System and method for freezing, separating and recycling carbon dioxide mixed gas under normal pressure

Abstract

The invention discloses a system and a method for freezing, separating and recycling carbon dioxide mixed gas under normal pressure, and relates to the technical field of recycling of combustion type flue gas carbon dioxide. The separation and recovery system comprises an ultralow-temperature CO2 separation tower and a large-temperature-difference special-temperature-zone heat pump, wherein the ultralow-temperature CO2 separation tower is connected with the large-temperature-difference special-temperature-zone heat pump through an ultralow-temperature cold source conveying pipe; the separation and recovery method comprises the following steps: quickly cooling flue gas or mixed gas containing carbon dioxide to below-78 DEG C by using a large-temperature-difference special-temperature-zone heat pump, immediately changing the carbon dioxide gas into carbon dioxide solid (dry ice), separating the carbon dioxide solid from other gases, separating the carbon dioxide solid out, and discharging other gases to obtain pure carbon dioxide. The system for recycling the carbon dioxide gas is simple, few in applied equipment and thorough and clean in recycling, and obtained carbon dioxide is pure; according to the method, the carbon dioxide gas in the discharged waste gas can be completely separated and recycled, zero carbon emission is achieved, the recycled carbon dioxide can be converted and utilized, and consumption of primary energy is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide recovery and utilization in a mixed gas containing carbon dioxide, particularly to the recovery and utilization of carbon dioxide in combustion flue gas, and specifically relates to a carbon dioxide mixed gas freezing separation and recovery system and method under normal pressure. Background Art

[0002] The social progress of mankind and the rapid development of industrialization have brought about a large amount of energy consumption and a huge amount of carbon dioxide gas emissions. The accumulation of carbon dioxide in the atmosphere has led to the rapid warming of the earth, triggering a large number of disastrous meteorological phenomena on the earth. The deterioration of the climate has forced us to quickly enter the historical stage of low-carbon development. Mankind must take effective measures as soon as possible and rely on scientific and technological progress to reduce carbon emissions to the lowest level. The survival of mankind requires the use of a large amount of energy, and energy is the main factor in carbon emissions. How to emit less carbon or no carbon when using a large amount of energy is an important direction in current environmental science research and also an innovative development direction of new quality productivity in the energy field. In recent years, a large number of research experiments have been carried out on the capture, separation, collection, storage, and conversion of carbon dioxide. The main process route is the chemical adsorption, desorption, separation, collection, storage, conversion, etc. of carbon dioxide gas. This method has the problems of short adsorbent life, high energy consumption, difficult storage, and high cost. Therefore, the capture and collection of carbon dioxide gas have not been widely applied.

[0003] The prior art patent with publication number CN 117679904 A discloses a method and system for recovering carbon dioxide from flue gas. The method includes the following steps: sending flue gas into a temperature swing adsorption tower for temperature swing adsorption treatment to obtain a first decarbonized gas; regenerating the first adsorbent filled in the temperature swing adsorption tower to obtain a first-stage concentrated gas; sending the first-stage concentrated gas into a pressure swing adsorption tower for pressure swing adsorption separation, and then desorbing the second adsorbent in the pressure swing adsorption tower to obtain a second decarbonized gas and a second-stage concentrated gas; The system includes a temperature swing adsorption tower, a pressure swing adsorption tower, a first storage tank, and a second storage tank; the second storage tank is connected to the pressure swing adsorption device; the top of the temperature swing adsorption tower is switchably connected to the first storage tank and the second storage tank; a first heat exchanger is arranged on the pipeline between the second storage tank and the top of the temperature swing adsorption tower; the bottom of the temperature swing adsorption tower is switchably connected to the first storage tank, a flue gas supply pipeline, and the second storage tank; The recovery method provided by the invention adopts a two-stage coupling process of temperature swing pressure adsorption. After the flue gas is sequentially subjected to temperature swing adsorption and pressure swing adsorption, a carbon dioxide capture rate of not less than 90% can be achieved. The flue gas is first subjected to temperature swing adsorption, and the adsorbent in the temperature swing adsorption tower is regenerated by using heat energy. The regeneration process includes the following steps: the heated high-concentration circulating gas is introduced into the temperature swing adsorption tower, the temperature swing adsorption tower is heated to the regeneration temperature, and the first adsorbent is desorbed to obtain a mixed gas of the primary concentrated gas and the high-concentration circulating gas after cooling; then the first decarbonized gas or low-concentration circulating gas is introduced into the temperature swing adsorption tower, the temperature swing adsorption tower is cooled to the pressure swing adsorption temperature, and the first decarbonized gas after heating is obtained. Since the heating and cooling of the adsorbent are very slow in the traditional temperature swing adsorption process, it is more suitable for treating flue gas with low carbon dioxide concentration; and the invention adopts the circulating gas thermal regeneration process, which can achieve rapid heating and cooling of the temperature swing adsorption tower, the regeneration efficiency of the first adsorbent is high, and the regeneration time matches the adsorption time.

[0004] However, the flue gas carbon dioxide recovery method and system in the above-mentioned prior art are actually physical adsorption methods. On the one hand, their technical maturity is low and there is a lack of large-scale technical verification experiments. In addition, the adsorbent can easily become ineffective due to poisoning by harmful components in the flue gas and quickly lose its adsorption capacity. On the other hand, since the desorption capacity of the adsorbent in the pressure change process is very limited, even if the circulating gas thermal regeneration process can improve the regeneration efficiency of the adsorbent, the regeneration process of the adsorbent also leads to the complicated process of the recovery method, and the treatment and replacement process of the adsorbent failure must also be considered. In particular, the desorption process needs to be completed under vacuum conditions, which increases the complexity of the recovery method and system, the operating cost is relatively high, the floor space is relatively large, and the subsequent maintenance cost is also high, resulting in high energy consumption and the inability to achieve long-term stable ultra-low emissions of emission indicators. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide at least a carbon dioxide mixed gas freezing separation and recovery system under normal pressure, which is simple and reasonable, has low energy consumption, and low subsequent maintenance costs, especially occupies a small area and has low operating costs, and is suitable for application and promotion.

[0006] The purpose of the present invention is also to provide a method for freezing, separating and recovering a carbon dioxide mixed gas under normal pressure, which method can not only achieve a simpler separation and recovery of carbon dioxide, but is also easy to operate and has high energy utilization rate. In particular, separation and recovery can be directly completed in a one-step process under normal pressure to obtain pure solid carbon dioxide, thereby achieving zero or micro-emissions of carbon dioxide.

[0007] The present invention is a method for separating, collecting, and recycling carbon dioxide by using the principle of physical phase change under normal pressure in a mixed gas containing carbon dioxide. This method is simple and feasible, and can be widely applied in the energy field and other fields, fundamentally solving the problem of a large amount of carbon dioxide emissions.

[0008] To achieve the above object, the present invention adopts the following technical solution. A carbon dioxide mixed gas cryogenic separation and recovery system under normal pressure includes an ultra-low temperature CO2 separation tower and a heat pump with a large temperature difference in a special temperature zone. The ultra-low temperature CO2 separation tower is connected to the heat pump with a large temperature difference in a special temperature zone through an ultra-low temperature cold source delivery pipe.

[0009] Further, a non-CO2 gas discharge port is provided above the ultra-low temperature CO2 separation tower, a solid CO2 collection bin is provided below it, a solid CO2 outlet is provided below the solid CO2 collection bin, a CO2 mixed gas inlet is provided on one side of the ultra-low temperature CO2 separation tower, and a separation tower ultra-low temperature cold source medium inlet and a separation tower ultra-low temperature cold source medium outlet are provided on the other side.

[0010] Further, a high-temperature hot water inlet and a high-temperature hot water outlet are provided above the heat pump with a large temperature difference in a special temperature zone, a heat pump power machine is provided on its side, and a heat pump ultra-low temperature cold source outlet and a heat pump ultra-low temperature cold source inlet are provided below it.

[0011] Further, the ultra-low temperature cold source delivery pipe includes an ultra-low temperature liquid supply pipe and an ultra-low temperature liquid return pipe. One end of the ultra-low temperature liquid supply pipe is connected to the separation tower ultra-low temperature cold source medium inlet, and the other end is connected to the heat pump ultra-low temperature cold source outlet; one end of the ultra-low temperature liquid return pipe is connected to the separation tower ultra-low temperature cold source medium outlet, and the other end is connected to the heat pump ultra-low temperature cold source inlet.

[0012] Preferably, the heat pump with a large temperature difference in a special temperature zone can quickly create a temperature difference of more than 200 °C, can directly reduce the temperature to below -80 °C in one step under normal pressure, and at the same time obtain a high temperature of more than 100 °C, which is convenient for recovering and utilizing heat.

[0013] Preferably, the heat pump with a large temperature difference in a special temperature zone adopts a Stirling heat pump unit or a reverse Brayton cycle heat pump unit.

[0014] Preferably, the ultra-low temperature environment inside the ultra-low temperature CO2 separation tower is uniform to ensure that the CO2 gas is completely and thoroughly quickly cooled to below -80 °C, and there should be no escaping CO2 gas to ensure complete separation of the CO2 gas.

[0015] Preferably, the ultra-low temperature cooling medium is an ultra-low temperature coolant, and the ultra-low temperature coolant is a coolant or cooling oil below -85 °C to -110 °C.

[0016] Preferably, the material of the ultra-low temperature CO2 separation tower is a low-temperature resistant material, which is one of a metal material, a plastic, and a resin resistant to -120°C; a packing layer is provided inside the ultra-low temperature CO2 separation tower. The packing layer is divided into a gas treatment packing layer and a gas liquid removal packing layer. The packing layer has a certain height, and a number of reticulated liquid film balls are installed in each packing layer. The reticulated liquid film ball is a spherical structure with a hollow inside and a reticulated outside. A liquid spraying device is provided above the gas treatment packing layer; a packing layer maintenance port is provided on the shell outside the packing layer.

[0017] A method for freezing separation and recovery of a carbon dioxide mixed gas under normal pressure. The technical idea is to use a special temperature zone heat pump with a large temperature difference to quickly cool flue gas or a mixed gas containing carbon dioxide to below -78°C. The carbon dioxide gas immediately becomes solid carbon dioxide (dry ice), separates from other gases, the solid carbon dioxide is separated out, and other gases are discharged, thus obtaining pure carbon dioxide. The carbon dioxide is filled into a special container for storage, and when in use, the solid carbon dioxide is gasified for utilization.

[0018] A method for freezing separation and recovery of a carbon dioxide mixed gas under normal pressure includes the following steps: S1: Start the special temperature zone heat pump with a large temperature difference. Driven by the heat pump power machine, heat is generated at the hot end of the special temperature zone heat pump with a large temperature difference to heat high-temperature hot water. The hot water enters the special temperature zone heat pump with a large temperature difference from the high-temperature hot water inlet and flows out from the high-temperature hot water outlet after being heated and raised in temperature by the hot end of the special temperature zone heat pump with a large temperature difference; S2: The cold end of the special temperature zone heat pump with a large temperature difference quickly becomes cold, generating a cold source below -80°C. Through the continuous circulation of the ultra-low temperature cooling medium, the ultra-low temperature cooling capacity is transported to the ultra-low temperature CO2 separation tower through the ultra-low temperature cold source delivery pipe; S3: When the temperature inside the ultra-low temperature CO2 separation tower is lower than -80°C, the CO2 mixed gas is sent into the ultra-low temperature CO2 separation tower from the CO2 mixed gas inlet of the ultra-low temperature CO2 separation tower. The CO2 mixed gas immediately cools down to below -80°C. At this time, the CO2 gas quickly directly becomes a solid crystal, the volume of CO2 shrinks by about 700 times, and the latent heat of phase change is released and recovered by the heat pump for utilization; S4: The solid CO2 crystals grow continuously. When they reach a certain extent, they fall to the solid CO2 collection bin at the bottom of the ultra-low temperature CO2 separation tower under the action of gravity, and other non-CO2 gases are discharged from the non-CO2 gas outlet at the upper part of the ultra-low temperature CO2 separation tower; thus far, the CO2 gas is separated from the CO2 mixed gas in the ultra-low temperature state, the CO2 gas becomes solid and is discharged from the solid CO2 outlet at the bottom of the ultra-low temperature CO2 separation tower, completing the separation and collection of CO2.

[0019] The beneficial effects of the present invention compared with the prior art are as follows: The physical property of carbon dioxide is that it exists in a gaseous state at normal temperature and pressure, and becomes a solid at normal pressure and -78°C, commonly known as dry ice, that is, solid carbon dioxide. The present invention uses a special temperature zone heat pump with a large temperature difference to quickly cool flue gas or a mixed gas containing carbon dioxide to below -78°C. The carbon dioxide gas immediately turns into solid carbon dioxide (dry ice), separates from other gases, the solid carbon dioxide is separated out, and other gases are discharged, thus obtaining pure carbon dioxide. The carbon dioxide is filled into a special container for storage, and when in use, the solid carbon dioxide is gasified for utilization. On the one hand, this method can very easily separate, recover and store carbon dioxide gas, and is especially suitable for the treatment of combustion flue gas or flue gas from smelting, ceramics, glass, etc. and carbon recovery, realizing zero carbon emissions in energy production and smelting production. And the recovered carbon dioxide can be used to manufacture gasoline, diesel, methanol, combustible gas, chemical raw materials, etc., and can also be used for cleaning treatment and special effects in entertainment venues. On the other hand, a special temperature zone heat pump with a large temperature difference is used to obtain an ultra-low temperature cold source. This kind of heat pump has a fast cooling speed, a large temperature difference and high energy efficiency, and can generate a temperature difference of more than 200°C in one step under normal pressure. Therefore, it can rapidly cool carbon dioxide gas under normal pressure, complete the phase change of carbon dioxide, produce dry ice and separate other gases. On the further hand, the heat generated during the manufacture of ultra-low temperature and the latent heat of phase change of carbon dioxide in the present invention can all be recovered for heat demand such as heating and hot water. The system for recovering carbon dioxide gas in the present invention is simple, with few application devices, and the recovery is thorough and clean, and the obtained carbon dioxide is pure. The method of the present invention can directly complete the separation and recovery of carbon dioxide gas in the exhaust gas under normal pressure through one step, realizing zero carbon emissions, and can also convert and utilize the recovered carbon dioxide, greatly reducing the consumption of primary energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic structural diagram of a recovery system described in the present invention; Reference numerals in the drawings: 1. Non-CO2 gas discharge port; 2. Ultra-low temperature CO2 separation tower; 3. CO2 mixed gas inlet; 4. Solid CO2 collection bin; 5. Solid CO2 outlet; 6. Separation tower ultra-low temperature cold source medium inlet; 7. Separation tower ultra-low temperature cold source medium outlet; 8. High-temperature hot water inlet; 9. High-temperature hot water outlet; 10. Special temperature zone heat pump with a large temperature difference; 11. Heat pump power machine; 12. Heat pump ultra-low temperature cold source outlet; 13. Heat pump ultra-low temperature cold source inlet; 14. Ultra-low temperature cold source delivery pipe; 141 - Ultra-low temperature liquid supply pipe; 142 - Ultra-low temperature liquid return pipe. DETAILED DESCRIPTION OF THE INVENTION

[0021] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0022] As Figure 1 shown, a cryogenic separation and recovery system for carbon dioxide mixed gas under normal pressure according to the present invention includes an ultra-low temperature CO2 separation tower 2 and a heat pump 10 with a large temperature difference in a special temperature zone. The ultra-low temperature CO2 separation tower 2 is connected to the heat pump 10 with a large temperature difference in a special temperature zone through an ultra-low temperature cold source delivery pipe 14. An outlet 1 for non-CO2 gas is provided above the ultra-low temperature CO2 separation tower 2, a solid CO2 collection bin 4 is provided below it, a solid CO2 outlet 5 is provided below the solid CO2 collection bin 4, a CO2 mixed gas inlet 3 is provided on one side of the ultra-low temperature CO2 separation tower 2, and an inlet 6 for the ultra-low temperature cold source medium of the separation tower and an outlet 7 for the ultra-low temperature cold source medium of the separation tower are provided on the other side. A high-temperature hot water inlet 8 and a high-temperature hot water outlet 9 are provided above the heat pump 10 with a large temperature difference in a special temperature zone, a heat pump power machine 11 is provided on its side, and a heat pump ultra-low temperature cold source outlet 12 and a heat pump ultra-low temperature cold source inlet 13 are provided below it. The ultra-low temperature cold source delivery pipe 14 includes an ultra-low temperature liquid supply pipe 141 and an ultra-low temperature liquid return pipe 142. One end of the ultra-low temperature liquid supply pipe 141 is connected to the inlet 6 for the ultra-low temperature cold source medium of the separation tower, and the other end is connected to the heat pump ultra-low temperature cold source outlet 12. One end of the ultra-low temperature liquid return pipe 142 is connected to the outlet 7 for the ultra-low temperature cold source medium of the separation tower, and the other end is connected to the heat pump ultra-low temperature cold source inlet 13.

[0023] In some embodiments, the heat pump with a large temperature difference in a special temperature zone can quickly create a temperature difference of more than 200 °C, can directly reduce the temperature to below -80 °C in one step under normal pressure, and simultaneously obtain a high temperature of more than 100 °C, which is convenient for recovering heat and utilization.

[0024] In some embodiments, the heat pump with a large temperature difference in a special temperature zone adopts a Stirling heat pump unit or a reverse Brayton cycle heat pump unit. The Stirling heat pump unit cools the ultra-low temperature medium to below -85 °C. Through a special device "Low-temperature Liquid Film Sphere Gas Treatment Device" or other low-temperature gas treatment equipment, the ultra-low temperature medium is brought into full contact with the flue gas. When the temperature of the flue gas drops below -78 °C, the carbon dioxide in the flue gas becomes solid carbon dioxide and is separated out. The solid is collected and recovered to obtain carbon dioxide, and other gases are discharged. The discharged non-CO2 gas is a low-temperature gas and can be used for cooling. When using solid carbon dioxide, it is first gasified, and electricity can be generated during the gasification process. The cold can be used to produce other products such as gasoline, diesel, and methanol.

[0025] In some embodiments, the ultra-low temperature CO2 separation tower has a uniform ultra-low temperature environment to ensure that the CO2 gas is completely and thoroughly cooled rapidly to below -80°C without any escaping CO2 gas, ensuring the complete separation of the CO2 gas.

[0026] In some embodiments, it is an ultra-low temperature coolant, and the ultra-low temperature coolant is a coolant or cooling oil with a temperature below -85°C to -110°C.

[0027] In some embodiments, the material of the ultra-low temperature CO2 separation tower is a low-temperature resistant material, and the low-temperature resistant material is one of a metal material, plastic, and resin resistant to -120°C; the interior of the ultra-low temperature CO2 separation tower is provided with a packing layer, which is divided into a gas treatment packing layer and a gas de-liquefaction packing layer. The packing layer has a certain height, and each packing layer is filled with a number of reticulated liquid film balls. The reticulated liquid film balls are spherical structures with an empty interior and an outer network. A liquid spraying device is provided above the gas treatment packing layer. A packing layer maintenance port is provided on the shell outside the packing layer.

[0028] In this embodiment, a method for cryogenic separation and recovery of carbon dioxide mixed gas under normal pressure according to the present invention includes the following steps: S1: Start the large temperature difference special temperature zone heat pump 10. Driven by the heat pump power machine 11, heat is generated at the hot end of the large temperature difference special temperature zone heat pump 10 to heat the high-temperature hot water. The hot water enters the heat pump from the high-temperature hot water inlet 8 and flows out from the high-temperature hot water outlet 9 after being heated and raised in temperature by the hot end of the large temperature difference special temperature zone heat pump 10; S2: The cold end of the large temperature difference special temperature zone heat pump 10 quickly cools down to generate a cold source below -80°C. Through the continuous circulation of the ultra-low temperature cooling medium, the ultra-low temperature cooling capacity is transported to the ultra-low temperature CO2 separation tower 2 through the ultra-low temperature cold source delivery pipe 14; S3: When the temperature inside the ultra-low temperature CO2 separation tower 2 is below -80°C, the CO2 mixed gas containing CO2 is sent into the ultra-low temperature CO2 separation tower 2 from the CO2 mixed gas inlet 3 of the ultra-low temperature CO2 separation tower 2. The CO2 mixed gas immediately cools down to below -80°C. At this time, the CO2 gas quickly directly becomes a solid crystal. The volume of CO2 shrinks by about 700 times, and the latent heat of phase change is released and recovered by the heat pump for utilization; S4: The solid crystals continue to grow. When they reach a certain extent, they fall to the solid CO2 collection bin 4 at the bottom of the ultra-low temperature CO2 separation tower 2 under the action of gravity, and other non-CO2 gases are discharged from the non-CO2 gas discharge port 1 at the upper part of the ultra-low temperature CO2 separation tower 2; thus, the CO2 gas is separated from the CO2 mixed gas in the ultra-low temperature state, and the CO2 gas becomes a solid and is discharged from the solid CO2 outlet 5 at the bottom of the ultra-low temperature CO2 separation tower 2, completing the separation and collection of CO2.

[0029] The present invention is applied to zero-carbon treatment of discharging mixed gas containing gaseous carbon dioxide, that is, separating and recovering carbon dioxide gas in the discharged gas completely. In the current process of human progress, industrialization generates a large amount of carbon emissions. Excessive carbon emissions lead to abnormal climate change and a significant increase in severe catastrophic natural disasters. The main substance of carbon emissions is the waste gas discharged in industrial production - carbon dioxide gas, such as the waste gas generated in the production processes that require high-temperature processing techniques like energy production, steelmaking, smelting, ceramics, glass, etc. Generally, these discharged waste gases contain 5% - 15% carbon dioxide gas. Due to the huge amount of waste gas emissions, the amount of carbon dioxide discharged into the atmosphere is also extremely large. The present invention can completely separate and recover carbon dioxide gas in the discharged waste gas, achieve zero carbon emissions, and can also convert and utilize the recovered carbon dioxide, greatly reducing the consumption of primary energy.

[0030] The system for recovering carbon dioxide gas in the present invention is simple, with few application devices, and the recovery is thorough and clean. The obtained carbon dioxide is pure and convenient for reuse. The heat and cold in the recovery process can be recovered and reused.

[0031] The conversion and utilization of the recovered pure solid carbon dioxide are of great significance and have high comprehensive utilization value. In the reuse process, combined heat and power generation can be carried out first, refrigerating while generating electricity, with high energy comprehensive utilization rate; the carbon dioxide gas after power generation can be hydrogenated to produce methanol, combustible gas, gasoline, diesel and other chemical products, etc. Currently, the technologies for synthesizing products from carbon dioxide are all mature. Combining with the pure carbon dioxide recovery technology of the present invention to form a new upstream and downstream industrial chain will bring good comprehensive economic benefits.

[0032] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A carbon dioxide mixed gas cryogenic separation and recovery system under normal pressure, characterized in that: It includes an ultra-low temperature CO2 separation tower (2) and a heat pump (10) with a large temperature difference in a special temperature zone. The ultra-low temperature CO2 separation tower (2) is connected to the heat pump (10) with a large temperature difference in a special temperature zone through an ultra-low temperature cold source transfer pipe (14).

2. The separation and recovery system according to claim 1, characterized in that: Above the ultra-low temperature CO2 separation tower (2), there is a non-CO2 gas discharge port (1). Below it, there is a solid CO2 collection bin (4). Below the solid CO2 collection bin (4), there is a solid CO2 outlet (5). On one side of the ultra-low temperature CO2 separation tower (2), there is a CO2 mixed gas inlet (3). On the other side, there are a separation tower ultra-low temperature cold source medium inlet (6) and a separation tower ultra-low temperature cold source medium outlet (7).

3. The separation and recovery system according to claim 1 or 2, characterized in that: Above the heat pump (10) with a large temperature difference in a special temperature zone, there are a high-temperature hot water inlet (8) and a high-temperature hot water outlet (9). On its side, there is a heat pump power machine (11). Below it, there are a heat pump ultra-low temperature cold source outlet (12) and a heat pump ultra-low temperature cold source inlet (13).

4. The separation and recovery system according to claim 1, wherein: The ultra-low temperature cold source transfer pipe (14) includes an ultra-low temperature liquid supply pipe (141) and an ultra-low temperature liquid return pipe (142). One end of the ultra-low temperature liquid supply pipe (141) is connected to the separation tower ultra-low temperature cold source medium inlet (6), and the other end is connected to the heat pump ultra-low temperature cold source outlet (12); one end of the ultra-low temperature liquid return pipe (142) is connected to the separation tower ultra-low temperature cold source medium outlet (7), and the other end is connected to the heat pump ultra-low temperature cold source inlet (13).

5. The separation and recovery system according to any one of claims 1 or 3, characterized in that: The heat pump (10) with a large temperature difference in a special temperature zone can quickly create a temperature difference of over 200 °C, can directly reduce the temperature to below -80 °C in one step under normal pressure, and at the same time obtain a high temperature of over 100 °C, which is convenient for heat recovery and utilization.

6. The separation and recovery system according to claim 5, wherein: The heat pump (10) with a large temperature difference in a special temperature zone uses a Stirling heat pump unit or a reverse Brayton cycle heat pump unit.

7. The separation and recovery system according to claim 1 or 2, characterized in that: Inside the ultra-low temperature CO2 separation tower (2), there is a uniform ultra-low temperature environment to ensure that CO2 gas is completely and thoroughly quickly cooled to below -80 °C, and there should be no escaping CO2 gas to ensure complete separation of CO2 gas.

8. The separation and recovery system according to claim 1 or 2, characterized in that: The material of the ultra-low temperature CO2 separation tower is a low-temperature resistant material, and the low-temperature resistant material is one of a metal material, plastic, or resin resistant to -120 °C; inside the ultra-low temperature CO2 separation tower, there is a packing layer, which is divided into a gas treatment packing layer and a gas de-liquefaction packing layer. The packing layer has a certain height, and each layer of the packing layer is filled with several reticulated liquid film balls. The reticulated liquid film balls are spherical structures with a hollow inside and a net outside. Above the gas treatment packing layer, there is a liquid spraying device; on the shell outside the packing layer, there is a packing layer maintenance port.

9. A separation and recovery method for a cryogenic separation and recovery system of a carbon dioxide mixed gas under normal pressure according to any one of claims 1-4, characterized in that: It includes the following steps: S1: Turn on the heat pump (10) with a large temperature difference in a special temperature zone. Driven by the heat pump power machine (11), heat is generated at the hot end of the heat pump (10) with a large temperature difference in a special temperature zone to heat the high-temperature hot water. The hot water enters the heat pump from the high-temperature hot water inlet (8), and after being heated and raised in temperature at the hot end of the heat pump (10) with a large temperature difference in a special temperature zone, it flows out from the high-temperature hot water outlet (9). S2: The cold end of the large temperature difference special temperature zone heat pump (10) cools rapidly, generating a cold source below -80°C, and through the continuous circulation of the ultra-low temperature cooling medium, the ultra-low temperature cold energy is transported to the ultra-low temperature CO2 separation tower (2) through the ultra-low temperature cold source transport pipe (14); S3: When the temperature inside the ultra-low temperature CO2 separation tower (2) is lower than -80°C, the CO2 mixed gas is fed into the ultra-low temperature CO2 separation tower (2) from the CO2 mixed gas inlet (3) of the ultra-low temperature CO2 separation tower (2), and the CO2 mixed gas is immediately cooled to below -80°C. At this time, the CO2 gas is quickly and directly transformed into solid crystals, the volume of CO2 is reduced by about 700 times, and the phase change latent heat is released, which is recovered and utilized by the heat pump; S4: The CO2 solid crystals continue to grow, and when they reach a certain size, they fall to the solid CO2 collection bin (4) at the bottom of the ultra-low temperature CO2 separation tower (2) under the action of gravity, and other non-CO2 gases are discharged from the non-CO2 gas outlet (1) at the top of the ultra-low temperature CO2 separation tower (2); at this point, the CO2 gas is separated from the CO2 mixed gas under an ultra-low temperature state, and the CO2 gas becomes solid and is discharged from the solid CO2 outlet (5) at the bottom of the ultra-low temperature CO2 separation tower (2), completing the separation and collection of CO2.

10. The separation and recovery method according to claim 9, characterized in that: The ultra-low temperature cooling medium is an ultra-low temperature cooling liquid, and the ultra-low temperature cooling liquid is a cooling liquid or cooling oil with a temperature lower than -85°C to -110°C.

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