Carbon dioxide recycling purification method and system

Abstract

The application discloses a carbon dioxide recycling purification method and system, and belongs to the technical field of material separation devices or systems. The application solves the problem of how to further reduce the purification cost. The application increases the pressure of raw material liquid CO2, and then gas-liquid separation is carried out to obtain liquid CO2 and first non-condensable gas. The liquid CO2 is sent into a purifier after being converted into gaseous CO2 by cooperating a gasification heat exchanger and a gasification heater. Then, refined gaseous CO2 is transported into the gasification heat exchanger for heat exchange as a heat source of the gasification heat exchanger. Then, the refined CO2 is heat-exchanged to a temperature lower than the boiling point after being increased, and then gas-liquid separation is carried out again to obtain finished liquid CO2 and second non-condensable gas. The non-condensable gas is used as a cooling source of a supercooling heat exchanger. In the application, the energy of liquid and gas at different temperatures in each stage of the purification process is utilized, the energy consumption of the whole purification process is reduced, and the whole purification process does not need expensive purification equipment, so that the purification cost is extremely low.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of substance separation devices or systems, and particularly relates to a carbon dioxide recycling purification method and system. BACKGROUND

[0002] Carbon dioxide is one of the main greenhouse gases, and its massive emission will cause global warming and exacerbate climate anomalies and extreme weather events. By recycling and utilizing carbon dioxide in flue gas, the emission of greenhouse gases can be effectively reduced, the trend of global warming can be slowed down, and the ecological environment can be protected. Recycling and purifying carbon dioxide can be used to produce various chemicals, fuels and building materials, etc., improve resource utilization, and reduce dependence on fossil fuels. Enterprises can reduce waste gas treatment costs by recycling carbon dioxide, and also bring additional economic benefits by using purified carbon dioxide to produce other products.

[0003] Flue gas generated in industrial activities contains a large amount of carbon dioxide, so extracting carbon dioxide from flue gas can not only convert it into valuable chemicals, but also reduce environmental pollution caused thereby.

[0004] Various carbon dioxide purification systems in the prior art either have high equipment investment or high energy consumption, and how to reduce the cost required for processing the largest byproduct in human history is a difficult problem to be explored in the field. SUMMARY

[0005] In view of the problem of how to further reduce the purification cost in the prior art, the application provides a carbon dioxide recycling purification method and system.

[0006] The technical scheme adopted by the application is as follows:

[0007] A carbon dioxide recycling purification method comprises the following steps:

[0008] S1: The raw material liquid CO2 is pressurized to increase the pressure of the CO2 to a specified storage pressure range (2-2.5 MPa) of the carbon dioxide storage tank;

[0009] S2: The pressurized raw material liquid CO2 is subjected to gas-liquid separation in a first gas-liquid separator to obtain preliminarily purified liquid CO2 and first non-condensable gas, and the first non-condensable gas is delivered to a subcooling heat exchanger as a cold source of the subcooling heat exchanger;

[0010] S3: The preliminarily purified liquid CO2 is heated and warmed in the gasification heat exchanger. If the liquid CO2 has been converted into gaseous CO2 after the heat exchange in the gasification heat exchanger, the gaseous CO2 is directly sent into the purifier to obtain refined gaseous CO2. If the liquid CO2 has not been converted into gaseous CO2 after the heat exchange in the gasification heat exchanger, the liquid CO2 is heated by the gasification heater to convert it into gaseous CO2, which is then sent into the purifier to obtain refined gaseous CO2;

[0011] S4: The refined gaseous CO2 discharged from the purifier is sequentially subjected to heat exchange and temperature reduction in the gasification heat exchanger and the supercooling heat exchanger, and is converted into refined liquid CO2.

[0012] S5: The refined liquid CO2 is transported to the second gas-liquid separator for gas-liquid separation again to obtain product liquid CO2 and second non-condensable gas, and the second non-condensable gas is transported into the supercooling heat exchanger as a cooling source of the supercooling heat exchanger.

[0013] Preferably, the pressure of the raw material liquid CO2 in the storage tank is 0.8 MPa, and the temperature is -50 to -60℃; and the pressure after pressurization in S1 is 2.5 MPa.

[0014] Preferably, the purification process of the purifier in S3 includes desulfurization, denitration, dehydration and dust removal.

[0015] A carbon dioxide recycling purification system for realizing the carbon dioxide recycling purification method, comprising:

[0016] A liquid pressurizing pump for compressing the raw material liquid CO2 to increase the pressure of the raw material liquid CO2 to the specified storage pressure range (2-2.5 MPa) of the carbon dioxide storage tank;

[0017] A first gas-liquid separator for gas-liquid separation of the pressurized raw material liquid CO2 to obtain first non-condensable gas and liquid CO2;

[0018] A gasification heat exchanger, the liquid outlet of the first gas-liquid separator is connected with the low-temperature loop inlet of the gasification heat exchanger, for increasing the temperature of the liquid CO2;

[0019] A gasification heater, the low-temperature loop outlet of the gasification heat exchanger is connected with the inlet of the gasification heater, for converting the liquid CO2 into gaseous CO2;

[0020] A purifier, the outlet of the gasification heater is connected with the inlet of the purifier, for purifying the gaseous CO2 to obtain refined gaseous CO2, and the outlet of the purifier is connected with the high-temperature loop inlet of the gasification heat exchanger, for preliminary temperature reduction of the gaseous CO2; the low-temperature loop outlet of the gasification heat exchanger is provided with a branch directly connected with the purifier without the gasification heater;

[0021] The subcooling heat exchanger connects the outlet of the high-temperature circuit of the gasification heater to the inlet of the high-temperature circuit of the subcooling heat exchanger, and is used to convert refined gaseous CO2 into liquid CO2.

[0022] The second gas-liquid separator is connected to the outlet of the high-temperature circuit of the subcooled heat exchanger and the inlet of the second gas-liquid separator. It is used to perform gas-liquid separation to obtain refined liquid CO2 and a second non-condensable gas.

[0023] The gas outlets of the first and second gas-liquid separators are both connected to the inlet of the low-temperature circuit of the subcooling heat exchanger, and the outlet of the low-temperature circuit of the subcooling heat exchanger is connected to the outside.

[0024] The liquid outlet of the second gas-liquid separator is connected to an external carbon dioxide liquid storage tank.

[0025] The gas outlets of the first and second gas-liquid separators are connected, and then connected to the low-temperature inlet of the subcooling heat exchanger. The low-temperature circuit outlet of the subcooling heat exchanger is open to the atmosphere.

[0026] Preferably, a first throttling valve is installed on the pipeline connecting the second gas-liquid separator and the low-temperature circuit of the subcooling heat exchanger for throttling and cooling, and a second throttling valve is installed on the pipeline connecting the first gas-liquid separator and the low-temperature circuit of the subcooling heat exchanger for throttling and cooling.

[0027] Preferably, the liquid outlet of the second gas-liquid separator is connected to a carbon dioxide liquid storage tank.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] This invention first pressurizes the raw material liquid CO2 to reach the storage pressure range specified by the carbon dioxide storage tank. Both the first and second gas-liquid separators operate at low temperatures. However, since complete insulation is impossible, external heat inevitably enters the gas-liquid separators through their outer shells, causing minor heating. This results in internal gas-liquid separation within both separators, achieving preliminary purification. To further purify the liquid CO2, it needs to be converted into gaseous carbon dioxide. To reduce energy consumption in this process, a vaporization heat exchanger is also included. During initial operation, the liquid CO2 is heated to gaseous CO2 using a vaporization heater. The gaseous CO2 is then sent to a purifier for further purification. The purified gas... The gaseous CO2 can be transported to a vaporization heat exchanger to exchange heat with the subsequently introduced low-temperature liquid CO2. At this point, it can be directly introduced into the purifier for purification without passing through a vaporization heater, greatly reducing energy consumption. The heat exchange lowers the temperature of the room-temperature gaseous CO2, reducing the energy required to convert it into liquid carbon dioxide. After exiting the vaporization heat exchanger, the gaseous CO2 enters a subcooling heat exchanger for further cooling until its temperature drops below its boiling point, becoming liquid. It is then separated by a second gas-liquid separator to obtain the finished liquid CO2. In this process, the subcooling heat exchanger uses the low-temperature non-condensable gas separated by the first and second gas-liquid separators as a cold source. A throttling valve can be used to further reduce the temperature of the non-condensable gas, thus requiring no additional energy consumption. This invention fully utilizes the energy of liquids and gases at different temperatures in each stage of the purification process, reducing the overall energy consumption of the purification process. The entire purification process does not require expensive purification equipment, resulting in extremely low purification costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the present invention;

[0031] Among them, 1-first gas-liquid separator, 2-second throttle valve, 3-subcooling heat exchanger, 4-first throttle valve, 5-second gas-liquid separator, 6-purifier, 7-gasification heater, 8-gasification heat exchanger, 9-liquid pressurization pump. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0033] In the description of the embodiments of this application, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] It should be noted that the non-condensable gas mentioned in this invention refers to a gas that will not condense into a liquid state under specific pressure and temperature. In addition, all devices and corresponding pipelines in this system that process materials at temperatures different from the ambient temperature are equipped with heat preservation measures. The heat preservation measures required for the first gas-liquid separator 1 and the second gas-liquid separator 5 need to control their daily heat exchange with the outside world to about 1% in order to achieve the purpose of micro-heating inside the first gas-liquid separator 1 and the second gas-liquid separator 5.

[0035] like Figure 1 As shown, a carbon dioxide recycling purification system includes:

[0036] Liquid pressurization pump 9 is used to compress the raw material liquid CO2, increasing the pressure of the raw material liquid CO2 to the storage pressure range specified by the carbon dioxide storage tank, that is, from 0.8 MPa to 2.5 MPa;

[0037] The first gas-liquid separator 1 is connected to the liquid pressurizing pump 9. The raw material liquid CO2 compressed by the liquid pressurizing pump 9 enters the first gas-liquid separator 1 for gas-liquid separation to obtain liquid CO2 and the first non-condensable gas. The gas outlet of the first gas-liquid separator 1 is connected to the low temperature circuit inlet of the subcooling heat exchanger 3.

[0038] The vaporization heat exchanger 8 includes a low-temperature circuit and a high-temperature circuit. The liquid outlet of the first gas-liquid separator 1 is connected to the low-temperature circuit. The raw material liquid CO2 is heated in the vaporization heat exchanger 8.

[0039] The gasification heater 7 is connected to the low-temperature circuit outlet of the gasification heat exchanger 8. The gasification heater 7 is used to heat liquid CO2 to convert it into gaseous CO2. The low-temperature circuit outlet of the gasification heat exchanger 8 is provided with a branch that is directly connected to the purifier 6 without passing through the gasification heater 7. A temperature sensor can be installed at the low-temperature circuit outlet of the gasification heat exchanger 8 to detect the temperature of the material discharged from the gasification heat exchanger 8. Valves are installed on the pipeline with the gasification heater 7 and on the pipeline directly connected to the purifier 6. One of the valves on the two pipelines can be closed according to the monitored temperature to achieve the effect of changing the treatment path according to the state of liquid CO2.

[0040] Purifier 6 is used to further purify gaseous CO2 to obtain refined gaseous CO2. Purifier 6 is connected to a high-temperature circuit. In this embodiment, purifier 6 includes desulfurization, denitrification, dehydration, and dust removal. Therefore, it includes an activated carbon fluidized bed adsorber, an adsorber, and a filter connected in sequence. The activated carbon fluidized bed adsorber removes sulfur and nitrate from gaseous CO2. Subcooling heat exchanger 3 includes a high-temperature circuit and a low-temperature circuit. The high-temperature circuit inlet of subcooling heat exchanger 3 is connected to the high-temperature circuit outlet of gasification heat exchanger 8. The gas outlet of the first gas-liquid separator 1 is connected to the low-temperature circuit of subcooling heat exchanger 3.

[0041] The second gas-liquid separator 5 has its inlet connected to the high-temperature circuit outlet of the subcooling heat exchanger 3. It is used to perform further gas-liquid separation on the refined liquid CO2 discharged from the high-temperature circuit of the subcooling heat exchanger 3 to obtain finished liquid CO2 and a second non-condensable gas. The gas outlet of the second gas-liquid separator 5 is connected to the low-temperature circuit of the subcooling heat exchanger 3.

[0042] A carbon dioxide recycling purification method, the specific steps of which are as follows:

[0043] S1: The raw material liquid CO2 is delivered to the liquid pressurization pump 9 for pressurization. The initial temperature of the raw material liquid CO2 entering the liquid pressurization pump 9 is -55℃ and the pressure is 0.8MPa. After being compressed by the liquid pressurization pump 9, the temperature is -54℃ and the pressure is 2.5MPa.

[0044] S2: Liquid CO2 at a temperature of -54℃ and a pressure of 2.5MPa enters the first gas-liquid separator 1 for gas-liquid separation, obtaining preliminarily purified liquid CO2 and a first non-condensable gas. The first non-condensable gas is transported from the gas outlet at the top of the first gas-liquid separator 1 to the low-temperature circuit of the subcooling heat exchanger 3, where it exchanges heat with the heat exchange medium of the subcooling heat exchanger 3 and serves as the cooling source for the subcooling heat exchanger 3.

[0045] S3: The preliminarily purified liquid CO2 enters the low-temperature circuit of the gasification heat exchanger 8 for heat exchange and temperature increase. If the liquid CO2 has been converted into gaseous CO2 after heat exchange in the gasification heat exchanger 8, the gaseous CO2 is directly sent to the purifier 6 for desulfurization, denitrification, dehydration, and dust removal, and further purified to obtain refined gaseous CO2. If the liquid CO2 has not been converted into gaseous CO2 after heat exchange in the gasification heat exchanger 8, the liquid CO2 will be heated by the gasification heater 7 to convert it into gaseous CO2, and then the gaseous CO2 will be sent to the purifier 6 for desulfurization, denitrification, dehydration, and dust removal, and further purified to obtain refined gaseous CO2.

[0046] S4: Refined gaseous CO2 is transported to the high-temperature circuit of the vaporization heat exchanger 8 for heat exchange, serving as the heat source for the vaporization heat exchanger 8. Then, the refined CO2, after heat exchange and with a reduced temperature, is transported to the high-temperature circuit of the subcooling heat exchanger 3 for heat exchange to a temperature of -55°C. During this process, the first non-condensable gas discharged from the first gas-liquid separator 1 and the second non-condensable gas discharged from the second gas-liquid separator 5 serve as the cooling source for the subcooling heat exchanger 3. In other embodiments, a first throttling valve 4 can be installed on the pipeline connecting the second gas-liquid separator 5 and the low-temperature circuit, and a second throttling valve 2 can be installed on the pipeline connecting the first gas-liquid separator 1 and the low-temperature circuit. By throttling and cooling the non-condensable gases through the first throttling valve 4 and the second throttling valve 2, the temperature of the heat exchange medium in the subcooling heat exchanger 3 is further reduced.

[0047] S5: The carbon dioxide after heat exchange in the subcooling heat exchanger 3 is fed into the second gas-liquid separator 5 for further gas-liquid separation to obtain the finished liquid CO2, which is then transported to the carbon dioxide liquid storage tank for storage; while the non-condensable gas separated by the second gas-liquid separator 5 is simply vented.

[0048] Current technology requires 90 to 100 kilowatt-hours of energy to purify one ton of carbon dioxide. Calculations show that the equipment cost in this embodiment is only 25% of similar equipment due to the absence of a fractionation tower and gas compressor; the unit energy consumption for purifying carbon dioxide is 1000 watt-hours per ton; the purity of the purified carbon dioxide obtained is 99.99%; 1000 (carbon dioxide processing capacity, kg) ÷ 3600 (time, sec) × (25 (post-processing pressure 2.5 MPa converted to mass, kg) - 8 (pre-processing pressure 0.8 MPa converted to mass, kg)) ÷ 9.8 (gravitational acceleration) = 0.368. Therefore, considering efficiency, taking one kilowatt-hour, the energy consumption of this invention is approximately 1% of the prior art.

[0049] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for purifying carbon dioxide through recycling, characterized in that: Includes the following steps: S1: Pressurize the raw material liquid CO2 to increase the pressure of CO2 from 0.8MPa to 2-2.5MPa. The temperature of the raw material liquid CO2 before pressurization is -50 to -60℃, and the temperature increases after pressurization. S2: The pressurized raw material liquid CO2 is separated into gas and liquid in the first gas-liquid separator to obtain pre-purified liquid CO2 and the first non-condensable gas. The first non-condensable gas is sent to the subcooling heat exchanger as the cooling source for the subcooling heat exchanger. S3: The preliminarily purified liquid CO2 is heated in the vaporization heat exchanger. If the liquid CO2 has been converted into gaseous CO2 after heat exchange in the vaporization heat exchanger, the gaseous CO2 is directly sent to the purifier for purification to obtain refined gaseous CO2. If the liquid CO2 has not been converted into gaseous CO2 after heat exchange in the vaporization heat exchanger, the liquid CO2 will be heated by the vaporization heater to convert it into gaseous CO2 before the gaseous CO2 is sent to the purifier for purification to obtain refined gaseous CO2. S4: The purified gaseous CO2 discharged from the purifier passes through the vaporization heat exchanger and the subcooling heat exchanger in sequence to exchange heat and cool down, and is then transformed into purified liquid CO2. S5: The refined liquid CO2 is sent to the second gas-liquid separator for further gas-liquid separation to obtain finished liquid CO2 and a second non-condensable gas. The second non-condensable gas is sent to the subcooling heat exchanger as the cooling source for the subcooling heat exchanger. The insulation measures for the first and second gas-liquid separators control their daily heat exchange with the outside environment to be 1%.

2. The carbon dioxide recycling purification method according to claim 1, characterized in that: The purification process of the S3 purifier includes: desulfurization, denitrification, dehydration, and dust removal.

3. A carbon dioxide recycling purification system, characterized in that: A method for implementing the carbon dioxide recycling purification method according to any one of claims 1-2 includes: A liquid pressurization pump is used to compress the raw material liquid CO2, increasing the pressure of the raw material liquid CO2 to the storage pressure range specified by the carbon dioxide storage tank; The first gas-liquid separator is used to separate the pressurized raw material liquid CO2 into gas and liquid components to obtain the first non-condensable gas and liquid CO2. The vaporization heat exchanger has its liquid outlet connected to the inlet of the low-temperature circuit of the first gas-liquid separator, which is used to increase the temperature of liquid CO2. The gasification heater, with the outlet of the low-temperature circuit of the gasification heat exchanger connected to the inlet of the gasification heater, is used to convert liquid CO2 into gaseous CO2; The purifier has a gasification heater outlet connected to the purifier inlet, used to purify gaseous CO2 to obtain refined gaseous CO2. The purifier outlet is connected to the high-temperature circuit inlet of the gasification heater to perform preliminary cooling of the gaseous CO2. The low-temperature circuit outlet of the gasification heat exchanger is provided with a branch that is directly connected to the purifier without passing through the gasification heater. The subcooling heat exchanger connects the outlet of the high-temperature circuit of the gasification heater to the inlet of the high-temperature circuit of the subcooling heat exchanger, and is used to convert refined gaseous CO2 into liquid CO2. The second gas-liquid separator is connected to the outlet of the high-temperature circuit of the subcooled heat exchanger and the inlet of the second gas-liquid separator. It is used to perform gas-liquid separation to obtain finished liquid CO2 and a second non-condensable gas. The gas outlets of the first and second gas-liquid separators are both connected to the inlet of the low-temperature circuit of the subcooling heat exchanger, and the outlet of the low-temperature circuit of the subcooling heat exchanger is connected to the outside. The liquid outlet of the second gas-liquid separator is connected to an external carbon dioxide liquid storage tank. The gas outlets of the first and second gas-liquid separators are connected, and then connected to the low-temperature inlet of the subcooling heat exchanger. The low-temperature circuit outlet of the subcooling heat exchanger is open to the atmosphere.

4. The carbon dioxide recycling purification system according to claim 3, characterized in that: A first throttling valve is installed on the pipeline connecting the second gas-liquid separator and the low-temperature circuit of the subcooling heat exchanger for throttling and cooling, and a second throttling valve is installed on the pipeline connecting the first gas-liquid separator and the low-temperature circuit of the subcooling heat exchanger for throttling and cooling.

5. A carbon dioxide recycling purification system according to claim 3, characterized in that: The liquid outlet of the second gas-liquid separator is connected to a carbon dioxide liquid storage tank.

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