Deep removal method of carbon capture escape absorbent

Abstract

The invention relates to a deep removal method of a carbon capture escape absorbent, which comprises the following steps: adding a bypass behind each compression stage of a multi-stage compression unit to lead out high-pressure CO2, converging the high-pressure CO2 led out by the plurality of bypasses, dividing the high-pressure CO2 into two paths, respectively introducing the high-pressure CO2 into a demister and a filter through two throttlers, converging absorbents captured by the demister and the filter, and uniformly returning the absorbents to an absorption tower, and entering the absorption-desorption circulation system again. According to the method, additional refrigeration equipment and an induction medium do not need to be introduced, an existing chemical absorption method carbon capture device is fully utilized, high-pressure CO2 is used for throttling and cooling to generate CO2 low-temperature fog drops, the chemical reaction efficiency of CO2 and organic amine is improved, the removal efficiency is improved, and compared with other technologies such as condensation and spraying, the method has the advantages that the cost is low, and the efficiency is high. Material consumption is not increased, the process is simple, the modification cost is low, and the effect is good.

Description

Technical Field

[0001] The invention relates to the field of emission reduction and carbon reduction of flue gas discharged from a carbon dioxide capture tower, and in particular to a process and method for deep removal of a carbon capture escape absorbent. Background Art

[0002] As the global climate change problem intensifies, reducing CO2 emissions has become the primary task for all countries to deal with the greenhouse effect and environmental pollution. Carbon capture and storage technology (CCS) in the use of fossil energy has gradually become an important technical path to reduce industrial emissions, especially CO2 emissions in the power and chemical industries. Absorption CO2 capture technology has become one of the most promising technologies with its high absorption efficiency and mature industrial application experience, especially showing great potential in large-scale industrial applications.

[0003] Absorption CO2 capture technology performs well in terms of CO2 capture efficiency. Amine absorbents are the mainstream choice in industrial applications due to their excellent 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 continues to decrease. However, with the continuous expansion of CO2 capture, the emission problem of amine absorbents has become increasingly apparent, especially the release of amine absorbents in steam and aerosols.

[0004] According to the latest research data, the emission concentration of amine absorbents can reach thousands of milligrams per cubic meter, which seriously affects the operational stability of the system and may cause a series of problems such as equipment corrosion and increased operating and maintenance costs. In addition, after amine absorbents are discharged into the atmosphere, they may act as precursors to air pollution, affecting environmental quality and air health.

[0005] In order to effectively control and reduce the escape and emission of absorbents, two major technical means are currently used: in-tower regulation and terminal removal. These two types of technologies each have their own application scenarios and advantages. Through synergy, they can minimize the emission of absorbents and improve the economy and environmental friendliness of the system.

[0006] The in-tower control technology reduces the volatilization and escape of the absorbent by optimizing the operating parameters in the absorption tower, thereby suppressing the emission of the absorbent from the source. The main control measures include the following aspects: 1) Dynamically adjust the liquid-gas ratio according to factors such as flue gas flow and absorbent concentration; 2) Dynamically adjust the amount of absorbent replenishment by real-time monitoring of absorbent concentration and actual operating conditions; 3) Maintain the temperature in the tower in a range that can efficiently absorb CO2 without causing excessive volatilization of the absorbent through technologies such as graded cooling, humidification and cooling, thereby reducing the escape of the absorbent; 4) Improve the airflow distribution structure in the tower and install demisters, atomizers and other devices in the tower. Through the above-mentioned in-tower control measures, the volatilization and escape of amine absorbents can be effectively reduced at the source, and emissions can be reduced. The in-tower control technology has low operating costs and technical complexity, and is suitable for most industrial applications.

[0007] However, although in-tower regulation can significantly reduce amine emissions, there is still a certain amount of absorbent emissions, so end-of-line removal is a necessary technical means.

[0008] The terminal removal technology mainly involves capturing and purifying the escaped amine substances through a series of equipment and processes after the outlet of the absorption tower. Common terminal removal technologies include wet electrostatic precipitators, Brownian diffusers, acid washing towers, etc. Among them, the acid washing tower has a high removal efficiency for gaseous organic amines, but a low removal efficiency for amine aerosols. Although wet electrostatic precipitators and Brownian diffusers can remove amine aerosols, the removal efficiency is still affected by the aerosol particle size.

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

[0010] CN 117531334 A discloses a physical-chemical coupling absorption and removal of carbon dioxide process and a phase-change absorbent, comprising a physical absorption tower, a chemical absorption tower, a desorption tower, a phase separation tank and a lean-rich liquid heat exchanger; after pretreatment, tail gas containing CO2 first enters the physical absorption tower to contact with an ionic liquid, and then enters the chemical absorption tower; the tail gas entering the chemical absorption tower reacts with an amine absorbent, and the purified tail gas is discharged from the top of the chemical absorption tower; the ionic liquid rich liquid after absorbing CO2 and the amine absorbent rich liquid after absorbing CO2 in the chemical absorption tower enter the phase separation tank; in the phase separation tank, the 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, the desorbed CO2 is discharged from the top of the desorption tower, and 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 existing technologies, it is urgent to develop a new technology that specifically targets the characteristics of amine aerosols and can efficiently and directional enrich and control amine emissions. This technology not only needs to improve the removal efficiency of amine aerosols, but also should be able to be organically combined with the existing chemical absorption carbon capture system, make full use of the operation and working conditions of the existing system, reduce the system's energy consumption, maintenance costs and equipment investment, and thus promote the practical application of amine carbon capture technology in large-scale carbon emission reduction. Summary of the invention

[0012] The object of the present invention is to provide a method for deep removal of carbon capture escaped absorbent, which realizes directional enrichment of organic amines by generating droplets through throttling of CO2 compressed by the carbon capture system, thereby improving the removal efficiency of the organic amine absorbent.

[0013] The flue gas at the outlet of the absorption tower and the outlet of the desorption tower of the existing chemical absorption carbon capture system need to pass through a water scrubber and a condenser respectively to deeply treat the escaped absorbent in the flue gas, but the treatment effect is insufficient. The present invention provides a device and method for deeply removing the escaped absorbent from carbon capture. It is mainly based on the existing chemical absorption carbon capture device. According to actual needs, a small amount of high-pressure CO2 after compression and heat exchange is flexibly extracted from different pressure levels of the compressor, and the high-pressure CO2 is throttled and cooled through a throttle to form CO2 low-temperature droplets. The CO2 low-temperature droplets are further introduced into the inlet of the demister at the outlet of the water scrubber and the inlet of the filter at the outlet of the condenser. The residual organic amine absorbent gas in the flue gas is induced to be enriched on the surface of the droplets through the CO2 low-temperature droplets, and then efficiently removed by the demister and the filter.

[0014] The present invention provides a method for deep removal of carbon capture escaped absorbent, in which a bypass is added after each compression stage of a multi-stage compression unit to draw out high-pressure CO2, the high-pressure CO2 drawn out from multiple bypasses are collected and divided into two paths to pass through two throttles to enter a demister and a filter respectively, the absorbent captured from the demister and the filter is combined and uniformly returned to the absorption tower to enter the absorption-desorption cycle system again.

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

[0016] Preferably, the multi-stage compression unit is a three-stage compression unit, including a primary compressor, a primary heat exchanger, a secondary compressor, a secondary heat exchanger, a tertiary compressor, and a tertiary heat exchanger; the bypass is respectively arranged after the primary heat exchanger, the secondary heat exchanger, and the tertiary heat exchanger.

[0017] Preferably, each bypass flow is no more than 1‰ of the total amount of flue gas at the outlet of the desorption tower, preferably no more than 0.5‰; preferably, the bypass flow is dynamically adjusted according to the flue gas flow at the outlet of the desorption tower.

[0018] Preferably, the bypass opening is adjusted according to the flue gas load, the bypass after the first stage heat exchange is opened at 0-50% load, the bypass after the second stage heat exchange is opened at 50-80% load, and the bypass after the third stage heat exchange is opened at 80-100% load.

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

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

[0021] Preferably, the throttles are arranged in an array at the smoke cross-sections at the demister inlet and the filter inlet; the throttles are preferably orifice plate throttles.

[0022] Preferably, the method can capture more than 99% of the liquid absorbent droplets, and the absorbent concentration in the flue gas after treatment is less than 0.5 mg / Nm 3 The total amount of absorbent recovered liquid accounts for more than 99% of the absorbent escaping from the outlet of the desorption tower.

[0023] The beneficial technical effects of the present invention are as follows: the present invention does not require the introduction of additional refrigeration equipment and inducing media, fully utilizes the existing chemical absorption carbon capture device, utilizes high-pressure CO2 throttling and cooling to produce CO2 low-temperature droplets, improves the chemical reaction efficiency of CO2 and organic amines, and achieves improved removal efficiency. Compared with existing condensation, spraying and other technologies, it does not increase material consumption, has a simple process, low transformation cost and good effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of the device for deep removal of carbon capture escaped adsorbent according to the present invention. DETAILED DESCRIPTION

[0025] The technical solution and application of the present invention will be clearly and completely described below through various embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0026] Example 1

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

[0028] According to the flue gas load of the coal-fired power plant, the bypass opening is dynamically adjusted: 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 does not exceed 1‰ of the total flow of the mainstream flue gas, that is, the bypass flow is controlled at 10Nm 3 / h or less. The bypass flow is precisely controlled by dynamically adjusting the valve. The bypass flue gas is controlled by a valve and divided into two paths. One path enters the demister and forms 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 forms CO2 low-temperature droplets after throttling and enters the filter to remove the escaped absorbent in the flue gas at the outlet of the desorption tower. To ensure the processing efficiency, the throttles are evenly arranged in an array in the flue gas cross-section at the inlet of the demister and the filter. The throttle is an orifice plate throttle. The two-way flow distribution ratio is 8:1, that is, 8Nm 3 / h and 2Nm 3 / h. After CO2 low-temperature droplets interact with the absorbent to enrich it, they are removed through the demister and filter. The demister is a multi-layer filler and a high-efficiency demister element. The captured absorbent liquid is collected through the recovery liquid loop 2. The filter uses a high-efficiency filter element. The captured absorbent is collected through the recovery liquid loop 1. The liquids in the recovery liquid loop 1 and loop 2 are combined and returned to the absorption tower and enter the absorption-desorption cycle system again.

[0029] The above process was actually tested, and the specific operating data and results are as follows: The absorbent droplet concentration in the flue gas at the outlet of the absorption tower is 30mg / Nm 3 The process can capture 99% of the liquid absorbent droplets, and the absorbent concentration in the flue gas after treatment is reduced to 0.3mg / Nm 3 The total amount of absorbent recovered liquid accounts for 99.5% of the absorbent escaping from the outlet of the desorption tower.

[0030] The present invention has the following advantages in the carbon capture system of coal-fired power plants: 1) No need to add additional equipment such as heat exchangers, fully utilizing existing process conditions, and the scheme is simple and feasible; 2) Efficient removal of escaping absorbent. Effectively reduce the escape of absorbent and avoid corrosion of subsequent equipment; 3) Recycling of absorbent. Greatly reduce absorbent loss and save operating costs; 4) Flexible process adjustment. The bypass flow and distribution ratio can be flexibly adjusted according to the flue gas load, with strong adaptability.

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

[0032] The present invention has been described in detail by general description and specific embodiments, but it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, these modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for deep removal of carbon capture escaped absorbent, wherein a bypass is added after each compression stage of a multi-stage compression unit to draw out high-pressure CO2, and the high-pressure CO2 drawn out from multiple bypasses are collected and divided into two paths and respectively passed through two throttles to enter a demister and a filter, and the absorbent captured from the demister and the filter is combined and returned to the absorption tower and enters the absorption-desorption cycle system again.

2. The method according to claim 1, characterized in that Independent temperature sensors, pressure sensors and valves are installed in each bypass, and the opening of the valves in each bypass is adjusted according to actual needs.

3. The method according to claim 1, characterized in that The multi-stage compression unit is a three-stage compression unit, including a primary compressor, a primary heat exchanger, a secondary compressor, a secondary heat exchanger, a tertiary compressor, and a tertiary heat exchanger; the bypass is respectively arranged after the primary heat exchanger, the secondary heat exchanger, and the tertiary heat exchanger.

4. The method according to claim 1, characterized in that Each bypass flow is no more than 1‰ of the total amount of flue gas at the outlet of the desorption tower, and preferably no more than 0.5‰; preferably, the bypass flow is dynamically adjusted according to the flue gas flow at the outlet of the desorption tower.

5. The method according to claim 4, characterized in that The bypass opening is adjusted according to the flue gas load. The bypass after the first stage heat exchange is opened at 0-50% load, the bypass after the second stage heat exchange is opened at 50-80% load, and the bypass after the third stage heat exchange is opened at 80-100% load.

6. The method according to claim 1, characterized in that The bypass flow rate of the demister and the bypass flow rate of the filter are Q1 and Q2 respectively, and the ratio of Q1 to Q2 is 3:2-9:

1.

7. The method according to claim 1, characterized in that For flue gas emitted from coal-fired power plants and steel mills, the ratio of Q1 to Q2 is 8:1-9:1; for flue gas emitted from cement kilns, the ratio of Q1 to Q2 is 7:1-8:1; for flue gas emitted from synthesis gas plants, the ratio of Q1 to Q2 is 3:2-4:

1.

8. The method according to claim 1, characterized in that The throttles are arranged in an array at the smoke cross-sections at the demister inlet and the filter inlet; the throttles are preferably orifice plate throttles.

9. The method according to claim 1, characterized in that The method can capture more than 99% of the liquid absorbent droplets, and the absorbent concentration in the flue gas after treatment is less than 0.5 mg / Nm 3 The total amount of absorbent recovered liquid accounts for more than 99% of the absorbent escaping from the outlet of the desorption tower.

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