Method for producing SO3

Abstract

The invention discloses a method for producing SO3, which comprises the following steps: carrying out combustion reaction on sulfur and first oxygen-containing gas, and outputting SO2-containing first mixed gas; the first mixed gas and second oxygen-containing gas are subjected to a catalytic oxidation reaction, and second mixed gas containing SO3 is obtained; carrying out first fuming sulfuric acid absorption treatment on the second mixed gas to obtain third mixed gas and second fuming sulfuric acid; circulating and returning the third mixed gas to be mixed with the sulfur and the first oxygen-containing gas; performing separation treatment on the second fuming sulfuric acid to obtain third fuming sulfuric acid and SO3 gas; and mixing the third fuming sulfuric acid with the first fuming sulfuric acid, and carrying out absorption treatment on the second mixed gas. The method can meet the practical requirements that the SO3 product is produced, but sulfuric acid is not produced or sulfuric acid is produced as little as possible.

Description

Technical Field

[0001] This application relates to the field of chemical technology, specifically to a method for producing SO3. Background Technology

[0002] SO3 is an important chemical raw material and is classified as a hazardous chemical. Its storage and transportation are quite troublesome. To facilitate production, many factories produce SO3 themselves. Currently, there are two main methods for producing SO3: fuming sulfuric acid evaporation and combined production. However, both of these methods have the problem of producing a relatively large amount of sulfuric acid. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in the related art.

[0004] Therefore, the first aspect of this application proposes a method for producing SO3, comprising: Sulfur is burned with a first oxygen-containing gas to produce a first mixed gas containing SO2; the first mixed gas is catalytically oxidized with a second oxygen-containing gas to produce a second mixed gas containing SO3; the second mixed gas is then subjected to absorption treatment with a first fuming sulfuric acid to produce a third mixed gas and a second fuming sulfuric acid; the third mixed gas is recycled back to be mixed with sulfur and the first oxygen-containing gas; the second fuming sulfuric acid is separated to produce a third fuming sulfuric acid and SO3 gas; the third fuming sulfuric acid is mixed with the first fuming sulfuric acid and then used to absorb the second mixed gas.

[0005] The method for producing SO3 provided in this application has a high sulfur utilization rate, does not produce low-value industrial sulfuric acid as a byproduct, generates less waste gas, and has a simple process flow. It can meet the needs of producing SO3 products without producing sulfuric acid or producing as little sulfuric acid as possible.

[0006] In some embodiments, the molar ratio of O2 to sulfur in the first oxygen-containing gas is (1-1.5):1.

[0007] In some embodiments, the third mixed gas is recycled back to the step of mixing with sulfur and oxygen-containing gas, wherein the molar ratio of the third mixed gas to sulfur is (2.5-3.5):1.

[0008] In some implementations, the reaction temperature of the combustion reaction is less than or equal to 1500°C.

[0009] In some embodiments, before the step of catalytically oxidizing the first mixed gas with the second oxygen-containing gas, the temperature of the first mixed gas is less than or equal to 450°C.

[0010] In some embodiments, the first mixed gas undergoes a heat exchange process before being catalytically oxidized with the second oxygen-containing gas.

[0011] In some embodiments, the step of catalytically oxidizing the first mixed gas with the second oxygen-containing gas includes at least one catalytic oxidation conversion reaction.

[0012] In some embodiments, the second mixed gas undergoes a second heat exchange treatment before being subjected to the first fuming sulfuric acid absorption treatment.

[0013] In some embodiments, in the step of treating the second mixed gas with first fuming sulfuric acid, the first fuming sulfuric acid has an absorption rate of 40%-60% for SO3 in the first mixed gas.

[0014] In some embodiments, a portion of the third mixed gas is used as a recirculating gas, which is mixed with sulfur and the first oxygen-containing gas; another portion of the third mixed gas is used as exhaust gas, which is then subjected to exhaust gas recovery treatment.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A process flow diagram for producing SO3 according to one embodiment of this application is shown.

[0017] Figure 2 A schematic diagram of an apparatus for producing SO3 according to one embodiment of this application is shown.

[0018] 101 - Sulfur incinerator; 102 - First heat exchanger; 103 - Converter; 104 - Second heat exchanger; 105 - Absorption tower; 106 - Fan; 107 - Evaporator; 108 - Tail gas processor. Detailed Implementation

[0019] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0021] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0022] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0023] Currently, there are two main methods for producing SO3: 1) Fuming sulfuric acid evaporation method: This method involves purchasing fuming sulfuric acid, heating and evaporating it, decomposing the sulfuric acid to produce SO3 gas, and then condensing the SO3 gas to obtain liquid SO3. This method is suitable for factories that do not have an acid production unit but need to use sulfuric acid and SO3. 2) Combined production method: This method mainly refers to sulfuric acid plants combining sulfuric acid production and SO3 production. A fuming sulfuric acid absorption tower is set up in the absorption process of the acid production system. The fuming sulfuric acid that absorbs SO3 from the flue gas from the acid production is then heated and decomposed to produce SO3. The remaining SO3 at the outlet of the fuming sulfuric acid absorption tower is sent to the acid production unit to produce industrial sulfuric acid. The core principle of this process is the same as that of the fuming sulfuric acid evaporation method. The combined production method has high output, simple process, and low product cost, and is currently the most common method for SO3 production.

[0024] However, in the fuming sulfuric acid evaporation process, the decomposition of fuming sulfuric acid produces a large amount of industrial sulfuric acid. In the combined production process, the flue gas for acid production comes from smelting flue gas or sulfur combustion. A fuming sulfuric acid absorption tower is installed in the dry absorption process. Since the absorption rate of fuming sulfuric acid for SO3 is about 60%, the unabsorbed approximately 40% of SO3 is absorbed by 98% sulfuric acid to produce approximately 98% industrial sulfuric acid. Both of these processes produce a large amount of sulfuric acid as a byproduct while producing SO3, but many factories using SO3 do not require large amounts of sulfuric acid. Therefore, a method for producing SO3 without producing sulfuric acid, or producing as little sulfuric acid as possible, has become a practical need.

[0025] Therefore, a first aspect of the embodiments of this application provides a method for producing SO3, comprising: The sulfur is reacted with the first oxygen-containing gas to produce a first mixed gas containing SO2. The first mixed gas is subjected to a catalytic oxidation reaction with a second oxygen-containing gas to obtain a second mixed gas containing SO3. The second mixed gas is subjected to first fuming sulfuric acid absorption treatment to obtain a third mixed gas and second fuming sulfuric acid; The third mixed gas is recycled back to be mixed with sulfur and the first oxygen-containing gas; The second fuming sulfuric acid was separated to obtain the third fuming sulfuric acid and SO3 gas; The third fuming sulfuric acid is mixed with the first fuming sulfuric acid to absorb the second mixed gas.

[0026] The combustion reaction of sulfur with the first oxygen-containing gas involves the oxidation of sulfur with oxygen in the first oxygen-containing gas to produce sulfur dioxide (SO2). This can be achieved by adding sulfur and the first oxygen-containing gas into a sulfur incinerator for combustion, resulting in a first mixed gas containing SO2; in addition, it may also contain other components of the first oxygen-containing gas (such as nitrogen).

[0027] The catalytic oxidation reaction between the first mixed gas and the second oxygen-containing gas involves the catalytic oxidation of SO2 in the first mixed gas with oxygen to produce SO3. This reaction is a reversible exothermic reaction under the action of a catalyst. Limited by the equilibrium conversion rate, some of the SO2 in the first mixed gas is converted to SO3. The catalytic oxidation reaction is: SO2 + 1 / 2O2 → SO3. Based on the composition of the first and second oxygen-containing gases, the resulting second mixed gas includes SO2, SO3, O2, and N2, etc.

[0028] SO3 in the second mixed gas was absorbed by the first fuming sulfuric acid, resulting in a second fuming sulfuric acid containing a higher concentration of SO3 and a third mixed gas with a reduced SO3 content.

[0029] The third mixed gas is recycled back to mix with sulfur and the first oxygen-containing gas, which can improve the utilization rate of sulfur. Therefore, the first mixed gas may include components such as SO2, SO3, and N2.

[0030] The second fuming sulfuric acid is separated by processes such as heating and evaporation, which releases more SO3. The SO3 is then cooled to obtain the SO3 product.

[0031] After separation, the SO3 content in the second fuming sulfuric acid is reduced, resulting in the third fuming sulfuric acid. The third fuming sulfuric acid is then recycled and mixed with the first fuming sulfuric acid to absorb and treat the second mixed gas, thus realizing the recycling of fuming sulfuric acid without producing low-value industrial sulfuric acid as a byproduct.

[0032] The SO3 production method provided in this application has a high sulfur utilization rate, does not produce low-value industrial sulfuric acid as a byproduct, generates less waste gas, and has a simple process flow. It can meet the needs of producing SO3 products, but a method that does not produce sulfuric acid or produces as little sulfuric acid as possible has become a real demand.

[0033] Furthermore, if sulfur is directly burned using oxygen-enriched combustion, the theoretical adiabatic temperature is too high, reaching 2600℃-2900℃, while the design temperature of the sulfur incinerator is approximately 1200℃. Therefore, it is difficult to connect a pure oxygen sulfur incinerator directly upstream of the SO3 production process. The embodiment of this application, however, mixes a lower-temperature third mixed gas with sulfur and the first oxygen-containing gas, which helps to lower the temperature inside the incinerator, ensuring effective combustion, protecting the sulfur incinerator equipment, and solving the problem of sulfur incinerator overheating.

[0034] As an example, liquid sulfur can be used.

[0035] As an example, the first oxygen-containing gas can be oxygen, oxygen-enriched air, or air. Further, the first oxygen-containing gas can be oxygen or oxygen-enriched air. The appropriate type of first oxygen-containing gas is selected based on the needs of different production schemes. Choosing air or oxygen-enriched air helps reduce raw material costs and lower the incineration reaction temperature; choosing oxygen or oxygen-enriched air helps reduce impurities introduced into the reaction system (such as nitrogen) and reduce waste gas generation.

[0036] In some embodiments of this application, the molar ratio of O2 to sulfur in the first oxygen-containing gas is (1-1.5):1.

[0037] In this embodiment, the molar ratio of O2 to sulfur in the first oxygen-containing gas satisfies the above conditions, which is beneficial to improve the combustion reaction efficiency and maintain a relatively low combustion temperature, thus protecting the safety of the sulfur incineration furnace equipment.

[0038] As an example, the molar ratio of O2 to sulfur in the first oxygen-containing gas is 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc.

[0039] In some embodiments of this application, in the step of recycling the third mixed gas back to mix with sulfur and oxygen-containing gas, the molar ratio of the third mixed gas to sulfur is (2.5-3.5):1.

[0040] In this embodiment, the molar ratio of the third mixed gas to sulfur satisfies the above conditions, which helps to reduce the combustion reaction temperature and meet the temperature resistance requirements of the sulfur incinerator; at the same time, it promotes the effective combustion reaction and produces sufficient SO2.

[0041] As examples, the molar ratio of the third mixed gas to sulfur is 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3.0:1, 3.1:1, 3.2:1, 3.3:1, 3.0:4, 3.5:1, etc.

[0042] In some embodiments of this application, the reaction temperature of the combustion reaction is less than or equal to 1500°C.

[0043] The embodiments of this application can reduce the temperature inside the incinerator by circulating a third mixed gas with sulfur and a first oxygen-containing gas at a lower temperature, thereby achieving an incineration reaction temperature of ≤1500℃, which can meet the temperature resistance and production safety requirements of the incineration reaction equipment.

[0044] In some embodiments of this application, before the step of catalytically oxidizing the first mixed gas with the second oxygen-containing gas, the temperature of the first mixed gas is less than or equal to 450°C.

[0045] Since the first mixed gas will subsequently undergo a catalytic oxidation reaction, the catalyst is prone to deactivation at high temperatures, affecting the effective conduct of the forward reaction. Based on the temperature resistance requirements of the equipment and catalyst for the catalytic oxidation reaction, the temperature of the first mixed gas can be maintained at a low level before the catalytic oxidation reaction. For example, the temperature of the first mixed gas is ≤450℃, ≤440℃, ≤430℃, ≤420℃, ≤410℃, ≤400℃, ≤390℃, etc.

[0046] In some embodiments of this application, the first mixed gas undergoes a heat exchange process before being catalytically oxidized with the second oxygen-containing gas.

[0047] Because the combustion reaction of sulfur has a high temperature, the temperature of the first mixed gas produced by the combustion reaction is also high. In order to ensure the effective progress of the subsequent catalytic oxidation reaction and solve the problem of catalyst deactivation at high temperature, the first mixed gas can be cooled down first so that the temperature of the first mixed gas meets the temperature resistance requirements of the equipment and catalyst for the catalytic oxidation reaction.

[0048] As an example, a heat exchanger, such as a waste heat boiler, can be used for primary heat exchange. The waste heat boiler removes the heat from the first mixed gas, thereby cooling the first mixed gas.

[0049] In some embodiments of this application, the step of catalytically oxidizing the first mixed gas with the second oxygen-containing gas includes at least one catalytic oxidation conversion reaction.

[0050] To meet higher conversion rate requirements, the first mixed gas can undergo a multi-stage catalytic oxidation conversion reaction.

[0051] Based on the performance requirements of the catalyst, the gas temperature output after each stage of catalytic oxidation conversion reaction can be controlled to ensure that the gas temperature for the next stage of catalytic oxidation conversion reaction is maintained at a low level (e.g., ≤650℃) to ensure the safety of catalyst use.

[0052] The first mixed gas undergoes a catalytic oxidation reaction within the converter to partially convert SO2 into SO3. The converter's inner shell is equipped with multiple catalyst layers, with heat exchangers, economizers, superheaters, boilers, and other equipment installed between each catalyst layer to cool the flue gas. A second oxygen-containing gas (such as oxygen, oxygen-enriched air, or air) can be added before the inlet of each catalyst layer to control the conversion rate under oxygen-deficient conditions and improve the overall conversion rate. After the converted flue gas recovers heat through heat exchange equipment such as economizers, superheaters, or boilers, it is then output as the second mixed gas for absorption treatment.

[0053] As an example, the converter is equipped with four catalyst layers in sequence. The first mixed gas enters the first catalyst layer for reaction, and part or all of the gas output from the reaction enters the waste heat boiler for heat exchange. The gas after heat exchange enters the second catalyst layer for further reaction. Part or all of the gas output from the second catalyst layer enters the steam superheater for heat exchange, and the gas after heat exchange enters the third catalyst layer for further reaction. Part or all of the gas output from the third catalyst layer enters the fourth catalyst layer for further reaction. The gas output from the fourth catalyst layer continues to be absorbed and treated in subsequent processes.

[0054] In addition, the oxygen ratio can be controlled by adjusting the intake of the second oxygen-containing gas, thereby regulating the conversion reaction rate of the catalytic oxidation reaction and effectively controlling the temperature to solve the problem of overheating in the conversion process.

[0055] In some embodiments of this application, the second mixed gas undergoes a second heat exchange treatment before being subjected to a first fuming sulfuric acid absorption treatment.

[0056] The second mixed gas output from the catalytic oxidation reaction is cooled by a secondary heat exchange and then enters the absorption tower. The SO3 in the second mixed gas is absorbed by the first fuming sulfuric acid, resulting in an increased concentration of SO3 in the second fuming sulfuric acid and a decreased SO3 content in the resulting third mixed gas.

[0057] As an example, secondary heat exchange can be achieved using a heat exchanger, such as a waste heat boiler, which removes the heat from the second mixed gas, thereby cooling the second mixed gas.

[0058] In some embodiments of this application, in the step of treating the second mixed gas with first fuming sulfuric acid, the first fuming sulfuric acid has an absorption rate of 40%-60% for SO3 in the first mixed gas.

[0059] The first fuming sulfuric acid can effectively absorb SO3 in the second mixed gas, resulting in a second fuming sulfuric acid with a high SO3 content. Then, the SO3 in the second fuming sulfuric acid can be separated by separation treatment (such as heating and evaporation treatment). The SO3 gas produced by decomposition is cooled to about 40°C and condensed into SO3 liquid product for storage.

[0060] As an example, SO3 in the second mixed gas is absorbed by first fuming sulfuric acid with a mass concentration of 105% in the absorber; the absorption rate of SO3 by the first fuming sulfuric acid is 50%; the mass concentration of the resulting second fuming sulfuric acid increases to 107%; a portion of the second fuming sulfuric acid is extracted and heated for decomposition, and the SO3 gas produced by the decomposition is cooled to 40°C and condensed into liquid SO3. The third fuming sulfuric acid with a mass concentration of 104% obtained after decomposition is returned to the absorber for recycling. The flue gas containing SO2 and SO3 in the third mixed gas output from the absorber outlet is returned to the sulfur incinerator for continued recycling via a blower.

[0061] As an example, the absorption rate of SO3 in the first mixed gas by the first fuming sulfuric acid is 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc.

[0062] In some embodiments of this application, a portion of the third mixed gas is used as a circulating gas, which is mixed with sulfur and the first oxygen-containing gas; another portion of the third mixed gas is used as exhaust gas, which is subjected to exhaust gas recovery treatment.

[0063] In this embodiment, a portion of the third mixed gas can be separated as tail gas and sent to a waste gas treatment process for treatment, such as removing O2, SO3 and acid foam from the tail gas before discharge; thereby improving the problem of impurity gas accumulation introduced by the first oxygen-containing gas and the second oxygen-containing gas.

[0064] In some embodiments of this application, a method for producing SO3 is provided, such as Figure 1 As shown, the specific process includes: The sulfur is reacted with the first oxygen-containing gas to produce a first mixed gas containing SO2. The first mixed gas is subjected to a heat exchange process to obtain a cooled first mixed gas. The cooled first mixed gas is subjected to a catalytic oxidation reaction with a second oxygen-containing gas to obtain a second mixed gas containing SO3. The second mixed gas is subjected to a second heat exchange treatment to obtain a cooled second mixed gas; The cooled second mixed gas is subjected to first fuming sulfuric acid absorption treatment to obtain a third mixed gas and second fuming sulfuric acid; The third mixed gas is divided into recirculated gas and exhaust gas. The recirculated gas is recycled back and mixed with sulfur and the first oxygen-containing gas; the exhaust gas is treated. The second fuming sulfuric acid was absorbed and separated to obtain the third fuming sulfuric acid and SO3 gas; The third fuming sulfuric acid is recycled back and mixed with the first fuming sulfuric acid to absorb the second mixed gas.

[0065] In some embodiments of this application, a method for producing SO3 is provided, such as Figure 2 As shown, the specific process includes: Sulfur and a first oxygen-containing gas undergo a combustion reaction in a sulfur incinerator 101, and are mixed with the circulating gas returned from the absorber tower 105 within the sulfur incinerator 101; the first mixed gas is output from the sulfur incinerator 101. The first mixed gas is cooled by the first heat exchanger 102 and then enters the converter 103, where the first mixed gas and the second oxygen-containing gas undergo a catalytic oxidation reaction; the second mixed gas is output from the converter 103. The second mixed gas is cooled by the second heat exchanger 104 and then enters the absorption tower 105; SO3 in the second mixed gas is absorbed by the first fuming sulfuric acid in the absorption tower 105; the second fuming sulfuric acid and the third mixed gas are output from the absorption tower 105. The third mixed gas is circulated by the blower 106, with part of it returning to the sulfur incinerator 101 to mix with sulfur and the first oxygen-containing gas; and part of it entering the exhaust gas processor 108 for waste gas treatment. A portion of the second fuming sulfuric acid is extracted and fed into evaporator 107 for heating treatment, outputting SO3 gas and the third fuming sulfuric acid; The third fuming sulfuric acid is returned to the absorption tower 105 and mixed with the first fuming sulfuric acid to absorb and treat the second mixed gas. The SO3 gas is cooled to obtain the final SO3 product.

[0066] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0067] Example (1) The circulating gas is returned to the sulfur incinerator 101. The amount of liquid sulfur, the amount of the first oxygen-containing gas, and the amount of circulating gas are determined according to the molar ratio of circulating gas to liquid sulfur of 3 and the molar ratio of oxygen in the first oxygen-containing gas to liquid sulfur of 1.5. Among them, the first oxygen-containing gas is pure oxygen. The first oxygen-containing gas, liquid sulfur, and circulating gas are introduced into the sulfur incinerator 101 to carry out the combustion reaction, realizing S+O2→SO2, that is, sulfur is burned to generate SO2. The composition of the first mixed gas output is: 44.45%SO2, 33.33%O2 and 22.22%SO3. The temperature of the first mixed gas is about 1400℃.

[0068] (2) The first mixed gas from the outlet of the sulfur incinerator 101 undergoes a heat exchange in the first heat exchanger 102 (a waste heat boiler is used in this embodiment) and is then cooled to about 420°C before being sent to the converter 103 for conversion. The converter 103 has three catalyst layers for three-stage conversion reactions, and heat recovery equipment is installed between each catalyst layer. The conversion process is speed-controlled. The flue gas exits the converter when the temperature of each catalyst layer reaches about 630°C. Then, the heat is recovered using the heat recovery equipment, and the temperature is lowered to about 420°C before being sent to the next catalyst layer. The total conversion rate of the conversion process is controlled at 50%. The composition of the second mixed gas after the reaction is 25% SO2, 25% O2 and 50% SO3. The second mixed gas undergoes a second heat exchange in the second heat exchanger 104 (a waste heat boiler is used in this embodiment) and is cooled to 200°C before being sent to the absorption tower 105.

[0069] (3) SO2 in the second mixed gas is absorbed by the first fuming sulfuric acid with a mass concentration of 104.5% in the absorption tower 105. The absorption rate is about 50%. The composition of the third mixed gas at the outlet of the absorption tower 105 is 33.3% SO2, 33.3% O2 ​​and 33.3% SO3. After the third mixed gas is cooled to 60°C, it is sent back to the sulfur incinerator 101 by the blower.

[0070] (4) After the first fuming sulfuric acid with a mass concentration of 104.5% absorbs SO2 from the second mixed gas in the absorption tower 105, a second fuming sulfuric acid with a mass concentration of 106.5% is generated at the bottom of the tower. The second fuming sulfuric acid with a mass concentration of 106.5% is sent to the evaporator 107 and heated by 0.6MPa saturated steam. The fuming sulfuric acid with a mass concentration of 106.5% decomposes and releases SO3 gas. The SO3 gas is cooled to about 40°C and condenses to form liquid SO3. After the second fuming sulfuric acid with a mass concentration of 106.5% releases SO3 upon heating, a third fuming sulfuric acid with a mass concentration of 104.5% is generated and returned to the absorption tower 105 for recycling.

[0071] In this embodiment, SO3 is produced without generating fuming sulfuric acid or sulfuric acid, resulting in a high sulfur utilization rate exceeding 99%. The relay blower pressure head in this embodiment is approximately 20 kPa, which can be met by using materials commonly used for sulfuric acid blowers.

[0072] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for producing SO3, characterized in that, include: The sulfur is reacted with the first oxygen-containing gas to produce a first mixed gas containing SO2. The first mixed gas is subjected to a catalytic oxidation reaction with a second oxygen-containing gas to obtain a second mixed gas containing SO3. The second mixed gas is subjected to a first fuming sulfuric acid absorption treatment to obtain a third mixed gas and a second fuming sulfuric acid; The third mixed gas is recycled back to be mixed with the sulfur and the first oxygen-containing gas; The second fuming sulfuric acid was separated to obtain a third fuming sulfuric acid and SO3 gas; The third fuming sulfuric acid is mixed with the first fuming sulfuric acid to absorb the second mixed gas.

2. The method according to claim 1, characterized in that, The molar ratio of O2 in the first oxygen-containing gas to the sulfur is (1-1.5):

1.

3. The method according to claim 1, characterized in that, The third mixed gas is recycled back to the step of mixing with the sulfur and the oxygen-containing gas, wherein the molar ratio of the third mixed gas to the sulfur is (2.5-3.5):

1.

4. The method according to claim 1, characterized in that, The reaction temperature of the combustion reaction is less than or equal to 1500°C.

5. The method according to claim 1, characterized in that, Before performing the step of catalytic oxidation of the first mixed gas with the second oxygen-containing gas, the temperature of the first mixed gas is less than or equal to 450°C.

6. The method according to claim 5, characterized in that, The first mixed gas undergoes a heat exchange process before being catalytically oxidized with the second oxygen-containing gas.

7. The method according to claim 1, characterized in that, The step of catalytically oxidizing the first mixed gas with the second oxygen-containing gas includes at least one catalytic oxidation conversion reaction.

8. The method according to any one of claims 1 to 7, characterized in that, The second mixed gas undergoes a second heat exchange treatment before being subjected to a first fuming sulfuric acid absorption treatment.

9. The method according to claim 1, characterized in that, In the step of subjecting the second mixed gas to first fuming sulfuric acid absorption treatment, the first fuming sulfuric acid has an absorption rate of 40%-60% for SO3 in the first mixed gas.

10. The method according to claim 1, characterized in that, A portion of the third mixed gas is used as a circulating gas, which is mixed with the sulfur and the first oxygen-containing gas; the other portion of the third mixed gas is used as exhaust gas, which is subjected to exhaust gas recovery treatment.

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