Carbon capture heat exchange energy-saving method and carbon capture energy-saving system

Abstract

The invention discloses a carbon capture heat exchange energy-saving method and a carbon capture energy-saving system. The carbon capture heat exchange energy-saving method comprises the following steps: dividing barren liquor discharged from a desorption tower into a first part of barren liquor and a second part of barren liquor, and adjusting the flow ratio of the first part of barren liquor to the second part of barren liquor; the first part of barren liquor is used for flash evaporation, and a gas phase after flash evaporation is pressurized and then conveyed into a desorption tower; a liquid phase obtained after flash evaporation of the first part of barren liquor and the second part of barren liquor are conveyed into a heat exchanger and exchange heat with rich liquor discharged from an absorption tower in the heat exchanger, the rich liquor obtained after heat exchange is conveyed into the desorption tower, and the barren liquor obtained after heat exchange is conveyed into the absorption tower. According to the carbon capture heat exchange energy-saving method provided by the embodiment of the invention, the utilization rate of the heat of the high-temperature barren liquor discharged by the desorption tower can be improved, and more surplus heat can be used for regeneration desorption of the rich liquor.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and in particular relates to a carbon capture heat exchange energy-saving method and a carbon capture energy-saving system. Background Art

[0002] The energy consumption of capturing carbon dioxide is relatively high, which affects its large-scale promotion and use.

[0003] In the related art, chemical absorption is used to capture and separate carbon dioxide. The rich liquid discharged from the absorption tower and the lean liquid discharged from the desorption tower are exchanged through a heat exchanger to recover energy. However, only part of the heat of the high-temperature lean liquid discharged from the desorption tower can be used in the heat exchanger to heat the rich liquid, resulting in low heat utilization. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, an embodiment of the present invention proposes a carbon capture heat exchange energy-saving method capable of improving heat utilization rate.

[0006] An embodiment of the present invention further provides a carbon capture energy-saving system.

[0007] The carbon capture heat exchange energy-saving method according to the embodiment of the present invention comprises the following steps:

[0008] dividing the lean liquid discharged from the desorption tower into a first portion of lean liquid and a second portion of lean liquid, and adjusting a flow ratio of the first portion of lean liquid to the second portion of lean liquid;

[0009] The first portion of lean liquid is used for flash evaporation, and the gas phase after flash evaporation is pressurized and transported into the desorption tower;

[0010] The liquid phase after flash evaporation of the first part of lean liquid and the second part of lean liquid are transported to a heat exchanger and exchange heat with the rich liquid discharged from the absorption tower in the heat exchanger. The rich liquid after heat exchange is transported to the desorption tower, and the lean liquid after heat exchange is transported to the absorption tower.

[0011] The carbon capture heat exchange energy-saving method of the embodiment of the present invention can improve the utilization rate of the heat of the high-temperature lean liquid discharged from the desorption tower, and can use more surplus heat for the regeneration and desorption of the rich liquid.

[0012] In some embodiments, the flow rate of the first portion of lean liquid accounts for 20% to 80% of the total flow rate of the lean liquid discharged from the desorption tower.

[0013] In some embodiments, the rich liquid discharged from the absorption tower is divided into a first part of rich liquid and a second part of rich liquid, and the desorption tower includes a first rich liquid inlet and a second rich liquid inlet arranged in sequence along the height direction of the desorption tower, and the first rich liquid inlet is located above the second rich liquid inlet in the height direction of the desorption tower, the first part of rich liquid is heat exchanged in the heat exchanger and transported into the desorption tower through the second rich liquid inlet, and the second part of rich liquid is directly transported into the desorption tower through the first rich liquid inlet.

[0014] In some embodiments, the first portion of rich liquid after heat exchange in the heat exchanger is divided into a plurality of first sub-portions of rich liquid, and the plurality of first sub-portions of rich liquid are respectively transported into the desorption tower through a plurality of second rich liquid inlets;

[0015] And / or, the second portion of rich liquid is divided into a plurality of second sub-portions of rich liquid, and the plurality of second sub-portions of rich liquid are respectively transported into the desorption tower through a plurality of the first rich liquid inlets.

[0016] The carbon capture energy-saving system of the embodiment of the present invention comprises an absorption tower, a desorption tower, a heat exchanger and a flash evaporation device connected to each other, wherein part of the lean liquid discharged from the desorption tower enters the flash evaporation device, and the gas phase discharged from the flash evaporation device enters the desorption tower;

[0017] The other part of the lean liquid discharged from the desorption tower and the liquid phase discharged from the flash evaporation device are transported to the heat exchanger, and after heat exchange with the rich liquid discharged from the absorption tower, flow into the absorption tower, and the rich liquid after heat exchange in the heat exchanger is transported to the desorption tower.

[0018] In some embodiments, the absorption tower has a rich liquid outlet and a lean liquid inlet, the desorption tower has a rich liquid inlet and a lean liquid outlet, the heat exchanger has a first flow channel and a second flow channel, the first flow channel is connected to the lean liquid outlet and the lean liquid inlet, and the second flow channel is connected to the rich liquid outlet and the rich liquid inlet;

[0019] The flash device comprises a flash tank and a compressor, wherein the flash tank has a flash inlet, a gas phase outlet and a liquid phase outlet, wherein the flash inlet is connected to the lean liquid outlet, the liquid phase outlet is connected to the first flow channel, and the gas phase outlet is connected to the desorption tower through the compressor.

[0020] In some embodiments, a first pump body is provided between the lean liquid outlet and the first flow channel, a second pump body is provided between the liquid phase outlet and the first flow channel, and a third pump body is provided between the rich liquid outlet and the second flow channel.

[0021] In some embodiments, a first condensing device is further included, the desorption tower has a first flue gas outlet, and the first condensing device is connected to the first flue gas outlet to recover condensate in the flue gas discharged from the first flue gas outlet;

[0022] And / or, further comprising a second condensing device, the absorption tower having a second flue gas outlet, the second condensing device being connected to the second flue gas outlet to recover condensate in the flue gas discharged from the second flue gas outlet;

[0023] And / or, further comprising a first cooler, the first cooler being arranged between the heat exchanger and the lean liquid inlet to cool the lean liquid entering the absorption tower to a first preset temperature;

[0024] And / or, the flow rate of the lean liquid delivered to the flash inlet accounts for 20% to 80% of the total flow rate of the lean liquid discharged from the lean liquid outlet.

[0025] In some embodiments, the rich liquid inlet includes a first rich liquid inlet and a second rich liquid inlet, the first rich liquid inlet is connected to the rich liquid outlet so that part of the rich liquid discharged from the absorption tower is transported into the desorption tower through the first rich liquid inlet, and the second rich liquid inlet is connected to the heat exchanger so that the other part of the rich liquid discharged from the absorption tower flows into the desorption tower through the second rich liquid inlet after heat exchange in the heat exchanger.

[0026] In some embodiments, there are multiple first rich liquid inlets, and the multiple first rich liquid inlets and the second rich liquid inlets are arranged in sequence along the height direction of the desorption tower, and the second rich liquid inlet is located below the multiple first rich liquid inlets in the height direction of the desorption tower;

[0027] And / or, there are multiple second rich liquid inlets, the first rich liquid inlet and the multiple second rich liquid inlets are arranged in sequence along the height direction of the desorption tower, and the first rich liquid inlet is located above the multiple second rich liquid inlets in the height direction of the desorption tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the carbon capture energy-saving system according to an embodiment of the present invention.

[0029] Figure 2 It is a process flow chart of a carbon capture energy-saving system in another embodiment of the present invention.

[0030] Reference numerals:

[0031] 1. Desorption tower; 11. Rich liquid inlet; 12. Lean liquid outlet; 13. First flue gas outlet; 14. Reboiler;

[0032] 2. Absorption tower; 21. Rich liquid outlet; 22. Lean liquid inlet; 23. Second flue gas outlet;

[0033] 3. Flash tank;

[0034] 4. Compressor;

[0035] 5. Heat exchanger;

[0036] 61. first pump body; 62. second pump body; 63. third pump body;

[0037] 71. A first water cooler; 72. A first gas-liquid separator;

[0038] 81. A second water cooler; 82. A second gas-liquid separator;

[0039] 91. The first cooler. DETAILED DESCRIPTION

[0040] 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.

[0041] The following combination Figure 1 and Figure 2 The carbon capture heat exchange energy-saving method and the carbon capture energy-saving system according to the embodiments of the present invention are described in detail.

[0042] The carbon capture heat exchange energy-saving method according to the embodiment of the present invention comprises the following steps:

[0043] The lean liquid discharged from the desorption tower 1 is divided into a first part of lean liquid and a second part of lean liquid, and the flow ratio of the first part of lean liquid and the second part of lean liquid is adjusted; the first part of lean liquid is used for flash evaporation, and the gas phase after flash evaporation is conveyed into the desorption tower 1 after pressurization; the liquid phase after flash evaporation of the first part of lean liquid and the second part of lean liquid are conveyed into the heat exchanger 5, and heat exchanged with the rich liquid discharged from the absorption tower 2 in the heat exchanger 5, and the rich liquid after heat exchange is conveyed into the desorption tower 1, and the lean liquid after heat exchange is conveyed into the absorption tower 2.

[0044] It should be understood that the desorption tower 1 is used to desorb the absorbent (rich liquid) that has absorbed carbon dioxide in the carbon capture system. The rich liquid needs to be heated during the process. Generally, the rich liquid in the desorption tower 1 is heated and desorbed by the reboiler 14 to separate carbon dioxide. The temperature of the absorbent (lean liquid) after separating carbon dioxide is relatively high, and the temperature can reach 120°C or even higher. If all of this heat is directly transferred to the heat exchanger 5 for heat exchange with the rich liquid discharged from the absorption tower 2, only a part of the excess heat can be absorbed by the rich liquid, resulting in low heat utilization. In the embodiment of the present invention, by flashing part of the lean liquid discharged from the desorption tower 1, the gas phase obtained after flashing is heated and then transported to the desorption tower 1, heat energy recovery is achieved, thereby improving heat utilization.

[0045] The liquid phase after flash evaporation and the remaining lean liquid are transported to the heat exchanger 5 for heat exchange. Without affecting the heating of the rich liquid discharged from the absorption tower 2, more surplus heat can be utilized to further improve the utilization rate of the heat in the lean liquid discharged from the desorption tower 1, thereby reducing the energy consumption and cost of carbon capture.

[0046] The carbon capture heat exchange energy-saving method of the embodiment of the present invention can improve the utilization rate of the heat of the high-temperature lean liquid discharged from the desorption tower 1, and can use more surplus heat for the regeneration and desorption of the rich liquid.

[0047] In some embodiments, the flow rate of the first portion of lean liquid accounts for 20% to 80% of the total flow rate of the lean liquid discharged from the desorption tower 1 .

[0048] In the flash pressurization process of the lean liquid, all the lean liquid is flash compressed, which easily leads to a large flow rate of gas mainly composed of water, a large investment in compression equipment, and a large power consumption for compression. In addition, since only a part of the heat in the high-temperature lean liquid is surplus and cannot be used to heat the rich liquid in the heat exchanger 5, the embodiment of the present invention further optimizes the heat utilization rate by reasonably designing the flow ratio of the first part of the lean liquid and the second part of the lean liquid.

[0049] Specifically, the flow rate of the first part of the lean liquid accounts for 20%, 25%, 47%, 75% to 80% of the total flow rate of the lean liquid discharged from the desorption tower 1. When the flow rate of the first part of the lean liquid is less than 20% of the total flow rate of the lean liquid discharged from the desorption tower 1, the waste heat in the high-temperature lean liquid cannot be fully utilized, and the heat utilization rate is too low. When the flow rate of the first part of the lean liquid is greater than 80% of the total flow rate of the lean liquid discharged from the desorption tower 1, the investment in compression equipment is large, the power consumption of compression is large, and the purpose of energy saving cannot be achieved.

[0050] Furthermore, the flow rate of the first portion of lean liquid accounts for 25% to 75% of the total flow rate of the lean liquid discharged from the desorption tower 1 .

[0051] When adjusting the flow of the first part of the lean liquid, the flow ratio of the first part of the lean liquid is reasonably controlled according to the flow of the rich liquid entering the heat exchanger 5. For example, when the flow of the rich liquid discharged from the absorption tower 2 entering the heat exchanger 5 increases, the flow ratio of the first part of the lean liquid is reduced; when the flow of the rich liquid discharged from the absorption tower 2 entering the heat exchanger 5 decreases, the flow ratio of the first part of the lean liquid is increased.

[0052] In some embodiments, the rich liquid discharged from the absorption tower 2 is divided into a first part of rich liquid and a second part of rich liquid. The desorption tower 1 includes a first rich liquid inlet and a second rich liquid inlet arranged in sequence along the height direction of the desorption tower 1. The first rich liquid inlet is located above the second rich liquid inlet in the height direction of the desorption tower 1. The first part of the rich liquid is heat exchanged in the heat exchanger 5 and transported into the desorption tower 1 through the second rich liquid inlet, and the second part of the rich liquid is directly transported into the desorption tower 1 through the first rich liquid inlet.

[0053] In the embodiment of the present invention, the rich liquid discharged from the absorption tower 2 is divided into two parts. One part is not heated by heat exchanger 5 and is directly transported to the desorption tower 1. The other part is transported to the desorption tower 1 after heat exchanger 5. Since the temperature of the carbon dioxide gas desorbed in the desorption tower 1 is relatively high, the rich liquid that has not been heated by the heat exchanger 5 falls from the top of the desorption tower 1, and the carbon dioxide gas flows upward from the bottom of the desorption tower 1. The carbon dioxide gas can transfer mass and heat with the rich liquid entering the desorption tower 1, so that the temperature of the rich liquid gradually increases during the downward flow, thereby realizing the recovery and utilization of the waste heat in the carbon dioxide.

[0054] In some embodiments, the first part of the rich liquid after heat exchange in the heat exchanger 5 is divided into multiple first sub-parts of rich liquids, and the multiple first sub-parts of rich liquids are respectively transported into the desorption tower 1 through multiple second rich liquid inlets; the second part of the rich liquid is divided into multiple second sub-parts of rich liquids, and the multiple second sub-parts of rich liquids are respectively transported into the desorption tower 1 through multiple first rich liquid inlets.

[0055] The rich liquid (the first part of the rich liquid) after heat exchange in the heat exchanger 5 can enter the desorption tower 1 through the second rich liquid inlet. The second rich liquid inlet can be one or more. For example, the multiple second rich liquid inlets are arranged in sequence along the height direction of the desorption tower 1, and the rich liquid (the first part of the rich liquid) after heat exchange in the heat exchanger 5 is diverted into the desorption tower 1.

[0056] The rich liquid (the second part of the rich liquid) that has not been heat exchanged by the heat exchanger 5 enters the analytical tower through the first rich liquid inlet. The first rich liquid inlet may be one or more. For example, the plurality of first rich liquid inlets are arranged in sequence along the height direction of the analytical tower. The rich liquid (the second part of the rich liquid) that has not been heat exchanged by the heat exchanger 5 is divided and enters the analytical tower.

[0057] The rich liquid can enter the desorption tower 1 through multiple inlets, which is convenient for liquid distribution on the one hand, and can also improve the effect of heat and mass transfer on the other hand, and improve the uniformity of the distribution of the rich liquid and the consistency of the temperature.

[0058] Since the temperature of the first portion of rich liquid is higher than that of the second portion of rich liquid, the first rich liquid inlet is located above the second rich liquid inlet.

[0059] Optionally, the number of the first rich liquid inlets is 2, 3, or 4, and the number of the second rich liquid inlets is 1, 2, or 3.

[0060] The carbon capture energy-saving system of the embodiment of the present invention includes an absorption tower 2, a desorption tower 1, a heat exchanger 5 and a flash evaporation device connected to each other. Part of the lean liquid discharged from the desorption tower 1 enters the flash evaporation device, and the gas phase discharged from the flash evaporation device enters the desorption tower 1; the other part of the lean liquid discharged from the desorption tower 1 and the liquid phase discharged from the flash evaporation device are transported to the heat exchanger 5, and after heat exchange with the rich liquid discharged from the absorption tower 2, they flow into the absorption tower 2, and the rich liquid after heat exchange in the heat exchanger 5 is transported to the desorption tower 1.

[0061] Flue gas containing carbon dioxide enters absorption tower 2 from the bottom of absorption tower 2, flue gas flows from bottom to top, and absorbent flows from top to bottom. Flue gas and absorbent are fully contacted in the packing layer to generate absorption reaction. The absorbent absorbs carbon dioxide and forms rich liquid, which is discharged from the bottom of absorption tower 2.

[0062] The desorption tower is used to heat the rich liquid, separate the carbon dioxide in the rich liquid, and desorb the rich liquid to form a lean liquid (the absorbent after the carbon dioxide is separated). The lean liquid can be circulated to the absorption tower 2 for repeated use.

[0063] Since the temperature of the rich liquid discharged from the absorption tower 2 is relatively low, the temperature of the lean liquid discharged from the desorption tower 1 is relatively high, and the absorption reaction between the absorbent and carbon dioxide in the absorption tower 2 is an exothermic reaction, the temperature of the absorbent needs to be lowered, and the rich liquid needs to be heated in the desorption tower 1. Therefore, by setting the heat exchanger 5, part of the heat of the high-temperature lean liquid discharged from the desorption tower 1 can be used to heat the rich liquid entering the desorption tower 1.

[0064] In actual applications, during the heat exchange process between the lean liquid and the rich liquid in the heat exchanger 5, the high-temperature lean liquid still has excess heat that cannot be utilized. The embodiment of the present invention flashes part of the lean liquid and uses more heat energy for desorption of the rich liquid in the desorption tower 1, thereby improving the heat recovery rate of the lean liquid discharged from the desorption tower 1.

[0065] In some embodiments, the absorption tower 2 has a rich liquid outlet 21 and a lean liquid inlet 22, the desorption tower 1 has a rich liquid inlet 11 and a lean liquid outlet 12, the heat exchanger 5 has a first flow channel and a second flow channel, the first flow channel is connected to the lean liquid outlet 12 and the lean liquid inlet 22, and the second flow channel is connected to the rich liquid outlet 21 and the rich liquid inlet 11; the flash evaporation device includes a flash tank 3 and a compressor 4, the flash tank 3 has a flash inlet, a gas phase outlet and a liquid phase outlet, the flash inlet is connected to the lean liquid outlet 12, the liquid phase outlet is connected to the first flow channel, and the gas phase outlet is connected to the desorption tower 1 through the compressor 4.

[0066] That is, the rich liquid outlet 21 is arranged at the bottom of the absorption tower 2, the lean liquid inlet 22 is arranged at the top of the absorption tower 2, the rich liquid inlet 11 is arranged at the top of the desorption tower 1, and the lean liquid outlet 12 is arranged at the bottom of the desorption tower 1. The high-temperature rich liquid part discharged from the bottom of the desorption tower 1 enters the flash tank 3 through the flash inlet, and the other part of the high-temperature rich liquid enters the first flow channel. The liquid phase in the flash tank 3 also enters the first flow channel through the liquid phase outlet discharge port. The lean liquid in the first flow channel exchanges heat with the rich liquid in the second flow channel and enters the lean liquid inlet 22. The rich liquid at the rich liquid outlet 21 is transported to the rich liquid inlet 11 after passing through the second flow channel and enters the desorption tower 1.

[0067] The compressor 4 pressurizes the gas phase at the gas phase outlet of the flash tank 3 and then transports it into the middle and lower part of the desorption tower 1 to heat the rich liquid in the desorption tower 1 .

[0068] Furthermore, the flow rate of the lean liquid delivered to the flash inlet accounts for 20% to 80% of the total flow rate of the lean liquid discharged from the lean liquid outlet 12 .

[0069] Specifically, the lean liquid flow rate transported into the flash evaporation inlet accounts for 20%, 25%, 47%, 75% to 80% of the total lean liquid flow rate discharged from the lean liquid outlet 12. When the lean liquid flow rate transported into the flash evaporation inlet is less than 20% of the total lean liquid flow rate discharged from the lean liquid outlet 12, the waste heat in the high-temperature lean liquid cannot be fully utilized, and the heat utilization rate is too low. When the lean liquid flow rate transported into the flash evaporation inlet is greater than 80% of the total lean liquid flow rate discharged from the lean liquid outlet 12, the investment in the compressor 4 is large, the compression power consumption is large, and the purpose of energy saving cannot be achieved.

[0070] In some embodiments, a first pump body 61 is provided between the lean liquid outlet 12 and the first flow channel, a second pump body 62 is provided between the liquid phase outlet and the first flow channel, and a third pump body 63 is provided between the rich liquid outlet 21 and the second flow channel. The first pump body 61 is used to pump the lean liquid at the bottom of the desorption tower 1 to the heat exchanger 5, the second pump body 62 is used to pump the liquid phase in the flash tank 3 to the heat exchanger 5, and the third pump body 63 is used to pump the rich liquid at the bottom of the absorption tower 2 to the heat exchanger 5.

[0071] In addition, a fourth pump body is provided, which is disposed between the lean liquid outlet 12 and the flash tank 3 , and is used to pump part of the lean liquid into the flash tank 3 .

[0072] In some embodiments, the carbon capture energy-saving system further includes a first condensing device, the desorption tower 1 has a first flue gas outlet 13 , and the first condensing device is connected to the first flue gas outlet 13 to recover condensate in the flue gas discharged from the first flue gas outlet 13 .

[0073] The first condensing device includes a first water cooler 71 and a first gas-liquid separator 72. The carbon dioxide gas discharged from the top of the desorption tower 1 is cooled by the first water cooler 71, and condensed water is separated in the first gas-liquid separator 72. This part of the condensed water flows back to the desorption tower 1. On the one hand, it can prevent the components in the absorbent from being lost with the carbon dioxide. On the other hand, the temperature of the condensed water is relatively high, and the temperature of the condensed water can be utilized. At the same time, the circulating water in the first water cooler 71 can be heated to recover the heat in the flue gas.

[0074] In some embodiments, the carbon capture energy-saving system further includes a second condensing device, the absorption tower 2 has a second flue gas outlet 23 , and the second condensing device is connected to the second flue gas outlet 23 to recover condensate in the flue gas discharged from the second flue gas outlet 23 .

[0075] The second condensing device includes a second water cooler 81 and a second gas-liquid separator 82. The carbon dioxide gas discharged from the top of the absorption tower 2 is cooled by the second water cooler 81, and condensed water is separated in the second gas-liquid separator 82. This part of condensed water flows back to the desorption tower 1, which can prevent the components in the absorbent from being lost with the flue gas.

[0076] In some embodiments, the carbon capture energy-saving system further includes a first cooler 91, which is disposed between the heat exchanger 5 and the lean liquid inlet 22 to cool the lean liquid entering the absorption tower 2 to a first preset temperature. The first preset temperature is an effective reaction temperature of the absorbent and carbon dioxide, for example, the first preset temperature is 35°C to 50°C.

[0077] The first cooler 91 cools the lean liquid by circulating water, and the first cooler 91 may be a shell and tube heat exchanger 5 .

[0078] In some embodiments, the rich liquid inlet 11 includes a first rich liquid inlet and a second rich liquid inlet, the first rich liquid inlet is connected to the rich liquid outlet 21, so that part of the rich liquid discharged from the absorption tower 2 is transported into the desorption tower 1 through the first rich liquid inlet, and the second rich liquid inlet is connected to the heat exchanger 5, so that the other part of the rich liquid discharged from the absorption tower 2 flows into the desorption tower 1 through the second rich liquid inlet after heat exchange in the heat exchanger 5.

[0079] In the embodiment of the present invention, the rich liquid discharged from the absorption tower 2 is divided into two parts. One part is not heated by heat exchanger 5 and is directly transported to the desorption tower 1. The other part is transported to the desorption tower 1 after heat exchange by heat exchanger 5. The rich liquid after heat exchange by heat exchanger 5 enters the desorption tower 1 through the second rich liquid inlet, and the rich liquid without heat exchange by heat exchanger 5 directly enters the desorption tower 1 through the first rich liquid inlet.

[0080] The rich liquid enters the desorption tower 1 after being diverted, and the heat of the carbon dioxide can be fully utilized to heat the rich liquid, thereby improving the utilization rate of the heat in the desorption tower 1.

[0081] Furthermore, there are multiple first rich liquid inlets, and the multiple first rich liquid inlets and second rich liquid inlets are arranged in sequence along the height direction of the desorption tower 1, and the second rich liquid inlet is located below the multiple first rich liquid inlets in the height direction of the desorption tower 1.

[0082] There are multiple second rich liquid inlets, the first rich liquid inlet and the multiple second rich liquid inlets are arranged in sequence along the height direction of the desorption tower 1 , and the first rich liquid inlet is located above the multiple second rich liquid inlets in the height direction of the desorption tower 1 .

[0083] That is to say, the rich liquid is further diverted, and the rich liquid after heat exchange in the heat exchanger 5 can enter the desorption tower 1 through the second rich liquid inlet. The second rich liquid inlet can be one or more. For example, the multiple second rich liquid inlets are arranged in sequence along the height direction of the desorption tower 1, and the rich liquid after heat exchange in the heat exchanger 5 is diverted into the desorption tower 1.

[0084] The rich liquid that has not been heat exchanged by the heat exchanger 5 enters the analytical tower through the first rich liquid inlet. The first rich liquid inlet may be one or more. For example, the plurality of first rich liquid inlets are arranged in sequence along the height direction of the analytical tower. The rich liquid that has not been heat exchanged by the heat exchanger 5 is divided and enters the analytical tower.

[0085] The rich liquid of the embodiment of the present invention can enter the desorption tower 1 through multiple inlets, which is convenient for liquid distribution on the one hand, and can also improve the effect of heat and mass transfer, and improve the uniformity of the distribution of the rich liquid and the consistency of temperature on the other hand. Since the temperature of the carbon dioxide gas in the desorption tower 1 gradually decreases during the rising process, the rich liquid of the embodiment of the present invention enters the desorption tower 1 through diversion, and the temperature of the rich liquid gradually increases from top to bottom along the height direction of the desorption tower 1. Therefore, the heat and mass transfer effect between the rich liquid at the top of the desorption tower 1 and the carbon dioxide gas can be guaranteed, and the waste heat in the carbon dioxide can be further fully utilized.

[0086] The carbon capture system includes a reboiler 14, which is connected to the desorption tower 1 and is used to heat the rich liquid in the desorption tower 1. Steam is introduced into the reboiler 14, and the steam consumes a lot of energy. When the carbon capture energy-saving system of the embodiment of the present invention is adopted, the energy consumption of capturing carbon dioxide in the gas mixture can be reduced by 5-15%. The scheme of the embodiment of the present invention is described in detail below in conjunction with specific embodiments.

[0087] Example 1: Flue gas including 12% carbon dioxide, 77% nitrogen, 6% oxygen and 5% water vapor, with a flow rate of 13500 standard cubic meters per hour, is contacted in an absorption tower with 30% 2-amino-2-methylpropanol (AMP) and 10% piperazine and a solvent with a carbon dioxide load of 0.15 with a flow rate of 50 cubic meters per hour, and the carbon dioxide absorption rate is 90%. In a process with an absorption tower, a desorption tower, a lean-rich liquid heat exchanger and a reboiler, and a rich liquid split ratio of 19%, the capture amount is 3 tons of carbon dioxide per hour, and the energy consumption for heating in the reboiler is 3.24 GJ / ton of carbon dioxide.

[0088] On the basis of the above process, some lean liquid flash evaporation heat exchange technology is added, using Figure 2 The process is modified to add a lean liquid flash tank and a flash gas compressor. The lean liquid split ratio is 25% of the lean liquid for lean liquid flash. The regeneration heat consumption is 3.01GJ / ton of carbon dioxide. The power consumption of the compressor is 20kwh, which is converted into a heat consumption of 0.06GJ / ton of carbon dioxide at steam temperature. The overall energy consumption is 3.01+0.06=3.07GJ / ton of carbon dioxide, which saves 5.2% energy compared with the original conventional process of 3.24GJ / ton of carbon dioxide.

[0089] Example 2: Under the same conditions as Example 1, the lean liquid with a lean liquid split ratio of 50% is used for lean liquid flash evaporation, and the regeneration heat consumption is 2.79GJ / ton of carbon dioxide. The power consumption of the compressor is 40kwh, which is converted into a heat consumption of 0.12GJ / ton of carbon dioxide at steam temperature. The overall energy consumption is 2.79+0.12=2.91GJ / ton of carbon dioxide, which saves 10.0% energy compared with 3.24GJ / ton of carbon dioxide in the original conventional process.

[0090] Example 3: Under the same conditions as Example 1, the lean liquid with a lean liquid split ratio of 75% is used for lean liquid flash evaporation, and the regeneration heat consumption is 2.59GJ / ton of carbon dioxide. The power consumption of the compressor is 61kwh, which is converted into a heat consumption of 0.18GJ / ton of carbon dioxide at steam temperature. The overall energy consumption is 2.59+0.18=2.77GJ / ton of carbon dioxide, which saves 14.5% energy compared with 3.24GJ / ton of carbon dioxide in the original conventional process.

[0091] In the embodiment of the present invention, the high-temperature lean liquid flowing out of the bottom of the desorption tower is divided into two parts, one part still flows to the lean-rich liquid heat exchanger to exchange heat with the rich liquid or part of the rich liquid, and the other part adopts the flash compression method to input the surplus heat of this part of the high-temperature lean liquid into the middle and lower part of the desorption tower through the compressed gas, thereby further reducing the regeneration heat consumption of the reboiler, and the flash residual liquid also enters the lean-rich liquid heat exchanger to heat the rich liquid or part of the rich liquid. This process can utilize the flash compression heat exchange of part of the lean liquid, which can reduce the energy consumption of carbon dioxide capture in the gas mixture by 5-15%.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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 capture heat exchange energy saving method, characterized in that: The following steps are involved: dividing the lean liquid discharged from the desorption tower into a first portion of lean liquid and a second portion of lean liquid, and adjusting a flow ratio of the first portion of lean liquid to the second portion of lean liquid; The first portion of lean liquid is used for flash evaporation, and the gas phase after flash evaporation is pressurized and transported into the desorption tower; The liquid phase after flash evaporation of the first part of lean liquid and the second part of lean liquid are transported to a heat exchanger and exchange heat with the rich liquid discharged from the absorption tower in the heat exchanger. The rich liquid after heat exchange is transported to the desorption tower, and the lean liquid after heat exchange is transported to the absorption tower.

2. The carbon capture heat exchange energy-saving method according to claim 1, characterized in that: The flow rate of the first part of lean liquid accounts for 20% to 80% of the total flow rate of lean liquid discharged from the desorption tower.

3. The carbon capture heat exchange energy saving method according to claim 1, characterized in that: The rich liquid discharged from the absorption tower is divided into a first part of rich liquid and a second part of rich liquid. The desorption tower comprises a first rich liquid inlet and a second rich liquid inlet arranged in sequence along the height direction of the desorption tower. The first rich liquid inlet is located above the second rich liquid inlet in the height direction of the desorption tower. The first part of rich liquid is heat exchanged in the heat exchanger and transported into the desorption tower through the second rich liquid inlet, and the second part of rich liquid is directly transported into the desorption tower through the first rich liquid inlet.

4. The carbon capture heat exchange energy saving method according to claim 3, characterized in that: The first part of the rich liquid after heat exchange in the heat exchanger is divided into a plurality of first sub-parts of rich liquid, and the plurality of first sub-parts of rich liquid are respectively transported into the desorption tower through a plurality of second rich liquid inlets; And / or, the second portion of rich liquid is divided into a plurality of second sub-portions of rich liquid, and the plurality of second sub-portions of rich liquid are respectively transported into the desorption tower through a plurality of the first rich liquid inlets.

5. A carbon capture energy-saving system, characterized in that: It includes an absorption tower, a desorption tower, a heat exchanger and a flash evaporation device connected to each other, part of the lean liquid discharged from the desorption tower enters the flash evaporation device, and the gas phase discharged from the flash evaporation device enters the desorption tower; The other part of the lean liquid discharged from the desorption tower and the liquid phase discharged from the flash evaporation device are transported to the heat exchanger, and after heat exchange with the rich liquid discharged from the absorption tower, flow into the absorption tower, and the rich liquid after heat exchange in the heat exchanger is transported to the desorption tower.

6. The carbon capture energy-saving system according to claim 5, characterized in that: The absorption tower has a rich liquid outlet and a lean liquid inlet, the desorption tower has a rich liquid inlet and a lean liquid outlet, the heat exchanger has a first flow channel and a second flow channel, the first flow channel is connected to the lean liquid outlet and the lean liquid inlet, and the second flow channel is connected to the rich liquid outlet and the rich liquid inlet; The flash device comprises a flash tank and a compressor, wherein the flash tank has a flash inlet, a gas phase outlet and a liquid phase outlet, wherein the flash inlet is connected to the lean liquid outlet, the liquid phase outlet is connected to the first flow channel, and the gas phase outlet is connected to the desorption tower through the compressor.

7. The carbon capture energy-saving system according to claim 6, characterized in that: A first pump body is provided between the lean liquid outlet and the first flow channel, a second pump body is provided between the liquid phase outlet and the first flow channel, and a third pump body is provided between the rich liquid outlet and the second flow channel.

8. The carbon capture energy-saving system according to claim 6, characterized in that: It also includes a first condensing device, the desorption tower has a first flue gas outlet, and the first condensing device is connected to the first flue gas outlet to recover condensate in the flue gas discharged from the first flue gas outlet; And / or, further comprising a second condensing device, the absorption tower having a second flue gas outlet, the second condensing device being connected to the second flue gas outlet to recover condensate in the flue gas discharged from the second flue gas outlet; And / or, further comprising a first cooler, the first cooler being arranged between the heat exchanger and the lean liquid inlet to cool the lean liquid entering the absorption tower to a first preset temperature; And / or, the flow rate of the lean liquid delivered to the flash inlet accounts for 20% to 80% of the total flow rate of the lean liquid discharged from the lean liquid outlet.

9. The carbon capture energy-saving system according to claim 5, characterized in that: The rich liquid inlet includes a first rich liquid inlet and a second rich liquid inlet, the first rich liquid inlet is connected to the rich liquid outlet so that part of the rich liquid discharged from the absorption tower is transported into the desorption tower through the first rich liquid inlet, and the second rich liquid inlet is connected to the heat exchanger so that the other part of the rich liquid discharged from the absorption tower flows into the desorption tower through the second rich liquid inlet after heat exchange in the heat exchanger.

10. The carbon capture energy-saving system according to claim 9, characterized in that: There are multiple first rich liquid inlets, and the multiple first rich liquid inlets and the second rich liquid inlets are arranged in sequence along the height direction of the desorption tower, and the second rich liquid inlet is located below the multiple first rich liquid inlets in the height direction of the desorption tower; And / or, there are multiple second rich liquid inlets, the first rich liquid inlet and the multiple second rich liquid inlets are arranged in sequence along the height direction of the desorption tower, and the first rich liquid inlet is located above the multiple second rich liquid inlets in the height direction of the desorption tower.

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