KR101438109B1 - Combined power generation system and method for capturing carbon dioxide in the combined power generation system - Google Patents

Abstract

A combined-cycle power generation system according to an embodiment of the present invention includes a natural gas synthesis device that generates synthesis gas in a gasifier after being supplied with coal and oxygen and then synthesizes methane through a methanation reactor, And a carbon dioxide supply unit for supplying carbon dioxide discharged from a carbon dioxide discharge facility adjacent to the fuel cell apparatus to a cathode electrode of the fuel cell apparatus.

Description

TECHNICAL FIELD [0001] The present invention relates to a combined power generation system and a combined power generation system for collecting carbon dioxide,

One embodiment of the invention relates to a combined power generation system comprising a combined natural gas synthesis unit and a fuel cell unit.

Natural gas synthesis system is a system for producing synthetic natural gas (hereinafter referred to as SNG). It is a system for gasification of coal and organic raw materials at high temperature and high pressure and then gas purification process to convert CO and H ₂ in syngas to 1 : ≪ / RTI > 3 to produce a gas containing methane as the main component. Synthetic natural gas is an alternative energy and can be synthesized from various organic raw materials. Synthetic natural gas has the advantage of being able to use the existing LNG supply chain as it is and can be used as raw material for synthetic petroleum and synthetic compound materials.

And, fuel cell devices are attracting attention as a high efficiency clean energy power generation system. 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. As such, the fuel cell can continuously generate electrical energy as fuel and oxygen are continuously supplied.

Coal-fired power plants, which produce electricity using coal as their main source, emit considerable amounts of carbon dioxide. Since carbon dioxide is a major target for greenhouse gas reduction, reducing the amount of carbon dioxide emitted from coal-fired power plants is a major challenge for coal-fired power plants.

Therefore, a method of collecting carbon dioxide and supplying it to the fuel cell device while realizing a more efficient power generation system by combining the natural gas synthesizing device and the fuel cell device can be considered.

It is an object of the present invention to provide a more efficient hybrid power generation system.

It is another object of the present invention to provide a combined power generation system having a carbon dioxide emission facility such as a natural gas synthesis apparatus, a fuel cell apparatus and a coal-fired power plant connected to each other, having a higher efficiency, and a higher carbon dioxide capture rate will be.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention provides a combined-cycle power generation system for generating methane from a gasifier, A fuel cell apparatus for generating electricity by receiving fuel containing methane from the natural gas synthesis apparatus, and a fuel cell system for generating carbon dioxide discharged from a power plant or a carbon dioxide discharge facility adjacent to the fuel cell apparatus, And a carbon dioxide supply unit for supplying the carbon dioxide to the electrode.

According to an example of the present invention, the fuel cell apparatus may include an anode electrode supplied with hydrogen formed from methane generated in the methanation reactor.

According to an embodiment of the present invention, the apparatus further comprises a first reactor for generating hydrogen and carbon dioxide through a water gas shift reaction using the fluid introduced from the gasifier, The unreacted gas may be supplied to the first reactor.

According to an embodiment of the present invention, the apparatus may further include a second reactor that receives the fluid discharged from the first reactor and separates carbon dioxide and sulfur compounds through physical or chemical separation.

According to an embodiment of the present invention, the carbon dioxide supply unit may further include a desulfurization device for removing sulfur from the exhaust gas discharged from the power plant, and a pressurizing device for pressurizing the carbon dioxide to a predetermined pressure or higher and supplying the carbon dioxide to the cathode electrode .

In another aspect of the present invention, there is provided a carbon dioxide capture method for a combined power generation system in which a natural gas synthesis apparatus, a fuel cell apparatus, and a thermal power plant are linked to each other, (CO ₃ ^{2 -} ) supplied to the cathode electrode, and then reacting with hydrogen at the anode electrode to convert the carbon dioxide to carbon dioxide, and supplying the carbon dioxide gas to the anode electrode And the discharged carbon dioxide is collected in the natural gas synthesis apparatus.

The combined power generation system according to at least one embodiment of the present invention configured as above can reduce the size, installation cost and operating cost of the carbon dioxide recovery device by using the fuel cell device for recovering the carbon dioxide discharged from the coal- have.

1 and 2 are conceptual views of a reaction process and apparatus of a natural gas synthesis apparatus according to an embodiment of the present invention.
3 is a conceptual view of a fuel cell apparatus related to the present invention.
4 is a conceptual diagram of a combined power generation system according to an embodiment of the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of collecting carbon dioxide in a combined power generation system and a combined power generation system 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 and 2 are conceptual views of a reaction process and apparatus of a natural gas synthesis apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the natural gas synthesis apparatus 100 is a process for gasifying (CO + H ₂ ) an inexpensive organic raw material (for example, coal or lignite) at high temperature and high pressure, It is a clean coal fuels technology that produces natural gas, synthetic petroleum, or electric power.

As shown in FIG. 2, raw material raw materials are mixed with oxygen in the gasifier 110 to produce hydrogen (H ₂ ) and carbon monoxide (CO), which are synthetic gases, at 1000 ° C. to 1600 ° C., (CO ₂ ), methane (CH ₄ ), sulfur compounds (for example, hydrogen sulfide (H ₂ S)) and ashes as byproducts.

The high-temperature gas is subjected to a gas purification process for removing contaminants such as dust, sulfur, and mercury through the gas purification unit 130 after recovering heat through the synthesis gas cooling unit 120. After the polluted gas purification process, a synthesis gas containing hydrogen, carbon monoxide, carbon dioxide, methane, and sulfur compounds as main components is produced, and the synthesis gas having such a composition is introduced into the first reactor 140 formed to perform the water gas transfer reaction .

Then, the synthesis gas introduced into the first reactor 140 generates H ₂ and CO ₂ through a water gas shift reaction (CO + H ₂ O? CO ₂ + H ₂ ), and then Rectisol (Hereinafter, referred to as a second reactor), and the second reactor 150 separates CO ₂ and sulfur components through physical and chemical separation. Here, the separated CO ₂ can be compressed and buried in the ground or reused. Or for enhanced oil recovery.

That is, the natural gas synthesis apparatus 100 includes a first reactor 140 for generating H ₂ and CO ₂ through a water gas shift reaction using an introduced fluid, And a second reactor 150 for separating CO ₂ and sulfur components.

The second reactor 150 is connected to the methanation reactor 160. The methanation reactor 160 may generate methane using carbon monoxide and hydrogen supplied from the second reactor 150 and may supply it to the fuel cell apparatus 200. Also, although not shown, the natural gas synthesis apparatus 100 and the power generation unit can be linked to each other so that methane generated from the natural gas synthesis apparatus 100 can be used.

The methanation process occurring in the methanation reactor 160 is a process in which hydrogen in the synthesis gas is reacted with carbon dioxide and carbon monoxide to convert it into methane. The reaction is carried out in the following reaction (i) and / or (ii).

_{CO + 3H 2 → CH 4 +} H 2 O (i)

CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O (ii)

The methanation reaction may be carried out under any conditions as long as the purpose of supplying the fuel cell gas containing methane to the coal gasification combined cycle fuel cell system of the present invention can be achieved, but since the methanation reaction is an exothermic reaction When the reaction temperature is lowered, the equilibrium concentration of carbon monoxide is lowered and the reaction rate is also slowed down. Therefore, the reaction temperature may be in the range of 100 to 400 ° C, 200 to 350 ° C, or 250 to 300 ° C.

The methanation reaction may be performed using at least one methanation catalyst selected from the group consisting of a nickel-based methanation catalyst, an iron-based methanation catalyst, and a ruthenium-based methanation catalyst.

As described above, since the natural gas synthesis apparatus 100 produces methane, oxygen, and a heat source that can be recycled by using low-cost coal, it is possible to provide a natural gas- .

3 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 reformer 210 for generating a byproduct containing hydrogen gas and heat by receiving a fuel from the fuel supplier and a fuel supplier for supplying a predetermined amount of fuel, And a stack portion for generating electricity and heat by an electrochemical reaction between hydrogen gas and oxygen supplied separately.

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 reformer unit 210, the reformer unit 210 performs steam reforming ) And water gas shift reaction are combined to generate hydrogen gas, reaction heat, and other by-products including water.

CH ₄ + 2H ₂ O - > 4H ₂ + CO ₂

In the stack portion, the hydrogen gas supplied from the reformer 210 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- ) Causing a chemical reaction to generate 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 _. If the exhaust gas having a low concentration of carbon dioxide in the thermal power plant 310 is supplied to the cathode electrode 230 of the fuel cell apparatus 200, only the carbon dioxide in the exhaust gas of the thermal power plant 310 is selectively supplied to the anode electrode 220 It is possible to concentrate carbon dioxide. This degree of concentration can be up to 90% of the carbon dioxide emissions from the thermal power plant 310.

In addition, the fuel cell apparatus 200 (molten carbonate fuel cell) according to the present invention can be divided into an internal reforming type and an external reforming type according to a natural gas reforming method. In particular, by using a fuel conversion method by internal reforming, It is possible to use natural gas as a direct fuel without installing a reformer after installing the catalyst inside the battery and reforming it. In addition, the heat generated in the stack portion during power generation is used in the reforming reaction, so that it is unnecessary to install a device for cooling the stack, which simplifies the system.

4 is a conceptual diagram of a combined power generation system according to an embodiment of the present invention.

Referring to FIG. 4, the fuel cell apparatus 200 is connected (supply line 181 -> supply line 252) to receive hydrogen from the natural gas synthesis apparatus 100. More specifically, the methane generated in the methanation reactor 160 is supplied to the reformer unit 210, the reformer unit 210 forms hydrogen and carbon dioxide through a chemical reaction, and the hydrogen generated in the reformer unit 210 And is supplied to the anode electrode 220 of the fuel cell apparatus 200.

As described above, hydrogen (H ₂ ) is supplied to the anode electrode 220 to generate water, carbon dioxide, and electrons (e) as an electrochemical oxidation reaction occurs with carbonate ions (CO ₃ ^{2 -} ). At this time, hydrogen and carbon monoxide are also supplied as byproducts. The discharge line of the anode electrode 220 is connected to the first reactor 140 so that the products other than the electrons are supplied to the first reactor 140 where the water gas transfer reaction takes place .

The mixed gas discharged from the anode electrode may include carbon monoxide, hydrogen, carbon dioxide, H ₂ O, and the like. Among these, hydrogen (H ₂ ) and carbon monoxide (CO) can be reused as unused fuel and can be supplied to the first reactor 140.

In this way, unused hydrogen (H ₂ ) and carbon monoxide (CO) are supplied from the anode electrode discharge line 251 to the first reactor 140 to cause a water gas shift reaction. The reaction formula here is as follows.

As a result, the overall power production efficiency can be maximized.

Also, the fuel cell apparatus 200 is connected to the carbon dioxide supply unit 320 through the supply line 311 to receive carbon dioxide from the carbon dioxide discharge facility 310, such as a coal-fired power plant. Since the flue gas of the carbon dioxide emission facility 310 contains unnecessary sulfur, the carbon dioxide supply unit 320 may include a desulfurization device. In addition, since the exhaust gas of the carbon dioxide exhausting facility 310 is low in pressure, the carbon dioxide supplying unit 320 may further include a pressurizing unit that pressurizes the carbon dioxide to a predetermined pressure or more and supplies the pressurized gas to the cathode electrode 230.

Thus, the present invention is being supplied through the supply line 321 to the cathode 230 of the carbon dioxide, the fuel cell apparatus 200 is discharged from the carbon dioxide emission facility (310), CO ₂ absorption with no additional collecting device to the stack unit The CO ₂ partial pressure is increased in the cathode electrode 230 of the stack portion to improve the power generation performance of the stack portion, thereby increasing the power production performance efficiency.

In addition, the fluid including the unused fuel discharged from the stack portion may be recycled to the first reactor 140 of the SNG production process to further cause a water gas transfer reaction, thereby improving the overall efficiency.

The carbon dioxide capture method of the combined power generation system according to the present invention includes the following steps. In the first step, the carbon dioxide discharged from the carbon dioxide discharge facility 310 such as a coal-fired power plant is supplied to the cathode electrode 230 of the fuel cell by desulfurization and pressurization.

In the second step, the carbon dioxide supplied to the cathode electrode 230 is converted to carbonic acid ions (CO ₃ ^{2 -} ), concentrated through the anode electrode 220, and discharged again as carbon dioxide from the anode electrode 220.

In the third step, the carbon dioxide discharged from the anode electrode 220 passes through the first reactor 140 and the second reactor 150 of the natural gas synthesis apparatus. The carbon dioxide passed through the second reactor 150 is separately separated and buried in the storage space after compression.

In this way, the combined power generation system according to the embodiment of the present invention can collect up to 90% of the carbon dioxide discharged from the carbon dioxide discharge facility 310.

The combined power generation system according to the present invention is related to the carbon dioxide discharge facility 310, the fuel cell apparatus 200, and the natural gas synthesis apparatus 100. That is, the coal-fired power plant, which is one of the carbon dioxide discharge facilities 310, uses carbon as the main material to produce electric energy and discharges the carbon dioxide. The natural gas synthesis apparatus 100 generates methane using an organic compound. The fuel cell apparatus 200 generates electrical energy using hydrogen generated in methane and carbon dioxide discharged from the carbon dioxide discharge facility 310, and concentrates and collects carbon dioxide.

The carbon dioxide capture method of the hybrid power generation system and the combined power generation system described above can be applied to a limited number of configurations and methods of the embodiments described above, Or some of them may be selectively combined.

Claims (6)

A natural gas synthesis system for producing synthesis gas from a gasifier supplied with coal and oxygen, and then synthesizing methane through a methanation reactor;
A fuel cell apparatus that receives fuel containing methane from the natural gas synthesis apparatus and generates electrical energy; And
And a carbon dioxide supply unit for supplying carbon dioxide discharged from a carbon dioxide discharge facility adjacent to the fuel cell apparatus to a cathode electrode of the fuel cell apparatus,
The fuel cell apparatus includes an anode electrode supplied with hydrogen formed from methane produced in the methanation reactor,
Further comprising a first reactor for producing hydrogen and carbon dioxide through a water gas shift reaction using a fluid introduced from the gasifier,
Wherein the mixed gas discharged from the anode electrode is supplied to the natural gas synthesis apparatus, and hydrogen and carbon monoxide, which are unreacted gases in the mixed gas, are reused in the first reactor. delete delete The method according to claim 1,
Further comprising a second reactor for receiving the fluid discharged from the first reactor and separating carbon dioxide and sulfur compounds through physical or chemical separation. The method according to claim 1,
The above-
Further comprising a desulfurizer for removing sulfur from the exhaust gas discharged from the carbon dioxide discharge facility, and a pressurizing device for pressurizing exhaust gas containing carbon dioxide to a predetermined pressure or higher and supplying the exhaust gas to the cathode electrode. A carbon dioxide capture method for a combined power generation system in which a natural gas synthesis apparatus, a fuel cell apparatus, and a carbon dioxide discharge facility are interconnected,
Supplying carbon dioxide discharged from the carbon dioxide discharge facility to a cathode electrode of the fuel cell apparatus;
The carbon dioxide supplied to the cathode electrode is converted into carbonate ion (CO ₃ ^2- ), then reacted with hydrogen at the anode electrode and converted back to carbon dioxide; And
Wherein the mixed gas discharged from the anode electrode is supplied to the natural gas synthesizer, and carbon dioxide in the mixed gas is collected in the natural gas synthesizer.

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