A co2 carrier BOG treatment system and method

Abstract

The application provides a CO2 transport ship BOG processing system and method, and the system comprises a CO2 liquid cargo tank, a stop valve, a compressor, a BOG heat exchanger, a check valve, a box type CO2 storage unit, a container and a CO2 steel cylinder. The system stores BOG generated in the CO2 transport process in the box type CO2 storage unit through pressurization and reliquefaction. Compared with traditional low-temperature reliquefaction, the application does not need a refrigeration system to cool the BOG, has smaller power consumption and is easy to implement, and greatly reduces the CO2 transport cost. Meanwhile, the method optimizes the number of box type CO2 storage units according to the length of the route and the different seasons, avoids the waste of resources caused by excessive box type CO2 storage units, and has high flexibility and practicality.

Description

Technical Field

[0001] This invention belongs to the field of marine technology, specifically relating to a BOG (Boat Oxide) handling system and method for CO2 transport ships. Background Technology

[0002] Currently, global warming continues as greenhouse gas emissions increase. CO2 is a major component of greenhouse gases, therefore its emissions need to be addressed. Typically, CO2 is captured and stored in specific locations, such as Iceland or the ocean floor. This process involves long-distance maritime transport, requiring the use of CO2 transport ships.

[0003] During maritime transport, CO2 is typically stored in liquid form to reduce storage volume. Liquid CO2 storage requires specific temperature and pressure conditions (typically -30°C to -50°C and 0.7 MPa to 1.5 MPa). Therefore, ship cargo tanks often employ a semi-cooled, semi-pressurized storage method (approximately -49°C and 0.7 MPa). However, this semi-cooled, semi-pressurized storage method has a significant temperature difference from the ambient environment, approximately 80°C to 90°C. Even with insulation around the CO2 cargo tank, CO2 vapors (BOG) are inevitably generated. BOG is typically liquefied using a refrigeration system and then returned to the CO2 cargo tank. However, due to the very low liquefaction temperature of BOG (approximately -30°C to -50°C) and the typically long routes of CO2 transport ships, the amount of BOG generated during transport is substantial. Therefore, the refrigeration process consumes significant power, requiring a large amount of the ship's electrical equipment.

[0004] BOG (Boiled Air Gaseous) generated during CO2 transportation can be reliquefied and stored under pressure, specifically by pressurizing the BOG to 70-80 bar and storing it in a pressure vessel. Compared to traditional cryogenic reliquefaction, pressurized reliquefaction of BOG eliminates the need for refrigeration, resulting in lower power consumption. However, due to the large volume of BOG generated during ship voyages, pressurized reliquefaction requires numerous pressure vessels to store CO2, which not only occupies significant ship space but also causes inconvenience during unloading.

[0005] To address the aforementioned problems, this invention proposes a BOG (Boiled Air Gathering) processing system and method for CO2 transport ships. It designs a box-type CO2 storage unit to pressurize and store CO2 BOG within it. Compared to traditional cryogenic reliquefaction of BOG, this invention significantly reduces the power consumption of BOG reliquefaction. Furthermore, by scientifically and rationally allocating the number of shipboard box-type CO2 storage units, this invention avoids the resource waste caused by equipping too many pressure vessels. Summary of the Invention

[0006] To substantially solve the above-mentioned problems, this invention proposes a BOG (Boiled Air Gathering) handling system and method for CO2 transport ships. The first objective of this invention is to provide a BOG handling system for CO2 transport ships, comprising: a CO2 cargo tank, a shut-off valve, a compressor, a BOG heat exchanger, a check valve, and a box-type CO2 storage unit.

[0007] The CO2 cargo tank is connected to a shut-off valve; the shut-off valve is connected to a compressor; the compressor is connected to a BOG heat exchanger; the BOG heat exchanger is connected to a check valve; and the check valve is connected to a box-type CO2 storage unit.

[0008] Furthermore, the containerized CO2 storage unit consists of a container and several CO2 cylinders inside it, with each CO2 cylinder connected to an interface via a pipe.

[0009] Furthermore, this system defines several box-type CO2 storage units, namely No.1, No.2...No.n.

[0010] During ship navigation, the liquid CO2 in the CO2 cargo tank exchanges heat with the BOG generated by natural heat exchange. After being pressurized by a compressor, it enters the BOG heat exchanger for heat exchange and is finally injected into the CO2 cylinder in the box-type CO2 storage unit for storage.

[0011] The second objective of this invention is to propose a CO2 transport ship BOG handling method based on the aforementioned CO2 transport ship BOG handling system. The purpose of this method is to optimize the allocation of the number of containerized CO2 storage units on the ship according to the length of the ship's route and the season, so as to avoid resource waste, and to efficiently and conveniently lift the containerized CO2 storage units on the ship to land when the ship docks.

[0012] The number of box-type CO2 storage units can be determined based on the length of the ship's voyage and the season, as shown in formula (1):

[0013]

[0014] Where N represents the number of box-type CO2 storage units equipped, rounded up;

[0015] V1 - Total volume of CO2 loaded in the ship's liquid cargo tanks, in m³ 3 ;

[0016] R - CO2 evaporation rate of the liquid cargo tank;

[0017] μ - seasonal coefficient;

[0018] ρ1 - Density of CO2 in the liquid cargo tank, kg / m³ 3 ;

[0019] T - Number of days at sea;

[0020] ρ2 - Density of CO2 inside the cylinder, kg / m³ 3 ;

[0021] The total volume of the CO2 cylinders in the V2-box type CO2 storage unit, in m³ 3 .

[0022] V2—Total volume of CO2 cylinders in the box-type CO2 storage unit, in meters. 3 .

[0023] The beneficial effects of this invention are:

[0024] 1. This invention ingeniously utilizes a box-type CO2 storage unit to store BOG (Boiled Air Gaseous) generated during CO2 transport by carriers. The system is simple and the overall process is easy to implement. Furthermore, compared to traditional cryogenic reliquefaction, this invention eliminates the need for refrigeration of the BOG, resulting in lower power consumption and significantly reducing CO2 transportation costs.

[0025] 2. In the CO2 transportation process, the present invention can flexibly allocate the number of box-type CO2 storage units according to the length of the route and the amount of BOG generated during CO2 transportation in different seasons, thus avoiding the waste of resources caused by equipping too many box-type CO2 storage units. Attached Figure Description

[0026] Appendix Figure 1 This is a system diagram of the present invention;

[0027] Appendix Figure 2 This is a schematic diagram of a box-type CO2 storage unit;

[0028] In the attached diagram: 1. CO2 liquid cargo tank; 2. Shut-off valve; 3. Compressor; 4. BOG heat exchanger; 5. Check valve; 6. Box-type CO2 storage unit; 601. Container; 602. CO2 cylinder. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] A BOG handling system for CO2 transport ships, such as Figure 1 , Figure 2 As shown, the system includes: CO2 liquid cargo tank 1, shut-off valve 2, compressor 3, BOG heat exchanger 4, check valve 5, box-type CO2 storage unit 6, container 601, and CO2 cylinder 602.

[0031] In this system, the CO2 cargo tank 1 is connected to a shut-off valve 2; the shut-off valve 2 is connected to a compressor 3; the compressor 3 is connected to a BOG heat exchanger 4; the BOG heat exchanger 4 is connected to a check valve 5; and the check valve 5 is connected to a box-type CO2 storage unit 6. The compressor 3 compresses and pressurizes the BOG; the BOG heat exchanger 4 exchanges heat between the compressed BOG and seawater, reducing the BOG temperature to room temperature.

[0032] Furthermore, the box-type CO2 storage unit 6 consists of a container 601 and several CO2 cylinders 602, with the interface of each CO2 cylinder 602 connected by a pipe.

[0033] Furthermore, this system defines several box-type CO2 storage units 6, namely No.1, No.2...No.n.

[0034] During the ship's voyage, the liquid CO2 in the CO2 cargo tank 1 exchanges heat with the natural environment to generate BOG. ​​It first enters the compressor 3 through the shut-off valve 2 to be pressurized. The temperature of the pressurized BOG rises, and then it enters the BOG heat exchanger 4 through the pipeline to exchange heat with seawater. Finally, it is injected into the box-type CO2 storage unit 6 through the check valve 5 for storage.

[0035] The second objective of this invention is to propose a CO2 carrier BOG handling method based on the aforementioned CO2 carrier BOG handling system. The purpose of this method is to optimize the number of containerized CO2 storage units 6 according to the length of the route and the season, reduce resource waste, and efficiently and conveniently lift the containerized CO2 storage units 6 to land when the ship docks for unloading.

[0036] During CO2 transport by carriers, the evaporation rate of CO2 changes with temperature; for example, the evaporation rate increases with rising temperature. Therefore, the amount of bound gas (BOG) generated from CO2 exchange with the external environment varies depending on the season and the length of the route. If the required number of containerized CO2 storage units (6) is based on the scenario of maximum CO2 evaporation rate and longest route, many of these units will be idle when the CO2 evaporation rate is low or the route is short, resulting in resource waste.

[0037] Based on the above two reasons, the number of containerized CO2 storage units 6 should be reasonably allocated according to the length of the flight route and the season. The number of containerized CO2 storage units 6 allocated is obtained from formula (1):

[0038]

[0039] Where N represents the number of box-type CO2 storage units equipped, rounded up;

[0040] V1—Total volume of CO2 loaded in the ship's liquid cargo tanks, in m³ 3 ;

[0041] R—CO2 evaporation rate of the liquid cargo tank;

[0042] μ—Seasonal coefficient;

[0043] ρ1—Density of CO2 in the liquid cargo tank, kg / m³ 3 ;

[0044] T—Number of days at sea;

[0045] ρ2 — Density of CO2 inside the cylinder, kg / m³ 3 ;

[0046] V2—Total volume of CO2 cylinders in the box-type CO2 storage unit, in meters. 3 .

[0047] The seasonal coefficient μ can be selected according to different seasons. It is 1 in spring and autumn. In summer, when the CO2 evaporation rate is high, the seasonal coefficient is greater than 1, usually 1.1 to 1.2. In winter, when the CO2 evaporation rate is low, the seasonal coefficient is less than 1, usually 0.80 to 0.95.

[0048] When the CO2 transport ship docks, the containerized CO2 storage unit 6 is lifted to land for CO2 recycling.

[0049] During the voyage of a CO2 transport ship, a significant temperature difference exists between the liquid CO2 in the CO2 cargo tank 1 and the natural environment, inevitably leading to the generation of bound gas (BOG). Traditionally, BOG is cooled and reliquefied using a refrigeration system before being returned to the CO2 cargo tank 1. However, due to the very low liquefaction temperature of BOG (approximately -30°C to -50°C) and the typically long routes of CO2 transport ships, the amount of BOG generated during transport is substantial, resulting in significant power consumption during the refrigeration process and requiring a large amount of the ship's electricity. The system of this invention, however, reliquefies BOG under pressure and stores it in CO2 cylinders 602 within the box-type CO2 storage unit 6, eliminating the power consumption of the refrigeration process and reducing the cost of CO2 reliquefaction.

[0050] The containerized CO2 storage unit 6 stores pressurized and reliquefied BOG. ​​Due to the influence of route length (voyage time) and seasonal temperature, the maximum number of containerized CO2 storage units 6 is usually configured based on the longest routes and the highest CO2 evaporation rate in summer. This increases CO2 storage costs and occupies more ship space. Conversely, when routes are shorter or the CO2 evaporation rate is lower in winter, the amount of BOG generated during ship transportation is relatively small, resulting in insufficient CO2 storage capacity in the containerized CO2 storage units 6, leading to low capacity utilization and serious resource waste. This method optimizes the configuration of the containerized CO2 storage units 6 according to the length of the ship's route and the season, avoiding the resource waste caused by equipping too many containerized CO2 storage units 6.

[0051] The above description is merely a preferred embodiment of the present invention. The specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for handling BOG (Bottom Gas) from CO2 transport ships, characterized in that: The method utilizes a CO2 carrier BOG handling system, which includes a CO2 cargo tank (1), a shut-off valve (2), a compressor (3), a BOG heat exchanger (4), a check valve (5), and a box-type CO2 storage unit (6). The CO2 liquid cargo tank (1) is connected in sequence to the shut-off valve (2), compressor (3), BOG heat exchanger (4), check valve (5), and box-type CO2 storage unit (6) via pipelines; The box-type CO2 storage unit (6) includes a container (601) and several CO2 cylinders (602); the CO2 cylinders (602) are placed inside the container (601), and each CO2 cylinder (602) is connected to the container via a pipe. The CO2 BOG in the CO2 cargo tank (1) is pressurized by the compressor (3), enters the BOG heat exchanger (4) for heat exchange, and is finally injected into the CO2 cylinder (602) in the box-type CO2 storage unit (6) for storage. The number of box-type CO2 storage units (6) is determined according to the number of days the ship sails and the seasonal coefficient, as shown in formula (1): （1） Wherein, N—the number of box-type CO2 storage units (6) equipped, rounded up; —Total volume of CO2 loaded in the ship's liquid cargo tanks, in m³ 3 ; R—CO2 evaporation rate of the liquid cargo tank; μ—Seasonal coefficient; —Density of CO2 in the liquid cargo tank, kg / m³ 3 ; T—Number of days at sea; —Density of CO2 inside the cylinder, kg / m³ 3 ; —The total volume of the CO2 cylinder (602) in the box-type CO2 storage unit (6), m 3 ; The seasonal coefficient μ should be selected according to different seasons. μ is 1 in spring and autumn, 1.1 to 1.2 in summer, and 0.80 to 0.95 in winter.

2. The method for handling BOG (Body Waste) on a CO2 transport ship according to claim 1, characterized in that: When the CO2 transport ship docks, the containerized CO2 storage unit (6) is hoisted to land.

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