A system and process for treating a low concentration COS-containing acid gas

Abstract

The present application belongs to the technical field of acid gas treatment, and relates to a low-concentration acid gas containing COS treatment system and treatment process. The low-concentration acid gas containing COS treatment system comprises a selective oxidation unit, a Claus and hydrolysis unit and an absorption conversion unit. The acid gas to be treated is sequentially subjected to the selective oxidation unit, the Claus and hydrolysis unit and the absorption conversion unit, and finally achieves high desulfurization purification, and is suitable for the low-concentration acid gas sulfur recovery process in oil refining, coal chemical industry, petroleum chemical industry and natural gas processing production.

Description

Technical Field

[0001] This invention belongs to the field of acid gas treatment technology, and relates to a low-concentration acid gas treatment system and process containing COS, especially suitable for the recovery and treatment process of sulfur in low-concentration acid gas in oil refining, coal chemical, petrochemical and natural gas processing. Background Technology

[0002] Since the 1970s, and especially since the 1990s, with the sharp rise in international oil prices, the cost of petroleum-based chemical processes has increased significantly. This has led to a renewed focus on coal chemical technology, resulting in the resurgence of traditional coal chemical technologies and the emergence of numerous new ones. my country is also committed to developing its coal chemical industry, using coal as a raw material to produce methanol, synthetic ammonia, coal-to-oil, and olefins, among other energy sources, to alleviate pressure on oil and gas resources.

[0003] Traditional coal chemical plants typically generate two streams of acidic gas during production. One stream is regeneration gas from the low-temperature methanol washing process, with a hydrogen sulfide concentration generally between 20-30%, which is usually treated by sending it to a sulfur recovery unit. The other stream is stripping gas from the condensate of various separators, with a hydrogen sulfide concentration generally less than 3%, which cannot be directly introduced into a sulfur recovery unit. Currently, most companies treat this gas by burning it with flares and then directly releasing it into the atmosphere, causing serious environmental pollution. In addition, some small oil refineries and purification plants also emit low-concentration hydrogen sulfide waste gas as a byproduct. This low-concentration acidic gas often contains a certain amount of COS. Building large-scale sulfur recovery units is clearly unsuitable and impractical for recovering this type of low-concentration acidic gas. Therefore, the treatment of low-concentration acidic gas has become an unavoidable problem in the chemical industry.

[0004] Chinese patent CN103566754A discloses a method for recovering sulfur from low-concentration acidic gas. This method employs a catalytic hydrogenation reaction to hydrolyze organic sulfur in the acidic gas into inorganic sulfides. The inorganic sulfides are then catalytically oxidized back to sulfur. The resulting reaction gas is cooled and condensed to separate liquid sulfur. The tail gas after sulfur separation is then washed with an alcohol-containing washing solution from a low-temperature methanol wash to absorb residual sulfides, thus achieving sulfur recovery. However, this process requires an external supply of hydrogen for the hydrogenation process, and methanol is a toxic substance, necessitating strict equipment sealing requirements, which presents certain difficulties for operation and maintenance.

[0005] Chinese patent CN111821844A discloses a desulfurization process combining dry and wet oxidation. This method uses a combination of dry selective oxidation and wet oxidation to convert hydrogen sulfide into sulfur. The acidic gas containing hydrogen sulfide first undergoes dry selective oxidation, recovering over 90% of the sulfur as sulfur. The remaining portion is treated by wet oxidation, and the exhaust gas meets ultra-low emission requirements. However, this method cannot effectively treat COS in the acidic gas, and the process uses an alkaline solution containing a complexed iron catalyst as an absorbent, resulting in high chemical solvent consumption and difficulty in treating iron-containing wastewater.

[0006] Chinese patent CN109019524A discloses a sulfur recovery process for low-to-medium concentration acidic gas. The main equipment, along the flow direction of the acidic gas, includes a combustion furnace, a two-stage Claus reactor, a selective hydrogenation reduction reactor, a selective oxidation reactor, a circulating absorption unit, and a liquid sulfur tank, connected in series. The circulating absorption unit includes an absorption tower, and the circulating absorbent is an alkaline solution and / or a calcium-containing solution, with the main water source being the condensate from the steam contained in the process gas. However, this process is complex, has high construction and operating costs, suffers from severe corrosion, and generates waste alkaline solution, creating new pollution.

[0007] Chinese patent CN105293446A discloses a low-sulfur emission sulfur recovery process for low-concentration acidic gas. Low-concentration acidic gas with an H2S content of less than 5% is treated by a selective oxidation reactor and two adsorption desulfurization towers that can be connected in parallel to achieve desulfurization. However, this process requires frequent regeneration of the adsorbent in the adsorption towers, suffers from easy adsorbent loss, is complex to operate, and has high replacement costs. Furthermore, COS cannot be effectively converted in either the selective oxidation reactor or the adsorption towers, which will affect the exhaust gas emissions.

[0008] Chinese patent CN104138713A discloses a method, apparatus, and reactor for recovering sulfur from acidic gas. The method involves catalytic oxidation to convert inorganic sulfides in the acidic gas into sulfur, followed by catalytic hydrolysis to convert organic sulfur in the acidic gas into inorganic sulfides. Finally, a secondary catalytic oxidation reaction is used to oxidize the remaining inorganic sulfur in the reaction gas back into sulfur. The tail gas is then washed with methanol and / or water. However, this method relies on the regeneration process in the preceding low-temperature methanol wash stage, which is impractical for production plants without such a system. Furthermore, the low-temperature methanol wash operates at low temperatures, placing high demands on the materials used in the equipment and piping.

[0009] Therefore, developing a treatment system and process suitable for solving the problem of treating low-concentration acidic gases is of positive significance for the treatment and recovery of low-concentration acidic gases. Summary of the Invention

[0010] Therefore, the technical problem to be solved by the present invention is to provide a low-concentration acid gas treatment system containing COS. The treatment system can simultaneously treat H2S and COS and fully recover sulfur resources. It can be widely used in the low-concentration acid gas sulfur recovery process in oil refining, coal chemical, petrochemical and natural gas processing production.

[0011] The second technical problem to be solved by the present invention is to provide a process for treating low-concentration acidic gas containing COS. The process can solve the current problem of difficult treatment of low-concentration acidic gas, and simultaneously treat H2S and COS, and fully recover sulfur resources. It has the advantages of simple operation and strong adaptability.

[0012] To solve the above-mentioned technical problems, the present invention provides a low-concentration acid gas treatment system containing COS, comprising a selective oxidation unit, a Claus and hydrolysis unit, and an absorption and conversion unit connected by pipelines.

[0013] The selective oxidation unit includes a selective oxidation reactor, which is equipped with a selective oxidation catalyst for converting H2S in the acidic gas into elemental S.

[0014] The Claus and hydrolysis unit includes a secondary reactor, which is equipped with a catalyst that has both organic sulfur hydrolysis activity and Claus activity, for performing Claus and hydrolysis reactions on the generated process gas.

[0015] The absorption and conversion unit includes an absorption tower and a regeneration tower connected by pipelines. The absorption tower is equipped with a desulfurizing agent, which is used to convert H2S into elemental S through a liquid-phase Claus reaction and dissolve it in the desulfurizing agent. The resulting S-rich desulfurizing agent then enters the regeneration tower for oxidative regeneration.

[0016] Specifically, the selective oxidation catalyst includes a silica-based selective oxidation catalyst. Specifically, the selective oxidation reactor is filled with a silica-based selective oxidation catalyst; preferably, the silica-based selective oxidation catalyst is a selective oxidation-specific catalyst developed by the Research Institute of Sinopec Qilu Branch.

[0017] Preferably, the SiO2 content in the silica-based selective oxidation catalyst is 50%-90%.

[0018] Preferably, the amount of the silica-based selective oxidation catalyst filled should be based on the reactor volume and filled into the entire bed.

[0019] Specifically, the selective oxidation unit also includes pipeline connections:

[0020] An acid gas buffer tank, wherein the inlet of the acid gas buffer tank is connected to an acid gas inlet pipe, and the outlet of the acid gas inlet pipe is connected to a first air pipe.

[0021] The first preheater has its inlet and outlet connected to the first air pipeline, and its outlet is connected to the inlet of the selective oxidation reactor.

[0022] A primary condenser, the shell-side inlet of which is connected to the outlet of the selective oxidation reactor, and the shell-side outlet of which is connected to the Claus and hydrolysis unit.

[0023] Specifically, the catalyst that combines organic sulfur hydrolysis activity and Claus activity includes titanium oxide-based organic sulfur hydrolysis catalysts.

[0024] Preferably, the TiO2 content in the titanium oxide-based organic sulfur hydrolysis catalyst is 70%-95%.

[0025] Specifically, the preferred catalyst, possessing both organic sulfur hydrolysis activity and Claus activity, is the LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The LS-981G catalyst is a titanium oxide-based organic sulfur hydrolysis catalyst, exhibiting high catalytic activity for both the hydrolysis of organic sulfides and the Claus reaction of H2S with SO2, nearly reaching thermodynamic equilibrium. It is insensitive to O2 poisoning, has a slow hydrolysis deactivation rate, and maintains relatively stable organic sulfur hydrolysis activity throughout its service life.

[0026] The organic sulfur hydrolysis catalyst, which combines organic sulfur hydrolysis activity and Claus activity, has a hydrolysis activity greater than 99.5%.

[0027] Specifically, the Claus and hydrolysis unit also includes pipeline connections:

[0028] The second reheater has its inlet connected to the shell-side outlet of the first-stage condenser and its outlet connected to the inlet of the second-stage reactor.

[0029] A secondary condenser, wherein the shell-side inlet of the secondary condenser is connected to the outlet of the secondary reactor;

[0030] The exhaust gas cooler has its inlet connected to the shell-side outlet of the secondary condenser and its outlet connected to the gas inlet of the absorption tower.

[0031] Specifically, the desulfurizing agent uses high-boiling-point organic solvents and organic amines with strong antioxidant capabilities as solvents. The organic amines can react with H2S in the gas and accelerate the dissolution rate of SO2 into the liquid phase, thus completing the liquid-phase Claus reaction in the organic solvent.

[0032] Preferably, the desulfurizing agent is a compound organic solvent, comprising a main component and compound components;

[0033] The main components of the desulfurizing agent include at least one of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, or tert-butyldiglycolamine;

[0034] The desulfurizing agent comprises at least one of benzyl alcohol, phenylethanol, polyethylene glycol dimethyl ether, or polyethylene glycol methyl butyl ether.

[0035] Preferably, the mass ratio of the main component to the compound component is 60%-90%: 10%-40%.

[0036] Specifically, the absorption and conversion unit also includes pipeline connections:

[0037] A rich liquid pump is connected to the liquid outlet of the absorption tower and the liquid inlet of the regeneration tower, respectively.

[0038] A cooling separation tank, the inlet of which is connected to the liquid outlet of the regeneration tower, and the liquid outlet of which is connected to the liquid inlet of the absorption tower via a lean liquid pump;

[0039] A second air duct is connected to the gas inlet of the regeneration tower;

[0040] A circulating air separator is provided, the inlet of which is connected to the gas outlet of the regeneration tower, and the gas outlet of which is connected to a first air pipe.

[0041] The present invention also discloses a process for treating low-concentration acidic gases containing COS based on the aforementioned processing system, comprising the following steps:

[0042] (1) Selective oxidation treatment

[0043] The low-concentration acidic gas containing COS to be treated is mixed with air, and the resulting mixed gas is fed into the selective oxidation reactor. Under the action of the selective oxidation catalyst, most of the H2S is converted into elemental S. The process gas after the reaction is then fed into the Claus and hydrolysis unit for further treatment.

[0044] (2) Claus and hydrolysis treatment

[0045] The process gas is introduced into the secondary reactor, where a Claus reaction and a hydrolysis reaction occur under the action of a catalyst that has both organic sulfur hydrolysis activity and Claus activity. The sulfur-containing tail gas is then introduced into the absorption and conversion unit for treatment.

[0046] (3) Absorption and conversion treatment

[0047] The sulfur-containing tail gas is introduced into the absorption tower and comes into contact with the desulfurizing agent. The H2S in the sulfur-containing tail gas undergoes a liquid-phase Claus reaction in the solution to be converted into elemental S and dissolved in the desulfurizing agent. The resulting S-rich desulfurizing agent enters the regeneration tower and is oxidized and regenerated by introducing air.

[0048] Specifically, the process for treating low-concentration acidic gas containing COS includes the following steps:

[0049] (1) Selective oxidation treatment

[0050] The low-concentration acidic gas containing COS to be treated enters the acidic gas buffer tank through the acidic gas inlet pipe. After the liquid droplets are separated, the gas is mixed with the air input from the first air pipe to obtain a mixed gas. The mixed gas is preheated by the first preheater and then enters the selective oxidation reactor. Under the action of the selective oxidation catalyst, most of the H2S is converted into elemental S. The process gas output from the selective oxidation reactor enters the first-stage condenser for cooling and condensation to separate liquid sulfur.

[0051] (2) Claus and hydrolysis treatment

[0052] The process gas after separating the liquid sulfur is fed into the second reheater for reheating to the required temperature, and then into the secondary reactor. Under the action of the catalyst, which has both organic sulfur hydrolysis activity and Claus activity, Claus and hydrolysis reactions occur. The sulfur-containing tail gas enters the secondary condenser for cooling and condensation to separate the liquid sulfur.

[0053] (3) Absorption and conversion treatment

[0054] After the sulfur-containing tail gas is cooled, it enters the absorption tower and contacts the desulfurizing agent. The H2S in the sulfur-containing tail gas undergoes a liquid-phase Claus reaction in the solution to be converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the absorption tower, while the S-rich desulfurizing agent enters the regeneration tower and is oxidized and regenerated by air through the second air pipe. The regenerated desulfurizing agent enters the cooling separation tank from the regeneration tower, and the regenerated gas is returned to the absorption tower or returned to the first air pipe as the raw gas for the mixed gas. After the elemental S in the regenerated desulfurizing agent is cooled, sulfur crystals precipitate in the cooling separation tank, and the desulfurizing agent is returned to the absorption tower for recycling.

[0055] Specifically, in the process for treating low-concentration acidic gas containing COS, in step (1): the concentration of COS in the low-concentration acidic gas is less than 1000 mg / m³. 3 The H2S content is less than 5 v / v%.

[0056] In the mixed gas, the volume ratio of O2 to H2S is 0.5-0.8:1, preferably 0.6-0.8:1.

[0057] In the preheating step, the mixed gas is heated to 180℃-220℃; the preheated gas specifically refers to the gas that the mixed gas enters the first preheater and is heated to 180℃-220℃ by medium-pressure saturated steam, preferably 190℃-210℃.

[0058] The bed temperature of the selective oxidation reactor is controlled at 200℃-250℃, preferably 210℃-240℃.

[0059] The selected oxidation reactor is an isothermal reactor with built-in coils and a steam drum. It uses saturated hot water for heat exchange to remove the heat generated during the oxidation reaction and produce steam as a byproduct. The temperature of the reactor bed is adjusted by regulating the steam pressure produced by the steam drum. The temperature difference of the bed is within 15°C.

[0060] In the condensation step, the cooling temperature of the primary condenser is controlled at 140℃-160℃. The process gas from the selective oxidation reactor enters the primary condenser for cooling and liquid sulfur separation. Specifically, the process gas from the selective oxidation reactor is cooled to 140℃-160℃ by the primary condenser, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0061] The air flow rate is determined by the acid gas flow rate and the sulfur content of the acid gas as determined by analysis, based on the amount of oxygen required for the chemical reaction.

[0062] Within the selective oxidation reactor, O2 introduced by air, under the action of a selective oxidation catalyst, converts over 90% of the H2S in the acidic gas into elemental S, as follows:

[0063] Reaction equation: 2H₂S + O₂ = 2 / x Sx + H₂O;

[0064] Side reaction: 2H2S + O2 = 2SO2 + 2H2O.

[0065] The process gas contains H2S ≤ 0.6% (v) and SO2 ≤ 0.2% (v).

[0066] Specifically, in the COS-containing low-concentration acid gas treatment process, in step (2):

[0067] The secondary reactor undergoes Claus and hydrolysis reactions. Specifically, the secondary reactor is packed with a catalyst that exhibits both organic sulfur hydrolysis and Claus activity, and both COS hydrolysis and Claus reactions occur simultaneously within the reactor.

[0068] COS + H2O = CO2 + H2S;

[0069] 2H2S + SO2 = 3 / x Sx + 2H2O.

[0070] The reheating temperature of the second reheater is 190℃-230℃, preferably 200℃-220℃;

[0071] The bed temperature of the secondary reactor is controlled at 210℃-250℃, preferably 220℃-240℃;

[0072] The cooling temperature of the secondary condenser is 120℃-140℃; the sulfur-containing tail gas enters the secondary condenser for cooling and condensation separation of liquid sulfur. Specifically, the sulfur-containing tail gas of the secondary reactor is cooled to 120℃-140℃ by the secondary condenser, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0073] Specifically, in the COS-containing low-concentration acid gas treatment process, in step (3):

[0074] The absorption temperature of the absorption tower is 40℃-60℃;

[0075] The regeneration temperature of the regeneration tower is 50℃-70℃.

[0076] Specifically, after the sulfur-containing tail gas is cooled, it enters the bottom of the absorption tower and preferably comes into countercurrent contact with the desulfurizing agent. Specifically, after the sulfur-containing tail gas is cooled by the tail gas cooler, it enters the bottom of the absorption tower and comes into countercurrent contact with the desulfurizing agent from the liquid inlet at the top of the absorption tower.

[0077] The H2S in the sulfur-containing tail gas undergoes a liquid-phase Claus reaction in solution to be converted into elemental S, which dissolves in the desulfurizing agent. Specifically, the organic amines in the desulfurizing agent combine with H2S in the sulfur-containing tail gas to form protonated polysulfides. The polysulfides then undergo a liquid-phase Claus reaction with SO2 in the sulfur-containing tail gas to be converted into elemental S, which dissolves in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower. The reaction mechanism is as follows:

[0078] H2S + R3N = R3NH + HS-;

[0079] 2R3NH+·HS-+SO2=3S+2R3N+2H2O;

[0080] Overall reaction: 2H2S + SO2 = 2H2O + 3S.

[0081] The regenerated gas is returned to the bottom of the absorption tower and / or returned to the first air pipeline as the raw material gas for the mixed gas. Specifically, the regenerated gas at the top of the regeneration tower can either return to the bottom of the absorption tower to oxidize H2S in the sulfur-containing tail gas into elemental S, which is then dissolved in the desulfurizing agent, thereby increasing the S yield in the absorption tower; or it can be separated by the regenerated gas separator and returned to the first air pipeline as the raw material gas for the mixed gas, saving air consumption; or a portion can return to the bottom of the absorption tower and a portion can return to the first air pipeline as the raw material gas for the mixed gas.

[0082] The regenerated gas is mainly composed of air. Recycling the regenerated gas to the absorption tower and / or the first air pipeline for reuse can improve the S recovery rate in the absorption tower and save air consumption.

[0083] The element S in the regenerated desulfurizing agent is cooled and then crystallizes into sulfur in the cooling separation tank. The desulfurizing agent is returned to the absorption tower for recycling. Specifically, the molten sulfur in the regenerated desulfurizing agent is cooled and crystallized into sulfur, which is discharged from the bottom to recover the sulfur. The separated desulfurizing agent is pumped back to the upper part of the absorption tower for recycling.

[0084] The H2S content in the purified gas is less than 10 mg / m³. 3 COS content less than 5mg / m 3 .

[0085] The rich desulfurizing agent enters the regeneration tower and is oxidized and regenerated by air. Specifically, air enters the lower part of the regeneration tower through the second air pipe and comes into countercurrent contact with the rich desulfurizing agent from the liquid inlet at the upper part of the regeneration tower. The residual H2S in the rich desulfurizing agent is converted into elemental S under the action of O2 in the air and dissolved in the regenerated desulfurizing agent.

[0086] The term "rich desulfurizing agent" specifically refers to the liquid at the lower liquid outlet of the absorption tower where H2S remains.

[0087] The COS-containing low-concentration acidic gas treatment system of this invention includes a selective oxidation unit, a Claus and hydrolysis unit, and an absorption and conversion unit. The acidic gas to be treated sequentially passes through the selective oxidation unit, the Claus and hydrolysis unit, and the absorption and conversion unit to ultimately achieve high-level desulfurization and purification. Specifically, the selective oxidation unit uses a selected selective oxidation catalyst to convert most of the H2S into elemental S; the Claus and hydrolysis unit uses a catalyst with both organic sulfur hydrolysis activity and Claus activity, enabling simultaneous treatment of H2S and COS; the absorption and conversion unit uses a liquid-phase desulfurizing agent that allows H2S to undergo a liquid-phase Claus reaction in the desulfurizing agent to convert into elemental S, simultaneously achieving H2S removal and sulfur resource recovery. The processing system described in this invention can achieve dual treatment of H2S and COS in low-concentration acidic gas, and the obtained regenerated gas can be returned to the absorption tower or the selective oxidation reactor to realize closed-loop circulation and recovery of sulfur resources without secondary pollution. It achieves efficient desulfurization of low-concentration acidic gas and fully recovers sulfur resources in acidic gas. It can achieve efficient removal of COS and H2S from low-concentration acidic gas and has the advantages of simple process, few reactors, and low equipment investment. It is suitable for the low-concentration acidic gas sulfur recovery process in oil refining, coal chemical, petrochemical and natural gas processing production.

[0088] The low-concentration acidic gas treatment process containing COS described in this invention achieves high-level desulfurization and purification by sequentially passing the acidic gas to be treated through a selective oxidation unit, a Claus and hydrolysis unit, and an absorption and conversion unit. The process employs a selective oxidation catalyst and a Claus and hydrolysis bifunctional catalyst in sequence, enabling dual conversion of COS and H2S without the need for additional organic sulfur hydrolysis catalysts or complex catalyst gradations. At the end of the process, an organic desulfurization solvent is used to treat the sulfur-containing tail gas, removing H2S and generating elemental sulfur through a liquid-phase Claus reaction, increasing the total sulfur yield of the unit and reducing the regeneration gas load. This process effectively solves the problem of treating low-concentration acidic gas. The entire absorption and regeneration process generates no waste liquid, and the regeneration gas produced by the unit is returned to the system, achieving a closed-loop cycle of sulfur resources. It boasts high desulfurization efficiency, does not generate secondary pollution, and has the advantages of simple operation, strong adaptability, and safety and environmental protection. The H2S content in the purified gas treated by the process described in this invention is less than 10 mg / m³. 3 COS content less than 5mg / m 3 It has a high processing efficiency. Attached Figure Description

[0089] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0090] Figure 1This is a schematic diagram of the structure of the COS-containing low-concentration acid gas treatment system;

[0091] The reference numerals in the diagram are as follows: 1-Acid gas inlet pipe; 2-First air pipe; 3-Acid gas buffer tank; 4-First preheater; 5-Selective oxidation reactor; 6-First-stage condenser; 7-Second reheater; 8-Second-stage reactor; 9-Second-stage condenser; 10-Absorber; 11-Rich liquid pump; 12-Regeneration tower; 13-Second air pipe; 14-Cooling separation tank; 15-Lean liquid pump; 16-Purified gas exhaust pipe; 17-First liquid sulfur pipe; 18-Second liquid sulfur pipe; 19-Crystallized sulfur pipe; 20-Circulating air separator; 21-Tail gas cooler. Detailed Implementation

[0092] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0093] like Figure 1 The structure shown in this invention, a low-concentration acidic gas treatment system containing COS, includes a selective oxidation unit, a Claus and hydrolysis unit, and an absorption and conversion unit connected by pipelines. The acidic gas sequentially passes through the selective oxidation unit, the Claus and hydrolysis unit, and the absorption and conversion unit to ultimately achieve high-level desulfurization and purification. Specifically, the selective oxidation unit converts most of the H2S into elemental S; the Claus and hydrolysis unit uses a catalyst with both organic sulfur hydrolysis activity and Claus activity to simultaneously treat H2S and COS; and the absorption and conversion unit uses a liquid-phase desulfurizing agent that allows H2S to undergo a liquid-phase Claus reaction in the desulfurizing agent to convert into elemental S, simultaneously achieving H2S removal and sulfur resource recovery.

[0094] like Figure 1 The structure shown indicates that the selective oxidation unit comprises, in sequence, an acid gas inlet pipe 1, an acid gas buffer tank 3, a first preheater 4, a selective oxidation reactor 5, and a first-stage condenser 6, and is equipped with a first air pipe 2; wherein,

[0095] The acid gas inlet pipe 1 is used to input the acid gas to be treated into the system for separation of liquid droplets, and the acid gas inlet pipe 1 is connected to the inlet of the acid gas buffer tank 3;

[0096] After the first air pipe 2 is merged with the outlet pipe of the acid gas buffer tank 3, it is connected to the inlet of the first preheater 4 to preheat the mixture of air and acid gas; the first air pipe 2 is also connected to the gas outlet of the circulating air separator 20 set in the system.

[0097] The outlet of the first preheater 4 is connected to the inlet of the selective oxidation reactor 5; the outlet of the selective oxidation reactor 5 is connected to the shell-side inlet of the first-stage condenser 6; the shell-side outlet of the first-stage condenser 6 is connected to the inlet of the second reheater 7; and a first liquid sulfur pipeline 17 is also provided at the outlet of the first-stage condenser 6 for separating liquid sulfur.

[0098] like Figure 1 The structure shown includes a Claus hydrolysis unit comprising a second reheater 7, a secondary reactor 8, a secondary condenser 9, and a tail gas cooler 21 connected in sequence; wherein,

[0099] The outlet of the second reheater 7 is connected to the inlet of the secondary reactor 8 for reheating the process gas; the outlet of the secondary reactor 8 is connected to the shell-side inlet of the secondary condenser 9; the shell-side outlet of the secondary condenser 9 is connected to the inlet of the tail gas cooler 21; a second liquid sulfur pipeline 18 is also provided at the outlet of the secondary condenser 9 for outputting liquid sulfur; the outlet of the tail gas cooler 21 is connected to the gas inlet at the bottom of the absorption tower 10.

[0100] like Figure 1 The structure shown indicates that the absorption and conversion unit comprises an absorption tower 10, a rich liquor pump 11, a regeneration tower 12, a cooling separation tank 14, and a lean liquor pump 15, connected in sequence; wherein,

[0101] The liquid outlet at the bottom of the absorption tower 10 is connected to the liquid inlet at the top of the regeneration tower 12 via a rich liquid pump 11; a purified gas venting pipe 16 is provided at the top of the absorption tower 10 for venting purified gas; the second air pipe 13 is connected to the gas inlet at the bottom of the regeneration tower 12 for inputting air to regenerate the desulfurizer; and the regeneration tower 12 is equipped with a heating device.

[0102] The gas outlet at the top of the regeneration tower 12 is connected to the gas inlet at the bottom of the absorption tower 10; the gas outlet at the top of the regeneration tower 12 is connected to the inlet of the circulating air separator 20; the gas outlet of the circulating air separator 20 is connected to the first air pipe 2; the liquid outlet at the bottom of the regeneration tower 12 is connected to the inlet of the cooling separation tank 14; the liquid outlet of the cooling separation tank 14 is connected to the liquid inlet at the top of the absorption tower 10 via a lean liquid pump 15; and a crystallization sulfur pipeline 19 is also provided at the outlet of the cooling separation tank 14 for collecting crystallization sulfur.

[0103] Example 1

[0104] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 3v / v%, COS content 800mg / m³) from a natural gas purification plant. 3The processing of ) includes the following steps:

[0105] (1) The low-concentration acidic gas containing COS to be treated is separated into droplets in the acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is controlled to be 0.6. The mixed gas is heated to 190°C by medium-pressure saturated steam in the first preheater 4 and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch and the bed temperature is controlled to be 210°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The H2S content in the process gas exiting the selective oxidation reactor 5 is 0.3v / v% and the SO2 content is 0.1v / v%. The process gas is cooled to 140°C by the first-stage condenser 6 and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0106] (2) The process gas after separating liquid sulfur is reheated to 200°C in the second reheater 7 and then enters the secondary reactor 8. The secondary reactor 8 is filled with LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 220°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo Claus reaction to generate elemental S, and COS is hydrolyzed to generate CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 125°C by the secondary condenser 9. The generated elemental sulfur is condensed and separated and enters the liquid sulfur pool.

[0107] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (N-methylcyclohexylamine 70v / v% + benzyl alcohol 30v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in sufficient desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 40℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 60℃. The regenerated gas returns to the bottom of the absorption tower 10, and the regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent is returned to the upper part of the absorption tower 10 for recycling via the lean liquid pump 15.

[0108] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 3 mg / m³. 3 COS content is 2mg / m 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0109] Example 2

[0110] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 5v / v%, COS content 500mg / m³) from a natural gas purification plant. 3 The processing of ) includes the following steps:

[0111] (1) The low-concentration acidic gas containing COS to be treated is separated into droplets in the acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is controlled to be 0.6. The mixed gas is heated to 190°C by medium-pressure saturated steam in the first preheater 4 and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch and the bed temperature is controlled to be 210°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The H2S content in the process gas exiting the selective oxidation reactor 5 is 0.4v / v% and the SO2 content is 0.15v / v%. The process gas is cooled to 140°C by the first-stage condenser 6 and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0112] (2) The process gas after separating liquid sulfur is reheated to 200°C in the second reheater 7 and then enters the secondary reactor 8. The secondary reactor 8 is filled with LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 220°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo Claus reaction to generate elemental S, and COS is hydrolyzed to generate CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 125°C by the secondary condenser 9. The generated elemental sulfur is condensed and separated and enters the liquid sulfur pool.

[0113] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (triethanolamine 30v / v% + diisopropanolamine 50v / v% + phenylethanol 20v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in the desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 40℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 60℃. The regenerated gas returns to the first air pipeline 2 via the circulating air separator 20. The regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent returns to the upper part of the absorption tower 10 via the lean liquid pump 15 for recycling.

[0114] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 2 mg / m³. 3 COS content is 1 mg / m³ 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0115] Example 3

[0116] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 3v / v%, COS content 800mg / m³) from a natural gas purification plant. 3 The processing of ) includes the following steps:

[0117] (1) Low-concentration acidic gas containing COS is separated into droplets in acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is 0.7. This mixed gas is heated to 200°C by medium-pressure saturated steam in the first preheater 4, and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch, and the bed temperature is controlled at 220°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The process gas exiting the selective oxidation reactor 5 has an H2S content of 0.25 v / v% and an SO2 content of 0.07 v / v%. The process gas is cooled to 150°C by the first-stage condenser 6, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0118] (2) The process gas after liquid sulfur separation enters the second reheater 7 and is reheated to 205°C. Then it enters the secondary reactor 8, which is filled with the LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 230°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo a Claus reaction to produce elemental S, and COS is hydrolyzed to produce CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 130°C by the secondary condenser 9, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0119] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (diisopropanolamine 70v / v% + phenylethanol 30v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in the desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 45℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 60℃. The regenerated gas returns to the bottom of the absorption tower 10, and the regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent is returned to the upper part of the absorption tower 10 for recycling via the lean liquid pump 15.

[0120] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 4 mg / m³. 3 COS content is 3mg / m 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0121] Example 4

[0122] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 2v / v%, COS content 600mg / m³) from a natural gas purification plant. 3 The processing of ) includes the following steps:

[0123] (1) Low-concentration acidic gas containing COS is separated into droplets in acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is 0.7. This mixed gas is heated to 200°C by medium-pressure saturated steam in the first preheater 4, and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch, and the bed temperature is controlled at 220°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The process gas exiting the selective oxidation reactor 5 has an H2S content of 0.2 v / v% and an SO2 content of 0.05 v / v%. The process gas is cooled to 150°C by the first-stage condenser 6, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0124] (2) The process gas after liquid sulfur separation enters the second reheater 7 and is reheated to 205°C. Then it enters the secondary reactor 8, which is filled with the LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 230°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo a Claus reaction to produce elemental S, and COS is hydrolyzed to produce CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 130°C by the secondary condenser 9, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0125] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (N-methyldiethanolamine 70v / v% + phenylethanol 10v / v% + polyethylene glycol dimethyl ether 20v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in the desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 45℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 60℃. The regenerated gas returns to the first air pipeline 2 via the circulating air separator 20. The regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent returns to the upper part of the absorption tower 10 via the lean liquid pump 15 for recycling.

[0126] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 2 mg / m³. 3 COS content is 2mg / m 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0127] Example 5

[0128] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 4v / v%, COS content 400mg / m³) from a natural gas purification plant. 3 The processing of ) includes the following steps:

[0129] (1) Low-concentration acidic gas containing COS is separated into droplets in acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is 0.65. This mixed gas is heated to 205°C by medium-pressure saturated steam in the first preheater 4, and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch, and the bed temperature is controlled at 230°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The process gas exiting the selective oxidation reactor 5 has an H2S content of 0.3 v / v% and an SO2 content of 0.1 v / v%. The process gas is cooled to 145°C by the first-stage condenser 6, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0130] (2) The process gas after liquid sulfur separation enters the second reheater 7 and is reheated to 210°C. Then it enters the secondary reactor 8, which is filled with the LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 235°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo a Claus reaction to produce elemental S, and COS is hydrolyzed to produce CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 125°C by the secondary condenser 9, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0131] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (N-methyldiethanolamine 75v / v% + phenylethanol 15v / v% + polyethylene glycol dimethyl ether 20v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in the desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 50℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 65℃. Half of the regenerated gas is returned to the bottom of the absorption tower 10, and half is returned to the first air pipeline 2 via the circulating air separator 20. The regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent is returned to the upper part of the absorption tower 10 for recycling via the lean liquid pump 15.

[0132] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 3 mg / m³. 3 COS content is 1 mg / m³ 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0133] Example 6

[0134] like Figure 1 The processing system shown in this embodiment is used to process acidic gas (hydrogen sulfide content 4v / v%, COS content 900mg / m³) from a natural gas purification plant. 3 The processing of ) includes the following steps:

[0135] (1) Low-concentration acidic gas containing COS is separated into droplets in acidic gas buffer tank 3 and then mixed with air from the first air pipeline 2 to obtain a mixed gas. The volume ratio of O2 to H2S in the mixed gas is 0.65. This mixed gas is heated to 205°C by medium-pressure saturated steam in the first preheater 4, and then enters the selective oxidation reactor 5. The reactor is filled with the selective oxidation catalyst LS-03 developed by the Research Institute of Sinopec Qilu Branch, and the bed temperature is controlled at 230°C. Under the action of the selective oxidation catalyst, more than 90% of H2S in the acidic gas is converted into elemental S. The process gas exiting the selective oxidation reactor 5 has an H2S content of 0.3 v / v% and an SO2 content of 0.1 v / v%. The process gas is cooled to 145°C by the first-stage condenser 6, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0136] (2) The process gas after liquid sulfur separation enters the second reheater 7 and is reheated to 210°C. Then it enters the secondary reactor 8, which is filled with the LS-981G catalyst developed by the Research Institute of Sinopec Qilu Branch. The bed temperature is controlled at 235°C. Under the action of the catalyst, H2S and SO2 in the process gas undergo a Claus reaction to produce elemental S, and COS is hydrolyzed to produce CO2 and H2S. The sulfur-containing tail gas at the outlet of the secondary reactor 8 is cooled to 125°C by the secondary condenser 9, and the generated elemental sulfur is condensed and separated into the liquid sulfur pool.

[0137] (3) After the sulfur-containing tail gas is cooled by the tail gas cooler 21, it enters the absorption tower 10 and comes into countercurrent contact with the desulfurizing agent (N-methyldiethanolamine 70v / v% + polyethylene glycol dimethyl ether 30v / v%). The H2S and SO2 in the sulfur-containing tail gas undergo a liquid-phase Claus reaction in the desulfurizing agent and are converted into elemental S and dissolved in the desulfurizing agent. The purified gas is discharged from the top of the absorption tower 10 through the purified gas exhaust pipe 16. The absorption temperature of the absorption tower 10 is 50℃. The rich desulfurizing agent at the liquid outlet of the lower part of the absorption tower 10 enters the regeneration tower 12 and comes into countercurrent contact with the air from the second air pipe 13 for regeneration. The residual H2S in the rich desulfurizing agent is converted into elemental S and dissolved in the regenerated desulfurizing agent. The regeneration temperature of the regeneration tower 12 is 65℃. One-third of the regenerated gas is returned to the bottom of the absorption tower 10, and two-thirds is returned to the first air pipeline 2 via the circulating air separator 20. The regenerated desulfurizing agent enters the cooling separation tank from the bottom of the regeneration tower 12. After the element S is cooled down, sulfur crystals are precipitated in the cooling separation tank 14 and discharged from the bottom to recover the sulfur. The desulfurizing agent is returned to the upper part of the absorption tower 10 via the lean liquid pump 15 for recycling.

[0138] Testing revealed that the H2S content in the purified gas after treatment by the process described in this embodiment was 5 mg / m³. 3 COS content is 3mg / m 3 Therefore, the process can achieve the treatment and recovery of acidic gases containing low concentrations of COS.

[0139] Comparative Example 1

[0140] This comparative example uses a domestic dry desulfurization technology to treat hydrogen sulfide content of 4v / v% and COS content of 900mg / m³. 3 The acidic gas is treated by selectively removing H2S using a solid iron oxide desulfurizing agent. Its main active component is iron oxide. The iron oxide in the desulfurizing agent absorbs H2S and reacts as follows:

[0141] Fe2O3·H2O+3H2S→Fe2S3·H2O+3H2O;

[0142] The acidic gas containing H2S to be treated is passed through a reactor bed packed with iron oxide catalyst, and the above reaction occurs at atmospheric pressure, thereby removing H2S from the acidic gas.

[0143] However, this desulfurizing agent is a non-regenerative desulfurizing agent and cannot effectively remove organic sulfur from natural gas. After desulfurization using this process, the H2S content in the purified gas is 100 mg / m³. 3 The COS content is 880 mg / m³ 3 .

[0144] Comparative Example 2

[0145] This comparative scheme uses selective oxidation combined with dry adsorption to treat hydrogen sulfide content of 4v / v% and COS content of 900 mg / m³. 3 The acidic gas to be treated first undergoes a selective oxidation unit to oxidize most of the H2S to elemental S, and then the remaining H2S or SO2 in the gas is adsorbed by an adsorbent.

[0146] The final H2S content in the exhaust gas was 8 mg / m³. 3 COS content is 600mg / m³ 3 Furthermore, the device experienced adsorbent clogging after six months of operation, making operation complex and incurring significant replacement costs.

[0147] Comparative Example 3

[0148] The low-concentration acid gas removal process described in this comparative example is based on the attached... Figure 1 The acid gas is treated by the acid gas treatment system shown. The content of each component in the low-concentration acid gas to be treated is the same as in Example 1. The difference between the implementation method and Example 1 is that the secondary reactor 8 is filled with an alumina-based Claus catalyst, and the other processes are the same as in Example 1.

[0149] In this comparative scheme, the final H2S content in the purified gas is 10 mg / m³. 3 COS content is 400mg / m³ 3 .

[0150] Comparative Example 4

[0151] The low-concentration acid gas removal process described in this comparative example is based on the attached... Figure 1 The acid gas is treated by the acid gas treatment system shown. The content of each component in the low concentration acid gas to be treated is the same as in Example 2. The difference between the implementation method and Example 2 is that the absorption temperature of the absorption tower 10 is 100°C, the regenerated gas is not returned to the system through the circulating air separator, and is discharged after being combined with the purified gas. Other processes are the same as in Example 2.

[0152] In this comparative scheme, the final H2S content in the exhaust gas is 100 mg / m³. 3 COS content is 3mg / m 3 .

[0153] In summary, the processing technology described in this invention can effectively treat acidic gases with low concentrations of COD and achieve sulfur recovery.

[0154] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A low-concentration acidic gas treatment system containing COS, characterized in that, This includes a selective oxidation unit with pipeline connections, a Claus and hydrolysis unit, and an absorption and conversion unit; The selective oxidation unit includes a selective oxidation reactor (5), which is provided with a selective oxidation catalyst for converting H2S in the acid gas into elemental S. The Claus and hydrolysis unit includes a secondary reactor (8), which is equipped with a catalyst that has both organic sulfur hydrolysis activity and Claus activity, for performing Claus and hydrolysis reactions on the generated process gas. The absorption and conversion unit includes an absorption tower (10) and a regeneration tower (12) connected by pipelines. The absorption tower (10) is equipped with a desulfurizing agent, which is used to convert H2S into element S through a liquid-phase Claus reaction and dissolve it in the desulfurizing agent. The resulting S-rich desulfurizing agent then enters the regeneration tower (12) for oxidation and regeneration. The selective oxidation unit further includes pipeline connections: An acid gas buffer tank (3) is provided, the inlet of which is connected to an acid gas inlet pipe (1), and the outlet of which is connected to a first air pipe (2). The inlet of the first preheater (4) is connected to the outlet of the acid gas inlet pipe (1) and the first air pipe (2). The outlet of the first preheater (4) is connected to the inlet of the selective oxidation reactor (5). A primary condenser (6) is provided, with its shell-side inlet connected to the outlet of the selective oxidation reactor (5) and its shell-side outlet connected to the Claus and hydrolysis unit. The Claus and hydrolysis unit also includes pipeline connections: The inlet of the second reheater (7) is connected to the shell-side outlet of the first-stage condenser (6), and the outlet of the second reheater (7) is connected to the inlet of the second-stage reactor (8). A secondary condenser (9) is provided, the shell-side inlet of which is connected to the outlet of the secondary reactor (8); The exhaust gas cooler (21) has its inlet connected to the shell-side outlet of the secondary condenser (9) and its outlet connected to the gas inlet of the absorption tower (10).

2. The low-concentration acidic gas treatment system containing COS according to claim 1, characterized in that, The selective oxidation catalyst includes a silica-based selective oxidation catalyst.

3. The low-concentration acidic gas treatment system containing COS according to claim 1 or 2, characterized in that, The catalysts that combine organic sulfur hydrolysis activity and Claus activity include titanium oxide-based organic sulfur hydrolysis catalysts.

4. The low-concentration acid gas treatment system containing COS according to any one of claims 1-2, characterized in that, The desulfurizing agent is a compound organic solvent, comprising a main component and compound components; The main components of the desulfurizing agent include at least one of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, or tert-butyldiglycolamine; The desulfurizing agent comprises at least one of benzyl alcohol, phenylethanol, polyethylene glycol dimethyl ether, or polyethylene glycol methyl butyl ether. The mass ratio of the main component to the compound component is 60%-90%: 10%-40%.

5. The low-concentration acidic gas treatment system containing COS according to claim 3, characterized in that, The desulfurizing agent is a compound organic solvent, comprising a main component and compound components; The main components of the desulfurizing agent include at least one of N-methylcyclohexylamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, or tert-butyldiglycolamine; The desulfurizing agent comprises at least one of benzyl alcohol, phenylethanol, polyethylene glycol dimethyl ether, or polyethylene glycol methyl butyl ether. The mass ratio of the main component to the compound component is 60%-90%: 10%-40%.

6. The low-concentration acid gas treatment system containing COS according to any one of claims 1-2, characterized in that, The absorption and conversion unit also includes pipeline connections: A rich liquid pump (11) is connected to the liquid outlet of the absorption tower (10) and the liquid inlet of the regeneration tower (12), respectively. Cooling separation tank (14), the inlet of which is connected to the liquid outlet of the regeneration tower (12), and the liquid outlet of which is connected to the liquid inlet of the absorption tower (10) via a lean liquid pump (15). The second air duct (13) is connected to the gas inlet of the regeneration tower (12); A circulating air separator (20) is provided, the inlet of which is connected to the gas outlet of the regeneration tower (12), and the gas outlet of which is connected to the first air pipe (2).

7. The low-concentration acidic gas treatment system containing COS according to claim 3, characterized in that, The absorption and conversion unit also includes pipeline connections: A rich liquid pump (11) is connected to the liquid outlet of the absorption tower (10) and the liquid inlet of the regeneration tower (12), respectively. Cooling separation tank (14), the inlet of which is connected to the liquid outlet of the regeneration tower (12), and the liquid outlet of which is connected to the liquid inlet of the absorption tower (10) via a lean liquid pump (15). The second air duct (13) is connected to the gas inlet of the regeneration tower (12); A circulating air separator (20) is provided, the inlet of which is connected to the gas outlet of the regeneration tower (12), and the gas outlet of which is connected to the first air pipe (2).

8. The low-concentration acidic gas treatment system containing COS according to claim 4, characterized in that, The absorption and conversion unit also includes pipeline connections: A rich liquid pump (11) is connected to the liquid outlet of the absorption tower (10) and the liquid inlet of the regeneration tower (12), respectively. Cooling separation tank (14), the inlet of which is connected to the liquid outlet of the regeneration tower (12), and the liquid outlet of which is connected to the liquid inlet of the absorption tower (10) via a lean liquid pump (15). The second air duct (13) is connected to the gas inlet of the regeneration tower (12); A circulating air separator (20) is provided, the inlet of which is connected to the gas outlet of the regeneration tower (12), and the gas outlet of which is connected to the first air pipe (2).

9. The low-concentration acidic gas treatment system containing COS according to claim 5, characterized in that, The absorption and conversion unit also includes pipeline connections: A rich liquid pump (11) is connected to the liquid outlet of the absorption tower (10) and the liquid inlet of the regeneration tower (12), respectively. Cooling separation tank (14), the inlet of which is connected to the liquid outlet of the regeneration tower (12), and the liquid outlet of which is connected to the liquid inlet of the absorption tower (10) via a lean liquid pump (15). The second air duct (13) is connected to the gas inlet of the regeneration tower (12); A circulating air separator (20) is provided, the inlet of which is connected to the gas outlet of the regeneration tower (12), and the gas outlet of which is connected to the first air pipe (2).

10. A process for treating low-concentration acidic gas containing COS based on the processing system according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Selective oxidation treatment The low-concentration acidic gas containing COS to be treated is mixed with air, and the resulting mixed gas is fed into the selective oxidation reactor (5). Under the action of the selective oxidation catalyst, most of the H2S is converted into elemental S. The process gas after the reaction is then fed into the Claus and hydrolysis unit for treatment. (2) Claus and hydrolysis treatment The process gas is introduced into the secondary reactor (8), where a Claus and hydrolysis reaction occurs under the action of a catalyst that has both organic sulfur hydrolysis activity and Claus activity. The sulfur-containing tail gas is then introduced into the absorption and conversion unit for treatment. (3) Absorption and conversion treatment The sulfur-containing tail gas is introduced into the absorption tower (10) and comes into contact with the desulfurizing agent. The H2S in the sulfur-containing tail gas undergoes a liquid-phase Claus reaction in the solution to be converted into elemental S and dissolved in the desulfurizing agent. The resulting S-rich desulfurizing agent enters the regeneration tower (12) and is oxidized and regenerated by introducing air.

11. The process for treating low-concentration acidic gas containing COS according to claim 10, characterized in that, Includes the following steps: (1) Selective oxidation treatment The low-concentration acidic gas containing COS to be treated enters the acidic gas buffer tank (3) through the acidic gas inlet pipe (1). After the liquid droplets are separated, the gas is mixed with the air input from the first air pipe (2) to obtain a mixed gas. The mixed gas is preheated by the first preheater (4) and then enters the selective oxidation reactor (5). Under the action of the selective oxidation catalyst, most of the H2S is converted into elemental S. The process gas output from the selective oxidation reactor (5) enters the first-stage condenser (6) for cooling and condensation to separate liquid sulfur. (2) Claus and hydrolysis treatment The process gas after separating the liquid sulfur is fed into the second reheater (7) for reheating to the required temperature, and then into the secondary reactor (8). Under the action of the catalyst which has both organic sulfur hydrolysis activity and Claus activity, Claus and hydrolysis reactions occur. The sulfur-containing tail gas enters the secondary condenser (9) for cooling and condensation to separate the liquid sulfur. (3) Absorption and conversion treatment After the sulfur-containing tail gas is cooled, it enters the absorption tower (10) and comes into contact with the desulfurizing agent. The H2S in the sulfur-containing tail gas undergoes a liquid-phase Claus reaction in the solution and is converted into element S and dissolved in the desulfurizing agent. The purified gas is discharged from the absorption tower (10), and the S-rich desulfurizing agent enters the regeneration tower (12) and is oxidized and regenerated by air through the second air pipe (13). The regenerated desulfurizing agent enters the cooling separation tank (14) from the regeneration tower (12), and the regenerated gas is returned to the absorption tower (10) or returned to the first air pipe (2) as the raw gas for the mixed gas. After the element S in the regenerated desulfurizing agent is cooled, sulfur crystals are precipitated in the cooling separation tank (14), and the desulfurizing agent is returned to the absorption tower (10) for recycling.

12. The process for treating low-concentration acidic gas containing COS according to claim 10 or 11, characterized in that: In step (1): In the low-concentration acidic gas, the concentration of COS is less than 1000 mg / m³. 3 H2S content less than 5v / v% In the mixed gas, the volume ratio of O2 to H2S is 0.5-0.8:1; In the preheating step, the mixed gas is controlled to be heated to 180℃-220℃; The bed temperature of the selective oxidation reactor is controlled at 200℃-250℃; In the condensation step, the cooling temperature of the first-stage condenser is controlled to be 140℃-160℃; In step (2): The reheating temperature of the second reheater (7) is 190℃-230℃; The bed temperature of the secondary reactor (8) is controlled at 210℃-250℃; The cooling temperature of the secondary condenser (9) is 120℃-140℃; In step (3): The absorption temperature of the absorption tower (10) is 40℃-60℃; The regeneration temperature of the regeneration tower (12) is 50℃-70℃.

Images