Coal chemical industry CO2 low-temperature trapping device and trapping method

Abstract

The invention discloses a coal chemical industry CO2 low-temperature trapping device and trapping method. The trapping device comprises a dehumidification tower, three packed beds arranged in parallel, a gas-liquid separation unit, a liquid nitrogen pipe, a nitrogen pipe and a CO2 removal gas pipe, the method comprises the following steps: performing gas-liquid separation at a low temperature to obtain part of liquid carbon dioxide, continuously cooling and desublimating particles of the liquefied and separated mixed gas in a packed bed when the particles encounter cold particles, separating out carbon dioxide, liquefying and collecting dry ice obtained by desublimation and separation through heat exchange with CO2-containing gas, and controlling the pressure and temperature of the dry ice to obtain the carbon dioxide. Therefore, the obtained dry ice can be directly melted into liquid carbon dioxide and cannot be gasified to enter gas, the system fully recovers the system cold capacity, the packed bed is adopted for condensation and condensation capture of carbon dioxide, the phenomenon of dry ice blockage of conventional equipment can be avoided, recompression of gas is not needed, energy consumption is low, and the capture purity of carbon dioxide is improved. And the capture rate of carbon dioxide is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture, and in particular to a coal chemical CO2 low-temperature capture device and a capture method. Background Art

[0002] Carbon dioxide is one of the most important greenhouse gases causing global climate change, and the issue of controlling carbon dioxide emissions has received widespread attention from countries around the world. As humans become more and more dependent on fossil energy, reducing carbon dioxide emissions has become a major issue that humans must solve and cannot avoid.

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

[0004] The capture of carbon dioxide in coal chemical industry usually adopts the following three methods: (1) Condensation method, for example, after the CO2 tail gas is separated from the gas and liquid, it enters the compressor to increase the pressure to 1.0MPa(A), cools it, and then enters the molecular sieve dehydration device to remove the H2O in the tail gas. It is then pressurized to 3.5MPa(A) by the compressor, cooled in the machine room, and cooled to below -32℃ by propylene refrigeration. About 60% of the CO2 is condensed and separated from the gas to obtain a liquid CO2 product with a purity of 96.2mol|%. The whole process has large power consumption, high operating cost and low recovery rate; (2) Adsorption separation method, for example, after the CO2 tail gas is separated from the gas and liquid, it enters the compressor to increase the pressure to 1.0MPa(A), cools it, and then enters the molecular sieve dehydration device to remove the H2O in the tail gas, and then the CO2 is adsorbed, desorbed and separated by the adsorption separation device (such as PSA), and then compressed and liquefied. The whole process requires frequent temperature and pressure adjustment, 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 the CO2 tail gas is separated from the gas and liquid, it enters the absorption tower for absorption with hot potassium alkali solution or MDEA as absorbent. A large amount of CO2 is absorbed and then analyzed in the analysis tower, and then it is pressurized to the target pressure of 10MPa(A) by the compressor. The second stage room is drawn out and enters the molecular sieve dehydration to remove the H2O in the gas. The whole process has high energy consumption and high equipment investment.

[0005] The document "Technical Features and Engineering Practice of the Whole Process of Yanchang Petroleum Carbon Capture, Utilization and Storage" (Applied Chemical Industry, Issue 7, 2020) discloses a carbon dioxide capture process. During the coal gasification process, the pressure swing adsorption tail gas is first washed with low-temperature methanol to absorb carbon dioxide, and then the temperature is increased and the pressure is reduced to desorb the carbon dioxide, and then after one-stage compression and two-stage cooling, liquid carbon dioxide is finally obtained.

[0006] In general, the existing carbon dioxide capture technology has a complex process flow, high equipment investment and energy consumption, especially for the condensation method, the compression cooling liquefaction process has high compression energy consumption and low carbon dioxide capture rate, with a total capture rate of only 60-70%; and for coal chemical CO2, such as CO2-containing synthesis gas, it is usually desorbed by low-temperature methanol washing to obtain normal pressure CO2 gas, which is then compressed and cooled for liquefaction capture, and the compression energy consumption is relatively high. Summary of the invention

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

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

[0009] Coal chemical CO2 low temperature capture device, the capture device comprises:

[0010] Dehumidification tower, used to remove water from CO2-containing gas to obtain dry CO2-containing gas;

[0011] Three packed beds are arranged in parallel, each of which comprises a feed inlet at the upper end and a discharge outlet at the lower end of the packed bed and a cold storage filler filled inside; the feed inlets of the three packed beds are respectively connected to a dehumidification tower through pipelines to receive the dried CO2-containing gas;

[0012] a liquid nitrogen pipe connected to a feed port of each packed bed for delivering liquid nitrogen;

[0013] A nitrogen pipe connected to a discharge port of each packed bed for conveying nitrogen;

[0014] A gas-liquid separation unit connected to the feed port and the discharge port of each packed bed, respectively, for receiving the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separating the liquid CO2 through gas-liquid separation, and sending the remaining gas after the CO2 is separated into the packed bed from the feed port of the packed bed; and

[0015] A de-CO2 gas pipe is respectively connected to the discharge port of each packed bed for conveying the de-CO2 gas.

[0016] In the present invention, a dehumidification tower is provided to dehydrate the CO2-containing gas to avoid adverse effects caused by freezing of water in the packed bed; the dehumidification tower is well known in the art, such as a dehumidification tower with built-in water-absorbing material.

[0017] Preferably, the capture device also includes a cold recovery device connected to the de-CO2 gas pipe, which is used to recover the cold in the de-CO2 gas; preferably, the cold recovery device is a heat exchanger, which is used to allow the CO2-containing gas from the dehumidification tower to exchange heat and cool down with the de-CO2 gas before entering the packed bed, thereby reducing the load on the packed bed.

[0018] In the present invention, the CO2-containing gas containing liquid CO2 is subjected to gas-liquid separation in a gas-liquid separation unit, for example, by a gas-liquid separator well known in the art. When the CO2 content in the remaining gas after separation is still high due to insufficient condensation in the early stage or the influence of subsequent temperature rise, the CO2 can be further condensed and separated into gas and liquid.

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

[0020] A first gas-liquid separator, for receiving the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separating the liquid CO2 through gas-liquid separation;

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

[0022] The second gas-liquid separator is used to perform gas-liquid separation on the gas phase cooled by the cooler to separate liquid CO2, and to feed the remaining gas obtained into the packed bed from the feed port of the packed bed.

[0023] In the present invention, in order to facilitate the convenient switching of materials entering the packed bed between different packed beds and to facilitate the convenient transportation of different materials at different stages of the same packed bed to different target objects, the pipelines connecting the CO2 removal pipe, the nitrogen pipe and the gas-liquid separation unit to the discharge port of each packed bed are all provided with valves; and the pipelines connecting the dehumidification tower, the liquid nitrogen pipe and the gas-liquid separation unit to the feed port of each packed bed are all provided with valves, such as PLC-controlled valves.

[0024] Preferably, a heat-insulating layer or a vacuum heat-insulating jacket is provided on the outside of the packed bed to reduce cold loss and lower energy consumption.

[0025] In order to achieve another aspect of the above-mentioned invention object, the present invention also provides a capture method for low-temperature capture of CO2 using the above-mentioned capture device, wherein the three packed beds are respectively a first packed bed, a second packed bed and a third packed bed;

[0026] The capture method comprises:

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

[0028] (2) After the CO2-containing gas containing liquid CO2 from the frosted packed bed is subjected to gas-liquid separation in the gas-liquid separation unit, the obtained liquid carbon dioxide is sent to storage, and the remaining gas after the CO2 is separated is sent to the second packed bed, which is now used as a cold storage packed bed, to perform contact heat exchange with the filler therein, so that the residual CO2 in the remaining gas condenses on the surface of the filler to form dry ice to obtain CO2-free gas after CO2 is removed and is led out through the CO2-free 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 regeneration packed bed, liquid nitrogen is introduced into the third packed bed, which is now the regeneration packed bed, so that the third packed bed is transformed into a new cold storage packed bed, and the liquid nitrogen is gasified into nitrogen and then led out through the nitrogen pipe, thereby completing a CO2 capture cycle;

[0030] (4) Switch the pipeline to send the dried CO2-containing gas into a new frosted packed bed so that steps (1)-(3) are repeated in the new frosted 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 in the dehumidification tower is sent to the first packed bed which serves as the frosted packed bed; preferably, the dried CO2-containing gas from the dehumidification tower is sent to the frosted packed bed after heat exchange and cooling with the de-CO2 gas from the de-CO2 gas pipe in a heat exchanger.

[0032] In addition, from the above, it is understood in the art that through pipeline switching such as opening or closing corresponding valves, a material will not enter different packed beds at the same time. For example, in the process of the dried CO2-containing gas entering the frosting packed bed, the remaining gas from the gas-liquid separation unit enters the cold storage packed bed, and the liquid nitrogen enters the regeneration packed bed; for the material leaving the packed bed, through pipeline switching 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 discharge port 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 discharged from the regeneration packed bed will enter the nitrogen pipe.

[0033] Furthermore, to ensure continuous operation, it is understood in the art that when the dried CO2-containing gas enters and switches to a new frosting packed bed, the remaining gas also needs to switch to a new cold storage packed bed, while the liquid nitrogen switches to a new regeneration packed bed.

[0034] In order to ensure the CO2 removal effect, it is understood in the art that the temperature of the cold storage packed bed can be further reduced and / or the amount of filler can be 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 has a particle size of 3-25 mm, such as spherical or irregular particles of 5, 8, 10, 15 or 20 mm.

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

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

[0039] The present invention uses a frosted packed bed to cool the CO2-containing gas in the coal chemical industry, such as the CO2-containing synthesis gas, to partially liquefy the carbon dioxide in the CO2-containing gas, and then uses a cold storage packed bed to cool the remaining carbon dioxide in the CO2-containing gas to condense into dry ice in the packed bed, and then uses the CO2-containing gas to melt the dry ice in the packed bed into liquid carbon dioxide without gasifying and entering the gas, and finally collects and stores the liquid carbon dioxide obtained in the above two processes; the process is simple, the investment is small, and no wastewater or waste gas is generated, thus saving the investment and treatment cost of wastewater and waste gas treatment; in addition, the present invention The three packed beds can be rotated between the frosting packed bed, the cold storage packed bed and the regeneration packed bed, so as to fully recover the system cooling capacity, improve the system utilization rate of the carbon capture device, and realize the continuous and uninterrupted capture of carbon dioxide; at the same time, the use of packed bed cold storage sublimation to capture carbon dioxide can avoid the dry ice freezing phenomenon of conventional equipment, and there is no need to recompress the gas, with low energy consumption. In addition, due to the synergistic increase in the capture of carbon dioxide sublimation, the capture purity of carbon dioxide is improved, and the purity is above 98wt%. At the same time, the carbon dioxide capture rate is also greatly improved, reaching more than 97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of an embodiment of the capture device of the present invention.

[0041] The reference numerals in the figures are described as follows:

[0042] 1-dehumidification tower; 2-cold recovery equipment; 3-packed 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 DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0045] Figure 1 A schematic diagram of an embodiment of the capture device provided by the present invention is shown, wherein the capture device comprises 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 the CO2-containing gas to obtain dry CO2-containing gas and avoid adverse effects caused by freezing of water 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] Taking into account the low temperature of the de-CO2 gas, its cold energy can be recovered to reduce system energy consumption. The capture device can also be provided with a cold energy recovery device 2, and the cold energy recovery device 2 is connected to the de-CO2 gas pipe for recovering the cold energy in the de-CO2 gas. In one embodiment, the cold energy recovery device is a heat exchanger for allowing the CO2-containing gas from the dehumidification tower to exchange heat and cool down with the de-CO2 gas before entering the packed bed, thereby reducing the load on the packed bed.

[0048] The packed bed 3 includes a feed port at the upper end and a discharge port at the lower end of the packed bed, and a cold storage filler filled inside; preferably, a thermal insulation layer is applied to the outside of the packed bed to reduce cold loss and energy consumption. The feed ports of the three packed beds are respectively connected to the cold recovery device 2 through pipelines to receive the dried and cooled CO2-containing gas. Those skilled in the art understand that when the cold recovery device is not provided, the feed port of the packed bed can be connected to the dehumidification tower 1. The cold storage filler can be sand, ceramic balls, glass, metal, concrete and / or encapsulated phase change materials. In a preferred embodiment, the filler has a particle size of 3-25 mm, such as spherical or irregular particles of 5, 8, 10 or 15 or 20 mm.

[0049] The gas-liquid separation unit 7 is connected to the feed port and the discharge port of each packed bed, respectively, and is used to receive the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separate the liquid CO2 through gas-liquid separation, and send the remaining gas after the CO2 is separated into the packed bed from the feed port of the packed bed. In one embodiment, the gas-liquid separation unit 7 includes:

[0050] A first gas-liquid separator 4 is used to receive the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separate the liquid CO2 through gas-liquid separation;

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

[0052] The second gas-liquid separator 6 is used to perform gas-liquid separation on the gas phase cooled by the cooler to separate liquid CO2, and to feed the remaining gas obtained into the packed bed from the feed port of the packed bed.

[0053] The liquid nitrogen pipe 8 is connected to the feed port of each packed bed for conveying liquid nitrogen.

[0054] The nitrogen pipe 9 is connected to the discharge port of each packed bed for conveying nitrogen.

[0055] The de-CO2 gas pipe 10 is respectively connected to the discharge port of each packed bed for conveying the de-CO2 gas.

[0056] The CO2 removal pipe, nitrogen pipe and pipelines connecting the gas-liquid separation unit to each packed bed outlet are all provided with valves; and the dehumidification tower, liquid nitrogen pipe and pipelines connecting the gas-liquid separation unit to each packed bed feed port are all provided with valves, such as PLC-controlled valves, so that materials can be quickly switched into different pipelines.

[0057] Take the CO2-containing synthesis gas obtained from the raw coal gas from the gasifier after dust removal and conversion treatment as an example (synthesis gas with a pressure of 3.0-8.0MpaG and a carbon dioxide content of 10-50v%). Figure 1 The process of treating CO2-containing gas by the device shown is as follows (wherein Figure 1 The three parallel packed beds shown in FIG. 1 are named as the first packed bed, the second packed bed and the third packed bed from left to right respectively):

[0058] The synthesis gas with a pressure of 3.0-8.0MpaG and a carbon dioxide content of 10-50v% is first dehumidified and dried in a dehumidification tower 1, and then the cold energy of the CO2-free gas leaving the packed bed 3 is recovered by the cold energy recovery device 2, and then enters the first packed bed which is now a frosted packed bed. The dry ice attached to the packing particles in the frosted packed bed is in direct contact with the gas for heat exchange, and the CO2 in the CO2-containing gas is condensed while the dry ice is completely melted into liquid carbon dioxide so that the packed bed can be regenerated. The formed gas-liquid mixture is discharged from the discharge port at the bottom of the frosted packed bed into the gas-liquid separation unit 7. At this time, the first packed bed is transformed into a new regenerated packed bed.

[0059] The formed gas-liquid mixture is discharged from the lower part 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. The gas is discharged from the top of the first gas-liquid separator 4 and sent to the cooler 5 to be cooled again. The gas-liquid compound obtained after the partial liquefaction of the carbon dioxide in the gas is sent to the second gas-liquid separator 6. The 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 remaining gas from the gas-liquid separation unit 7 is sent to the second packed bed which serves as the cold storage packed bed for direct gas-solid contact heat exchange. The remaining carbon dioxide gas in the remaining gas is completely condensed on the surface of the filler particles of the cold storage packed bed to form dry ice to obtain the de-CO2 gas after CO2 is removed, and is led out through the de-CO2 gas pipe 10. At this time, the second packed bed is transformed into a new frosted packed bed.

[0061] In the process of converting the first packed bed into the regeneration packed bed, liquid nitrogen is introduced into the third packed bed, which now serves as the regeneration packed bed, through the liquid nitrogen pipe 8. The liquid nitrogen is gasified into nitrogen gas, and the cold energy is stored in the filler particles of the third packed bed, so that the third packed bed is converted into a new cold storage packed bed. The liquid nitrogen is gasified into nitrogen gas and then led out through the nitrogen pipe 9, thereby completing a CO2 capture cycle.

[0062] Then, by switching the pipeline, the dried and cooled CO2-containing gas is sent to a new frosted packed bed, so that the above process is repeated in the new frosted 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, and each packed bed is controlled by valves to be in the cold storage, frosting and regeneration process, thereby improving the system utilization of the carbon capture device and realizing the uninterrupted capture of carbon dioxide.

[0063] The present invention is further described below with reference to the examples.

[0064] Example 1

[0065] Use Figure 1 The capture device shown and as described above Figure 1 The capture device shown in the figure processes the CO2-containing gas and captures the CO2 in the CO2-containing synthesis gas 1. 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, and the purity is 99.36wt%.

[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 Desublimation capture 183.15 3.31 45.49 Total capture rate 97.79

[0068] Note: The CO2 capture rate of desublimation 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 removing CO2 from the residual gas from the gas-liquid separation unit through the cold storage packed bed;

[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] Use Figure 1 The capture device shown and as described above Figure 1 The capture device shown in the figure processes the CO2-containing gas and captures the CO2 in the CO2-containing synthesis gas 2. 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, and the purity is 98.11wt%.

[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 Desublimation 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 contain a cooler and a second gas-liquid separator, and the remaining gas after the CO2-containing gas containing liquid CO2 from the packed bed is separated by the first gas-liquid separator is directly sent back to the packed bed. The CO2 capture rate is above 97.32% and the purity is above 99.38wt%.

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

[0077] It is easy to understand that the above embodiments are only examples for clear explanation and do not mean that the present invention is limited to them. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description, such as one or more of the first packed bed, the second packed bed and the third packed bed can be replaced by two or more packed beds in parallel or in series, or the three packed beds can be combined into one operating packed bed, and the liquefaction separation of CO2 and the switching of the packed bed as a frosting bed, a cold storage bed and a regeneration bed can be achieved by adopting intermittent operation. Of course, it is not necessary and impossible to list all the implementation methods here. And other obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. Coal chemical CO2 low temperature capture device, characterized in that: The capture device comprises: Dehumidification tower, used to remove water from CO2-containing gas to obtain dry CO2-containing gas; Three packed beds are arranged in parallel, each of which comprises a feed inlet at the upper end and a discharge outlet at the lower end of the packed bed and a cold storage filler filled inside; the feed inlets of the three packed beds are respectively connected to a dehumidification tower through pipelines to receive the dried CO2-containing gas; a liquid nitrogen pipe connected to a feed port of each packed bed for delivering liquid nitrogen; A nitrogen pipe connected to a discharge port of each packed bed for conveying nitrogen; A gas-liquid separation unit connected to the feed port and the discharge port of each packed bed, respectively, for receiving the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separating the liquid CO2 through gas-liquid separation, and sending the remaining gas after the CO2 is separated into the packed bed from the feed port of the packed bed; and A de-CO2 gas pipe is respectively connected to the discharge port of each packed bed for conveying the de-CO2 gas.

2. The capture device according to claim 1, characterized in that: The capture device also includes a cold recovery device connected to the de-CO2 gas pipe, which is used to recover the cold in the de-CO2 gas; Preferably, the cold recovery device is a heat exchanger, which is used to exchange heat and cool the CO2-containing gas from the dehumidification tower with the CO2-free gas before entering the packed bed.

3. The capture device according to claim 1, characterized in that: The gas-liquid separation unit comprises: A first gas-liquid separator, for receiving the CO2-containing gas containing liquid CO2 from the discharge port of the packed bed and separating the liquid CO2 through gas-liquid separation; a cooler connected to the gas phase outlet at the top of the first gas-liquid separator, for further condensing CO2 in the gas phase from the first gas-liquid separator; and The second gas-liquid separator is used to perform gas-liquid separation on the gas phase cooled by the cooler to separate liquid CO2, and to feed the remaining gas obtained into the packed bed from the feed port of the packed bed.

4. The capture device according to any one of claims 1 to 3, characterized in that: The CO2 removal pipe, nitrogen pipe and pipelines connecting the gas-liquid separation unit to each packed bed outlet are all provided with valves; The dehumidification tower, the liquid nitrogen pipe and the pipelines connecting the gas-liquid separation unit to each packed bed feed port are all provided with valves.

5. The capture device according to any one of claims 1 to 4, characterized in that: The outside of the packed bed is provided with a heat-insulating layer or a vacuum heat-insulating jacket.

6. The capture device according to any one of claims 1 to 5, characterized in that: The dehumidification tower is a dehumidification tower with built-in water-absorbing material.

7. A method for low-temperature capture of CO2 using the capture device according to any one of claims 1 to 6, characterized in that: The three packed beds are respectively a first packed bed, a second packed bed and a third packed bed; The capture method comprises: (1) The dried CO2-containing gas is sent to the first packed bed, which is now a frosted packed bed, and is directly in contact with the filler with dry ice attached to the frosted packed bed for heat exchange. The CO2 in the CO2-containing gas is partially condensed, and the dry ice is completely melted into liquid carbon dioxide so that the packed bed can be regenerated. The formed gas-liquid mixture is discharged from the discharge port at the bottom of the frosted packed bed into the gas-liquid separation unit. At this time, the first packed bed is transformed into a new regenerated packed bed; (2) After the CO2-containing gas containing liquid CO2 from the frosted packed bed is subjected to gas-liquid separation in the gas-liquid separation unit, the obtained liquid carbon dioxide is sent to storage, and the remaining gas after the CO2 is separated is sent to the second packed bed, which is now used as a cold storage packed bed, to perform contact heat exchange with the filler therein, so that the residual CO2 in the remaining gas condenses on the surface of the filler to form dry ice to obtain CO2-free gas after CO2 is removed and is led out through the CO2-free 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 regeneration packed bed, liquid nitrogen is introduced into the third packed bed, which is now the regeneration packed bed, so that the third packed bed is transformed into a new cold storage packed bed, and the liquid nitrogen is gasified into nitrogen and then led out through the nitrogen pipe, thereby completing a CO2 capture cycle; (4) Switch the pipeline to send the dried CO2-containing gas into a new frosted packed bed so that steps (1)-(3) are repeated in the new frosted packed bed, the new cold storage packed bed and the new regeneration packed bed to complete a new CO2 capture cycle.

8. The capture method according to claim 7, characterized in that: The CO2-containing gas dried in step (1) is sent to the frosting packed bed after heat exchange and cooling with the CO2-free gas from the CO2-free gas pipe in a heat exchanger.

9. The capture method according to claim 7 or 8, characterized in that: The filler is sand, ceramic balls, glass, metal, concrete and / or encapsulated phase change material; preferably, the filler has a spherical or irregular particle size of 3-25 mm.

10. The capture method according to any one of claims 7 to 9, characterized in that: The CO2-containing gas is a synthesis gas containing CO2 or a synthesis gas after CO conversion.

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