CN-121988141-A - Integrated carbon capture and low-grade energy comprehensive utilization system

CN121988141ACN 121988141 ACN121988141 ACN 121988141ACN-121988141-A

Abstract

The invention discloses an integrated carbon capturing and low-grade energy comprehensive utilization system and method, and relates to the technical field of carbon dioxide emission reduction, wherein the system comprises a carbon dioxide absorption tower, the bottom of the carbon dioxide absorption tower is connected with a middle buffer tower through a rich amine liquid conveying pipe, and the bottom of the middle buffer tower is connected with a carbon dioxide desorption tower through a semi-lean liquid conveying pipe; the carbon dioxide desorption tower is connected with a reboiler, the reboiler is connected with a flue gas inlet pipe and a flue gas conveying pipeline connected with the carbon dioxide absorption tower, a high-temperature evaporator is connected to the flue gas conveying pipeline, and the high-temperature evaporator is connected with a low-grade heat source power generation system through a pipeline. The regenerated hot lean solution is subjected to secondary flash evaporation through a flash evaporation tank, the gas phase is subjected to energy separation through a compression and vortex tube, cold and hot streams are respectively recycled for absorption cooling and desorption heating, and on the premise of not remarkably increasing the complexity of the system, the efficient integration and cascade utilization of various grade heat sources inside and outside a carbon capture system are realized, and the overall energy efficiency of the system is comprehensively improved.

Inventors

LIU HONG
ZHENG LANJIANG
Jiang e
LUO YI
LIU WEIWEI
DENG PING
WAN HAISHENG
LI YING
GUO LEI

Assignees

中国核动力研究设计院

Dates

Publication Date: 20260508
Application Date: 20260403

Claims (10)

1. The integrated carbon capturing and low-grade energy comprehensive utilization system is characterized by comprising a carbon dioxide absorption tower (01), wherein the bottom of the carbon dioxide absorption tower (01) is connected with an intermediate buffer tower (03) through a rich amine liquid conveying pipe (02), the bottom of the intermediate buffer tower (03) is connected with a carbon dioxide desorption tower (17) through a semi-lean liquid conveying pipe (04), the carbon dioxide desorption tower (17) is connected with a reboiler (18), the reboiler (18) is connected with a flue gas inlet pipe (27) and a flue gas conveying pipe (26) connected with the carbon dioxide absorption tower (01), a high-temperature evaporator (25) is connected to the flue gas conveying pipe (26), and the high-temperature evaporator (25) is connected with a low-grade heat source power generation system through a pipe.
2. The integrated carbon capturing and low grade energy comprehensive utilization system according to claim 1, wherein the low grade heat source power generation system comprises an expander (24) connected with the high temperature evaporator (25), an output shaft of the expander (24) is connected with a generator (23), the expander (24) is connected with a second flash tank (22), the second flash tank (22) is connected with a working medium pump (21), the working medium pump (21) is connected with the low temperature evaporator (20), and the low temperature evaporator (20) and the high temperature evaporator (25) are connected to form a circulation loop.
3. The integrated carbon capturing and low grade energy comprehensive utilization system according to claim 1, wherein a semi-lean liquid conveying pipeline (04) is connected to the bottom of the intermediate buffer tower (03), the semi-lean liquid conveying pipeline (04) is connected with a first semi-lean liquid conveying pipe (06) and a second semi-lean liquid conveying pipe (05) through a three-way joint, the first semi-lean liquid conveying pipe (06) is connected with a carbon dioxide desorption tower (17), and the second semi-lean liquid conveying pipe (05) is connected with the top of the carbon dioxide absorption tower (01).
4. The integrated carbon capturing and low grade energy comprehensive utilization system according to claim 2, wherein the bottom of the carbon dioxide desorption tower (17) is connected with a first flash tank (07) through a hot lean liquid conveying pipeline (08), the second flash tank (22) is also connected with a first compressor (28), the first compressor (28) is connected with a first vortex tube (29), the regenerated hot lean liquid is subjected to secondary flash evaporation through the second flash tank (22), the gas phase of the regenerated hot lean liquid is subjected to energy separation from the first vortex tube (29) through the first compressor (28), and cold and hot streams are respectively recycled for absorption cooling and desorption heating.
5. The integrated carbon capturing and low grade energy comprehensive utilization system according to claim 4, wherein a steam discharge pipe (12) is connected to the top of the first flash tank (07), a second vortex pipe (14) is connected to the steam discharge pipe (12), a hot flow air pipe (16) leading to the bottom of the carbon dioxide desorption tower (17) is connected to the second vortex pipe (14), a cold flow air pipe (15) leading to the top of the carbon dioxide absorption tower (01) is connected to the second vortex pipe (14), and/or a liquid phase conveying pipe (09) connected to the top of the carbon dioxide absorption tower (01) is connected to the bottom of the first flash tank (07), and a lean liquid pump (11) and a heat exchanger (10) are connected to the liquid phase conveying pipe (09).
6. The integrated carbon capture and low-grade energy comprehensive utilization system according to claim 5, wherein a second compressor (13) is connected to the steam discharge pipe (12).
7. The integrated carbon capture and low-grade energy comprehensive utilization system according to claim 2, wherein a low-pressure flash tower (19) is connected to the top of the intermediate buffer tower (03) through an air pipe, and the air pipe is connected to the low-temperature evaporator (20).
8. The application method of the integrated carbon capture and low-grade energy comprehensive utilization system is characterized by adopting the system of any one of claims 1-7, and the specific method is as follows: (1) The method comprises the steps of starting the carbon capture and the low-grade heat source power generation system in a cooperative mode, namely, enabling high-temperature flue gas to flow through a reboiler (18) of a carbon dioxide desorption tower (17) to provide heat for carbon dioxide desorption, enabling the high-temperature flue gas to flow through a high-temperature evaporator (25) to heat working media of the low-grade heat source power generation system, and enabling the cooled flue gas to enter a carbon dioxide absorption tower (01) to capture carbon dioxide; (2) The carbon trapping process comprises the steps of washing flue gas in an absorption tower by lean amine liquid, discharging purified gas, enabling the rich amine liquid to enter an intermediate buffer tower (03) for gas-liquid separation, enabling a tower top gas phase to flow through an evaporator I of a low-grade heat source power generation system subsystem, releasing heat and then enter a low-pressure flash tower (19) to obtain a CO2 product, enabling one part of tower bottom semi-lean liquid to flow back to the absorption tower, enabling the other part of tower bottom semi-lean liquid to flow back to the absorption tower, and enabling the other part of tower bottom semi-lean liquid to flow back to a vortex tube (14) for energy recovery after desorption and regeneration; (3) The low-grade heat source power generation system power generation process comprises the steps that working media of the low-grade heat source power generation system absorb waste heat of flue gas and waste heat of a carbon capturing process in a high-temperature evaporator (25) and a low-temperature evaporator (20) and are converted into high-pressure gas phase, the high-pressure working media drive an expander (24) to do work and drive a generator (23) to generate power, the spent gas after doing work is condensed into liquid through a second flash tank (22) and then pressurized by a working media pump (21), the liquid enters the low-temperature evaporator (20) and the high-temperature evaporator (25) again to circulate, the regenerated hot lean liquid is subjected to secondary flash evaporation through the second flash tank (22), the gas phase is separated from the first vortex tube (29) through a first compressor (28), and cold and hot streams are respectively recycled for absorption cooling and desorption heating.
9. The method for using the integrated carbon capture and low-grade energy comprehensive utilization system according to claim 8, wherein the temperature of the flue gas entering the system is controlled to be 250-550 ℃.
10. The method for using the integrated carbon capturing and low grade energy comprehensive utilization system according to claim 8, wherein the material inlet temperature of the low temperature evaporator (20) is controlled to be 75-85 ℃, and the working medium of the low grade heat source power generation system is heated to a saturated or superheated steam state of 65-80 ℃ in the low temperature evaporator (20).

Description

Integrated carbon capture and low-grade energy comprehensive utilization system Technical Field The invention relates to the technical field of carbon dioxide emission reduction, in particular to an integrated carbon capture and low-grade energy comprehensive utilization system. Background The amine method chemical absorption technology becomes a post-combustion carbon capture scheme with the most application prospect at present because of high maturity and stable capture efficiency. However, the technology faces a core contradiction which cannot be effectively solved for a long time, namely, a great amount of high-quality heat energy is consumed in the regeneration and desorption process, so that the energy consumption of the system is high, and the economic feasibility of large-scale commercial application of the technology is severely restricted. Meanwhile, a large amount of low-grade waste heat is not effectively utilized in the industrial process, and particularly, waste heat resources in various temperature ranges can be generated in the running process of the carbon capture system, so that how to efficiently integrate and utilize the dispersed heat energy with different grades becomes an important break-through for reducing the energy consumption of carbon capture. The prior art solutions have been explored in many ways to solve this problem, but all have obvious limitations. For example, patent document CN109681284B discloses a system and a method for capturing carbon dioxide by using power plant flue gas waste heat to generate power, which is technically characterized in that power plant flue gas waste heat is used to generate power to provide energy for a carbon dioxide capturing process. The scheme recognizes the value of flue gas waste heat utilization, but the design thought is single, and mainly focuses on the recovery of external flue gas waste heat, and cannot fully excavate and integrate a large amount of medium-low temperature process waste heat generated by the inside of the carbon capture system. Specifically, in the amine method carbon capture system, a large amount of carbon dioxide-rich gas with the temperature of 80-100 ℃ discharged from the top of the desorption tower, medium-temperature heat energy with the temperature of 60-80 ℃ released in the cooling process of regenerated lean solution, steam condensate water waste heat with the temperature of 120-140 ℃ generated by a reboiler and the like are heat sources with obvious utilization value, and the consideration of the internal heat sources in the scheme is obviously insufficient, so that the overall energy comprehensive utilization efficiency of the system has ceilings, and further breakthrough of energy consumption is difficult to realize. In addition, some technical solutions are dedicated to recovering waste heat in the carbon capturing system, but the implementation path is too complex, for example, a system for capturing waste heat in a CO 2 system by a multi-stage heat pump cascade recovery amine method is disclosed in patent document with publication number CN115654760a, and a complex architecture combining three-stage heat pump cascade with a low-grade heat source power generation system is adopted. Particularly in the actual industrial environment, the complex system has extremely high requirements on control precision, and the imbalance of any link can lead to the great reduction of the efficiency of the whole system and even influence the stable operation of the carbon capture main process, so that the engineering applicability and the economy of the technology are seriously questioned. In addition, some technical solutions specially optimized for the organic Rankine cycle, such as some thermally driven Rankine cycle systems, exist in the market, and the technical solutions aim to improve the utilization efficiency of the low-grade heat source power generation system for the low-grade heat source below 100 ℃ by introducing a booster component device. Although these technologies contribute to improving the performance of low-grade heat source power generation systems, they generally have a fundamental defect of insufficient deep combination with the specific application scenario of carbon capture. These technologies are often developed as general waste heat recovery schemes, and fail to fully consider the specific heat source characteristics, temperature distribution rules and process requirements of the carbon capture system. For example, the waste heat of the carbon capture system has the characteristics of continuous stability and wide temperature interval distribution, and a close coupling relationship exists between the heat source and the carbon capture main process, and the general low-grade heat source power generation system optimization technology lacks the targeted design for the specific application scene, so that the expected effect is difficult to be exerted in the actual carbon capture project. In summary