KR101454290B1 - Complex power generating system connected to the LNG Receiving terminal - Google Patents

Abstract

The combined power generation system associated with the LNG receiving station according to an embodiment of the present invention includes a compressor for receiving and compressing boil off gas (BOG) generated from liquefied natural gas of a liquefied natural gas reservoir or an LNG carrier, And a fuel converting unit for converting the evaporated gas supplied from the compressor into fuel and supplying the fuel to the anode electrode of the fuel cell apparatus.

Description

The complex power generation system connected to the LNG receiving terminal is connected to the LNG receiving terminal,

One embodiment of the present invention relates to a combined power generation system using evaporative gas generated at an LNG receiving station.

Fuel cell devices are an environmentally friendly energy device and are currently attracting attention as an alternative to fossil fuels. The fuel cell device is a power generation device that directly converts chemical energy into electric energy. The fuel containing hydrogen is continuously supplied, and at the same time, the air containing oxygen is continuously supplied, and the electrochemical reaction To directly convert the energy difference before and after the reaction into electric energy.

In addition, natural gas which is currently used in Korea is imported into a low-temperature liquid state (LNG) when it is imported from overseas, and is pressurized through facilities such as a cargo handling facility, a storage tank, a compressor and an evaporator, And is supplied at a first reduced pressure. At this time, the liquefied natural gas stored in the liquefied natural gas reservoir is vaporized into boil off gas (BOG), which contains about 99% of high purity methane.

Therefore, a power generation system capable of using the evaporation gas generated at the LNG receiving station as the fuel of the fuel cell apparatus can be considered.

It is an object of the present invention to provide a combined-cycle power generation system in which an evaporation gas generated at an LNG receiving station is fueled and supplied as fuel to a fuel cell apparatus.

In order to accomplish the object of the present invention, a combined power generation system connected to an LNG receiving station according to an embodiment of the present invention includes a boil off gas generated from a liquefied natural gas in a liquefied natural gas reservoir or an LNG carrier Gas, and BOG), and a fuel converting unit for converting the evaporated gas supplied from the compressor into fuel and supplying the fuel to the anode electrode of the fuel cell apparatus.

According to an example of the present invention, the fuel conversion unit may form hydrogen and carbon dioxide by reacting methane contained in the evaporated gas with water supplied from the outside.

According to an example of the present invention, the fuel cell apparatus may include a cathode electrode that receives carbon dioxide and oxygen from the outside and converts the carbon dioxide into carbonic acid ions (CO ₃ ^{2 -} ) to supply the carbon dioxide to the anode electrode.

According to an embodiment of the present invention, a heat exchange unit may be formed between the fuel conversion unit and the anode electrode so as to heat the fuel supplied to the anode electrode using heat emitted from the cathode electrode.

According to an example of the present invention, a supply line connected from the liquefied natural gas reservoir to a liquefied natural gas consumption unit and a heat exchanger connected to the evaporator of the supply line, and heating the evaporator using heat discharged from the cathode electrode And may further include a circulation line.

According to one embodiment of the present invention, the circulation line further comprises a heat reservoir for storing heat discharged from the cathode electrode, and the heat reservoir can be connected to the evaporator so that heat of the heat reservoir heats the evaporator have.

The combined power generation system associated with the LNG receiving station according to at least one embodiment of the present invention configured as described above is characterized in that the evaporation gas generated at the LNG receiving station is fueled and supplied as fuel to the fuel cell apparatus, A combined combined power generation system can be constructed.

Further, by supplying the arrangement of the fuel cell apparatus to the evaporator, the efficiency of the entire system can be increased.

In addition, since a high purity methane is supplied to the fuel cell device, a line reformer is not required, and thus a heat exchanger and the like necessary for heating the fuel supplied to the fuel cell device can be integrally used.

This can reduce the construction cost of the entire system as well as the maintenance cost required for the power generation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram showing the flow of LNG supplied from an LNG receiving station to a gas consuming point in connection with the embodiments of the present invention. FIG.
2 is a conceptual view of a fuel cell apparatus related to the present invention.
3 is a conceptual diagram of a combined power generation system associated with an LNG receiving station according to the first embodiment of the present invention;
4 is a conceptual diagram of a combined power generation system associated with an LNG receiving station according to a second embodiment of the present invention;

Hereinafter, a combined power generation system associated with an LNG receiving station according to the present invention will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role. In the present specification, the same or similar reference numerals are given to different embodiments in the same or similar configurations. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

1 is a conceptual diagram showing a flow of supplying LNG from a LNG (Liquefied Natural Gas) receiving station to a gas consuming point according to embodiments of the present invention.

Referring to FIG. 1, an LNG is supplied to and stored in a liquefied natural gas reservoir 120 in a floating suspended structure 110 (carrier, FSRU, etc.). The liquefied natural gas stored in the floating structure 110 or the liquefied natural gas reservoir 120 may be vaporized and become a boil off gas (BOG). At this time, the evaporated gas is separated into a natural boiled off gas generated by naturally vaporizing in the liquefied natural gas reservoir 120 and a forced boiled off gas generated by forced vaporization if necessary Can be distinguished.

Here, some of the natural evaporative gas and the forced evaporative gas may be supplied to the evaporative gas re-liquidator 122 through the low-pressure pump LP. Some of the liquefied natural gas stored in the floating structure 110 or the liquefied natural gas reservoir 120 can be forcibly evaporated by the evaporator 141. The forcedly evaporated gas may be compressed by the compressor 142 and then supplied to the evaporative gas re-liquidator 122.

The liquefied gas in the evaporation gas re-liquidator 122 is vaporized by a high pressure pump HP via an open rack vaporizer 132 or a submerged combustion vaporizer 133, Metering station 134 to the gas consumption unit.

At this time, the evaporated gas compressed by the compressor 142 contains high-quality methane, which can be used as fuel for the fuel cell apparatus 200. The present invention relates to a combined power generation system using evaporation gas produced at an LNG receiving station as fuel for a fuel cell device 200. Hereinafter, the configuration of the fuel cell device 200 will be briefly described, The combined power generation system linked to the LNG receiving terminal will be described in detail.

2 is a conceptual diagram of a fuel cell apparatus 200 related to the present invention.

The types of fuel cells include a phosphoric acid fuel cell, an alkaline fuel cell, a proton exchange membrane fuel cell, a molten carbonate fuel cell, a solid oxide Fuel cell (Solid Oxide Fuel Cell), direct methanol fuel cell (Direct Methanol Fuel Cell). The fuel cell types as described above operate by the same principle as fuel, but they are classified according to the type of fuel used, the operating temperature, the catalyst, and the like.

In particular, a molten carbonate fuel cell (MCFC) is operated at a high temperature of 650 ° C or higher, so that the electrochemical reaction rate is high, and nickel can be used instead of a platinum catalyst as an electrode material.

In addition, when the bottoming cycle using the heat recovery steam generator is applied, the heat efficiency of the entire power generation system can be increased to 60% or more by recovering the high-temperature waste heat.

In addition, since the molten carbonate fuel cell is operated at a high temperature, it can be employed as an internal reforming type in which a fuel reforming reaction is simultaneously carried out in a fuel cell stack where an electrochemical reaction occurs.

Since the internal reforming-type molten carbonate fuel cell utilizes the heat generated from the electrochemical reaction in the reforming reaction, which is a direct endothermic reaction without a separate external heat exchanger, the thermal efficiency of the entire system is further increased as compared with the externally reforming molten carbonate fuel cell And the system configuration is simplified at the same time.

The fuel cell apparatus 200 includes a fuel supply unit for supplying a certain amount of fuel, a reformer unit for generating a byproduct containing hydrogen gas and heat by receiving the fuel of the fuel supply unit, And a stack portion for generating electricity and heat by an electrochemical reaction of oxygen.

The stack portion may be formed by stacking a plurality of unit cells including a reformer 210, an anode electrode 220, an electrolyte membrane 240, and a cathode electrode 230.

The operation of the fuel cell module as described above is as follows.

First, when fuel and water containing liquefied natural gas (LNG) or methane (CH ₄ ) are supplied to the reforming unit in the fuel supply unit, steam reforming and aqueous transfer reaction Water Gas Shift Reaction), which generates hydrogen gas, reaction heat and other by-products including water.

CH ₄ + 2H ₂ O - > 4H ₂ + CO ₂

In the stack portion, hydrogen gas supplied from the reforming unit reacts with oxygen and carbon dioxide supplied to the cathode to form carbonate ions (CO ₃ ^2- ), and the generated carbonate ions (CO ₃ ^{2 -} ) undergoes an electrochemical reaction It generates electricity, heat and water.

First, the hydrogen gas (H ₂ ) is supplied to the anode (anode) 220 side to form carbonic acid ions (CO ₃ ^{2 -} ). And an electrochemical oxidation reaction takes place to produce water, carbon dioxide and electrons (e-).

H ₂ + CO ₃ ^{2 -} -> H ₂ O + CO ₂ + 2e ^-

In the cathode electrode (aka, air electrode 230), oxygen, carbon dioxide, and electrons supplied from the outside generate an electrochemical reduction reaction to generate carbonate ions (CO ₃ ^{2 -} ), reaction heat, and water. The carbonate ions generated in the cathode electrode 230 move from the cathode electrode 230 to the anode electrode 220 through the electrolyte of the electrolyte membrane 240 located between the cathode electrode 230 and the anode electrode 220, Electrons generated in the anode electrode 220 move through an external circuit while electric energy is generated by movement of electrons. At this time, the electrolyte is normally present in a solid state, but when the fuel cell system is operated normally, the temperature rises to about 650 ° C, and the electrolyte is liquefied.

(1/2) O _{2 +} CO ₂ + 2e ^- -> CO ₃ ^{2 -}

Here, CO ₂ is moved from the cathode electrode 230 to the anode electrode 220 through the electrolyte by an electrochemical reaction mechanism, and is concentrated _.

3 is a conceptual diagram of a combined power generation system associated with an LNG receiving station according to the first embodiment of the present invention.

3, the combined-cycle power generation system includes a boil-off gas (BOG) generated in devices for supplying liquefied natural gas in a LNG receiving station such as a fuel cell device 200, a liquefied natural gas storage, or an LNG carrier, And a compressor 142 for receiving and compressing the refrigerant.

The evaporator 141 may be configured to receive the liquefied natural gas from the liquefied natural gas reservoir 120 to form the evaporation gas as described above. The evaporation gas formed by the natural evaporation system or the forced evaporation system is first stored in the buffer tank 143 and then compressed to a certain pressure by the compressor 142. The compressed gas may be supplied to the fuel conversion unit 150.

Alternatively, only a part of the compressed gas may be supplied to the fuel conversion unit 150, and the remainder may be supplied to the evaporative gas re-liquidator 122. At this time, the liquefied gas in the evaporation gas re-liquidator 122 is vaporized by the seawater evaporator 132 or the underwater evaporator 133 via the high-pressure pump, and then is supplied to the gas consumption unit Can be supplied.

The fuel converting unit 150 converts the evaporated gas supplied from the evaporator 141 into fuel and supplies the fuel to the anode electrode of the fuel cell apparatus 200. The term "fueling" as used herein refers to reacting methane contained in the evaporated gas with water supplied from the outside to form hydrogen and oxygen. In other words, the fuel converting unit 150 functions as a reforming unit of the fuel cell apparatus 200.

As described above, since the present invention supplies the high-purity methane contained in the vaporized gas discharged from the LNG storage 121 and the LNG carrier 110 to the fuel cell apparatus 200, a line reformer is not required, A heat exchanger necessary for heating the fuel supplied to the apparatus 200, and the like can be integrally used.

The cathode electrode of the fuel cell device 200 is supplied with carbon dioxide and oxygen from the outside to convert it into carbonate ions (CO ₃ ^{2 -} ) and supply it to the anode electrode. The anode electrode includes hydrogen and carbonate ions (CO ₃ ^{2 -} ). To produce electrical energy.

At this time, waste gas contained in the exhaust gas together with the exhaust gas is discharged from the cathode electrode. A heat exchange unit 250 is formed on the line connecting the fuel conversion unit 150 and the anode electrode to reuse the waste heat. The waste heat is supplied to the heat exchanging unit 250, and the heat exchanging unit 250 heats the fuel supplied from the fuel converting unit 150 to the anode electrode.

The waste heat is supplied to the heat recovery unit 160 through the heat exchange unit 250. [

The heat recovery apparatus 160 is connected to a circulation line circulated to supply waste heat to the evaporator. At this time, the circulation line is connected to the evaporator 130 formed on the supply line connected from the liquefied natural gas reservoir 120 to the liquefied natural gas consumption unit 190 to supply heat to the evaporator 130. The evaporator 130 may be, for example, an underwater evaporator or a seawater evaporator. By recycling the waste heat in this manner, the thermal efficiency of the entire system can be increased. In the heat recovery apparatus 160, exhaust gas is at least partially discharged. Further, when no heat is supplied to the evaporator 130, waste heat can be discharged as hot water. This hot water can be supplied to each heat consumption unit.

The supply line is vaporized in the liquefied natural gas reservoir 120 through the high pressure pump by the seawater evaporator 132 or the underwater evaporator 133 and then supplied to the gas And is supplied to the consuming unit. An odorizer part 140 may be connected to the gas metering facility 134 to include an odorant in the gas supplied to the liquefied natural gas consumption unit 190.

4 is a conceptual diagram of a combined power generation system associated with an LNG receiving station according to a second embodiment of the present invention. The configuration of the combined power generation system associated with the LNG receiving station shown in FIG. 4, which is the same as or similar to the configuration shown in FIG. 3, will be omitted from the description of FIG.

Referring to FIG. 4, the combined power generation system may include a fuel cell apparatus 200 and an evaporator 141 for forcibly evaporating liquefied natural gas at an LNG receiving station.

The evaporator 141 receives the liquefied natural gas from the LNG carrier 110 or the liquefied natural gas reservoir 120 to form an evaporative gas. The formed evaporation gas is primarily stored in the buffer tank 143 and compressed to a certain pressure by the compressor 142. The compressed gas may be supplied to the fuel conversion unit 150.

The waste heat contained in the exhaust gas discharged from the cathode electrode is supplied to the heat recovery unit 160 through the heat exchange unit 250.

The heat recovery apparatus 160 is connected to a circulation line circulated to supply waste heat to the evaporator. At this time, the circulation line is connected to the evaporator 133 formed on the supply line connected from the liquefied natural gas reservoir 120 to the liquefied natural gas consumption unit 190 to supply heat to the evaporator 133. However, unlike the previous embodiments, the circulation line according to the present invention includes a thermal storage tank 170. When heat is not supplied to the evaporator 133, waste heat is continuously supplied to the heat storage 170 to maintain a constant temperature. When the evaporator 133 is driven, heat supplied from the heat storage 170 is used. As a result, the thermal efficiency of the system can be increased.

The combined power generation system associated with the LNG receiving station described above can be applied to all or some of the embodiments so that various modifications can be made to the embodiments and methods of the embodiments described above, May be selectively combined.

Claims (6)

A compressor for receiving and compressing boil off gas (BOG) generated from liquefied natural gas; And
And a fuel converting unit for converting the evaporated gas supplied from the compressor into fuel and supplying the fuel to the anode electrode of the fuel cell apparatus,
Wherein the fuel conversion unit reacts methane contained in the evaporation gas with water supplied from outside to form hydrogen and carbon dioxide,
The fuel cell apparatus includes a cathode electrode that receives carbon dioxide and oxygen from the outside and converts the carbon dioxide into carbonic acid ions (CO ₃ ^2- ) to supply the carbonic acid ions to the anode electrode,
A heat exchange portion is formed between the fuel conversion portion and the anode electrode so as to heat the fuel supplied to the anode electrode using the heat discharged from the cathode electrode,
A feed line from the liquefied natural gas reservoir to the liquefied natural gas consumption unit; And
And a circulation line connected to the evaporator of the supply line and heating the evaporator using heat discharged from the cathode electrode,
Characterized in that the circulation line further comprises a heat reservoir for storing heat discharged from the cathode electrode and the heat reservoir is connected to the evaporator so that the heat of the heat reservoir heats the evaporator. Combined power generation system. delete delete delete delete delete

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