BOG treatment system and method for CO2 transport ship

Abstract

The invention provides a CO2 transport ship BOG treatment system and method. 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. According to the system, BOG generated in the CO2 transportation process is stored in the box-type CO2 storage unit in a pressurization and reliquefaction mode. Compared with traditional low-temperature reliquefaction, a refrigerating system is not needed to cool BOG, power consumption is small, implementation is easy, and the CO2 transportation cost is greatly reduced. Meanwhile, according to the method, the ship is optimally provided with the number of the box-type CO2 storage units according to the length of the ship route and different seasons, resource waste caused by the fact that too many box-type CO2 storage units are arranged is avoided, and high flexibility and practicability are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ships, and in particular relates to a BOG treatment system and method for a CO2 transport ship. Background Art

[0002] Currently, with the increasing emission of greenhouse gases, global warming is still continuing. CO2 is the main component of greenhouse gases, so CO2 emissions need to be processed. Usually, CO2 is captured and then sealed in specific places, such as Iceland, the seabed, etc. This process involves long-distance sea transportation, which requires the use of CO2 transport ships to achieve this process.

[0003] In the process of marine transportation, in order to reduce the storage volume of CO2, it is usually stored in liquid form. The storage of liquid CO2 requires a certain temperature and pressure (temperature is usually -30℃~-50℃, pressure is 0.7MPa~1.5MPa). Therefore, at present, the ship cargo tank often uses semi-cold and semi-pressure (temperature is about -49℃, pressure is about 0.7MPa) to store CO2. The storage temperature of semi-cold and semi-pressure has a large temperature difference with the natural environment, about 80℃~90℃. Even if there is an insulation layer outside the CO2 cargo tank, it is inevitable to produce CO2 evaporation gas (BOG for short). For the treatment of BOG, the refrigeration system is usually used to cool down the BOG to reliquefy it, so that it flows back to the CO2 cargo tank. However, since the liquefaction temperature of BOG is very low (about -30℃~-50℃), and the route of CO2 transport ships is usually long, the amount of BOG generated during transportation is very large, so the refrigeration process will generate a large power consumption, which requires a large amount of electricity from the ship.

[0004] For the BOG generated during the transportation of CO2, it can also be reliquefied and stored by pressurizing it, that is, by pressurizing the BOG to 70bar~80bar and storing it in a pressure vessel. Compared with the traditional low-temperature reliquefaction method, the pressurized reliquefaction of BOG does not require refrigeration of BOG and consumes less power. However, due to the large amount of BOG generated during the voyage of the ship, the pressurized reliquefaction of BOG requires a lot of pressure vessels to store CO2, which not only takes up a lot of ship space, but also causes inconvenience during unloading.

[0005] Based on the above problems, the present invention proposes a BOG treatment system and method for a CO2 transport ship, designs a box-type CO2 storage unit, and stores the CO2 BOG under pressure. Compared with the traditional low-temperature reliquefaction of BOG, the present invention greatly reduces the power consumption of BOG reliquefaction. At the same time, the present invention avoids the waste of resources caused by equipping too many pressure vessels by scientifically and reasonably equipping the number of ship-borne box-type CO2 storage units. Summary of the invention

[0006] The present invention substantially solves the above problems and proposes a BOG treatment system and method for a CO2 transport ship. The first object of the present invention is to propose a BOG treatment system for a CO2 transport ship, which comprises: a CO2 liquid cargo tank, a stop valve, a compressor, a BOG heat exchanger, a check valve, and a box-type CO2 storage unit.

[0007] Wherein, the CO2 liquid cargo tank is connected to the stop valve; the stop valve is connected to the compressor; the compressor is connected to the BOG heat exchanger; the BOG heat exchanger is connected to the check valve; and the check valve is connected to the box-type CO2 storage unit.

[0008] Furthermore, the box-type CO2 storage unit is composed of a container and a plurality of CO2 cylinders therein, and the interfaces of each CO2 cylinder are connected by a pipeline.

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

[0010] During the voyage of the ship, the BOG generated by the heat exchange between the liquid CO2 in the CO2 cargo tank and the nature is pressurized by the compressor, 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 purpose of the present invention is to propose a CO2 transport ship BOG treatment method based on the above-mentioned CO2 transport ship BOG treatment system. The purpose of this method is to achieve the optimal allocation of the number of ship box-type CO2 storage units according to the length of the ship's route and the different seasons, avoid waste of resources, and when the ship is docked, efficiently and conveniently lift the ship's box-type CO2 storage units to land.

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

[0013]

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

[0015] V1-Total volume of CO2 loaded in the ship's cargo tank, m 3 ;

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

[0017] μ-seasonal coefficient;

[0018] ρ1-density of CO2 in liquid cargo tank, kg / m 3 ;

[0019] T-number of sailing days;

[0020] ρ2-density of CO2 in the cylinder, kg / m 3 ;

[0021] V2-Total volume of CO2 cylinders in the box-type CO2 storage unit, m 3 .

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

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention cleverly uses a box-type CO2 storage unit to store BOG generated during the transportation of CO2 transport ships. The system is simple and the overall process is easy to implement. Compared with traditional low-temperature reliquefaction, the present invention does not require refrigeration of BOG, consumes less power, and greatly reduces the transportation cost of CO2.

[0025] 2. During the CO2 transportation process, the present invention can flexibly configure the number of box-type CO2 storage units according to the length of the route and the amount of BOG generated during the CO2 transportation process in different seasons, thereby avoiding the waste of resources caused by equipping too many box-type CO2 storage units. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0028] In the attached figure: 1. CO2 liquid cargo tank; 2. stop valve; 3. compressor; 4. BOG heat exchanger; 5. check valve; 6. box-type CO2 storage unit; 601. container; 602. CO2 cylinder. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

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

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

[0032] Furthermore, the box-type CO2 storage unit 6 is composed of a container 601 and a plurality of CO2 cylinders 602, and the interfaces of each CO2 cylinder 602 are connected by a pipeline.

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

[0034] During the voyage of the ship, the BOG generated by the heat exchange between the liquid CO2 in the CO2 cargo tank 1 and the nature first enters the compressor 3 through the stop valve 2 to be pressurized. The temperature of the pressurized BOG increases, and then enters the BOG heat exchanger 4 through the pipeline to exchange heat with seawater, and finally is injected into the box-type CO2 storage unit 6 through the check valve 5 for storage.

[0035] The second purpose of the present invention is to propose a CO2 transport ship BOG treatment method based on the above-mentioned CO2 transport ship BOG treatment system. The purpose of this method is to optimize the number of box-type CO2 storage units 6 according to the length of the route and the different seasons, reduce resource waste, and when the ship docks and unloads, the box-type CO2 storage unit 6 can be efficiently and conveniently lifted to land.

[0036] During the transportation of CO2 by the ship, the evaporation rate of CO2 will change with the change of temperature. For example, when the temperature rises, the evaporation rate of CO2 will also increase. Therefore, in different seasons, the amount of BOG generated by the heat exchange between CO2 and the outside world will also change due to the temperature; and the amount of BOG generated during the ship transportation is also different for the length of the route. If the number of required box-type CO2 storage units 6 is equipped according to the situation of the maximum CO2 evaporation rate and the longest route, many box-type CO2 storage units 6 will be idle when the CO2 evaporation rate is low or the route is short, resulting in a waste of resources.

[0037] Based on the above two reasons, the number of box-type CO2 storage units 6 should be reasonably equipped according to the length of the route and the season. The number of box-type CO2 storage units 6 equipped is obtained by formula (1):

[0038]

[0039] Wherein, N is the number of box-type CO2 storage units, rounded up;

[0040] V1—Total volume of CO2 loaded in the ship's cargo tank, m 3 ;

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

[0042] μ—seasonal coefficient;

[0043] ρ1—density of CO2 in liquid cargo tank, kg / m 3 ;

[0044] T—number of sailing days;

[0045] ρ2—density of CO2 in the cylinder, kg / m 3 ;

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

[0047] Among them, the seasonal coefficient μ can select appropriate values ​​according to different seasons. It is 1 in spring and autumn. The CO2 evaporation rate is higher in summer, and the seasonal coefficient is greater than 1, usually 1.1-1.2; the CO2 evaporation rate is lower in winter, and the seasonal coefficient is less than 1, usually 0.80-0.95.

[0048] When the CO2 transport ship docks at the port, the box-type CO2 storage unit 6 is hoisted to land to recover and process the CO2.

[0049] During the voyage of the CO2 transport ship, there is a large temperature difference between the liquid CO2 in the CO2 cargo tank 1 and the natural environment, so BOG is inevitably produced. For the treatment of BOG, the traditional way is to cool the BOG through a refrigeration system and then liquefy it and recycle it into the CO2 cargo tank 1. However, since the liquefaction temperature of BOG is very low (about -30℃~-50℃), and the route of the CO2 transport ship is usually long, the amount of BOG produced during the transportation process is very large, so the refrigeration process will generate a large power consumption, and a large amount of electricity of the ship is required. The system of the present invention reliquefies the BOG by pressurizing it, and then reliquefies the BOG by pressurizing it and stores it in the CO2 cylinder 602 in the box-type CO2 storage unit 6, which saves the power consumption of the refrigeration process and reduces the cost of CO2 reliquefaction.

[0050] The box-type CO2 storage unit 6 stores the BOG after pressurization and reliquefaction. Due to the influence of the route length (navigation time) and seasonal temperature, the maximum number of box-type CO2 storage units 6 is usually equipped according to the longest route and the highest CO2 evaporation rate in summer, which will increase the cost of CO2 storage and occupy more ship space. When the route is short or the CO2 evaporation rate is low in winter, the BOG generated during ship transportation is relatively small, resulting in too little CO2 loaded in the box-type CO2 storage unit 6, and the capacity utilization rate is very low, causing serious waste of resources. This method optimizes the number of box-type CO2 storage units 6 according to the length of the ship's route and the different seasons, and avoids the waste of resources caused by equipping too many box-type CO2 storage units 6.

[0051] The above is only a preferred embodiment of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A BOG treatment system for a CO2 transport ship, characterized by: The system comprises a CO2 liquid cargo tank (1), a stop valve (2), a compressor (3), a BOG heat exchanger (4), a check valve (5), a box-type CO2 storage unit (6), a container (601), and a CO2 cylinder (602). The CO2 liquid cargo tank (1) is connected to a stop valve (2), a compressor (3), a BOG heat exchanger (4), a check valve (5), and a box-type CO2 storage unit (6) in sequence through pipelines; the box-type CO2 storage unit (6) includes a container (601) and a plurality of CO2 cylinders (602); the CO2 cylinders (602) are placed in the container (601), and the interfaces of each CO2 cylinder (602) are connected through pipelines.

2. A BOG treatment system for a CO2 transport ship according to claim 1, characterized in that: During the voyage of the ship, the BOG of CO2 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.

3. A CO2 transport ship BOG method based on the system, characterized in that: The number of box-type CO2 storage units (6) is determined according to the ship's sailing time and season, as shown in formula (1): Wherein, N is the number of box-type CO2 storage units, rounded up; V1—Total volume of CO2 loaded in the ship's cargo tank, m 3 ; R—CO2 evaporation rate of liquid cargo tank; μ—seasonal coefficient; ρ1—density of CO2 in liquid cargo tank, kg / m 3 ; T—number of sailing days; ρ2—density of CO2 in the cylinder, kg / m 3 ; V2—Total volume of CO2 cylinders in the box-type CO2 storage unit, m 3 .

4. The method for treating BOG of a CO2 transport ship according to claim 1, characterized in that: When the CO2 transport ship docks at the port, the box-type CO2 storage unit 6 is hoisted to land.

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