A composite absorbent, method, and system for capturing carbon dioxide.

Abstract

This invention discloses a composite absorbent, method, and system for capturing carbon dioxide. Based on a total weight of 100 parts, the composite absorbent comprises the following components in parts by weight: main absorbent: 10-30 parts, potassium carbonate and / or potassium bicarbonate; tertiary amine buffer salt: 8-20 parts, at least one of N,N-di(hydroxyethyl)glycine and tris(hydroxymethyl)methylglycine; compound corrosion inhibitor: 0.3-1 parts, comprising an organic corrosion inhibitor, a spatiotemporally complementary corrosion inhibitor, and a chloride ion complexing agent; stabilizer: 0.01-0.05 parts, composed of an antioxidant and a chelating agent; bactericide: 0.01-0.05 parts; defoamer: 0-0.01 parts; water: balance; the organic corrosion inhibitor comprises long-chain dicarboxylic acids, oxalate salts, benzoates, and benzotriazoles; the spatiotemporally complementary corrosion inhibitor is a mixture of vanadate and molybdate; and the chloride ion complexing agent is a cerium salt. The composite absorbent of this invention can significantly reduce energy consumption and overall costs when used for CO2 recovery.

Description

Technical Field

[0001] This invention relates to the field of carbon capture, utilization and storage (CCUS) technology, and in particular to a composite absorbent, method and system for capturing carbon dioxide. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) technology is a key means of reducing industrial carbon emissions. Traditional carbon capture technologies, such as the ethanolamine method (MEA) and the hot potassium carbonate method, suffer from problems such as high regeneration energy consumption (>120℃), severe equipment corrosion, and easy solvent degradation. Although the Tris-potassium carbonate system, which has emerged in recent years, has reduced the regeneration temperature to around 60℃, Tris, as a primary amine, still faces the risk of oxidative degradation during long-term operation, with an annual degradation rate of 2-5%, and its pH response characteristics need to be optimized for compatibility with the carbonate system.

[0003] Existing buffer salt systems still have shortcomings in long-term chemical stability, pH response accuracy, and equipment corrosion resistance, resulting in high operation and maintenance costs for carbon capture systems. Therefore, there is a need to develop a more stable, efficient, and longer-lasting carbon capture solution.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a composite absorbent, method, and system for capturing carbon dioxide that has better thermal response stability, longer cycle life, and lower corrosivity.

[0006] The present invention adopts the following technical solution: In a first aspect, a composite absorbent for capturing carbon dioxide is provided. Based on a total weight of 100 parts, the composite absorbent comprises the following components in parts by weight: main absorbent: 10-30 parts; tertiary amine buffer salt: 8-20 parts; compound corrosion inhibitor: 0.3-1 part; stabilizer: 0.01-0.05 parts; bactericide: 0.01-0.05 parts; defoamer: 0-0.01 parts; water: balance; the main absorbent is potassium carbonate and / or potassium bicarbonate; the tertiary amine buffer salt is N,N-di( The compound corrosion inhibitor comprises at least one of (hydroxyethyl)glycine (Bicine) and (tris(hydroxymethyl)methylglycine) (Tricine); the compound corrosion inhibitor comprises an organic corrosion inhibitor, a spatiotemporally complementary corrosion inhibitor, and a chloride ion complexing agent; wherein the organic corrosion inhibitor comprises long-chain dicarboxylic acids, oxalate salts, benzoates, and benzotriazoles; the spatiotemporally complementary corrosion inhibitor is a mixture of vanadate and molybdate; the chloride ion complexing agent is a cerium salt; the stabilizer is composed of an antioxidant and a chelating agent, used to inhibit the oxidative decomposition of the tertiary amine buffer salt.

[0007] In a second aspect, a method for capturing carbon dioxide using the composite absorbent described in the first aspect is provided, comprising the following steps: an absorption step: at a temperature of 0-40°C, industrial tail gas containing carbon dioxide is contacted with the composite absorbent to carry out a carbon dioxide absorption reaction, thereby obtaining a rich solution; a regeneration step: the rich solution is heated to 60-90°C to desorb and release the carbon dioxide absorbed in the rich solution, thereby obtaining a lean solution and carbon dioxide gas; and a recycling step: the lean solution is cooled and used as a circulating absorbent, which is then returned to the absorption step for recycling.

[0008] Thirdly, a carbon dioxide capture system is provided for implementing the method described in the second aspect, comprising: an absorption unit for contacting industrial exhaust gas with a composite absorbent to absorb carbon dioxide, resulting in a rich solution; a regeneration unit connected to the absorption unit for receiving and heating the rich solution from the absorption unit to desorb carbon dioxide, resulting in a lean solution and carbon dioxide gas; and an absorbent circulation and regulation unit connected to both the absorption unit and the regeneration unit for receiving the lean solution from the regeneration unit and, after regulation, returning it to the absorption unit for utilization.

[0009] The composite absorbent provided by this invention exhibits superior thermal response stability, longer cycle life, and lower corrosivity. Using this composite absorbent for CO2 recovery can significantly reduce carbon capture energy consumption and overall costs. Specifically, this invention has the following beneficial effects: 1. Achieved ultra-low energy consumption carbon dioxide capture: By using tertiary amine buffer salts (Bicine / Tricine) as the core component, which possess suitable temperature sensitivity (Bicine pKa≈8.35 at 25°C, temperature sensitivity ΔpKa / °C ≈ -0.018; Tricine pKa≈8.05 at 25°C, temperature sensitivity ΔpKa / °C ≈ -0.021), effective "thermally controlled pH swing" can be achieved under mild conditions of 60-90°C. (Thermally controlled pH swing refers to using temperature changes to drive the solution pH value to periodically swing between acidic and alkaline ranges, thereby achieving a "buffering-releasing" cycle of CO2, achieving the purpose of absorbing carbon dioxide at low temperatures and releasing carbon dioxide at high temperatures; and with the addition of tertiary amine buffer salts, the pH fluctuation range during the entire cycle is significantly narrowed, maintaining a pH value >7), driving the desorption of carbon dioxide. Compared with the traditional amine method requiring regeneration temperatures above 120°C, this significantly reduces regeneration energy consumption, down to 2.8-3.2 GJ / ton CO2. Meanwhile, controlling the regeneration temperature within a mild range of 60-90℃ can better adapt to low-grade industrial waste heat (such as power plant circulating water, data center heat dissipation, and flue gas recovery heat), achieving a regeneration process with almost "zero external steam purchase".

[0010] 2. Excellent long-term chemical stability: The chemical structure of tertiary amine buffer salts (tertiary amines) is more stable than that of primary amines (such as Tris), making them less susceptible to oxidative and microbial degradation. With the use of stabilizers, the annual degradation rate can be controlled to <1%, far lower than the 2-5% of the Tris system, significantly extending the service life of the composite absorbent and reducing maintenance costs.

[0011] 3. Achieves highly efficient equipment corrosion protection: Through a multi-layer synergistic corrosion inhibition system composed of organic corrosion inhibitors, spatiotemporally complementary corrosion inhibitors, and chloride ion complexing agents, an effective protective film can be formed on the surface of carbon steel equipment, controlling the uniform corrosion rate to below 0.08 mm / year, resulting in lower equipment investment (carbon steel can be used) and higher long-term reliability.

[0012] 4. Provides more precise process control: The pKa values ​​of Bicine and Tricine can be more precisely matched with the carbonate (and / or bicarbonate) buffer system, allowing the initial pH of the solution to be set higher (8.0-11.5) during the absorption phase (0-40°C), thereby obtaining a higher CO2 absorption capacity. During the regeneration phase (60-90°C), the pH value rises from 7.0-8.0, resulting in a stronger and more thorough regeneration drive. This more precise matching makes the pH control of the absorption and regeneration processes more tolerant and stable, improving the reliability and efficiency of the process operation, and is more conducive to large-scale industrial production and long-term stable operation.

[0013] 5. Wide industrial adaptability: The Bicine and Tricine structures have better tolerance to common flue gas impurities such as Cl⁻ and SO2, and the chloride ion complexing agent (cerium salt) can effectively inhibit pitting corrosion. Therefore, this composite absorbent has strong resistance to impurity interference and can treat industrial flue gas containing complex components such as Cl⁻ and SO2. It can be directly adapted to existing wet scrubbing equipment to achieve "plug and play" transformation and upgrading.

[0014] 6. Obtaining high-purity CO2 products: The regenerated CO2 gas has a purity of up to 99.5%, which can be directly used for chemical synthesis (such as the preparation of soda ash, ammonium bicarbonate, nano calcium carbonate, etc.), eliminating the expensive secondary distillation or purification process in traditional processes; at the same time, the high-purity CO2 produced by this invention can be coupled with the production of downstream high-value-added chemical products such as carbonates, ammonium bicarbonate, soda ash, formic acid, and oxalamide, transforming "carbon emissions" into "carbon assets" and forming a green circular economy model of "carbon capture-utilization-resource recovery".

[0015] This invention not only reduces the cost of carbon capture throughout its entire life cycle, but also builds a green and profitable industrial chain from industrial exhaust gas to high-value carbon products, applicable to carbon reduction transformation of high-carbon emission industries such as power plants, steel, cement, and chemicals. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the carbon dioxide capture system in Embodiment 3 of the present invention.

[0017] Figure 2 This is a detailed schematic diagram of the carbon dioxide capture system in Embodiment 3 of the present invention. Detailed Implementation

[0018] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0019] This invention provides a composite absorbent based on tertiary amine buffer salts, a method and system for capturing carbon dioxide using the absorbent. The core concept is to utilize the high chemical stability and suitable pKa temperature sensitivity of tertiary amine buffer salts (such as Bicine and Tricine), combined with a main absorbent and a multi-component synergistic corrosion inhibitor system, to achieve efficient, low-corrosion, and long-life carbon dioxide capture under mild conditions.

[0020] In a specific embodiment, based on a total weight of 100 parts of the composite absorbent, the composite absorbent comprises the following components in parts by weight: main absorbent: 10-30 parts; tertiary amine buffer salt: 8-20 parts; compound corrosion inhibitor: 0.3-1 part; stabilizer: 0.01-0.05 parts; bactericide: 0.01-0.05 parts; defoamer: 0-0.01 parts; water: balance; The primary absorbent is potassium carbonate and / or potassium bicarbonate; the tertiary amine buffer salt is at least one of N,N-di(hydroxyethyl)glycine (Bicine) and tri(hydroxymethyl)methylglycine (Tricine); the compound corrosion inhibitor comprises an organic corrosion inhibitor, a spatiotemporally complementary corrosion inhibitor, and a chloride ion complexing agent; wherein the organic corrosion inhibitor comprises long-chain dicarboxylic acids, oxalate salts, benzoates, and benzotriazoles; the spatiotemporally complementary corrosion inhibitor is a mixture of vanadate and molybdate; the chloride ion complexing agent is a cerium salt; the stabilizer consists of an antioxidant and a chelating agent, used to inhibit the oxidative decomposition of the tertiary amine buffer salt.

[0021] Among them, the spatiotemporally complementary corrosion inhibitor in the compound corrosion inhibitor exerts its protective effect through a unique synergistic mechanism: vanadate, due to its oxidizing properties, can preferentially induce the formation of a dense oxide passivation film on the metal surface, providing immediate protection and increasing the corrosion potential; molybdate, as an effective anodic inhibitor, further blocks microscopic anodic active points on the basis of the passivation film, forming a stable precipitation protective layer. When the two are compounded in a specific ratio, a dense composite film consisting of an inner passivation film and an outer precipitation film can be formed on the carbon steel surface. This composite film can effectively resist the attack of corrosive ions such as CO2 and Cl⁻. In organic corrosion inhibitors, long-chain dicarboxylic acids can form a porous, loose adsorption layer on carbon steel surfaces through multi-point anchoring. Small-molecule benzoates insert into the pores of this adsorption layer, filling tiny gaps to jointly construct a complete and dense physical barrier film, significantly reducing the film's porosity and permeability. Benzotriazoles coordinate with the metal surface through the nitrogen atoms on their heterocycles, occupying active sites and preventing Cl⁻ adsorption. Oxylenol salts compete with Cl⁻ for adsorption through their carboxyl and amide groups, and complex Fe²⁺ / Fe³⁺ in the solution, removing corrosion-inducing ions. The stable complexes formed by their complexation with metal ions can also be deposited at defects for local repair. Chloride ion complexing agents (cerium salts) effectively inhibit pitting corrosion. Through the synergistic effect of the components in the compound corrosion inhibitor, excellent corrosion inhibition performance (corrosion rate <0.08 mm / year) is achieved. Meanwhile, the antioxidant addresses the risk of oxidative degradation of tertiary amine buffer salts, the bactericide addresses the problem of microbial growth in the composite absorbent, and the defoamer addresses the foaming or bubbling problem of the composite absorbent. The three work together to form an active defense mechanism, which significantly extends the service life of the composite absorbent and reduces operation and maintenance costs.

[0022] In some preferred embodiments, based on a total weight of 100 parts of the composite absorbent liquid, the content of each component is as follows: main absorbent: 15-25 parts; tertiary amine buffer salt: 10-15 parts; compound corrosion inhibitor: 0.3-0.6 parts; stabilizer: 0.02-0.04 parts; bactericide: 0.01-0.04 parts; defoamer: 0-0.01 parts; water: balance.

[0023] In some preferred embodiments, the long-chain dicarboxylic acid salt is at least one of sebacate and dodecanoate.

[0024] In some preferred embodiments, the benzotriazole substance is at least one of benzotriazole (BTA) and methylbenzotriazole (TTA).

[0025] In some preferred embodiments, the compound corrosion inhibitor contains 1.5-2.5 parts potassium sebate, 0.8-1.5 parts potassium dodecanoate, 0.5-1.0 parts potassium oxalate, 0.3-0.6 parts sodium benzoate, and 0.03-0.08 parts benzotriazole.

[0026] In some preferred embodiments, the molar ratio of vanadate to molybdate in the spatiotemporally complementary corrosion inhibitor is 1:0.5 to 1:2.

[0027] In some preferred embodiments, the total amount of the spatiotemporally complementary corrosion inhibitor added to the composite absorbent is 300-500 ppm, and the amount of the chloride ion complexing agent added is 50-100 ppm.

[0028] In some preferred embodiments, the vanadate is sodium vanadate (NaVO3); the molybdate is sodium molybdate (Na2MoO4); and the cerium salt is at least one of cerium nitrate and cerium sulfate.

[0029] In some preferred embodiments, the stabilizer contains 0.01-0.03 parts of antioxidant and 0.02-0.05 parts of chelating agent; the antioxidant is propyl gallate (PG) or antioxidant 1010; and the chelating agent is citric acid or EDTA.

[0030] In some preferred embodiments, the bactericide is isothiazolinone (CIT / MIT), glutaraldehyde, quaternary ammonium salt (such as dodecyl dimethyl benzyl ammonium bromide), etc., with glutaraldehyde being preferred.

[0031] In some preferred embodiments, potassium carbonate is preferred as the primary absorbent.

[0032] In another specific embodiment, a method for capturing carbon dioxide using the composite absorbent is also provided, comprising the following steps: Absorption step: At a temperature of 0-40℃, the carbon dioxide-containing industrial tail gas is brought into contact with the composite absorbent liquid to carry out a carbon dioxide absorption reaction and obtain a rich liquid. Regeneration step: The rich solution is heated to 60-90°C to desorb and release the carbon dioxide absorbed in the rich solution, thereby obtaining a lean solution and carbon dioxide gas; Circulation step: The lean solution is cooled and used as a circulating absorbent, and then returned to the absorption step for reuse.

[0033] In some preferred embodiments, the liquid-to-gas ratio is 15-20 L / m³ during the absorption step. 3 The gas-liquid contact time is 10-30 seconds, and the initial pH value of the absorption process is controlled at 8.0-11.5; in the regeneration step, the pH value of the regeneration process increases from 7.0-8.0.

[0034] In some preferred embodiments, the regeneration step is carried out under slight negative pressure or normal pressure, with an operating pressure of 0.08-0.1 MPa.

[0035] In some preferred embodiments, the method further includes a compression liquefaction step: compressing, drying, and condensing the carbon dioxide gas obtained in the regeneration step to obtain a liquid carbon dioxide product.

[0036] In some preferred embodiments, the industrial exhaust gas originates from at least one of a coking plant, a chemical plant (including biochemical fermentation gases), a coal-fired power plant, a steel plant, and a cement plant.

[0037] In some preferred embodiments, a monitoring step is also included: real-time monitoring of the pH value of the circulating absorbent; comparing the monitored pH value with a preset target range; when the monitored value deviates from the target range, supplementing the circulating absorbent with the corresponding component of the composite absorbent to bring the pH value back to the target range; preferably, the preset target range is 8.0-11.5, and when the monitored value is not in the range of 8.0-11.5, supplementing the circulating absorbent with the main absorbent.

[0038] In some preferred embodiments, a pretreatment step is included before the absorption step: removing dust and impurities from the industrial exhaust gas, cooling the industrial exhaust gas to 40-45°C, and removing liquid water mist from the industrial exhaust gas.

[0039] In another specific embodiment, a carbon dioxide capture system is also provided for implementing the aforementioned liquid carbon dioxide capture method, comprising: an absorption unit for contacting industrial exhaust gas with a composite absorbent liquid to absorb carbon dioxide, thereby obtaining a rich liquid; a regeneration unit connected to the absorption unit for receiving and heating the rich liquid from the absorption unit to desorb carbon dioxide, thereby obtaining a lean liquid and carbon dioxide gas; and an absorbent liquid circulation and regulation unit connected to both the absorption unit and the regeneration unit for receiving the lean liquid from the regeneration unit and, after regulation, returning it to the absorption unit for utilization.

[0040] In some preferred embodiments, the absorbent circulation and control unit includes an online pH monitor and an automatic replenishment system. The online pH monitor is used to monitor the pH value of the lean solution, and the automatic replenishment system is used to replenish the lean solution with the components of the composite absorbent solution according to any one of claims 1-7 based on the monitoring results. Preferably, when the pH value of the lean solution monitored by the online pH monitor is not in the range of 8.0-11.5, the automatic replenishment system replenishes the lean solution with the main absorbent.

[0041] In some preferred embodiments, the system further includes an impurity control unit connected to the regeneration unit. The impurity control unit includes a bypass filter, a bactericide dosing device, and an antifoaming agent dosing device. The bypass filter is used to remove solid impurities from the lean solution obtained by the regeneration unit. The bactericide dosing device is used to control the growth of microorganisms in the lean solution obtained by the regeneration unit. The antifoaming agent dosing device is used to add antifoaming agent to the lean solution obtained by the regeneration unit to prevent foaming or bubbling.

[0042] In some preferred embodiments, the system further includes a pretreatment unit connected to the absorption unit, used to remove dust and impurities from the industrial exhaust gas, cool the industrial exhaust gas to 40-45°C, and remove liquid water mist from the industrial exhaust gas.

[0043] The present invention will be further illustrated below with more specific embodiments.

[0044] Example 1: Composite Absorbent Solution and Its Preparation This embodiment provides a composite absorbent for capturing carbon dioxide, which comprises the following components in parts by weight, based on a total weight of 100 parts: main absorbent: 15 parts; tertiary amine buffer salt: 15 parts; compound corrosion inhibitor: 0.5 parts; stabilizer: 0.03 parts; bactericide: 0.01 parts; water: balance.

[0045] The main absorbent is potassium carbonate; the tertiary amine buffer salt is N,N-di(hydroxyethyl)glycine (Bicine); the compound corrosion inhibitor includes an organic corrosion inhibitor (containing 2.0 parts potassium sebate, 1.2 parts potassium dodecanoate, 0.6 parts potassium oxalate, 0.5 parts sodium benzoate, and 0.05 parts benzotriazole), a spatiotemporally complementary corrosion inhibitor (a mixture of sodium vanadate and sodium molybdate, molar ratio 1:1, total addition amount 400 ppm), and a chloride ion complexing agent (cerium nitrate, addition amount 80 ppm); the stabilizer consists of an antioxidant (propyl gallate, 0.015 parts) and a chelating agent (EDTA, 0.035 parts); the bactericide is glutaraldehyde; and the defoamer is a silicone defoamer (such as Biospumex 153K).

[0046] Preparation method: First, dissolve the measured amount of potassium carbonate in deionized water and stir until completely dissolved; then add Bicine and continue stirring until completely dissolved; add each component of the organic corrosion inhibitor in sequence and stir until homogeneous; add the spatiotemporally complementary corrosion inhibitor and chloride ion complexing agent and stir until completely dissolved; finally add the stabilizer, bactericide and defoamer and stir until homogeneous to obtain the composite absorbent.

[0047] Example 2: Another composite absorbent and its preparation The difference between Example 2 and Example 1 is that the tertiary amine buffer salt Bicine in Example 1 is replaced with Tricine (tris(hydroxymethyl)methylglycine), otherwise it is the same as Example 1.

[0048] Example 3: Carbon Dioxide Capture System like Figure 1 and 2 As shown, this embodiment provides a carbon dioxide capture system, including: Pretreatment Unit 1: Used to remove dust and impurities from industrial exhaust gas, cool the industrial exhaust gas to 40-45℃, and remove liquid water mist from the industrial exhaust gas. In this embodiment, the pretreatment unit includes a cyclone dust collector, a bag filter, a cooling scrubbing tower, and a gas-liquid separator connected in sequence. The cyclone dust collector has a pressure drop of approximately 1000 Pa and is used to receive industrial exhaust gas containing CO2 and remove coarse dust particles (>10 μm) from the industrial exhaust gas source to prevent clogging of subsequent equipment and packing materials. The bag filter has a filtration accuracy of <1 μm and is used to finely filter the industrial exhaust gas treated by the cyclone dust collector to <10 mg / Nm³. 3This reduces contamination of the composite absorbent; the outlet temperature of the cooling scrubbing tower is 40-45℃, used to cool the high-temperature industrial exhaust gas (100-150℃) obtained after passing through the bag filter to 40-45℃, while removing acidic impurities such as SO2 and HCl; the water removal efficiency of the gas-liquid separator is >99%, used to remove liquid water mist entrained in the industrial exhaust gas after treatment by the cooling scrubbing tower, avoiding dilution of the composite absorbent.

[0049] Absorption Unit 2: Connected to Pretreatment Unit 1, in this embodiment, absorption unit 2 includes an absorption tower, an absorbent spray device, and a rich liquid storage tank. The inlet of the absorption tower, located at the bottom, is connected to the gas-liquid separator in pretreatment unit 1, and its interior is equipped with an absorption tower packing section. The absorption tower packing uses high specific surface area packing (metal perforated plate corrugated packing, specific surface area 250 m²). 2 / m 3 The pretreated industrial waste gas enters from the bottom of the absorption tower, while the composite absorbent is sprayed from the top of the tower by an absorbent spray device. The industrial waste gas and the composite absorbent are in full contact within the packing section of the absorption tower. The composite absorbent absorbs carbon dioxide from the industrial waste gas, producing a rich solution, which enters a rich solution storage tank from the bottom of the tower. The clean waste gas (containing a small amount of CO2) after decarbonization can be discharged from the top of the tower. In this embodiment, the height of the packing section of the absorption tower is 18-22 m, the absorption tower is made of carbon steel, the empty tower gas velocity is 1.0-1.5 m / s, the tower diameter is 2.5-3.0 m, the operating temperature is 40-45℃, the power is 15-20 kW, and the liquid-to-gas ratio is 15-20 L / m³. 3 CO2 removal rate >95%.

[0050] Regeneration Unit 3: Connected to Absorption Unit 2, it includes a lean-rich liquid heat exchanger, a regeneration tower, a reboiler, a lean liquid cooler, a first lean liquid storage tank, and a CO2 gas cooler. The rich liquid storage tank is connected to the regeneration tower via the lean-rich liquid heat exchanger, which is also connected to the first lean liquid storage tank and the lean liquid cooler. The reboiler and CO2 gas cooler are both connected to the regeneration tower. In this embodiment, the lean-rich liquid heat exchanger is a plate heat exchanger with a heat exchange area of ​​50-60 m². 2 The system connects to a rich solution storage tank via a rich solution pump and to a first lean solution storage tank via a lean solution pump. The low-temperature rich solution from the absorption unit is preheated in a rich-lean-lean solution heat exchanger using the high-temperature lean solution from the first lean solution storage tank before entering the regeneration tower. The regeneration tower has a packing section containing high specific surface area packing (metal perforated plate corrugated packing, specific surface area 250 m²). 2 / m 3The regeneration tower operates under vacuum (0.08 MPa). A reboiler utilizes low-temperature waste heat (60°C, such as 60-70°C industrial waste heat from power plant circulating water) to drive the desorption of CO2 from the rich liquor in the packed section of the regeneration tower, yielding lean liquor and high-temperature, high-purity CO2 (purity >99.5%). The high-temperature, high-purity CO2 is cooled to 40-50°C from the top of the regeneration tower by a CO2 gas cooler before being discharged. The lean liquor enters the first lean liquor storage tank from the bottom of the regeneration tower. The lean liquor in the first lean liquor storage tank is pumped to a lean-rich liquor heat exchanger to preheat the low-temperature rich liquor. After heat exchange in the lean-rich liquor heat exchanger, the lean liquor is cooled by a lean liquor cooler before entering the absorbent circulation and control unit 5. The regeneration tower is made of carbon steel, with a height of 15-18m, a bottom temperature of 60-90°C, a top temperature of 50-60°C, and uses 60-70°C industrial waste heat as the heat source.

[0051] Compression liquefaction unit 4: Connected to regeneration unit 3, it includes a multi-stage compressor (discharge pressure of 7.0-8.0 MPa, interstage cooling <45℃), a molecular sieve (such as 4A molecular sieve) dryer, a cryogenic condenser, and a liquid CO2 storage tank. The multi-stage compressor is connected to the CO2 gas cooler of the regeneration unit to compress the regenerated CO2 gas (about 0.08 MPa) step by step to the liquefaction pressure of 7.0-8.0 MPa. Then, the molecular sieve dryer is used to deeply remove trace amounts of moisture from the CO2 gas and dry it to a dew point below -60℃ to prevent ice blockage during the condensation process. Subsequently, the high-pressure CO2 gas is condensed into liquid CO2 in the cryogenic condenser using a refrigerant (such as -20℃ circulating brine) and stored in the liquid CO2 storage tank for transportation or use in subsequent chemical synthesis.

[0052] The absorbent circulation and control unit 5 is connected to both the impurity control unit 6 and the regeneration unit 3. The absorbent circulation and control unit 5 includes a second lean liquid storage tank, an online pH monitor, and an automatic replenishment system. In this embodiment, the lean liquid obtained after desorbing CO2 in the regeneration unit 3 recovers heat through a lean-rich liquid heat exchanger, is cooled by a lean liquid cooler, and then enters the second lean liquid storage tank to return to the absorption unit. Both the online pH monitor and the automatic replenishment system are connected to the second lean liquid storage tank. The automatic replenishment system is also connected to the online pH monitor, which monitors the pH value of the lean liquid in the second lean liquid storage tank. Based on the monitoring results of the online pH monitor, the automatic replenishment system automatically replenishes the components of the composite absorbent liquid to the second lean liquid storage tank, allowing the lean liquid in the second lean liquid storage tank to be used as circulating absorbent liquid and returned to the absorption unit for utilization (for example, the circulating absorbent liquid can be sent to the absorption tower for circulation via a circulation pump (such as a low-shear centrifugal pump with a power of 15-20 kW and a head of 30-40 m)).

[0053] Impurity Control Unit 6: Connected to Absorbent Circulation and Control Unit 5; Impurity Control Unit 6 includes a bypass filter (using a bag filter with a filtration accuracy of 5 μm), a bactericide dosing device, and an antifoaming agent dosing device; The bypass filter is connected to the second lean liquid storage tank and is used to remove solid impurities from the composite absorbent from the second lean liquid storage tank (e.g., by continuously removing suspended solids from the composite absorbent to control the suspended solids content <10 mg / L to prevent clogging of the packing) and return them to the second lean liquid storage tank; The bactericide dosing device is connected to the second lean liquid storage tank and is used to control microbial growth (e.g., a broad-spectrum bactericide (such as glutaraldehyde) can be periodically added to the second lean liquid storage tank to control microbial growth and control the total viable count <10). 4 (CFU / mL); The defoamer dosing device is connected to the second lean liquid storage tank and is used to add defoamer to the lean liquid to prevent the composite absorbent from foaming or forming bubbles.

[0054] Example 4: Method for capturing carbon dioxide This embodiment provides a method for capturing carbon dioxide using the carbon dioxide capture system in Embodiment 3 and the composite absorbent described in Embodiment 1 or Embodiment 2, including the following steps: Pretreatment steps: Remove dust and impurities from the carbon dioxide-containing industrial exhaust gas from the coal-fired power plant, cool the industrial exhaust gas to 40-45℃, and remove liquid water mist from the industrial exhaust gas.

[0055] Absorption step: At 30℃, the pretreated industrial tail gas and the composite absorbent (initial pH value 8.0-11.5) are brought into countercurrent contact in the absorption tower, with a liquid-to-gas ratio of 15-20 L / m³. 3 The gas-liquid contact time is 20 seconds to carry out the carbon dioxide absorption reaction and obtain a rich liquid.

[0056] Regeneration steps: The rich liquor is preheated through a rich-lean liquor heat exchanger and then enters the regeneration tower. It is heated to 60°C and operated at an operating pressure of 0.08 MPa to desorb and release the carbon dioxide absorbed in the rich liquor. During the regeneration process, the pH value rises from 7.0 to 8.0, and lean liquor and carbon dioxide gas are obtained.

[0057] Circulation steps: After heat exchange in the lean liquid heat exchanger, the lean liquid is cooled to 40°C in the lean liquid cooler and then returned to the absorption tower for recycling.

[0058] Compression liquefaction step: The carbon dioxide gas released in the regeneration step is compressed to 7.5 MPa, dried (dew point < -60℃) and condensed (-25℃) to obtain liquid carbon dioxide product with a purity ≥ 99.5%.

[0059] Monitoring steps: Monitor the pH value of the circulating absorbent in real time; compare the monitored pH value with the preset target range (pH 8.0-11.5); when the monitored value deviates from the target range (e.g., below 8.0), appropriately supplement the corresponding components of the composite absorbent (e.g., supplement the main absorbent) to bring the pH value back to the target range.

[0060] Comparative Example 1 Compared with Example 1, in Comparative Example 1, the tertiary amine buffer salt Bicine in Example 1 was replaced with Tris (tris(hydroxymethyl)aminomethane), and the compound corrosion inhibitor was removed. Otherwise, it was the same as in Example 1.

[0061] The following experiments were conducted to verify Examples 1, 2, and Comparative Example 1: Chemical stability testing: To verify the long-term chemical stability of the composite absorbent, a small-scale spray circulation experimental device (hereinafter referred to as the "device") was built in the laboratory. The device mainly includes a gas mixing tank, a glass absorption tower filled with packing material (1.5m high, 0.1m in diameter), a solution storage tank, a circulation pump, and a gas flow controller. During the experiment, the prepared composite absorbents of Example 1, Example 2, and Comparative Example 1 were added to the solution storage tank of the device, and the solution circulation spray density was controlled at 20 m³ / s. 3 / (m 2 Simulated flue gas, consisting of 15% CO2 and 85% N2 by volume, was introduced at a flow rate of 0.5 m / s (h). 3 The system operates at a rate of 30±1°C per hour. The composite absorbent continuously circulates within the system until absorption equilibrium is reached and the pH value stabilizes. Ventilation is then stopped, and only spraying circulation continues. Samples were taken from the solution storage tank at fixed intervals (e.g., day 91, day 182, and day 365) and analyzed at a constant temperature of 25°C as follows: 1. pH value: measured using a precision pH meter calibrated with standard buffer solution (model: InLab Routine Pro-ISM); 2. Main component mass ratio: the concentrations of potassium carbonate and tertiary amine buffer salt were determined by titration with standard hydrochloric acid solution, and the mass ratio of potassium carbonate to tertiary amine buffer salt was calculated; 3. Turbidity: measured using a portable turbidimeter (model: Hach / HACH2100Q); 4. Impurity peak percentage: after filtration, the samples were analyzed by HPLC (Agilent 1260, C18 column, mobile phase: 0.1% phosphoric acid aqueous solution-acetonitrile, gradient elution, UV detector 210 nm), and the percentage of degradation impurity peak area to total peak area was calculated.

[0062] The test results are shown in Table 1 below (the experiments on the three samples in the table were conducted simultaneously under exactly the same apparatus and operating conditions): Table 1 The table above shows that after one year of room temperature spraying cycles, the pH value of Comparative Example 1 decreased by 0.32 (the largest change); while that of Example 1 decreased by only 0.04; and that of Example 2 decreased by only 0.10. This indicates that Comparative Example 1 exhibits significant pH drift, while Examples 1 and 2 demonstrate superior long-term pH stability. Regarding the stability of the mass ratio of the main components, within one year, Comparative Example 1 decreased by 3.5%; Example 2 decreased by 0.9%; and Example 3 decreased by 0.11%. This indicates that Examples 1 and 2 are more stable than Comparative Example 1. Regarding turbidity changes, after one year, Comparative Example 1 increased by 5.078, Example 1 increased by 0.095, and Example 2 increased by 0.106. This indicates that the turbidity of the solution in Comparative Example 1 significantly increased after prolonged operation. Regarding the proportion of impurity peaks detected by HPLC, after one year, the proportion of impurity peaks in Comparative Example 1 increased by 2.136%, in Example 1 by 0.058%, and in Example 2 by 0.041%. This suggests that Comparative Example 1 may have experienced a significant increase in impurity content due to degradation of the main components. All the above test results were obtained under conditions of 25°C.

[0063] Corrosion performance testing: A one-year corrosion experiment was conducted on the composite absorbent solutions of Examples 1, 2, and Comparative Example 1 to test the corrosion rate of different materials. The corrosion performance test employed the weight loss method (referring to GB / T 18175-2000 "Determination of Corrosion Inhibition Performance of Water Treatment Agents - Rotary Coating Method"). Standard test pieces (50mm×25mm×2mm) of Q245R carbon steel, Q345R carbon steel, and 316L stainless steel were successively polished with 240-grit, 400-grit, and 600-grit wet sandpaper until the surface was smooth and free of scratches. After cleaning with acetone, drying, and accurate weighing, they were completely immersed in the composite absorbent solutions. The experiment was conducted under conditions of continuous CO2 gas (99.9% purity) at a rate of 100 mL / min to simulate the saturated CO2 environment inside the absorption tower. The test temperature was maintained at 30±1°C. The absorbent solution was replaced with fresh solution every 90 days to maintain the stability of the solution components. Five parallel samples were prepared for each material in each absorbent solution sample. The experimental period was one year. After the expiration, the test pieces were removed, surface corrosion products were removed according to standard methods, and the pieces were cleaned, dried, and weighed accurately again. The weight loss (i.e., mass loss) of the test pieces was calculated. Based on the density of the test pieces, the surface area of ​​the test pieces in contact with the composite absorbent solution, and the detection time (h), the annual average corrosion rate (mm / a) was obtained by substituting the values ​​into the formula: Corrosion rate = (mass loss × 8760) / (density × surface area × time). The test results are shown in Table 2 below. Table 2 The units of the test results in Table 2 above have all been converted to mm / a. As can be seen from Table 2, the corrosion rates of Example 1 and Example 2 on different materials are lower than those of Comparative Example 1.

[0064] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A composite absorbent for capturing carbon dioxide, characterized in that: Based on a total weight of 100 parts of the composite absorbent, the composite absorbent comprises the following components in parts by weight: main absorbent: 10-30 parts; tertiary amine buffer salt: 8-20 parts; Compound corrosion inhibitor: 0.3-1 part; Stabilizer: 0.01-0.05 parts; Bactericide: 0.01-0.05 parts; Defoamer: 0-0.01 parts; Water: balance; The main absorbent is potassium carbonate and / or potassium bicarbonate; The tertiary amine buffer salt is at least one of N,N-di(hydroxyethyl)glycine (Bicine) and tri(hydroxymethyl)methylglycine (Tricine); The compound corrosion inhibitor comprises an organic corrosion inhibitor, a spatiotemporally complementary corrosion inhibitor, and a chloride ion complexing agent; wherein, the organic corrosion inhibitor comprises long-chain dicarboxylic acids, oxalate salts, benzoates, and benzotriazoles; the spatiotemporally complementary corrosion inhibitor is a mixture of vanadate and molybdate; the chloride ion complexing agent is a cerium salt; The stabilizer is composed of an antioxidant and a chelating agent, used to inhibit the oxidative decomposition of the tertiary amine buffer salt.

2. The composite absorbent liquid according to claim 1, characterized in that, Based on a total weight of 100 parts of the composite absorbent, the content of each component is as follows: main absorbent: 15-25 parts; tertiary amine buffer salt: 10-15 parts; compound corrosion inhibitor: 0.3-0.6 parts; stabilizer: 0.02-0.04 parts; Fungicide: 0.01-0.04 parts; Defoamer: 0-0.01 parts; Water: Balance.

3. The composite absorbent liquid according to claim 1, characterized in that, The long-chain dicarboxylic acid salt is at least one of sebacic acid salt and dodecanoic acid salt; the benzotriazole substance is at least one of benzotriazole (BTA) and methylbenzotriazole (TTA); preferably, in the compound corrosion inhibitor, the organic corrosion inhibitor comprises 1.5-2.5 parts potassium sebacic acid, 0.8-1.5 parts potassium dodecanoic acid, 0.5-1.0 parts potassium oxalate, 0.3-0.6 parts sodium benzoate, and 0.03-0.08 parts benzotriazole substance.

4. The composite absorbent liquid according to claim 1, characterized in that, The molar ratio of vanadate to molybdate in the spatiotemporally complementary corrosion inhibitor is 1:0.5 to 1:

2.

5. The composite absorbent liquid according to claim 4, characterized in that, In the composite absorbent, the total amount of the spatiotemporally complementary corrosion inhibitor added is 300-500 ppm, and the amount of the chloride ion complexing agent added is 50-100 ppm.

6. The composite absorbent liquid according to claim 1, characterized in that, The vanadate is sodium vanadate (NaVO3); the molybdate is sodium molybdate (Na2MoO4); and the cerium salt is at least one of cerium nitrate and cerium sulfate.

7. The composite absorbent liquid according to claim 1, characterized in that, The stabilizer contains 0.01-0.03 parts of antioxidant and 0.02-0.05 parts of chelating agent; the antioxidant is propyl gallate (PG) or antioxidant 1010; the chelating agent is citric acid or EDTA.

8. A method for capturing carbon dioxide using the composite absorbent as described in any one of claims 1-7, characterized in that, Includes the following steps: Absorption step: At a temperature of 0-40℃, the industrial tail gas containing carbon dioxide is brought into contact with the composite absorbent liquid to carry out a carbon dioxide absorption reaction and obtain a rich liquid. Regeneration step: The rich solution is heated to 60-90°C to desorb and release the carbon dioxide absorbed in the rich solution, thereby obtaining a lean solution and carbon dioxide gas; Circulation step: The lean solution is cooled and used as a circulating absorbent, which is then returned to the absorption step for reuse.

9. The method according to claim 8, characterized in that: In the absorption step, the liquid-to-gas ratio is 15-20 L / m³. 3 The gas-liquid contact time is 10-30 seconds, and the initial pH value of the absorption process is controlled at 8.0-11.

5. In the regeneration step, the pH value of the regeneration process increases from 7.0 to 8.

0.

10. The method according to claim 8, characterized in that, The regeneration step is carried out under slight negative pressure or normal pressure, with an operating pressure of 0.08-0.1 MPa.

11. The method according to claim 8, characterized in that, The method further includes a compression liquefaction step: the carbon dioxide gas obtained in the regeneration step is compressed, dried and condensed to obtain a liquid carbon dioxide product.

12. The method according to claim 8, characterized in that, The industrial exhaust gas originates from at least one of a coking plant, chemical plant, coal-fired power plant, steel plant, and cement plant.

13. The method according to claim 8, characterized in that, The method also includes a monitoring step: real-time monitoring of the pH value of the circulating absorbent; comparing the monitored pH value with a preset target range; when the monitored value deviates from the target range, adding the corresponding component of the composite absorbent to the circulating absorbent to bring the pH value back to the target range; preferably, the preset target range is 8.0-11.5, and when the monitored value is not in the range of 8.0-11.5, adding the main absorbent to the circulating absorbent.

14. The method according to claim 8, characterized in that, Before the absorption step, a pretreatment step is also included: removing dust and impurities from the industrial exhaust gas, cooling the industrial exhaust gas to 40-45℃, and removing liquid water mist from the industrial exhaust gas.

15. A carbon dioxide capture system for implementing the method according to any one of claims 8-14, characterized in that, include: The absorption unit is used to contact industrial exhaust gas with a composite absorbent liquid to absorb carbon dioxide and obtain a rich liquid. A regeneration unit, connected to the absorption unit, is used to receive and heat the rich liquid from the absorption unit to desorb carbon dioxide, resulting in a lean liquid and carbon dioxide gas. An absorbent circulation and regulation unit is connected to both the absorption unit and the regeneration unit. It is used to receive the lean solution from the regeneration unit and, after regulation, return it to the absorption unit for use.

16. The system according to claim 15, characterized in that, The absorbent circulation and control unit includes an online pH monitor and an automatic replenishment system. The online pH monitor is used to monitor the pH value of the lean solution, and the automatic replenishment system is used to replenish the lean solution with the components of the composite absorbent solution according to any one of claims 1-7 based on the monitoring results. Preferably, when the pH value of the lean solution monitored by the online pH monitor is not in the range of 8.0-11.5, the automatic replenishment system replenishes the lean solution with the main absorbent.

17. The system according to claim 15, characterized in that, The system also includes an impurity control unit connected to the regeneration unit. The impurity control unit includes a bypass filter, a bactericide dosing device, and an antifoaming agent dosing device. The bypass filter is used to remove solid impurities from the lean liquid obtained by the regeneration unit. The bactericide dosing device is used to control the growth of microorganisms in the lean liquid obtained by the regeneration unit. The antifoaming agent dosing device is used to add antifoaming agent to the lean liquid obtained by the regeneration unit to prevent foaming or bubbling.

18. The system according to claim 15, characterized in that, The system also includes a pretreatment unit connected to the absorption unit, used to remove dust and impurities from the industrial exhaust gas, cool the industrial exhaust gas to 40-45°C, and remove liquid water mist from the industrial exhaust gas.

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