A carbon capture system based on heat pump heating of flash evaporation lean liquor and its operation method

Abstract

This invention discloses a carbon capture system and its operation method based on heat pump heating of flash-evapor lean liquor, belonging to the field of carbon capture and waste heat utilization. The system includes a carbon capture unit, a heat pump unit, a flue gas duct, and a hot water circulation duct. The carbon capture unit captures CO2 gas from the flue gas, while the heat pump unit recovers waste heat from the power plant flue gas and outputs medium-temperature waste heat to the flash tank, increasing the flash steam output. The flue gas duct allows high-temperature flue gas to be used sequentially for heating the generator and evaporator before entering the flue gas inlet at the bottom of the absorption tower. The hot water circulation duct transfers the heat output from the heat pump unit to the flash tank. This invention utilizes a heat pump to convert the low-temperature waste heat of the flue gas into latent heat of steam, reducing the steam demand of the reboiler, lowering the overall energy consumption of the power plant, and providing an energy-efficient and high-performance flue gas capture technology.

Description

Technical Field

[0001] This invention belongs to the field of carbon capture and waste heat utilization, specifically relating to a carbon capture system based on heat pump heating of flash evaporation lean liquor and its operation method. Background Technology

[0002] Fossil fuels dominate the energy production and consumption structure, and their combustion releases large amounts of carbon dioxide, contributing to global warming. Carbon capture technology is one of the key technologies for reducing carbon emissions. Post-combustion capture technology is currently the most mature and widely used carbon capture technology, and it is also easier to retrofit existing coal-fired power plants. Absorption carbon capture (ACC) has a fast absorption rate, high absorption efficiency, and lower requirements for flue gas pressure. It is a mature and reliable technology with relatively low investment costs and stable equipment operation, and has been widely used in post-combustion capture in coal-fired power plants.

[0003] Carbon capture systems applied in coal-fired power plants require the extraction of some high-temperature steam from the power generation system to drive solution desorption and regeneration, which may lead to a decrease in turbine power and consequently reduce power generation efficiency. To address the impact of carbon capture systems on power generation efficiency, researchers have explored improvements in absorption system processes, optimization of power plant energy dispatch, and utilization of waste heat, but it remains difficult to control the decrease in power generation efficiency to within 7%. The flue gas at the boiler outlet of coal-fired power plants still has a high temperature, and recovering and utilizing waste heat from the flue gas is an effective way to reduce the energy consumption of carbon capture systems. Because the reboiler temperature at the main heat-consuming end of traditional absorption carbon capture systems is high, the amount of usable waste heat from the flue gas is limited, restricting the energy-saving effect of waste heat recovery. Heat pump technology can recover and utilize the low-temperature waste heat from the flue gas and output higher-temperature heat to the carbon capture system. However, the combination of existing heat pumps with absorption carbon capture systems has many limitations. Traditional compression heat pumps face the limitation of excessive power consumption, the heat conversion efficiency of temperature-increasing absorption heat pumps is low, and the output temperature of incremental absorption heat pumps is difficult to meet the requirements of the reboiler. Therefore, the application of heat pumps combined with carbon capture systems in coal-fired power plants urgently needs further exploration and development. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of coal-fired power plants, such as the limited availability of waste heat from flue gas and the high efficiency reduction of power plant power generation due to carbon capture systems, and to provide a carbon capture system based on heat pump heating of flash-evaporated lean liquor and its operation method.

[0005] The specific technical solution adopted in this invention is as follows:

[0006] In a first aspect, the present invention provides a carbon capture system based on heat pump heating flash evaporation lean liquor, including a carbon capture unit, a heat pump unit, a flue gas flow channel and a hot water circulation channel;

[0007] The carbon capture unit is used to consume heat from the heat pump unit and the steam channel, and absorb and enrich CO2 in the flue gas in the flue gas channel; the heat pump unit is used to absorb the high temperature and low temperature waste heat of the flue gas in the flue gas channel, and output medium temperature waste heat to the flash tank; the flue gas channel is used to use the high temperature flue gas to heat the generator and evaporator in sequence, and then enters the flue gas inlet at the bottom of the absorption tower; the circulating water in the hot water circulation channel is used to absorb the heat output by the heat pump unit and enter the flash tank to exchange heat with the lean liquid.

[0008] Preferably, the carbon capture unit includes an absorption tower, a lean-rich liquid heat exchanger, a desorption tower, and a flash tank; the flue gas outlet at the top of the absorption tower is connected to the flue gas discharge channel, and the rich liquid outlet at the bottom is connected to the cold-side fluid channel inlet of the lean-rich liquid heat exchanger via a rich liquid pump; the cold-side fluid channel outlet of the lean-rich liquid heat exchanger is connected to the rich liquid inlet of the desorption tower; the gas phase outlet at the top of the desorption tower is connected to the heat source inlet of the product gas condenser, and the liquid phase outlet at the bottom is connected to the cold-side fluid channel inlet of the reboiler; the cold source inlet of the product gas condenser is connected to a first cold source, and the condensate outlet is connected to the condensate inlet at the top of the desorption tower; the gas phase... The outlet is connected to the CO2 product flow channel; the gas phase product outlet of the reboiler is connected to the gas phase inlet at the bottom of the desorption tower, the hot-side fluid channel inlet is connected to the steam flow channel, and the liquid phase product outlet is connected to the lean liquid inlet of the flash tank; the steam outlet at the top of the flash tank is connected to the gas phase inlet at the bottom of the desorption tower via a compressor, and the lean liquid outlet at the bottom is connected to the hot-side fluid channel inlet of the lean-rich liquid heat exchanger via a lean liquid pump; the hot-side fluid channel outlet of the lean-rich liquid heat exchanger is connected to the inlet of the lean liquid cooler, the cold source inlet is connected to the second cold source, and the outlet is connected to the lean liquid inlet at the top of the absorption tower; the inlet of the lean liquid cooler is also connected to the absorbent replenishment flow channel.

[0009] The heat pump unit includes a generator, a condenser, an absorber, an evaporator, and a solution heat exchanger. The solution outlet of the generator is connected to the hot-side fluid channel inlet of the solution heat exchanger via a solution throttling valve, and the steam outlet is connected to the hot-side fluid channel inlet of the condenser via a pipe. The hot-side fluid channel outlet of the solution heat exchanger is connected to the solution inlet of the absorber, and the cold-side fluid channel outlet is connected to the solution inlet of the generator. The solution outlet of the absorber is connected to the cold-side fluid channel inlet of the solution heat exchanger via a solution pump. The hot-side fluid channel outlet of the condenser is connected to the cold-side fluid channel inlet of the evaporator via a water throttling valve, and the cold-side fluid channel outlet of the evaporator is connected to the steam inlet of the absorber.

[0010] The flue gas flow channel passes sequentially through the hot-side fluid channels of the generator and evaporator, and finally connects to the flue gas inlet at the bottom of the absorption tower; the hot water circulation channel passes sequentially through the cold-side fluid channel of the absorber, the cold-side fluid channel of the condenser and the hot-side fluid channel of the flash tank, and then returns to the cold-side fluid channel of the absorber, forming a closed loop.

[0011] Furthermore, the steam source for the steam flow channel is exhaust gas from the power plant's steam turbine.

[0012] Furthermore, both the absorption tower and the desorption tower are packed distillation towers.

[0013] Furthermore, the packing material in the packed distillation column is one of Raschig rings, Pall rings, stepped rings, arc saddle packing, rectangular saddle packing, corrugated packing, corrugated mesh packing, or metal saddle ring packing.

[0014] Furthermore, the absorbent in the internal circulation path of the carbon capture unit is an inorganic alkaline solution or an organic amine solution.

[0015] Furthermore, the lean and rich liquid heat exchanger, condenser, evaporator, and solution heat exchanger are all indirect wall heat exchangers.

[0016] Furthermore, both the first and second cold sources are natural cold sources or refrigeration units.

[0017] Furthermore, the working fluid pair of the heat pump unit is an aqueous solution of lithium bromide and water.

[0018] Secondly, the present invention provides an operation method for a carbon capture system based on heat pump heating of flash evaporation lean liquor as described in any one of the first aspects, as follows:

[0019] The working process of the carbon capture unit is as follows:

[0020] The lean liquor is cooled by the lean liquor cooler and then enters from the lean liquor inlet at the top of the absorption tower. Inside the absorption tower, it undergoes heat and mass exchange with the flue gas to be treated, which enters the absorption tower through the flue gas inlet channel. The lean liquor absorbs CO2 from the flue gas, resulting in rich liquor and treated flue gas.

[0021] The treated flue gas is discharged through the flue gas emission channel; the rich liquid after CO2 absorption is driven by the rich liquid pump and enters the lean-rich liquid heat exchanger through the cold side fluid channel inlet, where it exchanges heat with the lean liquid from the liquid phase product outlet of the flash tank, becoming a high-temperature rich liquid; the high-temperature rich liquid enters the desorption tower through the rich liquid inlet, and desorbs CO2 under the purging of high-temperature steam entering through the gas phase inlet of the desorption tower; the desorbed CO2 and purging steam are discharged through the gas phase outlet at the top of the desorption tower and enter the product gas condenser; the absorbent components in the gas phase are cooled and liquefied in the product gas condenser, discharged through the condensate outlet and returned to the desorption tower; the remaining gas components are discharged through the gas phase outlet of the product gas condenser. The desorbed absorbent solution is collected through the CO2 product channel; the desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorption tower and enters the reboiler. The generated high-temperature steam enters the desorption tower from the gas phase inlet at the bottom of the desorption tower for purging; the remaining lean liquor enters the flash tank to flash and absorbs heat from the hot water circulation channel. The generated flash steam enters the compressor through the steam outlet above the flash tank. After being compressed, it enters the desorption tower from the gas phase inlet at the bottom of the desorption tower for purging. The remaining lean liquor is discharged through the liquid phase outlet at the bottom of the flash tank and is pumped into the hot side fluid channel inlet of the lean-rich liquor heat exchanger by the lean liquor pump to heat the rich liquor upstream of the desorption tower inlet; the lean liquor after heat exchange is mixed with the absorbent solution replenished by the absorbent replenishment channel and then enters the lean liquor cooler to complete the cycle;

[0022] The working process of the heat pump unit is as follows:

[0023] A dilute solution enters the generator's solution inlet from the cold-side fluid channel of the solution heat exchanger. Inside the generator, it exchanges heat with the high-temperature flue gas in the hot-side fluid channel, generating high-pressure steam and a concentrated solution. The high-pressure steam enters the condenser's hot-side fluid channel through the generator's steam outlet. In the condenser, it releases heat by supplying hot water to the cold-side fluid channel, forming condensate. The condensate enters a water throttling valve, expands into low-pressure water, and then enters the evaporator's cold-side fluid channel, where it exchanges heat with the low-temperature flue gas in the hot-side fluid channel, evaporating into low-pressure steam. The low-pressure steam enters the absorber's steam inlet, completing the water working fluid cycle. The concentrated solution enters the solution heat exchanger's hot-side fluid channel through the generator's solution outlet. After exchanging heat with the dilute solution in the cold-side fluid channel, it enters the absorber's solution inlet. In the absorber, it absorbs the low-pressure steam from the gas phase inlet and simultaneously exchanges heat with the circulating heating water in the cold-side fluid channel, generating a dilute solution. This dilute solution then enters the solution heat exchanger's cold-side fluid channel through the absorber's solution outlet, exchanges heat with the concentrated solution in the hot-side fluid channel, and then enters the generator's solution inlet, completing the solution working fluid cycle.

[0024] The working process of the flue gas flow channel is as follows:

[0025] High-temperature flue gas from the boiler enters the hot-side fluid channel of the generator, releasing heat and becoming medium-temperature flue gas; the medium-temperature flue gas enters the hot-side fluid channel of the evaporator, releasing heat and becoming low-temperature flue gas; the low-temperature flue gas enters the absorption tower through the flue gas inlet at the bottom of the absorption tower.

[0026] The working process of the hot water circulation channel is as follows:

[0027] Low-temperature hot water enters the cold-side fluid channel of the absorber, where it absorbs heat generated by the concentrated solution and low-pressure steam, becoming medium-temperature hot water. The medium-temperature hot water then enters the cold-side fluid channel of the condenser, where it absorbs the condensation heat of the high-pressure steam, becoming high-temperature hot water. The high-temperature hot water then enters the hot-side fluid channel of the flash tank, where it exchanges heat with the flash lean liquid, becoming low-temperature hot water. This low-temperature hot water then enters the cold-side fluid channel of the absorber through the outlet of the hot-side fluid channel, completing the cycle.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] This invention combines incremental heat pump technology, solution flash evaporation and recompression technology, and a carbon capture system to efficiently recover low-temperature waste heat from flue gas in coal-fired power plants. This reduces the heat load on the carbon capture system and decreases the amount of gas extracted from the turbine, thus minimizing the impact of the carbon capture system's operation on the power generation efficiency of the coal-fired power plant. Compared to existing technologies combining compression heat pumps and carbon capture systems, this invention provides a system with lower power consumption, solving the problem of high power consumption. Compared to existing technologies combining heating heat pumps and carbon capture systems, this invention offers higher efficiency in recovering low-temperature waste heat, solving the problem of low utilization rate of flue gas waste heat. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a preferred structure of the system of the present invention.

[0031] In the diagram: Carbon capture unit 101; Heat pump unit 102; Absorber tower 1; Lean liquid cooler 2; Rich liquid pump 3; Lean and rich liquid heat exchanger 4; Desorption tower 5; Product gas condenser 6; Reboiler 7; Compressor 8; Flash tank 9; Lean liquid pump 10; Generator 11; Condenser 12; Absorber 13; Evaporator 14; Solution throttling valve 15; Solution pump 16; Solution heat exchanger 17; Water throttling valve 18; Flue gas flow channel 19; Flue gas emission flow channel 20; First cold source 21; CO2 product flow channel 22; Absorbent replenishment flow channel 23; Second cold source 24; Steam flow channel 25; Circulating hot water supply flow channel 26. Detailed Implementation

[0032] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0033] This invention provides an absorption carbon capture system based on an incremental heat pump and lean liquor flash heating and recompression. The system can be divided into four parts: an absorption carbon capture unit 101, a heat pump unit 102, a flue gas flow channel 19, and a heating circulating water flow channel 26, as detailed below. Figure 1 As shown. The carbon capture unit 101 consumes heat from the heat pump unit 102 and the steam channel 25, absorbing and enriching CO2 in the flue gas within the flue gas duct 19; the heat pump unit 102 absorbs the high-temperature and low-temperature waste heat from the flue gas within the flue gas duct 19 and outputs medium-temperature waste heat to the flash tank 9, increasing the flash steam volume; the flue gas duct 19, after sequentially heating the generator 11 and evaporator 14, is introduced into the flue gas inlet at the bottom of the absorption tower 1; the circulating water in the heating circulating water channel 26 absorbs the heat output from the heat pump unit 102 and enters the flash tank 9 to exchange heat with the lean liquid, thus transferring the heat output from the heat pump unit 102 to the flash tank 9.

[0034] The structure and connection method of each unit will be explained in detail below.

[0035] In this embodiment, the carbon capture unit 101 mainly includes an absorption tower 1, a lean liquid cooler 2, a rich liquid pump 3, a lean and rich liquid heat exchanger 4, a desorption tower 5, a product gas condenser 6, a reboiler 7, a compressor 8, a flash tank 9, a lean liquid pump 10, a flue gas emission channel 20, a first cold source 21, a CO2 product channel 22, an absorbent replenishment channel 23, a second cold source 24, and a steam channel 25, which together constitute an internal circulation path.

[0036] It should be noted that an absorbent refers to a liquid that has different solubilities for the components of a gas mixture and can selectively absorb one or more of them, including physical absorbents and chemical absorbents. The carbon capture unit 101 is filled with an absorbent solution for absorbing and desorbing carbon dioxide, specifically an inorganic alkaline solution or an organic amine solution.

[0037] In addition, the lean and rich liquid heat exchanger 4, the reboiler 7 and the flash tank 9 each have a cold-side fluid channel and a hot-side fluid channel that can form a heat exchange.

[0038] like Figure 1 As shown, the bottom of the absorption tower 1 is provided with a flue gas inlet connected to the flue gas flow channel 19 for introducing the flue gas to be treated. The top of the absorption tower 1 is provided with a flue gas outlet connected to the flue gas discharge channel 20 for discharging the treated flue gas.

[0039] The bottom of the absorption tower 1 is also equipped with a rich liquid outlet, which is connected to the inlet of the rich liquid pump 3 via a pipeline. The outlet of the rich liquid pump 3 is connected to the inlet of the cold side fluid channel of the lean-rich liquid heat exchanger 4 via a pipeline. The outlet of the cold side fluid channel of the lean-rich liquid heat exchanger 4 is connected to the rich liquid inlet of the desorption tower 5 via a pipeline.

[0040] The gas phase outlet at the top of desorption tower 5 is connected to the heat source inlet of product gas condenser 6 via a pipeline. The cold source inlet of product gas condenser 6 is connected to the first cold source 21 via a pipeline. The condensate outlet of product gas condenser 6 is connected to the condensate inlet at the top of desorption tower 5 via a pipeline, and the gas phase outlet of condenser 6 is connected to the CO2 product flow channel 22 via a pipeline.

[0041] The liquid outlet at the bottom of desorption tower 5 is connected to the cold-side fluid channel inlet of reboiler 7 via a pipeline. The gaseous product outlet of reboiler 7 is connected to the gaseous inlet at the bottom of desorption tower 5 via a pipeline. The hot-side fluid channel inlet of reboiler 7 is connected to steam channel 25 via a pipeline. The liquid product outlet of reboiler 7 is connected to the lean liquid inlet of flash tank 9 via a pipeline.

[0042] In this embodiment, the steam source for steam flow channel 25 is an extraction steam turbine from a power plant. An extraction steam turbine is an industrial device that extracts a portion of steam from the intermediate stage of a steam turbine to supply heat energy to users, while also generating electricity. In this way, the extraction steam turbine meets both the electrical load demand and provides heat energy, improving the unit's thermal efficiency and economy.

[0043] In this embodiment, the product gas condenser 6 and the reboiler 7 have gas-liquid separation functions. The product gas condenser 6 condenses the distillate gas from the gas phase outlet of the desorption tower 5 into condensate and CO2 product. The condensate is returned to the desorption tower 5 through the condensate outlet of the product gas condenser 6. The CO2 product is discharged through the gas phase outlet of the product gas condenser 6 and collected through the CO2 product flow channel 22. The reboiler 7 separates the rich liquid from the liquid phase outlet of the desorption tower 5 into purge steam and lean liquid. The purge steam enters the desorption tower 5 through the gas phase product outlet of the reboiler 7 for purging, and the lean liquid flows to the lean-rich liquid heat exchanger 4 through the liquid phase product outlet of the reboiler 7.

[0044] The top steam outlet of the flash tank 9 is connected to the inlet of the compressor 8 via a pipe; the outlet of the compressor 8 is connected to the gas phase inlet at the bottom of the desorption tower 5 via a pipe.

[0045] The lean liquid outlet at the bottom of flash tank 9 is connected to the inlet of lean liquid pump 10 via a pipe. The outlet of lean liquid pump 10 is connected to the inlet of the hot-side fluid channel of lean-rich liquid heat exchanger 4 via a pipe. The outlet of the hot-side fluid channel of lean-rich liquid heat exchanger 4 is connected to the inlet of lean liquid cooler 2 via a pipe. The inlet of lean liquid cooler 2 is also connected to absorbent replenishment channel 23 for replenishing absorbent solution. The cold source inlet of lean liquid cooler 2 is connected to the second cold source 24 via a pipe. The outlet of lean liquid cooler 2 is connected to the lean liquid inlet at the top of absorption tower 1 via a pipe.

[0046] In this embodiment, the absorption tower 1 and desorption tower 5 are packed distillation towers. Selectable packing types include Raschig rings, Pall rings, stepped rings, arc saddle packing, rectangular saddle packing, corrugated packing, corrugated mesh packing, and metal saddle ring packing. In practical applications, different packing types can be selected based on temperature, pressure, material properties, equipment structure, and the requirements of the processed products to optimize the operating efficiency within the tower and improve separation efficiency.

[0047] In addition, the first cold source 21 and the second cold source 24 can be provided by natural cold sources, such as water or air, or by refrigeration units.

[0048] In this embodiment, the heat pump unit 102 mainly includes a generator 11, a condenser 12, an absorber 13, an evaporator 14, a solution throttling valve 15, a solution pump 16, a solution heat exchanger 17, and a water throttling valve 18, which together constitute an internal circulation path.

[0049] It should be noted that the working fluid pair in an absorption heat pump refers to the two different substances used in the absorption heat pump system (i.e., heat pump unit 102), typically including an absorbent and a working fluid. This working fluid pair works together to achieve cooling or heating functions by absorbing and releasing heat. The heat pump unit 102 is filled with a solution-water working fluid pair for absorbing and releasing heat, specifically a lithium bromide aqueous solution-water mixture.

[0050] In addition, the condenser 12, absorber 13, evaporator 14 and solution heat exchanger 17 each have a cold-side fluid channel and a hot-side fluid channel that can form a heat exchange.

[0051] The solution outlet of generator 11 is connected to the inlet of solution throttle valve 15 via a pipe. The outlet of throttle valve 15 is connected to the inlet of the hot-side fluid channel of solution heat exchanger 17 via a pipe. The outlet of the hot-side fluid channel of solution heat exchanger 17 is connected to the solution inlet of absorber 13 via a pipe. The solution outlet of absorber 13 is connected to the inlet of solution pump 16 via a pipe. The outlet of solution pump 16 is connected to the inlet of the cold-side fluid channel of solution heat exchanger 17 via a pipe. The outlet of the cold-side fluid channel of solution heat exchanger 17 is connected to the solution inlet of generator 11 via a pipe.

[0052] The steam outlet of generator 11 is connected to the hot-side fluid passage inlet of condenser 12 via a pipe. The hot-side fluid passage outlet of condenser 12 is connected to the inlet of water throttling valve 18 via a pipe. The outlet of water throttling valve 18 is connected to the cold-side fluid passage inlet of evaporator 14 via a pipe. The cold-side fluid passage outlet of evaporator 14 is connected to the steam inlet of absorber 13 via a pipe.

[0053] The flue gas flow channel 19 passes through the hot side fluid channels of the generator 11 and the evaporator 14 in sequence, and finally connects to the flue gas inlet at the bottom of the absorption tower 1.

[0054] The hot water circulation channel 26 passes through the cold side fluid channel of the absorber 13, the cold side fluid channel of the condenser 12, and the hot side fluid channel of the flash tank 9 in sequence, and then returns to the cold side fluid channel of the absorber 13, forming a closed loop.

[0055] In this embodiment, the lean and rich liquid heat exchanger 4 installed in the carbon capture unit 101 and the condenser 12, evaporator 14, and solution heat exchanger 17 installed in the heat pump unit 102 can all be indirect heat exchangers. Indirect heat exchangers can be classified into shell-and-tube heat exchangers, tube-and-shell heat exchangers, plate heat exchangers, and spray heat exchangers, depending on the form of the heat exchange surface. In practical applications, one type can be selected according to the requirements.

[0056] The operation method of the carbon capture system based on heat pump heating of flash-evaporized lean liquor described above is as follows:

[0057] The system achieves low-energy carbon capture through the combined operation of carbon capture unit 101 and heat pump unit 102. Carbon capture unit 101 consumes heat from heat pump unit 102 and steam channel 25, absorbing and enriching CO2 in flue gas. Heat pump unit 102 absorbs high-temperature and low-temperature waste heat from flue gas and outputs medium-temperature waste heat. Circulating water in hot water circulation channel 26 absorbs the heat output from the heat pump and enters flash tank 9 to exchange heat with lean liquor. Due to the low-pressure environment, the boiling point of the lean liquor in flash tank 9 is lowered, thus enabling it to absorb the medium-temperature waste heat from the circulating water.

[0058] 1) The working process of carbon capture unit 101 is as follows:

[0059] The lean liquor, after being cooled by the lean liquor cooler 2, enters from the lean liquor inlet at the top of the absorption tower 1. Inside the absorption tower 1, it undergoes heat and mass exchange with the flue gas to be treated, which enters the absorption tower 1 through the flue gas inlet channel 19. The lean liquor absorbs CO2 from the flue gas, resulting in rich liquor and treated flue gas.

[0060] The treated flue gas is discharged through flue gas emission channel 20. The rich liquid after CO2 absorption is connected to the inlet of the rich liquid pump 3 through a pipeline, and driven by the rich liquid pump 3, it enters the lean-rich liquid heat exchanger 4 through the cold side fluid channel inlet. In the lean-rich liquid heat exchanger 4, it exchanges heat with the lean liquid from the liquid phase product outlet of the flash tank 9, becoming a high-temperature rich liquid. The high-temperature rich liquid enters the desorption tower 5 through the rich liquid inlet, and CO2 is desorbed under the purging of high-temperature steam entering through the gas phase inlet of the desorption tower 5. The desorbed CO2 and purging steam are discharged through the gas phase outlet at the top of the desorption tower 5 and enter the product gas condenser 6. The absorbent components in the gas phase are cooled and liquefied in the product gas condenser 6, and discharged through the condensate outlet and returned to the desorption tower 5. The remaining gas components are discharged through the gas phase outlet of the product gas condenser 6 and collected through the CO2 product channel 22. The desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of desorption tower 5 and enters reboiler 7. The generated high-temperature steam enters desorption tower 5 from the gas phase inlet at the bottom of desorption tower 5 for purging. The remaining lean liquor enters flash tank 9 to flash and absorb heat from the hot water circulation channel 26. The generated flash steam enters compressor 8 through the steam outlet above flash tank 9. After being compressed, it enters desorption tower 5 from the gas phase inlet at the bottom of desorption tower 5 for purging. The remaining lean liquor is discharged from the liquid phase outlet at the bottom of flash tank 9 and is pumped by lean liquor pump 10 into the hot side fluid channel inlet of lean-rich liquor heat exchanger 4 to heat the rich liquor upstream of the inlet of desorption tower 5. After heat exchange, the lean liquor mixes with the absorbent solution replenished by absorbent replenishment channel 23 and enters lean liquor cooler 2 to complete the cycle.

[0061] It should be noted that during operation, absorbent solution can be added to the system through absorbent replenishment channel 23 to ensure a stable absorbent solution concentration in the system and balance the circulation loss.

[0062] 2) The working process of heat pump unit 102 is as follows:

[0063] A dilute solution enters the solution inlet of generator 11 from the cold-side fluid channel of solution heat exchanger 17. Inside generator 11, it exchanges heat with the high-temperature flue gas in the hot-side fluid channel, generating high-pressure steam and a concentrated solution. The high-pressure steam enters the hot-side fluid channel of condenser 12 through the steam outlet of generator 11. In condenser 12, it releases heat by supplying hot water to the circulating cold-side fluid channel, forming condensate. The condensate enters water throttling valve 18, expands into low-pressure water, and then enters the cold-side fluid channel of evaporator 14, where it exchanges heat with the low-temperature flue gas in the hot-side fluid channel, evaporating into low-pressure steam. The low-pressure steam enters the steam inlet of absorber 13, completing the water working fluid cycle. The concentrated solution enters the hot-side fluid channel of the solution heat exchanger 17 through the solution outlet of the generator 11. After exchanging heat with the dilute solution in the cold-side fluid channel, it enters the solution inlet of the absorber 13. In the absorber 13, it absorbs low-pressure steam from the gas phase inlet and simultaneously exchanges heat with the heating circulating water in the cold-side fluid channel to generate a dilute solution. The solution then enters the cold-side fluid channel of the solution heat exchanger 17 through the solution outlet of the absorber 13. After exchanging heat with the concentrated solution in the hot-side fluid channel, it enters the solution inlet of the generator 11, completing the solution working fluid circulation.

[0064] 3) The working process of flue gas flow duct 19 is as follows:

[0065] High-temperature flue gas from the boiler enters the hot-side fluid channel of generator 11, releasing heat and becoming medium-temperature flue gas. The medium-temperature flue gas then enters the hot-side fluid channel of the evaporator, releasing heat and becoming low-temperature flue gas. The low-temperature flue gas enters absorber 1 through the flue gas inlet at the bottom of absorber 1.

[0066] 4) The working process of the hot water circulation channel 26 is as follows:

[0067] Low-temperature hot water enters the cold-side fluid channel of absorber 13, absorbing heat from the concentrated solution and low-pressure steam to become medium-temperature hot water. The medium-temperature hot water then enters the cold-side fluid channel of condenser 12, absorbing the condensation heat of high-pressure steam to become high-temperature hot water. The high-temperature hot water then enters the hot-side fluid channel of flash tank 9, where it exchanges heat with the flash lean liquid to become low-temperature hot water. This low-temperature hot water then enters the cold-side fluid channel of absorber 13 through the hot-side fluid channel outlet, completing the cycle.

[0068] In summary, this invention provides a carbon capture system based on heat pump heating of flash-evaporated lean liquor. It utilizes an incremental heat pump to recover and utilize the low-temperature waste heat of flue gas, reducing the steam demand for the carbon capture system and thus mitigating its impact on power plant efficiency. The system achieves low-energy carbon capture through the combined operation of a carbon capture unit and a heat pump unit. The carbon capture unit incorporates a lean liquor flash-evaporation and recompression process, utilizing the latent heat of the lean liquor to generate additional steam while lowering the boiling point of the lean liquor. The heat pump unit employs a generator driven by high-temperature waste heat from the flue gas, recovers low-temperature waste heat from the flue gas using an evaporator, and outputs medium-temperature waste heat through a condenser and absorber to heat the flash-evaporated lean liquor with a lowered boiling point, further generating additional steam. Heat exchange between the carbon capture unit and the heat pump unit is achieved through a circulating hot water supply.

[0069] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A carbon capture system based on heat pump heating of flash-evaporized lean liquor, characterized in that, It includes a carbon capture unit (101), a heat pump unit (102), a flue gas flow channel (19), and a hot water circulation channel (26). The carbon capture unit (101) is used to consume heat from the heat pump unit (102) and the steam channel (25), and to absorb and enrich CO2 in the flue gas in the flue gas channel (19); the heat pump unit (102) is used to absorb the high temperature and low temperature waste heat of the flue gas in the flue gas channel (19), and output medium temperature waste heat to the flash tank (9); the flue gas channel (19) is used to use the high temperature flue gas to heat the generator (11) and evaporator (14) in sequence, and then enters the flue gas inlet at the bottom of the absorption tower (1); the hot water circulation channel (26) in The circulating water is used to absorb the heat output by the heat pump unit (102) and enters the flash tank (9) to exchange heat with the lean liquid; the carbon capture unit (101) includes an absorption tower (1), a lean-rich liquid heat exchanger (4), a desorption tower (5) and a flash tank (9); the flue gas emission outlet at the top of the absorption tower (1) is connected to the flue gas emission channel (20), and the rich liquid outlet at the bottom is connected to the cold side fluid channel inlet of the lean-rich liquid heat exchanger (4) via the rich liquid pump (3), and the cold side fluid channel outlet of the lean-rich liquid heat exchanger (4) is connected to the rich liquid inlet of the desorption tower (5); The gas phase outlet at the top of the desorption tower (5) is connected to the heat source inlet of the product gas condenser (6), and the liquid phase outlet at the bottom is connected to the cold side fluid channel inlet of the reboiler (7); the cold source inlet of the product gas condenser (6) is connected to the first cold source (21), the condensate outlet is connected to the condensate inlet at the top of the desorption tower (5), and the gas phase outlet is connected to the CO2 product flow channel (22); the gas phase product outlet of the reboiler (7) is connected to the gas phase inlet at the bottom of the desorption tower (5), the heat side fluid channel inlet is connected to the steam flow channel (25), and the liquid phase product outlet... The flash tank (9) is connected to the lean liquid inlet; the steam outlet at the top of the flash tank (9) is connected to the gas phase inlet at the bottom of the desorption tower (5) via the compressor (8), and the lean liquid outlet at the bottom is connected to the hot side fluid channel inlet of the lean-rich liquid heat exchanger (4) via the lean liquid pump (10); the hot side fluid channel outlet of the lean-rich liquid heat exchanger (4) is connected to the inlet of the lean liquid cooler (2), the cold source inlet is connected to the second cold source (24), and the outlet is connected to the lean liquid inlet at the top of the absorption tower (1); the inlet of the lean liquid cooler (2) is also connected to the absorbent replenishment channel (23); The heat pump unit (102) includes a generator (11), a condenser (12), an absorber (13), an evaporator (14), and a solution heat exchanger (17). The solution outlet of the generator (11) is connected to the hot-side fluid channel inlet of the solution heat exchanger (17) via a solution throttle valve (15), and the steam outlet is connected to the hot-side fluid channel inlet of the condenser (12) via a pipe. The hot-side fluid channel outlet of the solution heat exchanger (17) is connected to the solution inlet of the absorber (13), and the cold-side fluid channel outlet is connected to the solution inlet of the generator (11). The solution outlet of the absorber (13) is connected to the cold-side fluid channel inlet of the solution heat exchanger (17) via a solution pump (16). The hot-side fluid channel outlet of the condenser (12) is connected to the cold-side fluid channel inlet of the evaporator (14) via a water throttle valve (18), and the cold-side fluid channel outlet of the evaporator (14) is connected to the steam inlet of the absorber (13). The flue gas flow channel (19) passes through the hot side fluid channels of the generator (11) and the evaporator (14) in sequence, and finally connects to the flue gas inlet at the bottom of the absorption tower (1); the hot water circulation channel (26) passes through the cold side fluid channel of the absorber (13), the cold side fluid channel of the condenser (12) and the hot side fluid channel of the flash tank (9) in sequence, and then returns to the cold side fluid channel of the absorber (13), forming a closed loop.

2. The carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, The steam source for the steam flow channel (25) is the steam extracted from the power plant turbine.

3. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, Both the absorption tower (1) and the desorption tower (5) are packed distillation towers.

4. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 3, characterized in that, The packing material in the packed distillation column is one of Raschig rings, Pall rings, stepped rings, arc saddle packing, rectangular saddle packing, corrugated packing, corrugated mesh packing, or metal saddle ring packing.

5. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, The absorbent in the internal circulation path of the carbon capture unit (101) is an inorganic alkaline solution or an organic amine solution.

6. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, The lean and rich liquid heat exchanger (4), condenser (12), evaporator (14) and solution heat exchanger (17) are all indirect wall heat exchangers.

7. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, The first cold source (21) and the second cold source (24) are both natural cold sources or refrigeration units.

8. A carbon capture system based on heat pump-heated flash evaporation lean liquor according to claim 1, characterized in that, The working fluid pair of the heat pump unit (102) is an aqueous solution of lithium bromide and water.

9. A method for operating a carbon capture system based on heat pump heating of flash-evaporized lean liquor as described in any one of claims 1 to 8, characterized in that, The details are as follows: The working process of the carbon capture unit (101) is as follows: After being cooled by the lean liquid cooler (2), the lean liquid enters from the lean liquid inlet at the top of the absorption tower (1). In the absorption tower (1), it undergoes heat and mass exchange with the flue gas to be treated that enters the absorption tower (1) through the flue gas flow channel (19). The lean liquid absorbs CO2 from the flue gas to obtain rich liquid and treated flue gas. The treated flue gas is discharged through the flue gas discharge channel (20); the rich liquid after absorbing CO2 is driven by the rich liquid pump (3) and enters the lean-rich liquid heat exchanger (4) through the cold side fluid channel inlet of the lean-rich liquid heat exchanger (4). In the lean-rich liquid heat exchanger (4), it exchanges heat with the lean liquid from the liquid phase product outlet of the flash tank (9) and becomes a high-temperature rich liquid; the high-temperature rich liquid enters the desorption tower (5) through the rich liquid inlet of the desorption tower (5) and desorbs CO2 under the purging of the high-temperature steam entering through the gas phase inlet of the desorption tower (5); the desorbed CO2 and the purging steam are discharged through the gas phase outlet at the top of the desorption tower (5) and enter the product gas condenser (6); the absorbent components in the gas phase are cooled and liquefied in the product gas condenser (6), discharged through the condensate outlet and returned to the desorption tower (5); the remaining gas components are discharged through the gas phase outlet of the product gas condenser (6) and pass through the CO 2. Product flow channel (22) collection; the desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorption tower (5) and enters the reboiler (7). The generated high-temperature steam enters the desorption tower (5) from the gas phase inlet at the bottom of the desorption tower (5) for purging; the remaining lean liquid enters the flash tank (9) to flash and absorb heat from the hot water circulation channel (26). The generated flash steam enters the compressor (8) through the steam outlet above the flash tank (9). After being compressed, it enters the desorption tower (5) from the gas phase inlet at the bottom of the desorption tower (5) for purging. The remaining lean liquid is discharged through the liquid phase outlet at the bottom of the flash tank (9) and is pumped into the hot side fluid channel inlet of the lean and rich liquid heat exchanger (4) by the lean liquid pump (10) to heat the rich liquid upstream of the desorption tower (5) inlet; the lean liquid after heat exchange is mixed with the absorbent solution replenished by the absorbent replenishment channel (23) and enters the lean liquid cooler (2) to complete the cycle; The working process of the heat pump unit (102) is as follows: A dilute solution enters the solution inlet of the generator (11) from the cold-side fluid channel of the solution heat exchanger (17). In the generator (11), it exchanges heat with the high-temperature flue gas in the hot-side fluid channel, generating high-pressure steam and a concentrated solution. The high-pressure steam enters the hot-side fluid channel of the condenser (12) through the steam outlet of the generator (11). In the condenser (12), it releases heat by supplying hot water to the circulating cold-side fluid channel, forming condensate. The condensate enters the water throttling valve (18), expands into low-pressure water, and then enters the cold-side fluid channel of the evaporator (14). It exchanges heat with the low-temperature flue gas in the hot-side fluid channel, evaporating into low-pressure steam. The low-pressure steam then enters... The steam inlet of the absorber (13) completes the water working fluid circulation; the concentrated solution enters the hot side fluid channel of the solution heat exchanger (17) through the solution outlet of the generator (11), exchanges heat with the dilute solution in the cold side fluid channel and then enters the solution inlet of the absorber (13), absorbs the low-pressure steam from the gas phase inlet in the absorber (13), and at the same time exchanges heat with the heating circulating water in the cold side fluid channel to generate a dilute solution, which enters the cold side fluid channel of the solution heat exchanger (17) through the solution outlet of the absorber (13), exchanges heat with the concentrated solution in the hot side fluid channel and then enters the solution inlet of the generator (11) to complete the solution working fluid circulation; The working process of the flue gas flow channel (19) is as follows: High-temperature flue gas from the boiler enters the hot-side fluid channel of the generator (11) and releases heat to become medium-temperature flue gas; the medium-temperature flue gas enters the hot-side fluid channel of the evaporator (14) and releases heat to become low-temperature flue gas; the low-temperature flue gas enters the absorption tower (1) through the flue gas inlet at the bottom of the absorption tower (1). The working process of the hot water circulation channel (26) is as follows: Low-temperature hot water enters the cold-side fluid channel of the absorber (13), where it absorbs the heat generated by the concentrated solution and low-pressure steam to become medium-temperature hot water. The medium-temperature hot water enters the cold-side fluid channel of the condenser (12), where it absorbs the condensation heat of the high-pressure steam to become high-temperature hot water. The high-temperature hot water enters the hot-side fluid channel of the flash tank (9), where it exchanges heat with the flash lean liquid to become low-temperature hot water. It then enters the cold-side fluid channel of the absorber (13) through the outlet of the hot-side fluid channel to complete the cycle.

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