Coupling type carbon dioxide trapping system and method

Abstract

The invention relates to a coupling type carbon dioxide trapping system and method. The system comprises an absorption tower, a desorption tower, a rich amine solution buffer tank, a lean amine solution buffer tank, a gas-liquid separator, a reboiler, an electric heat pump heater, an electric heater, a lean and rich solution heat exchanger, a regenerated gas cooler, a lean solution cooler and an electric heat pump. The invention provides a novel carbon dioxide trapping system for realizing green electricity consumption by coupling a rich / lean amine solution buffer tank and an electric heat pump / electric heater. In the high electricity price period of the power grid load peak period, rich liquid is stored through the rich amine liquid buffer tank, the regeneration desorption and CO2 compression liquefaction process is not carried out, and the influence on unit output is avoided; in a low-electricity-price period of a power grid load trough period, renewable energy sources are used for abandoning electricity, an electric heat pump heater and an electric heater are used for heating and desorbing stored organic amine rich liquor, and regenerated barren liquor is stored in a barren amine liquor buffer tank at the same time so as to be used when a unit and a carbon capture island are in high loads.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, and more specifically, to a coupled carbon dioxide capture system and method. Background Technology

[0002] With increasingly stringent requirements for greenhouse gas emission reduction, carbon dioxide capture, utilization, and storage (CCUS) technology for coal-fired power units has become a key focus. Existing organic amine absorption-desorption processes, represented by monoethanolamine (MEA), are relatively mature. However, the desorption process requires heating the rich liquor to above 120°C, resulting in a regeneration energy consumption of approximately 2.5~3.5 GJ / tCO2, and CO2 compression and liquefaction energy consumption of approximately 150 kW·h / tCO2. The direct operation of the carbon capture system has high energy consumption. During peak electricity demand periods, the boilers and carbon capture islands of the units experience high loads. Traditional desorption tower regeneration processes require the extraction of large amounts of steam from the turbine extraction port, severely impacting turbine output. Simultaneously, CO2 compression and liquefaction energy consumption increases plant power consumption, reducing the unit's grid-connected power output. During off-peak electricity demand periods, grid dispatch typically requires units to operate at the lowest possible load depth for peak shaving, which can affect unit safety to some extent. When the unit operates at low load, the steam flow rate and extraction parameters of the steam turbine will decrease to some extent. Therefore, pressure-holding valves are needed to maintain the extraction pressure, which further reduces the unit efficiency. In addition, due to the intermittent, random, and volatile characteristics of renewable energy sources such as wind power and photovoltaics, the power grid cannot fully absorb their power generation, resulting in serious wind and solar curtailment. It is necessary to find ways to absorb renewable energy on a large scale.

[0003] CN115487649A discloses a carbon capture system and method for a coal-fired power generation unit coupled with a steam ejector. The system is characterized by coupling a steam ejector, using steam inlet to eject steam outlet from the low-pressure cylinder to obtain steam with suitable parameters as a heat source for the reboiler, recovering waste heat from the cold end of the unit, reducing the energy consumption of the carbon capture device, and reducing the resource consumption and CO2 emissions of the coal-fired power generation unit.

[0004] CN115463516B discloses a system and method for using flue gas waste heat for carbon capture and regeneration. In this system, a stream of flue gas from a boiler exchanges heat with an air preheater to obtain a first flue gas stream; another stream of flue gas from the boiler exchanges heat with the rich liquid in a reboiler to obtain a second flue gas stream; the first and second flue gas streams are combined and exchange heat with the rich liquid in the rich liquid reheater before entering the carbon capture absorption tower for carbon capture.

[0005] CN117000032A discloses a carbon capture system and method for coal-fired power units coupled with thermochemical energy storage. During full-load operation of the coal-fired power unit, CaO is used to absorb and capture CO2 from the flue gas at the tail end of the coal-fired boiler. During off-peak electricity demand, flue gas from the coal-fired boiler is extracted, and the heat from the flue gas is used to reduce CaCO3 in a calciner. The resulting CaO is stored in a CaO storage container, and a portion of the power generated by the coal-fired power unit drives the air separation unit. During peak electricity demand periods, a portion of the power from the energy storage device drives the air separation unit.

[0006] The existing carbon capture system for flue gas after combustion in coal-fired units does not take into account the decoupling of the absorption and regeneration processes in time and space. The carbon capture unit needs to operate continuously with the unit load, which will seriously affect the unit output during peak grid load periods. When the system load is low, it will face the problem of mismatch between turbine extraction parameters, affecting the unit efficiency and thus significantly increasing the direct and indirect operating costs of the decarbonization unit. Summary of the Invention

[0007] The purpose of this invention is to provide a coupled carbon dioxide capture system and method that can increase unit output during peak grid load periods and absorb renewable energy green electricity during off-peak periods to assist in deep peak shaving operation of the units.

[0008] To achieve the above objectives, the present invention provides a coupled carbon dioxide capture system, which includes an absorption tower, a desorption tower, a rich amine buffer tank, a lean amine buffer tank, a gas-liquid separator, a reboiler, an electric heat pump heater, an electric heater, a rich and lean liquid heat exchanger, a regenerated gas cooler, a lean liquid cooler, and an electric heat pump. The gas inlet of the absorption tower is connected to the outlet of the flue gas containing carbon dioxide; the rich liquid outlet of the absorption tower is connected to the rich liquid inlet of the rich amine buffer tank; the rich liquid outlet of the rich amine buffer tank is connected to the rich liquid inlet of the desorption tower through the lean-rich liquid heat exchanger; the lean liquid outlet of the desorption tower is connected to the lean liquid inlet of the lean amine buffer tank through the lean-rich liquid heat exchanger and the lean liquid cooler; and the lean liquid outlet of the lean amine buffer tank is connected to the lean liquid inlet of the absorption tower. The CO2 / water vapor mixture outlet of the desorption tower is connected to the CO2 / water vapor mixture inlet of the gas-liquid separator through the regeneration gas cooler. The CO2 gas outlet of the gas-liquid separator is connected to the CO2 gas inlet of the compression liquefaction unit, and the condensate water outlet is connected to the inlet of the absorbent storage tank. The rich liquid outlet of the desorption tower is connected to the first inlet of the reboiler, the inlet of the electric heat pump heater, and the inlet of the electric heater, respectively. The first outlet of the reboiler, the outlet of the electric heat pump heater, and the outlet of the electric heater are connected to the desorption tower, respectively. The steam extraction outlet of the power plant turbine is connected to the second inlet of the reboiler, and the second outlet of the reboiler is drained and connected to the unit condensate system. Optionally, the electric heat pump is used to extract waste heat from the CO2 / water vapor mixture at the outlet of the desorption tower, and after upgrading the waste heat, it is delivered to the electric heat pump heater to provide energy for the electric heat pump heater.

[0009] Optionally, the electric heater and the electric heat pump are connected to green electricity; the green electricity is equipped with an energy storage device and connected to a PLC control module.

[0010] Optionally, the rich amine buffer tank is equipped with an insulation layer and a temperature sensor; the lean amine buffer tank is equipped with a turbulence disturber, a temperature-level control system, and a flow buffer valve.

[0011] Another aspect of the present invention provides a coupled carbon dioxide capture method, which uses the coupled carbon dioxide capture system provided above by the present invention, and the method includes: The carbon dioxide-containing flue gas is brought into countercurrent contact with the absorbent in the absorption tower to absorb the carbon dioxide in the flue gas. The resulting rich liquid is then sent to a rich amine buffer tank for storage. The rich liquid in the rich amine buffer tank is sent to a lean-rich liquid heat exchanger for heat exchange and then sent to a desorption tower for desorption to obtain a lean liquid and a CO2 / water vapor mixture. The rich liquid is heated by a reboiler, an electric heat pump heater, and an electric heater. The PLC control module controls green electricity and the supporting energy storage device to supply power to the electric heat pump heater and the electric heater. The lean liquor is sent to the lean-rich liquor heat exchanger for heat exchange and then sent to the lean liquor cooler for further cooling; the cold lean liquor from the outlet of the lean liquor cooler is sent to the lean amine liquor buffer tank for storage; the lean liquor in the lean amine liquor buffer tank is sent to the absorption tower; After a portion of the waste heat is extracted from the CO2 / water vapor mixture using an electric heat pump, it is sent to a regenerated gas cooler for heat exchange and then to a gas-liquid separator for separation to obtain CO2 gas and condensate water.

[0012] Optionally, the temperature of the carbon dioxide-containing flue gas is 40-50°C.

[0013] Optionally, the absorbent is a 30-40 wt% monoethanolamine solution; the molar ratio of the absorbent to the CO2 gas is 0.4-0.5:1.

[0014] Optionally, the temperature of the rich amine buffer tank is ≥50℃; the temperature of the lean amine buffer tank is ≤40℃; and the inlet temperature of the lean amine in the absorption tower is 35-40℃.

[0015] Optionally, the temperature of the heated rich liquid is 120±2℃.

[0016] Optionally, the absolute pressure of the desorption tower is 0.14-0.18 MPa.

[0017] Optionally, the temperature of the CO2 / water vapor mixture at the outlet of the desorption tower is 75-95℃; after heat exchange by the regeneration gas cooler, the temperature of the CO2 / water vapor mixture is ≤40℃.

[0018] Through the above technical solution, this invention provides a novel carbon dioxide capture system for post-combustion flue gas of coal-fired power units that couples a rich / lean amine buffer tank with an electric heat pump / electric heater to achieve green electricity consumption. During peak electricity price periods, the rich amine buffer tank stores the organic amine rich solution without regeneration, desorption, or CO2 compression and liquefaction processes, thus avoiding impact on unit output. During off-peak electricity price periods, renewable energy curtailment is utilized, and the stored organic amine rich solution is heated and desorbed using an electric heat pump heater and an electric heater. Simultaneously, the regenerated lean organic amine solution is stored in the lean amine buffer tank for use during high load periods of the unit and carbon capture island.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the coupled carbon dioxide capture system of the present invention.

[0021] Explanation of reference numerals in the attached figures 1-Absorption tower, 2-Desorption tower, 3-Rich amine buffer tank, 4-Lean amine buffer tank, 5-Gas-liquid separator, 6-Reboiler, 7-Electric heat pump heater, 8-Electric heater, 9-Rich and lean amine heat exchanger, 10-Regenerated gas cooler, 11-Lean amine cooler, 12-Electric heat pump. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] This invention provides a coupled carbon dioxide capture system, such as... Figure 1 As shown, the system includes an absorption tower 1, a desorption tower 2, a rich amine buffer tank 3, a lean amine buffer tank 4, a gas-liquid separator 5, a reboiler 6, an electric heat pump heater 7, an electric heater 8, a lean and rich liquid heat exchanger 9, a regeneration gas cooler 10, a lean liquid cooler 11, and an electric heat pump 12. The gas inlet of the absorption tower 1 is connected to the outlet of the flue gas containing carbon dioxide; the rich liquid outlet of the absorption tower 1 is connected to the rich liquid inlet of the rich amine buffer tank 3; the rich liquid outlet of the rich amine buffer tank 3 is connected to the rich liquid inlet of the desorption tower 2 through the lean-rich liquid heat exchanger 9; the lean liquid outlet of the desorption tower 2 is connected to the lean liquid inlet of the lean amine buffer tank 4 through the lean-rich liquid heat exchanger 9 and the lean liquid cooler 11; and the lean liquid outlet of the lean amine buffer tank 4 is connected to the lean liquid inlet of the absorption tower 1. The CO2 / water vapor mixture outlet of the desorption tower 2 is connected to the CO2 / water vapor mixture inlet of the gas-liquid separator 5 through the regeneration gas cooler 10. The CO2 gas outlet of the gas-liquid separator 5 is connected to the CO2 gas inlet of the compression liquefaction device, and the condensate water outlet is connected to the inlet of the absorbent storage tank. The rich liquid outlet of the desorption tower 2 is connected to the first inlet of the reboiler 6, the inlet of the electric heat pump heater 7, and the inlet of the electric heater 8, respectively. The first outlet of the reboiler 6, the outlet of the electric heat pump heater 7, and the outlet of the electric heater 8 are connected to the desorption tower 2. The steam extraction outlet of the power plant turbine is connected to the second inlet of the reboiler 6. The second outlet of the reboiler 6 is drained and connected to the unit's condensate system.

[0024] According to the present invention, optionally, the electric heat pump 12 is used to extract waste heat from the CO2 / water vapor mixture at the outlet of the desorption tower 2, and after upgrading the waste heat, it is transported to the electric heat pump heater 7 to provide energy for the electric heat pump heater 7, thereby realizing energy transfer and upgrading between the CO2 / water vapor mixture, the electric heat pump, and the electric heat pump heater.

[0025] According to the present invention, optionally, the electric heater 8 and the electric heat pump 12 are connected to green electricity; the green electricity is equipped with an energy storage device to smooth load fluctuations, and the green electricity is also connected to a PLC control module.

[0026] Optionally, according to the present invention, the absorption tower 1 is used to absorb CO2 from the flue gas purified by the dust removal, desulfurization, and water washing process. The boiler flue gas enters the absorption tower after passing through the dust collector, desulfurization tower, and water washing tower in sequence, and comes into countercurrent contact with an organic amine solution with a concentration of 30-40 wt% to achieve chemical capture of CO2 in the flue gas, generating a CO2-rich amine solution. At the same time, the absorption tower is equipped with a novel high-efficiency small-toothed corner packing layer to enhance heat and mass transfer efficiency, and is equipped with an online CO2 concentration monitoring unit to adjust the circulation rate of the absorbent in real time.

[0027] According to the present invention, optionally, the rich amine buffer tank 3 is used to store rich organic amine solution, smoothing the amine flow rate and regeneration heat load between the absorption and desorption processes. The rich amine buffer tank of the present invention consists of a large vertical storage tank (preferably made of 304 stainless steel with an anti-corrosion coating) and a temperature control system. It has a rich amine solution storage capacity of ≥4 hours and achieves decoupling of the absorption-desorption process through a dual-tank design with a lean amine buffer tank. The tank is equipped with an insulation layer and a temperature sensor to maintain the rich solution temperature ≥50°C, ensuring the stability of the amine solution and reducing heat loss.

[0028] According to the present invention, optionally, the electric heat pump 12, the electric heat pump heater 7, and the electric heater 8 are used to heat and desorb organic amine-rich liquid using renewable energy surplus during off-peak electricity prices (nighttime or when grid load is low), replacing the steam extraction from the turbine used in the reboiler 6. The electric heat pump (COP≥4) is driven by renewable energy surplus electricity to improve the utilization of waste heat from the regenerated gas (CO2 / water vapor mixture) at the outlet of the desorption tower 2, reducing the cooling water consumption of the regenerated gas cooler 10. The heating process is linked to the green electricity grid price signal via a PLC module and is limited to activation during off-peak electricity price periods.

[0029] According to the present invention, optionally, the desorption tower 2 is used to pass preheated organic amine-rich solution into the desorption tower during off-peak electricity price periods to achieve carbon dioxide desorption and release high-purity CO2 gas. The desorption tower is equipped with a lean solution concentration feedback regulating valve to ensure solvent regeneration efficiency.

[0030] According to the present invention, optionally, the lean liquid cooler 11 is used to control the temperature of the lean liquid entering the lean amine buffer tank 4, the lean amine buffer tank 4 is used to store the lean organic amine liquid, the capacity of the lean amine buffer tank is symmetrically matched with the rich amine buffer tank (≥4 hours of lean liquid storage), and a built-in turbulence disturbance device is used to prevent amine liquid degradation; the temperature of the lean liquid is controlled below 40°C through temperature-level control, and a flow buffer valve is provided to smoothly deliver the lean liquid to the absorption tower, eliminating the influence of intermittent operation of the desorption process on the front-end absorption process section, and smoothing the amine liquid flow rate and regeneration heat load between the absorption process section and the desorption process section.

[0031] According to the present invention, optionally, the gas-liquid separator 5 is used to separate the regenerated gas obtained from the desorption tower 2, i.e., the CO2 / water vapor mixture. The separated CO2 gas is sent to the compression liquefaction unit, and the condensate is sent to the absorbent storage tank for makeup water. The compression liquefaction unit pressurizes the CO2 to above 2.6 MPa, and then cools it to -40°C to liquefy it for storage. The energy consumption for CO2 compression and liquefaction is approximately 150 kW·h / tCO2. The compression liquefaction process is carried out simultaneously with the rich liquid heating and desorption process, and is limited to operation during off-peak electricity price windows.

[0032] Another aspect of the present invention provides a coupled carbon dioxide capture method, which uses the coupled carbon dioxide capture system provided above by the present invention, and the method includes: The carbon dioxide-containing flue gas is brought into countercurrent contact with the absorbent in the absorption tower 1 to absorb the carbon dioxide in the flue gas, and the resulting rich liquid is sent to the rich amine buffer tank 3 for storage. The rich amine buffer tank 3 sends the rich amine solution to the lean-rich solution heat exchanger 9 for heat exchange, and then sends it to the desorption tower 2 for desorption to obtain a lean solution and a CO2 / water vapor mixture. An electric heat pump 12 extracts waste heat from the regeneration gas and raises its temperature, which is then used to heat a portion of the rich amine solution via an electric heat pump heater 7. An electric heater 8 directly heats another portion of the rich amine solution. The reboiler 6 uses steam extracted from a steam turbine to heat the rich amine solution, serving as a supplement and alternative to the electric heat pump heater 7 and electric heater 8 when green electricity is not used or is insufficient. A PLC control module controls the green electricity supply to the electric heat pump 12 and electric heater 8. The lean liquid is sent to the lean-rich liquid heat exchanger 9 for heat exchange, and then fully cooled by the lean liquid cooler 11 before being sent to the lean amine liquid buffer tank 4 for storage; the lean liquid in the lean amine liquid buffer tank 4 is then sent to the absorption tower 1. The CO2 / water vapor mixture is sent to the regenerated gas cooler 10 for heat exchange and then sent to the gas-liquid separator 5 for separation to obtain CO2 gas and condensate water; the CO2 gas is sent to the compression liquefaction unit and the condensate water is sent to the absorbent storage tank for makeup water.

[0033] According to the present invention, optionally, the temperature of the carbon dioxide-containing flue gas is 40-50°C.

[0034] According to the present invention, optionally, the absorbent is a 30-40 wt% monoethanolamine solution; the molar ratio of the absorbent to the CO2 gas is 0.4-0.5:1.

[0035] According to the present invention, optionally, the temperature of the rich amine buffer tank 3 is ≥50°C; the temperature of the lean amine buffer tank 4 is ≤40°C; and the inlet temperature of the lean amine in the absorption tower 1 is 35-40°C. The present invention controls the inlet temperature of the lean amine between 35-40°C to optimize the chemical reaction kinetics of the absorption process.

[0036] According to the present invention, optionally, the temperature of the heated rich liquid is 120±2℃.

[0037] According to the present invention, optionally, the absolute pressure of the desorption tower 2 is 0.14-0.18 MPa.

[0038] According to the present invention, optionally, the temperature of the CO2 / water vapor mixture at the outlet of the desorption tower 2 is 75-95°C; after the CO2 / water vapor mixture is heat-exchanged by the regeneration gas cooler 10, the temperature of the CO2 / water vapor mixture is ≤40°C.

[0039] Through the above technical solutions, this invention provides a novel carbon dioxide capture system for post-combustion flue gas of coal-fired power units, which couples rich / lean amine liquid buffer tanks and electric heat pumps / electric heaters to achieve green electricity consumption. The heat source for the desorption tower in this invention is mainly provided by off-peak electricity from renewable energy sources, significantly reducing reliance on turbine extraction steam and electricity during peak hours, thus lowering the energy consumption cost of the carbon capture system. Utilizing the peak-valley difference in electricity prices, the carbon capture system completes carbon dioxide desorption and compression during off-peak hours and absorbs carbon dioxide during peak hours, achieving cross-time coupling of energy consumption and supply, and improving the unit's output during peak grid load periods. The use of electric heat pump heaters and electric heaters solves the problem of mismatch between turbine extraction steam parameters and the regeneration process requirements of the carbon capture island during low-load periods, improving the overall thermal efficiency of the system. The use of rich and lean amine liquid buffer tanks to balance the absorbent flow rate and heat load alleviates the fluctuation problem of key operating parameters during system load changes, improving stability and flexibility.

[0040] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0041] Example This embodiment provides a coupled carbon dioxide capture method, the method comprising: The CO2-containing flue gas is countercurrently contacted with the absorbent in absorption tower 1 to absorb the carbon dioxide in the flue gas. The resulting rich solution is sent to the rich amine buffer tank 3 for storage. The temperature of the CO2-containing flue gas is 40°C. The absorbent is a 30wt% monoethanolamine solution. The molar ratio of the absorbent to the finally captured CO2 gas is 0.45:1. Based on 4 hours of full-load operation and 20 hours of peak-shaving operation per day, the daily CO2 capture amount is 325t, and the daily total circulation flow rate of the amine solution is 7800 t(Q). The rich amine buffer tank 3 is sent to the lean-rich amine heat exchanger 9 for heat exchange, and then sent to the desorption tower 2 for desorption to obtain a lean amine and CO2 / water vapor mixture. The temperature of the rich amine buffer tank 3 is 50°C. The rich amine is heated by electric heat pump heater 7 and electric heater 8. The PLC control module controls green electricity to supply power to the electric heat pump 12 and electric heater 8. The temperature of the heated rich amine is 120°C. The absolute pressure of the desorption tower 2 is 0.15 MPa. When green electricity is not used or the green electricity supply is insufficient, the reboiler 6 uses steam extracted from the steam turbine to heat the rich amine, as a supplement and replacement for the electric heat pump heater 7 and electric heater 8. The lean liquid is sent to the lean-rich liquid heat exchanger 9 for heat exchange, and then cooled to 40°C by the lean liquid cooler 11 before being sent to the lean amine liquid buffer tank 4 for storage. The lean liquid in the lean amine liquid buffer tank 4 is then sent to the absorption tower 1. The temperature of the lean liquid in the lean amine liquid buffer tank 4 is 40°C, and the inlet temperature of the lean liquid in the absorption tower 1 is 40°C. The CO2 / water vapor mixture is sent to the regenerated gas cooler 10 for heat exchange and then sent to the gas-liquid separator 5 for separation to obtain CO2 gas and condensate water. The CO2 gas goes to the compression liquefaction unit, and the condensate water goes to the absorbent storage tank for makeup water. After the CO2 / water vapor mixture passes through the regenerated gas cooler 10 for heat exchange, the temperature of the CO2 / water vapor mixture is 40°C.

[0042] The power consumption of the desorption process in this embodiment is 620.0 GJ / day (EC), equivalent to approximately 173,000.0 kWh / day. In existing carbon dioxide capture systems, high-temperature, high-pressure steam turbines are used to extract steam, indirectly heating the rich liquid, resulting in a heat energy consumption of 1300.0 GJ / day (HC).

[0043] In this embodiment, the unit energy consumption of the CO2 compression liquefaction process is 150 kWh / t CO2. Therefore, the energy consumption of the CO2 compression liquefaction process is 48,750 kWh / day.

[0044] The total cost of CO2 capture (desorption) and compression in the existing carbon capture system is RMB 45,500.0 per day. The total operating cost and total cost of the carbon dioxide capture (desorption) and compression process in this embodiment are shown in Table 1. When the average off-peak electricity price is RMB 0.1979 / kWh, the total cost of the carbon capture system in this embodiment is the same as that of the existing carbon capture system.

[0045] Table 1

[0046] Under different off-peak electricity prices, with a daily carbon dioxide capture volume of 325 tons as a benchmark, the cost changes of capture (desorption) and compression per unit of carbon dioxide were calculated, and the results are shown in Table 2. Table 2 shows that when the off-peak electricity price is below 0.15 yuan / kWh, the carbon capture system of this invention is more economical, reducing the capture cost per ton by 32.7 yuan.

[0047] Table 2

[0048] Under the condition that the investment cost of system upgrade changes, when the total cost of the carbon capture system in this embodiment is the same as the total cost of the existing carbon capture system, the corresponding average off-peak electricity price is shown in Table 3. Table 3 shows that the off-peak electricity price break-even point is not sensitive to the investment cost of system upgrade. When the investment cost of system upgrade increases by 20%, the off-peak electricity price break-even point only decreases by 0.0014 yuan / kWh.

[0049] Table 3

[0050] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0051] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0052] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A coupled carbon dioxide capture system, characterized in that, The system includes an absorption tower (1), a desorption tower (2), a rich amine buffer tank (3), a lean amine buffer tank (4), a gas-liquid separator (5), a reboiler (6), an electric heat pump heater (7), an electric heater (8), a lean and rich liquid heat exchanger (9), a regenerated gas cooler (10), a lean liquid cooler (11), and an electric heat pump (12). The gas inlet of the absorption tower (1) is connected to the outlet of the flue gas containing carbon dioxide; the rich liquid outlet of the absorption tower (1) is connected to the rich liquid inlet of the rich amine buffer tank (3); the rich liquid outlet of the rich amine buffer tank (3) is connected to the rich liquid inlet of the desorption tower (2) through the lean-rich liquid heat exchanger (9); the lean liquid outlet of the desorption tower (2) is connected to the lean liquid inlet of the lean amine buffer tank (4) through the lean-rich liquid heat exchanger (9) and the lean liquid cooler (11); and the lean liquid outlet of the lean amine buffer tank (4) is connected to the lean liquid inlet of the absorption tower (1). The CO2 / water vapor mixture outlet of the desorption tower (2) is connected to the CO2 / water vapor mixture inlet of the gas-liquid separator (5) through the regeneration gas cooler (10). The CO2 gas outlet of the gas-liquid separator (5) is connected to the CO2 gas inlet of the compression liquefaction device, and the condensate outlet is connected to the inlet of the absorbent storage tank. The rich liquid outlet of the desorption tower (2) is connected to the first inlet of the reboiler (6), the inlet of the electric heat pump heater (7), and the inlet of the electric heater (8), respectively. The first outlet of the reboiler (6), the outlet of the electric heat pump heater (7), and the outlet of the electric heater (8) are connected to the desorption tower (2), respectively. The steam extraction outlet of the power plant turbine is connected to the second inlet of the reboiler (6), and the second outlet of the reboiler (6) is connected to the unit condensate system.

2. The system according to claim 1, wherein, The electric heat pump (12) is used to extract waste heat from the CO2 / water vapor mixture at the outlet of the desorption tower (2), and after upgrading the waste heat, it is delivered to the electric heat pump heater (7) to provide energy for the electric heat pump heater (7).

3. The system according to claim 1, wherein, The electric heater (8) and the electric heat pump (12) are connected to green electricity; the green electricity is equipped with an energy storage device and connected to a PLC control module.

4. The system according to claim 1, wherein, The amine-rich liquid buffer tank (3) is equipped with an insulation layer and a temperature sensor; The lean amine buffer tank (4) is equipped with a turbulence disturber, a temperature-level control system and a flow buffer valve.

5. A coupled carbon dioxide capture method, characterized in that, This method uses the coupled carbon dioxide capture system according to any one of claims 1-4, and the method includes: The carbon dioxide-containing flue gas is brought into countercurrent contact with the absorbent in the absorption tower (1) to absorb the carbon dioxide in the flue gas, and the resulting rich liquid is sent to the rich amine buffer tank (3) for storage. The rich liquid in the rich amine buffer tank (3) is sent to the lean-rich liquid heat exchanger (9) for heat exchange and then sent to the desorption tower (2) for desorption to obtain lean liquid and CO2 / water vapor mixture; wherein, the rich liquid is heated by a reboiler (6), an electric heat pump heater (7) and an electric heater (8); the PLC control module controls the green electricity and the supporting energy storage device to supply power to the electric heat pump heater (7) and the electric heater (8); The lean liquid is sent to the lean-rich liquid heat exchanger (9) for heat exchange and then sent to the lean liquid cooler (11) for further cooling; the cold lean liquid at the outlet of the lean liquid cooler (11) is sent to the lean amine liquid buffer tank (4) for storage; the lean liquid in the lean amine liquid buffer tank (4) is sent to the absorption tower (1). After the CO2 / water vapor mixture is used to extract some of the residual heat through an electric heat pump (12), it is sent to a regenerated gas cooler (10) for heat exchange and then sent to a gas-liquid separator (5) for separation to obtain CO2 gas and condensate water.

6. The method according to claim 5, wherein, The temperature of the carbon dioxide-containing flue gas is 40-50℃; The absorbent is a 30-40 wt% monoethanolamine solution; the molar ratio of the absorbent to the CO2 gas is 0.4-0.5:

1.

7. The method according to claim 5, wherein, The temperature of the rich amine buffer tank (3) is ≥50℃; the temperature of the lean amine buffer tank (4) is ≤40℃; and the inlet temperature of the lean amine in the absorption tower (1) is 35-40℃.

8. The method according to claim 5, wherein the temperature of the heated rich liquid is 120±2℃.

9. The method according to claim 5, wherein, The absolute pressure of the desorption tower (2) is 0.14-0.18 MPa.

10. The method according to claim 5, wherein the temperature of the CO2 / water vapor mixture at the outlet of the desorption tower (2) is 75-95°C; After the CO2 / water vapor mixture is heat-exchanged by the regenerated gas cooler (10), the temperature of the CO2 / water vapor mixture is ≤40℃.

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