A liquefied carbon dioxide transport ship with variable design pressure

Abstract

The present invention discloses a liquefied carbon dioxide transport ship with a variable design pressure, comprising a low-pressure storage tank 4 for storing liquid carbon dioxide; the outlet of each of the low-pressure storage tanks 4 is connected to a high-pressure compressor 5 via a valve and a pipeline; the high-pressure compressor 5 is connected to a high-pressure storage tank 7 via a liquid cargo handling system 6; the liquid cargo handling system 6 is used to liquefy the collected carbon dioxide gas. The low-pressure storage tank 4 collects liquid carbon dioxide on shore and transports it to a deep-sea area or to a designated injection platform. The present invention uses a low-pressure storage tank instead of a traditional high-pressure storage tank, which is safer and more reliable on the one hand, and on the other hand reduces the thickness of the tank body, reduces construction costs and difficulty, and increases the added value of the product. The present invention sets up an independent high-pressure storage tank, which can be heated and pressurized when the cargo is unloaded, so as to facilitate the unloading of the cargo.

Description

Technical Field

[0001] The present invention relates to a transport ship, and more particularly to a liquefied carbon dioxide transport ship with variable design pressure. Background Art

[0002] The basic principle of liquefied carbon dioxide transportation is to utilize the triple point of carbon dioxide. At temperatures of -56°C and pressures above 6 kg, carbon dioxide remains liquid. In this state, it is compact and fluid, making it easy to store and transport. Liquefied carbon dioxide is stored and transported using a semi-refrigerated, semi-pressurized method. The design temperature is -56°C, and the pressure range is typically 6 kg to 18 kg. Carbon dioxide carriers generally use C-type storage tanks, which can withstand high pressures and have certain insulation properties.

[0003] like Figure 1 As shown, a typical transport and storage ship includes an office and living area 2, an engine room area 3, and a storage tank 4 and a liquid cargo handling system 6 for storing liquid carbon dioxide. In the figure, multiple liquid carbon dioxide storage tanks 4 are mainly connected to each other in parallel. Taking into account the characteristics of the triple point of carbon dioxide, carbon dioxide is generally stored in a C-type tank using a high-pressure and low-temperature storage method with a design pressure of up to 20 kilograms, which is far away from the triple point pressure. The main considerations are: on the one hand, the storage method itself has a relatively long pressure accumulation time and can withstand the increase in pipe pressure caused by temperature increase; on the other hand, the high-pressure designed liquid cargo handling system 6 can match the pressure of the loading and unloading terminal and shore station equipment, which can achieve efficient and stable loading and unloading and transmission of carbon dioxide.

[0004] The problem is that tank 4, with its design pressure of 20 kg, has strength limitations on the length and width of the storage tank, necessitating the use of high-strength steel exceeding regulatory requirements. The tank's plate thickness must reach approximately 50 mm, which is costly and difficult to construct. The tank's maximum external dimensions are limited to 50 meters, with a total capacity of approximately 5,000 cubic meters. This restricts the ability to load liquid CO2 into a single tank, making it uneconomical. The tank's weight is twice that of a conventional C-type tank, impacting the ship's overall loading and layout capabilities.

[0005] It's certain that different design pressures affect the thickness and sustained pressure duration of storage tanks. In conventional designs, tank thickness determines the design pressure. Thicker tanks have greater pressure-bearing capacity, but also increase construction difficulty and cost. To ensure the tank's strength, the tank body must be constructed of cryogenic steel approximately 50mm thick, which increases construction costs and complexity.

[0006] Furthermore, if low-pressure storage tanks are used, the storage state is 6-10 barg at temperatures around -50 degrees Celsius, close to the triple point of carbon dioxide, making its chemical state unstable and highly susceptible to change. If the pressure cannot be maintained, liquid carbon dioxide will quickly vaporize, leading to leakage and even safety issues. Once the tank pressure reaches the design pressure, the pressure can only be released by discharging carbon dioxide, resulting in greenhouse gas emissions. Summary of the Invention

[0007] This invention uses a CO2 transport vessel as a platform and employs a storage and processing system that integrates low-pressure and high-pressure tanks to achieve low-pressure CO2 storage and high-pressure collection and conversion. This design not only addresses the current issue of unstable storage conditions near the triple point during transportation, but also reduces the thickness of the CO2 tank from 40-50 mm to 15-20 mm, significantly reducing construction difficulty and costs and increasing the product's added value. The independent high-pressure storage tank facilitates cargo handling and unloading. Furthermore, the high-pressure storage tank solves the problem of matching the high-pressure manifold interface between the ship and the dock.

[0008] The carbon dioxide transport ship of the present invention combines low-pressure storage tanks and high-pressure storage tanks, which solves the problem that the carbon dioxide storage environment of traditional transport ships is close to the triple point of gas, the cargo state is unstable, and it is easy to vaporize and leak, making the storage of cargo more stable and safe.

[0009] To achieve the above objectives, the present invention provides a liquefied carbon dioxide transport vessel with a variable design pressure, comprising office and living quarters, an engine room, and low-pressure storage tanks for storing liquid carbon dioxide. The outlet of each low-pressure tank is connected to a high-pressure compressor via a valve and piping. The high-pressure compressor is connected to the high-pressure tanks via a liquid cargo handling system. The liquid cargo handling system is used to liquefy collected carbon dioxide gas. The low-pressure tanks collect liquid carbon dioxide onshore and transport it to deep-sea areas or designated injection platforms. The low-pressure tanks have a design pressure of 6 to 13 kilograms (6 to 13 kg), while the high-pressure tanks have a design pressure of 13 to 19 kilograms (13 to 19 kg).

[0010] In a preferred embodiment, a cab is provided on the top floor of the office and living area as an operation and command center.

[0011] In a preferred embodiment, the engine room area is where the ship's power system and personnel work.

[0012] Preferably, the high-pressure storage tank has a design pressure of 13-19 kg, is provided with an outlet, and is connected to a CO2 storage platform via a pipeline; the thickness of the low-pressure storage tank is 1 / 3 of the thickness of the high-pressure storage tank.

[0013] In a preferred embodiment, it also includes power and distribution systems, ballast systems, and fire and life-saving systems.

[0014] Preferably, the low-pressure storage tank is a C-type tank or a B-type tank.

[0015] In addition, the high-pressure storage tank is provided with an external transmission port at the bow or stern of the ship.

[0016] In addition, the carbon dioxide processing module is provided with an output port connected to a CO2 transport ship or a designated injection platform.

[0017] This invention redesigns existing CO2 tanks on CO2 carriers into low-temperature, low-pressure tanks, reducing weight, cost, and construction complexity. Low-pressure tanks are used in cargo holds, with a minimum design pressure of 6 kg. This allows for a tank wall thickness of approximately 15 mm, two-thirds the weight of conventional high-pressure tanks, and allows for unlimited tank size. Construction is simplified, and standard marine steel can meet design requirements.

[0018] This invention adds a 20 kg high-pressure compressor to the deck, primarily used to boost the pressure of boil-off gas from low-pressure cargo tanks. A high-pressure storage tank is also added to the deck to store boil-off gas from the tanks. Because boil-off gas transforms into a liquid at 20 kg pressure, its volume becomes 1 / 513.3 of its gaseous state. The tank's capacity is 1 / 28 of that of a cargo hold tank, allowing for sustained pressure maintenance for 30 days. The present invention also incorporates a loading and unloading manifold mounted on the high-pressure storage tank to mate with the high-pressure system at the terminal.

[0019] The present invention uses low-pressure storage tanks instead of traditional high-pressure storage tanks, which is safer and more reliable. It also reduces the thickness of the tank body, lowers construction costs and difficulty, and increases the added value of the product. The present invention also provides independent high-pressure storage tanks, which can be heated and pressurized during cargo unloading, facilitating cargo unloading. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structural layout of a commonly designed liquefied carbon dioxide carrier.

[0021] Figure 2 It is a schematic diagram of the structural arrangement of the liquefied carbon dioxide transport ship of the present invention. DETAILED DESCRIPTION

[0022] The ship of the present invention has both carbon dioxide transportation and storage functions, and its main components are as follows: a transport and storage ship 1, an office and living area 2, an engine room area 3, a low-pressure storage tank 4, a high-pressure compressor 5, a liquid cargo processing system 6, and a high-pressure storage tank 7.

[0023] The layout scheme and main functions of the present invention are as follows:

[0024] The carbon transport vessel 1 collects liquid carbon dioxide on shore through a semi-cold and semi-pressurized low-pressure storage tank 4 and transports it to a deep-sea area or a designated injection platform.

[0025] Office and living area 2 is the main place for personnel to live and work. The driver's cab is set up on the top floor as the operation and command center.

[0026] Engine room area 3: the main layout area of ​​the main engine and mechanical equipment, the ship's power system and personnel working space.

[0027] Low-pressure storage tank 4 uses a low-temperature low-pressure storage tank instead of a conventional low-temperature high-pressure storage tank, reducing the thickness of the tank, reducing construction costs and difficulty. The thickness and weight of the tank are about 1 / 3 of those of the high-pressure storage tank.

[0028] The high-pressure compressor 5 collects the vaporized carbon dioxide from the low-pressure storage tank, pressurizes it and liquefies it, and then transports it to the small high-pressure storage tank on the deck.

[0029] The liquid cargo handling system 6 liquefies the carbon dioxide gas collected by the air compressor.

[0030] The high-pressure storage tank 7 collects and stores the carbon dioxide generated in the cargo hold area. During unloading, the carbon dioxide can be heated and pressurized here and unloaded through pipelines.

[0031] The vessel of the present invention also includes necessary equipment and systems such as power and distribution systems, ballast systems, fire-fighting and life-saving systems, but is not limited to the above-mentioned devices and systems.

[0032] Implementation scheme and system principle of the present invention:

[0033] like Figure 2 The cargo hold storage tanks of the present invention utilize low-pressure tanks 4. Tank size is unrestricted; based on strength calculations, the tank thickness can be 1 / 3 that of the high-pressure tank. Low-pressure tanks withstand low pressure, and as the temperature rises, they generate boil-off gas (CO2). This CO2 is pressurized by a high-pressure compressor 5 and liquefied by the liquid cargo handling system, reducing its volume to 1 / 513.3 of its original volume before being stored in a high-pressure tank 7. The high-pressure tanks have a design pressure of 13-19 kg, compatible with loading and unloading terminals. The pressure can be adjusted to ensure ship-to-shore compatibility.

[0034] In order to illustrate the effect of the present invention, the calculation instructions for the volume ratio of the high-pressure storage tank and the low-pressure storage tank are as follows:

[0035] The formula for calculating the carbon dioxide evaporation rate is: , where Q is the volume of the tank, which is related to the length and diameter of the tank. h is the time, usually measured in hours. F is the heat flux, which is related to the insulation thickness, the bearing wood, and the cargo density and temperature pressure.

[0036] Under conditions of 250mm insulation thickness, a design pressure of 6 kg, and a temperature of -56°C, the 24-hour evaporation rate is 0.12%. This means that within 30 days, 3.6% of the total cargo hold capacity evaporates. This means that the volume of the high-pressure storage tank 7 on deck is 1 / 28 of the total volume of all low-pressure storage tanks 4 in the cargo hold. This means that a 200-cubic-meter high-pressure storage tank can meet the boil-off gas requirements of a 7,500-cubic-meter carrier and maintain a 30-day continuous pressure period.

[0037] The present invention can choose a mode in which the transport ship can export the LCO2 at the bow or at the stern; the LCO2 can be exported by the CO2 transport ship or input to the designated platform through the carbon dioxide treatment module; the LPLCO2 storage tank can be a C-type tank or a B-type tank.

[0038] The present invention changes the original carbon dioxide transport ship storage tank into a low-temperature low-pressure storage tank, which reduces weight, reduces cost and difficulty of work. The storage tank in the cargo hold adopts a low-pressure storage tank, and the design pressure can be as low as 6 kg. In this way, the wall thickness of the storage tank can be about 15 mm. Figure 1 The high-pressure storage tank 4 shown is 2 / 3 lighter, and its size is not limited. It is easy to construct, and ordinary marine steel can meet the design requirements.

[0039] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A liquefied carbon dioxide transport ship with a variable design pressure, comprising an office and living area (2) and an engine room area (3); characterized in that: It also includes a low-pressure storage tank (4) for storing liquid carbon dioxide; the outlet of each low-pressure storage tank (4) is connected to a high-pressure compressor (5) through a valve and a pipeline; the high-pressure compressor (5) is connected to the high-pressure storage tank (7) through a liquid cargo processing system (6); the liquid cargo processing system (6) is used to liquefy the collected carbon dioxide gas; The low-pressure storage tank (4) collects liquid carbon dioxide onshore and transports it to a deep-sea area or to a designated injection platform; The low-pressure storage tank (4) has a design pressure of 6-13 kg; the high-pressure storage tank has a design pressure of 13-19 kg.

2. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: The office and living area (2) has a cab on the top floor as an operation and command center.

3. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: The engine room area (3) is a working place for the ship's power system and personnel.

4. The liquefied carbon dioxide carrier with variable design pressure according to claim 1, characterized in that: The high-pressure storage tank (7) is provided with an outlet, which is connected to a CO2 storage platform via a pipeline; the thickness of the low-pressure storage tank (4) is 1 / 3 of the thickness of the high-pressure storage tank (7).

5. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: It also includes power and distribution systems, ballast systems, and fire and life-saving systems.

6. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: The low-pressure storage tank (4) is a C-type tank or a B-type tank.

7. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: The high-pressure storage tank is located at the bow or stern of the ship and is provided with an external transmission port.

8. The liquefied carbon dioxide transport ship with variable design pressure according to claim 1, characterized in that: The carbon dioxide processing module (6) is provided with an output port connected to a CO2 transport ship or a designated injection platform.

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