A method for unloading carbon dioxide
By designing a carbon dioxide unloading system and method, utilizing heaters to control temperature and unloading pumps to manage pressure, the safety hazards in the unloading process of liquid carbon dioxide were resolved, and a stable unloading process was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SINOTECH ENERGY CO LTD
- Filing Date
- 2025-11-11
- Publication Date
- 2026-07-10
AI Technical Summary
During the unloading of liquid carbon dioxide, how to maintain the pressure of the storage tank, pre-cooling pipelines and equipment, pressurization and post-unloading treatment pipelines to avoid the formation of solid dry ice and pipeline rupture.
A carbon dioxide unloading system was designed, comprising a liquid carbon dioxide storage tank, a heater, an unloading pump, a receiving tank, and multiple pipelines and control valves. The gas temperature and pressure are controlled by the heater, the unloading process is managed by the unloading pump and control valves, and safety valves and sensors are set up to monitor the status. The system includes a high-pressure carbon dioxide storage cylinder and a reliquefaction branch pipeline to handle overpressure gas.
It achieves safe and stable unloading of liquid carbon dioxide, avoids water freezing and dry ice formation, and ensures the safe operation of the unloading system.
Smart Images
Figure CN122359639A_ABST
Abstract
Description
[0001] This application claims priority to Chinese patent application CN2025101611320, filed on February 13, 2025, the contents of which are incorporated herein by reference. Technical Field
[0002] This invention relates to the field of carbon capture technology, and more specifically to a method for unloading carbon dioxide. Background Technology
[0003] In recent years, the combustion of fossil fuels has caused a series of environmental degradations, and the resulting greenhouse effect is gradually threatening human survival. Carbon dioxide (CO2) is the main factor causing global warming, a fact now universally acknowledged worldwide. Carbon Capture, Utilization and Storage (CCUS) technology, as an emerging technology that promises to achieve large-scale low-carbon utilization of fossil energy, has attracted high attention from the international community.
[0004] Carbon capture and storage (CCS) technology for ships is an important means and effective approach to achieving this goal. A key step in CCS is the compression and liquefaction of CO2 gas captured during ship operation, storing it in liquid tanks and then directly transferring it to CO2 carriers at ports or unloading it at specialized ports.
[0005] The storage of liquid CO2 requires high pressure. If the pressure is too low, solid dry ice will form, hindering CO2 transportation and even causing pipeline rupture. Therefore, during the unloading of liquid carbon dioxide, it is necessary to solve problems such as how to maintain the pressure of the storage tank, how to pre-cool the pipelines and equipment, how to pressurize the receiving tank, and how to handle the pipelines after unloading. Summary of the Invention
[0006] The purpose of this invention is to provide a safe and reliable unloading system and method for liquid carbon dioxide storage tanks.
[0007] To achieve the above objectives, the present invention provides a carbon dioxide unloading system, comprising a liquid carbon dioxide storage tank, a heater, an unloading pump disposed in the liquid carbon dioxide storage tank, a receiving tank, and several pipelines and control valves. The outlet of the liquid carbon dioxide storage tank is divided into a first pipeline and a second pipeline. The first pipeline leads to the heater, and the second pipeline leads to the first inlet of the receiving tank via a fifth control valve. The first pipeline is provided with a first control valve before entering the heater. The carbon dioxide outlet of the heater is divided into a third pipeline and a fourth pipeline after passing through the second control valve. The third pipeline is provided with a third control valve and is connected to the second inlet of the receiving tank. The fourth pipeline returns to the liquid carbon dioxide storage tank after passing through an eighth control valve.
[0008] The unloading system is provided with at least one pipeline leading to the atmosphere, and the pipeline is equipped with a control valve to control its opening and closing.
[0009] Preferably, a fifth control valve is provided on the second pipeline.
[0010] Preferably, the fourth pipeline is further provided with a reliquefaction branch pipeline for reliquefying the overpressurized carbon dioxide gas.
[0011] Preferably, a branch pipeline is provided between the third control valve and the second inlet of the receiving tank, and the branch pipeline is connected to the atmosphere after passing through the fourth control valve; the second pipeline is connected to an outlet connected to the atmosphere, and the opening and closing of the outlet is controlled by the sixth control valve; the fourth pipeline is connected to an outlet connected to the atmosphere, and the opening and closing of the outlet is controlled by the tenth control valve.
[0012] Preferably, a high-pressure carbon dioxide storage cylinder is also provided on one side of the second pipeline for inputting high-pressure carbon dioxide into the second pipeline.
[0013] Preferably, the first, second, third, and fourth pipelines are all equipped with safety valves.
[0014] Preferably, the liquid carbon dioxide storage tank, each pipeline and receiving tank are equipped with temperature sensors and pressure sensors, and at least one moisture content monitor is also installed in the pipeline.
[0015] The present invention also discloses the above-mentioned unloading method using a carbon dioxide unloading system, comprising:
[0016] S1, start the unloading pump and open the first control valve, the second control valve and the third control valve, and adjust the flow rate of the heating medium in the heater so that the gas temperature at the heater outlet is above 5°C.
[0017] S2, open the control valve of the pipeline leading to the atmosphere to purge the pipeline in the unloading system with carbon dioxide gas to remove water vapor from the pipeline.
[0018] S3, close the control valve of the pipeline leading to the atmosphere, open the second inlet of the receiving tank, adjust the flow rate of the heating medium in the heater so that the gas temperature at the heater outlet is above -20°C, and slowly fill the receiving tank with carbon dioxide gas at this temperature until the pressure of the receiving tank reaches 8 bar.
[0019] S4, close the first control valve, the second control valve, and the third control valve, and open the fifth control valve and the first inlet of the receiving tank to allow the pressure inside the receiving tank to continue to rise; when the pressure in the receiving tank is within 0.5 bar of the pressure inside the liquid carbon dioxide storage tank, open the third control valve and the eighth control valve to connect the return gas pipeline;
[0020] S5, after the liquid carbon dioxide is unloaded, close the first control valve, the second control valve, the third control valve, and the fifth control valve.
[0021] Preferably, a high-pressure carbon dioxide storage cylinder is provided on one side of the second pipeline. After step S5, the high-pressure carbon dioxide storage cylinder is opened to fill the second pipeline with gas, which is used to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.
[0022] Preferably, in step S4, if the pressure rise rate in the receiving tank is slow, the first control valve, the second control valve, and the third control valve are opened to vaporize a small amount of carbon dioxide into the receiving tank. When the pressure in the receiving tank is within 0.5 bar of the pressure in the liquid carbon dioxide storage tank, the first control valve and the second control valve are closed.
[0023] Preferably, the fourth pipeline is further provided with a reliquefaction branch pipeline for reliquefying the overpressurized carbon dioxide gas. In step S4, if the liquid carbon dioxide storage tank and receiving tank are overpressurized during the unloading process, the overpressurized gas is injected into the BOG reliquefaction branch pipeline to release it into the BOG reliquefaction system.
[0024] The beneficial effects of this invention include: through the improved unloading process design, the safety hazards such as water freezing, carbon dioxide forming dry ice, and excessive pressure in the unloading system are properly solved, so that the unloading system can operate safely and stably. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the ship carbon dioxide unloading system of the present invention.
[0026] Reference numerals in the attached diagram: 1-Liquid carbon dioxide storage tank; 2-Heater; 3-Unloading pump; 41-First control valve; 42-Second control valve; 43-Third control valve; 44-Fourth control valve; 45-Fifth control valve; 46-Sixth control valve; 47-Seventh control valve; 48-Eighth control valve; 49-Ninth control valve; 40-Tenth control valve; 51-First inlet of receiving tank; 52-Second inlet of receiving tank; 61-First pipeline; 62-Second pipeline; 63-Third pipeline; 64-Fourth pipeline. Detailed Implementation
[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] In the description of this invention, it should be noted that the terms "front", "rear", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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 limiting this invention.
[0029] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and do not refer to a limitation on time sequence, quantity, or importance. They should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, but are merely used to distinguish one technical feature from another in this technical solution. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Similarly, qualifiers such as "a" appearing herein do not refer to a limitation on quantity, but rather describe technical features not mentioned above. Likewise, unless a noun is modified by a specific quantifier, it should be considered herein to include both singular and plural forms; the technical solution may include a singular number of that technical feature or a plural number of that technical feature. Similarly, modifiers such as "approximately" or "about" appearing before numerals generally include the number itself, and their specific meaning should be understood in conjunction with the context.
[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0031] Unless otherwise specified, each aspect or embodiment defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.
[0032] like Figure 1 As shown, this invention discloses a carbon dioxide unloading system. It includes a liquid carbon dioxide storage tank 1, a heater 2, an unloading pump 3 installed in the liquid carbon dioxide storage tank 1, and a receiving tank (not shown). Furthermore, the unloading system also includes several pipelines and control valves.
[0033] The unloading pump 3 is used to extract liquid carbon dioxide from the liquid carbon dioxide storage tank 1. The outlet of the liquid carbon dioxide storage tank 1 is divided into two paths, referred to as the first pipeline 61 and the second pipeline 62. The first pipeline 61 leads to the heater 2, and the second pipeline 62 leads to the first inlet 51 of the receiving tank. The liquid carbon dioxide enters the receiving tank through the second pipeline 62. In some embodiments, the heat fluid in the heater 2 is water to save costs and meet the heating requirements for heating liquid carbon dioxide. A first control valve 41 is installed between the liquid carbon dioxide storage tank 1 and the heater 2 to control the flow rate of liquid carbon dioxide entering the heater 2. A seventh control valve 47 is used to control the water flow rate required by the heater 2. The carbon dioxide outlet of the heater 2 is divided into two paths after passing through the second control valve 42, referred to as the third pipeline 63 and the fourth pipeline 64. The third pipeline 63 is equipped with a third control valve 43 and is connected to the second inlet 52 of the receiving tank. The fourth pipeline 64 returns to the liquid carbon dioxide storage tank 1 after passing through an eighth control valve 48. The unloading system needs to have at least one pipeline connected to the atmosphere. Figure 1 As shown, a branch pipeline is provided between the third control valve 43 and the second inlet 52 of the receiving tank. This branch pipeline passes through the fourth control valve 44 and then leads to the atmosphere. The first inlet 51 and the second inlet 52 of the receiving tank are different inlets of the same receiving tank.
[0034] In some embodiments, the second pipeline 62 is provided with a fifth control valve 45 to control the flow rate of liquid carbon dioxide.
[0035] In some embodiments, the fourth pipeline 64 is further provided with a branch pipeline, namely a BOG reliquefaction branch pipeline, which is controlled by the ninth control valve 49 to open and close.
[0036] In some embodiments, a high-pressure carbon dioxide storage cylinder is also provided on one side of the second pipeline 62 for introducing high-pressure carbon dioxide into the second pipeline 62. The pressure inside the high-pressure carbon dioxide storage cylinder is above 25 bar.
[0037] In some embodiments, the second conduit 62 is connected to an outlet to the atmosphere, and the opening and closing of this outlet is controlled by a sixth control valve 46. The fourth conduit 64 is connected to an outlet to the atmosphere, and the opening and closing of this outlet is controlled by a tenth control valve 40.
[0038] In some embodiments, the first pipeline 61, the second pipeline 62, the third pipeline 63, and the fourth pipeline 64 are all equipped with safety valves.
[0039] In some embodiments, the liquid carbon dioxide storage tank 1, each pipeline, and the receiving tank are equipped with temperature and pressure sensors to monitor and control the operating status of the ship's carbon dioxide unloading system. The third pipeline 63 or the discharge main is also equipped with a water content monitor.
[0040] The method of operating the ship's carbon dioxide unloading system (i.e., the carbon dioxide unloading method) is illustrated in conjunction with the following embodiments.
[0041] Example 1
[0042] The method for unloading carbon dioxide includes:
[0043] S1: Initially, all valves in the system are closed, and the first inlet 51 and the second inlet 52 of the receiving tank are also closed. First, start the unloading pump 3 and open the first control valve 41, the second control valve 42, the third control valve 43, and the seventh control valve 47. Adjust the flow rate of the heating medium by adjusting the seventh control valve 47 so that the gas temperature at the heater outlet is above 5°C, and proceed to step S2.
[0044] Step S2 is the dehumidification stage. After step S1 is completed, the fourth control valve 44, the fifth control valve 45, the sixth control valve 46, and the tenth control valve 40 are opened to allow carbon dioxide gas to purge the first pipeline 61, the second pipeline 62, the third pipeline 63, and the fourth pipeline 64, thereby removing water vapor from the pipelines and preventing icing in subsequent processes. This step is completed when the moisture content in each pipeline is below 30 ppm.
[0045] S3. After dehumidification, the receiving tank needs to be pressurized. Since carbon dioxide easily forms dry ice at low temperatures, the pressure in the receiving tank should be greater than 8 bar before liquid carbon dioxide enters to prevent dry ice formation and potential safety hazards. Close the fourth control valve 44, fifth control valve 45, sixth control valve 46, and tenth control valve 40. Open the second inlet 52 of the receiving tank. Adjust the seventh control valve 47 to ensure the gas temperature at the heater outlet is above -20°C. Slowly fill the receiving tank with carbon dioxide gas at this temperature until the pressure in the receiving tank reaches 8 bar.
[0046] S4, when the pressure in the receiving tank reaches 8 bar, the first control valve 41, the second control valve 42, and the third control valve 43 are closed, and the fifth control valve 45 and the first inlet 51 of the receiving tank are opened, thereby delivering liquid carbon dioxide to the receiving tank. At this time, the pressure inside the receiving tank will continue to rise. In some embodiments, if the pressure rise rate inside the receiving tank is slow, the first control valve 41, the second control valve 42, and the third control valve 43 are opened to vaporize a small amount of carbon dioxide and enter the receiving tank, thereby increasing the pressure rise rate inside the receiving tank more quickly. When the pressure in the receiving tank is within 0.5 bar of the pressure in the liquid carbon dioxide storage tank 1, the first control valve 41 and the second control valve 42 are closed, and the third control valve 43 and the eighth control valve 8 are opened to connect the return gas pipeline. This allows the high-pressure carbon dioxide gas in the receiving tank to return to the liquid carbon dioxide storage tank 1, preventing the pressure inside the receiving tank from being too high, which would prevent the liquid carbon dioxide from being injected. In some implementations, if the liquid carbon dioxide storage tank 1 and the receiving tank experience overpressure during the unloading process, the ninth control valve 49 is opened to inject the overpressure gas into the BOG reliquefaction branch pipeline, allowing it to be released into the BOG reliquefaction system.
[0047] S5, after the liquid carbon dioxide is unloaded, close the first control valve 41, the second control valve 42, the third control valve 43, and the fifth control valve 45. The pipeline is still filled with liquid carbon dioxide after unloading. To transport the liquid carbon dioxide in the pipeline to the receiving tank, a high-pressure carbon dioxide storage cylinder is installed on one side of the second pipeline. Open the high-pressure carbon dioxide storage cylinder to fill the second pipeline with gas, which is used to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.
[0048] This invention is primarily used for unloading liquid carbon dioxide from ships, where the liquid carbon dioxide storage tank 1 is a marine liquid carbon dioxide storage tank, and the heat fluid in the heater 2 is seawater. However, this invention can also be used for unloading carbon dioxide on land.
[0049] In summary, due to the physical properties of liquid carbon dioxide requiring high pressure and low temperature, its unloading is a complex and dangerous process. This invention, through a well-designed unloading process, effectively solves the safety hazards such as water freezing, carbon dioxide forming dry ice, and excessive pressure within the unloading system, enabling the unloading system to operate safely and stably.
[0050] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A carbon dioxide unloading method, wherein the carbon dioxide unloading method uses a carbon dioxide unloading system, the carbon dioxide unloading system comprising a liquid carbon dioxide storage tank, a heater, an unloading pump disposed in the liquid carbon dioxide storage tank, a receiving tank, and a plurality of pipelines and control valves, characterized in that, The outlet of the liquid carbon dioxide storage tank is divided into a first pipeline and a second pipeline. The first pipeline leads to the heater, and the second pipeline leads to the first inlet of the receiving tank through a fifth control valve. The first pipeline is equipped with a first control valve before entering the heater. The carbon dioxide outlet of the heater is divided into a third pipeline and a fourth pipeline after passing through the second control valve. The third pipeline is equipped with a third control valve and is connected to the second inlet of the receiving tank. The fourth pipeline returns to the liquid carbon dioxide storage tank after passing through an eighth control valve. The unloading system is provided with at least one pipeline leading to the atmosphere, and the pipeline is equipped with a control valve to control its opening and closing; the fourth pipeline is also provided with a reliquefaction branch pipeline for reliquefying the overpressurized carbon dioxide gas. The carbon dioxide unloading method includes: S1, start the unloading pump and open the first control valve, the second control valve and the third control valve, and adjust the flow rate of the heating medium in the heater so that the gas temperature at the heater outlet is above 5°C. S2, open the control valve of the pipeline leading to the atmosphere to purge the pipeline in the unloading system with carbon dioxide gas to remove water vapor from the pipeline; S3, close the control valve of the pipeline leading to the atmosphere, open the second inlet of the receiving tank, adjust the flow rate of the heating medium in the heater so that the gas temperature at the heater outlet is above -20°C, and slowly fill the receiving tank with carbon dioxide gas at this temperature until the pressure of the receiving tank reaches 8 bar. S4, close the first control valve, the second control valve, and the third control valve, and open the fifth control valve and the first inlet of the receiving tank to allow the pressure inside the receiving tank to continue to rise; when the pressure in the receiving tank is within 0.5 bar of the pressure inside the liquid carbon dioxide storage tank, open the third control valve and the eighth control valve to connect the return gas pipeline. If the liquid carbon dioxide storage tank and receiving tank become overpressurized during the unloading process, the overpressurized gas will be injected into the BOG reliquefaction branch pipeline to release it into the BOG reliquefaction system. In step S4, if the pressure inside the receiving tank rises slowly, the first control valve, the second control valve, and the third control valve are opened to vaporize a small amount of carbon dioxide and enter the receiving tank. When the pressure in the receiving tank is within 0.5 bar of the pressure in the liquid carbon dioxide storage tank, the first control valve and the second control valve are closed. S5, after the liquid carbon dioxide is unloaded, close the first control valve, the second control valve, the third control valve, and the fifth control valve; A high-pressure carbon dioxide storage cylinder is provided on one side of the second pipeline. After step S5, the high-pressure carbon dioxide storage cylinder is opened to fill the second pipeline with gas, which is used to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.