A system and method for storing captured co2 in a full pressure lpg carrier cargo tank

Abstract

The present application belongs to the technical field of ship, and proposes a full-pressure type CO2 system and method for storing and capturing of LPG ship liquid cargo tank, which comprises a liquid CO2 storage tank, a compressor, a seawater heat exchanger, a stop valve and an LPG liquid cargo tank. The application ingeniously utilizes the sufficient storage space of the LPG liquid cargo tank when the LPG ship returns empty, compresses the gaseous CO2 captured by the ship, and stores it in the empty LPG liquid cargo tank. When the ship returns to the loading port, the gaseous CO2 is sent to the land for treatment. Through the method of the application, the LPG liquid cargo tank of the ship can maximize the storage of the CO2 captured when the ship returns empty, which not only can reduce the burden of the ship power grid, but also can save the economic cost of liquefied CO2, and has good economy and practicability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ships, and particularly relates to a CO2 system and method for storage and capture of a full-pressure type LPG ship liquid cargo tank. BACKGROUND

[0002] Liquefied petroleum gas (LPG for short) is a commonly used chemical raw material and a new type of energy, and its main component is hydrocarbon, including alkane and alkene such as propane and butane, and it has the advantages of being clean, low-carbon and abundant in source, and is a very important clean energy. An LPG ship is a ship for transporting liquefied petroleum gas, and the storage mode of liquefied petroleum gas on the ship is mainly divided into full cold type and full pressure type, and most small LPG ships usually use the full pressure type storage mode for transportation.

[0003] With the continuous development of the shipping industry in the direction of low carbonization, a relatively mature carbon capture and storage system (CCS for short) has been equipped on the ship, and the CCS is to capture the CO2 emitted by the ship's main engine during the ship's voyage, and then store it in the CO2 storage tank on the ship, and finally send it to land or handle it in other ways. For a typical 5000m 3 Taking the LPG "Zhaoyuan" ship as an example, the rated power of the ship's main engine is 2946kw, the actual running power is slightly smaller, the daily oil consumption is about 8.3t, and the ship will produce about 3.8t of CO2 for every 1t of fuel consumed. Assuming that the CO2 capture rate of the carbon capture device is 80%, about 25t of CO2 can be recovered per day of the ship's voyage, so the amount of CO2 captured by the ship every day is very large. CO2 is usually liquefied at a low temperature under a certain pressure, and the temperature of CO2 liquefaction is very low (the CO2 liquefaction temperature is about -50℃ when the gas pressure is 0.7MPa). Such a large amount of CO2 requires a large amount of cold energy for liquefaction, which requires the refrigeration equipment to consume a large amount of electricity, not only causing a large load on the ship's power grid, but also causing a large economic cost. In addition, the process of liquefying CO2 on the ship is relatively complex, and requires more professional ship technicians to operate and supervise, and based on the special environment on the ship, the cost of personnel will also become very high. Therefore, the cost of liquefying the captured CO2 on the ship is very high.

[0004] The above-mentioned "Zhaoyuan" ship is usually equipped with two LPG liquid cargo tanks, and the safety valve pressure of the liquid cargo tank is set to 17bar, and the total tank capacity is 5000m 3 When the fully loaded LPG ship arrives at the destination port to unload, the ship returns empty, and if the empty LPG liquid cargo tank is used to store the gaseous CO2 captured by the ship, it is known that the density of gaseous CO2 under the condition of 17bar pressure is 30kg / m 3Therefore, the captured gaseous CO2 is compressed to 17 bars and stored in the LPG liquid cargo tank, and the liquid cargo tank can store about 150 tons of gaseous CO2, which is about the amount of CO2 captured in 6 days of ship navigation. When the ship returns to the loading port, the gaseous CO2 is sent to the land for liquefaction or other treatment, and the space on the land is sufficient and has a more perfect CO2 liquefaction system, and the land has multiple treatment methods for the recovered gaseous CO2, and the cost of treating CO2 is much lower than the way of using low-temperature liquefied CO2 on the ship. Therefore, the way of treating the CO2 captured during the ship navigation can greatly reduce the cost of ship navigation and improve the economy of the ship.

[0005] Therefore, the way of treating the CO2 captured during the ship navigation can greatly reduce the cost of ship navigation and improve the economy of the ship. SUMMARY

[0006] The purpose of the present application is to solve the above problems, and a system and method for storing captured CO2 in the liquid cargo tank of a full-pressure LPG ship are provided. When the full-pressure LPG ship is empty and returns, the gaseous CO2 captured during the ship navigation is compressed and stored in the empty LPG liquid cargo tank. When the ship arrives at the loading port, the gaseous CO2 is sent to the land for treatment, thereby saving the cost of liquefying CO2 on the ship.

[0007] The first purpose of the present application is to provide a system for storing captured CO2 in the liquid cargo tank of a full-pressure LPG ship, which comprises: a liquid CO2 storage tank, a compressor, a seawater heat exchanger, a stop valve, and an LPG liquid cargo tank.

[0008] In the system, the ship engine is connected to the CO2 capture system through a pipeline, the CO2 capture system can capture and separate CO2 from the exhaust gas of the ship engine, and the remaining gas is discharged into the atmosphere. The pipeline is connected to the CO2 liquefaction system and the compressor, respectively. The CO2 liquefaction system is connected to the liquid CO2 storage tank through a pipeline.

[0009] The compressor is connected to the seawater heat exchanger, the stop valve, and the LPG liquid cargo tank through a pipeline, respectively. The compressor can compress gaseous CO2 and pass it into the LPG liquid cargo tank. The LPG liquid cargo tank is usually provided with two on the ship, and a stop valve is provided on the pipeline between the two LPG liquid cargo tanks and the seawater heat exchanger. The LPG liquid cargo tank is a full-pressure LPG liquid cargo tank made of pressure-resistant material.

[0010] When the ship sails full load, the exhaust gas emitted by the ship's main engine burning fuel enters the CO2 capture system, the CO2 in the exhaust gas is captured and separated in the CO2 capture system, and the remaining gas is discharged into the atmosphere, the captured CO2 is sent into the CO2 liquefaction system through the pipeline, the CO2 capture system is liquefied, and then the liquid CO2 flows into the liquid CO2 storage tank for storage, and when the ship arrives at the port, the liquid CO2 in the liquid CO2 storage tank is sent to the land for storage or other processing.

[0011] When the ship arrives at the destination port and the LPG in the LPG liquid cargo tank is unloaded, the ship sails empty, the exhaust gas emitted by the ship's main engine burning fuel enters the CO2 capture system, the CO2 in the exhaust gas is captured and separated in the CO2 capture system, and the remaining gas is discharged into the atmosphere, the captured CO2 enters the compressor through the pipeline, the compressor is pressurized to a certain pressure, and then the gaseous CO2 enters the seawater heat exchanger along the pipeline for cooling to normal temperature, and then the stop valve is opened, the gaseous CO2 enters the LPG liquid cargo tank along the pipeline for storage, and when the ship arrives at the port, the gaseous CO2 stored in the LPG liquid cargo tank is transported to the land for processing.

[0012] The second object of the present application is based on the above-mentioned full-pressure type LPG ship liquid cargo tank storage and capture CO2 system, a full-pressure type LPG ship liquid cargo tank storage and capture CO2 method is proposed, the main purpose of the method is to maximize the storage of the ship LPG liquid cargo tank when the ship sails empty.

[0013] Assuming that the maximum working pressure of the full-pressure type LPG ship liquid cargo tank is p, which is approximately the same as the set pressure p1 of the liquid cargo tank safety valve. V is the total tank capacity of the ship LPG liquid cargo tank, unit is m 3 , ρ is the density of gaseous CO2 corresponding to the pressure p, unit is kg / m 3 , t is the fuel consumption of the ship in a day, unit is ton / d, r is the CO2 capture rate of the ship, then the gaseous CO2 fills the LPG liquid cargo tank and reaches the maximum working pressure p of the liquid cargo tank, and the required sailing days T is:

[0014]

[0015] The method of the present application is suitable for both newly built ships and ships already in operation:

[0016] The first type is a newly built ship

[0017] For a newly built ship that has not yet been put into use, according to its planned route, select one of the longest segments, preliminarily estimate its sailing time x, and calculate T using the above formula, and compare x and T, which can be divided into the following two cases:

[0018] Case 1: When x≤T, the captured gaseous CO2 can be pressurized by the compressor to the same pressure as the LPG liquid cargo tank safety valve set pressure p1 during the empty voyage of the ship, and then stored in the LPG liquid cargo tank, and when the ship returns to the loading port, the part of gaseous CO2 is sent to the land for treatment.

[0019] Case 2: When x>T, the LPG liquid cargo tank wall can be appropriately thickened at the beginning of the ship construction, so that the maximum working pressure p of the LPG liquid cargo tank can be increased, and the safety valve set pressure p1 is also increased, so that T obtained according to the formula of T is larger, so that T≥x. By increasing the wall thickness, the maximum working pressure of the LPG liquid cargo tank can be increased, and the storage capacity of gaseous CO2 can be increased.

[0020] But limited by the maximum thickness of the liquid cargo tank wall, the maximum working pressure is not more than 30 bar, if 30 bar is used to replace p in the formula of T, T obtained is still less than x, then when the ship is put into use, the captured gaseous CO2 can be pressurized and stored in the LPG liquid cargo tank during the empty voyage of the ship, and the remaining days are treated by liquefaction, so that the gaseous CO2 is converted into liquid, and flows into the liquid CO2 storage tank for storage, and when the ship is docked at the port, the gaseous CO2 stored in the LPG liquid cargo tank and the liquid CO2 stored in the liquid CO2 storage tank are sent to the land for treatment.

[0021] Second type, the ship that has been put into operation

[0022] For the ship that has been put into operation, T is calculated by using the above formula, and by comparing x and T, the following two cases are divided:

[0023] Case 1: When the sailing time x≤T, the captured gaseous CO2 can be pressurized by the compressor to the same pressure as the LPG liquid cargo tank safety valve set pressure p1 during the empty voyage of the ship, and then stored in the LPG liquid cargo tank, and when the ship returns to the loading port, the part of gaseous CO2 is sent to the land for treatment.

[0024] Case 2: When the sailing time x>T, the captured gaseous CO2 can be pressurized and stored in the LPG liquid cargo tank during the empty voyage of the ship, and the remaining days are treated by liquefaction, so that the gaseous CO2 is converted into liquid, and flows into the liquid CO2 storage tank for storage, and when the ship is docked at the port, the gaseous CO2 stored in the LPG liquid cargo tank and the liquid CO2 stored in the liquid CO2 storage tank are sent to the land for treatment.

[0025] The beneficial effects of the present application are:

[0026] 1. The present application compresses the gaseous CO2 captured during the ship's voyage to a certain pressure and stores it in the empty LPG liquid cargo tank when the ship is sailing empty, and when the ship is at port, the gaseous CO2 can be sent to land for treatment, and the ship does not need to be liquefied during the empty voyage, which not only greatly reduces the burden of the ship's power grid and saves the cost of CO2 liquefaction, but also saves the cost of ship personnel for operating and managing CO2 liquefaction treatment, and has good economic efficiency.

[0027] 2. When the present application is implemented on a ship, only the captured gaseous CO2 needs to be compressed to a certain pressure and stored in the empty LPG liquid cargo tank, the process is simple, the operation difficulty is low, and the management and implementation are convenient, and it has strong practicability. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the system diagram of the present application;

[0029] Figure 2 is a position diagram of the LPG liquid cargo tank 5 on the ship;

[0030] In the drawings: 1. Liquid CO2 storage tank; 2. Compressor; 3. Sea water heat exchanger; 4. Stop valve; 5. LPG liquid cargo tank. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples.

[0032] A full-pressure type LPG ship liquid cargo tank system for storing captured CO2, as shown in Figure 1 , the system comprises a liquid CO2 storage tank 1, a compressor 2, a sea water heat exchanger 3, a stop valve 4, and an LPG liquid cargo tank 5.

[0033] In the present system, the ship's main engine is connected to the CO2 capture system through a pipeline, the CO2 capture system can separate and capture CO2 from the exhaust gas of the ship's main engine, and the remaining gas is discharged into the atmosphere, and one side of the CO2 capture system is connected to the CO2 liquefaction system through a pipeline, and the other side is connected to the compressor 2 through a pipeline. The CO2 liquefaction system is connected to the liquid CO2 storage tank 1 through a pipeline.

[0034] The compressor 2 is connected to the sea water heat exchanger 3, the stop valve 4 and the LPG liquid cargo tank 5 in sequence through a pipeline, wherein the compressor 2 can compress gaseous CO2 into the LPG liquid cargo tank 5, and the LPG liquid cargo tank 5 is usually provided with two on the ship, as Figure 2As shown, and a stop valve 4 is arranged on the pipeline between the two LPG liquid cargo tanks 5 and the seawater heat exchanger 3, the LPG liquid cargo tank 5 is a full-pressure LPG liquid cargo tank 5, and a pressure-resistant material is used, and the set pressure of the safety valve is the same as the working pressure of the LPG liquid cargo tank 5.

[0035] When the ship sails in full load, the tail gas discharged by the ship main engine burning fuel enters the CO2 capture system, the CO2 in the tail gas is captured and separated in the CO2 capture system, and the remaining gas is discharged into the atmosphere, the captured CO2 enters the CO2 liquefaction system through the pipeline, the CO2 capture system is liquefied, and then the liquid CO2 flows into the liquid CO2 storage tank 1 for storage, and when the ship arrives at the port, the liquid CO2 in the liquid CO2 storage tank 1 is sent to the land for storage or other treatment.

[0036] When the ship arrives at the destination port and the LPG in the LPG liquid cargo tank 5 is unloaded, the ship sails empty, the tail gas discharged by the ship main engine burning fuel enters the CO2 capture system, the CO2 in the tail gas is captured and separated in the CO2 capture system, and the remaining gas is discharged into the atmosphere, the captured CO2 enters the compressor 2 through the pipeline, the compressor 2 is pressurized and enters the LPG liquid cargo tank 5, the pressurized gaseous CO2 temperature rises, and then the gaseous CO2 enters the seawater heat exchanger 3 along the pipeline for cooling and heat exchange with seawater, and is cooled to normal temperature, then the stop valve 4 is opened, the gaseous CO2 enters the LPG liquid cargo tank 5 along the pipeline for storage, and when the ship arrives at the port, the gaseous CO2 stored in the LPG liquid cargo tank 5 is transported to the land for treatment.

[0037] Assuming that the maximum working pressure of the full-pressure LPG ship liquid cargo tank is p, which is approximately the same as the set pressure p1 of the liquid cargo tank safety valve. V is the total tank capacity of the ship LPG liquid cargo tank 5, unit is m 3 , ρ is the density of gaseous CO2 corresponding to the pressure p, unit is kg / m 3 , t is the fuel consumption of the ship in a day, unit is ton / d, r is the CO2 capture rate of the ship, then the number of days T required for gaseous CO2 to fill the LPG liquid cargo tank 5 and reach the maximum working pressure p of the liquid cargo tank is:

[0038]

[0039] The method of the application is suitable for both newly built ships and ships already in operation:

[0040] The first type is a newly built ship

[0041] For a newly built ship which has not yet been put into use, according to the planned route of operation, one of the longest voyage sections is selected, the sailing time x is preliminarily estimated, and T is calculated by using the above formula. By comparing x and T, the following two cases are divided:

[0042] Case 1: When x≤T, the captured gaseous CO2 can be pressurized to the same pressure as the safety valve setting pressure pi of the LPG liquid cargo tank 5 by the compressor 2 during the return voyage of the empty ship, and then stored in the LPG liquid cargo tank 5. When the ship returns to the loading port, the gaseous CO2 is sent to the land for treatment.

[0043] Case 2: When x>T, the maximum working pressure p of the LPG liquid cargo tank 5 can be increased by appropriately thickening the tank wall at the beginning of the ship construction, and the safety valve setting pressure pi is also increased, so that T obtained according to the above formula T is larger, and T≥x. By increasing the wall thickness, the maximum working pressure of the LPG liquid cargo tank 5 can be increased, and the storage capacity of gaseous CO2 can be increased.

[0044] Generally, the working pressure of the LPG liquid cargo tank 5 of a general full-pressure type LPG ship is about 20 bar. By increasing the wall thickness, the maximum working pressure of the LPG liquid cargo tank 5 can be increased to more than 20 bar, and the storage capacity of gaseous CO2 can be increased. For a typical 5000m 3 Taking the LPG "Zhaoyuan" ship as an example, it is assumed that the sailing time of the ship is 10 days, and the density under the condition of 30 bar pressure is 58.9 kg / m 3 If the captured gaseous CO2 is pressurized to 30 bar, T obtained according to the above formula T is about 11 days. It can be seen that by increasing the maximum working pressure of the LPG liquid cargo tank 5, the LPG liquid cargo tank 5 can completely store the CO2 captured during the 10-day voyage during the return voyage of the empty ship.

[0045] However, based on the cost problem, the thickness of the tank wall of the LPG liquid cargo tank 5 should not be too thick, so the maximum working pressure of the LPG liquid cargo tank 5 designed in the present application is generally not more than 30 bar. If the corresponding p under the condition of 30 bar is substituted into the formula T, the obtained T is still less than x. When the ship is put into use, the captured gaseous CO2 can be pressurized and stored in the LPG liquid cargo tank 5 during the return voyage of the empty ship, and the remaining days are used to change the gaseous CO2 into liquid by liquefaction treatment, and then flow into the liquid CO2 storage tank 1 for storage. When the ship arrives at the port, the gaseous CO2 stored in the LPG liquid cargo tank 5 and the liquid CO2 stored in the liquid CO2 storage tank 1 are sent to the land for treatment.

[0046] The second type is a ship which has been put into operation

[0047] For the ship that has been put into operation, T is calculated by using the above formula, and by comparing x and T, it is divided into the following two cases:

[0048] Case 1: When the sailing time x≤T, the captured gaseous CO2 can be pressurized to the same pressure as the LPG liquid cargo tank 5 safety valve set pressure p1 by the compressor 2 during the empty return voyage of the ship, and then stored in the LPG liquid cargo tank 5, and when the ship returns to the loading port, the part of gaseous CO2 is sent to the land for treatment.

[0049] Case 2: When the sailing time x>T, the captured gaseous CO2 can be pressurized and stored in the LPG liquid cargo tank 5 during the empty return voyage of the ship, and the remaining days of the captured CO2 are liquefied at a certain pressure by using low temperature method, so as to flow into the liquid CO2 storage tank 1 for storage, and when the ship docks at the port, the gaseous CO2 stored in the LPG liquid cargo tank 5 and the liquid CO2 stored in the liquid CO2 storage tank 1 are sent to the land for treatment.

[0050] During the sailing of the ship, a large amount of CO2 will be generated, if all the captured CO2 is liquefied, the refrigerating unit needs to be continuously operated, and the temperature of CO2 liquefaction is very low (when the gas pressure is 0.7 MPa, the CO2 liquefaction temperature is about-50℃), a large amount of cold energy needs to be consumed, which makes the power consumption of the ship large, and a large economic cost is generated. In addition, the CO2 liquefaction process has many links, and the management personnel need to have sufficient management experience and technical level, and the labor force required for supervision is high, which makes the personnel cost also increased. The LPG in the LPG liquid cargo tank 5 is unloaded when the ship arrives at the destination port, and the gaseous CO2 captured by the ship is introduced into the empty LPG liquid cargo tank 5 when the ship returns empty, and when the ship returns to the loading port, the part of CO2 is sent to the land for treatment, the space on the land is sufficient, and the CO2 liquefaction system and various treatment methods are more perfect, and the cost of CO2 treatment on the land is far lower than that on the ship. The whole operation process of the present application is simple and convenient to manage, the cost of liquefying CO2 during the return voyage can be saved, which is equivalent to saving about half of the cost of liquefying CO2 during the sailing of the ship, and has good economy and practicability.

[0051] The above is only a preferred embodiment of the present application, but when implemented, it is not limited by the above embodiments, it should be pointed out that for ordinary skilled in the art, without departing from the principle of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A method for storing captured CO2 in a full pressure LPG ship liquid cargo tank characterized in that: The system comprises a liquid CO2 storage tank (1), a compressor (2), a seawater heat exchanger (3), a stop valve (4), an LPG liquid cargo tank (5), The main engine of the ship is connected with the CO2 capture system through a pipeline, the CO2 capture system is connected with the compressor (2) through a pipeline, the compressor (2) is connected with the seawater heat exchanger (3), the stop valve (4) and the LPG liquid cargo tank (5) through a pipeline in sequence, A stop valve (4) is arranged on the pipeline between the LPG liquid cargo tank (5) and the seawater heat exchanger (3), the LPG liquid cargo tank (5) is a full-pressure liquid cargo tank, and a pressure-resistant material is adopted, and the maximum working pressure is the same as the set pressure of the liquid cargo tank safety valve, When the ship sails in full load, the exhaust gas discharged by the main engine of the ship enters the CO2 capture system, the CO2 in the exhaust gas is captured and separated in the CO2 capture system, the remaining gas is discharged into the atmosphere, the captured CO2 is sent into the CO2 liquefaction system through a pipeline, the CO2 captured is subjected to liquefaction treatment in the CO2 liquefaction system, and then the liquid CO2 flows into the liquid CO2 storage tank (1) for storage, When the ship arrives at the destination port and the LPG in the LPG liquid cargo tank (5) is unloaded, the ship sails in empty load, the exhaust gas discharged by the main engine of the ship enters the CO2 capture system, the CO2 in the exhaust gas is captured and separated in the CO2 capture system, the remaining gas is discharged into the atmosphere, the captured CO2 enters the compressor (2) through a pipeline, the compressor (2) pressurizes the gaseous CO2, the gaseous CO2 is sent into the seawater heat exchanger (3) for cooling, and finally the gaseous CO2 is introduced into the LPG liquid cargo tank (5) for storage, and when the ship is at the port, the gaseous CO2 stored in the LPG liquid cargo tank (5) is transported to the land for treatment.

2. The method of claim 1, wherein: The system is used for both newly-built ships and ships already put into operation, The first type is for a newly-built ship not yet put into operation, the number of days T required for filling the LPG liquid cargo tank (5) with gaseous CO2 and reaching the maximum working pressure of the liquid cargo tank is calculated, T is compared with the sailing time x of the ship, and there are two cases, Case 1, x≤T, when the ship sails in empty load, the captured gaseous CO2 is introduced into the LPG liquid cargo tank (5) for storage, Case 2, x>T, the LPG liquid cargo tank (5) is thickened at the beginning of construction, so that T is increased, if T≥x, when the ship sails in empty load, the captured gaseous CO2 is introduced into the LPG liquid cargo tank (5) for storage, if T is still less than x, during the period when the ship sails in empty load, the gaseous CO2 captured in T days is introduced into the LPG liquid cargo tank (5) for storage, and the gaseous CO2 in the remaining days is converted into liquid by liquefaction treatment and flows into the liquid CO2 storage tank (1) for storage, The second type is for a ship already put into operation, T is compared with x, and there are two cases, Case 1, x≤T, when the ship sails in empty load, the captured gaseous CO2 is introduced into the LPG liquid cargo tank (5) for storage, Case 2, when x > T, the gaseous CO2 captured in T days is passed into the LPG liquid cargo tank (5) for storage, and the remaining days are treated by liquefaction to convert gaseous CO2 into liquid, and flow into the liquid CO2 storage tank (1) for storage.

Images