KR20120090466A - Catalytic oxidizer system for molten carbonate fuel cell - Google Patents

Abstract

PURPOSE: A catalyst oxidation system is provided to be able to replace a catalyst when performance of a catalyst of a catalyst oxidizer inside a bare cell is reduced by electrolyte and reaction heat of high temperature. CONSTITUTION: A catalyst oxidation system comprises: a bare cell(100) in which fuel cell unit stacks are laminated; a catalyst oxidizer main body(200) inside the bare cell; an oxidation catalyst layer(220) inside the catalyst oxidizer main body, and in which a catalyst is removably accepted; a catalytic oxidizer open/close part(210) which is arranged in the catalyst oxidizer main body, corresponding with the location of the oxidation catalyst layer; and a bare cell open/close part arranged in a location corresponding with the catalytic oxidizer open/close part in the bare cell.

Description

Catalytic Oxidizer System for Molten Carbonate Fuel Cell

The present invention relates to a catalytic oxidation system of a molten carbonate fuel cell, and more particularly to a catalytic oxidizer capable of replacing a catalyst of a catalytic oxidizer located inside a vessel of a fuel cell outside the vessel.

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

A molten carbonate fuel cell (MCFC) is a unit cell of anode and cathode which is operated at a high temperature of more than 650 ^o C and is separated into an electrolyte that conducts electrically charged ions and a ceramic structure containing the matrix. It is composed.

In addition, the molten carbonate fuel cell generates electricity by supplying an oxidizing gas including oxygen and carbon dioxide to the cathode, and supplying hydrogen and a hydrocarbon-based gas capable of generating hydrogen to the anode, and a plurality of units to produce the desired power. The cells are stacked in series to form a fuel cell unit stack.

The oxidizing gas supplied to the cathode of the molten carbonate dye cell reacts with the cathode to receive free electrons, which react with the electrolyte to form carbonate ions. These carbonate ions move to the anode across the electrolyte in the matrix, and react with the hydrogen supplied to the anode to generate water and carbon dioxide and to generate free electrons. The free electrons are connected to the outside to generate electricity.

The electrolyte in the molten carbonate fuel cell comprises a molten carbonate salt mixture and typically consists of lithium carbonate, potassium carbonate, sodium carbonate and mixed carbonates thereof. These carbonate electrolytes are confined in the matrix, which is a ceramic structure, in the liquid state in the 550-650 ° C. operating temperature range of the molten carbonate fuel cell.

On the other hand, in general, an excess amount of oxidizing gas and fuel gas is supplied to the fuel cell than the fuel required for electricity production. This is to increase the generated power by increasing the reaction speed of the fuel cell and increasing the cell voltage.

However, such excess fuel gas lowers the efficiency of the entire fuel cell system and is reused through recirculation. The most common method of reusing fuel cell exhaust fuel is to recover heat by oxidizing excess fuel gas, and molten carbonate fuel. An oxidizer is placed in the bottom stream of battery anode exhaust and oxidized by mixing oxidizing gas of pure air and cathode exhaust.

In general, the oxidizer includes an oxidation catalyst and oxidizes carbon dioxide such as hydrogen, methane, and carbon monoxide contained in the anode exhaust gas, generates water vapor, carbon dioxide, and raises the temperature of the mixed gas. The mixed gas is recycled to the cathode inlet and used.

In this case, the catalytic oxidizer is generally composed of a mixer capable of mixing the cathode and the anode gas, a catalytic reactor in which the oxidation catalyst is located, a feeder for supplying the mixed gas after the oxidation to the cathode, etc. It is located inside the fuel cell vessel for recovery.

In the high temperature atmospheric and operating conditions of the molten carbonate fuel cell, the internal electrolyte is in a liquid state, and part of it is evaporated to form a gaseous form and mixed with the cathode and the anode gas. The anode and cathode gas containing the electrolyte is mixed in the catalytic oxidizer and the temperature is lowered to 300 ~ 500 ℃ to meet the external pure air. This temperature cooling causes the electrolyte particles in the mixed gas to solidify, and the solidified electrolyte particles accumulate in the catalyst layer in the catalytic oxidizer.

In general, the electrolyte particles accumulated in the oxidizer catalyst cover the active metal of the oxidation catalyst to reduce the catalyst performance, and the excessively accumulated electrolyte particles hinder the flow of the mixed gas, causing a pressure drop of the mixed gas crossing the catalyst layer. This pressure drop lowers the cathode inlet pressure and increases the pressure and deviation of the anode feed fuel to reduce stack long term operability. In addition, the change of the mixed gas pressure and the flow path in the oxidizer catalyst layer by the electrolyte particles induces non-uniform oxidation reaction in the oxidizer catalyst layer and increases the internal temperature deviation.

Such changes in pressure and temperature can interfere with the oxidation of the anode flue gas in the short term, resulting in a reduction in overall efficiency and stack voltage, and in the long term inhibiting the stability of the stack structure and reducing the life of the stack.

Therefore, the electrolyte contained in the anode and cathode exhaust gas must be removed before reaching the catalyst layer of the catalytic oxidizer, thereby maintaining a constant oxidation reaction, pressure, and temperature distribution.

In general, the removal of electrolyte particles uses a method of placing a structure responsible for electrolyte accumulation in front of the oxidation catalyst or using a solvent suitable for removing the electrolyte. However, such a method also has difficulty in removing the electrolyte completely. There is a problem with limitations in reproducing or improving performance.

FIG. 1 shows a configuration in which an oxidation catalyst is placed inside a stack vessel, and anode exhaust gas is recycled from inside or outside the stack to be fed to the catalytic oxidizer and oxidized.

At this time, a portion of the cathode exhaust gas is mixed together for supply of oxidizing gas, or external pure air is mixed and supplied. When using low temperature outside air, it is possible to reduce the temperature rise in the catalytic oxidizer, and to reduce the temperature deviation in the catalyst bed due to the excess air supply.

FIG. 2 shows a configuration in which a catalytic oxidizer is placed outside the stack vessel, and the anode exhaust gas is recycled outside the stack to be fed to the catalytic oxidizer and oxidized.

In this case, part of the cathode exhaust gas or pure air can be used as the oxidizing gas. Since this structure has a catalytic oxidizer outside the stack vessel, it is easy to replace the catalyst layer, to operate and maintain the oxidizer, and to maintain the gas temperature after the high temperature reaction. There is an advantage that can be supplied to the stack by adjusting, but as a separate space is required and the high temperature piping is lengthened, the cost of additional equipment is generated, and thermal efficiency may be reduced due to heat loss to the outside.

Therefore, if the performance is degraded by poisoning of the catalyst layer while using the internal catalytic oxidizer, a means of guiding fuel recycling to the outside and using an external catalytic oxidizer to secure operability may be considered. There is a disadvantage in that the exhaust gas recirculation pipe is discharged to the outside of the stack.

The present invention is to solve the above problems, and provides a catalytic oxidation system capable of replacing the catalyst to maintain the optimum performance when the catalyst of the catalytic oxidizer located inside the vessel is reduced by the electrolyte and high temperature reaction heat I would like to.

In addition, the present invention is to provide a catalytic oxidation system capable of individually replacing each of the oxidation catalyst layer positioned in parallel by adjusting the flow of the mixed gas passing through the catalyst layer of the catalytic oxidizer.

A catalytic oxidation system for molten carbonate fuel cells for achieving the technical problem is a vessel 100 in which a fuel cell unit stack is stacked therein, a catalytic oxidizer main body 200 provided in the vessel 100, and the catalytic oxidation Oxidation catalyst layer 220 provided inside the main body 200 and accommodated so that the catalyst is detachable, and a catalytic oxidizer opening part provided corresponding to the position of the oxidation catalyst layer 220 in the catalytic oxidizer main body 200. And a vessel opening portion 110 provided at a position corresponding to the catalytic oxidizer opening portion 210 in the vessel 210 and the catalytic oxidizer opening portion 210, and the catalytic oxidizer opening portion 210 and the vessel opening portion ( An internal blocking membrane 300 is disposed between the interior of the vessel 100 and the interior of the catalytic oxidizer main body 200 to block the movement of the catalyst oxidizer opening portion 210 and the vessel opening portion ( Catalyst bridge of oxidation catalyst layer 220 through 110 Characterized in that the possible.

In addition, the oxidation catalyst layer 220 is configured in plural with respect to the flow of the mixed gas flowing into the catalytic oxidizer main body, the flow path of the mixed gas passing through each oxidation catalyst layer 220 is configured separately and not mixed with each other. It may be characterized as not.

The upper and lower supports 400 may be positioned above and below the oxidation catalyst layer 220 to support the oxidation catalyst layer 220, and the upper and lower supports 400 may be metal porous plates.

In addition, the catalytic oxidizer main body 200 may further include a gas barrier layer 230 that blocks gas inflow into the oxidation catalyst layer 220 above and below the oxidation catalyst layer 220.

The present invention can be configured to replace the catalyst of the catalytic oxidizer located inside the vessel can be prevented from reducing the performance of the catalyst by the electrolyte and high temperature reaction heat.

In addition, the present invention may individually replace each of the oxidation catalyst layers positioned in parallel by adjusting the flow of the mixed gas passing through the catalyst layer when replacing the catalyst of the catalytic oxidizer.

Furthermore, by further including a vertical support consisting of a metal porous plate it is possible to efficiently recover the heat of the catalytic oxidizer while preventing excessive heat generation in the oxidation catalyst layer.

1 is a view schematically illustrating a configuration in which an anode exhaust gas is recycled and used inside a vessel of a molten carbonate fuel cell;
FIG. 2 is a view schematically illustrating a configuration in which the anode exhaust gas is recycled outside the vessel to replace the catalyst layer of the catalytic oxidizer in the molten carbonate fuel cell vessel;
3 schematically illustrates a vessel of a catalytic oxidation system in accordance with an embodiment of the present invention.
FIG. 4 is a schematic view showing the inner wall of the catalytic oxidizer body and the vessel of the catalytic oxidation system according to an embodiment of the present invention. FIG.
5 is a view schematically showing a state further including a gas barrier membrane of the catalytic oxidizer body of the catalytic oxidation system according to an embodiment of the present invention.
6 is a schematic view showing a state further including a gas barrier membrane of the catalytic oxidizer body of the catalytic oxidation system according to an embodiment of the present invention.
7 is a view schematically showing a state further including an upper and lower support in the catalytic oxidation system according to an embodiment of the present invention.
8 is a view schematically showing a state including both the gas barrier membrane and the upper and lower supports in the catalytic oxidation system according to an embodiment of the present invention.

The present invention provides a catalytic oxidizer structure capable of replacing the catalyst of the catalytic oxidizer located inside the vessel. Generally, the catalytic oxidizer is disconnected from the outside of the vessel, and the present invention changes the side of the catalyst layer of the catalytic oxidizer into an openable structure and makes it accessible from the outside of the vessel, thereby enabling the replacement of the catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and how to accomplish them, will become apparent by reference to the embodiments described in detail below with reference to the accompanying drawings. Hereinafter, a catalytic oxidation system of a molten carbonate fuel cell according to an embodiment of the present invention will be described with reference to the accompanying drawings.

3 and 4, a catalytic oxidation system of a molten carbonate fuel cell according to an embodiment of the present invention includes a vessel 100 in which a fuel cell unit stack is stacked therein and a catalyst provided in the vessel 100. An oxidizer main body 200, an oxidation catalyst layer 220 provided inside the catalytic oxidizer main body 200 and housed so that the catalyst is detachable, and a position of the oxidation catalyst layer 220 in the catalytic oxidizer main body 200. A catalytic oxidizer opening part 210 provided in correspondence with the vessel and a vessel opening part 110 provided in a position corresponding to the catalytic oxidizer opening part 210 in the vessel 100.

The vessel 100 has an internal space and includes a stack 120 in which a fuel cell unit stack is stacked therein to generate electricity, and a catalytic oxidizer is provided inside the vessel 100 to provide anode exhaust gas. It is recycled and used.

The catalytic oxidizer includes an oxidation catalyst layer (Catalyst Chamber) inside the catalytic oxidizer body 200 to cause a catalytic reaction, and the catalyst of the oxidation catalyst layer 220 is housed so as to be detachable so as to provide a catalyst when necessary. It has a replaceable structure.

The catalytic oxidizer main body 200 is provided with a catalytic oxidizer opening part 210 provided corresponding to the position of the oxidation catalyst layer 220 to thereby replace the catalyst of the oxidation catalyst layer 220.

In addition, the vessel 100 is provided with a vessel opening portion 110 corresponding to the position of the catalytic oxidizer opening portion 210 to replace the catalyst through the catalytic oxidizer opening portion 210 provided therein. A space for accessing the inside of the catalytic oxidizer body from the outside can be secured.

Furthermore, the catalyst oxidizer opening portion 210 is installed in the direction of the vessel 100 in the oxidation chamber of the catalyst oxidizer, which is generally integrally sealed, and an internal barrier layer is formed between the vessel and the catalyst oxidizer main body 200. The 300 is installed to prevent the fluid inside the vessel 100 from flowing into the catalytic oxidizer.

That is, between the catalytic oxidizer opening part 210 and the vessel opening part 110, an internal blocking membrane 300 for blocking fluid movement between the interior of the vessel 100 and the interior of the catalytic oxidizer body 200. Is provided has a structure capable of replacing the catalyst of the oxidation catalyst layer 220 through the catalytic oxidizer opening portion 210 and the vessel opening portion 110.

Referring to FIG. 5, an airtight structure of the vessel 100 and the catalytic oxidizer main body 200 and the oxidation catalyst layer 220 by the internal barrier layer 300 may be further understood. The fluid cannot be introduced into the catalytic oxidizer body 200.

 Referring to FIG. 6, the oxidation catalyst layer 220 is configured in plural with respect to the flow of the mixed gas flowing into the catalytic oxidizer main body, and the flow path of the mixed gas passing through each oxidation catalyst layer 220 is configured separately. To have a structure that does not mix with each other.

Accordingly, since the oxidation catalyst layer is configured in parallel to the flow direction of the mixed gas, the mixing of the fluid does not occur between the oxidation catalyst layers so that individual catalysts can be replaced.

Further, by installing a separate gas barrier layer 230 on the upper and lower portions of the oxidation catalyst layer 220 to limit the inflow of the mixed gas of the oxidation catalyst layer 220 to replace the catalyst by the gas barrier membrane 230 when the catalyst is replaced. I could do it.

In addition, the catalytic oxidizer is to burn the flammable gas contained in the fluid to recover its heat. When the flammable gas reacts with the catalyst layer unevenly, a hot spot occurs in a portion of the catalyst layer. May occur.

In order to minimize this, it is necessary to first use a metal support for the catalyst itself or a metal plate having high thermal conductivity to support the catalyst layer in order to uniformly mix the gas or quickly discharge the generated heat to the surroundings.

 Referring to FIG. 7, the upper and lower supports 400 may be disposed above and below the oxidation catalyst layer 220 to support the oxidation catalyst layer 220, and the upper and lower supports 400 may be formed of a metal porous plate. Thus, the temperature of the mixed gas may be uniformly transmitted to the oxidation catalyst layer, and the high temperature heat after the oxidation reaction may be uniformly spread over the oxidation catalyst layer.

Furthermore, when the upper and lower supports 400 are used as the metal porous plate, the oxidation catalyst layer 220 itself may be made of metal, or in the future, a ceramic catalyst may be used, thereby improving heat transfer.

Referring to FIG. 8, the gas barrier membrane 230 and the upper and lower supports 400 may be provided separately or together, respectively, and may be variously implemented according to the type and configuration of a stack or a catalytic combustor.

The catalyst of the catalytic oxidizer may be formed by an active metal of Pt or Pd series, a support of a honeycomb structure of ceramic or metal material, or may be formed of an active metal of MnO 2 or CuO series.

In addition, by using the catalytic oxidizer configuration applied in the present invention, when replacing the degraded catalyst layer, in order to minimize the impact on the stack, it is possible to minimize the pressure difference between the electric load and the cathode and the anode, It is desirable to replace the catalyst while paying attention to the risk of leakage.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains can understand that the present invention may be implemented in other specific forms without changing the technical spirit or essential features of the present invention. will be.

Therefore, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, And all changes or modifications derived from equivalents thereof should be construed as being included within the scope of the present invention.

100; Vessel 110; Vessel Opening Department
120; Stack 200; Catalytic oxidizer body
210; Catalytic oxidizer opening 220; Oxidation catalyst layer
230; Gas barrier 300; Internal barrier
400; Up and down support

Claims (4)

A vessel 100 in which a fuel cell unit stack is stacked therein;
A catalytic oxidizer body 200 provided inside the vessel 100;
An oxidation catalyst layer 220 provided inside the catalytic oxidizer main body 200 and housed so that the catalyst is detachable;
The catalytic oxidizer opening part 210 is provided in the catalytic oxidizer main body 200 corresponding to the position of the oxidation catalyst layer 220.
The vessel 100 includes a vessel opening portion 110 provided at a position corresponding to the catalytic oxidizer opening portion 210,
An internal blocking membrane 300 is provided between the catalytic oxidizer opening part 210 and the vessel opening part 110 to block fluid movement between the interior of the vessel 100 and the interior of the catalytic oxidizer main body 200. Catalytic oxidation system for a molten carbonate fuel cell, characterized in that the catalyst replacement of the oxidation catalyst layer 220 through the catalytic oxidizer opening portion 210 and the vessel opening portion 110. The method of claim 1,
The oxidation catalyst layer 220 is composed of a plurality with respect to the flow of the mixed gas flowing into the catalytic oxidizer body
The flow path of the mixed gas passing through each oxidation catalyst layer 220 is configured separately and is not mixed with each other, the catalytic oxidation system for molten carbonate fuel cell. The method of claim 1,
It further includes a vertical support (400) positioned above and below the oxidation catalyst layer 220 to support the oxidation catalyst layer 220,
The upper and lower supports 400 is a catalytic oxidation system for molten carbonate fuel cell, characterized in that the metal porous plate. 4. The method according to any one of claims 1 to 3,
Catalytic oxidation for molten carbonate fuel cells, characterized in that the catalytic oxidizer main body 200 further comprises a gas barrier layer 230 for blocking the gas flow into the oxidation catalyst layer 220 above and below the oxidation catalyst layer 220. system.

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