Selective desulfurization absorbent, system and process for blast furnace gas with high carbon-sulfur ratio

Abstract

The invention relates to a selective desulfurization absorbent, system and process for blast furnace gas with a high carbon-sulfur ratio. The absorbent comprises a main agent and an additional additive accounting for 0.01-0.8% of the total mass of the main agent, the main agent comprises the following components in percentage by mass: 5-15% of an alcohol amine absorbent, 30-50% of a physical solvent, 25-45% of a catalytic promoter and the balance of water; wherein the physical solvent contains a sulfur-containing functional group or an ether-containing functional group; the catalytic promoter comprises a sterically hindered amine or a cyclic amine. According to the invention, the alkylol amine absorbent with stable performance is matched with the physical solvent with similar compatibility characteristics and the catalytic promoter with steric hindrance effect, and efficient dissolution, intraphase mass transfer and transfer hydrolysis of organic sulfur are remarkably promoted through a steric hindrance effect-group synergy action mechanism; a synergistic reaction path of dissolution-transfer-catalytic hydrolysis-chemical absorption is formed, so that the effects of selectively and highly desulfurizing and reducing the co-absorption amount of carbon are achieved, and the energy consumption of a subsequent process is favorably reduced.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection, and specifically relates to a selective desulfurization absorbent, system and process for blast furnace gas with a high carbon-to-sulfur ratio. Background Technology

[0002] In the iron and steel metallurgical industry, the coal-dominated energy structure and the long-process production structure result in high emissions of CO2 and sulfur pollutants. Blast furnace gas, as one of the main byproducts of ironmaking in steel enterprises, has a large output and complex composition, containing pollutants such as CO, CO2, and sulfides. CO2 emissions from the blast furnace ironmaking stage account for 73% of the total emissions from the entire long-process production, with CO2 concentrations in blast furnace gas typically ranging from 15% to 25%, making it a key area for carbon emission reduction in the steel industry. Blast furnace gas contains approximately 100 mg / m³ of CO2. 3 ~300 mg / m 3 The gas contains sulfides (mainly COS and H2S, with occasional trace amounts of CS2), of which inorganic sulfur (H2S) accounts for about 30%–40% and organic sulfur (COS) accounts for about 60%–70%, with a high carbon-to-sulfur ratio of about 1500–2500. COS removal from coal gas is a key challenge because COS is chemically stable and hardly reacts with water or conventional alkaline absorbents (such as alkanolamines) at room temperature and pressure. Industrially, it usually needs to be hydrolyzed into H2S before removal, which increases desulfurization costs.

[0003] Existing technologies such as "catalytic hydrolysis + dry adsorption" and "catalytic hydrolysis + N-methyldiethanolamine split process" suffer from problems such as long process flow, high investment, and complex operation. Chemical absorption methods have high desulfurization and decarbonization performance, especially in the effective catalytic removal of organic sulfur. However, the triple characteristics of blast furnace gas—high CO2 concentration, low total sulfur content, and high proportion of organic sulfur—lead to the following problems with traditional amine methods (such as MDEA) for desulfurization: 1) The large amount of co-absorption of CO2 significantly increases the load on the regeneration tower, resulting in high regeneration energy consumption; 2) It has virtually no ability to remove COS, making it impossible to achieve highly selective desulfurization and difficult to meet the ultra-low total sulfur emission requirement of ≤35mg / Nm³. 3 (Calculated as SO2); 3) Simultaneous strong absorption of CO2 and H2S, which is prone to "overload" under high CO2 background, resulting in a decrease in desulfurization efficiency.

[0004] Therefore, given the high carbon-to-sulfur ratio of steel gas and the limitations of existing organic amine desulfurization technology, there is an urgent need to develop a new type of absorbent with high selectivity for desulfurization, low carbonization, and compatibility with organic sulfur conversion, in order to achieve deep desulfurization and decarbonization in the steel industry, solve the "sulfur hazard" problem, enhance the resource value of coal gas, and ultimately promote the green and low-carbon transformation of the steel industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a selective desulfurization absorbent, system and process for high carbon-to-sulfur ratio blast furnace gas, solving the technical problems of high CO2 co-absorption rate and poor desulfurization effect of high carbon-to-sulfur ratio blast furnace gas in the prior art.

[0006] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: In a first aspect, the present invention provides a selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas, comprising a main agent and an additive comprising 0.01 to 0.8% of the total mass of the main agent; the main agent comprises, by mass percentage: 5 to 15% amine absorbent, 30 to 50% physical solvent, 25 to 45% catalytic aid, and the balance being water; wherein the physical solvent contains sulfur-containing functional groups or ether-containing functional groups; the catalytic aid comprises sterically hindered amines or cyclic amines.

[0007] Secondly, the present invention provides a selective desulfurization system for high carbon-to-sulfur ratio blast furnace gas, comprising an absorption unit, wherein the absorption unit includes a pretreatment tower, an absorption tower, and a water washing tower connected together; wherein the pretreatment tower is used for alkaline washing of blast furnace gas and discharges saturated wet gas; the absorption tower is used for countercurrent absorption and desulfurization of saturated wet gas through the above-mentioned selective desulfurization absorbent and discharges deacidified gas and amine-rich liquid; the water washing tower is used for capturing amine liquid droplets in deacidified gas and discharging desulfurized and decarbonized gas.

[0008] Thirdly, the present invention provides a selective desulfurization process for blast furnace gas with a high carbon-to-sulfur ratio, comprising the following steps: blast furnace gas is treated with alkali washing to obtain saturated wet gas; the saturated wet gas is subjected to countercurrent absorption desulfurization treatment by a selective desulfurization absorbent to obtain deacidified gas and amine-rich liquid; the deacidified gas is treated with water washing to discharge desulfurized and decarbonized gas.

[0009] Compared with the prior art, the beneficial effects of the present invention include: This invention's selective desulfurization absorbent utilizes a stable alkanolamine absorbent, combined with a physical solvent possessing similar compatibility properties and a steric hindrance catalyst to form a complex amine system. Through a "steric hindrance effect-group synergy" mechanism, it significantly promotes the efficient dissolution, intraphase mass transfer, and transfer hydrolysis of organic sulfur, forming a synergistic reaction pathway of dissolution-transfer-catalytic hydrolysis-chemical absorption. This absorbent overcomes the bottleneck of preferential CO2 absorption in traditional amine absorbents, efficiently solving the key problem of organic sulfur removal from steelmaking gas. It offers significant process simplification, efficiency improvement, and potential cost advantages, achieving selective high desulfurization while reducing carbon co-absorption, reaching a desulfurization rate of ≥86% and a decarbonization rate of 15-28%, which helps reduce energy consumption in subsequent desorption and other processes. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the system structure of the present invention; wherein, 1-Absorption unit; 101-Pretreatment tower, 102-Absorption tower, 103-Water washing tower, 104-First water washing circulation pump, 105-Interstage cooling pump, 106-Interstage cooling heat exchanger, 107-Second water washing circulation pump. 2-Desorption unit; 201-Amine liquid storage tank, 202-Rich liquid pump, 203-Rich and lean liquid heat exchanger, 204-Rich liquid heater, 205-Desorption tower, 206-Lean liquid pump, 207-Cooler, 208-Reboiler, 209-Circulation pump; 3-Separation unit; 301-Gas-liquid separator; 302-Dry desulfurization tower; 303-Dry desulfurization regeneration tower; 304-Regeneration gas cooler; 305-Condensate circulation pump. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0012] For blast furnace gas with extremely high carbon-to-sulfur ratios (1500-2500), this invention provides a selective desulfurization absorbent, system, and process for high carbon-to-sulfur ratio blast furnace gas. This absorbent is a novel composite absorbent with high selectivity amine-based desulfurization and low carbon dioxide desorption. By adjusting the absorbent formulation and matching it with an energy-saving capture process system, this invention enables the absorbent to achieve highly selective desulfurization (H2S, COS), low CO2 co-absorption rate, and low-energy regeneration in the blast furnace gas purification process. This solves the problems of high energy consumption and equipment redundancy in traditional step-by-step processing technologies, while also possessing high efficiency, economy, and environmental friendliness, promoting the green and low-carbon development of the steel industry. The high efficiency, synergy, and energy-saving characteristics of this technology make it promising for application in promoting carbon emission reduction and in-depth pollutant treatment in industries such as steel, coking, and coal chemicals, helping enterprises reduce overall environmental costs and achieve green and low-carbon development.

[0013] In a first aspect, the present invention provides a selective desulfurization absorbent for blast furnace gas with a high carbon-to-sulfur ratio, comprising a main agent and an additive accounting for 0.01 to 0.8% of the total mass of the main agent; By mass percentage, the main agent comprises: 5-15% amine absorbent, 30-50% physical solvent, 25-45% catalyst, and the balance being water; wherein the physical solvent contains sulfur-containing or ether-containing functional groups; the catalyst includes sterically hindered amines or cyclic amines.

[0014] Addressing the core characteristics of blast furnace gas—high CO2, low total sulfur, and predominantly organic sulfur—this invention develops a highly selective compound desulfurization absorbent suitable for blast furnace gas in the steel industry, especially for high C / S ratio blast furnace gas. This absorbent possesses the dual functions of efficient sulfide removal and synergistic decarbonization. The invention constructs a stable amine absorbent as the main absorbent component, combined with a physical solvent with similar compatibility and a steric hindrance catalyst to form a composite amine system. Through a steric hindrance effect-group synergy mechanism, it significantly promotes the efficient dissolution, intraphase mass transfer, and transfer hydrolysis of organic sulfur, forming a synergistic reaction pathway of dissolution-transfer-catalytic hydrolysis-chemical absorption. This absorbent overcomes the bottleneck of preferential CO2 absorption in traditional amine absorbents, efficiently solving the key problem of organic sulfur removal in steel industry gas. It offers significant process simplification, efficiency improvement, and potential cost advantages, and can be extended to similar scenarios such as coke oven gas and converter gas.

[0015] Preferably, the amine absorbent includes one or more of N-methyldiethanolamine, ethanolamine, N,N-diethylethanolamine, diethylethanolamine, diisopropanolamine, triisopropanolamine, and N-methylbenzylethanolamine, with N-methyldiethanolamine being more preferred.

[0016] The amine absorbent used in this invention has high thermal stability and intrinsic carbon-sulfur selectivity. Its absorption mechanism is mainly as follows: RNH + H2S RNH2 + + HS - (1) 2RNH +CO2 RNHCOONHR(2) Preferably, the physical solvent includes one or more of sulfolane, dimethyl sulfoxide, polyethylene glycol dimethyl ether, diethyl sulfoxide, diphenyl sulfide, tetrahydrothiophene, etc., with dimethyl sulfoxide being more preferred.

[0017] The physical solvent of this invention contains specific sulfur-containing or ether-containing functional groups (sulfone groups, thioether groups, etc.) with strong polar bonds. Through their own polarity and the special electronic structure of sulfur atoms, they form strong intermolecular forces with COS and H2S, such as dipole-dipole interactions, sulfur-sulfur specific interactions, and weak hydrogen bonds, thereby reducing the Gibbs free energy during the dissolution process and achieving efficient dissolution. The physical solvent of this invention accelerates the dissolution of sulfides, acts as a bridge, and promotes mass transfer of sulfides in the absorbent.

[0018] Preferably, the catalyst promoter includes one or more of 2-piperidine ethanol, 2-amino-2-methyl-1-propanol, morpholine, N-methylpiperazine, hydroxyethylpiperazine, aminoethylpiperazine, anhydrous piperazine, etc., with morpholine being more preferred.

[0019] The catalyst used in this invention is a sterically hindered amine or cyclic amine, which can catalyze the hydrolysis of COS. The mechanism of action is as follows: following the zwitterionic mechanism (COS + H₂O → CO₂ + H₂S), the lone pair electrons in the nitrogen atom of the catalyst molecule attack the C=O of COS, forming a thiocarbamate intermediate. Subsequently, the intermediate undergoes deprotonation and hydrolysis to generate H₂S and release the original amine. The strong basicity of the catalyst not only enables efficient COS hydrolysis but also absorbs CO₂ and H₂S in the reaction atmosphere, as well as the H₂S obtained from COS hydrolysis, achieving selective high desulfurization and low decarbonization.

[0020] Preferably, the added additives include antioxidants and defoamers.

[0021] Further preferred antioxidants include one or more of sodium sulfite, acetaldehyde oxime, ethylenediaminetetraacetic acid, tert-butylhydroquinone, chromium trioxide, N,N-diphenyl-p-phenylenediamine, copper acetate, and hydroquinone, with N,N-diphenyl-p-phenylenediamine being more preferred.

[0022] More preferably, the amount of antioxidant used accounts for 0.01 to 0.5% of the total mass of the main agent.

[0023] More preferably, the defoamer includes one or more of polydimethylsiloxane, dodecyl dimethylamine oxide, polysiloxane, aniline, stearylamine, polyoxyethylene-polyoxypropylene block copolymer, and triethylenetetramine, with polydimethylsiloxane being more preferred.

[0024] More preferably, the amount of defoamer used accounts for 0.001 to 0.3% of the total mass of the main agent.

[0025] Preferably, the preparation steps of the selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas include: dissolving the alkanolamine absorbent in water and mixing it evenly; adding a physical solvent and a catalytic aid under stirring conditions and mixing evenly; and then adding an external additive and mixing evenly to obtain the final product.

[0026] In a further preferred embodiment, the amine absorbent is dissolved in water and stirred for 5–30 min; after adding the additives, stirring is continued for 5–30 min to ensure that all components are fully mixed until the system is homogeneous and transparent.

[0027] Secondly, the present invention provides a selective desulfurization system for high carbon-to-sulfur ratio blast furnace gas, comprising an absorption unit 1, wherein the absorption unit 1 includes a pretreatment tower 101, an absorption tower 102, and a water washing tower 103 connected together; wherein, the pretreatment tower 101 is used for alkaline washing of blast furnace gas and discharges saturated wet gas; the absorption tower 102 is used for countercurrent absorption desulfurization of saturated wet gas using a selective desulfurization absorbent and discharges deacidified gas and amine-rich liquid; the water washing tower 103 is used for capturing amine liquid droplets in the deacidified gas and discharging desulfurized and decarbonized gas and dilute amine liquid.

[0028] In the present invention, by using a selective desulfurization absorbent, a desulfurization rate of ≥86% and a decarburization rate of 15 - 28% can be achieved.

[0029] In some embodiments, the absorption unit 1 further includes a first water wash circulation pump 104 for circulating and spraying the alkaline solution. The inlet end of the first water wash circulation pump 104 is connected to the lower part of the pretreatment tower 101, and the outlet end is connected to the upper part of the pretreatment tower 101.

[0030] In some embodiments, the absorption unit 1 further includes an inter-stage cooling pump 105 and an inter-stage cooling heat exchanger 106 for regulating the temperature of the entire absorption tower 102.

[0031] In some embodiments, the absorption unit 1 further includes a second water wash circulation pump 107 supporting the water wash tower 103 to wash the coal gas in circulation until a certain concentration is reached to form dilute amine solution. After the acid-removed coal gas captures the amine liquid droplets carried in the coal gas through the water wash tower 103, it becomes desulfurized and decarbonized coal gas and returns to the coal gas pipeline network for reuse. The dilute amine solution generated at the bottom of the tower is pumped back to the absorption tower 102 for recycling to control the amine consumption.

[0032] In the absorption section: The raw coal gas enters the pretreatment tower 101 and makes countercurrent contact with the circulated and sprayed alkaline solution. After removing the residual chloride ions and impurities in the coal gas through constant-temperature water washing, saturated wet coal gas is formed. The saturated wet coal gas discharged from the pretreatment tower 101 enters from the bottom of the absorption tower 102 and rises along the structured packing layer in the tower, making countercurrent contact mass transfer with the compound-type selective desulfurization absorbent sprayed from the top of the tower. The alkanolamine absorbent in the selective desulfurization absorbent used in the present invention has high thermal stability and intrinsic carbon-sulfur selectivity. The catalytic assistant hydrolyzes the difficult-to-absorb organic sulfur COS into H2S through dissolution and catalytic hydrolysis, and simultaneously completes the selective absorption of H2S, COS, and CO2. Through its cooperation, high-selectivity desulfurization and low decarburization are achieved, obtaining acid-removed coal gas and rich amine solution. To maintain the absorption efficiency, an inter-stage cooling pump 105 and an inter-stage cooling heat exchanger 106 are provided on the side line of the absorption tower 102 to cool the high-temperature lean amine solution in the middle and upper parts with circulating cooling water and then pump it to the middle and lower parts to maintain the temperature of the entire absorption tower within a suitable temperature range. The lean amine solution becomes rich amine solution after absorbing CO2 and sulfides in the saturated wet coal gas and enters the amine liquid storage tank 201 in the desorption unit 2.

[0033] Preferably, the selective desulfurization system of the present invention further includes a desorption unit 2 and a separation unit 3. The desorption unit 2 is used to desorb the rich amine solution to obtain regenerated lean amine solution and regenerated mixed gas. The regenerated lean amine solution is transported to the absorption tower 102 for recycling; the separation unit 3 is used to separate and recover the regenerated mixed gas.

[0034] In some embodiments, the desorption unit 2 includes a lean-rich liquid heat exchanger 203, a desorption tower 205, and a cooler 207. The lean-rich liquid heat exchanger 203 is used for heat exchange between the rich amine liquid and the regenerated lean amine liquid; the desorption tower 205 is used for desorption of the rich amine liquid; and the cooler 207 is used for cooling the regenerated lean amine liquid after heat exchange and sending it into the absorption tower 102.

[0035] In some embodiments, a heating device is provided at the bottom of the desorption tower 205, including but not limited to a reboiler.

[0036] Specifically, the desorption unit 2 includes an amine storage tank 201, a rich liquid pump 202, a lean-rich liquid heat exchanger 203, a rich liquid heater 204, a desorption tower 205, a lean liquid pump 206, a cooler 207, a reboiler 208, and a circulation pump 209. The amine storage tank 201 is connected to the first inlet of the lean-rich liquid heat exchanger 203 via the rich liquid pump 202. The first outlet of the lean-rich liquid heat exchanger 203 is connected to the upper inlet of the desorption tower 205 via the rich liquid heater 204. The top of the desorption tower 205 has an outlet for discharging the regenerated mixed gas. The bottom outlet of the desorption tower 205 is connected to the lower side wall inlet of the desorption tower 205 via the circulation pump 209 and the reboiler 208. The desorption tower 205 is connected to the second inlet of the lean-rich liquid heat exchanger 203 via the lean liquid pump 206. The second outlet of the lean-rich liquid heat exchanger 203 is connected to the upper inlet of the absorption tower 102 via the cooler 207.

[0037] In the desorption section: the rich amine solution, rich in COS, H2S, and CO2, is drawn by the rich solution pump 202 and successively preheated in multiple stages through the lean-rich solution heat exchanger 203 and the rich solution heater 204 to gradually increase its temperature. The heated rich amine solution enters from the top of the desorption tower 205 and flows downwards within the tower. A reboiler 208 is installed at the bottom of the tower to continuously supply heat, maintaining the temperature of the tower bottom and ensuring complete desorption of the acidic gases bound in the amine solution. The regenerated lean amine solution recovers heat through the lean-rich solution heat exchanger 203, is cooled by the cooler 207, and then sent to the absorption tower 102 for recycling.

[0038] In some embodiments, the separation unit 3 includes a gas-liquid separator 301, a dry desulfurization tower 302, and a dry desulfurization regeneration tower 303. The gas-liquid separator 301 is used to separate the cooled regeneration mixture into gas and liquid. The dry desulfurization tower 302 is used to perform dry desulfurization on the separated regeneration mixture to obtain purified CO2. The dry desulfurization regeneration tower 303 is used to regenerate the desulfurizing agent that is saturated with adsorption in the dry desulfurization tower 302.

[0039] In the separation section: the regenerated mixed gas desorbed from desorption tower 205 is a high-temperature acidic gas (mainly containing H2S, CO2, and water vapor). After preliminary cooling by regenerated gas cooler 304, it enters gas-liquid separator 301 for gas-liquid separation. The condensate is periodically returned to desorption tower 205 via condensate circulation pump 305 to maintain system water balance and recover amine components. After drying and dehydration, the regenerated mixed gas enters the dry desulfurization section. It first passes through dry desulfurization tower 302 filled with desulfurizing agent, where H2S is selectively adsorbed after sufficient reaction, thereby purifying CO2. The high-purity CO2 discharged from the top of dry desulfurization tower 303, after filtration and impurity removal, can be combined with converter injection steelmaking process to reduce coke and N2 / Ar usage or used to prepare high-value-added products, achieving resource recycling. To ensure continuous operation, dry desulfurization tower 302 and dry desulfurization regeneration tower 303 adopt a "two-tower switching" mode, achieving alternating operation. The adsorption-saturated desulfurizing agent is regenerated in the dry desulfurization regeneration tower 303 under high temperature and oxygen-containing atmosphere. The released elemental sulfur can be further recovered, and the desulfurizing agent can be recycled, thus achieving sustainable operation of the system. The specific desulfurizing agent is quite common, and any commercially available product can be used; no specific limitation is made here.

[0040] It is understood that in this invention, both the absorption tower and the regeneration tower are structured packed towers; the lean and rich liquid heat exchangers are plate heat exchangers; and the rich liquid heater is a shell-and-tube heater.

[0041] This invention enables efficient and selective integrated desulfurization and decarbonization in a high carbon-to-sulfur ratio atmosphere, reducing the cost of step-by-step desulfurization and decarbonization operations.

[0042] Thirdly, the present invention provides a selective desulfurization process for blast furnace gas with a high carbon-to-sulfur ratio, comprising the following steps: Blast furnace gas is treated with alkali to obtain saturated wet gas; Saturated wet coal gas is subjected to countercurrent absorption desulfurization treatment with a selective desulfurization absorbent to obtain deacidified coal gas and amine-rich liquid; The deacidified coal gas is treated with water to produce desulfurized and decarbonized coal gas.

[0043] Preferably, the carbon-to-sulfur ratio in the blast furnace gas is 500–5000, more preferably 1500–2500. It should be noted that the carbon-to-sulfur ratio mentioned in this invention refers to the volume ratio of CO2 to total sulfur in the blast furnace gas. In the selective desulfurization process of this invention, by using a selective desulfurization absorbent for countercurrent absorption desulfurization treatment, a high desulfurization rate can be maintained even under high CO2 interference.

[0044] Preferably, the amine-rich solution is in the range of 80-104. o C is desorbed to obtain regenerated lean amine solution and regenerated mixed gas; the regenerated lean amine solution is returned to the countercurrent absorption desulfurization treatment step for recycling.

[0045] The present invention will be further described in detail below through specific embodiments.

[0046] Example 1 A selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas, the preparation steps of which include: Weigh 10 kg of N-methyldiethanolamine and dissolve it in 20 kg of deionized water. Stir for 20 min until the mixture is homogeneous. Then, slowly add 40 kg of dimethyl sulfoxide and 30 kg of morpholine while continuously stirring until the mixture is homogeneous. Next, add 0.015 kg of N,N-diphenyl-p-phenylenediamine and 0.005 kg of polydimethylsiloxane to the mixture in sequence, and continue stirring for 20 min to ensure that all components are fully mixed until the system is homogeneous and transparent, thus obtaining the compound absorbent.

[0047] A selective desulfurization process for blast furnace gas with a high carbon-to-sulfur ratio includes the following steps: Step 1: Raw coal gas (23.5% CO2, 30 ppm H2S + 70 ppm COS) enters pretreatment tower 101, where it comes into countercurrent contact with the circulating alkaline solution (sodium hydroxide solution) and passes through 40... o After constant-temperature alkaline washing removes residual chloride ions and impurities from the coal gas, saturated wet coal gas is formed. This gas enters from the bottom of absorption tower 102 and rises along the structured packing layer inside the tower, where it mixes with the 40% saturated coal gas sprayed from the top of the tower. o C selective desulfurization absorbent forms a countercurrent contact mass transfer, and through the dissolution and catalytic hydrolysis of catalytic aids, it hydrolyzes the difficult-to-absorb organic sulfur COS into H2S. At the same time, it works together with other components in the selective desulfurization absorbent to selectively absorb H2S, COS and CO2, and obtain deacidified coal gas and amine-rich liquid.

[0048] Step 2: Remove acidic gases from 48 o The desulfurized and decarbonized coal gas passes through a water washing tower 103 to capture amine droplets, becoming desulfurized and decarbonized coal gas, which is then returned to the coal gas pipeline for reuse. The dilute amine solution produced at the bottom of the water washing tower 103 is pumped back to the absorption tower 102 for recycling, thus controlling amine consumption. To maintain absorption efficiency, an interstage cooling heat exchanger 106 is installed on the side of the absorption tower 102 to cool the upper and middle sections of the 46... o The high-temperature lean amine solution was cooled to 38°C by circulating cooling water. o After C, the gas is drawn into the lower part of the absorption tower to maintain the overall temperature of the absorption tower 102 within a suitable range. The lean amine, after absorbing CO2 and sulfides from the coal gas, becomes 44... o C-rich amine solution enters amine solution storage tank 201.

[0049] Step 3: The amine-rich solution, rich in COS, H2S, and CO2, is drawn by the rich solution pump 202 and preheated in multiple stages through the lean and rich solution heat exchanger 203 and the rich solution heater 204, gradually increasing the temperature to 90°C. oC. The heated amine-rich solution enters from the top of the desorption tower 205 and flows downwards within the tower. A reboiler 208 is installed at the bottom of the tower to continuously supply heat and maintain the bottom temperature of the desorption tower 205 at 103°C. o C, to ensure complete desorption of the acidic gases bound in the rich amine solution. The regenerated lean amine solution, after recovering heat via the lean-rich solution heat exchanger 203, is cooled to 40°C via the cooler 207. o C is transported to absorption tower 102 for recycling.

[0050] The 65% desorbed by the desorption tower 205 o The acidic regeneration mixture (mainly containing H2S, CO2 and water vapor) is initially cooled by the regeneration gas cooler 304 and then enters the gas-liquid separator 301 for gas-liquid separation. The condensate is periodically returned to the desorption tower 205 to maintain the system water balance and recover amine components.

[0051] Step 4: 35 o After being dried and dehydrated, the C-regenerated mixed gas enters the dry desulfurization section. It first passes through dry desulfurization tower 302, which is filled with desulfurizing agent. After sufficient reaction, H2S is selectively adsorbed, thereby purifying CO2. 30% CO2 is discharged from the top of dry desulfurization tower 302. o High-purity CO2, after filtration and impurity removal, can be combined with converter injection steelmaking processes to reduce the use of coke and N2 / Ar, or used to prepare high-value-added products, achieving resource recycling. To ensure continuous operation, the dry desulfurization tower 302 and the dry desulfurization regeneration tower 303 adopt a "two-tower switching" mode, achieving alternating operation. The adsorbed saturated desulfurizing agent is heated to 70°C in the dry desulfurization regeneration tower 303. o Regeneration is carried out under an oxygen-containing atmosphere (C), and the released elemental sulfur can be further recovered, allowing the desulfurizing agent to be recycled and reused, thereby achieving sustainable operation of the system.

[0052] Through desulfurization and decarbonization performance tests, it was found that under high carbon and low sulfur conditions, the selective desulfurization absorbent compounded in this invention can achieve a removal rate of 80% H2S, 95% COS and 28% CO2, while maintaining a total sulfur removal rate of 90%.

[0053] Example 2 Compared with Example 1, the only difference is that the ratio of absorbent remains unchanged, but the desorption temperature of desorption tower 205 is changed to 85°C. o C. Other steps and conditions are the same as in Example 1.

[0054] Using the same test conditions to evaluate the desulfurization and decarbonization performance, this example can achieve a 73% H2S removal rate, a 92% COS removal rate, and a 15% CO2 removal rate, while maintaining a total sulfur removal rate of 86%, meeting the ultra-low emission requirements of the steel industry.

[0055] Comparative Example 1 Compared with Example 1, the only difference is that the amount of morpholine in the absorbent is adjusted to 10 kg and the amount of water is adjusted to 40 kg (maintaining a total amount of 100 kg); the other steps and conditions are the same as in Example 1.

[0056] Using the same test conditions to evaluate the desulfurization and decarbonization performance, this example can achieve a 32% H2S removal rate, a 50% COS removal rate, and a 16% CO2 removal rate, while maintaining a total sulfur removal rate of 45%.

[0057] Comparative Example 2 Compared with Example 1, the only difference is that the amount of morpholine in the absorbent is adjusted to 20 kg and the amount of water is adjusted to 30 kg (maintaining a total amount of 100 kg); the other steps and conditions are the same as in Example 1.

[0058] Using the same test conditions to evaluate the desulfurization and decarbonization performance, this example can achieve a 40% H2S removal rate, a 60% COS removal rate, and an 18% CO2 removal rate, while maintaining a total sulfur removal rate of 54%.

[0059] Comparative Example 3 Compared with Example 1, the only difference is that the amount of dimethyl sulfoxide in the absorbent is adjusted to 20 kg and the amount of water is adjusted to 40 kg (maintaining a total amount of 100 kg); the other steps and conditions are the same as in Example 1.

[0060] Using the same test conditions to evaluate the desulfurization and decarbonization performance, this example can achieve a 56% H2S removal rate, a 68% COS removal rate, and a 25% CO2 removal rate, while maintaining a total sulfur removal rate of 65%.

[0061] Compared to Example 1, Example 2 used the same ratio of absorbent for absorption, at 85 o At the desorption temperature of C, good selective desulfurization performance can be achieved, significantly reducing regeneration energy consumption compared to conventional decarbonization absorbents. This demonstrates that lowering the desorption temperature in the system of this invention helps reduce CO2 absorption while having a relatively small impact on sulfides, thus achieving both high selective desulfurization and low decarbonization.

[0062] Compared to Example 1, reducing the content of the catalytic promoter morpholine in Comparative Examples 1 and 2 significantly reduced the desulfurization and decarbonization rates, indicating that morpholine is the main active component in the selective desulfurization absorbent. This is because morpholine is a secondary amine with active hydrogen atoms, enabling rapid absorption of H2S and CO2. The removal of COS involves physical dissolution, chemical absorption, and catalytic hydrolysis. COS is accelerated to dissolve via dimethyl sulfoxide, and then mass-transferred to morpholine for alkaline-catalyzed hydrolysis to H2S and CO2. The reduced morpholine content decreases the number of active sites for absorbing H2S and COS, as well as the number of alkaline sites for catalyzing COS, leading to a decrease in the absorption efficiency of acidic components. Simultaneously, the steric hindrance effect of morpholine's cyclic structure inhibits the binding of CO2 to alkaline sites, while its inhibitory effect on H2S is weak, which is beneficial for highly selective desulfurization and reduces the amount of carbon co-absorbed.

[0063] Compared to Example 1, Comparative Example 3, by reducing the dimethyl sulfoxide (DMSO) content, also decreased the absorption rates of H2S and CO2, particularly COS. This is because the sulfone group (-SO2-) of DMSO can form strong intermolecular forces with COS and H2S through electronic polarity and electron electronic structure characteristics, such as dipole-dipole interactions, sulfur-sulfur specific interactions, and weak hydrogen bonds. This reduces the Gibbs free energy of the dissolution process, achieving efficient dissolution and mass transfer. Low concentrations of DMSO will reduce the solubility of H2S and COS, especially COS, resulting in a lower COS content available for alkaline catalytic hydrolysis and thus a lower overall COS removal rate.

[0064] In summary, this invention promotes the dissolution and mass transfer of sulfides by designing physical solvents, combines them with cyclic amines that have steric hindrance effects to catalytically hydrolyze COS, inhibit CO2 and promote H2S absorption, and employs low-temperature desorption, thereby achieving low-energy consumption and highly selective desulfurization of blast furnace gas and reducing the operating costs of desulfurization in the steel industry.

[0065] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas, characterized in that, It includes the main agent and additives accounting for 0.01 to 0.8% of the total mass of the main agent; The main agent comprises, by mass percentage: 5-15% amine absorbent, 30-50% physical solvent, 25-45% catalyst, and the balance being water; The physical solvent contains sulfur-containing or ether-containing functional groups; the catalyst promoter includes sterically hindered amines or cyclic amines.

2. The selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas according to claim 1, characterized in that, The amine absorbent includes one or more of N-methyldiethanolamine, ethanolamine, N,N-diethylethanolamine, diethylethanolamine, diisopropanolamine, triisopropanolamine, and N-methylbenzylethanolamine.

3. The selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas according to claim 1, characterized in that, The physical solvent includes one or more of sulfolane, dimethyl sulfoxide, polyethylene glycol dimethyl ether, diethyl sulfoxide, diphenyl sulfide, and tetrahydrothiophene.

4. The selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas according to claim 1, characterized in that, The catalyst promoter includes one or more of 2-piperidine ethanol, 2-amino-2-methyl-1-propanol, morpholine, N-methylpiperazine, hydroxyethylpiperazine, aminoethylpiperazine, and anhydrous piperazine.

5. The selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas according to claim 1, characterized in that, The added additives include antioxidants and defoamers; The antioxidants include one or more of sodium sulfite, acetaldehyde oxime, ethylenediaminetetraacetic acid, tert-butylhydroquinone, chromium trioxide, N,N-diphenyl-p-phenylenediamine, copper acetate, and hydroquinone. The antioxidant is used at a concentration of 0.01% to 0.5% of the total mass of the main agent; The defoamer includes one or more of polydimethylsiloxane, dodecyl dimethylamine oxide, polysiloxane, aniline, stearylamine, polyoxyethylene-polyoxypropylene block copolymer, and triethylenetetramine; The amount of defoamer used accounts for 0.001 to 0.3% of the total mass of the main agent.

6. The selective desulfurization absorbent for high carbon-to-sulfur ratio blast furnace gas according to claim 1, characterized in that, The preparation steps of the selective desulfurization absorbent include: dissolving the alkanolamine absorbent in water and mixing it evenly; adding a physical solvent and a catalytic aid under stirring conditions and mixing evenly; and then adding an external aid and mixing evenly to obtain the absorbent.

7. A selective desulfurization system for high carbon-to-sulfur ratio blast furnace gas, characterized in that, The system includes an absorption unit, which comprises a pretreatment tower, an absorption tower, and a washing tower connected together; wherein, The pretreatment tower is used for alkaline washing of blast furnace gas and discharge of saturated wet gas. The absorption tower is used to perform countercurrent absorption and desulfurization of saturated wet coal gas using the selective desulfurization absorbent according to any one of claims 1-6, and to discharge deacidified coal gas and amine-rich liquid. The water washing tower is used to capture amine droplets in the deacidified coal gas and discharge the desulfurized and decarbonized coal gas and dilute amine liquid.

8. The selective desulfurization system for high carbon-to-sulfur ratio blast furnace gas according to claim 7, characterized in that, The absorption unit also includes an interstage cooling pump and an interstage cooling heat exchanger disposed on the side of the absorption tower for regulating the temperature of the absorption tower. The selective desulfurization system further includes a desorption unit and a separation unit. The desorption unit is used to desorb the rich amine liquid to obtain a regenerated lean amine liquid and a regenerated mixed gas. The regenerated lean amine liquid is transported to the absorption tower for recycling. The separation unit is used to separate and recover the regenerated mixed gas.

9. A selective desulfurization process for blast furnace gas with a high carbon-to-sulfur ratio, characterized in that, Includes the following steps: Blast furnace gas is treated with alkali to obtain saturated wet gas; The saturated wet coal gas is subjected to countercurrent absorption desulfurization treatment by the selective desulfurization absorbent according to any one of claims 1-6 to obtain deacidified coal gas and amine-rich liquid; The deacidified coal gas is treated with water to produce desulfurized and decarbonized coal gas.

10. The selective desulfurization process for high carbon-to-sulfur ratio blast furnace gas according to claim 9, characterized in that, The carbon-to-sulfur ratio in the blast furnace gas is 1500–2500; The amine-rich solution is at 80-104 o C is desorbed to obtain regenerated lean amine solution and regenerated mixed gas; the regenerated lean amine solution is returned to the countercurrent absorption desulfurization treatment step for recycling.

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