Carbon dioxide trapping system and method based on flash evaporation and multi-stage heat exchange

Abstract

The invention discloses a carbon dioxide trapping system and method based on flash evaporation and multi-stage heat exchange, the carbon dioxide trapping system based on flash evaporation and multi-stage heat exchange comprises a first tower body, a second tower body, a flash evaporation device, a first heat exchanger and a second heat exchanger, the first tower body is provided with a first inlet and a first outlet; the second tower body is provided with a second inlet and a second outlet; the flash evaporation device is provided with a third inlet, a gas phase outlet and a liquid phase outlet; the gas phase outlet is connected with the second tower body, the liquid phase outlet is connected with a hot side inlet of the second heat exchanger, a cold side outlet of the first heat exchanger and a cold side outlet of the second heat exchanger are both connected with a second inlet of the second tower body, and hot side outlets of the first heat exchanger and the second heat exchanger are both connected with a first inlet of the first tower body; the first outlet is connected with cold side inlets of the first heat exchanger and the second heat exchanger, and the second outlet is connected with the third inlet and a hot side inlet of the first heat exchanger. The invention can improve the utilization rate of heat and reduce the energy consumption and cost of carbon capture.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and in particular relates to a carbon dioxide capture system and method based on flash evaporation and multi-stage heat exchange. Background Art

[0002] The emission of greenhouse gases such as carbon dioxide is a major factor causing climate change. A large amount of industrial flue gas emitted by coal-fired power plants contains 5% to 30% carbon dioxide. The gas pressure is normal pressure, and can only be captured and separated by chemical absorption. However, there are still problems with capture energy consumption and high costs, which affect large-scale promotion and use. Summary of the invention

[0003] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0004] The inventors realized that the related art uses part of the heat of the high-temperature lean liquid to heat the cold fluid outside the capture system, which makes the process flow complicated and the optimization and control of the process parameters of the whole system difficult.

[0005] The inventors also realized that flash compressing all high-temperature lean liquid would result in a large gas flow rate consisting mainly of water vapor, a large investment in compression equipment, and a high power consumption for compression.

[0006] The inventors also realized that only part of the heat in the high-temperature lean liquid is surplus and cannot be used to effectively heat the rich liquid in the lean-rich liquid heat exchanger.

[0007] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0008] To this end, an embodiment of the present invention proposes a carbon dioxide capture system based on flash evaporation and multi-stage heat exchange, which can improve the utilization rate of heat and reduce the energy consumption and cost of carbon capture.

[0009] An embodiment of the present invention further provides a carbon dioxide capture method based on flash evaporation and multi-stage heat exchange.

[0010] The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange of the embodiment of the present invention comprises a first tower body, a second tower body, a flash evaporation device, a first heat exchanger and a second heat exchanger connected to each other, wherein the first tower body is used for a solvent and a mixed gas to contact and react to capture carbon dioxide in the mixed gas, the second tower body is used for heating the solvent that has absorbed carbon dioxide to desorb carbon dioxide, the first tower body has a first inlet and a first outlet, the second tower body has a second inlet and a second outlet, and the flash evaporation device has a third inlet, a gas phase outlet and a liquid phase outlet;

[0011] The gas phase outlet is connected to the second tower body, the liquid phase outlet is connected to the hot side inlet of the second heat exchanger, the cold side outlet of the first heat exchanger and the cold side outlet of the second heat exchanger are both connected to the second inlet of the second tower body, and the hot side outlet of the first heat exchanger and the hot side outlet of the second heat exchanger are both connected to the first inlet of the first tower body;

[0012] The first outlet is connected to the cold side inlet of the first heat exchanger and the cold side inlet of the second heat exchanger to transport at least part of the solvent discharged from the first outlet to the first heat exchanger and at least part of the solvent to the second heat exchanger, and the second outlet is connected to the third inlet and the hot side inlet of the first heat exchanger to transport at least part of the solvent discharged from the second outlet to the flash device and at least part of the solvent to the first heat exchanger.

[0013] The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange in the embodiment of the present invention diverts the lean liquid so that part of the lean liquid directly exchanges heat with the rich liquid, while the other part of the lean liquid recovers part of the heat after flash evaporation, and then exchanges heat with part of the rich liquid, thereby realizing multi-stage heat exchange to obtain rich liquids of different temperatures so that they can be transported to the second tower body at different stages during the desorption process, thereby improving the utilization rate of heat and reducing the energy consumption and cost of carbon capture.

[0014] In some embodiments, there are plural second inlets, and the second inlet connected to the second heat exchanger is higher in the vertical direction than the second inlet connected to the first heat exchanger.

[0015] In some embodiments, a first rich liquid pipeline is further included, and the first outlet is connected to one of the second inlets in the second tower body through the first rich liquid pipeline, so that part of the solvent discharged from the first outlet is directly transported into the second tower body.

[0016] In some embodiments, the second inlet connected to the first rich liquid pipeline is higher in the vertical direction than the other second inlets;

[0017] And / or, it also includes a third heat exchanger, the top of the second tower body has an outlet, the outlet is connected to the hot side inlet of the third heat exchanger, and the cold side pipeline of the third heat exchanger is connected in series to the first rich liquid pipeline.

[0018] In some embodiments, a first lean liquid pipeline is provided between the second outlet and the third inlet of the flash device, and a second lean liquid pipeline is provided between the second outlet and the hot side inlet of the first heat exchanger, and the solvent flow in the first lean liquid pipeline accounts for 20% to 80% of the total flow of the second outlet.

[0019] In some embodiments, a compressor is further included, and the compressor is disposed between the gas phase outlet and the second tower body;

[0020] And / or, the gas phase outlet of the flash evaporation device is connected to the middle and lower part of the inner cavity of the second tower body.

[0021] In some embodiments, a lean liquid cooler is further included, wherein the inlet end of the lean liquid cooler is connected to the hot side outlet of the first heat exchanger and the hot side outlet of the second heat exchanger, and the outlet end of the lean liquid cooler is connected to the first inlet of the first tower body, for cooling the solvent transported into the lean liquid cooler to a first preset temperature.

[0022] In some embodiments, a lean liquid pump and a rich liquid pump are further included, the second outlet and the liquid phase outlet are both connected to the lean liquid pump, and the first outlet is connected to the rich liquid pump.

[0023] In some embodiments, a reboiler is further included, wherein the reboiler is connected to the second tower body to heat the solvent at the bottom of the second tower body.

[0024] The carbon dioxide capture method based on flash evaporation and multi-stage heat exchange of an embodiment of the present invention uses the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange in any of the above embodiments to capture carbon, and the method includes:

[0025] The lean liquid transported into the first tower body contacts with the mixed gas to capture carbon dioxide in the mixed gas, and the rich liquid is discharged from the first outlet of the first tower body;

[0026] The rich liquid transported into the second tower body is heated to desorb carbon dioxide, and the lean liquid is discharged from the second outlet of the second tower body;

[0027] Adjusting the flow rate of the lean liquid and the flow rate of the rich liquid transported into the first heat exchanger so that the lean liquid transported into the first heat exchanger is transported into the first tower body after being cooled by heat exchange, and the rich liquid transported into the first heat exchanger is transported into the second tower body after being heated by heat exchange;

[0028] The remaining lean liquid is transported into the flash device, and the flow rate of the rich liquid transported into the second heat exchanger is adjusted, the gas phase after flashing in the flash device is transported into the second tower body, and the liquid phase remaining after flashing is transported into the second heat exchanger, so that the lean liquid transported into the second heat exchanger is transported into the first tower body after being cooled by heat exchange, and the rich liquid transported into the second heat exchanger is transported into the second tower body after being heated by heat exchange;

[0029] The remaining rich liquid discharged from the first outlet is directly transported to the second tower body, or the remaining rich liquid discharged from the first outlet is heat-exchanged with the gas discharged from the second tower body and then transported to the second tower body after the temperature is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of a carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to an embodiment of the present invention.

[0031] Figure 2 It is a schematic structural diagram of a carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to another embodiment of the present invention.

[0032] Figure 3 It is a flow chart of a carbon dioxide capture method based on flash evaporation and multi-stage heat exchange according to an embodiment of the present invention.

[0033] Reference numerals:

[0034] 1. First tower body; 2. Second tower body; 3. First heat exchanger; 4. Second heat exchanger; 5. Flash device; 6. Lean liquid cooler; 7. Compressor; 8. Lean liquid pump; 9. Rich liquid pump; 10. First inlet; 11. First outlet; 12. Second inlet; 13. Second outlet; 14. Third inlet; 15. Gas phase outlet; 16. Liquid phase outlet; 18. Reboiler;

[0035] 21. First rich liquid pipeline; 22. First lean liquid pipeline; 23. Second lean liquid pipeline. DETAILED DESCRIPTION

[0036] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0037] like Figure 1 As shown, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange of an embodiment of the present invention includes a first tower body 1, a second tower body 2, a flash evaporation device 5, a first heat exchanger 3 and a second heat exchanger 4 connected to each other. The first tower body 1 is used for the contact reaction between the solvent and the mixed gas to capture the carbon dioxide in the mixed gas, and the second tower body 2 is used for heating the solvent that absorbs the carbon dioxide to desorb the carbon dioxide. The first tower body 1 has a first inlet 10 and a first outlet 11, the second tower body 2 has a second inlet 12 and a second outlet 13, and the flash evaporation device 5 has a third inlet 14, a gas phase outlet 15 and a liquid phase outlet 16.

[0038] The gas phase outlet 15 is connected to the second tower body 2, the liquid phase outlet 16 is connected to the hot side inlet of the second heat exchanger 4, the cold side outlet of the first heat exchanger 3 and the cold side outlet of the second heat exchanger 4 are both connected to the second inlet 12 of the second tower body 2, and the hot side outlet of the first heat exchanger 3 and the hot side outlet of the second heat exchanger 4 are both connected to the first inlet 10 of the first tower body 1.

[0039] The first outlet 11 is connected to the cold side inlet of the first heat exchanger 3 and the cold side inlet of the second heat exchanger 4 so as to transport at least part of the solvent discharged from the first outlet 11 to the first heat exchanger 3 and at least part of the solvent to the second heat exchanger 4. The second outlet 13 is connected to the third inlet 14 and the hot side inlet of the first heat exchanger 3 so as to transport at least part of the solvent discharged from the second outlet 13 to the flash evaporation device 5 and at least part of the solvent to the first heat exchanger 3.

[0040] The first tower body 1 of the embodiment of the present invention is an absorption tower. The solvent introduced into the first tower body 1 contacts with carbon dioxide and an absorption reaction occurs. The second tower body 2 is a desorption tower. The solvent absorbed with carbon dioxide and transported into the second tower body 2 is heated and then desorbed to release carbon dioxide. The desorbed solvent is then transported to the first tower body 1 for reuse.

[0041] Since the absorption reaction of the solvent and carbon dioxide in the first tower body 1 requires a low temperature, and the solvent absorbed by carbon dioxide in the second tower body 2 needs to be desorbed at a high temperature during desorption, the solvent consumes a lot of energy during the circulation process between the first tower body 1 and the second tower body 2, and the temperature difference between different solvents is large.

[0042] Among them, the solvent transported into the first tower body 1 is a low-temperature lean liquid, the solvent discharged from the first tower body 1 is a low-temperature rich liquid, the solvent transported into the second tower body 2 is a rich liquid, and the solvent discharged from the second tower body 2 is a high-temperature lean liquid. The rich liquid is the solvent that absorbs carbon dioxide, and the lean liquid is the solvent after desorbing carbon dioxide.

[0043] The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange in the embodiment of the present invention diverts the lean liquid so that part of the lean liquid directly exchanges heat with part of the rich liquid in the first heat exchanger 3, while the other part of the lean liquid recovers part of the heat after flash evaporation, and then exchanges heat with part of the rich liquid, thereby realizing multi-stage heat exchange to obtain rich liquids of different temperatures so that they can be transported to the second tower body 2 at different stages during the desorption process, thereby improving the utilization rate of heat and reducing the energy consumption and cost of carbon capture.

[0044] Furthermore, in the embodiment of the present invention, the rich liquid discharged from the first tower body 1 is heated by heat exchange in different ways, so that the rich liquid transported to the desorption tower has multiple temperatures. By reasonably arranging different rich liquid inlets, the heat utilization rate in the desorption tower can be improved to achieve the purpose of energy saving and consumption reduction.

[0045] In some embodiments, there are multiple second inlets 12 , and the second inlet 12 connected to the second heat exchanger 4 is higher in the vertical direction than the second inlet 12 connected to the first heat exchanger 3 .

[0046] In the embodiment of the present invention, a plurality of second inlets 12 are arranged and distributed at different heights on the second tower body 2 in the vertical direction. By delivering rich liquids of different temperatures into the second tower body 2 through different second inlets 12, the liquid distribution method of the rich liquid can be optimized, and the temperature of the rich liquid in the second tower body 2 can be made to form a gradient change, gradually increasing from top to bottom. Since the temperature of the carbon dioxide gas desorbed from the rich liquid in the second tower body 2 after heating and temperature rise is relatively high, the carbon dioxide gas can exchange heat with the rich liquid during the rising process, thereby realizing the recycling of the heat in the carbon dioxide.

[0047] The embodiment of the present invention ensures that more heat of the high-temperature lean liquid discharged from the second tower body 2 can be absorbed and reused, while also enabling the rich liquid discharged from the first tower body 1 to be heated by heat exchange in different forms, thereby making full use of the thermal energy in the lean liquid with high quality heat and the lean liquid with low quality heat.

[0048] like Figure 2 As shown, in some embodiments, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange also includes a first rich liquid pipeline 21, and the first outlet 11 is connected to one of the second inlets 12 in the second tower body 2 through the first rich liquid pipeline 21, so that part of the solvent discharged from the first outlet 11 is directly transported into the second tower body 2.

[0049] By arranging the first rich liquid pipeline 21, part of the rich liquid discharged from the first tower body 1 can flow directly to the second tower body 2. At this time, the rich liquid temperature is the lowest. Therefore, the second inlet 12 connected to the first rich liquid pipeline 21 is higher in the vertical direction than other second inlets 12.

[0050] Optionally, the second inlet 12 connected to the first rich liquid pipeline 21, the second inlet 12 connected to the second heat exchanger 4, and the second inlet 12 connected to the first heat exchanger 3 are arranged in sequence from high to low in the vertical direction, and the temperature of the rich liquid also increases sequentially.

[0051] Furthermore, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange also includes a third heat exchanger. The top of the second tower body 2 has an outlet, which is connected to the hot side inlet of the third heat exchanger. The cold side pipeline of the third heat exchanger is connected in series to the first rich liquid pipeline 21.

[0052] The carbon dioxide desorbed from the second tower body 2 carries a large amount of heat, which is of relatively low quality and is often directly discharged. In the embodiment of the present invention, three heat exchangers are arranged, and a part of the low-temperature rich liquid discharged from the first outlet 11 of the first tower body 1 is directly or indirectly contacted with the carbon dioxide gas discharged from the second tower body 2 for heat exchange, so as to further recover the heat in the gas, reuse the low-quality heat, improve the heat recycling efficiency, and further reduce energy consumption.

[0053] In some embodiments, a first lean liquid pipeline 22 is provided between the second outlet 13 and the third inlet 14 of the flash device 5, and a second lean liquid pipeline 23 is provided between the second outlet 13 and the hot side inlet of the first heat exchanger 3, and the solvent flow in the first lean liquid pipeline 22 accounts for 20% to 80% of the total flow of the second outlet 13.

[0054] Specifically, the solvent flow in the first lean liquid pipeline 22 accounts for 20%, 23%, 30%, 450%, 66%, 75%, 78% or 80% of the total flow of the second outlet 13. When the solvent flow in the first lean liquid pipeline 22 is less than 20%, the performance of the flash evaporation device 5 cannot be fully utilized, and the flash evaporation device 5 also has a certain energy consumption, resulting in poor practicality, affecting the energy recovery efficiency of the entire system, and the energy saving rate is low. When the solvent flow in the first lean liquid pipeline 22 is greater than 80%, it will cause the flash evaporation device 5 to be overloaded, and the flow of the high-temperature lean liquid flowing into the first heat exchanger 3 is too small, and the low-temperature rich liquid flowing into the first heat exchanger 3 cannot be fully heated and heated, affecting the liquid distribution effect of the rich liquid in the second tower body 2.

[0055] In some embodiments, the flash evaporation device 5 further comprises a compressor 7, which is disposed between the gas phase outlet 15 and the second tower body 2. The compressor 7 is used to compress the flashed gas phase and then transport it into the second tower body 2.

[0056] Optionally, the flash device 5 and the compressor 7 can be one group or multiple groups. The model and quantity of the flash device 5 can be reasonably selected according to the processing capacity of the solvent absorption carbon capture system and the flow ratio allocated to the flash device 5.

[0057] Further, the gas phase outlet 15 of the flash evaporation device 5 is connected to the middle and lower part of the inner cavity of the second tower body 2. It should be understood that the solvent at the bottom of the second tower body 2 is heated and reboiled by the reboiler 18 to achieve desorption, and the compressed gas phase is transported into the middle and lower part of the second tower body 2, which can increase the heat of the middle and lower part of the second tower body 2, avoid the heat from flowing directly out of the second tower body 2 with the desorbed carbon dioxide, reduce the energy consumed by the reboiler 18, and at the same time, the low-temperature rich liquid entering from the top of the second tower body 2 can be gradually heated and heated during the descent process, reducing the energy consumption and desorption cost of the second tower body 2.

[0058] In some embodiments, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange also includes a lean liquid cooler 6, the inlet end of the lean liquid cooler 6 is connected to the hot side outlet of the first heat exchanger 3 and the hot side outlet of the second heat exchanger 4, and the outlet end of the lean liquid cooler 6 is connected to the first inlet 10 of the first tower body 1, which is used to cool the solvent transported into the lean liquid cooler 6 to a first preset temperature.

[0059] Since the temperature at which the solvent in the first tower body 1 absorbs carbon dioxide is relatively low, the embodiment of the present invention provides a lean liquid cooler 6 to cool the lean liquid entering the first tower body 1 through the first inlet 10, thereby ensuring that the temperature of the lean liquid entering the first tower body 1 is lower than the first preset temperature, thereby improving the carbon capture effect.

[0060] Specifically, the first preset temperature may be 30 degrees Celsius to 45 degrees Celsius.

[0061] In some embodiments, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange further includes a lean liquid pump 8 and a rich liquid pump 9 , the second outlet 13 and the liquid phase outlet 16 are both connected to the lean liquid pump 8 , and the first outlet 11 is connected to the rich liquid pump 9 .

[0062] The embodiment of the present invention arranges a lean liquid pump 8 or a rich liquid pump 9 on the corresponding pipeline, so as to pressurize and transport the solvent in the pipeline, thereby ensuring the normal and stable circulation flow of the entire system.

[0063] In some embodiments, the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange further includes a reboiler 18, which is connected to the second tower body 2 to heat the solvent at the bottom of the second tower body 2. Steam is introduced into the reboiler 18, and the steam and the solvent transported into the reboiler 18 are used for heat exchange to achieve desorption of the solvent, so that the solvent can be recycled and reused after desorbing carbon dioxide.

[0064] like Figure 3 As shown, the carbon dioxide capture method based on flash evaporation and multi-stage heat exchange in an embodiment of the present invention uses the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange in any of the above embodiments to capture carbon, and the method includes:

[0065] S101, the lean liquid transported into the first tower body contacts the mixed gas to capture carbon dioxide in the mixed gas, and the rich liquid is discharged from the first outlet of the first tower body.

[0066] S102, the rich liquid transported into the second tower body is heated to desorb carbon dioxide, and the lean liquid is discharged from the second outlet of the second tower body.

[0067] In order to ensure the normal and efficient progress of the absorption reaction, the temperature in the first tower body is relatively low. In order to ensure the normal and efficient progress of the desorption reaction in the second tower body, the temperature in the second tower body is relatively high. Therefore, the temperature of the rich liquid discharged from the first outlet is relatively low, and the temperature of the lean liquid discharged from the second outlet is relatively high.

[0068] S103, adjusting the flow rate of the lean liquid and the flow rate of the rich liquid transported into the first heat exchanger so that the lean liquid transported into the first heat exchanger is transported into the first tower body after being cooled by heat exchange, and the rich liquid transported into the first heat exchanger is transported into the second tower body after being heated by heat exchange.

[0069] S104, conveying the remaining lean liquid into the flash evaporation device, and adjusting the flow rate of the rich liquid conveyed into the second heat exchanger, the gas phase after flash evaporation in the flash evaporation device is conveyed into the second tower body, and the liquid phase remaining after flash evaporation is conveyed into the second heat exchanger, so that the lean liquid conveyed into the second heat exchanger is conveyed into the first tower body after being cooled by heat exchange, and the rich liquid conveyed into the second heat exchanger is conveyed into the second tower body after being heated by heat exchange.

[0070] S105, directly conveying the remaining rich liquid discharged from the first outlet into the second tower body, or conveying the remaining rich liquid discharged from the first outlet into the second tower body after heat exchange with the gas discharged from the second tower body and heating it up.

[0071] The embodiment of the present invention not only divides the lean liquid into two parts, and recovers heat through heat exchange and flash evaporation respectively, but also can divide the rich liquid into three parts, and recover heat through heat exchange with the lean liquid, heat exchange with the carbon dioxide gas discharged from the second tower body, and heat exchange with the liquid phase discharged from the flash evaporation device respectively, thereby reducing the energy consumption and cost of the entire system, contributing to the efficient use of heat, and facilitating the promotion and application of the carbon capture system.

[0072] The following is described in conjunction with specific embodiments:

[0073] Example 1: A stream of 12% CO2, 77% N2, 6% O2 and 5% H2O at a flow rate of 13500 Nm3 / h is contacted with 30% 2-amino-2-methylpropanol (AMP) and 10% piperazine at a flow rate of 50 m3 / h and a solvent with a CO2 load of 0.15 in an absorber, and the CO2 absorption rate is 90%. In a process having an absorber, a desorber, a lean-rich liquid heat exchanger and a reboiler, and a rich liquid split ratio of 19%, the capture amount is 3 tons of CO2 / h, and the energy consumption for heating in the reboiler is 3.24 GJ / ton of CO2.

[0074] On the basis of the above process, the embodiment of the present invention adds partial lean liquid flash evaporation and residual liquid independent heat exchange technology. The system and method of the embodiment of the present invention are adopted. The lean liquid with a lean liquid split ratio of 25% is used for lean liquid flash evaporation, the rich liquid separation ratio is 0.14 for direct desorption tower top, and the rich liquid split ratio is 0.10 for heat exchange with flash residual liquid. The regeneration heat consumption is 2.84GJ / ton CO2. The power consumption of the compressor is 20kwh, which is converted into a heat consumption of 0.06GJ / ton CO2 at steam temperature. The overall energy consumption is 2.84+0.06=2.90GJ / ton CO2, which saves 10.6% energy compared with 3.24GJ / ton CO2 of the conventional process in the related art.

[0075] Embodiment 2:

[0076] Under the same conditions as in Example 1, the lean liquid with a lean liquid split ratio of 50% is used for lean liquid flash evaporation, the rich liquid separation ratio is 0.12 for direct desorption tower top, the rich liquid split ratio is 0.35 for heat exchange with flash residual liquid, and the regeneration heat consumption is 2.69GJ / ton CO2. The power consumption of the compressor is 39kwh, which is converted into a heat consumption of 0.11GJ / ton CO2 at steam temperature. The overall energy consumption is 2.69+0.11=2.80GJ / ton CO2, which is 13.5% energy-saving compared with 3.24GJ / ton CO2 of the conventional process in the related art.

[0077] Example 3

[0078] Under the same conditions as in Example 1, the lean liquid with a lean liquid split ratio of 75% is used for lean liquid flash evaporation, the rich liquid separation ratio is 0.06 for direct desorption tower top, the rich liquid split ratio is 0.65 for heat exchange with flash residual liquid, and the regeneration heat consumption is 2.61GJ / ton CO2. The power consumption of the compressor is 58kwh, which is converted into a heat consumption of 0.17GJ / ton CO2 at steam temperature. The overall energy consumption is 2.61+0.17=2.78GJ / ton CO2, which is 14.3% energy-saving compared with 3.24GJ / ton CO2 of the conventional process in the related art.

[0079] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0080] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0081] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0082] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0083] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0084] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A carbon dioxide capture system based on flash evaporation and multi-stage heat exchange, characterized in that: The invention comprises a first tower body, a second tower body, a flash evaporation device, a first heat exchanger and a second heat exchanger connected to each other, wherein the first tower body is used for a solvent and a mixed gas to contact and react to capture carbon dioxide in the mixed gas, the second tower body is used for heating the solvent that has absorbed carbon dioxide to desorb the carbon dioxide, the first tower body has a first inlet and a first outlet, the second tower body has a second inlet and a second outlet, and the flash evaporation device has a third inlet, a gas phase outlet and a liquid phase outlet; The gas phase outlet is connected to the second tower body, the liquid phase outlet is connected to the hot side inlet of the second heat exchanger, the cold side outlet of the first heat exchanger and the cold side outlet of the second heat exchanger are both connected to the second inlet of the second tower body, and the hot side outlet of the first heat exchanger and the hot side outlet of the second heat exchanger are both connected to the first inlet of the first tower body; The first outlet is connected to the cold side inlet of the first heat exchanger and the cold side inlet of the second heat exchanger to transport at least part of the solvent discharged from the first outlet to the first heat exchanger and at least part of the solvent to the second heat exchanger, and the second outlet is connected to the third inlet and the hot side inlet of the first heat exchanger to transport at least part of the solvent discharged from the second outlet to the flash device and at least part of the solvent to the first heat exchanger.

2. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 1, characterized in that: There are multiple second inlets, and the second inlet connected to the second heat exchanger is higher in the vertical direction than the second inlet connected to the first heat exchanger.

3. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 2, characterized in that: It also includes a first rich liquid pipeline, through which the first outlet is connected to one of the second inlets in the second tower body, so that part of the solvent discharged from the first outlet is directly transported into the second tower body.

4. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 3, characterized in that: The second inlet connected to the first rich liquid pipeline is higher in the vertical direction than the other second inlets; And / or, it also includes a third heat exchanger, the top of the second tower body has an outlet, the outlet is connected to the hot side inlet of the third heat exchanger, and the cold side pipeline of the third heat exchanger is connected in series to the first rich liquid pipeline.

5. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to any one of claims 1 to 4, characterized in that: A first lean liquid pipeline is provided between the second outlet and the third inlet of the flash device, and a second lean liquid pipeline is provided between the second outlet and the hot side inlet of the first heat exchanger. The solvent flow in the first lean liquid pipeline accounts for 20% to 80% of the total flow of the second outlet.

6. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 1, characterized in that: It also includes a compressor, which is arranged between the gas phase outlet and the second tower body; And / or, the gas phase outlet of the flash evaporation device is connected to the middle and lower part of the inner cavity of the second tower body.

7. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 1, characterized in that: It also includes a lean liquid cooler, the inlet end of the lean liquid cooler is connected to the hot side outlet of the first heat exchanger and the hot side outlet of the second heat exchanger, and the outlet end of the lean liquid cooler is connected to the first inlet of the first tower body, for cooling the solvent transported into the lean liquid cooler to a first preset temperature.

8. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 1, characterized in that: It also includes a lean liquid pump and a rich liquid pump. The second outlet and the liquid phase outlet are both connected to the lean liquid pump, and the first outlet is connected to the rich liquid pump.

9. The carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to claim 1, characterized in that: It also includes a reboiler, which is connected to the second tower body to heat the solvent at the bottom of the second tower body.

10. A method for capturing carbon dioxide based on flash evaporation and multi-stage heat exchange, characterized in that: Carbon capture is performed using the carbon dioxide capture system based on flash evaporation and multi-stage heat exchange according to any one of claims 1 to 9, the method comprising: The lean liquid transported into the first tower body contacts with the mixed gas to capture carbon dioxide in the mixed gas, and the rich liquid is discharged from the first outlet of the first tower body; The rich liquid transported into the second tower body is heated to desorb carbon dioxide, and the lean liquid is discharged from the second outlet of the second tower body; Adjusting the flow rate of the lean liquid and the flow rate of the rich liquid transported into the first heat exchanger so that the lean liquid transported into the first heat exchanger is transported into the first tower body after being cooled by heat exchange, and the rich liquid transported into the first heat exchanger is transported into the second tower body after being heated by heat exchange; The remaining lean liquid is transported into the flash device, and the flow rate of the rich liquid transported into the second heat exchanger is adjusted, the gas phase after flashing in the flash device is transported into the second tower body, and the liquid phase remaining after flashing is transported into the second heat exchanger, so that the lean liquid transported into the second heat exchanger is transported into the first tower body after being cooled by heat exchange, and the rich liquid transported into the second heat exchanger is transported into the second tower body after being heated by heat exchange; The remaining rich liquid discharged from the first outlet is directly transported to the second tower body, or the remaining rich liquid discharged from the first outlet is heat-exchanged with the gas discharged from the second tower body and then transported to the second tower body after the temperature is increased.

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