Co-cavity type carbon capture system for LNG (Liquefied Natural Gas) ship

Abstract

The invention belongs to the field of ship energy conservation and emission reduction, and discloses a co-cavity type carbon capture system for an LNG ship, the system comprises a carbon capture system, the carbon capture system comprises a carbon capture unit, the carbon capture unit comprises a desorption tower, and an integrated reboiler and a heat recovery condenser are arranged in the carbon capture unit along the vertical direction of the desorption tower; a CO2 regeneration area is arranged in the desorption tower and is positioned between the integrated reboiler and the heat recovery condenser; the CO2 post-treatment unit comprises a CO2 condenser I and a CO2 condenser II, a pipe side outlet of the CO2 post-treatment unit is communicated with a cold side inlet of the CO2 condenser II, and a cold source of the CO2 condenser I is an LNG cold source. According to the invention, cold energy in LNG gasification is utilized to liquefy CO2, and a flue gas waste heat utilization position is embedded into the lower half section of the desorption tower, so that the purposes of improving the preheating utilization efficiency and reducing the occupied space are achieved; after desorption is completed, a CO2 steam mixture preheats a rich solvent, corresponding steam is condensed and liquefied, and the co-cavity type desorption tower reduces additional energy consumption for capturing CO2, reduces heat loss and improves the space utilization rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ship energy saving and emission reduction, and particularly relates to a common cavity type carbon capture system for LNG ship. BACKGROUND

[0002] Global shipping industry undertakes about 80% of international trade transportation tasks, and the CO2 emissions generated account for 3% of the global total. In the latest "Fourth IMO GHG Study" (2020), it is estimated that the global CO2 emissions in 2018 will reach 365 billion tons in 2024, and the shipping emissions will rise to 10.6 billion tons. The International Maritime Organization (IMO) has issued the Energy Efficiency Design Index (EEDI) and the Energy Efficiency Operational Indicator (EEOI) to constrain the carbon emissions of ships during design and operation, so as to achieve the goal of the Paris Agreement.

[0003] Under the promotion of the above standards, various energy saving and carbon reduction measures have emerged. Among them, the development of renewable fuels has great potential, but the mature application of new fuels still needs time. Liquid natural gas (LNG) combined with carbon capture technology can solve the problem of carbon reduction of ships. Among them, LNG can reduce 90% of SOx, 80% of NOx, 20% of CO2 and 100% of particulate matter. The carbon capture system can achieve more than 90% of the degree of carbon dioxide capture in flue gas, and under the assistance of LNG cold energy, the captured CO2 can be liquefied and stored on the ship, providing convenience for carbon transportation and carbon trading. The development of dual-fuel engines for ships makes LNG ocean-going ships gradually develop. It is estimated that the market share of LNG ships will reach 39% in 2050.

[0004] In order to solve the problem of carbon emissions of LNG power ships, the chemical absorption method in the post-combustion carbon capture system is the most effective. The chemical absorption method has the advantages of large treatment scale, solution reuse, high capture rate, etc., and can adapt to the ship environment. Therefore, this method has become the mainstream method of ship carbon reduction. However, a large amount of heat is required for the capture process, and a large amount of cold energy is required as the cold source for CO2 liquefaction for convenient storage.

[0005] The application of carbon capture systems on ships requires a large amount of space, which is in contradiction with the compactness of the ship. In the prior art, a Chinese patent with the patent number CN119425314A discloses a compact ship exhaust carbon dioxide capture system and capture method. The invention patent includes the whole process of carbon dioxide capture, regeneration, pressurization and liquefaction, and also considers the space optimization problem of the ship carbon capture system. However, the multi-stage flash evaporation method and the external flue gas waste heat recovery device still do not maximize the space utilization. A national patent with the patent number CN119983896A discloses a waste heat recovery system, a carbon dioxide capture device and a ship. The patent combines the heat of the ship flue gas to provide CO2 capture desorption, and improves the heat utilization rate of the carbon capture system. However, the influence of space on the ship is not considered. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a co-cavity type carbon capture system for LNG ships, which aims to meet the requirements of the International Maritime Organization for carbon emissions, while reducing energy consumption and optimizing space to overcome the obstacles to the industrialization of ship carbon capture systems.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A co-cavity type carbon capture system for LNG ships, comprising, a carbon capture unit, which comprises a desorption tower having an integrated reboiler and a heat recovery condenser inside along its vertical upward direction; and the inside of the desorption tower also has a CO2 regeneration zone, which is located between the integrated reboiler and the heat recovery condenser; a CO2 post-processing unit, comprising CO2 condenser one and CO2 condenser two, the tube side outlet of which is connected to the cold side inlet of CO2 condenser two, the cold source of CO2 condenser one is LNG cold source, and the hot side inlet of CO2 condenser two is connected to the inside of the desorption tower through the tower top of the desorption tower, for providing cold energy released during LNG gasification to CO2 liquefaction; The ship flue gas outlet is connected with the inlet of the outer high-efficiency heat exchange pipeline in the integrated reboiler; the outlet of the outer high-efficiency heat exchange pipeline is connected with the hot side inlet of the flue gas secondary regenerator; the integrated reboiler further comprises an inner heat exchange pipeline which is connected with the steam generator of the ship; the hot side outlet of the flue gas secondary regenerator is connected with external equipment one; the cold side inlet of the flue gas secondary regenerator is connected with the outlet of the heat recovery condenser; the inlet of the heat recovery condenser is connected with external equipment two; the cold side outlet of the flue gas secondary regenerator is connected with the inlet of the lean-rich liquid regenerator; the outlet of the lean-rich liquid regenerator is connected with the sidewall of the desorption tower; the connection position is between the lower end of the heat recovery condenser and the upper end of the CO2 regeneration zone, and the position for flue gas waste heat utilization is embedded in the lower half of the desorption tower, so that the preheating utilization efficiency is improved and the space occupation is reduced.

[0008] Preferably, the outer high-efficiency heat exchange pipeline and the inner heat exchange pipeline are in the form of a coil, and the outer high-efficiency heat exchange pipeline and the inner heat exchange pipeline are integrated.

[0009] Preferably, the inlet of the inner heat exchange pipeline is connected with the steam generator on the ship, and the steam generator belongs to the additional heat provided by the ship and is used to supplement the insufficient flue gas heat; the outlet of the inner heat exchange pipeline is connected with the water return port of the steam generator.

[0010] Preferably, the area between the coils of the outer high-efficiency heat exchange pipeline and the inner heat exchange pipeline and the tower wall of the desorption tower is filled with stainless steel wires, so as to enhance the heat transfer area and improve the heat transfer efficiency.

[0011] Preferably, the coils of the heat recovery condenser and the tower wall of the desorption tower are filled with stainless steel wires, so as to increase the heat exchange area of the heat recovery condenser and improve the heat transfer efficiency.

[0012] Preferably, the carbon capture system further comprises an absorption tower, a rich liquid pump, a lean liquid pump, a flue gas cooler, and a flue gas tertiary regenerator. The flue gas cooler is external equipment one, the hot side outlet of the flue gas secondary regenerator is connected with the inlet of the flue gas cooler, the outlet of the flue gas cooler is connected with the inlet of the flue gas tertiary regenerator, the outlet of the flue gas tertiary regenerator is upward and located in the interior of the absorption tower, the inner bottom of the absorption tower is connected with the inlet of the rich liquid pump, The rich liquid pump is external equipment two, the outlet of the rich liquid pump is connected with the inlet of the heat recovery condenser through the upper end of the sidewall of the desorption tower; the liquid outlet at the bottom of the desorption tower is connected with the inlet of the lean liquid pump; the outlet of the lean liquid pump is connected with the hot side inlet of the lean-rich liquid regenerator; the hot side outlet of the lean-rich liquid regenerator is connected with the inlet of the top side of the absorption tower.

[0013] Preferably, the flue gas tertiary regenerator is located at the inner bottom of the absorption tower.

[0014] Preferably, the CO2 post-processing unit further comprises a CO2 gas-liquid separator, a regulating stop valve, a CO2 dryer, a low-pressure CO2 storage tank, and a CO2 compressor. The middle outlet of the desorption tower is connected to the liquid inlet of the CO2 gas-liquid separator; the top gas outlet of the desorption tower is connected to the two-heat-side inlet of the CO2 condenser; the two-heat-side outlet of the CO2 condenser is connected to the inlet of the CO2 gas-liquid separator; the liquid outlet of the CO2 gas-liquid separator is connected to the inlet of the lean liquid pump; the gas outlet of the CO2 gas-liquid separator is connected to the inlet of the regulating stop valve; the outlet of the regulating stop valve is connected to the inlet of the CO2 dryer; the outlet of the CO2 dryer is connected to the inlet of the low-pressure CO2 storage tank; the outlet of the low-pressure CO2 storage tank is connected to the inlet of the CO2 compressor; the outlet of the CO2 compressor is connected to the one-shell-side inlet of the CO2 condenser; the one-shell-side outlet of the CO2 condenser is connected to the CO2 liquid storage tank; and the two-cold-side outlet of the CO2 condenser is connected to the subsequent natural gas pipeline.

[0015] Preferably, the carbon capture system further comprises a flue gas post-processing unit, which comprises a lean carbon flue gas condenser and a lean carbon flue gas gas-liquid separator. The outlet of the top of the absorption tower is connected to the inlet of the lean carbon flue gas condenser; the hot-side outlet of the lean carbon flue gas condenser is connected to the inlet of the lean carbon flue gas gas-liquid separator; the liquid outlet of the lean carbon flue gas gas-liquid separator is connected to the inlet of the rich liquid pump; the gas outlet of the lean carbon flue gas gas-liquid separator is connected to the ship flue gas pipeline; and the cold-side inlet of the lean carbon flue gas condenser is connected to the seawater inlet for cooling.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. In the present application, the released cold energy in the LNG gasification process is used to provide liquefaction for CO2, and the flue gas waste heat utilization position is embedded in the lower half of the desorption tower, so as to improve the preheating utilization efficiency and reduce the space occupation. At the same time, in terms of internal waste heat utilization of the system, the CO2 vapor mixture after desorption is used to preheat the rich solvent, and the corresponding steam is condensed and liquefied. This part is embedded in the upper half of the desorption tower. The co-cavity desorption tower formed by multiple components reduces the additional energy consumption required for CO2 capture, reduces heat loss, improves space utilization, and is theoretically mature and highly implementable.

[0017] 2. In the present application, the utilization degree of the flue gas waste heat of the ship is extremely high; the flue gas waste heat is divided into three levels of gradient utilization, the high-grade heat source is used to provide regeneration heat in the desorption tower, the medium-grade heat source is used for three-stage preheating of the rich solvent, and the low-grade heat source is used for one-stage preheating of the rich solvent; the high utilization degree of the flue gas waste heat reduces the demand of the carbon capture system for external energy and reduces the cost of carbon capture.

[0018] 3. Because the flue gas three-stage regenerator is embedded in the absorption tower in the application, the space utilization rate of the ship carbon capture system is improved; the storage area of the rich solvent at the bottom of the absorption tower is necessary for the rich liquid pump inlet buffer, and the flue gas three-stage regenerator is designed by using the inherent characteristics, so that the space is shared, and the energy utilization efficiency is improved.

[0019] 4. Because of the two-stage waste heat recovery structure in the system in the application, in addition to the heat exchange of the rich-liquid and lean-liquid regenerator in the main flow path, a large amount of remaining latent heat in the regeneration heat is recovered by the heat recovery condenser, so as to reduce the heat demand of the carbon capture system and reduce the cooling burden of the system.

[0020] 5. Because the design of the common cavity desorption tower in the application integrates the reboiler, the CO2 regeneration process and the heat recovery condenser in the desorption tower, the arrangement relationship among the three is cleverly combined with the gravity action of the solvent and the flow path of the flue gas, which greatly reduces the space occupation of the capture system; the integrated design reduces the overall heat loss. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The flow chart of the whole system of the application is shown in the figure. Figure 2 The structure diagram of the integrated reboiler in the application is shown in the figure.

[0022] In the figure: capture unit 100; absorption tower 101; desorption tower 102; integrated reboiler 103; outer high-efficiency heat exchange pipeline 1031; inner heat exchange pipeline 1032; heat recovery condenser 104; rich liquid pump 105; lean liquid pump 106; flue gas two-stage regenerator 107; rich-liquid and lean-liquid regenerator 108; flue gas cooler 109; flue gas three-stage regenerator 110; CO2 post-processing unit 200; CO2 condenser two 201; carbon dioxide gas-liquid separator 202; regulating stop valve 203; CO2 dryer 204; low-pressure CO2 gas storage tank 205; CO2 compressor 206; CO2 condenser one 207; flue gas post-processing unit 300; carbon-poor flue gas condenser 301; carbon-poor flue gas gas-liquid separator 302. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, purposes and effects realized by the application easy to understand, the technical solutions of the application are specifically described in the following embodiments combined with the drawings. It should be noted that the description of these embodiments is used to help understand the application, but does not constitute a limitation on the application.

[0024] As Figure 1As shown, a common cavity type carbon capture system for LNG ship includes a carbon capture unit 100, which includes a desorption tower 102, which has an integrated reboiler 103 and a heat recovery condenser 104 inside along its vertical upward direction, a rich liquid pump 105, a lean liquid pump 106, a flue gas secondary regenerator 107, a lean-rich liquid regenerator 108, a flue gas cooler 109, a flue gas tertiary regenerator 110; and the inside of the desorption tower 102 also has a CO2 regeneration zone (i.e. desorption tower packing section) between the integrated reboiler 103 and the heat recovery condenser 104; and the integrated reboiler 103 can directly utilize flue gas, improving the space utilization rate of the ship carbon capture system and improving the flue gas waste heat utilization efficiency.

[0025] As shown, Figure 2 the ship flue gas outlet is connected to the inlet of the outer layer high-efficiency heat exchange pipeline 1031 (for realizing sufficient heat exchange by high-temperature flue gas) in the integrated reboiler 103; the outlet of the outer layer high-efficiency heat exchange pipeline 1031 is connected to the hot side inlet of the flue gas secondary regenerator 107; the integrated reboiler 103 also includes an inner layer heat exchange pipeline 1032, which is connected to the steam generator on the ship (specifically: the inlet of the inner layer heat exchange pipeline is connected to the steam generator on the ship, and the steam generator is used to supplement the case of insufficient flue gas heat; the outlet of the inner layer heat exchange pipeline is connected to the steam generator backwater port), the hot side outlet of the flue gas secondary regenerator 107 is connected to the inlet of the flue gas cooler 109; the outlet of the flue gas cooler 109 is connected to the inlet of the flue gas tertiary regenerator 110; the adjustment of the air cooling frequency of the flue gas cooler 109 can control the degree of heating of the rich solvent under the action of the flue gas tertiary regenerator 110; the outlet of the flue gas tertiary regenerator 110 is in the absorption tower 101 and faces upward; the flue gas tertiary regenerator 110 is the first heating preheater of the rich solvent; the lean solvent in the absorption tower 101 is sprayed from the top and down, and the enrichment reaction occurs in the absorption tower packing section and the flue gas; the solvent after the enrichment reaction becomes the rich solvent; in addition, in this embodiment, the flue gas tertiary regenerator 110 is arranged in the absorption tower 101, which can improve the space utilization rate of the ship carbon capture system; the storage area of the rich solvent at the bottom of the absorption tower is necessary for the rich liquid pump inlet buffer, and the flue gas tertiary regenerator is designed to utilize the inherent characteristics, so that the space is shared, and the energy utilization efficiency is improved.

[0026] The flue gas post-processing unit 300 mainly comprises a lean carbon flue gas condenser 301 and a lean carbon flue gas gas-liquid separator 302. The inlet of the lean carbon flue gas condenser is connected with the outlet at the top of the absorption tower, the hot side outlet of the lean carbon flue gas condenser is connected with the inlet of the lean carbon flue gas gas-liquid separator, the liquid phase outlet of the lean carbon flue gas gas-liquid separator is connected with the inlet of the rich liquid pump, the gas phase outlet of the lean carbon flue gas gas-liquid separator is connected with the flue gas pipeline of the ship, the cold side inlet of the lean carbon flue gas condenser is connected with seawater for cooling, that is, the outlet at the top of the absorption tower 101 is connected with the hot side inlet of the lean carbon flue gas condenser 301, the hot side outlet of the lean carbon flue gas condenser 301 is connected with the inlet of the lean carbon flue gas gas-liquid separator 302, the liquid phase outlet of the lean carbon flue gas gas-liquid separator 302 is connected with the inlet of the rich liquid pump 105, the rich solvent is accumulated at the bottom of the absorption tower 101 and waits for the rich liquid pump 105 to transport, the rich solvent is preheated under the action of the flue gas three-stage regenerator 110, the gas phase outlet of the lean carbon flue gas gas-liquid separator 302 is connected with the flue gas pipeline of the ship, and the cold side inlet of the lean carbon flue gas condenser 301 is connected with seawater for cooling. The liquid phase outlet at the bottom of the absorption tower 101 is connected with the inlet of the rich liquid pump 105, the outlet of the rich liquid pump 105 is connected with the inlet of the heat recovery condenser 104, the outlet of the heat recovery condenser 104 is connected with the cold side inlet of the flue gas two-stage regenerator 107, the cold side outlet of the flue gas two-stage regenerator 107 is connected with the cold side inlet of the lean and rich liquid regenerator 108, the cold side outlet of the lean and rich liquid regenerator 108 is connected with the middle inlet of the desorption tower 102, and the connection is located between the lower end of the heat recovery condenser 104 and the upper end of the CO2 regeneration zone, so as to embed the position for flue gas waste heat utilization into the lower half of the desorption tower 102, so as to improve the preheating utilization efficiency and reduce the space occupation; in addition, the steam is liquefied on the heat recovery condenser 104 and falls to the collector integrated in the heat recovery condenser 104 under the action of gravity, the flue gas flows upward according to the pressure, and the downward flowing liquid is collected in the collector, which can collect the falling liquid and does not affect the upward flowing gas; the purpose is to save space, so as to improve the integration degree and reduce the heat loss, and the essence is to reduce the total contact area of the equipment with the outside.

[0027] The bottom liquid outlet of the desorption tower 102 is connected with the inlet of the lean liquid pump 106; the outlet of the lean liquid pump 106 is connected with the hot side inlet of the lean- rich liquid regenerator 108; the hot side outlet of the lean- rich liquid regenerator 108 is connected with the top side inlet of the absorption tower 101; the heat recovery condenser 104 is embedded in the middle- upper section of the desorption tower 102, the low- temperature solvent flows in the coil of the heat recovery condenser 104, and the high- temperature steam flows outside the coil to realize heat exchange; the coil of the heat recovery condenser 104 and the tower wall of the desorption tower 102 are filled with stainless steel wires to increase the heat exchange area of the heat recovery condenser 104 and improve the heat transfer efficiency; the condensed water on the coil of the heat recovery condenser 104 flows downward and slides to the peripheral groove on the minaret collector at the bottom of the heat recovery condenser 104, and then flows out from the middle- section outlet of the desorption tower 102, so as not to interfere with the temperature system of the lower section of the desorption tower 102; in addition, there is a double- stage waste heat recovery structure in the system, that is, after the CO2 is regenerated in the CO2 regeneration area, the waste heat in the desorption tower 102 is divided into two parts; one part is sent to the lean- rich liquid regenerator 108 by the lean liquid pump 106 at the bottom to recover the waste heat, which is the first waste heat recovery structure; the other part is the heat of the remaining steam and carbon dioxide moving upward in the desorption tower 102, which is recovered by heat exchange through the heat recovery condenser 104, which is the second waste heat recovery structure, and the first waste heat recovery structure and the second waste heat recovery structure are combined into a double- stage waste heat recovery structure.

[0028] The CO2 post-processing unit 200 includes a CO2 condenser two 201, a CO2 gas-liquid separator 202, an adjusting stop valve 203, a CO2 dryer 204, a low-pressure CO2 storage tank 205, a CO2 compressor 206, and a CO2 condenser one 207; the pipe side outlet of the CO2 condenser one 207 is connected with the cold side inlet of the CO2 condenser two 201, the cold source of the CO2 condenser one 207 is an LNG cold source, and the hot side inlet of the CO2 condenser two 207 is connected with the inside of the desorption tower 102 through the top of the desorption tower 102, which is used to provide the released cold energy in the LNG gasification process for CO2 liquefaction; The middle section outlet of the desorption tower 102 is connected with the liquid phase inlet of the CO2 gas-liquid separator 202; the top gas outlet of the desorption tower 102 is connected with the hot side inlet of the CO2 condenser 201; the hot side outlet of the CO2 condenser 201 is connected with the inlet of the CO2 gas-liquid separator 202; the liquid phase outlet of the CO2 gas-liquid separator 202 is connected with the inlet of the lean liquid pump 106; the gas phase outlet of the CO2 gas-liquid separator 202 is connected with the inlet of the regulating stop valve 203; the outlet of the regulating stop valve 203 is connected with the inlet of the CO2 dryer 204; the opening degree of the regulating stop valve 203 can regulate the pressure value in the desorption tower 103, so as to regulate the content of the transport steam in the desorption tower 102; when the content of the steam is too small, the heat transfer effect is poor and the CO2 regeneration effect is poor; when the content of the steam is too large, a large amount of steam flows back through condensation, thereby causing low heat utilization rate; when the opening degree of the regulating valve 203 is reduced, the gas in the desorption tower 102 is accumulated, the pressure is increased, and the content of the steam is reduced; when the opening degree of the regulating valve 203 is increased, the gas in the desorption tower 102 is released, the pressure is reduced, and the content of the steam is increased; The outlet of the CO2 dryer 204 is connected with the inlet of the low-pressure CO2 storage tank 205; the outlet of the low-pressure CO2 storage tank 205 is connected with the inlet of the CO2 compressor 206; the outlet of the CO2 compressor 206 is connected with the shell side inlet of the CO2 condenser 207; the shell side outlet of the CO2 condenser 207 is connected with the CO2 liquid storage tank; the tube side inlet of the CO2 condenser two 207 is the LNG input port; the tube side outlet of the CO2 condenser two 207 is connected with the cold side inlet of the CO2 condenser one 201; the cold side outlet of the CO2 condenser one 201 is connected with the subsequent natural gas flow direction; The outer high-efficiency heat exchange pipeline 1031 and the inner heat exchange pipeline 1032 are in the form of a coil pipe, and the outer high-efficiency heat exchange pipeline 1031 and the inner heat exchange pipeline 1032 are coiled together; the inlet of the inner heat exchange pipeline 1032 is connected with a steam generator on the ship; the steam generator belongs to additional heat provided by the ship, and is used for supplementing the case that the heat of the flue gas is insufficient; the outlet of the inner heat exchange pipeline 1032 is connected with a steam generator backwater port (the inner heat exchange pipeline 1032 flows with the cylinder sleeve water of the main engine of the ship, so as to realize the heat exchange between the cylinder sleeve water and the absorbent); in addition, a cylinder sleeve water flow regulating valve (not shown in the figure) is installed on the high-efficiency heat exchange pipeline 1031; the opening degree of the cylinder sleeve water flow regulating valve depends on whether the heat provided by the high-efficiency heat exchange pipeline 1031 can meet the heat demand of the absorbent. The area between the coils of the outer high-efficiency heat exchange pipeline 1031 and the inner heat exchange pipeline 1032 in the integrated reboiler 103 and the area between the coils and the tower wall of the desorption tower 103 are filled with stainless steel wires to enhance the heat transfer area and improve the heat transfer efficiency.

[0029] In addition, the waste heat of the flue gas in the present application is divided into three levels of gradient utilization, the high-grade heat source is used to provide the regeneration heat in the desorption tower, the medium-grade heat source is used to preheat the rich solvent in three stages, and the low-grade heat source is used to preheat the rich solvent in one stage; specifically, the integrated reboiler 103 completes the high-grade heat above 120°C for carbon dioxide regeneration (four-stage temperature rise of the rich solvent), the flue gas secondary regenerator 107 completes the medium-grade heat above 70°C for the three-stage temperature rise of the rich solvent, the flue gas tertiary regenerator 110 completes the low-grade heat above 40°C for the one-stage temperature rise of the rich solvent, and the flue gas cooler 109 dynamically adjusts and controls the waste heat of the flue gas to meet the requirement of 40°C at the outlet of the flue gas tertiary regenerator 110; the high utilization degree of the waste heat of the flue gas reduces the demand of the carbon capture system for external energy and reduces the cost of carbon capture; in addition, the heating of the rich solvent is divided into four stages, the flue gas tertiary regenerator 110 completes the first-stage heating, the target temperature is 50-60°C, the heat recovery condenser 104 completes the second-stage heating, the target temperature is 65-80°C, the flue gas secondary regenerator 107 completes the third-stage heating, the target temperature is 90-100°C, and the integrated reboiler 103 completes the final heating to achieve the desorption temperature of 115°C.

[0030] The steam in the integrated reboiler 103 exchanges heat with the rich solvent through the CO2 regeneration zone, and the steam and the carbon dioxide mixture in the heat recovery condenser 104 are cooled and condensed, and the condensed water is collected and flows into the CO2 gas-liquid separator 202; The collector at the bottom of the heat recovery condenser 104 is shaped like a pagoda (as shown in Figure 1 ), the cold solvent falls by gravity and is collected to the edge along the shape of the collector, and the gas flows upward through the gap between the two layers of the tower top to avoid interference of the condensed water on the lower heat system.

[0031] The regulating stop valve 203 controls the outflow of the regenerated CO2, the controlled opening degree is based on the CO2 regeneration rate in the desorption tower 102 and the consumption rate of CO2 in the low-pressure CO2 storage tank 205, and the control target is the internal pressure of the desorption tower 102, which determines the reduction amount of the CO2 regeneration energy consumption.

[0032] The low-pressure CO2 storage tank 205 has a pressure, and the CO2 compressor 206 compresses the CO2 to 5MPa; the energy consumption is greatly reduced, the CO2 condenser 207 is connected to the 10°C low-temperature water to complete the liquefaction of CO2, and then the cooling water is connected to the CO2 condenser 201 to realize the condensation of the liquid in the CO2.

[0033] The following will be described in combination with a specific embodiment: A Kamsarmax type ship equipped with dual-fuel main engine (Wärtsilä 12V50DF) is taken as the reference ship. The ship has a deadweight of 81190 DWT, a reference speed of 14 knots, and a maximum continuous power of 9930 kW. The solvent used by the carbon capture system is MEA solvent (monoethanolamine solvent); the ship flue gas enters from the inlet of the outer high-efficiency heat exchange pipeline 1031, and the inlet temperature is 268℃. After heat exchange, the outer high-efficiency heat exchange pipeline 1031 outputs at a temperature of 105℃. The ship provides an additional heat source in the form of steam into the inlet of the inner heat exchange pipeline 1032, and the outlet of the inner heat exchange pipeline 1032 returns to the steam generator of the ship. This loop is opened when the flue gas heat is insufficient, and the steam flow is adjusted according to the size of the heat gap. Further flue gas enters the flue gas secondary regenerator 107 at 105℃, providing heat to the rich solvent and flowing out at 60℃. The temperature of the flue gas is adjusted by the flue gas cooler 109, so that the flue gas flows out from the outlet of the flue gas tertiary regenerator 110 at a temperature of 40℃. At this time, the flue gas is released in the absorption tower 101, and the rich solvent is fully contacted with the lean solvent in the packing section of the absorption tower to perform a chemical reaction. The rich solvent is preheated in the flue gas tertiary regenerator 110, and the output temperature reaches 44℃. The flue gas after the absorption reaction is heated to 45℃ under the action of reaction heat, and then flows out from the top outlet of the absorption tower 101, and is cooled in the carbon-lean flue gas cooler 301. Under the action of seawater as a cold source, the carbon-lean flue gas is cooled to 23℃. After gas-liquid separation, the dry carbon-lean flue gas is discharged into the ship exhaust, and the separated liquid is returned to the system by the action of the rich liquid pump 105.

[0034] The MEA solvent reacts with the flue gas in the absorption tower 101 to obtain rich solvent, which is accumulated in the flue gas tertiary regenerator 110 at the bottom of the absorption tower 101, and buffers the pumping of the rich liquid pump 105 while being heat-exchanged. The rich liquid pump 105 sends 44℃ rich solvent to the heat recovery condenser 104 for secondary preheating, and the temperature rises to 55℃. Then, the temperature rises to 60℃ under the tertiary preheating of the flue gas secondary regenerator 107. The temperature rises to 104℃ in the lean and rich liquid regenerator 108, and then enters the middle inlet of the desorption tower 102. The packing section of the desorption tower 102 (i.e. the CO2 regeneration zone) and the steam heat exchange raise the temperature to 115℃. When the rich solvent is desorbed at this temperature, a large amount of CO2 is regenerated, and the rich solvent enters the integrated reboiler 103. Due to sufficient heat, the rich solvent will be desorbed again, and the rich solvent is converted into lean solvent in this process. The lean liquid pump 106 pumps the 117℃ lean solvent in the integrated reboiler 103 to the lean and rich liquid regenerator 108, and transfers heat to the rich solvent, and the lean solvent is cooled to 65℃. Then the lean solvent is sent to the top side inlet of the absorption tower 101 and sprayed in the absorption tower 101. This process realizes the process of transporting CO2 from the flue gas to an independent space. The efficient use of multiple spaces and heat makes the system more compact, the energy utilization rate is higher, and the demand for external heat is smaller.

[0035] The regenerated CO2 and the steam which is not exchanged heat enter the heat recovery condenser 104 together in the packing section of the desorption tower 102. The mixed gas is cooled to 45℃ in this area, most of the steam condensate falls into the collector of the heat recovery condenser 104, and is guided into the CO2 gas-liquid separator 202. The remaining gas is further cooled in the CO2 condenser 201 to separate the residual moisture. The dry CO2 gas is output from the gas outlet of the CO2 gas-liquid separator 202, and is output under the adjustment of the regulating stop valve 203. The regulating stop valve 203 controls the pressure level in the desorption tower by controlling the pressure drop of the CO2 output. The change of the desorption tower pressure will affect the temperature and yield of the steam, thereby inversely adjusting the heat transfer amount of the regeneration process in the desorption tower. The carbon dioxide passing through the CO2 dryer 204, the low-pressure CO2 storage tank 205 and the CO2 compressor 206 enters the CO2 condenser two 207 under the adjustment of the regulating stop valve 203. The LNG is gasified in the tube side of the CO2 condenser two 207 to generate a large amount of high-grade cold energy. The high-pressure CO2 is cooled and liquefied and output, and is stored in the CO2 liquid storage tank. The low-grade cold energy generated by the gradient utilization of the LNG is used for the steam cooling and condensation in the CO2 condenser one 201. The natural gas after gasification is output from the system, and is further temperature adjusted to be used as a ship fuel.

[0036] The application solves the problems of high energy consumption and the demand for cold energy required for liquefaction by gradient utilization of the cold energy in the LNG gasification process and gradient utilization of the flue gas waste heat to capture CO2 in the ship flue gas. Meanwhile, the co-cavity desorption tower and the absorption tower are designed to greatly reduce the system space occupation, improve the space utilization of the carbon capture system on the ship, and have good technical feasibility and economy.

[0037] The above embodiments are preferred cases of the application and do not limit the protection scope of the application. Various modifications or changes made by those skilled in the art within the scope of the appended claims without creative labor are still within the protection scope of the patent.

Claims

1. A common cavity carbon capture system for an LNG carrier, characterized by; The carbon capture system comprises, a carbon capture unit comprising, a desorption tower, the inside of which has an integrated reboiler and a heat recovery condenser vertically upward along the inside thereof; and the inside of the desorption tower further has a CO2 regeneration zone, which is located between the integrated reboiler and the heat recovery condenser; a CO2 post-treatment unit comprising, a CO2 condenser one and a CO2 condenser two, the tube side outlet of which is connected to the cold side inlet of the CO2 condenser two, and the cold source of the CO2 condenser one is an LNG cold source, and the hot side inlet of the CO2 condenser two is connected to the inside of the desorption tower through the tower top of the desorption tower, for providing the released cold energy in the LNG gasification process to the CO2 liquefaction; a ship flue gas outlet is connected to the inlet of the outer layer high-efficiency heat exchange pipeline in the integrated reboiler; the outlet of the outer layer high-efficiency heat exchange pipeline is connected to the hot side inlet of the flue gas secondary regenerator; the integrated reboiler further comprises an inner layer heat exchange pipeline, which is connected to the steam generator on the ship; the hot side outlet of the flue gas secondary regenerator is connected to external equipment one; the cold side inlet of the flue gas secondary regenerator is connected to the outlet of the heat recovery condenser; the inlet of the heat recovery condenser is connected to external equipment two; the cold side outlet of the flue gas secondary regenerator is connected to the inlet of the lean-rich liquid regenerator; the outlet of the lean-rich liquid regenerator is connected to the sidewall of the desorption tower, and the connection is located between the lower end of the heat recovery condenser and the upper end of the CO2 regeneration zone, so as to embed the position for utilizing the flue gas waste heat into the lower half of the desorption tower, so as to improve the preheating utilization efficiency and reduce the space occupation.

2. A co-cavity carbon capture system for an LNG carrier according to claim 1, characterized in that: The outer layer high-efficiency heat exchange pipeline and the inner layer heat exchange pipeline are in a coil structure, and the outer layer high-efficiency heat exchange pipeline and the inner layer heat exchange pipeline are coiled together.

3. The common cavity type carbon capture system for an LNG ship according to claim 2, characterized in that: the inlet of the inner layer heat exchange pipeline is connected to the steam generator on the ship, and the steam generator is used to supplement the insufficient flue gas heat; and the outlet of the inner layer heat exchange pipeline is connected to the water return port of the steam generator.

4. The common cavity type carbon capture system for an LNG ship according to claim 3, characterized in that: the area between the coils of the outer layer high-efficiency heat exchange pipeline and the inner layer heat exchange pipeline and the tower wall of the desorption tower is filled with stainless steel wires, for enhancing the heat transfer area and improving the heat transfer efficiency.

5. A co-cavern carbon capture system for an LNG carrier according to claim 4, characterized in that: The area between the coils of the heat recovery condenser and the tower wall of the desorption tower is filled with stainless steel wires, for increasing the heat transfer area of the heat recovery condenser and improving the heat transfer efficiency.

6. A co-cavern carbon capture system for an LNG carrier according to claim 5, characterized in that: The carbon capture system further comprises, an absorption tower, a rich liquid pump, a lean liquid pump, a flue gas cooler, and a flue gas tertiary regenerator; wherein the flue gas cooler is external equipment one, the hot side outlet of the flue gas secondary regenerator is connected to the inlet of the flue gas cooler, the outlet of the flue gas cooler is connected to the inlet of the flue gas tertiary regenerator, the outlet of the flue gas tertiary regenerator is upward and located in the inside of the absorption tower, and the inside bottom of the absorption tower is connected to the inlet of the rich liquid pump. The rich liquid pump is an external device two, the outlet of the rich liquid pump is connected with the inlet of the heat recovery condenser through the upper end of the sidewall of the desorption tower; the liquid outlet at the bottom of the desorption tower is connected with the inlet of the lean liquid pump; the outlet of the lean liquid pump is connected with the hot side inlet of the lean-rich liquid regenerator; the hot side outlet of the lean-rich liquid regenerator is connected with the side inlet at the top of the absorption tower.

7. A co-cavity carbon capture system for an LNG carrier according to claim 6, characterized in that: The third-stage flue gas regenerator is located at the bottom of the absorption tower.

8. A co-cavity carbon capture system for an LNG carrier according to claim 7, characterized in that: The CO2 post-processing unit further comprises a CO2 gas-liquid separator, an adjusting stop valve, a CO2 dryer, a low-pressure CO2 storage tank and a CO2 compressor. The outlet at the middle section of the desorption tower is connected with the liquid inlet of the CO2 gas-liquid separator; the gas outlet at the top of the desorption tower is connected with the hot side inlet of the CO2 condenser two; the hot side outlet of the CO2 condenser two is connected with the inlet of the CO2 gas-liquid separator; the liquid outlet of the CO2 gas-liquid separator is connected with the inlet of the lean liquid pump; the gas outlet of the CO2 gas-liquid separator is connected with the inlet of the adjusting stop valve; the outlet of the adjusting stop valve is connected with the inlet of the CO2 dryer; the outlet of the CO2 dryer is connected with the inlet of the low-pressure CO2 storage tank; the outlet of the low-pressure CO2 storage tank is connected with the inlet of the CO2 compressor; the outlet of the CO2 compressor is connected with the shell side inlet of the CO2 condenser one; the shell side outlet of the CO2 condenser one is connected with the CO2 liquid storage tank; and the cold side outlet of the CO2 condenser two is connected with the subsequent natural gas pipeline.

9. A co-cavity carbon capture system for an LNG carrier according to claim 8, characterized in that: The carbon capture system further comprises a flue gas post-processing unit, which comprises a lean carbon flue gas condenser and a lean carbon flue gas gas-liquid separator. The inlet of the lean carbon flue gas condenser is connected with the outlet at the top of the absorption tower; the hot side outlet of the lean carbon flue gas condenser is connected with the inlet of the lean carbon flue gas gas-liquid separator; the liquid outlet of the lean carbon flue gas gas-liquid separator is connected with the inlet of the rich liquid pump; and the gas outlet of the lean carbon flue gas gas-liquid separator is connected with the flue gas pipeline of the ship; and the cold side inlet of the lean carbon flue gas condenser is connected with the seawater for cooling.

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