Carbon capture system and process method for waste heat recovery

Abstract

The invention discloses a waste heat recovery carbon capture system and process method.The system comprises an absorption tower used for receiving barren liquor, absorbing input flue gas, generating purified gas, discharging the purified gas from the top, generating rich liquor and conveying the rich liquor to a conveying pump from the bottom; the bottom is connected to the regeneration tower through a delivery pump and a first heat exchanger, and is used for pressurizing and preheating rich liquor through the delivery pump and the first heat exchanger and delivering the rich liquor to the regeneration tower; the regeneration tower is used for heating the rich liquor, generating CO2 and discharging the CO2 from the top of the regeneration tower, and generating hot barren liquor and discharging the hot barren liquor from the bottom of the regeneration tower; the flash evaporation structure is respectively connected to the bottom of the regeneration tower and the first heat exchanger and is used for carrying out flash evaporation on the hot barren liquor to generate mixed gas and new barren liquor; wherein the mixed gas returns to the regeneration tower, and the new barren liquor is cooled by the first heat exchanger and then is conveyed to the top. Therefore, by adding the flash evaporation structure, heat recovery with lower consumption is realized, the burden of the reboiler is reduced, and meanwhile, the cycle efficiency of carbon capture is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and particularly to a carbon capture system with waste heat recovery and a process method. Background Art

[0002] In the context of the global response to climate change, the issue of carbon emissions has become the focus of widespread international attention. As a major carbon emitter, China shoulders a significant responsibility in the global carbon emission reduction campaign. The issue of carbon emissions not only poses great pressure on the ecological environment but also challenges sustainable development.

[0003] In the domestic energy sector, the carbon dioxide emissions of thermal power units account for approximately 45% of the total fossil energy emissions in the country. As a result, the power industry faces an extremely arduous task of carbon emission reduction. To achieve low-carbon transformation, Carbon Capture Utilization and Storage (CCUS) technology has become the main approach for large-scale low-carbon utilization of fossil fuels such as coal. Among various carbon dioxide capture technologies, the chemical absorption method, due to its good adaptability to flue gas and relatively mature technical characteristics, is the main way to capture carbon dioxide in coal-fired power plants at the present stage.

[0004] However, the capture of carbon dioxide by the chemical absorption method is achieved through a chemical reaction between the absorbent and carbon dioxide. Since the traditional thermal regeneration method heats the rich liquid to a relatively high temperature and side reactions occur in actual chemical reactions, the energy consumption and absorbent loss are too large. Summary of the Invention

[0005] The present invention provides a carbon capture system with waste heat recovery and a process method, which solves the technical problem that in the traditional carbon capture solution, due to the traditional thermal regeneration method heating the rich liquid to a relatively high temperature and side reactions occurring in actual chemical reactions, the energy consumption and absorbent loss are too large.

[0006] A carbon capture system with waste heat recovery provided by the present invention includes an absorption tower, a transfer pump, a first heat exchanger, a regeneration tower, and a flash structure;

[0007] The absorption tower is used to receive lean liquid to absorb the input flue gas, generate a purified gas and discharge it from the top of the absorption tower, and generate rich liquid and convey it from the bottom of the absorption tower to the transfer pump;

[0008] The bottom of the absorption tower is connected to the regeneration tower via a transfer pump and a first heat exchanger, and is used to pressurize and preheat the rich liquid through the transfer pump and the first heat exchanger and convey it to the regeneration tower;

[0009] The regeneration tower is used to heat the rich liquid to generate CO 2And is discharged from the top of the regeneration tower, generating hot lean liquid and discharging it from the bottom of the regeneration tower;

[0010] The flash structure is respectively connected to the bottom of the regeneration tower and the first heat exchanger, and is used for flashing the hot lean liquid to generate a mixed gas and new lean liquid; wherein, the mixed gas returns to the regeneration tower, and the new lean liquid is cooled by the first heat exchanger and then transported to the top of the absorption tower.

[0011] Optionally, the flash structure includes a reboiler, a flash tank and a compression mechanism connected in sequence;

[0012] The reboiler is connected to the bottom of the regeneration tower, and is used for receiving the hot lean liquid for partial vaporization and returning it to the regeneration tower, and transporting the unvaporized hot lean liquid to the flash tank;

[0013] The unvaporized hot lean liquid is flashed by the flash tank to generate a mixed gas and return it to the regeneration tower through the compression mechanism, and new lean liquid is generated and transported to the first heat exchanger.

[0014] Optionally, the compression mechanism is a steam ejector or a compressor.

[0015] Optionally, the flash vacuum degree in the flash tank is 45 - 55 kPa, and most preferably 55 kPa.

[0016] Optionally, the lean liquid is a solution composed of N - methyldiethanolamine with a mass fraction of 20% and piperazine with a mass fraction of 10%.

[0017] Optionally, the temperature of the input flue gas is 313.15 - 323.15 K, and the pressure is 1.0 - 1.2 atm.

[0018] Optionally, the mixed gas includes H 2 O and CO 2 .

[0019] Optionally, a second heat exchanger is connected to the top of the regeneration tower, and is used for recovering the heat of the CO 2 generated by the regeneration tower.

[0020] Optionally, the first heat exchanger includes a heater and a cooler;

[0021] The heater is used for preheating the rich liquid and transporting it to the top of the regeneration tower;

[0022] The cooler is used for cooling the new lean liquid generated by the flash structure and transporting it to the top of the absorption tower.

[0023] The present invention also provides a carbon capture process method for waste heat recovery, which is applied to the carbon capture system for waste heat recovery described in any one of the above, and the method includes:

[0024] Receiving lean liquid through an absorption tower to absorb the input flue gas, generating a purified gas and discharging it from the top of the absorption tower, generating rich liquid and transporting it from the bottom of the absorption tower to a delivery pump;

[0025] Pressurizing and preheating the rich liquid through the delivery pump and a first heat exchanger and transporting it to the top of a regeneration tower;

[0026] Heating the rich liquid through the regeneration tower to generate CO 2 and discharging it from the top of the regeneration tower, generating hot lean liquid and transporting it from the bottom of the regeneration tower to a flash structure;

[0027] Flashing the hot lean liquid through the flash structure to generate a mixed gas and returning it to the bottom of the regeneration tower, generating new lean liquid and transporting it to the top of the absorption tower through the first heat exchanger.

[0028] It can be seen from the above technical solutions that the present invention has the following advantages:

[0029] The present invention provides a carbon capture system and process method for waste heat recovery. The system includes an absorption tower, a delivery pump, a first heat exchanger, a regeneration tower and a flash structure; the absorption tower is used to receive lean liquid to absorb the input flue gas, generate a purified gas and discharge it from the top of the absorption tower, generate rich liquid and transport it from the bottom of the absorption tower to the delivery pump; the bottom of the absorption tower is connected to the regeneration tower through the delivery pump and the first heat exchanger, and is used to pressurize and preheat the rich liquid through the delivery pump and the first heat exchanger and transport it to the regeneration tower; the regeneration tower is used to heat the rich liquid to generate CO 2 and discharge it from the top of the regeneration tower, generate hot lean liquid and discharge it from the bottom of the regeneration tower; the flash structure is respectively connected to the bottom of the regeneration tower and the first heat exchanger, and is used to flash the hot lean liquid to generate a mixed gas and new lean liquid; wherein, the mixed gas returns to the regeneration tower, and the new lean liquid is transported to the top of the absorption tower after being cooled by the first heat exchanger. Thus, more low-consumption heat recovery is achieved by adding the flash structure, reducing the burden on the reboiler while improving the cycle efficiency of carbon capture. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1Structural block diagram of a carbon capture system with waste heat recovery provided by an embodiment of the present invention;

[0032] Figure 2 Refined structural block diagram of a carbon capture system with waste heat recovery provided by an embodiment of the present invention;

[0033] Figure 3 Line graph showing the influence of the flashing vacuum degree on the regeneration energy consumption when only the MVR process is turned on for the lean heat solution in the system provided by an embodiment of the present invention;

[0034] Figure 4 Step flow chart of a carbon capture process method with waste heat recovery provided by an embodiment of the present invention.

[0035] Reference numerals: 11, absorption tower; 12, transfer pump; 13, first heat exchanger; 21, regeneration tower; 22, flashing structure; 23, second heat exchanger; 131, heater; 132, cooler; 221, reboiler; 222, flash tank; 223, compression mechanism. Detailed implementation manners

[0036] An embodiment of the present invention provides a carbon capture system and a process method with waste heat recovery, which are used to solve the technical problems that in traditional carbon capture solutions, due to heating the rich solution to a relatively high temperature by the traditional thermal regeneration method and the generation of side reactions in actual chemical reactions, the energy consumption and the loss of absorbent are too large.

[0037] To make the objectives, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] Please refer to Figure 1 , Figure 1 Structural block diagram of a carbon capture system with waste heat recovery provided by an embodiment of the present invention.

[0039] A carbon capture system with waste heat recovery provided by the present invention includes an absorption tower 11, a transfer pump 12, a first heat exchanger 13, a regeneration tower 21, and a flashing structure 22;

[0040] The absorption tower 11 is used to receive lean solution to absorb the input flue gas, generate purified gas and discharge it from the top of the absorption tower 11, and generate rich solution and transport it from the bottom of the absorption tower 11 to the transfer pump 12;

[0041] The bottom of the absorption tower 11 is connected to the regeneration tower 21 via a transfer pump 12 and a first heat exchanger 13, for pressurizing and preheating the rich liquid through the transfer pump 12 and the first heat exchanger 13 and transporting it to the regeneration tower 21;

[0042] The regeneration tower 21 is used for heating the rich liquid to generate CO 2 and discharging it from the top of the regeneration tower 21, generating hot lean liquid and discharging it from the bottom of the regeneration tower 21;

[0043] The flash structure 22 is respectively connected to the bottom of the regeneration tower 21 and the first heat exchanger 13, for flashing the hot lean liquid to generate a mixed gas and new lean liquid; wherein, the mixed gas returns to the regeneration tower 21, and the new lean liquid is transported to the top of the absorption tower 11 after being cooled by the first heat exchanger 13.

[0044] In the embodiment of the present invention, the absorption tower 11, the transfer pump 12, the first heat exchanger 13, the regeneration tower 21 and the flash structure 22 are connected by pipelines. The input flue gas is input from the bottom of the absorption tower 11 and reacts countercurrently with the lean liquid input from the top of the absorption tower 11. The lean liquid absorbs CO in the input flue gas 2 , generating rich liquid and flowing out from the bottom of the absorption tower 11 to the transfer pump 12. The rich liquid is pressurized by the transfer pump 12 and then transported to the first heat exchanger 13. The pressurized rich liquid is preheated to a predetermined temperature by the first heat exchanger 13 and then sent to the regeneration tower 21 for desorption. The rich liquid is heated by gas heat exchange in the regeneration tower 21 to generate CO 2 and discharged from the top of the regeneration tower 21, generating hot lean liquid and sent out from the bottom of the regeneration tower 21 to the flash structure 22. The hot lean liquid is flashed by the flash structure 22 to achieve gas-liquid separation, generating a mixed gas with a certain amount of heat and returning it to the regeneration tower 21, thereby reducing the demand for regeneration steam in the regeneration tower 21 and realizing heat recovery of the hot lean liquid. At the same time, the new lean liquid produced is cooled by the first heat exchanger 13 and then transported to the top of the absorption tower 11 to achieve the carbon capture cycle of the absorption tower 11.

[0045] In the absorption tower 11, the input flue gas enters from the bottom of the absorption tower 11 and flows upward. The lean liquid, i.e., the mixed amine absorbent, is sprayed downward from the top of the absorption tower 11 in a spray state and flows downward along the packing or tray in the absorption tower 11 under the action of gravity, making full contact with the rising input flue gas. When the lean liquid contacts the input flue gas, a chemical reaction occurs, so that most of the CO in the input flue gas is absorbed by the lean liquid 2 , and the purified flue gas is discharged from the top of the absorption tower 11, while the lean liquid absorbs CO 2 and generates rich liquid, which continues to flow downward to the bottom of the absorption tower 11 and is discharged to the transfer pump 12.

[0046] After the rich liquid is pressurized by the transfer pump 12 and preheated by the first heat exchanger 13, it enters from the top of the regeneration tower 21, and in the regeneration tower 21, it undergoes countercurrent heat exchange with heating media such as high-temperature steam or hot air rising from the bottom of the regeneration tower 21, thereby breaking the chemical bond between CO 2 and the absorbent, causing CO 2 to escape from the rich liquid, causing the carbonic acid in the rich liquid to decompose into carbon dioxide and water, the bicarbonate will also undergo a decomposition reaction, releasing carbon dioxide, and the combination of the amine absorbent and carbon dioxide will also dissociate, thereby generating CO 2 which is discharged from the top of the regeneration tower 21, and the rich liquid after desorption, since most of the CO 2 has been released, produces lean liquid that flows out from the bottom of the regeneration tower 21 to the flash structure 22.

[0047] In addition, a condenser can be provided at the top of the desorption tower (i.e., the regeneration tower 21) to cool and condense the water vapor in the gas phase into water, which flows back into the desorption tower, while carbon dioxide is collected as the product gas.

[0048] Among them, the CO 2 capture scale of the system is 1×10 6 t / a, the designed annual operating time is 5500 h / a, the flue gas treatment volume is 1083.625 t / h, and the CO 2 capture rate is 90%.

[0049] In an example of the present invention, the input flue gas consists of 18.64% CO 2 , 72.11% N 2 , 4.37% H 2 O and 4.88% O 2 by mass fraction. The temperature of the input flue gas is 323.15K and the pressure is 1.2 atm.

[0050] In this embodiment, the input flue gas is the pre-treated flue gas, and the pre-treatment operation can include but is not limited to steps such as dust removal, desulfurization, cooling, and water removal, so as to remove residual sulfur and nitrogen oxides and dust particles in the flue gas and reduce the impact on the absorption tower 11 or the lean liquid absorption process.

[0051] In an example of the present invention, the lean liquid is a solution composed of 20% N-methyldiethanolamine and 10% piperazine by mass fraction.

[0052] In this embodiment, the lean liquid uses a mixed amine absorbent composed of N-methyldiethanolamine (MDEA) and piperazine (PZ). In this absorbent, MDEA accounts for 20% and PZ accounts for 10%. It combines the high selectivity of MDEA for carbon dioxide and the rapid absorption activity of PZ. Before transporting the lean liquid to the absorption tower 11, according to the key parameters of the absorption tower 11, including the flow rate and composition of the raw gas, as well as the expected carbon dioxide absorption efficiency to be achieved, the lean liquid and rich liquid loads are also determined. Based on these parameters, the molar flow rate of carbon dioxide to be absorbed is calculated through the flow rate of the raw gas, the carbon dioxide content, and the absorption efficiency. Then, according to the difference between the lean liquid and rich liquid loads, the amount of carbon dioxide that can be absorbed per mole of absorbent is obtained. Furthermore, the molar flow rate of the absorbent is obtained by dividing the molar flow rate of carbon dioxide to be absorbed by this value. Considering the operating condition fluctuations in actual operation, a safety factor of 1.1 - 1.5 is introduced to correct the calculation result. Finally, combined with the composition and density of the absorbent, the corrected molar flow rate of the absorbent is converted into a volume flow rate. In this embodiment, the absorbent stably enters the absorption tower 11 at a temperature of 313.15K and a pressure of 1.0 atm. At this time, the absorbent is in the lean liquid state, and its lean liquid load is controlled within the range.

[0053] In an example of the present invention, the mixed gas includes H 2 O and CO 2 .

[0054] In this embodiment, after the flash evaporation of the hot lean liquid by the flash evaporation structure 22, gas-liquid separation is achieved to generate a mixed gas and a new lean liquid. The main components of the mixed gas are H 2 O and CO 2 . The mixed gas is compressed and sent back to the regeneration tower 21. The sensible heat of the hot lean liquid returns to the regeneration process in the form of the latent heat of the mixed gas, significantly reducing the demand for regeneration steam in the regeneration tower 21 and effectively sharing the heat load of the reboiler 221 in the flash evaporation structure 22.

[0055] In an example of the present invention, the flash evaporation structure 22 includes a reboiler 221, a flash tank 222, and a compression mechanism 223 connected in sequence;

[0056] The reboiler 221 is connected to the bottom of the regeneration tower 21, used to receive the hot lean liquid for partial vaporization and return it to the regeneration tower 21, and transport the unvaporized hot lean liquid to the flash tank 222;

[0057] The unvaporized hot lean liquid is flash-evaporated through the flash tank 222 to generate a mixed gas, which is returned to the regeneration tower 21 through the compression mechanism 223, and the new lean liquid is transported to the first heat exchanger 13.

[0058] Please refer to Figure 2, in this embodiment, the flash evaporation structure 22 includes a reboiler 221, a flash tank 222, and a compression mechanism 223 connected by pipelines. After the rich liquid is heated in the regeneration tower 21 to produce hot lean liquid, the reboiler 221 receives the hot lean liquid flowing out of the pipeline. Since there is heat loss of the hot lean liquid during the transmission process, at this time, the reboiler 221 heats the hot lean liquid to the boiling point to partially vaporize it, and the vapor returns to the regeneration tower 21 along another pipeline to provide heating gas, while the unvaporized hot lean liquid is transported to the flash tank 222 along the bottom pipeline for further flash evaporation. A certain amount of unvaporized hot lean liquid passes through throttling elements such as throttle valves to instantaneously reduce the pressure of the hot lean liquid. After entering the flash tank 222, due to the sudden pressure drop, part of the hot lean liquid flashes into a gas phase (i.e., mixed gas), and the gas phase with a smaller density rises to the top of the flash tank 222 and is discharged through the pipeline; while the unvaporized liquid remains at the bottom of the tank and flows out from the bottom outlet to the cooler 132. The mixed gas is pressurized by the compression mechanism 223 and sent back to the regeneration tower 21, and the sensible heat of the hot lean liquid returns to the regeneration process in the form of the latent heat of the mixed gas. This process can significantly reduce the demand for regeneration steam in the tower and share the heat load of the reboiler 221. However, at the same time, the temperature of the lean liquid after the MVR process is relatively lower than that of the hot lean liquid at the bottom of the regeneration tower 21, which will lead to a decrease in the temperature of the hot rich liquid at the inlet of the regeneration tower 21 and a reduction in the cooling water consumption of the lean liquid cooler 132. The specific design of the flash evaporation pressure needs to be based on the pressure inside the regeneration tower 21

[0059] Among them, the reboiler 221 usually consists of two parts: a heating chamber and an evaporation chamber. The heating chamber contains tube bundles or heating elements, and heat is transferred to the liquid to be heated inside the tubes by the flow of a hot fluid (such as steam, hot water, etc.) outside or inside the tubes. The evaporation chamber is the space where the liquid vaporizes after heating. The vaporized steam is discharged from the top, and the unvaporized liquid returns to the system for circulation.

[0060] Furthermore, the compression mechanism 223 is a steam ejector or a compressor.

[0061] The steam ejector is based on the Venturi effect. High-pressure steam (working steam) is ejected at high speed through a nozzle, forming a low-pressure area in the mixing chamber of the ejector to suck in low-pressure steam (ejector steam). The two kinds of steam are mixed in the mixing chamber and then enter the diffuser together. In the diffuser, the speed gradually decreases and the pressure gradually increases, and finally it is discharged at a higher pressure. It mainly consists of parts such as a nozzle, a mixing chamber, and a diffuser. The nozzle enables the working steam to obtain a high speed, the mixing chamber is used for the mixing of the two kinds of steam, and the diffuser converts the kinetic energy of the mixed steam into pressure energy.

[0062] The compressor is a steam compressor, which increases the pressure of the steam through mechanical work. Common types include centrifugal compressors and screw compressors. The centrifugal compressor uses the centrifugal force generated by the rotation of the impeller to accelerate the steam, and then converts the velocity energy into pressure energy in the diffuser; the screw compressor compresses the steam through a pair of meshing screws to increase the steam pressure.

[0063] Furthermore, the flashing vacuum degree in the flash tank 222 is 45 - 55 kPa.

[0064] In this embodiment, for the MVR flashing technology, the outlet pressure of the compressor determines the outlet temperature of the flashing steam. Generally, it is required that the saturation vapor temperature of the compressed outlet steam is close to the bottom temperature of the regeneration tower 21. When designing, the outlet pressure of the compressor can be determined according to the boiling point of the absorbent liquid at the bottom of the regeneration tower 21. The vacuum degree of the flash tank 222 determines the amount of flashing steam. The greater the vacuum degree, the greater the flashing amount. However, the vacuum degree also causes an increase in the compressor boost pressure, resulting in more power consumption. To clarify the influence of the flashing vacuum degree on the regeneration energy consumption of the carbon capture system, the loads of the carbon capture reboiler 221 at vacuum degrees of 10, 20, 30, 40, and 50 kPa were investigated. The specific results are shown in Figure 3 . From Figure 3 it can be seen that the load of the reboiler 221 of the regeneration tower 21 continuously decreases as the flashing vacuum degree increases. When the vacuum degree is 50 kPa, the regeneration energy consumption reaches the lowest value, which is 3.08 GJ / tCO 2 , a 12% reduction compared to the basic process.

[0065] In an example of the present invention, a second heat exchanger 23 is connected to the top of the regeneration tower 21 for recovering the heat of the CO 2 generated by the regeneration tower 21.

[0066] In an example of the present invention, the first heat exchanger 13 includes a heater 131 and a cooler 132;

[0067] The heater 131 is used to preheat the rich liquid and transport it to the top of the regeneration tower 21;

[0068] The cooler 132 is used to cool the newly generated lean liquid from the flashing structure 22 and transport it to the top of the absorption tower 11.

[0069] In this embodiment, the first heat exchanger 13 includes a heater 131 and a cooler 132. The rich liquid after pressurization is preheated by the heater 131 to a preset temperature and then transported to the top of the regeneration tower 21 for input, so as to reduce the load of the reboiler 221. Since the new lean liquid generated after the flash tank 222 flashes the hot lean liquid usually still has a relatively high temperature, in order to facilitate the subsequent carbon capture cycle, the new lean liquid is cooled by the cooler 132 and then transported to the top of the absorption tower 11, so as to perform carbon capture on the input flue gas again in the absorption tower 11.

[0070] Among them, the lean liquid cooled by the cooler 132 can also be stored in a buffer device, and the absorbent concentration in the lean liquid is detected in the buffer device, that is, whether the mass fractions of N-methyldiethanolamine MDEA and piperazine PZ meet the requirements. If the requirements are met, it is directly transported to the top of the absorption tower 11. If the requirements are not met, the corresponding solvent is added according to the concentration difference until the mass fraction meets the requirements.

[0071] In an embodiment of the present invention, a carbon capture system with waste heat recovery is provided, including an absorption tower, a transfer pump, a first heat exchanger, a regeneration tower and a flash structure; the absorption tower is used to receive lean liquid to absorb the input flue gas, generate purified gas and discharge it from the top of the absorption tower, and generate rich liquid and transport it from the bottom of the absorption tower to the transfer pump; the bottom of the absorption tower is connected to the regeneration tower through the transfer pump and the first heat exchanger, and is used to pressurize and preheat the rich liquid through the transfer pump and the first heat exchanger and transport it to the regeneration tower; the regeneration tower is used to heat the rich liquid, generate CO 2 and discharge it from the top of the regeneration tower, and generate hot lean liquid and discharge it from the bottom of the regeneration tower; the flash structure is respectively connected to the bottom of the regeneration tower and the first heat exchanger, and is used to flash the hot lean liquid to generate a mixed gas and a new lean liquid; wherein, the mixed gas returns to the regeneration tower, and the new lean liquid is cooled by the first heat exchanger and then transported to the top of the absorption tower. Thus, the addition of the flash structure realizes lower-consumption heat recovery, reduces the burden on the reboiler, and improves the carbon capture cycle efficiency at the same time.

[0072] Please refer to Figure 4 , Figure 4 which shows the step flow chart of a carbon capture process method with waste heat recovery in an embodiment of the present invention.

[0073] An embodiment of the present invention provides a carbon capture process method with waste heat recovery, which is applied to the carbon capture system with waste heat recovery in any of the above embodiments. The method includes the following steps:

[0074] Step 401, the absorption tower receives lean liquid to absorb the input flue gas, generates purified gas and discharges it from the top of the absorption tower, and generates rich liquid and transports it from the bottom of the absorption tower to the transfer pump;

[0075] Step 402: Pressurize and preheat the rich liquid through a transfer pump and a first heat exchanger, and then transfer it to the top of the regeneration tower.

[0076] Step 403: Heat the rich liquid in the regeneration tower to generate CO 2 which is discharged from the top of the regeneration tower, and generate hot lean liquid which is transferred from the bottom of the regeneration tower to the flash structure.

[0077] Step 404: Flash the hot lean liquid through the flash structure to generate a mixed gas which is returned to the bottom of the regeneration tower, and generate new lean liquid which is transferred to the top of the absorption tower through the first heat exchanger.

[0078] The lean liquid is a solution composed of N-methyldiethanolamine with a mass fraction of 20% and piperazine with a mass fraction of 10%.

[0079] In the embodiment of the present invention, the absorption tower receives the lean liquid to absorb the input flue gas, generates purified gas which is discharged from the top of the absorption tower, and generates rich liquid which is transferred from the bottom of the absorption tower to the transfer pump; pressurize and preheat the rich liquid through the transfer pump and the first heat exchanger and transfer it to the top of the regeneration tower; heat the rich liquid in the regeneration tower to generate CO 2 which is discharged from the top of the regeneration tower, and generate hot lean liquid which is transferred from the bottom of the regeneration tower to the flash structure; flash the hot lean liquid through the flash structure to generate a mixed gas which is returned to the bottom of the regeneration tower, and generate new lean liquid which is transferred to the top of the absorption tower through the first heat exchanger. Thus, a carbon capture cycle process with low energy consumption is realized in combination with the corresponding system, and carbon capture is carried out with lean liquid of specific components, effectively improving the carbon capture efficiency.

[0080] In several embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are merely illustrative. For example, the division of the modules is only a logical function division. In actual implementation, there may be other division methods. For example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the displayed or discussed coupling or direct coupling or communication connection between each other can be through some interfaces. The indirect coupling or communication connection of the system or module can be in electrical, mechanical or other forms.

[0081] The modules described as separation components may or may not be physically separated. The components displayed as modules may or may not be physical modules, that is, they can be located in one place, or they can be distributed to multiple network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0082] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A waste heat recovery carbon capture system, characterized in that: It includes an absorption tower, a delivery pump, a first heat exchanger, a regeneration tower and a flash evaporation structure; The absorption tower is used to receive the lean liquid to absorb the input flue gas, generate purified gas and discharge it from the top of the absorption tower, generate rich liquid and deliver it to the delivery pump from the bottom of the absorption tower; The bottom of the absorption tower is connected to the regeneration tower via a delivery pump and a first heat exchanger, so as to pressurize and preheat the rich liquid through the delivery pump and the first heat exchanger and deliver it to the regeneration tower; The regeneration tower is used to heat the rich liquid, produce CO2 and discharge it from the top of the regeneration tower, and produce hot lean liquid and discharge it from the bottom of the regeneration tower; The flash structure is connected to the bottom of the regeneration tower and the first heat exchanger respectively, and is used to flash the hot lean liquid to generate a mixed gas and a new lean liquid; wherein the mixed gas is returned to the regeneration tower, and the new lean liquid is transported to the top of the absorption tower after being cooled by the first heat exchanger.

2. The system according to claim 1, characterized in that The flash structure comprises a reboiler, a flash tank and a compression mechanism connected in sequence; The reboiler is connected to the bottom of the regeneration tower, and is used to receive the hot lean liquid, partially vaporize it and return it to the regeneration tower, and transport the unvaporized hot lean liquid to the flash tank; The unvaporized hot lean liquid is flashed by the flash tank to generate a mixed gas, which is returned to the regeneration tower through the compression mechanism to generate new lean liquid which is transported to the first heat exchanger.

3. The system according to claim 2, characterized in that The compression mechanism is a steam ejector or a compressor.

4. The system according to claim 2, characterized in that The flash vacuum degree in the flash tank is 45-55 kPa.

5. The system according to claim 1, characterized in that The lean solution is a solution composed of 20% by mass of N-methyldiethanolamine and 10% by mass of piperazine.

6. The system according to claim 1, characterized in that The temperature of the input flue gas is 313.15-323.15K, and the pressure is 1.0-1.2atm.

7. The system according to claim 1, characterized in that The mixed gas includes H2O and CO2.

8. The system according to claim 1, characterized in that A second heat exchanger is connected to the top of the regeneration tower to recover the heat of the CO2 generated by the regeneration tower.

9. The system according to claim 1, characterized in that The first heat exchanger includes a heater and a cooler; The heater is used to preheat the rich liquid and transport it to the top of the regeneration tower; The cooler is used to cool down the new lean liquid generated by the flash evaporation structure and transport it to the top of the absorption tower.

10. A waste heat recovery carbon capture process, characterized in that: A carbon capture system for waste heat recovery according to any one of claims 1 to 9, the method comprising: The lean liquid is received by the absorption tower to absorb the input flue gas, and the purified gas is generated and discharged from the top of the absorption tower, and the rich liquid is generated and delivered to the delivery pump from the bottom of the absorption tower; The rich liquid is pressurized and preheated by the delivery pump and the first heat exchanger and delivered to the top of the regeneration tower; The rich liquid is heated by the regeneration tower to generate CO2 which is discharged from the top of the regeneration tower, and hot lean liquid is generated which is transported from the bottom of the regeneration tower to a flash structure; The hot lean liquid is flashed by the flash structure to generate a mixed gas which is returned to the bottom of the regeneration tower, and a new lean liquid is generated which is transported to the top of the absorption tower through the first heat exchanger.

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