Carbon capture system based on heat pump preheating pregnant solution and operation method of carbon capture system

Abstract

The invention discloses a carbon capture system based on a heat pump preheating pregnant solution and an operation method of the carbon capture system, and belongs to the field of absorption carbon capture and waste heat utilization. The system comprises an absorption carbon capture unit, a heat pump unit, a flue gas flow channel and a hot water supply circulation flow channel, the absorption carbon capture unit is used for capturing CO2 gas in flue gas, and the heat pump unit is used for recovering flue gas waste heat of a power plant and outputting medium-temperature waste heat to the rich liquid preheater; the flue gas runner is used for introducing high-temperature flue gas into a flue gas inlet in the bottom of the absorption tower after the high-temperature flue gas is sequentially used for heating the generator and the evaporator; the heat supply circulating water flow channel is used for transferring heat output by the heat pump unit to the rich liquid preheater. An incremental absorption heat pump and a barren liquor flash evaporation recompression technology are used, and a medium-temperature heat source is generated by utilizing waste heat of flue gas and supplied to rich liquor at an inlet of the desorption tower, so that the temperature of the top of the desorption tower is increased.

Description

Technical Field

[0001] The present invention belongs to the field of carbon capture by absorption and waste heat utilization, and in particular relates to a carbon capture system based on heat pump preheating of rich liquid and an operation method thereof. Background Art

[0002] Fossil fuels dominate the energy production and consumption structure. Their combustion will release a large amount of carbon dioxide, leading to global warming. Carbon capture technology is one of the key technologies to reduce carbon emissions and achieve carbon peak and carbon neutrality goals. Post-combustion capture technology is currently the most mature and widely used carbon capture technology, and it is easier to transform existing coal-fired power plants. Absorption carbon capture has a fast absorption rate, high absorption efficiency, and low requirements for flue gas pressure. The technology is mature and reliable, the investment cost is relatively low, and the equipment operates stably. It has been widely used in post-combustion capture in coal-fired power plants.

[0003] The absorption carbon capture system applied to coal-fired power plants needs to extract part of the high-temperature steam in the power generation system to drive the solution desorption and regeneration, which may cause the turbine power to drop, thereby reducing the power generation efficiency. In order to solve the problem of the carbon capture system affecting the power generation efficiency, researchers have explored the improvement of the absorption system process, the optimization of power plant energy scheduling, and the utilization of waste heat in the power plant, but it is still difficult to control the decline in power generation efficiency within 7%. The flue gas at the boiler outlet of a coal-fired power plant still has a high temperature. Recycling and utilizing the waste heat of the flue gas is an effective way to reduce the energy consumption of the carbon capture system. Due to the high temperature of the main hot end reboiler of the traditional absorption carbon capture system, the available flue gas waste heat is less, which limits the energy-saving effect of flue gas waste heat recovery. Heat pump technology can recycle the low-temperature waste heat of the flue gas and output higher temperature heat to the carbon capture system. However, the combination of existing heat pumps and absorption carbon capture systems has many limitations. The traditional compression heat pump faces the limitation of excessive power consumption, the heat conversion efficiency of the warming absorption heat pump is low, and the output temperature of the incremental absorption heat pump is difficult to meet the reboiler requirements. 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 the present invention is to solve the defects of less available flue gas waste heat in coal-fired power plants and the absorption carbon capture system that reduces the power generation efficiency of the power plants, and to provide a carbon capture system based on heat pump preheating rich liquid and its operation method.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] In a first aspect, the present invention provides a carbon capture system based on heat pump preheating of rich liquid, comprising an absorption carbon capture unit, a heat pump unit, a flue gas flow channel and a hot water circulation flow channel.

[0007] The absorption carbon capture unit is used to consume the heat from the heat pump unit and the steam flow channel, absorb and enrich the CO2 in the flue gas in the flue gas flow 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 flow channel, and output the medium-temperature waste heat to the rich liquid preheater; the flue gas flow channel is used to use the high-temperature flue gas for heating the generator and the evaporator in turn, and then pass it into the flue gas inlet at the bottom of the absorption tower; the circulating water in the hot water circulation flow channel is used to absorb the heat output by the heat pump unit, and enter the rich liquid preheater to exchange heat with the rich liquid.

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

[0009] The heat pump unit comprises 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 through a solution throttle valve, and the steam outlet is connected to the hot side fluid channel inlet of the condenser; 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 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 through a solution pump; the hot side fluid channel outlet of the condenser is connected to the cold side fluid channel inlet of the evaporator through a water throttle 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 passage passes through the hot side fluid passage of the generator and the evaporator in sequence, and finally communicates with the flue gas inlet at the bottom of the absorption tower;

[0011] The hot water supply circulation channel passes 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 rich liquid preheater in sequence, and then returns to the cold side fluid channel of the absorber to form a closed cycle.

[0012] Furthermore, the steam source of the steam flow channel is exhaust from a steam turbine in a power plant.

[0013] Furthermore, the absorption tower and the desorption tower are both packed distillation towers.

[0014] Furthermore, the packing in the packed distillation tower is one of Raschig rings, Pall rings, step rings, arc saddle packing, rectangular saddle packing, corrugated packing, corrugated mesh packing or metal saddle ring packing.

[0015] Furthermore, the absorbent in the internal circulation path of the carbon capture absorption unit is an inorganic alkaline solution or an organic amine solution.

[0016] Furthermore, the lean-rich liquid heat exchanger, rich liquid preheater, condenser, evaporator and solution heat exchanger are all partition-wall heat exchangers.

[0017] Furthermore, the first cold source and the second cold source are both natural cold sources or refrigeration units.

[0018] Furthermore, the working fluid pair of the heat pump unit is lithium bromide aqueous solution-water.

[0019] In a second aspect, the present invention provides an operating method of a carbon capture system based on preheating rich liquid with a heat pump according to any one of the first aspects, which is as follows:

[0020] The working process of the carbon capture unit is as follows:

[0021] After being cooled by the lean liquid cooler, the lean liquid enters from the lean liquid inlet at the top of the absorption tower, and exchanges heat and mass with the untreated flue gas entering the absorption tower through the flue gas inlet flow channel in the absorption tower; the lean liquid absorbs CO2 in the flue gas to obtain rich liquid and treated flue gas; the treated flue gas is discharged through the flue gas discharge flow channel; the rich liquid after absorbing CO2 is connected to the inlet of the rich liquid pump through a pipeline, and enters the lean and rich liquid heat exchanger through the cold side fluid channel inlet of the lean and rich liquid heat exchanger under the drive of the rich liquid pump, and exchanges heat with the lean liquid from the lean liquid outlet of the flash tank in the lean and rich liquid heat exchanger to become high-temperature rich liquid; the high-temperature rich liquid enters the rich liquid preheater, absorbs heat from the hot water circulation flow channel to further heat up, and then enters the desorption tower through the rich liquid inlet of the desorption tower, and desorbs CO2 under the purge of high-temperature steam entering through the gas phase inlet of the desorption tower; the desorbed CO2 and the purge steam are discharged through the gas phase outlet at the top of the desorption tower and enter Product gas condenser, the absorbent components in the gas phase are cooled and liquefied in the product gas condenser, discharged through the condensed water outlet and refluxed into the desorption tower; the remaining gas components are discharged through the gas phase outlet of the product gas condenser and collected through the CO2 product flow channel; the desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorption tower and enters the reboiler, and 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 liquid enters the flash tank for flash evaporation, and the generated flash steam enters the compressor through the steam outlet above the flash tank, and after being compressed, enters the desorption tower from the gas phase inlet at the bottom of the desorption tower for purging, and the remaining lean liquid is discharged through the lean liquid outlet at the bottom of the flash tank, and is passed into the hot side fluid channel inlet of the lean-rich liquid heat exchanger by the lean liquid pump to heat the rich liquid from the rich liquid outlet at the bottom of the absorption tower; the lean liquid after heat exchange is mixed with the absorbent solution replenished by the absorbent replenishing flow channel and enters the lean liquid cooler to complete the cycle;

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

[0023] The dilute solution enters the solution inlet of the generator from the cold side fluid channel of the solution heat exchanger, exchanges heat with the high temperature flue gas in the hot side fluid channel in the generator, and generates high pressure steam and concentrated solution; the high pressure steam enters the hot side fluid channel of the condenser through the steam outlet of the generator, releases heat to the circulating hot water supply in the cold side fluid channel in the condenser, and forms condensed water; the condensed water enters the water throttle valve, expands into low pressure water, and then enters the cold side fluid channel of the evaporator, exchanges heat with the low temperature flue gas in the hot side fluid channel, and evaporates into low pressure steam; the low pressure steam enters the steam inlet of the absorber, and the water working medium cycle is completed; the concentrated solution enters the hot side fluid channel of the solution heat exchanger through the solution outlet of the generator, exchanges heat with the dilute solution in the cold side fluid channel, and then enters the solution inlet of the absorber, absorbs the low pressure steam from the steam inlet in the absorber, and simultaneously exchanges heat with the heating circulating water in the cold side fluid channel, and generates a dilute solution, enters the cold side fluid channel of the solution heat exchanger through the solution outlet of the absorber, exchanges heat with the concentrated solution in the hot side fluid channel, and then enters the solution inlet of the generator, and the solution working medium cycle is completed;

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

[0025] The high-temperature flue gas from the boiler enters the hot side fluid channel of the generator, releases heat and becomes medium-temperature flue gas; the medium-temperature flue gas enters the hot side fluid channel of the evaporator, releases heat and becomes 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] The low-temperature hot water absorbs the heat generated by the low-pressure steam absorbed by the concentrated solution in the cold-side fluid channel of the absorber to become medium-temperature hot water; the medium-temperature hot water enters the cold-side fluid channel of the condenser to absorb 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 rich liquid preheater to become low-temperature hot water after heat exchange with the rich liquid, and enters the cold-side fluid channel of the absorber through the outlet of the hot-side fluid channel to complete the cycle.

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

[0029] The system of the present invention combines incremental heat pump technology, solution flash recompression technology and rich liquid preheating technology with an absorption carbon capture system, which can efficiently recover low-temperature waste heat from flue gas in coal-fired power plants, increase the top temperature of the desorption tower, and strengthen CO2 desorption, thereby reducing the amount of air extracted from the steam turbine, so that the power generation efficiency of coal-fired power plants is less affected by the operation of the carbon capture system. Compared with the existing technology combining compression heat pumps with absorption carbon capture systems, the system provided by the present invention has lower power consumption and solves the problem of high power consumption; compared with the existing technology combining temperature-raising heat pumps with absorption carbon capture systems, the present invention has a higher recovery efficiency of low-temperature waste heat and solves the problem of low utilization of flue gas waste heat. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] In the figure: absorption carbon capture unit 101; heat pump unit 102; absorption tower 1; lean liquid cooler 2; rich liquid pump 3; lean and rich liquid heat exchanger 4; rich liquid preheater 5; desorption tower 6; product gas condenser 7; reboiler 8; compressor 9; flash tank 10; lean liquid pump 11; generator 12; condenser 13; absorber 14; evaporator 15; solution throttle valve 16; solution pump 17; solution heat exchanger 18; water throttle valve 19; flue gas flow channel 20; flue gas emission flow channel 21; first cold source 22; CO2 product flow channel 23; absorbent replenishment flow channel 24; second cold source 25; steam flow channel 26; circulating hot water supply flow channel 27. DETAILED DESCRIPTION

[0032] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0033] The present invention provides a carbon capture system based on heat pump preheating rich liquid, which can be divided into four parts, namely, an absorption carbon capture unit 101, a heat pump unit 102, a flue gas flow channel 20 and a heating circulating water flow channel 27. Figure 1 As shown. Among them, the carbon capture unit 101 is used to consume the heat from the heat pump unit 102 and the steam flow channel 26, absorb and enrich the CO2 in the flue gas in the flue gas flow channel 19; the heat pump unit 102 is used to recover the waste heat of the flue gas in the power plant, absorb the high temperature and low temperature waste heat of the flue gas in the flue gas flow channel 19, and output the medium temperature waste heat to the rich liquid preheater 5 to increase the top temperature of the desorption tower 6; the flue gas flow channel 20 is used to use the high temperature flue gas for heating the generator 12 and the evaporator 15 in turn, and then pass it into the flue gas inlet at the bottom of the absorption tower 1; the circulating water in the heating circulating water flow channel 27 is used to absorb the heat output by the heat pump unit 102, and enter the rich liquid preheater 5 to exchange heat with the rich liquid, that is, to transfer the heat output by the heat pump unit 102 to the rich liquid preheater 5.

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

[0035] In this embodiment, the absorption carbon capture unit 101 includes an absorption tower 1, a lean liquid cooler 2, a rich liquid pump 3, a lean and rich liquid heat exchanger 4, a rich liquid preheater 5, a desorption tower 6, a product gas condenser 7, a reboiler 8, a compressor 9, a flash tank 10, a lean liquid pump 11, a flue gas emission channel 21, a first cold source 22, a CO2 product channel 23, an absorbent replenishing channel 24, a second cold source 25 and a steam channel 26, which together constitute an internal circulation passage.

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

[0037] In addition, the lean-rich liquid heat exchanger 4 , the rich liquid preheater 5 , and the reboiler 8 each have a cold-side fluid passage and a hot-side fluid passage therein for 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 20 for introducing the flue gas to be treated. The top of the absorption tower 1 is provided with a flue gas discharge outlet connected to the flue gas discharge channel 21 for discharging the treated flue gas.

[0039] The bottom of the absorption tower 1 is also provided with a rich liquid outlet, which is connected to the inlet of the rich liquid pump 3 through a pipeline. The outlet of the rich liquid pump 3 is connected to the cold side fluid channel inlet of the lean-rich liquid heat exchanger 4 through a pipeline. The cold side fluid channel outlet of the lean-rich liquid heat exchanger 4 is connected to the cold side fluid channel inlet of the rich liquid preheater 5 through a pipeline. The cold side fluid channel outlet of the rich liquid preheater 5 is connected to the rich liquid inlet of the desorption tower 6 through a pipeline.

[0040] The gas phase outlet at the top of the desorption tower 6 is connected to the heat source inlet of the product gas condenser 7 through a pipeline. The cold source inlet of the product gas condenser 7 is connected to the first cold source 22 through a pipeline. The condensed water outlet of the product gas condenser 7 is connected to the condensed water inlet at the top of the desorption tower 6 through a pipeline. The gas phase outlet of the product gas condenser 7 is connected to the CO2 product flow channel 23 through a pipeline.

[0041] The liquid phase outlet at the bottom of the desorption tower 6 is connected to the cold side fluid channel inlet of the reboiler 8 through a pipeline. The gas phase product outlet of the reboiler 8 is connected to the gas phase inlet at the bottom of the desorption tower 6 through a pipeline. The hot side fluid channel inlet of the reboiler 8 is connected to the steam flow channel 26 through a pipeline. The liquid phase product outlet of the reboiler 8 is connected to the lean liquid inlet of the flash tank 10 through a pipeline.

[0042] In this embodiment, the steam source of the steam flow channel 26 is the extraction steam turbine of the power plant. The extraction steam turbine is an industrial equipment that extracts a portion of steam from the middle stage of the steam turbine to supply thermal energy to users and generate electricity at the same time. In this way, the extraction steam turbine not only meets the demand of electrical load, but also provides thermal energy, thereby improving the thermal efficiency and economy of the unit.

[0043] In this embodiment, the product gas condenser 7 and the reboiler 8 have a gas-liquid separation function. The product gas condenser 7 condenses the distilled gas from the gas phase outlet of the desorption tower 6 into condensed water and CO2 products. The condensed water flows back to the desorption tower 6 through the condensed water outlet of the product gas condenser 7. The CO2 product is discharged through the gas phase outlet of the product gas condenser 7 and collected through the CO2 product flow channel 23. The reboiler 8 divides the rich liquid from the liquid phase outlet of the desorption tower 6 into purge steam and lean liquid. The purge steam enters the desorption tower 6 through the gas phase product outlet of the reboiler 7 for purge, and the lean liquid flows to the lean-rich liquid heat exchanger 4 through the liquid phase product outlet of the reboiler 8.

[0044] The top steam outlet of the flash tank 10 is connected to the inlet of the compressor 9 through a pipeline; the outlet of the compressor 9 is connected to the gas phase inlet at the bottom of the desorption tower 6 through a pipeline.

[0045] The lean liquid outlet at the bottom of the flash tank 10 is connected to the inlet of the lean liquid pump 11 through a pipeline. The outlet of the lean liquid pump 11 is connected to the hot side fluid channel inlet of the lean-rich liquid heat exchanger 4 through a pipeline. 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 through a pipeline. The inlet of the lean liquid cooler 2 is also connected to the absorbent replenishing flow channel 24 for replenishing the absorbent solution. The cold source inlet of the lean liquid cooler 2 is connected to the second cold source 25 through a pipeline. The outlet of the lean liquid cooler 2 is connected to the lean liquid inlet at the top of the absorption tower 1 through a pipeline.

[0046] In this embodiment, the absorption tower 1 and the desorption tower 6 are packed distillation towers, and the available packing types include Raschig rings, ball rings, step rings, arc saddle packings, rectangular saddle packings, corrugated packings, corrugated mesh packings, and metal saddle ring packings. In actual applications, different packings can be selected according to temperature, pressure, material properties, equipment structure, and product treatment requirements to optimize the operating efficiency in the tower and improve the separation efficiency.

[0047] It should be noted that the first cold source 22 and the second cold source 25 can be provided by natural cold sources, such as water, wind, etc., or by a refrigeration unit.

[0048] In this embodiment, the heat pump unit 102 mainly includes a generator 12, a condenser 13, an absorber 14, an evaporator 15, a solution throttle valve 16, a solution pump 17, a solution heat exchanger 18 and a water throttle valve 19, which together constitute an internal circulation path.

[0049] It should be noted that the working fluid pair of an absorption heat pump refers to two different substances used in an absorption heat pump system, usually including an absorbent and a working fluid. Such a 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 lithium bromide aqueous solution-water.

[0050] In addition, the condenser 13, the absorber 14, the evaporator 15 and the solution heat exchanger 18 have cold-side fluid channels and hot-side fluid channels therein respectively for performing heat exchange.

[0051] The solution outlet of the generator 12 is communicated with the inlet of the solution throttle valve 16 through a pipeline. The outlet of the solution throttle valve 16 is communicated with the hot side fluid channel inlet of the solution heat exchanger 18 through a pipeline. The hot side fluid channel outlet of the solution heat exchanger 18 is communicated with the solution inlet of the absorber 14 through a pipeline. The solution outlet of the absorber 14 is communicated with the inlet of the solution pump 17 through a pipeline. The outlet of the solution pump 17 is communicated with the cold side fluid channel inlet of the solution heat exchanger 18 through a pipeline. The cold side fluid channel outlet of the solution heat exchanger 18 is communicated with the solution inlet of the generator 12 through a pipeline.

[0052] The steam outlet of the generator 12 is communicated with the hot side fluid channel inlet of the condenser 13 through a pipe. The hot side fluid channel outlet of the condenser is communicated with the inlet of the water throttle valve 19 through a pipe. The outlet of the water throttle valve 19 is communicated with the cold side fluid channel inlet of the evaporator 15 through a pipe. The cold side fluid channel outlet of the evaporator 15 is communicated with the steam inlet of the absorber 14 through a pipe.

[0053] The flue gas flow channel 20 passes through the hot side fluid channels of the generator 12 and the evaporator 15 in sequence, and finally communicates with the flue gas inlet at the bottom of the absorption tower 1.

[0054] The hot water circulation channel 27 passes through the cold side fluid channel of the absorber 14, the cold side fluid channel of the condenser 13 and the hot side fluid channel of the rich liquid preheater 5 in sequence, and then returns to the cold side fluid channel of the absorber 14 to form a closed cycle.

[0055] In this embodiment, the lean-rich liquid heat exchanger 4 and the rich liquid preheater 5 provided in the carbon capture absorption unit 101 and the condenser 13, the evaporator 15 and the solution heat exchanger 18 provided in the heat pump unit 102 adopt a partition-type heat exchanger. The partition-type heat exchanger can be divided into a shell-and-tube heat exchanger, a shell-and-tube heat exchanger, a plate heat exchanger and a spray heat exchanger according to different forms of the heat exchange surface. In actual application, one can be selected according to the needs.

[0056] Using the above carbon capture system based on heat pump preheating of rich liquid, the present invention also provides an operation method, which is as follows:

[0057] The system realizes low-energy carbon capture through the joint operation of the carbon capture unit 101 and the heat pump unit 102. The carbon capture unit 101 consumes heat from the heat pump unit 102 and the steam flow channel 26 to absorb and enrich CO2 in the flue gas. The heat pump unit 102 absorbs high-temperature and low-temperature waste heat from the flue gas and outputs medium-temperature waste heat. The circulating water in the hot water circulation channel 27 absorbs the heat output by the heat pump and enters the rich liquid preheater 5 to exchange heat with the rich liquid. The lean liquid in the lean-rich liquid heat exchanger 4 has a lower outlet rich liquid temperature due to the lower flash evaporation temperature, so the rich liquid can absorb the medium-temperature waste heat of the circulating water in the rich liquid preheater 5.

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

[0059] 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, and exchanges heat and mass with the flue gas to be treated that enters the absorption tower 1 through the flue gas inlet flow channel 20. The lean liquid absorbs CO2 in the flue gas to obtain rich liquid and treated flue gas.

[0060] The treated flue gas is discharged through the flue gas discharge flow channel 21. The rich liquid after absorbing CO2 is connected to the inlet of the rich liquid pump 3 through a pipeline, and enters the lean-rich liquid heat exchanger 4 through the cold side fluid channel inlet of the lean-rich liquid heat exchanger 4 under the drive of the rich liquid pump 3, and performs heat exchange with the lean liquid from the lean liquid outlet of the flash tank 10 in the lean-rich liquid heat exchanger 4 to become a high-temperature rich liquid. The high-temperature rich liquid enters the desorption tower 6 through the rich liquid inlet of the desorption tower 6, and desorbs CO2 under the purge of the high-temperature steam entering through the gas phase inlet of the desorption tower 6. The desorbed CO2 and the purge steam are discharged through the gas phase outlet at the top of the desorption tower 6 and enter the product gas condenser 7. The absorbent components in the gas phase are cooled and liquefied in the product gas condenser 7, discharged through the condensed water outlet and refluxed to the desorption tower 6. The remaining gas components are discharged through the gas phase outlet of the product gas condenser 7 and collected through the CO2 product flow channel 23. The desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorber 6 and enters the reboiler 8. The generated high-temperature steam enters the desorber 6 from the gas phase inlet at the bottom of the desorber 6 for purging. The remaining lean liquid enters the flash tank 10 for flash evaporation. The generated flash steam enters the compressor 9 through the steam outlet above the flash tank 10. After being compressed, it enters the desorber 6 from the gas phase inlet at the bottom of the desorber 6 for purging. The remaining lean liquid is discharged through the lean liquid outlet at the bottom of the flash tank 10 and is passed into the hot side fluid channel inlet of the lean-rich liquid heat exchanger 4 by the lean liquid pump 11 to heat the rich liquid from the rich liquid outlet at the bottom of the absorber 1. The lean liquid after heat exchange is mixed with the absorbent solution supplemented by the absorbent supplementary flow channel 24 and enters the lean liquid cooler 2 to complete the cycle.

[0061] It should be noted that during operation, absorbent solution can be added to the system through the absorbent replenishment channel 24 to ensure that the concentration of the absorbent solution in the system is stable to balance the circulation loss.

[0062] The working process of the heat pump unit is as follows: the dilute solution enters the solution inlet of the generator 12 from the cold side fluid channel of the solution heat exchanger 18, and exchanges heat with the high-temperature flue gas in the hot side fluid channel in the generator 12 to generate high-pressure steam and concentrated solution. The high-pressure steam enters the hot side fluid channel of the condenser 13 through the steam outlet of the generator 12, and releases heat to the circulating hot water supply in the cold side fluid channel in the condenser 13 to form condensed water. The condensed water enters the water throttle valve 19, expands into low-pressure water, and then enters the cold side fluid channel of the evaporator 15, exchanges heat with the low-temperature flue gas in the hot side fluid channel, and evaporates into low-pressure steam. The low-pressure steam enters the steam inlet of the absorber 14 to complete the water working medium cycle.

[0063] The concentrated solution passes through the solution outlet of the generator 12, enters the hot side fluid channel of the solution heat exchanger 18, exchanges heat with the dilute solution in the cold side fluid channel, and then enters the solution inlet of the absorber 14. In the absorber 14, the low-pressure steam from the steam inlet is absorbed, and at the same time, heat is exchanged with the heating circulating water in the cold side fluid channel to generate a dilute solution. The dilute solution enters the cold side fluid channel of the solution heat exchanger through the solution outlet of the absorber 14, exchanges heat with the concentrated solution in the hot side fluid channel, and then enters the solution inlet of the generator 12, completing the solution working fluid cycle.

[0064] The working process of the flue gas flow channel 20 is as follows: the high-temperature flue gas from the boiler enters the hot side fluid channel of the generator 12, releases heat and becomes medium-temperature flue gas. The medium-temperature flue gas enters the hot side fluid channel of the evaporator, releases heat and becomes 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 1.

[0065] The working process of the hot water circulation channel 27 is as follows: the low-temperature hot water absorbs the heat generated by the low-pressure steam absorbed by the concentrated solution in the cold side fluid channel of the absorber 14 to become medium-temperature hot water. The medium-temperature hot water enters the cold side fluid channel of the condenser 13 to absorb 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 rich liquid preheater 5 to become low-temperature hot water after heat exchange with the rich liquid, and enters the cold side fluid channel of the absorber 14 through the hot side fluid channel outlet to complete the cycle.

[0066] In general, the present invention provides a carbon capture system based on heat pump preheating of rich liquid, which utilizes an incremental heat pump to recycle the low-temperature waste heat of flue gas, increase the top temperature of the desorption tower, enhance the desorption of CO2 at the top of the absorption tower, and reduce the demand for steam in the operation of the carbon capture system, thereby reducing the impact on the power generation efficiency of the power plant. The system achieves low-energy carbon capture through the joint operation of the carbon capture unit and the heat pump unit. The carbon capture unit combines the lean liquid flash recompression process, and while using the latent heat of the lean liquid to generate additional steam, it reduces the temperature of the lean liquid and the temperature of the rich liquid at the outlet of the lean-rich liquid heat exchanger. The heat pump unit uses a generator driven by high-temperature waste heat of flue gas, uses an evaporator to recover low-temperature waste heat of flue gas, and outputs medium-temperature waste heat through a condenser and an absorber to heat the rich liquid at the outlet of the lean-rich liquid heat exchanger, thereby increasing the top temperature of the desorption tower. The heat exchange between the carbon capture unit and the heat pump unit is achieved by circulating hot water.

[0067] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A carbon capture system based on heat pump preheating rich liquid, characterized in that: It comprises a carbon capture unit (101), a heat pump unit (102), a flue gas flow channel (19) and a hot water circulation flow channel (26); The carbon capture absorption unit (101) is used to consume heat from the heat pump unit (102) and the steam flow channel (26), absorb and enrich CO2 in the flue gas in the flue gas flow 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 flow channel (19), and output the medium-temperature waste heat to the rich liquid preheater (5); the flue gas flow channel (19) is used to use the high-temperature flue gas for heating the generator (12) and the evaporator (15) in turn, and then pass it into the flue gas inlet at the bottom of the absorption tower (1); the circulating water in the hot water circulation flow channel (26) is used to absorb the heat output by the heat pump unit (102), and enter the rich liquid preheater (5) to exchange heat with the rich liquid.

2. A carbon capture system based on heat pump preheating rich liquid according to claim 1, characterized in that: The carbon capture unit (101) comprises an absorption tower (1), a lean-rich liquid heat exchanger (4), a rich liquid preheater (5), a desorption tower (6) and a flash tank (10); the flue gas discharge outlet at the top of the absorption tower (1) is connected to the flue gas discharge flow channel (21), 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) through a rich liquid pump (3); the cold side fluid channel outlet of the lean-rich liquid heat exchanger (4) is connected to the rich liquid preheater (5) The cold side fluid channel inlet of the rich liquid preheater (5) is connected, the cold side fluid channel outlet of the rich liquid preheater (5) is connected to the rich liquid inlet of the desorption tower (6); the gas phase outlet at the top of the desorption tower (6) is connected to the heat source inlet of the product gas condenser (7), and the liquid phase outlet at the bottom of the tower is connected to the cold side fluid channel inlet of the reboiler (8); the cold source inlet of the product gas condenser (7) is connected to the first cold source (22), and the condensed water outlet is connected to the condensed water inlet at the top of the desorption tower (6). The gas phase outlet is connected to the CO2 product flow channel (23); the gas phase product outlet of the reboiler (8) is connected to the gas phase inlet at the bottom of the desorption tower (6), the hot side fluid channel inlet is connected to the steam flow channel (26), and the liquid phase product outlet is connected to the lean liquid inlet of the flash tank (10); the top steam outlet of the flash tank (10) is connected to the inlet of the compressor (9), and the bottom lean liquid outlet is connected to the inlet of the lean liquid pump (11); the outlet of the compressor (9) is connected to the gas phase inlet at the bottom of the desorption tower (6); the outlet of the lean liquid pump (11) is connected to the hot side fluid channel inlet of the lean-rich liquid heat exchanger (4), and 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 inlet of the lean liquid cooler (2) is also connected to the absorbent replenishing flow channel (24), the cold source inlet is connected to the second cold source (25), and the outlet is connected to the lean liquid inlet at the top of the absorption tower (1); The heat pump unit (102) comprises a generator (12), a condenser (13), an absorber (14), an evaporator (15) and a solution heat exchanger (18); the solution outlet of the generator (12) is connected to the hot side fluid channel inlet of the solution heat exchanger (18) via a solution throttle valve (16), and the steam outlet is connected to the hot side fluid channel inlet of the condenser (13); the hot side fluid channel outlet of the solution heat exchanger (18) is connected to the solution inlet of the absorber (14), and the cold side fluid outlet is connected to the solution inlet of the generator (12); the solution outlet of the absorber (14) is connected to the cold side fluid channel inlet of the solution heat exchanger (18) via a solution pump (17); the hot side fluid channel outlet of the condenser (13) is connected to the cold side fluid channel inlet of the evaporator (15) via a water throttle valve (19), and the cold side fluid channel outlet of the evaporator (15) is connected to the steam inlet of the absorber (14); The flue gas flow channel (20) passes through the hot side fluid channel of the generator (12) and the evaporator (15) in sequence, and finally communicates with the flue gas inlet at the bottom of the absorption tower (1); The hot water supply circulation channel (27) passes through the cold side fluid channel of the absorber (14), the cold side fluid channel of the condenser (13) and the hot side fluid channel of the rich liquid preheater (5) in sequence, and then returns to the cold side fluid channel of the absorber (14), forming a closed cycle.

3. A carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The steam source of the steam flow channel (26) is exhaust gas from a steam turbine in a power plant.

4. A carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The absorption tower (1) and the desorption tower (6) are both packed distillation towers.

5. A carbon capture system based on heat pump preheating rich liquid according to claim 4, characterized in that: The packing in the packed distillation tower is one of Raschig rings, ball rings, step rings, arc saddle packing, rectangular saddle packing, corrugated packing, corrugated mesh packing or metal saddle ring packing.

6. A carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The absorbent in the internal circulation path of the carbon capture absorption unit (101) is an inorganic alkaline solution or an organic amine solution.

7. A carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The lean-rich liquid heat exchanger (4), the rich liquid preheater (5), the condenser (13), the evaporator (15) and the solution heat exchanger (18) are all partition-type heat exchangers.

8. The carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The first cold source (22) and the second cold source (25) are both natural cold sources or refrigeration units.

9. A carbon capture system based on heat pump preheating rich liquid according to claim 2, characterized in that: The working fluid pair of the heat pump unit (102) is lithium bromide aqueous solution-water.

10. An operating method of a carbon capture system based on heat pump preheating rich liquid according to any one of claims 2 to 9, 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), and exchanges heat and mass with the flue gas to be treated that enters the absorption tower (1) through the flue gas inlet channel (20) in the absorption tower (1); The lean liquid absorbs CO2 in the flue gas to obtain rich liquid and treated flue gas; the treated flue gas is discharged through the flue gas discharge channel (21); the rich liquid after absorbing CO2 is connected to the inlet of the rich liquid pump (3) through a pipeline, and enters the lean-rich liquid heat exchanger (4) through the cold side fluid channel inlet of the lean-rich liquid heat exchanger (4) under the drive of the rich liquid pump (3), and performs heat exchange with the lean liquid from the lean liquid outlet of the flash tank (10) in the lean-rich liquid heat exchanger (4) to become a high-temperature rich liquid; the high-temperature The rich liquid enters the rich liquid preheater (5), absorbs heat from the hot water circulation channel (26) to further increase its temperature, and then enters the desorption tower (6) through the rich liquid inlet of the desorption tower (6), and desorbs CO2 under the purge of high-temperature steam entering through the gas phase inlet of the desorption tower (6); the desorbed CO2 and the purge steam are discharged through the gas phase outlet at the top of the desorption tower (6) and enter the product gas condenser (7), and the absorbent components in the gas phase are cooled and liquefied in the product gas condenser (7), and discharged through the condensed water outlet. The desorbed liquid is discharged from the outlet of the product gas condenser (7) and refluxed into the desorption tower (6); the remaining gas components are discharged through the gas phase outlet of the product gas condenser (7) and collected through the CO2 product flow channel (23); the desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorption tower (6) and enters the reboiler (8), and the generated high-temperature steam enters the desorption tower (6) from the gas phase inlet at the bottom of the desorption tower (6) for purging; the remaining lean liquid enters the flash tank (10) for flash evaporation, and the generated flash steam passes through the flash tank (10) The steam outlet of the desorption tower (1) enters the compressor (9), and after being compressed, enters the desorption tower (6) from the gas phase inlet at the bottom of the desorption tower (6) for purging. The remaining lean liquid is discharged through the lean liquid outlet at the bottom of the flash tank (10), and is passed through the lean liquid pump (11) to the hot side fluid channel inlet of the lean-rich liquid heat exchanger (4), heating the rich liquid from the rich liquid outlet at the bottom of the absorption tower (1); the lean liquid after heat exchange is mixed with the absorbent solution supplemented by the absorbent supplement channel (24) and enters the lean liquid cooler (2) to complete the cycle; The working process of the heat pump unit (102) is as follows: The dilute solution enters the solution inlet of the generator (12) from the cold side fluid channel of the solution heat exchanger (18), exchanges heat with the high temperature flue gas in the hot side fluid channel in the generator (12), and generates high pressure steam and concentrated solution; the high pressure steam enters the hot side fluid channel of the condenser (13) through the steam outlet of the generator (12), releases heat to the circulating hot water supply in the cold side fluid channel in the condenser (13), and forms condensed water; the condensed water enters the water throttle valve (19), expands into low pressure water, and then enters the cold side fluid channel of the evaporator (15), exchanges heat with the low temperature flue gas in the hot side fluid channel, and evaporates into low pressure steam; the low pressure steam The concentrated solution passes through the solution outlet of the generator (12) and enters the hot side fluid channel of the solution heat exchanger (18), exchanges heat with the dilute solution in the cold side fluid channel, and then enters the solution inlet of the absorber (14), absorbs the low-pressure steam from the steam inlet in the absorber (14), and simultaneously exchanges heat with the heating circulating water in the cold side fluid channel to generate a dilute solution, which passes through the solution outlet of the absorber (14) and enters the cold side fluid channel of the solution heat exchanger, exchanges heat with the concentrated solution in the hot side fluid channel, and then enters the solution inlet of the generator (12), completing the solution working medium cycle; The working process of the flue gas flow channel (20) is as follows: The high-temperature flue gas from the boiler enters the hot-side fluid channel of the generator (12), releases heat and becomes medium-temperature flue gas; the medium-temperature flue gas enters the hot-side fluid channel of the evaporator (15), releases heat and becomes 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 (1); The working process of the hot water circulation channel (27) is as follows: The low-temperature hot water absorbs the heat generated by the concentrated solution absorbing the low-pressure steam in the cold-side fluid channel of the absorber (14), and becomes medium-temperature hot water; the medium-temperature hot water enters the cold-side fluid channel of the condenser (13), absorbs the condensation heat of the high-pressure steam, and becomes high-temperature hot water; the high-temperature hot water enters the hot-side fluid channel of the rich liquid preheater (5), exchanges heat with the rich liquid, and becomes low-temperature hot water, and enters the cold-side fluid channel of the absorber (14) through the outlet of the hot-side fluid channel, completing the cycle.

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