Process for cyclically trapping carbon dioxide
By combining multi-stage adsorption and membrane separation methods, along with staged desorption and electrochemical regeneration, the problems of low carbon dioxide capture efficiency and high cost in existing technologies have been solved, achieving efficient and low-energy carbon dioxide capture and resource utilization.
Patent Information
- Application Number
- CN202511432000.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-09
- Publication Date
- 2026-01-02
AI Technical Summary
Existing chemical absorption methods are inefficient and costly in capturing carbon dioxide, which limits their industrial applications and results in excessive energy consumption.
By combining multi-stage adsorption and membrane separation methods, using composite absorbents and physical absorbents, and combining staged desorption and electrochemical regeneration, the temperature and pressure of flue gas are regulated through a waste heat recovery device to achieve efficient capture of carbon dioxide and resource utilization.
It improves the capture efficiency and purity of carbon dioxide, reduces industrial costs and energy consumption, realizes the high-purity preparation of carbon dioxide and the recycling of by-products, and reduces waste emissions.
Smart Images
Figure CN121243944A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of carbon dioxide capture technology, in particular to a cyclic carbon dioxide capture process. BACKGROUND
[0002] As the main culprit of atmospheric greenhouse effect and an important factor of global weather anomalies, the reduction of carbon dioxide has become one of the important research topics in the world. According to the authoritative statistical data, the annual emission of carbon dioxide is showing an increasing trend. By the end of 2006, the global carbon dioxide emissions reached 6.2 billion tons, and the level of carbon dioxide in the atmosphere is 27% higher than that in the past 650,000 years. This serious figure shows that the problem of carbon dioxide emissions is urgent. Among the many sources of carbon dioxide emissions, coal-fired power plants account for the majority, followed by industrial waste gas emissions, global automobile exhaust emissions and some domestic waste gas emissions. The large amount of exhaust gas emissions greatly increases the proportion of carbon dioxide in the air, significantly changes the air quality in a short time, and thus causes serious greenhouse effect. Since coal-fired power plants are a long-term stable source of carbon dioxide emissions, therefore, it is of great significance to do a good job in carbon dioxide emission reduction for China to get rid of the shackles of emission reduction targets and achieve sustainable development.
[0003] There are many methods for capturing carbon dioxide, and the chemical absorption method is commonly used in industry. The principle is that the carbon dioxide produced by industry reacts with the chemical absorbent to be absorbed, and the solution that has absorbed carbon dioxide is released from the regeneration tower to release carbon dioxide. The solution after releasing carbon dioxide can be used to absorb carbon dioxide again to realize cyclic utilization. In the early stage, sodium carbonate was commonly used as a chemical absorbent for absorbing carbon dioxide. After absorbing carbon dioxide, sodium carbonate generates NaHCO3, which is then decomposed into Na2CO3 and carbon dioxide. However, in the decomposition reaction process, due to the low reaction temperature, the reaction efficiency is greatly affected, and the absorption speed is slow and the effect is poor, which causes high industrial cost and energy consumption, limiting the large-scale application and development of this method. SUMMARY
[0004] In order to at least solve one of the above technical problems, the purpose of the present application is to provide a cyclic carbon dioxide capture process to reduce industrial cost and energy consumption.
[0005] To achieve the above purpose, the present application provides the following technical solutions:
[0006] A cyclic carbon dioxide capture process, comprising the following steps:
[0007] First step, pretreatment: dust removal and desulfurization and denitrification treatment, and temperature and pressure adjustment;
[0008] Second step, capture: multi-stage adsorption method and membrane separation method are adopted;
[0009] Third step, regeneration: fractional desorption and electrochemical regeneration are adopted;
[0010] Fourth step, product output and resource utilization: high-purity CO2 preparation and by-product recycling are carried out.
[0011] Preferably, the dust removal and desulfurization and denitrification treatment in the first step specifically comprises: removing particulate matters in flue gas by using high-efficiency dust removal equipment; reducing SO2 concentration by wet desulfurization or dry desulfurization; and reducing NOx emission by denitrification treatment.
[0012] Preferably, the temperature and pressure adjustment in the first step specifically comprises: reducing the flue gas temperature to 40-60℃ by using waste heat recovery device; and pressurizing the low-concentration CO2 flue gas to 1.5-2.0 MPa.
[0013] Preferably, the multi-stage adsorption method in the second step specifically comprises: using a primary absorption tower and a secondary absorption tower; the primary absorption tower uses a composite absorbent to capture CO2 by chemical absorption; the secondary absorption tower further absorbs residual CO2 by physical absorbent; and the primary absorption tower and the secondary absorption tower are connected by a cooling pipeline.
[0014] Preferably, the membrane separation method in the second step specifically comprises: a mixed matrix membrane is arranged at the rear end of the primary absorption tower, and the mixed matrix membrane further purifies CO2 by using the difference in permeation rate of CO2 and N2.
[0015] Preferably, the composite absorbent is amine-based ionic liquid and sodium carbonate; the physical absorbent is polyethylene glycol dimethyl ether; and the material of the mixed matrix membrane is polyimide.
[0016] Preferably, the fractional desorption in the third step specifically comprises: using a desorption tower and a regeneration tower to divide the rich liquid at the bottom of the secondary absorption tower into two parts, one part directly enters the top of the desorption tower to recover heat, and the other part enters the upper part of the regeneration tower after heat exchange.
[0017] Preferably, the electrochemical regeneration in the third step specifically comprises: for high-concentration CO2 flue gas, using an electrochemical membrane reactor to electrolyze sodium bicarbonate solution under a direct current field to directly generate CO2 and NaOH.
[0018] Preferably, the high-purity CO2 preparation in the fourth step specifically comprises: converting the captured CO2 into liquid product by compression and liquefaction process;
[0019] Preferably, the by-product recycling in the fourth step specifically comprises: recycling the generated NaOH solution to the first step; and the heat generated in the third step is used for preheating flue gas or power generation.
[0020] The present application has the following beneficial effects:
[0021] I. Pretreatment stage: The waste heat recovery device is used to reduce the temperature of the flue gas to an appropriate range, and the low-concentration CO2 flue gas is pressurized. The use of the waste heat recovery device realizes the secondary utilization of energy, reduces the additional energy input; reasonable temperature and pressure adjustment helps the subsequent capture process to be carried out under more optimal conditions, improves the overall efficiency, and reduces energy consumption.
[0022] II. Capture stage: In the multi-stage adsorption method, the primary absorption tower uses a composite absorbent (amine-based ionic liquid and sodium carbonate), and the secondary absorption tower uses a physical absorbent (polyethylene glycol dimethyl ether). Different absorbents exert their respective advantages, improving the absorption efficiency of carbon dioxide and reducing the use amount and circulation frequency of the absorbent, thereby reducing the cost. The membrane separation method uses a mixed matrix membrane (polyimide material) to further purify CO2 by taking advantage of the difference in permeation rate between CO2 and N2. This method is simple to operate and has low energy consumption, which can effectively reduce industrial costs and energy consumption compared with traditional methods.
[0023] III. Regeneration stage: The graded desorption uses a desorption tower and a regeneration tower to reasonably distribute the rich liquid at the bottom of the secondary absorption tower. Part of the liquid is directly introduced into the top of the desorption tower to recover heat, and the other part is introduced into the upper part of the regeneration tower after heat exchange. This method fully utilizes the heat in the system, reduces the input of external heat, and reduces energy consumption. Electrochemical regeneration uses an electrochemical membrane reactor to electrolyze sodium bicarbonate solution under a direct current electric field to directly generate CO2 and NaOH. This method has high regeneration efficiency, relatively low energy consumption, and can obtain valuable byproduct NaOH.
[0024] IV. Product output and resource utilization stage: The regenerated NaOH solution is reused in the pretreatment stage, reducing the amount of NaOH purchased; the heat generated during the capture process is used to preheat the flue gas or generate electricity, realizing the recycling of energy and further reducing industrial costs.
[0025] V. Multi-stage adsorption method: The primary absorption tower uses the chemical absorption of a composite absorbent to capture most of the CO2, and the secondary absorption tower further absorbs the residual CO2 through a physical absorbent. The combination of the two-stage adsorption greatly improves the carbon dioxide capture rate and can more thoroughly remove carbon dioxide from the flue gas.
[0026] VI. Membrane separation method assistance: A mixed matrix membrane is set at the back end of the primary absorption tower to further purify CO2 from the gas after multi-stage adsorption by taking advantage of the difference in permeation rate between CO2 and N2, further improving the purity and capture efficiency of carbon dioxide.
[0027] Seven, high-purity CO2 preparation: through compression and liquefaction process, the captured CO2 is converted into liquid product, which can obtain high-purity carbon dioxide, meet the market demand for high-quality carbon dioxide, and improve the added value of the product.
[0028] Eight, by-product recycling: the generated NaOH solution is reused to the pretreatment stage, realizing the effective utilization of by-products and reducing waste emissions; the heat generated in the capture process is used for preheating flue gas or power generation, which converts the otherwise wasted heat into useful energy, realizing the comprehensive utilization of resources.
[0029] Nine, pretreatment operation optimization: high-efficiency dust removal equipment is used to remove particulate matter in flue gas, SO2 concentration is reduced by wet desulfurization or dry desulfurization, denitration treatment is carried out to reduce NOx emission, and temperature and pressure are adjusted at the same time, which provides good raw gas conditions for subsequent capture process, and is conducive to the stable operation of the whole process.
[0030] Ten, combination of fractional desorption and electrochemical regeneration: fractional desorption reasonably shunts treatment according to different conditions of rich liquid, which improves the heat recovery rate; electrochemical regeneration provides an efficient and stable method for regeneration of high-concentration CO2 flue gas, and the combination of the two makes the regeneration process more flexible and efficient, and improves the stability and reliability of the whole carbon capture and storage process. BRIEF DESCRIPTION OF DRAWINGS
[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.
[0032] Figure 1 Flowchart of the embodiments of the present application. DETAILED DESCRIPTION
[0033] The technical solutions of the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0034] Embodiment one
[0035] As Figure 1 shown
[0036] pretreatment
[0037] High-efficiency bag-type dust collector is used to remove particulate matters in flue gas, ensuring that the concentration of particulate matters is less than 30 mg / m³.
[0038] The concentration of SO2 is reduced by wet limestone-gypsum desulfurization method, ensuring that the concentration of SO2 emissions is less than 100 mg / m³.
[0039] Selective catalytic reduction (SCR) denitration technology is used to reduce NOx emissions, ensuring that the concentration of NOx emissions is less than 100 mg / m³.
[0040] The temperature of flue gas is reduced from the initial 150°C to 40°C using a waste heat recovery device, and the low-concentration CO2 flue gas is pressurized to 1.5 MPa.
[0041] Capture
[0042] Multi-stage adsorption method: a composite absorbent composed of amine-based ionic liquid and sodium carbonate in a mass ratio of 1:1 is used in the primary absorption tower to capture CO2 by chemical absorption; polyethylene glycol dimethyl ether is used as a physical absorbent in the secondary absorption tower to further absorb residual CO2; a cooling pipeline is used to connect the primary absorption tower and the secondary absorption tower, with a cooling water flow rate of 5 m³ / h to reduce the temperature of the gas at the outlet of the primary absorption tower to 30°C before entering the secondary absorption tower.
[0043] Membrane separation method: a mixed matrix membrane made of polyimide is installed at the rear end of the primary absorption tower to further purify CO2 by taking advantage of the difference in permeation rates between CO2 and N2; the membrane area is 10 m², and the operating pressure is 1.2 MPa.
[0044] Regeneration
[0045] Fractional desorption: the rich liquid at the bottom of the secondary absorption tower is divided into two parts, one of which is directly introduced into the top of the desorption tower to recover heat, and the other part is introduced into the upper part of the regeneration tower after heat exchange; the operating temperature of the desorption tower is 100°C, and the operating temperature of the regeneration tower is 110°C.
[0046] Electrochemical regeneration: for high-concentration CO2 flue gas (CO2 concentration higher than 80%), an electrochemical membrane reactor is used to electrolyze sodium bicarbonate solution under a direct current field, with a current density of 100 A / m², to directly generate CO2 and NaOH.
[0047] Product output and resource utilization
[0048] High-purity CO2 preparation: the captured CO2 is converted into a liquid product under the conditions of a pressure of 5 MPa and a temperature of -20°C through compression and liquefaction processes.
[0049] Byproduct recycling: The regenerated NaOH solution is reused in the wet desulfurization process in the pretreatment stage. The heat generated in the capture process is used to preheat the flue gas entering the pretreatment system to 80°C through a heat exchanger, and part of the heat is used for power generation, with a power generation capacity of 50 kW.
[0050] Example Two
[0051] Pretreatment
[0052] The particulate matter in the flue gas is removed by an electric precipitator, with a particulate matter emission concentration of less than 25 mg / m³.
[0053] The SO2 concentration is reduced by dry desulfurization (activated carbon adsorption method), with an SO2 emission concentration of less than 80 mg / m³.
[0054] The SNCR (selective non-catalytic reduction) denitrification technology is used to reduce NOx emissions, ensuring that the NOx emission concentration is less than 80 mg / m³.
[0055] The flue gas temperature is reduced from the initial 180°C to 50°C using a waste heat recovery device, and the low-concentration CO2 flue gas is pressurized to 1.8 MPa.
[0056] Capture
[0057] Multi-stage adsorption method: The first absorption tower uses a composite absorbent composed of amine-based ionic liquid and sodium carbonate in a mass ratio of 1:2, and the second absorption tower uses polyethylene glycol dimethyl ether as a physical absorbent. The cooling water flow rate in the cooling pipeline between the first and second absorption towers is 8 m³ / h, and the gas temperature at the outlet of the first absorption tower is reduced to 35°C before entering the second absorption tower.
[0058] Membrane separation method: A mixed matrix membrane made of polyimide is installed at the rear end of the first absorption tower, with a membrane area of 15 m² and an operating pressure of 1.5 MPa.
[0059] Regeneration
[0060] Fractional desorption: The desorption tower operates at a temperature of 105°C, and the regeneration tower operates at a temperature of 115°C.
[0061] Electrochemical regeneration: The current density is 120 A / m².
[0062] Product output and resource utilization
[0063] High-purity CO2 preparation: The captured CO2 is converted into a liquid product under conditions of a pressure of 6 MPa and a temperature of -25°C.
[0064] Byproduct recycling: the regenerated NaOH solution is reused in the pretreatment stage; the heat generated in the capture process is used to preheat the flue gas entering the pretreatment system to 90°C, with a power generation of 60 kW.
[0065] Example Three
[0066] Pretreatment
[0067] High-efficiency cyclone dust collectors and bag dust collectors are used to remove particulate matter in the flue gas, with the particulate matter emission concentration being less than 20 mg / m³.
[0068] The SO2 concentration is reduced by wet ammonia desulfurization, with the SO2 emission concentration being less than 60 mg / m³.
[0069] SCR and SNCR denitration technologies are used to reduce NOx emissions, ensuring that the NOx emission concentration is less than 60 mg / m³.
[0070] A waste heat recovery device is used to reduce the flue gas temperature from the initial 200°C to 60°C, and the low-concentration CO2 flue gas is pressurized to 2.0 MPa.
[0071] Capture
[0072] Multi-stage adsorption method: a composite absorbent of amine-based ionic liquid and sodium carbonate mixed at a mass ratio of 2:1 is used in the primary absorption tower, and polyethylene glycol dimethyl ether is used as a physical absorbent in the secondary absorption tower. The cooling water flow rate in the cooling pipeline between the primary absorption tower and the secondary absorption tower is 10 m³ / h, and the gas temperature at the outlet of the primary absorption tower is reduced to 40°C before entering the secondary absorption tower.
[0073] Membrane separation method: a mixed matrix membrane made of polyimide is installed at the rear end of the primary absorption tower, with a membrane area of 20 m² and an operating pressure of 1.8 MPa.
[0074] Regeneration
[0075] Staged desorption: the desorption tower operates at a temperature of 110°C, and the regeneration tower operates at a temperature of 120°C.
[0076] Electrochemical regeneration: the current density is 150 A / m².
[0077] Product output and resource utilization
[0078] High-purity CO2 preparation: the captured CO2 is converted into a liquid product under the conditions of a pressure of 7 MPa and a temperature of -30°C.
[0079] Byproduct recycling: The generated NaOH solution is reused in the pretreatment stage; the heat generated in the capture process is used to preheat the flue gas entering the pretreatment system to 100°C, with a power generation of 70kW.
[0080] The specific experimental data is arranged in Table 1.
[0081] Table 1: Experimental data arrangement table
[0082] Experimental items Example 1 Example 2 Example 3 Particulate emission concentration after pretreatment (mg / m3) 28 23 18 SO2emission concentration (mg / m3) after pretreatment 95 75 55 NOx emission concentration after pretreatment (mg / m3) 95 78 58 Flue gas temperature after pretreatment (°C) 40 50 60 Flue gas pressure after pretreatment (MPa) 1.5 1.8 2 CO2 absorption rate (%) of primary absorption tower 85 88 90 Secondary absorption tower CO2 absorption rate (%) 10 12 15 CO2 purity after membrane separation (%) 95 96 97 Desorption tower operating temperature (°C) 100 105 110 Regeneration tower operating temperature (°C) 110 115 120 Electrochemical regeneration current density (A / m2) 100 120 150 Liquid CO2product purity (%) 99.5 99.6 99.7 NaOH solution reuse rate (%) 90 92 95 Flue gas preheating temperature (°C) 80 90 100 Power generation (kW) 50 60 70
[0083] Experimental data analysis
[0084] Pretreatment effect
[0085] Technical principle: Through different types of dust removal, desulfurization, denitrification equipment and temperature and pressure adjusting devices, the particulate matter, SO2, NOx and other pollutants in the flue gas are removed, and the flue gas is adjusted to the appropriate temperature and pressure, providing good raw gas conditions for the subsequent capture process.
[0086] Technical effect: From the experimental data, it can be seen that with the optimization of pretreatment equipment and process, the emission concentration of particulate matter, SO2 and NOx after pretreatment gradually decreases, indicating that the pretreatment effect gradually increases. At the same time, the flue gas temperature and pressure can be accurately adjusted to the set value, providing stable and high-quality raw gas for the subsequent capture process, which is beneficial to improve the capture efficiency and stability of the entire process.
[0087] Capture effect
[0088] Technical principle: In the multi-stage adsorption method, the primary absorption tower uses the chemical absorption of composite absorbent to capture most of the CO2, and the secondary absorption tower further absorbs the residual CO2 through physical absorbent, and the combination of the two stages of adsorption improves the CO2 absorption rate; the membrane separation method uses the difference in permeation rate of CO2 and N2 in the mixed matrix membrane to purify the gas.
[0089] Technical effect: The experimental data shows that the CO2 absorption rate of the primary absorption tower is between 85% and 90%, and the CO2 absorption rate of the secondary absorption tower is between 10% and 15%, and after two-stage adsorption and membrane separation, the CO2 purity can reach 95% - 97%, indicating that the combination of multi-stage adsorption and membrane separation can effectively improve the capture efficiency and purity of CO2.
[0090] Regeneration effect
[0091] Technical principle: The fractional desorption uses desorption tower and regeneration tower to process the rich liquid by splitting, making full use of the heat in the system; the electrochemical regeneration uses direct current field to electrolyze sodium bicarbonate solution, directly generating CO2 and NaOH, with high regeneration efficiency.
[0092] Technical effects: With the increase of the operating temperature of the desorption tower and the regeneration tower and the current density of electrochemical regeneration, the regeneration process is more efficient, which can provide sufficient absorbent for subsequent capture and ensure the continuous and stable operation of the entire cyclic capture process.
[0093] Product output and resource utilization effect
[0094] Technical principle: The captured CO2 is converted into high-purity liquid product through compression and liquefaction process; the generated NaOH solution is reused to the pretreatment stage, and the heat generated in the capture process is used to preheat the flue gas or generate power, realizing the recycling of resources.
[0095] Technical effects: Experimental data show that the purity of liquid CO2 product can reach 99.5%-99.7%, the reuse rate of NaOH solution is between 90%-95%, and the flue gas preheating temperature and power generation capacity also increase with the optimization of the process, indicating that the process can realize the output of high-quality products and effective recycling of resources, reduce industrial costs, and improve economic and environmental benefits.
[0096] The above is only a specific embodiment of the present application, but the technical features of the present application are not limited thereto. Any simple change, equivalent replacement or modification made on the basis of the present application to solve the same technical problem and achieve the same technical effect is covered by the protection scope of the present application.
Claims
1. A cyclic carbon dioxide capture process, characterized in that, Includes the following steps: first step ， Pretreatment: Dust removal, desulfurization and denitrification, as well as temperature and pressure regulation are carried out; The second step, Collection: Multi-stage adsorption and membrane separation methods are employed; The third step, regeneration: employs staged desorption and electrochemical regeneration; The fourth step is product output and resource utilization: high-purity CO2 preparation and by-product recycling.
2. The carbon dioxide cyclic capture process according to claim 1, characterized in that, The dust removal, desulfurization, and denitrification treatment in the first step specifically involves: using high-efficiency dust removal equipment to remove particulate matter from flue gas; reducing SO2 concentration through wet or dry desulfurization; and reducing NOx emissions through denitrification treatment.
3. The carbon dioxide cyclic capture process according to claim 2, characterized in that, The temperature and pressure regulation in the first step specifically involves: using a waste heat recovery device to reduce the flue gas temperature to 40-60℃; and pressurizing the low-concentration CO2 flue gas to 1.5-2.0 MPa.
4. The carbon dioxide cyclic capture process according to claim 1, characterized in that, The multi-stage adsorption method in the second step specifically involves: using a primary absorption tower and a secondary absorption tower; the primary absorption tower uses a composite absorbent to chemically absorb and capture CO2; the secondary absorption tower further absorbs residual CO2 using a physical absorbent; and the primary and secondary absorption towers are connected by a cooling pipe.
5. The carbon dioxide cyclic capture process according to claim 4, characterized in that, The membrane separation method in the second step is as follows: a mixed matrix membrane is installed at the rear end of the primary absorption tower, and the mixed matrix membrane further purifies CO2 by utilizing the difference in permeation rates between CO2 and N2.
6. The carbon dioxide cyclic capture process according to claim 5, characterized in that, The composite absorbent is an amine ionic liquid and sodium carbonate; the physical absorbent is polyethylene glycol dimethyl ether; and the mixed matrix membrane is made of polyimide.
7. The carbon dioxide cyclic capture process according to claim 1, characterized in that, The third step of staged desorption specifically involves using a desorption tower and a regeneration tower to divide the rich liquid at the bottom of the secondary absorption tower into two parts. One part directly enters the top of the desorption tower to recover heat, while the other part enters from the upper part of the regeneration tower after heat exchange.
8. The carbon dioxide cyclic capture process according to claim 7, characterized in that, The electrochemical regeneration in the third step specifically involves using an electrochemical membrane reactor to electrolyze sodium bicarbonate solution under a DC electric field to directly generate CO2 and NaOH for high-concentration CO2 flue gas.
9. The carbon dioxide cyclic capture process according to claim 1, characterized in that, The preparation of high-purity CO2 in the fourth step specifically involves converting the captured CO2 into a liquid product through compression and liquefaction processes.
10. A cyclic carbon dioxide capture process according to claim 9, characterized in that, The recycling of byproducts in the fourth step specifically involves: reusing the NaOH solution generated during regeneration back into the first step; and using the heat generated in the third step to preheat flue gas or generate electricity.