Carbon capture optimization energy-saving method for high-humidity flue gas
By coupling the HFO-1336mzzZ refrigeration cycle mechanism to the carbon capture system, the problem of latent heat waste in high-humidity flue gas is solved, an efficient and energy-saving carbon capture method is realized, and the demand for external steam and cooling water consumption are reduced.
Patent Information
- Application Number
- CN202511070726.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-31
- Publication Date
- 2025-09-19
AI Technical Summary
The existing technology has huge problems of latent heat waste and high energy consumption in the carbon capture process of high-humidity flue gas. The traditional method fails to effectively integrate the recovery of latent heat in the flue gas and optimize the carbon capture process.
A refrigeration cycle based on HFO-1336mzzZ refrigerant is coupled to the carbon capture system. The refrigeration cycle evaporator is used to replace the water scrubber for cooling, recover the latent heat of the flue gas, and generate high-grade steam through a compressor. The desorption liquid is preheated by the condenser to replace part of the external steam demand.
It achieved a 38.9% saving in external steam during the carbon capture process, effectively recovered the latent heat of flue gas, optimized energy consumption, and reduced cooling water consumption.
Smart Images
Figure CN120667732A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of carbon capture, and in particular relates to a carbon capture optimization and energy-saving method for high-humidity flue gas. Background Art
[0002] Flue gas carbon capture refers to the technology used to separate and recover carbon dioxide (CO2) from flue gases emitted by industrial combustion processes (such as coal-fired power plants, steel mills, and cement plants). Among the various capture technology routes, chemical absorption is widely considered to be the most promising option for large-scale application due to its relatively mature technology and high CO2 capture efficiency (typically exceeding 90%). Flue gas carbon capture is a key negative carbon technology for achieving large-scale CO2 emission reductions and mitigating global warming. It is crucial for regions and industries with a high reliance on fossil fuels such as coal to achieve carbon neutrality goals.
[0003] Industrial flue gas, exemplified by the flue gas from municipal solid waste incineration, has a distinct characteristic that distinguishes it from conventional coal-fired flue gas: an extremely high moisture content (humidity), typically reaching 20%-25% by volume, far exceeding the approximately 5-10% moisture content of conventional coal-fired flue gas. This high moisture content stems from the high moisture content of the waste itself and the oxidation of hydrogen during combustion. This high moisture content not only implies that the flue gas contains an extremely rich latent heat resource, but also represents the enormous amount of heat released during the subsequent purification and cooling processes due to the condensation (phase change) of water vapor.
[0004] Therefore, the core technical problem that needs to be solved urgently is: in the carbon capture process of high-humidity flue gas (such as flue gas from municipal solid waste incineration), the use of traditional chemical absorption processes faces a core technical bottleneck that needs to be solved urgently: huge latent heat waste and high-energy consumption of cooling sources. The traditional process usually requires the high-temperature and high-humidity flue gas to be cooled significantly first. This process consumes a large amount of cooling water, but causes a large amount of high-quality latent heat contained in the wet flue gas (especially the condensation heat of water vapor) to be released inefficiently and directly discarded. At the same time, the subsequent solvent regeneration requires a large amount of high-quality heat source. At present, there is a lack of an effectively integrated energy-saving method that can systematically recover the latent heat in high-humidity flue gas and optimize it for the carbon capture process. Summary of the Invention
[0005] In order to solve the problems existing in the prior art, the present invention proposes an optimized energy-saving method for carbon capture of high-humidity flue gas, with the aim of solving the problem that the prior art still lacks an effectively integrated optimized energy-saving method that can systematically recover the latent heat in high-humidity flue gas and optimize it for the carbon capture process.
[0006] The present invention proposes the following technical solutions to solve the technical problems:
[0007] A method for optimizing energy conservation by carbon capture of high-humidity flue gas is characterized by comprising the following steps:
[0008] Step 1: Based on the heat and temperature characteristics of the carbon capture system, a refrigeration cycle based on HFO-1336mzzZ refrigerant is coupled to the original carbon capture system to save external steam;
[0009] Step 2: The refrigerant HFO-1336mzzZ is combined with the refrigeration cycle mechanism, and the temperature coupling parameters are optimized to achieve the comprehensive effect of replacing cooling and supplementing heat source.
[0010] Furthermore, the refrigeration cycle mechanism of the step one utilizes the refrigeration cycle evaporator of the refrigeration cycle mechanism to replace the water washing tower for cooling. The flue gas after cooling enters the absorption tower and performs heat and mass transfer with the circulating absorption liquid in the tower. CO2 is absorbed in the circulating absorption liquid to form a rich liquid. The temperature of the rich liquid is lower than that of the lean liquid after desorption (higher temperature), and heat exchange is performed to recover heat. Finally, the desorption tower is used for desorption to release CO2 gas. The desorption process requires a high-temperature heat source for heating. The lean liquid after desorption is transported by a circulation pump, and the temperature of the absorption tower is further reduced through the lean-rich liquid heat exchanger and the cooler, and then enters the absorption tower to complete the cycle.
[0011] 1. The method for optimizing energy conservation and carbon capture of high-humidity flue gas according to claim 1 is characterized in that the refrigeration cycle mechanism of step 1 includes a refrigeration cycle evaporator, a compressor, a cooler and an expansion valve, and utilizes the heat absorption characteristic of the evaporator to recover the latent heat of flue gas vaporization and achieve the purpose of cooling; utilizes the temperature increase characteristic of the compressor to form high-quality refrigerant steam; utilizes the heat release characteristic of the condenser to preheat the desorption liquid before external steam heating, thereby saving the demand for external steam.
[0012] Furthermore, the refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T1 of the carbon capture system after entering the refrigeration cycle evaporator is set to 45-50° C., so as to achieve the cooling effect of T1 instead of the water scrubber.
[0013] Furthermore, the refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are: Specifically, through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T2 before compression of the refrigeration cycle is approximately equal to 110° C., so as to ensure that the temperature T2 at the compressor inlet is not too high, while reducing the heat exchange efficiency requirement of the refrigeration cycle evaporator.
[0014] Furthermore, the refrigerant HFO-1336mzzZ in step 2 is combined with a refrigeration cycle mechanism, and preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, the refrigeration cycle expansion valve, and the refrigerant cooling and reflux of the refrigeration cycle system, the temperature T3 after refrigeration cycle compression is made to be 140-145° C., so as to ensure that the temperature T3 is neither too high nor too low. If the T3 temperature is too high, the chemical agent in the absorption liquid will be easily decomposed when entering the desorption tower, while if it is too low, it will be detrimental to its heat exchange efficiency in the desorption tower.
[0015] Furthermore, the refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T4 before refrigeration expansion is approximately 110-120° C., so as to match the desorption temperature of the circulating absorption liquid desorption process.
[0016] Furthermore, the refrigerant HFO-1336mzzZ combined with the refrigeration cycle mechanism in step 2 preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, T5 is set to 35-40°C, thereby ensuring a heat exchange temperature difference of approximately 10°C with T1 and controlling the temperature of T1.
[0017] Advantages and effects of the present invention
[0018] Eliminate the conventional flue gas carbon capture scrubber and replace some of the steam used in the desorption process. Taking the highly humid flue gas from a typical waste incineration plant as an example, with a typical volumetric composition of 0.23% H2O, 0.09% CO2, 0.61% N2, and 0.07% O2, the calculated flue gas flow rate is 1000 kg / s, with a combined H2O and CO2 mass flow rate of 151 kg / s H2O and 144 kg / s CO2. With a feed temperature of 140°C and a temperature drop to 50°C, this generates an enhanced latent heat capacity of 79 kgH2O / s. Assuming 1.2 kg of steam is required to capture 1 kg of CO2, a total of 172.8 kg is required. Assuming a 15% heat loss in the new refrigeration cycle heat exchange process, the savings in external steam used in the desorption process are 38.9%. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 Optimize process roadmap;
[0020] Figure 2 Principle of coupled cycle temperature optimization; DETAILED DESCRIPTION
[0021] 1. Design Difficulties: The difficulty lies in the fact that the temperature coupling of the refrigeration cycle needs to exactly match the needs of the carbon capture system in order to achieve the comprehensive effect of replacing cooling and supplementing heat sources. Each temperature link needs to be selected just right and carefully designed. Figure 2 As shown, for this purpose, the present invention designs T1 = 45-50°C, T2≈110°C, T3 = 140-145°C, T4≈110-120°C, T5 = 35-40°C).
[0022] 2. Innovations: One innovation: Coupling a refrigeration cycle based on HFO-1336mzzZ refrigerant to replace the water scrubber for cooling and save external steam; Two innovations: The refrigeration cycle includes an evaporator, a compressor, a cooler, and an expansion valve. The evaporator absorbs heat to recover the latent heat of flue gas vaporization, the compressor forms high-grade steam, and the condenser preheats the desorption liquid; Three innovations: Optimizing temperature coupling parameters (T1 = 45-50°C, T2≈110°C, T3 = 140-145°C, T4≈110-120°C, T5 = 35-40°C) to achieve coordinated cooling and heat source supplementation.
[0023] 3. Original intention of the design: To solve the problem that the traditional method of cooling high-temperature and high-humidity flue gas requires a large amount of cooling water during the large-scale cooling process, while a large amount of high-quality latent heat in the wet flue gas, especially the condensation heat of water vapor, is directly discarded, and the subsequent solvent regeneration requires a large amount of high-quality heat source.
[0024] 4. Solution: ① Couple a refrigeration cycle to the existing carbon capture system, utilizing the heat absorption characteristics of the evaporator of the refrigeration cycle to recover the latent heat of flue gas vaporization and achieve the purpose of cooling; ② Utilize the heating characteristics of the compressor of the refrigeration cycle to form high-quality refrigerant vapor; ③ Utilize the heat release characteristics of the condenser of the refrigeration cycle to preheat the desorption liquid (the desorption liquid is used to release CO2 gas) before external steam heating, so as to achieve the demand of saving external steam.
[0025] 5. The difference between this application and the prior art: The prior art only involves recycling the absorption liquid, while the present invention involves both absorption liquid recycling and refrigeration recycling. The refrigeration recycling and absorption liquid recycling are not directly related, but are linked by a thermal cycle. The absorption liquid recycling involves the following steps: flue gas, after being washed with water, enters the absorption tower; passes through the circulating liquid, which absorbs carbon dioxide, turning it into a carbon dioxide-rich rich liquid; this carbon dioxide-rich rich liquid is heated by steam in the desorption tower to remove the carbon dioxide, and the circulating liquid is then recycled. The refrigeration cycle mechanism of the present invention replaces the water washing tower used for cooling in the original system by a refrigeration cycle evaporator, and replaces a part of the external steam heating in the original system by a refrigeration cycle condenser. The replacement of a part means that the heating inlet of the decomposition liquid is changed from one inlet to two inlets, and the refrigeration cycle condenser is used to release heat to the decomposition liquid. The reason for the heat release of the condenser is that the temperature of the absorption liquid is lower than the temperature of the high-temperature and high-pressure refrigerant vapor compressed by the compressor. When the high-temperature and high-pressure refrigerant vapor encounters the decomposition liquid with a lower temperature than itself, it releases heat to it. The process of releasing heat is the process of replenishing and saving external steam.
[0026] Based on the above principles, the present invention designs a carbon capture optimization and energy saving method for high humidity flue gas. Figure 1-2 As shown, its characteristics are that it includes the following steps:
[0027] Step 1: Based on the heat and temperature characteristics of the carbon capture system, a refrigeration cycle based on HFO-1336mzzZ refrigerant is coupled to the original carbon capture system to save external steam;
[0028] Step 2: The refrigerant HFO-1336mzzZ is combined with the refrigeration cycle mechanism, and the temperature coupling parameters are optimized to achieve the comprehensive effect of replacing cooling and supplementing heat source.
[0029] The refrigeration cycle mechanism of the step one utilizes the refrigeration cycle evaporator of the refrigeration cycle mechanism to replace the water washing tower for cooling. The flue gas after cooling enters the absorption tower and performs heat and mass transfer with the circulating absorption liquid in the tower. CO2 is absorbed in the circulating absorption liquid to form a rich liquid. The temperature of the rich liquid is lower than that of the lean liquid after desorption (higher temperature), and heat exchange is performed to recover heat. Finally, the desorption tower is used for desorption to release CO2 gas. The desorption process requires a high-temperature heat source for heating. The lean liquid after desorption is transported by a circulation pump, and the temperature of the absorption tower is further reduced through the lean-rich liquid heat exchanger and the cooler, and then enters the absorption tower to complete the cycle.
[0030] The refrigeration cycle mechanism of step 1 includes a refrigeration cycle evaporator, a compressor, a cooler and an expansion valve. The evaporator's heat absorption characteristic is used to recover the flue gas vaporization latent heat and achieve the purpose of cooling; the compressor's temperature increase characteristic is used to form high-quality refrigerant steam; and the condenser's heat release characteristic is used to preheat the desorption liquid before external steam heating, thereby saving external steam demand.
[0031] The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are as follows: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T1 of the carbon capture system after entering the refrigeration cycle evaporator is set to 45-50° C., so as to achieve the cooling effect of the water scrubber instead of the temperature T1.
[0032] The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are: Specifically, through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T2 before the refrigeration cycle compression is approximately equal to 110° C., so as to ensure that the temperature T2 at the compressor inlet is not too high, while reducing the heat exchange efficiency requirement of the refrigeration cycle evaporator.
[0033] The refrigerant HFO-1336mzzZ in step 2 is combined with a refrigeration cycle mechanism, and preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, the refrigeration cycle expansion valve, and the refrigerant cooling and reflux of the refrigeration cycle system, the temperature T3 after refrigeration cycle compression is set to 140-145° C., so as to ensure that the temperature T3 is neither too high nor too low. If the T3 temperature is too high, the chemical agent in the absorption liquid will be easily decomposed when entering the desorption tower, while if it is too low, it will be detrimental to its heat exchange efficiency in the desorption tower.
[0034] The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T4 before refrigeration expansion is approximately 110-120°C to match the desorption temperature of the circulating absorption liquid desorption process.
[0035] The refrigerant HFO-1336mzzZ combined with the refrigeration cycle mechanism in step 2 preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, T5 is set to 35-40°C, thereby ensuring a heat exchange temperature difference of approximately 10°C with T1 and controlling the temperature of T1.
[0036] Example 1
[0037] Process systems such as Figure 1 :The raw flue gas needs to be cooled before entering the absorption tower for absorption (low temperature is conducive to absorption). The optimized process uses a refrigeration cycle evaporator instead of a water scrubber for cooling. The cooled flue gas enters the absorption tower and conducts heat and mass transfer with the circulating absorption liquid in the tower. CO2 is absorbed in the circulating absorption liquid to form a rich liquid. The rich liquid temperature is lower than the lean liquid after desorption (higher temperature), so heat exchange is performed to recover heat. Finally, the desorption tower desorbs and releases CO2 gas. The desorption process requires a high-temperature heat source for heating. The lean liquid after desorption is transported by a circulating pump, passes through the lean-rich liquid heat exchanger and cooler (to further reduce the temperature of the absorption tower), and enters the absorption tower to complete the cycle.
[0038] Based on the heat and temperature characteristics of the carbon capture system, a refrigeration cycle based on HFO-1336mzzZ refrigerant was coupled, consisting of an evaporator, compressor, cooler, and expansion valve. The evaporator's heat absorption characteristic is used to recover the flue gas's latent heat of vaporization and achieve temperature reduction. The compressor's temperature increase characteristic is used to generate high-quality refrigerant vapor. The condenser's heat release characteristic is used to preheat the desorption liquid before external steam heating, thus reducing the need for external steam.
[0039] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the above embodiments as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.
Claims
1. A method for optimizing energy conservation by carbon capture of high-humidity flue gas, characterized in that: The following steps are involved: 、 Step 1: Based on the heat and temperature characteristics of the carbon capture system, a refrigeration cycle based on HFO-1336mzzZ refrigerant is coupled to the original carbon capture system to save external steam; Step 2: The refrigerant HFO-1336mzzZ is combined with the refrigeration cycle mechanism, and the temperature coupling parameters are optimized to achieve the comprehensive effect of replacing cooling and supplementing heat source.
2. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 1, characterized in that: The refrigeration cycle mechanism of the step one utilizes the refrigeration cycle evaporator of the refrigeration cycle mechanism to replace the water washing tower for cooling. The flue gas after cooling enters the absorption tower and performs heat and mass transfer with the circulating absorption liquid in the tower. CO2 is absorbed in the circulating absorption liquid to form a rich liquid. The temperature of the rich liquid is lower than that of the lean liquid after desorption (higher temperature), and heat exchange is performed to recover heat. Finally, the desorption tower is used for desorption to release CO2 gas. The desorption process requires a high-temperature heat source for heating. The lean liquid after desorption is transported by a circulation pump, and the temperature of the absorption tower is further reduced through the lean-rich liquid heat exchanger and the cooler, and then enters the absorption tower to complete the cycle.
3. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 1, characterized in that: The refrigeration cycle mechanism of step 1 includes a refrigeration cycle evaporator, a compressor, a cooler and an expansion valve. The evaporator's heat absorption characteristic is used to recover the flue gas vaporization latent heat and achieve the purpose of cooling; the compressor's temperature increase characteristic is used to form high-quality refrigerant steam; and the condenser's heat release characteristic is used to preheat the desorption liquid before external steam heating, thereby saving external steam demand.
4. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 1, characterized in that: The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are as follows: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T1 of the carbon capture system after entering the refrigeration cycle evaporator is set to 45-50° C., so as to achieve the cooling effect of the water scrubber instead of the temperature T1.
5. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 4, characterized in that: The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are: Specifically, through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T2 before the refrigeration cycle compression is approximately equal to 110° C., so as to ensure that the temperature T2 at the compressor inlet is not too high, while reducing the heat exchange efficiency requirement of the refrigeration cycle evaporator.
6. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 4, characterized in that: The refrigerant HFO-1336mzzZ in step 2 is combined with a refrigeration cycle mechanism, and preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, the refrigeration cycle expansion valve, and the refrigerant cooling and reflux of the refrigeration cycle system, the temperature T3 after refrigeration cycle compression is set to 140-145° C., so as to ensure that the temperature T3 is neither too high nor too low. If the T3 temperature is too high, the chemical agent in the absorption liquid will be easily decomposed when entering the desorption tower, while if it is too low, it will be detrimental to its heat exchange efficiency in the desorption tower.
7. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 4, characterized in that: The refrigerant HFO-1336mzzZ in step 2 is combined with the refrigeration cycle mechanism, and the preferred temperature coupling parameters are: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor and the refrigeration cycle expansion valve of the refrigeration cycle system, the temperature T4 before refrigeration expansion is approximately 110-120°C to match the desorption temperature of the circulating absorption liquid desorption process.
8. The method for optimizing energy conservation by carbon capture of high-humidity flue gas according to claim 4, characterized in that: The refrigerant HFO-1336mzzZ combined with the refrigeration cycle mechanism in step 2 preferably has a temperature coupling parameter, specifically: through the organic coordination of the refrigerant HFO-1336mzzZ, the refrigeration cycle compressor, and the refrigeration cycle expansion valve of the refrigeration cycle system, T5 is set to 35-40°C, thereby ensuring a heat exchange temperature difference of approximately 10°C with T1 and controlling the temperature of T1.