mm sieve to obtain fine sulfide gold sand particles, then mix it with water, add ball milling media, ball mill for 35 minutes, and discharge to obtain ball milling slurry; the ratio of fine sulfide gold sand particles to water is 1g:1mL; the ball milling media is obtained by mixing zirconia balls with diameters of 25mm, 15mm and 8mm in a mass ratio of 1:2:2; the total mass ratio of fine sulfide gold sand particles to water and the mass ratio of ball milling media is 1:2.

[0044] Step (2): Mix the ball mill slurry and sodium carbonate solution, heat to 45℃, stir at 600 rpm for 2.5 h, filter, and obtain filter cake; add the filter cake to solution s, stir at 500 rpm for 2 h at room temperature, filter, and perform three-stage countercurrent washing until the pH of the washing liquid is 6.5, filter under pressure at 0.6 MPa for 30 min, and then dry at 105℃ for 6 h to obtain pretreated sulfur gold sand; the ratio of ball mill slurry to sodium carbonate solution is 1 g: 2.5 mL; the mass fraction of sodium carbonate solution is 3%; the ratio of filter cake to solution s is 1 g: 2.5 mL; solution s is a mixture of 0.8 mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 65.5:1; during the three-stage countercurrent washing process, the washing water and the material form a countercurrent washing, the stirring speed is controlled at 400 r / min during each washing process, and the single stirring and washing time is set to 5 min.

[0045] The purity of the obtained high-purity sulfuric acid is 99.34%.

[0046] Example 5 A process for preparing high-purity sulfuric acid includes the following steps: Step (1): Crush pyrite (supplier: Hubei Shineng Chemical Technology Co., Ltd., 1 ton) and pass it through a 100-mesh sieve to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace, use an air blower to send air into the fluidized bed furnace, heat to 900℃ for fluidized bed roasting for 2.3 hours, the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing and impurity removal, cool to 68℃, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; The ratio of crushed pyrite to pretreated pyrite sand is 7.5g:2.5g, and the ratio of air to roasting raw materials is 4.0 Nm³ / kg. The inlet temperature of the waste heat boiler is controlled at 900℃, the outlet temperature at 360℃, and the working steam pressure at 1.4MPa. The inlet velocity of the furnace gas entering the cyclone separator is 19m / s, and the equipment pressure drop is 1.1kPa. In the electrostatic precipitator, the furnace gas temperature is controlled at 340℃, the secondary DC voltage is 50kV, the working current is 120mA, the furnace gas velocity is 0.8m / s, and the residence time of the furnace gas in the electrostatic precipitator is 5.0s. The inlet temperature of the first-stage electrostatic precipitator is controlled at 38℃, the secondary voltage at 50kV, and the outlet acid mist concentration at 30mg / Nm³. The inlet temperature of the second-stage electrostatic precipitator is controlled at 38℃, the secondary voltage at 58kV, and the outlet acid mist concentration at 5mg / Nm³.

[0047] The drying tower uses 94% sulfuric acid as the spray acid solution at a temperature of 30℃. The furnace gas is drawn from bottom to top, while the spray acid solution is drawn from top to bottom. The ratio of furnace gas to spray acid solution is 1 m³ / s. 3 The gas flow rate is 10L, the gas velocity is 0.75m / s, the residence time of the gas in the drying tower is 15s, and the pressure in the drying tower is -8kPa.

[0048] Step (II): The dried furnace gas is preheated to 400°C via a preheater and then enters a converter containing the SO2 conversion catalyst obtained in Example 2. After a conversion reaction at 400°C for 2.5 hours, high-temperature furnace gas is obtained. The high-temperature furnace gas is then cooled to 180°C via a preheater and sequentially enters a nicotinic acid absorption tower and a first absorption tower for absorption. After absorption in the first absorption tower, it is further cooled to 155°C via a postheater and then enters a second absorption tower for absorption, yielding high-purity sulfuric acid. Nicotinic acid (99.9% purity) at 70°C is used in the nicotinic acid absorption tower for absorption, with the liquid-to-gas ratio controlled at 14 L / Nm³. 3 Both the first and second absorption towers use sulfuric acid at 75℃ and a mass fraction of 98% for absorption. The liquid-to-gas ratio in the first absorption tower is controlled at 12 L / Nm³. 3 The liquid-to-gas ratio in the second absorption tower is controlled at 10 L / Nm³. 3 The volumetric flow rate of the dried furnace gas and the ratio of the loading volume of the SO2 conversion catalyst obtained in Example 2 are 800 Nm³. 3 / h:1m 3 .

[0049] The preparation method of pretreated sulfur gold sand includes the following steps: Step (1): Mechanically crush the gold oxide slurry through a 2mm sieve to obtain fine gold oxide slurry particles, then mix it with water, add ball milling media, ball mill for 37 minutes, and discharge the material to obtain ball milling slurry; the ratio of fine gold oxide slurry particles to water is 1g:1.3mL; the ball milling media is obtained by mixing zirconia balls with diameters of 25mm, 15mm and 8mm in a mass ratio of 1:2:2; the total mass ratio of fine gold oxide slurry particles to water and the mass ratio of ball milling media is 1.3:2.

[0050] Step (2): Mix the ball mill slurry and sodium carbonate solution, heat to 50℃, stir at 600 rpm for 2.8 h, filter, and obtain filter cake; add the filter cake to solution s, stir at 500 rpm for 2.3 h at room temperature, filter, and perform three-stage countercurrent washing until the pH of the washing liquid is 7.0, filter under pressure at 0.6 MPa for 30 min, and then dry at 105℃ for 6 h to obtain pretreated sulfur gold sand; the ratio of ball mill slurry to sodium carbonate solution is 1 g: 2.8 mL; the mass fraction of sodium carbonate solution is 4%; the ratio of filter cake to solution s is 1 g: 3.0 mL; solution s is a mixture of 0.8 mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 66.0: 1; during the three-stage countercurrent washing process, the washing water and the material form a countercurrent washing, the stirring speed is controlled at 400 r / min during each washing process, and the single stirring and washing time is set to 5 min.

[0051] The purity of the obtained high-purity sulfuric acid is 99.25%.

[0052] Example 6 A process for preparing high-purity sulfuric acid includes the following steps: Step (1): Crush pyrite (supplier: Hubei Shineng Chemical Technology Co., Ltd., 1 ton) and pass it through a 100-mesh sieve to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace, use an air blower to send air into the fluidized bed furnace, heat to 950℃ for fluidized bed roasting for 2.5 hours, the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing and impurity removal, cool to 70℃, and pass the furnace gas from the dynamic scrubbing tower through a first-stage electrostatic precipitator and a second-stage electrostatic precipitator to remove acid mist, and then enter a drying tower for drying to obtain dried furnace gas; The ratio of crushed pyrite to pretreated pyrite sand is 8g:3g, and the ratio of air to roasting raw materials is 4.5 Nm³ / kg. The inlet temperature of the waste heat boiler is controlled at 950℃, the outlet temperature at 380℃, and the working steam pressure at 1.6MPa. The inlet velocity of the furnace gas entering the cyclone separator is 22m / s, and the equipment pressure drop is 1.5kPa. In the electrostatic precipitator, the operating furnace gas temperature is controlled at 360℃, the secondary DC voltage is 55kV, the working current is 160mA, the furnace gas velocity is 1.0m / s, and the residence time of the furnace gas in the electrostatic precipitator is 5.0s. The inlet temperature of the first-stage electrostatic precipitator is controlled at 38℃, the secondary voltage at 50kV, and the outlet acid mist concentration at 30mg / Nm³. The inlet temperature of the second-stage electrostatic precipitator is controlled at 38℃, the secondary voltage at 60kV, and the outlet acid mist concentration at 5mg / Nm³.

[0053] The drying tower uses 95% sulfuric acid as the spray acid solution at a temperature of 35°C. The furnace gas is drawn from bottom to top, while the spray acid solution is drawn from top to bottom. The ratio of furnace gas to spray acid solution is 1 m³ / s. 3 The gas flow rate is 12L, the gas velocity is 0.9m / s, the residence time of the gas in the drying tower is 18s, and the pressure in the drying tower is -7kPa.

[0054] Step (II): The dried furnace gas is preheated to 420°C via a preheater and then enters a converter containing the SO2 conversion catalyst obtained in Example 3. After a conversion reaction at 420°C for 3.0 hours, high-temperature furnace gas is obtained. The high-temperature furnace gas is then cooled to 190°C via a preheater and sequentially enters a nicotinic acid absorption tower and a first absorption tower for absorption. After absorption in the first absorption tower, it is further cooled to 160°C via a postheater and then enters a second absorption tower for absorption to obtain high-purity sulfuric acid. Nicotinic acid (99.9% purity) at 80°C is used in the nicotinic acid absorption tower for absorption, and the liquid-to-gas ratio is controlled at 16 L / Nm³. 3 Both the first and second absorption towers use sulfuric acid at 80℃ and a mass fraction of 98% for absorption. The liquid-to-gas ratio in the first absorption tower is controlled at 14 L / Nm³. 3 The liquid-to-gas ratio in the second absorption tower is controlled at 12 L / Nm³. 3 The volumetric flow rate of the dried furnace gas and the ratio of the loading volume of the SO2 conversion catalyst obtained in Example 3 are 900 Nm³. 3 / h:1m 3 .

[0055] The preparation method of pretreated sulfur gold sand includes the following steps: Step (1): Mechanically crush the sulfide gold sand through a 2mm sieve to obtain fine sulfide gold sand particles, then mix it with water, add ball milling media, ball mill for 40 minutes, and discharge to obtain ball milling slurry; the ratio of fine sulfide gold sand particles to water is 1g:1.5mL; the ball milling media is obtained by mixing zirconia balls with diameters of 25mm, 15mm and 8mm in a mass ratio of 1:2:2; the total mass ratio of fine sulfide gold sand particles to water and the mass ratio of ball milling media is 1.5:2.

[0056] Step (2): Mix the ball mill slurry and sodium carbonate solution, heat to 55℃, stir at 600 rpm for 3 hours, filter to obtain filter cake; add the filter cake to solution s, stir at 500 rpm for 2.5 hours at room temperature, filter, and perform three-stage countercurrent washing until the pH of the washing liquid is 7.5, filter under pressure at 0.6 MPa for 30 minutes, and then dry at 105℃ for 6 hours to obtain pretreated sulfur gold sand; the ratio of ball mill slurry to sodium carbonate solution is 1 g: 3.0 mL; the mass fraction of sodium carbonate solution is 5%; the ratio of filter cake to solution s is 1 g: 3.5 mL; solution s is a mixture of 0.8 mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 66.5:1; during the three-stage countercurrent washing process, the washing water and the material form a countercurrent washing, the stirring speed is controlled at 400 r / min during each washing process, and the single stirring and washing time is set to 5 min.

[0057] The purity of the obtained high-purity sulfuric acid is 99.60%.

[0058] Comparative Example 1 Compared with Example 6, the ball milling slurry in step (2) of the pretreated sulfur gold sand preparation process was first treated with solution s and then treated with sodium carbonate solution to obtain pretreated sulfur gold sand-1. Pretreated sulfur gold sand-1 was used to replace the pretreated sulfur gold sand, and the rest was completely the same as in Example 6 to obtain high-purity sulfuric acid. Specifically as follows: Step (2): Add the ball mill slurry to solution s, stir at 500 rpm for 2.5 h at room temperature, filter to obtain filter cake-1; mix filter cake-1 and sodium carbonate solution, heat to 55℃, stir at 600 rpm for 3 h, filter, and perform three-stage countercurrent washing until the pH of the washing solution is 7.5, filter under pressure at 0.6 MPa for 30 min, and then dry at 105℃ for 6 h to obtain pretreated sulfur gold sand-1; the volume ratio of ball mill slurry to solution s is 1 g: 3.5 mL; solution s is a mixture of 0.8 mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 66.5:1; the volume ratio of filter cake-1 to sodium carbonate solution is 1: 3.0 mL; the mass fraction of sodium carbonate solution is 5%.

[0059] The purity of the obtained high-purity sulfuric acid is 98.14%.

[0060] Comparative Example 2 Compared with Example 6, the modified support in the preparation process of the catalyst for SO2 conversion was replaced with modified support-1, and the rest was exactly the same as in Example 6, to obtain high-purity sulfuric acid; Preparation process of modified carrier-1: Ureapropyltriethoxysilane was mixed with an aqueous ethanol solution and stirred at room temperature for 15 min. The pH of the system was adjusted to 5.0 with acetic acid to obtain hydrolysate-1. Activated γ-alumina and hydrolysate-1 were mixed, heated to 60 °C, stirred at 400 rpm for 2.5 h, allowed to stand for 10 min, dried at 110 °C for 6 h, and then heated to 320 °C at a rate of 7 °C / min and held for 2.5 h to obtain modified carrier-1. The volume ratio of ureapropyltriethoxysilane to aqueous ethanol solution was 3.5 g: 100 mL. The aqueous ethanol solution was obtained by mixing ethanol and water at a volume ratio of 9:1, with an ethanol volume fraction of 95%. The volume ratio of activated γ-alumina to hydrolysate was 2 g: 10 mL.

[0061] The purity of the obtained high-purity sulfuric acid is 98.46%.

[0062] Comparative Example 3 Compared with Example 6, the modified support in the preparation process of the catalyst for SO2 conversion was replaced with modified support-2, and the rest was exactly the same as in Example 6, to obtain high-purity sulfuric acid; Preparation process of modified carrier-2: N-[3-(trimethoxysilyl)propyl]ethylenediamine was mixed with an aqueous ethanol solution and stirred at room temperature for 15 min. The pH of the system was adjusted to 5.0 with acetic acid to obtain hydrolysate-2. Activated γ-alumina and hydrolysate-2 were mixed, heated to 60℃, stirred at 400 rpm for 2.5 h, allowed to stand for 10 min, dried at 110℃ for 6 h, and then heated to 320℃ at a rate of 7℃ / min and held for 2.5 h to obtain the modified support. The ratio of N-[3-(trimethoxysilyl)propyl]ethylenediamine to aqueous ethanol solution was 3.5 g: 100 mL. The aqueous ethanol solution was obtained by mixing ethanol and water at a volume ratio of 9:1, with an ethanol volume fraction of 95%. The ratio of activated γ-alumina to hydrolysate-2 was 2 g: 10 mL.

[0063] The purity of the obtained high-purity sulfuric acid is 98.51%.

[0064] Comparative Example 4 Compared with Example 6, the modified support in step A3 of the preparation process of the SO2 conversion catalyst was first impregnated in ammonium metavanadate solution and then impregnated in mixed solution to obtain SO2 conversion catalyst-1. The SO2 conversion catalyst-1 was used to replace the SO2 conversion catalyst, and the rest was completely the same as in Example 6 to obtain high-purity sulfuric acid. Specifically as follows: Step A3: Mix the modified support and ammonium metavanadate solution, heat to 55°C, add aluminum sol (supplier: Jinan Feiyue Chemical Co., Ltd., 25 kg), stir at 500 rpm for 2.5 h, filter, and dry the resulting filter cake at 90°C for 2.5 h to obtain dried filter cake-1; add dried filter cake-1 to the mixed solution, stir at 500 rpm for 2 h at room temperature, filter, dry filter cake-2 at 80°C for 2.5 h, then dry at 110°C for 4 h, then calcine at a higher temperature, and cool to room temperature in the furnace to obtain SO2 conversion catalyst-1.

[0065] The ratio of modified carrier, ammonium metavanadate solution, and aluminum sol was 1 g: 9 mL: 1.0 mL; the molar concentration of ammonium metavanadate solution was 0.35 mol / L; the ratio of dried filter cake-1 to mixed solution was 1 g: 10 mL; the mixed solution was obtained by mixing cerium nitrate, lanthanum nitrate, and water in a ratio of 0.1 mol: 0.04 mol: 1 L and stirring for 15 min; the heating and calcination process was as follows: the temperature was increased to 230℃ at a rate of 2.5℃ / min, held for 2 h, and then increased to 400℃ and held for 3.5 h.

[0066] The purity of the obtained high-purity sulfuric acid is 98.06%.

[0067] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A process for preparing high-purity sulfuric acid, characterized in that: The steps include the following: Step (1): Crush and sieve the pyrite to obtain crushed pyrite; mix the crushed pyrite with pretreated pyrite sand to obtain roasting raw material; send the roasting raw material into a fluidized bed furnace and introduce air for roasting; the high-temperature furnace gas generated by fluidized bed roasting enters the waste heat boiler, and then passes through a cyclone separator and an electrostatic precipitator for purification to obtain pre-purified furnace gas; pass the pre-purified furnace gas into a dynamic wave scrubbing tower for washing; the furnace gas from the dynamic scrubbing tower passes through a primary electrostatic precipitator and a secondary electrostatic precipitator to remove acid mist, and then enters a drying tower for drying to obtain dried furnace gas; Step (2): The dried furnace gas is preheated and then enters a converter containing a catalyst for SO2 conversion to carry out the conversion reaction, resulting in high-temperature furnace gas after conversion. After the high-temperature furnace gas is cooled down, it is then sequentially absorbed by the nicotinic acid absorption tower and the first absorption tower. After absorption by the first absorption tower, it is further cooled down and then absorbed by the second absorption tower to obtain high-purity sulfuric acid.

2. The preparation process of high-purity sulfuric acid according to claim 1, characterized in that: In step (i), the ratio of crushed pyrite to pretreated pyrite sand is 7-8g:2-3g; the ratio of air to roasting raw materials is 3.5-4.5Nm. 3 / kg.

3. The preparation process of high-purity sulfuric acid according to claim 1, characterized in that: In step (ii), the nicotinic acid absorption tower uses nicotinic acid at 60-80℃ for absorption, and the liquid-to-gas ratio is controlled at 12-16 L / Nm³. 3 Both the first and second absorption towers use sulfuric acid at 70-80℃ and a mass fraction of 98% for absorption. The liquid-to-gas ratio in the first absorption tower is controlled at 10-14 L / Nm³. 3 The liquid-to-gas ratio in the second absorption tower is controlled at 8-12 L / Nm³. 3 The volumetric flow rate of the dried furnace gas and the proportion of the catalyst loading volume for SO2 conversion are 700-900 Nm³. 3 / h:1m 3 .

4. The preparation process of high-purity sulfuric acid according to claim 1, characterized in that: The preparation method of the pretreated sulfur gold sand includes the following steps: Step (1): Crush and sieve the sulfur gold sand to obtain fine sulfur gold sand particles, then mix it with water, add ball milling media, and ball mill to obtain ball milling slurry; Step (2): Mix the ball mill slurry and sodium carbonate solution, heat and stir, filter to obtain filter cake; add the filter cake to solution s, stir, filter, perform three-stage countercurrent washing, control the pH of the washing liquid, filter under pressure, dry to obtain pretreated sulfur gold sand.

5. The preparation process of high-purity sulfuric acid according to claim 4, characterized in that: In step (1), the ratio of the fine sulfur gold sand particles to water is 1g:1-1.5mL; the ball milling media is obtained by mixing zirconia balls with diameters of 25mm, 15mm and 8mm in a mass ratio of 1:2:2; the total mass ratio of the fine sulfur gold sand particles to water and the mass ratio of the ball milling media is 1-1.5:

2.

6. The preparation process of high-purity sulfuric acid according to claim 4, characterized in that: In step (2), the ratio of ball mill slurry to sodium carbonate solution is 1g:2.5-3.0mL; the mass fraction of sodium carbonate solution is 3-5%; the ratio of filter cake to solution s is 1g:2.5-3.5mL; solution s is a mixture of 0.8mol / L sulfuric acid solution and 30% hydrogen peroxide at a volume ratio of 65.5-66.5:

1.

7. The preparation process of high-purity sulfuric acid according to claim 1, characterized in that: The catalyst for SO2 conversion is prepared by the following steps: Step A1: Place γ-alumina in a protective gas atmosphere, heat and hold it at that temperature, then cool it with the furnace, and transfer it to a reaction vessel. After introducing a protective gas, seal the reaction vessel, continue heating, then introduce steam, control the pressure inside the reaction vessel, hold it at that temperature, stop introducing steam, cool it, remove it and wash it, and finally dry it to obtain activated γ-alumina. Step A2: Mix ureapropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine with an aqueous ethanol solution, stir, adjust the pH of the system to obtain a hydrolysate; mix activated γ-alumina with the hydrolysate, heat and stir, let stand, dry, raise the temperature and keep warm to obtain a modified carrier; Step A3: Add the modified support to the mixed solution, stir, filter, and dry to obtain a dry filter cake; mix the dry filter cake and ammonium metavanadate solution, heat, add aluminum sol, stir, filter, dry, then calcine at a higher temperature, and cool with the furnace to obtain a catalyst for SO2 conversion.

8. The preparation process of high-purity sulfuric acid according to claim 7, characterized in that: In step A2, the ratio of ureapropyltriethoxysilane to N-[3-(trimethoxysilyl)propyl]ethylenediamine is 13.5-14.5g:4-5g; the ratio of the total mass of ureapropyltriethoxysilane and N-[3-(trimethoxysilyl)propyl]ethylenediamine to the volume of the ethanol aqueous solution is 3-3.5g:100mL.

9. The preparation process of high-purity sulfuric acid according to claim 7, characterized in that: In step A3, the ratio of the modified carrier to the mixed solution is 1g:8-10mL; the mixed solution is obtained by mixing cerium nitrate, lanthanum nitrate, and water in a ratio of 0.05-0.1mol:0.02-0.04mol:1L and stirring for 10-15min; the ratio of the dried filter cake, ammonium metavanadate solution, and aluminum sol is 1g:7-9mL:0.5-1.0mL; the molar concentration of the ammonium metavanadate solution is 0.25-0.35mol / L.

10. The process for preparing high-purity sulfuric acid according to claim 7, characterized in that: In step A3, the heating and calcination process is as follows: the temperature is increased to 220-230℃ at a rate of 2-2.5℃ / min, held for 1.5-2h, and then increased to 380-400℃ and held for 3-3.5h.