Liquefied carbon dioxide heating equipment and liquefied carbon dioxide heating method

Abstract

To suitably raise the temperature of liquefied carbon dioxide in CCS.SOLUTION: A liquefied carbon dioxide temperature rising facility 10 includes: a heat medium temperature rising device 18 that receives a supply of seawater and a heat medium and raises the temperature of the heat medium by heat exchange with the seawater; a heat exchanger for temperature rising 16 that raises the temperature of liquefied carbon dioxide to a predetermined temperature by heat exchange with the heat medium whose temperature has been raised by the heat medium temperature rising device 18; and a heat medium temperature control section 30 to perform control so that the temperature of the heat medium supplied to the heat medium temperature rising device 18 can reach a freezing temperature of the seawater or higher.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] CCS (Carbon Dioxide Capture and Storage) is a global warming countermeasure that involves capturing CO2 from a CO2 source (such as flue gas from a coal-fired power plant) using methods such as chemical absorption, compressing it, and injecting it in a supercritical state into an underground aquifer (reservoir) shielded by rock or other barriers, for storage. (For more information on CCS, see Patent Documents 1 and 2, for example.)

[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 the storage site. At the storage site, the liquefied carbon dioxide is injected from the liquefied carbon dioxide transport ship into the aquifer below the seabed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-31154 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-72012 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] Some kind of heat source is required to heat the liquefied carbon dioxide, but the available heat sources are limited given the conditions on board a liquefied carbon dioxide transport ship. One possible method is to generate hot water using a hot water boiler and heat exchange the hot water with the liquefied carbon dioxide to heat the liquefied carbon dioxide. However, this method has the problem of increasing costs because the hot water boiler consumes a large amount of fuel, and also of CO2 emissions associated with fuel consumption.

[0007] The present invention has been made in view of the above circumstances, and its purpose is to provide a technology that can suitably raise the temperature of liquefied carbon dioxide gas in a CCS. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the liquefied carbon dioxide heating equipment of the present invention comprises a heat medium heater that receives a supply of seawater and a heat medium and heats the heat medium by heat exchange with the seawater, a heating heat exchanger that heats the liquefied carbon dioxide to a predetermined temperature by heat exchange with the heat medium heated in the heat medium heater, and a heat medium temperature control unit that controls the temperature of the heat medium supplied to the heat medium heater so that it is above the freezing temperature of seawater.

[0009] Another aspect of the present invention is a method for heating liquefied carbon dioxide, which includes the steps of supplying seawater and a heat medium to a heat medium heater, using the heat medium heater to heat the heat medium by heat exchange with the seawater, heating the liquefied carbon dioxide to a predetermined temperature by heat exchange with the heat medium, and controlling the temperature of the heat medium supplied to the heat medium heater so that it is equal to or higher than the freezing point of seawater. [Effects of the Invention]

[0010] According to the present invention, a technique can be provided that can suitably increase the temperature of liquefied carbon dioxide gas in a CCS. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic flow of a CCS in which liquefied carbon dioxide heating equipment according to an embodiment of the present invention is used. [Figure 2] FIG. 1 is a diagram for explaining a liquefied carbon dioxide gas heating equipment according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating a liquefied carbon dioxide gas heating facility according to another 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] Figure 1 is a diagram showing the outline of the flow of CCS using liquefied carbon dioxide heating equipment according to an embodiment of the present invention. Figure 1 shows a CCS that uses liquefied carbon dioxide transportation and injection. Other CCS methods include the subsea pipeline method and the ERD (Extended Reach Drilling) method.

[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, and stored in a tank on land in the form of liquefied carbon dioxide. The liquefied carbon dioxide is loaded from the tank onto a liquefied carbon dioxide transport ship 100 and transported by ship to a storage site 102 on the ocean 110.

[0015] The liquefied carbon dioxide gas loaded onto the liquefied carbon dioxide gas transport vessel 100 is pressurized and heated by the liquefied carbon dioxide gas heating equipment 10 installed on the liquefied carbon dioxide gas transport vessel 100, and then injected from the liquefied carbon dioxide gas transport vessel 100 into the aquifer 114 at the storage point 102. The aquifer 114 is a layer further below the insulating layer 112 located below the seabed.

[0016] In the CCS shown in Figure 1, liquefied carbon dioxide is sent to a well head 106 installed on the seabed via a flexible riser pipe (FRP) for connecting to subsea facilities. The liquefied carbon dioxide is then sent to a Xmas tree 108 via a flow line 107 laid on the seabed. A Xmas tree is a group of valves that control the pressure of fluid produced from a well. In the Xmas tree 108, the liquefied carbon dioxide is injected into an aquifer 114.

[0017] In the above, the liquefied carbon dioxide heating equipment 10 is installed on a liquefied carbon dioxide transport ship 100, but the liquefied carbon dioxide heating equipment 10 may also be installed on a bottom-mounted platform installed on the ocean or on a floating body moored on the ocean (FSO: Floating Storage and Offloading or Buoy).

[0018] 2 is a diagram illustrating a liquefied carbon dioxide heating system 10 according to an embodiment of the present invention. The liquefied carbon dioxide heating system 10 is a system that pressurizes liquefied carbon dioxide (for example, -10°C / 2.289 MPa to -50°C / 0.684 MPa) transported by ship in order to inject it into a reservoir (aquifer) on the seabed, and heats the liquefied carbon dioxide to prevent freezing of surrounding water and blockage due to the formation of CO2 hydrate when the liquefied carbon dioxide is injected into the reservoir.

[0019] Here, the injection conditions for CCS will be explained. (1) Press-in pressure The injection pressure varies depending on the depth of the reservoir, its permeability, and the strength of the shielding layer, but is generally expressed as "Static Head + 3 MPa ~ the failure pressure of the shielding layer" at the injection point. In the case of CCS in an underground reservoir on the seabed, taking into account an injection depth of 2000m to 3000m, the density of liquefied carbon dioxide, and pressure loss in the well, the optimum injection pressure is around 10 MPa to 13 MPa at Christmas tree 108 on the seabed (see Figure 1). (2) Indentation temperature When liquefied carbon dioxide is injected into the reservoir (aquifer 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 no blockage due to CO2 hydrate formation has occurred when injected at 0°C in past CCS cases, it is preferable to inject liquefied carbon dioxide at a temperature of 0°C or higher.

[0020] As shown in FIG. 2 , the liquefied carbon dioxide heating equipment 10 includes a storage tank 12, a booster pump 14, a heating heat exchanger 16, a heat medium heater 18, a seawater pump 20, a heat medium drum 22, a heat medium pump 24, and a heat medium temperature control unit 30.

[0021] The storage tank 12 stores liquefied carbon dioxide gas (liquefied CO2). The temperature of the liquefied carbon dioxide gas may be -10°C to -50°C, and the pressure of the liquefied carbon dioxide gas may be 2.289 MPa to 0.684 MPa. The liquefied carbon dioxide gas stored in the storage tank 12 is supplied to a booster pump 14.

[0022] The boost pump 14 boosts the liquefied carbon dioxide gas supplied from the storage tank 12 to a predetermined pressure (for example, 10 MPa or more). The liquefied carbon dioxide gas pressurized by the boost pump 14 is supplied to a heat exchanger 16 for heating.

[0023] The heating heat exchanger 16 is a cylindrical-shell multi-tube heat exchanger having a plurality of heat transfer tubes housed within a cylindrical shell. In this embodiment, the cylindrical shell and heat transfer tubes of the heating heat exchanger are both made of ordinary steel. Liquefied carbon dioxide gas from the boost pump 14 is supplied to the tube side of the heating heat exchanger 16. The liquefied carbon dioxide gas is input to the tube side inlet 16a of the heating heat exchanger 16 and output from the tube side outlet 16b. Meanwhile, a heat transfer medium is supplied to the shell side of the heating heat exchanger 16. The heat transfer medium is input to the shell side inlet 16c of the heating heat exchanger 16 via line 33 and output from the shell side outlet 16d. The heating heat exchanger 16 exchanges heat between the liquefied carbon dioxide gas supplied to the tube side and the heat transfer medium supplied to the shell side, thereby heating the liquefied carbon dioxide gas to a predetermined temperature (0°C or higher).

[0024] The heat medium used is one that does not freeze even at the temperature (-10°C to -50°C) of the liquefied carbon dioxide gas supplied to the heating heat exchanger 16 (antifreeze liquid). Examples of such heat medium include an ethylene glycol aqueous solution, a propylene glycol aqueous solution, a mixed solution of an ethylene glycol aqueous solution and an propylene glycol aqueous solution, or a hydrocarbon compound solution. The content of ethylene glycol, propylene glycol, hydrocarbon compound, etc. in each solution is set so that it does not freeze at the temperature of the liquefied carbon dioxide gas supplied, and is set to, for example, 10 wt% or more of ethylene glycol or 10 wt% or more of propylene glycol. These solutions preferably contain a rust inhibitor.

[0025] The heat medium output from the shell side outlet 16d of the heating heat exchanger 16 is supplied to the heat medium drum 22 via a line 34. The heat medium is then supplied to the heat medium heater 18 by the heat medium pump 24.

[0026] The heat medium temperature control unit 30 controls the temperature of the heat medium supplied to the heat medium heater 18 so that it is equal to or higher than the freezing temperature (-2°C) of seawater. The heat medium temperature control unit 30 includes a control valve 26 and a temperature sensor .

[0027] 2, the control valve 26 is installed in a bypass line 32 that bypasses the shell side inlet 16c and shell side outlet 16d of the heating heat exchanger 16. That is, the bypass line 32 bypasses a line 33 that connects the heat medium outlet 18b of the heat medium heater 18 and the shell side inlet 16c of the heating heat exchanger 16, and a line 34 that connects the shell side outlet 16d of the heating heat exchanger 16 and the inlet 22a of the heat medium drum 22.

[0028] The temperature sensor 28 is disposed so as to detect the temperature of the heat medium after the heat medium output from the shell side outlet 16d of the heating heat exchanger 16 and the heat medium from the bypass line 32 are joined together. Based on the value detected by the temperature sensor 28, the control valve 26 controls the flow rate of the heat medium flowing through the bypass line 32 so that the temperature of the heat medium after joining, i.e., the temperature of the heat medium supplied to the heat medium drum 22, is equal to or higher than the freezing temperature of seawater (-2°C).

[0029] The heat medium heater 18 receives seawater (e.g., 5°C or higher) and a heat medium (-2°C or higher) and heats the heat medium through heat exchange with the seawater. In this embodiment, the heat medium heater 18 is a plate-type heat exchanger equipped with titanium plates, which have excellent seawater corrosion resistance and abrasion resistance. Plate-type heat exchangers are characterized by their high heat transfer characteristics. In a plate-type heat exchanger, the fluid flows in approximately parallel flows, has a high heat transfer coefficient, has little deviation from one location to another, and is capable of sufficient heat exchange even with a temperature difference of 2°C between the fluids. Seawater is input to the seawater inlet 18c of the heat medium heater 18 by the seawater pump 20 and is output from the seawater outlet 18d of the heat medium heater 18. Meanwhile, the heat medium is input to the heat medium inlet 18a of the heat medium heater 18 and is output from the heat medium outlet 18b of the heat medium heater 18.

[0030] The operation of the liquefied carbon dioxide heating equipment 10 will be described using specific temperature examples. Here, we consider a case where liquefied carbon dioxide at -20°C and 1.97 MPa is pressurized and heated to 0°C and 10 MPa. The heat medium heater 18 receives, for example, seawater at 7°C and a heat medium (ethylene glycol aqueous solution: freezing temperature -23°C) at -1°C and heats the heat medium to 5°C. The heat medium heated by the heat medium heater 18 is supplied to the shell side inlet 16c of the heating heat exchanger 16 via line 33. The pressure boost pump 14 pressurizes the liquefied carbon dioxide at -20°C and 1.97 MPa to -20°C and 10.5 MPa. The heating heat exchanger 16 heats the liquefied carbon dioxide at -20°C and 10.5 MPa supplied to the pipe side inlet 16a to 0°C (10.2 MPa) by heat exchange with the 5°C heat medium. When liquefied carbon dioxide gas at -46°C and 0.80 MPa is pressurized and heated to 0°C and 10 MPa, the temperature at the outlet of the booster pump 14 becomes -46°C and 10.5 MPa, and the temperature and pressure at other locations remain the same.

[0031] The above has described the configuration of the liquefied carbon dioxide gas heating equipment 10 according to this embodiment. According to the liquefied carbon dioxide gas heating equipment 10 according to this embodiment, seawater is used to heat the liquefied carbon dioxide gas, which reduces costs compared to using a hot water boiler that requires fuel, and also emits very little CO2.

[0032] The lowest temperature of seawater in winter on the Sea of ​​Japan side is 6°C to 8°C (4°C to 6°C in the North Sea). If liquefied carbon dioxide at -10°C to -50°C is directly heat-exchanged with such low-temperature seawater, the seawater may freeze inside the heat exchanger, causing the heat exchanger to become clogged. Therefore, by exchanging heat between liquefied carbon dioxide and a heat medium with a low freezing temperature, as in the liquefied carbon dioxide heating equipment 10 of this embodiment, it is possible to prevent the heat exchanger from becoming clogged.

[0033] Heat exchange occurs between the seawater and the heat medium in the heat medium heater 18. However, in the liquefied carbon dioxide heating equipment 10 according to this embodiment, the heat medium temperature control unit 30 controls the temperature of the heat medium input to the heat medium inlet 18a of the heat medium heater 18 to be equal to or higher than the freezing temperature of seawater (approximately -2°C), so that freezing of seawater does not occur in the heat medium heater 18.

[0034] In the liquefied carbon dioxide heating equipment 10 according to this embodiment, the fluid supplied to the heating heat exchanger 16 is less corrosive, so ordinary steel can be used as the material instead of expensive titanium. As a result, the cost of the cylindrical-shell multi-tube type heating heat exchanger 16 can be significantly reduced.

[0035] In the liquefied carbon dioxide heating equipment 10 according to this embodiment, the heat medium heater 18 is a plate-type heat exchanger equipped with titanium plates, which have excellent resistance to seawater corrosion and abrasion. Titanium is used for seawater corrosion resistance, but the plate thickness is thin, at 0.4 mm to 0.7 mm, so the heat medium heater 18 is less expensive than a cylindrical-shell multi-tube heat exchanger that uses titanium heat transfer tubes.

[0036] Fig. 3 is a diagram illustrating a liquefied carbon dioxide gas heating equipment 40 according to another embodiment of the present invention. The liquefied carbon dioxide gas heating equipment 40 shown in Fig. 3 differs from the liquefied carbon dioxide gas heating equipment 10 shown in Fig. 2 in that it further includes a liquefied carbon dioxide gas vaporization heat exchanger 42.

[0037] The liquefied carbon dioxide gas vaporization heat exchanger 42 is a cylindrical-shell multi-tube heat exchanger, and the cylindrical shell and heat transfer tubes are both made of ordinary steel. A portion of the heat medium from the heat medium outlet 18b of the heat medium heater 18 is supplied to the tube side of the liquefied carbon dioxide gas vaporization heat exchanger 42. The heat medium is input to the tube-side inlet 42a of the liquefied carbon dioxide gas vaporization heat exchanger 42, output from the tube-side outlet 42b, and merged with the heat medium from the heating heat exchanger 16 via line 34. Meanwhile, a portion of the liquefied carbon dioxide gas from the storage tank 12 is supplied to the shell side of the liquefied carbon dioxide gas vaporization heat exchanger 42. The liquefied carbon dioxide gas is input to the shell-side inlet 42c of the liquefied carbon dioxide gas vaporization heat exchanger 42, heat-exchanges with the heat medium, is vaporized, and is output from the shell-side outlet 42d. The carbon dioxide gas output from the shell side outlet 42d of the liquefied carbon dioxide gas vaporization heat exchanger 42 is supplied to the storage tank 12 as return gas.

[0038] In the liquefied carbon dioxide heating equipment 40 of this embodiment, a portion of the liquefied carbon dioxide is vaporized and supplied to the storage tank 12 as a return, thereby preventing a drop in pressure in the storage tank 12 due to the discharge of liquefied carbon dioxide.

[0039] The operation of the liquefied carbon dioxide heating equipment 40 will be described using specific temperature examples. Here, we consider a case where liquefied carbon dioxide at -20°C and 1.97 MPa is pressurized and heated to 0°C and 10 MPa. The heat medium heater 18 receives, for example, seawater at 7°C and a heat medium (ethylene glycol aqueous solution: freezing temperature -23°C) at -1°C, and heats the heat medium to 5°C. The heat medium heated by the heat medium heater 18 is supplied to the shell side inlet 16c of the heating heat exchanger 16 via line 33. The pressure boost pump 14 pressurizes the liquefied carbon dioxide at -20°C and 1.97 MPa to -20°C and 10.5 MPa. The heating heat exchanger 16 heats the liquefied carbon dioxide at -20°C and 10.5 MPa supplied to the pipe side inlet 16a to 0°C (10.2 MPa) by heat exchange with the 5°C heat medium. A portion of the liquefied carbon dioxide gas at -20°C and 1.97 MPa is supplied to the shell side inlet 42c of the liquefied carbon dioxide gas vaporization heat exchanger 42. The liquefied carbon dioxide gas vaporization heat exchanger 42 vaporizes the liquefied carbon dioxide gas supplied to the shell side inlet 42c by heat exchange with a 5°C heat medium supplied to the pipe side inlet 42a, and outputs the vaporized gas from the shell side outlet 42d (-20°C, 1.97 MPa). When the pressure and temperature of liquefied carbon dioxide gas at -46°C and 0.80 MPa is increased to 0°C and 10 MPa, the outlet of the boost pump 14 is -46°C and 10.5 MPa, and the shell side outlet 42d of the liquefied carbon dioxide gas vaporization heat exchanger 42 is -46°C and 0.80 MPa, with the temperatures and pressures at other locations remaining the same.

[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. [Explanation of symbols]

[0041] 10,40 Liquefied carbon dioxide heating equipment, 12 Storage tank, 14 Booster pump, 16 Heat exchanger for heating, 18 Heat medium heater, 20 Seawater pump, 22 Heat medium drum, 26 Control valve, 28 Temperature sensor, 30 Heat medium temperature control unit, 32 Bypass line, 42 Liquefied carbon dioxide vaporization heat exchanger, 100 Liquefied CO2 transport ship.

Claims

1. a heat medium heater that receives seawater and a heat medium and raises the temperature of the heat medium by heat exchange with the seawater; a heating heat exchanger that heats the liquefied carbon dioxide gas to a predetermined temperature by heat exchange with the heat medium heated by the heat medium heater; a heat medium temperature control unit including a control valve provided in a bypass line that bypasses a first line that supplies the heat medium from the heat medium heater to the temperature-raising heat exchanger and a second line that supplies the heat medium from the temperature-raising heat exchanger to the heat medium heater, wherein the control valve controls the flow rate of the heat medium flowing through the bypass line so that the temperature of the heat medium supplied to the heat medium heater through the second line is equal to or higher than the freezing temperature of the seawater; A liquefied carbon dioxide gas heating system comprising:

2. the heating heat exchanger is a cylindrical-shell multi-tube heat exchanger having a plurality of heat transfer tubes housed in a cylindrical shell, The liquefied carbon dioxide gas is supplied to the heat transfer tube side of the heating heat exchanger, 2. The liquefied carbon dioxide heating facility according to claim 1, wherein the heat medium from the heat medium heater is supplied to the cylindrical shell side of the heating heat exchanger.

3. 3. The liquefied carbon dioxide heating equipment according to claim 2, wherein the cylindrical shell and the heat transfer tubes of the heating heat exchanger are both made of steel.

4. 4. A liquefied carbon dioxide heating system as described in any one of claims 1 to 3, wherein the heat medium is an ethylene glycol aqueous solution, a propylene glycol aqueous solution, a mixed solution of an ethylene glycol aqueous solution and a propylene glycol aqueous solution, or a solution of a hydrocarbon compound.

5. 5. The liquefied carbon dioxide heating system according to claim 1, wherein the heat medium heater is a plate-type heat exchanger having titanium plates.

6. A heat medium heater that receives seawater and a heat medium and heats the heat medium by heat exchange with the seawater; a heating heat exchanger that heats the liquefied carbon dioxide gas to a predetermined temperature by heat exchange with the heat medium heated by the heat medium heater; a heat medium temperature control unit that controls the temperature of the heat medium supplied to the heat medium heater so that the temperature is equal to or higher than the freezing temperature of the seawater; a storage tank for storing the liquefied carbon dioxide gas to be supplied to the heating heat exchanger; a liquefied carbon dioxide vaporization heat exchanger that receives a portion of the liquefied carbon dioxide from the storage tank and a portion of the heat medium from the heat medium heater, and vaporizes the liquefied carbon dioxide by heat exchange with the heat medium, The liquefied carbon dioxide gas heating equipment is characterized in that the carbon dioxide gas vaporized in the liquefied carbon dioxide gas vaporization heat exchanger is supplied to the storage tank.

7. supplying seawater and a heat medium to a heat medium heater; raising the temperature of the heat medium by heat exchange with the seawater using the heat medium heater; a step of heating the liquefied carbon dioxide gas to a predetermined temperature by heat exchange with the heat medium using a heating heat exchanger; using a control valve provided in a bypass line that bypasses a first line that supplies the heat medium from the heat medium heater toward the heating heat exchanger and a second line that supplies the heat medium from the heating heat exchanger toward the heat medium heater, to control the flow rate of the heat medium flowing through the bypass line so that the temperature of the heat medium supplied to the heat medium heater becomes equal to or higher than the freezing temperature of the seawater; A method for raising the temperature of liquefied carbon dioxide gas, comprising:

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