A small scale selective oxidation sulfur recovery unit and method

Abstract

This invention provides a small-scale selective oxidation sulfur recovery device and method. The device includes: a main combustion furnace, a steam generator, a sulfur condenser, a heater, a Claus reactor, a selective catalytic oxidation reactor, and a blower connected in sequence. The blower is connected to main regulating air and fine-tuning air pipelines. A fixed amount of air supplied by the blower through the main regulating air pipeline is mixed with acidic gas containing H2S and enters the main combustion furnace for combustion to generate high-temperature process gas. After recovering liquid sulfur through the steam generator and sulfur condenser, the process gas is heated by the heater and sent to the Claus reactor to undergo a Claus reaction. The produced process gas is mixed with a fixed amount of air supplied by the fine-tuning air pipeline and undergoes a selective oxidation reaction of H2S in the selective catalytic oxidation reactor. The produced process gas is then recovered as liquid sulfur through the sulfur condenser. This simplifies the process flow and reduces the required equipment investment while ensuring sulfur recovery output, thus improving the economic efficiency of small-scale sulfur recovery production.

Description

Technical Field

[0001] This invention relates to sulfur oxide recovery technology, and more particularly to a small-scale selective sulfur oxide recovery device and method with an annual output of less than 5,000 tons. Background Technology

[0002] The Claus process is currently the main process method widely used for recovering sulfur from gases containing H2S. The Claus reaction that occurs is: 2 H2S + SO2 → 3 / n Sn + 2 H2O.

[0003] This reaction is limited by the Claus thermodynamic constant and is a reversible equilibrium reaction. A multi-stage reaction and a multi-stage sulfur condenser are required. This involves condensing and recovering the elemental sulfur produced in the previous reactor, then reheating the process gas before sending it to the next reactor to continue the reaction. This is necessary to encourage the reaction to continue in a direction favorable to the formation of elemental sulfur and improve the sulfur recovery rate.

[0004] Currently, conventional selective sulfur oxidation recovery devices, such as Figure 1 As shown, it mainly consists of two parts: the Claus section and the selective oxidation section. The Claus section typically uses two or three Claus reactors, achieving sulfur recovery rates of approximately 95% and 98% respectively. Each stage is equipped with the necessary process gas heater and sulfur condenser, and the total sulfur recovery rate of the Claus section is generally around 96-98%. Adding the selective oxidation section, the sulfur recovery rate can generally reach 99.5%.

[0005] The SCOT process can achieve higher sulfur recovery rates, such as over 99.98%, but it is more complex and requires more investment. Therefore, generally speaking, the SCOT process is usually used for capacities of 20,000 tons / year or more, while selective oxidation processes are usually used for capacities of less than 20,000 tons / year.

[0006] For small-scale sulfur recovery units (such as those below 5000 tons / year), a conflict often arises between sulfur recovery rate and unit investment. For example... Figure 1 As shown, conventional selective oxidation processes are lengthy and involve numerous equipment units because each stage of the Claus reaction and catalytic oxidation reaction requires heating, reaction, and condensation. Therefore, for small-scale sulfur recovery units, achieving a high sulfur recovery rate with the simplest possible process remains a core challenge for those skilled in the art. Summary of the Invention

[0007] Therefore, the main objective of this invention is to provide a small-scale selective sulfur oxidation recovery device and method to simplify the process flow and reduce the required equipment investment, while ensuring sulfur recovery output, thereby improving the economic efficiency of small-scale sulfur recovery production.

[0008] To achieve the above objectives, according to a first aspect of the present invention, a small-scale selective sulfur oxidation recovery device is provided, comprising: a main combustion furnace, a steam generator, a sulfur condenser, a heater, a Claus reactor, a selective catalytic oxidation reactor, and a blower connected in sequence. The blower is connected to main regulating air and fine-tuning air pipelines. A fixed amount of air supplied by the blower through the main regulating air pipeline is mixed with acidic gas containing H2S and enters the main combustion furnace for combustion to generate high-temperature process gas. After recovering liquid sulfur through the steam generator and the sulfur condenser, the process gas is heated by the heater and sent to the Claus reactor to undergo a Claus reaction. The produced process gas is mixed with a fixed amount of air supplied by the fine-tuning air pipeline and undergoes a selective oxidation reaction of H2S in the selective catalytic oxidation reactor. The produced process gas is then recovered from liquid sulfur through the sulfur condenser.

[0009] In a possible preferred embodiment, the number of stages of the heater is determined according to the number of stages of the Claus reactor, and is two or three stages.

[0010] In a possible preferred embodiment, the process gas after selective oxidation reaction is cooled and then produced by a sulfur condenser to recover liquid sulfur, and then enters the tail gas treatment unit via a sulfur trap.

[0011] In a possible preferred embodiment, the small-scale selective sulfur oxidation recovery device further includes a liquid sulfur pool for collecting sulfur obtained from the steam generator, sulfur condenser, and sulfur trap.

[0012] In a possible preferred embodiment, the heater is heated by any of the following methods: indirect heating with medium-pressure steam, heating by thermal mixing, heating in an online furnace, electric heating, or gas-to-gas heat exchange heating.

[0013] To achieve the above objectives, according to a second aspect of the present invention, a small-scale selective sulfur oxidation recovery method is also provided, comprising the following steps: mixing acidic gas containing H2S with a fixed amount of air to burn approximately 1 / 3 of the acidic gas in a main combustion furnace; the process gas then enters a steam generator for cooling, producing medium-pressure saturated steam as a byproduct which is incorporated into the steam pipeline network; the process gas then enters a primary sulfur condenser for cooling to condense and separate sulfur; the process gas is then heated by a primary heater with medium-pressure saturated steam and enters a primary Claus reactor, where H2S reacts with SO2 to generate elemental sulfur via a Claus catalyst; the process gas then enters a secondary sulfur condenser for cooling to separate sulfur; the process gas is then heated by a secondary heater with medium-pressure saturated steam and enters a secondary Claus reactor, where H2S reacts with SO2 to generate elemental sulfur via a Claus catalyst; the process gas is then mixed with a fixed amount of air and enters a selective catalytic oxidation reactor, where H2S reacts with oxygen via a selective oxidation catalyst to generate elemental sulfur; the produced process gas is then separated from sulfur via a tertiary sulfur condenser.

[0014] In a possible preferred embodiment, the small-scale selective sulfur oxidation recovery method further includes the following steps: the process gas produced by the three-stage sulfur condenser is further subjected to a sulfur trap to capture sulfur in the process gas before entering the tail gas treatment unit.

[0015] In a possible preferred embodiment, the process gas temperature after combustion in the main combustion furnace is 1000℃-1350℃; the process gas temperature after cooling in the steam generator is 300℃-350℃, and 4.0MPaG medium-pressure saturated steam is produced as a byproduct; the process gas temperature after cooling in the first-stage sulfur condenser is 160℃-170℃; the process gas temperature after heating in the first-stage heater is raised to 230℃-240℃; the first-stage Claus reactor produces process gas at 320℃; the process gas temperature after cooling in the second-stage sulfur condenser is 160℃-170℃; the process gas temperature after heating in the second-stage heater is raised to 210℃-220℃; the second-stage Claus reactor produces process gas at 230℃; the selective catalytic oxidation reactor produces process gas at 240℃-270℃; and the process gas temperature after cooling in the third-stage sulfur condenser is 130℃-160℃.

[0016] In a possible preferred embodiment, the small-scale selective sulfur oxidation recovery method further includes the steps of: monitoring the oxygen content and temperature of the process gas at the outlet of the selective catalytic oxidation reactor, and appropriately supplementing a quantitative amount of air to control the outlet process gas temperature to not exceed 270 °C, and to ensure catalyst selectivity.

[0017] In a possible preferred embodiment, the amount of catalyst loaded in each stage of the Claus reactor and the selective catalytic oxidation reactor is preferably determined by the flow rate of the process gas, wherein the first-stage Claus reactor 5 receives a process gas flow rate of 144~1439 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.3~2.7m³. 3 The second-stage Claus reactor 8 receives process gas at a flow rate of 144~1437 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 Selective catalytic oxidation reactor 9, when the process gas flow rate it receives is 144~1437 Nm³ 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 .

[0018] The small-scale selective oxidation sulfur recovery device and method provided by this invention can significantly simplify the complexity of the original process and reduce the number of equipment while maintaining the sulfur recovery rate of the selective oxidation process, making it particularly suitable for small-scale sulfur recovery. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of a conventional selective sulfur oxidation recovery device in the background art;

[0021] Figure 2 This is a schematic diagram illustrating the structural concept of the small-scale selective sulfur oxidation recovery device of the present invention;

[0022] Figure 3 This is a schematic diagram of the specific structure of the small-scale selective sulfur oxide recovery device of the present invention.

[0023] Explanation of reference numerals in the attached figures

[0024] 1. Main combustion furnace, 2. Steam generator, 3. Primary sulfur condenser, 4. Primary heater, 5. Primary Claus reactor, 6. Secondary sulfur condenser, 7. Secondary heater, 8. Secondary Claus reactor, 9. Selective catalytic oxidation reactor, 10. Tertiary sulfur condenser, 11. Sulfur trap, 12. Blower, 13. Liquid sulfur pool. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of the present invention, the specific technical solutions of the present invention will be clearly and completely described below in conjunction with embodiments, so as to help those skilled in the art further understand the present invention. Obviously, the embodiments described in this application are merely some embodiments of the present invention, and not all embodiments. It should be noted that, for those skilled in the art, the embodiments and features in the embodiments of this application can be combined with each other without departing from the concept of the present invention and without conflict. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the disclosure and protection scope of the present invention.

[0026] Furthermore, the terms "first," "second," etc., used in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those described herein. At the same time, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. Unless otherwise expressly specified and limited, the terms "set," "arranged," "installed," "connected," and "linked" should be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two elements. Those skilled in the art can understand the specific meaning of the above terms in this case based on the specific circumstances and in conjunction with existing technology.

[0027] To simplify the process and reduce the required equipment investment, while ensuring sulfur recovery output, and to improve the economics of small-scale sulfur recovery production, such as... Figures 2 to 3 As shown, the small-scale selective sulfur oxidation recovery device provided by the present invention includes: a main combustion furnace 1 (such as an acid gas combustion furnace), a steam generator 2, a first to third stage sulfur condenser 10, a first to second stage heater 7, a first to second stage Claus reactor 8, a selective catalytic oxidation reactor 9, and a blower 12 connected in sequence.

[0028] The blower 12 is connected to main air regulating and fine air regulating pipelines. The blower 12 provides a fixed amount of air through the main air regulating pipeline to mix with acidic gas containing H2S and enter the main combustion furnace 1. After burning about 1 / 3 of the acidic gas, high-temperature process gas is generated. After steam generation by the steam generator 2, the gas is cooled down and sent to the first-stage sulfur condenser 3 to recover liquid sulfur. After the process gas is cooled down, it is heated by the first-stage heater 4 and then sent to the first-stage Claus reactor 5 to undergo the Claus reaction. The process gas produced can be sent to the selective catalytic oxidation reactor 9 to undergo the selective oxidation reaction of H2S. Alternatively, one or more stages of Claus reactors and corresponding heaters and sulfur condensers can be added to improve the sulfur recovery rate.

[0029] For example, the process gas produced by the first-stage Claus reactor 5 is used to recover liquid sulfur through the second-stage sulfur condenser 6. The process gas then exits and is heated by the second-stage heater 7 before being sent to the second-stage Claus reactor 8 to undergo the Claus reaction. Finally, after undergoing the Claus reaction in the final-stage Claus reactor, the H2S concentration of the process gas entering the selective oxidation reaction inlet is generally required to be 0.6-1 v%. Therefore, in the optional example, the upstream process flow design should be based on the composition of the feed gas, and a two-stage or three-stage Claus reactor can be used to meet the hydrogen sulfide concentration requirements.

[0030] Finally, after the Claus reaction occurs in the final stage Claus reactor, the produced process gas is mixed with a fixed amount of air provided by the fine-tuning air duct and then undergoes a selective oxidation reaction of H2S in the selective catalytic oxidation reactor 9. The produced process gas is then passed through the three-stage sulfur condenser 10 to recover liquid sulfur, which can ensure the sulfur recovery rate.

[0031] In addition, in other equivalent alternative examples, a selective catalytic oxidation catalyst bed can be arranged in the same shell within the final Claus reactor to replace the selective catalytic oxidation reactor 9, thereby miniaturizing and modularizing the device. This allows for further catalytic conversion of the remaining H2S in the process gas into elemental sulfur, while minimizing the generation of SO2. Due to the high catalyst conversion rate and selectivity, the sulfur recovery rate is increased by 1-2% compared to the conventional Claus scheme, and one heater and sulfur condenser are reduced compared to the conventional selective oxidation process.

[0032] To further improve the sulfur recovery rate, in a preferred example, the process gas after the selective oxidation reaction is cooled and then passes through a sulfur condenser to recover liquid sulfur, and can then enter the tail gas treatment unit via a sulfur trap 11.

[0033] Furthermore, such as Figure 3 As shown, in order to facilitate the collection and recovery of liquid sulfur, in a preferred example, the small-scale selective sulfur oxidation recovery device further includes: a liquid sulfur pool 13 for collecting the sulfur obtained from the steam generator 2, sulfur condensers 3, 6, 10, and sulfur collector 11.

[0034] Furthermore, in a preferred embodiment, the heater can be heated using any of the following methods: indirect heating with medium-pressure steam, heating by thermal mixing, heating in an online furnace, electric heating, or gas-to-gas heat exchange heating. Simultaneously, the steam generator 2 can also produce medium-pressure saturated steam, low-pressure steam, or very low-pressure steam, the steam pressure of which can be adjusted according to the plant's pipeline network conditions.

[0035] On the other hand, corresponding to the above-mentioned device example, the present invention also provides a small-scale selective sulfur oxidation recovery method. Taking the recovery of 3,000 tons / year of sulfur as an example, the method includes the following steps: mixing acid gas containing H2S with a fixed amount of air so that about 1 / 3 of the acid gas is burned in the main combustion furnace 1, the process gas enters the steam generator 2 for cooling, and the by-product medium-pressure saturated steam is incorporated into the steam pipeline network, while the process gas enters the first-stage sulfur condenser 3 for cooling, so as to condense and separate sulfur.

[0036] After the process gas is heated by medium-pressure saturated steam in the primary heater 4, it enters the primary Claus reactor 5. After H2S and SO2 react to form elemental sulfur by the Claus catalyst, the process gas enters the secondary sulfur condenser 6 to cool down and separate the sulfur.

[0037] After being heated by medium-pressure saturated steam in the secondary heater 7, the process gas enters the secondary Claus reactor 8. After reacting H2S and SO2 with the Claus catalyst to produce elemental sulfur, the process gas is mixed with a fixed amount of air to achieve an H2S:SO2 ratio of >2:1 and then enters the selective catalytic oxidation reactor 9. After reacting H2S and oxygen with the selective oxidation catalyst to produce elemental sulfur, the produced process gas is then separated into sulfur by the tertiary sulfur condenser 10.

[0038] Specifically, the process gas temperature after combustion in the main combustion furnace 1 is preferably 1000℃-1350℃; the process gas temperature after cooling in the steam generator 2 is 300℃-350℃, and 4.0MPaG medium-pressure saturated steam is produced as a byproduct and incorporated into the plant's steam pipeline network. The process gas at the outlet of the steam generator 2 is cooled to 160℃-170℃ by the first-stage sulfur condenser 3, and sulfur is separated by condensation.

[0039] Afterwards, the process gas enters the first-stage heater 4 and is heated to 230 ℃-240 ℃ by medium-pressure steam. Then, it enters the first-stage Claus reactor 5. Under the action of the Claus catalyst in the first-stage Claus reactor 55, H2S reacts with SO2 to produce elemental sulfur. The reaction then produces process gas at 320 ℃, which enters the second-stage sulfur condenser 6 to cool down to 160 ℃-170 ℃, so that sulfur can be separated by condensation.

[0040] The process gas is then heated by medium-pressure steam in the secondary heater 7 to 210 ℃-220 ℃. It then enters the secondary Claus reactor 8, where H2S reacts with SO2 to produce elemental sulfur under the action of the Claus catalyst, producing process gas at 230 ℃. This process gas then enters the selective catalytic oxidation reactor 9, producing process gas at 240 ℃-270 ℃. Finally, it enters the tertiary sulfur condenser 10, where the cooled process gas is 130 ℃-160 ℃ and sulfur is separated by condensation.

[0041] To further improve the sulfur recovery rate, in a preferred example, the small-scale selective oxidation sulfur recovery method further includes the following steps: the process gas produced by the three-stage sulfur condenser 10 is further subjected to sulfur capture by the sulfur trap 11 before entering the tail gas treatment unit.

[0042] In addition, in a preferred embodiment, a process gas thermometer and an oxygen content analyzer can be installed at the outlet of the selective catalytic oxidation reactor 9 to monitor the oxygen content and temperature of the process gas at the outlet of the selective catalytic oxidation reactor 9, so as to appropriately supplement a certain amount of air to control the degree of catalytic oxidation reaction, thereby controlling the temperature rise of the process gas, for example, adjusting the outlet process gas temperature to not exceed 270 ℃, so as to ensure catalyst selectivity and prevent excessive oxygen content from reducing catalyst selectivity.

[0043] Meanwhile, the amount of catalyst loaded in each stage of the Claus reactor and the selective catalytic oxidation reactor is preferably determined by the flow rate of the process gas. Specifically, in the first-stage Claus reactor 5, the process gas flow rate it receives is 144~1439 Nm³. 3 At a rate of [number] / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.3~2.7m³. 3 The second-stage Claus reactor 8 receives process gas at a flow rate of 144~1437 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 Selective catalytic oxidation reactor 9, when the process gas flow rate it receives is 144~1437 Nm³ 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 .

[0044] Therefore, by setting up the above example, it is equivalent to setting the complexity of the two-stage Claus process, that is, using only two heating, reaction and cooling processes, to achieve a sulfur recovery rate of over 98%, which is about 1%-2% higher than the conventional two-stage Claus process.

[0045] In summary, the small-scale selective oxidation sulfur recovery device and method provided by this invention fully utilizes the low temperature rise of the second or third stage Claus reactor. By directly arranging the selective oxidation reactor after the second or third stage Claus reactor, the complexity of the original process can be greatly simplified and the number of equipment reduced while maintaining the sulfur recovery rate of the selective oxidation process. It is especially suitable for small-scale sulfur recovery.

[0046] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The present invention is limited only by the claims and their full scope and equivalents. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

[0047] Those skilled in the art will understand that, besides implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0048] Furthermore, all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0049] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A small-scale selective sulfur oxidation recovery device, comprising: The system is sequentially connected to a main combustion furnace, a steam generator, a sulfur condenser, a heater, a Claus reactor, a selective catalytic oxidation reactor, a blower, a process gas thermometer, and an oxygen content analyzer. The blower is connected to main and fine-tuning air ducts. A fixed amount of air supplied by the blower through the main air duct mixes with acidic gas containing H2S and enters the main combustion furnace for combustion of 1 / 3, simultaneously generating high-temperature process gas. After the liquid sulfur is recovered by the steam generator and sulfur condenser, the process gas is heated by the heater and sent to the first-stage Claus reactor to undergo a Claus reaction. After the catalyst reacts H2S with SO2 to produce elemental sulfur, the produced process gas enters the second-stage sulfur condenser for cooling and sulfur separation. The process gas is then heated by medium-pressure saturated steam by the second-stage heater and enters the second-stage Claus reactor. After the catalyst reacts H2S with SO2 to produce elemental sulfur, the process gas is mixed with a fixed amount of air supplied by the fine-tuning air duct to achieve an H2S:SO2 ratio of >2:

1. Then, a selective oxidation reaction of H2S occurs in the selective catalytic oxidation reactor. The produced process gas is then recovered by the third-stage sulfur condenser. The process gas thermometer and oxygen content analyzer are installed at the outlet of the selective catalytic oxidation reactor to monitor the oxygen content and air temperature of the process gas at the outlet, adjust the amount of air added, and control the temperature rise of the process gas during the catalytic oxidation reaction to not exceed 270 ℃ to maintain the selectivity of the catalyst. In the Claus reactors and selective catalytic oxidation reactors at each stage, the amount of catalyst loaded is determined by the flow rate of the process gas. For the first-stage Claus reactor, the process gas flow rate received is 144~1439 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.3~2.7m³. 3 A two-stage Claus reactor, receiving process gas at a flow rate of 144~1437 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 Selective catalytic oxidation reactor, when the process gas flow rate it receives is 144~1437 Nm³ 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 .

2. The small-scale selective sulfur oxide recovery device according to claim 1, wherein the number of stages of the heater is determined according to the number of stages of the Claus reactor, and is two-stage or three-stage.

3. The small-scale selective oxidation sulfur recovery device according to claim 1, wherein the process gas after the selective oxidation reaction is recycled by a sulfur condenser to recover liquid sulfur, and the cooled process gas is then introduced into the tail gas treatment unit via a sulfur trap.

4. The small-scale selective sulfur oxide recovery device according to claim 1, further comprising: Liquid sulfur pool to collect sulfur obtained from steam generator, sulfur condenser and sulfur trap.

5. The small-scale selective sulfur oxide recovery device according to claim 1, wherein the heater is heated by any one of the following methods: indirect heating with medium-pressure steam, heating by thermal mixing, heating with an online heating furnace, electric heating, or gas-to-gas heat exchange heating.

6. A small-scale selective sulfur oxidation recovery method, comprising the following steps: Acidic gas containing H2S is mixed with a fixed amount of air, and after the acidic gas is burned by 1 / 3 in the main combustion furnace, the process gas enters the steam generator for cooling, and produces medium-pressure saturated steam as a byproduct which is then incorporated into the steam pipeline network. The process gas then enters the first-stage sulfur condenser for cooling to separate sulfur. After that, the process gas is heated with medium-pressure saturated steam in the first-stage heater and enters the first-stage Claus reactor. After reacting H2S with SO2 to produce elemental sulfur by a catalyst, the process gas enters the second-stage sulfur condenser for cooling to separate sulfur. After that, the process gas is heated with medium-pressure saturated steam in the second-stage heater and enters the second-stage Claus reactor. After reacting H2S with SO2 to produce elemental sulfur by a catalyst, the process gas is mixed with a fixed amount of air to achieve an H2S:SO2 ratio of >2:1 and then enters the selective catalytic oxidation reactor. After reacting H2S with oxygen to produce elemental sulfur by a catalyst, the produced process gas is then separated from sulfur in the third-stage sulfur condenser. The steps also include: monitoring the oxygen content and temperature of the process gas at the outlet of the selective catalytic oxidation reactor, and appropriately adding a fixed amount of air to control the outlet process gas temperature to not exceed 270 °C, and to ensure catalyst selectivity; The steps also include: in each stage of the Claus reactor and the selective catalytic oxidation reactor, the amount of catalyst loaded is determined by the flow rate of the process gas, wherein in the first-stage Claus reactor, the process gas flow rate received is 144~1439 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.3~2.7m³. 3 A two-stage Claus reactor, receiving process gas at a flow rate of 144~1437 Nm³. 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 Selective catalytic oxidation reactor, when the process gas flow rate it receives is 144~1437 Nm³ 3 At a rate of / h, the amount of aluminum-based or titanium-based catalyst packed inside is 0.2~2m³. 3 .

7. The small-scale selective sulfur oxide recovery method according to claim 6, wherein the steps further include: The process gas produced by the three-stage sulfur condenser is further processed by a sulfur trap to capture sulfur in the process gas before entering the tail gas treatment unit.

8. The small-scale selective sulfur oxidation recovery method according to claim 6, wherein the process gas temperature after combustion in the main combustion furnace is 1000℃-1350℃; the process gas temperature after cooling in the steam generator is 300℃-350℃, and 4.0MPaG medium-pressure saturated steam is produced as a byproduct; the process gas temperature after cooling in the primary sulfur condenser is 160℃-170℃; the process gas temperature after heating in the primary heater is raised to 230℃-240℃; the primary Claus reactor produces process gas at 320℃; the process gas temperature after cooling in the secondary sulfur condenser is 160℃-170℃; the process gas temperature after heating in the secondary heater is raised to 210℃-220℃; the secondary Claus reactor produces process gas at 230℃; the selective catalytic oxidation reactor produces process gas at 240℃-270℃; and the process gas temperature after cooling in the tertiary sulfur condenser is 130℃-160℃.

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