A CO2 capture device and method

Abstract

This invention relates to the field of carbon dioxide capture technology, specifically to a CO2 capture device and method. The capture device includes a small-channel absorber, a phase-separating tank I, a desorber, and a phase-separating tank II connected in sequence. The small-channel absorber comprises a first tube bundle formed by multiple first small channels, used to mix the raw gas and an ionic liquid absorbent or lean liquid. The phase-separating tank I is used to perform a first phase separation treatment on the mixture, with the gas phase being exhaustable gas after CO2 removal and the liquid phase being a CO2-rich liquid, which is then passed into the desorber for heating to achieve CO2 desorption. The small-channel design solves the problems associated with microchannels. Simultaneously, the kinetic energy of the ship's movement in waves disturbs the fluid within the small-channel tubes, promoting microbubble aggregation and reducing the supercooled section of the rich liquid within the tubes. Furthermore, the kinetic energy of the ship's movement enhances the circulation within the liquid column during Taylor flow, thereby strengthening Taylor mass transfer.

Description

Technical Field

[0001] This invention patent relates to the field of carbon dioxide capture technology, specifically to a CO2 capture device and capture method. Background Technology

[0002] Carbon capture technology, as a strategic technology that promises to enable large-scale low-carbon utilization of fossil energy, has the potential to significantly reduce greenhouse gas emissions throughout the entire life cycle of traditional energy-intensive industries. It is an important means to reduce carbon dioxide emissions, ensure energy security, build ecological civilization, and achieve sustainable development in the future.

[0003] Absorption is currently the most mature and widely used CO2 capture technology, characterized by good capture effect, high absorption efficiency, and large processing capacity. However, traditional absorption methods use tower equipment, which presents the following problems when applied on ships or in small spaces: 1) Space is limited, while tower equipment is usually large; 2) The tower equipment's center of gravity can shift under the action of waves, causing channeling or uneven flow of fluid on the packing or sieve plates, resulting in insufficient gas-liquid contact and significantly affecting mass transfer.

[0004] Carbon capture using microchannel mass transfer requires solvents with low corrosivity; otherwise, the microchannels are easily corroded and perforated. Traditional organic amine solutions are severely corrosive to equipment and therefore unsuitable for such microchannel systems. Next-generation green solvents, ionic liquids, offer high carbon dioxide solubility and low equipment corrosivity, making them suitable for microchannel devices. Furthermore, microchannel devices are better suited for high-pressure physical absorption in gas separation because the large gas volume at low pressures necessitates an excessive number of microchannel tubes, making fabrication difficult. Ionic liquids, with their extremely low vapor pressure, are suitable for high-pressure absorption, allowing for direct heating and desorption of high-pressure carbon dioxide (with minimal loss of ionic liquid during desorption at high pressure), eliminating the need for subsequent carbon dioxide compression.

[0005] However, existing microchannel-based ionic liquid carbon capture technologies still have the following problems:

[0006] 1) Ionic liquids have very high viscosity at low temperatures, which can cause a huge pressure drop in microchannels;

[0007] 2) Marine carbon capture involves a large gas flow rate, and even under high pressure, the number of microchannel tubes required is still extremely large, making the equipment manufacturing process very difficult.

[0008] 3) Even after the raw gas is washed with water, it may still contain a certain amount of fine impurities, which may clog the microchannel tube. Summary of the Invention

[0009] To address the issue of large footprint in current CO2 capture devices, this invention overcomes the shortcomings of ionic liquid Taylor flow carbon capture in microchannels by employing small channels to achieve ionic liquid Taylor flow carbon capture. It should be noted that channels with a width less than 1 mm are generally defined as microchannels; the small channels in this invention have a width greater than microchannels but still significantly smaller than conventional pipes.

[0010] The solution of the present invention is as follows:

[0011] In a first aspect, the present invention protects a CO2 capture device, comprising a small channel absorber, a phase separation tank I, a desorber, and a phase separation tank II connected in sequence.

[0012] The small channel absorber includes a first tube bundle formed by a plurality of first small channels; the inner diameter of the first small channel is 2-4 mm, preferably 3-4 mm.

[0013] The small-channel absorber is used to mix the raw gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet in the first small channel to obtain a mixture;

[0014] The outlet of the first small channel tube is connected to the inlet of the phase separation tank I;

[0015] The phase separation tank I is used to perform a first phase separation treatment on the mixture. The resulting gas phase is a ventable gas after CO2 removal, which is discharged through the gas phase outlet of the phase separation tank I. The resulting liquid phase is a CO2-rich liquid, which is introduced into the desorber.

[0016] The desorber is used to heat the rich liquid from phase separation tank I to achieve CO2 desorption;

[0017] The phase separation tank II is used to perform a second phase separation process on the material after the desorber, resulting in a gas phase of CO2 and a liquid phase of lean liquid after CO2 removal.

[0018] The gas-liquid transport characteristics of ionic liquids in small channels include: the high specific surface tension of ionic liquids allows the system to maintain a Taylor flow pattern at a fairly wide gas-liquid velocity ratio in small channels with a scale larger than that of microchannels; the high viscosity of ionic liquids also results in relatively low backmixing of the system even in small channels with a slightly larger scale; and small channels can withstand a certain amount of fine impurities without clogging.

[0019] The ionic liquid CO2 capture device provided by this invention solves the problems of microchannels by setting up small channels. At the same time, it utilizes the kinetic energy of the ship's turbulence in the waves to disturb the fluid in the small channel tube, promote the coalescence of microbubbles, and reduce the supercooled section of the rich liquid in the tube. In addition, it can also use the kinetic energy of the ship's turbulence to enhance the circulation in the liquid column during Taylor flow transmission, thereby enhancing Taylor flow mass transfer.

[0020] As a specific embodiment of the present invention, the small channel absorber further includes a plurality of Y-type mixers; the first end of the Y-type mixer is connected to the inlet of the first small channel, the second end is connected to the gas phase inlet, and the third end is connected to the liquid phase inlet;

[0021] The Y-type mixer is used to mix the raw material gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet before introducing them into the first small channel.

[0022] By combining a Y-type mixer with the turbulence of a ship, the separation of bubbles from the pipe wall at the Y-type mixer can be accelerated, the bubble size can be reduced, and the initial specific surface area of ​​the bubbles can be increased (increasing the mass transfer area); thus enhancing the absorption efficiency of ionic liquids.

[0023] As a specific embodiment of the present invention, the small channel absorber further includes multiple variable-size uniformly distributed tubes;

[0024] The variable-size uniform distribution tubes are arranged side by side on the tube sheet, with a gap between two adjacent variable-size uniform distribution tubes; preferably, the bottom of the variable-size uniform distribution tube and the tube sheet can be an integral structure.

[0025] The variable-size uniform distribution tube has a tapered structure from front to rear; the rear end of the variable-size uniform distribution tube has a closed structure; the front end of the variable-size uniform distribution tube is connected to the liquid phase inlet of the small channel absorber; preferably, the inclination angle of the tapered structure is 5-15 degrees.

[0026] The bottom of the variable-size uniform distribution tube is provided with multiple first openings that penetrate the tube sheet; the first openings are connected to the third end of the Y-type mixer;

[0027] The gas phase inlet of the small channel absorber is connected to the gap between two adjacent variable-size uniformly distributed tubes.

[0028] The tube sheet at the gap has multiple second openings; the second openings are connected to the second end of the Y-type mixer.

[0029] As a specific embodiment of the present invention, the tube sheet is fixed to the ground or the hull of a ship.

[0030] In a specific embodiment of the present invention, the second and third ends of the Y-type mixer of the small channel absorber are fixed to the tube sheet.

[0031] In a specific embodiment of the present invention, a variable-size uniformly distributed tube is fixed to a tube sheet.

[0032] As a specific embodiment of the present invention, the variable-size uniform distribution tube has a triangular structure, and the height of the end of the triangular channel of the variable-size uniform distribution tube is related to the length of the uniform distribution tube. When the length of the uniform distribution tube is less than 1m, the design value of the height of the end of the triangular channel is the diameter of the small channel tube. When the length of the uniform distribution tube is greater than 1m, the design value of the height of the end of the triangular channel is 1 / 2 of the diameter of the small channel tube.

[0033] As a specific embodiment of the present invention, a first partition is provided at the front end of the gap between adjacent variable-size uniformly distributed tubes.

[0034] In a specific embodiment of the present invention, the first partition is an inverted trapezoid, which matches the variable-size uniform distribution tube and is fixed to the side wall of the uniform distribution tube.

[0035] Physical absorption occurs within the small-channel absorber, resulting in relatively low heat of absorption; therefore, air cooling is employed. The inlet section utilizes a variable-size uniform distribution tube. Gas enters the second end of the Y-type mixer through the gap between adjacent variable-size uniform distribution tubes and the second opening. Meanwhile, lean liquid is first diverted laterally into the front end of the variable-size uniform distribution tube, then enters the third end of the Y-type mixer through the first opening within the tube. Gas and liquid mix within the Y-type mixer. Gas passing through the first end of the Y-type mixer then enters the small-channel absorber, achieving CO2 absorption.

[0036] The special structure of the variable-size uniformly distributed tube ensures that the flow velocity in the small liquid channel is in a near-uniform state. According to computational fluid dynamics simulation, for high-viscosity fluids, the tapered structure of the variable-size uniformly distributed tube can make the flow velocity difference between each small channel tube smaller.

[0037] The first tube bundle of the small-channel absorber is brazed to the outlet tube sheet and the inlet tube sheet, which are then welded to the hull. This utilizes the kinetic energy of the ship's movement at sea to enhance the circulation of the Taylor flow column (the circulation of the Taylor flow column is slower under static and steady conditions due to the higher viscosity of the ionic liquid), promoting liquid phase surface renewal and enhancing mass transfer. The small-channel absorber also includes upper and lower heads; the upper head contains multiple variable-size uniformly distributed tubes and a Y-type mixer; the lower head has an outlet connected to the feed inlet of the phase separation tank I.

[0038] In a specific embodiment of the present invention, the desorber is a small-channel desorber; the small-channel desorber includes a second tube bundle composed of a plurality of second small channels; the inner diameter of the second small channel is 2-4 mm, preferably 2.5-4 mm;

[0039] The inlet of the second small channel is connected to the outlet of the phase separation tank I;

[0040] The outlet of the second small channel is connected to the inlet of the phase-separating tank II;

[0041] The second tube bundle is provided with an insulated outer shell;

[0042] As a specific embodiment of the present invention, a pressure reducing valve is provided between the small channel desorber and the phase separation tank I.

[0043] As a specific embodiment of the present invention, the length of the small channel in the small channel desorber is 1.2-2 times the length of the small channel in the small channel absorber.

[0044] In a specific embodiment of the present invention, the gas phase inlet is provided with a multi-stage compression refrigeration system and a phase separation tank III; the gas phase inlet is connected to the inlet of the multi-stage compression refrigeration system; the outlet of the multi-stage compression refrigeration system is connected to the inlet of the phase separation tank III; the multi-stage compression refrigeration system is used to compress and cool the raw material gas introduced through the gas phase inlet, and then introduce it into the phase separation tank III.

[0045] The phase separation tank III is used to perform a third phase separation on the compressed and cooled raw gas, with the gas phase entering the small channel absorber and the liquid phase being condensate.

[0046] As a specific embodiment of the present invention, the multi-stage compression refrigeration system includes a multi-stage compression interstage refrigeration heat exchanger and a cooling heat exchanger connected in sequence.

[0047] The multi-stage compression interstage refrigeration heat exchanger is used to compress and cool the raw gas.

[0048] The cooling heat exchanger is used to further cool the compressed and cooled raw gas, causing the liquid in it to condense.

[0049] In a specific embodiment of the present invention, the heat-insulating shell is divided into two parts: a circulating water heating section near the outlet of the second small channel and a waste heat recovery section near the inlet of the second small channel; the circulating water heating section is used to heat the mixed liquid in the second small channel for CO2 desorption; the waste heat recovery section is used to recover the heat of the liquid phase in the phase separation tank II, the inlet of the waste heat recovery section is connected to the lean liquid outlet of the phase separation tank II, and the outlet of the waste heat recovery section is connected to the liquid phase inlet.

[0050] As a specific embodiment of the present invention, the circulating water heating section is provided with baffles arranged at uniform intervals.

[0051] As a specific embodiment of the present invention, the waste heat recovery section is provided with baffles arranged at uneven intervals, wherein the spacing is larger closer to the inlet end of the second small channel; more preferably, the spacing is proportionally related from sparse to dense; even more preferably, the minimum spacing is 0.03-0.05m and the maximum spacing is no more than 0.2m; preferably 0.15-0.2m.

[0052] As a specific embodiment of the present invention, the circulating water outlet of the circulating water heating section is sequentially connected to a multi-stage compression refrigeration system, a temperature control heat exchanger, a pump, and the circulating water inlet of the circulating water heating section.

[0053] The use of a small-channel desorber can create Taylor flow during desorption, improving mass transfer efficiency. The small-channel desorber of this invention employs a shell-and-tube-like structure. After the rich solution enters the tube side, it is heated and desorbed to produce carbon dioxide. After phase separation, the carbon dioxide is pressurized by a pump and returned to the insulated outer shell (shell layer) for countercurrent heating of the rich solution in the lean solution waste heat recovery section. The baffles in the waste heat recovery section are non-uniformly spaced; that is, the baffles are spaced further apart closer to the tube inlet and closer together closer to the partition, with the spacing proportional to the distance from sparse to dense. As the temperature of the lean solution in the insulated outer shell (shell layer) decreases, the viscosity of the lean solution increases significantly. The viscosity is highest closer to the lean solution outlet (i.e., closer to the tube inlet). The larger plate spacing reduces pressure drop and provides sufficient flow space along the small-channel pipeline, preventing the high-viscosity lean solution from forming large flow dead zones between the tube bundles. The circulating water heating zone of the small-channel desorber further heats the rich solution with circulating water, ensuring it reaches the final set temperature.

[0054] As a specific embodiment of the present invention, the lean liquid outlet of the phase separation tank II is provided with an absorbent filling port for replenishing absorbent;

[0055] As a specific embodiment of the present invention, the gas phase outlet of the phase separation tank I is provided with a turbine for recovering residual energy;

[0056] As a specific embodiment of the present invention, a hydraulic turbine is provided between the phase-separating tank I and the temperature-controlled heat exchanger for recovering residual fluid energy.

[0057] The two ends of the second small channel within the small-channel desorber are vacuum brazed to the tube sheet, which is welded to the ground or ship's hull. This utilizes the kinetic energy of the ship's movement in waves to turbulence the fluid within the small channel, promoting microbubble coalescence and reducing the subcooled section within the tube. Simultaneously, the kinetic energy of the ship's movement enhances circulation within the liquid column during Taylor flow, thereby strengthening Taylor mass transfer. The second tube bundle of the small-channel desorber employs a design with no tubes in the baffle window area to avoid impact from high-pressure fluid on the tube bundle and prevent vibration problems.

[0058] A second aspect of the present invention protects a CO2 capture method for a CO2 capture device, comprising: mixing a raw material gas introduced through the gas phase inlet of a small-channel absorber with an ionic liquid absorbent introduced through the liquid phase inlet of the small-channel absorber in a first small channel to obtain a mixture; the mixture enters a phase separation tank I for a first phase separation treatment to obtain a dischargeable gas with CO2 removed and a CO2-rich liquid; then the rich liquid is introduced into a desorber for CO2 desorption treatment, and then enters a phase separation tank II for a second phase separation treatment to obtain CO2 and a CO2-removed lean liquid;

[0059] In a specific embodiment of the present invention, after the lean liquid recovers heat, it enters the liquid phase inlet of the small channel absorber.

[0060] In a specific embodiment of the present invention, the raw material gas and the ionic liquid absorbent are mixed in a Y-type mixer and then introduced into the first small channel.

[0061] In a specific embodiment of the present invention, the raw material gas enters the gap between two adjacent variable-size uniform distribution tubes through the gas inlet of the small channel absorber, passes through the second opening on the tube sheet, and enters the second end inlet of the Y-type mixer; the ionic liquid absorbent enters the variable-size uniform distribution tube through the gas inlet of the small channel absorber and through the front end of the variable-size uniform distribution tube, flows through the first opening, and enters the first end inlet of the Y-type mixer; the raw material gas and the ionic liquid absorbent are mixed in the Y-type mixer and then enter the first small channel to mix, forming a Taylor flow.

[0062] In a specific embodiment of the present invention, the rich liquid is introduced into the second small channel of the small channel desorber for CO2 desorption treatment.

[0063] As a specific embodiment of the present invention, the circulating water flowing out of the circulating water heating section of the small channel desorber is heat exchanged through a multi-stage compression refrigeration system, and then heated by a temperature-controlled heat exchanger before being reintroduced into the circulating water heating section of the small channel desorber.

[0064] In a specific embodiment of the present invention, the lean liquid flowing out of phase separation tank II is connected to the inlet of the waste heat recovery section, and then flows into the liquid phase inlet of the variable-size uniform distribution pipe.

[0065] As a specific embodiment of the present invention, the flow rate of the ionic liquid absorbent is 0.1-0.6 m / s; and / or the flow rate of the raw material gas is 0.2-0.6 m / s.

[0066] As a specific embodiment of the present invention, the ionic liquid should have a viscosity of less than 100 mPa·s at room temperature (around 293.15 K), and the more significant the change in carbon dioxide solubility with temperature, the better; preferably, the viscosity at room temperature is 10-100 mPa·s.

[0067] As a specific embodiment of the present invention, the conditions for CO2 desorption are a pressure of 20-40 bar, preferably 25-35 bar, and a temperature of 110-130°C;

[0068] In a specific embodiment of the present invention, the raw gas passes through a multi-stage compression and refrigeration system to achieve a pressure of 70-150 bar, preferably 75-135 bar.

[0069] Carbon dioxide obtained from marine carbon capture requires high-pressure storage. However, high-pressure ionic liquids can directly produce high-pressure carbon dioxide for storage through physical absorption followed by appropriate decompression and heating desorption. Therefore, the device provided by this invention is more suitable for a process of high-pressure absorption (multi-stage compression) followed by heating desorption. Small-channel tubes, due to their strong pressure-bearing capacity (3mm inner diameter, 1mm shell thickness), exhibit a circumferential stress of 7.515MPa under an internal pressure of 100bar. Furthermore, the allowable stress range of 316L stainless steel, which can be used as the raw material for small-channel tubes, is 90–95MPa within the temperature range covered in this technology. Therefore, small channels can maintain considerably high mechanical stability in high-pressure absorption and desorption processes.

[0070] The beneficial effects of this invention are:

[0071] (1) The CO2 capture device provided by this invention solves the problems of microchannels by setting up small channels. At the same time, it can also use the kinetic energy of the ship's turbulence in the waves to disturb the fluid in the small channel, promote the coalescence of microbubbles, and reduce the supercooled section of the rich liquid in the tube. At the same time, it can also use the kinetic energy of the ship's turbulence to enhance the circulation in the liquid column during Taylor flow, thereby enhancing Taylor flow mass transfer. Furthermore, the high specific surface tension of the ionic liquid allows the system to maintain the Taylor flow pattern at a fairly wide gas-liquid velocity ratio in small channels with a scale larger than that of microchannels. The high viscosity of the ionic liquid also makes the backmixing of the system relatively small even in small channels with a slightly larger scale. The small channels can withstand a certain amount of fine impurities without clogging.

[0072] (2) The Y-type mixer can be combined with the turbulence of the ship to accelerate the separation of bubbles from the pipe wall at the Y-type mixer, reduce the bubble size, and increase the initial specific surface area of ​​the bubbles; thus enhancing the adsorption effect of ionic liquids. The special structure of the variable-size uniformly distributed tube ensures that the flow velocity in the liquid small channel tube is in a near-uniform state; according to computational fluid dynamics simulation, for high viscosity fluids, the tapered structure of the variable-size uniformly distributed tube can make the velocity difference between each small channel tube smaller.

[0073] (3) The CO2 capture device provided by this invention is compact and effective, making it suitable for use on ships or in small spaces. For example, to achieve the same CO2 capture effect, the main equipment of a 1.7t / hr processing capacity system (10,000-ton-class equipment) using the device provided by this invention only requires two small channel absorbers with an area of ​​approximately 1.8m*1.6m*1m (considering the size of the end cap) and four pressure-bearing small channel desorbers with an inner diameter of 1m and a height of 1.5m. In contrast, the traditional 10,000-ton-class capture process requires an absorption tower and desorption tower approximately ten meters high (this number needs to be increased considering the channeling and uneven flow caused by ship turbulence), as well as complex piping. Therefore, the device provided by this invention has a significant advantage in terms of compactness. Furthermore, it does not need to consider the impact of ship turbulence on mass transfer. Considering the valuable space resources of ships, this invention patent has broad application prospects in ship carbon capture. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the CO2 capture device in Example 1;

[0075] Figure 2 This is a schematic diagram of the inlet portion of the small-channel absorber in Example 1;

[0076] Figure 3 This is a schematic diagram of the internal structure of the variable-size uniformly distributed tube of the small-channel absorber in Example 1;

[0077] Figure 4 This is a schematic diagram of the tube sheet openings of the small channel absorber in Example 1;

[0078] Figure 5 This is a schematic diagram of the heat-insulating outer shell structure of the small-channel desorber in Example 1;

[0079] Figure 6 This is a schematic diagram of the inlet cross-section of the variable-size uniformly distributed pipe in Example 1;

[0080] Explanation of reference numerals in the attached figures:

[0081] 1-Small channel absorber, 2-Small channel desorber, 3-Air-cooled fan, 4-Turbine, 5-Phase separation tank I, 6-Phase separation tank II, 7-Temperature control heat exchanger, 8-Phase separation tank III, 9-Pressure reducing valve, 10-Lean liquid cooler. Detailed Implementation

[0082] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0083] Example 1

[0084] A CO2 capture device, such as Figure 1 As shown, it includes a small channel absorber 1, a phase separation tank I 5, a desorber, and a phase separation tank II 6 connected in sequence;

[0085] The small channel absorber 1 includes a first tube bundle formed by a plurality of first small channels; the inner diameter of the first small channel is 2-4 mm, preferably 3-4 mm.

[0086] The small-channel absorber 1 is used to mix the raw gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet in the first small channel to obtain a mixture; its inlet structure is as follows. Figure 2 As shown;

[0087] The small channel absorber 1 also includes multiple Y-type mixers;

[0088] The Y-type mixer is connected at one end to the inlet of the first small channel, at the second end to the gas phase inlet, and at the third end to the liquid phase inlet.

[0089] The Y-type mixer is used to mix the raw material gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet before introducing them into the first small channel.

[0090] The small channel absorber 1 also includes multiple variable-size uniformly distributed tubes; its internal structure is as follows: Figure 3 As shown;

[0091] The variable-size uniformly distributed tubes are arranged side by side on the tube sheet, and there is a gap between two adjacent variable-size uniformly distributed tubes; the bottom of the variable-size uniformly distributed tubes and the tube sheet can be an integral structure.

[0092] The variable-size uniform distribution tube has a tapered structure from front to rear; the rear end of the variable-size uniform distribution tube is a closed structure; the front end of the variable-size uniform distribution tube is connected to the liquid inlet of the small channel absorber 1; the inclination angle of the tapered structure is 5-15 degrees.

[0093] The bottom of the variable-size uniformly distributed tube is provided with multiple first openings that penetrate the tube sheet; the structural schematic diagram is shown below. Figure 4 As shown; the first opening is connected to the third end of the Y-type mixer;

[0094] The gas phase inlet of the small channel absorber 1 is connected to the gap between two adjacent variable-size uniformly distributed tubes; the structural layout is as follows. Figure 6 As shown;

[0095] Multiple second openings are provided on the tube sheet at the gap; structural schematic diagram is shown below. Figure 4 As shown; the second opening is connected to the second end of the Y-type mixer;

[0096] The tube sheet is fixed to the hull;

[0097] The two inlets of the Y-type mixer of the small channel absorber 1 are fixed to the tube sheet;

[0098] Variable-size uniformly distributed tubes are fixed to the tube sheet;

[0099] A first partition is provided at the front end of the gap between adjacent variable-size uniform distribution tubes. The first partition is an inverted trapezoid, which matches the variable-size uniform distribution tube and is fixed to the side wall of the uniform distribution tube.

[0100] The outlet of the first small channel tube is connected to the inlet of the phase separation tank I5;

[0101] The phase separation tank I5 is used to perform a first phase separation treatment on the mixture. The resulting gas phase is a gas that has been de-CO2 removed and is discharged through the gas phase outlet of the phase separation tank I5. The resulting liquid phase is a CO2-rich liquid that is fed into the desorber.

[0102] The desorber is a small-channel desorber 2; the small-channel desorber 2 includes a second tube bundle composed of multiple second small channels; the inner diameter of the second small channel is 2-4 mm, preferably 2.5-4 mm;

[0103] The inlet of the second small channel is connected to the outlet of the phase separation tank I5;

[0104] The outlet of the second small channel is connected to the inlet of the phase-separating tank II 6;

[0105] A pressure reducing valve is provided between the small channel desorber 2 and the phase separation tank I 5;

[0106] The second tube bundle is externally equipped with an insulating shell; the specific structure is as follows: Figure 5 As shown;

[0107] The heat-insulating shell is divided into two parts: a circulating water heating section near the outlet of the second small channel and a waste heat recovery section near the inlet of the second small channel. The circulating water heating section is used to heat the mixed liquid in the second small channel for CO2 desorption. The waste heat recovery section is used to recover the heat of the liquid phase in the phase separation tank II 6. The inlet of the waste heat recovery section is connected to the lean liquid outlet of the phase separation tank II 6, and the outlet of the waste heat recovery section is connected to the liquid phase inlet.

[0108] Preferably, the circulating water heating section is provided with baffles arranged at uniform intervals;

[0109] Preferably, the waste heat recovery section is provided with baffles that are not evenly spaced, wherein the spacing is larger closer to the inlet of the second small channel; more preferably, the spacing is proportionally proportional from sparse to dense; even more preferably, the minimum spacing is 0.03-0.05m and the maximum spacing is no more than 0.2m; preferably, it is 0.15-0.2m.

[0110] The circulating water outlet of the circulating water heating section is sequentially connected to the multi-stage compression refrigeration system, the temperature control heat exchanger 7, the pump, and the circulating water inlet of the circulating water heating section.

[0111] The gas phase outlet of the phase separation tank I5 is equipped with a turbine for recovering residual energy;

[0112] A hydraulic turbine is provided between the phase separation tank I5 and the temperature control heat exchanger 7 to recover residual fluid energy.

[0113] The length of the second small channel is 1.2 to 2 times that of the first small channel.

[0114] The desorber is used to heat the rich liquid from the phase separation tank I5 to achieve CO2 desorption.

[0115] The phase separation tank II6 is used to perform a second phase separation process on the material after the desorber, resulting in a gas phase of CO2 and a liquid phase of lean liquid after CO2 removal.

[0116] The lean liquid outlet of the phase separation tank II6 is equipped with an absorbent filling port for replenishing absorbent.

[0117] The gas phase inlet is equipped with a multi-stage compression refrigeration system and a phase separation tank Ⅲ8;

[0118] The gas phase inlet is connected to the inlet of the multi-stage compression refrigeration system; the outlet of the multi-stage compression refrigeration system is connected to the inlet of phase-splitting tank Ⅲ8.

[0119] The multi-stage compression refrigeration system is used to compress and cool the raw material gas introduced through the gas phase inlet, and then introduce it into the phase separation tank III;

[0120] The phase separation tank Ⅲ is used to perform a third phase separation on the compressed and cooled raw gas, with the gas phase entering the small channel absorber 1; the liquid phase is condensate.

[0121] Preferably, the multi-stage compression refrigeration system includes a multi-stage compression interstage refrigeration heat exchanger and a cooling heat exchanger connected in sequence;

[0122] The multi-stage compression interstage refrigeration heat exchanger is used to compress and cool the raw gas.

[0123] The cooling heat exchanger is used to further cool the compressed and cooled raw gas, causing the liquid in it to condense.

[0124] Example 2

[0125] The CO2 capture method using the above-mentioned device includes:

[0126] The raw gas (exhaust gas from the ship's power system) after multi-stage compression and cooling first enters phase separation tank III8 to separate the condensate (mainly water) produced during compression. It then enters the gas phase inlet section of small-channel absorber 1 and mixes with lean ionic liquid from the absorbent filling port via a Y-type mixer. Carbon dioxide is then separated from the raw gas and adsorbed within small-channel absorber 1. Small-channel absorber 1 uses air cooling to remove heat accumulated inside the small-channel tube bundle. The stream leaving the small-channel absorber enters phase separation tank I5 for phase separation. The high-pressure purified gas (emissionable gas after CO2 removal) from the gas phase outlet of phase separation tank I5 enters turbine 4 to recover residual pressure. The rich liquid from the liquid phase outlet of phase separation tank I5 is appropriately depressurized by a pressure reducing valve and then enters small-channel desorber 2 for heating and desorption treatment. It then enters phase separation tank II6 for the second phase separation treatment, yielding a certain amount of regenerated gas, i.e., high-pressure carbon dioxide. The high-pressure carbon dioxide from the gas phase outlet of phase separation tank II6 is stored in a subsequent high-pressure storage tank. The hot lean liquid from the liquid phase outlet of phase separator II6 is pressurized by a pump and enters the waste heat recovery section of small channel desorber 2 to initially heat the tube-side fluid and recover waste heat. After the waste heat is recovered, the lean liquid is cooled by cooling water and returned to the liquid phase inlet of small channel absorber 1 to complete the cycle.

[0127] The circulating water heating section of the small channel desorber 2 uses circulating water heating. The circulating water is heated by the waste heat of the raw material gas and the waste heat of the interstage refrigeration of the multi-stage compression. After being pressurized by the pump, it is heated to the specified temperature by the temperature control heat exchanger and then circulated back to the circulating water heating section of the small channel desorber to further heat the rich liquid fluid.

[0128] The lean solution is the absorbent before absorption after desorption (a carbon dioxide-poor absorbent solution), while the rich solution is the absorbent before desorption after absorption (a carbon dioxide-rich absorbent solution).

[0129] Example 3

[0130] A marine carbon capture method for 1.7 tons of carbon dioxide per hour, with the following feed gas composition:

[0131]

[0132] The ionic liquid used is [C4mim][DCA](1-4-alkyl-3-methylimidazolium Dicyanamide), which has a viscosity of less than 100 mPa·s at room temperature (around 293.15 K) and a solubility that changes significantly with temperature.

[0133] The multi-stage compression employs a 5-stage isobar compression ratio to compress the feed gas to 100 bar, achieving a compression efficiency of 0.72. The outlet temperature of each stage is between 270°C and 290°C. Circulating water is used to cool the outlet gas of each stage to 120-140°C to recover waste heat. Finned tube heat exchangers are used to enhance the heat transfer coefficient on the gas side. After compression, the gas is further cooled to room temperature and enters phase separation tank III to separate condensed water. The gas outlet then enters a small-channel absorber. A pressure reducing valve reduces the rich liquid pressure to 30 bar. In this embodiment, the addition of a hydraulic turbine is not considered.

[0134] The apparent molar fraction of carbon dioxide in the lean solution was 0.13, and the lean solution flow rate was 0.009 m. 3 / s, gas phase flow rate 0.017m 3 / s, the temperature of the gas and liquid phases entering the absorber is controlled at 15 degrees. Single tube experiments show that Taylor flow can be stably formed near this gas-liquid flow ratio and flow rate, and the ionic liquid is in excess to ensure the capture rate.

[0135] Single-tube experiments show that, under the aforementioned operating conditions, the Taylor flow volumetric mass transfer coefficient within the first 3mm small channel is approximately 0.5s². -1 See the design of the uniformly distributed pipe inlet. Figure 5 The tilt angle is 5 degrees. Phase equilibrium data were calculated using the ePC-SAFT model. Based on the two-film theory, the length of the first small channel required to achieve 95% saturation absorption is approximately 0.66 m. Considering that the variable-size uniform distribution tube cannot guarantee 100% uniform distribution, a margin should be appropriately increased. Simulation experiment: Simulating installation 17 m above the sea surface, the wave effect was simulated by a six-degree-of-freedom parallel platform, with a wave amplitude of 0.3 m and a period of 15 s. The results show that a first small channel length of 0.9 m can stably guarantee the capture rate under the above conditions. For the small-channel desorber, considering the existence of a supercooled section within the small channel tube and the need to consider heat transfer effects during desorption, the required length of the second small channel of the small-channel desorber should be greater than the length of the first small channel of the absorber. Based on simulation data, the required length of the small channel in the small-channel desorber should be greater than 1 m. In summary, the length of the small channel in the small-channel absorber in this embodiment is taken as 0.9 m, and the actual length of the small channel in the small-channel tube desorber is 1.2 m.

[0136] The average gas velocity in the first small channel is 0.167 m / s. The small channel desorber uses 8776 tubes, and the small channel absorber uses 22264 tubes. The circulating water recovery section of the small channel desorber in the pilot plant is 0.4 m long. The pump at the inlet of the circulating water heating section pressurizes the circulating water to 2.5 bar and heats it to 120 degrees Celsius, with a total flow rate of 0.02 m³ / s. 3The flow rate is 4 mm / s, with 7 uniformly arranged baffles (0.05 m spacing, 4 mm thickness). Pilot-scale results show that the pressure drop in this section is 0.24 bar, and the outlet temperature is 92 degrees Celsius. Single-tube experiments show that this section can heat the rich liquid temperature from 68 degrees Celsius to 110 degrees Celsius while simultaneously desorbing a certain amount of carbon dioxide. The waste heat recovery section of the small-channel desorber is 0.8 m long and uses 7 baffles (the spacing from the shell-side inlet of the waste heat recovery section is 0.048 m, 0.057 m, 0.069 m, 0.083 m, 0.099 m, 0.12 m, 0.14 m, 0.616 m, 0.184 m, approximately forming a geometric series with 0.048 m as the first term and a common ratio of 1.2; the baffle thickness is 3 mm). The inlet temperature of the waste heat recovery section is 106 degrees Celsius, and the outlet temperature is 25 degrees Celsius. Single-tube experiments show that this section can raise the temperature of the mixed liquid in the second small channel to 59 degrees Celsius and release a small amount of carbon dioxide, initially forming irregular bubbles in the tube (irregular bubbles in the circulating water heating section coalesce into stable Taylor flow bubbles). The small channel tubes are arranged in a staggered array. Considering that the waste heat recovery section needs to withstand pressure, four small channel desorbers with an inner diameter of about 1.2m and insulated shells connected in parallel can meet the desorption requirements. For the small channel absorbers, the centroidal spacing of the small channels in the vertical airflow direction is 6mm, and the spacing in the airflow direction is 12mm. In a set of small channel absorbers, with a fan diameter of 1m, 24,000 tubes can be arranged in a rectangular area of ​​1.2m * 1.44m (vertical airflow direction * airflow direction), so a set of such small channel absorbers can meet the absorption requirements.

[0137] Based on the empirical correlation of Taylor flow pressure drop in microchannels proposed in Chemical Engineering Journal, 2019, 373:437-445, the pressure drop of the microchannel absorber can be calculated to be approximately 2.4 bar, and the pressure drop of the microchannel desorber (taking the viscosity at the qualitative temperature) is approximately 2.6 bar. The final carbon dioxide pressure obtained is >25 bar, which meets the requirements for ship transportation without the need for further compression units.

[0138] Based on the PC-SAFT equation (Ind.Eng.Chem.Res.2001,40,(4),1244-1260.), a 5-stage turbine was used to recover the residual energy of the purified gas. The turbine efficiency was set to 0.72, and the efficiency of the ionic liquid pressurizing pump was set to 0.7 (the viscosity of the ionic liquid is low at high temperatures, resulting in higher pump efficiency). Combined with simulation results, the average energy consumption of the method in this embodiment is 3.7 GJ / tCO2 (the carbon dioxide capture rate is between 89% and 93%), with the main part of the energy consumption coming from multi-stage compression. If a more efficient compressor and turbine (currently both set to 0.72) are used, the total energy consumption is expected to be further reduced.

[0139] Example 4

[0140] The inclination angle of the small channel of the ionic liquid marine CO2 capture device is set to 2 degrees, and the rest is the same as in Example 1. The length of the absorption tube is still 0.9m.

[0141] The method for capturing CO2 on ships is described in Examples 2 and 3.

[0142] Simulation experiments show that an excessively small tilt angle results in insufficient uniform distribution of the liquid phase, and some fluids in the pipe fail to form a stable Taylor flow, causing the overall carbon dioxide capture rate to fluctuate between 70% and 87%. Although the regeneration heat consumption decreases, it cannot compensate for the excessive compression work caused by the decrease in the capture rate. The comprehensive simulation results show that the average energy consumption of this embodiment reaches 3.9 GJ / t CO2.

[0143] Compared to Example 3, the reduced tilt angle resulted in an overall carbon dioxide capture rate between 70% and 87%. Energy consumption also increased slightly.

[0144] Example 5

[0145] The waste heat recovery section of the small-channel desorber in the ionic liquid marine CO2 capture device adopts a baffle plate uniformly distributed design, also using 7 plates, and the rest is the same as in Example 1.

[0146] The method for capturing CO2 on ships is described in Examples 2 and 3.

[0147] Because a flow dead zone exists within the small-channel tube bundle near the shell-side outlet of the waste heat recovery section of the small-channel desorber, the recovery of lean liquid waste heat in the waste heat recovery section is insufficient, leading to an increase in the heat required for the subsequent circulating water heating section. In this embodiment, the average energy consumption is 3.9 GJ / t CO2. Furthermore, after a period of operation, the cooling capacity required by the lean liquid cooler will gradually increase to ensure the temperature of the lean liquid entering the small-channel absorber.

[0148] Compared with Example 3, the waste heat recovery section adopts a baffle plate uniform distribution design, which improves the overall energy consumption. In addition, the overall energy consumption will gradually increase with the increase of operating time.

[0149] Example 6

[0150] The ionic liquid marine CO2 capture device is described in Example 1.

[0151] The method for capturing CO2 on ships is the same as in Examples 2 and 3, except that the simulation experiment uses a wave-free effect.

[0152] Due to the high surface tension of the ionic liquid, the initial Taylor flow bubble size at the Y-type mixer of the small-channel absorber is relatively large under conditions without ship turbulence (single-tube experiments show that under the aforementioned gas-liquid conditions, the average length of the initial bubble without turbulence is approximately 6 mm, while under simulated ship conditions, the average length of the initial bubble is 3 mm). This leads to a decrease in collection efficiency and makes it impossible to enhance the Taylor flow liquid column circulation through ship turbulence (single-tube experiments show that under the aforementioned gas-liquid conditions, the Taylor flow volumetric mass transfer coefficient without turbulence is 0.22 s). -1 Under simulated marine conditions, the average volumetric mass transfer coefficient increased to 0.5 s². -1 Therefore, the collection efficiency of the absorption device is significantly lower than that under conditions of turbulence. Simulation results show that, under these conditions, the energy consumption of the aforementioned design is 4.0 GJ / t CO2.

[0153] Compared to Example 3, the device of the present invention is more suitable for use under ship turbulence conditions, but has low capture efficiency and high energy consumption. More specifically, for regenerated gas, ship turbulence reduces the length of the subcooled section inside the small channel and promotes microbubble coalescence, accelerating the formation of Taylor flow and enhancing gas-liquid transfer. For the insulation shell, ship turbulence can also reduce the flow dead zone inside the small channel bundle and enhance transfer.

[0154] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A CO2 capture device, characterized in that, It includes a small channel absorber (1), a phase separation tank I (5), a desorber, and a phase separation tank II (6) connected in sequence; The small channel absorber (1) includes a first tube bundle formed by a plurality of first small channels; the inner diameter of the first small channel is 2-4 mm, preferably 3-4 mm; The small channel absorber (1) is used to mix the raw gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet in the first small channel to obtain a mixture; The outlet of the first small channel tube is connected to the inlet of the phase separation tank I (5); The phase separation tank I (5) is used to perform a first phase separation treatment on the mixture. The resulting gas phase is a gas that has been de-CO2 removed and is discharged through the gas phase outlet of the phase separation tank I (5). The resulting liquid phase is a rich liquid that absorbs CO2 and is introduced into the desorber. The desorber is used to heat the rich liquid from the phase separation tank I (5) to achieve CO2 desorption; The phase separation tank II (6) is used to perform a second phase separation process on the material after the desorber, and the resulting gas phase is CO2 and the liquid phase is lean liquid after CO2 removal.

2. The CO2 capture device according to claim 1, characterized in that, The small channel absorber (1) also includes multiple Y-type mixers; The Y-type mixer is connected at one end to the inlet of the first small channel, at the second end to the gas phase inlet, and at the third end to the liquid phase inlet. The Y-type mixer is used to mix the raw material gas introduced through the gas phase inlet and the ionic liquid absorbent introduced through the liquid phase inlet before introducing them into the first small channel.

3. The CO2 capture device according to claim 2, characterized in that, The small channel absorber (1) also includes multiple variable-size uniformly distributed tubes; The variable-size uniform distribution tubes are arranged side by side on the tube sheet, with a gap between two adjacent variable-size uniform distribution tubes; preferably, the bottom of the variable-size uniform distribution tube and the tube sheet can be an integral structure. The variable-size uniform distribution tube has a tapered structure from front to rear; the rear end of the variable-size uniform distribution tube has a closed structure; the front end of the variable-size uniform distribution tube is connected to the liquid inlet of the small channel absorber (1); preferably, the inclination angle of the tapered structure is 5-15 degrees. The bottom of the variable-size uniform distribution tube is provided with multiple first openings that penetrate the tube sheet; the first openings are connected to the third end of the Y-type mixer; The gas phase inlet of the small channel absorber (1) is connected to the gap between two adjacent variable-size uniform distribution tubes; The tube sheet at the gap is provided with multiple second openings; the second openings are connected to the second end of the Y-type mixer; Preferably, the tube sheet is fixed to the ground or the hull of a ship; Preferably, the second and third ends of the Y-type mixer of the small channel absorber (1) are fixed to the tube sheet; Preferably, the variable-size uniformly distributed tube is fixed to the tube sheet; Preferably, a first partition is provided at the front end of the gap between adjacent variable-size uniformly distributed tubes.

4. The CO2 capture device according to any one of claims 1-3, characterized in that, The desorber is a small-channel desorber (2); the small-channel desorber (2) includes a second tube bundle composed of multiple second small channels; the inner diameter of the second small channel is 2-4 mm, preferably 2.5-4 mm; The inlet of the second small channel is connected to the outlet of the phase separation tank I (5); The outlet of the second small channel is connected to the inlet of the phase separation tank II (6); The second tube bundle is provided with an insulated outer shell; And / or, a pressure reducing valve is provided between the small channel desorber (2) and the phase separation tank I (5).

5. The CO2 capture device according to claim 4, characterized in that, The length of the second small channel is 1.2 to 2 times that of the first small channel.

6. The CO2 capture device according to any one of claims 1-5, characterized in that, The gas phase inlet is equipped with a multi-stage compression refrigeration system and a phase separation tank Ⅲ (8); the gas phase inlet is connected to the inlet of the multi-stage compression refrigeration system; the outlet of the multi-stage compression refrigeration system is connected to the inlet of the phase separation tank Ⅲ (8); The multi-stage compression refrigeration system is used to compress and cool the raw material gas introduced through the gas phase inlet, and then introduce it into the phase separation tank III; The phase separation tank Ⅲ is used to perform a third phase separation on the compressed and cooled raw material gas, and the gas phase enters the small channel absorber (1); The liquid phase is condensate; Preferably, the multi-stage compression refrigeration system includes a multi-stage compression interstage refrigeration heat exchanger and a cooling heat exchanger connected in sequence; The multi-stage compression interstage refrigeration heat exchanger is used to compress and cool the raw gas. The cooling heat exchanger is used to further cool the compressed and cooled raw gas, causing the liquid in it to condense.

7. The CO2 capture device according to claim 4, characterized in that, The heat-insulating shell is divided into two parts: a circulating water heating section near the outlet of the second small channel and a waste heat recovery section near the inlet of the second small channel. The circulating water heating section is used to heat the mixed liquid in the second small channel for CO2 desorption. The waste heat recovery section is used to recover the heat of the liquid phase in the phase separation tank II (6). The inlet of the waste heat recovery section is connected to the lean liquid outlet of the phase separation tank II (6), and the outlet of the waste heat recovery section is connected to the liquid phase inlet. Preferably, the circulating water heating section is provided with baffles arranged at uniform intervals; Preferably, the waste heat recovery section is equipped with baffles arranged at uneven intervals, with the spacing being larger closer to the inlet of the second small channel; more preferably, the spacing is proportionally increased from sparse to dense; even more preferably, the minimum spacing is 0.03-0.05m, and the maximum spacing does not exceed 0.2m; preferably, it is 0.15-0.2m. Preferably, the circulating water outlet of the circulating water heating section is sequentially connected to a multi-stage compression refrigeration system, a temperature control heat exchanger (7), a pump, and the circulating water inlet of the circulating water heating section; Preferably, the lean liquid outlet of the phase separation tank II (6) is provided with an absorbent filling port for replenishing absorbent.

8. A CO2 capture method using the CO2 capture device according to any one of claims 1-7, characterized in that, include: The raw material gas introduced through the gas phase inlet of the small channel absorber (1) is mixed with the ionic liquid absorbent introduced through the liquid phase inlet of the small channel absorber (1) in the first small channel to obtain a mixture; the mixture enters the phase separation tank I (5) for the first phase separation treatment to obtain a dischargeable gas with CO2 removed and a rich liquid with CO2 absorbed; then the rich liquid is introduced into the desorber for CO2 desorption treatment, and then enters the phase separation tank II (6) for the second phase separation treatment to obtain CO2 and a lean liquid with CO2 removed; Preferably, after the lean liquid recovers heat, it enters the liquid phase inlet of the small channel absorber (1).

9. The CO2 capture method according to claim 8, characterized in that, The raw material gas and ionic liquid absorbent are mixed in a Y-type mixer and then introduced into the first small channel; Preferably, the raw material gas enters the gap between two adjacent variable-size uniform distribution tubes through the gas inlet of the small channel absorber (1), passes through the second opening on the tube sheet, and enters the second end inlet of the Y-type mixer; the ionic liquid absorbent enters the variable-size uniform distribution tube through the gas inlet of the small channel absorber (1) and through the front end of the variable-size uniform distribution tube, flows through the first opening, and enters the first end inlet of the Y-type mixer; the raw material gas and the ionic liquid absorbent are mixed in the Y-type mixer and then mixed in the first small channel to obtain a mixture; And / or, the rich liquid is introduced into the second small channel of the small channel desorber (2) for CO2 desorption treatment.

10. The CO2 capture method according to claim 8 or 9, characterized in that, The flow rate of the ionic liquid absorbent is 0.1-0.6 m / s; And / or, the flow rate of the raw material gas is 0.2-0.6 m / s; And / or, the ionic liquid absorbent has a viscosity of less than 100 mPa·s at room temperature; preferably, the viscosity at room temperature is between 10 and 100 mPa·s. And / or, the conditions for CO2 desorption are a pressure of 20-40 bar, preferably 25-35 bar; and a temperature of 110-130°C. And / or, the raw gas passes through a multi-stage compression and refrigeration system to achieve a pressure of 70-150 bar, preferably 75-135 bar.

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