KR101343376B1 - Catalytic oxidizer and fuel cell system having the same - Google Patents

Abstract

A catalytic combustor of a fuel cell system is disclosed. Catalytic combustor of the fuel cell system according to an aspect of the present invention, in the catalytic combustor of the fuel cell system to perform the recycling between the same electrode and / or the electrode at the anode and the cathode, by a separate signal of high temperature and high pressure Steam is injected directly into the rectifier on which the electrolyte is deposited to directly dissolve and remove the electrolyte, a hydrophilic material.

Description

Catalytic Combustor and Fuel Cell System with the Same {CATALYTIC OXIDIZER AND FUEL CELL SYSTEM HAVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalytic combustion device, and more particularly, to a catalytic combustion device capable of improving operational stability and increasing durability of a fuel cell.

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.

Of these, molten carbonate fuel cells (MCFCs) operate at high temperatures of 650 ° C or higher, so the electrochemical reaction rate is fast, and nickel can be used instead of platinum catalysts as an electrode material. Even carbon monoxide, which acts as a poisoning substance on the platinum electrode, can be used as fuel through a water gas shift reaction. In addition, the molten carbonate fuel cell provides the selectivity of various fuels such as coal gas, natural gas, methanol, biomass, etc. as a characteristic of the nickel electrode. The molten carbonate fuel cell can increase the thermal efficiency of the entire power generation system to more than 60% by recovering and using high-quality waste heat as a bottom cycle using a heat recovery steam generator. In addition, the high temperature operating characteristics of the molten carbonate fuel cell provide an advantage of enabling the use of an internal reforming form in which a fuel reforming reaction is simultaneously performed in a fuel cell stack in which an electrochemical reaction occurs. Since the internally reformed molten carbonate fuel cell uses the heat generated from the electrochemical reaction in a reforming reaction that is a direct endothermic reaction without a separate external heat exchanger, the thermal efficiency of the entire system is further increased compared to the externally reformed molten carbonate fuel cell. Increasingly, the system configuration is simplified. In addition, the molten carbonate fuel cell is capable of small decentralized power generation and can be installed near a large city where electricity consumption is high, thereby reducing transmission and distribution losses.

A fuel cell typically consists of a stack that produces power and a Balance of Plant (BOP), which is a complex of components needed to operate the stack. In general, a fuel cell system supplies hydrogen directly to a fuel cell stack anode (anode) through a peripheral auxiliary device, or converts hydrocarbon-based fuel into hydrogen using a reformer mounted in a stack or peripheral auxiliary device, and is supplied as a reducing agent. The stack cathode (cathode), which is an anode, is mainly supplied with air as an oxidant. The ionization reaction between the feed gas and the catalyst generated at both the anode and cathode electrodes of the stack, and the chemical energy of the reaction gas supplied by the electrolyte that transfers ions from the electrode where the ions are generated to the counter electrode are converted into electrical energy.

The fuel cell power generation system recycles and / or recycles (hereinafter referred to as "recirculation") between the same electrode or another electrode to increase efficiency. In particular, in the case of molten carbonate fuel cells, carbon dioxide is produced in the anode reaction and carbon dioxide is consumed in the reaction of the cathode, so that carbon dioxide necessary for the cathode reaction is recycled to the cathode in order to simplify the system and maximize efficiency. It is common to feed through.

However, since a fuel cell is typically supplied with a large amount of fuel compared to a stoichiometric ratio for stable operation, a certain amount of unreacted fuel components are present in the exhaust gas in addition to carbon dioxide. If it is recycled to the cathode side without removing it, the system efficiency is reduced as much as the unreacted fuel, and the reducing gas and the unreacted fuel gas react directly on the cathode side without passing through the electrolyte, thereby greatly reducing the stack voltage. In addition, when such a direct reaction is large and fast, combustion may occur inside the stack.

To prevent this, the unreacted fuel component in the anode exhaust must be removed before recycling, which is responsible for the catalytic burner. Catalytic burners generate heat by oxidizing an unreacted fuel gas and an oxidant gas introduced thereto using a catalyst. This heat is used to raise the temperature of the incoming oxidant gas to the operating temperature of the fuel cell stack. In particular, the catalytic combustor has a wider flammability range than a general flame combustor, which can stably oxidize and remove unreacted fuel components having low concentrations.The combustion temperature is relatively low, and the poisoning of electrodes and catalysts generated from high temperature flame combustion such as nitrogen oxide It has the advantage of not producing substances and harmful emissions. Catalytic burners also have the advantage that the heat transfer from the catalyst surface to the gas is much more stable than flame combustion.

The anode exhaust gas may include impurities such as moisture or electrolyte particles in addition to the above-described carbon dioxide or unreacted fuel gas. Particularly, the anode exhaust gas may have a high viscosity and exist in a liquid state or a solid state below the operating temperature of the fuel cell. In particular, in the case of catalytic combustion, the mixing with the relatively low temperature gas supplied to the cathode occurs, and since the catalyst or the filter having a narrow flow path exists, deposition of electrolyte particles is likely to occur. Electrolyte particles can be easily deposited on porous catalyst combustor catalysts such as Honeycomb in the mixer where the temperature is lowered by the fresh air introduced.The deposited electrolyte particles block the flow path to increase the flow unevenness and increase the differential pressure. This prevents normal catalytic reactions, lowers combustion efficiency and causes unreacted fuel components to enter the cathode. Increasing the differential pressure and decreasing the combustion efficiency greatly affect the operation of the entire fuel cell system, and if a large amount of reactant gas is concentrated as part of the catalyst due to flow irregularities, hot spots are formed and the catalyst is permanent. Phosphorus can result in loss of performance.

Various ideas for stabilizing the operation of fuel cell catalysts, i.e., fuel cell system, and extending the operating time by providing a means such as a filter for removing impurities at the front end of the catalytic combustor or removing the deposited electrolyte to prevent this. Is presented.

In Korean Patent Laid-Open No. 2008-0033487, two stages of catalysts having different cell densities (ie, honeycomb channels per unit area) are connected in series, and the electrolyte density is designed to lower the cell density of the catalyst located in front of the electrolyte. Delay the increase in the differential pressure. In this case, since the cell density of the rear stage catalyst is very high to determine the differential pressure of the entire flow, the electrolyte particles deposited on the shear catalyst do not significantly affect the overall differential pressure. However, this does not solve the problem merely by temporarily delaying the increase in the differential pressure due to electrolyte deposition, and there is a problem that all electrolytes are not deposited on the catalyst located at the front end.

In addition, Korean Patent Application No. 2007-7017366 proposes a method of removing an electrolyte without separating the catalytic combustor during the entire inspection period of a fuel cell system by filling a specific solvent into the catalytic combustor. In general, the electrolyte used in the molten carbonate fuel cell stack is known to be hydrophilic and can be removed by water. Therefore, it is not necessary to use a specific solvent, and such a method does not need to separate and decompose the catalytic combustor. Although simple, it also has the limitation that removal of the deposited electrolyte is possible only when the operation is stopped.

Accordingly, the present invention has been made to solve the above-mentioned problems, and to provide a catalytic combustion apparatus that can improve the operational stability and durability of a fuel cell by removing the deposited electrolyte.

Other objects of the present invention will become more apparent through the following preferred embodiments.

Catalytic combustor of the fuel cell system according to an aspect of the present invention, in the catalytic combustor of the fuel cell system to perform the recycling between the same electrode and / or the electrode at the anode and the cathode, by a separate signal of high temperature and high pressure Steam is injected directly into the rectifier on which the electrolyte is deposited to directly dissolve and remove the electrolyte, a hydrophilic material.

Catalytic combustion apparatus according to the present invention may have one or more of the following features. For example, the steam may be part of the steam used in the aqueous reaction for hydrocarbon reforming or may be supplied from a separate steam generator.

The signal transmitted to the catalytic combustor may be a differential pressure signal for the front and rear ends of the catalytic combustor.

Catalytic combustor of the fuel cell system according to another aspect of the present invention, in the catalytic combustor of the fuel cell system to perform the recirculation between the same electrode or the electrode at the anode and the cathode, the uniform flow of the mixed gas flowing into the catalyst and Including a rectifier to remove impurities, the rectifier is a current is applied to remove the deposited electrolyte when a certain level of differential pressure is sensed.

Catalytic combustion apparatus according to the present invention may have one or more of the following features. For example, the current supplied to the rectifier may be electrical energy generated in the stack or electrical energy supplied separately from the outside.

The present invention can provide a catalytic combustor capable of improving operating stability and increasing durability of a fuel cell by removing the deposited electrolyte.

1 is a schematic diagram of a catalytic combustor according to an embodiment of the present invention.
FIG. 2 is an enlarged view of the rectifier of the catalytic burner of FIG.
3 is an enlarged cross section of the catalyst of the catalytic burner of FIG.
4 is a schematic diagram of a catalytic combustor rectifier according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout the specification and claims. The description will be omitted.

1 is a schematic diagram of a catalytic burner 100 according to an embodiment of the present invention, and FIGS. 2 and 3 are enlarged views of the rectifier 102 and the catalyst 103 included in the catalytic burner 100 of FIG. 1. to be.

1 to 3, the anode exhaust gas is recycled to the anode or recycled to the cathode by a device (not shown) such as a blower or ejector. The anode exhaust gas containing the unreacted fuel component recycled to the double cathode is mixed with the oxidant gas through the inlet pipe 101 and supplied to the catalyst 103.

The catalyst 103 has an enlarged cross section 103 'and a honeycomb shape to maximize the contact area with the reaction gas. The anode exhaust gas and the cathode gas mixed gas are mixed into the inlet pipe 101 or through a separate mixing device (not shown) and supplied to the rectifier 102.

The rectifier 102 functions as a kind of filter that equalizes the flow of the mixed gas flowing into the catalyst 103 to maximize catalyst utilization and prevent hot spots and remove impurities such as electrolyte particles. Rectifier 102 may be in the form of a honeycomb, such as catalyst 103 ', or may be comprised of a kind of porous plate having the same cross-sectional area as catalyst 103, such as 102'. The rectifier 102 is composed of a metal material having high temperature durability, such as the catalytic burner 100, and the processed many holes 104 form a slight differential pressure to uniformly mix the flow of the mixed gas supplied to the catalyst 103. The gas is allowed to reach uniformly over the entire area of the catalyst 103.

The anode exhaust gas at a high temperature (eg, less than 650 ° C.) is mixed with a relatively low temperature cathode gas in the catalytic combustion inlet pipe 101 so that the composition becomes uniform while the temperature is lowered. When the temperature of the mixed gas is lowered below a specific temperature (for example, 350 ° C.), the electrolyte particles contained in the anode exhaust gas undergo a phase change, and the liquid 104 is formed in the hole 104 processed in the rectifier 102 'in a liquid or solid state. I'm calm. Holes 105 deposited by electrolyte particles no longer allow mixed gas to pass, resulting in flow unevenness, which reduces catalyst utilization and permanently damages hot spots on the catalyst when the flow is concentrated in certain areas. Will be added.

The present invention proposes a method for removing electrolyte particles deposited inside a catalytic combustor by using the following examples by using electrolyte particles because they are hydrophilic and can be dissolved with water, and vaporize again at a predetermined temperature or more.

The catalytic combustor 100 according to the present invention shown in FIG. 1 is provided with a port 106 through which steam can be supplied. In the case of an internal reforming fuel cell such as a molten carbonate fuel cell, a high temperature steam is supplied for reforming a natural gas supplied as a fuel. The deposition of electrolyte particles is applied to the pressure gauges 107 and 108. When a predetermined differential pressure is detected, some of the steam is injected to the rectifier 102 through the port 106. The steam having a high temperature and high pressure compared to the mixed gas supplied to the catalytic combustor 100 may dissolve and remove the electrolyte particles deposited in the holes 104 processed in the rectifier 102.

4 is a diagram illustrating a rectifier 102 'of a catalytic combustor in accordance with one embodiment of the present invention.

When a differential pressure of a predetermined level or more is detected through the pressure gauges 107 and 108 of the catalytic combustion device 100, a constant current is applied through the terminal 202 installed in the rectifier 102 ′. An insulation material 203 is provided outside the rectifier 102 'to insulate the rectifier 102' from the catalytic burner 100, so that the temperature of the rectifier 102 'is increased when a current is applied. As the temperature of the rectifier 102 'rises, the temperature of the hole 201 in which the electrolyte is deposited increases, and when the temperature rises above the vaporization temperature of the electrolyte particles, the deposited electrolyte gradually vaporizes and is removed from the hole. In this case, the supplied current may utilize current generated from an external or fuel cell stack.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

100: catalytic combustion 101: inlet pipe
102: combustor 103: catalyst
104: Hall 105: Calm Hall
106: port 107, 108: pressure gauge
202: terminal 203: insulating material

Claims (8)

In the catalytic combustor of a fuel cell system performing recycling between the same electrode or the electrodes at the anode and the cathode,
A rectifier for equalizing the flow of the mixed gas flowing into the catalyst and removing impurities; And
A port for supplying steam to the rectifier;
By a separate signal, steam, which is hotter and higher pressure than the mixed gas, is directly injected into the rectifier in which the electrolyte is deposited through the port to directly dissolve and remove the electrolyte, which is a hydrophilic substance,
The steam is catalytic combustion, characterized in that supplied from a portion or a separate steam generator of the steam used for the aqueous reaction for the hydrocarbon-based hydrogen reforming. delete delete The method of claim 1,
The signal is a catalytic combustion, characterized in that the differential pressure signal for the front and rear ends of the catalytic combustion. delete delete delete A fuel cell system comprising the catalytic combustion device of claim 1.

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