A carbon capture system based on heat pump preheating of rich liquid and a method of operating the same

Abstract

The application discloses a carbon capture system based on heat pump preheating of rich liquid and an operation method thereof, 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 heating water circulation flow channel. The absorption carbon capture unit is used for capturing CO2 gas in flue gas, the heat pump unit is used for recovering waste heat of power plant flue gas and outputting medium-temperature waste heat to a rich liquid preheater, the flue gas flow channel is used for sequentially supplying high-temperature flue gas to the heating of a generator and an evaporator, and then inputting the flue gas into a flue gas inlet at the bottom of an absorption tower, and the heating water circulation flow channel is used for transmitting heat output by the heat pump unit to the rich liquid preheater. The application uses an incremental absorption heat pump and lean liquid flash evaporation recompression technology, utilizes waste heat of flue gas to generate a medium-temperature heat source, and supplies the medium-temperature heat source to rich liquid at an inlet of a desorption tower, so that the temperature at the top of the desorption tower is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of carbon capture and waste heat utilization, and particularly relates to a carbon capture system based on heat pump preheating of rich solution and a method for operating the same. BACKGROUND

[0002] Fossil fuels dominate the energy production and consumption structure, and their combustion releases a large amount of carbon dioxide, leading to global warming. Carbon capture technology is one of the key technologies for reducing carbon emissions. Post-combustion capture technology is the most mature and widely used carbon capture technology at present, and is easier to modify on existing coal-fired power plants. Absorption carbon capture has fast absorption rate, high absorption efficiency, and lower requirement for flue gas pressure, and is mature, reliable, relatively low in investment cost, stable in equipment operation, and has been widely used in post-combustion capture of 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 regeneration, which may cause the power of the steam turbine to decrease, thereby reducing the power generation efficiency. In order to solve the problem of the influence of the carbon capture system on the power generation efficiency, researchers have explored in the aspects of absorption system process improvement, power plant energy scheduling optimization, and power plant waste heat utilization, but it is still difficult to control the decrease of the power generation efficiency within 7%. The boiler outlet flue gas of the coal-fired power plant still has a relatively high temperature, and the recovery and utilization of the flue gas waste heat is an effective way to reduce the energy consumption of the carbon capture system. Since the main heat sink of the traditional absorption carbon capture system is the reboiler with a relatively high temperature, the available flue gas waste heat is less, which limits the energy-saving effect of the flue gas waste heat recovery. The heat pump technology can recover and utilize the low-temperature waste heat of the flue gas and output heat with a relatively high temperature to the carbon capture system. However, the combination of the existing heat pump and the absorption carbon capture system has many limitations. The traditional compression heat pump faces the limitation of high power consumption, the heat conversion efficiency of the temperature-increasing absorption heat pump is relatively low, and the output temperature of the incremental absorption heat pump is difficult to meet the requirement of the reboiler. Therefore, the combination of the heat pump and the carbon capture system in the application of the coal-fired power plant needs to be further explored and developed. SUMMARY

[0004] The present application aims to solve the defects that the available flue gas waste heat of the coal-fired power plant is less and the absorption carbon capture system reduces the power generation efficiency of the power plant to a higher degree, and provides a carbon capture system based on heat pump preheating of rich solution and a method for operating the same.

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

[0006] In a first aspect, the present application provides a carbon capture system based on heat pump preheating of rich solution, which comprises an absorption carbon capture unit, a heat pump unit, a flue gas flow channel, and a heat supply water circulation channel.

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

[0008] As preferred, the absorption carbon capture unit comprises an absorption tower, a lean-rich liquid heat exchanger, a rich liquid preheater, a desorption tower and a flash tank; a flue gas discharge outlet at the top of the absorption tower is communicated with a flue gas discharge flow channel, and a rich liquid outlet at the bottom is communicated with an inlet of a cold side fluid channel of the lean-rich liquid heat exchanger through a rich liquid pump; an outlet of the cold side fluid channel of the lean-rich liquid heat exchanger is communicated with an inlet of a cold side fluid channel of the rich liquid preheater, and an outlet of the cold side fluid channel of the rich liquid preheater is communicated with a rich liquid inlet of the desorption tower; a gas phase outlet at the top of the desorption tower is communicated with a heat source inlet of a product gas condenser, and a liquid phase outlet at the bottom is communicated with an inlet of a cold side fluid channel of a reboiler; a cold source inlet of the product gas condenser is communicated with a first cold source, a condensed water outlet is communicated with a condensed water inlet at the top of the desorption tower, and a gas phase outlet is communicated with a CO2 product flow channel; a gas phase product outlet of the reboiler is communicated with a gas phase inlet at the bottom of the desorption tower, a hot side fluid channel inlet is communicated with a steam flow channel, and a liquid phase product outlet is communicated with a lean liquid inlet of the flash tank; a top steam outlet of the flash tank is connected with an inlet of a compressor, and a lean liquid outlet at the bottom is communicated with an inlet of a lean liquid pump; an outlet of the compressor is communicated with the gas phase inlet at the bottom of the desorption tower; an outlet of the lean liquid pump is communicated with an inlet of a hot side fluid channel of the lean-rich liquid heat exchanger, and an outlet of the hot side fluid channel of the lean-rich liquid heat exchanger is communicated with an inlet of a lean liquid cooler; the inlet of the lean liquid cooler is also communicated with an absorbent supplement flow channel, a cold source inlet is communicated with a second cold source, and an outlet is communicated with a 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; a solution outlet of the generator is communicated with an inlet of a hot side fluid channel of the solution heat exchanger through a solution throttling valve, and a steam outlet is communicated with an inlet of a hot side fluid channel of the condenser; a hot side fluid channel outlet of the solution heat exchanger is communicated with a solution inlet of the absorber, and a cold side fluid outlet is communicated with a solution inlet of the generator; a solution outlet of the absorber is communicated with an inlet of a cold side fluid channel of the solution heat exchanger through a solution pump; a hot side fluid channel outlet of the condenser is communicated with an inlet of a cold side fluid channel of the evaporator through a water throttling valve, and a cold side fluid channel outlet of the evaporator is communicated with a steam inlet of the absorber;

[0010] The flue gas flow channel sequentially passes through the hot side fluid channels of the generator and the evaporator, and finally is communicated with the flue gas inlet at the bottom of the absorption tower;

[0011] The hot water 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 heat pump preheating of rich liquid according to any one of the first aspects, as follows:

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

[0021] The lean liquid is cooled by a lean liquid cooler and then enters the absorption tower from the lean liquid inlet at the top of the absorption tower, and exchanges heat and mass with the flue gas to be treated entering the absorption tower through the flue gas inlet channel; 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; the rich liquid after absorbing CO2 is communicated with the inlet of the rich liquid pump through a pipeline, and enters the lean-rich liquid heat exchanger through the cold side fluid channel inlet of the lean-rich liquid heat exchanger under the driving of the rich liquid pump, and exchanges heat with the lean liquid from the lean liquid outlet of the flash tank in the lean-rich liquid heat exchanger to become high-temperature rich liquid; the high-temperature rich liquid enters the rich liquid preheater, absorbs heat from the heat supply water circulation channel to further increase the temperature, and then enters the desorption tower through the rich liquid inlet of the desorption tower, and desorbs CO2 under the blowing of high-temperature steam entering through the gas phase inlet of the desorption tower; the desorbed CO2 and the blowing steam are discharged through the gas phase outlet at the top of the desorption tower, enter the product gas condenser, the absorbent components in the gas phase are liquefied by cooling in the product gas condenser, are discharged through the condensed water outlet and flow back to the desorption tower, and the remaining gas components are discharged through the gas phase outlet of the product gas condenser and collected through the CO2 product channel; the desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of the desorption tower, enters the reboiler, and the generated high-temperature steam enters the desorption tower through the gas phase inlet at the bottom of the desorption tower for blowing; the remaining lean liquid enters the flash tank for flashing, the generated flash steam enters the compressor through the steam outlet above the flash tank, is compressed and then enters the desorption tower through the gas phase inlet at the bottom of the desorption tower for blowing, and the remaining lean liquid is discharged through the lean liquid outlet at the bottom of the flash tank and is introduced 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 heat-exchanged lean liquid is mixed with the absorbent solution supplemented by the absorbent supplement channel and then 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 from the cold side fluid channel of the solution heat exchanger enters the solution inlet of the generator, and exchanges heat with the high-temperature flue gas in the hot side fluid channel in the generator to generate 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, and releases heat to the circulating heating water in the cold side fluid channel of the condenser to form condensed water; the condensed water enters the water throttling valve, expands into low-pressure water, and then enters the cold side fluid channel of the evaporator to exchange heat with the low-temperature flue gas in the hot side fluid channel and evaporate into low-pressure steam; the low-pressure steam enters the steam inlet of the absorber to complete the water working medium cycle; 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, exchanges heat with the circulating heating water in the cold side fluid channel, generates dilute solution, and then 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 to complete the solution working medium cycle.

[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 to release heat and become medium-temperature flue gas; the medium-temperature flue gas enters the hot side fluid channel of the evaporator to release heat and become 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 heating water circulation flow channel is as follows:

[0027] The low-temperature heating water in the cold side fluid channel of the absorber absorbs the heat generated by the concentrated solution absorbing the low-pressure steam to become medium-temperature heating water; the medium-temperature heating water enters the cold side fluid channel of the condenser to absorb the condensation heat of the high-pressure steam and become high-temperature heating water; the high-temperature heating water enters the hot side fluid channel of the rich liquid preheater, exchanges heat with the rich liquid to become low-temperature heating water, and then 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 application has the following beneficial effects:

[0029] The system of the present application combines the incremental heat pump technology, the solution flash evaporation re-compression technology and the rich liquid preheating technology with the absorption carbon capture system, can efficiently recover the low-temperature waste heat of the flue gas in the coal-fired power plant, improve the temperature at the top of the desorption tower, strengthen the CO2 desorption, and further reduce the extraction amount from the steam turbine, so that the influence of the carbon capture system operation on the power generation efficiency of the coal-fired power plant is reduced. Compared with the existing compression heat pump combined with the absorption carbon capture system, the system provided by the present application has lower power consumption, solving the problem of high power consumption; compared with the existing heating heat pump combined with the absorption carbon capture system, the system has higher recovery efficiency of low-temperature waste heat, solving the problem of low flue gas waste heat utilization rate. BRIEF DESCRIPTION OF DRAWINGS

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

[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-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 discharge flow channel 21; first cold source 22; CO2 product flow channel 23; absorbent supplement flow channel 24; second cold source 25; steam flow channel 26; circulating heat supply water flow channel 27. DETAILED DESCRIPTION

[0032] The present application will be further described and explained with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment in the present application can be combined accordingly without conflict.

[0033] The present application provides a carbon capture system based on heat pump preheating of rich liquid, which can be divided into four parts, namely absorption carbon capture unit 101, heat pump unit 102, flue gas flow channel 20 and heat supply circulating water flow channel 27, as shown in the specific embodiment. Figure 1 The absorption carbon capture 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 recover the flue gas waste heat of 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 medium-temperature waste heat to the rich liquid preheater 5 to improve the temperature at the top of the desorption tower 6; the flue gas flow channel 20 is used to pass the high-temperature flue gas into the flue gas inlet at the bottom of the absorption tower 1 after being used for heat supply of the generator 12 and the evaporator 15 in turn; the circulating water in the heat supply circulating water flow channel 27 is used to absorb the heat output by the heat pump unit 102, and enters the rich liquid preheater 5 to exchange heat with the rich liquid, i.e. 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 exhaust channel 21, a first cold source 22, a CO2 product channel 23, an absorbent replenishment channel 24, a second cold source 25 and a steam channel 26, which together constitute an internal circulation path.

[0036] It should be noted that an absorbent refers to a liquid that selectively absorbs one or more components of a gas mixture due to its varying solubility. This includes 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 may be used.

[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 channel and a hot-side fluid channel 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 absorption tower 1 is also provided with a rich liquid outlet, which is connected to the inlet of rich liquid pump 3 via a pipeline. The outlet of rich liquid pump 3 is connected to the cold-side fluid channel inlet of lean-rich liquid heat exchanger 4 via a pipeline. The cold-side fluid channel outlet of lean-rich liquid heat exchanger 4 is connected to the cold-side fluid channel inlet of rich liquid preheater 5 via a pipeline. The cold-side fluid channel outlet of rich liquid preheater 5 is connected to the rich liquid inlet of desorption tower 6 via 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 via a pipeline. The cold source inlet of the product gas condenser 7 is connected to the first cold source 22 via 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 via a pipeline. The gas phase outlet of the product gas condenser 7 is connected to the CO2 product flow channel 23 via 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 via 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 via a pipeline. The hot side fluid channel inlet of the reboiler 8 is connected to the steam flow channel 26 via a pipeline. The liquid phase product outlet of the reboiler 8 is connected to the lean liquid inlet of the flash tank 10 via 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 which extracts a part of steam from the middle stage of the steam turbine to supply heat energy to the user, while still generating electricity. In this way, the extraction steam turbine not only meets the demand of the electric load, but also provides heat 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 gas-liquid separation function. The product gas condenser 7 condenses the distillate gas from the gas phase outlet of the desorption tower 6 into condensed water and CO2 product. 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 purging, 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 communicated with 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 communicated with the inlet of the lean liquid pump 11 through a pipeline. The outlet of the lean liquid pump 11 is communicated with the inlet of the hot side fluid channel of the lean- rich liquid heat exchanger 4 through a pipeline. The outlet of the hot side fluid channel of the lean- rich liquid heat exchanger 4 is communicated with the inlet of the lean liquid cooler 2 through a pipeline. The inlet of the lean liquid cooler 2 is also communicated with the absorbent supplement flow channel 24 for supplementing the absorbent solution. The cold source inlet of the lean liquid cooler 2 is communicated with the second cold source 25 through a pipeline. The outlet of the lean liquid cooler 2 is communicated with 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 selected as packed rectification towers. The optional packing types include Raschig ring, Pall ring, stepped ring, arc saddle packing, square saddle packing, corrugated packing, corrugated mesh packing and metal saddle ring packing, etc. In actual application, different packings can be selected according to the temperature, pressure, material properties, equipment structure and requirements for processing products, so as 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 refrigeration units.

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

[0049] It should be noted that the working pair of the absorption heat pump refers to two different substances used in the absorption heat pump system, usually including an absorbent and a working substance. Such working pair works together to achieve refrigeration or heating function by absorbing and releasing heat. The heat pump unit 102 is filled with a solution-water working 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 each have a cold side fluid passage and a hot side fluid passage capable of constituting heat exchange.

[0051] The solution outlet of the generator 12 is communicated with the inlet of the solution throttling valve 16 through a pipeline. The outlet of the solution throttling valve 16 is communicated with the hot side fluid passage inlet of the solution heat exchanger 18 through a pipeline. The hot side fluid passage 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 passage inlet of the solution heat exchanger 18 through a pipeline. The cold side fluid passage 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 passage inlet of the condenser 13 through a pipeline. The hot side fluid passage outlet of the condenser is communicated with the inlet of the water throttling valve 19 through a pipeline. The outlet of the water throttling valve 19 is communicated with the cold side fluid passage inlet of the evaporator 15 through a pipeline. The cold side fluid passage outlet of the evaporator 15 is communicated with the steam inlet of the absorber 14 through a pipeline.

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

[0054] The heating water circulation flow channel 27 passes through the cold side fluid passage of the absorber 14, the cold side fluid passage of the condenser 13 and the hot side fluid passage of the rich solution preheater 5 in turn, and then returns to the cold side fluid passage of the absorber 14, constituting a closed circulation.

[0055] In the embodiment, the lean-rich liquid heat exchanger 4 and the rich liquid preheater 5 arranged in the carbon capture unit 101 and the condenser 13, the evaporator 15 and the solution heat exchanger 18 arranged in the heat pump unit 102 are all wall-type heat exchangers. The wall-type heat exchangers can be divided into the following types according to the different forms of the heat exchange surface: the tube-in-tube heat exchanger, the shell-and-tube heat exchanger, the plate heat exchanger and the spray heat exchanger, etc. One of them can be selected according to the actual application requirements.

[0056] Based on the carbon capture system with the rich liquid preheated by the heat pump, the application further provides an operation method, which is specifically as follows:

[0057] The system realizes the low-energy-consumption carbon capture through the combined operation of the carbon capture unit 101 and the heat pump unit 102. The carbon capture unit 101 consumes the heat from the heat pump unit 102 and the steam flow channel 26 to absorb and enrich the CO2 in the flue gas. The heat pump unit 102 absorbs the high-temperature and low-temperature waste heat of the flue gas and outputs the medium-temperature waste heat. The circulating water in the heating water circulation flow 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 that 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] The lean liquid enters the lean liquid inlet at the top of the absorption tower 1 after being cooled by the lean liquid cooler 2 and exchanges heat and mass with the flue gas to be treated entering the absorption tower 1 through the flue gas inlet flow channel 20 in the absorption tower 1. The lean liquid absorbs the CO2 in the flue gas to obtain the rich liquid and the treated flue gas.

[0060] The treated flue gas is discharged through flue gas discharge channel 21. The CO2 absorbed rich solution is communicated with the inlet of rich solution pump 3 through a pipeline and enters the cold side fluid passage inlet of lean-rich solution heat exchanger 4 under the drive of rich solution pump 3, exchanges heat with the lean solution from the lean solution outlet of flash tank 10 in lean-rich solution heat exchanger 4, and becomes high-temperature rich solution. The high-temperature rich solution enters desorption tower 6 through the rich solution inlet of desorption tower 6, and desorbs CO2 under the high-temperature steam blowing from the high-temperature steam blowing inlet of desorption tower 6. The desorbed CO2 and the blowing steam are discharged through the gas phase outlet at the top of desorption tower 6, enter product gas condenser 7, and the absorbent components in the gas phase are liquefied in product gas condenser 7, discharged through the condensate outlet and returned to desorption tower 6. The remaining gas components are discharged through the gas phase outlet of product gas condenser 7 and collected through CO2 product channel 23. The desorbed absorbent solution is discharged from the liquid phase outlet at the bottom of desorption tower 6, enters reboiler 8, and the generated high-temperature steam enters desorption tower 6 from the gas phase inlet at the bottom of desorption tower 6 for blowing. The remaining lean solution is flashed in flash tank 10, the generated flash steam enters compressor 9 through the steam outlet above flash tank 10, is compressed and enters desorption tower 6 from the gas phase inlet at the bottom of desorption tower 6 for blowing, and the remaining lean solution is discharged through the lean solution outlet at the bottom of flash tank 10, is communicated with the inlet of lean solution pump 11, enters the hot side fluid passage inlet of lean-rich solution heat exchanger 4, heats the rich solution from the rich solution outlet at the bottom of absorption tower 1, and is mixed with the absorbent solution supplemented by absorbent supplement channel 24 to complete the cycle after cooling in lean solution cooler 2.

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

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

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

[0065] The working process of the circulating hot water supply flow channel 27 is as follows: low-temperature hot water in the cold side fluid channel of the absorber 14 absorbs heat generated by the concentrated solution absorbing low-pressure steam to become medium-temperature hot water. The medium-temperature hot water enters the cold side fluid channel of the condenser 13, absorbs the condensation heat of 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, exchanges heat with the rich liquid to become low-temperature hot water, and enters the cold side fluid channel of the absorber 14 through the hot side fluid channel outlet to complete the cycle.

[0066] In summary, the carbon capture system based on the heat pump preheating of the rich liquid provided by the application recycles the low-temperature waste heat of the flue gas by using the incremental heat pump, improves the temperature at the top of the absorption tower, enhances the desorption of CO2 at the top of the absorption tower, reduces the demand for steam in the operation of the carbon capture system, and thus reduces the impact on the power generation efficiency of the power plant. The system realizes low-energy-consumption carbon capture through the combined operation of the carbon capture unit and the heat pump unit. The carbon capture unit combines the lean liquid flash evaporation and recompression process, uses the latent heat of the lean liquid to generate additional steam, and 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 the flue gas high-temperature waste heat to drive the generator, recycles the low-temperature waste heat of the flue gas by using the evaporator, and outputs medium-temperature waste heat through the condenser and the absorber to heat the rich liquid at the outlet of the lean-rich liquid heat exchanger and improve the temperature at the top of the desorption tower. The heat exchange between the carbon capture unit and the heat pump unit is realized by circulating the hot water.

[0067] The above-described embodiments are only a preferred scheme of the application, and are not intended to limit the application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the application. Therefore, any technical scheme obtained by equivalent replacement or equivalent transformation falls within the protection scope of the application.

Claims

1. A carbon capture system based on heat pump preheating of rich liquid, characterized by, The system comprises an absorption carbon capture unit (101), a heat pump unit (102), a flue gas flow channel (20) and a heat supply water circulation flow channel (27); The absorption carbon capture unit (101) is used for absorbing and enriching CO2 in the flue gas in the flue gas flow channel (20) by consuming heat from the heat pump unit (102) and the steam flow channel (26); the heat pump unit (102) is used for absorbing high-temperature and low-temperature waste heat of the flue gas in the flue gas flow channel (20) and outputting medium-temperature waste heat to the rich-liquid preheater (5); the flue gas flow channel (20) is used for sequentially supplying high-temperature flue gas to the generator (12) and the evaporator (15) and then passing the flue gas into the flue gas inlet at the bottom of the absorption tower (1); and the circulating water in the heat supply water circulation flow channel (27) is used for absorbing heat output by the heat pump unit (102) and entering the rich-liquid preheater (5) to exchange heat with rich liquid; The absorption 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 communicated with the flue gas discharge flow channel (21), the rich-liquid outlet at the bottom of the absorption tower (1) is communicated with the fluid channel inlet at the cold side of the lean-rich liquid heat exchanger (4) through the rich-liquid pump (3), the fluid channel outlet at the cold side of the lean-rich liquid heat exchanger (4) is communicated with the fluid channel inlet at the cold side of the rich-liquid preheater (5), the fluid channel outlet at the cold side of the rich-liquid preheater (5) is communicated with the rich-liquid inlet of the desorption tower (6), the gas phase outlet at the top of the desorption tower (6) is communicated with the heat source inlet of the product gas condenser (7), and the liquid phase outlet at the bottom of the desorption tower (6) is communicated with the fluid channel inlet at the cold side of the reboiler (8); the cold source inlet of the product gas condenser (7) is communicated with the first cold source (22), the condensed water outlet is communicated with the condensed water inlet at the top of the desorption tower (6), and the gas phase outlet is communicated with the CO2 product flow channel (23); the gas phase product outlet of the reboiler (8) is communicated with the gas phase inlet at the bottom of the desorption tower (6), the heat side fluid channel inlet is communicated with the steam flow channel (26), and the liquid phase product outlet is communicated with the lean-liquid inlet of the flash tank (10); the top steam outlet of the flash tank (10) is connected with the inlet of the compressor (9), and the lean-liquid outlet at the bottom is communicated with the inlet of the lean-liquid pump (11); the outlet of the compressor (9) is communicated with the gas phase inlet at the bottom of the desorption tower (6); the outlet of the lean-liquid pump (11) is communicated with the heat side fluid channel inlet of the lean-rich liquid heat exchanger (4), and the heat side fluid channel outlet of the lean-rich liquid heat exchanger (4) is communicated with the inlet of the lean-liquid cooler (2); the inlet of the lean-liquid cooler (2) is also communicated with the absorbent supplement flow channel (24), the cold source inlet is communicated with the second cold source (25), and the outlet is communicated with 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); a solution outlet of the generator (12) is communicated with an inlet of a hot-side fluid channel of the solution heat exchanger (18) through a solution throttle valve (16), and a steam outlet is communicated with an inlet of a hot-side fluid channel of the condenser (13); an outlet of the hot-side fluid channel of the solution heat exchanger (18) is communicated with a solution inlet of the absorber (14), and a cold-side fluid outlet is communicated with a solution inlet of the generator (12); a solution outlet of the absorber (14) is communicated with an inlet of a cold-side fluid channel of the solution heat exchanger (18) through a solution pump (17); an outlet of the hot-side fluid channel of the condenser (13) is communicated with an inlet of a cold-side fluid channel of the evaporator (15) through a water throttle valve (19), and an outlet of the cold-side fluid channel of the evaporator (15) is communicated with a steam inlet of the absorber (14); The flue gas flow channel (20) sequentially passes through the hot-side fluid channels of the generator (12) and the evaporator (15), and finally is communicated with a flue gas inlet at the bottom of the absorption tower (1); The hot water supply circulating flow channel (27) sequentially 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), and then returns to the cold-side fluid channel of the absorber (14), thereby forming a closed cycle.

2. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, The steam source of the steam flow channel (26) is the extraction steam of a steam turbine of a power plant.

3. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, Both the absorption tower (1) and the desorption tower (6) are packed rectification towers.

4. A carbon capture system based on heat pump preheating of rich liquid according to claim 3, characterized in that, The packing in the packed rectification tower is one of Raschig rings, Pall rings, stepped rings, arc saddle packing, square saddle packing, corrugated packing, corrugated mesh packing or metal saddle ring packing.

5. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, The absorbent in the internal circulation passage of the absorption carbon capture unit (101) is an inorganic alkali solution or an organic amine solution.

6. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, Both 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 partition wall heat exchangers.

7. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, Both the first cold source (22) and the second cold source (25) are natural cold sources or refrigeration units.

8. A carbon capture system based on heat pump preheating of rich liquid according to claim 1, characterized in that, The working medium pair of the heat pump unit (102) is lithium bromide aqueous solution-water.

9. A method of operating a carbon capture system based on heat pump preheating of rich liquid according to any one of claims 1 to 8, characterized in that, The working process of the carbon capture unit (101) is as follows: The working process of the carbon capture unit (101) is as follows: The lean liquid is cooled by the lean liquid cooler (2) and then enters the absorption tower (1) 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 entering the absorption tower (1) through the flue gas flow channel (20); 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 (21); the rich liquid after absorbing CO2 is communicated with 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 passage inlet of the lean-rich liquid heat exchanger (4) under the driving of the rich liquid pump (3), and exchanges heat with the lean liquid from the lean liquid outlet of the flash tank (10) in the lean-rich liquid heat exchanger (4) to become high-temperature rich liquid; the high-temperature rich liquid enters the rich liquid preheater (5), absorbs heat from the heat supply water circulation flow channel (27) to further increase the temperature, and then enters the desorption tower (6) through the rich liquid inlet of the desorption tower (6), and desorbs CO2 under the high-temperature steam blowing from the gas phase inlet of the desorption tower (6); the desorbed CO2 and the blowing steam are discharged through the gas phase outlet at the top of the desorption tower (6), enter the product gas condenser (7), the absorbent components in the gas phase are liquefied by cooling in the product gas condenser (7), are discharged through the condensed water outlet and flow back to the desorption tower (6), and 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), enters the reboiler (8), the generated high-temperature steam enters the desorption tower (6) from the gas phase inlet at the bottom of the desorption tower (6) to perform blowing; the remaining lean liquid enters the flash tank (10) to flash, the generated flash steam enters the compressor (9) through the steam outlet above the flash tank (10), is compressed and then enters the desorption tower (6) from the gas phase inlet at the bottom of the desorption tower (6) to perform blowing, and the remaining lean liquid is discharged from the lean liquid outlet at the bottom of the flash tank (10) and is introduced into the hot side fluid passage 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 absorption tower (1); the lean liquid after heat exchange is mixed with the absorbent solution supplemented by the absorbent supplement flow channel (24) and then 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 from the cold side fluid passage of the solution heat exchanger (18) enters the solution inlet of the generator (12), and exchanges heat with the high-temperature flue gas in the hot side fluid passage in the generator (12) to generate high-pressure steam and concentrated solution; the high-pressure steam enters the hot side fluid passage of the condenser (13) through the steam outlet of the generator (12), and releases heat to the circulating heating water in the cold side fluid passage of the condenser (13) to form condensed water; the condensed water enters the water throttling valve (19), expands into low-pressure water, and then enters the cold side fluid passage of the evaporator (15) to exchange heat with the low-temperature flue gas in the hot side fluid passage and evaporate into low-pressure steam; the low-pressure steam enters the steam inlet of the absorber (14) to complete the water working medium cycle; the concentrated solution passes through the solution outlet of the generator (12), enters the hot side fluid passage of the solution heat exchanger (18), exchanges heat with the dilute solution in the cold side fluid passage, and then enters the solution inlet of the absorber (14), absorbs the low-pressure steam from the steam inlet in the absorber (14), exchanges heat with the circulating heating water in the cold side fluid passage, generates dilute solution, and then enters the cold side fluid passage of the solution heat exchanger through the solution outlet of the absorber (14), exchanges heat with the concentrated solution in the hot side fluid passage, and then enters the solution inlet of the generator (12) to complete 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 passage of the generator (12) to release heat and become medium-temperature flue gas; the medium-temperature flue gas enters the hot side fluid passage of the evaporator (15) to release heat and 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; The working process of the heating water circulation flow channel (27) is as follows: The low-temperature heating water in the cold side fluid passage of the absorber (14) absorbs the heat generated by the concentrated solution absorbing the low-pressure steam to become medium-temperature heating water; the medium-temperature heating water enters the cold side fluid passage of the condenser (13) to absorb the condensation heat of the high-pressure steam and become high-temperature heating water; the high-temperature heating water enters the hot side fluid passage of the rich liquid preheater (5), exchanges heat with the rich liquid to become low-temperature heating water, and then enters the cold side fluid passage of the absorber (14) through the hot side fluid passage outlet to complete the cycle.

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