Carbon dioxide unloading system and method

Abstract

The carbon dioxide unloading system comprises a liquid carbon dioxide storage tank, a heater, an unloading pump, a receiving tank, a plurality of pipelines and a control valve, an outlet of the liquid carbon dioxide storage tank is divided into a first pipeline and a second pipeline, the first pipeline is communicated with the heater, and the second pipeline is communicated with the receiving tank. The second pipeline is communicated to a first inlet of the receiving tank through a fifth control valve; the first pipeline is provided with a first control valve before entering the heater; the carbon dioxide outlet end 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 communicated with a second inlet of the receiving tank, and the fourth pipeline passes through an eighth control valve and then returns to the liquid carbon dioxide storage tank; the unloading system is provided with at least one pipeline leading to the atmosphere. Through the perfect unloading process flow design, the potential safety hazards that water is frozen, carbon dioxide forms dry ice, the pressure in the unloading system is too high and the like are properly solved, and the unloading system can operate safely and stably.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon capture, and in particular to a carbon dioxide unloading system and method. Background Art

[0002] In recent years, the burning of fossil fuels has caused a series of environmental deterioration, and the resulting greenhouse effect has gradually threatened human survival. Carbon dioxide (CO2) is the main factor causing global warming, which has been unanimously recognized worldwide. Carbon Capture, Utilization and Storage (CCUS) technology, as an emerging technology that is expected to achieve large-scale low-carbon utilization of fossil energy, has received great attention from the international community.

[0003] Carbon capture technology for ships is an important means and effective way to achieve this goal. The CO2 gas captured during the operation of the ship is compressed and liquefied and stored in liquid storage tanks, and then directly transferred to CO2 transport ships at the port or unloaded at a professional port, which is an important step in carbon capture and storage.

[0004] The storage of liquid CO2 requires a high pressure. If the pressure is too low, solid dry ice will be formed, which will hinder the transportation of CO2 and even cause the rupture of the pipeline. Therefore, in the unloading of liquid CO2, how to maintain the pressure of the storage tank, how to pre-cool the pipeline and equipment, how to pressurize the receiving tank, and how to deal with the pipeline after unloading are all problems that need to be solved. Summary of the invention

[0005] The object of the present invention is to provide a safe and reliable unloading system and method for a liquid carbon dioxide storage tank.

[0006] In order to achieve the above-mentioned object, the present invention provides a carbon dioxide unloading system, comprising a liquid carbon dioxide storage tank, a heater, an unloading pump arranged in the liquid carbon dioxide storage tank, a receiving tank, and a plurality of pipelines and control valves, wherein the outlet of the liquid carbon dioxide storage tank is divided into a first pipeline and a second pipeline, wherein 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 provided with a first control valve before entering the heater; the carbon dioxide outlet end 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, and 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 a control valve is provided on the pipeline to control its opening and closing.

[0007] Preferably, a fifth control valve is provided on the second pipeline.

[0008] Preferably, the fourth pipeline is further provided with a reliquefaction branch pipeline for reliquefying the overpressure carbon dioxide gas.

[0009] Preferably, a branch pipeline is provided between the third control valve and the second inlet of the receiving tank, and the branch pipeline leads to the atmosphere after passing through the fourth control valve; the second pipeline is connected to an outlet leading 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 leading to the atmosphere, and the opening and closing of the outlet is controlled by the tenth control valve.

[0010] Preferably, a high-pressure carbon dioxide storage cylinder is further provided on one side of the second pipeline for inputting high-pressure carbon dioxide into the second pipeline.

[0011] Preferably, the first pipeline, the second pipeline, the third pipeline and the fourth pipeline are all provided with safety valves.

[0012] Preferably, the liquid carbon dioxide storage tank, each pipeline and the receiving tank are provided with a temperature sensor and a pressure sensor, and at least one water content monitor is also provided in the pipeline.

[0013] The present invention also discloses an unloading method using the carbon dioxide unloading system, comprising: 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, opening the control valve of the pipeline leading to the atmosphere, so that the carbon dioxide gas is purged through the pipeline in the unloading system to discharge the water vapor in the pipeline; S3, closing the control valve of the pipeline leading to the atmosphere, opening the second inlet of the receiving tank, adjusting the flow rate of the heating medium in the heater so that the gas temperature at the outlet of the heater is above -20°C, and slowly filling the carbon dioxide gas at this temperature into the receiving tank 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, open the fifth control valve and the first inlet of the receiving tank, so that the pressure in the receiving tank continues to rise; when the pressure of the receiving tank is within 0.5 bar of the pressure in the liquid carbon dioxide storage tank, open the third control valve and the eighth control valve to connect the return air pipeline; S5, after completing the unloading of the liquid carbon dioxide, close the first control valve, the second control valve, the third control valve, and the fifth control valve.

[0014] Preferably, a high-pressure carbon dioxide gas cylinder is provided on one side of the second pipeline. After step S5, the high-pressure carbon dioxide gas cylinder is opened to inflate the second pipeline to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.

[0015] Preferably, in step S4, if the pressure in 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 into the receiving tank. When the pressure of the receiving tank differs from the pressure in the liquid carbon dioxide storage tank by less than 0.5 bar, the first control valve and the second control valve are closed.

[0016] Preferably, the fourth pipeline is further provided with a reliquefaction branch pipeline for reliquefying the overpressure carbon dioxide gas. In step S4, if the liquid carbon dioxide storage tank and the receiving tank are overpressured during the unloading process, the overpressure gas is injected into the BOG reliquefaction branch pipeline to be discharged into the BOG reliquefaction system.

[0017] The beneficial effects of the present invention include: through a perfect unloading process flow 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a ship carbon dioxide unloading system according to the present invention.

[0019] Figure markings: 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 DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the terms "front", "rear", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0022] In addition, the terms "first", "second", etc. are only used for descriptive purposes, and do not refer to the limitation of time sequence, quantity, or importance. They cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features, but are only for distinguishing one technical feature from another technical feature in the technical solution. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically specified. Similarly, the qualifiers similar to "one" appearing in this article do not refer to the limitation of quantity, but describe technical features that have not appeared in the previous text. Similarly, unless it is a noun modified by a specific quantitative quantifier, it should be regarded as including both singular and plural forms in this article, and the technical solution can include both singular and plural technical features. Similarly, modifiers similar to "approximately" and "approximately" appearing before the numerals in this article usually include the number itself, and their specific meanings should be understood in conjunction with the context.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] Unless clearly indicated to the contrary, each aspect or embodiment defined herein may be combined with any other aspect or embodiments. In particular, any feature indicated as preferred or advantageous may be combined with any other feature indicated as preferred or advantageous.

[0025] like Figure 1 As shown, the present invention discloses a carbon dioxide unloading system. It comprises a liquid carbon dioxide storage tank 1, a heater 2, an unloading pump 3 arranged in the liquid carbon dioxide storage tank 1, and a receiving tank (not shown in the figure). In addition, the unloading system also comprises a number of pipelines and control valves.

[0026] The unloading pump 3 is used to extract the 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 routes, which are respectively denoted 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, and the liquid carbon dioxide enters the receiving tank through the second pipeline 62. In some embodiments, the hot fluid in the heater 2 is water, in order to save costs and meet the heating requirements for heating liquid carbon dioxide. A first control valve 41 is provided between the liquid carbon dioxide storage tank 1 and the heater 2 to control the flow of liquid carbon dioxide into the heater 2. The seventh control valve 47 is used to control the water flow required by the heater 2. The carbon dioxide outlet of the heater 2 is divided into two routes after passing through the second control valve 42, which are respectively denoted as the third pipeline 63 and the fourth pipeline 64. The third pipeline 63 is provided with a third control valve 43, which 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 the eighth control valve 48. Among them, the unloading system needs to be provided with at least one pipeline leading to the atmosphere. As Figure 1 As shown, a branch pipeline is provided between the third control valve 43 and the second inlet 52 of the receiving tank, and the branch pipeline is connected to the atmosphere after passing through the fourth control valve 44. The first inlet 51 of the receiving tank and the second inlet 52 of the receiving tank are different inlets of the same receiving tank.

[0027] In some implementations, a fifth control valve 45 is disposed on the second pipeline 62 to control the flow rate of the liquid carbon dioxide.

[0028] In some implementations, the fourth pipeline 64 is further provided with a branch pipeline, namely, a BOG reliquefaction branch pipeline, the opening and closing of which is controlled by a ninth control valve 49 .

[0029] In some embodiments, a high-pressure carbon dioxide gas cylinder is further provided on one side of the second pipeline 62, for inputting high-pressure carbon dioxide into the second pipeline 62. The pressure in the high-pressure carbon dioxide gas cylinder is above 25 bar.

[0030] In some embodiments, the second pipeline 62 is connected to an outlet leading to the atmosphere, and the outlet is controlled by the sixth control valve 46. The fourth pipeline 64 is connected to an outlet leading to the atmosphere, and the outlet is controlled by the tenth control valve 40.

[0031] In some implementations, the first pipeline 61 , the second pipeline 62 , the third pipeline 63 , and the fourth pipeline 64 are all provided with safety valves.

[0032] In some embodiments, the liquid carbon dioxide storage tank 1, each pipeline and the receiving tank are equipped with temperature sensors 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 pipe is also equipped with a water content monitor.

[0033] The method for operating the ship carbon dioxide unloading system (ie, the carbon dioxide unloading method) is described in conjunction with the following embodiments.

[0034] Example 1

[0035] The method for unloading carbon dioxide comprises: S1, all valves in the system are initially closed, and the first inlet 51 and the second inlet 52 of the receiving tank are also closed. First, the unloading pump 3 is started and the first control valve 41, the second control valve 42, the third control valve 43 and the seventh control valve 47 are opened. The flow rate of the heating medium is controlled by adjusting the seventh control valve 47 so that the gas temperature at the heater outlet is above 5°C, and then step S2 is entered.

[0036] S2, this step 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 so that the carbon dioxide gas is purged to the first pipeline 61, the second pipeline 62, the third pipeline 63, and the fourth pipeline 64 to discharge the water vapor in the pipeline to prevent ice formation in the subsequent process. This step is completed until the water content in each pipeline is below 30ppm.

[0037] S3, after dehumidification is completed, the receiving tank needs to be pressurized. Since carbon dioxide is easily throttled to form dry ice at low temperatures, the pressure of the receiving tank should be greater than 8 bar before the liquid carbon dioxide enters the receiving tank to prevent the carbon dioxide from forming dry ice and causing safety hazards. Close the fourth control valve 44, the fifth control valve 45, the sixth control valve 46, and the tenth control valve 40, open the second inlet 52 of the receiving tank, adjust the seventh control valve 47, so that the gas temperature at the outlet of the heater is above -20°C, and slowly fill the carbon dioxide gas at this temperature into the receiving tank until the pressure of the receiving tank reaches 8 bar.

[0038] S4, when the pressure of the receiving tank reaches 8bar, close the first control valve 41, the second control valve 42, and the third control valve 43, open the fifth control valve 45 and the first inlet 51 of the receiving tank, so as to deliver the liquid carbon dioxide to the receiving tank. At this time, the pressure in the receiving tank will continue to rise. In some embodiments, if the pressure in the receiving tank rises slowly, open the first control valve 41, the second control valve 42, and the third control valve 43 to vaporize a small amount of carbon dioxide into the receiving tank to increase the pressure rise rate in the receiving tank faster. When the pressure of the receiving tank differs from the pressure in the liquid carbon dioxide storage tank 1 by less than 0.5bar, make the first control valve 41 and the second control valve 42 in a closed state, open the third control valve 43 and the eighth control valve 48, and connect the return air pipeline. The high-pressure carbon dioxide gas in the receiving tank can return to the liquid carbon dioxide storage tank 1 to avoid excessive pressure in the receiving tank, which makes it impossible to inject liquid carbon dioxide. In some embodiments, if the liquid carbon dioxide storage tank 1 and the receiving tank are over-pressurized during the unloading process, the ninth control valve 49 is opened to inject the over-pressure gas into the BOG reliquefaction branch pipeline to discharge it into the BOG reliquefaction system.

[0039] S5, after the liquid carbon dioxide is unloaded, the first control valve 41, the second control valve 42, the third control valve 43, and the fifth control valve 45 are closed. After unloading, the pipeline is still full of liquid carbon dioxide. In order to transport the liquid carbon dioxide in the pipeline to the receiving tank, a high-pressure carbon dioxide gas cylinder is provided on one side of the second pipeline 62. The high-pressure carbon dioxide gas cylinder is opened to inflate the second pipeline 62, so as to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.

[0040] The present invention is mainly used for unloading liquid carbon dioxide on board a ship, in which case the liquid carbon dioxide storage tank 1 is a ship-used liquid carbon dioxide storage tank, and the thermal fluid in the heater 2 is seawater. However, the present invention can also be used for unloading carbon dioxide on land.

[0041] In summary, due to the physical properties of liquid carbon dioxide itself requiring high pressure and low temperature, its unloading is a complex and dangerous process. The present invention properly solves the safety hazards such as water freezing, carbon dioxide forming dry ice, and excessive pressure in the unloading system through a complete unloading process flow design, so that the unloading system can operate safely and stably.

[0042] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A carbon dioxide unloading system, comprising a liquid carbon dioxide storage tank, a heater, an unloading pump and a receiving tank provided in the liquid carbon dioxide storage 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 provided with a first control valve before entering the heater; the carbon dioxide outlet end 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, and 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 a control valve is provided on the pipeline to control its opening and closing.

2. The carbon dioxide unloading system according to claim 1, characterized in that: The second pipeline is provided with a fifth control valve.

3. The carbon dioxide unloading system according to claim 1, characterized in that: The fourth pipeline is also provided with a reliquefaction branch pipeline for reliquefying the overpressure carbon dioxide gas.

4. The carbon dioxide unloading system according to claim 1, characterized in that: A branch pipeline is set between the third control valve and the second inlet of the receiving tank, and the branch pipeline leads to the atmosphere after passing through the fourth control valve; the second pipeline is connected to an outlet leading 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 leading to the atmosphere, and the opening and closing of the outlet is controlled by the tenth control valve.

5. The carbon dioxide unloading system according to claim 1, characterized in that: A high-pressure carbon dioxide gas cylinder is also provided on one side of the second pipeline for inputting high-pressure carbon dioxide into the second pipeline.

6. The carbon dioxide unloading system according to claim 1, characterized in that: The first pipeline, the second pipeline, the third pipeline and the fourth pipeline are all provided with safety valves.

7. The carbon dioxide unloading system according to claim 1, characterized in that: The liquid carbon dioxide storage tank, each pipeline and the receiving tank are all provided with a temperature sensor and a pressure sensor, and at least one water content monitor is also provided in the pipeline.

8. A method for unloading carbon dioxide using the carbon dioxide unloading system according to any one of claims 1 to 7, characterized in that: Include: 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, opening the control valve of the pipeline leading to the atmosphere, so that the carbon dioxide gas is purged through the pipeline in the unloading system to discharge the water vapor in the pipeline; S3, closing the control valve of the pipeline leading to the atmosphere, opening the second inlet of the receiving tank, adjusting the flow rate of the heating medium in the heater so that the gas temperature at the outlet of the heater is above -20°C, and slowly filling the carbon dioxide gas at this temperature into the receiving tank 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, open the fifth control valve and the first inlet of the receiving tank, so that the pressure in the receiving tank continues to rise; when the pressure of the receiving tank is within 0.5 bar of the pressure in the liquid carbon dioxide storage tank, open the third control valve and the eighth control valve to connect the return air pipeline; S5, after completing the unloading of the liquid carbon dioxide, close the first control valve, the second control valve, the third control valve, and the fifth control valve.

9. The uninstallation method according to claim 8, characterized in that: A high-pressure carbon dioxide gas cylinder is provided on one side of the second pipeline. After step S5, the high-pressure carbon dioxide gas cylinder is opened to inflate the second pipeline to blow the residual liquid carbon dioxide in the pipeline into the receiving tank.

10. The uninstallation method according to claim 8, characterized in that: In step S4, if the pressure in 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 into the receiving tank. When the pressure of the receiving tank differs from the pressure in the liquid carbon dioxide storage tank by less than 0.5 bar, the first control valve and the second control valve are closed.

11. The uninstallation method according to claim 8, characterized in that: The fourth pipeline is also provided with a reliquefaction branch pipeline for reliquefying the overpressure carbon dioxide gas. In step S4, if the liquid carbon dioxide storage tank and the receiving tank are overpressured during the unloading process, the overpressure gas is injected into the BOG reliquefaction branch pipeline to be discharged into the BOG reliquefaction system.

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