KR101177648B1 - Solid oxide fuel cells fueled by gasificating of solid carbon - Google Patents

Abstract

A solid oxide fuel cell according to an embodiment of the present invention includes a honeycomb including a solid carbon fuel and a gasification catalyst, a fuel electrode supplied with a fuel gas generated by gasifying the solid carbon fuel of the honeycomb, and one surface of the fuel electrode. The formed electrolyte layer and the cathode formed on the other surface of the electrolyte layer. In honeycomb, the use of a mixture of solid carbon fuel and a gasification catalyst can promote the gasification reaction to achieve a high power density. In addition, in the solid oxide fuel cell according to an embodiment of the present invention, by using the solid carbon fuel from which ash is removed, it is possible to prevent deterioration of activity due to interaction with the nonvolatile inorganic material of the gasification catalyst. In addition, since the performance deterioration of the fuel cell due to the deposition of nonvolatile inorganic materials can be prevented, it is possible to achieve universalization and economical improvement of the solid oxide fuel cell. Furthermore, the solid oxide fuel cell according to an embodiment of the present invention, by using a porous cartridge for supporting the honeycomb, can selectively permeate only the fuel gas and facilitate the recovery and recycling of the catalyst inorganic material remaining after the gasification reaction. have.

Description

SOLID OXIDE FUEL CELLS FUELED BY GASIFICATING OF SOLID CARBON}

Disclosed is a solid oxide fuel cell using gaseous solid gas as a fuel. More specifically, a fuel cell that improves the output density and economics of a solid oxide fuel cell is disclosed.

A direct carbon fuel cell is a fuel cell that uses a carbon-containing solid material as a fuel, and generates electricity through a reaction between a carbon fuel and an oxygen anion provided through an electrolyte. Pyrolyzed products such as starch, fiberboard, waste tires, wood, and carbon such as graphite, coal, activated carbon, coke, char Solid materials containing abundantly may be used as the carbon fuel. In this case, the open circuit voltage is 0.8 ~ 1.3 V is obtained, the reactivity of the carbon is affected by the particle size and shape, in general, the performance is improved as the specific surface area of the carbon fuel increases. The theoretical power generation efficiency of a direct carbon fuel cell is more than twice as good as that of the combustion reaction. High efficiency can reduce the amount of carbon used, thereby reducing the generation of carbon dioxide. In addition, carbon fuel has a high energy density compared to conventional hydrogen, methane, gasoline and diesel fuels. This is because a relatively high amount of oxygen can be consumed by the high oxidation state of carbon. Solid carbon fuels are not flammable / explosive and therefore safe to use, are easier to transport than gaseous fuels, and are generally less expensive.

Carbon is inert at room temperature / atmospheric conditions and can therefore be used as fuel only at temperatures above 400 ° C. Therefore, application has been made mainly to high temperature fuel cells. Three types of direct carbon fuel cells have been studied. The first is the use of solid carbon as the anode in molten hydroxide electrolytes (Zecevic et al., Carbon, 42, 1983-1993, 2004), and the second is molten carbonate. Alternatively, the mass transport of the solid carbon fuel may be improved by mixing carbon with molten tin as a cathode (US Patent No. 6,692,861 to Tao et al. And U.S. Pat. 2007/0269688). However, since molten salts have a large corrosiveness, deterioration of cell performance over time is inevitable. The last method is based on a conventional solid oxide fuel cell (SOFC), using solid carbon instead of gaseous fuel such as hydrogen / hydrocarbon at the cathode (Chuang, US Patent Publication 2007/0212584). Due to the lack of a triple phase boundary due to the use of solid fuels, participation in the electrochemical reaction of carbon is insignificant, mainly hydrocarbon, hydrogen, and carbon monoxide gases produced by pyrolysis of carbon components participate in the electricity production reaction. Due to the small contact area between the solid fuel and the electrode / electrolyte, the reduction in performance due to corrosion can be neglected, but practical efficiency has not been achieved until now, and also non-volatile ash and elemental carbon Degradation of cell performance is caused by the deposition of carbon) components.

Steam gasification of coal is generally achieved at a rate of production of syngas (syngas, a mixture of hydrogen and carbon monoxide), which is practical when carried out at high temperatures above 1000 ° C. and at high pressures of ˜30 bar. Since gasification conditions at high temperatures and pressures are accompanied by deterioration of economic efficiency and process risks, many studies have been conducted for gasification under mild conditions. Low grade coal having high reactivity can be gasified at a low temperature of 1000 ° C. or lower, but has not yet been put to practical use due to problems such as high water content. Coal steam gasification at low temperatures (800-1000 ° C.) and low pressures (<5 bar) can be realized through the introduction of catalysts. Alkali, alkaline earth, and some transition metal materials are used as catalysts, which speed up the gasification rate and increase the production rate of hydrogen useful as fuel. However, the catalyst used has a problem that it is difficult to recycle the catalyst by interaction with the inorganic ash.

Provided is a solid oxide fuel cell which uses solid carbon as a fuel.

A solid oxide fuel cell according to an exemplary embodiment of the present invention includes a honeycomb including a solid carbon fuel and a gasification catalyst, a fuel electrode supplied with a fuel gas generated by gasifying the solid carbon fuel, and an electrolyte layer formed on one surface of the fuel electrode. And an air electrode formed on the other surface of the electrolyte layer.

In the solid oxide fuel cell according to one aspect of the present invention, the solid carbon fuel may include solid coal or solid carbon having an ash content of 1% by weight or less.

In the solid oxide fuel cell according to an embodiment of the present invention, the solid carbon having an ash content of 1% by weight or less may be graphite, activated carbon, or carbon black.

In the solid oxide fuel cell according to an aspect of the present invention, the solid coal having an ash content of 1% by weight or less may include coal containing 1 to 30% of ash in an organic solvent at a temperature of 200 to 450 ° C. and 1 to 30 bar. After extraction at a pressure of may be prepared by drying.

In the solid oxide fuel cell according to the present invention, the organic solvent is 1-methylnaphthalene, 1-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone, carbon disulfide (CS _2). ), Light cycle oil, or tetralin.

In the solid oxide fuel cell according to an embodiment of the present invention, the electrolyte layer may have a thickness of 30 to 300 µm, the cathode may have a thickness of 10 to 70 µm, and the anode may have a thickness of 30 to 300 µm.

In the solid oxide fuel cell according to the present invention, the pore size of the honeycomb may be 50 to 400 cpsi (cells per square inch).

In the solid oxide fuel cell according to an aspect of the present invention, the honeycomb may further include a caking agent.

In the solid oxide fuel cell according to an embodiment of the present invention, the gasification catalyst may be an alkali metal compound, an alkali earth metal compound, or a transition metal compound.

In the solid oxide fuel cell according to one aspect of the present invention, the solid oxide fuel cell may further include a porous cartridge for supporting the honeycomb.

In the solid oxide fuel cell according to one aspect of the present invention, the cartridge may selectively permeate the fuel gas.

In the solid oxide fuel cell according to one side of the present invention, the cartridge may be made of pores of 10 to 50 ㎛.

In the solid oxide fuel cell according to one aspect of the present invention, the cartridge may be made of cordierite, silicon carbide (SiC), ceramic fibrous material, or metal fibrous material.

A solid oxide fuel cell according to an embodiment of the present invention includes a honeycomb including a solid carbon fuel and a gasification catalyst, a fuel electrode supplied with a fuel gas generated by gasifying the solid carbon fuel of the honeycomb, and one surface of the fuel electrode. The formed electrolyte layer and the cathode formed on the other surface of the electrolyte layer. In honeycomb, the use of a mixture of solid carbon fuel and a gasification catalyst can promote the gasification reaction to achieve a high power density.

In addition, in the solid oxide fuel cell according to an embodiment of the present invention, by using the solid carbon fuel from which ash is removed, it is possible to prevent deterioration of activity due to interaction with the nonvolatile inorganic material of the gasification catalyst. In addition, since the performance deterioration of the fuel cell due to the deposition of nonvolatile inorganic materials can be prevented, it is possible to achieve universalization and economical improvement of the solid oxide fuel cell.

Furthermore, the solid oxide fuel cell according to an embodiment of the present invention, by using a porous cartridge for supporting the honeycomb, can selectively permeate only the fuel gas and facilitate the recovery and recycling of the catalyst inorganic material remaining after the gasification reaction. have.

1 is a view schematically showing a solid oxide fuel cell including a honeycomb and a cartridge according to an embodiment of the present invention.

In the description of the embodiments, when described as being formed "on" or "under" of each layer, air electrode or fuel electrode, "on" and "under" are described. “Includes” both “directly” or “indirectly” other components. In addition, the upper or lower reference of each component is described with reference to the drawings.

Hereinafter, a solid oxide fuel cell according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a view schematically showing a solid oxide fuel cell including a honeycomb and a cartridge according to an embodiment of the present invention.

Referring to FIG. 1, a solid oxide fuel cell according to an exemplary embodiment of the present invention includes a honeycomb 2 including a solid carbon fuel and a gasification catalyst and a fuel generated by gasifying a solid carbon fuel of the honeycomb 2. A fuel electrode 3 to which gas is supplied, an electrolyte layer 5 formed on one surface of the fuel electrode 3, and an air electrode 4 formed on the other surface of the electrolyte layer 5 are included.

The solid oxide fuel cell according to an embodiment of the present invention gasifies the solid carbon fuel through internal reforming and directly supplies it as fuel to the carbon fuel cell. That is, the gasification catalyst is mixed with the ash-free solid carbon fuel to make honeycomb 2, and the carbon-vapor reaction of the steam steam 6 and the carbon fuel disposed on the honeycomb 2 is performed. The produced gas is supplied to the anode 3.

The solid oxide fuel cell is operated through the reaction at the cathode 4 and the reaction at the anode 3 as follows. That is, as the air 7 is electrochemically reduced in the cathode 4, oxygen ions are generated, and the generated oxygen ions diffuse through the pores of the electrolyte layer 5, and hydrogen, hydrocarbons, carbon monoxide, and the like are discharged from the anode 3. Electrochemically oxidizes by combining with oxygen ions in) gives off electrons and generates electricity by generating water or carbon dioxide.

Reaction at the cathode _{^{O 2 + 4e - ⇔ 2O 2}} -

Reaction in the fuel electrode _{^{2O 2 - + 2H 2 ⇔ 2H}} 2 O + 4e -

The electrolyte layer 5 should have a high conductivity of oxygen ions but little electron conductivity. In addition, the electrolyte layer 5 should be bonded to the air electrode 4 and the fuel electrode 3 well, and can be compact so that gas does not pass. Furthermore, the electrolyte layer 5 should be excellent in chemical stability under oxidation and reduction conditions in the temperature range of 800 ~ 1000 ℃. The electrolyte layer 5 may be made of Yttria stabilized zirconia (YSZ) that selectively permeates oxygen ions, but is not limited thereto.

The cathode 4 should be porous to allow oxygen to diffuse, and have excellent electron and oxygen ion conductivity. In addition, the cathode 4 should have a low polarization resistance against oxygen reduction reaction and excellent phase stability under high temperature oxygen airflow. Furthermore, the cathode 5 should be chemically stable at the interface with the electrolyte, and may have a similar coefficient of thermal expansion as other materials. The cathode 5 may be lanthanum manganese (La _0.8 Sr _0.2 MnO _3-x ) doped with 20% strontium (Sr), but is not limited thereto.

The anode 3 must be porous to allow hydrogen to diffuse, and have excellent electron and ion conductivity. In addition, the anode 3 should have a low polarization resistance in the oxidation reaction of hydrogen and excellent phase stability under a high temperature hydrogen stream. Further, the anode 3 should be chemically stable at the interface with the electrolyte, and may have a similar thermal expansion coefficient to other materials. The anode 3 may be used by sintering a mixture of nickel oxide and yttria stabilized zirconia (YSZ), but is not limited thereto.

In the solid oxide fuel cell according to an embodiment of the present invention, by forming a honeycomb 2 mixed with a solid carbon fuel and a gasification catalyst, the solid carbon fuel of the honeycomb 2 and water vapor 6 are generated to react. Fuel gas may be supplied to the anode 3. The solid carbon fuel included in the honeycomb 2 may include coal or solid carbon having an ash content of 1% by weight or less. That is, the solid carbon fuel hardly contains ash which causes catalyst deactivation, thereby preventing the deposition of ash.

The solid carbon fuel included in the honeycomb (2) is pulverized to 500 μm or less by mixing 10 to 100% by weight of coal having an ash content of 1% by weight or less and 0 to 90% of solid carbon having an ash content of 1% by weight or less, and then 0 to 20 wt% of the following caking agent may be added, mixed and then molded into a machine.

The solid carbon having an ash content of 1 wt% or less may be graphite, activated carbon, or carbon black, and may include a carbon material having a carbon content of 90% or more. Solid ash having an ash content of 1% by weight or less may be prepared by extracting coal containing 1 to 30% of ash in an organic solvent at a temperature of 200 to 450 ° C. and a pressure of 1 to 30 bar, followed by drying. Here, the ash content is silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), iron oxide (FeOx), calcium oxide (CaO), magnesium oxide (MgO), titanium oxide (TiO ₂ ), sodium oxide (Na ₂ O It may include inorganic materials such as), but is not limited thereto. In addition, the organic solvent used is 1-methylnaphthalene, N-methyl-2-pyrrolidone, carbon disulfide (CS ₂ ), light cycle oil ), Or tetralin.

By using the solid carbon fuel from which ash is removed in this way, it is possible to prevent the deterioration of the fuel cell due to deposition of nonvolatile inorganic materials, thereby achieving the generalization and economical efficiency of the solid oxide fuel cell.

In addition, a gasification catalyst for promoting the gasification of solid carbon fuel can be included in the honeycomb 2 together. Gasification catalysts include alkali metal compounds such as sodium chloride (NaCl) and potassium carbonate (K ₂ CO ₃ ), alkaline earth metal compounds such as calcium oxide (CaO), iron (Fe) and Transition metal compounds such as nickel (Ni), or mixtures thereof. Due to the gasification catalyst contained in the honeycomb 2, it is possible to promote the carbon-vapor reaction to achieve a high power density.

The method of supporting the catalyst in solid carbon fuel is performed by impregnation, solid phase mixing using mortar & pestle, and dispersion of the solid fuel in the aqueous solution of the catalyst compound to optimize the dispersion and increase the reactivity by the catalyst. After the pH adjustment, a method of supporting the catalyst may be used.

Gasifiers may have limited properties of fuel materials, depending on their type. For example, in fixed bed gasifiers, fuels with high mechanical strength are suitable because the fuel must be non-caking for permeation of water vapor. Entrained bed gasifiers exhibit higher efficiency with smaller particle sizes, so the fuel has to be pulverized into much smaller particles than other reactors.

Solid oxide fuel cell according to an embodiment of the present invention can minimize the restriction due to the physical properties of the fuel through the honeycomb (2) as described above. More specifically, the mixture of the solid carbon fuel and the gasification catalyst included in the honeycomb 2 reacts with the water vapor 6 at 700 to 1000 ° C., which is the operating temperature of the solid oxide fuel cell, to produce fuel gas. At this time, since the reaction between the water vapor 6 and the solid carbon fuel is activated through the gasification catalyst, the contact between the reactant and the catalyst may be an important factor in determining the production efficiency. Therefore, honeycomb (2) containing a mixture of solid carbon fuel and gasification catalyst is manufactured in a pore size of 50 to 400 cpsi (cells per square inch) to increase the surface area to expand the contact with gaseous water vapor, thereby increasing the carbon-vapor. May promote the reaction.

In addition, in the solid oxide fuel cell according to one aspect of the present invention, the honeycomb 2 further includes a caking agent to facilitate honeycomb molding of the mixture of the solid carbon fuel and the gasification catalyst. The caking agent may be, but is not limited to, molasses, starch, or pitch.

Furthermore, the honeycomb 2 comprising a solid carbon fuel and a gasification catalyst is arranged in close proximity to the anode 3 and shares the heat source used in the fuel cell so that heating is not necessary because no additional heating device is required. Can further reduce energy consumption.

The solid oxide fuel cell according to the exemplary embodiment of the present invention may be manufactured with a fuel electrode (2) supported type or an electrolyte (5) supported type structure in order to secure mechanical strength. The electrolyte layer 5 has a thickness of 30 to 300 μm, the air electrode 4 has a thickness of 10 to 70 μm, and the fuel electrode 3 has a thickness of 30 to 300 μm, thereby securing mechanical strength.

Solid oxide fuel cell according to one side of the present invention may further include a porous cartridge (1) for supporting the honeycomb (2). That is, the honeycomb 2 may be accommodated in the cartridge 1 for the recovery and recycling of the catalyst inorganic material. It may further include a cartridge support 8 for supporting the cartridge 1.

The cartridge 1 can selectively permeate only the fuel gas produced by the reaction of the solid carbon fuel with the water vapor 6. The cartridge 1 may be made of pores of 10 to 50 μm. The cartridge 1 may be made of cordierite, silicon carbide (SiC), ceramic fibrous material, or metal fibrous material.

All carbon fuel is consumed by the reaction of solid carbon fuel and steam, but catalytic inorganics (sodium chloride, potassium carbonate, calcium oxide, iron and nickel compounds, etc.) remain. If these inorganic materials are continuously accumulated on the surface of the anode, the generated fuel gas may be prevented from moving to the anode, thereby reducing the efficiency of the fuel cell. Therefore, the solid oxide fuel cell according to one aspect of the present invention includes the cartridge as described above, so that the fuel gas is permeated and the catalyst inorganic material is filtered so that the catalyst inorganic material can be easily recovered through cartridge replacement after the carbon fuel is exhausted. have. Furthermore, economic efficiency can be ensured by recycling the catalyst and the like collected from the recovered cartridge.

As a result, a solid oxide fuel cell according to an embodiment of the present invention includes a honeycomb including a solid carbon fuel and a gasification catalyst, a fuel electrode supplied with a fuel gas generated by gasifying the solid carbon fuel of the honeycomb, and the fuel electrode. An electrolyte layer formed on one surface and the air electrode formed on the other surface of the electrolyte layer. In honeycomb, the use of a mixture of solid carbon fuel and a gasification catalyst can promote the gasification reaction to achieve a high power density.

In addition, in the solid oxide fuel cell according to an embodiment of the present invention, by using the solid carbon fuel from which ash is removed, it is possible to prevent deterioration of activity due to interaction with the nonvolatile inorganic material of the gasification catalyst. In addition, since the performance deterioration of the fuel cell due to the deposition of nonvolatile inorganic materials can be prevented, it is possible to achieve the generalization and economical improvement of the solid oxide fuel cell.

Furthermore, the solid oxide fuel cell according to an embodiment of the present invention, by using a porous cartridge for supporting the honeycomb, can selectively permeate only the fuel gas and facilitate the recovery and recycling of the catalyst inorganic material remaining after the gasification reaction. have.

Solid oxide fuel cell Fuel electrode , Electrolyte layer , Air pole  making

In the flat fuel cell, a mixture of nickel and yttria stabilized zirconia (YSZ) 4: 4 was sintered to make a gas permeable porous fuel electrode 3 having a thickness of about 200 μm, and used as a support. One surface of the anode was repeatedly dip coated with an yttria stabilized zirconia (YSZ) electrolyte solution (5) to coat an electrolyte of about 30 μm thickness, and 20% of strontium (Sr) was doped over the electrolyte. lanthanum manganese night (La Sr _{0 .8 .2 0 -x} MnO ₃₎ by sintering after a slurry (slurry), screen printing (screen printing) made the cathode (5) of about 50 ㎛ thickness.

Production of Coal as Solid Carbon Raw Material

Ash (bituminous ash) having an ash content of about 12% was removed by thermal extraction using 1-methylnaphthalene, an organic solvent. The raw coal is pulverized to 75 μm or less and placed in a 0.5 L autoclave and placed in a 1-methylnaphthalene solvent which is 5 times the mass of the raw coal and stirred. The residual oxygen was removed using nitrogen and then maintained at a temperature of 370 ° C. and a pressure of 30 bar for 1 hour while stirring. The heat-treated mixture was separated from the soluble and insoluble components using a stainless steel filter. Of these, ash-free solubles were flowed with nitrogen in a vacuum oven at about 100 ° C. and dried to prepare coal as a solid carbon raw material. The coal produced typically contained up to 200 ppm of ash.

Dispersion of Gasification Catalyst

5 wt% potassium carbonate (K ₂ CO ₃ ) catalyst was mixed with the solid carbon fuel and then supported on the solid fuel using a solid phase mixing method using mortar & pestle.

Of catalyst and solid carbon fuel mixture Honeycomb ( honeycomb Molding

80 g of the coal prepared above and 20 g of ash-free solid carbon were mixed and put into a screw crusher equipped with a 200 mesh screen at the front end, and pulverized and mixed to 75 μm or less. Since 2% by weight of starch and a small amount of water to the total mass was added and mixed, the machine was molded 100 cpsi honeycomb.

Preparation of Cartridge Supports

Inorganic raw materials boehmite, kaolin, talc, and steatite are mixed in an appropriate amount to form cordierite (Mg, Fe) ₂ Al ₄ Si ₅ O ₁₈ ) The particle size was set to 40 μm or less by using a ball mill. An appropriate amount of water, mineral oil, and oleic acid were added to the mold as a molding agent, followed by sintering to prepare a cartridge support.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be modified. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

1: cartridge 2: honeycomb
3: fuel electrode 4: air electrode
5: electrolyte layer 6: steam steam
7: air 8: cartridge support

Claims (13)

In a solid oxide fuel cell using a solid carbon fuel gasified as a fuel,
Honeycombs including solid carbon fuels and gasification catalysts;
A fuel electrode to which a fuel gas generated by gasifying the solid carbon fuel is supplied;
An electrolyte layer formed on one surface of the fuel electrode; And
Solid oxide fuel cell comprising an air electrode formed on the other side of the electrolyte layer.
The method of claim 1,
The solid carbon fuel is a solid oxide fuel cell comprising a solid coal or solid carbon having an ash content of 1% by weight or less.
The method of claim 2,
The solid carbon having an ash content of 1% by weight or less is graphite, activated carbon, or carbon black.
The method of claim 2,
The solid coal having ash content of 1% by weight or less is a solid oxide fuel prepared by extracting coal containing 1 to 30% of ash in an organic solvent at a temperature of 200 to 450 ° C. and a pressure of 1 to 30 bar and then drying it. battery.
The method of claim 4, wherein
The organic solvent is 1-methylnaphthalene, N-methyl-2-pyrrolidone, carbon disulfide (CS ₂ ), light cycle oil, or Tetralin solid oxide fuel cell.
The method of claim 1,
The electrolyte layer is 30 ~ 300 ㎛ thick, the cathode is 10 ~ 70 ㎛ thick and the anode is 30 ~ 300 ㎛ thick solid oxide fuel cell.
The method of claim 1,
The honeycomb pore size is 50 ~ 400 cpsi (cells per square inch) solid oxide fuel cell.
The method of claim 1,
The honeycomb solid oxide fuel cell further comprises a caking agent (caking agent).
The method of claim 1,
The gasification catalyst is an alkali metal compound, an alkaline earth metal compound, or a transition metal compound.
The method of claim 1,
Solid oxide fuel cell further comprises a porous cartridge for supporting the honeycomb.
The method of claim 10,
And the cartridge selectively permeates the fuel gas.
The method of claim 10,
The cartridge is a solid oxide fuel cell consisting of pores of 10 ~ 50 ㎛.
The method of claim 10,
The cartridge is a solid oxide fuel cell made of cordierite, silicon carbide (SiC), ceramic fibrous material, or metal fibrous material.

Images