A liquid-phase carbon dioxide rectification purification system and method

Abstract

The application belongs to the technical field of carbon dioxide purification, and particularly relates to a liquid-phase carbon dioxide rectification and purification system and method, which comprises a rectification tower, a reboiler and a refrigeration unit, the rectification tower is provided with a first inlet suitable for the first liquid source to enter; the reboiler is provided with a first material channel and a second material channel capable of heat exchange; the inlet of the first material channel is used for the second liquid source to enter, and the outlet is communicated with the rectification tower; the inlet of the second material channel is communicated with the rectification tower, and the liquid-phase outlet is communicated with a finished product storage tank; the refrigeration unit comprises a supercooler and a cryogenic cooler; the first liquid source is medium-pressure low-temperature liquid-phase carbon dioxide, and the second liquid source is high-pressure normal-temperature liquid-phase carbon dioxide. The application can simultaneously realize rectification and purification of liquid-phase carbon dioxide with different pressures and temperatures, and can utilize the liquid-phase carbon dioxide with higher temperature as a heat source in the purification process, thereby realizing heat recycling.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide purification technology, and specifically relates to a liquid phase carbon dioxide distillation purification system and method. Background Technology

[0002] On the other hand, carbon dioxide is a valuable resource with high civilian and industrial value, and it has shown good development prospects in fields such as greenhouse vegetable fertilization, vegetable and meat preservation, oil and gas flooding, and the production of biodegradable plastics.

[0003] Low-temperature methanol washing purifies process gas while releasing a large amount of carbon dioxide. Capturing carbon dioxide and obtaining carbon dioxide products during this process can increase added value and improve enterprise efficiency. Summary of the Invention

[0004] In view of the problems mentioned in the background art, the present invention provides a liquid phase carbon dioxide distillation purification system and method.

[0005] The first aspect of this invention provides a liquid-phase carbon dioxide distillation purification system, comprising:

[0006] The distillation column is provided with a first inlet, a second inlet, a first outlet, and a second outlet; the first inlet is used for the inlet of a first liquid source, and the first outlet is used for the outlet of a gas phase flow.

[0007] The reboiler has a first material channel and a second material channel for heat exchange; the inlet of the first material channel is used for the entry of the second liquid source, and the outlet is connected to the second inlet; the inlet of the second material channel is connected to the second outlet, and the liquid phase outlet is connected to the finished product storage tank.

[0008] The refrigeration unit includes a cryocooler disposed between the first material channel and the second inlet and a subcooler disposed between the second material channel and the finished product storage tank;

[0009] The first liquid source is medium-pressure, low-temperature liquid carbon dioxide, and the second liquid source is high-pressure, room-temperature liquid carbon dioxide.

[0010] The liquid-phase carbon dioxide distillation purification system proposed in this invention may also have the following additional technical features:

[0011] In one specific embodiment of the present invention, the distillation column further includes a third inlet; the second material channel also has a gas phase outlet, which is connected to the third inlet.

[0012] In one specific embodiment of the present invention, a cold energy recovery unit is further included. The cold energy recovery unit is provided with a first heat exchange channel and a second heat exchange channel for heat exchange. The first heat exchange channel is connected between the outlet of the first material channel and the cryogenic device, and the inlet of the second heat exchange channel is connected to the first outlet.

[0013] In one specific embodiment of the present invention, the pressure of the first liquid source is 2.4±0.1MPa and the temperature is -16±1℃; the pressure of the carbon dioxide liquid phase in the second liquid source is 6.9±0.1MPa and the temperature is 20±1℃.

[0014] In one specific embodiment of the present invention, a high-pressure ambient temperature liquefaction unit is further included, through which carbon dioxide raw material gas is processed to obtain a first liquid source and a second liquid source.

[0015] In one specific embodiment of the present invention, the first outlet and the second inlet are located at the top of the distillation column, the second outlet is located at the bottom of the distillation column, and the first inlet and the third inlet are located in the middle of the distillation column.

[0016] In one specific embodiment of the present invention, the refrigeration unit has a cooling load of -30℃ and a COP>1.9.

[0017] A second aspect of the present invention also provides a liquid-phase carbon dioxide distillation purification method, implemented using the liquid-phase carbon dioxide distillation purification system described in any one of the above claims, comprising the following steps:

[0018] The second liquid source enters the first material channel of the reboiler and exchanges heat with the liquid phase in the second material channel. After being cooled by the cryocooler, it enters the distillation column through the second inlet.

[0019] The first liquid source enters the distillation column through the first inlet and undergoes gas-liquid separation together with the carbon dioxide that enters the distillation column through the second inlet. The resulting gas phase is discharged through the first outlet, and the resulting liquid carbon dioxide enters the second material channel of the reboiler through the second outlet.

[0020] The liquid carbon dioxide in the second material channel exchanges heat with the first material channel, causing the light components to evaporate. The resulting liquid carbon dioxide is then sent to the subcooler for heat exchange to obtain the finished liquid carbon dioxide.

[0021] In one specific embodiment of the present invention, the liquid phase flowing out of the first material channel outlet exchanges heat with the gas phase discharged through the first outlet, and then exchanges heat again in the cryogenic chamber, before entering the distillation column through the second inlet.

[0022] In one specific embodiment of the present invention, the light components obtained by evaporation in the second material channel enter the distillation column through the third inlet and undergo gas-liquid separation in the distillation column.

[0023] The liquid-phase carbon dioxide distillation purification system provided by this invention includes a distillation column, a reboiler, and a refrigeration unit. The distillation column has a first inlet for a first liquid source to enter. The reboiler has a first material channel and a second material channel for heat exchange. The inlet of the first material channel is for a second liquid source to enter, and its outlet is connected to a second inlet of the distillation column. The inlet of the second material channel is connected to a second outlet, and the liquid phase outlet is connected to a finished product storage tank. Thus, high-pressure, room-temperature liquid carbon dioxide can enter the first material channel as a heat source for the reboiler to heat the fluid in the second material channel. After heat exchange, the second liquid source enters the distillation column and undergoes gas-liquid separation together with the first liquid source. The separated liquid phase enters the second material channel and is heated and evaporated by the second liquid source in the first material channel to remove light components. After cooling, pure liquid carbon dioxide is obtained. In other words, this invention can simultaneously achieve the distillation purification of liquid carbon dioxide at various pressures and temperatures, and can utilize high-temperature liquid carbon dioxide as a heat source during the purification process, thereby achieving heat recovery and utilization. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a liquid-phase carbon dioxide distillation and purification system according to a specific embodiment of the present invention;

[0026] Figure 2 This is a partial structural diagram of a high-pressure ambient temperature liquefaction unit in a specific embodiment of the present invention;

[0027] Figure 3 This is a flowchart illustrating a specific embodiment of the liquid-phase carbon dioxide distillation purification method of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 10-Distillation column, 20-Reboiler, 30-Refrigeration unit, 31-Cryogenic cooler, 32-Subcooler, 40-Cold energy recovery unit, 50-First liquid source, 60-Second liquid source, 70-Impurity gas, 80-First gas-liquid separator, 90-Second gas-liquid separator. Detailed Implementation

[0030] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0031] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0032] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0033] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented as "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.

[0034] like Figure 1-2 As shown, the first aspect of the present invention provides a liquid-phase carbon dioxide distillation purification system, including a distillation column 10, a reboiler 20, and a refrigeration unit 30. The distillation column 10 is provided with a first inlet, a second inlet, a first outlet, and a second outlet. The first inlet is for the entry of a first liquid source 50, and the first outlet is for the exit of a gas phase flow. The reboiler 20 is provided with a first material channel and a second material channel for heat exchange. The inlet of the first material channel is for the entry of a second liquid source 60, and the outlet is connected to the second inlet. The inlet of the second material channel is connected to the second outlet, and the liquid phase outlet is connected to the finished product storage tank. The refrigeration unit 30 includes a cryotherm 31 located between the first material channel and the second inlet, and a subcooler 32 located between the second material channel and the finished product storage tank. The first liquid source 50 is medium-pressure low-temperature liquid-phase carbon dioxide, and the second liquid source 60 is high-pressure room-temperature liquid-phase carbon dioxide.

[0035] The first liquid source 50 and the second liquid source 60 of the present invention are formed by liquefying carbon dioxide feed gas. The carbon dioxide feed gas comes from the low-temperature methanol washing section in the ammonia / urea synthesis unit. The incoming gas pressure is about 0.133 MPa (A) and the temperature is room temperature. The feed gas contains 96.6593% carbon dioxide gas by volume, and also contains trace components such as hydrogen, nitrogen, carbon monoxide, hydrocarbons, and hydrogen sulfide.

[0036] Distillation column 10 is a tower-type gas-liquid contact device that utilizes the different volatility of the components in a mixture—that is, the different vapor pressures of the components at the same temperature—to transfer the lighter components (low-boiling substances) in the liquid phase to the gas phase during contact and collect at the top of the column, while the heavier components (high-boiling substances) in the gas phase are transferred to the liquid phase during contact and collect at the bottom of the column, thereby achieving separation. In this embodiment, distillation column 10 is a columnar packed column and is mainly used for further purification of liquid carbon dioxide, thereby removing the lighter components from the liquid carbon dioxide and improving the purity of the liquid carbon dioxide product. Based on the separation requirements of carbon dioxide, the pressure load of distillation column 10 in this embodiment is approximately 2.4 ± 0.1 MPa (A), and the packing of distillation column 10 uses 250Y structured packing, with an operating flexibility controlled between 70-110%.

[0037] The reboiler 20 is a heating and evaporation device used in conjunction with the distillation column 10 to re-vaporize the liquid through heat exchange. Specifically, the reboiler 20 includes a first material channel for carrying the heating medium and a second material channel for carrying the heated medium. The second material channel is connected to the bottom of the distillation column 10 and is adapted to siphon the liquid phase collected at the bottom of the distillation column 10 into the second channel so that the light components are evaporated.

[0038] The first liquid source 50 enters the distillation column 10 directly, and the second liquid source 60, as a heating medium, enters the distillation column 10 through the first material channel. Then, the first liquid source 50 and the second liquid source 60 achieve distillation and purification in the second material channel of the distillation column 10 and the reboiler 20.

[0039] The cryogenic cooler 31 is used to cool the second liquid source 60 through the first material channel to reach the preset temperature, and the subcooler 32 is used to cool the final product so that the liquid carbon dioxide product has the same temperature.

[0040] The first liquid source 50 and the second liquid source 60 can be stored in the first storage tank and the second storage tank, respectively. The first storage tank and the second storage tank can be transported to the distillation and purification system and connected to the distillation and purification system to provide liquid carbon dioxide to the distillation and purification system. The first liquid source 50 and the second liquid source 60 can also be transported to the low-temperature purification system via a corresponding pipeline set between the high-pressure ambient temperature liquefaction system and the low-temperature purification system. Of the two methods mentioned above, the tank storage and transportation method is mainly used for long-distance transportation, while the pipeline transportation method can be used for both short-distance and long-distance transportation, and the specific method can be selected according to the needs.

[0041] This invention provides a liquid-phase carbon dioxide distillation purification system. By using the first material channel in the reboiler 20, which provides a heat source, as the channel for the second liquid source 60 to enter the distillation column 10, the second liquid source 60 can not only heat the fluid in the second material channel, but also, after heat exchange, enter the distillation column 10 to perform gas-liquid separation together with the first liquid source 50. The separated liquid phase enters the second material channel and is heated and evaporated by the second liquid source 60 in the first material channel to remove light components. After cooling, pure carbon dioxide liquid phase is obtained. In other words, this invention can simultaneously achieve the distillation purification of liquid-phase carbon dioxide at various pressures and temperatures, and can utilize the higher-temperature liquid-phase carbon dioxide as a heat source during the purification process, thereby achieving heat recovery and utilization.

[0042] In one specific embodiment of the present invention, the distillation column 10 further includes a third inlet; the second material channel also has a gas phase outlet, which is connected to the third inlet. This arrangement allows the gas phase separated at the reboiler 20 to re-enter the distillation column 10 for further distillation separation. This avoids the direct emission and loss of some carbon dioxide gas, thereby improving the carbon dioxide absorption rate. Furthermore, it recovers the cooling energy of this portion of the gas, preventing the loss of cooling energy.

[0043] In one specific embodiment of the present invention, a cold energy recovery unit 40 is further included. The cold energy recovery unit 40 is provided with a first heat exchange channel and a second heat exchange channel for heat exchange. The first heat exchange channel is connected between the outlet of the first material channel and the cryogenic device 31, and the inlet of the second heat exchange channel is connected to the first outlet.

[0044] The temperature at the top of distillation column 10 is approximately -24.78℃, meaning the temperature of the non-condensable gas collected at the top of the column is also -24.78℃. This non-condensable gas, when discharged through the first outlet, enters the second heat exchange channel via a pipeline and can be used to cool the medium in the first heat exchange channel, thereby recovering heat and improving the utilization rate of cooling capacity. Specifically, the medium in the first heat exchange channel is high-pressure, room-temperature liquid carbon dioxide flowing out from the first material channel outlet of reboiler 20.

[0045] In one specific embodiment of the present invention, the pressure of the first liquid source 50 is 2.4±0.1MPa and the temperature is -16±1℃; the pressure of the carbon dioxide liquid phase in the second liquid source 60 is 6.9±0.1MPa and the temperature is 20±1℃.

[0046] In one specific embodiment of the present invention, a high-pressure ambient temperature liquefaction unit is also included, through which carbon dioxide raw material gas is liquefied to obtain a first liquid source 50 and a second liquid source 60.

[0047] Specifically, the high-pressure ambient temperature liquefaction unit includes a high-pressure compression component and an ambient temperature-low temperature refrigeration component. The carbon dioxide raw material gas is processed sequentially by the high-pressure compression component and the ambient temperature-low temperature refrigeration component to obtain a first liquid source 50 with medium pressure and low temperature and a second liquid source 60 with high pressure and ambient temperature.

[0048] The high-pressure ambient-temperature liquefaction unit employs a high-pressure compression component to ultimately increase the pressure of carbon dioxide, thereby achieving a higher liquefaction temperature. In this embodiment, the high-pressure compression component increases the pressure of the carbon dioxide feed gas to 6.9 MPa. At this pressure, the liquefaction temperature of carbon dioxide is 29°C, which can then be liquefied to approximately 20°C by the ambient-low temperature refrigeration component, thus achieving ambient-temperature liquefaction of carbon dioxide. Based on the characteristic that high-pressure carbon dioxide has a higher liquefaction temperature, the high-pressure ambient-temperature liquefaction system reduces the cooling energy required for carbon dioxide liquefaction by increasing the pressure of the carbon dioxide feed gas, thereby reducing the use of ammonia or Freon and thus being environmentally friendly. Simultaneously, the small temperature difference between the liquid carbon dioxide at 20°C and the ambient temperature further reduces the difficulty of storing liquid carbon dioxide.

[0049] The high-pressure, ambient-temperature liquefaction unit can simultaneously produce two types of liquid carbon dioxide at different pressures and temperatures: a first liquid source 50 with medium-pressure, low-temperature liquid phase and a second liquid source 60 with high-pressure, ambient-temperature liquid phase. By producing liquid carbon dioxide at different pressures and temperatures, the carbon dioxide recovery rate is improved.

[0050] Specifically, the high-pressure compression assembly includes a multi-stage low-pressure compressor and a multi-stage high-pressure compressor. The front end of the multi-stage low-pressure compressor is connected to a carbon dioxide feed gas source, and the rear end of the multi-stage high-pressure compressor is connected to a room temperature-low temperature refrigeration assembly.

[0051] The multi-stage low-pressure compressor is a twin-shaft, four-stage low-pressure compressor, and the multi-stage high-pressure compressor is a tri-shaft, five-stage high-pressure compressor. The combination of these two compressors forms an integrated gearbox-type centrifugal compressor, with each stage impeller being an advanced three-dimensional flow impeller. In both the multi-stage low-pressure and high-pressure compressors, every two stages operate at a single rotational speed. By increasing the rotational speed, each impeller stage achieves high performance, resulting in an overall efficiency exceeding 82%. Furthermore, each impeller outlet is cooled, achieving near-isothermal compression and saving approximately 10% in energy compared to single-shaft units.

[0052] By optimizing the existing compressor structure and layout, the oil tank and heat exchanger can double as compressor skid mounts. The compressor main unit, drive motor, lubrication system, and cooling system are integrated into a skid-mounted configuration, significantly reducing the footprint and on-site construction workload. The high-pressure compression assembly mainly consists of three skids: the low-pressure cylinder skid (including the low-pressure cylinder main unit, cooling system, and base), the drive motor skid, and the high-pressure cylinder skid (including the high-pressure cylinder main unit, cooling system, and base). The individual skids arrive on site and are then assembled into a complete skid for use.

[0053] In use, air-driven inlet guide vanes are installed at the front end of the first-stage impeller and the front end of the fifth-stage impeller. The air-driven actuator drives the connecting rod to move up and down, which in turn drives the turntable to rotate. Finally, the turntable drives all the blades to rotate, thereby adjusting the flow rate. This can improve the intake conditions and enable the compressor to operate efficiently and stably within the flow range of 70-105%.

[0054] Multistage low-pressure compressors can also be three-stage low-pressure compressors, five-stage low-pressure compressors, etc., and multistage high-pressure compressors can also be three-stage high-pressure compressors, four-stage high-pressure compressors, or six-stage high-pressure compressors, etc., depending on the specific needs.

[0055] By setting up multi-stage low-pressure compressors and multi-stage high-pressure compressors, the carbon dioxide gas source is compressed in stages and steps, which is beneficial to the smooth progress of the compression process and the staged release of heat. In this embodiment, the pressure at the end of the last five-stage high-pressure compressor is 6.9±0.1MPa, at which the liquefaction temperature of carbon dioxide is 29°C.

[0056] The ambient temperature-low temperature refrigeration assembly includes a primary condenser, a secondary condenser, a first gas-liquid separator 80, and a second gas-liquid separator 90. The primary condenser is connected to the high-pressure compressor unit and is used to perform ambient temperature refrigeration on the raw material gas compressed under high pressure. The secondary condenser is connected to the primary condenser and is used to perform low-temperature pre-cooling on the raw material gas cooled by the primary condenser to obtain a mixed phase. The first gas-liquid separator 80 is connected to the secondary condenser and is used to perform gas-liquid separation on the mixed phase. The separated liquid phase carbon dioxide is the second liquid source 60. The second gas-liquid separator 90 is connected to the gas phase outlet of the first gas-liquid separator 80 through a pressure relief valve and is used to perform pressure reduction and secondary gas-liquid separation on the gas phase separated by the first gas-liquid separator 80. The separated liquid phase carbon dioxide is the first liquid source 50, and the separated gas phase is the impurity gas 70.

[0057] The refrigeration liquefaction temperature of the first-stage condenser is 20℃, and the pressure is 6.95 MPa.

[0058] The secondary condenser is an 8℃ ambient temperature refrigeration unit 30 with a COP≥6. After passing through the secondary condenser, the carbon dioxide feed gas is cooled to 20℃. At this point, most of the carbon dioxide is liquefied into a liquid phase, while trace impurity gases 70 remain in a non-condensable state, thus forming a gas-liquid mixture.

[0059] The first gas-liquid separator 80 is a horizontal gas-liquid separator, mainly used to remove non-condensable gases from the gas-liquid mixture, preventing the medium from flowing between the two phases in the pipeline, and facilitating further purification of carbon dioxide liquid in the subsequent refining system. The liquid phase separated in the first gas-liquid separator 80 is the second liquid source 60, with a pressure of 6.9±0.1MPa and a temperature of 20℃.

[0060] The second gas-liquid separator 90 is a vertical gas-liquid separator, connected to the gas phase outlet of the first gas-liquid separator 80. The high-pressure non-condensable gas separated from the first gas-liquid separator 80 is pressure-reduced and throttled to 2.5 MPa (A), with a temperature of approximately -16°C, before entering the second gas-liquid separator 90 for further gas-liquid separation and recovery of carbon dioxide. The liquid phase separated by the second gas-liquid separator 90 is the first liquid source 50, with a pressure of 2.5 MPa and a temperature of approximately -16°C. The gas phase separated by the second gas-liquid separator 90 is the impurity gas 70.

[0061] In one specific embodiment of the present invention, the first outlet and the second inlet are located at the top of the distillation column 10, the second outlet is located at the bottom of the distillation column 10, and the first inlet and the third inlet are located in the middle of the distillation column 10.

[0062] In one specific embodiment of the present invention, the refrigeration unit 30 has a refrigeration load of -30℃ and a COP>1.9.

[0063] In one specific embodiment of the present invention, the reboiler 20 is a kettle-type reboiler 20, and specifically includes a shell with a constricted opening and a double-pass U-shaped tube structure that is sealed to the opening of the shell by a piston. The inner cavity of the U-shaped tube structure forms a first material channel, and the inner cavity of the shell forms a second material channel. The liquid phase entering the first material channel and the liquid phase entering the second material channel can exchange heat through the U-shaped tube structure.

[0064] The bottom of the second material channel is also equipped with a vertically arranged overflow baffle. The inlet and liquid phase outlet of the second material channel are located on opposite sides of the overflow baffle. The inlet of the second material channel is located on the side of the overflow baffle corresponding to the U-shaped conduit, and the liquid phase outlet is located on the side of the overflow baffle opposite to the U-shaped conduit. The liquid phase collected at the bottom of the distillation column 10 enters the second material channel through the second outlet and is heated on the side of the overflow baffle opposite to the U-shaped conduit to evaporate the non-condensable gases. When the liquid level of the remaining liquid phase is higher than the overflow baffle, it passes over the overflow baffle and flows out through the liquid phase outlet of the second material channel. After being cooled by the cooler 32, the finished product, liquid carbon dioxide, is obtained.

[0065] like Figure 3 As shown, a second aspect of the present invention also provides a liquid-phase carbon dioxide distillation purification method, implemented using the liquid-phase carbon dioxide distillation purification system described in any one of the above claims, comprising the following steps:

[0066] The second liquid source 60 enters the first material channel of the reboiler 20 and exchanges heat with the liquid phase in the second material channel. After being cooled by the cryocooler 31, it enters the distillation column 10 through the second inlet.

[0067] The first liquid source 50 enters the distillation column 10 through the first inlet and undergoes gas-liquid separation together with the carbon dioxide entering the distillation column 10 through the second inlet. The resulting gas phase is discharged through the first outlet, and the resulting liquid carbon dioxide enters the second material channel of the reboiler 20 through the second outlet.

[0068] The liquid carbon dioxide in the second material channel exchanges heat with the first material channel, causing the light components to evaporate. The resulting liquid carbon dioxide is then sent to the subcooler 32 for heat exchange to obtain the finished liquid carbon dioxide.

[0069] Specifically, the pressure of the first liquid source 50 is about 2.5 MPa and the temperature is about -16℃. The first liquid source 50 enters the distillation column 10 from the first inlet in the middle of the distillation column 10.

[0070] In one specific embodiment of the present invention, the liquid phase flowing out of the first material channel outlet exchanges heat with the gas phase discharged through the first outlet, and then exchanges heat again in the cryogenic cooler 31, and then enters the distillation column 10 through the second inlet.

[0071] In one specific embodiment of the present invention, the light components obtained by evaporation in the second material channel enter the distillation column 10 through the third inlet and undergo gas-liquid separation in the distillation column 10.

[0072] The pressure of the second liquid source 60 is 6.9±0.1MPa and the temperature is 20℃. After entering the first material channel of the reboiler 20, the second liquid source 60 undergoes heat exchange and cooling with the medium in the second material channel. Then, it undergoes heat exchange and cooling with the non-condensable gas at the top of the distillation column 10 through the cold energy recovery unit 40. After that, it undergoes heat exchange and cooling again through the cryogenic unit 31. Then, it is depressurized to 2.4±0.1MPa through the pressure relief valve and enters the distillation column 10 through the second inlet.

[0073] The pressure of the first liquid source 50 is 2.4±0.1MPa and the temperature is -16℃. The first liquid source 50 enters the distillation column 10 through the first inlet.

[0074] The first liquid source 50 and the second liquid source 60 entering the distillation column 10 undergo gas-liquid separation within the distillation column 10. The gas is collected at the top of the distillation column 10 and discharged from the distillation column 10 through the first outlet. The discharged non-condensable gas exchanges heat with the second liquid source 60 at the cold energy recovery unit 40 to recover the cold source. The liquid is collected at the bottom of the distillation column 10 and enters the second material channel of the reboiler 20 through the second outlet under the action of siphon.

[0075] In the reboiler 20, the liquid phase entering the second material channel is heated by the medium in the first material channel, thereby causing the non-condensable gas to evaporate. The evaporated gas re-enters the distillation column 10 through the third inlet for gas-liquid separation. The remaining liquid phase flows out of the second material channel through the overflow baffle and is then subcooled by the cooler 32 to obtain a liquid carbon dioxide product of consistent quality.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A liquid-phase carbon dioxide distillation purification system, characterized in that, include: The distillation column is provided with a first inlet, a second inlet, a first outlet, and a second outlet; the first inlet is used for the inlet of a first liquid source, and the first outlet is used for the outlet of a gas phase flow. The reboiler has a first material channel and a second material channel for heat exchange; the inlet of the first material channel is used for the entry of the second liquid source, and the outlet is connected to the second inlet; the inlet of the second material channel is connected to the second outlet, and the liquid phase outlet is connected to the finished product storage tank. The refrigeration unit includes a cryocooler disposed between the first material channel and the second inlet, and a subcooler disposed between the second material channel and the finished product storage tank; The first liquid source is medium-pressure, low-temperature liquid carbon dioxide, and the second liquid source is high-pressure, room-temperature liquid carbon dioxide.

2. The liquid-phase carbon dioxide distillation purification system according to claim 1, characterized in that, The distillation column also includes a third inlet; the second material channel also has a gas phase outlet, which is connected to the third inlet.

3. The liquid-phase carbon dioxide distillation purification system according to claim 1, characterized in that, It also includes a cold energy recovery unit, which has a first heat exchange channel and a second heat exchange channel for heat exchange. The first heat exchange channel is connected between the outlet of the first material channel and the cryogenic device, and the inlet of the second heat exchange channel is connected to the first outlet.

4. The liquid-phase carbon dioxide distillation purification system according to claim 1, characterized in that, The pressure of the first liquid source is 2.4±0.1MPa and the temperature is -16±1℃; the pressure of the carbon dioxide liquid phase in the second liquid source is 6.9±0.1MPa and the temperature is 20±1℃.

5. The liquid-phase carbon dioxide distillation purification system according to claim 4, characterized in that, It also includes a high-pressure ambient temperature liquefaction unit, through which carbon dioxide raw material gas is processed to obtain a first liquid source and a second liquid source.

6. The liquid-phase carbon dioxide distillation purification system according to claim 2, characterized in that, The first outlet and the second inlet are located at the top of the distillation column, the second outlet is located at the bottom of the distillation column, and the first inlet and the third inlet are located in the middle of the distillation column.

7. The liquid-phase carbon dioxide distillation purification system according to claim 1, characterized in that, The refrigeration unit has a cooling load of -30℃ and a COP > 1.

9.

8. A method for purifying carbon dioxide by liquid-phase distillation, characterized in that, The purification is achieved using the liquid-phase carbon dioxide distillation system according to any one of claims 1-7, comprising the following steps: The second liquid source enters the first material channel of the reboiler and exchanges heat with the liquid phase in the second material channel. After being cooled by the cryocooler, it enters the distillation column through the second inlet. The first liquid source enters the distillation column through the first inlet and undergoes gas-liquid separation together with the carbon dioxide that enters the distillation column through the second inlet. The resulting gas phase is discharged through the first outlet, and the resulting liquid carbon dioxide enters the second material channel of the reboiler through the second outlet. The liquid carbon dioxide in the second material channel exchanges heat with the first material channel, causing the light components to evaporate. The resulting liquid carbon dioxide is then sent to the subcooler for heat exchange to obtain the finished liquid carbon dioxide.

9. The liquid-phase carbon dioxide distillation purification method according to claim 8, characterized in that, The liquid phase flowing out of the first material channel outlet exchanges heat with the gas phase discharged through the first outlet, and then exchanges heat again in the cryogenic chamber before entering the distillation column through the second inlet.

10. The liquid-phase carbon dioxide distillation purification method according to claim 8, characterized in that, The light components obtained from evaporation in the second material channel enter the distillation column through the third inlet, where gas-liquid separation takes place.

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