JPH02307803A - Production of gaseous fuel for phosphoric acid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a catalyst and to obtain the gaseous fuel having a high hydrogen partial pressure by highly desulfurizing a raw fuel with a copper-zinc-based desulfurizing agent and then steam-reforming the fuel using a specified catalyst. CONSTITUTION:A raw fuel (e.g. propane, natural gas, LPG, etc.) is desulfurized with a copper-zinc-based desulfurizing agent and then steam-reformed in the production of a gaseous fuel for a phosphoric acid electrolyte fuel cell using a gaseous fuel consisting essentially of hydrogen. In this case, the S/C is adjusted to 0.7-2.5 when an Ru-based catalyst is used as the steam reforming catalyst and to 1.5-3.5 when an Ni-based catalyst is used, and then the raw fuel is steam- reformed and converted to a gaseous fuel consisting essentially of hydrogen. Since the raw fuel is highly desulfurized, the deterioration of the catalyst is prevented, a gaseous fuel having a high hydrogen partial pressure is obtained, and the fuel cell is stably operated for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing fuel gas for a fuel cell. More specifically, the present invention relates to a method for producing a fuel gas to be supplied to a fuel electrode of a phosphoric acid electrolyte fuel cell using phosphoric acid as an electrolyte.

<Prior Art> Fuel cells have conventionally been known as a system that directly converts chemical energy contained in fuel into electrical energy.

In this fuel cell, a pair of porous electrodes consisting of a fuel electrode and an oxidizer electrode are placed opposite each other with an electrolyte layer holding an electrolyte sandwiched between them to form a fuel cell. By bringing an oxidizing agent such as air into contact with the back side of the oxidizing agent electrode, electrical energy is extracted from between the two electrodes by utilizing the electrochemical reaction that occurs at this time. As long as fuel gas and oxidizer are supplied, electrical energy can be extracted with high conversion efficiency, and practical research is being actively conducted because it is advantageous in terms of energy conservation and environmental protection. Although various types of fuel cells are known, phosphoric acid electrolyte fuel cells (hereinafter referred to as phosphoric acid fuel cells) that use phosphoric acid in the electrolyte layer are widely used as low-temperature fuel cells.

In phosphoric acid fuel cells, hydrogen is used as a fuel, and this hydrogen is usually methane, ethane, propane, butane, natural gas, naphtha, kerosene, diesel oil, liquefied petroleum gas (
It is obtained by subjecting raw fuels such as LPG) and city gas to a steam reforming reaction to convert them into fuel gas whose main component is hydrogen.

The sulfur component in the raw fuel mentioned above poisons the steam reforming catalyst (for example, Rj+ type catalyst, Ni type catalyst, etc.), and for example, the sulfur content in the raw fuel is reduced to 0. Even at about 1 ppm, about 90% of the surface of the Ru-based catalyst or Ni-based catalyst is covered with sulfur in a short time, resulting in a significant deterioration of catalytic activity.

Under such circumstances, the raw fuel is subjected to a desulfurization reaction before being subjected to a steam reforming reaction.

Conventionally, typical desulfurization methods performed prior to steam reforming of raw fuels are Ni-Mo or C desulfurization methods.

-H2 generated after hydrogenolyzing organic sulfur compounds in raw fuel at 350 to 400°C in the presence of a Mo-based catalyst
This is a hydrodesulfurization method in which S is removed by adsorption on ZnO at -1,350 to 400°C.

FIG. 3 is a system diagram showing an overview of the basic configuration of a typical example of a phosphoric acid fuel cell power generation system having a desulfurization device using a hydrodesulfurization method and a steam reforming device. In the figure, raw fuel 1 is mixed with a fuel gas containing hydrogen as a main component, which is led from a carbon oxide shift converter 5 (described later), and introduced into a hydrodesulfurizer 2a. The hydrodesulfurizer 2a includes, in order from the raw fuel inlet side, a hydrogenation layer filled with a Ni-Mo based catalyst, a Co-Mo based catalyst, etc., and an adsorption layer filled with a sucking desulfurizing agent such as ZnO. Consists of. Raw fuel 1 is 350 in heater
After being heated to ~400°C, hydrogen is added in the hydrogenation layer to convert the sulfur component in the raw fuel to H2S, and the generated H2S is then adsorbed and removed in the adsorption layer, and the raw fuel 1 is desulfurized. After the desulfurized raw fuel 1 is mixed with steam in a mixer 3, it is introduced into a steam reformer 4 filled with Ru-based catalyst, Ni-based catalyst, etc., and is converted into hydrogen as a main component through a steam reforming reaction. It is converted into fuel gas and discharged. The carbon monoxide contained in the discharged fuel gas is absorbed by the catalyst (
In order to prevent poisoning (for example, PT catalyst, etc.) and to increase conversion efficiency to hydrogen, the carbon monoxide is introduced into a carbon monoxide shift converter 5 filled with a shift catalyst, and the -carbon oxide is converted into hydrogen and carbon dioxide. - Part of the fuel gas discharged from the carbon oxide shift converter 5 is sent to the hydrodesulfurizer 2a, and the rest is sent to the fuel electrode 7 of the phosphoric acid fuel cell main body 6 and used as fuel. Hydrogen in the fuel gas that has flowed into the fuel electrode 7 undergoes an electrochemical reaction with oxygen in the air 9 that has flowed into the oxidizer electrode 10 by the compressor 8, and as a result, a portion of the fuel gas is consumed and electricity is generated. Energy is obtained and water is produced as a by-product.

The fuel gas discharged from the fuel electrode 7 is transferred to the steam reformer 4
The air is sent to the burner 11 of the steam reformer 11 and joins with the air supplied from the compressor 8, is burned in the burner 11, and is used as a heating source for the steam reformer 4. The exhaust gas containing water vapor discharged from the burner 11 passes through the heat exchanger 12, and then is separated into steam and water by the condenser 13, and the separated gas is exhausted. In addition, the aggregated water is removed from the water supply line 14.
The water flows through the water supply pump 15 and the cooling water pump 16, and is sent to the phosphoric acid fuel cell main body 6, where it is used for cooling. Cooling water discharged from the phosphoric acid fuel cell main body 6 is sent to a steam separator 18 via a heat exchanger 17, and is separated into water and steam. The separated water passes through the cooling water pump 16 and is circulated for cooling the phosphoric acid fuel cell main body 6, and the water vapor is sent to the mixer 3 where it is mixed with the desulfurized raw fuel 1 and then steam reformed. It is sent to the reformer 4 and used for the steam reforming reaction.

In such a fuel cell power generation system, the fuel gas supplied to the fuel electrode is mainly hydrogen, which is a reaction product of the steam reforming reaction, carbon dioxide, which is a reaction product of the -carbon oxide transformation reaction, and steam reforming reaction. It is made up of surplus water vapor that was not used in the sintering process, and the higher the hydrogen partial pressure in the sintering gas, the higher the power generation efficiency. However, it is difficult to reduce the content of carbon dioxide, which is a reaction product of the -carbon oxide modification reaction. Therefore, in order to increase the hydrogen partial pressure in the fuel gas, the lower the S/C (number of moles of steam per mole of carbon in the hydrocarbon in the raw fuel) in the steam reforming reaction, the less excess steam will be produced. It is advantageous. However, when the S/C is lowered, the reaction product of the steam reforming reaction °
The content of carbon monoxide in the fuel gas increases, and the concentration of carbon monoxide remaining in the fuel gas increases even after being converted by a carbon oxide shift converter. As mentioned above, carbon monoxide poisons the catalyst in the fuel electrode of a phosphoric acid fuel cell, causing deterioration of the catalyst, so if fuel gas with a high concentration of remaining carbon oxide is used, the power generation efficiency of the fuel cell will decrease. There is a problem with doing so.

In addition, in the hydrodesulfurization process, if the raw fuel contains more than a certain amount of organic sulfur compounds, especially persistent organic sulfur compounds such as thiophene and dimethyl sulfide, undecomposed substances may slip. Therefore, it passes through without being adsorbed by ZnO.

In addition, for adsorption desulfurization, for example, Z n O + H2S ”:, Z n S + H2
Because of the equilibrium represented by 0ZnO+CO8'';ZnS+CO2, the amounts of H2S, CO8, etc. do not fall below a certain value.This tendency is particularly significant when H20 and CO2 are present.

Furthermore, if the desulfurization system is unstable during startup or shutdown of the device, sulfur may scatter from the adsorption desulfurization catalyst, increasing the sulfur concentration in the raw fuel. Therefore, in the current desulfurization process, the sulfur concentration in the raw fuel after refining ranges from several ppm to 0.5 ppm. It is carried out at a level of 1ppm, and the poisoning of the steam reforming catalyst cannot be sufficiently suppressed. Such reduction in catalyst activity due to sulfur poisoning promotes carbon deposition, but conventionally, in order to prevent this, operation has been carried out with a large S/C. In other words, when the S/C is lowered, carbon is deposited on the catalyst layer due to deterioration of the catalyst, causing a pressure difference, and the raw fuel begins to be discharged in an undecomposed state, making it difficult for the fuel cell to operate stably for a long period of time. The problem is that I can't drive.

Furthermore, it is necessary to increase the amount of catalyst filled in the steam reformer in anticipation of deactivation of the catalyst due to sulfur. This increases the size of the steam reformer and makes it difficult to downsize the fuel cell.

As mentioned above, in fuel cell power generation, it is advantageous to lower the S/C in that the hydrogen partial pressure in the fuel gas can be increased. However, due to the problems mentioned above, S/
It is difficult to lower C. For example, when a Ni catalyst is used as a steam reforming catalyst, the S/C is 3.5 or less, and even when a Ru-based catalyst with high catalytic activity is used, the S/C is 2. ，
Setting it to 5 or less is a problem; normally, the S/C is adjusted for one week so that it becomes 3 or more for Ru-based catalysts and 4 or more for Ni-based catalysts, and then subjected to the steam reforming reaction. As a result, the water vapor content in the fuel gas increases, making it difficult to increase the hydrogen partial pressure.

The present invention was devised to solve the above-mentioned problems of the prior art, and as a result of various studies by the present inventors, it is possible to achieve steam reforming even at low S/C by highly desulfurizing the raw fuel. This method was completed after discovering that catalyst deterioration can be prevented, fuel gas with high hydrogen partial pressure can be obtained, and fuel cells can be operated stably for long periods of time.

Means and operation for solving the above problems> The method for producing fuel gas for a fuel cell of the present invention, which has been made to solve the above problems, is to produce a fuel gas containing hydrogen as a main component by subjecting raw fuel to a steam reforming reaction. In the method for producing fuel gas for a phosphoric acid fuel cell using the fuel gas, the raw fuel is desulfurized using a copper-zinc desulfurizing agent, and then the steam reforming catalyst is
If the steam reforming catalyst is a Ni-based catalyst, the S/C should be set to 0.7 to 2.5, and if the steam reforming catalyst is a Ni-based catalyst, the S/C should be set to 1.5 to 3.
．． 5, and then subjected to a steam reforming reaction to convert the raw fuel into a fuel gas containing hydrogen as a main component. In the present invention, the copper-zinc desulfurization agent refers to copper and zinc components (for example, zinc oxide, etc.)
It means a desulfurizing agent that contains at least the following, and may further contain other components such as an aluminum component (for example, aluminum oxide, etc.) and a chromium component (for example, chromium oxide, etc.).

In the fuel gas production method of the present invention, the raw fuel is desulfurized using a copper-zinc desulfurization agent, and the copper-zinc desulfurization agent reduces the sulfur compound content in the raw fuel to 5 ppb (as sulfur, the same hereinafter). Hereinafter, it can be generally set to 0.1 ppb or less, and poisoning of the steam reforming catalyst in the subsequent steam reforming reaction is suppressed. Therefore, since the steam reforming catalyst can maintain high activity for a long time, the steam reforming reaction is possible even at low S/C, and the hydrogen partial pressure in the fuel gas can be increased.

In the present invention having the above structure, the copper-zinc desulfurization agent used for desulfurization of raw fuel is, for example,
Copper-zinc desulfurization agents disclosed in No. 2-279867 and Japanese Patent Application No. 62-279868 are mentioned, and the same publication includes:
Desulfurization agents whose main components are copper and zinc oxide (hereinafter referred to as copper-zinc desulfurization agents) and desulfurization agents whose main components are copper, zinc oxide, and aluminum oxide (hereinafter referred to as copper-zinc-aluminum desulfurization agents), respectively. Disclosed. More specifically,
These desulfurizing agents are prepared by the following method.

(1) Copper-zinc desulfurization agent: Uses an aqueous solution containing a copper compound (e.g., copper nitrate, steel acetate, etc.) and a zinc compound (e.g., zinc nitrate, zinc acetate, etc.) and an aqueous solution of an alkaline substance (e.g., sodium carbonate, etc.) Then, a precipitate is produced by a conventional coprecipitation method. The formed precipitate is dried and calcined (about 300°C) to form a copper oxide-zinc oxide mixture (in atomic ratio, usually copper:zinc-1=about 0.
3 to 10, preferably 1: about 0.5 to 3, more preferably 1: about 1 to 2.3), the hydrogen content is 6% by volume or less, more preferably 0.5 to 4% by volume. The above mixture is reduced at about 150 to 300° C. in the presence of hydrogen gas diluted with an inert gas (for example, nitrogen gas) so as to achieve the desired temperature. The copper-zinc desulfurization agent thus obtained may contain other components, such as chromium oxide.

(2) Copper-zinc-aluminum desulfurization agent Copper compounds (e.g. copper nitrate, copper acetate, etc.), zinc compounds (
Co-precipitation by a conventional method using an aqueous solution containing an aluminum compound (e.g., aluminum nitrate, sodium aluminate, etc.) and an aqueous solution of an alkaline substance (e.g., sodium carbonate, etc.). A method is used to form a precipitate. The generated precipitate was dried and calcined (30
(approximately 0°C) and then prepare a copper oxide-zinc oxide-aluminum oxide mixture (in atomic ratio, usually copper:zinc nialium-1
: about 0.3-10: about 0.05-2, preferably 1: about 0.6-3: about 0.3-1), then hydrogen-containing 'm6
The above mixture is reduced at about 150 to 300°C in the presence of hydrogen gas diluted with an inert gas (e.g., nitrogen gas, etc.) so that the concentration is less than or equal to 0.5 to 4% by volume. Process. Copper obtained in this way -
The zinc-aluminum desulfurization agent may contain other components, such as chromium oxide.

The copper-zinc desulfurization agent obtained by methods (1) and (2) above has fine particulate copper with a large surface area uniformly dispersed in zinc oxide (and aluminum oxide), and It is highly active due to chemical interaction with zinc (and aluminum oxide). Therefore, by using these desulfurization agents, it is possible to reliably reduce the sulfur content in raw fuel to 5 ppb or less, usually 0.1 ppb or less, and also to ensure that persistent sulfur compounds such as thiophene and dimethyl sulfide are removed. Can be removed. Desulfurization using the above-mentioned copper-zinc desulfurization agent is normally carried out at a temperature of 10 to 400°C, although the setting is appropriately determined depending on the sulfur content in the raw fuel.
degree, preferably about 150 to 250°C, pressure 0 to 10
kg/C-・G degree, GH8V (Gaseous Ho
urly 5pace Velocity) 500~
It is held at around 3,000.

In addition, when the raw fuel contains a large amount of sulfur component, the sulfur content in the raw fuel is reduced to 1 to 0. It is preferable to perform the above desulfurization after primary desulfurization to reduce the amount to about 1 ppm. According to this method, the amount of copper-zinc desulfurization agent used can be reduced.

Although the secondary desulfurization can be carried out by a conventional method, it is preferable to carry out the adsorption desulfurization method from the viewpoint of operational simplicity and desulfurization efficiency. An example of the adsorption desulfurization method is an adsorption desulfurization method using a ZnO-based desulfurization agent.
By adopting conditions of ~10kg/c-φG and approximately GH8V100O, the sulfur content in raw fuel can be reduced to ~1~
0. It can be reduced to about lppm. Note that the adsorption desulfurization method is not limited to the above example, and various conditions can be adopted.

Furthermore, when the raw fuel contains a persistent organic sulfur compound such as thiophene or dimethyl sulfide, the raw fuel is first subjected to hydrodesulfurization, then the above-mentioned adsorption desulfurization, and then
Desulfurization is preferably carried out using a copper-zinc desulfurization agent. According to this method, the content of organic sulfur compounds in the raw fuel can be reduced, and the amount of copper-zinc desulfurization agent used can be reduced. Hydrodesulfurization can be carried out by a conventional method, for example, in the presence of a Ni-Mo based catalyst, Co-Mo based catalyst, etc. at a temperature of 350 to 400 ml.
Approximately 00℃, pressure O ~ 10kg/c-・G, GHS
Although the test is carried out under conditions of about V3000, the conditions are not limited to this.

The raw fuel desulfurized by the above method is then mixed with steam and subjected to a steam reforming reaction.

At this time, if the steam reforming catalyst is a Ru-based catalyst, the S/C
is adjusted to be 0.7 to 2.5, and when the steam reforming catalyst is a Ni-based catalyst, S/C is adjusted to be 1.5 to 3.5. If the S/C is less than the lower limit of the above range, carbon will be deposited on the reforming catalyst, which is undesirable, and even if the S/C exceeds the upper limit of the above range, the steam reforming reaction will proceed, but the water vapor content in the generated fuel gas will decrease. The pressure becomes high and the object of the present invention cannot be achieved. The reaction temperature, reaction pressure, etc. of the steam reforming reaction are carried out under the same conditions as the steam reforming reaction of conventional fuel cells.
temperature, exit temperature about 50℃~900℃, reaction pressure 0~
It is carried out at approximately 10 kg/c/g. In this way, the raw fuel is converted into fuel gas containing hydrogen as a main component.

In the present invention, the raw fuel used is methane,
Ethane, propane, butane, natural gas, naphtha, LPG
, city gas, and mixtures thereof.

Hereinafter, the present invention will be explained in more detail based on the accompanying drawings.

FIG. 1 is a schematic diagram of one embodiment of a phosphoric acid fuel cell power generation system using the fuel gas production method of the present invention, and the same parts as in FIG. 3 are denoted by the same reference numerals. In the figure, the desulfurization equipment is composed of a hydrodesulfurizer 2a filled with a hydrogenation catalyst and an adsorption desulfurization agent, and a copper-zinc desulfurization agent 2b filled with a copper-zinc desulfurization agent. In this example, a desulfurization pipe filled with a hydrogenation catalyst, an adsorption desulfurization agent, and a copper-zinc desulfurization agent in order from the inlet side of the raw fuel 1 is used.

In FIG. 1, raw fuel 1 is mixed with a fuel gas containing hydrogen as a main component derived from a carbon oxide shift converter 5 at an appropriate mixing ratio (
For example, it is mixed at a concentration of about 2% by volume based on the raw fuel,
It is introduced into the hydrodesulfurizer 2a. The hydrodesulfurizer 2a sequentially processes raw fuel 1 from the inlet side, for example, Ni-Mo-based, Co-
It is composed of a hydrogenation layer filled with a Mo-based catalyst, etc., and an adsorption layer filled with an adsorption desulfurization agent such as ZnO. In the above-mentioned hydrogenation layer, the raw fuel 1 is hydrogenated under the above-mentioned conditions, and then the generated sulfur components such as H2S are absorbed by the adsorption layer under the above-mentioned conditions and then subjected to subsequent desulfurization.

Next, the raw fuel 1 that has been desulfurized is further desulfurized in a copper-zinc desulfurizer 2b filled with a steel-zinc desulfurizer. Desulfurization in the copper-zinc desulfurizer 2b is performed under the desulfurization conditions described above, but the conditions are not limited to these.

The raw fuel 1 discharged from the desulfurizer 2b has a sulfur content of 5
It is desulfurized to ppb or less, usually 0.1 ppb or less.

The raw fuel 1 desulfurized in this way is mixed with steam in a mixer 3, and when the steam reforming catalyst is a Ru-based catalyst, the steam reforming is carried out so that the S/C is 0.7 to 2.5. quality catalyst is N
In the case of an i-type catalyst, after adjusting the S/C to 1.5 to 3.5, it is introduced into the steam reformer 4 and subjected to a steam reforming reaction to produce a fuel containing hydrogen as the main component. converted to gas.

The steam reformer 4 uses a steam reformer filled with a Ru-based catalyst or a Ni-based catalyst, similar to the steam reformer of a conventional fuel cell, and performs a steam reforming reaction under the above conditions. be exposed. The fuel gas mainly composed of hydrogen discharged from the steam reformer 4 is sent to the carbon monoxide shift converter 5 filled with a low-temperature carbon oxide shift catalyst that is highly active even at low temperatures.
- Increased hydrogen content with reduced carbon oxide content.

Next, the fuel gas discharged from the carbon oxide shift converter 5 is sent to the fuel electrode 7 of the phosphoric acid fuel cell main body 6, where it is electrochemically combined with oxygen in the air 9 flowing into the oxidizer electrode 10 by the compressor 8. A reaction takes place, and as a result, part of the fuel gas is consumed, electrical energy is obtained, and water is produced as a by-product.

In addition, processing of the fuel gas discharged from the fuel electrode 7 (for example, sending it to the burner 11, burning it, and using it as a heating source for the steam reformer 4, etc.), processing of the exhaust gas discharged from the oxidizer electrode 10, The cooling of the fuel cell main body 6, the cooling water circuit, etc. are the same as those of the conventional device.

Figure 2 is a schematic diagram of another embodiment of a phosphoric acid fuel cell power generation system using the fuel gas production method of the present invention. This method is suitable for producing fuel gas when using hydrocarbons containing organic sulfur compounds, such as city gas containing dimethyl sulfide as an odorant. In addition, the third
The same parts as those in the figure are given the same reference numerals.

In Figure 2, the raw fuel 1 is preheated by a separately provided heater or heat exchanger as necessary, and then flows into a copper-zinc desulfurizer 2b filled with a copper-zinc desulfurizer. do. Desulfurization in the desulfurizer 2b is performed under the desulfurization conditions described above. The raw fuel 1 discharged from the desulfurizer 2b has a reduced content of organic sulfur compounds such as dimethyl sulfide, and has a sulfur content of 5 ppb or less, usually 0.1 ppb.
desulfurized to below b. Desulfurized raw fuel 1
is introduced into the mixer 3 and is subsequently processed in the same manner as described for the system of FIG. That is, after raw fuel 1 and steam are mixed to achieve an appropriate S/C depending on the catalyst type, they are subjected to a steam reforming reaction in a steam reformer 4 to produce a fuel gas containing hydrogen as a main component. It is then led to the fuel electrode 7 of the phosphoric acid fuel cell main body 6 via the carbon monoxide transformer 5, where it is converted into electrical energy by an electrochemical reaction.

The present invention is not limited to the above example, and can be implemented with various modifications without changing the gist of the invention. For example, in FIG. The desulfurization equipment is composed of desulfurization pipes filled with added catalyst, adsorption desulfurization agent, and copper-zinc desulfurization agent.
Hydrodesulfurization equipment filled with hydrogenation catalyst and adsorption desulfurization agent as desulfurization equipment? 52a and a copper-zinc desulfurizer 2b filled with a copper-zinc desulfurizer may be separated.

Further, the fuel cell power generation system using the fuel gas production method of the present invention can be implemented with a system that is equipped with various conventionally known mechanisms. For example, in the system shown in FIGS. A mechanism that controls the fuel gas supplied to the electrode 7 and air 9 supplied to the oxidizer electrode 10 according to the electrical load, and a mechanism that detects the differential pressure between the fuel electrode 7 and the oxidizer electrode 10 and adjusts the differential pressure. may be provided, and a plurality of phosphoric acid fuel cell bodies 6 may be connected in parallel or in series. Furthermore, a mechanism is provided in which a fuel recirculation fan is provided between the fuel gas supply line and the fuel gas discharge line of the fuel electrode 7 to return a part of the discharged fuel gas to the fuel electrode 7;
An air recirculation fan is provided between the air supply line and the air discharge line of the oxidizer electrode 10, and a part of the exhausted air is transferred to the oxidizer electrode 10.
A mechanism may be provided to return the By providing these recirculation mechanisms, it is possible to reuse the reactive gas after the electrode reaction, and also to adjust the hydrogen concentration of the exhaust fuel gas and the oxygen concentration of the exhaust air, and to adjust the load fluctuation of the fuel cell. I can do it.

<Examples> Hereinafter, the present invention will be explained in more detail based on Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples.

Reference Example 1 Naphtha with a sulfur content of 100 ppm was prepared according to a conventional method.
First, the temperature was 380°C in the presence of a Ni-Mo-based hydrodesulfurization catalyst.
, pressure 8kg/cj ・G, L HS V (Liqu
id Hourly 5pace Velocity)
2. Hydrogen/naphtha - After hydrogenolysis under conditions of 0.1 (molar ratio), it was brought into contact with a ZnO-based adsorption desulfurization agent to carry out secondary adsorption desulfurization. The sulfur content in the obtained primary adsorption desulfurization naphtha was approximately 2 ppm.

On the other hand, a sodium carbonate aqueous solution was added as an alkaline substance to a mixed aqueous solution containing copper nitrate, zinc nitrate, and aluminum nitrate, and after washing and filtering the resulting precipitate,
/8 inch x 1/8 inch diameter,
It was fired at about 400°C. Next, the fired body (copper oxide 45
%, zinc oxide 45%, aluminum oxide 10%) 100
Nitrogen gas containing 2% by volume of hydrogen was passed through a desulfurization apparatus filled with cc and reduced at a temperature of about 200°C to obtain a copper-zinc-aluminum desulfurization agent. Next, the primary adsorption desulfurization naphtha obtained above was passed through the desulfurization agent at a temperature of 3
Desulfurization was carried out at 50°C and a pressure of 8 kg/c-G. The sulfur content in the resulting desulfurized naphtha was below 0.11 pb over 7000 hours of operation.

Using the highly desulfurized naphtha obtained in this way as a raw material, using a flow-type pseudo-adiabatic reactor (diameter 20 mm), Ru-based catalyst (Ru 2% by weight supported on γ-alumina carrier) or Ni
System catalyst (prepared by coprecipitation method, NiO content 50% by weight)
Low-temperature steam reforming was carried out under the conditions shown in Table 1 while varying the S/C, and the amount of carbon precipitated on the catalyst at the inlet of the reactor was measured.

Table 1 Reaction temperature (inlet) 490℃ (adiabatic) Reaction pressure
8 kg/c C/G naphtha flow rate
160cc/h Catalyst amount 100cc H2/naphtha 0.1 (molar ratio) The relationship between the amount of carbon deposited on the catalyst at the reactor inlet and S/C is
As shown in the figure. In FIG. 4, curve A is the case when a Ru-based catalyst is used, and curve B is the case when a Ni-based catalyst is used.

As is clear from Fig. 4, S/C is up to 0.7 when Ru-based catalyst is used, and S/C is up to 0.7 when Ni-based catalyst is used.
Even when /C was lowered to 1.5, substantially no carbon was deposited on the catalyst.

On the other hand, as a result of the same test as above using the primary adsorption desulfurization naphtha with a sulfur content of 2 ppm, the S/C was 2.5 or less in the case of the Ru-based catalyst, and the S/C was 2.5 or less when the Ni-based catalyst was used. When S/C was 3.5 or less, carbon deposition was observed on the catalyst.

Example 1 A test was conducted using the fuel cell power generation system shown in FIG. In addition, Ru catalyst (Ru2
%,Aj! zo3 carrying) 5Ω (gas density 0.8kg
/Ω) steam reformer (catalyst layer length approximately 1m)
was used. In addition, as a desulfurization device, a sodium carbonate aqueous solution is added as an alkaline substance to a mixed aqueous solution containing copper nitrate, zinc nitrate, and aluminum nitrate, and after washing and filtering the resulting precipitate, a 1/8 inch high Diameter 1/8
The tablets are compressed into inch-sized tablets, fired at about 400°C, and then the fired body (45% copper oxide, 45% zinc oxide, 10% aluminum oxide) is heated using nitrogen gas containing 2% by volume of hydrogen. A desulfurization device (desulfurization layer length (approximately 50 cm) was used.

After preheating 13 A (10 ni''/h) of city gas consisting of the components shown in Table 2 below to 380°C as raw fuel, 0.2 Nm'/h of recycled reformed gas (i.e. -carbon oxide The desulfurized gas was introduced into the above-mentioned desulfurization equipment together with the fuel gas recycled from the shift converter (fuel gas recycled from the shift converter) and desulfurized.
A steam reforming reaction was carried out at 65° C. (outlet) and a reaction pressure of 0.2 kg/c+f·G.

The steam-reformed fuel gas is transferred to a heat exchanger type heat exchanger filled with a commercially available low-temperature carbon oxide shift catalyst (equivalent to G-66B).
After being transformed in a carbon oxide transformer under the conditions of a transformer outlet temperature of 190°C and a reaction pressure of 0.2 kg/c-G, the air electrode is guided to the fuel electrode of the fuel cell main body and introduced to the oxidizer electrode. By reacting with the oxygen inside, electrical energy was extracted.

Table 2 Methane 86.9% by volume Ethane
8.1% by volume propane
3.7% by volume butane
1.3% by volume odorant dimethyl sulfide 3+
ag-9/Nm't-butyl mercaptan 2 mg
-8/N m' In the above test, the composition of the fuel gas at the steam reformer outlet and the -carbon oxide shift converter outlet was investigated. The results are shown in Table 3 (unit: volume %, same below).

(Left below) Table 3 Steam reforming - carbon oxide equipment outlet Metamorphic Masuda 11 H258,569,2 CH43,93,9 CO11,50,8 CO26,817,6 H2019,38,5 Also, desulfurization, at the equipment outlet The sulfur content in the gas was measured over time, and even after 2000 hours, the sulfur content was below 0.1 lppb, and no deterioration of the catalytic activity of the steam reforming catalyst was observed even after 2000 hours, indicating that the reaction had started. The same activity as immediately after was maintained, and the fuel cell operated normally even at low S/C.

Comparative Example 1 A test was conducted in the same manner as in Example 1 except that the S/C was set to 3.0, and the steam reformer outlet and -
The composition of the fuel gas at the carbon oxide transformer outlet was investigated.

The results are shown in Table 4.

Table 4 Steam reforming - Carbon oxide device outlet Shift converter outlet H253,761,6 CH41,41,4 Co 8. 2 0.3CO28,
015,9 H2028,720,8 As shown in Table 4 above, when S/C-3,0, the water vapor content in the fuel gas discharged from the carbon oxide shift converter increases significantly, As a result, the hydrogen content decreased.

Comparative Example 2 Instead of the copper-zinc-aluminum desulfurization agent of Example 1,
Commercially available 7. The same test as in Example 1 was conducted using the same fuel cell power generation device as in Example 1, except that a desulfurization device filled with the amount of no@attachment/detachment/demixing agent was used.

As a result, the sulfur content of the gas at the desulfurizer outlet immediately after the start of the reaction was 0.2 ppm, and remained almost unchanged thereafter, but after 500 hours, the methane slip at the reformer outlet increased. The fuel cell's electrical output began to decline, and eventually the device had to be shut down. At this time, the reforming catalyst had almost completely deteriorated.

Example 2 Full range naphtha (sulfur content 100p) was used as raw fuel.
After vaporizing pm100pp/h and preheating to 380℃,
0. It was introduced into the same desulfurization apparatus as in Example 1 together with 2 Nm'/h of recycled reformed gas for desulfurization. The desulfurized gas was subjected to a steam reforming reaction in the same manner as in Example 1, and the fuel cell was operated.

In the above test, the composition of the fuel gas at the steam reformer outlet and the carbon oxide shift converter outlet was investigated. The results are shown in Table 5.

(Left below) Table 5 Steam reforming - Carbon oxide device outlet Shift converter outlet H253,566, I CH43,43,4 CO13,61,0 CO29,3° 22.0 H2020,27,6 Also, desulfurization device outlet The sulfur content in the gas was measured over time, and even after 2000 hours, the sulfur content remained
, 1 ppb or less, and the steam reforming catalyst shows no deterioration in catalytic activity even after 2000 hours, maintaining the same activity as immediately after the start of the reaction, and the fuel cell operates normally even at low S/C. It worked.

Comparative Example 3 The same test as in Example 2 was conducted using the same apparatus as in Comparative Example 2.

As a result, the sulfur content of the gas at the desulfurizer outlet immediately after the start of the reaction was 0.4 ppm, and remained almost unchanged thereafter, but after 200 hours, the slip of the feedstock hydrocarbon at the reformer outlet increased. However, the electrical output of the fuel cell began to decline, and eventually the equipment had to be shut down.

At this time, the reforming catalyst had almost completely deteriorated.

Example 3 LPG (sulfur content 5ppm) 10Ω as raw fuel
After vaporizing /h and preheating to 380 °C, 0.2 Nm
It was introduced into the same desulfurization apparatus as in Example 1 together with recycled reformed gas of 1/h to perform desulfurization. Example 1 of desulfurized gas
The fuel cell was operated by subjecting it to a steam reforming reaction in the same manner as above.

In the above test, the composition of the fuel gas at the steam reformer outlet and the carbon oxide shift converter outlet was investigated. The results are shown in Table 6.

(Left below) Table 6 Steam reforming - Carbon oxide unit outlet Shift converter outlet H254,867,0 CH43,53,5 Co 13.1 0.9CO28,6
20,8 H2020,07,8 In addition, the sulfur content in the gas at the desulfurization equipment outlet was measured over time by a! 1, but even after 2000 hours the sulfur content was below 0.1 ppb, and the steam reforming catalyst
No deterioration of the catalyst activity was observed even after the passage of time, and the same activity as immediately after the start of the reaction was maintained, and the fuel cell operated normally even at low S/C.

Comparative Example 4 Using the same apparatus as Comparative Example 2, the same test as in Example 3 was conducted.

As a result, the amount of gold in the gas at the outlet of the desulfurization equipment immediately after the start of the reaction was 0.2 ppm, which remained almost unchanged thereafter, but after 500 hours, slipping of feedstock hydrocarbons at the exit of the reformer started to occur. The electrical output of the fuel cell began to decrease, and eventually the device had to be shut down. At this time, the reforming catalyst had almost completely deteriorated.

Example 4 A test was conducted using the fuel cell power generation system shown in FIG. In addition, as a steam reformer, Ru catalyst (R
u2%, Al+203 supported) 5g (bulk density approx. 0.8
Steam reformer filled with 1 kg/j (catalyst layer length approx. 1
m) was used. In addition, as a desulfurization device, a sodium carbonate aqueous solution is added as an alkaline substance to a mixed aqueous solution containing copper nitrate and zinc nitrate, and after washing and filtering the resulting precipitate, The sintered body [copper:zinc - about 1:1 (atomic ratio)] is heated to about 300°C using nitrogen gas containing 2% by volume of hydrogen. A desulfurization device (desulfurization layer length: about 50 cm) filled with 20Ω of a copper-zinc desulfurization agent obtained by reduction treatment at 200° C. was used.

As the raw fuel, the city gas 13A used in Example 1 was preheated to 170° C. with a heater, and then introduced into the desulfurization apparatus at a rate of 10 m'/h to be desulfurized. The desulfurized gas was introduced into a steam reformer, S/C-2,2, reaction temperature 450°C (inlet) and 665°C (outlet), reaction pressure 0.2kg/cd・
It was subjected to a steam reforming reaction at G. The steam-reformed fuel gas is passed through a heat exchanger-type carbon oxide shift converter filled with a commercially available low-temperature carbon oxide shift catalyst (equivalent to G-66B) at a temperature of 190°C at the outlet of the converter and a reaction pressure of 0. .2kg/cd・G
After being metamorphosed under the following conditions, it is guided to the fuel electrode of the fuel cell body,
Electrical energy was extracted by reacting with the oxygen in the air introduced into the oxidizer electrode.

In the above test, the composition of the fuel gas at the steam reformer outlet and the carbon oxide shift converter outlet was investigated. The results are shown in Table 7.

(Left below) Table 7 Steam reforming - Carbon oxide equipment outlet Transformed product II H257,667,8 CH43,13,1 CO10,70,6 CO27,217,4 H2021,311,1 Also, at the desulfurization equipment outlet The sulfur content in the gas was fixed at Δ or 1 over time, but even after 2000 hours, the sulfur content was less than 0.1 ppb, and the steam reforming catalyst
No deterioration of the catalyst activity was observed even after the passage of time, and the same activity as immediately after the start of the reaction was maintained, and the fuel cell operated normally even at low S/C.

Example 5 In Example 4, a Ni-based catalyst (
The same test as in Example 4 was conducted except that Ni content was 14%) and S/C was 2.5.

In the above test, the composition of the fuel gas at the steam reformer outlet and the carbon oxide shift converter outlet was investigated. The results are shown in Table 8. In addition, the sulfur content in the gas at the desulfurization equipment outlet remained 0.0% even after 2000 hours.
1 ppb or less, and the steam reforming catalyst shows no deterioration in catalytic activity even after 2000 hours, maintaining the same activity as immediately after the start of the reaction, and the fuel cell operates normally even at low S/C. did.

Table 8 Steam reforming - Carbon oxide device outlet Shift converter outlet H256,265,5 CH42,32,3 CO9,70,4 CO27,616,9 H2024,214,9 <Effects of the invention> The fuel gas of the present invention According to the manufacturing method, a copper-zinc desulfurization agent is used as the desulfurization agent, which can highly desulfurize the raw fuel and suppress the poisoning of the steam reforming catalyst in the subsequent steam reforming reaction. Therefore, even at a low S/C, it is possible to obtain fuel gas with high hydrogen partial pressure with sufficient steam reforming reaction efficiency. Furthermore, since the steam reforming catalyst maintains high activity for a long time, the fuel cell can be stably operated for a long time with a small amount of reforming catalyst, and the reformer can be made smaller.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of a phosphoric acid fuel cell power generation system using the fuel gas production method of the present invention, FIG. 3 is a schematic diagram of a conventional phosphoric acid fuel cell power generation system, and FIG. 4 1 is a diagram showing the relationship between S/C and the amount of carbon deposited on a catalyst in a steam reforming reaction. 1... Raw fuel 2a... Hydrodesulfurizer 2b
Copper-zinc desulfurizer 3 Mixer 4 Steam reformer 5 Carbon oxide shift converter 6 Phosphoric acid fuel cell body 7 Fuel electrode 8...・Compressor 9
...Air 10...Oxidizer electrode 11...
・Burner 12...Heat exchanger 13...Condenser 14...Water supply line 15...Water supply pump IB...Cooling water pump 17...Heat exchanger 18...Steam water separator 19 ...electrical load

Claims (1)

[Claims] 1. In a method for producing fuel gas for a phosphoric acid electrolyte fuel cell using fuel gas containing hydrogen as a main component, the raw fuel is copper-based.
Desulfurization is performed using a zinc-based desulfurization agent, and then the raw fuel and steam are mixed so that the amount of steam is 0.7 per mole of hydrocarbon carbon in the raw fuel.
Phosphoric acid characterized by comprising a step of mixing the raw fuel at a ratio of ~2.5 moles and then subjecting it to a steam reforming reaction using a Ru-based catalyst to convert the raw fuel into a fuel gas containing hydrogen as the main component. A method for producing fuel gas for an electrolyte fuel cell. 2. In the method for producing fuel gas for a phosphoric acid electrolyte fuel cell using fuel gas containing hydrogen as the main component, the raw fuel is copper-based.
Desulfurization is performed using a zinc-based desulfurization agent, and then the raw fuel and steam are mixed so that the amount of steam is 1.5 per mole of hydrocarbon carbon in the raw fuel.
Phosphoric acid characterized by including a step of mixing the raw fuel at a ratio of ~3.5 moles and then subjecting it to a steam reforming reaction using a Ni-based catalyst to convert the raw fuel into a fuel gas containing hydrogen as the main component. A method for producing fuel gas for an electrolyte fuel cell. 3. The method for producing fuel gas for a phosphoric acid electrolyte fuel cell according to claim 1 or 2, wherein the sulfur content of the raw fuel is desulfurized to 5 ppb or less. 4. The method for producing fuel gas for a phosphoric acid electrolyte fuel cell according to claim 3, wherein the sulfur content of the raw fuel is desulfurized to 0.1 ppb or less. 5. The copper-zinc desulfurization agent is a desulfurization agent obtained by hydrogen reduction of a copper oxide-zinc oxide mixture prepared by a coprecipitation method using a copper compound and a zinc compound, or a copper compound, a zinc compound, and an aluminum compound. Production of a fuel gas for a phosphoric acid electrolyte fuel cell according to any one of claims 1 to 4, which is a desulfurizing agent obtained by hydrogen reduction of a copper oxide-zinc oxide-aluminum oxide mixture prepared by a coprecipitation method. Method.