A purification system and method for hydrogen sulfide-containing acid gases

Abstract

This application relates to the field of hydrogen sulfide purification technology, and more particularly to a purification system and method for hydrogen sulfide-containing acidic gas. The purification system includes: an absorption section comprising a hydrogen sulfide-containing acidic gas conduit, a first absorber, a second absorber, and a purified gas discharge pipe; a heat exchange and cooling section comprising a heat exchanger and a cooler; a combined separator comprising a first baffle, a second baffle, and a tail gas discharge pipe, the first and second baffles dividing the combined separator into a primary separation zone, a secondary separation zone, and a tertiary separation zone; each separation zone comprising a gas reservoir, a flash section, and a liquid reservoir; each flash section is equipped with a feed distributor; the shell-side outlet of the cooler is connected to the absorbent inlets of the first absorber, the second absorber, and each gas reservoir; and a separation unit comprising a separation tower and a lean absorbent booster pump. This purification system, through enhanced absorption, staged deep flash evaporation, distillation purification, and tail gas reflux design, reduces the hydrogen sulfide content in the tail gas while increasing the purity of the hydrogen sulfide.

Description

Technical Field

[0001] This application relates to the field of hydrogen sulfide purification technology, and in particular to a purification system and method for hydrogen sulfide-containing acidic gas. Background Technology

[0002] Refinery gas, natural gas, and syngas produced in the chemical refining industry all contain acidic gaseous components such as hydrogen sulfide and carbon dioxide, as well as other components such as hydrocarbons, water, and ammonia. Hydrogen sulfide, a colorless, toxic gas with a rotten egg odor, causes extremely serious environmental pollution and must be treated to render it harmless. Currently, the main treatment method is to first separate hydrogen sulfide from refinery gas, natural gas, and syngas, and then use it as a raw material to produce sulfur-containing chemical products such as sulfur, sulfuric acid, sodium hydrosulfide, thiophenol, and thiourea. However, practical experience shows that excessive carbon dioxide in hydrogen sulfide can adversely affect the production of sulfur-containing chemical products. For example, when using hydrogen sulfide gas containing carbon dioxide as a raw material to produce sulfur, carbon dioxide dilutes the concentration of hydrogen sulfide in the acid gas, lowers the temperature of the acid gas combustion furnace, and also reacts directly with hydrogen sulfide to generate excessive COS and CS2 byproducts. The presence of these byproducts reduces the quality of the sulfur product. When using hydrogen sulfide gas containing carbon dioxide and sodium hydroxide as a raw material to produce sodium hydrosulfide, carbon dioxide easily reacts directly with sodium hydroxide to generate sodium carbonate or sodium bicarbonate byproducts. These byproducts not only reduce the quality of the sodium hydrosulfide product, but also combine with water to form hydrated crystals such as sodium carbonate nonahydrate. These hydrated crystals can clog equipment and pipelines, affecting the normal production of sodium hydrosulfide. Therefore, it is urgent to purify hydrogen sulfide gas.

[0003] At present, the purification technologies for hydrogen sulfide are: (1) Purification operation is carried out by purifying hydrogen sulfide in oil refinery tail gas through a two-stage absorption-two-stage regeneration process. The specific process is as follows: use a certain concentration of amine-containing solution to absorb hydrogen sulfide in oil refinery tail gas in the first-stage absorption tower to obtain hydrogen sulfide-rich solution; introduce the hydrogen sulfide-rich solution into the first-stage regeneration tower for regeneration, obtain the first-stage regeneration tower top gas at the top of the first-stage regeneration tower, and then enter the second-stage regeneration tower for regeneration, and obtain purified hydrogen sulfide acid gas product at the top of the second-stage regeneration tower. (2) Purification of hydrogen sulfide by pressure swing adsorption (PSA) involves the following process: using an adsorption tower as the equipment, a vacuum process is performed within the adsorption tower: adsorption process → pressure equalization process → reverse release process → vacuum process → pressure equalization process → final pressure increase process. Two to six adsorption towers with these vacuum processes are connected in series. Acidic gas containing hydrogen sulfide is sequentially purified through the adsorption towers until a highly purified hydrogen sulfide acidic gas product is obtained. However, these purification technologies result in high hydrogen sulfide content in the exhaust gas, making direct emission difficult. Summary of the Invention

[0004] This application provides a purification system and method for hydrogen sulfide-containing acidic gas to solve the following technical problem: how to improve the purity of hydrogen sulfide under emission tail gas conditions with low hydrogen sulfide content. In a first aspect, embodiments of this application provide a purification system for hydrogen sulfide-containing acidic gas, the purification system comprising: The absorption section includes a hydrogen sulfide-containing acid gas conduit, a first absorber, a second absorber, and a purified gas discharge pipe. The outlet of the hydrogen sulfide-containing acid gas conduit is connected to the inlet of the first absorber. The second absorber includes, from top to bottom, a gas-liquid separator, a gas-liquid contact section, and a rich absorbent buffer section. The outlet of the first absorber is connected to the rich absorbent buffer section. The inlet of the purified gas discharge pipe is connected to the top outlet of the second absorber. The heat exchange and cooling section includes a heat exchanger and a cooler. The shell-side inlet of the heat exchanger is connected to the outlet of the rich absorbent buffer section, and the tube-side outlet of the heat exchanger is connected to the shell-side inlet of the cooler. A combined separator includes a first partition, a second partition, and an exhaust pipe. The first and second partitions are fixedly connected within the combined separator, dividing it into a primary separation zone, a secondary separation zone, and a tertiary separation zone. The primary separation zone includes a through-flow primary gas manifold, a primary flash evaporation section, and a primary liquid manifold, with the primary gas manifold positioned above the primary flash evaporation section and the primary flash evaporation section positioned above the primary liquid manifold. The secondary separation zone includes a secondary gas manifold, a secondary flash evaporation section, and a secondary liquid manifold, with the secondary gas manifold positioned above the secondary flash evaporation section and the secondary flash evaporation section positioned above the secondary liquid manifold. The tertiary separation zone includes a tertiary steam manifold, a tertiary flash evaporation section, and a tertiary liquid manifold. A three-stage gas manifold is positioned above the three-stage flash evaporation section, which is positioned above the three-stage liquid manifold. The first-stage flash evaporation section is equipped with a first-stage feed distributor, the inlet of which is connected to the shell-side outlet of the heat exchanger. The second-stage flash evaporation section is equipped with a second-stage feed distributor, the inlet of which is connected to the outlet of the first-stage liquid manifold. The third-stage flash evaporation section is equipped with a third-stage feed distributor, the inlet of which is connected to the outlet of the second-stage liquid manifold. The outlet of the first-stage gas manifold is connected to the inlet of the second-stage gas manifold, and the outlet of the second-stage gas manifold is connected to the inlet of the third-stage gas manifold. The outlet of the third-stage gas manifold is connected to the inlet of the exhaust gas discharge pipe. The shell-side outlet of the cooler is simultaneously connected to the absorbent inlets of the first absorber, the second absorber, the primary gas chamber, the secondary gas chamber, and the tertiary gas chamber. The absorbent inlet of the primary gas chamber is located at the top of the primary gas chamber, the absorbent inlet of the secondary gas chamber is located above the air inlet of the secondary gas chamber, and the absorbent inlet of the tertiary gas chamber is located above the air inlet of the tertiary gas chamber. The absorbent inlet of the second absorber is located between the gas-liquid contact section and the gas-liquid separator. The separation unit includes a separation tower and a lean absorbent booster pump. The outlet of the three-stage liquid tank is connected to the inlet of the separation tower, the bottom outlet of the separation tower is connected to the inlet of the lean absorbent booster pump, and the outlet of the lean absorbent booster pump is connected to the tube-side inlet of the heat exchanger.

[0005] Optionally, the primary gas tank is provided with a primary absorption section located below the absorbent inlet of the primary gas tank; the secondary gas tank is provided with a secondary absorption section located between the absorbent inlet and the air inlet of the secondary gas tank; and the tertiary absorption section is located between the absorbent inlet and the air inlet of the tertiary gas tank.

[0006] Optionally, a primary heater is provided in the primary separation zone, and the primary heater is located at the bottom of the primary flash section; A secondary heater is provided in the secondary separation zone, and the secondary heater is located at the bottom of the secondary flash section; The three-stage separation zone is equipped with a three-stage heater, which is located at the bottom of the three-stage flash section.

[0007] Optionally, the purification system further includes: The pressure reducing valve assembly includes a primary pressure reducing valve, a secondary pressure reducing valve, and a tertiary pressure reducing valve. The primary pressure reducing valve is fixedly connected between the heat exchanger and the primary feed distributor. The secondary pressure reducing valve is fixedly connected between the primary liquid reservoir and the secondary feed distributor. The tertiary pressure reducing valve is fixedly connected between the secondary liquid reservoir and the tertiary feed distributor.

[0008] Optionally, the second absorber is provided with a rich absorbent isolation plate and a rich absorbent booster pump. The rich absorbent isolation plate is vertically arranged in the rich absorbent buffer section, and the rich absorbent isolation plate divides the rich absorbent buffer section into a primary rich absorbent buffer section and a secondary rich absorbent buffer section. The top of the primary rich absorbent buffer section and the secondary rich absorbent buffer section have a through gas phase space. The inlet of the rich absorbent booster pump is connected to the outlet of the primary rich absorbent buffer section, and the outlet of the rich absorbent booster pump is connected to the middle inlet of the gas-liquid contact section.

[0009] Optionally, the primary feed distributor, the secondary feed distributor, and the tertiary feed distributor are each provided with two strip-shaped slots, one of which is positioned facing one end of the combined separator, and the other of which is positioned facing the other end of the combined separator.

[0010] Optionally, the opening width W of the strip-shaped slot satisfies: W = 2.5 × d 2 / (D-250), Equation 1; In Formula 1, d is the shell-side outlet diameter of the heat exchanger in mm; D is the diameter of the combined separator in mm, and D≥300mm.

[0011] Optionally, the separation unit further includes a condenser, a reflux tank, a reflux pump, a reboiler, and a hydrogen sulfide outlet pipe. The inlet of the condenser is connected to the top outlet of the separation tower, the outlet of the condenser is connected to the inlet of the reflux tank, the upper outlet of the reflux tank is connected to the inlet of the hydrogen sulfide outlet pipe, the lower outlet of the reflux tank is connected to the inlet of the reflux pump, the outlet of the reflux pump is connected to the top inlet of the separation tower, the inlet of the reboiler is connected to the bottom inlet of the separation tower, and the outlet of the reboiler is connected to the bottom side inlet of the separation tower.

[0012] Optionally, the purification system further includes: An exhaust gas compressor, wherein the inlet of the exhaust gas compressor is connected to a branch outlet of the exhaust gas discharge pipe, and the outlet of the exhaust gas compressor is connected to a branch inlet of the hydrogen sulfide-containing acidic gas conduit.

[0013] Secondly, embodiments of this application provide a method for purifying a hydrogen sulfide-containing acidic gas, the purification method being adapted to the purification system described in the first aspect, the purification method comprising: The first lean solution is used to absorb the acidic gas containing hydrogen sulfide to obtain a first gas-liquid two-phase mixture; The first gas-liquid two-phase mixture is separated to obtain a crude absorbent liquid and a crude purified gas; The crude absorbent is used to perform a second absorption on the crude purified gas to obtain a primary rich absorbent and a preliminary purified gas. The second lean liquid is subjected to a first countercurrent contact reaction with the pre-purified gas to obtain a secondary rich absorbent liquid and purified gas. The primary rich absorbent and the secondary rich absorbent are mixed to obtain a rich absorbent; The rich absorbent liquid is heated and depressurized in a first stage to obtain a second gas-liquid two-phase mixture. The second gas-liquid two-phase mixture was subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution; The hydrogen sulfide-rich solution is separated to obtain hydrogen sulfide gas and a lean absorbent solution; The lean absorbent is subjected to two-stage cooling and splitting in sequence to obtain a split lean absorbent; A portion of the diverted lean solution is returned to the first absorber for recycling as the first lean solution. A portion of the diverted lean solution is returned to the first countercurrent contact reaction and recycled as the second lean solution.

[0014] Optionally, the second gas-liquid two-phase mixture is subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution, including the following steps: The second gas-liquid two-phase mixture is subjected to a first-stage flash evaporation to obtain a first-stage flash vapor and a first-stage rich liquid. The third lean liquid is reacted with a portion of the first-stage flash vapor in a second countercurrent contact reaction to obtain the first absorbent liquid; The first absorbent and the first rich solution are mixed to obtain the second rich solution; The second rich liquid is subjected to two-stage depressurization and two-stage flash evaporation to obtain a second-stage flash vapor and a third rich liquid. The fourth lean liquid is subjected to a third countercurrent contact reaction with a portion of the second-stage flash vapor and the remaining first-stage flash vapor to obtain the second absorbent liquid; The second absorbent and the third enriched solution are mixed to obtain a fourth enriched solution; The fourth rich liquid is subjected to three stages of depressurization and three stages of flash evaporation to obtain three stages of flash vapor and the fifth rich liquid. The fifth lean liquid is subjected to a fourth countercurrent contact reaction with the remaining first-stage flash vapor, the remaining second-stage flash vapor, and all the third-stage flash vapor to obtain the third absorbent and tail gas. The third absorbent and the fifth rich solution are mixed to obtain a hydrogen sulfide-rich solution; Specifically, a portion of the depleted lean solution is returned to the second countercurrent contact reaction for reuse as the third lean solution; a portion of the depleted lean solution is returned to the third countercurrent contact reaction for reuse as the fourth lean solution; and the remaining depleted lean solution is returned to the fourth countercurrent contact reaction for reuse as the fifth lean solution.

[0015] Optionally, the temperature of the first-stage flash evaporation is 55°C to 75°C, the temperature of the second-stage flash evaporation is 65°C to 85°C, and the temperature of the third-stage flash evaporation is 75°C to 95°C. The pressure P3 of the third-stage flash evaporation is 0.15 MPa to 0.25 MPa, and the pressures P1 of the first-stage flash evaporation and P2 of the second-stage flash evaporation satisfy the following: P1 = (0.8 to 1.2) × r 2 ×P3, and P2 = (0.8 to 1.2) × r × P3, Equation 2, In Equation 2, r is the pressure drop coefficient, and r satisfies: P0 is the pressure of the second absorption, in MPa.

[0016] Optionally, the pressure P0 of the second absorption satisfies: (Pw-0.3MPa)≤P0≤(Pw-0.1MPa), Equation 3, In Equation 3, Pw is the introduction pressure of the acidic gas containing hydrogen sulfide, and the unit is MPa.

[0017] Optionally, the volumetric flow rate of the first-stage flash vapor is 30 to 1000 times the volumetric flow rate of the third lean solution; and / or The volumetric flow rate of the secondary flash vapor is 40 to 1250 times that of the volumetric flow rate of the fourth lean solution; and / or The volumetric flow rate of the third-stage flash vapor is 50 to 1500 times that of the fifth lean liquid.

[0018] Optionally, the temperature of the first absorption is from 10°C to 50°C; and / or The temperature of the second absorption is 10°C to 50°C; and / or The temperature of the first countercurrent contact reaction is 10°C to 50°C.

[0019] Optionally, the secondary cooling includes a first cooling and a second cooling, wherein the endpoint temperature of the first cooling is 70°C to 95°C and the endpoint temperature of the second cooling is 15°C to 45°C.

[0020] Optionally, the separation includes rectification separation and stripping separation, wherein the temperature of the rectification separation is 105°C to 115°C and the pressure of the rectification separation is 150 kPa to 250 kPa; and the temperature of the stripping separation is 115°C to 145°C.

[0021] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a purification system for hydrogen sulfide-containing acidic gas. The system uses a first absorber to mix the absorbent with the hydrogen sulfide-containing acidic gas, achieving initial absorption of the hydrogen sulfide. The unabsorbed hydrogen sulfide-containing acidic gas and the pre-purified gas released during the initial absorption process then enter a second absorber for deep absorption, transferring the hydrogen sulfide from the gas phase to the liquid phase, forming a hydrogen sulfide-rich absorbent. This rich absorbent is then processed by a heat exchanger and cooler to recover its heat, aiding in the subsequent removal of impurities during combined separation. The rich absorbent, after being processed by the heat exchanger and cooler, undergoes sequential processing in a primary separation zone, a secondary separation zone, and a tertiary separation zone during combined separation. In each separation zone, a flash evaporation section and a feed distributor convert carbon dioxide and light hydrocarbon components in the rich absorbent into the gas phase, while the hydrogen sulfide remains in the liquid phase. Simultaneously, the carbon dioxide and light hydrocarbon components converted to the gas phase undergo multi-stage countercurrent contact with the lean absorbent in the gas chamber of each separation zone, effectively separating hydrogen sulfide entrained in the gas phase, reducing the hydrogen sulfide content in the final tail gas, and recovering the hydrogen sulfide in the gas phase as a liquid phase. Finally, a hydrogen sulfide-rich solution is formed in the three-stage liquid chamber of the combined separator. This hydrogen sulfide-rich solution is subsequently separated by a separation tower to convert into high-purity hydrogen sulfide gas product and lean absorbent. The lean absorbent is returned to the heat exchanger and cooler via a lean absorbent booster pump, and then recirculated to the first absorber, second absorber, and combined separator, ensuring a stable absorbent concentration and sufficient activity throughout the purification system, and reducing the accumulation of impurities in the absorbent during the circulation process. Therefore, in the purification system provided in this application embodiment, the acidic gas containing hydrogen sulfide undergoes multiple alternating absorption and desorption processes, so that the hydrogen sulfide in the acidic gas containing hydrogen sulfide is gradually enriched in the hydrogen sulfide-rich solution, and the hydrogen sulfide-rich solution then enters the subsequent separation tower for desorption, ultimately obtaining a high-purity hydrogen sulfide gas product. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 1 of this application; Figure 2 This is a schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 2 of this application; Figure 3 This is a schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 3 of this application; Figure 4 This is a schematic diagram of the liquid transfer zone structure of the second absorber in the purification system provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of the strip groove in the purification system provided in the embodiments of this application; Figure 6 A schematic flowchart of a method for purifying hydrogen sulfide-containing acidic gas provided in an embodiment of this application; Figure 7 A detailed flowchart illustrating a method for purifying hydrogen sulfide-containing acidic gas, provided for an embodiment of this application; Figure 8 for Figure 7 The continuation; Among them, 1-first absorber, 2-second absorber, 21-gas-liquid separator, 22-gas-liquid contact section, 23-rich absorbent buffer section, 24-first-stage rich absorbent buffer section, 25-second-stage rich absorbent buffer section, 26-rich absorbent isolation plate, 27-liquid transfer zone, 271-gravity guide pipe, 272-inlet baffle, 273-outlet baffle, 274-bottom plate, 3-hydrogen sulfide-containing acidic gas duct, 31-lean absorbent booster pump, 32-rich absorbent booster pump, 4-heat exchange and cooling section, 41-heat exchanger, 42-cooler, 5-pressure reducing valve group, 51-first-stage pressure reducing valve, 52-second-stage pressure reducing valve. 53 - Three-stage pressure reducing valve; 6 - Combined separator; 61 - Primary separation zone; 611 - Primary air reservoir; 6111 - Primary absorption section; 612 - Primary flash section; 6121 - Primary feed distributor; 613 - Primary liquid reservoir; 614 - Primary heater; 62 - Secondary separation zone; 621 - Secondary air reservoir; 6211 - Secondary absorption section; 622 - Secondary flash section; 6221 - Secondary feed distributor; 623 - Secondary liquid reservoir; 624 - Secondary heater; 63 - Tertiary separation zone; 631 - Tertiary air reservoir; 6311 - Tertiary absorption section; 632 - Tertiary flash section; 6321 - Tertiary feed distributor. 633-Third-stage liquid tank, 634-Third-stage heater, 64-First baffle, 65-Second baffle, 66-Tail gas discharge pipe, 7-Separation tower, 71-Condenser, 72-Reflux tank, 73-Reflux pump, 74-Reboiler, 75-Hydrogen sulfide discharge pipe, 8-Tail gas compressor, 9-Purified gas discharge pipe, 10-Striped orifice. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] The range descriptions used in this application, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and others used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained by purchasing from the market or by existing methods.

[0027] It should be noted that, regarding the prior art (1) described in the background art, the inventors have found that: this technology only performs secondary purification of oil refining tail gas, and the purification process is relatively complex, resulting in high equipment costs and complex operation; regarding the prior art (2) described in the background art, the inventors have found that: the hydrogen sulfide content in the final exhaust gas obtained by this technology is generally around 500 mg / Nm³. 3 Up to 680 mg / Nm 3 Furthermore, the emissions from the waste gas, even after subsequent incineration, fail to meet the sulfur dioxide concentration requirement of ≤400 mg / Nm³ as stipulated in GB 31570-2015 "Emission Standard of Pollutants for Petroleum Refining Industry". 3 In addition to the requirements, many pressure swing adsorption processes also have disadvantages such as complex regeneration operations, low hydrogen sulfide recovery rates, and high toxicity of the adsorbents used in pressure swing adsorption.

[0028] Therefore, it is currently difficult to improve the purity of hydrogen sulfide gas while ensuring that the hydrogen sulfide content in the purified gas meets the actual requirements or relevant standards.

[0029] Figure 1 An exemplary schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 1 of this application is shown. like Figure 1 As shown in the figure, this application provides a purification system for hydrogen sulfide-containing acidic gas, the purification system comprising: The absorption section includes a hydrogen sulfide-containing acid gas conduit 3, a first absorber 1, a second absorber 2, and a purified gas discharge pipe 9. The outlet of the hydrogen sulfide-containing acid gas conduit 3 is connected to the inlet of the first absorber 1. The second absorber 2 includes, from top to bottom, a gas-liquid separator 21, a gas-liquid contact section 22, and a rich absorbent buffer section 23. The outlet of the first absorber 1 is connected to the rich absorbent buffer section 23. The inlet of the purified gas discharge pipe 9 is connected to the top outlet of the second absorber 2. The heat exchange and cooling section 4 includes a heat exchanger 41 and a cooler 42. The shell-side inlet of the heat exchanger 41 is connected to the outlet of the rich absorbent buffer section 23, and the tube-side outlet of the heat exchanger 41 is connected to the shell-side inlet of the cooler 42. The combined separator 6 includes a first partition 64, a second partition 65, and an exhaust pipe 66. The first partition 64 and the second partition 65 are fixedly connected inside the combined separator 6, dividing the combined separator 6 into a primary separation zone 61, a secondary separation zone 62, and a tertiary separation zone 63. The primary separation zone 61 includes a through-flow primary gas manifold 611, a primary flash evaporation section 612, and a primary liquid manifold 613. The primary gas manifold 611 is disposed within the primary flash evaporation section. Above section 612, the primary flash section 612 is positioned above the primary liquid reservoir 613; the secondary separation zone 62 includes a secondary gas reservoir 621, a secondary flash section 622, and a secondary liquid reservoir 623, with the secondary gas reservoir 621 positioned above the secondary flash section 622 and the secondary flash section 622 positioned above the secondary liquid reservoir 623; the tertiary separation zone 63 includes a tertiary steam reservoir, a tertiary flash section 632, and a tertiary liquid reservoir 633. The three-stage gas manifold 631 is positioned above the three-stage flash section 632, which is positioned above the three-stage liquid manifold 633. The first-stage flash section 612 is equipped with a first-stage feed distributor 6121, the inlet of which is connected to the shell-side outlet of the heat exchanger 41. The second-stage flash section 622 is equipped with a second-stage feed distributor 6221, the inlet of which is connected to the shell-side outlet of the heat exchanger 41. The discharge port of the first-stage liquid reservoir 613 is connected to the discharge port of the second-stage liquid reservoir 623. The discharge port of the first-stage gas reservoir 611 is connected to the air inlet of the second-stage gas reservoir 621. The discharge port of the second-stage gas reservoir 621 is connected to the air inlet of the third-stage gas reservoir 631. The discharge port of the third-stage gas reservoir 631 is connected to the air inlet of the exhaust gas discharge pipe 66. The shell-side outlet of the cooler 42 is simultaneously connected to the absorbent inlets of the first absorber 1, the second absorber 2, the primary air chamber 611, the secondary air chamber 621, and the tertiary air chamber 631. The absorbent inlet of the primary air chamber 611 is located at the upper part of the primary air chamber 611, the absorbent inlet of the secondary air chamber 621 is located above the air inlet of the secondary air chamber 621, and the absorbent inlet of the tertiary air chamber 631 is located above the air inlet of the tertiary air chamber 631. The absorbent inlet of the second absorber 2 is located between the gas-liquid contact section 22 and the gas-liquid separator 21. The separation unit includes a separation tower 7 and a lean absorbent booster pump 31. The outlet of the three-stage liquid tank 633 is connected to the inlet of the separation tower 7, the bottom outlet of the separation tower 7 is connected to the inlet of the lean absorbent booster pump 31, and the outlet of the lean absorbent booster pump 31 is connected to the tube-side inlet of the heat exchanger 41.

[0030] It should be noted that the hydrogen sulfide-containing acidic gas introduced into the purification system through the hydrogen sulfide-containing acidic gas conduit 3 can be selected from refinery gas, natural gas, syngas, solvent regeneration acidic gas, and acidic water stripping acidic gas. The hydrogen sulfide-containing acidic gas used in this application mainly contains hydrogen sulfide, carbon dioxide, and light hydrocarbon components. The temperature of the hydrogen sulfide-containing acidic gas entering the purification system is 10°C to 50°C, and the pressure is ≥1.0 MPa (absolute pressure).

[0031] It should be noted that the purification system utilizes amine solutions for the selective absorption of hydrogen sulfide from acidic gases containing hydrogen sulfide in the first absorber 1, second absorber 2, primary flash evaporation section 612, primary liquid tank 613, secondary flash evaporation section 622, secondary liquid tank 623, tertiary flash evaporation section 632, and tertiary liquid tank 633. These amine solutions are generally methyl diethanolamine (MDEA) solution, polyethylene glycol dimethyl ether (NHD) solution, or activated MDEA solution. Activated MDEA solution involves adding a small amount of additives (such as antifoaming agents, corrosion inhibitors, antioxidants, or activators) to the MDEA solution. The absorbent used in this application is generally an activated MDEA solution, such as ADIP-X™, aMDEA®, or UCARSOL™ AP series activated MDEA solutions. The absorption process of this absorbent for hydrogen sulfide-containing acidic gases includes: 1. Absorption process of hydrogen sulfide: The unpaired electrons on the nitrogen atoms of MDEA make the MDEA solution as a whole alkaline, which allows the MDEA solution to directly undergo a proton transfer reaction with hydrogen sulfide. This proton transfer reaction can be completed instantaneously. The specific reaction equation is as follows: H2S+C6H 15 O2N C6H 15 O2NH+ +HS - (1) 2. Carbon dioxide absorption process: The carbon dioxide absorption process of MDEA is more complex than that of hydrogen sulfide, and it can only occur under liquid phase conditions. The specific reaction equation is as follows: C6H 15 O2N+CO2+H2O C6H 15 O2NH + +HCO3 - (2), Reaction (1) is an instantaneous reaction, where hydrogen sulfide crosses the MDEA solution interface and enters the bulk liquid phase of the MDEA solution faster than carbon dioxide. In contrast, the reaction rate between carbon dioxide and MDEA solution in reaction (2) is slower. Carbon dioxide first enters the gas film containing hydrogen sulfide acidic gas from the gas phase, then passes through the gas-liquid interface between the MDEA solution and the hydrogen sulfide acidic gas and enters the liquid film of the MDEA solution, and finally enters the bulk liquid phase of the MDEA solution. Only in the bulk liquid phase of the MDEA solution will carbon dioxide react with OH- in the MDEA solution. - The reaction forms HCO3 - This process demonstrates that the reaction between carbon dioxide and MDEA solution is a slow reaction controlled by the liquid film of the MDEA solution. Based on the difference in reaction rates between hydrogen sulfide and carbon dioxide in the MDEA solution, the concentration of hydrogen sulfide in the hydrogen sulfide-containing acidic gas can be increased through selective absorption by the MDEA solution. Specifically, by optimizing the contact time, contact area, and contact temperature between the MDEA solution and hydrogen sulfide and carbon dioxide in the hydrogen sulfide-containing acidic gas, the selective absorption of hydrogen sulfide by the MDEA solution can be improved, causing the absorption of hydrogen sulfide-containing acidic gas by the MDEA solution to proceed in a direction favorable to hydrogen sulfide absorption, thereby achieving the purification of hydrogen sulfide in the hydrogen sulfide-containing acidic gas. In addition, while the MDEA solution and hydrogen sulfide are chemically absorbed, the MDEA solution also physically dissolves H2S, CO2, and light hydrocarbon components. Furthermore, dissolved CO2 and light hydrocarbons (represented by methane and ethane) are generally more readily desorbed from the amine-rich solution because their Henry's Law constant is usually greater than that of H2S (specific data are shown in Table 1), which further enhances the enrichment effect of H2S. For example, in an MDEA activation solution with a mass fraction of 49.26% (with 0.83% piperazine added as an activator), the Henry's constant of each component can clearly reflect this physical property of dissolution and desorption.

[0032] Table 1. Distribution of Henry's Law constant in activated MDEA solution

[0033] According to the Henry's Law constants in Table 1, the Henry's Law constants for carbon dioxide and light hydrocarbon components (methane and ethane) are much higher than those for hydrogen sulfide. This indicates that carbon dioxide and light hydrocarbon components are more volatile than hydrogen sulfide in activated MDEA solution. Furthermore, in activated MDEA solution, hydrogen sulfide reacts with MDEA to produce C6H. 15 O2NH + ·HS - The protonated amine salt has a strong chemical bond, and in the activated MDEA solution, carbon dioxide reacts with MDEA to produce C6H. 15 O2NH + HCO3 - Ion pairs. Based on the analysis of the results of Henry's Law constant, it can be seen that by appropriately increasing the temperature of the absorbent that has absorbed the hydrogen sulfide-containing acidic gas or decreasing the pressure of the absorbent that has absorbed the hydrogen sulfide-containing acidic gas, more carbon dioxide and light hydrocarbon components can be desorbed from the absorbent-activated MDEA solution, thereby obtaining hydrogen sulfide gas with higher purity in subsequent separation or desorption processes.

[0034] It should be noted that in the first absorber 1, the hydrogen sulfide-containing acidic gas undergoes gas-liquid mass transfer with the first lean liquid from the cooler 42. Compared with the carbon dioxide in the hydrogen sulfide-containing acidic gas, the first lean liquid can absorb the hydrogen sulfide in the hydrogen sulfide-containing acidic gas more quickly. Therefore, the countercurrent contact time between the first lean liquid and the hydrogen sulfide-containing acidic gas in the first absorber 1 can be controlled within the range of 0.3s to 3.0s to complete the mass transfer between the first lean liquid and the hydrogen sulfide-containing acidic gas in a very short time, avoid the first lean liquid absorbing too much carbon dioxide, and complete the initial selective absorption of hydrogen sulfide in the hydrogen sulfide-containing acidic gas.

[0035] It should be noted that the first absorber 1 can be either a static mixer or an ejector. Considering the throughput of hydrogen sulfide-containing acidic gas, this application selects a static mixer, which offers good mixing performance, high mixing efficiency, simple structure, small size, durability, and low operating costs. In the first absorber 1, through special internal components, the hydrogen sulfide-containing acidic gas and the first lean liquid are forcibly cut, twisted, separated, and remixed. Simultaneously, the axial flow splitting and radial turbulent mixing of the first absorber 1 work together, enhancing the selective absorption of hydrogen sulfide from the hydrogen sulfide-containing acidic gas by the first lean liquid.

[0036] It should be noted that the first absorber 1 can use either an SX-type static mixer or an SV-type static mixer. The SX-type static mixer uses metal strips arranged at 45° angles to form a "multi-X" geometric structure, which serves as mixing elements. Each mixing element is assembled at a 90° stagger within the pipe of the SX-type static mixer. The SV-type static mixer uses several corrugated sheets with "V"-shaped geometric structures arranged in a specific way to form cylinders, which also serve as mixing elements, each assembled at a 90° stagger within the pipe of the SV-type static mixer. The length-to-diameter ratio of the first absorber 1 can be 3 to 15, and the volume ratio of the gas phase to the liquid phase in the first absorber 1 can be (5.0 to 200.0):1. At the outlet end of the first absorber 1, the apparent linear velocity of the first gas-liquid two-phase mixture can be controlled within the range of 0.5 m / s to 10.0 m / s.

[0037] It should be noted that in the first absorber 1, the volume of hydrogen sulfide in the hydrogen sulfide-containing acidic gas absorbed by the first lean liquid can be 30.0% to 60.0% of the total volume of hydrogen sulfide in the hydrogen sulfide-containing acidic gas. That is, the hydrogen sulfide removal rate of the first absorber 1 for the hydrogen sulfide-containing acidic gas can be 30.0% to 60.0%. After the hydrogen sulfide in the hydrogen sulfide-containing acidic gas is completely absorbed, the first lean liquid becomes a crude absorbent, and the hydrogen sulfide-containing acidic gas that has been preliminarily desorbed is used as the crude purified gas.

[0038] It should be noted that in the second absorber 2, the top gas-liquid separator 21 can be one or a combination of wire mesh demister, baffle demister, cyclone tube demister, and fiber bed demister. This gas-liquid separator 21 can remove more than 99.9% of the liquid droplets from the purified gas at the top of the second absorber 2.

[0039] It should be noted that in the second absorber 2, the gas-liquid contact section 22 in the middle part of the second absorber 2 is mainly used for gas-liquid contact and mass transfer, heat transfer and countercurrent contact reaction. The internal components used in the gas-liquid contact section 22 can be trays or packing. When the internal components of the gas-liquid contact section 22 are trays, the number of trays in the gas-liquid contact section 22 can be from 3 to 40, and the tray spacing can be from 600 mm to 2000 mm. For example, the tray spacing can be 600 mm, 800 mm, 1000 mm, 1200 mm, 1400 mm, 1600 mm, 1800 mm, or 2000 mm. When the internal components of the gas-liquid contact section 22 are packing, the number of packing sections in the gas-liquid contact section 22 can be from 1 to 10, and the height of each packing section can be from 0.5 m to 2.0 m. A liquid redistributor can be installed between two adjacent packing sections, and the liquid in the liquid redistributor does not come into contact with the rising gas in the gas-liquid contact section 22. In addition, the bed diameter of the packing section in the gas-liquid contact section 22 can be 1250 Nm per square meter of bed cross-sectional area. 3 / h to 2500Nm 3 The volumetric flow rate of hydrogen sulfide-containing acidic gas was determined at / h (volume flow rate under standard conditions of 0℃ and 101.325 kPa).

[0040] It should be noted that in the second absorber 2, the rich absorbent buffer section 23 at the bottom of the second absorber 2 can be a vertical cylindrical container or a horizontal cylindrical container. The dimensions of the rich absorbent buffer section 23 need to meet the following requirements: when the normal liquid level in the rich absorbent buffer section 23 is set to 50% of the full level, the buffering time of the coarse absorbent can be maintained within the range of 10 minutes to 40 minutes. When the rich absorbent buffer section 23 is a vertical cylindrical container, the height-to-diameter ratio of the rich absorbent buffer section 23 can be 3 to 6; when the rich absorbent buffer section 23 is a horizontal cylindrical container, the length-to-diameter ratio of the rich absorbent buffer section 23 can be 3 to 6. In addition, the connecting pipe between the rich absorbent buffer section 23 and the first absorber 1 should be as short as possible, and the number of elbows or reversing fittings on the connecting pipe between the rich absorbent buffer section 23 and the first absorber 1 should not exceed 3, so as to reduce the extra contact time of the first gas-liquid two-phase mixture in the connecting pipe, thereby minimizing the amount of carbon dioxide absorbed by the first lean liquid from the hydrogen sulfide-containing acidic gas.

[0041] It should be noted that in the rich absorbent buffer section 23 of the second absorber 2, the first gas-liquid two-phase mixture undergoes gas-phase and liquid-phase separation in the rich absorbent buffer section 23. The separated liquid is the crude absorbent. The crude absorbent is buffered at the bottom of the rich absorbent buffer section 23 to further remove the gas carried by the crude absorbent, resulting in crude purified gas. This crude purified gas flows upward to the gas-liquid contact section 22. In the gas-liquid contact section 22, the crude purified gas and the second lean liquid from the cooler 42 undergo a first countercurrent contact reaction for mass and heat transfer. After passing through the gas-liquid separator 21 to remove the carried droplets, it is discharged from the second absorber 2 as purified gas. The second lean liquid that has absorbed hydrogen sulfide from the crude purified gas can be used as the secondary rich absorbent. This secondary rich absorbent flows downward into the bottom of the rich absorbent buffer section 23 for buffering. After further separation of the carried gas, the crude absorbent and the subsequently entering secondary rich absorbent are mixed in the rich absorbent buffer section 23 to form a rich absorbent.

[0042] Figure 4 An exemplary schematic diagram of the liquid transfer zone structure of the second absorber in the purification system provided in this application embodiment is shown; It should be noted that when the volume fraction of carbon dioxide in the hydrogen sulfide-containing acidic gas is greater than or equal to 5.0%, the internal components of the gas-liquid contact section 22 in the second absorber 2 can use trays. The interior of the second absorber 2 can be configured as follows: Figure 4The multiple liquid transfer zones 27 shown are disposed within the gas-liquid contact section 22. Each liquid transfer zone 27 consists of a gravity guide pipe 271, an inlet baffle 272, an outlet baffle 273, and a bottom plate 274. The inlet baffle 272 is vertically installed above the plane of any tray in the second absorber 2, and a buffer zone is formed between the inlet baffle 272, the inner wall of the second absorber 2, and the tray. This buffer zone is used to receive the second lean liquid from outside the second absorber 2. The outlet baffle 273 is parallel to the inlet baffle 272 and is set on the vertical plane of any tray in the second absorber 2. The bottom of the outlet baffle 273 is fixedly connected to the bottom plate 274 and is fixedly connected to the inner wall of the second absorber 2 through the bottom plate 274. The bottom plate 274 is set below the tray. The outlet baffle 273, the bottom plate 274, and the inner wall of the second absorber 2 form a liquid collection hopper. A through hole can be opened at the center of the bottom plate 274, through which the bottom plate 274 can be connected to the gravity guide pipe 271. In the buffer zone, the level of the second lean liquid gradually rises due to the obstruction of the inlet baffle 272. When the level of the second lean liquid is the same as the height of the inlet baffle 272, the second lean liquid overflows into the mass transfer zone in the middle of the tray. In the mass transfer zone, the second lean liquid comes into countercurrent contact with the crude purified gas that penetrates the tray internals (usually a float valve or tray sieve holes) from bottom to top to complete the mass transfer between the second lean liquid and the crude purified gas. After the mass transfer is completed, the second lean liquid, which has absorbed hydrogen sulfide from the crude purified gas, flows laterally along the tray to the outlet baffle 273 and falls into the liquid. In the collection hopper, the second lean liquid, which has absorbed hydrogen sulfide from the crude purified gas, is buffered and the carried gas (generally containing carbon dioxide) is separated to avoid prolonged contact between carbon dioxide in the gas and the second lean liquid. Then, the second lean liquid enters the gravity guide pipe 271 through the through hole of the bottom plate 274. Under the action of gravity, the second lean liquid enters the next liquid transfer zone 27 for circulation treatment. After the last liquid transfer zone 27 is completed, the second lean liquid enters the rich absorbent buffer section 23 as a secondary rich absorbent.

[0043] It should be noted that the height of the inlet weir (functionally similar to the inlet baffle 272 in this application) in traditional trays is usually 6mm to 12mm lower than the height of the outlet weir (functionally similar to the outlet baffle 273 in this application). This results in gaps between the liquid inlet and outlet of the traditional tray, causing pressure drops in the liquid phase flowing through it and allowing external gases to escape or escape through these gaps. In contrast, the heights of the inlet baffle 272 and the outlet baffle 273 in this application can be the same to avoid gaps between the liquid inlet and outlet of the tray. Therefore, based on the liquid transfer zone 27 provided in the gas-liquid contact section 22, the gas-liquid contact time between the second lean liquid and the crude purified gas can be effectively shortened, and the amount of carbon dioxide entrained in the second lean liquid can be reduced, ensuring the selective absorption efficiency of hydrogen sulfide in the crude purified gas by the second lean liquid.

[0044] It should be noted that in the combined separator 6, the combined separator 6 can be a cylindrical horizontal container. In this case, the diameters of the first partition 64 and the second partition 65 can be the same as the diameter of the combined separator 6, so as to strictly divide the combined separator 6 into three parts: the primary separation zone 61, the secondary separation zone 62, and the tertiary separation zone 63, and to prevent cross-contamination of materials in adjacent separation zones. The first partition 64 and the second partition 65 can be selected using blind flanges, elliptical heads, flat caps, or other forms of isolation elements.

[0045] It should be noted that in the combined separator 6, the primary feed distributor 6121, the secondary feed distributor 6221 and the tertiary feed distributor 6321 can all be tubular distributors with 90° elbows pointing to the end of the combined separator 6 and anti-impact plates installed at the end, or semi-open tubular distributors with the opening facing upwards can be used. When the primary feed distributor 6121, the secondary feed distributor 6221, and the tertiary feed distributor 6321 use semi-open tubular distributors, the primary feed distributor 6121, the secondary feed distributor 6221, and the tertiary feed distributor 6321 can use straight tubular distributors with strip-shaped slots 10. The primary feed distributor 6121, the secondary feed distributor 6221, and the tertiary feed distributor 6321 do not need to strictly limit the volume fraction of the gas phase in the feed. Furthermore, since the primary feed distributor 6121, the secondary feed distributor 6221, and the tertiary feed distributor 6321 have high separation efficiency and low outlet material flow rate, there is no need to set up an additional anti-impact plate structure.

[0046] It should be noted that in the combined separator 6, the rich absorbent liquid at the bottom of the rich absorbent buffer section 23 of the second absorber 2 is heated by the heat exchanger 41 and depressurized by the first-stage pressure reducing valve 51. As the temperature rises and the pressure decreases, the rich absorbent liquid can change from a liquid phase to a gas-liquid two-phase phase, resulting in a second gas-liquid two-phase mixture. This second gas-liquid two-phase mixture is introduced into the first-stage flash section 612 through the first-stage feed distributor 6121 for gas-liquid separation. The gas separated by gas-liquid separation is the first-stage flash vapor, which contains hydrogen sulfide, carbon dioxide, and light hydrocarbon components. The liquid separated by gas-liquid separation is the first rich liquid, which contains the remaining hydrogen sulfide, carbon dioxide, and light hydrocarbon components. During the flash evaporation process in the first-stage flash section 612, carbon dioxide and light hydrocarbon components are more volatile than hydrogen sulfide, making them easier to flash out. This results in a higher proportion of carbon dioxide and light hydrocarbon components flashing out of the second gas-liquid two-phase mixture compared to hydrogen sulfide; that is, the flash evaporation rate of carbon dioxide and light hydrocarbon components in the second gas-liquid two-phase mixture is higher than that of hydrogen sulfide. Furthermore, the first-stage flash vapor enters the first-stage gas reservoir 611 from bottom to top within the first-stage flash section 612. When it rises to the first-stage absorption section 6111, it undergoes a second countercurrent contact reaction with the third lean liquid from the cooler 42, completing mass and heat transfer. The third lean liquid selectively absorbs some of the hydrogen sulfide from the primary flash vapor, while the primary flash vapor, having removed some of the hydrogen sulfide, is discharged from the top of the primary gas reservoir 611 and enters the lower part of the secondary gas reservoir 621. The third lean liquid, having absorbed some of the hydrogen sulfide, flows from top to bottom into the primary liquid reservoir 613 as the first absorbent. In the primary liquid reservoir 613, the first absorbent separates the gas it carries and then mixes with the first rich liquid in the primary liquid reservoir 613 to form the second rich liquid.

[0047] The second rich liquid has a higher concentration of hydrogen sulfide and a lower concentration of carbon dioxide and light hydrocarbon components compared to the rich absorbent entering the combined separator 6. After being depressurized and throttled by the secondary pressure-reducing valve 52, the second rich liquid is introduced into the secondary flash section 622 by the secondary feed distributor 6221, where gas-liquid separation occurs. The gas separated by gas-liquid separation is the secondary flash vapor, which contains hydrogen sulfide, carbon dioxide, and light hydrocarbon components. The liquid separated by gas-liquid separation is the third rich liquid, which contains the remaining hydrogen sulfide, carbon dioxide, and light hydrocarbon components. During the flash evaporation process in the secondary flash section 622, since carbon dioxide and light hydrocarbon components are more volatile than hydrogen sulfide, they are more easily flashed out. This results in a higher proportion of carbon dioxide and light hydrocarbon components being flashed out of the second rich liquid compared to hydrogen sulfide, meaning the flash evaporation rate of carbon dioxide and light hydrocarbon components in the second rich liquid is higher than that of hydrogen sulfide. Furthermore, the secondary flash vapor enters the secondary gas chamber 621 from bottom to top within the secondary flash section 622. When it rises to the bottom of the secondary absorption section 6211, the secondary flash vapor mixes with the primary flash vapor from the top of the primary gas chamber 611 and enters the secondary absorption section 6211 from bottom to top, where it undergoes a third countercurrent contact reaction with the fourth lean liquid from the outlet of the cooler 42, completing mass and heat transfer. The fourth lean liquid selectively absorbs some of the hydrogen sulfide from the secondary flash vapor and the primary flash vapor. The mixture of the secondary flash vapor and the primary flash vapor, after some hydrogen sulfide has been removed, exits from the top of the secondary gas chamber 621 and enters the lower part of the tertiary gas chamber 631. The fourth lean liquid, having absorbed some hydrogen sulfide, flows from top to bottom into the secondary liquid chamber 623 as the second absorbent. In the secondary liquid chamber 623, the second absorbent separates the carried gas and then mixes with the third rich liquid within the secondary liquid chamber 623 to form the fourth rich liquid.

[0048] Compared to the second rich liquid, the fourth rich liquid has a higher concentration of hydrogen sulfide, a lower concentration of carbon dioxide, and a lower concentration of light hydrocarbon components. After being depressurized and throttled by a three-stage pressure-reducing valve 53, the fourth rich liquid is introduced into the three-stage flash evaporation section 632 by a three-stage feed distributor 6321. Gas-liquid separation occurs in the three-stage flash evaporation section 632. The separated gas is the three-stage flash vapor, containing hydrogen sulfide, carbon dioxide, and light hydrocarbon components. The separated liquid is the fifth rich liquid, containing the remaining hydrogen sulfide, carbon dioxide, and light hydrocarbon components. During the flash evaporation process in the three-stage flash evaporation section 632, carbon dioxide and light hydrocarbon components are more volatile than hydrogen sulfide, making them more easily flashed out. This results in a higher proportion of carbon dioxide and light hydrocarbon components being flashed out in the fifth rich liquid compared to hydrogen sulfide; that is, the flash evaporation rate of carbon dioxide and light hydrocarbon components in the fifth rich liquid is higher than that of hydrogen sulfide. Furthermore, the third-stage flash vapor enters the third-stage gas chamber 631 from bottom to top within the third-stage flash section 632. When the third-stage flash vapor rises to the bottom of the third-stage absorption section 6311, it mixes with the mixture of the second-stage flash vapor and the first-stage flash vapor from the second-stage gas chamber 621 and enters the third-stage absorption section 6311 from bottom to top. There, it undergoes a fourth countercurrent contact reaction with the fifth lean liquid from the outlet of the cooler 42, thus completing mass and heat transfer. The fifth lean solution selectively absorbs hydrogen sulfide from the mixture of the third, second, and first stage flash vapors. The mixture of the third, second, and first stage flash vapors, now free of hydrogen sulfide, exits from the top of the third-stage gas chamber 631 and enters the tail gas discharge pipe 66 as part of the tail gas purification system. The fifth lean solution, having absorbed some hydrogen sulfide, flows downwards into the third-stage liquid chamber 633 as the third absorbent. In the third-stage liquid chamber 633, the carried gases are separated, and then the solution mixes with the fifth rich solution to form a hydrogen sulfide-rich solution. Compared to the fourth rich solution, the hydrogen sulfide-rich solution has a higher concentration of hydrogen sulfide and lower concentrations of carbon dioxide and light hydrocarbon components.

[0049] It should be noted that the primary feed distributor 6121, the secondary feed distributor 6221, and the tertiary feed distributor 6321 all have the same structural form.

[0050] It should be noted that in this purification system, the hydrogen sulfide gas, purified gas, and tail gas leaving the system inevitably carry away some of the water circulating within the system, causing fluctuations in the concentration of various liquid phase materials. Therefore, it is necessary to replenish water into the purification system. The device with the most concentrated liquid phase materials in this purification system is the lean absorbent booster pump 31. Therefore, water replenished from outside the system can be introduced into the purification system through the inlet of the lean absorbent booster pump 31 to keep the concentration of the lean absorbent solution stable. The water replenished from outside the system can be deoxygenated water.

[0051] In some optional embodiments, the primary air chamber 611 is provided with a primary absorption section 6111, which is located below the absorbent inlet of the primary air chamber 611; the secondary air chamber 621 is provided with a secondary absorption section 6211, which is located between the absorbent inlet and the air inlet of the secondary air chamber 621; and the tertiary absorption section 6311 is located between the absorbent inlet and the air inlet of the tertiary air chamber 631.

[0052] In these embodiments, a primary absorption section 6111 is provided in the primary gas reservoir 611, a secondary absorption section 6211 is provided in the secondary gas reservoir 621, and a tertiary absorption section 6311 is provided in the tertiary gas reservoir 631. In these absorption sections, the flash vapor moves upward from bottom to top, while the lean liquid flows downward from top to bottom. Therefore, the flash vapor and the lean liquid can fully engage in countercurrent contact for mass and heat transfer in the absorption sections. The lean liquid (third, fourth, and fifth lean liquids) can selectively absorb hydrogen sulfide from the flash vapor (primary flash vapor, secondary flash vapor, and tertiary flash vapor) multiple times. These lean liquids that have absorbed hydrogen sulfide are eventually enriched to form a hydrogen sulfide-rich solution.

[0053] It should be noted that the mass and heat transfer internals used in the primary absorption section 6111, the secondary absorption section 6211, and the tertiary absorption section 6311 can be either trays or packed sections. When the internals of these absorption sections are trays, the number of trays in each absorption section can be 4 to 12; when the internals are packed sections, the number of packing sections can be 1 to 3, and the height of each packing section can be 0.5m to 2.0m. A liquid redistributor can be installed between adjacent packing sections, and the liquid in the liquid redistributor will not come into contact with the rising flash vapor in these absorption sections. Furthermore, the bed diameter of the packed sections in these absorption sections can be 200 Nm per square meter of bed cross-sectional area. 3 / h to 2000Nm 3 The design considers flash steam at a flow rate of / h (volume flow rate under standard conditions of 0℃ and 101.325 kPa). Specifically, in the primary absorption section 6111, the bed diameter of the packing section of the primary absorption section 6111 can be 200 Nm per square meter of bed cross-sectional area. 3 / h to 1000Nm 3 The design incorporates a single-stage flash vapor volume of / h; in the secondary absorption section 6211, the bed diameter of the packing section of the secondary absorption section 6211 can be 250 Nm per square meter of bed cross-sectional area. 3 / h to 1500Nm 3The design incorporates a two-stage flash steam system; in the three-stage absorption section 6311, the bed diameter of the packing section can be 300 Nm per square meter of bed cross-sectional area. 3 / h to 2000Nm 3 The design incorporates a three-stage flash vapor system.

[0054] In some optional embodiments, a primary heater 614 is provided in the primary separation zone 61, and the primary heater 614 is located at the bottom of the primary flash section 612; A secondary heater 624 is provided in the secondary separation zone 62, and the secondary heater 624 is located at the bottom of the secondary flash section 622; A three-stage heater 634 is provided in the three-stage separation zone 63, and the three-stage heater 634 is located at the bottom of the three-stage flash section 632.

[0055] In these embodiments, a primary heater 614 is installed at the bottom of the primary separation zone 61 and the primary flash evaporation section 612. The primary heater 614 heats the first or second rich liquid, promoting the escape and separation of more carbon dioxide and light hydrocarbon components from these rich liquids, thereby improving the flash evaporation effect of the primary flash evaporation section 612 and increasing the concentration of hydrogen sulfide in the final hydrogen sulfide-rich solution. Similarly, a secondary heater 624 is installed at the bottom of the secondary separation zone 62 and the secondary flash evaporation section 622. The secondary heater 624 heats the third or fourth rich liquid, promoting the escape and separation of more carbon dioxide and light hydrocarbon components from these rich liquids, thereby improving the flash evaporation effect of the secondary flash evaporation section 622 and increasing the concentration of hydrogen sulfide in the final hydrogen sulfide-rich solution. Similarly, a three-stage heater 634 is installed at the bottom of the three-stage separation zone 63 and the three-stage flash evaporation section 632. The fifth rich liquid or hydrogen sulfide rich solution can be heated by the three-stage heater 634 to promote the escape and separation of more carbon dioxide and light hydrocarbon components in these rich liquids, improve the flash evaporation effect of the three-stage flash evaporation section 632, and help increase the concentration of hydrogen sulfide in the final hydrogen sulfide rich solution.

[0056] It should be noted that the heat source used by the primary heater 614, the secondary heater 624, and the tertiary heater 634 can be steam, a hot process fluid, an electrically heated resistance wire, or other heating element. The inlet temperature of the primary heater 614, the secondary heater 624, and the tertiary heater 634 is in the range of 80°C to 150°C.

[0057] In some optional implementations, the purification system further includes: The pressure reducing valve assembly 5 includes a primary pressure reducing valve 51, a secondary pressure reducing valve 52, and a tertiary pressure reducing valve 53. The primary pressure reducing valve 51 is fixedly connected between the heat exchanger 41 and the primary feed distributor 6121. The secondary pressure reducing valve 52 is fixedly connected between the primary liquid reservoir 613 and the secondary feed distributor 6221. The tertiary pressure reducing valve 53 is fixedly connected between the secondary liquid reservoir 623 and the tertiary feed distributor 6321.

[0058] In these embodiments, a pressure-reducing valve group 5, including a first-stage pressure-reducing valve 51, a second-stage pressure-reducing valve 52, and a third-stage pressure-reducing valve 53, is introduced into the purification system. After being heated by the heat exchanger 41, the pressure of the rich absorbent liquid is reduced by the first-stage pressure-reducing valve 51, causing the rich absorbent liquid to change from a liquid phase to a first gas-liquid two-phase mixture, which is beneficial for the subsequent separation of more carbon dioxide and light hydrocarbons. The pressure of the second rich liquid is reduced by the second-stage pressure-reducing valve 52, which is also beneficial for the subsequent separation of more carbon dioxide and light hydrocarbons. The pressure of the fourth rich liquid is reduced by the third-stage pressure-reducing valve 53, which is also beneficial for the subsequent separation of more carbon dioxide and light hydrocarbons.

[0059] Figure 2 An exemplary schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 2 of this application is shown. In some alternative implementations, such as Figure 2 As shown, the second absorber 2 is equipped with a rich absorbent isolation plate 26 and a rich absorbent booster pump 32. The rich absorbent isolation plate 26 is vertically arranged in the rich absorbent buffer section 23, and the rich absorbent isolation plate 26 divides the rich absorbent buffer section 23 into a primary rich absorbent buffer section 24 and a secondary rich absorbent buffer section 25. The tops of the primary rich absorbent buffer section 24 and the secondary rich absorbent buffer section 25 have a through gas phase space. The inlet of the rich absorbent booster pump 32 is connected to the outlet of the primary rich absorbent buffer section 24, and the outlet of the rich absorbent booster pump 32 is connected to the middle inlet of the gas-liquid contact section 22.

[0060] In these embodiments, a rich absorbent buffer plate 26 is introduced into the second absorber 2. The rich absorbent buffer plate 26 divides the original rich absorbent buffer section 23 into two independent areas: a primary rich absorbent buffer section 24 located on one side of the buffer plate and a secondary rich absorbent buffer section 25 located on the other side of the buffer plate. The primary rich absorbent buffer section 24 receives the coarse absorbent from the first absorber 1, and the secondary rich absorbent buffer section 25 receives both the primary and secondary rich absorbents from the second absorber 2. The primary rich absorbent buffer section 24... The rich absorbent booster pump 32, located between the outlet of the first-stage rich absorbent buffer section 24 and the inlet of the middle section of the gas-liquid contact section 22, can introduce the coarse absorbent in the first-stage rich absorbent buffer section 24 into the middle section of the gas-liquid contact section 22 for second absorption, resulting in first-stage rich absorbent and pre-purified gas. The pre-purified gas continues to flow upward and undergoes a first countercurrent contact reaction with the second lean liquid from the cooler 42 to obtain second-stage rich absorbent and purified gas. Thus, mass and heat transfer between gas and liquid can be effectively realized in the gas-liquid contact section 22, ultimately resulting in purified gas with low hydrogen sulfide content and rich absorbent with high hydrogen sulfide content.

[0061] It should be noted that in the second absorber 2 with the introduction of the rich absorbent buffer plate 26, the first-stage rich absorbent buffer section 24 is used to receive the first gas-liquid two-phase mixture discharged from the first absorber 1 and to separate the first gas-liquid two-phase mixture into crude purified gas and crude absorbent. The crude absorbent remains in the first-stage rich absorbent buffer section 24, while the crude purified gas flows upward to the gas phase space at the top of the first-stage rich absorbent buffer section 24, and then enters the gas phase space at the top of the second-stage rich absorbent buffer section 25 through the gas phase space between the rich absorbent buffer plate 26 and the second absorber 2. It then enters the gas-liquid contact section 22 in the second absorber 2 to undergo a second absorption with the crude absorbent. At the same time, the crude absorbent in the first-stage rich absorbent buffer section 24 is introduced into the middle section of the gas-liquid contact section 22 through the rich absorbent booster pump 32 to undergo a second absorption with the crude purified gas, resulting in a first-stage rich absorbent and a preliminary purified gas. The pre-purified gas and the second lean liquid undergo a first countercurrent contact reaction, which allows the hydrogen sulfide in the pre-purified gas to be absorbed by the second lean liquid. The second lean liquid, which has absorbed hydrogen sulfide, mixes with the first-level rich absorbent as a secondary rich absorbent during the downward flow process. It then enters the secondary rich absorbent buffer section 25 below for buffering, releasing the gas it carries and forming a rich absorbent.

[0062] It should be noted that the height of the rich absorbent buffer plate 26 must be higher than the highest operating liquid level of the first-stage rich absorbent buffer section 24, so that the first-stage rich absorbent in the first-stage rich absorbent buffer section 24 cannot overflow into the second-stage rich absorbent buffer section 25, and can only be discharged from the bottom of the first-stage rich absorbent buffer section 24 through the rich absorbent booster pump 32.

[0063] It should be noted that because the actual acid gas load of the coarse absorbent (the total amount of hydrogen sulfide and carbon dioxide absorbed through physical dissolution and chemical absorption) is lower than the theoretical acid gas load of the coarse absorbent (the theoretical maximum amount of hydrogen sulfide and carbon dioxide absorbed through physical dissolution and chemical absorption), the coarse absorbent has residual absorption capacity. The rich absorbent isolation plate 26 and the rich absorbent booster pump 32 can introduce the coarse absorbent into the gas-liquid contact section 22. In the gas-liquid contact section 22, the coarse absorbent will undergo a second absorption with the crude purified gas to further absorb hydrogen sulfide from the crude purified gas. This process not only makes full use of the residual absorption capacity of the coarse absorbent, but also shares the absorption load of the second lean liquid, effectively reducing the circulation flow rate of the second lean liquid and the cooling load of the cooler 42.

[0064] Figure 5 An exemplary schematic diagram of the structure of the strip groove in the purification system provided in this application embodiment is shown; In some alternative implementations, such as Figure 5 As shown, the primary feed distributor 6121, the secondary feed distributor 6221 and the tertiary feed distributor 6321 are each provided with two strip-shaped slots 10. One strip-shaped slot 10 is provided facing one end of the combined separator 6, and the other strip-shaped slot 10 is provided facing the other end of the combined separator 6.

[0065] In these embodiments, strip-shaped slots 10 are provided in the primary feed distributor 6121, the secondary feed distributor 6221 and the tertiary feed distributor 6321. The material can be directly dispersed from both sides through the strip-shaped slots 10, which can greatly improve the dispersion uniformity of the material and reduce the outlet material flow rate, which is conducive to the subsequent countercurrent contact reaction of each stage in a stable state.

[0066] In some optional embodiments, the opening width W of the strip-shaped slot 10 satisfies: W = 2.5 × d 2 / (D-250), Equation 1; In Formula 1, d is the diameter of the shell-side outlet of the heat exchanger 41 in mm; D is the diameter of the combined separator 6 in mm, and D≥300mm.

[0067] In these embodiments, the shell-side outlet diameter d of heat exchanger 41 and the diameter D of combined separator 6 are used as parameters, and the formula W=2.5×d is applied. 2 / (D-250) Determining the opening width W of the strip groove 10 can promote the material to be dispersed from both sides at a gentle flow rate, which is beneficial for the subsequent countercurrent contact reaction at each stage to proceed in a stable state.

[0068] It should be noted that, according to W=2.5×d 2If the value calculated by / (D-250) is less than 30mm, W is directly set to 30mm.

[0069] It should be noted that the top of any feed distributor containing the strip-shaped slot 10 is 100mm lower than the top of the combined separator 6. A blind plate with a thickness of 6mm to 16mm can be installed on the top of any feed distributor containing the strip-shaped slot 10 to ensure that the material can only be discharged through the strip-shaped slot 10. In addition, the bottom of the strip-shaped slot 10 is 50mm higher than the highest liquid level in the first-stage flash section 612, the second-stage flash section 622, or the third-stage flash section 632 to effectively prevent backflow of rich liquid in the first-stage flash section 612, the second-stage flash section 622, or the third-stage flash section 632, and to ensure the stable operation of the first-stage feed distributor 6121, the second-stage feed distributor 6221, and the third-stage feed distributor 6321.

[0070] In some optional embodiments, the separation unit further includes a condenser 71, a reflux tank 72, a reflux pump 73, a reboiler 74, and a hydrogen sulfide outlet pipe 75. The inlet of the condenser 71 is connected to the top outlet of the separation tower 7, the outlet of the condenser 71 is connected to the inlet of the reflux tank 72, the upper outlet of the reflux tank 72 is connected to the inlet of the hydrogen sulfide outlet pipe 75, the lower outlet of the reflux tank 72 is connected to the inlet of the reflux pump 73, the outlet of the reflux pump 73 is connected to the top inlet of the separation tower 7, the inlet of the reboiler 74 is connected to the bottom inlet of the separation tower 7, and the outlet of the reboiler 74 is connected to the bottom side inlet of the separation tower 7.

[0071] In these embodiments, based on the separation tower 7 of the separation unit, a set of supporting equipment including a condenser 71, a reflux tank 72, a reflux pump 73, a reboiler 74, and a hydrogen sulfide outlet pipe 75 is provided. The reboiler 74 provides heat to cause the separation tower 7 to separate the light hydrogen sulfide component and the heavy component containing MDEA in the hydrogen sulfide-rich solution. The distillate from the top of the separation tower 7 forms a reflux solution containing hydrogen sulfide gas after passing through the condenser 71 and the reflux tank 72. The hydrogen sulfide gas, as a high-purity hydrogen sulfide gas product, is discharged from the purification system through the hydrogen sulfide outlet pipe 75, while the reflux solution is returned to the separation tower 7 by the reflux pump 73. The heavy component is collected at the bottom of the separation tower 7 to form a lean absorbent. These lean absorbents can be subsequently cooled by the heat exchanger 41 and the cooler 42 and then split into a first lean solution, a second lean solution, a third lean solution, a fourth lean solution, and a fifth lean solution, realizing the recycling of the absorbent.

[0072] It should be noted that in the separation unit, after separation by separation tower 7, light components such as hydrogen sulfide in the hydrogen sulfide-rich solution flow upward to the top of separation tower 7, while heavy components such as MDEA flow downward to the bottom of separation tower 7, continuously releasing hydrogen sulfide components during the flow, ultimately forming a lean absorbent at the bottom of separation tower 7. The distillate from the top of separation tower 7 is cooled to 35°C to 45°C by condenser 71, and then enters reflux tank 72 for gas-liquid separation, forming hydrogen sulfide-containing gas and reflux solution. The reflux solution is pressurized by reflux pump 73 and returned to the top of separation tower 7; while the hydrogen sulfide-containing gas is discharged from the system as a high-purity hydrogen sulfide product. Simultaneously, the reboiler at the bottom of the tower continuously provides the necessary heat for the separation process through external heat source circulation.

[0073] It should be noted that the separation tower 7 can be a tray type or a packed tower structure. To meet the separation requirements of hydrogen sulfide-rich solutions, the separation tower 7 can be equipped with a rectification section and a stripping section. When the separation tower 7 is a tray type structure, the number of trays in the rectification section can be 2 to 4, while the number of trays in the stripping section can be 15 to 30. In addition, to effectively separate the light and heavy components of hydrogen sulfide in the hydrogen sulfide-rich solution, the top temperature of the separation tower 7 can be 105℃ to 115℃, the bottom temperature of the separation tower 7 can be 115℃ to 145℃, the top pressure of the separation tower 7 can be 150kPa to 250kPa (absolute pressure), and the reflux ratio of the separation tower 7 can be 0.5 to 10.0.

[0074] It should be noted that the lean absorbent obtained from the bottom of separation tower 7 enters the tube side of heat exchanger 41, where it exchanges heat with the rich absorbent in the shell side of heat exchanger 41, reducing its temperature to 70°C to 95°C. It then enters the shell side of cooler 42 and is further cooled to 15°C to 45°C. The cooled lean absorbent is finally distributed to the first absorber 1, the second absorber 2, the primary gas reservoir 611, the secondary gas reservoir 621, and the tertiary gas reservoir 631.

[0075] Figure 3 An exemplary schematic diagram of a purification system for hydrogen sulfide-containing acidic gas provided in Embodiment 3 of this application is shown. In some alternative implementations, such as Figure 3 As shown, the purification system further includes: The exhaust gas compressor 8 has its inlet connected to the branch outlet of the exhaust gas discharge pipe 66, and its outlet connected to the branch inlet of the hydrogen sulfide-containing acid gas conduit 3.

[0076] In these embodiments, an exhaust gas compressor 8 is installed at the branch outlet of the exhaust gas discharge pipe 66. After being compressed and pressurized by the exhaust gas compressor 8, the exhaust gas can be sent back to the branch inlet of the hydrogen sulfide-containing acid gas duct 3 and re-enter the purification system. There, it will undergo a countercurrent contact reaction with the different lean liquid in the purification system, thereby further removing residual hydrogen sulfide from the exhaust gas, effectively reducing the concentration of hydrogen sulfide in the exhaust gas, and improving the overall recovery rate of hydrogen sulfide products.

[0077] It should be noted that the higher the power of the exhaust gas compressor 8, the greater the flow rate of the exhaust gas returned to the purification system, the higher the recovery rate of hydrogen sulfide, and the lower the hydrogen sulfide content of the final output exhaust gas. The mass flow rate of the exhaust gas returned to the purification system can be 0 to 15 times the mass flow rate of the exhaust gas discharged from the purification system through the exhaust gas discharge pipe 66.

[0078] It should be noted that this application provides a purification system for hydrogen sulfide-containing acidic gas. This purification system employs a synergistic design across the entire process—enhanced absorption, staged deep flash evaporation, distillation purification, and tail gas reflux—to significantly improve the purity of the target product, hydrogen sulfide, while achieving low hydrogen sulfide emissions from the tail gas. The specific mechanism is as follows: 1. Absorption section: efficiently captures hydrogen sulfide to obtain purified gas with low hydrogen sulfide content and absorbent liquid with high hydrogen sulfide content.

[0079] The core function of the absorption section is to maximize the transfer of hydrogen sulfide from the acidic gas containing hydrogen sulfide to the absorbent (reducing the hydrogen sulfide content directly emitted into the purified gas), while simultaneously generating a hydrogen sulfide-rich absorbent liquid (providing high-quality feedstock for the subsequent purification process in combined separator 6). Key design features include: (1) Enhancing mass transfer through rich liquid staged buffering and mid-stage reflux: The first absorber 1 initially absorbs the hydrogen sulfide-containing acidic gas, capturing most of the hydrogen sulfide and forming a first gas-liquid two-phase mixture. This mixture is then separated into a coarse purified gas and a coarse absorbent. The coarse purified gas flows upwards to the gas phase space at the top of the first-stage rich absorbent buffer section 24, and then enters the gas-liquid contact section 22 of the second absorber 2 for a second absorption with the coarse absorbent. Simultaneously, the coarse absorbent in the first-stage rich absorbent buffer section 24 is introduced into the middle section of the gas-liquid contact section 22 via the rich absorbent booster pump 32, where it undergoes a second absorption with the coarse purified gas, resulting in a first-stage rich absorbent and a preliminary purified gas. The preliminary purified gas undergoes a first countercurrent contact reaction with the second lean absorbent, causing the hydrogen sulfide in the preliminary purified gas to be absorbed by the second lean absorbent. The second lean absorbent, having absorbed the hydrogen sulfide, mixes with the first-stage rich absorbent during the downward flow and enters the lower second-stage rich absorbent buffer section 25 for buffering, releasing the carried gas and forming a rich absorbent. This is equivalent to a dual reaction of countercurrent contact between the second lean solution and the crude purified gas, plus mid-stage replenishment, which improves the absorption efficiency of hydrogen sulfide in the crude purified gas, avoids the escape of hydrogen sulfide in the crude purified gas due to insufficient gas-liquid contact, and also reduces the amount of second lean solution used.

[0080] (2) After the lean absorbent is heated by the heat exchanger 41, it is cooled by the cooler 42. The first lean liquid and the second lean liquid at low temperature enter the first absorber 1 and the second absorber 2 respectively. The low temperature operation of the first absorber 1 and the second absorber 2 can improve the absorption degree of hydrogen sulfide by the absorbent (the physical or chemical absorption efficiency of MDEA for hydrogen sulfide increases with decreasing temperature), ensuring that hydrogen sulfide in the acidic gas containing hydrogen sulfide is deeply captured, resulting in a higher concentration of hydrogen sulfide in the rich absorbent.

[0081] 2. Combined Separator 6: Staged absorption and desorption are coupled to enhance the selective absorption of hydrogen sulfide. The combined separator 6 employs a coupled process of "three-stage gradient depressurization flash evaporation + absorption + desorption" to progressively desorb and separate impurity components from the rich liquid, achieving deep removal of residual hydrogen sulfide from the exhaust gas while purifying it. Key design features include: (1) Three-stage gradient pressure reduction flash evaporation (with pressure reduction valve group 5): After heat exchange in heat exchanger 41, the rich absorbent is depressurized by first-stage pressure-reducing valve 51 and enters first-stage flash evaporation section 612, where most of the volatile carbon dioxide and light hydrocarbon components can be flashed out at a lower pressure. The second rich liquid in first-stage liquid tank 613 is further depressurized by second-stage pressure-reducing valve 52 and enters second-stage flash evaporation section 622 to release more carbon dioxide and light hydrocarbon components. Finally, it is reduced to the minimum pressure by third-stage pressure-reducing valve 53, and the deep removal of carbon dioxide and light hydrocarbon components is completed in third-stage flash evaporation section 632.

[0082] The advantages of gradient depressurization are: avoiding the problems of violent flashing and gas-liquid entrainment caused by single depressurization, ensuring that the light hydrocarbon components of carbon dioxide can be separated smoothly and fully in each stage, reducing the residual impurities in the liquid phase (improving the purity of hydrogen sulfide gas obtained from subsequent separation tower 7), while the concentration of carbon dioxide and light hydrocarbon components in the gas phase increases step by step, resulting in higher carbon dioxide and light hydrocarbon component content and lower hydrogen sulfide content in the tail gas; and lower carbon dioxide and light hydrocarbon component content and higher hydrogen sulfide content in the hydrogen sulfide-rich solution.

[0083] Staged heating promotes flash evaporation: Heaters are installed at the bottom of the first-stage flash evaporation section 612 to the third-stage flash evaporation section 632. Through the synergistic effect of "pressure reduction + temperature increase", the interaction force between carbon dioxide, light hydrocarbons and absorbent is further weakened, thereby more thoroughly driving the impurity components remaining in the rich liquid to the gas phase. This significantly increases the hydrogen sulfide content in the rich liquid of each liquid package, which not only reduces the energy consumption of the separation tower 7, but also improves the purity of the final hydrogen sulfide product.

[0084] (2) Uniform feeding and gas-phase mass transfer purification: Specially designed feed distributor: Each stage of the feed distributor is equipped with two strip-shaped slots 10 facing both ends of the combined separator 6, and the opening width is calculated according to the formula W=2.5×d. 2 The (D-250) design ensures the smooth operation of the first-stage, second-stage, and third-stage flash evaporation, avoids incomplete flash evaporation caused by local liquid accumulation in the flash evaporation section, and improves the efficiency of the second, third, and fourth countercurrent contact reactions.

[0085] Secondary absorption within the gas chamber: Low-temperature lean absorbent is directly fed into the gas chamber above the inlet of each stage through pipelines. Passing through designated absorption sections (the primary absorption section 6111 is below the absorbent inlet, while the secondary and tertiary absorption sections 6211 and 6311 are between the absorbent inlet and the inlet), the flash vapor (containing a small amount of hydrogen sulfide) undergoes multi-stage countercurrent contact with the corresponding lean solution: in the primary absorption section 6111, the primary flash vapor contacts the third lean solution; in the secondary absorption section 6211, the remaining primary and secondary flash vapors contact the fourth lean solution; and in the tertiary absorption section 6311, the remaining primary, secondary, and tertiary flash vapors contact the fifth lean solution. This secondary absorption process captures absorbent droplets entrained in the gas phase, reducing the liquid impurity content in the tail gas; it also reabsorbs any remaining trace amounts of hydrogen sulfide in the gas phase, further reducing the hydrogen sulfide concentration in the tail gas, thus achieving integrated "flash evaporation + purification" treatment.

[0086] 3. Separation Unit: Distillation and purification to achieve high-purity hydrogen sulfide production. Separation tower 7 is the core of the final purification of hydrogen sulfide. Through rectification and stripping, hydrogen sulfide vapor can be removed from the hydrogen sulfide-rich solution. Key design features include: The hydrogen sulfide-rich solution (mainly containing hydrogen sulfide and absorbent) in the three-stage liquid package 633 enters the separation column 7. The reboiler 74 at the bottom of the separation column 7 provides heat, causing the hydrogen sulfide (light component) in the hydrogen sulfide-rich solution entering the separation column 7 to rise with the gas phase, while the absorbent (heavy component) remains at the bottom of the column, forming a distillation process in which the gas phase moves upward and the liquid phase moves downward. Finally, the lean absorbent is separated at the bottom of the separation column 7, while the high-purity hydrogen sulfide gas product is separated at the top of the separation column 7.

[0087] The lean absorbent is delivered by the lean absorbent booster pump 31. It first enters the heat exchanger 41 as a heat source to heat the rich absorbent in the shell side of the heat exchanger 41. Then it flows into the cooler 42 to cool down, and finally is distributed through the pipeline system into the first lean solution, the second lean solution, the third lean solution, the fourth lean solution, and the fifth lean solution, which are returned to the first absorber 1, the second absorber 2, and the combined separator 6 for recycling, respectively. This circulation process ensures that the absorbent regains its activity and continuously and efficiently captures hydrogen sulfide in the hydrogen sulfide-containing acidic gas, forming a closed loop of "absorption-separation-regeneration", which provides an important guarantee for improving the purity of the final hydrogen sulfide product.

[0088] 4. Exhaust Gas Compressor 8: Exhaust gas recirculation and recovery, achieving low hydrogen sulfide emissions. The purification system can be additionally equipped with a tail gas compressor 8, which compresses the tail gas containing a small amount of hydrogen sulfide in the tail gas discharge pipe 66 and returns it to the inlet of the hydrogen sulfide-containing acid gas conduit 3 for re-entry into the purification system for processing. The introduction of the tail gas compressor 8 can further reduce the hydrogen sulfide content in the tail gas, helping to achieve the goal of near-zero emissions of hydrogen sulfide in the tail gas and maximizing resource utilization. At the same time, the hydrogen sulfide in the returned tail gas can be further treated through absorption, flash evaporation, and distillation processes, which can further improve the overall recovery rate of hydrogen sulfide and the purity of the final hydrogen sulfide gas product.

[0089] In summary, the present application provides a purification system for hydrogen sulfide-containing acidic gas. This purification system achieves the final purification of hydrogen sulfide gas through deep absorption of hydrogen sulfide in the hydrogen sulfide-containing acidic gas, staged flash evaporation to enhance intermediate purification of the hydrogen sulfide-containing acidic gas, distillation cycle to achieve purification of the final hydrogen sulfide gas, and the elimination of tail gas end emission. The entire process design ensures near-zero hydrogen sulfide emission in the tail gas while achieving high purity and high yield of hydrogen sulfide gas.

[0090] Figure 6 An exemplary schematic diagram of a purification method for hydrogen sulfide-containing acidic gas provided in an embodiment of this application is shown. Based on a general inventive concept, such as Figure 6 As shown in the embodiment of this application, a method for purifying a hydrogen sulfide-containing acidic gas is provided. The purification method is adapted to the purification system and includes: S1. The first lean solution is used to absorb the acidic gas containing hydrogen sulfide to obtain a first gas-liquid two-phase mixture; S2. Separate the first gas-liquid two-phase mixture to obtain a crude absorbent liquid and a crude purified gas; S3. The crude absorbent liquid is used to perform a second absorption on the crude purified gas to obtain a primary rich absorbent liquid and a preliminary purified gas. S4. The second lean liquid is subjected to a first countercurrent contact reaction with the preliminary purified gas to obtain a secondary rich absorbent liquid and purified gas; S5. Mix the primary rich absorbent and the secondary rich absorbent to obtain a rich absorbent; S6. The rich absorbent liquid is heated and depressurized in a first stage to obtain a second gas-liquid two-phase mixture; S7. The second gas-liquid two-phase mixture is subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution; S8. Separate the hydrogen sulfide-rich solution to obtain hydrogen sulfide gas and lean absorbent; S9. The lean absorbent is subjected to two-stage cooling and splitting in sequence to obtain a split lean absorbent; S10. A portion of the diverted lean solution is returned to the first absorber for recycling as the first lean solution; S11. A portion of the diverted lean solution is returned to the first countercurrent contact reaction and recycled as the second lean solution.

[0091] The purification method is based on the purification system described above. The specific steps of the purification method can be referred to the above embodiments. Since the purification method adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0092] Figure 7 A detailed flowchart illustrating a method for purifying hydrogen sulfide-containing acidic gas according to an embodiment of this application is shown as an example. Figure 8 for Figure 7 The continuation; In some alternative implementations, such as Figure 7 and Figure 8 As shown, the second gas-liquid two-phase mixture is subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution, including the following steps: S701. The second gas-liquid two-phase mixture is subjected to a first-stage flash evaporation to obtain a first-stage flash vapor and a first rich liquid; S702. The third lean liquid is reacted with a portion of the first-stage flash vapor in a second countercurrent contact reaction to obtain the first absorbent liquid; S703. Mix the first absorbent and the first rich solution to obtain the second rich solution; S704. The second rich liquid is subjected to two-stage depressurization and two-stage flash evaporation in sequence to obtain a second-stage flash vapor and a third rich liquid; S705. The fourth lean liquid is subjected to a third countercurrent contact reaction with a portion of the second-stage flash vapor and the remaining first-stage flash vapor to obtain the second absorbent liquid; S706. The second absorbent and the third rich liquid are mixed to obtain a fourth rich liquid; S707. The fourth rich liquid is subjected to three-stage depressurization and three-stage flash evaporation in sequence to obtain three-stage flash vapor and the fifth rich liquid; S708. The fifth lean liquid is subjected to a fourth countercurrent contact reaction with the remaining first-stage flash vapor, the remaining second-stage flash vapor and all the third-stage flash vapor to obtain the third absorbent and tail gas. S709. Mix the third absorbent and the fifth rich solution to obtain a hydrogen sulfide-rich solution; Specifically, a portion of the depleted lean solution is returned to the second countercurrent contact reaction for reuse as the third lean solution; a portion of the depleted lean solution is returned to the third countercurrent contact reaction for reuse as the fourth lean solution; and the remaining depleted lean solution is returned to the fourth countercurrent contact reaction for reuse as the fifth lean solution.

[0093] In these embodiments, the second gas-liquid two-phase mixture undergoes a first-stage flash evaporation to form a first-stage flash vapor and a first rich liquid. The first-stage flash vapor is then reacted with a third lean liquid in a second countercurrent contact reaction. The third lean liquid absorbs some of the hydrogen sulfide from the first-stage flash vapor, forming a first absorbent. The first absorbent and the first rich liquid are mixed to form a second rich liquid. The second rich liquid then undergoes a second-stage depressurization and a second-stage flash evaporation to form a second-stage flash vapor and a third rich liquid. Subsequently, the second-stage flash vapor and the remaining first-stage flash vapor undergo a third countercurrent contact reaction with a fourth lean liquid. The fourth lean liquid absorbs some of the hydrogen sulfide from the first-stage flash vapor. The remaining hydrogen sulfide in the first-stage flash vapor is partially absorbed to form the second absorbent. The second absorbent and the third rich liquid are mixed to form the fourth rich liquid. The fourth rich liquid then undergoes three stages of depressurization and three stages of flash evaporation to form the third-stage flash vapor and the fifth rich liquid. Subsequently, all the third-stage flash vapor, the remaining first-stage flash vapor, the remaining second-stage flash vapor and the fifth lean liquid undergo a fourth countercurrent contact reaction. The fifth lean liquid absorbs all the hydrogen sulfide in the third-stage flash vapor, the remaining first-stage flash vapor and the remaining second-stage flash vapor to form the third absorbent. The third absorbent and the fifth rich liquid are mixed to form a hydrogen sulfide-rich solution.

[0094] It should be noted that the main differences between the first lean solution, the second lean solution, the third lean solution, the fourth lean solution, the fifth lean solution, the lean absorbent solution, the rich absorbent solution, and the hydrogen sulfide-rich solution lie in the different contents of hydrogen sulfide and impurities. Among them, since the first lean solution, the second lean solution, the third lean solution, the fourth lean solution, and the fifth lean solution are all part of the lean absorbent solution, theoretically the contents of hydrogen sulfide and impurities of the first lean solution, the second lean solution, the third lean solution, the fourth lean solution, and the fifth lean solution are the same.

[0095] In some optional embodiments, the temperature of the first-stage flash evaporation is 55°C to 75°C, the temperature of the second-stage flash evaporation is 65°C to 85°C, and the temperature of the third-stage flash evaporation is 75°C to 95°C. The pressure P3 of the third-stage flash evaporation is 0.15 MPa to 0.25 MPa, and the pressures P1 of the first-stage flash evaporation and P2 of the second-stage flash evaporation satisfy the following: P1 = (0.8 to 1.2) × r 2 ×P3, and P2 = (0.8 to 1.2) × r × P3, Equation 2, In Equation 2, r is the pressure drop coefficient, and r satisfies: P0 is the pressure of the second absorption; the units of P0, P1, P2 and P3 are all MPa.

[0096] In these embodiments, the temperature is 55°C to 75°C and the pressure P1 satisfies P1 = (0.8 to 1.2) × r 2 The first-stage flash evaporation at ×P3 can transfer more carbon dioxide and light hydrocarbon components from the rich absorbent to the first-stage flash vapor, while more hydrogen sulfide remains in the liquid phase, thus obtaining a first rich solution with a higher hydrogen sulfide concentration than the rich absorbent. The second-stage flash evaporation at a temperature of 65℃ to 85℃ and a pressure P2 satisfying P2 = (0.8 to 1.2) × r × P3 can promote the transfer of more carbon dioxide and light hydrocarbon components from the second rich solution after the second depressurization to the second-stage flash vapor, while more hydrogen sulfide remains in the liquid phase, thus obtaining a third rich solution with a higher hydrogen sulfide concentration than the first rich solution. The third-stage flash evaporation at a temperature of 75℃ to 95℃ and a pressure of 0.15 MPa to 0.25 MPa can promote the transfer of more carbon dioxide and light hydrocarbon components from the fourth rich solution after the third depressurization to the third-stage flash vapor, while more hydrogen sulfide remains in the liquid phase, thus obtaining a fifth rich solution with a higher hydrogen sulfide concentration than the third rich solution.

[0097] The temperature for the first-stage flash evaporation can be 55℃, 60℃, 65℃, 70℃, or 75℃.

[0098] The temperature for the secondary flash evaporation can be 65℃, 70℃, 75℃, 80℃, or 85℃.

[0099] The temperature for the three-stage flash evaporation can be 75℃, 80℃, 85℃, 90℃, or 95℃.

[0100] The pressure of the three-stage flash evaporation can be 0.15MPa, 0.16MPa, 0.17MPa, 0.18MPa, 0.19MPa, 0.20MPa, 0.21MPa, 0.22MPa, 0.23MPa, 0.24MPa or 0.25MPa.

[0101] It should be noted that, according to the formula shown in Equation 2, when P1 > P0, in order to ensure the stable operation of the purification system, the pressure P1 of the first-stage flash evaporation needs to be controlled to be equivalent to the pressure of the second-stage absorption, i.e., P1 = P0; when P1 < P2, in order to ensure the stable operation of the purification system, the pressure P2 of the second-stage flash evaporation needs to be controlled to be equivalent to the pressure P1 of the first-stage flash evaporation, i.e., P2 = P1; when P3 > P2, in order to ensure the stable operation of the purification system, the pressure P3 of the third-stage flash evaporation needs to be controlled to be equivalent to the pressure P2 of the second-stage flash evaporation, i.e., P3 = P2.

[0102] In some alternative implementations, the pressure P0 of the second absorption satisfies: (Pw-0.3MPa)≤P0≤(Pw-0.1MPa), Equation 3, In Equation 3, Pw is the introduction pressure of the acidic gas containing hydrogen sulfide, and the unit is MPa.

[0103] In these embodiments, the first absorption at a pressure of Pw can promote sufficient mixing and absorption of the hydrogen sulfide-containing acidic gas and the first lean solution.

[0104] It should be noted that the pressure P0 of the second absorption is the top pressure of the second absorber 2 in the purification system.

[0105] In some alternative embodiments, the volumetric flow rate of the first-stage flash vapor is 30 to 1000 times the volumetric flow rate of the third lean solution; and / or The volumetric flow rate of the secondary flash vapor is 40 to 1250 times that of the volumetric flow rate of the fourth lean solution; and / or The volumetric flow rate of the third-stage flash vapor is 50 to 1500 times that of the fifth lean liquid.

[0106] In these embodiments, efficient absorption of flash vapor at each stage is achieved through multi-stage countercurrent contact of primary flash vapor and third lean liquid, secondary flash vapor and fourth lean liquid, and tertiary flash vapor and fifth lean liquid. Specifically, the first-stage flash vapor (with a volumetric flow rate 30 to 1000 times that of the third lean solution) undergoes a second countercurrent contact reaction with the third lean solution, where the third lean solution absorbs some of the hydrogen sulfide from the first-stage flash vapor, forming a first absorbent containing hydrogen sulfide. The second-stage flash vapor (with a volumetric flow rate 40 to 1250 times that of the fourth lean solution) and the remaining first-stage flash vapor undergo a third countercurrent contact reaction with the fourth lean solution, further absorbing hydrogen sulfide from the second-stage flash vapor and the remaining first-stage flash vapor, generating a second absorbent. The third-stage flash vapor (with a volumetric flow rate 50 to 1500 times that of the third-stage flash vapor in the fifth lean solution), the remaining first-stage flash vapor, and the remaining second-stage flash vapor undergo a fourth countercurrent contact reaction with the fifth lean solution, where the fifth lean solution absorbs the hydrogen sulfide from the third-stage flash vapor, the remaining first-stage flash vapor, and the remaining second-stage flash vapor, forming a third absorbent. Therefore, the multi-stage absorption process involving the third, fourth, and fifth lean solutions significantly improves the absorption efficiency of hydrogen sulfide, providing a crucial guarantee for ultimately obtaining a high-concentration hydrogen sulfide-rich solution.

[0107] The volumetric flow rate of the first-stage flash vapor can be 30, 40, 50, 100, 150, 200, 250, 300, 350, 500, 600, 700, 800, 900, or 1000 times that of the third lean liquid.

[0108] The volumetric flow rate of the secondary flash vapor can be 40, 50, 100, 150, 200, 250, 500, 750, 1000, or 1250 times that of the fourth lean solution.

[0109] The volumetric flow rate of the third-stage flash vapor can be 50, 100, 150, 200, 250, 300, 350, 500, 750, 1000, 1250, or 1500 times that of the fifth lean liquid.

[0110] It should be noted that by adjusting the flow rate of different lean solutions, as well as parameters such as the temperature and pressure of different flash evaporations, the content of carbon dioxide and light hydrocarbon components in the final hydrogen sulfide-rich solution can be controlled.

[0111] In some alternative embodiments, the temperature of the first absorption is from 10°C to 50°C; and / or The temperature of the second absorption is 10°C to 50°C; and / or The temperature of the first countercurrent contact reaction is 10°C to 50°C.

[0112] In these embodiments, the first absorption at a temperature of 10°C to 50°C allows for sufficient reaction and mixing between the first lean liquid and the hydrogen sulfide-containing acidic gas, forming a first gas-liquid two-phase mixture; while the second absorption at a temperature of 10°C to 50°C and the first countercurrent contact reaction at a temperature of 10°C to 50°C allow for sufficient first countercurrent contact reaction between the crude purified gas and the crude absorbent liquid, forming a secondary rich absorbent liquid, which is beneficial for obtaining a rich absorbent liquid with a high hydrogen sulfide concentration.

[0113] The temperature of the first absorption can be 10℃, 20℃, 30℃, 40℃ or 50℃.

[0114] The temperature for the second absorption can be 10℃, 20℃, 30℃, 40℃ or 50℃.

[0115] The temperature of the first countercurrent contact reaction can be 10℃, 20℃, 30℃, 40℃ or 50℃.

[0116] In some alternative implementations, the secondary cooling includes a first cooling and a second cooling, wherein the endpoint temperature of the first cooling is 70°C to 95°C and the endpoint temperature of the second cooling is 15°C to 45°C.

[0117] In these embodiments, the first cooling with an endpoint temperature of 70°C to 95°C allows the heat of the lean absorbent to be fully utilized, which helps to reduce the load of the second cooling; the second cooling with an endpoint temperature of 15°C to 45°C can promote the lean absorbent to better absorb hydrogen sulfide from various acidic gases.

[0118] The endpoint temperature of the first cooling can be 70°C, 75°C, 80°C, 85°C, 90°C, or 95°C.

[0119] The endpoint temperature of the second cooling can be 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or 45°C.

[0120] In some optional embodiments, the separation includes distillation separation and stripping separation, wherein the distillation separation is carried out at a temperature of 105°C to 115°C and a pressure of 150 kPa to 250 kPa; and the stripping separation is carried out at a temperature of 115°C to 145°C.

[0121] In these embodiments, distillation separation at a temperature of 105°C to 115°C and a pressure of 150 kPa to 250 kPa can promote the complete separation of the heavy components in the light components of hydrogen sulfide, forming a high-purity hydrogen sulfide gas product; in addition, stripping separation at a temperature of 115°C to 145°C can allow the small amount of hydrogen sulfide in the heavy components to be fully vaporized, reducing the hydrogen sulfide content in the lean absorbent.

[0122] The distillation separation temperature can be 105℃, 106℃, 107℃, 108℃, 109℃, 110℃ or 115℃.

[0123] The pressure for this distillation separation can be 150 kPa, 160 kPa, 170 kPa, 180 kPa, 190 kPa, 200 kPa, 210 kPa, 220 kPa, 230 kPa, 240 kPa or 250 kPa.

[0124] The distillation separation temperature can be 115℃, 120℃, 125℃, 130℃, 135℃, 140℃ or 145℃.

[0125] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0126] Example 1 like Figure 1 As shown, a purification system for hydrogen sulfide-containing acidic gas is provided. The purification system includes: The absorption section includes a hydrogen sulfide acid gas conduit 3, a first absorber 1, a second absorber 2, and a purified gas discharge pipe 9. The outlet of the hydrogen sulfide acid gas conduit 3 is connected to the inlet of the first absorber 1. The second absorber 2 includes a gas-liquid separator 21, a gas-liquid contact section 22, and a rich absorbent buffer section 23 from top to bottom. The outlet of the first absorber 1 is connected to the rich absorbent buffer section 23. The inlet of the purified gas discharge pipe 9 is connected to the top outlet of the second absorber 2. The heat exchange and cooling section 4 includes a heat exchanger 41 and a cooler 42. The shell-side inlet of the heat exchanger 41 is connected to the outlet of the rich absorbent buffer section 23, and the tube-side outlet of the heat exchanger 41 is connected to the shell-side inlet of the cooler 42. The combined separator 6 includes a first partition 64, a second partition 65, and an exhaust pipe 66. The first partition 64 and the second partition 65 are fixedly connected inside the combined separator 6, dividing the combined separator 6 into a primary separation zone 61, a secondary separation zone 62, and a tertiary separation zone 63. The primary separation zone 61 includes a through-flow primary gas manifold 611, a primary flash section 612, and a primary liquid manifold 613. The primary gas manifold 611 is located above the primary flash section 612, and the primary flash section 612 is located above the primary liquid manifold 613. The secondary separation zone 62 includes a secondary gas manifold 621, a secondary flash section 622, and a secondary liquid manifold 623. The secondary gas manifold 621 is located above the secondary flash section 622, and the secondary flash section 622 is located above the secondary liquid manifold 623. The tertiary separation zone 63 includes a tertiary steam manifold 622, a tertiary flash section 622, and a tertiary liquid manifold 623. 33. A third-stage air manifold 631 is positioned above a third-stage flash section 632, which is positioned above a third-stage liquid manifold 633. A first-stage flash section 612 is equipped with a first-stage feed distributor 6121, the inlet of which is connected to the shell-side outlet of the heat exchanger 41. A second-stage flash section 622 is equipped with a second-stage feed distributor 6221, the inlet of which is connected to... The discharge port of the primary liquid reservoir 613 is connected to the discharge port of the secondary liquid reservoir 623. The discharge port of the primary flash evaporation section 632 is connected to the discharge port of the secondary liquid reservoir 623. The discharge port of the primary gas reservoir 611 is connected to the discharge port of the secondary gas reservoir 621. The discharge port of the secondary gas reservoir 621 is connected to the discharge port of the tertiary gas reservoir 631. The discharge port of the tertiary gas reservoir 631 is connected to the discharge port of the exhaust gas pipe 66. The shell-side outlet of the cooler 42 is simultaneously connected to the absorbent inlets of the first absorber 1, the second absorber 2, the first-stage air chamber 611, the second-stage air chamber 621, and the third-stage air chamber 631. The absorbent inlet of the first-stage air chamber 611 is located at the top of the first-stage air chamber 611, the absorbent inlet of the second-stage air chamber 621 is located above the air inlet of the second-stage air chamber 621, and the absorbent inlet of the third-stage air chamber 631 is located above the air inlet of the third-stage air chamber 621. The absorbent inlet of the second absorber 2 is located between the gas-liquid contact section 22 and the gas-liquid separator 21. The separation unit includes a separation tower 7 and a lean absorbent booster pump 31. The outlet of the three-stage liquid tank 633 is connected to the inlet of the separation tower 7. The bottom outlet of the separation tower 7 is connected to the inlet of the lean absorbent booster pump 31. The outlet of the lean absorbent booster pump 31 is connected to the tube-side inlet of the heat exchanger 41.

[0127] The primary air chamber 611 is equipped with a primary absorption section 6111, which is located below the absorbent inlet of the primary air chamber 611. The secondary air chamber 621 is equipped with a secondary absorption section 6211, which is located between the absorbent inlet and the air inlet of the secondary air chamber 621. The tertiary absorption section 6311 is located between the absorbent inlet and the air inlet of the tertiary air chamber 631.

[0128] A primary heater 614 is provided in the primary separation zone 61, and the primary heater 614 is located at the bottom of the primary flash section 612; A secondary heater 624 is provided in the secondary separation zone 62, and the secondary heater 624 is located at the bottom of the secondary flash section 622; A three-stage heater 634 is provided in the three-stage separation zone 63, and the three-stage heater 634 is located at the bottom of the three-stage flash section 632.

[0129] The purification system also includes: The pressure reducing valve assembly 5 includes a primary pressure reducing valve 51, a secondary pressure reducing valve 52, and a tertiary pressure reducing valve 53. The primary pressure reducing valve 51 is fixedly connected between the heat exchanger 41 and the primary feed distributor 6121. The secondary pressure reducing valve 52 is fixedly connected between the primary liquid reservoir 613 and the secondary feed distributor 6221. The tertiary pressure reducing valve 53 is fixedly connected between the secondary liquid reservoir 623 and the tertiary feed distributor 6321.

[0130] The primary feed distributor 6121, the secondary feed distributor 6221 and the tertiary feed distributor 6321 are all provided with two strip-shaped slots 10. One strip-shaped slot 10 is set towards one end of the combined separator 6, and the other strip-shaped slot 10 is set towards the other end of the combined separator 6.

[0131] The opening width W of the slot 10 satisfies: W = 2.5 × d 2 / (D-250), Equation 1; In Equation 1, d is the diameter of the shell-side outlet of heat exchanger 41 in mm; D is the diameter of combined separator 6 in mm, and D≥300mm.

[0132] The separation unit also includes a condenser 71, a reflux tank 72, a reflux pump 73, a reboiler 74, and a hydrogen sulfide outlet pipe 75. The inlet of the condenser 71 is connected to the top outlet of the separation tower 7, the outlet of the condenser 71 is connected to the inlet of the reflux tank 72, the upper outlet of the reflux tank 72 is connected to the inlet of the hydrogen sulfide outlet pipe 75, the lower outlet of the reflux tank 72 is connected to the inlet of the reflux pump 73, the outlet of the reflux pump 73 is connected to the top inlet of the separation tower 7, the inlet of the reboiler 74 is connected to the bottom inlet of the separation tower 7, and the outlet of the reboiler 74 is connected to the bottom side inlet of the separation tower 7.

[0133] The hydrogen sulfide-containing acidic gas from a certain factory is used as raw material. The temperature of the hydrogen sulfide-containing acidic gas is 38℃, the pressure is 3.0MPa (absolute pressure), and the flow rate is 10000kg / h. The composition of the hydrogen sulfide-containing acidic gas is shown in Table 2.

[0134] Table 2. Composition of hydrogen sulfide-containing acidic gas in a certain factory

[0135] The purification system and method provided in this application use an activated MDEA solution as an absorbent. The activated MDEA solution, by mass fraction, comprises: MDEA: 40.0%, tert-butylaminoethoxyethanol (activator): 6.0%, and water: 54.0%. The hydrogen sulfide in the hydrogen sulfide-containing acidic gas shown in Table 2 is purified, requiring a hydrogen sulfide volume fraction of not less than 99.0% after purification.

[0136] In the purification system, the first absorber 1 uses an SX static mixer, the second absorber 2 uses a plate column with 32 trays, and the separation column 7 uses a plate column with 36 trays.

[0137] like Figure 7 and Figure 8 As shown, a method for purifying a hydrogen sulfide-containing acidic gas is provided. The purification method is adapted to a purification system and includes the following steps: S1. The first lean solution is used to absorb the acidic gas containing hydrogen sulfide to obtain a first gas-liquid two-phase mixture; S2. Separate the first gas-liquid two-phase mixture to obtain a crude absorbent liquid and a crude purified gas; S3. The crude absorbent liquid is used to perform a second absorption on the crude purified gas to obtain a primary rich absorbent liquid and a preliminary purified gas. S4. The second lean liquid is reacted with the preliminary purified gas in a first countercurrent contact reaction to obtain the second rich absorbent liquid and purified gas. S5. Mix the primary rich absorbent and the secondary rich absorbent to obtain a rich absorbent; S6. The rich absorbent liquid is heated and depressurized in one stage to obtain a second gas-liquid two-phase mixture; S701. The second gas-liquid two-phase mixture is subjected to a first-stage flash evaporation to obtain a first-stage flash vapor and a first-stage rich liquid; S702. The third lean liquid is reacted with a portion of the first-stage flash vapor in a second countercurrent contact reaction to obtain the first absorbent liquid; S703. Mix the first absorbent and the first rich solution to obtain the second rich solution; S704. The second rich liquid is subjected to two-stage depressurization and two-stage flash evaporation in sequence to obtain a second-stage flash vapor and a third rich liquid; S705. The fourth lean liquid is reacted with part of the secondary flash vapor and the remaining primary flash vapor in a third countercurrent contact reaction to obtain the second absorbent liquid; S706. Mix the second absorbent and the third rich solution to obtain the fourth rich solution; S707. The fourth rich liquid is subjected to three-stage depressurization and three-stage flash evaporation to obtain three-stage flash vapor and the fifth rich liquid; S708. The fifth lean liquid is reacted with the remaining first-stage flash vapor, the remaining second-stage flash vapor and all third-stage flash vapor in a fourth countercurrent contact reaction to obtain the third absorbent liquid and tail gas. S709. Mix the third absorbent and the fifth rich solution to obtain a hydrogen sulfide-rich solution; Specifically, a portion of the depleted lean solution is returned to the second countercurrent contact reaction and recycled as the third lean solution; a portion of the depleted lean solution is returned to the third countercurrent contact reaction and recycled as the fourth lean solution; and the remaining depleted lean solution is returned to the fourth countercurrent contact reaction and recycled as the fifth lean solution. S7. Separate the hydrogen sulfide-rich solution to obtain hydrogen sulfide gas and lean absorbent; S8. The lean absorbent is subjected to two-stage cooling and splitting in sequence to obtain a split lean solution; S9. A portion of the diverted lean solution is returned to the first absorber and recycled as the first lean solution. S10. A portion of the lean liquor is returned to the first countercurrent contact reaction and recycled as the second lean liquor.

[0138] The temperature for the first-stage flash evaporation is 70℃, the temperature for the second-stage flash evaporation is 78℃, and the temperature for the third-stage flash evaporation is 86℃. The pressure for the third-stage flash evaporation is 0.20 MPa. The pressures P1 for the first-stage flash evaporation and P2 for the second-stage flash evaporation satisfy the following: P1 = (0.8 to 1.2) × r 2 ×P3, and P2 = (0.8 to 1.2) × r × P3, Equation 2, In Equation 2, r is the pressure drop coefficient, and r satisfies: P0 is the pressure of the second absorption, in MPa, and has a value of 2.9 MPa.

[0139] The pressure P0 of the second absorption satisfies: (Pw-0.3MPa)≤P0≤(Pw-0.1MPa), Equation 3, In Equation 3, Pw is the introduction pressure of the acidic gas containing hydrogen sulfide, in MPa; the value of Pw is 3.0 MPa.

[0140] The flow rate of the first lean solution is 66 t / h, the flow rate of the second lean solution is 120 t / h, the flow rate of the third lean solution is 5.6 t / h, the flow rate of the fourth lean solution is 3.8 t / h, and the flow rate of the fifth lean solution is 3.2 t / h.

[0141] The volumetric flow rate of the first-stage flash vapor was 74.6 times that of the third-stage lean liquid. The volumetric flow rate of the secondary flash vapor was 134.7 times that of the fourth lean solution. The volumetric flow rate of the third-stage flash vapor was 146.6 times that of the fifth-stage lean liquid.

[0142] The temperature of the first absorption is 38℃; The temperature of the second absorption is 42℃; The first countercurrent contact reaction temperature is 38℃.

[0143] The secondary cooling includes first cooling and second cooling. The endpoint temperature of the first cooling includes the heating endpoint temperature of the rich absorbent and the cooling endpoint temperature of the diverted lean liquid. The heating endpoint temperature of the rich absorbent is 70.0℃, and the cooling endpoint temperature of the diverted lean liquid is 89.0℃.

[0144] The final temperature of the second cooling cycle is 32°C.

[0145] The separation includes rectification separation and stripping separation. The temperature for rectification separation is 108℃ (top temperature of the separation column) and the pressure for rectification separation is 160kPa (top pressure of the separation column). The temperature for stripping separation is 129℃ (bottom temperature of the separation column) and the reflux ratio of the separation column is 3.6.

[0146] Example 2 Compared to Example 1, Example 2 differs as follows; all other aspects are the same: like Figure 2 As shown, the second absorber 2 is equipped with a rich absorbent isolation plate 26 and a rich absorbent booster pump 32. The rich absorbent isolation plate 26 is vertically arranged in the rich absorbent buffer section 23, which divides the rich absorbent buffer section 23 into a primary rich absorbent buffer section 24 and a secondary rich absorbent buffer section 25. The tops of the primary rich absorbent buffer section 24 and the secondary rich absorbent buffer section 25 have a through gas phase space. The inlet of the rich absorbent booster pump 32 is connected to the outlet of the primary rich absorbent buffer section 24, and the outlet of the rich absorbent booster pump 32 is connected to the middle inlet of the gas-liquid contact section 22.

[0147] Example 3 Compared to Example 2, Example 3 differs as follows; all other aspects are the same: like Figure 3 As shown, the purification system also includes: The exhaust gas compressor 8 has its inlet connected to a branch outlet of the exhaust gas discharge pipe 66, and its outlet connected to a branch inlet of the hydrogen sulfide-containing acid gas conduit 3. At this time, the mass flow rate of the exhaust gas returning to the purification system is three times the mass flow rate of the exhaust gas discharged from the exhaust gas discharge pipe 66 to the outside of the purification system.

[0148] Comparative Example 1 Compared to Example 1, Comparative Example 1 differs as follows, while all other aspects remain the same: Without using the combined separator 6 with the first partition 64 and the second partition 65, the combined separator 6 is directly opened. At this time, the first-stage flash section 612, the second-stage flash section 622 and the third-stage flash section 632 form a continuous single-stage flash section, while the first-stage gas manifold 611, the second-stage gas manifold 621 and the third-stage gas manifold 631 are merged into a single gas manifold, and the first-stage liquid manifold 613, the second-stage liquid manifold 623 and the third-stage liquid manifold 633 are merged into a single liquid manifold. At this time, the flash temperature in this single-stage flash section is 86℃ and the flash pressure is 0.2MPa.

[0149] Comparative Example 2 Compared to Comparative Example 1, Comparative Example 2 differs as follows; all other differences are the same: Without using the second absorber 2, the hydrogen sulfide-containing gas is directly introduced into the first absorber 1, and then into the combined separator 6 of the single-stage flash section of Comparative Example 1.

[0150] Relevant experimental and effect data: 1. The mass flow rate and composition of each inlet and outlet material in the purification device of Example 1 are shown in Table 3.

[0151] Table 3. Distribution of each inlet and outlet material in the purification device of Example 1

[0152] As shown in Table 3, the purification system for hydrogen sulfide-containing acidic gas provided in this application embodiment reduces the hydrogen sulfide content in the purified gas through deep absorption, enhances intermediate purification of hydrogen sulfide-containing acidic gas through staged flash evaporation, achieves final purification of hydrogen sulfide gas through distillation circulation, and eliminates end-of-pipe hydrogen sulfide emissions. The entire process design can effectively improve the purity of hydrogen sulfide gas to over 99.5%. This hydrogen sulfide gas can meet the requirements of actual production and can be used to produce high-quality sodium hydrosulfide products or sold directly as hydrogen sulfide gas products.

[0153] 2. The rich absorbent isolation plate 26 and rich absorbent booster pump 32 introduced in Example 2 can reduce the flow rate of the second lean liquid to 99t / h, and reduce the energy consumption of the overall purification system by 7.6%.

[0154] 3. The exhaust gas compressor 8 introduced in Example 3 can recirculate most of the exhaust gas to the hydrogen sulfide-containing acid gas duct 3 and re-enter the purification system, effectively reducing the hydrogen sulfide content in the exhaust gas. The volume fraction of hydrogen sulfide in the exhaust gas is reduced from 1.62 × 10⁻⁶ in Example 1. -4 Reduced to 9.28×10 -5 .

[0155] 4. In Comparative Example 1, the combined separator 6 without a multi-stage flash evaporation section was used to treat the second gas-liquid two-phase mixture. Only a single flash evaporation was performed on the second gas-liquid two-phase mixture. This resulted in a hydrogen sulfide volume fraction of only 98.5632% in the final hydrogen sulfide gas, and a hydrogen sulfide volume fraction of 2.36 × 10⁻⁶ in the tail gas. -4 In contrast, Comparative Example 2 did not use the second absorber 2. Compared to Comparative Example 1, the final hydrogen sulfide gas had a hydrogen sulfide volume fraction of only 95.1219%, and the exhaust gas had a hydrogen sulfide volume fraction of only 1.27%.

[0156] In summary, the present application provides a purification system for hydrogen sulfide-containing acidic gas. This purification system, through a synergistic design of enhanced absorption → staged deep flash evaporation → distillation purification → tail gas reflux, achieves ultra-low emissions of hydrogen sulfide in the tail gas while significantly improving the purity of the target product, hydrogen sulfide gas.

[0157] In addition, the present application provides a purification system for hydrogen sulfide-containing acidic gas. This purification system can effectively control the impurity content in the hydrogen sulfide-rich solution entering the separation tower 7 by adjusting the operating temperature and pressure of the first-stage flash section 612, the second-stage flash section 622, the third-stage flash section 632, the cooling temperature of the cooler 42, and the first lean liquid flow rate, the second lean liquid flow rate, the third lean liquid flow rate, the fourth lean liquid flow rate, and the fifth lean liquid flow rate. This ensures that the carbon dioxide content in the hydrogen sulfide-rich solution is less than or equal to 2000 mg / kg, and the light hydrocarbon component content is less than or equal to 200 mg / kg.

[0158] Furthermore, this application provides a purification system for hydrogen sulfide-containing acidic gas. This system employs a comprehensive design that reduces the hydrogen sulfide content in the purified gas through deep absorption, enhances intermediate purification of the hydrogen sulfide-containing acidic gas through staged flash evaporation, achieves final purification of the hydrogen sulfide gas through distillation circulation, and eliminates end-of-pipe hydrogen sulfide emissions. Multiple countercurrent contacts shorten the gas-liquid contact time, ensuring selective absorption of hydrogen sulfide by the absorbent, thereby obtaining high-purity hydrogen sulfide gas products and tail gas and purified gas with low hydrogen sulfide content. Additionally, this purification system can achieve multiple heating, depressurization, and flash evaporation of the rich absorbent liquid using a single combined separator 6 and a pressure-reducing valve group. Compared to the large amount of equipment required for a single flash evaporation, this purification system has the advantages of a simple process, low equipment investment costs, and a small overall footprint.

[0159] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A purification system for acidic gases containing hydrogen sulfide, characterized in that, The purification system includes: The absorption section includes a hydrogen sulfide-containing acid gas conduit, a first absorber, a second absorber, and a purified gas discharge pipe. The outlet of the hydrogen sulfide-containing acid gas conduit is connected to the inlet of the first absorber. The second absorber includes, from top to bottom, a gas-liquid separator, a gas-liquid contact section, and a rich absorbent buffer section. The outlet of the first absorber is connected to the rich absorbent buffer section. The inlet of the purified gas discharge pipe is connected to the top outlet of the second absorber. The heat exchange and cooling section includes a heat exchanger and a cooler. The shell-side inlet of the heat exchanger is connected to the outlet of the rich absorbent buffer section, and the tube-side outlet of the heat exchanger is connected to the shell-side inlet of the cooler. A combined separator includes a first partition, a second partition, and an exhaust pipe. The first and second partitions are fixedly connected within the combined separator, dividing it into a primary separation zone, a secondary separation zone, and a tertiary separation zone. The primary separation zone includes a through-flow primary gas manifold, a primary flash evaporation section, and a primary liquid manifold, with the primary gas manifold positioned above the primary flash evaporation section and the primary flash evaporation section positioned above the primary liquid manifold. The secondary separation zone includes a secondary gas manifold, a secondary flash evaporation section, and a secondary liquid manifold, with the secondary gas manifold positioned above the secondary flash evaporation section and the secondary flash evaporation section positioned above the secondary liquid manifold. The tertiary separation zone includes a tertiary steam manifold, a tertiary flash evaporation section, and a tertiary liquid manifold. A three-stage gas manifold is positioned above the three-stage flash evaporation section, which is positioned above the three-stage liquid manifold. The first-stage flash evaporation section is equipped with a first-stage feed distributor, the inlet of which is connected to the shell-side outlet of the heat exchanger. The second-stage flash evaporation section is equipped with a second-stage feed distributor, the inlet of which is connected to the outlet of the first-stage liquid manifold. The third-stage flash evaporation section is equipped with a third-stage feed distributor, the inlet of which is connected to the outlet of the second-stage liquid manifold. The outlet of the first-stage gas manifold is connected to the inlet of the second-stage gas manifold, and the outlet of the second-stage gas manifold is connected to the inlet of the third-stage gas manifold. The outlet of the third-stage gas manifold is connected to the inlet of the exhaust gas discharge pipe. The shell-side outlet of the cooler is simultaneously connected to the absorbent inlets of the first absorber, the second absorber, the primary gas chamber, the secondary gas chamber, and the tertiary gas chamber. The absorbent inlet of the primary gas chamber is located at the top of the primary gas chamber, the absorbent inlet of the secondary gas chamber is located above the air inlet of the secondary gas chamber, and the absorbent inlet of the tertiary gas chamber is located above the air inlet of the tertiary gas chamber. The absorbent inlet of the second absorber is located between the gas-liquid contact section and the gas-liquid separator. The separation unit includes a separation tower and a lean absorbent booster pump. The outlet of the three-stage liquid tank is connected to the inlet of the separation tower, the bottom outlet of the separation tower is connected to the inlet of the lean absorbent booster pump, and the outlet of the lean absorbent booster pump is connected to the tube-side inlet of the heat exchanger.

2. The purification system according to claim 1, characterized in that, The primary air tank is provided with a primary absorption section, which is located below the absorbent inlet of the primary air tank. The secondary air tank is provided with a secondary absorption section, which is located between the absorbent inlet and the air inlet of the secondary air tank. The tertiary absorption section is located between the absorbent inlet and the air inlet of the tertiary air tank.

3. The purification system according to claim 1, characterized in that, A primary heater is provided in the primary separation zone, and the primary heater is located at the bottom of the primary flash section; A secondary heater is provided in the secondary separation zone, and the secondary heater is located at the bottom of the secondary flash section; The three-stage separation zone is equipped with a three-stage heater, which is located at the bottom of the three-stage flash section.

4. The purification system according to claim 1, characterized in that, The purification system also includes: The pressure reducing valve assembly includes a primary pressure reducing valve, a secondary pressure reducing valve, and a tertiary pressure reducing valve. The primary pressure reducing valve is fixedly connected between the heat exchanger and the primary feed distributor. The secondary pressure reducing valve is fixedly connected between the primary liquid reservoir and the secondary feed distributor. The tertiary pressure reducing valve is fixedly connected between the secondary liquid reservoir and the tertiary feed distributor.

5. The purification system according to claim 1, characterized in that, The second absorber is equipped with a rich absorbent isolation plate and a rich absorbent booster pump. The rich absorbent isolation plate is vertically arranged in the rich absorbent buffer section, and the rich absorbent isolation plate divides the rich absorbent buffer section into a primary rich absorbent buffer section and a secondary rich absorbent buffer section. The top of the primary rich absorbent buffer section and the secondary rich absorbent buffer section have a through gas phase space. The inlet of the rich absorbent booster pump is connected to the outlet of the primary rich absorbent buffer section, and the outlet of the rich absorbent booster pump is connected to the middle inlet of the gas-liquid contact section.

6. The purification system according to claim 1, characterized in that, The primary feed distributor, the secondary feed distributor, and the tertiary feed distributor are each provided with two strip-shaped slots, one of which is positioned facing one end of the combined separator, and the other of which is positioned facing the other end of the combined separator.

7. The purification system according to claim 6, characterized in that, The opening width W of the strip-shaped slot satisfies: W = 2.5 × d 2 / (D-250), Equation 1; In Formula 1, d is the shell-side outlet diameter of the heat exchanger in mm; D is the diameter of the combined separator in mm, and D≥300mm.

8. The purification system according to claim 1, characterized in that, The separation unit further includes a condenser, a reflux tank, a reflux pump, a reboiler, and a hydrogen sulfide outlet pipe. The inlet of the condenser is connected to the top outlet of the separation tower, the outlet of the condenser is connected to the inlet of the reflux tank, the upper outlet of the reflux tank is connected to the inlet of the hydrogen sulfide outlet pipe, the lower outlet of the reflux tank is connected to the inlet of the reflux pump, the outlet of the reflux pump is connected to the top inlet of the separation tower, the inlet of the reboiler is connected to the bottom inlet of the separation tower, and the outlet of the reboiler is connected to the bottom side inlet of the separation tower.

9. The purification system according to claim 1, characterized in that, The purification system also includes: An exhaust gas compressor, wherein the inlet of the exhaust gas compressor is connected to a branch outlet of the exhaust gas discharge pipe, and the outlet of the exhaust gas compressor is connected to a branch inlet of the hydrogen sulfide-containing acidic gas conduit.

10. A method for purifying an acidic gas containing hydrogen sulfide, characterized in that, The purification method is adapted to the purification system according to any one of claims 1 to 9, and the purification method includes: The first lean solution is used to absorb the acidic gas containing hydrogen sulfide to obtain a first gas-liquid two-phase mixture; The first gas-liquid two-phase mixture is separated to obtain a crude absorbent liquid and a crude purified gas; The crude absorbent is used to perform a second absorption on the crude purified gas to obtain a primary rich absorbent and a preliminary purified gas. The second lean solution is used to perform a first countercurrent contact reaction with the pre-purified gas to obtain a secondary rich absorbent and purified gas. The primary rich absorbent and the secondary rich absorbent are mixed to obtain a rich absorbent; The rich absorbent liquid is heated and depressurized in a first stage to obtain a second gas-liquid two-phase mixture. The second gas-liquid two-phase mixture was subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution; The hydrogen sulfide-rich solution is separated to obtain hydrogen sulfide gas and a lean absorbent solution; The lean absorbent is subjected to two-stage cooling and splitting in sequence to obtain a split lean absorbent; A portion of the diverted lean solution is returned to the first absorber for recycling as the first lean solution. A portion of the diverted lean solution is returned to the first countercurrent contact reaction and recycled as the second lean solution.

11. The purification method according to claim 10, characterized in that, The second gas-liquid two-phase mixture is subjected to multi-stage flash evaporation to obtain a hydrogen sulfide-rich solution, including the following steps: The second gas-liquid two-phase mixture is subjected to a first-stage flash evaporation to obtain a first-stage flash vapor and a first-stage rich liquid. The third lean liquid is reacted with a portion of the first-stage flash vapor in a second countercurrent contact reaction to obtain the first absorbent liquid; The first absorbent and the first rich solution are mixed to obtain the second rich solution; The second rich liquid is subjected to two-stage depressurization and two-stage flash evaporation to obtain a second-stage flash vapor and a third rich liquid. The fourth lean liquid is subjected to a third countercurrent contact reaction with a portion of the second-stage flash vapor and the remaining first-stage flash vapor to obtain the second absorbent liquid; The second absorbent and the third enriched solution are mixed to obtain a fourth enriched solution; The fourth rich liquid is subjected to three stages of depressurization and three stages of flash evaporation to obtain three stages of flash vapor and the fifth rich liquid. The fifth lean liquid is subjected to a fourth countercurrent contact reaction with the remaining first-stage flash vapor, the remaining second-stage flash vapor, and all the third-stage flash vapor to obtain the third absorbent and tail gas. The third absorbent and the fifth rich solution are mixed to obtain a hydrogen sulfide-rich solution; Specifically, a portion of the depleted lean solution is returned to the second countercurrent contact reaction for reuse as the third lean solution; a portion of the depleted lean solution is returned to the third countercurrent contact reaction for reuse as the fourth lean solution; and the remaining depleted lean solution is returned to the fourth countercurrent contact reaction for reuse as the fifth lean solution.

12. The purification method according to claim 11, characterized in that, The temperature of the first-stage flash evaporation is 55°C to 75°C, the temperature of the second-stage flash evaporation is 65°C to 85°C, and the temperature of the third-stage flash evaporation is 75°C to 95°C. The pressure P3 of the third-stage flash evaporation is 0.15 MPa to 0.25 MPa, and the pressures P1 of the first-stage flash evaporation and P2 of the second-stage flash evaporation satisfy the following: P1 = (0.8 to 1.2) × r 2 ×P3, and P2 = (0.8 to 1.2) × r × P3, Equation 2, In Equation 2, r is the pressure drop coefficient, and r satisfies: P0 is the pressure of the second absorption; the units of P0, P1, P2 and P3 are all MPa.

13. The purification method according to claim 10 or 12, characterized in that, The pressure P0 of the second absorption satisfies: (Pw-0.3MPa)≤P0≤(Pw-0.1MPa), Equation 3, In Equation 3, Pw is the introduction pressure of the acidic gas containing hydrogen sulfide, and the unit is MPa.

14. The purification method according to claim 11, characterized in that, The volumetric flow rate of the first-stage flash vapor is 30 to 1000 times that of the third lean liquid; and / or The volumetric flow rate of the secondary flash vapor is 40 to 1250 times that of the volumetric flow rate of the fourth lean solution; and / or The volumetric flow rate of the third-stage flash vapor is 50 to 1500 times that of the fifth lean liquid.

15. The purification method according to claim 10, characterized in that, The temperature of the first absorption is 10°C to 50°C; and / or The temperature of the second absorption is 10°C to 50°C; and / or The temperature of the first countercurrent contact reaction is 10°C to 50°C.

16. The purification method according to claim 10, characterized in that, The secondary cooling includes a first cooling and a second cooling, with the endpoint temperature of the first cooling being 70°C to 95°C and the endpoint temperature of the second cooling being 15°C to 45°C.

17. The purification method according to claim 10, characterized in that, The separation includes rectification separation and stripping separation. The temperature of the rectification separation is 105°C to 115°C, and the pressure of the rectification separation is 150 kPa to 250 kPa. The temperature of the stripping separation is 115°C to 145°C.

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