JP3997476B2 - Fuel cell power generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generator that generates electricity based on an electrochemical reaction between a fuel gas obtained by steam reforming a raw fuel containing kerosene or gasoline and an oxidant gas (air).
[0002]
[Prior art]
There are various types of fuel cells incorporated in the fuel cell power generator, depending on the type of electrolyte, the type of reforming raw material, and the like. A solid polymer electrolyte fuel cell is well known as a relatively low type fuel cell.
[0003]
This solid polymer electrolyte fuel cell is similar to a phosphoric acid fuel cell, for example, in hydrogen and air in a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas (city gas). Oxygen is supplied to the fuel electrode and the air electrode of the fuel cell, respectively, and electricity is generated based on the electrochemical reaction.
[0004]
In addition, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to the raw fuel and reforming is promoted by a catalyst in a fuel reformer. It is necessary to constantly replenish the amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water to be used needs to be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device is usually used.
[0005]
On the other hand, in the electrochemical reaction of the fuel cell, power generation product water is generated, and in the fuel reformer, combustion product water is generated with combustion for catalyst heating for performing a steam reforming reaction which is an endothermic reaction constantly. These generated waters have fewer impurities than normal tap water, and if these generated waters are used as raw water, the load on the water treatment device can be reduced. Therefore, a recovery water tank and an exhaust gas cooler are added. A method of recovering these generated waters to obtain supply water for generating reformed steam is usually employed.
[0006]
Further, in the electrochemical reaction of the fuel cell, heat is generated along with the reaction, and a part of the exhaust heat energy is stored as hot water in a hot water storage tank and supplied for hot water supply or heating.
[0007]
FIG. 3 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generator using city gas as a raw fuel.
[0008]
In the fuel cell 10 schematically shown in FIG. 3, a cooling plate (not shown) having a cooling pipe or a cooling groove is provided and stacked each time a plurality of unit cells each having a fuel electrode 10a and an air electrode 10b are stacked. It is comprised by.
[0009]
The raw fuel is first supplied to the reformer 11 together with the reforming steam, and is reformed into hydrogen and carbon monoxide by the following reaction. As the reforming catalyst, a noble metal catalyst or a nickel catalyst is used.
[0010]
CH ₄ + H ₂ O → 3H ₂ + CO (endothermic reaction)
Thereafter, this reformed gas is supplied to the CO converter 12, and the following reaction reduces the carbon dioxide in the reformed gas to about 1%. As the CO conversion catalyst, a noble metal catalyst or a copper-zinc catalyst is used.
[0011]
CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction)
Thereafter, the carbon monoxide in the reformed gas is reduced to about 10 ppm by the following reaction that is further supplied to the CO remover 13 and selectively oxidized with the air supplied by the blower. 10a.
[0012]
CO + 1 / 2O ₂ → CO ₂ (exothermic reaction)
As described above, when the reforming reaction is performed in the reformer 11, it is necessary to supply water vapor. In the polymer electrolyte fuel cell power generator, the sensible heat of the combustion exhaust gas from the reformer 11 and CO conversion are used as the heat source. In general, the heat of reaction of the vessel 12 and the CO remover 13 is used. Therefore, a reforming steam supply line 15 is provided to sequentially flow the reforming water supplied by the pump 54 through the CO converter 12, the CO remover 13, and the steam generator 14 in series. Heat is received from each reactor to form steam, and this steam and raw fuel are mixed and introduced into the reformer 11 from the reforming steam supply line 15. In FIG. 3, the reforming water flow line to the CO converter 12 and the CO remover 13 is omitted.
[0013]
In addition, since each of the reactors performs a chemical reaction using a catalyst, it is necessary to raise the temperature to an appropriate temperature in advance when the fuel cell power generator is started. Appropriate temperatures for each reactor are outlined below. Reformer: 500-700 ° C, CO converter: 300-200 ° C, CO remover: 200-100 ° C. The left side of the temperature range indicates the reactor inlet temperature, and the right side indicates the reactor outlet temperature.
[0014]
For this reason, the reformer 11 is normally heated by burning the hydrogen supplied from the exhaust hydrogen supply line 19 of the fuel cell with a burner installed in the reformer. The temperature is raised by introducing raw fuel through an auxiliary combustion line (not shown) and burning it with a burner. In addition, the steam generator 14 is also heated by the combustion exhaust gas from the reformer. On the other hand, the CO transformer 12 and the CO remover 13 are heated by an electric heater (not shown) provided individually. Combustion air is introduced into the burner by a combustion air blower 18. Reference numeral 18a denotes a reaction air blower for supplying reaction air and CO selective oxidation air in the CO remover to the air electrode of the fuel cell main body.
[0015]
Further, the city gas is first introduced into the desulfurizer 16 by the city gas booster blower 17, and after the sulfur component contained in the city gas is removed, the city gas is introduced into the catalytic reactor of the reformer 11, and the combustion exhaust gas. As a result, the fuel gas is reformed while being supplied with heat, and becomes a hydrogen-rich fuel gas.
[0016]
Next, the cooling water system device 50 and the recovered water system device 30 of the fuel cell in FIG. 3 will be described below. The coolant system device 50 includes a battery coolant cooler 51, a cathode offgas cooler 52, an exhaust gas cooler 53 for combustion exhaust gas, a pure water tank 55, a battery coolant circulating pump 54, and other piping.
[0017]
The fuel cell 10 is operated at about 80 ° C. as described above, cooled by the water flowing from the pure water tank 55 by the battery cooling water circulation pump 54, and removed by the battery cooling water cooler 51. The battery cooling water cooler 51 is supplied with, for example, about 50 ° C. water supplied from a circulating water lead-out line 56 connected to a hot water storage tank (not shown in FIG. 3). Thereafter, the temperature is raised to, for example, about 60 ° C. via the cathode off-gas cooler 52 and the exhaust gas cooler 53 for the combustion exhaust gas, and is returned to the hot water storage tank from the circulating water lead-out line 57. The pure water tank 55 is provided with a liquid level gauge. When the liquid level reaches the lower limit, recovered water, which will be described later, is intermittently replenished via the water treatment device 35.
[0018]
Next, the recovered water system device 30 will be described. The recovered water system device 30 includes a recovered water tank 31, a recovered water pump 33, a recovered water cooler 34, and the like. Off-air and combustion exhaust gas cooled by the cathode off-gas cooler 52 and the combustion exhaust gas cooler 53 are introduced into the upper part of the recovered water tank 31, and the water content contained in the air and gas is sprinkled in the upper part. By condensing the cooling water from the apparatus, it is condensed and recovered in the lower part of the recovered water tank 31. The recovered water is cooled by the recovered water cooler 34 and introduced into the watering device. A cooling water direct contact type condenser having a packed bed such as a Raschig ring may be provided at the subsequent stage of the watering device.
[0019]
As described above, the recovered water is purified by a water treatment device and used as makeup water. A liquid level gauge is also provided below the recovered water tank 31. When the water in the recovered water tank is insufficient, city water is supplied as makeup water.
[0020]
By the way, in the fuel cell power generation apparatus shown in FIG. 3, as shown as the integrated reforming system device 20, at least the reformer 11 and the steam generator 14 have an integral structure, and in some cases, CO conversion is performed. A unit or a CO eliminator with an integrated structure is also used.
[0021]
FIG. 4 shows an example of the configuration of the reforming system disclosed in Japanese Patent Application No. 2000-309075 filed from the same applicant as the present applicant. The fuel reformer shown in FIG. 4 has a catalyst layer provided in a hollow cylindrical shape, and a steam generating means for generating reforming steam outside the catalyst layer is concentric with the cylindrical axis of the catalyst layer. Are arranged in a shape. The example shown in FIG. 4 shows an example in which the CO transformer is also provided concentrically and integrated, and various modifications have been filed for this type of configuration.
[0022]
The reforming system shown in FIG. 4 generates reforming steam that generates reforming steam by heating reforming water outside a fuel reforming means that reforms raw fuel gas into reformed gas having a high hydrogen concentration. The fuel reformer 12B is provided with a means, and a CO transformer 14A disposed on the outer periphery of the fuel reformer 12B via a heat insulating layer 41.
[0023]
That is, the fuel reformer 12B basically has a triple cylindrical structure including an inner cylinder, an intermediate cylinder, and an outer cylinder. A burner 1 is installed in the lower part of the space inside the inner cylinder, and fuel electrode exhaust gas containing hydrogen discharged from the fuel electrode of the fuel cell is introduced together with air and burned. The combustion gas flows through the innermost space from the lower part to the upper part as a heat medium for heating the raw fuel gas, and is discharged from the upper end.
[0024]
A space formed by the inner cylinder and the intermediate cylinder adjacent to the outer side of the innermost space is filled with a fuel reforming catalyst 6 and is heated by a combustion gas flowing through the innermost space to a predetermined temperature. Retained. The raw fuel gas is guided to the inside of the catalyst 6 from the inlet provided in the upper part, heated as it flows to the lower part, and simultaneously reformed into a reformed gas having a high hydrogen concentration. The obtained high-temperature reformed gas is led to the outer space formed by the intermediate cylinder and the outer cylinder at the lower end, flows upward, and is then discharged from the fuel reformer 12B.
[0025]
A reforming water pipe 7 for heating the reforming water and generating reforming steam is spirally wound around the outer periphery of the outer cylinder of the fuel reformer 12B, and the high temperature flowing in the inner space The reforming steam is generated by effectively using the heat of the reformed gas. The obtained reforming steam is taken out from the fuel reformer 12B, mixed with the raw fuel sent from the outside, and guided to the reforming catalyst layer. The reforming steam temperature is usually 250 ° C. In FIG. 4, part number 42 represents a CO shift catalyst.
[0026]
By the way, in recent years, expectation for a fuel cell vehicle equipped with a solid polymer fuel cell has been gathered. Fuel cell vehicles also require means for supplying hydrogen to the fuel cell main body, and high pressure hydrogen cylinder mounting system, hydrogen storage alloy mounting system, or liquid fuel fuel reforming system has been studied as the means.
[0027]
The high-pressure hydrogen cylinder mounting method has a problem of high danger, and the hydrogen storage alloy mounting method has a problem that the size must be excessive when a travel distance is secured to some extent. In contrast, fuel reforming methods for liquid fuels, in particular, gasoline reforming methods that are easy to handle as well as conventional gasoline vehicles and infrastructure development is progressing, and liquid fuels are relatively reforming. A method of reforming fuel by mounting an easy methanol fuel is considered to be a highly practical method.
[0028]
Under the circumstances as described above, fuel cell power generators using fuel gas obtained by steam reforming raw fuel containing kerosene or gasoline, including stationary fuel cells other than fuel cell vehicles, have recently been developed. Attention has been paid.
[0029]
By the way, the liquid fuel such as kerosene or gasoline contains a lot of higher hydrocarbons, and therefore requires a different reforming technique from lower hydrocarbons such as city gas. In general, water is vaporized by the heat of the reforming reaction equipment to form water vapor, and a method of vaporizing the water vapor and liquid fuel by introducing it into a fuel vaporizer (ejector) is considered promising. Note that when the water vapor and the liquid fuel are mixed in the fuel vaporizer, the flow rate ratio is controlled so that a predetermined steam / carbon ratio is obtained. In addition, since the liquid fuel includes a plurality of components having different boiling points, the temperature is controlled to be about 300 ° C. so as to maintain the gas state when the water vapor and the liquid fuel are mixed.
[0030]
FIG. 2 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generator using kerosene as a raw fuel. In FIG. 2, members having the same functions as those shown in FIG. 3 or FIG. In FIG. 2, for convenience of explanation, the cooling water system equipment and the recovered water system equipment in FIG. 3 are omitted. Also, the reformer 11 in FIG. 2 shows a configuration in which the CO converter 12 is integrated, as in FIG.
[0031]
The basic difference between FIG. 2 and FIG. 3 is that, in FIG. 2, water is evaporated by the heat of the reforming reaction equipment into steam, and this steam and liquid fuel are introduced into a fuel vaporizer (ejector). Thus, the liquid fuel is vaporized. That is, in FIG. 2, the reformed raw fuel is sent from a kerosene tank 21 to an ejector 23 as a vaporizer by a kerosene pump 22. On the other hand, the pure water delivered by the water supply pump 25 is converted into steam of 300 ° C. or higher by the heat of the reforming equipment, that is, the exhaust heat of the CO remover 13 and the CO transformer 12, and then introduced into the ejector 23. Mix with kerosene.
[0032]
After the kerosene is vaporized by the high-temperature steam in the ejector 23, the air-fuel mixture is supplied to the reformer 11 through the line 23a. In order to prevent coking of the catalyst layer, the catalyst layer inlet temperature in the reformer 11 is usually 300 ° C., which is lower than that of city gas, and the catalyst layer outlet temperature is maintained at 700 ° C. The reformed gas reformed to hydrogen by the reforming catalyst layer is supplied to the reaction catalyst layer of the CO converter 12 through the fuel gas line 24a. In FIG. 2, the part number 19a is a drain tank provided on the exhaust hydrogen supply line 19 of the fuel cell.
[0033]
[Problems to be solved by the invention]
By the way, the conventional fuel cell power generator using raw fuel containing kerosene or gasoline has the following problems.
[0034]
For example, when reforming kerosene, which is a liquid fuel, as fuel, the reformer output gas temperature is radiated and cooled in the connecting pipe to the CO converter, and a part of the unreformed kerosene is condensed and liquefied. Even if kerosene is completely vaporized without being condensed and supplied as a gas into the CO converter, the CO conversion reaction temperature is about 200 ° C. at the outlet of the catalyst layer. There is a problem that a part of the water is condensed in the CO shift catalyst layer and stays in the reactor.
[0035]
Even if kerosene components with a relatively high boiling point that do not condense inside the CO converter, the operating temperature of the CO remover disposed downstream of the CO converter is 200 ° C to 100 ° C. A portion of the unreformed kerosene condenses in the inlet piping line or inside the CO remover.
[0036]
When reforming a liquid fuel containing higher hydrocarbons with different boiling points as described above, the unreformed raw fuel condenses and stays inside the gas supply pipe or adheres to the catalyst layer inside the reactor. However, the fuel reforming performance is affected, and not only a predetermined hydrogen concentration cannot be obtained, but also a concentration fluctuation may occur, and the gas composition may become unstable.
[0037]
Further, in the above case, the CO concentration in the resulting reformed gas becomes high, and it is difficult to lower it to a predetermined CO concentration, and there is a risk of supplying CO that is a poisonous substance for the battery at a high concentration. Accompanied by. Moreover, once kerosene adheres to the inside of the pipe, even if the kerosene is raised to a 100% reforming rate (conversion rate) in the subsequent operation, the kerosene adhering to the inside of the pipe is once entrained. Therefore, it becomes a factor of performance degradation.
[0038]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an unreformed raw fuel in a CO converter and a CO remover in a fuel cell power generator using raw fuel containing kerosene or gasoline. In other words, the hydrogen concentration and the CO concentration in the reformed gas are maintained at predetermined concentrations to improve the reliability.
[0039]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention generates electricity based on an electrochemical reaction between fuel gas obtained by steam reforming raw fuel containing kerosene or gasoline and air as an oxidant gas. Gas derived from the fuel reformer in a fuel cell power generation apparatus having a fuel cell, a fuel reformer, a CO converter, a CO remover, and a steam generator for generating reforming steam An unreformed raw fuel recovery means for condensing and recovering at least a part of the unreformed raw fuel contained therein is provided on the fuel gas line between the fuel reformer and the CO converter. (Invention of Claim 1).
[0040]
According to the above, since the reformed fuel gas is condensed and recovered before reaching the CO converter, at least a part of the unreformed raw fuel (mostly according to the embodiment) is contained in the CO converter and the CO remover. It can be prevented in advance.
[0041]
As an embodiment of the invention of claim 1, the inventions of claims 2 to 5 below are preferable. That is, in the fuel cell power generator according to claim 1, the unreformed raw fuel recovery means is a raw fuel recovery tank provided with a fuel gas cooling means (invention of claim 2). 3. The fuel cell power generator according to claim 2, wherein the raw fuel recovery tank includes a CO converter so that the condensed and recovered liquid unreformed raw fuel is not scattered in the fuel gas on the fuel gas line. (Invention of claim 3).
[0042]
According to the above, the structure of the recovery means becomes simple, and unreformed raw fuel can be reliably recovered to prevent adhesion to the subsequent equipment.
[0043]
Further, from the viewpoint of effectively using the recovered unreformed raw fuel, the inventions of the following claims 4 to 5 are preferable. That is, the fuel cell power generator according to any one of claims 1 to 3, further comprising an auxiliary combustion line for combusting and using the condensed and recovered liquid unreformed raw fuel in a burner for the fuel reformer. (Invention of claim 4).
[0044]
As an embodiment of the invention of claim 4, the invention of claim 5 below is suitable. That is, in the fuel cell power generator according to claim 4, the auxiliary combustion line introduces both raw fuel including the kerosene or gasoline and the condensed / recovered liquid unreformed raw fuel. The raw fuel recovery tank includes an auxiliary combustion tank and an auxiliary combustion pump for leading both raw fuels to the burner, and the raw fuel recovery tank has a liquid level gauge. Based on the measured value of the liquid level gauge, the raw fuel recovery tank in the raw fuel recovery tank is not modified. It is assumed that the raw material fuel is transferred to the auxiliary combustion tank.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below with reference to the drawings.
[0046]
FIG. 1 is a system diagram showing an embodiment according to the present invention, and members having the same functions as those in FIG. Differences in system configuration between FIG. 1 and FIG. 2 are as follows.
[0047]
That is, in FIG. 1, a raw fuel recovery tank 26 as an unreformed raw fuel recovery means for condensing and recovering at least a part of the unreformed raw fuel contained in the fuel gas derived from the reformer 11, A point provided on the fuel gas line 24 a between the reformer 11 and the CO converter 12, and auxiliary combustion for using the condensed and recovered liquid unreformed raw fuel in the burner 1 for the reformer The line 27 is provided.
[0048]
However, the auxiliary combustion line 27 is provided with an auxiliary combustion tank 28 and an auxiliary combustion pump 27 for introducing the raw fuel and the recovered raw unreformed raw fuel into the burner 1. The raw fuel recovery tank 26 has a liquid level gauge (not shown), and a pump (not shown) that transfers unreformed raw fuel in the raw fuel recovery tank 26 to the auxiliary combustion tank 28 based on the measured value of the liquid level gauge. Means and a control device.
[0049]
In the above configuration, the raw fuel recovery tank 26 is preferably provided with a fuel gas cooling means (not shown). When kerosene is used as the raw fuel by the cooling means, for example, the temperature of the raw fuel recovery tank 26 is set to a predetermined temperature. By cooling to a low temperature (for example, 90 ° C. lower than that of the CO remover), the high boiling point component of the predetermined temperature or higher is condensed and recovered in the raw fuel recovery tank, and condensation in the CO converter and CO remover can be prevented. . When the raw fuel recovery tank 26 has a sufficient cooling area, as shown in FIG. 1, the raw fuel recovery tank 26 does not need to include any special cooling means.
[0050]
In addition, the raw fuel recovery tank 26 has a detection function such as a liquid level sensor so that it can be discharged quickly by detecting the amount of condensed kerosene, and unreformed kerosene scatters and adheres to the downstream piping. A collection tank was arranged so as not to cause the damage. As a result, the performance of the CO converter and CO remover can be sufficiently maintained, and the hydrogen concentration and the CO concentration can be stably supplied. As a result, the reliability of the entire reforming system can be increased.
[0051]
Furthermore, it has become possible to use unreformed kerosene that has not been reformed as a burner combustion fuel that uses the heat source of the reformer, thereby improving the efficiency of the fuel cell. The raw fuel in the auxiliary combustion tank 28 is also used when the reformer 11 is started.
[0052]
【The invention's effect】
As described above, according to the present invention, a fuel cell that generates electricity based on an electrochemical reaction between a fuel gas obtained by steam reforming a raw fuel containing kerosene or gasoline and air as an oxidant gas; In a fuel cell power generation device having a fuel reformer, a CO converter, a CO remover, and a steam generator for generating reforming steam, the fuel gas is derived from the fuel reformer. Since the unreformed raw fuel recovery means for condensing and recovering at least a part of the unreformed raw fuel is provided on the fuel gas line between the fuel reformer and the CO converter,
At least a part of the unreformed raw fuel (mostly according to the embodiment) is prevented from being introduced into the CO converter and the CO remover, and the hydrogen concentration and CO concentration in the reformed gas are set to predetermined concentrations. Therefore, reliability can be improved.
[0053]
In addition, since the recovered unreformed raw fuel is burned by the reformer burner, it is possible to improve the efficiency of the power generator.
[Brief description of the drawings]
FIG. 1 is a system diagram related to an embodiment of a fuel cell power generator of the present invention. FIG. 2 is a system diagram showing an example of a conventional fuel cell power generator. FIG. 3 is a system showing an example of a different conventional fuel cell power generator. [Fig. 4] Cross-sectional view showing an example of an integrated reforming system [Explanation of symbols]
1: burner, 10: fuel cell, 11: reformer, 12: CO converter, 13: CO remover, 16: desulfurizer, 21: kerosene tank, 23: ejector, 24a: fuel gas line, 26: raw Fuel recovery tank, 27: auxiliary combustion line, 28: auxiliary combustion tank, 29: auxiliary combustion pump.

Claims (5)

A fuel cell that generates electricity based on an electrochemical reaction between a fuel gas obtained by steam reforming a raw fuel containing kerosene or gasoline and air as an oxidant gas, a fuel reformer, and a CO converter And a fuel cell power generator having a CO remover and a steam generator for generating reforming steam,
Unreformed raw fuel recovery means for condensing and recovering at least a part of the unreformed raw fuel contained in the fuel gas derived from the fuel reformer is provided between the fuel reformer and the CO converter. A fuel cell power generator provided on a fuel gas line.   2. The fuel cell power generator according to claim 1, wherein the unreformed raw fuel recovery means is a raw fuel recovery tank provided with a fuel gas cooling means.   3. The fuel cell power generator according to claim 2, wherein the raw fuel recovery tank is disposed below the CO converter so that the condensed and recovered liquid unreformed raw fuel is not scattered in the fuel gas on the fuel gas line. A fuel cell power generator, which is disposed in   4. The fuel cell power generator according to claim 1, further comprising an auxiliary combustion line for combusting and using the condensed and recovered liquid unreformed raw fuel in a burner for the fuel reformer. A fuel cell power generator.   5. The fuel cell power generator according to claim 4, wherein the auxiliary combustion line introduces both raw fuels of the raw fuel containing the kerosene or gasoline and the condensed / recovered liquid unreformed raw fuel. The raw fuel recovery tank has a liquid level gauge, and the unreformed raw fuel in the raw fuel recovery tank is based on the measured value of the liquid level gauge. A fuel cell power generator comprising a structure for transferring the fuel to the auxiliary combustion tank.

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