A high-purity carbon dioxide preparation system and preparation process

Abstract

The present invention discloses a high-purity carbon dioxide preparation system and preparation process thereof. The system includes a light removal distillation tower, a heavy removal distillation tower, a diaphragm circulation machine and a residual cold recovery device. The light removal distillation tower is connected to the heavy removal distillation tower, the diaphragm circulation machine is connected to the heavy removal distillation tower, and the residual cold recovery device is connected to the diaphragm circulation machine and the light removal distillation tower. The preparation process includes the following steps: 1) evaporation and vaporization; 2) distillation and heavy removal; 3) tail gas residual cold recovery; 4) low-temperature distillation and light removal. The present invention obtains high-purity CO2 by removing various heavy component impurities and various non-condensable light component impurities in the raw material CO2 through a low-temperature double distillation system; through the heat pump refrigeration technology, the CO2 raw material is made into both material and refrigerant, and the latent heat of vaporization of the low-temperature liquid CO2 raw material is fully utilized, without the need to configure an independent refrigeration system, thereby greatly reducing refrigeration energy consumption.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide preparation, and in particular relates to a high-purity carbon dioxide preparation system and a preparation process thereof. Background Art

[0002] Liquid carbon dioxide has a wide range of uses. It can be used as a refrigerant for food preservation and artificial rainfall. It is also an industrial raw material for the production of soda ash, urea, and soft drinks. It can also be used as a coolant, welding, foundry industry, soft drinks, fire extinguishing agents, carbonate production, pesticides, and more. In the existing technology, carbon dioxide is usually purified by distillation to obtain a liquid carbon dioxide product.

[0003] On April 12, 2022, China Patent disclosed a utility model patent named A distillation system for purifying carbon dioxide from alcohol tail gas (Announcement No.: CN216259170U). Its technical solution records: the raw liquid CO2 enters the first distillation tower B through the first liquid inlet and evaporates in the first distillation tower B through the built-in first evaporator C. The heavy components such as water and alcohol in the raw CO2 are enriched and removed at the bottom of the tower, and carbon dioxide and light components are extracted from the gas phase at the top of the tower. The gaseous feed gas from the top of the first distillation tower B is combined with the gaseous CO2 from the top of the second distillation tower F and then condensed in the primary condenser D. The gaseous phase then flows to the first gas-liquid separator E for gas-liquid separation. The liquid phase is combined with the liquid phase at the bottom of the secondary separator H and used as reflux to flow to the second distillation tower F for distillation. The gaseous phase is then condensed again in the secondary condenser G and then transferred to the secondary separator H for gas-liquid separation. The non-condensable gas phase is recovered in the residual cooling recovery unit and then discharged. The liquid phase is combined with the liquid phase at the bottom of the primary separator E and used as reflux to flow to the second distillation tower F. Industrial-grade liquid CO2 can be produced in the liquid phase in the middle of the second distillation tower F, and food-grade liquid CO2 (99.995% purity) can be produced in the liquid phase at the bottom of the tower.

[0004] However, the above-mentioned distillation system has a complicated process and many equipments, and also needs to be equipped with a dedicated refrigeration ice machine system or supporting refrigeration public works, which has a high equipment investment cost. The first distillation tower B used to remove heavy components has a poor removal effect of heavy components due to the lack of liquid CO2 reflux and only relies on evaporation. The purity of the product liquid CO2 cannot be further improved, and the latent heat of vaporization of the liquid CO2 raw material cannot be effectively utilized. The cooling capacity required by the first and second condensers needs to be provided by the ice machine refrigeration system or refrigeration public works, and the energy consumption per unit product is high. The evaporation of the raw liquid CO2 in the tower kettle of the first distillation tower B consumes a lot of heat, and corresponding public works are required to provide heat, which also has the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies in the existing technology and provide a technical solution for a high-purity carbon dioxide preparation system and its preparation process. Various heavy component impurities and various non-condensable light component impurities in the raw material CO2 are removed separately through a low-temperature double distillation system to obtain high-purity CO2; through heat pump refrigeration technology, the CO2 raw material is made both a material and a refrigerant, and the latent heat of vaporization of the low-temperature liquid CO2 raw material is fully utilized, without the need for an independent refrigeration system, thereby greatly reducing refrigeration energy consumption.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A high-purity carbon dioxide preparation system includes a light removal distillation tower, a heavy removal distillation tower, a diaphragm circulation machine and a residual cooling recovery device. The light removal distillation tower is connected to a raw liquid pipeline. The raw liquid food-grade CO2 enters the light removal distillation tower through the raw liquid pipeline. The raw liquid pipeline is provided with a raw liquid pressure reducing valve. The raw liquid food-grade CO2 is decompressed by the raw liquid pressure reducing valve. The top of the light removal distillation tower is connected to a non-condensable gas pipeline. The non-condensable gas pipeline is provided with a pressure control valve. The bottom of the light removal distillation tower is connected to the bottom of the tower. It is connected to the product pipeline, the light removal distillation tower is connected to the heavy removal distillation tower through a gas-liquid mixing pipeline, the bottom of the heavy removal distillation tower is connected to the residual liquid pipeline one, the top of the heavy removal distillation tower is connected to the raw gas pipeline one, the diaphragm circulation machine is connected to the heavy removal distillation tower through the raw gas pipeline one, the residual cooling recovery device is connected to the diaphragm circulation machine through the raw gas pipeline two, the residual cooling recovery device is connected to the raw gas pipeline three, the mixing pipe and the discharge pipe, the raw gas pipeline three is connected to the light removal distillation tower, and the mixing pipe is connected to the non-condensable gas pipeline.

[0008] Furthermore, the residual liquid pipeline 1 is connected to the residual liquid pipeline 2, and the residual liquid pipeline 2 is connected to the top of the de-heavy distillation tower. A liquid level control valve is connected between the residual liquid pipeline 1 and the residual liquid pipeline 2. The residual liquid transported out of the residual liquid pipeline 1 is depressurized by the liquid level control valve. The decompression of the residual liquid will cause part of the residual liquid to vaporize into a gas-liquid mixture with a lower temperature. The residual liquid is then transported back to the top condenser 1 at the top of the de-heavy distillation tower through the residual liquid pipeline 2 to evaporate and vaporize and recover the latent heat of vaporization of the residual liquid. The residual liquid exchanges heat with the raw gas-liquid mixture transported to the de-heavy distillation tower to recover part of the excess cold.

[0009] Furthermore, a residual liquid waste gas pipeline is connected to the top of the de-heavy distillation tower, and the residual liquid waste gas pipeline is connected to the mixing tube. A pressure control valve 2 is provided on the residual liquid waste gas pipeline. The pressure control valve 2 performs a re-decompression operation on the residual liquid waste gas after the latent heat of vaporization is recovered, and then the residual liquid is transported to the mixing tube through the residual liquid waste gas pipeline, and then transported to the residual cold recovery device to recover the residual cold again, thereby fully recovering the residual liquid and residual cold and reducing energy consumption loss.

[0010] Furthermore, a top condenser 1 is provided at the top of the de-light distillation tower, and the top condenser 1 serves as a heat exchange device to facilitate heat exchange between the raw material liquid food-grade CO2 and the rising air flow in the de-light distillation tower.

[0011] Furthermore, a second top condenser is provided at the top of the heavy-removal distillation tower. The second top condenser serves as a heat exchange device to facilitate heat exchange between the rising airflow and the residual liquid in the heavy-removal distillation tower.

[0012] The preparation process of the high-purity carbon dioxide preparation system includes the following steps:

[0013] 1) After the raw material liquid food-grade CO2 is decompressed by the raw material liquid pressure reducing valve, it enters the top condenser at the top of the de-light distillation tower through the raw material liquid pipeline for evaporation and vaporization. The evaporated raw material gas-liquid mixture enters the de-heavy distillation tower through the gas-liquid mixing pipeline;

[0014] 2) The raw gas-liquid mixture enters the de-heavy distillation tower for distillation to remove heavy impurities. The residual liquid containing heavy impurities is discharged through the residual liquid pipeline 1. The raw gas after the heavy impurities are removed is extracted from the gas phase at the top of the de-heavy distillation tower and sent to the diaphragm circulation machine through the raw gas pipeline 1;

[0015] 3) The diaphragm circulator boosts the pressure of the incoming raw gas, which is then fed into the residual cooling recovery device via raw gas pipeline 2. The raw gas is pre-cooled by exchanging heat with the non-condensable tail gas discharged from the non-condensable gas pipeline, and then fed into the light removal distillation tower via raw gas pipeline 3. The non-condensable tail gas exchanges heat with the raw gas, recovers the pre-cooling, and reduces energy consumption.

[0016] 4) The pre-cooled raw gas enters the de-light fractionation tower for low-temperature distillation to remove the light component impurities remaining in the raw gas. The non-condensable tail gas containing light component impurities is discharged through the non-condensable gas pipeline, and the liquid CO2 with light component impurities removed is produced from the product pipeline in the tower kettle of the de-light fractionation tower. Low-temperature double distillation is used to remove various heavy component impurities (relative to CO2) and various non-condensable light component impurities (relative to CO2) in the raw CO2, thereby obtaining high-purity CO2 with higher purity.

[0017] Furthermore, in step 2), the residual liquid discharged from the residual liquid pipeline 1 is subjected to the decompression treatment of the liquid level control valve, and then enters the top condenser 2 at the top of the de-weighting distillation tower through the residual liquid pipeline 2, exchanges heat with the raw gas-liquid mixture transported from the gas-liquid mixing pipeline, and is then discharged from the residual liquid waste gas pipeline. After the decompression treatment of the pressure control valve 2, it is mixed with the non-condensable tail gas discharged from the non-condensable gas pipeline in the mixing pipe, and then goes to the residual cold recovery device to recover the residual cold, and is then discharged from the discharge pipe. The residual liquid is subjected to two-stage residual cold recovery, which maximizes the recovery of the residual liquid residual cold and reduces energy consumption.

[0018] Furthermore, in step 3), after the raw gas enters the de-lightening distillation tower from the raw gas pipeline three, the raw gas rises in the de-lightening distillation tower to the top condenser one, and exchanges heat with the raw liquid food-grade CO2 transported from the raw liquid pipeline. The raw liquid food-grade CO2 absorbs heat and evaporates and vaporizes, and the raw gas releases heat and condenses and liquefies. The raw CO2 is used as a refrigerant for refrigeration, replacing the refrigeration of the existing refrigeration unit or the cooling of the public works, completely recovering the latent heat of vaporization of the raw liquid food-grade CO2, and greatly reducing the energy consumption of the system.

[0019] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0020] The present invention adopts low-temperature double distillation technology, and the light component impurities in the raw material CO2 are removed in the light degassing distillation tower, and the heavy component impurities in the raw material CO2 are removed in the heavy degassing distillation tower, and finally high-purity liquid CO2 is obtained in the tower kettle of the light degassing distillation tower. The present invention adopts heat pump technology, and through the heat pump refrigeration technology, the CO2 raw material is made into both material and refrigerant, and the diaphragm circulation machine is both a heat pump and a CO2 raw gas circulation booster, which fully utilizes the latent heat of vaporization of the low-temperature liquid CO2 raw material and does not need to be configured with an independent refrigeration system. In the present invention, the residual cold recovery device and the heavy degassing distillation tower top condenser are combined to fully recover various residual colds in the low-temperature double distillation system (residual cold of the low-temperature non-condensable tail gas of the light degassing distillation tower, and low-temperature residual liquid and latent heat of vaporization containing heavy component impurities in the heavy degassing distillation tower). The residual liquid evaporation pressure is controlled by the second pressure control valve to avoid dry ice from clogging pipelines and equipment during the recovery of the residual liquid residual cold.

[0021] The process flow of the present invention is simple, the structure is clear, the number of equipment is small, and the heat pump process technology is used to fully utilize the evaporation latent cooling of the material. There is no need for supporting special cooling and heating utilities, which lowers the investment threshold and saves investment. The raw material liquid CO2 is used as the refrigerant for refrigeration, replacing the refrigeration of the existing refrigeration unit or public engineering cooling. The raw material liquid CO2 is completely recovered. The latent heat of vaporization of the raw material liquid CO2 is greatly reduced, and the energy consumption of the system is greatly reduced. The energy consumption per ton of high-purity liquid CO2 product is 6.35-6.86Kw·h (the higher the concentration of raw material liquid CO2, the lower the energy consumption). The existing patented technology consumes 62.65 to 66.38 Kw·h of energy per ton of industrial (food) grade liquid CO2 product, saving about 90%. It has a two-stage recovery of residual liquid and residual cooling to avoid dry ice clogging pipelines and equipment after the residual liquid is decompressed, and maximizes the recovery of residual liquid and residual cooling, which can reduce energy consumption by about 10%. It also uses low-temperature double distillation technology to separately remove various heavy component impurities (relative to CO2) and various non-condensable light component impurities (relative to CO2) in the raw CO2 to obtain higher purity high-purity CO2 (>99.999%). BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings:

[0023] Figure 1 It is a structural diagram of the prior art;

[0024] Figure 2 The figure is a schematic structural diagram of a system for preparing high-purity carbon dioxide according to the present invention.

[0025] In the figure: 1-raw liquid pipeline; 2-gas-liquid mixing pipeline; 3-raw gas pipeline 1; 4-raw gas pipeline 2; 5-raw gas pipeline 3; 6-product pipeline; 7-non-condensable gas pipeline; 8-residual liquid pipeline 1; 9-residual liquid pipeline 2; 10-residual liquid waste gas pipeline; 11-mixing pipe; 12-discharge pipe; F1-raw liquid pressure reducing valve; F2-pressure control valve 1; F3-liquid level control valve; F4-pressure control valve 2; 101-light removal distillation tower; 102-heavy removal distillation tower; 103-diaphragm circulation machine; 104-residual cooling recovery device. DETAILED DESCRIPTION

[0026] like Figure 2 As shown, a high-purity carbon dioxide preparation system of the present invention includes a light degassing distillation tower 101, a heavy degassing distillation tower 102, a diaphragm circulation machine 103 and a residual cooling recovery device 104. The light degassing distillation tower 101 is connected to a raw liquid pipeline 1, and the raw liquid food-grade CO2 enters the light degassing distillation tower 101 through the raw liquid pipeline 1. A raw liquid pressure reducing valve F1 is provided on the raw liquid pipeline 1, and the raw liquid food-grade CO2 is depressurized by the raw liquid pressure reducing valve F1. The top of the light degassing distillation tower 101 is connected to a non-condensable gas pipeline 7, and a pressure control valve F2 is provided on the non-condensable gas pipeline 7. The bottom of the light degassing distillation tower 101 is connected to The product pipeline 6, the light removal distillation tower 101 is connected to the heavy removal distillation tower 102 through the gas-liquid mixing pipeline 2, the bottom of the heavy removal distillation tower 102 is connected to the residual liquid pipeline 8, the top of the heavy removal distillation tower 102 is connected to the raw gas pipeline 3, the diaphragm circulation machine 103 is connected to the heavy removal distillation tower 102 through the raw gas pipeline 3, the residual cooling recovery device 104 is connected to the diaphragm circulation machine 103 through the raw gas pipeline 24, the residual cooling recovery device 104 is connected to the raw gas pipeline 3 5, the mixing pipe 11 and the discharge pipe 12, the raw gas pipeline 3 5 is connected to the light removal distillation tower 101, and the mixing pipe 11 is connected to the non-condensable gas pipeline 7.

[0027] The residual liquid pipeline 18 is connected to the residual liquid pipeline 29, and the residual liquid pipeline 29 is connected to the top of the de-heavy distillation tower 102. A liquid level control valve F3 is connected between the residual liquid pipeline 18 and the residual liquid pipeline 29. The residual liquid transported out of the residual liquid pipeline 18 is depressurized by the liquid level control valve F3. The decompression of the residual liquid will cause part of the residual liquid to vaporize into a gas-liquid mixture with a lower temperature. The residual liquid is then transported back to the top condenser 1 at the top of the de-heavy distillation tower 102 through the residual liquid pipeline 29 to evaporate and vaporize to recover the latent heat of vaporization of the residual liquid. The residual liquid exchanges heat with the raw gas-liquid mixture transported to the de-heavy distillation tower 102 to recover part of the excess cold.

[0028] The top of the de-heavy distillation tower 102 is connected to a residual liquid waste gas pipeline 10, which is connected to a mixing pipe 11. A pressure control valve F4 is provided on the residual liquid waste gas pipeline 10. The pressure control valve F4 performs a re-decompression operation on the residual liquid waste gas after recovering the latent heat of vaporization, and then transports the residual liquid to the mixing pipe 11 through the residual liquid waste gas pipeline 10, and then transports it to the residual cold recovery device 104 to recover the residual cold again, thereby fully recovering the residual liquid and residual cold and reducing energy consumption losses.

[0029] The top of the light-removal distillation tower 101 is provided with a first overhead condenser, which serves as a heat exchange device to facilitate heat exchange between the raw material liquid food-grade CO2 and the rising airflow in the light-removal distillation tower 101. The top of the heavy-removal distillation tower 102 is provided with a second overhead condenser, which serves as a heat exchange device to facilitate heat exchange between the rising airflow in the heavy-removal distillation tower 102 and the residual liquid.

[0030] The preparation process of the high-purity carbon dioxide preparation system includes the following steps:

[0031] 1) After the raw liquid food-grade CO2 is decompressed by the raw liquid pressure reducing valve F1, it enters the top condenser of the light removal distillation tower 101 through the raw liquid pipeline 1 for evaporation and vaporization. The evaporated raw gas-liquid mixture enters the heavy removal distillation tower 102 through the gas-liquid mixing pipeline 2;

[0032] 2) The raw gas-liquid mixture enters the de-heavy distillation tower 102 for cryogenic distillation to remove heavy impurities. The residual liquid containing the heavy impurities is discharged through the residual liquid pipeline-8. The raw gas after the heavy impurities are removed is extracted from the gas phase at the top of the de-heavy distillation tower 102 and sent to the diaphragm circulation machine 103 through the raw gas pipeline-3;

[0033] The residual liquid discharged from the residual liquid pipeline 1 8 is decompressed by the liquid level control valve F3, and then enters the top condenser 2 at the top of the de-weighting distillation tower 102 through the residual liquid pipeline 2 9. After heat exchange with the raw gas-liquid mixture transported from the gas-liquid mixing pipeline 2, it is discharged from the residual liquid waste gas pipeline 10. After decompression by the pressure control valve 2 F4, it is mixed with the non-condensable tail gas discharged from the non-condensable gas pipeline 7 in the mixing pipe 11, and then goes to the residual cold recovery device 104 to recover the residual cold. After that, it is discharged from the discharge pipe 12. The residual liquid undergoes two-stage residual cold recovery, maximizing the recovery of residual liquid residual cold and reducing energy consumption.

[0034] 3) The diaphragm circulator 103 pressurizes the incoming raw gas, which is then fed into the residual cooling recovery device 104 via the raw gas pipeline 2 4 . The raw gas is pre-cooled by exchanging heat with the non-condensable tail gas discharged from the non-condensable gas pipeline 7 . The raw gas is then fed into the light removal distillation tower 101 via the raw gas pipeline 3 5 . The non-condensable tail gas exchanges heat with the raw gas, recovering the pre-cooling and reducing energy consumption.

[0035] After the raw gas enters the de-light fractionation tower 101 from the raw gas pipeline 3 5, the raw gas rises in the de-light fractionation tower 101 and flows into the tower top condenser 1, exchanging heat with the raw liquid food-grade CO2 delivered from the raw liquid pipeline 1. The raw liquid food-grade CO2 absorbs heat and evaporates, while the raw gas releases heat and condenses and liquefies. The raw CO2 is used as a refrigerant for refrigeration, replacing the refrigeration of the existing refrigeration unit or the cooling of the public works, completely recovering the latent heat of vaporization of the raw liquid food-grade CO2, and greatly reducing the energy consumption of the system.

[0036] 4) The pre-cooled raw gas enters the light component removal distillation tower 101 for low-temperature distillation to remove the light component impurities remaining in the raw gas. The non-condensable tail gas containing light component impurities is discharged through the non-condensable gas pipeline 7, and the liquid CO2 with light component impurities removed is produced from the bottom of the light component removal distillation tower 101 through the product pipeline 6. Low-temperature double distillation is used to remove various heavy component impurities (relative to CO2) and various non-condensable light component impurities (relative to CO2) in the raw CO2, thereby obtaining high-purity CO2 with higher purity.

[0037] The present invention adopts low-temperature double distillation technology, and the light component impurities in the raw material CO2 are removed in the light fractionation tower 101, and the heavy component impurities in the raw material CO2 are removed in the heavy fractionation tower 102, and finally high-purity liquid CO2 is obtained in the tower bottom of the light fractionation tower 101. The present invention adopts heat pump technology, and the CO2 raw material is both a material and a refrigerant through heat pump refrigeration technology. The diaphragm cycler 103 is both a heat pump and a CO2 raw gas circulation booster, which fully utilizes the latent heat of vaporization of the low-temperature liquid CO2 raw material and does not require an independent refrigeration system. In the present invention, the residual cold recovery device 104 and the top condenser of the heavy fractionation tower 102 are combined to fully recover various residual colds in the low-temperature double distillation system (residual cold of the low-temperature non-condensable tail gas of the light fractionation tower 101, and low-temperature residual liquid and latent heat of vaporization of the heavy component impurities in the heavy fractionation tower 102). The residual liquid evaporation pressure is controlled by the pressure control valve F4 to avoid dry ice from clogging pipelines and equipment during the recovery of the residual liquid residual cold.

[0038] The process flow of the present invention is simple, the structure is clear, the number of equipment is small, and the heat pump process technology is used to fully utilize the evaporation latent cooling of the material. There is no need for supporting special cooling and heating utilities, which lowers the investment threshold and saves investment. The raw material liquid CO2 is used as the refrigerant for refrigeration, replacing the refrigeration of the existing refrigeration unit or public engineering cooling. The raw material liquid CO2 is completely recovered. The latent heat of vaporization of the raw material liquid CO2 is greatly reduced, and the energy consumption of the system is greatly reduced. The energy consumption per ton of high-purity liquid CO2 product is 6.35-6.86Kw·h (the higher the concentration of raw material liquid CO2, the lower the energy consumption). The existing patented technology consumes 62.65 to 66.38 Kw·h of energy per ton of industrial (food) grade liquid CO2 product, saving about 90%. It has a two-stage recovery of residual liquid and residual cooling to avoid dry ice clogging pipelines and equipment after the residual liquid is decompressed, and maximizes the recovery of residual liquid and residual cooling, which can reduce energy consumption by about 10%. It also uses low-temperature double distillation technology to separately remove various heavy component impurities (relative to CO2) and various non-condensable light component impurities (relative to CO2) in the raw CO2 to obtain higher purity high-purity CO2 (>99.999%).

[0039] The present invention adopts low-temperature double distillation technology, and removes light components and heavy components impurities in the raw material CO2 through the light removal distillation tower 101 and the heavy removal distillation tower 102 respectively, and finally obtains high-purity liquid CO2 in the tower kettle of the light removal distillation tower 101. The specific process is as follows: the raw liquid food-grade CO2 with a purity of 99.9% and a temperature of -25°C and 1.85Mpa is reduced to 1.4Mpa and -30°C by the raw liquid pressure reducing valve F1, and enters the top condenser of the light removal distillation tower 101 through the raw liquid pipeline 1 to be evaporated and vaporized (the vaporization rate is about 90%). The evaporated gas-liquid mixture is about -23°C, and then enters the heavy removal distillation tower 102 through the gas-liquid mixing pipeline 2 to be distilled to remove water, alcohol, residual sulfur, aldehyde, C4 and above heavy components impurities in the raw material CO2. The residual liquid containing heavy components impurities at 1.4Mpa and -28°C is discharged through the liquid level control valve F3 and the residual liquid pipeline 8, and the -28°C and 1.4 The clean raw gas of 2.5 MPa is extracted from the gas phase at the top of the de-heavy distillation tower 102, and is sent to the diaphragm circulation machine 103 through the raw gas pipeline 1-3 to be pressurized to 2.3 MPa and 3°C, and then sent to the residual cooling recovery device 104 through the raw gas pipeline 2-4 to exchange heat with the low-temperature non-condensable tail gas, and is pre-cooled to -5°C and sent to the de-light distillation tower 101 through the raw gas pipeline 3-5 for low-temperature distillation to remove the remaining nitrogen, oxygen, carbon monoxide, C3 and lower hydrocarbons and other light component impurities in the raw gas; the -25°C, 2.3 MPa non-condensable tail gas containing light component impurities is discharged through the non-condensable gas pipeline, and the high-purity liquid CO2 (CO2 purity > 99.9999%) is extracted from the bottom of the de-light distillation tower 101 through the product pipeline 67.

[0040] The present invention adopts heat pump refrigeration technology, so that the CO2 raw material is both a material and a refrigerant, and the diaphragm circulation machine 103 is both a heat pump and a CO2 raw gas circulation booster, which fully utilizes the latent heat of vaporization of the low-temperature liquid CO2 raw material and does not require the configuration of an independent refrigeration system. The specific process is as follows: the clean raw material gas at -28°C and 1.4Mpa from the top of the de-heavy distillation tower 102 is sent to the diaphragm circulation machine 103 through the raw gas pipeline 13 to be pressurized to 2.3Mpa and 3°C, and is sent to the residual cooling recovery device 104 through the raw gas pipeline 24 to exchange heat with the low-temperature non-condensable tail gas, and is pre-cooled to -5°C and sent to the de-light distillation tower 101 through the raw gas pipeline 35. The rising air flow at -15°C in the de-light distillation tower 101 is used as a heat source for the heat pump and condensed at the top of the de-light distillation tower 101 The raw liquid food-grade CO2 at -25°C, 1.85 MPa and 99.9% purity is condensed in the first device and the heat is released to evaporate the raw liquid food-grade CO2; the raw liquid food-grade CO2 at -25°C, 1.85 MPa and 99.9% purity is reduced to 1.4 MPa and -30°C by the raw liquid pressure reducing valve F1 as a heat pump cold source, and enters the top condenser of the de-light distillation tower 101 through the raw liquid pipeline 1 to evaporate and absorb heat, condensing the -15°C rising air flow in the de-light distillation tower 101, thereby completing a heat pump cycle (open heat pump cycle).

[0041] The present invention adopts the residual cold recovery technology, and fully recovers various residual colds in the low-temperature double distillation system (residual cold of the low-temperature non-condensable tail gas of the light-removal distillation tower 101, and low-temperature residual liquid containing heavy component impurities and latent heat of vaporization of the heavy-removal distillation tower 102) through the combination of the residual cold recovery device 104 and the top condenser of the heavy-removal distillation tower 102. The evaporation pressure of the residual liquid is controlled by the second pressure control valve F4 to avoid dry ice from clogging pipelines and equipment during the recovery of the residual liquid residual cold. The specific process is as follows:

[0042] Residual cooling recovery of residual liquid containing heavy component impurities:

[0043] The residual liquid gas-liquid mixture at 0.6 MPa and -50°C from the residual liquid pipeline 9 is first evaporated and gasified in the top condenser 2 of the de-heaving distillation tower 102 to recover the latent heat of vaporization of the residual liquid, and then is reduced in pressure to 0.05 MPa and -45°C through the residual liquid waste gas pipeline 10 and the pressure control valve 2 F4 and sent to the mixing pipe 11 through the residual liquid waste gas pipeline 10, and then sent to the residual cold recovery device 104 to recover the residual cold again.

[0044] Non-condensable tail gas residual cooling recovery:

[0045] The non-condensable tail gas at -25°C and 2.3 MPa from the non-condensable gas pipeline 7 is reduced in pressure to 0.05 MPa and -55°C via the pressure control valve F2, and is transported to the mixing pipe 11 via the non-condensable gas pipeline 7, where it is mixed with the residual liquid waste gas from the residual liquid waste gas pipeline 10. The mixed tail gas at -48°C and 0.05 MPa is recovered by the residual cooling recovery device 104 to 0°C and then discharged through the exhaust pipe.

[0046] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements, or modifications based on the present invention to achieve substantially the same technical effects are all within the scope of protection of the present invention.

Claims

1. A system for preparing high-purity carbon dioxide, characterized in that include: A de-light distillation tower, wherein the de-light distillation tower is connected to a raw liquid pipeline, and the raw liquid food-grade CO2 enters a top condenser provided at the top of the de-light distillation tower through the raw liquid pipeline, and a raw liquid pressure reducing valve is provided on the raw liquid pipeline, and the raw liquid food-grade CO2 is depressurized by the raw liquid pressure reducing valve; The top of the light removal distillation tower is connected to a non-condensable gas pipeline, on which a pressure control valve 1 is provided, and the bottom of the light removal distillation tower is connected to a product pipeline; A de-heavy distillation tower, wherein the de-light distillation tower is connected to the de-heavy distillation tower via a gas-liquid mixing pipeline, the bottom of the de-heavy distillation tower is connected to a residual liquid pipeline 1, and the top of the de-heavy distillation tower is connected to a raw gas pipeline 1; a diaphragm circulator, the diaphragm circulator being connected to the weight removal distillation tower via the raw gas pipeline 1; The waste cooling recovery device is connected to the diaphragm circulation machine through the raw gas pipeline 2. The waste cooling recovery device is connected to the raw gas pipeline 3, the mixing tube and the discharge pipe. The raw gas pipeline 3 is connected to the light removal distillation tower, and the mixing tube is connected to the non-condensable gas pipeline.

2. A high-purity carbon dioxide production system according to claim 1, characterized in that: The residual liquid pipeline 1 is connected to the residual liquid pipeline 2, the residual liquid pipeline 2 is connected to the top of the de-heavy distillation tower, and a liquid level control valve is connected between the residual liquid pipeline 1 and the residual liquid pipeline 2.

3. A high-purity carbon dioxide production system according to claim 1, characterized in that: The top of the de-heavy distillation tower is connected to a residual liquid waste gas pipeline, the residual liquid waste gas pipeline is communicated with the mixing pipe, and a second pressure control valve is provided on the residual liquid waste gas pipeline.

4. A high-purity carbon dioxide production system according to claim 1, characterized in that: A second top condenser is provided at the top of the weight-removing distillation tower.

5. A preparation process for a high-purity carbon dioxide preparation system according to claim 1, characterized in that: The steps include: 1) After the raw material liquid food-grade CO2 is reduced in pressure by the raw material liquid pressure reducing valve, it enters the top condenser at the top of the de-light distillation tower through the raw material liquid pipeline for evaporation and vaporization. The evaporated raw material gas-liquid mixture enters the de-heavy distillation tower through the gas-liquid mixing pipeline; 2) The raw gas-liquid mixture enters the de-heavy distillation tower and undergoes distillation to remove heavy impurities. The residual liquid containing heavy impurities is discharged through the residual liquid pipeline 1. The raw gas after the heavy impurities are removed is extracted from the gas phase at the top of the de-heavy distillation tower and sent to the diaphragm circulation machine through the raw gas pipeline 1. 3) The diaphragm circulator boosts the pressure of the incoming raw gas, which is then fed into the residual cooling recovery device via raw gas pipeline 2. The gas is then heat-exchanged with the non-condensable tail gas discharged from the non-condensable gas pipeline. The raw gas is pre-cooled and then fed into the light removal distillation tower via raw gas pipeline 3. 4) The pre-cooled raw gas enters the de-light fractionation tower for distillation to remove the remaining light component impurities in the raw gas. The non-condensable tail gas containing light component impurities is discharged through the non-condensable gas pipeline, and the liquid CO2 with light component impurities removed is produced from the product pipeline in the kettle of the de-light fractionation tower.

6. The process for preparing a high-purity carbon dioxide production system according to claim 5, characterized in that: In the step 2), the residual liquid discharged from the residual liquid pipeline 1 is subjected to a decompression treatment by the liquid level control valve, and then enters the top condenser 2 at the top of the de-weighting distillation tower through the residual liquid pipeline 2, exchanges heat with the raw gas-liquid mixture transported from the gas-liquid mixing pipeline, and is then discharged from the residual liquid waste gas pipeline. After being decompressed by the pressure control valve 2, it is mixed with the non-condensable tail gas discharged from the non-condensable gas pipeline in the mixing pipe, and then goes to the residual cold recovery device to recover the residual cold, and then is discharged from the discharge pipe.

7. The process for preparing a high-purity carbon dioxide production system according to claim 5, characterized in that: In step 3), after the raw gas enters the de-light distillation tower from the raw gas pipeline 3, the raw gas rises in the de-light distillation tower to the top condenser 1, and exchanges heat with the raw liquid food-grade CO2 transported from the raw liquid pipeline 1. The raw liquid food-grade CO2 absorbs heat and evaporates, and the raw gas releases heat and condenses and liquefies.

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