Liquefied carbon dioxide gas injection system and liquefied carbon dioxide gas injection method

Abstract

To provide a liquefied carbon dioxide gas press-injection system capable of press-injection of liquefied carbon dioxide gas to sea bottom at low cost.SOLUTION: A liquefied carbon dioxide gas press-injection system 10 includes: a floating body 12 moored off shore; a temperature and pressure raising facility 18 loaded on the floating body 12 and for raising temperature and pressure of liquefied carbon dioxide gas; a loading hose 14 for feeding liquefied carbon dioxide gas from a liquefied carbon dioxide gas storage tank 20 in a liquefied carbon dioxide gas transporting vessel 100 to the temperature and pressure raising facility 18 of the floating body 12; and a flexible riser pipe 16 connected to the floating body 12 and for press-injecting the liquefied carbon dioxide gas having temperature and pressure raised by the temperature and pressure raising facility 18 to the sea bottom.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a system and method for injecting liquefied carbon dioxide (liquefied CO2) in CCS (Carbon Capture and Storage). [Background technology]

[0002] CCS (Carbon dioxide capture and storage) is a measure to combat global warming, in which CO2 is captured from its source (such as flue gas from a coal-fired power plant) using methods such as chemical absorption, compressed and liquefied, and then injected in a supercritical state into an underground aquifer (reservoir) shielded by bedrock or other barriers, where it is stored.

[0003] There are various methods for CCS, one of which is the liquefied carbon dioxide transportation and injection method. In this method, the separated and captured CO2 is compressed and liquefied, and temporarily stored in tanks on land in the form of liquefied carbon dioxide. From the tanks, it is loaded onto a liquefied carbon dioxide transport ship and transported by ship to a storage site. At the storage site, the liquefied carbon dioxide is injected from the liquefied carbon dioxide transport ship into an aquifer beneath the seabed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-84630 Summary of the Invention [Problem to be solved by the invention]

[0005] When injecting liquefied carbon dioxide into a reservoir (aquifer), in order to prevent the surrounding water from freezing and to prevent blockage due to the formation of CO2 hydrate, the liquefied carbon dioxide (for example, -10°C / 2.289 MPa to -50°C / 0.684 MPa) is pressurized to a specified pressure (10 MPa or more), and then heated to above 0°C before injection.

[0006] When liquefied carbon dioxide is heated and pressurized on board a liquefied carbon dioxide transport vessel and then injected into the seabed, a flexible riser pipe must be connected to the vessel before injection begins, and then removed from the vessel after injection is complete.This work must be carried out every time the vessel arrives.However, this method has the problem of increasing costs for manufacturing, installing, and maintaining a specialized subsea system that is highly reliable and durable.

[0007] The present invention has been made in consideration of these circumstances, and its purpose is to provide a liquefied carbon dioxide injection system and a liquefied carbon dioxide injection method that can inject liquefied carbon dioxide into the seabed at low cost. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the present invention provides a liquefied carbon dioxide injection system comprising a float moored on the ocean, heating and pressurizing equipment mounted on the float for heating and pressurizing liquefied carbon dioxide, a loading hose for transporting liquefied carbon dioxide from a liquefied carbon dioxide storage tank in a liquefied carbon dioxide transport vessel to the heating and pressurizing equipment on the float, and a flexible riser pipe connected to the float for transporting the liquefied carbon dioxide heated and pressurized by the heating and pressurizing equipment to the seabed for injection. The float does not have a tank for storing liquefied carbon dioxide, and the injection system is remotely operated from the transport vessel for unmanned operation.

[0009] Another aspect of the present invention is a method for injecting liquefied carbon dioxide, which includes the steps of: approaching a float moored on the ocean with a liquefied carbon dioxide transport vessel; connecting a gangway provided on the liquefied carbon dioxide transport vessel to the float and having workers transfer from the liquefied carbon dioxide transport vessel to the float; connecting a liquefied carbon dioxide storage tank in the liquefied carbon dioxide transport vessel to heating and pressurization equipment mounted on the float with a loading hose; sending liquefied carbon dioxide from the liquefied carbon dioxide storage tank to the heating and pressurization equipment via the loading hose; heating and pressurizing the liquefied carbon dioxide with the heating and pressurization equipment; and sending the heated and pressurized liquefied carbon dioxide to the seabed through a flexible riser pipe and injecting it. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a liquefied carbon dioxide injection system and a liquefied carbon dioxide injection method that can inject liquefied carbon dioxide into the seabed at low cost. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic flow of a CCS in which a liquefied carbon dioxide injection system according to an embodiment of the present invention is used. [Figure 2] 1 is a schematic diagram of a liquefied carbon dioxide gas injection system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below based on preferred embodiments with reference to the drawings. The following configurations are for illustrative purposes only to facilitate understanding of the present disclosure, and the scope of the present disclosure is defined solely by the appended claims. Identical or equivalent components and parts shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted where appropriate. Furthermore, the dimensions of the components in each drawing are enlarged or reduced as appropriate to facilitate understanding. Furthermore, some components that are not important for explaining the embodiments in each drawing are omitted.

[0013] Fig. 1 is a diagram showing a schematic flow of a CCS using a liquefied carbon dioxide injection system according to an embodiment of the present invention. Fig. 1 shows a CCS that uses liquefied carbon dioxide transportation and injection.

[0014] In CCS, CO2 is separated and captured from a CO2 source, such as flue gas from a coal-fired power plant, using, for example, chemical absorption. The captured CO2 is then compressed and liquefied by a compression and liquefaction unit 101 and stored in a land-based tank 102 in the form of liquefied carbon dioxide. The liquefied carbon dioxide is loaded from the tank 102 onto a liquefied carbon dioxide transport ship 100 using a loading arm 103, and transported by ship to a floating body 12 moored on the ocean 110.

[0015] The liquefied carbon dioxide gas loaded on the liquefied carbon dioxide gas transport vessel 100 is sent to the heating and pressurizing equipment mounted on the float 12 via a loading hose 14. The liquefied carbon dioxide gas that has been heated and pressurized by the heating and pressurizing equipment is sent to a wellhead equipment 104 installed on the seabed 112 via a flexible riser pipe 16. The liquefied carbon dioxide gas is injected by the wellhead equipment 104 into a reservoir 114 below the seabed.

[0016] 2 is a schematic diagram of a liquefied carbon dioxide injection system 10 according to an embodiment of the present invention. The liquefied carbon dioxide injection system 10 includes a float 12 moored on the ocean 110, a heating and pressurizing facility 18 mounted on the float 12, a loading hose 14 connecting a liquefied carbon dioxide transport vessel 100 and the float 12, a flexible riser pipe 16 permanently connected to the float 12, and a gangway 24 stretched between the liquefied carbon dioxide transport vessel 100 and the float 12.

[0017] The liquefied carbon dioxide gas transport ship 100 includes a liquefied carbon dioxide gas storage tank 20 and a gangway 24. The liquefied carbon dioxide gas storage tank 20 stores liquefied carbon dioxide gas (liquefied CO2). The temperature of the liquefied carbon dioxide gas may be, for example, -10°C to -50°C, and the pressure of the liquefied carbon dioxide gas may be, for example, 2.289 MPa to 0.684 MPa.

[0018] The gangway 24 is a movable connecting bridge (telescopic gangway) that allows workers to move between the liquefied carbon dioxide transport ship 100 and the floating body 12, and has the functions of moving, raising, lowering, and extending. The gangway 24 is installed on the liquefied carbon dioxide transport ship 100. When the liquefied carbon dioxide transport ship 100 approaches the floating body 12, the gangway 24 is stretched from the liquefied carbon dioxide transport ship 100 to the floating body 12.

[0019] The float 12 is an advanced spar (SPAR (cylindrical)) type simple floating offshore base. Advanced spar type floats are characterized by their small size and low pitching. The float 12 comprises an upper hull section 30 located above sea level, a lower hull section 32 located underwater, and a column section 34 connecting the upper hull section 30 and the lower hull section 32. The advanced spar type float reduces pitching by the upper hull section 30 and the lower hull section 32 canceling out the pressure of waves. In addition, because the advanced spar type float has a smaller draft than a normal spar type float, it can be constructed and transported in an upright position and installed in relatively shallow waters.

[0020] 2, a mooring line 36 extending from the seabed is connected to the lower hull section 32. A turntable 38 is provided on top of the upper hull section 30, and a loading hose reel 40 and a mooring hawser winch 42 are installed on the turntable 38.

[0021] The upper hull 30 of the float 12 is provided with a heating and pressurizing system 18 and a power generation system 19 that supplies power to the heating and pressurizing system 18. The heating and pressurizing system 18 is a system that increases the pressure of liquefied carbon dioxide gas (for example, -10°C / 2.289 MPa to -50°C / 0.684 MPa) received via the loading hose 14 in order to inject it into a reservoir 114 (see FIG. 1) on the seabed, and also increases the temperature of the liquefied carbon dioxide gas when it is injected into the reservoir 114 in order to prevent freezing of the surrounding water and blockage due to the formation of CO2 hydrate.

[0022] Here, the conditions for injecting liquefied carbon dioxide gas in CCS will be explained. (1) Pressurization pressure The injection pressure varies depending on the depth and permeability of the reservoir 114, but is generally expressed as "Static Head + 3 MPa ~ Breakdown pressure of the shielding layer" at the injection point. In the case of CCS in the seabed reservoir 114, taking into account the injection depth, density of the liquefied carbon dioxide, and pressure loss in the well, the optimum injection pressure is approximately 10 MPa to 20 MPa at the seabed wellhead facility 104 (see Figure 1). (2) Indentation temperature When liquefied carbon dioxide is injected into the reservoir 114, it must be heated before injection to prevent the surrounding water from freezing (above 0°C) and to prevent blockage due to CO2 hydrate formation (below 5°C). Considering that in past CCS cases no blockage due to CO2 hydrate formation occurred when injected at 0°C, it is preferable that the injection temperature of liquefied carbon dioxide be 0°C or higher.

[0023] The loading hose 14 is a hose for sending liquefied carbon dioxide 22 stored in a liquefied carbon dioxide storage tank 20 inside the liquefied carbon dioxide transport ship 100 to the heating and pressurizing equipment 18 of the floating body 12. The loading hose 14 connects the liquefied carbon dioxide storage tank 20 and the heating and pressurizing equipment 18. A hose other than the loading hose 14 may be interposed between the liquefied carbon dioxide storage tank 20 and the heating and pressurizing equipment 18. The liquefied carbon dioxide 22 is transferred using a cargo pump 21. A drum (not shown) for temporarily storing the liquefied carbon dioxide 22 from the liquefied carbon dioxide storage tank 20 may be arranged before the heating and pressurizing equipment 18.

[0024] The liquefied carbon dioxide gas heated and pressurized by the heating and pressurizing equipment 18 is sent to the wellhead equipment 104 on the seabed via the flexible riser pipe 16 and is injected into the reservoir 114. One end of the flexible riser pipe 16 is permanently connected to the upper hull portion 30 of the floater 12, and the other end of the flexible riser pipe 16 is connected to the wellhead equipment 104 on the seabed (see FIG. 1). Note that although one flexible riser pipe 16 is shown in FIG. 2, multiple flexible riser pipes 16 may be arranged as shown in FIG. 1.

[0025] Next, a method for injecting liquefied carbon dioxide gas using the liquefied carbon dioxide gas injection system 10 will be described.

[0026] First, the liquefied carbon dioxide gas transport vessel 100 approaches the floating body 12 moored on the ocean. Then, the mooring hawser 44 is used to move the liquefied carbon dioxide gas transport vessel 100 close to the floating body 12 to a position about 30 m away.

[0027] Next, the gangway 24 provided on the liquefied carbon dioxide transport ship 100 is connected to the floating body 12. Workers move from the liquefied carbon dioxide transport ship 100 to the floating body 12 via the gangway.

[0028] Next, the loading hose 14 wound around the loading hose reel 40 of the float 12 is let out and connected to the bow loading system 48 provided on the liquefied carbon dioxide transport ship 100. This connects the liquefied carbon dioxide storage tank 20 in the liquefied carbon dioxide transport ship 100 and the heating and pressurizing equipment 18 installed on the float 12.

[0029] The workers who have moved to the floater 12 start up the power generation equipment 19 and heating and pressurizing equipment 18 on the floater 12. Liquefied carbon dioxide is sent from the liquefied carbon dioxide storage tank 20 to the heating and pressurizing equipment 18 via the loading hose 14. The heating and pressurizing equipment 18 raises the temperature (to approximately 0°C) and pressure (to approximately 10 MPaG) of the liquefied carbon dioxide that it has received. The liquefied carbon dioxide that has been heated and pressurized by the heating and pressurizing equipment 18 is sent to the seabed via the flexible riser pipe 16, and injection into the reservoir 114 begins.

[0030] After the injection of liquefied carbon dioxide has begun, the workers use the gangway 24 to return to the liquefied carbon dioxide transport vessel 100. The float 12 is left unmanned. After the workers return to the liquefied carbon dioxide transport vessel 100, the gangway 24 is moved away from the float 12. The liquefied carbon dioxide transport vessel 100 is then moved to a position away from the float 12. The liquefied carbon dioxide transport vessel 100 is moored by the mooring hawser 44 at a position approximately 100 m to 120 m away from the float 12.

[0031] Thereafter, steady-state injection of liquefied carbon dioxide begins. Until the subsea injection of the liquefied carbon dioxide 22 stored in the liquefied carbon dioxide storage tank 20 of the liquefied carbon dioxide transport vessel 100 is completed, the power generation equipment 19 and heating and pressurization equipment 18 of the floater 12 are operated unmanned and are monitored and operated remotely from the liquefied carbon dioxide transport vessel 100.

[0032] Every fixed time (8 to 12 hours), workers inspect the operating status of the float 12's facilities, equipment, instruments, etc. During inspection, the liquefied carbon dioxide transport vessel 100 is brought close to the float, the gangway 24 is connected to the float 12, and the workers move from the liquefied carbon dioxide transport vessel 100 to the float 12 to perform the inspection work. After the inspection work is completed, the workers return from the float 12 to the liquefied carbon dioxide transport vessel 100. Then, the gangway 24 is moved away from the float 12, and the liquefied carbon dioxide transport vessel 100 is moved to a position away from the float 12 and moored. The same applies when a malfunction occurs in the float 12's facilities, etc.

[0033] After the entire amount of liquefied carbon dioxide 22 stored in the liquefied carbon dioxide storage tank 20 has been injected into the seabed, the detachment work begins. The liquefied carbon dioxide transport vessel 100 is brought close to the float, and the gangway 24 is connected to the float 12. Workers move from the liquefied carbon dioxide transport vessel 100 to the float 12, shut down the power generation equipment 19 and the heating and pressurization equipment 18, and stop the injection of liquefied carbon dioxide. The loading hose 14 is then detached from the liquefied carbon dioxide transport vessel 100 and wound up by the loading hose reel 40 on the turntable 38 of the float 12. After the workmen return to the liquefied carbon dioxide transport vessel 100, the gangway 24 is detached from the float 12. After the mooring hawser 44 is detached from the liquefied carbon dioxide transport vessel 100, the liquefied carbon dioxide transport vessel 100 detaches from the float 12 using the propulsion device. The mooring hawser 44 is kept floating on the sea until the next liquefied carbon dioxide transport vessel 100 arrives.

[0034] The above has described the liquefied carbon dioxide injection system 10 according to an embodiment of the present invention. In the liquefied carbon dioxide injection system 10 according to this embodiment, liquefied carbon dioxide is supplied directly from the liquefied carbon dioxide storage tank 20 of the liquefied carbon dioxide transport vessel 100 to the heating and pressurizing equipment 18 of the float 12, so there is no need to provide a tank for storing liquefied carbon dioxide on the float 12. In other words, the liquefied carbon dioxide storage tank 20 that is originally provided on the liquefied carbon dioxide transport vessel 100 is reused as a storage tank. As a result, the float 12 can be made smaller and the construction cost of the float 12 can be significantly reduced.

[0035] The liquefied carbon dioxide injection system 10 according to this embodiment employs an advanced spar-type float because it allows for the float 12 to be made smaller. The advanced spar-type float is characterized by its resistance to rocking even in rough waves, allowing the heating and pressurization equipment 18 to continue operating stably without stopping even under rough ocean waves. Furthermore, because the advanced spar-type float rocks less even in rough waves, the load on the connection between the flexible riser pipe 16 and the float 12 is reduced. As a result, the service life of the flexible riser pipe 16 can be extended.

[0036] Furthermore, in the liquefied carbon dioxide injection system 10 according to this embodiment, workers use the gangway 24 to move from the liquefied carbon dioxide transport vessel 100 to the floating body 12 to perform work only when necessary, such as when starting up the heating and pressurizing equipment 18. This eliminates the need for workers to be permanently stationed on the floating body 12, enabling the floating body 12 to be unmanned. After steady-state injection operation begins, the floating body 12's equipment is remotely monitored and operated from the liquefied carbon dioxide transport vessel 100. As a result, there is no need to provide facilities (such as living facilities) for workers to be permanently stationed on the floating body 12, reducing the construction costs of the floating body 12. Furthermore, since permanent stationing on the floating body 12 is no longer necessary, labor costs can be reduced, enabling further cost reductions. The motion-absorbing gangway system allows workers to move smoothly even in rough ocean waves.

[0037] Furthermore, in the liquefied carbon dioxide injection system 10 according to this embodiment, a gangway 24 is used for transferring workers from the liquefied carbon dioxide transport vessel 100 to the floating body 12. This makes it possible for workers to transfer in high waves compared to when workers are transferred using a small vessel, which improves the efficiency of the loading hose connection work and the operating rate of the entire injection work process. It also reduces the risk of workers being left behind on the floating body for long periods of time, thereby improving safety.

[0038] Furthermore, in the liquefied carbon dioxide injection system 10 according to this embodiment, the floating body 12 is equipped with the heating and pressurizing equipment 18, so the pressure of the liquefied carbon dioxide can be kept low (for example, 0.684 MPa to 2.289 MPa) when it is transferred from the liquefied carbon dioxide transport vessel 100 to the floating body 12. This eliminates the need to attach and detach high-pressure pipes, improving workability. Furthermore, by installing the heating and pressurizing equipment 18 on the floating body 12, it is no longer necessary to install heating and pressurizing equipment on the liquefied carbon dioxide transport vessel 100, so the construction cost of the liquefied carbon dioxide transport vessel 100 can be significantly reduced.

[0039] Furthermore, in the liquefied carbon dioxide injection system 10 according to this embodiment, the flexible riser pipe 16, which is a high-pressure pipe, is constantly connected to the floating body 12. This eliminates the need to attach and detach the flexible riser pipe 16 when starting or finishing the seabed injection work of liquefied carbon dioxide, and also eliminates the need for a special and expensive underwater system connecting the transport ship to the seabed, thereby improving work efficiency.

[0040] The present invention has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and treatment processes, and that such modifications are also within the scope of the present invention.

[0041] For example, in the above-described embodiment, an advanced spar type float is used as the float, but the float is not limited to the advanced spar type and may be a normal spar type float. [Explanation of symbols]

[0042] 10 Liquefied carbon dioxide injection system, 12 Floating body, 14 Loading hose, 16 Flexible riser pipe, 18 Heating and pressurizing equipment, 19 Power generation equipment, 20 Liquefied carbon dioxide storage tank, 21 Cargo pump, 22 Liquefied carbon dioxide, 24 Gangway, 30 Upper hull section, 32 Lower hull section, 34 Column section, 36 Mooring line, 38 Turntable, 40 Loading hose reel, 42 Mooring hawser winch, 44 Mooring hawser, 48 Bow loading system, 100 Liquefied carbon dioxide transport ship, 101 Compression and liquefaction equipment, 102 Tank, 103 Loading arm, 104 Wellhead equipment.

Claims

1. A liquefied carbon dioxide injection system that injects liquefied carbon dioxide loaded on a liquefied carbon dioxide transport ship into the seabed, An advanced spar type floating body moored on the ocean, the advanced spar type floating body not having a storage tank for liquefied carbon dioxide gas; a heating and pressurizing facility for heating and pressurizing liquefied carbon dioxide gas, the heating and pressurizing facility being mounted on the advanced spar-type floating body; a loading hose for sending liquefied carbon dioxide from a liquefied carbon dioxide storage tank in the liquefied carbon dioxide transport ship to the heating and pressurizing equipment of the advanced spar-type float; a flexible riser pipe connected to the advanced spar-type float for sending and injecting the liquefied carbon dioxide gas heated and pressurized by the heating and pressurizing equipment to the seabed; A liquefied carbon dioxide gas injection system comprising:

2. The liquefied carbon dioxide injection system described in claim 1, characterized in that the heating and pressurizing equipment installed on the advanced spar type float is operated unmanned by remote control from the liquefied carbon dioxide transport ship, and the advanced spar type float is not equipped with living facilities for workers.

3. A liquefied carbon dioxide injection system as described in claim 1 or 2, further comprising a gangway that allows workers to move between the liquefied carbon dioxide transport ship and the advanced spar-type floating body.

4. 4. A liquefied carbon dioxide gas injection system according to claim 1, wherein the flexible riser pipe is permanently connected to the advanced spar type floating body.

5. A liquefied carbon dioxide injection method for injecting liquefied carbon dioxide loaded on a liquefied carbon dioxide transport ship into the seabed, comprising: a step of approaching an advanced spar type float moored on the ocean by the liquefied carbon dioxide transport ship, the advanced spar type float not having a storage tank for liquefied carbon dioxide; a step of connecting a gangway provided on the liquefied carbon dioxide transport ship to the advanced spar type float and having workers transfer from the liquefied carbon dioxide transport ship to the advanced spar type float; a step of connecting a liquefied carbon dioxide storage tank in the liquefied carbon dioxide transport ship and a heating and pressurizing facility mounted on the advanced spar-type floating body by a loading hose; Sending liquefied carbon dioxide from the liquefied carbon dioxide storage tank to the heating and pressurizing equipment through the loading hose; A step of increasing the temperature and pressure of liquefied carbon dioxide gas by the temperature and pressure increasing equipment; sending the heated and pressurized liquefied carbon dioxide gas to the seabed through a flexible riser pipe and injecting it; A method for injecting liquefied carbon dioxide gas, comprising:

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