CN1790788A

CN1790788A - Fuel cell, operating method thereof, sintering furnace, and power generator

Info

Publication number: CN1790788A
Application number: CNA2005101302531A
Authority: CN
Inventors: 藏岛吉彦; 本多俊彦
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2004-12-13
Filing date: 2005-12-12
Publication date: 2006-06-21
Anticipated expiration: 2025-12-12
Also published as: CN100440596C

Abstract

A molten carbonate fuel cell, operating method of the fuel cell, sintering furnace equipped with the fuel cell, and power generator, wherein a cathode gas with a high carbon dioxide concentration can be obtained without a process of increasing the carbon dioxide concentration, and the heat of furnace exhaust gas can be effectively reclaimed and the fuel consumption can be reduced. The cathode gas is a gas containing a furnace exhaust gas discharged from an industrial furnace for heating materials. Alternatively, the furnace exhaust gas can be used to pre-heat air to be fed to the cathode of the fuel cell. The carbon dioxide concentration of the cathode gas is 0.1-50 vol%.

Description

Fuel cell, method for operating the same, sintering furnace, and generator

Technical Field

The invention relates to a fuel cell, a method of operating a fuelcell, a sintering furnace and a generator. More particularly, the present invention relates to a molten carbonate fuel cell, a method of operating the fuel cell, a sintering furnace equipped with the fuel cell, and a generator, wherein a gas comprising a furnace off-gas released from an industrial furnace heating a material as a carbon dioxide source, a mixed gas of the furnace off-gas and a cathode gas or a cathode preheating gas is used as a cathode gas of a molten carbonate fuel cell, or a cathode-use preheating gas which is a gas preheated using a furnace exhaust gas as a heat source, wherein, in the case where furnace off-gas or mixed gas is used as the cathode gas, the cathode gas containing carbon dioxide at a high concentration can be obtained by a method not requiring an increase in the carbon dioxide concentration, in the case of using the preheating gas for the cathode, the heat of the furnace exhaust gas can be efficiently recovered, and the consumption of fuel is reduced.

Background

Generally, oxygen and carbon dioxide contained in air are used as oxygen and carbon dioxide supplied to the cathode side of the molten carbonate fuel cell. Gases with high concentrations of carbon dioxide are advantageous for activating the fuel cell reaction. For this reason, carbon dioxide in the air in an amount of not more than 0.03% by volume is generally used after the carbon dioxide concentration is increased. For example, a method of generating carbon dioxide on the anode side by an electrochemical reaction in the operation of a fuel cell, and recovering an exhaust gas containing such carbon dioxide is applied to concentrate carbon dioxide in a gas (cathode gas) supplied to the cathode side. However, since the fuel cell reaction is mild immediately after the start-up, the amount of carbon dioxide generated on the anode side is too small to increase the concentration of carbon dioxide in the gas supplied to the cathode side by recovering the anode off-gas. One method of concentrating carbon dioxide by a Pressure Swing Adsorption (PSA) system before being fed to the cathode side requires energy from the compressed air, resulting in high energy costs. In other molten carbonate fuel cells that do not use a PSA system, at start-up, a portion of the cell fuel is combusted to produce heat and carbon dioxide. The generated heat is used to heat the fuel cell unit to an operating temperature, while carbon dioxide is used to supply the cathode side. This method also wastes energy by burning fuel gas (for example, Japanese patent application laid-open No. 1993-8989899).

Various industrial furnaces have been used in various industrial fields to heat various materials. Industrial furnaces that burn fossil energy to heat materials can produce a large amount of high-temperature exhaust gas (furnace exhaust gas) containing carbon dioxide, while generating heat by combustion of fuel. From the standpoint of the adverse effects of high temperature flue gases on the environment at present, it is a very beneficial matter to recover and reuse the heat carried by the furnace flue gases. Moreover, the problem of carbon dioxide-containing exhaust gas is particularly significantly associated with global warming and the like in recent years. There is a strong need to efficiently collect heat from industrial furnace exhaust gases while reducing the amount of carbon dioxide it contains.

On the other hand, there has not been much research into recovering heat for ceramic or similar sintering furnaces and reducing the amount of carbon dioxide in the exhaust gases produced thereby, these furnaces being relatively small industrial furnaces. The carbon dioxide-containing combustion gas for heating the sintering material in the sintering furnace is released into the air as it is. In contrast, for example, a method of recovering the heat energy of the exhaust gas by returning the exhaust gas discharged from the sintering furnace to the sintering furnace has been devised (for example, Japanese patent application No. 2002-. This method can recover a part of the heat energy in the exhaust gas and reduce the total amount of fuel, thereby enabling to reduce the amount of carbon dioxide generated. However, the reduction of the amount of carbon dioxide is limited.

Disclosure of Invention

The present invention addresses the problems in prior art molten carbonate fuel cells, including the need for additional energy to supply gas containing a high carbon dioxide concentration to the cathode side and the inefficient recovery of furnace exhaust heat. In particular, an object of the present invention is to provide a molten carbonate fuel cell and an operation method of the fuel cell, which includes using a cathode gas, i.e., a furnace off-gas discharged from an industrial furnace heating materials as a carbon dioxide source, a mixture (mixed gas) of the furnace off-gas and a cathode gas or a cathode preheating gas, or the cathode preheating gas, which is a cathode gas preheated using the furnace off-gas as a heat source. When the furnace off-gas or the mixed gas is used as the cathode gas, the gas containing carbon dioxide at a high concentration can be supplied to the cathode side without using additional energy, because the furnace off-gas containing carbon dioxide released from the sintering furnace can be used without any treatment for increasing the carbon dioxide concentration. When the preheating gas is used for the cathode, the heat of the furnace exhaust gas can be efficiently recovered, and the fuel consumption can also be reduced. It is another object of the present invention to provide a sintering furnace and a generator including supplying furnace off-gas or mixed gas containing carbon dioxide released from the sintering furnace to the cathode side of a fuel cell without any treatment for increasing the carbon dioxide concentration, thus ensuring that high-concentration carbon dioxide gas is supplied to the cathode side without using additional energy, or supplying pre-heating gas for the cathode to the cathode side of the fuel cell, thus ensuring effective use of the furnace off-gas.

The above objects can be achieved in the present invention by the following fuel cell, its operation method, sintering furnace, and generator.

(1) A fuel cell comprising a cathode, an anode and an electrolyte layer containing molten carbonate between the cathode and the anode, a gas containing oxygen and carbon dioxide (cathode gas) supplied to the cathode side and a gas containing hydrogen (anode gas) supplied to the anode side to generate electric energy, wherein the cathode gas is a gas comprising a furnace off-gas discharged from an industrial furnace heating a material, a mixed gas of the furnace off-gas and a cathode gas or a cathode-use preheating gas, the cathode-use preheating gas is a cathode gas preheated using the furnace off-gas as a heat source, and the concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

(2) The fuel cell according to the above (1), wherein when the cathode gas contains a furnace off-gas or a mixed gas, the industrial furnace is a sintering furnace that heats the material using a combustion gas generated by combusting a fuel, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the material to be heated.

(3) The fuel cell according to the above (2), wherein the fuel is a hydrocarbon-containing fuel.

(4) The fuel cell according to the above (3), wherein thehydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

(5) The fuel cell according to any one of the above (1) to (4), wherein the cathode gas is preheated using a catalyst combustor.

(6) The fuel cell according to the foregoing (5), wherein the heat source of the catalyst combustor is anode off-gas discharged from the anode.

(7) The fuel cell according to any one of the above (1) to (6), wherein when the cathode gas contains a cathode preheat gas, the cathode preheat gas is preheated by a heat exchanger using the furnace off-gas as a heat source.

(8) The fuel cell according to any one of the above (1) to (7), wherein the anode gas uses hydrogen contained in a reformed gas reformed in a steam reformer installed in an industrial furnace.

(9) A method of operating a fuel cell provided with a cathode, an anode, and an electrolyte layer containing molten carbonate between the cathode and the anode, the method comprising: a gas containing oxygen and carbon dioxide (cathode gas) is supplied to the cathode side, and a gas containing hydrogen (anode gas) is supplied to the anode side to generate electric power, wherein the cathode gas includes furnace off-gas discharged from an industrial furnace that heats a material, a mixed gas of the furnace off-gas and a cathode gas or a cathode preheating gas, or the cathode preheating gas, the cathode preheating gas is a cathode gas preheated using the furnace off-gas as a heat source, and the concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

(10) The method according to the above (9), wherein, when the cathode gas contains a furnace off-gas or a mixed gas, the industrial furnace is a sintering furnace for heating the material using a combustion gas generated by combusting a fuel, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the material to be heated.

(11) The method according to the foregoing (10), wherein the fuel is a hydrocarbon-containing fuel.

(12) The method according to the above (11), wherein the hydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

(13) The method according to any one of the above (9) to (12), in which the cathode gas is preheated using a catalyst combustor.

(14) The method according to the foregoing (13), wherein the heat source of the catalyst combustor is anode off-gas discharged from the anode.

(15) The method according to any one of the above (9) to (14), wherein when the cathode gas contains a cathode preheating gas, the cathode preheating gas is preheated by a heat exchanger using the furnace off-gas as a heat source.

(16) The method according to any one of the above (9) to (15), wherein the anode gas uses hydrogen contained in a reformed gas reformed in a steam reformer installed in an industrial furnace.

(17) A sintering furnace comprising a combustion chamber for combusting a hydrocarbon-containing fuel to produce a combustion gas, a sintering furnace main body for heating and sintering a material brought therein by the combustion gas and releasing the combustion gas as a furnace off-gas and/or a decomposition gas produced by decomposition of an organic material contained in the heated material, and the fuel cell according to the foregoing (1) to (8), the fuel cell being installed so that the furnace off-gas released from the sintering furnace main body is supplied as a cathode gas to a cathode side.

(18) The sintering furnace according to the foregoing (17), further comprising a steam reformer for performing a reforming reaction for producing a reformed gas containing hydrogen and carbon dioxide obtained by passing a hydrocarbon into the furnace and steam.

(19) The sintering furnace according to the foregoing (18), wherein the steam reformer comprises a low-temperature reforming portion having a metal reaction tube or a ceramic reaction tube for causing the steam reforming reaction to occur therein and a reforming catalyst packed in the reaction tube for accelerating the steam reforming reaction, and a high-temperature reforming portion having a ceramic reaction tube for causing the steam reaction to react therein.

(20) The sintering furnace according to the above (18) or (19), wherein the steam reformer is installed in the sintering furnace main body and/or the furnace exhaust gas flow passage, the low temperature reforming part is provided at a position heated to 600 to 1,000 ℃, and the high temperature reforming part is provided at a position heated to 1,000 to 1,800 ℃.

(21) The sintering furnace according to the foregoing (18) to (20), wherein part or all of the hydrogen contained in the reformed gas is used as the anode gas.

(22) The sintering furnace according to any one of the above (18) to (21), further comprising a hydrogen separator for selectively separating hydrogen from the reformed gas formed by the steam reformer into a hydrogen fuel including hydrogen as a main component and a residual gas containing carbon dioxide by introducing the reformed gas thereto.

(23) The sintering furnace according to the foregoing (22), further comprising a carbon dioxide fixer to fix carbon dioxide in theresidual gas separated by the hydrogen separator, and/or to fix carbon dioxide contained in the anode gas (anode off-gas) discharged from the molten carbonate fuel cell.

(24) The sintering furnace according to any one of the above (17) to (22), wherein the sintering furnace main body continuously introduces the material to heat, and continuously carries out the heated material.

(25) The sintering furnace according to any one of the above (17) to (24), wherein the material to be heated is ceramic.

(26) The sintering furnace according to any one of the above (17) to (25), wherein the material to be heated is of a honeycomb structure.

(27) A power generator comprising a fuel cell including a cathode, an anode, an electrolyte layer containing molten carbonate between the cathode and the anode, a cathode gas supply device supplying a gas containing oxygen and carbon dioxide (cathode gas) to the cathode, and an anode gas supply device supplying a gas containing hydrogen (anode gas) to the anode to generate electric power, wherein the cathode gas supply device has a furnace off-gas supply device which can supply furnace off-gas discharged from an industrial furnace which heats a material, and/or a cathode gas supply device which can supply cathode gas to the cathode, the cathode gas supplied to the cathode by the cathode gas supply device containing furnace off-gas carried by the furnace off-gas supply device, a mixed gas of the furnace off-gas and the cathode gas or a cathode preheating gas carried by the cathode gas supply device, or a cathode-use preheated gas which is a cathode-use gas (cathode-use preheated gas) preheated using a furnace exhaust gas as a heat source, wherein the concentration of carbon dioxide in the cathode-use gas is 0.1 to 50% by volume.

(28) The power generator according to the above (27), wherein, when the cathode gas contains a furnace off-gas or a mixed gas, the industrial furnace is a sintering furnace that heats the material using a combustion gas generated by burning a fuel, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the material to be heated.

(29) The power generator according to the foregoing (28), wherein the fuel is a hydrocarbon-containing fuel.

(30) The power generator according to the foregoing (29), wherein the hydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

(31) The power generator according to any one of the above (27) to (30), wherein the cathode gas is preheated using a catalyst combustor.

(32) The power generator according to the foregoing (31), wherein the heat source of the catalyst combustor is anode off-gas discharged from the anode.

(33) The power generator according to any one of the above (27) to (32), wherein the engine further comprises a heat exchanger, and the preheating gas for the cathode is preheated by the heat exchanger using the furnace exhaust gas as a heat source. .

(34) The power generator according to any one of the above (27) to (33), wherein the engine further comprises a steam reformer, and the anode gas uses hydrogen contained in a reformed gas reformed in the steam reformer.

Drawings

Fig. 1 is a schematic cross-sectional view of one embodiment of a fuel cell of the present invention.

FIG. 2 is a schematic block flow diagram of one embodiment of a sintering furnace of the present invention.

FIG. 3 is a block flow diagram of one embodiment of the generator of the present invention.

Detailed Description

According to the fuel cell of the present invention, when furnace off-gas, or mixed gas of furnace off-gas and cathode gas or cathode preheating gas is used as cathode gas, the furnace off-gas containing carbon dioxide released from the sintering furnace can be used as cathode gas of the molten carbonate fuel cell without any process of increasing the carbon dioxide concentration. Therefore, electric power can be generated by supplying a gas of high concentration carbon dioxide without additional energy. When the cathode preheat gas is used, the heat of the furnace exhaust gas can be efficiently recovered, and the fuel consumption can be reduced. According to the method for operating a fuel cell of the present invention, in the case of using the furnace off-gas or the mixed gas as the cathode gas, the furnace off-gas containing carbon dioxide released from the sintering furnace can be used as the cathode gas of the molten carbonate fuel cell without any process of increasing the carbon dioxide concentration. Therefore, electric power can be generated by supplying a gas of high concentration carbon dioxide without additional energy. When the cathode preheat gas is used, the heat of the furnace exhaust gas can be efficiently recovered, and the fuel consumption can be reduced. According to the sintering furnace and the generator of the present invention, when the furnace off-gas or the mixed gas is used as the cathode gas, the furnace off-gas containing carbon dioxide released from the sintering furnace main body can be supplied to the cathode side of the fuel cell without any process of increasing the carbon dioxide concentration. Therefore,electric energy can be generated by supplying gas having a high concentration of carbon dioxide on the cathode side without additional energy. When the cathode preheat gas is used, the heat of the furnace exhaust gas can be efficiently recovered, and the fuel consumption can be reduced.

Embodiments of the present invention are described below with reference to the drawings. However, the present invention is not limited to the following embodiments. Various modifications and improvements may be made to the invention based on the knowledge of those skilled in the art without departing from the scope of the invention.

Fig. 1 is a schematic cross-sectional view of one embodiment of a fuel cell of the present invention. As shown in fig. 1, a fuel cell 1 of this embodiment includes a cathode 2, an anode 3, and an electrolyte layer 4 containing molten carbonate between the cathode 2 and the anode 3. A gas (cathode gas) 21 containing oxygen and carbon dioxide is supplied to the cathode 2 side, and a gas (anode gas) 23 containing hydrogen is supplied to the anode 3 side to generate electric power. The cathode gas 21 is a gas containing a furnace off-gas discharged from an industrial furnace that heats a material, a mixed gas of the furnace off-gas and a cathode gas or a cathode preheating gas that is a cathode gas preheated using the furnace off-gas as a heat source, or a cathode preheating gas. The concentration of carbon dioxide in the cathode gas 21 is 0.1 to 50% by volume. The concentration of carbon dioxide in the cathode gas 21 is preferably 10 to 45% by volume, more preferably 20 to 40% by volume. If the concentration of carbon dioxide is less than 0.1% by volume, the electrochemical reaction may be very mild, and if it exceeds 50% by volume, the amount of oxygen molecules may be insufficient to generate sufficient carbonate ions. When the cathode gas 21 contains a furnace off-gas or a mixed gas, the industrial furnace is preferably a sintering furnace that heats the material using a combustion gas generated by burning a fuel, and the furnace off-gas is preferably an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the material to be heated. The use of the gas containing the decomposed exhaust gas as the cathode gas 21 can eliminate the need for burning the decomposed exhaust gas into a nontoxic gas using an afterburner or the like disposed outside the furnace (detoxification treatment). Performing the detoxification treatment within the fuel cell unit may save fuel required for the operation of the afterburner or similar device. The cathode gas 21 may be a mixture of a furnace off-gas containing a high carbon dioxide concentration discharged from a sintering furnace and oxygen (combustion off-gas and/or decomposition off-gas), or a mixture of the furnace off-gas (combustion off-gas and/or decomposition off-gas) and a cathode gas or a cathode preheating gas. When the furnace off-gas (combustion off-gas and/or decomposition off-gas) and the cathode gas or the cathode preheat gas are mixed (if a mixed gas is used), the ratio of the furnace off-gas (combustion off-gas and/or decomposition off-gas) to the cathode gas or the cathode preheat gas is preferably 100: 0 to 1: 4. Although the cathode gas 21 containing an appropriate carbon dioxide concentration can be obtained without using any process such as a PSA concentration method to increase the carbon dioxide concentration, the carbon dioxide concentration can be optimized by adopting any such method of increasing the carbon dioxide concentration. In this case, the cost of the process for increasing the carbon dioxide concentration is very low because furnace off-gas (combustion off-gas and/or decomposition off-gas) containing carbon dioxide at a high concentration is used as the cathode gas 21. The above discussion is based on the assumption that furnace off-gas is used as the source of carbon dioxide for the cathode gas 21. In the case where it is more important to reduce the fuel consumption by efficiently recovering the heat of the furnace off-gas, the cathode gas 21 may not contain the furnace off-gas, and may be composed of only the preheated cathode gas that has been heated using the furnace off-gas as the heat source.

In this method, when the furnace off-gas or the mixed gas is used as the cathode gas 21 in the fuel cell 1 of the present embodiment, the furnace off-gas (combustion off-gas and/or decomposition off-gas) containing carbon dioxide released from an industrial furnace (e.g., a sintering furnace) can be used as the cathode gas 21 of the fuel cell 1 without any process of increasing the carbon dioxide concentration. Therefore, electric energy can be generated by supplying the gas containing carbon dioxide at a high concentration to the cathode 2 side without additional energy.

In this embodiment, the industrial furnace is a device for heating materials. For example, sintering furnaces heat and sinter materials using combustion gases generated by burning fuel. The fuel used in the sintering furnace is preferably a hydrocarbon-containing fuel, and in particular, at least one fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil. The term "town gas" represents a gas containing 70 to 90% by volume of methane as a main component and other hydrocarbons such as ethane, propane and butane.

In the fuel cell 1 of this embodiment, the cathode gas 21 enters the cathode gas passage 5 from the cathode gas inlet 6 and is supplied to the cathode 2, wherein the cathode gas 21 is supplied with carbon dioxide and oxygen and is released as cathode off-gas through the cathode off-gas outlet 7. The anode gas 23 enters the anode gas passage 8 from the anode gas inlet 9 and is supplied to the anode 3, wherein the anode gas 23 is supplied with hydrogen and is discharged as anode off-gas through the anode off-gas outlet 10. Electrons generated by the reaction at the cathode 2 and anode 3 travel from the anode 3 to the cathode 2, as a path 25, and are used as electrical energy at a load 31. When the cathode gas 21 or the anode gas 23 contains foreign substances such as dust, it is preferable to remove these foreign substances using a filter before these gases are sent into the cathode gas passage 5 or the anode gas passage 8.

Typical reactions that occur in the fuel cell of the present invention (molten carbonate fuel cell) are as follows:

(1) on the cathode side:

(2) carbonate ion (CO)₃ ^2-) Is transported to the anode side through the electrolyte layer.

(3) On the anode side:

(4) when the anode gas contains CO, the following reaction occurs on the anode side.

The hydrogen produced in this reaction is used as H in the anode side reaction (3)₂。

Fig. 2 is a schematic block flow diagram of one embodiment of the sintering furnace of the present invention, which is equipped with a fuel cell. An embodiment of the fuel cell of the present invention can be explained with reference to fig. 2. When the cathode gas 51 (labeled as numeral 21 in fig. 1) contains furnace off-gas or mixed gas, the furnace off-gas 72 or mixed gas 72a contained in the cathode gas 51 is preferably preheated in the catalyst combustion chamber 42a, particularly when the furnace off-gas 72 or mixed gas 72a contains relatively low-temperature decomposed off-gas. In this method, particularly in the case where the furnace off-gas 72 contains a decomposition off-gas, the cathode gas can be sufficiently converted into a nontoxic gas by preheating in the catalyst combustion chamber 42 a. Since the cathode 42 is generally heated to 600-650 ℃, the decomposition exhaust gas remains sufficiently nontoxic even if it is directly supplied to the cathode 42. In this case, although the heat source (fuel) for the catalyst combustor 42a is preferably the anode off-gas 54 discharged from the anode 43 from the viewpoint of thermal efficiency, the fuel may be supplied from other sources.

In addition to the furnace off-gas as a component of the mixed gas 72a, the cathode gas 73 or the cathode preheat gas 73b is also used for the above-mentioned application. Since air is often used as the cathode gas 73 at room temperature, it is more preferable to use the cathode warm-up gas 73b to reduce the amount of the anode off-gas 54 used to heat the catalyst combustion chamber 42a and to improve the power generation efficiency, for example, the cathode warm-up gas 73b has been warmed up in the heat exchanger 73a using the furnace off-gas as the heat source. A gas that does not contain the furnace off-gas 72 but contains only the cathode preheat gas 73b may be used as the cathode gas 51. Here, the anode off-gas 54 is a gas released from the fuel unconsumed portion. Therefore, a decrease in the amount of anode off-gas may result in a decrease in the amount of fuel. The energy yield here is a value obtained by dividing the generated electric energy by the input fuel energy. The energy produced using lower amounts of fuel may increase energy yield. The remaining anode off-gas 54 contains hydrogen gas and the like, and therefore, can be used as fuel for the fuel cell or released to the outside of the fuel cell unit as needed. In this case, although the heat source (fuel) for the heat exchanger 73a is preferably thefurnace off-gas 72 from the viewpoint of thermal efficiency, the fuel may be supplied from other sources. Combustible components (hydrogen and carbon monoxide) are preferably combusted in the anode exhaust 54 of the catalyst combustor 42a and air is injected therein to heat the air and produce the carbon dioxide required for the cathode 42. However, since the carbon dioxide concentration may be insufficient in the case of using only the anode off-gas 54, it is preferable to circulate a part of the cathode off-gas 52 as the cathode gas 51. When the carbon dioxide supplied to the cathode 42 is insufficient, the circulation ratio of the cathode off-gas needs to be increased to maintain a stable carbon dioxide concentration.

The anode gas 53 (numeral 23 in fig. 1) contains hydrogen gas, and its concentration is preferably 100 to 50% by volume, and more preferably 90 to 70% by volume. As the anode gas 53, a reformed gas containing hydrogen and carbon dioxide, which is obtained by reforming a hydrocarbon and water using a steam reformer 63 installed on an industrial furnace, can be used. The reformed gas may be used as it is or after using the hydrogen separator 64 to selectively separate hydrogen from the reformed gas to increase the hydrogen concentration.

In the fuel cell of the present embodiment, lithium-containing nickel oxide and the like can be used as the cathode material. As the material of the anode, aluminum-containing nickel, chromium-containing nickel, and the like can be provided. As a material of the electrolyte layer, molten carbonate-infiltrated lithium aluminate (LiAlO) may be used₂). Although the forms of the fuel cell, the cathode, the anode, and the electrolyte layer are not particularly limited, a laminate formed by interposing a plate-shaped cathode, a plate-shaped anode, and a plate-shaped electrolyte layer therebetween may be put in a cylindrical fuel cell container.

As the molten carbonate, sodium carbonate, lithium carbonate, potassium carbonate and the like can be used alone or in combination.

The reaction temperature of the fuel cell in the fuel cell 1 of the present embodiment is preferably 500 to 700 ℃. If it is less than 500 ℃, the carbonate goes into an insufficient molten state, with the result that the conductivity is lowered. If it is higher than 700 c, not only the volatilization amount of the molten carbonate is increased, with the result that the amount of the electrolyte is reduced, but also the strength of stainless steel, which is a structural material of the structural unit of the fuel cell, is reduced, which results in deformation of the fuel cell.

One embodiment of the fuel cell operation method of the present invention is described below. As shown in fig. 1, the operation method of the present embodiment includes supplying a cathode gas 21 containing carbon dioxide and oxygen to the cathode 2 side, and supplying an anode gas 23 containing hydrogen to the anode 3 to generate electric power, wherein the cathode gas is a gas containing a furnace off-gas (combustion off-gas and/or decomposition off-gas) discharged from an industrial furnace that heats a material, a mixed gas of the furnace off-gas and a cathode gas or a cathode preheating gas, or the cathode preheating gas, the cathode preheating gas is a cathode gas preheated using the furnace off-gas as a heat source, and the concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

In the operation method of the present embodiment, the concentration of carbon dioxide in the cathode gas 21 is preferably 10 to 45% by volume, and more preferably 20 to 40% by volume. If the concentration of carbon dioxide is less than 0.1% by volume, the reaction of the fuel cell may occur very gently, and if it exceeds 50% by volume, the amount of oxygen molecules may be insufficient to generatesufficient carbonate ions. The cathode gas 21 may contain only a furnace off-gas containing carbon dioxide and oxygen (combustion off-gas and/or decomposition off-gas) at a high concentration released from the sintering furnace, or may be a mixture of the furnace off-gas (combustion off-gas and/or decomposition off-gas) and a cathode gas or a cathode preheating gas. When the furnace off-gas (combustion off-gas and/or decomposition off-gas) and the cathode gas or the cathode preheat gas are mixed (in the case of using a mixed gas), the ratio of the furnace off-gas (combustion off-gas and/or decomposition off-gas) to the cathode gas or the cathode preheat gas is preferably 100: 0 to 1: 4. Although the cathode gas 21 containing an appropriate carbon dioxide concentration can be obtained without using any process for increasing the carbon dioxide concentration using, for example, a PSA concentration method, the carbon dioxide concentration can be optimized by adopting any such method for increasing the carbon dioxide concentration. In this case, the cost of the process for increasing the carbon dioxide concentration is very low because furnace off-gas (combustion off-gas and/or decomposition off-gas) containing carbon dioxide at a high concentration is used as the cathode gas 21. The above discussion is based on the assumption that furnace off-gas is used as the carbon dioxide source for the cathode gas 21. In the case where it is more important to reduce fuel consumption by efficiently recovering the heat of the furnace off-gas, the cathode gas 21 may not contain the furnace off-gas, but may be composed of only the preheated cathode gas that has been heated using the furnace off-gas as the heat source.

In this method, when the furnace off-gas or the mixed gas is used as the cathode gas 21 in the operation method of the present embodiment, the furnace off-gas (combustion off-gas and/or decomposition off-gas) containing carbon dioxide released from an industrialfurnace (e.g., a sintering furnace) can be used as the cathode gas of the fuel cell without any process of increasing the carbon dioxide concentration. Therefore, electric energy can be generated by supplying the cathode side with the gas containing carbon dioxide at a high concentration without additional energy.

The other compositions, use conditions and the like of the operation method of the fuel cell in the present embodiment are the same as those of the fuel cell of the present invention already discussed. The same effect can be achieved by adopting such a composition, use conditions, and the like in this embodiment.

Next, a sintering furnace of the present invention equipped with the above-described fuel cell (hereinafter simply referred to as "sintering furnace") is described. As shown in fig. 2, the sintering furnace 100 of this embodiment includes a combustion furnace 62 for combusting a hydrocarbon-containing fuel 71 to generate a combustion gas, a sintering furnace main body 61 for heating and sintering a material brought therein by the combustion gas and releasing the combustion gas as a furnace off-gas 72 (combustion off-gas and/or decomposition gas) after sintering, and the above-described fuel cell 41, and the fuel cell 41 is provided such that the furnace off-gas 72 (combustion off-gas and/or decomposition gas) released from the sintering furnace main body 61 is supplied to the cathode 42 side as a cathode gas 51. The content of carbon dioxide in the cathode gas 51 is 0.1 to 50% by volume, preferably 10 to 45% by volume, and more preferably 20 to 40% by volume. If the concentration of carbon dioxide is less than 0.1% by volume, the fuel cell reaction will occur very gently; if it exceeds 50% by volume, the amount of oxygen molecules may be insufficient to generate sufficient carbonate ions. The cathode gas 51 may be a furnace off-gas 72 (combustion off-gas and/or decomposition gas) containing high concentration of carbon dioxidereleased from the sintering furnace main body 61 while containing oxygen, or may be a mixture of the furnace off-gas 72 (combustion off-gas and/or decomposition gas) and air 73 for a cathode gas or preheated air 73b for a cathode preheated gas. When the furnace off-gas (combustion off-gas and/or decomposition off-gas) 72 and the cathode gas 73 or the cathode preheat gas 73b are mixed (when a mixed gas is used), the ratio of the furnace off-gas (combustion off-gas and/or decomposition off-gas) 72 to the cathode gas 73 or the cathode preheat gas 73b is preferably 100: 0 to 1: 4. Although the cathode gas 51 containing an appropriate carbon dioxide concentration can be obtained without using any process of increasing the carbon dioxide concentration using, for example, a PSA concentration method, the carbon dioxide concentration can be optimized by any such method of increasing the carbon dioxide concentration. In this case, the cost of the process for increasing the carbon dioxide concentration is very low because the furnace off-gas (combustion off-gas and/or decomposition off-gas) 72 containing carbon dioxide at a high concentration is used as the cathode gas 51. The above discussion is based on the assumption that furnace off-gas is used as the carbon dioxide source for the cathode gas 51. In the case where it is more important to reduce the fuel consumption by efficiently recovering the heat of the furnace off-gas, the cathode gas 21 may not contain the furnace off-gas, but may be composed of only the preheating gas for the cathode that has been heated using the furnace off-gas as the heat source.

In this manner, when the sintering furnace of the present invention is used in which the sintering furnace main body is equipped with the fuel cell, the furnace off-gas (combustion off-gas and/or decomposition off-gas) containing carbon dioxide released from the sintering furnace main body is supplied to the cathode side of the fuel cell without any process of increasing the carbon dioxide concentration. Therefore, it is possible to generate electric energy by supplying a gas of high concentration of carbon dioxide to the cathode side without additional energy, and in addition, it is possible to effectively utilize furnace off-gas (combustion off-gas and/or decomposition off-gas) generated in the sintering furnace main body. Also, the amount of carbon dioxide released into the air can be reduced by fixing carbon dioxide contained in the fuel cell anode off-gas using a carbon dioxide fixer or the like.

In the sintering furnace of this embodiment, the fuel cell is equipped with a cathode 42, an anode 43, and an electrolyte layer 44 containing molten carbonate between the cathode 42 and the anode 43. A gas containing oxygen and carbon dioxide (cathode gas 51) is supplied to the cathode 42 side, and a gas containing hydrogen (anode gas 53) is supplied to the anode 43 side to generate electric power. The composition, use conditions, and the like of the fuel cell are the same as those of the fuel cell described previously, and the same effects can be obtained by employing such composition, use conditions, and the like.

As shown in fig. 2, in the sintering furnace 100 of the present embodiment, the sintering furnace main body 61 is not particularly limited. A conventional apparatus may be used in which a material to be sintered, such as ceramics and the like, is conveyed and then sintered by combustion gas generated by burning hydrocarbon-containing fuel 71 using an available burner 61. The material is preferably fired into a ceramic honeycomb structure. The ceramic honeycomb structure of this embodiment is a structure formed of a ceramic substance having a plurality of cells divided as partitions of fluid passages. The sintering furnace main body 61 may be of a batch type, which intermittently sinters a unit generation sintered material. However, more preferably a continuous type sintering furnace main body 61, a substance sintered into, for example, a ceramic honeycomb structure may be continuously fed thereinto, heated and sintered therein, and fed out after sintering.

As shown in fig. 2, the sintering furnace 100 of this embodiment is not particularly limited to the combustion furnace 62, and the hydrocarbon-containing fuel 71 can be efficiently combusted in the furnace. The combustion furnace 62 may be installed outside the sintering furnace main body and designed to input combustion gas to the sintering furnace main body 61 through a pipe, or the combustion furnace 62 may be installed inside the sintering furnace main body 61. The sintering furnace main body 61 may be provided with one, two or more combustion furnaces 62 according to the capacity of the combustion furnace 62, the size of the sintering furnace main body 61, and the like. As the burner 62, any type of burner having a burner equipped with a line for inputting air and fuel may be used. Preferably, a regenerative burner is used, wherein the air used for combustion is preheated. Hydrocarbonaceous fuel 71 can be obtained by supplying hydrocarbonaceous fuel 85 through a hydrocarbonaceous fuel supply apparatus (not shown). Part of the hydrogen fuel 83 supplied from the hydrogen separator 64 may be mixed. Adding the hydrogen fuel 83 supplied from the hydrogen separator 64 can reduce the fuel consumption. The hydrocarbon-containing fuel 85 is preferably at least one fuel selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

As shown in fig. 2, the sintering furnace 100 of this embodiment is preferably provided with a steam reformer 63 in which a hydrocarbon-containing material 81 to be reformed and steam introduced thereinto are heated and reacted into a reformed gas 82 containing hydrogen and carbon dioxide, a hydrogen separator 64 in which hydrogen contained in the reformed gas 82 formed in the steam reformer 63 is selectively separated to obtain a hydrogen fuel including hydrogen as a main component and a residual gas 84 containing carbon dioxide, and a carbon dioxide fixer 65 for fixing carbon dioxide in the residual gas 84 so that carbon dioxide cannot be released to the outside in a gaseous state. In fig. 2, each device is connected to the other devices by pipes for fuel flow and transport.

In this method, part of the combustion heat generated in the sintering furnace main body 61 is recovered in the steam reformer 63 to generate the reformed gas 82 containing hydrogen gas, which is used as the anode gas 53, or hydrogen gas is separated therefrom by the hydrogen separator 64 to be used as the anode gas 53. The residual gas component after being used as the anode gas 53 is released as the anode off-gas 54. Since the anode off-gas 54 contains carbon dioxide, the gas may be mixed with the cathode gas 51 or supplied to the carbon dioxide fixer 65 so that the carbon dioxide is absorbed. The furnace off-gas (combustion off-gas and/or decomposition gas) 72 released from the sintering furnace main body 61 preferably supplies heat to the steam reformer 63, and then the gas is preferably used as the cathode gas 51. When used as the cathode gas 51, the residual gas is released as the cathode off-gas 52.

The carbon dioxide fixing device 65 is designed to use sodium hydroxide as a fixing agent 88 for fixing carbon dioxide introduced therein, bring the fixing agent 88 into contact with the residual gas 84 and further cause the fixing agent 88 to absorb carbon dioxide contained in the residual gas 84 to produce sodium carbonate, and release a waste liquid containing sodium carbonate. Any material that can react with or absorb carbon dioxide may be used as the fixing agent 88 without any particular limitation, and for example, NaO may be usedH、Mg(OH)₂And the like.

The sintering furnace 100 of this embodiment is preferably designed to generate a steam reforming reaction in a steam reformer 63 installed in a passage of the sintering furnace main body 61 and the furnace off-gas (combustion off-gas and/or decomposition off-gas) 72, heating the material to be reformed 81 flowing in the steam reformer 63 by the combustion gas (furnace off-gas) and/or by radiant heat of the combustion gas from the material to be sintered, the sintering device, and the furnace wall (passage wall of the furnace off-gas (combustion off-gas and/or decomposition off-gas)). The resulting reformed gas 82 is supplied to the hydrogen separator 64 and separated into hydrogen fuel 83 and residual gas 84. A hydrogen fuel 83 (hydrogen fuel for the anode 86) is preferably used as the anode gas 53. In this manner, high purity hydrogen gas can be used for the fuel cell. The reformed gas 82 may be directly supplied to the anode 43 as the anode reformed gas 82 a. As the anode gas 53 supplied to the fuel cell 41, an anode hydrocarbon-containing gas 87 supplied by a hydrogen supply device (not shown) may be used. As the hydrogen supply device, a steam reforming hydrogen generator, a hydrogen holder, a hydrogen tank, and the like can be used.

The heat of the combustion gas can be used for the endothermic reforming reaction of the starting materials in the steam reformer. In this way, a part of the heat contained in the combustion gases, which would otherwise be rejected, can be utilized effectively.

The steam reformer 63 used in the sintering furnace 100 of this embodiment is not particularly limited. Any equipment that can be installed in the passage of the sintering furnace main body 61 and the furnace off-gas (combustion gas and/or decomposition off-gas) 72 and that can allow the steam reforming reaction to occur using the supplied heat can be used. For example, such a device may be a reaction tube made of metal or ceramic equipped with a reforming catalyst at a temperature below 1000 ℃. When the temperature is higher than or equal to 1000 ℃, a ceramic reaction tube may be used. As the steam reformer 63 including the above-described combination, a unit may be used which includes a low-temperature reforming part having a metal reaction tube or a ceramic reaction tube for causing a steam reforming reaction to occur therein and a reforming catalyst packed in the reaction tube for accelerating the steam reforming reaction, and a high-temperature reforming part having a ceramic reaction tube for causing a steam reforming reaction to occur therein. In the above unit, the steam reformer 63 is preferably installed in the sintering furnace main body 61 and/or a flow passage of furnace exhaust gas (combustion exhaust gas and/or decomposition gas) 72, the low temperature reforming part is disposed at a position heated to 600 to 1,000 ℃, and the high temperature reforming part is disposed at a position heated to 1,000 to 1,800 ℃. The metal reaction tube is suitable for use at temperatures below 1,000 c because the heat resistance temperature is not high enough. However, since the tubes are packed with a catalyst that enhances the steam reforming reaction, the reaction can sufficiently occur in the tubes. The ceramic reaction tube can allow the reaction to sufficiently perform the steam reforming reaction without the presence of a reforming catalyst because the ceramic reaction tube can be used at a high temperature of 1,000 c or more. The ceramic reaction tube may be used by charging a reforming catalyst at a temperature of 1,000 ℃ or lower.

In fig. 2, a steam reformer 63 is installed in the passage of the sintering furnace main body 61 and furnace off-gas (combustion gas and/or decomposition off-gas) 72. A steam reformer 63 may be installed on the sintering furnace main body 61 or the exhaust gas passage.

The hydrocarbon-containing material 81 to be reformed to be supplied to the steam reformer 63 is preferably a mixture obtained by supplying a hydrocarbon and steam from a hydrocarbon supply device (not shown) and a steam supply device (not shown), respectively, to a mixer (not shown). Any conventional hydrocarbon supply equipment may be used without any particular limitation. For example, when using town gas, hydrocarbons may be supplied from an existing gas pipe. If no piping is available, a gas tank may be installed to supply hydrocarbons from the tank through the piping. Other hydrocarbons such as liquefied petroleum gas and kerosene may also be supplied by installing pipes in the same manner, or supplied from a storage facility such as a tank, a barrel, or the like through a pipe. In this case, the liquefied hydrocarbon material is vaporized by heating before being supplied to the reformer. If necessary, a booster pump may be used to increase the air pressure. This is an effective method for carrying out the reaction, because the reaction amount can be increased with the pressure of the raw material. A general steam supply device may be used without particular limitation. For example, a conventional boiler, a waste heat recovery boiler using waste heat from a furnace or other heat source, and the like may be used.

As the material of the ceramic reaction tube in the steam reformer 63, at least one ceramic selected from the group consisting of silicon nitride, silicon carbide, aluminum nitride, alumina, and zirconia is preferably used. The use of such a ceramic having high thermal resistance can ensure that the steam reforming reaction proceeds at high temperature. As examples of the metal reaction tube material, SUS309, SUS310, SCH22CF (HK40), SCH24CF (H.P.), HA230, and the like can be used.

When the reaction tube is corroded by the air in the sintering furnace 100, the reaction tube is inserted into a hole drilled in the heat-resistant brick so that heat can be transferred into the reaction tube through the brick. The reaction tubes are also protected from corrosion by the heat resistant bricks which trap the corrosive gases in the structure.

As the reforming catalyst used in the steam reformer 63, a nickel catalyst such as Synetix catalyst manufactured by Johnson Matthey co. As other effective catalysts, nickel catalysts, copper catalysts, transition metal catalysts, platinum catalysts, and the like can also be provided. As a preferred example of the steam reforming reaction using a nickel-containing catalyst, an ICI process may be provided by heating at a temperature of 700 to 950 ℃ and 1.01X 10⁵～40.52×10⁵(N/m²) And in the presence of a nickel-containing catalyst, a mixture of hydrogen (4 moles) and carbon dioxide (1 mole) is produced from methane (1 mole) and water (2 moles) via an endothermic reaction.

The reaction ratio of the hydrocarbon and water (the ratio of the amount of actually produced hydrogen to the amount of theoretically produced hydrogen) in the steam reformer 63 is preferably 50 mol% or more. If less than 50 mol%, the fuel consumption increases. The reaction ratio of hydrocarbon and water is preferably as high as possible.

The content of hydrogen in the reformed gas generated from the steam reformer 63 is preferably 10 to 80 mol%, and the content of carbon dioxide is preferably 1 to 20 mol%.

As the hydrocarbon used as a raw material for the steam reforming reaction in the steam reformer 63, methane, ethane, propane, butane, and the like can be used. Among them, methane is preferred.

When the ceramic reaction tube 24 is used for the steam reforming reaction, the hydrocarbon and water preferably react at 1,000 to 1,800 ℃ to generate hydrogen and carbon dioxide.

As shown in fig. 2, in the sintering furnace 100 of this embodiment, the hydrogen separator 64 selectively separates the reformed gas 82 containing hydrogen and carbon dioxide generated in the steam reformer 63 into the hydrogen fuel 83 including hydrogen as the main component and the residual gas 84 containing carbon dioxide. The hydrogen separator 64 is not particularly limited as long as the apparatus can selectively separate hydrogen from a mixed gas containing hydrogen. For example, a system may be used which comprises a cylindrical hydrogen separator made of a film of palladium or a palladium-containing alloy and a cylindrical container made of stainless steel or the like, the hydrogen separator being arranged therein so that the air inside the cylinder of the hydrogen separator can be cut off from the air outside the cylinder. A mixed gas containing hydrogen is injected into the cylindrical container and then introduced into the inside of the hydrogen separation membrane cylinder to allow hydrogen to selectively permeate from the inside to the outside of the hydrogen separation membrane. The hydrogen gas flowing to the outside of the hydrogen separation membrane is sent to the outside of the cylindrical container as hydrogen fuel 83. It is also possible to pass other gases through the inside of the hydrogen separation membrane as residual gas 84 and to send them to the outside of the cylindrical vessel. The mixed gas containing hydrogen may be introduced to the outside of the hydrogen separation membrane cylinder and the hydrogen may be flowed to the inside of the hydrogen separation membrane cylinder. The separated hydrogen is used as a hydrogen fuel 83 containing hydrogen as a main component, and a residual gas 84 containing other gases including carbon dioxide is input to the carbon dioxide fixer 65. The carbon dioxide containing residue gas 84 may be mixed with the cathode gas 51 to use the carbon dioxide in a fuel cell to generate electrical energy. The term "contains hydrogen as a main component" used for the hydrogen fuel 83 means that the hydrogen content in the fuel is 50%by volume or more. The cylindrical container does not have to be cylindrical, but can be any shape having an inner space, such as a box shape. In order to improve mechanical strength, the hydrogen separation membrane may be installed on the surface or inside of a permeable material such as ceramic. The hydrogen separation membrane does not have to be cylindrical, and may be planar or any other shape.

The hydrogen separator 64 may be integrally formed with the steam reformer 63 such that hydrogen generated in the steam reformer 63 can be selectively separated by the hydrogen separator 64 installed at the steam reformer 63 and used as the hydrogen fuel 83 after being released from the steam reformer 63. As a method of installing the hydrogen separator 64 in the steam reformer 63, there is a method of providing a cylindrical hydrogen separation membrane in the hydrogen separator 64 and packing a reforming catalyst in a cylinder. In this case, since the hydrogen separation membrane functions as the hydrogen separator 64, the hydrogen separator 64 functioning is provided in the steam reformer 63. With this system, the reformed hydrocarbon-containing raw material 81 is injected into the hydrogen separation membrane cylinder and converted into hydrogen by the reaction catalyzed by the reforming catalyst loaded into the hydrogen separation membrane cylinder, and the produced hydrogen can be transported to the outside of the cylinder through the hydrogen separation membrane.

Hydrogen separation efficiency of separating hydrogen from the reformed gas 82 using the hydrogen separator 64, according to the residual amount of hydrogen in the reformed gas 82: the amount of the separated hydrogen is preferably 50: 50 to 1: 99 (volume ratio). If it is less than 50: 50 (volume ratio), the fuel may not be fully utilized. Although a high separation efficiency is desired, as the recovery efficiency of hydrogen for fuel, 1: 99 (volume ratio) is also sufficient. Higher separation efficiency may require higher cost.

As shown in fig. 2, in the sintering furnace 100 of this embodiment, the carbon dioxide holder 65 holds carbon dioxide in the residual gas 84 separated from the hydrogen separator 64 so that the carbon dioxide cannot be released to the outside in a gaseous state. The carbon dioxide fixing device 65 is not particularly limited as long as it is a device capable of fixing carbon dioxide in the residual gas 84 so that carbon dioxide cannot be released to the outside in a gaseous state. One example of a method that may be suitable for fixing carbon dioxide includes providing an aqueous solution of sodium hydroxide as a carbon dioxide fixing agent 88 in a vessel, bubbling the solution and gas through the residual gas 84 by passing the residual gas 84 through the aqueous solution of sodium hydroxide, and reacting the carbon dioxide in the residual gas 84 with sodium hydroxide to form sodium carbonate. Since the anode off-gas 54 discharged from the fuel cell 41 contains carbon dioxide, the gas is passed to the carbon dioxide fixing device 65 to absorb carbon dioxide. Here, "fixing carbon dioxide" means a process of operating carbon dioxide, for example, by causing carbon dioxide to react with or be absorbed by other compounds, so that carbon dioxide cannot be released in a gaseous state.

When a sodium hydroxide-containing substance (solution), such as the above-described aqueous sodium hydroxide solution, is used as the fixing agent 88, sodium carbonate is obtained in the carbon dioxide fixing vessel 65. The waste liquid 89 released from the carbon dioxide holder 65 may be removed as a sodium carbonate-containing solution. In this way, the carbon dioxide holder 65 can be used as a sodium carbonate production facility. The carbon dioxide holder 65 is described in more detail below in relation to the case where the carbon dioxide holder 65 is used as a sodium carbonate production facility.

There is no particular limitation in the structure of the container used as the carbon dioxide fixer 65, as long as the container can contain therein an aqueous sodium hydroxide solution that reacts with carbon dioxide and then generates sodium carbonate. For example, a cylindrical vessel having at least one inlet pipe for introducing residual gas and sodium hydroxide and an outlet for discharging waste liquid (hereinafter referred to as "sodium carbonate-containing solution") may be used. There is no particular limitation on the shape of the container. A cylinder, a polygonal cylinder such as a cylinder having a square bottom surface (including a box shape), a cylinder having a bottom surface of any other shape (including a box shape), and the like can be used. The carbon dioxide holder 65 may be equipped with a stirrer and a jacket or coil for heating or cooling, if desired. A batch or semi-batch type carbon dioxide holder 65 may be used. The batch type carbon dioxide fixing apparatus 65 uses one vessel of the above type to react carbon dioxide and sodium hydroxide by supplying residual gas. When almost all the sodium hydroxide has reacted, the flow of residual gas is stopped and the final solution containing sodium carbonate is removed, followed by reinjection of sodium hydroxide into the vessel and supply of residual gas. In a semi-batch type carbon dioxide holder, two or more vessels of the above type are used. When almost all the sodium hydroxide in one of the vessels has reacted, the residual gas flow is switched to the other vessel, where the formation of sodium carbonate begins, and the sodium carbonate-containing solution is released in the vessel where almost all the sodium hydroxide has reacted.

As a method for producing sodium carbonate by fixing carbon dioxide, there is provided a method of recycling an aqueous sodium hydroxide solution as a fixing agent 88, and supplying a residual gas 84 to the recycled aqueous sodium hydroxide solution to react sodium hydroxide and carbon dioxide. As a method of circulating the aqueous sodium hydroxide solution (which may also contain sodium carbonate generated in the reaction), a method of transporting the aqueous sodium hydroxide solution discharged from the vessel through a pipe and returning the discharged solution to the vessel may be used. In this case, the carbon dioxide fixer 65 may be operated continuously, sodium hydroxide is continuously fed to the circulation system, and a part of the circulated sodium carbonate-containing aqueous solution is continuously removed from the system composed of sodium hydroxide and the reaction-generated sodium carbonate-containing aqueous solution as the sodium carbonate-containing aqueous solution (waste liquid) 89.

When the carbon dioxide fixing device 65 is used as a sodium carbonate production facility, the carbon dioxide content in the residual gas 84 after separating hydrogen from the reformed gas 82 using the hydrogen separator 64 is preferably 15 to 99.9% by weight, more preferably 60% by weight or more. If less than 15% by weight, impurities are increased in the residual gas 84, so that it becomes difficult to obtain high-purity sodium carbonate by purifying the sodium carbonate-containing waste liquid 89 discharged from the carbon dioxide fixer 65.

When the residual gas 84 contains a large amount of carbon monoxide produced as a byproduct in the steam reformer 63, a carbon monoxide converter may be installed to supply the residual gas 84 thereto. It is preferable to use a carbon monoxide converter in which the residual gas 84 controlled at 350 to 360 ℃ is contacted with an Fe-Cr based catalyst to convert carbon monoxide. In this carbon monoxide converter, carbon monoxide reacts with water to produce hydrogen and carbon dioxide. The carbon monoxide converter may reduce the concentration of carbon monoxide in the residue gas 84 by converting the carbon monoxide in the residue gas 84 to carbon dioxide. Since hydrogen is produced in addition to carbon dioxide at the carbon monoxide converter, the residue gas 84 removed from the carbon monoxide converter can be processed in a hydrogen separator to collect hydrogen, which can be used by mixing with the anode gas 53. In this case, a hydrogen separator may be installed and the residue gas 84 may be input thereto, or the hydrogen separator 64 may be used in which a part of the residue gas 84 may be separated and then input to the hydrogen separator 64 together with the reformed gas 82, thereby recycling a part of the residue gas 84. As a result of the carbon monoxide conversion, the residual gas 84 whose carbon dioxide concentration is increased (or the residual gas 84 discharged from the hydrogen separator when the treatment is performed using the hydrogen separator) is input to the carbon dioxide fixing device 65.

The sodium carbonate produced in the carbon dioxide holder 65 is discharged from the carbon dioxide holder 65 as a waste liquid (sodium carbonate-containing solution) 89, which is preferably purified in a sodium carbonate purification step (not shown) and removed as high-purity sodium carbonate. For this purpose, the sodium carbonate content in the sodium carbonate-containing solution 89 produced by the carbon dioxide fixing device 65 is preferably 80 to 99.9% by weight, more preferably 95% by weight or more, of the components excluding water. If less than 80% by weight, it may be difficult to increase the purity of the sodium carbonate obtained in the sodium carbonate purification step (not shown).

In order to increase the purity of the sodium carbonate obtained by purification by this method, it is desirable to react with carbon dioxide using high-purity sodium hydroxide when using the carbon dioxide holder 65. Specifically, the content of sodium hydroxide in the components other than water (the total amount of the fixing agent 88 when the fixing agent 88 does not contain water) in the fixing agent 88 added to the carbon dioxide fixing device 65 is preferably 80 to 99.9% by weight, more preferably 95% by weight or more. If less than 80% by weight, it may be difficult to increase the purity of the sodium carbonate obtained by the purification. As the fixing agent 88, the above-mentioned aqueous sodium hydroxide solution may be used, or molten sodium hydroxide may be used. When an aqueous sodium hydroxide solution is used as the fixing agent 88, the content of sodium hydroxide in the aqueous sodium hydroxide solution is preferably 30 to 95% by weight. If less than 30%, the carbon dioxide may not be sufficiently reacted due to the low concentration of sodium hydroxide, resulting in a high carbon dioxide concentration in the gas released from the carbon dioxide holder. If it is higher than 95% by weight, the fluidity of sodium hydroxide is deteriorated due to the high viscosity of the solution, which may result in difficulty in effective reaction with carbon dioxide.

The sodium carbonate-containing solution 68 discharged from the carbon dioxide fixer 65 is purified using a purification step (not shown) to obtain sodium carbonate having a purity of preferably 98 to 99.9% by weight, more preferably 99.0% by weight or more. Sodium carbonate of 98% by weight or more purity can be used in fields requiring high purity sodium carbonate, such as optical glass, medical equipment, and the like. The purity of the sodium carbonate is preferably as high as possible. The content of sodium carbonate in the entire sodium carbonate aqueous solution 89 is preferably 60 to 95% by weight. If it is less than 60% by weight, it may be difficult to obtain sodium carbonate crystals due to the low concentration of sodium carbonate. If it is more than 95% by weight, the fluidity is deteriorated due to the excessively high concentration of the sodium carbonate crystal slurry obtained by the sodium carbonate crystallization.

As a purification method of the sodium carbonate-containing solution 89 released from the carbon dioxide fixer 65, a method of causing precipitation of sodium carbonate crystals and separating the precipitated sodium carbonate from the mother liquor is preferable. The sodium carbonate is preferably purified by purification steps (not shown) including the use of a crystallizer (not shown) to precipitate sodium carbonate crystals from the sodium carbonate-containing solution 89 and a filter (not shown) to separate the sodium carbonate crystals produced in the crystallizer from the mother liquor.

Next, a generator of the present invention equipped with the above fuel cell is described. FIG. 3 is a block flow diagram of one embodiment of the generator of the present invention. As shown in FIG. 3, a power generator 200 of the present invention includes a fuel cell 141 having a cathode 142, an anode 143, and an electrolyte layer 144 containing molten carbonate between the cathode 142 and the anode 143, and further includes a cathode gas supply device 190 supplying a cathode gas 151 containing oxygen and carbon dioxide to the cathode 142, and an anode gas supply device 195 supplying an anode gas 153 containing hydrogen to the anode 143 to generate electric power by supplying the cathode gas 151 to the cathode 142 and supplying the anode gas 153 to the anode 143, wherein the cathode gas supply device 190 has a furnace off-gas supply device 191 which can supply a furnace off-gas 172 released from an industrial furnace (sintering furnace) 100a of a heating material to the cathode 142, and/or a cathode gas supply device 192 which can supply a cathode gas 173 to the cathode 142, and the cathode gas 151 supplied to the cathode 142 by the cathode gas supply device 190 includes a furnace off-gas supply device 191 shipped by the furnace off-gas supply device 191 The off-gas 172, or a mixed gas 172a of the furnace off-gas 172 and the cathode gas 173 or the cathode pre-heating gas 173b sent by the cathode gas supply means 192, or the cathode pre-heating gas 173b, which is a cathode gas pre-heated using the furnace off-gas 172 as a heat source, and the concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

In the embodiment, when the cathode gas 151 is the furnace off-gas 172 or the mixed gas 172a, the industrial furnace is preferably a sintering furnace 100a that heats the material by combustion gas generated by burning the fuel 171, and the furnace off-gas 172 is an off-gas of the combustion gas (combustion off-gas) and/or decomposition gas (decomposition off-gas) generated by decomposition of the organic material contained in the heated material.

Fuel 171 is preferably a hydrocarbon-containing fuel.

The hydrocarbon-containing fuel 171 is preferably at least one fuel selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

The generator is preferably also provided with a catalyst combustor 142a, and the cathode gas 151 is preferably heated using the catalyst combustor 142 a.

The heat source of the catalyst combustor 142a is preferably anode off-gas 154 released from the anode 143.

The power generator is preferably further provided with a heat exchanger 173a, and the cathode preheating gas 173 is preferably preheated by the heat exchanger 173a using the furnace off-gas 172 as a heat source.

Preferably, the generator is further provided with a steam reformer 163, and the cathode gas 153 uses hydrogen gas contained in the reformed gas 182 reformed in the steam reformer 163.

The other components, conditions of use and the like of the generator are the sameas those of the fuel cell and the method of operation of the fuel cell already discussed. For example, although not shown in fig. 3, the generator may be further equipped with a hydrogen separator 64, a carbon dioxide holder 65, and the like as shown in fig. 2. These devices, conditions of use, and the like may be employed to the same effect.

The fuel cell, the operating method of the fuel cell, the sintering furnace, and the generator of the present invention supply the following gases with a high carbon dioxide concentration to the cathode without a process of concentrating the carbon dioxide concentration in the air, and can efficiently recover the heat of the furnace exhaust gas, thereby reducing the fuel consumption, wherein one of the gases includes: furnace off-gas (combustion off-gas and/or decomposition off-gas) discharged from a sintering furnace used for sintering ceramics and the like in the ceramic industry, mixed gas of the furnace off-gas and a cathode gas or a cathode-use preheating gas, or cathode-use preheating gas, which is a cathode gas preheated using the furnace off-gas as a heat source. Therefore, the fuel cell, the operating method of the fuel cell, the sintering furnace, and the generator of the present invention are effectively applied to the manufacture of molten carbonate fuel cells and generators, and to various industrial fields using the molten carbonate fuel cells and generators.

Claims

1. A fuel cell comprising

A cathode electrode, which is provided with a cathode,

an anode and

an electrolyte layer comprising molten carbonate between the cathode and the anode,

a gas containing oxygen and carbon dioxide (cathode gas) supplied to the cathode side and a gas containing hydrogen (anode gas) supplied to the anode side to generate electric power,

wherein the cathode gas is a gas containing a furnace off-gas discharged from an industrial furnace for heating a material, a mixed gas of the furnace off-gas and a cathode gas or a cathode preheating gas, the cathode preheating gas is a cathode gas preheated using the furnace off-gas as a heat source, and a concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

2. The fuel cell according to claim 1, wherein when the cathode gas contains a furnace off-gas or a mixed gas, the industrial furnace is a sintering furnace that heats the material using a combustion gas generated by burning a fuel, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the heated material.

3. The fuel cell of claim 2, wherein the fuel is a hydrocarbon-containing fuel.

4. A fuel cell according to claim 3, wherein the hydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel oil, and heavy oil.

5. The fuel cell according to claim 1, wherein the cathode gas is preheated using a catalyst combustor.

6. The fuel cell according to claim 5, wherein the heat source of the catalyst combustor is anode off-gas discharged from the anode.

7. The fuel cell according to claim 1, wherein when the cathode gas contains a preheating gas for cathode, the preheating gas for cathode is preheated by a heat exchanger using the furnace off-gas as a heat source.

8. The fuel cell according to claim 1, wherein the anode gas uses hydrogen contained in a reformed gas reformed in a steam reformer installed on an industrial furnace.

9. A method of operating a fuel cell provided with a cathode, an anode and an electrolyte layer containing molten carbonate between the cathode and the anode,

the method comprises the following steps:

a gas containing oxygen and carbon dioxide (cathode gas) is supplied to the cathode side,

a gas containing hydrogen (anode gas) is supplied to the anode side to generate electric power,

wherein the cathode gas is a gas containing a furnace exhaust gas discharged from an industrial furnace heating a material, a mixed gas of the furnace exhaust gas and a cathode gas or a cathode preheating gas, the cathode preheating gas is a cathode gas preheated using the furnace exhaust gas as a heat source, and a concentration of carbon dioxide in the cathode gas is 0.1 to 50% by volume.

10. The method according to claim 9, wherein, when the cathode gas contains a furnace off-gas or a mixed gas, the industrial furnace is a sintering furnace that heats the material using a combustion gas generated by burning a fuel, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the heated material.

11. The method of claim 10 wherein the fuel is a hydrocarbon-containing fuel.

12. The method of claim 11 wherein the hydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel fuel, and heavy oil.

13. The method of claim 9, wherein the cathode gas is preheated using a catalyst combustor.

14. The method according to claim 13, wherein the heat source of the catalyst combustor is anode off-gas discharged from the anode.

15. The method according to claim 9, wherein when the cathode gas contains a cathode-use preheating gas, the cathode-use preheating gas is preheated by a heat exchanger using the furnace off-gas as a heat source.

16. The method according to claim 9, wherein the anode gas uses hydrogen contained in a reformed gas reformed in a steam reformer installed on an industrial furnace.

17. A sintering furnace comprising a combustion chamber for combusting a hydrocarbon-containing fuel to produce a combustion gas, a sintering furnace main body for heating and sintering a material brought therein by the combustion gas and releasing the combustion gas as a furnace off-gas and/or a decomposition gas produced by decomposition of an organic material contained in the heated material, and a fuel cell according to claim 1, the fuel cell being arranged such that the furnace off-gas released from the sintering furnace main body is supplied as a cathode gas to a cathode side.

18. The sintering furnace according to claim 17, further comprising a steam reformer to perform a steam reforming reaction that produces a reformed gas containing hydrogen and carbon dioxide from the hydrocarbon that entered the furnace and steam.

19. The sintering furnace according to claim 18, wherein the steam reformer comprises a low temperature reforming part having a metal reaction tube or a ceramic reaction tube for causing the steam reforming reaction to occur therein, and a reforming catalyst packed in the reaction tube for accelerating the steam reforming reaction, and the steam reformer further comprises a high temperature reforming part having a ceramic reaction tube for causing the steam reaction to react therein.

20. The sintering furnace according to claim 18, wherein the steam reformer is installed in the sintering furnace main body and/or the furnace exhaust gas flow passage, the low temperature reforming part is provided at a position heated to 600 to 1,000 ℃, and the high temperature reforming part is provided at a position heated to 1,000 to 1,800 ℃.

21. The sintering furnace according to claim 18, wherein part or all of the hydrogen contained in the reformed gas is used as the anode gas.

22. The sintering furnace according to claim 18, further comprising a hydrogen separator for selectively separating hydrogen from the reformed gas formed by the steam reformer into hydrogen fuel including hydrogen as a main component and a residual gas containing carbon dioxide by introducing the reformed gas thereto.

23. The sintering furnace according to claim 22, further comprising a carbon dioxide fixer to fix carbon dioxide in the residual gas separated by the hydrogen separator, and/or to fix carbon dioxide contained in the anode gas (anode off-gas) released from the molten carbonate fuel cell.

24. The sintering furnace according to claim 17, wherein the furnace body continuously introduces material for heating and continuously outputs the heated material.

25. The sintering furnace according to claim 17, wherein the material to be heated is ceramic.

26. The sintering furnace according to claim 17, wherein the material to be heated is a honeycomb structure.

27. An electric generator comprising

A fuel cell comprising a cathode, an anode, an electrolyte layer comprising molten carbonate between the cathode and the anode,

a cathode gas supply device that supplies a gas containing oxygen and carbon dioxide (cathode gas) to the cathode, an

An anode gas supply device that supplies a hydrogen-containing gas (anode gas) to the anode to generate electric power,

wherein the cathode gas supply means has furnace exhaust gas supply means for supplying furnace exhaust gas discharged from the industrial furnace for heating the material, and/or cathode gas supply means for supplying cathode gas to the cathode, the cathode gas supplied to the cathode by the cathode gas supply means comprising the furnace exhaust gas delivered by the furnace exhaust gas supply means, a mixed gas of the furnace exhaust gas and the cathode gas or the cathode gas delivered by the cathode gas supply means, or a cathode-use preheating gas, the cathode-use preheating gas being a cathode gas preheated using the furnace exhaust gas as a heat source, the concentration of carbon dioxide in the cathode gas being 0.1 to 50% by volume.

28. The power generator according to claim 27, wherein the industrial furnace is a sintering furnace that heats a material using a combustion gas generated by burning a fuel when the cathode gas contains a furnace off-gas or a mixed gas, and the furnace off-gas is an off-gas of the combustion gas (combustion off-gas) and/or a decomposition gas (decomposition off-gas) generated by decomposition of an organic material contained in the heated material.

29. The electrical generator of claim 28 wherein the fuel is a hydrocarbon-containing fuel.

30. The electrical generator of claim 29 wherein the hydrocarbon-containing fuel is selected from the group consisting of town gas, liquefied natural gas, liquefied petroleum gas, diesel fuel, and heavy oil.

31. The generator of claim 27 wherein the engine further comprises a catalyst combustor, the cathode being preheated with gas using the catalyst combustor.

32. The generator of claim 31 wherein the heat source for the catalyst combustor is anode exhaust gas released from the anode.

33. The generator of claim 27 wherein the engine further comprises a heat exchanger, the preheated gas for the cathode being preheated by the heat exchanger using said furnace exhaust gas as a heat source.

34. The generator of claim 27 wherein the engine further comprises a steam reformer, the anode gas using hydrogen contained in a reformate gas, the reformate gas being reformed in the steam reformer.