A direct air capture system and method with steam recycling

Abstract

The application discloses a direct air capture system and method with steam recycling, which comprises a first adsorption and desorption tower and a second adsorption and desorption tower for adsorbing CO2 in air, the first adsorption and desorption tower and the second adsorption and desorption tower are used for desorbing the adsorbed CO2 in the tower by high-temperature steam; the first adsorption and desorption tower and the second adsorption and desorption tower are connected with the input end of a first pipeline, the first pipeline is used for discharging low CO2 content gas; a steam generator is connected with the inlets of the first adsorption and desorption tower and the second adsorption and desorption tower through a second pipeline; the first adsorption and desorption tower and the second adsorption and desorption tower are connected with the input end of a third pipeline, the output end of the third pipeline is connected with a separation device and a circulating pump, and the third pipeline is used for transmitting CO2-containing steam discharged from the first adsorption and desorption tower and the second adsorption and desorption tower. The steam consumption is reduced, and the CO2 concentration of product gas is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon dioxide capture, and in particular to a direct air capture system and method with steam recycling. BACKGROUND

[0002] With the development of social economy and the increase of human activities, the concentration of greenhouse gases dominated by CO2 in the atmosphere continues to grow, ultimately leading to global climate change and ocean acidification, which has had many adverse effects on the ecosystem and human production and life. Carbon capture, utilization and storage (CCUS) is an important technical guarantee for the whole society to reduce carbon emissions. Although traditional carbon capture modes can achieve partial decarbonization of large point sources, distributed carbon emissions such as agriculture and transportation must rely on direct air carbon dioxide capture (DAC). The existing Chinese patent with publication number CN114939323A and patent name "Low-energy-consumption air direct carbon capture system" discloses a carbon capture system, which includes an adsorption / desorption / regeneration device, a heater, a cooler, and an air suction device. The original air passes through the air suction device and the adsorption / desorption / regeneration device to form purified air. The carbon dioxide of the desorption medium is heated by the heater and then sent into the adsorbent material of the adsorption / desorption / regeneration device. The carbon dioxide of the desorption medium carries part of the carbon dioxide captured by the adsorbent material, which is enriched after passing through the cooler. The enriched carbon dioxide and part of the carbon dioxide are heated by the heater and then sent into the adsorbent material of the adsorption / desorption / regeneration device.

[0003] The existing Chinese patent with publication number CN112169537A and patent name "Quick temperature swing adsorption rotary wheel type direct air carbon dioxide capture system and method" discloses a carbon dioxide capture system, which includes a rotary wheel, an adsorption flow path, and a regeneration flow path. The regeneration gas flows in the second direction opposite to the first direction in the regeneration flow path. The regeneration gas is water vapor generated by a water vapor generator. The heated regeneration gas flows through the regeneration area of the rotary wheel and then enters the condenser to be condensed. The condensed liquid is condensed water. The condensed water flows into the water vapor generator through the condensation pipeline. The gas separated by condensation is collected carbon dioxide gas.

[0004] Solid adsorption method can adsorb CO2 in air at normal temperature and pressure, and can be regenerated by lower temperature (80-100℃) provided by industrial waste heat or light heat, etc. The process has no water consumption, has certain technical advantages, and becomes the mainstream technical scheme in the field of direct air capture. At present, the adsorbent applied to DAC is mainly amine modified chemical adsorbent. Such adsorbent will not produce strong competitive adsorption of H2O and CO2, so steam regeneration can be used, and it has been widely studied and concerned. At present, DAC technology is in the initial stage of development, and the cost and energy consumption are high. According to estimation, with the iteration and development of technology, the final operation cost of adsorption DAC is expected to be reduced to 29-91$ / tCO2.

[0005] Although solid adsorption method has been widely concerned, it still faces the following main challenges:

[0006] 1) The use of steam regeneration is beneficial to the chemical adsorption and desorption process and the improvement of product gas purity, but the heating and evaporation of water will consume a large amount of energy.

[0007] 2) The regenerated steam is not recycled, and the CO2 content of the product gas is low, which will consume a large amount of energy when directly condensed.

[0008] In summary, at present, DAC technology is in the initial stage of development, and the cost and energy consumption are high. Solid adsorption method is the current mainstream technical scheme, and has a wide cost reduction space (29-91$ / tCO2). However, the traditional adsorption method has problems such as large amount of regeneration steam, high energy consumption in evaporation and condensation process, and it is particularly necessary to study new steam recycling direct air CO2 capture technology. SUMMARY

[0009] The purpose of the present application is to provide a steam recycling direct air capture system and method, which can reduce the amount of steam while increasing the CO2 concentration of product gas and significantly reducing the energy consumption of the capture process.

[0010] To achieve the above purpose, the present application provides a steam recycling direct air capture system, which comprises a first adsorption tower, a second adsorption tower, a first pipeline, a second pipeline and a third pipeline.

[0011] The first adsorption tower and the second adsorption tower are used for adsorbing and separating CO2 in air, and the first adsorption tower and the second adsorption tower are used for desorbing the adsorbed CO2 in the tower by high-temperature steam.

[0012] The first adsorption tower and the second adsorption tower are connected with the input end of the first pipeline, and the first pipeline is used for discharging low CO2 content gas.

[0013] The steam generator is connected with the inlets of the first and second adsorption and desorption towers through the second pipeline respectively;

[0014] The first and second adsorption and desorption towers are connected with the input end of the third pipeline, and the output end of the third pipeline is connected with the separation device and the circulating pump, and the third pipeline is used for transmitting the CO2-containing steam discharged by the first and second adsorption and desorption towers;

[0015] The first and second adsorption and desorption towers are in cross conversion working mode, that is, the first and second adsorption and desorption towers are in adsorption and desorption states respectively.

[0016] Further, the output end of the third pipeline is connected with the inlet of the circulating pump, the outlet of the circulating pump is connected with the input end of the second pipeline, and the output end of the second pipeline is connected with the inlets of the first and second adsorption and desorption towers respectively.

[0017] Further, the separation device comprises a cooling device and a gas-liquid separator, the output end of the third pipeline is connected with the cooling device, and the cooling device is connected with the gas-liquid separator;

[0018] The cooling device is used for cooling the CO2-carrying steam output by the third pipeline, and the gas-liquid separator is used for separating CO2 and liquid water;

[0019] The cooling device is a condenser, the condenser is connected with a cooling tower, and the cooling tower is used for providing refrigerant to the condenser.

[0020] Further, the air pump is connected with the inlets of the first and second adsorption and desorption towers through the fourth pipeline respectively;

[0021] The air pump is used for outputting air to the first and second adsorption and desorption towers.

[0022] Further, the control valves are installed on the first and second pipelines;

[0023] The control valve on the first pipeline is used for distributing the communication between the outlets of the first and second adsorption and desorption towers and the first pipeline;

[0024] The control valve on the second pipeline is used for distributing the communication between the inlets of the first and second adsorption and desorption towers and the steam generator and the circulating pump.

[0025] Further, the control valves are installed on the third and fourth pipelines;

[0026] The control valve on the third pipeline is used to distribute the communication between the outlets of the first and second adsorption towers and the third pipeline;

[0027] The control valve on the fourth pipeline is used to distribute the communication between the inlets of the first and second adsorption towers and the air pump.

[0028] Further, the first and second adsorption towers are provided with a gas distributor and an adsorbent.

[0029] Based on the same inventive concept, the present application also provides a direct air capture method with steam recycling, which is applied to the direct air capture system with steam recycling, and includes a CO2 adsorption process and a CO2 desorption process,

[0030] The CO2 adsorption process includes:

[0031] The first or second adsorption tower selectively adsorbs CO2 from external air through a gas distributor and an adsorbent, and forms low-CO2-content gas which is discharged through a first pipeline;

[0032] The CO2 desorption process includes:

[0033] The steam generator inputs high-temperature steam into the first or second adsorption tower, and the high-temperature steam flows through the gas distributor and the adsorbent to desorb CO2 in the adsorbent, thereby generating steam carrying CO2;

[0034] Part of the steam carrying CO2 is transported to a separation device through a third pipeline for gas liquefaction and gas-liquid separation, and gaseous CO2 and liquid waste are discharged;

[0035] Another part of the steam carrying CO2 is transported to the first or second adsorption tower through the third pipeline by a circulating pump, and continues to desorb CO2.

[0036] Further, the air pump is used to pump external air into the first or second adsorption tower.

[0037] Further, the part of the steam carrying CO2 is transported to the separation device through the third pipeline for gas liquefaction and gas-liquid separation, which includes,

[0038] Part of the steam carrying CO2 is transported to a condenser through a third pipeline for gas liquefaction, and the condenser transports the generated liquid to a gas-liquid separation device for gas-liquid separation.

[0039] The technical effects and advantages of the present application are: 1. The present application focuses on the DAC technology of vapor-assisted temperature swing adsorption, and the part of steam (containing CO2) of the product gas in the desorption process is recycled into the regeneration gas, which reduces the steam consumption, increases the CO2 concentration of the product gas, and significantly reduces the energy consumption of the capture process;

[0040] 2. The present application reduces the steam supply amount by recycling high-temperature steam through a circulating pump, and the heat consumption is reduced; due to the reduced processing capacity of the condenser, the cold consumption is also reduced; the steam return amount can be flexibly adjusted and controlled for the CO2 capture effect and economic benefit.

[0041] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the structure indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0043] Figure 1 A structure schematic diagram of a direct air capture system with steam recycling of an embodiment of the present application;

[0044] Figure 2 A three-state schematic diagram of a pipeline controlled by a control valve in an embodiment of the present application;

[0045] In the figure, 1 is an air pump, 2 is a steam generator, 3 is a first adsorption and desorption tower, 4 is a second adsorption and desorption tower, 5 is a condenser, 6 is a gas-liquid separator, 7 is a cooling tower, 8 is a circulating pump, 9 is a first pipeline, 10 is a second pipeline, 11 is a third pipeline, 12 is a fourth pipeline, and 13 is a control valve. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings of the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0047] To solve the problems in the prior art, the embodiment of the present application discloses a direct air capture system with steam recycling, which comprises a first adsorption desorption tower 3, a second adsorption desorption tower 4, a first pipeline 9, a second pipeline 10, a third pipeline 11 and the like,

[0048] The first adsorption desorption tower 3 and the second adsorption desorption tower 4 are cross-converted in operation, that is, the first adsorption desorption tower 3 and the second adsorption desorption tower 4 are respectively in adsorption and desorption states during operation. For example, when tower A is in the adsorption state, tower B must be in the desorption state. After the adsorption and desorption of the two towers are completed, the function conversion is performed, the A tower is converted to be in the desorption state, and the B tower is converted to be in the adsorption state, and the cross-reciprocal operation is performed.

[0049] Therefore, the first adsorption desorption tower 3 and the second adsorption desorption tower 4 can be used for adsorbing and separating CO2 in air, and the first adsorption desorption tower 3 and the second adsorption desorption tower 4 can also be used for desorbing the adsorbed CO2 in the towers by high-temperature steam.

[0050] The inlets of the first adsorption desorption tower 3 and the second adsorption desorption tower 4 are respectively connected with the air pump 1 through the fourth pipeline 12, and the gas distributors and adsorbers are installed in the first desorption tower and the second adsorption desorption tower 4. The outlets of the first adsorption desorption tower 3 and the second adsorption desorption tower 4 are connected with the input end of the first pipeline 9, and the first pipeline 9 is used for discharging low-CO2-content gas.

[0051] As shown in the figure, the CO2 adsorption process of the system is as follows:

[0052] The air pump 1 is used for pumping external air into the first adsorption desorption tower 3 or the second adsorption desorption tower 4 from top to bottom. After the external air enters the adsorption desorption tower, the selective adsorption and separation of CO2 in the air are performed through the gas distributors and adsorbers, and finally the low-CO2-content gas is directly discharged from the first pipeline 9.

[0053] The steam generator 2 is connected with the inlets of the first adsorption desorption tower 3 and the second adsorption desorption tower 4 through the second pipeline 10, and is used for providing steam for the desorption process of CO2. The outlets of the first adsorption desorption tower 3 and the second adsorption desorption tower 4 are connected with the input end of the third pipeline 11, the output end of the third pipeline 11 is connected with the separation device, and the third pipeline 11 is used for transmitting the CO2-containing steam discharged from the first adsorption desorption tower 3 and the second adsorption desorption tower 4.

[0054] The output end of the third pipeline 11 is connected with the inlet of the circulating pump 8, the outlet of the circulating pump 8 is connected with the input end of the second pipeline 10, and the output end of the second pipeline 10 is connected with the inlets of the first and second adsorption and desorption towers 3 and 4 respectively; and the circulating pump 8 is used for recycling part of the steam in the CO2 desorption process.

[0055] The separation device comprises a cooling device and a gas-liquid separator 6, the output end of the third pipeline 11 is connected with the cooling device, and the cooling device is connected with the gas-liquid separator 6; the cooling device is used for cooling the steam carrying CO2 output by the third pipeline 11, and the gas-liquid separator 6 is used for separating CO2 and liquid water; wherein the cooling device is a condenser 5, the condenser 5 is connected with a cooling tower 7, the condenser 5 is used for cooling the steam carrying CO2 to change it from gas to liquid, and the cooling tower 7 is used for providing refrigerant to the condenser 5.

[0056] As shown in the figure, the CO2 desorption process of the system of the application is as follows:

[0057] After the high-temperature steam output by the steam generator 2 enters the first or second adsorption and desorption tower 3 or 4, the high-temperature steam flows through the gas distributor and the adsorbent in the tower to desorb and release CO2 in the adsorbent, generates steam carrying CO2, and is discharged from the outlet of the first or second adsorption and desorption tower 3 or 4 to the third pipeline 11;

[0058] Part of the steam carrying CO2 is transmitted to the circulating pump 8 through the third pipeline 11, and is returned to the inlet of the first or second adsorption and desorption tower 3 or 4 through the circulating pump 8 and the fourth pipeline 12, and enters the adsorption and desorption tower to continue the CO2 desorption and release;

[0059] Another part of the steam carrying CO2 is transmitted to the condenser 5 through the third pipeline 11 to be liquefied, and finally completes gas-liquid separation through the gas-liquid separator 6 to discharge gaseous CO2 and liquid waste.

[0060] In some specific embodiments, control valves 13 are installed on the first, second, third and fourth pipelines 9, 10, 11 and 12, and the state mode (adsorption or desorption) of the first and second adsorption and desorption towers 3 and 4 is mainly realized through the control valves 13;

[0061] The control valve 13 on the first pipeline 9 is used to distribute the communication between the outlets of the first and second adsorption and desorption towers 3 and 4 and the first pipeline 9.

[0062] The control valve 13 on the second pipeline 10 is used to distribute the communication between the inlets of the first and second adsorption and desorption towers 3 and 4 and the steam generator 2 and the circulating pump 8.

[0063] The control valve 13 on the third pipeline 11 is used to distribute the communication between the outlets of the first and second adsorption towers 3 and 4 and the third pipeline 11.

[0064] The control valve 13 on the fourth pipeline 12 is used to distribute the communication between the inlets of the first and second adsorption towers 3 and 4 and the air pump 1.

[0065] As shown in the figure, the control valve 13 can control the state of the pipeline: two connection states and a cut-off state.

[0066] Based on the steam recycling direct air capture system of the embodiment of the present application, the embodiment of the present application also provides a steam recycling direct air capture method, and the capture method includes a CO2 adsorption process and a CO2 desorption process,

[0067] The CO2 adsorption process includes: the first or second adsorption tower 3 or 4 performs selective adsorption of CO2 from external air through a gas distributor and an adsorbent, and a low-CO2-content gas is discharged through the first pipeline 9.

[0068] The CO2 desorption process includes: high-temperature steam is input into the first or second adsorption tower 3 or 4 through the steam generator 2, the high-temperature steam flows through the gas distributor and the adsorbent to desorb the CO2 in the adsorbent, and steam carrying CO2 is generated;

[0069] The part of the steam carrying CO2 is transported to a separation device through the third pipeline 11 for gas liquefaction and gas-liquid separation, and gaseous CO2 and liquid waste are discharged;

[0070] The other part of the steam carrying CO2 is transported to the first or second adsorption tower 3 or 4 through the third pipeline 11 to continue the desorption of CO2.

[0071] In some specific embodiments, the external air is pumped into the first or second adsorption tower 3 or 4 through the air pump 1.

[0072] In some specific embodiments, the part of the steam carrying CO2 is transported to a separation device through the third pipeline 11 for gas liquefaction and gas-liquid separation, including,

[0073] The part of the steam carrying CO2 is transported to a condenser 5 through the third pipeline 11 for gas liquefaction, and the condenser 5 transports the generated liquid to a gas-liquid separation device for gas-liquid separation.

[0074] Embodiment one:

[0075] The first adsorption-desorption tower 3 enters the adsorption stage, the second adsorption-desorption tower 4 enters the desorption stage, the air pump 1 is opened to introduce air into the first adsorption-desorption tower 3, and the air inlet flow is 300 Nm 3 / h, and the CO2 in the air is directly discharged from the first pipeline 9 after being selectively adsorbed by the first adsorption tower.

[0076] The steam generator 2 supplies steam into the second adsorption-desorption tower 4, the evaporation amount is 120 L / min; the circulating pump 8 is opened and the circulating reflux ratio is set to control the circulating steam amount after desorption, indirectly control the energy consumption, and the rest of the steam enters the condenser 5 and the gas-liquid separator 6 to perform condensation phase change and gas-liquid separation, and CO2 product gas with a concentration of more than 95% and waste liquid are obtained.

[0077] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for the purpose of limiting the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included in the scope of protection of the present application.

Claims

1. A direct air capture system with steam recycling, characterized in that, The system comprises a steam generator (2), a first adsorption-desorption tower (3), a second adsorption-desorption tower (4), a first pipeline (9), a second pipeline (10) and a third pipeline (11). The first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are used for adsorbing CO2 in air, and the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are used for desorbing the adsorbed CO2 in the towers by high-temperature steam. The first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are connected with the input end of the first pipeline (9), and the first pipeline (9) is used for discharging low-CO2-content gas. The steam generator (2) is connected with the inlets of the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) through the second pipeline (10). The first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are connected with the input end of the third pipeline (11), the output end of the third pipeline (11) is connected with a separation device and a circulating pump (8), and the third pipeline (11) is used for transmitting CO2-containing steam discharged from the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4). The first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are in cross conversion working mode, that is, the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) are in adsorption and desorption states respectively. The output end of the third pipeline (11) is connected with the inlet of the circulating pump (8), the outlet of the circulating pump (8) is connected with the input end of the second pipeline (10), and the output end of the second pipeline (10) is connected with the inlets of the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) respectively; wherein the circulating steam amount after desorption is controlled by setting a circulating reflux ratio. The separation device comprises a cooling device and a gas-liquid separator (6), the output end of the third pipeline (11) is connected with the cooling device, and the cooling device is connected with the gas-liquid separator (6); the cooling device is used for cooling the CO2-carrying steam output by the third pipeline (11), and the gas-liquid separator (6) is used for separating CO2 and liquid water; wherein the cooling device is a condenser (5), the condenser (5) is connected with a cooling tower (7), and the cooling tower (7) is used for providing refrigerant to the condenser (5). An air pump (1) is connected with the inlets of the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) through a fourth pipeline (12); the air pump (1) is used for outputting air to the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4).

2. The direct air capture system with steam recycling according to claim 1, wherein control valves (13) are installed on the first pipeline (9) and the second pipeline (10); The control valve (13) on the first pipeline (9) is used for distributing the communication between the outlets of the first adsorption-desorption tower (3) and the second adsorption-desorption tower (4) and the first pipeline (9). ​ ​ ​ The control valve (13) on the second pipeline (10) is used to distribute the communication between the inlets of the first and second adsorption towers (3, 4) and the steam generator (2) and the circulating pump (8).

3. The direct air capture system of claim 2, wherein, The control valve (13) is installed on the third and fourth pipelines (11, 12); The control valve (13) on the third pipeline (11) is used to distribute the communication between the outlets of the first and second adsorption towers (3, 4) and the third pipeline (11); The control valve (13) on the fourth pipeline (12) is used to distribute the communication between the inlets of the first and second adsorption towers (3, 4) and the air pump (1).

4. The direct air capture system of claim 1 or 3, wherein, The first and second adsorption towers (3, 4) are provided with a gas distributor and an adsorber.

5. A direct air capture method with steam recycling, characterized in that, The capture method is applied to the direct air capture system of any one of claims 1 to 4, and the capture method comprises a CO2 adsorption process and a CO2 desorption process, The CO2 adsorption process comprises: The first or second adsorption tower (3, 4) selectively adsorbs CO2 from the external air through the gas distributor and the adsorber, and the low-CO2-content gas is discharged through the first pipeline (9); The CO2 desorption process comprises: The high-temperature steam is input into the first or second adsorption tower (3, 4) through the steam generator (2), and the high-temperature steam flows through the gas distributor and the adsorber to desorb the CO2 in the adsorber, thereby generating steam carrying CO2; A portion of the steam carrying CO2 is transported to the separation device through the third pipeline (11) for gas liquefaction and gas-liquid separation, and gaseous CO2 and liquid waste are discharged; Another portion of the steam carrying CO2 is transported to the circulating pump (8) through the third pipeline (11) and then back to the first or second adsorption tower (3, 4) for continuous desorption of CO2.

6. The direct air capture method of claim 5, wherein, The external air is pumped into the first or second adsorption tower (3, 4) by the air pump (1).

7. A direct air capture method with steam cycle utilization according to claim 5 or 6, wherein, The portion of the steam carrying CO2 is transported to the separation device through the third pipeline (11) for gas liquefaction and gas-liquid separation, which comprises, A portion of the steam carrying CO2 is transported to the condenser (5) through the third pipeline (11) for gas liquefaction, and the condenser (5) transports the generated liquid to the gas-liquid separation device for gas-liquid separation.

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