Low temperature sublimation co2 capture system
By integrating LNG cold energy and carbon capture technology, and utilizing propane as an intermediate refrigerant in a low-temperature sublimation CO2 capture system, the problems of high energy consumption and space limitations in marine carbon capture have been solved, achieving efficient and low-energy CO2 capture and purification, suitable for the limited space of ships.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI CANYANG ENVIRONMENTAL PROTECTION TECHNOLOGY CO LTD
- Filing Date
- 2025-05-07
- Publication Date
- 2026-06-16
AI Technical Summary
Existing marine carbon capture technologies face challenges such as high energy consumption, system complexity, high investment costs, and space limitations. In particular, during low-temperature CO2 capture, excessive energy consumption and the formation of CO2 frost layers lead to a decrease in heat transfer rate.
A cryogenic sublimation CO2 capture system is designed, integrating LNG cold energy and carbon capture technology. Propane is used as an intermediate refrigerant, and CO2 is efficiently captured and purified through a cooling, sublimation separation and purification liquefaction module combined with an energy recovery module.
It significantly reduces CO2 capture energy consumption, improves capture rate and product purity, reduces cold energy waste and environmental cold pollution, and is suitable for use in confined spaces on ships.
Smart Images
Figure CN224358220U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of ship carbon emission reduction technology, specifically to a low-temperature sublimation CO2 capture system. Background Technology
[0002] With green energy conservation becoming a central theme, the shipping industry is facing immense pressure and challenges. Shipping is by far the most efficient mode of commercial transport, accounting for over 90% of global trade transport. The industry's greenhouse gas emissions account for approximately 3% of global total emissions. In April 2018, the International Maritime Organization (IMO) strategic meeting developed a preliminary strategy aimed at reducing annual greenhouse gas emissions by at least 50% by 2050 compared to 2008 levels.
[0003] The technological routes for reducing CO2 emissions mainly include three levels: (1) improving energy conversion efficiency; (2) developing CO2 capture and storage technologies; and (3) developing alternative energy sources. Given the current global economic development and energy demand, it is difficult to significantly improve energy conversion efficiency in the short term.
[0004] Developing marine carbon capture technology is crucial for reducing CO2 emissions from the global shipping industry. Marine carbon capture utilizes carbon capture and storage (CCS) technology to capture and store CO2 on ships. However, current marine carbon capture technologies face challenges such as system complexity, high investment costs, and high energy consumption. The energy supply capacity of ship energy systems limits the power supply capacity of marine carbon capture systems. Furthermore, limited space and stability are significant constraints on the application of marine carbon capture technology.
[0005] When LNG is used as a power source for shipping vessels, it needs to be vaporized before being supplied to the ship's main engine. However, most current LNG vaporization terminals release the cold energy into seawater or the atmosphere. This results in the waste of high-quality cold energy and causes cold pollution to the environment. Using this released cold energy in CO2 capture processes can significantly save energy.
[0006] Cryogenic CO2 capture technology is an effective marine carbon capture technology that separates CO2 from the gas into liquid or solid states through phase change. Solid and liquid pure CO2 are easy to store and have economic value. This method can capture high-purity CO2 with relatively low energy consumption.
[0007] However, the application of cryogenic CO2 capture technology on ships still faces some technical challenges. First, considering that CO2 liquefaction occurs at pressures above 5.1 bar, directly pressurizing flue gas containing 4%-5% CO2 molar fraction results in excessively high energy consumption, which is unacceptable. Second, when using the CO2 sublimation separation principle at atmospheric pressure, CO2 frost easily forms on the surface of the heat exchanger, leading to a decrease in heat transfer rate, and these frost layers are difficult to remove continuously. Utility Model Content
[0008] The purpose of this invention is to provide a new cryogenic sublimation CO2 capture system that integrates LNG cold energy utilization with marine carbon capture technology, which can significantly reduce energy consumption and improve the feasibility of CO2 capture in LNG-powered ships.
[0009] To solve the above-mentioned technical problems, this utility model provides a low-temperature sublimation CO2 capture system, which includes a cooling and drying module, a medium cooling module, a sublimation separation module, a purification and liquefaction module, and a recovery module.
[0010] The cooling and drying module includes a seawater cooler, a gas-liquid separator, a fan, a drying filter, and a precooler. The seawater cooler is connected to the gas-liquid separator via a pipeline, and the gas-liquid separator is connected to the drying filter via a pipeline. A fan is installed between the gas-liquid separator and the drying filter, and the drying filter is connected to the precooler via a pipeline.
[0011] The sublimation separation module includes an LNG storage tank, a first heat exchanger, a pressurizing pump, and a seawater heater. The LNG storage tank is connected to the first heat exchanger via a pipeline. A pressurizing pump is installed between the LNG storage tank and the first heat exchanger. The first heat exchanger is connected to the precooler of the cooling and drying module via a pipeline. The precooler is connected to the seawater heater via a pipeline.
[0012] The sublimation separation module includes a second heat exchanger, a sublimation reactor, a solid-liquid separator, and a mixer. The precooler of the cooling and drying module is also connected to the second heat exchanger via a pipeline. The second heat exchanger is connected to the sublimation reactor via a pipeline. The sublimation reactor is connected to the solid-liquid separator via a pipeline. The solid-liquid separator is connected to the mixer via a pipeline. The mixer is connected to the first heat exchanger of the sublimation separation module via a pipeline. A transfer pump is provided between the mixer and the first heat exchanger.
[0013] The purification and liquefaction module includes a third heat exchanger, a fourth heat exchanger, a melting heater, a gas-liquid separator, a primary compressor, and a secondary compressor. The solid-liquid separator of the sublimation separation module is connected to the third heat exchanger via a pipeline. The third heat exchanger is connected to the fourth heat exchanger via a pipeline, and a secondary compressor is installed between them. The fourth heat exchanger is connected to the melting heater via a pipeline. The melting heater is connected to the gas-liquid separator via a pipeline. The gas-liquid separator is connected back to the fourth heat exchanger, and a primary compressor is installed between them. The gas-liquid separator is connected to the mixer of the sublimation separation module via a pipeline.
[0014] Beneficial effects of this utility model
[0015] This invention relates to a ship exhaust carbon dioxide capture system and method, which offers significant advantages. By utilizing the cold energy of LNG, energy consumption during CO2 capture is reduced, achieving a unit capture energy consumption as low as 5.72 MJ / kg compared to traditional technologies. The use of propane as an intermediate refrigerant, with its low melting point and excellent thermodynamic properties, allows CO2 to be efficiently sublimated and separated at low temperatures, avoiding the problem of reduced heat transfer efficiency caused by frost formation on the heat exchanger surface during traditional sublimation processes. Through optimized design, this system achieves a CO2 capture rate of 92.87% and a CO2 product purity of 96.49%, significantly improving both the efficiency and quality of carbon capture.
[0016] This invention's system effectively utilizes the cold energy of LNG on ships, achieving cascaded energy utilization and reducing cold energy waste and environmental pollution. Furthermore, the system's compact design makes it suitable for the limited space of ships, demonstrating promising engineering application prospects. Attached Figure Description
[0017] Figure 1 The flowchart of the marine carbon capture system for treating exhaust gas from LNG-powered ships is shown below. Detailed Implementation
[0018] This invention utilizes the cold energy of LNG to lower the temperature of CO2, causing it to sublimate and transform into a solid state, which is then separated. This solid CO2 is further melted and pressurized, transforming into a higher-density liquid CO2. This liquid CO2 can be stored on the ship until it reaches port for CO2 treatment, thus achieving CO2 capture from the combustion exhaust of LNG-powered ships.
[0019] Specifically, the marine exhaust carbon dioxide capture system provided by this utility model includes a cooling and drying module, a medium cooling module, a sublimation and separation module, a purification and liquefaction module, and a recovery module.
[0020] The cooling and drying module includes a seawater cooler, a gas-liquid separator, a fan, a drying filter, and a precooler. The exhaust gas from the ship's engine first enters the seawater cooler for cooling, then undergoes preliminary dehydration in the gas-liquid separator. Next, the exhaust gas is pressurized by the fan and enters the drying filter for deep dehydration, and finally, it is cooled again by the precooler.
[0021] The medium cooling module uses propane as a refrigerant. Propane absorbs cold energy from LNG. After exiting the LNG storage tank, the LNG is pressurized by pump number one and releases its cold energy successively in the first heat exchanger and precooler 5. In the first heat exchanger, LNG exchanges heat with liquid propane, lowering the propane's temperature. In the precooler, LNG exchanges heat with pre-treated exhaust gas, further cooling the exhaust gas. Afterward, the LNG enters the seawater heater, releasing its cold energy to the seawater to meet the temperature requirements for entering the engine.
[0022] The sublimation separation module includes a second heat exchanger, a sublimation reactor, and a solid-liquid separator. The exhaust gas, cooled by the precooler, enters the second heat exchanger and, after deep precooling, enters the sublimation reactor. Propane from the propane recycling system, cooled by the first heat exchanger, is sprayed into the sublimation reactor and directly contacts the CO2 in the exhaust gas, causing the CO2 to sublimate into a solid phase. The slurry containing solid CO2 and liquid propane exits from the bottom of the sublimation reactor and enters the solid-liquid separator for separation. The separated liquid propane enters the mixer and is then pumped back into the first heat exchanger by a second pump for recycling; the remaining clean gas exits from the top of the sublimation reactor, recovers its cold energy in the second heat exchanger, and is then discharged from the system.
[0023] The purification and liquefaction module includes a third heat exchanger, a fourth heat exchanger, a melting heater, a gas-liquid separator, a primary compressor, and a secondary compressor. The slurry discharged from the solid-liquid separator passes sequentially through the third and fourth heat exchangers, and is then heated to -60°C in the melting heater, causing the solid-phase CO2 to sublimate into a gaseous phase. The CO2 gas and liquid propane enter the gas-liquid separator for separation. The liquid propane is discharged from the bottom and circulated in the mixer; the CO2 gas is discharged from the top, first compressed by the primary compressor, then enters the fourth heat exchanger to absorb its own cooling energy, and is further compressed by the secondary compressor, absorbing cooling energy again in the third heat exchanger, ultimately yielding a liquid CO2 product with a purity greater than 95%, suitable for storage.
[0024] The recovery module is responsible for recovering the cold and heat energy generated in the system. For example, the cold energy of the residual flue gas is recovered through a heat recovery heat exchanger for pre-cooling the tail gas; the cold energy of the mixed slurry is recovered for condensing CO2 products; the cold energy released by LNG is used not only for the CO2 capture process but also for the pre-cooling of the tail gas; and the energy carried by propane is also recovered and reused before entering the next cycle.
[0025] When using this system for carbon dioxide capture from ship exhaust, the high-temperature exhaust gas from the ship's engine is first introduced into the cooling and drying module for pretreatment following the cooling, dehydration, and drying steps described above. Next, the pretreated exhaust gas enters the intermediate medium cooling module, where it is further cooled using propane via the cold energy of LNG. Then, the cooled exhaust gas enters the sublimation separation module, where CO2 sublimates and separates from the exhaust gas. The separated CO2-containing slurry enters the purification and liquefaction module, where it undergoes heating sublimation, gas-liquid separation, compression, and cooling to ultimately obtain a high-purity liquid CO2 product. Throughout the entire process, the energy recovery module continuously recovers energy from the system to reduce energy consumption.
[0026] The following embodiments and accompanying drawings are used to describe in detail the implementation of this utility model, so that the process of how this utility model uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.
[0027] like Figure 1 As shown, the marine exhaust carbon dioxide capture system provided by this utility model includes a cooling and drying module, a medium cooling module, a sublimation and separation module, a purification and liquefaction module, and a recovery module. The cooling and drying module includes a seawater cooler 1, a gas-liquid separator 2, a fan 3, a drying filter 4, and a precooler 5.
[0028] The medium cooling module uses propane as a refrigerant. Propane absorbs cold energy from LNG. After exiting the LNG storage tank 20, the LNG is pressurized by pump 6 and releases its cold energy successively in the first heat exchanger 7 and the precooler 5. In the first heat exchanger 7, LNG exchanges heat with liquid propane, lowering the propane's temperature. In the precooler 5, LNG exchanges heat with pre-treated exhaust gas, further cooling the exhaust gas. Afterward, the LNG enters the seawater heater 8, releasing its cold energy to the seawater to meet the temperature requirements for entering the engine.
[0029] The sublimation separation module includes a second heat exchanger 9, a sublimation reactor 10, and a solid-liquid separator 11. The exhaust gas, cooled by the precooler 5, enters the second heat exchanger 9 and is deeply precooled before entering the sublimation reactor 10. Liquid propane from the propane circulation system, after being cooled by the first heat exchanger 7, directly contacts the CO2 in the exhaust gas through a spray in the sublimation reactor 10, causing the CO2 to sublimate into a solid phase. The slurry containing solid CO2 and liquid propane is discharged from the bottom of the sublimation reactor 10 and enters the solid-liquid separator 11 for separation. The separated liquid propane enters the mixer 12 and is then pumped back into the first heat exchanger 7 by the second pump 13 for recycling; the remaining clean gas is discharged from the top of the sublimation reactor 10, recovers its cold energy in the second heat exchanger 9, and is then discharged from the system.
[0030] The purification and liquefaction module includes a third heat exchanger 14, a fourth heat exchanger 15, a melting heater 16, a gas-liquid separator 17, a primary compressor 18, and a secondary compressor 19. The slurry discharged from the solid-liquid separator 11 passes sequentially through the third and fourth heat exchangers 14 and 15, and is then heated to -60°C in the melting heater 16, causing the solid-phase CO2 to sublimate into the gas phase. CO2 gas and liquid propane enter the gas-liquid separator 17 for separation. Liquid propane is discharged from the bottom and fed into the mixer 12 for circulation via a pressurization pump 21; CO2 gas is discharged from the top, first compressed by the primary compressor 18, then enters the fourth heat exchanger 15 to absorb its own cooling energy, and is further compressed by the secondary compressor 19, absorbing cooling energy in the third heat exchanger 14, ultimately yielding a liquid CO2 product with a purity greater than 95%, which is easy to store.
[0031] The recovery module is responsible for recovering the cold and heat energy generated in the system. For example, the cold energy of the residual flue gas is recovered through a heat recovery heat exchanger for pre-cooling the tail gas; the cold energy of the mixed slurry is recovered for condensing CO2 products; the cold energy released by LNG is used not only for the CO2 capture process but also for the pre-cooling of the tail gas; and the energy carried by propane is also recovered and reused before entering the next cycle.
[0032] This invention uses propane as the intermediate refrigerant. Propane has a suitable boiling point range and a high latent heat of vaporization, which enables it to efficiently transfer heat during heat exchange. Propane is chemically stable and causes minimal environmental pollution under normal operating conditions, making it a relatively environmentally friendly refrigerant. However, propane is also flammable, and safety regulations must be strictly followed during its use, including measures such as good ventilation and prohibition of open flames. Propane absorbs the cold energy of LNG and achieves heat exchange by thoroughly mixing with CO2 through spraying. This process effectively condenses and separates CO2 from the ship's exhaust gas. The specific workflow is as follows:
[0033] (a) Cooling and drying process
[0034] The exhaust gas from the marine engine, at 250°C and 1 bar, is first cooled to approximately 30°C by a seawater cooler 1. Then, the exhaust gas enters a gas-liquid separator 2 to initially remove moisture. Next, a blower 3 slightly compresses the gas to 1.4 bar before sending it to a dryer filter 4 for further dehydration. Finally, the exhaust gas enters a precooler 5 for further cooling to approximately 30°C.
[0035] (b) Intermediate medium cooling process
[0036] Propane is a colorless gas that is volatile at room temperature and pressure. Its boiling point is -42.1℃ and its melting point is -187.7℃. It is chemically stable in low-temperature environments and does not readily undergo phase transitions. When used as an intermediate refrigerant in CO2 separation, propane remains liquid throughout the system, significantly improving CO2 separation efficiency. LNG at -162℃, pumped from the LNG tank, is pressurized by pump 6 and enters the first heat exchanger 7, where it releases cold energy and exchanges heat with liquid propane. The LNG discharged from the first heat exchanger 7 then enters the precooler 5, where it again releases cold energy and exchanges heat with exhaust gas. Following this, the exhaust gas enters the seawater heater 8, completing a third release of cold energy to reach the temperature required for injection into the engine.
[0037] (c) Sublimation CO2 separation process
[0038] The exhaust gas from precooler 5 is deeply precooled to -75°C in the second heat exchanger 9 before entering the sublimation reactor 10. Liquid propane from the propane cycle is cooled to -155°C by the first heat exchanger 7 and then directly contacts the CO2 in the exhaust gas via spray before entering the sublimation reactor 10 together. Under these conditions, the CO2 sublimates into a solid. The slurry containing solid CO2 and liquid propane flows out from the bottom of the sublimation reactor 10 and enters the solid-liquid separator 11. The separated liquid propane enters the mixer 12 and is then pumped back to the first heat exchanger 7 by the second pump 13 to participate in the next cycle. The remaining clean gas is discharged from the top of the sublimation reactor 10, where its cold energy is recovered first in the second heat exchanger 9 before being discharged from the system.
[0039] (d) CO2 purification and liquefaction process
[0040] The slurry containing solid CO2 and liquid propane discharged from the bottom of the sublimation reactor 10 passes sequentially through the third heat exchanger 14 and the fourth heat exchanger 15. Then, it is heated to -60°C in the melting heater 16, where the solid CO2 sublimates into a gaseous state. The generated CO2 gas and liquid propane enter the gas-liquid separator 17 for separation. The liquid propane is discharged from the bottom of the gas-liquid separator 17, enters the mixer 12, and is then pumped by the second pump 13 to the first heat exchanger 7 for recycling. Simultaneously, the CO2 gas separated from the top of the gas-liquid separator 17 is first compressed by the first-stage compressor 18 and then sent to the fourth heat exchanger 15 to absorb its own cold energy. Finally, the CO2 gas is further compressed by the second-stage compressor 19 and absorbs cold energy in the third heat exchanger 14, ultimately yielding a liquid CO2 product with a purity greater than 95%, which is stored in liquid form for convenient subsequent storage and processing.
[0041] All of the above-described primary implementations of this intellectual property right do not limit other forms of implementation of this new product and / or new method. Those skilled in the art will utilize this important information to modify the above content to achieve similar implementations. However, all modifications or alterations based on this utility model are reserved rights.
[0042] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this utility model without departing from its technical solution shall still fall within the protection scope of this utility model.
Claims
1. A low-temperature sublimation CO2 capture system, characterized in that: It includes a cooling and drying module, a media cooling module, a sublimation and separation module, a purification and liquefaction module, and a recovery module; The cooling and drying module includes a seawater cooler, a gas-liquid separator, a fan, a drying filter, and a precooler. The seawater cooler is connected to the gas-liquid separator via a pipeline, and the gas-liquid separator is connected to the drying filter via a pipeline. A fan is installed between the gas-liquid separator and the drying filter. The drying filter is connected to the precooler via a pipeline. The medium cooling module includes an LNG storage tank, a first heat exchanger, a pressurizing pump, and a seawater heater. The LNG storage tank is connected to the first heat exchanger via a pipeline. A pressurizing pump is installed between the LNG storage tank and the first heat exchanger. The first heat exchanger is connected to the precooler of the cooling and drying module via a pipeline. The precooler is connected to the seawater heater via a pipeline. The sublimation separation module includes a second heat exchanger, a sublimation reactor, a solid-liquid separator, and a mixer. The precooler of the cooling and drying module is also connected to the second heat exchanger via a pipeline. The second heat exchanger is connected to the sublimation reactor via a pipeline. The sublimation reactor is connected to the solid-liquid separator via a pipeline. The solid-liquid separator is connected to the mixer via a pipeline. The mixer is connected to the first heat exchanger of the sublimation separation module via a pipeline. A transfer pump is provided between the mixer and the first heat exchanger. The purification and liquefaction module includes a third heat exchanger, a fourth heat exchanger, a melting heater, a gas-liquid separator, a primary compressor, and a secondary compressor. The solid-liquid separator of the sublimation separation module is connected to the third heat exchanger via a pipeline. The third heat exchanger is connected to the fourth heat exchanger via a pipeline, and a secondary compressor is installed between them. The fourth heat exchanger is connected to the melting heater via a pipeline. The melting heater is connected to the gas-liquid separator via a pipeline. The gas-liquid separator is connected back to the fourth heat exchanger, and a primary compressor is installed between them. The gas-liquid separator is connected to the mixer of the sublimation separation module via a pipeline.