A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials.

Abstract

This invention discloses a method for preparing sulfuric acid or ammonium bisulfate from sulfate materials. The method involves: freezing a mixed stock solution containing ammonium sulfate and HCl to crystallize the mixture, followed by solid-liquid separation to obtain ammonium chloride crystals and a crystallized liquid. When the mixed stock solution contains Cl... ‑ With NH4 + When the molar ratio of Cl is 1~1.2:1, sulfuric acid is obtained by evaporation and concentration of the crystallized solution; when the mixed original solution contains Cl... ‑ With NH4 + When the molar ratio is 0.5~0.6:1, the crystallized liquid is concentrated by evaporation and solid-liquid separation. The resulting ammonium bisulfate-containing filtrate is then cooled, crystallized, and separated again to obtain ammonium bisulfate. The NH3 and HCl obtained from the thermal decomposition of ammonium chloride crystals are collected and recycled. The ammonium sulfate in the mixed solution comes from the finished ammonium sulfate raw material or is obtained from non-ammonium sulfate raw materials through a conversion reaction. This method is simple, low-cost, and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of green chemistry and environmental protection, and specifically relates to a method for preparing sulfuric acid or ammonium bisulfate using sulfate materials. Background Technology

[0002] Sulfuric acid is a strong acid with the chemical formula H₂SO₄. It is an important industrial raw material used in the manufacture of fertilizers, pharmaceuticals, explosives, pigments, detergents, and batteries, and is also widely used in petroleum purification, metal smelting, and dye industries. After use, sulfuric acid is mostly converted into sulfates, primarily in the form of calcium sulfate, sodium sulfate, and ammonium sulfate. Due to its reactive nature, direct regeneration of sulfuric acid from sulfates is difficult. In-situ regeneration is only possible in a few cases, such as electrolysis of copper sulfate solution, electrolysis of manganese sulfate solution, and passing H₂S into copper sulfate solution. Although calcium sulfate (gypsum) can also be used to produce sulfuric acid, it requires high-temperature calcination to decompose and release SO₂, which is then catalytically converted to SO₃. The SO₃ is then absorbed by dilute sulfuric acid to obtain the sulfuric acid product. However, industrially, sulfuric acid produced using gypsum as a raw material and employing a high-temperature calcination process is costly and economically unfeasible. Currently, large quantities of industrial gypsum are piling up both domestically and internationally, urgently requiring suitable methods for their disposal.

[0003] Ammonium bisulfate is also an inorganic compound with the chemical formula NH4HSO4, belonging to the acidic salt class. It is widely used in chemical, metallurgical, agricultural, and pesticide industries. Ammonium bisulfate can be used as a nitrogen fertilizer to provide the nitrogen element needed for plant growth. It can also be used to prepare other compounds, such as metal sulfides, ammonia, and sulfur dioxide. Furthermore, it can be used as a raw material in the production of pesticides, gunpowder, and welding agents. The main production methods for ammonium bisulfate are: the sulfuric acid-ammonia neutralization method and the ammonium sulfate solution-sulfuric acid acidification method. In the first method, ammonia gas is passed into sulfuric acid suspended in water, then the resulting ammonium sulfate is removed by filtration, and finally the solution is concentrated to obtain solid ammonium bisulfate. In the second method, sulfuric acid is first stirred and added to the ammonium sulfate solution at a molar ratio of 1:1, and then the solution is concentrated to obtain solid ammonium bisulfate. Both of these production methods for ammonium bisulfate are relatively expensive and consume large amounts of sulfuric acid.

[0004] Therefore, there is an urgent need to develop a method that can efficiently utilize low-cost sulfate materials to prepare sulfuric acid or ammonium bisulfate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing sulfuric acid or ammonium bisulfate from sulfate materials. This method is simple, highly efficient, low-cost, environmentally friendly, and suitable for industrial production.

[0006] To achieve the above-mentioned technical objectives, this invention provides a method for preparing sulfuric acid or ammonium bisulfate from sulfate materials. The method involves: freezing a mixed stock solution containing ammonium sulfate and HCl to achieve solid-liquid separation, yielding ammonium chloride crystals and a crystallized liquid. When the mixed stock solution contains Cl... - With NH4 + When the molar ratio of Cl is 1~1.2:1, sulfuric acid is obtained by evaporation and concentration of the crystallized solution; when the mixed original solution contains Cl... - With NH4 + When the molar ratio is 0.5~0.6:1, the crystallized liquid is concentrated by evaporation and solid-liquid separation. The resulting ammonium bisulfate-containing filtrate is then cooled, crystallized, and separated to obtain ammonium bisulfate. The NH3 and HCl obtained from the thermal decomposition of ammonium chloride crystals are collected and recycled. The ammonium sulfate in the mixed original solution comes from the finished ammonium sulfate raw material or is obtained from non-ammonium sulfate raw materials through a conversion reaction.

[0007] Sulfuric acid is a non-volatile acid, while hydrochloric acid is a volatile acid. Existing techniques typically involve adding the non-volatile acid to a volatile salt solution and then evaporating to prepare the volatile acid. However, this invention utilizes the solubility of ammonium chloride in supercritical aqueous solutions (NH4+) by freeze-crystallizing a mixed stock solution containing ammonium sulfate and HCl. + (The ions crystallize out deeply in the form of NH4Cl), which can be used to reverse-phase the production of sulfuric acid or ammonium bisulfate. Among these,

[0008] As a preferred embodiment, the mixed stock solution containing ammonium sulfate and HCl is prepared by mixing solid ammonium sulfate or ammonium sulfate solution with hydrochloric acid, or by passing HCl gas through an ammonium sulfate solution.

[0009] As a preferred embodiment, the ammonium sulfate solution has a mass concentration of 35-45%. This mass concentration of ammonium sulfate solution indicates that it is a saturated or nearly saturated ammonium sulfate solution. Using this concentration of ammonium sulfate solution facilitates the freeze-crystallization of ammonium chloride while reducing the burden of evaporation and concentration of the resulting sulfuric acid or ammonium bisulfate solution.

[0010] As a preferred embodiment, the hydrochloric acid has a mass concentration of 30-40%. Using hydrochloric acid of this concentration is beneficial for improving the efficiency of freeze crystallization.

[0011] As a preferred embodiment, the conditions for freeze crystallization are: temperature of -30℃ to 0℃ and time of 2 to 24 hours. When the product to be prepared is ammonium bisulfate, the freeze crystallization temperature is further preferably -15℃ to 0℃.

[0012] As a preferred option, when the product being prepared is sulfuric acid, the temperature for evaporation and concentration of the crystallized liquid is 115~337℃.

[0013] As a preferred embodiment, when the product prepared is ammonium bisulfate, the temperature for evaporation and concentration of the crystallized liquid is 115~147℃. The ammonium bisulfate filtrate is then cooled, crystallized, and separated into solid and liquid components. The resulting filtrate is then returned to prepare a mixed stock solution containing ammonium sulfate and HCl.

[0014] As a preferred option, the HCl generated during the evaporation and concentration process is collected and recycled to prepare a mixed stock solution containing ammonium sulfate and HCl. The condensate generated during the evaporation and concentration process is neutralized with ammonia or lime milk and then recycled.

[0015] As a preferred embodiment, the method for obtaining ammonium sulfate from non-ammonium sulfate raw materials through a conversion reaction is as follows: When the non-ammonium sulfate raw material is a water-soluble sulfate, a sulfate precipitant is added to the non-ammonium sulfate raw material solution to carry out a precipitation reaction. After solid-liquid separation, a sulfate slag phase is obtained. The sulfate slag phase is mixed with water to make pulp, and ammonia is added to adjust the pH value of the pulp to ≥8. Then, at least one of the following conversion agents, namely ammonium carbonate, ammonium carbonate solution, ammonium bicarbonate, ammonium bicarbonate solution, carbon dioxide, and carbonic acid, is added to the pulp to carry out carbonation conversion. After solid-liquid separation, conversion slag and ammonium sulfate solution are obtained. The amount of water required for pulping is calculated based on the formation of an ammonium sulfate solution with a mass concentration of 35-45% after carbonation conversion. The ammonium sulfate solution is directly used to prepare a mixed stock solution containing ammonium sulfate and HCl, or it is obtained by evaporation and crystallization, and the resulting ammonium sulfate crystals are then used to prepare a mixed stock solution containing ammonium sulfate and HCl. The washing water obtained after washing the conversion slag with water is returned to the carbonation conversion process for recycling.

[0016] When the sulfate raw material for non-ammonium sulfate is a non-water-soluble sulfate, ammonium sulfate can be prepared directly according to the above-mentioned method for treating the sulfate residue phase. That is, non-water-soluble sulfate is directly converted into ammonium sulfate solution through a carbonation transformation process.

[0017] As can be seen from the above, the ammonium sulfate solution obtained by the carbonation transformation process of this invention has a mass concentration of 35-45%, which can be used openly as a raw material for the production of sulfuric acid or ammonium bisulfate. Alternatively, the open-circuit solution can be first evaporated and concentrated, then crystallized or fractionally crystallized to obtain ammonium sulfate crystals, which can then be used as a raw material for the production of sulfuric acid or ammonium bisulfate. Furthermore, this invention can utilize non-ammonium sulfate sulfate raw materials to prepare ammonium sulfate, and then use the ammonium sulfate to prepare sulfuric acid or ammonium bisulfate. Moreover, this invention has no special requirements for non-ammonium sulfate sulfate raw materials, greatly expanding the range of raw materials and increasing its applicability. Sulfate materials include sulfate-containing mineral raw materials and sulfate-containing materials formed during industrial production processes, existing in solid or liquid form. The washing water from the above-mentioned transformation slag is a dilute ammonium sulfate solution, which is returned for the preparation of the sulfate slag phase pulp.

[0018] As a preferred embodiment, the sulfate precipitant includes at least one of a calcium compound and a strontium compound. This type of substance is most suitable for sulfate precipitation and enrichment according to the present invention.

[0019] As a preferred embodiment, the calcium compound includes at least one of calcium chloride, calcium nitrate, calcium oxide, calcium hydroxide, and calcium carbonate.

[0020] As a preferred embodiment, the strontium compound includes at least one of strontium chloride, strontium nitrate, strontium oxide, strontium hydroxide, and strontium carbonate.

[0021] As a preferred embodiment, the sulfate precipitant contains Ca... 2+ With Sr 2+ The total molar amount of SO4 2- 1 to 1.5 times that.

[0022] As a preferred embodiment, the precipitation reaction conditions are: temperature of 15~85℃ and time of 0.25~2.5h.

[0023] As a preferred option, the conditions for carbonation transformation are: the amount of transforming agent added is 1.1 to 1.5 times the amount required for the theoretical reaction, the temperature is 5 to 45°C, and the time is 1 to 3 hours.

[0024] As a preferred embodiment, the transformation residue is washed with water at a solid-liquid ratio of 1:0.6~1.2 g / mL.

[0025] As a preferred option, the transformation residue obtained from carbonation transformation is recycled as a precipitant for enriching sulfate ions.

[0026] As a preferred option, the ammonium sulfate solution obtained by carbonation conversion is decomposed by heating to break down the residual ammonium carbonate in the solution.

[0027] As a preferred method, the thermal decomposition of ammonium chloride crystals is as follows: ammonium bisulfate or sodium bisulfate is used as the thermal decomposition medium for ammonium chloride, so that ammonium chloride releases HCl and NH3 sequentially at temperatures of 150~230℃ and 280~350℃ respectively.

[0028] Alternatively, magnesium oxide can be used as the thermal decomposition medium for ammonium chloride, allowing ammonium chloride to release ammonia at 105~135℃ and hydrogen chloride at 250~750℃.

[0029] As a preferred method, the liquid containing ammonium chloride is added to the melt of ammonium bisulfate or sodium bisulfate at a temperature of 150~230℃ to carry out a thermal decomposition reaction, releasing HCl gas which is collected, and then the temperature is raised to 280~350℃ to release NH3 which is collected.

[0030] As a preferred method, magnesium oxide is added to the ammonium chloride solution and heated to 105~135℃ to carry out a thermal decomposition reaction, releasing NH3 which is collected. Then, the solution is heated to 250~750℃ to release HCl gas which is collected.

[0031] Compared with existing technologies, the present invention has the following advantages and effects:

[0032] (1) This invention can easily and efficiently prepare sulfuric acid or ammonium bisulfate from sulfate materials, which not only solves the problem of increasingly scarce sulfur resources faced by traditional sulfuric acid production processes, but also reduces or avoids the environmental hazards caused by sulfate waste generated after the use of sulfuric acid, creating more favorable conditions for the sustainable development of the chemical and metallurgical industries.

[0033] (2) This invention realizes the strategic concept of energy for resources. HCl can be prepared by thermal decomposition of ammonium chloride, and the obtained HCl is added to the ammonium sulfate solution obtained by the transformation of sulfate materials. Ammonium chloride is separated by freezing crystallization, so that ammonium sulfate is converted into sulfuric acid or ammonium bisulfate. The obtained ammonium chloride is returned to the pyrolysis process for recycling. The whole process is green, low-carbon, clean and environmentally friendly.

[0034] (3) The method is simple, low-cost, and suitable for large-scale industrial production. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments. These embodiments are intended to illustrate the present invention and not to further limit the present invention.

[0036] Example 1

[0037] One kg of phosphogypsum with a calcium sulfate dihydrate content of 91.5% produced during the wet-process phosphoric acid production process was slurried with water at a solid-liquid ratio of 1:1 g / mL. First, 6 mol / L ammonia was added to maintain the solution pH ≥ 8.0. Then, ammonium bicarbonate was slowly added in batches at a CO2 / Ca molar ratio of 1.1:1. The mixture was stirred at room temperature for 2.5 hours, and filtered to obtain a transformation slag containing calcium carbonate and a transformation liquid containing ammonium sulfate. The transformation slag was then washed with water at a solid-liquid ratio of 1:1 g / mL. The washed transformation slag was used as a raw material for building materials production, and the resulting washing water was returned as slurry water. The transformation liquid containing ammonium sulfate was stirred and heated to 90℃ to decompose the residual ammonium carbonate salts, yielding an ammonium sulfate solution with a concentration of 41.6%. Then, according to Cl... - / NH4 +With a molar ratio of 1.1:1, HCl gas is introduced into the ammonium sulfate solution, and the solution is frozen at -20°C for 10 hours to convert the ammonium sulfate into ammonium chloride, which crystallizes out. The crystals are filtered to obtain ammonium chloride crystals and the mother liquor. The mother liquor is then evaporated and concentrated to a boiling point of 125.5°C, and cooled to obtain a 56.8% sulfuric acid solution. This sulfuric acid solution is recycled back to the wet-process phosphoric acid production process. The obtained ammonium chloride crystals are then pyrolyzed using ammonium bisulfate as the pyrolysis medium. Ammonium chloride is first mixed with water at a solid-liquid ratio of 1:1 g / mL to form a slurry. This slurry is then slowly added to the ammonium bisulfate melt at 170-210°C, releasing HCl gas. The HCl gas is collected and recycled back to the ammonium sulfate conversion process. The melt after HCl release is then heated to 280-350°C to release NH3. The NH3 is collected and recycled back to the phosphogypsum conversion process, thus achieving a clean production process for preparing sulfuric acid from phosphogypsum.

[0038] Example 2

[0039] Take 1500g of natural sodium sulfate, add water at a solid / liquid ratio of 1:2g / mL and stir until dissolved at 40℃. Filter to obtain a saturated sodium sulfate solution, and then dissolve it according to Ca... 2+ SO4 2- Calcium chloride dihydrate was added in batches to the obtained sodium sulfate solution at a molar ratio of 1.1:1 to precipitate and enrich sulfate ions. The mixture was filtered in stages, and the resulting calcium sulfate enriched residue and sodium chloride crystals were obtained. The sodium chloride crystals were then washed with a saturated sodium chloride solution and dried to obtain industrial sodium chloride with a purity of 99.6%. The calcium sulfate enriched residue was then slurried with water at a solid-liquid ratio of 1:1 g / mL. Ammonia was added to adjust the pH of the slurry to ≥8.0, and CO2 was slowly introduced at a CO2 / Ca molar ratio of 1.2:1. The mixture was stirred at room temperature for 2 hours, filtered, and the residue was converted to a transformation residue containing calcium carbonate and a transformation liquid containing ammonium sulfate. The transformation residue was washed with water at a solid-liquid ratio of 1:1 g / mL, dried, and then calcined with industrial ammonium chloride to obtain calcium chloride. This calcium chloride was used for further sulfate precipitation and enrichment, and the corresponding wash water was returned to the slurrying step. The transformation liquid was stirred and heated to 87°C to decompose the residual ammonium carbonate, yielding an ammonium sulfate solution with a concentration of 43.1%. Then, according to Cl... - / NH4 +With a molar ratio of 1.2:1, 38% concentrated hydrochloric acid was added to an ammonium sulfate solution, and the solution was frozen at -25°C for 16 hours to allow ammonium chloride to crystallize deeply. The ammonium chloride crystals and the mother liquor were obtained by filtration. The mother liquor was then heated and evaporated to concentrate the solution. After the solution temperature reached 295°C, it was allowed to cool, and the supernatant was sulfuric acid with a concentration of 95.6%. The obtained ammonium chloride crystals were then pyrolyzed using magnesium oxide as the pyrolysis medium. Ammonium chloride was first dissolved in water by stirring, and then magnesium oxide was added. The solution was heated to rapidly release NH3 at a temperature of 105-135°C. The temperature of the slurry after ammonia release was then raised to 250-550°C, causing the magnesium chloride formed by ammonia release to hydrolyze and release HCl gas. The resulting NH3 and HCl gas were collected and recycled back into the process to achieve a clean production process for sulfuric acid preparation from Glauber's salt.

[0040] Example 3

[0041] Take SO4 at pH 2.1 2- 5m³ of sulfate-containing industrial waste liquid with an ion concentration of 87.6 g / L. 3 Stir and heat until the solution temperature reaches 60℃, then add -500 mesh strontium ore powder. Once the solution pH reaches 4.1, adjust the pH to 7.6 using strontium hydroxide. Then, slowly add strontium chloride solution to precipitate and enrich sulfur, waiting for SO4 to form. 2- When the ion concentration decreased to 2.3 g / L, the addition of strontium chloride was stopped. The mixture was stirred at 63°C for 0.5 h, filtered, and washed to obtain a strontium sulfate precipitate enriched residue. First, the obtained strontium sulfate precipitate enriched residue was mixed with water at a solid-liquid ratio of 1:0.8 g / mL to form a slurry. Then, NH3 was added to the slurry, and CO2 was introduced at a CO2 / Sr molar ratio of 1.2:1, maintaining pH ≥ 8.0. Carbonation was carried out at room temperature for 1.5 h to completely convert the strontium sulfate into strontium carbonate. The residue containing strontium carbonate and a solution containing ammonium sulfate were obtained by filtration. The residue containing strontium carbonate was washed again with water at a solid-liquid ratio of 1:0.8 g / mL, and the corresponding wash water was returned for the slurrying step. The solution containing ammonium sulfate was stirred and heated to 85°C to decompose the residual ammonium carbonate, yielding a 35.3% ammonium sulfate solution. Then, the solution was further processed according to Cl... - / NH4 + With a molar ratio of 0.51:1, 30% industrial hydrochloric acid was added to the ammonium sulfate solution, and the mixture was frozen at -15°C for 6 hours, utilizing NH4+. + The common ion effect produced by the ions forces the added Cl to - Ions and NH4 +Ions crystallize out as NH4Cl, and the filtration yields ammonium chloride crystals and its crystallized liquid. The crystallized liquid is evaporated and concentrated. When the solution temperature rises to 127°C, it is filtered while hot to remove the precipitated solids such as ammonium sulfate. The filtrate is cooled and crystallized, and the filtration yields ammonium bisulfate crystals and its crystallization mother liquor. The obtained crystallization mother liquor is returned to the ammonium sulfate conversion process (preparation of a mixture of ammonium sulfate and hydrochloric acid) for use. The condensate produced by evaporation and concentration is neutralized with ammonia and returned to the process for use. The obtained ammonium chloride is pyrolyzed to produce NH3 and HCl gases, which are used for the production of ammonium bisulfate, thus realizing a clean production process for preparing ammonium bisulfate from sulfate-containing industrial wastewater.

Claims

1. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials, characterized in that: A mixed stock solution containing ammonium sulfate and HCl was subjected to freeze crystallization, followed by solid-liquid separation to obtain ammonium chloride crystals and a crystallized liquid. When the Cl in the mixed stock solution... - With NH4 + When the molar ratio of Cl is 1~1.2:1, sulfuric acid is obtained by evaporation and concentration of the crystallized solution; when the mixed original solution contains Cl... - With NH4 + When the molar ratio is 0.5~0.6:1, the crystallized liquid is concentrated by evaporation and solid-liquid separation. The resulting ammonium bisulfate-containing filtrate is then cooled, crystallized, and separated to obtain ammonium bisulfate. The NH3 and HCl obtained from the thermal decomposition of ammonium chloride crystals are collected and recycled. The ammonium sulfate in the mixed original solution comes from the finished ammonium sulfate raw material or is obtained from non-ammonium sulfate raw materials through a conversion reaction.

2. The method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 1, characterized in that: The mixed stock solution containing ammonium sulfate and HCl is prepared by mixing solid ammonium sulfate or ammonium sulfate solution with hydrochloric acid, or by passing HCl gas through an ammonium sulfate solution.

3. The method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 2, characterized in that: The mass concentration of the ammonium sulfate solution is 35-45%; The mass concentration of the hydrochloric acid is 30-40%.

4. The method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 1, characterized in that: The conditions for the freeze-crystallization are: temperature -30℃ to 0℃, time 2 to 24 hours.

5. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 1, characterized in that: When the product prepared is sulfuric acid, the temperature for evaporation and concentration of the crystallized liquid is 115~337℃. When the product prepared is ammonium bisulfate, the temperature for evaporation and concentration of the crystallized liquid is 115~147℃.

6. The method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 1, characterized in that: The method for obtaining ammonium sulfate from non-ammonium sulfate raw materials through a conversion reaction is as follows: When the non-ammonium sulfate raw material is a water-soluble sulfate, a sulfate precipitant is added to the non-ammonium sulfate raw material solution to carry out a precipitation reaction. After solid-liquid separation, a sulfate slag phase is obtained. The sulfate slag phase is mixed with water to make pulp, and ammonia is added to adjust the pH value of the pulp to ≥8. Then, at least one of the following conversion agents, namely ammonium carbonate, ammonium carbonate solution, ammonium bicarbonate, ammonium bicarbonate solution, carbon dioxide, and carbonic acid, is added to the pulp to carry out carbonation conversion. After solid-liquid separation, conversion slag and ammonium sulfate solution are obtained. The amount of water required for pulping is calculated based on the formation of an ammonium sulfate solution with a mass concentration of 35~45% after carbonation conversion. The ammonium sulfate solution is heat-treated at a temperature of 80~95℃ and then directly used to prepare a mixed stock solution containing ammonium sulfate and HCl, or it can be crystallized by evaporation and then used to prepare a mixed stock solution containing ammonium sulfate and HCl. The washing water obtained after washing the conversion slag with water is returned to the carbonation conversion process for recycling. When the sulfate raw material for non-ammonium sulfate is a non-water-soluble sulfate, ammonium sulfate can be prepared directly according to the above-mentioned treatment method for sulfate residue phase.

7. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 6, characterized in that: The sulfate precipitant includes at least one of calcium compounds and strontium compounds.

8. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 7, characterized in that: The calcium compound includes at least one of calcium chloride, calcium nitrate, calcium oxide, calcium hydroxide, and calcium carbonate; The strontium compound includes at least one of strontium chloride, strontium nitrate, strontium oxide, strontium hydroxide, and strontium carbonate.

9. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 7 or 8, characterized in that: Ca in sulfate precipitant 2+ With Sr 2+ The total molar amount of SO4 2- 1 to 1.5 times; The precipitation reaction conditions are: temperature 15~85℃, time 0.25~2.5h.

10. A method for preparing sulfuric acid or ammonium bisulfate from sulfate materials according to claim 6, characterized in that: The conditions for carbonation transformation are: the amount of transforming agent added is 1.1 to 1.5 times the amount required for the theoretical reaction, the temperature is 5 to 45°C, and the time is 1 to 3 hours.