A carbon capture escape absorbent deep removal method

Abstract

A kind of carbon capture escape absorbent deep removal method, each compression stage of multistage compression unit is additionally provided with a bypass leading high pressure CO2, the high pressure CO2 of multiple bypasses is collected and then is divided into two paths and is respectively passed into demister and filter, the absorbent captured from demister and filter is converged and then is uniformly returned to absorption tower, and is entered into absorption-desorption circulation system again.The method does not need to introduce additional refrigeration equipment and inducing medium, fully utilizes existing chemical absorption method carbon capture device, utilizes high pressure CO2 throttling cooling to generate CO2 low temperature mist, improves the chemical reaction efficiency of CO2 and organic amine, realizes the improvement of removal efficiency, compared with existing condensation, spraying and other technologies, does not increase material consumption, process is simple, transformation cost is low, and effect is good.

Description

Technical Field

[0001] This invention relates to the field of emission reduction and carbon reduction in flue gas from carbon dioxide capture towers, and in particular to a deep removal process and method for carbon capture escape absorbents. Background Technology

[0002] Carbon capture and storage (CCS) technology for fossil fuel use is gradually becoming an important technological approach to reduce industrial emissions, especially CO2 emissions from the power and chemical industries. Absorption-based CO2 capture technology, with its high absorption efficiency and mature industrial application experience, has become one of the most promising technologies, showing great potential, particularly in large-scale industrial applications.

[0003] Absorption-based CO2 capture technology demonstrates excellent CO2 capture efficiency, and amine absorbents are the mainstream choice for industrial applications due to their superior absorption capacity and low cost. With the development of new absorbents and optimization of absorption processes, the operating cost of amine-based chemical absorption CO2 capture systems is continuously decreasing. However, as the scale of CO2 capture continues to expand, the emission problems of amine absorbents are becoming increasingly apparent, especially the release of amine absorbents in vapor and aerosol form.

[0004] According to the latest research data, the emission concentration of amine absorbents can reach thousands of milligrams per cubic meter, severely affecting the operational stability of the system and potentially causing a series of problems such as equipment corrosion and increased operating and maintenance costs. Furthermore, once released into the atmosphere, amine absorbents may act as precursors to air pollution, impacting environmental quality and air health.

[0005] To effectively control and reduce absorbent escape and emissions, two main technical approaches are currently employed: in-tower regulation and end-of-pipe removal. Each of these technologies has its own application scenarios and advantages; through synergy, they can minimize absorbent emissions and improve the system's economic efficiency and environmental friendliness.

[0006] In-tower control technology optimizes operating parameters within the absorption tower to reduce absorbent volatilization and dispersion, thereby suppressing absorbent emissions at the source. The main control measures include: 1) dynamically adjusting the liquid-to-gas ratio based on factors such as flue gas flow rate and absorbent concentration; 2) dynamically adjusting the absorbent replenishment amount by real-time monitoring of absorbent concentration and actual operating conditions; 3) maintaining the tower temperature within a range that efficiently absorbs CO2 without causing excessive absorbent volatilization through staged cooling, humidification, and temperature reduction technologies, thus reducing absorbent dispersion; and 4) improving the airflow distribution structure within the tower and installing devices such as demisters and atomizing plates. Through these in-tower control measures, the volatilization and dispersion of amine absorbents can be effectively reduced at the source, lowering emissions. Furthermore, in-tower control technology has low operating costs and technical complexity, making it suitable for most industrial applications.

[0007] However, although the tower regulation can significantly reduce the emission of amines, there is still a certain amount of absorbent emissions, so end removal is a necessary technical means.

[0008] The end removal technology mainly captures and purifies the escaped amine substances after the outlet of the absorption tower through a series of equipment and processes. Common end removal technologies include wet electrostatic precipitator, Brown diffuser, acid washing tower, etc. The acid washing tower has a high removal efficiency for gaseous organic amines, but a low removal efficiency for amine aerosols. Although the wet electrostatic precipitator and the Brown diffuser can remove amine aerosols, the removal efficiency is still affected by the particle size of the aerosols.

[0009] CA 114632402A discloses a flue gas carbon dioxide capture system and a capture method. The system includes an absorption part and a resolution part. The absorption part includes an absorption tower for absorbing carbon dioxide. The resolution part includes a first resolution tower and a second resolution tower for thermal resolution to regenerate carbon dioxide. The pressure of the first resolution tower is greater than that of the second resolution tower. The method uses two desorption towers with different pressures, which is suitable for increasing the pressure and improving the rate of the regeneration reaction, thereby reducing the residence time required for rich liquid regeneration.

[0010] CN 117531334 A discloses a physical-chemical coupled absorption process for removing carbon dioxide and a phase change absorbent. The process includes a physical absorption tower, a chemical absorption tower, a desorption tower, a phase separation tank, and a lean-rich liquid heat exchanger. The tail gas containing CO2 is pretreated and then enters the physical absorption tower to contact with ionic liquid, and then enters the chemical absorption tower. The tail gas entering the chemical absorption tower reacts with the amine absorbent, and the purified tail gas is discharged from the top of the chemical absorption tower. The ionic liquid rich in CO2 and the amine absorbent rich in CO2 enter the phase separation tank. In the phase separation tank, CO2 in the ionic liquid rich liquid is transferred to the amine absorbent rich liquid, the ionic liquid lean liquid returns to the physical absorption tower for reuse, and the amine absorbent rich liquid enters the desorption tower through the lean-rich liquid heat exchanger. The amine absorbent rich liquid is heated and desorbed in the desorption tower, and the desorbed CO2 is discharged from the top of the desorption tower. The amine absorbent lean liquid enters the chemical absorption tower through the lean-rich liquid heat exchanger for new absorption.

[0011] Therefore, in view of the limitations of the prior art, it is urgent to develop a new technology that is specifically designed for amine aerosol characteristics and can efficiently and directionally enrich and control amine emissions. This technology not only needs to improve the removal efficiency of amine aerosols, but also should be organically combined with the existing chemical absorption carbon capture system, fully utilize the operation and working conditions of the existing system, and reduce the energy consumption, maintenance cost and equipment investment of the system, so as to promote the practical application of amine method carbon capture technology in large-scale carbon emission reduction. SUMMARY

[0012] The application aims to provide a carbon capture escape absorbent deep removal method, which realizes directional enrichment of organic amine by throttling liquid drops of compressed CO2 in a carbon capture system, so as to improve the removal efficiency of the organic amine absorbent.

[0013] The existing chemical absorption carbon capture system needs to be respectively subjected to water washing tower and condenser for deep treatment of the escape absorbent in the flue gas at the outlet of the absorption tower and the flue gas at the outlet of the desorption tower, but the treatment effect is insufficient. The application provides a carbon capture escape absorbent deep removal device and method, which mainly flexibly extracts a small amount of compressed and heat-exchanged high-pressure CO2 from different pressure levels of the compressor according to actual needs on the basis of the existing chemical absorption carbon capture device, throttles and cools the high-pressure CO2 through a throttle, and forms CO2 low-temperature mist drops, further introduces the CO2 low-temperature mist drops into the inlet of the demister at the outlet of the water washing tower and the inlet of the filter at the outlet of the condenser respectively, and induces the residual organic amine absorbent gas in the flue gas to be directionally enriched on the surface of the mist drops through the CO2 low-temperature mist drops, and then the organic amine absorbent gas is efficiently removed by the demister and the filter.

[0014] The application provides a carbon capture escape absorbent deep removal method, which adds one bypass to extract high-pressure CO2 after each compression level of a multi-stage compression unit, collects the high-pressure CO2 extracted from the multiple bypasses, and then divides the high-pressure CO2 into two paths to be introduced into a demister and a filter through two throttles respectively, and returns the absorbent collected from the demister and the filter to the absorption tower to enter the absorption-desorption circulation system again.

[0015] Preferably, an independent temperature sensor, a pressure sensor and a valve are arranged in each bypass, and the opening of the valve in each bypass is adjusted according to actual needs.

[0016] Preferably, the multi-stage compression unit is a three-stage compression unit, which comprises a primary compressor, a primary heat exchanger, a secondary compressor, a secondary heat exchanger, a tertiary compressor and a tertiary heat exchanger, and the bypasses are arranged after the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger respectively.

[0017] Preferably, the flow rate of each bypass is not more than 1‰ of the total amount of flue gas at the outlet of the desorption tower, and preferably not more than 0.5‰, and the flow rate of the bypass is dynamically adjusted according to the flow rate of the flue gas at the outlet of the desorption tower.

[0018] Preferably, the opening of the bypass is adjusted according to the flue gas load, the bypass after the primary heat exchanger is opened at a load of 0-50%, the bypass after the secondary heat exchanger is opened at a load of 50-80%, and the bypass after the tertiary heat exchanger is opened at a load of 80-100%.

[0019] Preferably, the bypass flow rate connected to the demister and the bypass flow rate connected to the filter are Q1 and Q2 respectively, and the ratio of Q1 to Q2 is 3:2-9:1.

[0020] Preferably, the ratio of Q1 to Q2 is 8:1-9:1 for flue gas discharged by coal-fired power plants and steel plants, the ratio of Q1 to Q2 is 7:1-8:1 for flue gas discharged by cement kilns, and the ratio of Q1 to Q2 is 3:2-4:1 for flue gas discharged by synthetic gas plants.

[0021] Preferably, the throttles are arranged in an array at the flue gas cross section of the inlet of the mist eliminator and the inlet of the filter; the throttle is preferably an orifice plate throttle.

[0022] Preferably, the method has a capture rate of liquid absorbent droplets of more than 99%, and the concentration of absorbent in the treated flue gas is less than 0.5 mg / Nm 3 , and the total amount of recovered absorbent liquid accounts for more than 99% of the escaped absorbent at the outlet of the desorption tower.

[0023] The beneficial technical effects of the present application: the present application does not need to introduce additional refrigeration equipment and inducing medium, fully utilizes the existing chemical absorption method carbon capture device, utilizes high-pressure CO2 throttling to produce CO2 low-temperature droplets, improves the chemical reaction efficiency of CO2 and organic amine, realizes the improvement of removal efficiency, compared with the existing condensation, spraying and other technologies, does not increase the material consumption, the process is simple, the modification cost is low, and the effect is good. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The process diagram of the carbon capture escaped absorbent deep removal device described in the present application. DETAILED DESCRIPTION

[0025] The technical solutions and applications of the present application will be described below through various embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, not all.

[0026] Example 1

[0027] This embodiment is based on a carbon capture experimental device for simulated flue gas of a certain coal-fired power plant. The coal-fired flue gas captures CO2 by absorption method, and the outlet flue gas of the desorption tower is entrained with a small amount of escaped absorbent droplets and fine particles. In order to reduce the loss of absorbent and reduce the corrosion risk of subsequent equipment, the carbon capture escaped absorbent deep removal process and method of the present application are used for treatment. The total flue gas flow of the desorption tower of the carbon capture device of the coal-fired power plant is 10000 Nm 3The main component of the / h is CO2 (more than 95%), and the outlet temperature is 100°C, and the pressure is close to normal pressure. The flue gas at the outlet of the desorption tower enters the three-stage compression and heat exchange device in turn through the main flow pipeline: after the flue gas is compressed and heat-exchanged in the first stage, the pressure is increased from normal pressure to 0.8 MPa, and the temperature is reduced from 100°C to 50°C; after the flue gas is compressed and heat-exchanged in the second stage, the pressure is further increased to 1.5 MPa, and the temperature is reduced to 40°C; after the flue gas is compressed and heat-exchanged in the third stage, the pressure reaches 2.5 MPa, and the temperature is reduced to 30°C.

[0028] According to the flue gas load of the coal-fired power plant, the bypass is opened dynamically: when the load is low (0-50%), the bypass after the first-stage compression and heat exchange is opened; when the load is medium (50-80%), the bypass after the second-stage compression and heat exchange is opened; when the load is high (80-100%), the bypass after the third-stage compression and heat exchange is opened. The total flow of the bypass system is not more than 1‰ of the total flow of the main flue gas, that is, the bypass flow is controlled to be less than or equal to 10 Nm 3 / h. The bypass flue gas passes through the valve to control the flow, and is divided into two paths: one path enters the mist eliminator to form CO2 low-temperature droplets after throttling, which are used to enrich and remove the escaped absorbent in the flue gas at the outlet of the absorption tower; the other path enters the filter to form CO2 low-temperature droplets after throttling, which are used to remove the escaped absorbent in the flue gas at the outlet of the desorption tower. In order to ensure the treatment efficiency, the throttling devices are arranged in an array manner in the flue gas cross section at the inlet of the mist eliminator and the filter. The throttling devices are in the form of orifice plate throttling devices. The flow distribution ratio of the two paths is 8:1, that is, 8 Nm 3 / h and 2 Nm 3 / h respectively. The CO2 low-temperature droplets interact with the absorbent to enrich it, and then the enriched absorbent is removed through the mist eliminator and the filter. The mist eliminator is a multi-layer filler and a high-efficiency mist elimination element, and the captured absorbent liquid is collected through the recovery liquid circuit 2. The filter uses a high-efficiency filter element, and the captured absorbent is collected through the recovery liquid circuit 1. The liquids in the recovery liquid circuits 1 and 2 are combined and then returned to the absorption tower to enter the absorption-desorption circulation system again.

[0029] The above process is actually tested, and the specific operation data and effects are as follows: the absorbent droplet concentration in the flue gas at the outlet of the absorption tower is 30 mg / Nm 3 , the capture rate of the liquid absorbent droplets by the process method reaches 99%, the absorbent concentration in the treated flue gas is reduced to 0.3 mg / Nm 3 , and the total amount of the recovered absorbent liquid accounts for 99.5% of the escaped absorbent at the outlet of the desorption tower.

[0030] The present application has the following advantages in the carbon capture system of the coal-fired power plant: 1) without adding additional heat exchanger and other equipment, fully utilizing the existing process conditions, simple and feasible scheme; 2) high-efficiency removal of escape absorbent. Effectively reducing the escape of absorbent, avoiding the corrosion of subsequent equipment; 3) absorbent recycling. Greatly reducing the absorbent loss, saving the operation cost; 4) process adjustment flexibility. The bypass flow and distribution ratio can be flexibly adjusted according to the flue gas load, and the adaptability is strong.

[0031] In addition, the process of the present application is also applicable to the flue gas treatment of other industries, such as steel plants, cement kilns and synthetic gas production processes.

[0032] The present application has been described in detail with general description and specific embodiments, but some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of the present application.

Claims

1. A method for deep removal of carbon capture escape absorbent, a bypass is added after each compression stage of a multi-stage compression unit to lead out high-pressure CO2, the high-pressure CO2 led out from multiple bypasses is collected and divided into two paths, one path enters a demister to form CO2 low-temperature mist droplets after throttling, to enrich and remove the escape absorbent in the flue gas at the outlet of an absorption tower; the other path enters a filter to remove the escape absorbent in the flue gas at the outlet of a desorption tower after throttling to form CO2 low-temperature mist droplets; the absorbent captured from the demister and the filter is combined and returned to the absorption tower to enter the absorption-desorption circulation system again; each compressor of the multi-stage compression unit comprises a heat exchanger; the desorption tower, the condenser, the filter and the multi-stage compression unit are connected in sequence.

2. The method of claim 1, wherein An independent temperature sensor, a pressure sensor and a valve are arranged at each bypass, and the opening of the valve at each bypass is adjusted according to actual needs.

3. The method of claim 1, wherein The multi-stage compression unit is a three-stage compression unit, comprising a primary compressor, a primary heat exchanger, a secondary compressor, a secondary heat exchanger, a tertiary compressor and a tertiary heat exchanger; the bypasses are arranged after the primary heat exchanger, the secondary heat exchanger and the tertiary heat exchanger respectively.

4. The method of claim 1, wherein The flow rate of each bypass is not greater than 1‰ of the total amount of flue gas at the outlet of the desorption tower.

5. The method of claim 4, wherein The flow rate of the bypass is dynamically adjusted according to the flow rate of the flue gas at the outlet of the desorption tower.

6. The method of claim 5, wherein The opening of the bypass is adjusted according to the flue gas load, the bypass after the primary heat exchanger is opened at a load of 0-50%, the bypass after the secondary heat exchanger is opened at a load of 50-80%, and the bypass after the tertiary heat exchanger is opened at a load of 80-100%.

7. The method of claim 1, wherein The bypass flow rate connected to the demister and the bypass flow rate connected to the filter are Q1 and Q2 respectively, and the ratio of Q1 to Q2 is 3:2-9:

1.

8. The method of claim 1, wherein The bypass flow rate connected to the demister and the bypass flow rate connected to the filter are Q1 and Q2 respectively, and for the flue gas discharged by a coal-fired power plant and a steel plant, the ratio of Q1 to Q2 is 8:1-9:1, for the flue gas discharged by a cement kiln, the ratio of Q1 to Q2 is 7:1-8:1, and for the flue gas discharged by a synthetic gas device, the ratio of Q1 to Q2 is 3:2-4:

1.

9. The method of claim 1, wherein The throttlers are arranged in an array at the flue gas cross section at the inlet of the demister and the inlet of the filter.

10. The method of claim 1, wherein The capture rate of liquid absorbent droplets in the method is more than 99%, the concentration of absorbent in the treated flue gas is less than 0.5 mg / Nm3, and the total amount of absorbent recovery liquid accounts for more than 99% of the escape absorbent at the outlet of the desorption tower.

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