KR20150045033A - Superconducting cooling system and cooling method - Google Patents

Abstract

A superconducting cooling system for a liquefied gas carrier is disclosed. The superconducting cooling system includes an LNG storage tank, a first refrigerant line through which the LNG supplied from the LNG storage tank is circulated, a second refrigerant line through which refrigerant for cooling the superconducting device circulates, a heat exchange And a floating structure having such a superconducting cooling system.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a superconducting cooling system,

The present invention relates to a cooling system of a superconducting device, and relates to a superconducting cooling system and a cooling method using LNG as a coolant of a coolant for cooling a superconducting device of a liquefied gas carrier.

As global demand for fossil fuels grows, energy companies are tracking hydrocarbon resources located in farther distant areas of the world. This tracking occurs both on land and at sea. One type of fossil fuel is natural gas. The phrase "natural gas" generally refers to methane. Natural gas may also include trace elements of ethane, propane and helium, nitrogen, CO ₂ and H ₂ S. Commercially available amounts of natural gas are often found in locations remote from the existing natural gas market. Therefore, it is necessary to transport the natural gas at a considerable distance. This is often done by tankers across large waters. It is known to liquefy natural gas in order to increase the volume capacity of the tank for the gas product being transported. Liquefaction is achieved by cooling the gaseous product and condensing it into a liquid state. This in turn reduces its volume for economic transport to distant markets. Condensed natural gas products are commonly referred to as liquefied natural gas or "LNG ". LNG accounts for about 1/600 of the volume of gaseous natural gas. LNG is generally odorless, colorless, nontoxic and noncorrosive. Specified LNG carriers have been designed to transport LNG. In addition, an LNG terminal has been constructed to house the unloaded LNG and to vaporize it again in its natural gas state. In some cases, the unloaded LNG is stored in a tank near the coast or coast, or in an underground reservoir. In other cases, the unloaded LNG is discharged into the natural gas transmission grid for the existing natural gas market. In the area of original manufacture, a liquefaction process is performed in the LNG plant, which can be very capital intensive. The large refrigeration unit is required to cool the natural gas to the required temperature for the phase change to the liquid state. In the case of methane, the condensation point is approximately -162 ° C (-260 ° F). In an LNG plant, one or more refrigerant streams are placed in heat exchange with the natural gas at the time of manufacture. The refrigerant is typically a pure constituent hydrocarbon such as methane, ethane, ethylene, propane, butane, pentane or mixtures of these components. Nitrogen can also be used as a blend.

At present, LNG carriers that transport LNG (liquefied natural gas) use boil-off gas of LNG as a cargo as fuel for diesel generators, and propel electric propulsion motors to drive propelled electric power. However, in order to realize a more efficient electric propulsion system, development of a gas-fired superconducting electric propulsion ship employing a superconducting motor is under consideration. Recently, the superconducting motor has been cooled to about -196 DEG C by a heat pump using helium as a refrigerant. Further, Misumus strontium calcium copper oxide (BSCCO) is cooled to about 96K to 107K (about -178 DEG C to -166 DEG C ) Is designed to maintain the superconducting state.

Generally, in the case of a device using superconducting characteristics such as a superconducting cable, a superconducting fault current limiter, a superconducting generator, and a superconducting motor, the superconducting system must have a separate cooling system in order to lower the temperature to the critical temperature. In a small-sized superconducting machine, liquid nitrogen can be sub-cooled only by attaching a small cryocooler to a cryostat. However, in a large-sized system such as a superconducting generator and a motor, And a separate cooling system for circulation is needed. Such a cooling system should be connected to a cryostat for superconducting power devices so that supercooled liquid nitrogen can be smoothly supplied and circulated at a constant temperature and pressure to the superconducting system and it should be able to supply subcooled liquid nitrogen of 66 to 80K .

The conventional cooling system includes a gas-liquid separator for supplying only pure liquid nitrogen, a liquid nitrogen pressure tank for regulating the pressure of the supplied liquid nitrogen, a cooling box for a refrigerator, a pressure-cooled cooling box, a cooler, . As described above, in the conventional cooling system for a superconducting power device, the cooler, the cooling box, and the tank that function as the respective functions are separated, and the arrangement and the configuration are complicated. Especially, in the case of the large superconducting system, There is a problem in that it is difficult to operate, maintain and manage.

Prior Art 1: Korean Patent Application Publication No. 10-2011-0121202 (Published on November 7, 2011) Prior art 2: Korean patent publication 10-2012-0128641 (published on November 27, 2012)

In order to solve such conventional problems, the present invention provides LNG of the LNG storage tank as a coolant for refrigerant circulating in the superconducting device, thereby replacing the cooling equipment of the superconducting system, There is purpose in.

It is also intended to supply the natural gas, which is natural vaporized, to the driving engine as fuel by transferring the cold heat of the LNG to the refrigerant of the superconducting device without installing a separate LNG regeneration device.

According to an aspect of the present invention, there is provided a superconducting cooling system comprising: an LNG storage tank; A superconducting device comprising a superconducting material; A first refrigerant line through which the LNG supplied from the LNG storage tank is circulated; A second refrigerant line through which the refrigerant for cooling the superconducting device to below the critical temperature is circulated; And a heat exchanger for transferring the cold heat of the LNG to the refrigerant.

According to one embodiment, the LNG storage tank of the superconducting cooling system may be a cargo tank.

According to one embodiment, the superconducting cooling system may further include a heat pump for re-cooling the LNG or the generated BOG, which has lost the cold heat in the first refrigerant line, and is returned to the LNG storage tank.

According to one embodiment, the heat exchanger of the superconducting cooling system may further include a fuel supply path connected to a drive system that uses the BOG generated from the first refrigerant line or the heat exchanger as a fuel.

According to an embodiment, the superconducting cooling system may further include a controller for selectively supplying the generated BOG to at least one of the heat pump or the drive engine according to a fuel requirement of the drive engine.

According to one embodiment, the superconducting cooling system may further comprise a regeneration device that vaporizes the LNG of the LNG storage tank and supplies it to the drive train as fuel.

According to one embodiment, the superconducting cooling system may further include a controller for controlling the LNG of the LNG storage tank to be supplied to either the regenerator or the first refrigerant line.

According to another aspect of the present invention, a ship or a marine structure having the above-described superconducting cooling system can be provided.

According to another aspect of the present invention, there is provided a superconducting cooling method using LNG in an LNG storage tank, comprising: supplying LNG to a first refrigerant line in the LNG storage tank; Line refrigerant; And a superconducting cooling method for cooling the superconducting device by the coolant of the second coolant line obtained by the cold heat may be provided.

As described above, according to the present invention, it is not necessary to provide a separate cooling device by using LNG as a coolant for refrigerant circulated for cooling the superconducting device, thereby obtaining a spatial gain for installing the equipment in the ship, The maintenance and maintenance cost of the cooling system for maintaining the critical temperature of the apparatus can be reduced.

1 is a graph illustrating the superconducting phenomenon of the superconducting cooling system according to the present invention.
2 is a block diagram of a superconducting cooling system in accordance with the present invention.
3 is a block diagram of a superconducting cooling system in accordance with an embodiment of the present invention.
4 is a block diagram of a superconducting cooling system according to another embodiment of the present invention.
5 is a flowchart of a superconducting cooling method according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided as examples for allowing a person skilled in the art to sufficiently convey the idea of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms.

Superconductivity refers to a phenomenon in which when the metal is cooled below a certain temperature (Tc; see FIG. 1), the electrical resistance completely disappears and the current is allowed to flow unlimitedly. Referring to the graph of FIG. 1, in the case of a non-superconductive metal, a predetermined resistance is obtained even if the temperature is lower than a predetermined temperature Tc. In the case of a superconductor, Can be completely eliminated.

The superconducting device 130 used in the present invention can reduce electrical loss and energy efficiency, volume, weight, noise, and vibration by replacing existing copper wires with superconducting wires that do not have electrical loss, There is an advantage that the power device can be miniaturized and the efficiency can be increased. In the case of a superconducting motor, the size of the motor is reduced to ½ or less, which is more effective in a special situation where all the equipment is installed in a limited space.

2 is a block diagram of a superconducting cooling system according to the present invention. 2, the superconducting cooling system 100 includes an LNG storage tank for storing low temperature LNG, a first refrigerant line 140 for circulating the LNG, a second refrigerant line 150 for cooling the superconducting device 130, A heat exchanger 120 for exchanging heat between the LNG and the refrigerant, and a superconducting device 130.

The LNG storage tank 110 is thermally insulated using a heat insulating material and has a separate cooling system (not shown) to maintain the low temperature (-162 ° C) LNG state. The first refrigerant line 140 may be provided with a pump (not shown) for circulating the LNG, and the LNG at a low temperature by the pump may circulate the refrigerant through the heat exchanger 120 ).

The first refrigerant line 140 is connected between the LNG storage tank 110 and the heat exchanger 120 and supplies the LNG from the LNG storage tank 110 to the heat exchanger 120. The heat exchanged LNG in the heat exchanger 120 is returned to the LNG storage tank 110 through the first refrigerant line 140. A pump (not shown) may be installed in the first refrigerant line 140 to circulate the LNG. Also, the BOG generated during the circulation of the first refrigerant line 140 is also circulated along the LNG circulation path of the first refrigerant line 140.

The second refrigerant line (150) circulates the refrigerant to cool the superconducting device (130). The refrigerant obtains cold heat from the LNG in the heat exchanger (120) and flows into the superconducting device (130). The refrigerant that has undergone heat exchange with the LNG maintains a temperature state for cooling the superconducting device 130 to below the critical temperature. The second refrigerant line 150 may further include a cooling device (not shown) for keeping the refrigerant obtained by cooling the refrigerant at a low temperature or lowering the temperature to -162 ° C or lower. The refrigerant obtained by the cold heat is supplied to the superconducting device 130, and a pump (not shown) may be included for this purpose.

Also, the refrigerant cooled by the superconducting device 130 may be discharged to the outside and stored in a refrigerant tank (not shown), and the superconducting device 130 may continuously receive a separate refrigerant from the outside.

The heat exchanger 120 exchanges heat between the LNG introduced through the first refrigerant line 140 and the refrigerant introduced through the second refrigerant line 150. The heat exchanger 120 has a function of dissipating heat so that the cold heat of the LNG is transferred only to the refrigerant and does not escape to the outside.

3 is a block diagram of a superconducting cooling system in accordance with an embodiment of the present invention. The embodiment of FIG. 3 is generally similar to the superconducting cooling system of FIG. 2, but differs in that it further includes a heat pump 122. The description of the same configuration will be omitted, and the differences will be described in detail below.

The heat pump 122 is a device for cooling the LNG or BOG that has lost the cold heat to return to the LNG storage tank 110 again. The heat pump 122 is connected to the first refrigerant line 140 and can supply the cold heat to the LNG circulating along the first refrigerant line 140 to be re-cooled to a temperature before passing through the heat exchanger 120 have. At this time, cold heat may be supplied to the BOG circulating through the first refrigerant line 140 to re-liquefy by the LNG.

The heat pump 122 may be installed outside the first refrigerant line 140 to introduce a refrigerant for supplying cold heat to the first refrigerant line 140.

The LNG stored in the LNG storage tank 110 is introduced into the heat exchanger 120 through the first pump 112 along the first refrigerant line 140. The refrigerant obtained in the heat exchanger 120, 2 pump 132 along the second refrigerant line 150 to cool the superconducting device 130. At this time, the LNG or BOG that has lost the cold heat is re-cooled by the heat pump 122 and returned to the LNG storage tank.

4 is a block diagram of a superconducting cooling system according to another embodiment of the present invention. FIG. 4 is generally similar to the superconducting cooling system of FIG. 3, but differs in that it further includes a controller 124. The description of the same configuration will be omitted, and the differences will be described in detail below.

The control unit 124 is connected to the LNG storage tank 110 and selectively supplies the LNG stored in the LNG storage tank to the regenerator 160 or the first refrigerant line 140.

The regeneration unit 160 is a unit for vaporizing the LNG to supply BOG to a drive engine used as fuel, which is a vaporized gas of the LNG. For example, the regasifier 160 can compress the LNG with a high pressure pump and vaporize the LNG using the heat of the seawater. The vaporized BOG is supplied as fuel for the drive engine.

Also, the control unit 124 may control the BOG generated in the first refrigerant line 140 and the heat exchanger to be supplied to the heat pump 122 or the driving engine. As described above, the BOG circulating the first refrigerant line 140 to be used as a fuel to a driving engine such as a propulsion device or a power generator of a ship using fuel gas is supplied to the driving engine by the control part 124 . For example, the control unit 124 may supply the BOG to the superconducting device 130 as fuel for the power plant. Further, when the fuel supply to the drive engine is sufficient, the control unit 124 can control the BOG to be re-liquefied by the heat pump 122. That is, the control unit 124 may send the BOG that has passed through the heat exchanger 120 to the heat pump 122 or to the drive engine depending on the required fuel amount of the drive engine. The LNG circulating through the first refrigerant line passing through the heat exchanger may be controlled by the control unit 124 such that it is sent to the heat pump and re-cooled back to the LNG storage tank in the same manner as the BOG. The above process can be performed by the 3-way valve 126 when BOG is supplied to the heat pump or the drive engine by the control unit.

5 is a flowchart of a superconducting cooling method according to an embodiment of the present invention. LNG is supplied from the LNG storage tank to the heat exchanger through the first refrigerant line at step S520, and the refrigerant circulating through the second refrigerant line is heat-exchanged with the LNG at the heat exchanger S530), and the refrigerant circulating in the second refrigerant line absorbing the cold heat flows into the superconducting device and is cooled (S540).

100: superconducting cooling system 110: LNG storage tank
112: first pump 120: heat exchanger
122: heat pump 124:
130: superconducting device 132: second pump
140: first refrigerant line 150: second refrigerant line
160: Regenerator

Claims (9)

LNG storage tank;
A superconducting device comprising a superconducting material;
A first refrigerant line through which the LNG supplied from the LNG storage tank is circulated;
A second refrigerant line through which the refrigerant for cooling the superconducting device to below the critical temperature is circulated; And
And a heat exchanger for transferring the cold heat of the LNG to the refrigerant. The method according to claim 1,
Wherein the LNG storage tank is a cargo tank. The method according to claim 1,
Further comprising a heat pump which is driven to re-cool the LNG or BOG generated in the first refrigerant line, and return to the LNG storage tank. The method according to claim 1,
Wherein the heat exchanger further comprises a fuel supply path connected to a driving engine that uses BOG generated in the first refrigerant line or the heat exchanger as fuel. The method of claim 4,
Further comprising a controller for selectively supplying the generated BOG to at least one of the heat pump and the drive engine according to a required fuel amount of the drive engine. The method according to claim 1,
Further comprising a regeneration device for vaporizing the LNG of the LNG storage tank and supplying it as fuel to a drive engine. The method of claim 6,
Further comprising a controller for controlling the LNG of the LNG storage tank to be supplied to either the regenerator or the first refrigerant line. A ship or marine structure having a superconducting cooling system according to any one of claims 1 to 7. A superconducting cooling method using LNG in an LNG storage tank,
Supplying LNG from the LNG storage tank to the first refrigerant line;
Transferring the cold heat of the LNG to the refrigerant of the second refrigerant line using a heat exchanger; And
And cooling the superconducting device with the refrigerant of the second refrigerant line obtained by the cold heat.

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