Waste heat recovery system, carbon dioxide trapping device and ship

Abstract

The invention relates to the technical field of carbon dioxide capture, and discloses a waste heat recovery system which comprises a flue gas waste heat utilization channel, a flue gas heat exchanger, a carbon dioxide desorption unit, an intermediate circulation unit and a waste heat recovery unit. The carbon dioxide desorption unit is connected with the flue gas heat exchanger, the intermediate circulation unit and the waste heat recovery unit, and the intermediate circulation unit is connected with the flue gas heat exchanger and the waste heat recovery unit. Flue gas in the flue gas waste heat utilization channel exchanges heat with the carbon dioxide desorption unit and the intermediate circulation unit through a flue gas heat exchanger. According to the waste heat recycling system, secondary recycling is conducted on waste heat in smoke, waste heat of barren liquor obtained after desorption is also recycled, energy recycling of the system is achieved, energy consumption of the system is reduced, and the invention further discloses a carbon dioxide trapping device and a ship.

Description

Technical Field

[0001] The present application relates to the technical field of carbon dioxide capture, and in particular to a waste heat recovery system, a carbon dioxide capture device and a ship. Background Art

[0002] As the greenhouse effect becomes increasingly serious, a wave of carbon emission reduction has been set off around the world. In the shipping sector, in order to reduce carbon emissions, the 2023 IMO Ship Greenhouse Gas (GHG) Emission Reduction Strategy was adopted at the 80th meeting of MEPC in 2023. The strategy proposes that the greenhouse gas emissions of the shipping industry will be reduced by 20% by 2030 compared with 2008, by 70% by 2040, and by 2050 to achieve the goal of net zero emissions.

[0003] At present, the amine method of carbon dioxide capture technology is one of the most widely used carbon dioxide capture technologies. The amine method of carbon dioxide capture technology is a method of separating carbon dioxide from flue gas by chemically reacting amine solution with carbon dioxide. In this process, the amine solution plays a role in absorbing and separating carbon dioxide. Generally speaking, the amine solution can convert carbon dioxide into carbonate compounds by absorbing carbon dioxide, and then release carbon dioxide from the solution by heating or decompression to achieve carbon dioxide capture and recovery. The existing amine method of carbon dioxide capture technology still has the disadvantage of high energy consumption. In the traditional CO2 desorption process, a large amount of heat input is required to generate high-temperature steam. High-temperature steam is used for CO2 desorption reaction. It is usually necessary to set up additional heating boilers and other devices to provide high-temperature steam. At the same time, the flue gas generated by the ship after decarbonization treatment still has a large amount of waste heat, but it is directly discharged into the air. This not only leads to large heat loss, making the overall energy consumption of the CO2 capture system high, but also causes a large amount of waste heat to be wasted. Summary of the invention

[0004] In order to solve the above-mentioned problems, the present invention provides a waste heat recovery system, a carbon dioxide capture device and a ship, which not only recycle the waste heat in the flue gas for secondary utilization, but also recover the waste heat of the lean liquid after desorption, thereby realizing the energy recycling of the system and reducing the energy consumption of the system.

[0005] The present invention provides a waste heat recovery system for a carbon dioxide capture device, comprising: a flue gas waste heat utilization channel, a flue gas heat exchanger, a carbon dioxide desorption unit, an intermediate circulation unit and a waste heat recovery unit, wherein the flue gas heat exchanger is arranged on the flue gas waste heat utilization channel, the carbon dioxide desorption unit is used to desorb the rich liquid from the carbon dioxide absorption unit of the carbon dioxide capture device and send part of the produced lean liquid to the carbon dioxide absorption unit and the produced carbon dioxide to the carbon dioxide recovery unit of the carbon dioxide capture device, the carbon dioxide desorption unit is respectively connected to the flue gas heat exchanger, the intermediate circulation unit and the waste heat recovery unit. The intermediate circulation unit is connected with the waste heat recovery unit, the intermediate circulation unit is used to cool the flue gas heat exchanger and preheat the lean liquid before desorption of the carbon dioxide desorption unit through circulating water, the intermediate circulation unit is respectively connected with the flue gas heat exchanger and the waste heat recovery unit, the waste heat recovery unit is used to exchange heat between the lean liquid after desorption of the carbon dioxide desorption unit and the circulating water of the intermediate circulation unit, and the flue gas in the flue gas waste heat utilization channel exchanges heat with the carbon dioxide desorption unit and the intermediate circulation unit respectively through the flue gas heat exchanger.

[0006] In one embodiment, the carbon dioxide desorption unit includes a desorption tower, a reboiler and a lean liquid pump. The desorption tower is used to desorb the rich liquid and send part of the produced lean liquid to the carbon dioxide absorption unit and the produced carbon dioxide to the carbon dioxide recovery unit. The first lean liquid outlet of the desorption tower is connected to the heat exchange inlet of the flue gas heat exchanger through a channel, the lean liquid inlet of the desorption tower is connected to the heat exchange outlet of the flue gas heat exchanger through a channel, the lean liquid inlet of the reboiler is connected to the first lean liquid outlet of the desorption tower through a channel, the lean liquid outlet of the reboiler is connected to the lean liquid inlet of the desorption tower through a channel, the reboiler is connected to the intermediate circulation unit, the desorption tower is connected to the waste heat recovery unit, and the lean liquid pump is arranged in the channel between the first lean liquid outlet of the desorption tower and the heat exchange inlet of the flue gas heat exchanger.

[0007] In one embodiment, the desorption tower includes a spray device for spraying the rich liquid, the spray device is connected to the carbon dioxide absorption unit, the top of the desorption tower is provided with a carbon dioxide outlet connected to the carbon dioxide recovery unit, and the desorption tower is also provided with a second lean liquid outlet for connecting to the carbon dioxide absorption unit. In one embodiment, the intermediate circulation unit includes a circulating water tank storing circulating water, a steam buffer tank for preheating the lean liquid of the desorption tower before desorption, a circulating water pump and a gas-liquid separator, the heat exchange outlet of the flue gas heat exchanger is connected to the inlet of the gas-liquid separator through a channel, the outlet of the gas-liquid separator is respectively connected to the inlet of the circulating water tank and the inlet of the steam buffer tank, the outlet of the circulating water tank is connected to the heat exchange inlet of the flue gas heat exchanger through a channel, the outlet of the steam buffer tank is connected to the circulating water inlet of the reboiler through a channel, the circulating water outlet of the reboiler is connected to the inlet of the circulating water tank through a channel, the circulating water tank is connected to the waste heat recovery unit, and the circulating water pump is arranged in the channel between the outlet of the circulating water tank and the heat exchange inlet of the flue gas heat exchanger.

[0008] In one embodiment, the waste heat recovery unit includes a preheater for performing heat exchange between the desorbed lean liquid of the desorber and the circulating water in the circulating water tank, the lean liquid inlet of the preheater is connected to the first lean liquid outlet of the desorber via a channel, the lean liquid outlet of the preheater is connected to the lean liquid inlet of the desorber via a channel, the circulating water inlet of the preheater is connected to the outlet of the circulating water tank via a channel, and the circulating water outlet of the preheater is connected to the channel between the outlet of the circulating water tank and the heat exchange inlet of the flue gas heat exchanger.

[0009] In one embodiment, the carbon dioxide desorption unit further includes a first lean liquid supply valve, a second lean liquid supply valve and a lean liquid reflux valve, the first lean liquid supply valve being arranged in the channel between the first lean liquid outlet of the desorption tower and the heat exchange inlet of the flue gas heat exchanger, the second lean liquid supply valve being arranged in the channel between the lean liquid inlet of the reboiler and the first lean liquid outlet of the desorption tower, and the lean liquid reflux valve being arranged in the channel between the lean liquid inlet of the desorption tower and the heat exchange outlet of the flue gas heat exchanger.

[0010] In one embodiment, the intermediate circulation unit also includes a circulating water regulating valve, a circulating water reflux valve and a steam regulating valve. The circulating water regulating valve is arranged in the channel between the outlet of the circulating water tank and the heat exchange inlet of the flue gas heat exchanger, the circulating water reflux valve is arranged in the channel between the heat exchange outlet of the flue gas heat exchanger and the inlet of the gas-liquid separator, and the steam regulating valve is arranged in the channel between the outlet of the steam buffer tank and the circulating water inlet of the reboiler.

[0011] In one embodiment, the waste heat recovery unit also includes a third lean liquid supply valve and a circulating water supply valve, the third lean liquid supply valve is arranged in the channel between the lean liquid inlet of the preheater and the first lean liquid outlet of the desorption tower, and the circulating water supply valve is arranged in the channel between the circulating water inlet of the preheater and the outlet of the circulating water tank.

[0012] In one embodiment, the flue gas heat exchanger includes a smoke interface, a bellows expansion joint and a limiter arranged at both ends of the smoke gas heat exchanger. The bellows expansion joint is arranged on the smoke interface at the top of the smoke gas heat exchanger. The limiter is used to limit the movement of the bellows expansion joint. The flue gas waste heat utilization channel is connected to the smoke interfaces at both ends of the smoke gas heat exchanger.

[0013] In one embodiment, the flue gas heat exchanger includes a plurality of heat exchange plates arranged inside the flue gas heat exchanger and a flue gas flow channel formed by gaps between adjacent heat exchange plates, the flue gas flow channel is connected to the flue gas interfaces at both ends of the flue gas heat exchanger, and a heat exchange flow channel is provided in the heat exchange plate, and the heat exchange flow channel is connected to the heat exchange inlet and the heat exchange outlet of the flue gas heat exchanger.

[0014] In one embodiment, the thickness L of the flue gas flow channel and the volume V of the heat exchange plate satisfy: L:V=0.000008mm -2 ~0.000015mm -2 .

[0015] Another embodiment of the present application further provides a carbon dioxide capture device, including a carbon dioxide absorption unit, a carbon dioxide recovery unit and the above-mentioned waste heat recovery system, wherein the carbon dioxide desorption unit is connected to the carbon dioxide absorption unit and the carbon dioxide recovery unit respectively.

[0016] Another embodiment of the present application further provides a ship, comprising the above-mentioned carbon dioxide capture device.

[0017] The beneficial effects of the present invention are as follows: the flue gas in the flue gas waste heat utilization channel exchanges heat with the carbon dioxide desorption unit through the flue gas heat exchanger, providing thermal energy for the carbon dioxide desorption unit to desorb carbon dioxide; the flue gas exchanges heat with the circulating water in the intermediate circulation unit through the flue gas heat exchanger, on the one hand, the flue gas heat exchanger is cooled, and on the other hand, the stored heat is used to preheat the lean liquid before desorption of the carbon dioxide desorption unit, not only the waste heat in the flue gas is recycled for a second time, but also the waste heat of the lean liquid after desorption is recycled, thereby realizing the energy recycling of the system and reducing the energy consumption of the system, and at the same time making the temperature of the flue gas heat exchanger after cooling down basically consistent with the temperature of the lean liquid after preheating, thereby preventing the temperature difference from being too large when the flue gas exchanges heat with the carbon dioxide desorption unit through the flue gas heat exchanger, causing the flue gas heat exchanger to age and fail rapidly, which is beneficial to the stability and safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a schematic structural diagram of a waste heat recovery system for a carbon dioxide capture device according to an embodiment of the present invention.

[0020] Figure 2 It is a schematic structural diagram of a flue gas heat exchanger according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the description of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connection" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0023] The directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front”, “back”, “top”, “bottom”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of description and simplified description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0024] The terms "first", "second", "third" and the like are merely used to distinguish elements of similar nature, and do not indicate or imply relative importance or a particular order.

[0025] The terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of the elements listed and may also include additional elements not expressly listed.

[0026] Please refer to Figure 1-2, which shows a waste heat recovery system for a carbon dioxide capture device provided in an embodiment of the present invention, comprising: a flue gas waste heat utilization channel 1, a flue gas heat exchanger 2, a carbon dioxide desorption unit 3, an intermediate circulation unit 4 and a waste heat recovery unit 5, the flue gas heat exchanger 2 is arranged on the flue gas waste heat utilization channel 1, the carbon dioxide desorption unit 3 is used to desorb the rich liquid from the carbon dioxide absorption unit of the carbon dioxide capture device and send part of the produced lean liquid to the carbon dioxide absorption unit and the produced carbon dioxide to the carbon dioxide recovery unit of the carbon dioxide capture device, the carbon dioxide desorption unit 3 They are respectively connected to the flue gas heat exchanger 2, the intermediate circulation unit 4 and the waste heat recovery unit 5. The intermediate circulation unit 4 is used to cool the flue gas heat exchanger 2 and preheat the lean liquid before desorption of the carbon dioxide desorption unit 3 through circulating water. The intermediate circulation unit 4 is respectively connected to the flue gas heat exchanger 2 and the waste heat recovery unit 5. The waste heat recovery unit 5 is used to exchange heat between the lean liquid after desorption of the carbon dioxide desorption unit 3 and the circulating water of the intermediate circulation unit 4. The flue gas waste heat utilization channel 1 exchanges heat with the carbon dioxide desorption unit 3 and the intermediate circulation unit 4 through the flue gas heat exchanger 2.

[0027] like Figure 1 As shown, in this embodiment, the rich liquid is an alcohol amine solution that absorbs carbon dioxide, the lean liquid is an alcohol amine solution that does not absorb carbon dioxide, and the flue gas in the flue gas waste heat utilization channel 1 is the high-temperature exhaust gas generated by the ship engine obtained by cooling pretreatment.

[0028] First, the circulating water in the intermediate circulation unit 4 is controlled to exchange heat with the flue gas through the flue gas heat exchanger 2, so that part of the waste heat is stored in the form of water vapor, and at the same time the temperature of the flue gas heat exchanger 2 is reduced to a preset temperature, and the water vapor stored in the intermediate circulation unit 4 preheats the lean liquid before desorption of the carbon dioxide desorption unit 3 until it reaches the preset temperature; then the carbon dioxide capture device is switched to the operating state, and the preheated lean liquid before desorption exchanges heat with the flue gas through the flue gas heat exchanger 2. The temperature difference between the temperature of the flue gas heat exchanger 2 and the temperature of the preheated lean liquid before desorption is small, which effectively protects the flue gas heat exchanger 2 and prevents its aging, and is beneficial to the stability and safety of the system. The high-temperature lean liquid after the heat exchange reacts with the rich liquid from the carbon dioxide absorption unit of the carbon dioxide capture device to produce the desorbed lean liquid and carbon dioxide, and the carbon dioxide is sent to the carbon dioxide recovery unit of the carbon dioxide capture device. The unit is used for recovery, and the lean liquid after desorption still has waste heat. A part of the lean liquid after desorption enters the waste heat recovery unit 5 to exchange heat with the circulating water of the intermediate circulation unit 4 (preheating) to recover the waste heat of the lean liquid after desorption, and the other part is sent to the carbon dioxide absorption unit for subsequent carbon dioxide absorption, and the preheated circulating water enters again through the flue gas heat exchanger 2 to exchange heat with the flue gas, preparing for the carbon dioxide capture device to be switched to the off state; the carbon dioxide capture device is switched to the off state, and the circulating water in the intermediate circulation unit 4 is controlled to exchange heat with the flue gas through the flue gas heat exchanger 2, so that part of the waste heat is stored in the form of water vapor, and at the same time, the temperature of the flue gas heat exchanger 2 is reduced to a preset temperature, and the water vapor stored in the intermediate circulation unit 4 preheats the lean liquid before desorption of the carbon dioxide desorption unit 3 until it reaches the preset temperature, preparing for the carbon dioxide capture device to be switched to the operating state.

[0029] The flue gas in the flue gas waste heat utilization channel 1 exchanges heat with the carbon dioxide desorption unit 3 through the flue gas heat exchanger 2, providing thermal energy for the carbon dioxide desorption unit 3 to desorb carbon dioxide. The flue gas exchanges heat with the circulating water in the intermediate circulation unit 4 through the flue gas heat exchanger 2. On the one hand, the flue gas heat exchanger 2 is cooled, and on the other hand, the stored heat is used to preheat the lean liquid before desorption of the carbon dioxide desorption unit 3. Not only is the waste heat in the flue gas recycled for a second time, but the waste heat of the lean liquid after desorption is also recycled through the waste heat recovery unit 5, realizing the energy recycling of the system and reducing the energy consumption of the system. At the same time, the temperature of the flue gas heat exchanger 2 after cooling is basically consistent with the temperature of the lean liquid after preheating, preventing the temperature difference from being too large when the flue gas exchanges heat with the carbon dioxide desorption unit 3 through the flue gas heat exchanger 2, causing the flue gas heat exchanger to accelerate aging and failure, which is beneficial to the stability and safety of the system.

[0030] Since the flue gas always passes through the flue gas heat exchanger 1 when the ship is sailing, and only one flue gas heat exchanger 1 is used for multiple heat exchanges in the present invention, when the carbon dioxide capture device is turned on, there is not only a risk of hot start, but also the flue gas heat exchanger 1 is easily damaged by thermal aging due to the temperature difference, which may lead to a safety accident in serious cases. The intermediate circulation unit 4 is used to preheat the lean liquid before desorption in the carbon dioxide desorption unit 3, and the flue gas heat exchanger 1 is cooled simultaneously, gradually transitioning to a suitable temperature, and then the carbon dioxide capture device is started; before the carbon dioxide capture device is shut down, the waste heat recovery unit 5 is used to preheat the circulating water of the intermediate circulation unit 4 with the waste heat of the lean liquid after desorption, and gradually transitioning to a suitable temperature before switching to the closed state of the carbon dioxide capture device. In this way, the problem of equipment instability and shutdown or damage caused by frequent start and stop of the carbon dioxide capture device when the ship is docked or leaving the port can be solved, and at the same time, the flue gas heat exchanger 1 is protected, its service life is increased, and the overall stability of the system and the safety of the equipment are improved.

[0031] In one embodiment, the carbon dioxide desorption unit 3 includes a desorption tower 31, a reboiler 32 and a lean liquid pump 33. The desorption tower 31 is used to desorb the rich liquid and send part of the produced lean liquid to the carbon dioxide absorption unit and the produced carbon dioxide to the carbon dioxide recovery unit. The first lean liquid outlet 312 of the desorption tower 31 is connected to the heat exchange inlet 26 of the flue gas heat exchanger 2 through a channel, the lean liquid inlet of the desorption tower 31 is connected to the heat exchange outlet of the flue gas heat exchanger 2 through a channel, the lean liquid inlet of the reboiler 32 is connected to the first lean liquid outlet 312 of the desorption tower 31 through a channel, the lean liquid outlet of the reboiler 32 is connected to the lean liquid inlet of the desorption tower 31 through a channel, the reboiler 32 is connected to the intermediate circulation unit 4, the desorption tower 31 is connected to the waste heat recovery unit 5, and the lean liquid pump 33 is arranged in the channel between the first lean liquid outlet 312 of the desorption tower 31 and the heat exchange inlet 26 of the flue gas heat exchanger 2.

[0032] like Figure 1-Figure 2As shown, in this embodiment, before switching to the carbon dioxide capture device on state, the lean liquid in the desorption tower 31 enters the lean liquid inlet of the reboiler 32 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33 to be preheated with the circulating water in the intermediate circulation unit 4, and the lean liquid after preheating flows from the lean liquid outlet of the reboiler 32 through the lean liquid inlet of the desorption tower 31 into the desorption tower 31 until it is preheated to a preset temperature and then stops preheating, switches to the carbon dioxide capture device on state, and the preheated lean liquid enters the heat exchange inlet 26 of the flue gas heat exchanger 2 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33. Heat exchange is carried out, and the heated lean liquid returns to the desorption tower 31 through the heat exchange outlet of the flue gas heat exchanger 2 and the lean liquid inlet of the desorption tower 31 to undergo desorption reaction with the rich liquid to produce desorbed lean liquid and carbon dioxide. Part of the desorbed lean liquid enters the carbon dioxide absorption unit, and the carbon dioxide enters the carbon dioxide recovery unit. After desorption is completed, part of the desorbed lean liquid enters the waste heat recovery unit 5 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33 for heat exchange, and the circulating water in the intermediate circulation unit 4 is preheated, thereby realizing the recovery and utilization of the waste heat of the desorbed lean liquid, reducing energy consumption, and realizing the energy recycling of the system.

[0033] In one embodiment, the desorption tower 31 includes a spray device 311 for spraying rich liquid, the spray device 311 is connected to the carbon dioxide absorption unit, and a carbon dioxide outlet connected to the carbon dioxide recovery unit is provided at the top of the desorption tower 31. The desorption tower 31 is also provided with a second lean liquid outlet 313 for connecting to the carbon dioxide absorption unit. like Figure 1-Figure 2 As shown, in this embodiment, the spray device 311 is arranged at the top of the desorption tower 31, and the rich liquid is evenly sprayed in the desorption tower 31 through the spray device 311, so as to promote the desorption reaction, and the carbon dioxide generated after desorption enters the carbon dioxide recovery unit through the carbon dioxide outlet for recycling, and part of the lean liquid after desorption enters the carbon dioxide absorption unit from the second lean liquid outlet 313, so as to realize recycling.

[0034] In one embodiment, the intermediate circulation unit 4 includes a circulating water tank 41 storing circulating water, a steam buffer tank 42 for preheating the lean liquid of the desorption tower 31 before desorption, a circulating water pump 43 and a gas-liquid separator 46, the heat exchange outlet of the flue gas heat exchanger 2 is connected to the inlet of the gas-liquid separator 46 through a channel, the outlet of the gas-liquid separator 46 is respectively connected to the inlet of the circulating water tank 41 and the inlet of the steam buffer tank 42, the outlet of the circulating water tank 41 is connected to the heat exchange inlet 26 of the flue gas heat exchanger 2 through a channel, the outlet of the steam buffer tank 42 is connected to the circulating water inlet of the reboiler 32 through a channel, the circulating water outlet of the reboiler 32 is connected to the inlet of the circulating water tank 41 through a channel, the circulating water tank 41 is connected to the waste heat recovery unit 5, and the circulating water pump 43 is arranged in the channel between the outlet of the circulating water tank 41 and the heat exchange inlet 26 of the flue gas heat exchanger 2.

[0035] like Figure 1-Figure 2 As shown, in this embodiment, when the carbon dioxide capture device is closed, the circulating water in the circulating water tank 41 enters the flue gas heat exchanger 2 from the outlet of the circulating water tank 41 to the heat exchange inlet 26 of the flue gas heat exchanger 2 through the circulating water pump 43 to exchange heat with the flue gas. After the heat exchange, the circulating water is in a gas-liquid coexistence state. The gas-liquid coexistence circulating water enters the gas-liquid separator 46 from the heat exchange outlet of the flue gas heat exchanger 2 for diversion, so that the liquid circulating water flows into the circulating water tank 41 and the water vapor enters the steam buffer tank 42 for storage. Before the carbon dioxide capture device is turned on, the circulating water enters the flue gas heat exchanger 2 to continue to exchange heat with the flue gas, and the temperature of the flue gas heat exchanger 2 is reduced to a preset temperature. The stored water vapor and the newly generated water vapor are discharged from the outlet of the steam buffer tank 42 through the recirculation. The circulating water inlet of the boiler 32 enters the reboiler 32 to preheat the lean liquid until it is preheated to a preset temperature. The generated liquid circulating water returns to the circulating water tank 41 from the circulating water outlet of the reboiler 32 through the inlet of the circulating water tank 41 for recycling. Before the carbon dioxide capture device is shut down, the circulating water in the circulating water tank 41 exchanges heat with the desorbed lean liquid through the waste heat recovery unit 5. The preheated circulating water then enters the flue gas heat exchanger 2, gradually transitions to a suitable temperature, and then switches to the closed state of the carbon dioxide capture device. By using the waste heat of the circulating water, not only the waste heat of the lean liquid after desorption is recovered, but also the damage to the flue gas heat exchanger 2 caused by the excessive temperature difference between the circulating water and the flue gas heat exchanger 2 is avoided, thereby improving the service life of the flue gas heat exchanger 2 and further ensuring the stability and safety of the system.

[0036] In one embodiment, a detector for detecting the content of alcohol amine is provided in the circulating water tank 41 .

[0037] When the carbon dioxide capture device is started and stopped for a certain number of times, a detector is used to detect and determine whether the alcohol amine content in the circulating water tank exceeds the standard. If it exceeds the standard, the circulating water in the circulating water tank needs to be replaced. The original excessive circulating water in the circulating water tank is introduced into the desorption tower 31, and high-purity alcohol amine is added for mixing to make up for the loss, which is used for the circulation of alcohol amine solution inside the carbon dioxide capture device.

[0038] In one embodiment, the waste heat recovery unit 5 includes a preheater 51 for performing heat exchange between the desorbed lean liquid of the desorber 31 and the circulating water in the circulating water tank 41, the lean liquid inlet of the preheater 51 is connected to the first lean liquid outlet 312 of the desorber 31 via a channel, the lean liquid outlet of the preheater 51 is connected to the lean liquid inlet of the desorber 31 via a channel, the circulating water inlet of the preheater 51 is connected to the outlet of the circulating water tank 41 via a channel, and the circulating water outlet of the preheater 51 is connected to the channel between the outlet of the circulating water tank 41 and the heat exchange inlet 26 of the flue gas heat exchanger 2.

[0039] like Figure 1-Figure 2 As shown, the waste heat of the desorbed lean liquid is recovered through the preheater 51, so that the energy recycling of the system is realized and the energy consumption of the system is reduced.

[0040] In one embodiment, the carbon dioxide desorption unit 3 also includes a first lean liquid supply valve 34, a second lean liquid supply valve 35 and a lean liquid reflux valve 36. The first lean liquid supply valve 34 is arranged in the channel between the first lean liquid outlet 312 of the desorption tower 31 and the heat exchange inlet 26 of the flue gas heat exchanger 2, the second lean liquid supply valve 35 is arranged in the channel between the lean liquid inlet of the reboiler 32 and the first lean liquid outlet 312 of the desorption tower 31, and the lean liquid reflux valve 36 is arranged in the channel between the lean liquid inlet of the desorption tower 31 and the heat exchange outlet of the flue gas heat exchanger 2.

[0041] like Figure 1-Figure 2 As shown, in the present embodiment, the first lean liquid supply valve 34 is used to control the openness of the channel between the first lean liquid outlet 312 of the desorption tower 31 and the heat exchange inlet 26 of the flue gas heat exchanger 2, the second lean liquid supply valve 35 is used to control the openness of the channel between the lean liquid inlet of the reboiler 32 and the first lean liquid outlet 312 of the desorption tower 31, and the lean liquid reflux valve 36 is used to control the openness of the channel between the lean liquid inlet of the desorption tower 31 and the heat exchange outlet of the flue gas heat exchanger 2.

[0042] In one embodiment, the intermediate circulation unit 4 also includes a circulating water regulating valve 44, a circulating water reflux valve 45 and a steam regulating valve 47. The circulating water regulating valve 44 is arranged in the channel between the outlet of the circulating water tank 41 and the heat exchange inlet 26 of the flue gas heat exchanger 2, the circulating water reflux valve 45 is arranged in the channel between the heat exchange outlet of the flue gas heat exchanger 2 and the inlet of the gas-liquid separator 46, and the steam regulating valve 47 is arranged in the channel between the outlet of the steam buffer tank 42 and the circulating water inlet of the reboiler 32.

[0043] like Figure 1-Figure 2 As shown, in the present embodiment, the circulating water regulating valve 44 is used to control the flow rate of circulating water in the channel between the outlet of the circulating water tank 41 and the heat exchange inlet 26 of the flue gas heat exchanger 2, so as to control the cooling of the flue gas heat exchanger 2 to a preset temperature, the circulating water reflux valve 45 is used to control the on-off of the channel between the heat exchange outlet of the flue gas heat exchanger 2 and the inlet of the gas-liquid separator 46, and the steam regulating valve 47 is used to control the water vapor flow rate in the channel between the outlet of the steam buffer tank 42 and the circulating water inlet of the reboiler 32, so as to adjust the preheating of the lean liquid.

[0044] In one embodiment, the waste heat recovery unit 5 also includes a third lean liquid supply valve 52 and a circulating water supply valve 53. The third lean liquid supply valve 52 is arranged in the channel between the lean liquid inlet of the preheater 51 and the first lean liquid outlet 312 of the desorption tower 31, and the circulating water supply valve 53 is arranged in the channel between the circulating water inlet of the preheater 51 and the outlet of the circulating water tank 41.

[0045] like Figure 1 As shown, in this embodiment, the third lean liquid supply valve 52 is used to control the openness of the channel between the lean liquid inlet of the preheater 51 and the first lean liquid outlet 312 of the desorption tower 31, and the circulating water supply valve 53 is used to control the openness of the channel between the circulating water inlet of the preheater 51 and the outlet of the circulating water tank 41.

[0046] In one embodiment, the flue gas heat exchanger 2 includes a flue gas interface 23, a bellows expansion joint 21 and a limiter 22 arranged at both ends of the flue gas heat exchanger 2. The bellows expansion joint 21 is arranged on the flue gas interface 23 at the top of the flue gas heat exchanger 2. The limiter 22 is used to limit the movement of the bellows expansion joint 21. The flue gas waste heat utilization channel 1 is connected to the flue gas interface 23 at both ends of the flue gas heat exchanger 2.

[0047] like Figure 2 As shown, in this embodiment, by setting the bellows expansion joint 21 and the limiter 22, the problem of insufficient space on the ship and inability to set up bypass waste heat recovery is solved, while at the same time, the accelerated failure of the flue gas heat exchanger 2 due to high-temperature expansion and the impact of the ship's shaking on the flue gas heat exchanger 2 are avoided.

[0048] In one embodiment, the flue gas heat exchanger 2 includes a plurality of heat exchange plates 24 arranged inside the flue gas heat exchanger 2 and a flue gas flow channel 25 formed by gaps between adjacent heat exchange plates 24. The flue gas flow channel 25 is connected to the flue gas interfaces 23 at both ends of the flue gas heat exchanger 2. A heat exchange flow channel is provided in the heat exchange plate 24, and the heat exchange flow channel is connected to the heat exchange inlet 26 of the flue gas heat exchanger 2 and the heat exchange outlet of the flue gas heat exchanger 2.

[0049] like Figure 2As shown, in this embodiment, the flue gas in the flue gas waste heat utilization channel 1 passes through the flue gas interface 23 and the flue gas flow channel 25 at the bottom of the flue gas heat exchanger 2 in sequence, and then from the flue gas interface 23 at the top of the flue gas heat exchanger 2, the flue gas exchanges heat with the circulating water or lean liquid in the heat exchange flow channel in the flue gas flow channel 25, thereby recovering the waste heat in the flue gas and reducing energy consumption.

[0050] like Figure 1 As shown, the main working process of the waste heat recovery system of the embodiment of the present invention is as follows: When the carbon dioxide capture device is closed, the circulating water regulating valve 44 and the circulating water reflux valve 45 are opened, the other valves are closed, and the circulating water pump 43 is turned on. The circulating water in the circulating water tank 41 enters the flue gas heat exchanger 2 from the outlet of the circulating water tank 41 through the heat exchange inlet 26 of the flue gas heat exchanger 2 through the circulating water pump 43, and exchanges heat with the flue gas cooled to 185°C~200°C in the flue gas waste heat utilization channel 1, so as to heat and gasify the circulating water. The circulating water regulating valve 44 is adjusted to control the circulating water volume to generate water vapor at 3.5 bar and 140°C. The circulating water with both gas and liquid coexists enters the gas-liquid separator 46 from the heat exchange outlet of the flue gas heat exchanger 2 for diversion, so that the liquid circulating water flows into the circulating water tank 41, and the water vapor enters the steam buffer tank 42 for storage; When the carbon dioxide capture device is ready to switch from the closed state to the open state, the circulating water regulating valve 44 and the circulating water reflux valve 45 are still in the open state, and then the steam regulating valve 47 and the second lean liquid supply valve 35 are opened, and the lean liquid pump 33 is turned on. The lean liquid in the desorption tower 31 enters the lean liquid inlet of the reboiler 32 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33 and is heated by water vapor in the reboiler 32 and flows from the lean liquid outlet of the reboiler 32 through the lean liquid inlet of the desorption tower 31 into the desorption tower 31 for preheating circulation. The circulating water regulating valve 44 is adjusted synchronously until the temperature of the lean liquid rises to 110°C, and the flow rate of the circulating water is increased to control the temperature of the flue gas heat exchanger 2 to drop to 110°C. At this time, there is no temperature difference when switching the working conditions, which plays a good protective role for the flue gas heat exchanger 2 and prolongs its service life. At this time, the circulating water regulating valve 44, the circulating water reflux valve 45, the steam regulating valve 47 and the second lean liquid supply valve 35 are closed, the circulating water pump 43 is shut down, the first lean liquid supply valve 34 and the lean liquid reflux valve 36 are opened, and the carbon dioxide capture device is switched to the open state; When the carbon dioxide capture device is turned on, the first lean liquid supply valve 34 and the lean liquid reflux valve 36 are opened, and the other valves are closed. The lean liquid pump 33 is opened, and the lean liquid preheated to 110°C enters the heat exchange inlet 26 of the flue gas heat exchanger 2 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33 for heat exchange. The generated high-temperature lean liquid returns to the desorption tower 31 through the heat exchange outlet of the flue gas heat exchanger 2 and the lean liquid inlet of the desorption tower 31. The rich liquid from the carbon dioxide absorption unit is sprayed out from the spray device 311 and undergoes desorption reaction with the high-temperature lean liquid. The generated carbon dioxide enters the carbon dioxide recovery unit through the carbon dioxide outlet for recycling, and the generated part of the desorbed lean liquid enters the carbon dioxide absorption unit through the second lean liquid outlet 313, thereby realizing recycling. After desorption is completed, the first lean liquid supply valve 34 and the lean liquid reflux valve 36 are closed; When the carbon dioxide capture device is ready to switch from the open state to the closed state, the first lean liquid supply valve 34 and the lean liquid return valve 36 are closed, the third lean liquid supply valve 52, the circulating water supply valve 53, the circulating water regulating valve 44 and the circulating water return valve 45 are opened, the circulating water pump 43 is turned on, and the circulating water in the circulating water tank 41 enters the preheater 51 from the outlet of the circulating water tank 41 through the circulating water inlet of the preheater 51 through the circulating water pump 43, and the desorbed lean liquid enters the preheater 51 from the first lean liquid outlet 312 of the desorption tower 31 through the lean liquid pump 33. The lean liquid inlet of the preheater 51 exchanges heat with the circulating water to preheat the circulating water and recover the preheated lean liquid after desorption. The preheated circulating water enters the flue gas heat exchanger 2 through the circulating water outlet of the preheater 51, the outlet of the circulating water tank 41 and the channel between the heat exchange inlet 26 of the flue gas heat exchanger 2. The temperature of the flue gas heat exchanger 2 is gradually stabilized by adjusting the circulating water regulating valve 44. After stabilization, the third lean liquid supply valve 52, the circulating water supply valve 53 and the lean liquid pump 33 are closed, and the carbon dioxide capture device is switched to the closed state.

[0051] In one embodiment, the thickness L of the flue gas flow channel 25 and the volume V of the heat exchange plate 24 satisfy: L:V=0.000008mm -2 ~0.000015mm -2 .

[0052] The volume V of the heat exchange plate 24 is the volume of a single heat exchange plate 24. By designing the thickness L of the flue gas flow channel 25 and the volume V of the heat exchange plate 24, the heat exchange efficiency of the flue gas heat exchanger 2 is improved, which is explained below through comparative example 1 and embodiments 1 to 3.

[0053]

[0054] It can be seen from the table that the flue gas heat exchanger provided in the present application improves the heat exchange efficiency and has a better heat exchange effect.

[0055] Another embodiment of the present application further provides a carbon dioxide capture device, including a carbon dioxide absorption unit, a carbon dioxide recovery unit and the above-mentioned waste heat recovery system, and the carbon dioxide desorption unit 3 is connected to the carbon dioxide absorption unit and the carbon dioxide recovery unit respectively.

[0056] The carbon dioxide capture device not only recycles the waste heat of the ship's exhaust gas, but also recovers the waste heat of the lean liquid after desorption, realizing the energy recycling of the system and reducing the energy consumption of the system. At the same time, it solves the unstable factors caused by the frequent start and stop of the carbon dioxide capture device, ensures the safe operation of the equipment, and achieves the goal of efficient energy saving and emission reduction.

[0057] Another embodiment of the present application further provides a ship, comprising the above-mentioned carbon dioxide capture device.

[0058] The ship realizes overall energy recycling, reduces overall energy consumption, and thus reduces operating costs.

[0059] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A waste heat recovery system for a carbon dioxide capture device, characterized in that: include: A flue gas waste heat utilization channel (1), a flue gas heat exchanger (2), a carbon dioxide desorption unit (3), an intermediate circulation unit (4) and a waste heat recovery unit (5), wherein the flue gas heat exchanger (2) is arranged on the flue gas waste heat utilization channel (1), the carbon dioxide desorption unit (3) is used to desorb the rich liquid from the carbon dioxide absorption unit of the carbon dioxide capture device and send part of the produced lean liquid to the carbon dioxide absorption unit and the produced carbon dioxide to the carbon dioxide recovery unit of the carbon dioxide capture device, and the carbon dioxide desorption unit (3) is respectively connected to the flue gas heat exchanger (2), the intermediate circulation unit (4) and the waste heat recovery unit (5). The intermediate circulation unit (4) is used to cool the flue gas heat exchanger (2) and preheat the lean liquid of the carbon dioxide desorption unit (3) before desorption through circulating water. The intermediate circulation unit (4) is connected to the flue gas heat exchanger (2) and the waste heat recovery unit (5) respectively. The waste heat recovery unit (5) is used to perform heat exchange between the lean liquid after desorption of the carbon dioxide desorption unit (3) and the circulating water of the intermediate circulation unit (4). The flue gas in the flue gas waste heat utilization channel (1) is used to perform heat exchange with the carbon dioxide desorption unit (3) and the intermediate circulation unit (4) respectively through the flue gas heat exchanger (2).

2. The waste heat recovery system according to claim 1, characterized in that: The carbon dioxide desorption unit (3) comprises a desorption tower (31), a reboiler (32) and a lean liquid pump (33); the desorption tower (31) is used to desorb the rich liquid and send part of the lean liquid produced to the carbon dioxide absorption unit and send the produced carbon dioxide to the carbon dioxide recovery unit; a first lean liquid outlet (312) of the desorption tower (31) is connected to a heat exchange inlet (26) of the flue gas heat exchanger (2) via a channel; and a lean liquid inlet of the desorption tower (31) is connected to a heat exchange outlet of the flue gas heat exchanger (2) via a channel. The lean liquid inlet of the reboiler (32) is connected to the first lean liquid outlet (312) of the desorption tower (31) through a channel, the lean liquid outlet of the reboiler (32) is connected to the lean liquid inlet of the desorption tower (31) through a channel, the reboiler (32) is connected to the intermediate circulation unit (4), the desorption tower (31) is connected to the waste heat recovery unit (5), and the lean liquid pump (33) is arranged in the channel between the first lean liquid outlet (312) of the desorption tower (31) and the heat exchange inlet (26) of the flue gas heat exchanger (2).

3. The waste heat recovery system according to claim 2, characterized in that: The desorption tower (31) comprises a spray device (311) for spraying the rich liquid, the spray device (311) being connected to the carbon dioxide absorption unit, a carbon dioxide outlet connected to the carbon dioxide recovery unit being provided at the top of the desorption tower (31), and a second lean liquid outlet (313) connected to the carbon dioxide absorption unit being further provided.

4. The waste heat recovery system according to claim 2, characterized in that: The intermediate circulation unit (4) comprises a circulating water tank (41) storing circulating water, a steam buffer tank (42) for preheating lean liquid before desorption of the desorption tower (31), a circulating water pump (43) and a gas-liquid separator (46), the heat exchange outlet of the flue gas heat exchanger (2) and the inlet of the gas-liquid separator (46) being connected via a channel, the outlet of the gas-liquid separator (46) being connected to the inlet of the circulating water tank (41) and the inlet of the steam buffer tank (42), respectively, the outlet of the circulating water tank (41) and the inlet of the steam buffer tank (42) being connected to the inlet of the circulating water tank (41). The outlet is connected to the heat exchange inlet (26) of the flue gas heat exchanger (2) via a channel, the outlet of the steam buffer tank (42) is connected to the circulating water inlet of the reboiler (32) via a channel, the circulating water outlet of the reboiler (32) is connected to the inlet of the circulating water tank (41) via a channel, the circulating water tank (41) is connected to the waste heat recovery unit (5), and the circulating water pump (43) is arranged in the channel between the outlet of the circulating water tank (41) and the heat exchange inlet (26) of the flue gas heat exchanger (2).

5. The waste heat recovery system according to claim 4, characterized in that: The waste heat recovery unit (5) comprises a preheater (51) for performing heat exchange between the desorbed lean liquid of the desorber (31) and the circulating water in the circulating water tank (41); the lean liquid inlet of the preheater (51) is connected to the first lean liquid outlet (312) of the desorber (31) via a channel; the lean liquid outlet of the preheater (51) is connected to the lean liquid inlet of the desorber (31) via a channel; the circulating water inlet of the preheater (51) is connected to the outlet of the circulating water tank (41) via a channel; and the circulating water outlet of the preheater (51) is connected to the outlet of the circulating water tank (41) and the channel between the heat exchange inlet (26) of the flue gas heat exchanger (2).

6. The waste heat recovery system according to claim 5, characterized in that: Include at least one of the following: The carbon dioxide desorption unit (3) further comprises a first lean liquid supply valve (34), a second lean liquid supply valve (35) and a lean liquid reflux valve (36), wherein the first lean liquid supply valve (34) is arranged in a channel between a first lean liquid outlet (312) of the desorption tower (31) and a heat exchange inlet (26) of the flue gas heat exchanger (2), the second lean liquid supply valve (35) is arranged in a channel between a lean liquid inlet of the reboiler (32) and the first lean liquid outlet (312) of the desorption tower (31), and the lean liquid reflux valve (36) is arranged in a channel between a lean liquid inlet of the desorption tower (31) and a heat exchange outlet of the flue gas heat exchanger (2); The intermediate circulation unit (4) further comprises a circulating water regulating valve (44), a circulating water reflux valve (45) and a steam regulating valve (47); the circulating water regulating valve (44) is arranged in a channel between an outlet of the circulating water tank (41) and a heat exchange inlet (26) of the flue gas heat exchanger (2); the circulating water reflux valve (45) is arranged in a channel between the heat exchange outlet of the flue gas heat exchanger (2) and an inlet of the gas-liquid separator (46); and the steam regulating valve (47) is arranged in a channel between an outlet of the steam buffer tank (42) and a circulating water inlet of the reboiler (32); The waste heat recovery unit (5) further comprises a third lean liquid supply valve (52) and a circulating water supply valve (53); the third lean liquid supply valve (52) is arranged in a passage between a lean liquid inlet of the preheater (51) and a first lean liquid outlet (312) of the desorption tower (31); and the circulating water supply valve (53) is arranged in a passage between a circulating water inlet of the preheater (51) and an outlet of the circulating water tank (41).

7. The waste heat recovery system according to claim 2, characterized in that: The flue gas heat exchanger (2) comprises a flue gas interface (23), a bellows expansion joint (21) and a stopper (22) arranged at both ends of the flue gas heat exchanger (2); the bellows expansion joint (21) is arranged on the flue gas interface (23) at the top end of the flue gas heat exchanger (2); the stopper (22) is used to limit the movement of the bellows expansion joint (21); and the flue gas waste heat utilization channel (1) is connected to the flue gas interfaces (23) at both ends of the flue gas heat exchanger (2).

8. The waste heat recovery system according to claim 7, characterized in that: The flue gas heat exchanger (2) comprises a plurality of heat exchange plates (24) arranged inside the flue gas heat exchanger (2) and a flue gas flow channel (25) formed by gaps between adjacent heat exchange plates (24), the flue gas flow channel (25) being in communication with flue gas interfaces (23) at both ends of the flue gas heat exchanger (2), a heat exchange flow channel being arranged inside the heat exchange plates (24), the heat exchange flow channel being in communication with a heat exchange inlet (26) of the flue gas heat exchanger (2) and a heat exchange outlet of the flue gas heat exchanger (2).

9. A carbon dioxide capture device, characterized in that: It comprises a carbon dioxide absorption unit, a carbon dioxide recovery unit and a waste heat recovery system according to any one of claims 1 to 8, wherein the carbon dioxide desorption unit (3) is connected to the carbon dioxide absorption unit and the carbon dioxide recovery unit respectively.

10. A ship, characterized in that: Comprising the carbon dioxide capture device as claimed in claim 9.

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