CO2 chemical absorption system and method for enhanced waste heat recovery using hydrophilic-hydrophobic double membrane heat exchanger

Abstract

The present invention discloses a CO2 chemical absorption system and method for enhancing waste heat recovery by using a hydrophilic / hydrophobic double membrane heat exchanger, which includes a CO2 absorption device, a CO2 regeneration device, a rich liquid pump, a lean liquid pump, a lean liquid cooler, a three-way diverter valve, a lean-rich liquid heat exchanger, a booster fan, and a regeneration gas waste heat recovery unit. The present invention uses a hydrophobic membrane heat exchanger and a hydrophilic membrane heat exchanger in combination as the heat exchange medium between the regeneration gas and the cold rich liquid, and can effectively recover water vapor and liquid water respectively according to different working conditions, and realizes the enhancement of convective heat exchange from the regeneration gas to the cold rich liquid from two aspects of fully utilizing the latent heat of water vapor and promoting the mass transfer of water vapor / liquid water to enhance convective heat exchange, so that the waste heat recovery efficiency of the regeneration gas is greatly enhanced. At the same time, the various combination modes will also be suitable for the waste heat recovery needs in large-scale industrial applications.

Description

Technical Field

[0001] The present invention relates to the technical field of energy saving and consumption reduction of a CO2 chemical absorption process in a CO2-rich gas, and specifically to a CO2 chemical absorption system and method for enhancing waste heat recovery by a hydrophilic-hydrophobic double-membrane heat exchanger. Background Art

[0002] Climate change has become a hot issue of concern to the international community. In order to limit the global average temperature rise to no more than 1.5℃ compared to the pre-industrial level in this century, governments around the world are actively formulating carbon emission reduction policies. Carbon capture and storage (CCS) technology has become a focus of attention as one of the key technologies to significantly reduce greenhouse gas emissions in the near future. The key lies in the separation of CO2. Among the many CO2 separation technologies, the CO2 chemical absorption carbon capture process using organic amines such as ethanolamine as absorbent has the advantages of mature technology, simple operation, low gas cleanliness requirements, no need to pressurize the gas, and high purity of CO2 products. It is highly valued and is one of the feasible ways to reduce CO2 emissions on a large scale.

[0003] The key to CO2 chemical absorption technology is to reduce system energy consumption, especially the thermal regeneration energy consumption of rich CO2 absorbent solution (referred to as rich liquid), because it can account for more than 60% of the total system energy consumption. In the traditional rich liquid thermal regeneration process, a large amount of water needs to be evaporated from the lean CO2 absorbent solution (referred to as lean liquid) at the bottom of the regeneration tower to maintain the regeneration driving force, resulting in a large amount of water vapor in the regeneration gas discharged from the top of the regeneration tower (usually a mixture of CO2 and H2O(g), with a molar ratio of CO2 and H2O(g) of up to 1:2), with a high temperature and large latent heat (~920-1840kJ / kgCO2). In the traditional chemical absorption process, this part of the heat is usually taken away by the external circulating cooling water in the regeneration gas cooler outside the regeneration tower, resulting in heat waste. If this part of the waste heat is recycled, the energy consumption of rich liquid regeneration can be reduced.

[0004] The waste heat recovery of the high-temperature regenerated gas at the top of the hot regeneration tower currently mainly adopts the rich-split process (U.S. Patent 4152217), that is, the regenerated gas is directly sprayed and cooled with the split cold rich liquid, but this method is limited by the split amount of the cold rich liquid, and the gas-liquid contact time is short, and the system consumption reduction effect is limited. Therefore, the researchers introduced a universal heat exchanger as a heat exchange medium between the split cold rich liquid and the regenerated gas, but its economic heat exchange temperature difference is generally about 20K (Kelvin). In order to obtain greater heat exchange performance, a larger heat exchange area is usually required. At this time, the heat pipe can be used as a high-efficiency phase change heat exchange element to replace the universal heat exchanger (Chinese patent CN201810763899.0), thereby enhancing the waste heat recovery performance and reducing the heat exchange area. However, in order to avoid mixing of cold and hot fluids, the heat transfer method of conventional heat exchangers is still limited to heat conduction. The patent (Chinese patent CN201710371929.9) provides a method for enhancing waste heat recovery performance based on water vapor mass transfer by using a hollow ceramic membrane contactor as a heat exchanger. It is based on the heat and mass coupling transfer of water vapor, and achieves the enhancement of waste heat recovery of regenerated gas from three aspects: thermal conductivity enhancement, water vapor / water mass transfer convection heat transfer enhancement, and gas phase thermal resistance reduction. However, relevant studies have pointed out that in the process of waste heat recovery of inorganic hollow membrane contactors (ceramic membrane heat exchangers), there is mass transfer of liquid water and water vapor at the same time, of which the liquid water mass transfer flux accounts for more than 85%, and the water vapor mass transfer flux is less than 15%, but the heat carried by the water vapor mass transfer accounts for more than 70%, which shows that the key to using membrane heat exchangers for waste heat recovery is to directly recover water vapor in the regenerated gas. Summary of the invention

[0005] The present invention provides a CO2 chemical absorption system and method for enhancing waste heat recovery by a hydrophilic-hydrophobic double membrane heat exchanger. The system and method can, on the basis of maintaining the original mature CO2 absorption and rich liquid thermal regeneration technology, effectively recover water vapor in the regenerated gas and condensed liquid water formed after the regenerated gas is cooled by combining a hydrophobic membrane heat exchanger with a hydrophilic membrane heat exchanger, respectively, so as to achieve the enhancement of waste heat recovery of the high-temperature regenerated gas (a mixture of CO2 and H2O(g)) discharged from the top of the thermal regeneration tower by the rich liquid from two aspects: fully utilizing the latent heat of water vapor and promoting the water vapor / liquid water mass transfer to enhance convective heat exchange. At the same time, the combination mode of the proposed multiple membrane heat exchangers can also provide a reference for the layout and selection of membrane heat exchangers for large-scale industrial waste heat recovery, so as to reduce the volume and investment of the heat exchanger required for the waste heat recovery of the regenerated gas.

[0006] To achieve this purpose, the present invention is a CO2 chemical absorption system with a hydrophilic-hydrophobic double-membrane heat exchanger to enhance waste heat recovery, which includes a CO2 absorption device, a three-way diverter valve, a lean-rich liquid heat exchanger, a regenerated gas waste heat recovery unit, a CO2 regeneration device, a reboiler, a rich liquid pump, a lean liquid pump, a lean liquid cooler, and a booster fan whose output end is connected to the air inlet of the CO2 absorption device, wherein the liquid outlet of the CO2 absorption device is connected to the first port of the three-way diverter valve through the rich liquid pump, the second port of the three-way diverter valve is connected to the low-temperature rich liquid inlet of the lean-rich liquid heat exchanger, the third port of the three-way diverter valve is connected to the rich liquid inlet of the regenerated gas waste heat recovery unit, the high-temperature rich liquid outlet of the lean-rich liquid heat exchanger is connected to the first rich liquid input port of the CO2 regeneration device, and the bottom liquid discharge port of the CO2 regeneration device is connected to the rich liquid input port of the reboiler. The lean liquid output port of the reboiler is connected to the high-temperature lean liquid inlet of the lean-rich liquid heat exchanger, the top exhaust port of the reboiler is connected to the bottom air inlet of the CO2 regeneration equipment, the reboiler also has a steam input port and a high-temperature water output port, the top exhaust port of the CO2 regeneration equipment is connected to the regeneration gas inlet of the regeneration gas, the condensed water outlet of the regeneration gas waste heat recovery unit is connected to the top condensed water reflux inlet of the CO2 regeneration equipment, the rich liquid outlet of the regeneration gas waste heat recovery unit is connected to the second rich liquid input port of the CO2 regeneration equipment, the regeneration gas waste heat recovery unit also has a regeneration gas outlet, the low-temperature lean liquid output port of the lean-rich liquid heat exchanger is connected to the lean liquid inlet of the lean liquid cooler, the lean liquid outlet of the lean liquid cooler is connected to the absorbent input port of the CO2 absorption equipment through a lean liquid pump, and a top exhaust port is also provided on the top of the CO2 absorption equipment.

[0007] A CO2 chemical absorption method based on the above system comprises the following steps:

[0008] Step 1: The CO2-rich gas is pressurized by the booster fan and enters the CO2 absorption device through the air inlet, and forms a countercurrent contact with the CO2 chemical absorbent entering from the absorbent inlet of the CO2 absorption device. The CO2 in the CO2-rich gas is absorbed, and the purified gas is discharged from the top exhaust port after being defogged from the top of the CO2 absorption device. The initial absorbent-rich CO2 solution generated after the absorbent in the CO2 absorption device absorbs CO2 enters the rich liquid pump from the liquid outlet of the CO2 absorption device;

[0009] Step 2: The initial absorbent rich CO2 solution is pumped into the three-way diverter valve through the rich liquid pump for diversion. The first part of the initial absorbent rich CO2 solution after diversion enters the lean-rich liquid heat exchanger through the second port of the three-way diverter valve, and performs heat exchange with the high-temperature hot lean liquid of 100-120°C discharged from the lean liquid outlet of the reboiler in the heat exchanger. The first part of the initial absorbent rich CO2 solution after heating then enters the first rich liquid inlet of the CO2 regeneration device;

[0010] Step 3: The initial absorbent rich CO2 solution enters the three-way diverter valve through the rich liquid pump for diversion. The second part of the initial absorbent rich CO2 solution after diversion enters the rich liquid inlet of the regeneration gas waste heat recovery unit through the third port of the three-way diverter valve. The second part of the initial absorbent rich CO2 solution is reversely contacted with the regeneration gas entering the regeneration gas waste heat recovery unit from the exhaust port at the top of the CO2 regeneration equipment in the regeneration gas waste heat recovery unit. The second part of the initial absorbent rich CO2 solution after recovering the waste heat enters the second rich liquid input port of the CO2 regeneration equipment through the rich liquid outlet. The condensed water generated by the cooling of the regeneration gas in the regeneration gas waste heat recovery unit refluxes to the condensed water reflux inlet at the top of the CO2 regeneration equipment through the condensed water outlet. The regeneration gas after heat exchange is discharged from the regeneration gas outlet of the regeneration gas waste heat recovery unit.

[0011] Step 4: The first part of the initial absorbent-rich CO2 solution that enters the CO2 regeneration device through the first rich liquid input port and passes through the heat exchanger and the second part of the initial absorbent-rich CO2 solution that recovers waste heat that enters the CO2 regeneration device through the second rich liquid input port are reversely contacted with CO2 and H2O(g) regeneration gas in the CO2 regeneration device for reheating, and then flow into the reboiler from the bottom output port of the CO2 regeneration device to be heated and separated from CO2 and the absorbent. The CO2 heated and separated in the reboiler carries saturated water vapor and flows upward along the CO2 regeneration device from the top exhaust port of the reboiler through the bottom air inlet of the CO2 regeneration device;

[0012] Step 5: The high-temperature lean liquid of 100-120°C obtained after regeneration in the reboiler enters the lean-rich liquid heat exchanger through the lean liquid outlet of the reboiler for primary cooling, and then is secondary cooled to the required temperature through the lean liquid cooler and returned to the CO2 absorption equipment to absorb CO2 again.

[0013] Beneficial effects of the present invention:

[0014] 1. The present invention uses a hydrophobic membrane heat exchanger and a hydrophilic membrane heat exchanger in combination as the heat exchange medium between the regeneration gas at the top of the CO2 thermal regeneration tower and the cold rich liquid diverted before the lean-rich liquid heat exchanger. The hydrophobic membrane heat exchanger is used to efficiently recover the water vapor in the regeneration gas to maximize the latent heat recovery. The hydrophilic membrane heat exchanger is used to further recover the water vapor and liquid water in the regeneration gas, thereby strengthening the total amount of water mass transfer and further improving the waste heat recovery efficiency. The combined operation of the two will have a good potential for reducing the regeneration heat consumption.

[0015] 2. In view of different working conditions, the present invention provides a variety of different membrane heat exchanger combination modes, which can strengthen the heat transfer from the regenerated gas to the cold rich liquid from the aspects of making full use of each heat exchanger unit and effectively recovering the thermal energy of the high-temperature section of the regenerated gas, thereby enhancing the waste heat recovery efficiency of the regenerated gas, thereby facilitating the expansion of the membrane waste heat recovery system and will be suitable for the waste heat recovery needs in large-scale industrial applications.

[0016] 3. The gas-liquid diversion scheme constructed by the present invention can further enhance the waste heat recovery performance while meeting the layout, land occupation, loading and unloading requirements of the waste heat recovery system in different industrial actual situations, thereby achieving unique advantages such as low investment, compact structure, and convenient loading and unloading. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 This is a schematic diagram of the structure of the flow diversion scheme 1 (gas-liquid non-diversion) of the present invention;

[0019] Figure 3 It is a structural schematic diagram of the flow splitting scheme 2 of the present invention (liquid phase flow splitting, gas phase non-flow splitting);

[0020] Figure 4 It is a structural schematic diagram of the diversion scheme 3 of the present invention (gas phase diversion, liquid phase non-diversion);

[0021] Figure 5 It is a schematic diagram of the structure of the diversion scheme 4 (gas-liquid diversion) of the present invention.

[0022] Among them, 1-boosting fan, 2-CO2 absorption equipment, 2.1-air inlet, 2.2-liquid outlet, 2.3-absorption liquid input port, 2.4-top exhaust port, 3-rich liquid pump, 4-three-way diverter valve, 4.1-first port, 4.2-second port, 4.3-third port, 5-lean and rich liquid heat exchanger, 5.1-low-temperature rich liquid inlet, 5.2-high-temperature lean liquid inlet, 5.3-high-temperature rich liquid outlet, 5.4-low-temperature lean liquid outlet, 6-lean liquid cooler, 6.1-lean liquid outlet, 6.2-lean liquid inlet, 7-lean liquid pump, 8-regeneration gas waste heat recovery Unit, 8.1—Rich liquid inlet, 8.2—Condensate outlet, 8.3—Regeneration gas inlet, 8.4—Rich liquid outlet, 8.5—Regeneration gas outlet, 9—CO2 regeneration equipment, 9.1—First rich liquid inlet, 9.2—Bottom drain outlet, 9.3—Bottom air inlet, 9.4—Second rich liquid inlet, 9.5—Top exhaust outlet, 9.6—Top condensate reflux inlet, 10—Reboiler, 10.1—Rich liquid inlet, 10.2—Lean liquid outlet, 10.3—High temperature water outlet, 10.4—Steam inlet, 10.5—Reboiler top exhaust outlet

[0023] Diversion scheme 1 (gas-liquid flow is not divided, such as Figure 2), 11—first membrane heat exchanger unit, 8.1—rich liquid inlet, 11.1—condensed water outlet of the first membrane heat exchanger unit, 11.2—regeneration gas inlet of the first membrane heat exchanger unit, 11.3—rich liquid outlet of the first membrane heat exchanger unit, 8.5—regeneration gas outlet, 12—second membrane heat exchanger unit, 12.1—condensed water inlet of the second membrane heat exchanger unit, 8.4—rich liquid outlet, 8.2—condensed water outlet, 8.3—regeneration gas inlet, 12.2—rich liquid inlet of the second membrane heat exchanger unit, 12.3—regeneration gas outlet of the second membrane heat exchanger unit

[0024] Dividing scheme 2 (liquid phase diverting, gas phase not diverting, such as Figure 3 ), 13—third membrane heat exchanger unit, 8.1—rich liquid inlet, 13.1—rich liquid inlet of the third membrane heat exchanger unit, 13.2—condensed water outlet of the third membrane heat exchanger unit, 13.3—regeneration gas inlet of the third membrane heat exchanger unit, 13.4—rich liquid outlet of the third membrane heat exchanger unit, 8.5—regeneration gas outlet, 14—fourth membrane heat exchanger unit, 14.1—condensed water inlet of the fourth membrane heat exchanger unit, 14.2—rich liquid inlet of the fourth membrane heat exchanger unit, 8.2—condensed water outlet, 8.3—regeneration gas inlet, 14.3—rich liquid outlet of the fourth membrane heat exchanger unit, 14.4—regeneration gas outlet of the fourth membrane heat exchanger unit, 8.4—rich liquid outlet

[0025] Dividing scheme 3 (gas phase diverting, liquid phase not diverting, such as Figure 4 ), 15—fifth membrane heat exchanger unit, 15.1—regeneration gas outlet of fifth membrane heat exchanger unit, 8.1—rich liquid inlet, 15.2—condensate outlet of fifth membrane heat exchanger unit, 15.3—regeneration gas inlet of fifth membrane heat exchanger unit, 15.4—rich liquid outlet of fifth membrane heat exchanger unit, 16—sixth membrane heat exchanger unit, 16.1—regeneration gas outlet of sixth membrane heat exchanger unit, 16.2—rich liquid inlet of sixth membrane heat exchanger unit, 16.3—regeneration gas inlet of sixth membrane heat exchanger unit, 16.4—condensate outlet of sixth membrane heat exchanger unit, 8.2—condensate outlet, 8.3—regeneration gas inlet, 8.4—rich liquid outlet, 8.5—regeneration gas outlet

[0026] Diversion scheme 4 (gas-liquid equal diversion, such as Figure 5), 17—the seventh membrane heat exchanger unit, 17.1—the regeneration gas outlet of the seventh membrane heat exchanger unit, 17.2—the rich liquid inlet of the seventh membrane heat exchanger unit, 17.3—the condensate outlet of the seventh membrane heat exchanger unit, 17.4—the regeneration gas inlet of the seventh membrane heat exchanger unit, 17.5—the rich liquid outlet of the seventh membrane heat exchanger unit, 18—the eighth membrane heat exchanger unit, 18.1—the condensate inlet of the eighth membrane heat exchanger unit, 18.2—the rich liquid inlet of the eighth membrane heat exchanger unit, 8.2—the condensate outlet, 18.3—the regeneration gas inlet of the eighth membrane heat exchanger unit, 18.4—the rich liquid outlet of the eighth membrane heat exchanger unit, 18.5—the regeneration gas outlet of the eighth membrane heat exchanger unit, 8.1—the rich liquid inlet, 8.3—the regeneration gas inlet, 8.4—the rich liquid outlet, 8.5—the regeneration gas outlet. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0028] High temperature resistant hydrophobic porous membranes (such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)) are often used for water vapor separation, which can block liquid water at the gas-membrane interface, while water vapor can pass through the porous membrane depending on partial pressure. The separation mechanism will be beneficial to the recovery of water vapor. In addition, hydrophilic porous membranes (such as ceramic membranes and polyetheretherketone (PEEK)) are affected by capillary condensation or multilayer diffusion, which will be beneficial to the joint transfer of liquid water and water vapor. Based on this, in order to enhance the membrane waste heat recovery performance and adapt to large-scale industrial waste heat recovery applications, it is proposed to use hydrophobic membrane heat exchangers and hydrophilic membrane heat exchangers as basic heat recovery units, and to enhance the system and method of membrane waste heat recovery by adopting different combination modes (including membrane unit types and gas-liquid diversion methods).

[0029] The hydrophilic-hydrophobic double membrane heat exchanger designed by the present invention can enhance the CO2 chemical absorption system for waste heat recovery, such as Figure 1As shown, it includes a CO2 absorption device 2, a three-way diverter valve 4, a lean-rich liquid heat exchanger 5, a regeneration gas waste heat recovery unit 8, a CO2 regeneration device 9, a reboiler 10, a rich liquid pump 3, a lean liquid pump 7, a lean liquid cooler 6, and a booster fan 1 whose output end is connected to the air inlet 2.1 of the CO2 absorption device 2, wherein the liquid outlet 2.2 of the CO2 absorption device 2 is connected to the first port 4.1 of the three-way diverter valve 4 through the rich liquid pump 3, and the second port 4.2 of the three-way diverter valve 4 is connected to the low-temperature rich liquid (about 40-50°C) inlet of the lean-rich liquid heat exchanger 5 The third port 4.3 of the three-way diverter valve 4 is connected to the rich liquid inlet 8.1 of the regeneration gas waste heat recovery unit 8, the high-temperature rich liquid (about 80-100°C, specifically determined by the regeneration temperature and the economic heat exchange temperature difference of the rich and lean liquid heat exchanger) outlet 5.3 of the lean and rich liquid heat exchanger 5 is connected to the first rich liquid input port 9.1 of the CO2 regeneration device 9, the bottom drain port 9.2 of the CO2 regeneration device 9 is connected to the rich liquid input port 10.1 of the reboiler 10, and the lean liquid output port 10.2 of the reboiler 10 is connected to the high-temperature lean liquid ( The reboiler 10 also has a steam input port 10.4 and a high-temperature water (temperature is substantially equivalent to the input steam temperature) output port 10.3. The top exhaust port 9.5 of the CO2 regeneration device 9 is connected to the regeneration gas inlet 8.3 of the regeneration gas waste heat recovery unit 8. The condensed water outlet 8.2 of the regeneration gas waste heat recovery unit 8 is connected to the top of the CO2 regeneration device 9. The condensed water reflux inlet 9.6, the rich liquid outlet 8.4 of the regeneration gas waste heat recovery unit 8 is connected to the second rich liquid input port 9.4 of the CO2 regeneration equipment 9, the regeneration gas waste heat recovery unit 8 also has a regeneration gas outlet 8.5, the low-temperature lean liquid (about 60-70°C) output port 5.4 of the lean-rich liquid heat exchanger 5 is connected to the lean liquid inlet 6.2 of the lean liquid cooler 6, the lean liquid outlet 6.1 of the lean liquid cooler 6 is connected to the absorbent input port 2.3 of the CO2 absorption equipment 2 through a lean liquid pump 7, and the top of the CO2 absorption equipment 2 is also provided with a top exhaust port 2.4.

[0030] A CO2 chemical absorption method based on the above system comprises the following steps:

[0031] Step 1: The CO2-rich gas is pressurized by the booster fan 1 and enters the CO2 absorption device 2 through the air inlet 2.1, and forms a countercurrent contact with the CO2 chemical absorbent entering from the absorbent input port 2.3 in the CO2 absorption device 2. The CO2 in the CO2-rich gas is absorbed, and the purified gas is discharged from the top exhaust port 2.4 after being defogged from the top of the CO2 absorption device. The initial absorbent-rich CO2 solution generated after the absorbent in the CO2 absorption device 2 absorbs CO2 enters the rich liquid pump 3 from the liquid outlet 2.2 of the CO2 absorption device 2;

[0032] Step 2: The initial absorbent rich CO2 solution is pumped into the three-way diverter valve 4 through the rich liquid pump 3 for diversion. The first part of the initial absorbent rich CO2 solution after diversion enters the lean-rich liquid heat exchanger 5 through the second port 4.2 of the three-way diverter valve 4, and performs heat exchange with the high-temperature hot lean liquid of 100-120°C (determined by the absorbent type and regeneration temperature) discharged from the lean liquid outlet 10.2 of the reboiler 10 in the heat exchanger 5. The first part of the initial absorbent rich CO2 solution after heating then enters the first rich liquid input port 9.1 of the CO2 regeneration device 9;

[0033] Step 3: The initial absorbent rich CO2 solution enters the three-way diverter valve 4 through the rich liquid pump 3 for diversion. The second part of the initial absorbent rich CO2 solution after diversion enters the rich liquid inlet 8.1 of the regeneration gas waste heat recovery unit 8 through the third port 4.3 of the three-way diverter valve 4. The second part of the initial absorbent rich CO2 solution is reversely contacted with the regeneration gas entering the regeneration gas waste heat recovery unit 8 from the top exhaust port 9.5 of the CO2 regeneration device 9 in the regeneration gas waste heat recovery unit 8. The second part of the initial absorbent rich CO2 solution after recovering the waste heat enters the second rich liquid input port 9.4 of the CO2 regeneration device 9 through the rich liquid outlet 8.4. The condensed water generated by the cooling of the regeneration gas in the regeneration gas waste heat recovery unit 8 flows back to the condensed water reflux inlet 9.6 at the top of the CO2 regeneration device 9 through the condensed water outlet 8.2. The regeneration gas after heat exchange is discharged from the regeneration gas outlet 8.5 of the regeneration gas waste heat recovery unit 8.

[0034] Step 4: The first part of the initial absorbent-rich CO2 solution that passes through the heat exchanger 5 and enters the CO2 regeneration device 9 through the first rich liquid input port 9.1 and the second part of the initial absorbent-rich CO2 solution that recovers the waste heat and enters the CO2 regeneration device 9 through the second rich liquid input port 9.4 are reversely contacted with CO2 and H2O(g) regeneration gas in the CO2 regeneration device 9 for reheating, and then flow into the reboiler 10 from the bottom output port 9.2 of the CO2 regeneration device 9 to be heated and separated from CO2 and the absorbent. The CO2 heated and separated in the reboiler 10 carries saturated water vapor and flows upward along the CO2 regeneration device from the exhaust port 10.5 at the top of the reboiler through the bottom air inlet 9.3 of the CO2 regeneration device 9;

[0035] Step 5: The high-temperature lean liquid of 100-120°C obtained after regeneration in the reboiler 10 enters the lean-rich liquid heat exchanger 5 through the reboiler lean liquid outlet 10.2 for primary cooling, and then is secondary cooled to the required temperature (about 30-50°C) through the lean liquid cooler 6 and then returns to the CO2 absorption device 2 to absorb CO2 again.

[0036] The above step 3 has the following parallel diversion schemes:

[0037] The present invention split scheme 1 (gas-liquid is not split, such as Figure 2 ), the regeneration gas waste heat recovery unit 8 comprises a first membrane heat exchanger unit 11 and a second membrane heat exchanger unit 12, the first membrane heat exchanger unit 11 having a rich liquid inlet 8.1, a regeneration gas outlet 8.5, a first membrane heat exchanger unit condensate outlet 11.1, a first membrane heat exchanger unit regeneration gas inlet 11.2, and a first membrane heat exchanger unit rich liquid outlet 11.3, the second membrane heat exchanger unit 12 having a condensate outlet 8.2, a regeneration gas inlet 8.3, a rich liquid outlet 8.4, a first membrane heat exchanger unit condensate outlet 11.5, a first membrane heat exchanger unit condensate outlet 11.6, a first membrane heat exchanger unit condensate outlet 11.7, a first membrane heat exchanger unit condensate outlet 11.8, a first membrane heat exchanger unit condensate outlet 11.9, a first membrane heat exchanger unit condensate outlet 11.1, a first membrane heat exchanger unit regeneration gas inlet 11.2, and a first membrane heat exchanger unit rich liquid outlet 11.3. The second membrane heat exchanger unit condensate inlet 12.1, the second membrane heat exchanger unit rich liquid inlet 12.2, and the second membrane heat exchanger unit regeneration gas outlet 12.3, wherein the first membrane heat exchanger unit condensate outlet 11.1 is connected to the second membrane heat exchanger unit condensate inlet 12.1, the second membrane heat exchanger unit regeneration gas outlet 12.3 is connected to the first membrane heat exchanger unit regeneration gas inlet 11.2, and the first membrane heat exchanger unit rich liquid outlet 11.3 is connected to the second membrane heat exchanger unit rich liquid inlet 12.2;

[0038] The third port 4.3 of the three-way diverter valve 4 is connected to the rich liquid inlet 8.1, the condensed water outlet 8.2 is connected to the top condensed water reflux inlet 9.6 of the CO2 regeneration device 9, the rich liquid outlet 8.4 is connected to the second rich liquid input port 9.4 of the CO2 regeneration device 9, and the top exhaust port 9.5 of the CO2 regeneration device 9 is connected to the regeneration gas inlet 8.3.

[0039] In the step 3, the specific recovery steps of the regeneration gas waste heat recovery unit 8 using the diversion scheme 1 are as follows: the second part of the initial rich liquid enters the rich liquid inlet 8.1 of the first membrane heat exchanger unit 11, and then exchanges heat with the hot regeneration gas flowing in the opposite direction. The second part of the initial rich liquid after the heat exchange is discharged from the rich liquid outlet 11.3 of the first membrane heat exchanger unit and enters the rich liquid inlet 12.2 of the second membrane heat exchanger unit. After heat exchange with the regeneration gas flowing in the opposite direction again, it is discharged from the rich liquid outlet 8.4 of the second membrane heat exchanger unit 12 and enters the second rich liquid input port 9.4 of the CO2 regeneration device 9. The regeneration gas discharged from the exhaust port 9.5 at the top of the CO2 regeneration device 9 passes through the regeneration gas inlet 8.3 of the second membrane heat exchanger unit 12 to the regeneration gas outlet 12.3 of the second membrane heat exchanger unit, and then to the regeneration gas inlet 11.2 of the first membrane heat exchanger unit, and finally discharged from the regeneration gas outlet 8.5 of the first membrane heat exchanger 11.

[0040] Diversion scheme 1 (gas-liquid flow is not divided, such as Figure 2) includes four combinations, namely, combination 1-4. For the waste heat recovery of high-temperature mixed gas rich in water vapor (above about 90°C), combination 2 is recommended first, that is, firstly, a hydrophobic membrane heat exchanger is used to contact the high-temperature mixed gas, and the water vapor in the mixed gas is efficiently recovered by using the characteristics of the hydrophobic membrane, so as to maximize the latent heat recovery in the water vapor. After the mixed gas is cooled by the hydrophobic membrane heat exchanger, the water vapor / liquid water in the cooled mixed gas is jointly recovered by the hydrophilic membrane heat exchanger, in order to further improve the waste heat recovery efficiency by enhancing the total amount of water mass transfer. It is worth noting that in the waste heat recovery of high-temperature mixed gas rich in water vapor, the latent heat released by water vapor mass transfer dominates the total amount of heat recovery. Therefore, combination 3 can also be applied under such conditions. If the hydrophilic membrane heat exchanger has good thermal conductivity (such as a hydrophilic ceramic membrane heat exchanger), it can have a better heat recovery effect on the latent heat released by the condensation of water vapor regardless of whether the water vapor is transferred. At the same time, the hydrophilic membrane is more conducive to water mass transfer than the hydrophobic membrane. Therefore, based on the different types of membrane materials, combination 4 is also practical under specific working conditions;

[0041] The splitting scheme 2 of the present invention (liquid phase splitting, gas phase non-split, such as Figure 3 ), the regeneration gas waste heat recovery unit 8 includes a third membrane heat exchanger unit 13 and a fourth membrane heat exchanger unit 14, the third membrane heat exchanger unit 13 has a regeneration gas outlet 8.5, a third membrane heat exchanger unit rich liquid inlet 13.1, a third membrane heat exchanger unit condensate outlet 13.2, a third membrane heat exchanger unit regeneration gas inlet 13.3, and a third membrane heat exchanger unit rich liquid outlet 13.4, the fourth membrane heat exchanger unit 14 has a fourth membrane heat exchanger unit condensate inlet 14.1, a fourth membrane heat exchanger unit rich liquid inlet 14.2, a fourth membrane heat exchanger unit rich liquid outlet 14.3, and ... The membrane heat exchanger unit has a regeneration gas outlet 14.4, a condensed water outlet 8.2, and a regeneration gas inlet 8.3, wherein the rich liquid inlet 8.1 is respectively connected to the rich liquid inlet 13.1 of the third membrane heat exchanger unit and the rich liquid inlet 14.2 of the fourth membrane heat exchanger unit, the condensed water outlet 13.2 of the third membrane heat exchanger unit is connected to the condensed water inlet 14.1 of the fourth membrane heat exchanger unit, the regeneration gas outlet 14.4 of the fourth membrane heat exchanger unit is connected to the regeneration gas inlet 13.3 of the third membrane heat exchanger unit, and the rich liquid outlet 13.4 of the third membrane heat exchanger unit and the rich liquid outlet 14.3 of the fourth membrane heat exchanger unit are both connected to the rich liquid outlet 8.4.

[0042] In the step 3, the specific recovery steps of the regeneration gas waste heat recovery unit 8 using the diversion scheme 2 are as follows: the second part of the initial rich liquid is diverted (the diversion ratio is 20-80%) and enters the rich liquid inlet 13.1 of the third membrane heat exchanger unit and the rich liquid inlet 14.2 of the fourth membrane heat exchanger unit respectively. After heat exchange with the regeneration gas flowing in the reverse direction, it is discharged from the rich liquid outlet 13.4 of the third membrane heat exchanger unit and the rich liquid outlet 14.3 of the fourth membrane heat exchanger unit respectively to merge and flow into the second rich liquid inlet 9.4 of the CO2 regeneration device 9. The regeneration gas discharged from the exhaust port 9.5 at the top of the CO2 regeneration device 9 passes through the regeneration gas inlet 8.3 of the fourth membrane heat exchanger unit 14 to the regeneration gas outlet 14.4 of the fourth membrane heat exchanger unit, and then to the regeneration gas inlet 13.3 of the third membrane heat exchanger unit, and finally discharged from the regeneration gas outlet 8.5 of the third membrane heat exchanger unit 13.

[0043] Scheme 2 (liquid phase split, gas phase non-split, such as Figure 3 ) also includes four combinations, namely, combinations 5-8. For the working conditions where the liquid phase flow rate is too large, the liquid phase splitting process is adopted, which can make full use of the temperature difference between the low-temperature liquid phase (about 40-50°C) and the high-temperature mixed gas (about 90°C or above) to enhance the heat exchange, so as to avoid the polarization of the heat exchange effect of the two heat exchanger units in the combined heat exchanger;

[0044] The splitting scheme 3 of the present invention (gas phase splitting, liquid phase non-split, such as Figure 4 ): The regeneration gas waste heat recovery unit 8 includes a fifth membrane heat exchanger unit 15 and a sixth membrane heat exchanger unit 16, wherein the fifth membrane heat exchanger unit 15 includes a fifth membrane heat exchanger unit regeneration gas outlet 15.1, a fifth membrane heat exchanger unit condensate outlet 15.2, a fifth membrane heat exchanger unit regeneration gas inlet 15.3, a fifth membrane heat exchanger unit rich liquid outlet 15.4 and a rich liquid inlet 8.1, and the sixth membrane heat exchanger unit 16 includes a sixth membrane heat exchanger unit regeneration gas outlet 16.1, a sixth membrane heat exchanger unit rich liquid inlet 16.2, a sixth membrane heat exchanger unit regeneration gas inlet 16.3, ...4, a sixth membrane heat exchanger unit regeneration gas inlet 16.5, a sixth membrane heat exchanger unit regeneration gas outlet 16.6, a sixth membrane heat exchanger unit regeneration gas outlet 16.7, a sixth membrane heat exchanger unit regeneration gas outlet 16.8, a sixth membrane heat exchanger unit regeneration gas outlet 16.9, a sixth membrane heat exchanger unit regeneration gas outlet 16.1, a sixth membrane heat exchanger unit rich liquid inlet 16.1, a sixth membrane heat exchanger unit regeneration gas outlet 16.1, a sixth membrane heat exchanger unit regeneration gas outlet 16.9, a sixth membrane heat exchanger unit regeneration gas outlet 16.1, a sixth membrane heat exchanger unit regeneration gas outlet 16.1, a sixth membrane heat exchanger unit regeneration gas outlet 16.2, a sixth membrane heat exchanger unit regeneration gas outlet 16.3, a sixth membrane heat exchanger unit regeneration gas outlet 16.4, a sixth membrane heat exchanger unit regeneration gas outlet 16 The six membrane heat exchanger units have a condensed water outlet 16.4 and a rich liquid outlet 8.4, the fifth membrane heat exchanger unit regeneration gas outlet 15.1 and the sixth membrane heat exchanger unit regeneration gas outlet 16.1 are both connected to the regeneration gas outlet 8.5, the fifth membrane heat exchanger unit rich liquid outlet 15.4 is connected to the sixth membrane heat exchanger unit rich liquid inlet 16.2, the regeneration gas inlet 8.3 is connected to the fifth membrane heat exchanger unit regeneration gas inlet 15.3 and the sixth membrane heat exchanger unit regeneration gas inlet 16.3, the fifth membrane heat exchanger unit condensed water outlet 15.2 and the sixth membrane heat exchanger unit condensed water outlet 16.4 are connected to the condensed water outlet 8.2.

[0045] In step 3, the specific recovery steps of the regeneration gas waste heat recovery unit 8 using the diversion scheme 3 are as follows: the second part of the initial rich liquid enters the rich liquid inlet 8.1 of the fifth membrane heat exchanger unit 15, exchanges heat with the regeneration gas flowing in the opposite direction, and is discharged from the rich liquid outlet 15.4 of the fifth membrane heat exchanger unit and enters the rich liquid inlet 16.2 of the sixth membrane heat exchanger unit, exchanges heat with the regeneration gas flowing in the opposite direction again, and then is discharged from the rich liquid outlet 8.4 of the sixth membrane heat exchanger unit 16 and enters the second rich liquid input of the CO2 regeneration device 9. The regeneration gas discharged from the exhaust port 9.5 at the top of the CO2 regeneration device 9 is split (the split ratio is 20-80%) and enters the regeneration gas inlet 15.3 of the fifth membrane heat exchanger unit and the regeneration gas inlet 16.3 of the sixth membrane heat exchanger unit respectively. After heat exchange with the second part of the initial rich liquid flowing in the countercurrent direction, it is discharged from the regeneration gas outlet 15.1 of the fifth membrane heat exchanger unit and the regeneration gas outlet 16.1 of the sixth membrane heat exchanger unit respectively and merges to be discharged from the regeneration gas outlet 8.5 of the regeneration gas waste heat recovery unit (8).

[0046] Scheme 3 (gas phase split, liquid phase non-split, such as Figure 4 ) includes four combinations, namely, combinations 9-12. According to the heat release and heat transfer characteristics of the high-temperature gas phase side, the heat exchange efficiency of the high-temperature section of the mixed gas (gas phase inlet section) is relatively high. Therefore, diverting the gas phase side will be beneficial for the combined membrane heat exchanger to effectively recover the heat of the high-temperature section of the mixed gas. Specifically, the type of membrane unit can be selected according to the temperature, pressure, and water vapor content of the mixed gas, so as to reasonably select the configuration combination 9-12. At the same time, gas phase diversion can also be applied to the working conditions when the gas phase side flow is too large or the liquid phase side flow is too small;

[0047] The present invention split flow scheme 4 (gas-liquid split flow, such as Figure 5), the regeneration gas waste heat recovery unit 8 includes a seventh membrane heat exchanger unit 17 and an eighth membrane heat exchanger unit 18, wherein the seventh membrane heat exchanger unit 17 includes a seventh membrane heat exchanger unit regeneration gas outlet 17.1, a seventh membrane heat exchanger unit rich liquid inlet 17.2, a seventh membrane heat exchanger unit condensate outlet 17.3, a seventh membrane heat exchanger unit regeneration gas inlet 17.4 and a seventh membrane heat exchanger unit rich liquid outlet 17.5, and the eighth membrane heat exchanger unit 18 includes an eighth membrane heat exchanger unit condensate inlet 18.1, an eighth membrane heat exchanger unit rich liquid inlet 18.2, a condensate outlet 8.2, an eighth membrane heat exchanger unit regeneration gas inlet 18.3, an eighth membrane heat exchanger unit rich liquid outlet 18.4 and an eighth membrane heat exchanger unit The regeneration gas outlet 18.5 of the membrane heat exchanger unit is connected to the regeneration gas outlet 18.5 of the membrane heat exchanger unit, the rich liquid inlet 8.1 is connected to the rich liquid inlet 17.2 of the seventh membrane heat exchanger unit and the rich liquid inlet 18.2 of the eighth membrane heat exchanger unit respectively, the regeneration gas outlet 17.1 of the seventh membrane heat exchanger unit and the regeneration gas outlet 18.5 of the eighth membrane heat exchanger unit are connected to the regeneration gas outlet 8.5 respectively, the rich liquid outlet 17.5 of the seventh membrane heat exchanger unit and the rich liquid outlet 18.4 of the eighth membrane heat exchanger unit are connected to the rich liquid outlet 8.4 respectively, the regeneration gas inlet 8.3 is connected to the regeneration gas inlet 17.4 of the seventh membrane heat exchanger unit and the regeneration gas inlet 18.3 of the eighth membrane heat exchanger unit respectively, and the condensate outlet 17.3 of the seventh membrane heat exchanger unit is connected to the condensate inlet 18.1 of the eighth membrane heat exchanger unit.

[0048] In step 3, the specific recovery steps of the regeneration gas waste heat recovery unit 8 using the diversion scheme 4 are as follows: the second part of the initial rich liquid is diverted (the diversion ratio is 20-80%), and enters the rich liquid inlet 17.2 of the seventh membrane heat exchanger unit and the rich liquid inlet 18.2 of the eighth membrane heat exchanger unit respectively, and after heat exchange with the regeneration gas flowing in the reverse direction, it is discharged from the rich liquid outlet 17.5 of the seventh membrane heat exchanger unit and the rich liquid outlet 18.4 of the eighth membrane heat exchanger unit respectively to merge and flow into the second rich liquid input of the CO2 regeneration device 9. The regeneration gas discharged from the exhaust port 9.5 at the top of the CO2 regeneration device 9 is diverted (the diversion ratio is 20-80%), and enters the regeneration gas inlet 17.4 of the seventh membrane heat exchanger unit and the regeneration gas inlet 18.3 of the eighth membrane heat exchanger unit respectively, and after heat exchange with the second part of the initial rich liquid flowing in the countercurrent direction, it is discharged from the regeneration gas outlet 17.1 of the seventh membrane heat exchanger unit and the regeneration gas outlet 18.5 of the eighth membrane heat exchanger unit, and then merged and discharged from the regeneration gas outlet 8.5 of the regeneration gas waste heat recovery unit 8.

[0049] Scheme 4 (gas-liquid split flow, such as Figure 5 ) includes combination 13-16, and provides a gas-liquid split flow process to meet the needs of actual working site layout and flexible loading and unloading, and recovers heat from the diverted high-temperature gas phase (about 90°C or above) through the diverted low-temperature liquid phase (about 40-50°C).

[0050] Table 1: Summary of flow splitting methods and membrane heat exchanger unit types under different combination modes

[0051]

[0052] In the above Table 1, combination 1 specifically means that the membrane heat exchanger unit 11 is a hydrophobic membrane unit, and the membrane heat exchanger unit 12 is a hydrophilic membrane unit, combination 2 specifically means that the membrane heat exchanger unit 11 is a hydrophilic membrane unit, and the membrane heat exchanger unit 12 is a hydrophobic membrane unit, combination 3 specifically means that the membrane heat exchanger unit 11 is a hydrophobic membrane unit, and the membrane heat exchanger unit 12 is a hydrophobic membrane unit, combination 4 specifically means that the membrane heat exchanger unit 11 is a hydrophilic membrane unit, and the membrane heat exchanger unit 12 is a hydrophilic membrane unit, and so on, constituting combinations 5-16 respectively.

[0053] In step 1 of the above technical solution, the purified gas is discharged from the top exhaust port 2.4 from the top of the CO2 absorption device 2 after being defogged.

[0054] In steps 2 and 5 of the above technical solution, the temperature of the high-temperature lean liquid obtained after regeneration in the reboiler 10 is specifically determined by the absorbent type and the regeneration temperature.

[0055] In step 2 of the above technical solution, the initial rich liquid temperature discharged from the liquid outlet 2.2 at the bottom end of the CO2 absorption device 2 is 40-55°C, and the flow at the second port and the third port of the diverter valve is adjusted by controlling the three-way diverter valve 4 so that the rich liquid diversion ratio between the third port and the first port of the diverter valve is 10-30%.

[0056] In step 3 of the above technical solution, due to different diversion methods, the regeneration gas waste heat recovery unit 8 provides four diversion schemes, and according to different types of membrane heat exchanger units, each diversion scheme provides four schemes, so the regeneration gas waste heat recovery unit 8 has a total of 16 different situations.

[0057] In step 3 of the above technical solution, liquid water condensed from the regenerated gas on the gas phase side of the regenerated gas waste heat recovery unit 8 will flow back to the CO2 regeneration equipment 9 through the top condensate reflux inlet 9.6 of the CO2 regeneration equipment 9, and the total amount of gas-liquid phase recovered water in the waste heat membrane recovery unit will keep the absorbent mass concentration constant.

[0058] In the above technical solution, the reboiler 10 in step 4 is heated by external steam, and the heating temperature of the CO2-rich solution entering the reboiler 10 is 100-120°C (the specific heating temperature can be determined by the characteristics of the selected CO2 chemical absorbent).

[0059] In the above technical solution, the structure and type of the CO2 absorption device 2 and the CO2 regeneration device 9 are not limited, and either a traditional packed tower structure or a new hollow fiber membrane contactor structure can be used.

[0060] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A CO2 chemical absorption system with hydrophilic-hydrophobic double membrane heat exchanger to enhance waste heat recovery, characterized in that: It comprises a CO2 absorption device (2), a three-way diverter valve (4), a lean-rich liquid heat exchanger (5), a regeneration gas waste heat recovery unit (8), a CO2 regeneration device (9), a reboiler (10), a rich liquid pump (3), a lean liquid pump (7), a lean liquid cooler (6), and a booster fan (1) whose output end is connected to an air inlet (2.1) of the CO2 absorption device (2), wherein a liquid outlet (2.2) of the CO2 absorption device (2) is connected to a first port (4.1) of the three-way diverter valve (4) through a rich liquid pump (3), and a second port (4.2) of the three-way diverter valve (4) is connected to a second port (4.3) of the three-way diverter valve (4). The low-temperature rich liquid inlet (5.1) of the lean-rich liquid heat exchanger (5) is connected, the third port (4.3) of the three-way diverter valve (4) is connected to the rich liquid inlet (8.1) of the regeneration gas waste heat recovery unit (8), the high-temperature rich liquid outlet (5.3) of the lean-rich liquid heat exchanger (5) is connected to the first rich liquid input port (9.1) of the CO2 regeneration device (9), the bottom liquid discharge port (9.2) of the CO2 regeneration device (9) is connected to the rich liquid input port (10.1) of the reboiler (10), and the lean liquid output port (10.2) of the reboiler (10) is connected to the high-temperature outlet (9.3) of the lean-rich liquid heat exchanger (5). The top exhaust port (10.5) of the reboiler (10) is connected to the bottom air inlet (9.3) of the CO2 regeneration device (9), and the reboiler (10) also has a steam input port (10.4) and a high-temperature water output port (10.3). The top exhaust port (9.5) of the CO2 regeneration device (9) is connected to the regeneration gas inlet (8.3) of the regeneration gas waste heat recovery unit (8), and the condensed water outlet (8.2) of the regeneration gas waste heat recovery unit (8) is connected to the top condensed water reflux inlet (9.6) of the CO2 regeneration device (9). The rich liquid outlet (8.4) of the heat recovery unit (8) is connected to the second rich liquid inlet (9.4) of the CO2 regeneration device (9), the regeneration gas waste heat recovery unit (8) also has a regeneration gas outlet (8.5), the low-temperature lean liquid output port (5.4) of the lean-rich liquid heat exchanger (5) is connected to the lean liquid inlet (6.2) of the lean liquid cooler (6), the lean liquid outlet (6.1) of the lean liquid cooler (6) is connected to the absorbent inlet (2.3) of the CO2 absorption device (2) via a lean liquid pump (7), and the top of the CO2 absorption device (2) is also provided with a top exhaust port (2.4); The regeneration gas waste heat recovery unit (8) comprises a first membrane heat exchanger (11) and a second membrane heat exchanger unit (12), wherein the first membrane heat exchanger (11) has a rich liquid inlet (8.1), a regeneration gas outlet (8.5), a first membrane heat exchanger condensate outlet (11.1), a first membrane heat exchanger regeneration gas inlet (11.2), and a first membrane heat exchanger rich liquid outlet (11.3), and the second membrane heat exchanger unit (12) has a condensate outlet (8.2), a regeneration gas inlet (8.3), a rich liquid outlet (8.4), A condensed water inlet (12.1) of the second membrane heat exchanger unit, a rich liquid inlet (12.2) of the second membrane heat exchanger unit, and a regenerated gas outlet (12.3) of the second membrane heat exchanger unit, wherein the condensed water outlet (11.1) of the first membrane heat exchanger is connected to the condensed water inlet (12.1) of the second membrane heat exchanger unit, the regenerated gas outlet (12.3) of the second membrane heat exchanger unit is connected to the regenerated gas inlet (11.2) of the first membrane heat exchanger, and the rich liquid outlet (11.3) of the first membrane heat exchanger is connected to the rich liquid inlet (12.2) of the second membrane heat exchanger unit; The third port (4.3) of the three-way diverter valve (4) is connected to the rich liquid inlet (8.1), the condensed water outlet (8.2) is connected to the top condensed water return inlet (9.6) of the CO2 regeneration device (9), the rich liquid outlet (8.4) is connected to the second rich liquid input port (9.4) of the CO2 regeneration device (9), and the top exhaust port (9.5) of the CO2 regeneration device (9) is connected to the regeneration gas inlet (8.3); Alternatively, the regeneration gas waste heat recovery unit (8) comprises a third membrane heat exchanger unit (13) and a fourth membrane heat exchanger unit (14), wherein the third membrane heat exchanger unit (13) has a regeneration gas outlet (8.5), a third membrane heat exchanger unit rich liquid inlet (13.1), a third membrane heat exchanger unit condensate outlet (13.2), a third membrane heat exchanger unit regeneration gas inlet (13.3), and a third membrane heat exchanger unit rich liquid outlet (13.4), and the fourth membrane heat exchanger unit (14) has a fourth membrane heat exchanger unit condensate inlet (14.1), a fourth membrane heat exchanger unit rich liquid inlet (14.2), a fourth membrane heat exchanger unit rich liquid outlet (14.3), and ... The membrane heat exchanger unit has a regeneration gas outlet (14.4), a condensed water outlet (8.2), and a regeneration gas inlet (8.3), wherein the rich liquid inlet (8.1) is respectively connected to the rich liquid inlet (13.1) of the third membrane heat exchanger unit and the rich liquid inlet (14.2) of the fourth membrane heat exchanger unit, the condensed water outlet (13.2) of the third membrane heat exchanger unit is connected to the condensed water inlet (14.1) of the fourth membrane heat exchanger unit, the regeneration gas outlet (14.4) of the fourth membrane heat exchanger unit is connected to the regeneration gas inlet (13.3) of the third membrane heat exchanger unit, and the rich liquid outlet (13.4) of the third membrane heat exchanger unit and the rich liquid outlet (14.3) of the fourth membrane heat exchanger unit are both connected to the rich liquid outlet (8.4); Alternatively, the regeneration gas waste heat recovery unit (8) comprises a fifth membrane heat exchanger unit (15) and a sixth membrane heat exchanger unit (16), wherein the fifth membrane heat exchanger unit (15) comprises a fifth membrane heat exchanger unit regeneration gas outlet (15.1), a fifth membrane heat exchanger unit condensate outlet (15.2), a fifth membrane heat exchanger unit regeneration gas inlet (15.3), a fifth membrane heat exchanger unit rich liquid outlet (15.4) and a rich liquid inlet (8.1), and the sixth membrane heat exchanger unit (16) comprises a sixth membrane heat exchanger unit regeneration gas outlet (16.1), a sixth membrane heat exchanger unit rich liquid inlet (16.2), a sixth membrane heat exchanger unit regeneration gas inlet (16.3), ... fifth membrane heat exchanger unit regeneration gas outlet (16.1), a sixth membrane heat exchanger unit regeneration gas outlet (16.3), a sixth membrane heat exchanger unit regeneration gas outlet (16.1), a sixth membrane heat exchanger unit regeneration gas outlet (16.3), a sixth membrane heat exchanger unit regeneration gas outlet (16.3), a sixth membrane heat exchanger unit regeneration gas outlet (16.1), a sixth membrane heat exchanger unit regeneration gas outlet (16.2), a sixth membrane heat exchanger unit regeneration gas outlet (16.3), a fifth membrane heat exchanger unit regeneration gas outlet (16.3), a fifth membrane heat exchanger unit regeneration gas outlet (16.3), a fifth membrane heat exchanger unit regeneration gas outlet (16.3), a fifth membrane heat exchanger unit regeneration gas outlet (16.3), a fifth membrane heat exchanger unit regeneration The six membrane heat exchanger units have condensed water outlets (16.4) and rich liquid outlets (8.4); the regeneration gas outlet (15.1) of the fifth membrane heat exchanger unit and the regeneration gas outlet (16.1) of the sixth membrane heat exchanger unit are both connected to the regeneration gas outlet (8.5); the rich liquid outlet (15.4) of the fifth membrane heat exchanger unit is connected to the rich liquid inlet (16.2) of the sixth membrane heat exchanger unit; the regeneration gas inlet (8.3) is connected to the regeneration gas inlet (15.3) of the fifth membrane heat exchanger unit and the regeneration gas inlet (16.3) of the sixth membrane heat exchanger unit; the condensed water outlet (15.2) of the fifth membrane heat exchanger unit and the condensed water outlet (16.4) of the sixth membrane heat exchanger unit are connected to the condensed water outlet (8.2); Alternatively, the regeneration gas waste heat recovery unit (8) comprises a seventh membrane heat exchanger unit (17) and an eighth membrane heat exchanger unit (18), wherein the seventh membrane heat exchanger unit (17) comprises a seventh membrane heat exchanger unit regeneration gas outlet (17.1), a seventh membrane heat exchanger unit rich liquid inlet (17.2), a seventh membrane heat exchanger unit condensate outlet (17.3), a seventh membrane heat exchanger unit regeneration gas inlet (17.4) and a seventh membrane heat exchanger unit rich liquid outlet (17.5), and the eighth membrane heat exchanger unit (18) comprises an eighth membrane heat exchanger unit condensate inlet (18.1), an eighth membrane heat exchanger unit rich liquid inlet (18.2), a condensate outlet (8.2), an eighth membrane heat exchanger unit regeneration gas inlet (18.3), an eighth membrane heat exchanger unit rich liquid outlet (18.4) and an eighth membrane heat exchanger unit The regeneration gas outlet (18.5) of the membrane heat exchanger unit is connected to the regeneration gas outlet (18.5) of the membrane heat exchanger unit, the rich liquid inlet (8.1) is respectively connected to the rich liquid inlet (17.2) of the seventh membrane heat exchanger unit and the rich liquid inlet (18.2) of the eighth membrane heat exchanger unit, the regeneration gas outlet (17.1) of the seventh membrane heat exchanger unit and the regeneration gas outlet (18.5) of the eighth membrane heat exchanger unit are respectively connected to the regeneration gas outlet (8.5), the rich liquid outlet (17.5) of the seventh membrane heat exchanger unit and the rich liquid outlet (18.4) of the eighth membrane heat exchanger unit are respectively connected to the rich liquid outlet (8.4), the regeneration gas inlet (8.3) is respectively connected to the regeneration gas inlet (17.4) of the seventh membrane heat exchanger unit and the regeneration gas inlet (18.3) of the eighth membrane heat exchanger unit, and the condensate outlet (17.3) of the seventh membrane heat exchanger unit is connected to the condensate inlet (18.1) of the eighth membrane heat exchanger unit; The hydrophilic-hydrophobic double membrane heat exchanger is a heat exchanger that combines a hydrophobic membrane heat exchanger and a hydrophilic membrane heat exchanger, wherein the first membrane heat exchanger (11) is a hydrophobic membrane unit and the second membrane heat exchanger unit (12) is a hydrophilic membrane unit, or the first membrane heat exchanger (11) is a hydrophilic membrane unit and the second membrane heat exchanger unit (12) is a hydrophobic membrane unit; The third membrane heat exchanger unit (13) is a hydrophobic membrane unit, and the fourth membrane heat exchanger unit (14) is a hydrophilic membrane unit, or the third membrane heat exchanger unit (13) is a hydrophilic membrane unit, and the fourth membrane heat exchanger unit (14) is a hydrophobic membrane unit; The fifth membrane heat exchanger unit (15) is a hydrophobic membrane unit, and the sixth membrane heat exchanger unit (16) is a hydrophilic membrane unit, or the fifth membrane heat exchanger unit (15) is a hydrophilic membrane unit, and the sixth membrane heat exchanger unit (16) is a hydrophobic membrane unit; The seventh membrane heat exchanger unit (17) is a hydrophobic membrane unit and the eighth membrane heat exchanger unit (18) is a hydrophilic membrane unit, or the seventh membrane heat exchanger unit (17) is a hydrophilic membrane unit and the eighth membrane heat exchanger unit (18) is a hydrophobic membrane unit.

2. A CO2 chemical absorption method based on the system of claim 1, characterized in that: It includes the following steps: Step 1: The CO2-rich gas is pressurized by the booster fan (1) and enters the CO2 absorption device (2) through the air inlet (2.1), and forms a countercurrent contact with the CO2 chemical absorbent entering from the absorbent input port (2.3) in the CO2 absorption device (2). The CO2 in the CO2-rich gas is absorbed, and the purified gas is discharged from the top exhaust port (2.4) after being defogged from the top of the CO2 absorption device. The initial absorbent-rich CO2 solution generated after the absorbent in the CO2 absorption device (2) absorbs CO2 enters the rich liquid pump (3) from the liquid outlet (2.2) of the CO2 absorption device (2); Step 2: The initial absorbent rich CO2 solution is pumped into the three-way diverter valve (4) through the rich liquid pump (3) for diversion. The first part of the initial absorbent rich CO2 solution after diversion enters the lean-rich liquid heat exchanger (5) through the second port (4.2) of the three-way diverter valve (4). In the heat exchanger (5), heat is exchanged with the high-temperature hot lean liquid of 100 to 120° C. discharged from the lean liquid outlet (10.2) of the reboiler (10). The first part of the initial absorbent rich CO2 solution after heating then enters the first rich liquid inlet (9.1) of the CO2 regeneration device (9); Step 3: The initial absorbent rich CO2 solution enters the three-way diverter valve (4) through the rich liquid pump (3) for diversion. The second part of the initial absorbent rich CO2 solution after diversion enters the rich liquid inlet (8.1) of the regeneration gas waste heat recovery unit (8) through the third port (4.3) of the three-way diverter valve (4). The second part of the initial absorbent rich CO2 solution enters the regeneration gas waste heat recovery unit (8) through the third port (4.3) of the three-way diverter valve (4). The second part of the initial absorbent rich CO2 solution enters the regeneration gas waste heat recovery unit (8) from the top exhaust port (9.5) of the CO2 regeneration device (9) in the regeneration gas waste heat recovery unit (8). The regenerated gas is subjected to reverse contact, and the second part of the initial absorbent rich CO2 solution after waste heat recovery enters the second rich liquid inlet (9.4) of the CO2 regeneration device (9) through the rich liquid outlet (8.4). The condensed water generated by the regenerated gas due to cooling in the regenerated gas waste heat recovery unit (8) flows back to the condensed water return inlet (9.6) at the top of the CO2 regeneration device (9) through the condensed water outlet (8.2). The regenerated gas after heat exchange is discharged from the regenerated gas outlet (8.5) of the regenerated gas waste heat recovery unit (8); Step 4: The first part of the initial absorbent-rich CO2 solution that passes through the heat exchanger (5) and enters the CO2 regeneration device (9) through the first rich liquid input port (9.1) and the second part of the initial absorbent-rich CO2 solution that recovers the waste heat and enters the CO2 regeneration device (9) through the second rich liquid input port (9.4) are reversely contacted with CO2 and H2O (g) regeneration gas in the CO2 regeneration device (9) for reheating, and then flow into the reboiler (10) from the bottom discharge port (9.2) of the CO2 regeneration device (9) to heat and separate CO2 and absorbent. The CO2 heated and separated in the reboiler (10) carries saturated water vapor and flows upward along the CO2 regeneration device from the exhaust port (10.5) at the top of the reboiler through the bottom air inlet (9.3) of the CO2 regeneration device (9); Step 5: The high-temperature lean liquid at 100-120° C. obtained after regeneration in the reboiler (10) enters the lean-rich liquid heat exchanger (5) through the reboiler lean liquid outlet (10.2) for primary cooling, and then is secondary cooled to the required temperature through the lean liquid cooler (6) and returns to the CO2 absorption device (2) to absorb CO2 again.

3. The CO2 chemical absorption method according to claim 2, characterized in that: In step 3, the specific recovery steps of the regeneration gas waste heat recovery unit (8) are as follows: the second part of the initial rich liquid enters the rich liquid inlet (8.1) of the first membrane heat exchanger (11), and then exchanges heat with the hot regeneration gas flowing in the opposite direction. After the heat exchange, the second part of the initial rich liquid is discharged from the rich liquid outlet (11.3) of the first membrane heat exchanger and enters the rich liquid inlet (12.2) of the second membrane heat exchanger unit. After heat exchange with the regeneration gas flowing in the opposite direction again, it is discharged from the rich liquid outlet (8.4) of the second membrane heat exchanger unit (12) and enters the second rich liquid input port (9.4) of the CO2 regeneration device (9). The regeneration gas discharged from the top exhaust port (9.5) of the CO2 regeneration device (9) passes through the regeneration gas inlet (8.3) of the second membrane heat exchanger unit (12) to the regeneration gas outlet (12.3) of the second membrane heat exchanger unit, and then to the regeneration gas inlet (11.2) of the first membrane heat exchanger, and finally discharged from the regeneration gas outlet (8.5) of the first membrane heat exchanger (11).

4. The CO2 chemical absorption method according to claim 2, characterized in that: In step 3, the specific recovery steps of the regeneration gas waste heat recovery unit (8) are as follows: the second part of the initial rich liquid is divided and enters the rich liquid inlet (13.1) of the third membrane heat exchanger unit and the rich liquid inlet (14.2) of the fourth membrane heat exchanger unit respectively. After heat exchange with the regeneration gas flowing in the opposite direction, it is discharged from the rich liquid outlet (13.4) of the third membrane heat exchanger unit and the rich liquid outlet (14.3) of the fourth membrane heat exchanger unit respectively to merge and flow into the second rich liquid inlet (9.4) of the CO2 regeneration device (9). The regeneration gas discharged from the top exhaust port (9.5) of the CO2 regeneration device (9) passes through the regeneration gas inlet (8.3) of the fourth membrane heat exchanger unit (14) to the regeneration gas outlet (14.4) of the fourth membrane heat exchanger unit, and then to the regeneration gas inlet (13.3) of the third membrane heat exchanger unit, and finally discharged from the regeneration gas outlet (8.5) of the third membrane heat exchanger unit (13).

5. The CO2 chemical absorption method according to claim 2, characterized in that: In step 3, the specific recovery steps of the regeneration gas waste heat recovery unit (8) are as follows: the second part of the initial rich liquid enters the rich liquid inlet (8.1) of the fifth membrane heat exchanger unit (15), exchanges heat with the regeneration gas flowing in the opposite direction, is discharged from the rich liquid outlet (15.4) of the fifth membrane heat exchanger unit and enters the rich liquid inlet (16.2) of the sixth membrane heat exchanger unit, exchanges heat with the regeneration gas flowing in the opposite direction again, and then is discharged from the rich liquid outlet (8.4) of the sixth membrane heat exchanger unit (16) and enters the second rich liquid of the CO2 regeneration device (9). The regeneration gas discharged from the top exhaust port (9.5) of the CO2 regeneration device (9) is divided and enters the regeneration gas inlet (15.3) of the fifth membrane heat exchanger unit and the regeneration gas inlet (16.3) of the sixth membrane heat exchanger unit respectively. After heat exchange with the second part of the initial rich liquid flowing in the countercurrent direction, it is discharged from the regeneration gas outlet (15.1) of the fifth membrane heat exchanger unit and the regeneration gas outlet (16.1) of the sixth membrane heat exchanger unit respectively and merges to be discharged from the regeneration gas outlet (8.5) of the regeneration gas waste heat recovery unit (8).

6. The CO2 chemical absorption method according to claim 2, characterized in that: In the step 3, the second part of the initial rich liquid is divided and enters the rich liquid inlet (17.2) of the seventh membrane heat exchanger unit and the rich liquid inlet (18.2) of the eighth membrane heat exchanger unit respectively. After heat exchange with the regeneration gas flowing in the countercurrent direction, it is discharged from the rich liquid outlet (17.5) of the seventh membrane heat exchanger unit and the rich liquid outlet (18.4) of the eighth membrane heat exchanger unit respectively, and then merges and flows into the second rich liquid inlet (9.4) of the CO2 regeneration device (9). The regeneration gas discharged from the top exhaust port (9.5) of the CO2 regeneration device (9) is divided and enters the regeneration gas inlet (17.4) of the seventh membrane heat exchanger unit and the regeneration gas inlet (18.3) of the eighth membrane heat exchanger unit respectively. After heat exchange with the second part of the initial rich liquid flowing in the countercurrent direction, it is discharged from the regeneration gas outlet (17.1) of the seventh membrane heat exchanger unit and the regeneration gas outlet (18.5) of the eighth membrane heat exchanger unit respectively, and then merges and is discharged from the regeneration gas outlet (8.5) of the regeneration gas waste heat recovery unit (8).

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