Coal chemical co2 low-temperature capturing device and capturing method

Abstract

The application discloses a coal chemical CO2 low-temperature capturing device and a capturing method. The capturing device comprises a dehumidification tower, three filling beds arranged in parallel, a gas-liquid separation unit, a liquid nitrogen pipe, a nitrogen pipe and a CO2 removal gas pipe. The application firstly carries out gas-liquid separation in a low-temperature mode to obtain part of liquid carbon dioxide. The mixed gas after liquefied separation continues to be cooled and condensed in the filling bed, and the carbon dioxide is separated out. The dry ice obtained by condensation separation is liquefied and collected by heat exchange with the CO2-containing gas, and the pressure and temperature are controlled, so that the obtained dry ice can be directly melted into liquid carbon dioxide and will not be gasified into gas. The system fully recovers the cold energy of the system. The dry ice is condensed and captured by the filling bed to capture the carbon dioxide, which can avoid the dry ice freezing and blocking phenomenon of the conventional equipment. The gas does not need to be re-compressed, the energy consumption is low, the capturing purity of the carbon dioxide is improved, and the carbon dioxide capturing rate is increased.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture technology, and in particular to a low-temperature CO2 capture device and capture method for coal chemical industry. Background Technology

[0002] Carbon dioxide is one of the most significant greenhouse gases causing global climate change, and controlling its emissions has become a major concern for countries worldwide. As humanity's reliance on fossil fuels grows, carbon dioxide emission reduction has become an unavoidable and critical issue that must be addressed.

[0003] Currently, widely recognized CO2 emission reduction pathways include energy conservation, development of low-carbon energy (such as nuclear energy and renewable energy), CO2 conversion, increasing biological carbon sinks, and CO2 capture. Among these, CO2 capture is one of the most promising solutions to address climate change, and CO2 capture technology has become a research hotspot in various countries and an important strategy for the international community to reduce greenhouse gas emissions.

[0004] The following three methods are commonly used for carbon dioxide capture in coal chemical industry: (1) Condensation method. For example, after CO2 tail gas is separated by gas and liquid, it is pressurized to 1.0 MPa (A) by a compressor and cooled. Then it is fed into a molecular sieve dehydration device to remove H2O from the tail gas. After being pressurized to 3.5 MPa (A) by a compressor, it is cooled in the machine and then cooled to below -32°C by propylene refrigeration. About 60% of CO2 is condensed and then separated by gas and liquid to obtain a liquid CO2 product with a purity of 96.2 mol%. The whole process consumes a lot of electricity, has high operating costs, and low recovery rate; (2) Adsorption separation method, for example, after CO2 tail gas is separated by gas and liquid, it is pressurized to 1.0 MPa (A) by a compressor and cooled before entering a molecular sieve dehydration device to remove H2O from the tail gas. Then, CO2 is adsorbed and desorbed by an adsorption separation device (such as PSA) and then compressed and liquefied. The whole process requires frequent temperature and pressure adjustments, and there are problems such as low separation efficiency, slow desorption rate, long cooling process, and high cost of capturing flue gas with low carbon dioxide content; (3) Absorption method, for example, after CO2 tail gas is separated by gas and liquid, it is absorbed in an absorption tower with hot potassium alkali solution or MDEA as absorbent. After a large amount of CO2 is absorbed, it is desorbed in the desorption tower and then pressurized to the target pressure of 10 MPa (A) by a compressor. The second stage machine extracts the gas into a molecular sieve dehydration device to remove H2O from the gas. The whole process consumes a lot of energy and has high equipment investment.

[0005] The paper “Technical Features and Engineering Practices of the Entire Process of Carbon Capture, Utilization and Storage in Petroleum” (Applied Chemical Industry, No. 7, 2020) discloses a carbon dioxide capture process. In the process of coal gasification, the pressure swing adsorption tail gas first absorbs carbon dioxide through low-temperature methanol washing, then desorbs carbon dioxide by heating and depressurizing, and finally obtains liquid carbon dioxide through primary compression and two-stage cooling.

[0006] Overall, existing carbon dioxide capture technologies involve complex processes, high equipment investment, and high energy consumption. In particular, for the condensation method, the compression-cooling-liquefaction process has high compression energy consumption and low carbon dioxide capture rate, with an overall capture rate of only 60-70%. For CO2 from coal chemical processes, such as syngas containing CO2, CO2 is usually obtained by low-temperature methanol washing and desorption to obtain atmospheric pressure CO2 gas, which is then compressed and cooled for liquefaction and capture. However, the compression energy consumption is relatively high. Summary of the Invention

[0007] In view of the shortcomings and deficiencies of existing condensation carbon dioxide capture technology, such as high energy consumption and low capture efficiency, this invention aims to provide a low-temperature CO2 capture device and method for coal chemical industry. Carbon dioxide capture based on the carbon dioxide capture method and device of this invention helps to reduce energy consumption and improve capture rate.

[0008] To achieve one aspect of the above-mentioned objectives, the present invention employs the following technical aspects:

[0009] A low-temperature CO2 capture device for coal chemical industry, the capture device comprising:

[0010] A dehumidification tower is used to remove water from CO2-containing gas to obtain dried CO2-containing gas.

[0011] Three packed beds are arranged in parallel. Each packed bed includes a feed inlet at the upper end and a discharge outlet at the lower end, as well as internal cold storage packing. The feed inlets of the three packed beds are respectively connected to a dehumidification tower via pipelines to receive dried CO2-containing gas.

[0012] Liquid nitrogen pipes are connected to the feed inlets of each packed bed for conveying liquid nitrogen;

[0013] Nitrogen pipes are connected to the outlet of each packed bed for conveying nitrogen gas;

[0014] A gas-liquid separation unit, connected to the inlet and outlet of each packed bed, receives CO2-containing gas (containing liquid CO2) from the outlet of the packed bed and separates the liquid CO2 through gas-liquid separation. The remaining gas after CO2 separation is then fed back into the packed bed through the inlet.

[0015] Each of these is connected to the outlet of each packed bed for conveying de-CO2 gas.

[0016] In this invention, a dehumidification tower is provided to dehydrate CO2-containing gas and prevent moisture from freezing in the packed bed, which would have adverse effects. The dehumidification tower is well known in the art, such as a dehumidification tower with built-in water-absorbing material.

[0017] Preferably, the collection device further includes a cold energy recovery device connected to the CO2 removal gas pipe for recovering the cold energy in the CO2 removal gas; preferably, the cold energy recovery device is a heat exchanger for exchanging heat with the CO2 removal gas before the CO2-containing gas from the dehumidification tower enters the packed bed to reduce the load on the packed bed.

[0018] In this invention, CO2-containing gas containing liquid CO2 undergoes gas-liquid separation in a gas-liquid separation unit, for example, using a gas-liquid separator well-known in the art. If, after separation, the CO2 content in the remaining gas is still high due to insufficient initial condensation or the effect of subsequent heating, further condensation and gas-liquid separation of CO2 can be performed.

[0019] In a preferred embodiment, the gas-liquid separation unit includes:

[0020] The first gas-liquid separator is used to receive CO2-containing gas containing liquid CO2 at the outlet of the self-packed bed and separate liquid CO2 through gas-liquid separation.

[0021] A cooler, connected to the gas phase outlet at the top of the first gas-liquid separator, is used to further condense the CO2 in the gas phase from the first gas-liquid separator, for example, using liquid nitrogen condensation; and

[0022] The second gas-liquid separator is used to separate liquid CO2 from the gas phase cooled by the cooler, and the remaining gas is fed into the packed bed through the feed inlet of the packed bed.

[0023] In this invention, in order to facilitate the convenient switching of materials entering the packed bed between different packed beds and to facilitate the convenient delivery of different materials in different stages of the same packed bed to different target objects, valves are provided on the pipelines of the CO2 removal pipe, nitrogen pipe and gas-liquid separation unit connected to the outlet of each packed bed; and valves, such as PLC-controlled valves, are provided on the pipelines of the dehumidification tower, liquid nitrogen pipe and gas-liquid separation unit connected to the inlet of each packed bed.

[0024] Preferably, the outer surface of the filling bed is covered with an insulation layer or a vacuum insulation jacket to reduce cold loss and lower energy consumption.

[0025] In another aspect of achieving the above-mentioned objective, the present invention also provides a method for low-temperature CO2 capture using the above-mentioned capture device, wherein the three packing beds are a first packing bed, a second packing bed, and a third packing bed.

[0026] The capture method includes:

[0027] (1) The dried CO2-containing gas is sent into the first filling bed, which is now a frosted filling bed, and directly contacts the packing material with dry ice attached in the frosted filling bed for heat exchange. The CO2 in the CO2-containing gas is partially condensed while the dry ice is completely melted into liquid carbon dioxide so that the filling bed can be regenerated. The gas-liquid mixture formed is discharged from the outlet at the bottom of the frosted filling bed and enters the gas-liquid separation unit. At this time, the first filling bed is transformed into a new regenerated filling bed.

[0028] (2) After the liquid CO2-containing gas from the frosted packed bed is separated into liquid and gas in the gas-liquid separation unit, the resulting liquid carbon dioxide is sent to storage. The remaining gas after CO2 separation is sent to the second packed bed, which is now a cold storage packed bed, to exchange heat with the packing material. The residual CO2 in the remaining gas is sublimated on the surface of the packing material to form dry ice, so as to obtain de-CO2 gas after CO2 removal and lead it out through the de-CO2 gas pipe. At this time, the second packed bed is transformed into a new frosted packed bed.

[0029] (3) During the process of the first packed bed being transformed into the regenerated packed bed, liquid nitrogen is introduced into the third packed bed, which is now the regenerated packed bed, so that the third packed bed is transformed into a new cold storage packed bed. The liquid nitrogen is vaporized into nitrogen gas and then led out through the nitrogen gas pipe, thus completing one CO2 capture cycle.

[0030] (4) Switch the pipeline to send the dried CO2-containing gas into the new frosting packed bed so that steps (1)-(3) can be repeated in the new frosting packed bed, the new cold storage packed bed and the new regeneration packed bed to complete a new CO2 capture cycle.

[0031] In step (1), the CO2-containing gas dried by the dehumidification tower is sent into the first filling bed, which is now the frosting filling bed; preferably, the CO2-containing gas dried by the dehumidification tower is sent into the frosting filling bed after being cooled by exchanging heat with the de-CO2 gas from the de-CO2 gas pipe through a heat exchanger.

[0032] Furthermore, as described above, it is understood in the art that by switching pipelines, such as opening or closing corresponding valves, a material will not simultaneously enter different packed beds. For example, during the process of dried CO2-containing gas entering the frosting packed bed, the residual gas from the gas-liquid separation unit enters the cold storage packed bed, while the liquid nitrogen enters the regeneration packed bed. For materials leaving the packed bed, by switching pipelines, such as opening or closing corresponding valves, the same material leaving the packed bed will not enter different target objects. For example, the gas-liquid mixture discharged from the outlet at the bottom of the frosting packed bed will enter the gas-liquid separation unit, the de-CO2 gas discharged from the cold storage packed bed will enter the de-CO2 gas pipe, and the nitrogen gas discharged from the regeneration packed bed will enter the nitrogen pipe.

[0033] In addition, to ensure continuous operation, it is understood in the art that when the dried CO2-containing gas enters the new frosting-filled bed, the remaining gas also needs to be switched to the new cold storage-filled bed, while the liquid nitrogen is switched to the new regeneration-filled bed.

[0034] To ensure effective CO2 removal, it is understood in the art that the temperature of the cold storage packed bed can be further reduced and / or the amount of packing material increased to further increase the cold storage capacity.

[0035] In some embodiments, the filler is sand, ceramic balls, glass, metal, concrete, and / or encapsulated phase change material.

[0036] In a preferred embodiment, the filler is a spherical or irregular particle with a particle size of 3-25 mm, such as 5, 8, 10, 15, or 20 mm.

[0037] In some embodiments, the CO2-containing gas is CO2-containing syngas or syngas after CO conversion, with a pressure of 3.0-8.0 MPaG, such as 4.0 MPaG or 6.0 MPaG, and a carbon dioxide content of 10-50 v%, such as 30 v% or 40 v%. For example, it is CO2-containing syngas obtained from crude coal gas from a gasifier after dust removal and conversion treatment. Since the high-pressure gas is directly processed, it is beneficial to save energy and reduce consumption.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] This invention addresses CO2-containing gases, such as CO2-containing syngas, in the coal chemical industry. First-stage cooling via a frosting packed bed liquefies some of the carbon dioxide in the CO2-containing gas. Second-stage cooling via a regenerative packed bed condenses the remaining carbon dioxide into dry ice within the packed bed. The dry ice is then melted into liquid carbon dioxide using CO2-containing gas without vaporization. Finally, the liquid carbon dioxide obtained from these two processes is collected and stored. The process is simple, requires minimal investment, and generates no wastewater or waste gas, saving on wastewater and waste gas treatment investment and costs. Furthermore, this invention… The three packed beds can rotate between the frosting packed bed, the cold storage packed bed, and the regeneration packed bed, thereby fully recovering the system's cold energy, improving the system utilization rate of the carbon capture device, and achieving continuous and uninterrupted capture of carbon dioxide. At the same time, the use of packed bed cold storage and sublimation capture of carbon dioxide can avoid the dry ice blockage phenomenon of conventional equipment, eliminate the need for gas recompression, reduce energy consumption, and improve the purity of carbon dioxide capture due to the synergistic increase in carbon dioxide sublimation capture, with a purity of over 98 wt%, while the carbon dioxide capture rate is also greatly improved, reaching over 97%. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of one embodiment of the trapping device of the present invention.

[0041] The annotations in the figure are explained as follows:

[0042] 1-Dehumidification tower; 2-Cold energy recovery equipment; 3-Burnt bed; 4-First gas-liquid separator; 5-Cooler; 6-Second gas-liquid separator; 7-Gas-liquid separation unit; 8-Liquid nitrogen pipe; 9-Nitrogen pipe; 10-CO2 removal pipe. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0045] Figure 1 The diagram shows an embodiment of the collection device provided by the present invention, which includes a dehumidification tower 1, three packed beds 3 arranged in parallel, a gas-liquid separation unit 7, a liquid nitrogen pipe 8, a nitrogen pipe 9, and a CO2 removal pipe 10.

[0046] The dehumidification tower 1 is used to remove water from CO2-containing gas to obtain dried CO2-containing gas, thus avoiding the adverse effects of water freezing in the packed bed. The dehumidification tower is well known in the art, such as a dehumidification tower with built-in water-absorbing material.

[0047] Considering the low temperature of the de-CO2 gas, its cold energy can be recovered to reduce system energy consumption. The collection device can also be equipped with a cold energy recovery device 2, which is connected to the de-CO2 gas pipe and is used to recover the cold energy in the de-CO2 gas. In one embodiment, the cold energy recovery device is a heat exchanger, which is used to exchange heat with the de-CO2 gas from the dehumidification tower before entering the packed bed to reduce the temperature of the de-CO2 gas, thereby reducing the load on the packed bed.

[0048] The packed bed 3 includes an inlet at the upper end and an outlet at the lower end, respectively, and is filled with cold storage packing material. Preferably, the packed bed is covered with an insulation layer to reduce cold loss and energy consumption. The inlets of the three packed beds are respectively connected to the cold energy recovery device 2 via pipelines to receive the dried and cooled CO2-containing gas. Those skilled in the art will understand that when the cold energy recovery device is not installed, the inlets of the packed beds can be connected to the dehumidification tower 1. The cold storage packing material can be sand, ceramic balls, glass, metal, concrete, and / or encapsulated phase change materials. In a preferred embodiment, the particle size of the packing material is 3-25 mm, such as spherical or irregular particles of 5, 8, 10, 15, or 20 mm.

[0049] The gas-liquid separation unit 7 is connected to the inlet and outlet of each packed bed, respectively. It receives CO2-containing gas (containing liquid CO2) from the outlet of the packed bed and separates the liquid CO2 through gas-liquid separation. The remaining gas after CO2 separation is then fed back into the packed bed through the inlet. In one embodiment, the gas-liquid separation unit 7 includes:

[0050] The first gas-liquid separator 4 is used to receive CO2-containing gas containing liquid CO2 at the outlet of the self-filled bed and separate liquid CO2 through gas-liquid separation.

[0051] Cooler 5, connected to the gas phase outlet at the top of the first gas-liquid separator, is used to further condense the CO2 in the gas phase from the first gas-liquid separator, for example, using liquid nitrogen condensation; and

[0052] The second gas-liquid separator 6 is used to separate liquid CO2 from the gas phase cooled by the cooler, and to send the remaining gas into the packed bed through the feed inlet of the packed bed.

[0053] The liquid nitrogen pipes 8 are connected to the feed inlets of each packed bed for conveying liquid nitrogen.

[0054] The nitrogen pipes 9 are connected to the outlet of each packed bed and are used to transport nitrogen.

[0055] The CO2 removal gas pipes 10 are connected to the outlet of each packed bed and are used to transport CO2 removal gas.

[0056] Valves are installed on the pipelines connecting the CO2 removal gas pipe, nitrogen pipe, and gas-liquid separation unit to the outlet of each packed bed; and valves, such as PLC-controlled valves, are installed on the pipelines connecting the dehumidification tower, liquid nitrogen pipe, and gas-liquid separation unit to the inlet of each packed bed, so that materials can be quickly switched to different pipelines.

[0057] Taking the CO2-containing syngas obtained from the crude coal gas from the gasifier after dust removal and shifting treatment as an example (syngas with a pressure of 3.0-8.0 MPaG and a carbon dioxide content of 10-50 vol%), Figure 1 The device shown below processes CO2-containing gas as follows (wherein, as shown in the diagram). Figure 1 The three parallel packed beds shown are named, from left to right, the first packed bed, the second packed bed, and the third packed bed:

[0058] Synthesis gas with a pressure of 3.0-8.0 MPaG and a carbon dioxide content of 10-50% is first dehumidified and dried by dehumidification tower 1. Then, after recovering the cold energy of the de-CO2 gas leaving the packed bed 3 by cold energy recovery device 2, it enters the first packed bed, which is now a frosted packed bed. In the frosted packed bed, the dry ice attached to the packing particles directly contacts the gas for heat exchange. The CO2 in the CO2-containing gas is condensed, and at the same time, the dry ice is completely melted into liquid carbon dioxide so that the packed bed can be regenerated. The gas-liquid mixture formed is discharged from the outlet at the bottom of the frosted packed bed and enters the gas-liquid separation unit 7. At this time, the first packed bed is transformed into a new regenerated packed bed.

[0059] The resulting gas-liquid mixture is discharged from the bottom of the frosted packed bed and then enters the first gas-liquid separator 4 for gas-liquid separation. Liquid carbon dioxide is discharged from the bottom of the first gas-liquid separator 4 and sent to the liquid carbon dioxide storage tank for storage. Gas is discharged from the top of the first gas-liquid separator 4 and sent to the cooler 5 for further cooling. The gas-liquid compound obtained after partial liquefaction of carbon dioxide in the gas is sent to the second gas-liquid separator 6. Liquid carbon dioxide is discharged from the bottom of the second gas-liquid separator 6 and sent to the liquid carbon dioxide storage tank for storage. The remaining gas is discharged from the top of the second gas-liquid separator 6.

[0060] The residual gas from the gas-liquid separation unit 7 is sent to the second packed bed, which is now a cold storage packed bed, for direct gas-solid contact heat exchange. All the residual carbon dioxide gas in the residual gas sublimates on the surface of the packing particles of the cold storage packed bed to form dry ice to obtain de-CO2 gas after CO2 removal, which is then led out through the de-CO2 gas pipe 10. At this time, the second packed bed is transformed into a new frosting packed bed.

[0061] During the process of transforming the first packed bed into a regenerated packed bed, liquid nitrogen is introduced into the third packed bed, which is now a regenerated packed bed, through the liquid nitrogen pipe 8. The liquid nitrogen is vaporized into nitrogen gas, and the cold energy is stored in the packing particles of the third packed bed, transforming the third packed bed into a new cold storage packed bed. After the liquid nitrogen is vaporized into nitrogen gas, it is led out through the nitrogen pipe 9, thus completing one CO2 capture cycle.

[0062] Then, by switching pipelines, the dried and cooled CO2-containing gas is sent to a new frosting packed bed, so that the above process can be repeated in the new frosting packed bed, the new cold storage packed bed, and the new regeneration packed bed to complete a new CO2 capture cycle. The carbon dioxide sublimation capture process is based on the switching operation of three parallel packed beds, including pipeline switching. Valves control each packed bed to be in the cold storage, frosting, and regeneration processes respectively, improving the system utilization rate of the carbon capture device and realizing uninterrupted capture of carbon dioxide.

[0063] The present invention will be further illustrated below with reference to the embodiments.

[0064] Example 1

[0065] Adopting such Figure 1 The trapping device shown and as described above Figure 1 The capture device shown is used to process CO2-containing gas. It captures CO2 in syngas 1 containing CO2. The relevant process parameters and experimental data are shown in Table 1 below. The liquid CO2 separated by the gas-liquid separation unit is sent to the liquid CO2 storage tank. The liquid CO2 in the liquid CO2 storage tank is sampled and tested. The purity is 99.36 wt%.

[0066] Table 1

[0067] Syngas 1 N2 CO2 CH4 CO H2 H2S Temperature, K Pressure, MPa CO2 capture rate v％ 0.61 41.45 1.15 1.57 55.02 0.2000 313.15 3.35 wt.% 0.8453 90.24 0.9127 2.175 5.487 0.3372 Liquefaction capture 223.14 3.34 52.30 Condensation Capture 183.15 3.31 45.49 Total capture rate 97.79

[0068] Note: The CO2 capture rate of sublimation capture refers to the ratio of the amount of CO2 removed to the amount of CO2 in the CO2-containing gas during the process of obtaining de-CO2 gas from the residual gas from the gas-liquid separation unit through the cold storage packed bed treatment.

[0069] The total CO2 capture rate refers to the ratio of the amount of liquid CO2 obtained by the gas-liquid separation unit to the amount of CO2 in the CO2-containing gas.

[0070] Example 2

[0071] Adopting such Figure 1 The trapping device shown and as described above Figure 1 The capture device shown is used to process CO2-containing gas. It captures CO2 in the synthesis gas 2 containing CO2. The relevant process parameters and experimental data are shown in Table 2 below. The liquid CO2 separated by the gas-liquid separation unit is sent to the liquid CO2 storage tank. The liquid CO2 in the liquid CO2 storage tank is sampled and tested. The purity is 98.11 wt%.

[0072] Table 2

[0073] Syngas 2 N2 CO2 CH4 CO H2 H2S Temperature, K Pressure, MPa CO2 capture rate v％ 0.38 30.04 3.00 22.31 46.91 0.06 313.75 5.80 wt.% 0.5167 64.21 0.2337 30.35 4.593 0.09931 Liquefaction capture 223.15 5.79 48.06 Condensation Capture 183.15 5.76 49.05 Total capture rate 97.11

[0074] Example 3

[0075] The difference from Example 1 is that the gas-liquid separation unit does not include a cooler and a second gas-liquid separator. The residual gas containing liquid CO2 from the packed bed, after being separated by the first gas-liquid separator, is directly returned to the packed bed. The CO2 capture rate is above 97.32%, and the purity is above 99.38 wt%.

[0076] As can be seen from the above, when using the collection device and method of the present invention to collect CO2 in the process of CO2 gas, the CO2 collection rate can reach more than 97% and the purity is more than 98 wt%.

[0077] It is readily understood that the above embodiments are merely illustrative examples for clarity and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. For example, one or more of the first, second, and third packed beds can be replaced with two or more packed beds connected in parallel or series, or the three packed beds can be combined into a single operating packed bed, achieving CO2 liquefaction and separation, and switching the packed bed between frosting beds, cold storage beds, and regeneration beds through intermittent operation. Of course, it is neither necessary nor possible to exhaustively describe all possible embodiments. Other obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A method for low-temperature CO2 capture using a capture device, characterized in that, The trapping device includes: A dehumidification tower is used to remove water from CO2-containing gas to obtain dried CO2-containing gas. Three packed beds are arranged in parallel. Each packed bed includes a feed inlet at the upper end and a discharge outlet at the lower end, as well as internal cold storage packing. The feed inlets of the three packed beds are respectively connected to a dehumidification tower via pipelines to receive dried CO2-containing gas. Liquid nitrogen pipes are connected to the feed inlets of each packed bed for conveying liquid nitrogen; Nitrogen pipes are connected to the outlet of each packed bed for conveying nitrogen gas; A gas-liquid separation unit, connected to the inlet and outlet of each packed bed, receives CO2-containing gas (containing liquid CO2) from the outlet of the packed bed and separates the liquid CO2 through gas-liquid separation. The remaining gas after CO2 separation is then fed back into the packed bed through the inlet. Each is connected to the outlet of the packed bed for conveying de-CO2 gas; The three packing beds are referred to as the first packing bed, the second packing bed, and the third packing bed; The capture method includes: (1) The dried CO2-containing gas is sent into the first filling bed, which is now a frosted filling bed, and directly contacts the packing material with dry ice attached in the frosted filling bed for heat exchange. The CO2 in the CO2-containing gas is partially condensed while the dry ice is completely melted into liquid carbon dioxide so that the filling bed can be regenerated. The gas-liquid mixture formed is discharged from the outlet at the bottom of the frosted filling bed and enters the gas-liquid separation unit. At this time, the first filling bed is transformed into a new regenerated filling bed. (2) After the liquid CO2-containing gas from the frosted packed bed is separated into liquid and gas in the gas-liquid separation unit, the resulting liquid carbon dioxide is sent to storage. The remaining gas after CO2 separation is sent to the second packed bed, which is now a cold storage packed bed, to exchange heat with the packing material therein. The residual CO2 in the remaining gas is sublimated on the surface of the packing material to form dry ice to obtain de-CO2 gas after CO2 removal and is led out through the de-CO2 gas pipe. At this time, the second packed bed is transformed into a new frosted packed bed. (3) During the process of the first packed bed being transformed into the regenerated packed bed, liquid nitrogen is introduced into the third packed bed, which is now the regenerated packed bed, so that the third packed bed is transformed into a new cold storage packed bed. The liquid nitrogen is vaporized into nitrogen gas and then led out through the nitrogen gas pipe, thus completing one CO2 capture cycle. (4) Switch the pipeline to send the dried CO2-containing gas into the new frosting packed bed so that steps (1)-(3) can be repeated in the new frosting packed bed, the new cold storage packed bed and the new regeneration packed bed to complete a new CO2 capture cycle.

2. The trapping method of claim 1, wherein, The collection device also includes a cold energy recovery device connected to the CO2 removal gas pipe, used to recover the cold energy in the CO2 removal gas.

3. The collection method according to claim 2, characterized in that, The cold energy recovery device is a heat exchanger used to cool the CO2-containing gas from the dehumidification tower by exchanging heat with the de-CO2 gas before it enters the packed bed.

4. The collection method according to claim 1, characterized in that, The gas-liquid separation unit includes: The first gas-liquid separator is used to receive CO2-containing gas containing liquid CO2 at the outlet of the self-packed bed and separate liquid CO2 through gas-liquid separation. A cooler, connected to the gas phase outlet at the top of the first gas-liquid separator, is used to further condense the CO2 in the gas phase from the first gas-liquid separator; and The second gas-liquid separator is used to separate liquid CO2 from the gas phase cooled by the cooler, and the remaining gas is fed into the packed bed from the feed port of the packed bed.

5. The collection method according to any one of claims 1-4, characterized in that, Valves are installed on the pipelines connecting the CO2 removal pipe, nitrogen pipe, and gas-liquid separation unit to the outlet of each packed bed; Valves are installed on the pipelines connecting the dehumidification tower, liquid nitrogen pipe, and gas-liquid separation unit to each packed bed inlet.

6. The capture method according to any one of claims 1-4, characterized in that, The filling bed is covered with an insulation layer or a vacuum insulation jacket.

7. The collection method according to any one of claims 1-4, characterized in that, The dehumidification tower is a dehumidification tower with built-in water-absorbing material.

8. The collection method according to claim 1, characterized in that, In step (1), the dried CO2-containing gas is cooled down by exchanging heat with the de-CO2 gas from the de-CO2 gas pipe through a heat exchanger before being sent to the frosting packed bed.

9. The collection method according to claim 1 or 8, characterized in that, The filler is sand, ceramic balls, glass, metal, concrete, and / or encapsulated phase change material.

10. The collection method according to claim 9, characterized in that, The filler consists of spherical or irregular particles with a particle size of 3-25 mm.

11. The capture method according to any one of claims 1, 8, and 10, characterized in that, The CO2-containing gas is either CO2-containing syngas or syngas that has undergone CO conversion.

Images