Method for decomposing ammonium sulfate under assistance of metal oxide
By mixing and calculating ammonium sulfate powder with zinc oxide and performing two stages of thermal decomposition, the problem of difficulty in sufficient recovery of ammonia and sulfur in ammonium sulfate waste liquid in the prior art is solved, and efficient resource recovery and ammonium sulfate decomposition are achieved.
Patent Information
- Application Number
- CN202411937098.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-04-01
AI Technical Summary
In the prior art, it is difficult to fully recover ammonia and sulfur in ammonium sulfate waste liquid, resulting in low resource reuse efficiency.
By mixing and calculating ammonium sulfate powder with zinc oxide, two stages of thermal decomposition are performed to release and recover ammonia and sulfur gases, the decomposition of ammonium sulfate and efficient recovery of resources are achieved.
The ammonia recovery rate reached more than 91% and sulfur recovery rate reached more than 95%, fully solving the problems of ammonium sulfate waste liquid treatment and resource reuse.
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Figure CN119735219A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the technical field of chemical wastewater treatment, and in particular relates to a method for decomposing ammonium sulfate with the assistance of metal oxides. Background Art
[0002] A large amount of ammonium sulfate waste liquid is generated in the production process of manganese-based materials and other chemical materials. The long-term storage of ammonium sulfate waste liquid has caused great environmental pressure on enterprises. At present, some ammonium sulfate waste liquid is mainly used as fertilizer and mineral processing agent after evaporation and crystallization. However, with the continuous expansion of the main industry, the amount of ammonium sulfate waste liquid has also increased sharply. The current conventional disposal method is no longer sufficient to achieve large-scale disposal of ammonium sulfate waste liquid. It is urgent to develop a new green, environmentally friendly and efficient ammonium sulfate waste liquid disposal process.
[0003] For the production of manganese-based materials, the most ideal method for ammonium sulfate is to recycle it into ammonia and sulfide. There are literature reports that ammonia and sulfur can be recovered by decomposing ammonium sulfate, but it is difficult to separate the products by directly decomposing ammonium sulfate. Some researchers have successfully separated ammonia and sulfur by adding carriers such as calcium oxide, iron oxide and other metal oxides. However, the amount of ammonia released in the current process is low, making it difficult to fully recover ammonia and sulfur. Summary of the invention
[0004] In order to overcome the problem that it is difficult to fully recover ammonia and sulfur in the prior art, the present application provides a method for decomposing ammonium sulfate with the assistance of metal oxides. Through two-stage thermal decomposition, the purpose of releasing and recovering ammonia and sulfur is achieved, thereby realizing the treatment of ammonium sulfate wastewater and the reuse of raw materials.
[0005] In order to solve the above technical problems, the technical solutions proposed in this application are as follows:
[0006] A method for decomposing ammonium sulfate with the assistance of metal oxides comprises the following steps:
[0007] S1, evaporating and crystallizing industrial ammonium sulfate waste liquid, and fully grinding and sieving the obtained crystals to obtain ammonium sulfate powder;
[0008] S2, mixing the ammonium sulfate powder obtained in step S1 with zinc oxide uniformly, and roasting to obtain a roasting product and ammonia, and recovering the ammonia through double-circulation concentration;
[0009] S3, calcining the roasted product obtained in step S2 to obtain zinc oxide powder and sulfur dioxide, and liquefying and recovering the sulfur dioxide; cooling the zinc oxide powder to 250-300° C., returning to step S2 for repeated use, and after being reused 50-80 times, centrifugally separating and removing impurities, and then returning to step S2 for repeated use, wherein the process of centrifugation separation and impurity removal is as follows: centrifugation time 20-30 min, rotation speed 2000 r / min.
[0010] Industrial ammonium sulfate waste liquid contains impurities such as calcium sulfate and magnesium sulfate. Zinc oxide powder will be mixed in during the production process. After multiple cycles, the accumulation will affect the reaction between zinc oxide and ammonium sulfate. Therefore, impurities need to be removed after multiple cycles.
[0011] In the present application, ammonium sulfate powder prepared from ammonium sulfate waste liquid is mixed with metal oxide zinc oxide powder and roasted to obtain zinc sulfate and ammonia gas, which can release all the ammonium in the ammonium sulfate to obtain ammonia gas. The zinc sulfate is further roasted to obtain zinc oxide and sulfur dioxide gas. The zinc oxide can continue to be used for the decomposition of ammonium sulfate, and the sulfur element can be completely converted into sulfur dioxide gas, thereby fully realizing the decomposition of ammonium sulfate.
[0012] In some embodiments, in step S1, the pH of industrial ammonium sulfate waste liquid is adjusted to 3.5-5.5 and then evaporated and crystallized, and the evaporation temperature is 100-200° C.; the ammonium sulfate powder is screened with an accuracy of 100-400 mesh.
[0013] In some embodiments, the calcination conditions in step S2 are: in an inert atmosphere at a temperature of 450-500°C. Calcining ammonium sulfate and zinc oxide at 450-550°C is conducive to converting all the ammonium in the ammonium sulfate into ammonia. Below 450°C, the reaction temperature cannot be reached and the ammonium sulfate will self-decompose. Above 550°C, the generated metal sulfate may undergo a decomposition reaction, resulting in incomplete separation of ammonia and sulfur.
[0014] In some embodiments, the inert atmosphere is nitrogen, and the amount of nitrogen introduced is 0.1-1.0 L / min. In the present application, inert gas is introduced in step S2 to prevent oxidation of ammonium sulfate, which results in a reduction in ammonia recovery.
[0015] In some embodiments, in step S2, the molar ratio of ammonium sulfate to zinc oxide is 1:1.5 to 2. In the present application, the molar ratio of zinc oxide to ammonium sulfate is 1:1.5 to 2, the ammonium sulfate is completely decomposed, and the heating cost can be controlled.
[0016] In some embodiments, in step S2, the calcination is performed in a tube furnace, the heating rate of the tube furnace is 3-10°C / min, and the calcination time is 1-3h. In the present application, the gradual heating is adopted to prevent the excessively fast heating rate from causing a large amount of self-decomposition of ammonium sulfate and causing the loss of ammonia.
[0017] In some embodiments, the double-circulation concentration process is: under conditions below 30°C, water is circulated to capture ammonia gas to produce dilute ammonia water, and the dilute ammonia water is circulated through a distillation tower and then absorbed and condensed at the top of the tower to obtain ammonia water, wherein the concentration of the ammonia water is ≥15wt%.
[0018] In some embodiments, the calcination conditions in step S3 are: in an inert atmosphere at a temperature of 780-800° C. If zinc sulfate is calcined at less than 750° C., the metal sulfate cannot be completely decomposed, and if it is calcined at more than 800° C., it may lead to over-calcination and produce impurities such as ZnS.
[0019] In some embodiments, in step S3, the inert atmosphere is nitrogen, and the amount of nitrogen introduced is 0.1-1.0 L / min. The inert gas is introduced to prevent the ammonia from being oxidized.
[0020] In some embodiments, the process for liquefying sulfur dioxide is as follows: in a gas liquefaction device, the temperature is ≤-10°C and the pressure is 1.5 to 2 MPa.
[0021] In some embodiments, in step S3, calcination is performed in a tubular furnace, the heating rate of the tubular furnace is 3-10°C / min, and the calcination time is 1.5-3h. The temperature is gradually increased to prevent the temperature from increasing too quickly and causing local overheating.
[0022] In this application, the chemical reaction formula involved in step S2 is as follows:
[0023] (NH4)2SO4→NH4HSO4+NH3↑
[0024] (NH4)2SO4+ZnO→ZnSO4+2NH3↑+H2O
[0025] NH4HSO4+ZnO→ZnSO4+2NH3↑+H2O
[0026] NH3+H2O→NH4OH
[0027] The chemical reaction formula involved in step S3 is:
[0028] ZnSO4→ZnO+SO2↑+1 / 2O2↑
[0029] Compared with the prior art, the beneficial effects of this application are:
[0030] (1) In the present application, zinc oxide is used to decompose ammonium sulfate to achieve efficient circulation of metal oxides. The entire process basically does not generate or discharge waste. The process is clean, efficient, and low-cost, providing a practical new idea for the disposal of ammonium sulfate.
[0031] (2) The present application fully realizes the decomposition of ammonium sulfate, wherein the ammonia recovery rate reaches more than 91% and the sulfur recovery rate reaches more than 95%. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0033] Figure 1 A schematic diagram of the process flow of this application;
[0034] Figure 2 This is the characteristic diffraction peak pattern of the product of ammonium sulfate and zinc oxide at 450° C. detected by X-ray diffraction in Example 1 of the present application. DETAILED DESCRIPTION
[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0036] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.
[0037] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, a~b (i.e. a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple, respectively.
[0038] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the implementation regulations of this application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.
[0039] The terms used in the embodiments of the present application are only for the purpose of describing specific implementation rules, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the implementation rules of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.
[0040] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.
[0041] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.
[0042] Unless otherwise defined, all professional terms used below have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.
[0043] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.
[0044] The present application provides a method for decomposing ammonium sulfate with the assistance of metal oxides, the process flow is as follows Figure 1 As shown, the method steps are as follows:
[0045] S1. Adjust the pH value of industrial ammonium sulfate waste liquid to 3.5-5.5, then evaporate and crystallize at 100-200°C to obtain ammonium sulfate crystals. Grind and sieve the ammonium sulfate crystals with a sieving accuracy of 100-400 meshes to obtain ammonium sulfate powder.
[0046] S2. Mix zinc oxide powder and ammonium sulfate powder obtained in S1 at a molar ratio of 1:1.5-2, place in a tubular furnace, and heat to 450-550°C at a heating rate of 3-10°C / min under a nitrogen atmosphere at a gas introduction rate of 0.1-1.0 L / min. The calcination time is 1-3 h. The products are ammonia and zinc sulfate. The ammonia is captured to obtain ammonia water, and the ammonia is recovered by double circulation concentration.
[0047] S3, the zinc sulfate obtained in S2 is placed in a tubular furnace again, calcined and decomposed in a nitrogen atmosphere, the heating rate of the tubular furnace is 3-10℃ / min, the calcination temperature is 750-800℃, the calcination time is 1.5-3h, sulfur dioxide gas and zinc oxide powder are obtained, and the zinc oxide powder is reused in step S2. The obtained sulfur dioxide is made into liquefied sulfur dioxide through a gas liquefaction device, and the liquefaction pressure is 2.5-5MPa; the zinc oxide powder is cooled to 250-300℃, returned to step S2 for repeated use, and after repeated use for 50-80 times, it is centrifugally separated and impurities are removed and then returned to step S2 for repeated use. The process of centrifugal separation and impurity removal is: centrifugal time 20-30min, speed 2000r / min.
[0048] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.
[0049] In order to enable the above implementation details and operations of the present application to be clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the embodiments of the present application, the above technical solutions are illustrated by means of multiple embodiments below.
[0050] Example 1
[0051] A method for decomposing ammonium sulfate with the assistance of metal oxides, the specific operation is as follows:
[0052] S1. Take 100 mL of industrial ammonium sulfate waste liquid with a concentration of 9%, adjust the pH value to 5.0, then evaporate and crystallize at 150° C., filter and dry to obtain ammonium sulfate crystals; then grind and sieve the ammonium sulfate crystals with a sieving accuracy of 200 meshes to obtain 8.3 g of ammonium sulfate powder.
[0053] S2. The molar ratio of zinc oxide to ammonium sulfate is 1:1.5, and the mixture is fully mixed and placed in a tube furnace. Under a nitrogen atmosphere, the gas flow rate is 1.0 L / min, and the temperature is raised to 450°C at a heating rate of 5°C / min, and maintained for 1 hour. The product ammonia gas is circulated and absorbed by water, and after circulating in a distillation tower, it is absorbed and condensed at the top of the tower to obtain ≥15wt% ammonia water, and the zinc sulfate is further calcined. The prepared zinc sulfate is tested by X-ray diffraction, and the results are as follows: Figure 2 As shown, the characterization results show that the product is mainly zinc sulfate.
[0054] S3, zinc sulfate is placed in a tube furnace again, and in a nitrogen atmosphere, the gas flow rate is 1.0L / min, and the temperature is raised to 750°C at a heating rate of 5°C / min, and maintained for 1.5h to obtain zinc oxide powder and sulfur dioxide, and the zinc oxide powder is reused in the front-end process. After the zinc oxide powder is reused 50 to 80 times, it is centrifugally separated and impurities are removed and then returned to step S2 for reuse. The process of centrifugal separation and impurity removal is: centrifugal time 20 to 30min, speed 2000r / min.
[0055] After being cooled to room temperature, the sulfur dioxide is fed into a gas liquefaction device to produce liquefied sulfur dioxide at -10°C and 3MPa high pressure.
[0056] Example 2
[0057] A method for decomposing ammonium sulfate with the assistance of metal oxides, the specific operation is as follows:
[0058] S1. Take 200 mL of industrial ammonium sulfate waste liquid with a concentration of 9%, adjust the pH value to 4.5, then evaporate and crystallize at 200° C., filter and dry to obtain ammonium sulfate crystals; then grind and sieve the ammonium sulfate crystals with a sieving accuracy of 200 meshes to obtain 17.2 g of ammonium sulfate powder.
[0059] S2. The zinc oxide and ammonium sulfate are fully mixed in a molar ratio of 1:2, placed in a tubular furnace, and heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere at a gas introduction rate of 0.5.0 L / min, and maintained for 1 hour. The product ammonia is absorbed by water in a circulation manner, and after circulating in a distillation tower, it is absorbed and condensed at the top of the tower to obtain ≥15wt% ammonia water zinc sulfate, which is further calcined.
[0060] S3. Place the zinc sulfate in the tubular furnace again, and in a nitrogen atmosphere, introduce a gas at a rate of 0.5.0 L / min, heat the temperature to 750°C at a heating rate of 5°C / min, and maintain for 1.5 hours to obtain zinc oxide powder and sulfur dioxide. The zinc oxide powder is recycled to the front-end process; after the sulfur dioxide is cooled to room temperature, it is input into a gas liquefaction device to obtain liquefied sulfur dioxide at -10°C and a high pressure of 3 MPa.
[0061] Example 3
[0062] A method for decomposing ammonium sulfate with the assistance of metal oxides, the specific operation is as follows:
[0063] S1. Take 500 mL of industrial ammonium sulfate waste liquid with a concentration of 9%, adjust the pH value to 4, then evaporate and crystallize at 200° C., filter and dry to obtain ammonium sulfate crystals; then grind and sieve the ammonium sulfate crystals with a sieving accuracy of 100 meshes to obtain 42.5 g of ammonium sulfate powder.
[0064] S2. The zinc oxide and ammonium sulfate are fully mixed in a molar ratio of 1:2, placed in a tubular furnace, and heated to 500°C at a heating rate of 5°C / min under a nitrogen atmosphere at a gas introduction rate of 0.1 L / min, and maintained for 1 hour. The product ammonia is absorbed by water in a circulation manner, and after circulating in a distillation tower, it is absorbed and condensed at the top of the tower to obtain ≥15wt% ammonia water, and the zinc sulfate is further calcined.
[0065] S3. Place the zinc sulfate in the tube furnace again, and heat it to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere with a gas introduction rate of 0.1 L / min, and maintain it for 1.5 hours to obtain zinc oxide powder and sulfur dioxide. The zinc oxide powder is recycled to the front-end process; after the sulfur dioxide is cooled to room temperature, it is input into the gas liquefaction device to obtain liquefied sulfur dioxide at -10°C and 3MPa high pressure.
[0066] Comparative Example 1:
[0067] A method for decomposing ammonium sulfate with the assistance of metal oxides, the difference from Example 1 is that "zinc oxide" is replaced by "iron oxide", and the rest is the same as Example 1. As a result, both the ammonia recovery rate and the sulfur recovery rate are reduced, because the reaction activity of iron oxide with ammonium sulfate is low, resulting in unsatisfactory ammonia release, which further affects the sulfur release.
[0068] Comparative Example 2:
[0069] A method for decomposing ammonium sulfate with the assistance of metal oxides, the difference from Example 1 is that "zinc oxide" is replaced by "aluminum oxide", and the rest is the same as Example 1. Results The ammonia recovery rate and sulfur recovery rate of the alumina-assisted pyrolysis of ammonium sulfate are both low, because part of the ammonium sulfate undergoes self-pyrolysis when the alumina reacts with the ammonium sulfate at 450°C.
[0070] Comparative Example 3:
[0071] A method for decomposing ammonium sulfate with the assistance of metal oxides, the difference from Example 1 is that "zinc oxide" is replaced by "copper oxide", and the rest is the same as Example 1. Results The ammonia recovery rate and sulfur recovery rate of copper oxide-assisted pyrolysis of ammonium sulfate are ideal, but copper oxide has a high cost and is not adopted in this application.
[0072] Comparative Example 4:
[0073] A method for decomposing ammonium sulfate with the aid of metal oxides, the difference from Example 1 is that "zinc oxide" is replaced by "calcium oxide", and the rest is the same as Example 1. As a result, the ammonia recovery rate is equivalent to that of Example 1, and the sulfur recovery rate is lower. The reason is that the sulfur release rate is low when calcium sulfate is heated and decomposed.
[0074] Comparative Example 5:
[0075] A method for decomposing ammonium sulfate with the assistance of metal oxides, which differs from Example 1 in that "the reaction temperature of zinc oxide and ammonium sulfate in a tube furnace is 300° C.", and the rest is the same as Example 1.
[0076] Comparative Example 6:
[0077] A method for decomposing ammonium sulfate with the assistance of metal oxides, which differs from Example 1 in that "the reaction temperature of zinc oxide and ammonium sulfate in a tube furnace is 600° C.", and the rest is the same as Example 1.
[0078] Comparative Example 7:
[0079] A method for decomposing ammonium sulfate with the assistance of metal oxides, which differs from Example 1 in that "the reaction temperature of zinc sulfate in a tube furnace is 600° C.", and the rest is the same as Example 1.
[0080] Comparative Example 8:
[0081] A method for decomposing ammonium sulfate with the assistance of metal oxides, which differs from Example 1 in that "the reaction temperature of zinc sulfate and ammonium sulfate in a tube furnace is 850° C.", and the rest is the same as Example 1.
[0082] Comparative Example 9:
[0083] A method for decomposing ammonium sulfate with the assistance of metal oxides, which differs from Example 1 in that "both calcinations are carried out under normal atmosphere", and the rest is the same as Example 1.
[0084] The recovery rates of ammonia and sulfur in the examples and comparative examples were tested, and the results are shown in Table 1 below:
[0085] Table 1: Recovery rates of ammonia and sulfur in Examples and Comparative Examples
[0086] name Ammonia recovery rate Sulfur recovery rate Example 1 95.33％ 98.60％ Example 2 95.56％ 99.12％ Example 3 91.37％ 99.07％ Example 4 95.14％ 98.95％ Comparative Example 1 77.59％ 82.14％ Comparative Example 2 85.51％ 91.69％ Comparative Example 3 89.50％ 92.76％ Comparative Example 4 95.82％ 44.59％ Comparative Example 5 49.77％ 32.06％ Comparative Example 6 85.82％ 87.51％ Comparative Example 7 93.34％ 60.83％ Comparative Example 8 87.74％ 89.45％ Comparative Example 9 62.70％ 98.59％
[0087] In the embodiment, ammonium sulfate powder prepared from ammonium sulfate waste liquid is mixed with metal oxide zinc oxide powder and roasted to obtain zinc sulfate and ammonia, which can release all the ammonium in the ammonium sulfate to obtain ammonia, and further roast the zinc sulfate to obtain zinc oxide and sulfur dioxide gas, the zinc oxide can continue to be used for the decomposition of ammonium sulfate, and the sulfur element can be completely converted into sulfur dioxide gas, the ammonia recovery rate reaches more than 91%, the sulfur recovery rate reaches more than 98%, and the decomposition of ammonium sulfate is fully realized at 99.12%. However, the conditions of each comparative example are different, and the ammonia recovery rate and sulfur recovery rate are both low, and they cannot be fully recovered.
[0088] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.
[0089] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.
Claims
1. A method for decomposing ammonium sulfate with the assistance of metal oxides, characterized in that: The following steps are involved: S1, evaporating and crystallizing industrial ammonium sulfate waste liquid, and fully grinding and sieving the obtained crystals to obtain ammonium sulfate powder; S2, mixing the ammonium sulfate powder obtained in step S1 with zinc oxide uniformly, and roasting to obtain a roasting product and ammonia, and recovering the ammonia through double-circulation concentration; S3, calcining the roasted product obtained in step S2 to obtain zinc oxide powder and sulfur dioxide, and liquefying and recovering the sulfur dioxide; cooling the zinc oxide powder to 250-300° C., returning to step S2 for repeated use, and after being reused 50-80 times, centrifugally separating and removing impurities, and then returning to step S2 for repeated use, wherein the process of centrifugation separation and impurity removal is as follows: centrifugation time 20-30 min, rotation speed 2000 r / min.
2. The method for decomposing ammonium sulfate with the assistance of metal oxides according to claim 1, characterized in that: In step S1, the pH value of industrial ammonium sulfate waste liquid is adjusted to 3.5-5.5 and then evaporated and crystallized, and the evaporation temperature is 100-200° C.; the ammonium sulfate powder is screened with an accuracy of 100-400 meshes.
3. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: The calcination conditions in step S2 are: in an inert atmosphere, the temperature is 450-500° C., the inert atmosphere is nitrogen, and the amount of nitrogen introduced is 0.1-1.0 L / min.
4. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: In step S2, the amount of ammonium sulfate and zinc oxide added is 1:1.5-2 in a molar ratio.
5. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: In step S2, calcination is performed in a tubular furnace, the heating rate of the tubular furnace is 3 to 10°C / min, and the calcination time is 1 to 3 hours.
6. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: The double-circulation concentration process is as follows: under the condition of less than 30° C., water is circulated to capture ammonia gas to form dilute ammonia water, and the dilute ammonia water is circulated through a distillation tower and then absorbed and condensed at the top of the tower to obtain ammonia water, wherein the concentration of the ammonia water is ≥15wt%.
7. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: The calcination conditions in step S3 are: in an inert atmosphere at a temperature of 780-800° C. In step S3 , the inert atmosphere is nitrogen, and the amount of nitrogen introduced is 0.1-1.0 L / min.
8. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: The process of liquefying sulfur dioxide is as follows: in a gas liquefaction device, the temperature is ≤-10°C and the pressure is 1.5-2Mpa.
9. The method for decomposing ammonium sulfate with assistance of metal oxides according to claim 1, characterized in that: In step S3, calcination is carried out in a tubular furnace, the heating rate of the tubular furnace is 3 to 10°C / min, and the calcination time is 1.5 to 3 hours.