Energy-saving carbon capture system based on back pressure engine residual pressure utilization

Abstract

The application relates to the field of carbon capture technology of coal-fired power stations, and discloses an energy-saving carbon capture system based on back pressure machine residual pressure utilization, which comprises a medium-pressure cylinder, a low-pressure cylinder, a back pressure machine body, a reboiler, an absorption tower, a regeneration tower and a multi-stage compressor; a steam extraction pipeline is connected to a steam connection pipe of the medium-pressure cylinder and the low-pressure cylinder, the steam extraction pipeline is connected with a steam inlet of the back pressure machine body, a steam outlet of the back pressure machine body is connected with an inlet of the reboiler, a drainage side of the reboiler is communicated with a condenser, a liquid phase outlet at the bottom of the absorption tower is connected with an inlet of the regeneration tower through a rich liquid pump and a heat exchanger, the bottom of the regeneration tower is connected with the reboiler, the reboiler is connected with the absorption tower through a lean liquid pump to form an absorbent circulating loop, and a gas outlet of the regeneration tower is connected with the multi-stage compressor. The application realizes high-parameter steam extraction direct reduction of product heat supply through work of the back pressure machine, reduces system heat loss and power consumption, realizes flexible coupling of steam extraction through a stable flow and pressure mechanism, and gives consideration to stable carbon capture and flexible peak shaving of the unit.

Description

Technical Field

[0001] This application relates to the field of carbon capture technology for coal-fired power plants, specifically an energy-saving carbon capture system based on the utilization of residual pressure from a back pressure unit. Background Technology

[0002] Conventional coal-fired power plants use chemical absorption to capture carbon in flue gas. In this process, the desorption reaction of the absorbent requires a large amount of heat energy. The existing heating scheme mainly involves directly extracting high-quality steam from the steam connection pipe of the generator set, cooling and depressurizing it before sending it to the reboiler to provide heat for the desorption reaction.

[0003] However, the aforementioned existing technologies have significant limitations in practical applications. The steam parameters extracted from the generator set are between 0.4 and 0.6 MPa and 220 and 350°C, while the actual steam parameters required for the desorption reaction are approximately 0.27 MPa and 130°C. The difference between these parameters is significant. The forced cooling and decompression process to achieve matching results in the direct loss of steam pressure energy and excess heat energy. At the same time, the operation of various equipment in the carbon capture system requires additional power consumption from the generator set. This energy utilization method exacerbates the energy consumption burden of the unit, leading to a significant energy efficiency penalty in the carbon capture process.

[0004] Furthermore, since the steam supply for the carbon capture system comes directly from the extraction steam from the generator unit, the carbon capture system and the generator unit must maintain forced synchronous operation. Currently, thermal power units generally undertake grid peak shaving tasks and need to frequently perform flexible operations such as load increases and decreases. During the peak shaving period of the unit under different operating conditions, the amount of extraction steam for heating will fluctuate greatly, which cannot meet the stable heating demand of the carbon capture system under the rated carbon capture capacity. If the stable operation of the carbon capture system is prioritized, the load adjustment range of the generator unit must be artificially limited. This not only reduces the operational flexibility of the unit, but also makes it difficult for the power plant to successfully complete the peak shaving tasks assigned by the grid. The rigid coupling between supply and demand makes it difficult to balance carbon capture efficiency and power plant operational flexibility. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides an energy-saving carbon capture system based on the utilization of residual pressure from a back-pressure compressor. This system solves the problems of high energy loss during the heating and pressure reduction process in existing coal-fired power plant carbon capture systems, as well as the limitation of peak-shaving flexibility caused by direct steam extraction, which forces the carbon capture system to operate synchronously with the generator unit.

[0006] To achieve the above objectives, this application provides the following technical solution: an energy-saving carbon capture system based on the utilization of residual pressure in a back pressure compressor, comprising a medium-pressure cylinder, a low-pressure cylinder, a back pressure compressor body, and a reboiler. The medium-pressure cylinder and the low-pressure cylinder are coaxially connected via a rotating shaft. A steam connecting pipe connects the steam outlet of the medium-pressure cylinder and the steam inlet of the low-pressure cylinder. An extraction steam pipe is connected to the steam connecting pipe and is connected to the steam inlet of the back pressure compressor body. The steam outlet of the back pressure compressor body is connected to the steam inlet of the reboiler.

[0007] Preferably, the system further includes a condensate cooler and a condenser; the condensate outlet of the reboiler is connected to the condensate cooler, and the condensate cooler is connected to the condenser via a condensate pipe.

[0008] Preferably, the system further includes an absorption tower, a rich liquid pump, a lean-rich liquid heat exchanger, and a regeneration tower; the bottom liquid outlet of the absorption tower is connected to the rich liquid pump, the rich liquid pump is connected to the cold flow inlet of the lean-rich liquid heat exchanger, and the cold flow outlet of the lean-rich liquid heat exchanger is connected to the inlet of the regeneration tower.

[0009] Preferably, the bottom outlet of the regeneration tower is connected to the reboiler.

[0010] Preferably, the system further includes a lean solution pump and a lean solution cooler; the reboiler is connected to the liquid phase inlet of the absorption tower in sequence through the lean solution pump, the lean-rich solution heat exchanger and the lean solution cooler.

[0011] Preferably, the system further includes a regenerated gas cooler, a gas-liquid separator, and a multi-stage compressor; the gas outlet of the regeneration tower is connected to the regenerated gas cooler.

[0012] Preferably, the regenerated gas cooler is connected to the gas-liquid separator.

[0013] Preferably, the gas-liquid separator is connected to the multi-stage compressor.

[0014] Preferably, the absorption tower is provided with a flue gas inlet.

[0015] Preferably, the absorption tower is also provided with a chemical absorbent inlet.

[0016] This application provides an energy-saving carbon capture system based on the utilization of residual pressure in a back-pressure compressor. It has the following beneficial effects:

[0017] 1. This application connects the back pressure turbine body between the extraction steam pipeline of the medium and low pressure cylinder and the reboiler, so that the high-parameter extraction steam expands and does work to generate electricity inside the back pressure turbine. The generated electricity is directly supplied to the carbon capture equipment to reduce the additional power consumption of the unit. At the same time, the steam undergoes physical degradation after doing work in the back pressure turbine, and the discharged low-parameter steam directly meets the desorption and heating requirements of the reboiler. There is no need to add an additional desuperheating and depressurization device, avoiding the heat loss generated by the traditional direct extraction steam depressurization process and improving the overall energy utilization rate of the power plant.

[0018] 2. This application utilizes the mechanism of dynamically adjusting its own working load by the back pressure turbine itself. When the generator set load increases or decreases, causing fluctuations in the front-end steam extraction, the back pressure turbine performs flow and pressure stabilization on the unstable extraction steam, ensuring that the steam flow and parameters output to the reboiler remain constant. This operating mode enables the unit's steam extraction and heat supply to form a flexible coupling, removing the restriction of forced synchronous operation between the unit and the carbon capture system. While ensuring stable heat supply from the carbon capture system, it does not interfere with the load regulation range of the generator set, ensuring the power plant's peak shaving flexibility.

[0019] 3. This application utilizes the extraction steam pipe led out from the steam connection pipe to form a power supply branch through the series connection of the back pressure turbine body and the reboiler. This structure is compact and can be directly connected to the existing carbon capture unit in engineering applications without making significant changes to the main physical structure of the generator set. It can better adapt to the integration and transformation needs of the existing coal-fired power plant carbon capture system, reducing the engineering implementation difficulty and transformation cost of the system. Attached Figure Description

[0020] Figure 1 This is a floor plan of this application.

[0021] The components include: 1. Medium-pressure cylinder; 2. Low-pressure cylinder; 3. Back pressure compressor body; 4. Lean liquid pump; 5. Reboiler; 6. Drain cooler; 7. Regeneration tower; 8. Regeneration gas cooler; 9. Gas-liquid separator; 10. Multistage compressor; 11. Absorption tower; 12. Rich liquid pump; 13. Lean liquid cooler; and 14. Lean and rich liquid heat exchanger. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] Please see the appendix Figure 1This application provides an energy-saving carbon capture system based on the utilization of residual pressure from a back-pressure compressor. The system includes a medium-pressure cylinder 1 that discharges high-parameter steam to provide a high-parameter steam source for the power cycle of the generator set and subsequent steam extraction; a low-pressure cylinder 2 that receives the residual steam discharged from the medium-pressure cylinder 1 to continue the power cycle of the generator set; a back-pressure compressor body 3 that receives the high-parameter steam and expands it to generate electricity; simultaneously, the high-parameter steam undergoes physical degradation treatment, the power load is dynamically adjusted, and the steam is subjected to flow and pressure stabilization treatment to ensure that the steam flow rate and parameters output to the reboiler 5 are constant; and the reboiler 5 receives the degraded steam delivered by the back-pressure compressor body 3 as a heat source for heating, while simultaneously condensing the degraded steam after heat release and cooling into condensate and discharging it. The intermediate-pressure cylinder 1 and the low-pressure cylinder 2 are coaxially connected by a rotating shaft. A steam connecting pipe connects the steam outlet of the intermediate-pressure cylinder 1 and the steam inlet of the low-pressure cylinder 2. An extraction steam pipe is connected to the steam connecting pipe. The extraction steam pipe is connected to the steam inlet of the back-pressure unit 3. The steam outlet of the back-pressure unit 3 is connected to the steam inlet of the reboiler 5. The system also includes a condensate cooler 6 that receives the condensate discharged from the reboiler 5, performs cooling treatment on the condensate, and then discharges it into the condenser. The condensate outlet of the reboiler 5 is connected to the condensate cooler 6, and the condensate cooler 6 is connected to the condenser through a condensate pipe.

[0024] Please see the appendix Figure 1 In a preferred embodiment of this application, the system further includes an absorption tower 11 that receives desulfurized flue gas and chemical absorbent, provides space for the flue gas and chemical absorbent to undergo chemical absorption reaction to capture carbon dioxide, and discharges the rich liquid formed after absorption saturation from the bottom of the tower. The rich liquid pump 12 pressurizes and drives the rich liquid discharged from the absorption tower 11 to be sent to the lean-rich liquid heat exchanger 14 for preheating. The lean-rich liquid heat exchanger 14 preheats the rich liquid before it enters the regeneration tower 7, and performs heat transfer and cooling on the liquid that subsequently flows into the absorption tower 11. The regeneration tower 7 receives the preheated rich liquid. During the downward flow of the rich liquid, the desorption operation is carried out in conjunction with the heat provided by the reboiler 5, and the high-concentration carbon dioxide gas escapes from the top of the column and the lean liquid after complete desorption is discharged from the bottom of the column; the liquid phase outlet at the bottom of the absorption column 11 is connected to the rich liquid pump 12, the rich liquid pump 12 is connected to the cold flow inlet of the lean and rich liquid heat exchanger 14, the cold flow outlet of the lean and rich liquid heat exchanger 14 is connected to the inlet of the regeneration column 7, and the bottom outlet of the regeneration column 7 is connected to the reboiler 5. The system also includes a lean liquor pump 4 to extract lean liquor from the liquid phase outlet of the reboiler 5 and pressurize it into the hot flow channel of the lean-rich liquor heat exchanger 14 and the lean liquor cooler 13 to receive the lean liquor after heat exchange and cooling, and to perform deep cooling on the lean liquor so that the lean liquor meets the conditions for reflux to the absorption tower 11; the reboiler 5 is connected to the liquid phase inlet of the absorption tower 11 in sequence through the lean liquor pump 4, the lean-rich liquor heat exchanger 14 and the lean liquor cooler 13. The system also includes a regenerated gas cooler 8 that receives high-concentration carbon dioxide gas escaping from the regeneration tower 7 and performs preliminary physical cooling on the high-concentration carbon dioxide gas; a gas-liquid separator 9 that receives the cooled carbon dioxide gas and performs gas-liquid separation to remove residual moisture, thus purifying the carbon dioxide gas; and a multi-stage compressor 10 that receives the purified carbon dioxide gas from the gas-liquid separator 9 and performs a stepped pressurization and compression operation to complete the collection of carbon capture products. The gas outlet of the regeneration tower 7 is connected to the regenerated gas cooler 8, the regenerated gas cooler 8 is connected to the gas-liquid separator 9, the gas-liquid separator 9 is connected to the multi-stage compressor 10, and the absorption tower 11 is provided with a flue gas inlet and a chemical absorbent inlet.

[0025] Working principle: When the system enters the operating state, the generator set starts its power cycle. The high-parameter steam discharged from the intermediate-pressure cylinder 1 is originally scheduled to enter the low-pressure cylinder 2 through the steam connection pipe. At this time, the extraction pipe extracts part of the high-parameter steam from the connection pipe and introduces it into the steam inlet of the back-pressure unit 3. The extracted steam expands and does work inside the back-pressure unit 3, driving the connected power generation equipment to generate electricity. This electricity is directly delivered to the power-consuming equipment of the carbon capture system to reduce the power load of the unit. At the same time, after the steam does work in the back-pressure unit 3, it undergoes physical degradation treatment, and the parameters are reduced to the set range required for the desorption reaction. The degraded exhaust steam is discharged from the steam outlet of the back-pressure unit 3 and enters the steam inlet of the reboiler 5 for desorption and heating. The steam that has released heat condenses into condensate, which flows into the condensate cooler 6 through the condensate outlet of the reboiler 5 for cooling and temperature reduction. Finally, it is discharged into the condenser along the condensate pipe to complete the water-side thermodynamic cycle.

[0026] Simultaneous decarbonization is performed. After desulfurization, the flue gas and chemical absorbent are introduced into the absorption tower 11 through their respective inlets. In the tower, a chemical absorption reaction occurs to capture carbon dioxide in the flue gas. After absorption saturation, the rich liquid formed is discharged from the liquid phase outlet at the bottom of the absorption tower 11. It is then pressurized by the rich liquid pump 12 and driven into the cold flow inlet of the lean-rich liquid heat exchanger 14. After heat exchange and preheating, it is injected into the inlet of the regeneration tower 7 through the cold flow outlet. In the regeneration tower 7, the rich liquid flows downward. The reboiler 5 uses the degraded steam heat source delivered by the back pressure machine body 3 to boil and vaporize the rich liquid at the bottom of the tower for desorption, releasing carbon dioxide gas. The lean liquid after complete desorption flows into the liquid phase outlet of the reboiler 5 through the bottom outlet. Then, it is pumped out by the lean liquid pump 4 and pumped in reverse into the hot flow channel of the lean-rich liquid heat exchanger 14 to transfer heat and cool the front-end rich liquid. It is then introduced into the lean liquid cooler 13 for deep cooling and finally flows back to the absorption tower 11 to maintain the closed-loop circulation of the absorbent.

[0027] For the gas generated by desorption, the high-concentration carbon dioxide escapes from the gas outlet of the self-regeneration tower 7 and is transported to the regeneration gas cooler 8 for preliminary physical cooling. Then it is introduced into the gas-liquid separator 9 to perform gas-liquid separation to remove residual moisture. The purified gas is finally introduced into the multi-stage compressor 10 to perform stepped pressure boosting and compression operations to complete the collection of carbon capture products.

[0028] When the generator unit responds to the grid peak shaving task and operates with load increases and decreases, causing fluctuations in the amount of steam extracted in the extraction pipeline, the back pressure unit 3 plays a buffer regulation mechanism. The back pressure unit 3 dynamically adjusts its own working load according to the amount of steam extracted for heating required for the carbon capture system to achieve the rated carbon capture capacity. It performs flow and pressure stabilization treatment on the unstable extraction steam input from the front end, ensuring that the exhaust steam flow and parameters output to the reboiler 5 are constant. This operating mode enables the heating supply and the unit's steam extraction to form a flexible coupling. Under the premise of completely removing the physical restrictions of forced synchronous operation between the unit and the carbon capture system and not restricting the load regulation range of the generator unit, it ensures the stable heating demand of the carbon capture system.

[0029] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An energy-saving carbon capture system based on the utilization of residual pressure in a back pressure compressor, comprising a medium-pressure cylinder (1), a low-pressure cylinder (2), a back pressure compressor body (3), and a reboiler (5), characterized in that, The intermediate pressure cylinder (1) and the low pressure cylinder (2) are coaxially connected by a rotating shaft. A steam connecting pipe is connected between the steam outlet of the intermediate pressure cylinder (1) and the steam inlet of the low pressure cylinder (2). A steam extraction pipe is connected to the steam connecting pipe. The steam extraction pipe is connected to the steam inlet of the back pressure machine body (3). The steam outlet of the back pressure machine body (3) is connected to the steam inlet of the reboiler (5).

2. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 1, characterized in that, The system also includes a condensate cooler (6) and a condenser; the condensate outlet of the reboiler (5) is connected to the condensate cooler (6), and the condensate cooler (6) is connected to the condenser through a condensate pipe.

3. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 1, characterized in that, The system also includes an absorption tower (11), a rich liquid pump (12), a lean-rich liquid heat exchanger (14), and a regeneration tower (7); the bottom liquid outlet of the absorption tower (11) is connected to the rich liquid pump (12), the rich liquid pump (12) is connected to the cold flow inlet of the lean-rich liquid heat exchanger (14), and the cold flow outlet of the lean-rich liquid heat exchanger (14) is connected to the inlet of the regeneration tower (7).

4. The energy-saving carbon capture system based on back pressure utilization of the compressor according to claim 3, characterized in that, The bottom outlet of the regeneration tower (7) is connected to the reboiler (5).

5. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 4, characterized in that, The system also includes a lean liquid pump (4) and a lean liquid cooler (13); the reboiler (5) is connected to the liquid inlet of the absorption tower (11) in sequence through the lean liquid pump (4), the lean and rich liquid heat exchanger (14) and the lean liquid cooler (13).

6. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 3, characterized in that, The system also includes a regenerated gas cooler (8), a gas-liquid separator (9), and a multi-stage compressor (10); the gas outlet of the regeneration tower (7) is connected to the regenerated gas cooler (8).

7. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 6, characterized in that, The regenerated gas cooler (8) is connected to the gas-liquid separator (9).

8. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 7, characterized in that, The gas-liquid separator (9) is connected to the multi-stage compressor (10).

9. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 3, characterized in that, The absorption tower (11) is equipped with a flue gas inlet.

10. The energy-saving carbon capture system based on back pressure utilization of a back pressure compressor according to claim 3, characterized in that, The absorption tower (11) is also equipped with a chemical absorbent inlet.

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