JP2006277980A - Desulfurization method of fuel for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a desulfurization method by which sulfur content of a fuel for fuel cell can be removed efficiently up to extremely low concentration with a minimum amount of desulfurizing agent and leaking of a sulfur compound to the downstream side can be controlled even if there were temporary fluctuations in the impurities and sulfur content concentration of this fuel, a method of reforming the fuel for fuel cell desulfurized by this desulfurization method and producing hydrogen for fuel cell, and a fuel cell system using the hydrogen produced by this method. <P>SOLUTION: This is a method of desulfurizing fuel cell fuel using a desulfurizing device installed in a fuel cell system and equipped with a front desulfurizer and a rear desulfurizer. The desulfurizing agent in the front desulfurizer is replaced periodically and the desulfurizing agent in the rear desulfurizer is used semi-permanently. A method of reforming the fuel cell fuel desulfurized by this desulfurization method and producing hydrogen for fuel cell is provided, and a fuel cell system to use the hydrogen produced by this method is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell fuel desulfurization method, a fuel cell hydrogen production method, and a fuel cell system. More specifically, the present invention relates to a fuel cell fuel desulfurization agent that efficiently removes sulfur content of a fuel cell fuel to a very low concentration. In addition, a desulfurization method capable of controlling the leakage of sulfur compounds to the downstream side even in the case of temporary impurity and sulfur concentration fluctuations of the fuel, and a fuel cell fuel desulfurized by this desulfurization method The present invention relates to a method for producing hydrogen for a fuel cell by reforming, and a fuel cell system using hydrogen produced by this method.

  In recent years, new energy technology has attracted attention due to environmental problems, and fuel cells are attracting attention as one of the new energy technologies. This fuel cell converts chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen, and has a feature of high energy use efficiency. Alternatively, research into practical use is actively conducted for automobiles and the like. For this fuel cell, types such as a phosphoric acid type, a molten carbonate type, a solid oxide type, and a solid polymer type are known depending on the type of electrolyte used. On the other hand, as a hydrogen source, liquefied natural gas mainly composed of methanol and methane, city gas mainly composed of this natural gas, synthetic liquid fuel using liquefied natural gas, liquefied petroleum gas, and petroleum-based naphtha The use of kerosene and other hydrocarbon oils has been studied.

  Usually, about 2 to 50 mass ppm of sulfur compounds are present as impurities in hydrocarbon fuels used in fuel cell power generation systems. This sulfur compound is a catalyst poison for a catalyst used in a reformer used in the production of hydrogen for fuel cells and a catalyst used in fuel cells, and therefore needs to be removed. For this reason, a desulfurizer for removing sulfur compounds in the fuel is generally installed upstream of the reformer. As liquefied petroleum gas fuels used in household and commercial fuel cell systems, some types of impurities such as sulfur species, olefins, and methanol are distributed to a certain extent. Some fuels are used. Therefore, the desulfurizer is designed to set a large amount of the desulfurizing agent to be filled in the desulfurizer in order to ensure extremely high safety.

As a desulfurizer, a desulfurizer is disclosed in which a plurality of sulfur adsorbing portions are connected in series, and the adsorbing portions are detachable (see, for example, Patent Document 1). In this Patent Document 1, at least one adsorbing portion on the upstream side with respect to the flow direction of the fuel gas is removed, and at least one adsorbing portion filled with unused adsorbent is removed from the removed adsorbing portion. A maintenance method for replenishing downstream is disclosed.
However, even when such a desulfurizer is used, if the sulfur content leaks from the desulfurizer to the subsequent stage, the reforming catalyst is damaged even if the sulfur content is very small. The amount will be insufficient. Therefore, when the reforming catalyst is damaged, it is necessary to remove and replace an expensive reformer.
Therefore, it is necessary to prevent the sulfur compound from leaking out of the desulfurizer even in a trace amount. City gas, liquefied petroleum gas (LP gas), dimethyl ether, naphtha, kerosene, and the like, which are fuels for fuel cells, contain water that affects the performance of the desulfurization agent. In addition to moisture, the LP gas contains methanol that affects the performance of the desulfurization agent, and the type and content of sulfur compounds contained in the LP gas are not constant. The LP gas sealed in the gas cylinder has a characteristic that the sulfur concentration in the raw fuel gas increases with consumption.

JP 2000-119667 A

  Under such circumstances, the present invention can efficiently remove the sulfur content of the fuel cell fuel to a very low concentration with a minimum amount of desulfurizing agent, and also in the temporary impurity and sulfur content variation of the fuel. In addition, a desulfurization method capable of controlling leakage of sulfur compounds to the downstream side, a method for producing hydrogen for fuel cells by reforming fuel for fuel cells desulfurized by the desulfurization method, and the method An object of the present invention is to provide a fuel cell system using hydrogen produced by the above method.

As a result of various researches to achieve the above object, the present inventors have periodically replaced the desulfurization agent in the first-stage desulfurizer in the desulfurization apparatus including the first-stage desulfurizer and the second-stage desulfurizer. It has been found that a desulfurization method using a desulfurization agent in a desulfurizer semipermanently can solve the above problems. The present invention has been completed based on such findings.
That is, the present invention provides the following desulfurization method, fuel cell hydrogen production method, and fuel cell system.

1. A method of desulfurizing fuel for a fuel cell using a desulfurization apparatus that is disposed in a fuel cell system and includes a first-stage desulfurizer and a second-stage desulfurizer, and periodically replacing a desulfurization agent in the first-stage desulfurizer, 1. A method for desulfurizing a fuel for a fuel cell, wherein the desulfurizing agent in the latter-stage desulfurizer is used semipermanently. 2. The fuel for fuel cell according to 1 above, wherein the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0.2-2. Desulfurization method.
3. 3. The fuel cell fuel desulfurization method according to 1 or 2 above, wherein the sulfur content adsorption amount per 1 kW of fuel cell output is 2 g or more in the front stage desulfurizer and 0.5 g or more in the rear stage desulfurizer.
4). 5. The fuel cell fuel desulfurization method according to any one of the above 1 to 4, wherein the fuel cell fuel is a gaseous hydrocarbon compound.
5. 5. The desulfurization agent charged in the first-stage desulfurizer and the second-stage desulfurizer is a desulfurization agent having the ability to adsorb carbonyl sulfide, hydrogen sulfide, mercaptans, sulfides, and disulfides. A method for desulfurizing fuel for a fuel cell.
6). Any of 1 to 5 above, wherein the desulfurizing agent is (A) a desulfurizing agent containing zeolite and / or (B) a desulfurizing agent containing at least one selected from a metal element, a metal oxide and a metal component-supported oxide. 2. A method for desulfurizing a fuel for a fuel cell according to 1.
7). 7. The fuel cell fuel desulfurization method according to 6 above, wherein the zeolite is a zeolite having a beta (BEA) structure and / or a zeolite having a faujasite (FAU) structure.
8). The desulfurizing agent containing zeolite is selected from the group consisting of Ag component, Cu component, Ni component, Zn component, Mn component, Fe component, Co component, alkali metal component, alkaline earth metal component and rare earth metal component together with zeolite. 8. The fuel cell fuel desulfurization method according to 6 or 7 above, comprising at least one metal component.
9. A desulfurization agent containing at least one selected from metal elements, metal oxides and metal component-supported oxides is an Ag component, Cu component, Ni component, Zn component, Mn component, Fe component, Co component, Al component, Si 9. The fuel cell fuel desulfurization method according to any one of the above 6 to 8, comprising at least one metal component selected from the group consisting of a component, an alkali metal component, an alkaline earth metal component, and a rare earth metal component.
10. A method for producing hydrogen for a fuel cell, comprising reforming the fuel for a fuel cell desulfurized by the desulfurization method according to any one of 1 to 9 above.
11. 11. The method for producing hydrogen for fuel cells as described in 10 above, wherein the reforming is steam reforming, partial oxidation reforming, or autothermal reforming.
12 12. The method for producing hydrogen for fuel cells as described in 10 or 11 above, wherein the catalyst used for reforming is a ruthenium catalyst or a nickel catalyst.
13. 13. The method for producing hydrogen for fuel cells as described in 12 above, wherein the carrier component of the catalyst used for reforming contains at least one selected from manganese oxide, cerium oxide, and zirconium oxide.
14 14. A fuel cell system using hydrogen produced by the method according to any one of 10 to 13 above.

  According to the desulfurization method of the present invention, the sulfur content of the fuel cell fuel can be efficiently removed to a very low concentration with a minimum amount of the desulfurization agent, and the temporary impurities and the sulfur content concentration of the fuel can be reduced. In addition, since leakage of sulfur compounds to the downstream side can be controlled, poisoning of sulfur in the reformer catalyst and the fuel cell catalyst mounted in the fuel cell system can be prevented.

A fuel cell fuel desulfurization method according to the present invention is a desulfurization method using a desulfurization apparatus that is disposed in a fuel cell system and includes a first-stage desulfurizer and a second-stage desulfurizer, and includes a desulfurization agent in the first-stage desulfurizer. This is a desulfurization method in which the desulfurization agent in the latter-stage desulfurizer is semipermanently exchanged periodically.
In the desulfurization method of the present invention, the desulfurization performance of the pre-desulfurizer is preferably 2 g or more, more preferably 3 to 50 g per 1 kW of fuel cell output. The desulfurization performance of the post-stage desulfurizer is preferably 0.5 g or more, more preferably 1 g or more per 1 kW of fuel cell output.
When the sulfur adsorption amount in the pre-desulfurizer is 2 g or more, the replacement cycle of the pre-desulfurizer becomes long, so that the labor of the replacement work can be reduced. Moreover, when the sulfur content adsorption amount in the latter-stage desulfurizer is 0.5 g or more, the sulfur compound can be removed by the latter-stage desulfurizer even when the sulfur compound leaks from the former-stage desulfurizer.

In the desulfurization method of the present invention, the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0.2-2. preferable. When this ratio is 0.2 or more, the replacement cycle of the pre-desulfurizer becomes long, so that the labor of the replacement work can be reduced. In addition, when this ratio is 2 or less, the desulfurization function works effectively even if trace impurities temporarily increase.
In the present invention, the desulfurizing agent in the former stage desulfurizer needs to be periodically replaced. The period is calculated from the average value of the sulfur content in the fuel cell fuel to be used, the amount of fuel cell fuel used or the fuel cell system operating time (power generation amount).

  Examples of the fuel for the fuel cell according to the present invention include gaseous hydrocarbon compounds and liquid hydrocarbon compounds. The desulfurization method of the present invention is effective for desulfurization treatment of gaseous hydrocarbon compounds, particularly LP gas. . Examples of the gaseous hydrocarbon compound include natural gas in addition to LP gas, and examples of the liquid hydrocarbon compound include kerosene, light oil, naphtha, and gasoline.

  Usually, in liquefied petroleum gas used as fuel for fuel cells, a small amount of sulfur component not removed in the crude oil refining process and sulfur component added as an odorant, for example, mercaptans such as methyl mercaptan, carbonyl sulfide , Sulfur compounds such as hydrogen sulfide, sulfides and disulfides are included. When hydrogen for fuel cells is produced by reforming liquefied petroleum gas, it is required to reduce these sulfur compounds as much as possible in order to prevent poisoning of the catalyst as described above. Therefore, a desulfurization process is performed using a conventionally known desulfurizing agent. One type of desulfurizing agent may be used, or a combination of desulfurizing agents having different adsorption characteristics for each sulfur compound may be used. In order to maximize performance, it is desirable to use liquefied petroleum gas or the like having as low a sulfur content as possible.

  There is no restriction | limiting in particular as a zeolite type desulfurization agent (henceforth a desulfurization agent A) used by this invention, A conventionally well-known thing can be used, As this zeolite type desulfurization agent, beta ( (BEA) zeolite having a structure (β-type zeolite), zeolite having a faujasite (FAU) structure, X-type zeolite, Y-type zeolite, etc. Preferable examples include those carrying at least one metal component selected from Cu component, Ni component, Zn component, Mn component, Fe component, Co component, alkali metal component, alkaline earth metal component and rare earth metal component. it can. Here, preferred examples of the alkali metal component include potassium and sodium, examples of the alkaline earth metal component include calcium and magnesium, and examples of the rare earth metal component include lanthanum and cerium. Among these metal components, an Ag component and / or a Cu component are particularly preferable. Moreover, as a zeolite, the zeolite which has a beta (BEA) structure and the zeolite which has a faujasite (FAU) structure are preferable.

The zeolitic desulfurizing agent can be prepared by supporting the metal component on the zeolite. Specifically, an aqueous solution containing a water-soluble compound of a target metal component is brought into contact with a zeolite by a stirring method, an impregnation method, a distribution method, etc., and then washed with water and then dried and fired. It is done.
The content of the metal component in the zeolitic desulfurizing agent thus obtained is usually 1 to 40% by mass, preferably 5 to 30% by mass as a metal.

A desulfurization agent comprising at least one selected from metal elements, metal oxides and metal component-supported oxides (hereinafter sometimes referred to as desulfurization agent B) is an Ag component, a Cu component, a Ni component, a Zn component, or a Mn component. A desulfurizing agent containing at least one metal component selected from among Fe component, Co component, Al component, Si component, alkali metal component, alkaline earth metal component, and rare earth metal component is preferable. Here, preferred examples of the alkali metal component include potassium and sodium, examples of the alkaline earth metal component include calcium and magnesium, and examples of the rare earth metal component include lanthanum and cerium.
The desulfurizing agent B is preferably a porous inorganic oxide carrier on which each metal component is supported, and in particular, one in which at least one of an Ag component, a Cu component and a Ni component is supported is preferable. Each metal component can be supported by a normal supporting method such as a coprecipitation method or an impregnation method.

Examples of the porous inorganic oxide carrier include at least one selected from silica, alumina, silica-alumina, titania, zirconia, magnesia, diatomaceous earth, white clay, clay, and zinc oxide. A car alumina support is preferred.
Below, the preparation method of the Ni-Cu type | system | group desulfurization agent which uses the suitable silica alumina as a support | carrier as this desulfurization agent B is demonstrated.
In the desulfurizing agent B, from the viewpoint of desulfurization performance and mechanical strength of the desulfurizing agent, the supported total metal content (as oxide) is usually 5 to 90% by mass, and the support is 95 to 10% by mass. The range is preferable, and the total metal content (as oxide) is 40 to 90% by mass, more preferably 70 to 90% by mass when supported by the coprecipitation method, and 5 to 5 when supported by the impregnation method. It is preferable that it is 40 mass%.
First, an acidic aqueous solution or aqueous dispersion containing a nickel source, a copper source and / or an aluminum source, and a basic aqueous solution containing a silicon source and an inorganic base are prepared. Examples of the nickel source used in the former acidic aqueous solution or aqueous dispersion include nickel chloride, nickel nitrate, nickel sulfate, nickel acetate, nickel carbonate and hydrates thereof, and examples of the copper source include copper chloride, Examples thereof include copper nitrate, copper sulfate, copper acetate, and hydrates thereof. These nickel sources and copper sources may be used alone or in combination of two or more.

  Examples of the aluminum source include hydrated alumina such as pseudo boehmite, boehmite alumina, bayerite, and gypsite, and γ-alumina. Among these, pseudo boehmite, boehmite alumina, and γ-alumina are preferable. These can be used in the form of powder or sol. Moreover, this aluminum source may use 1 type, and may be used in combination of 2 or more type.

On the other hand, the silicon source used in the basic aqueous solution is not particularly limited as long as it is soluble in an alkaline aqueous solution and becomes silica upon firing. For example, orthosilicic acid, metasilicic acid, and their sodium salts A potassium salt, water glass, etc. are mentioned. These may be used singly or in combination of two or more, but water glass which is a kind of sodium silicate hydrate is particularly suitable.
The inorganic base is preferably an alkali metal carbonate or hydroxide, and examples thereof include sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide. One of these may be used, or two or more may be used in combination, but sodium carbonate alone or a combination of sodium carbonate and sodium hydroxide is particularly suitable. The amount of the inorganic base used is advantageously selected so that, when the acidic aqueous solution or aqueous dispersion and the basic aqueous solution are mixed in the next step, the mixed solution is substantially neutral to base. .
In addition, the inorganic base may be used in the total amount for the preparation of the basic aqueous solution, or a part thereof may be added to the acidic aqueous solution or the mixture of the aqueous dispersion and the basic aqueous solution in the next step. May be.

The acidic aqueous solution or aqueous dispersion thus prepared and the basic aqueous solution are each heated to about 50 to 90 ° C., and then both are mixed. After mixing, if necessary, an aqueous solution containing an inorganic base heated to 50 to 90 ° C. is further added, and the mixture is stirred at a temperature of about 50 to 90 ° C. for about 0.5 to 3 hours to react. To complete.
Next, the produced solid is sufficiently washed and separated into solid and liquid, or the produced solid is separated into solid and liquid and then washed sufficiently, and then this solid is obtained at a temperature of about 80 to 150 ° C. by a known method. Dry at a temperature of The desulfurization agent B in which the nickel component and the copper component are supported on the carrier is obtained by firing the dried product thus obtained, preferably at a temperature in the range of 200 to 400 ° C. When the firing temperature is out of the above range, it is difficult to obtain a Ni—Cu desulfurizing agent having desired performance.

Next, a method for preparing a silver-supported desulfurizing agent using alumina as a carrier suitable as the desulfurizing agent B will be described.
From the viewpoint of desulfurization performance, the supported amount of silver component is preferably in the range of 5 to 30% by mass. An aqueous solution containing a silver source is prepared. Examples of the silver source include silver nitrate, silver acetate, and silver sulfate. These silver sources may be used alone or in combination. Examples of the alumina include γ-type, φ-type, χ-type, δ-type, and η-type alumina, and γ-type, χ-type, and η-type are preferably used. A desulfurization agent in which an aqueous solution containing the silver source is impregnated and supported on alumina, dried at a temperature of about 80 to 150 ° C., and then fired at a temperature of about 200 to 400 ° C. to support a silver component on an alumina carrier. B is obtained.

The conditions for the desulfurization treatment by the desulfurization method of the present invention can be appropriately selected according to the properties of the fuel cell fuel raw material, and are not particularly limited, but the desulfurization is usually in the range of -40 to 300 ° C. Can do. When a gaseous hydrocarbon compound such as liquefied petroleum gas is used as the raw material, the temperature is about −40 to 200 ° C., the pressure is about 0 to 0.2 Mpa · G, and the gas hourly space velocity (GHSV) is 50 to 1500 h ^−1. The desulfurization treatment is preferably performed under the conditions described above. At this time, if necessary, a small amount of hydrogen may coexist. By appropriately selecting the desulfurization conditions within the above range, a gaseous hydrocarbon compound having a sulfur content of 0.2 mass ppm or less can be obtained.

Next, the method for producing hydrogen for a fuel cell according to the present invention more specifically performs steam reforming, partial oxidation reforming or autothermal reforming on the fuel for the fuel cell desulfurized as described above, and more specifically. Hydrogen for fuel cells is produced by contacting with a steam reforming catalyst, partial oxidation reforming catalyst or autothermal reforming catalyst.
There is no restriction | limiting in particular as a reforming catalyst used here, Arbitrary things can be suitably selected and used from the well-known things conventionally known as a hydrocarbon reforming catalyst. As such a reforming catalyst, for example, a catalyst in which noble metal such as nickel, zirconium, ruthenium, rhodium or platinum is supported on a suitable carrier can be exemplified. The supported metal may be one kind or a combination of two or more kinds. Of these catalysts, nickel-supported catalysts (hereinafter referred to as nickel-based catalysts) and ruthenium-supported catalysts (hereinafter referred to as ruthenium-based catalysts) are preferable. The effect of suppressing carbon deposition during quality treatment or autothermal reforming treatment is great.
The carrier for supporting the reforming catalyst preferably contains manganese oxide, cerium oxide, zirconium oxide or the like, and particularly preferably a carrier containing at least one of these.

In the case of a nickel-based catalyst, the supported amount of nickel is preferably in the range of 3 to 60% by mass based on the carrier. When the supported amount is within the above range, the activity of the steam reforming catalyst, the partial oxidation reforming catalyst or the autothermal reforming catalyst is sufficiently exhibited, and it is economically advantageous. In view of catalyst activity and economy, the more preferable amount of nickel is 5 to 50% by mass, and particularly preferably 10 to 30% by mass.
In the case of a ruthenium-based catalyst, the supported amount of ruthenium is preferably in the range of 0.05 to 20% by mass based on the carrier. When the supported amount of ruthenium is within the above range, the activity of the steam reforming catalyst, the partial oxidation reforming catalyst or the autothermal reforming catalyst is sufficiently exhibited and it is economically advantageous. Considering catalytic activity and economic efficiency, the more preferable loading of ruthenium is 0.05 to 15% by mass, and particularly preferably 0.1 to 2% by mass.

As a reaction condition in the steam reforming treatment, steam / carbon (molar ratio), which is a ratio between steam and carbon derived from the raw material, is usually selected in the range of 1.5 to 10. When the steam / carbon (molar ratio) is 1.5 or more, the amount of hydrogen generated is sufficient, and when it is 10 or less, excess water vapor is not required, so heat loss is small and hydrogen production can be performed efficiently. . From the above viewpoint, the steam / carbon (molar ratio) is preferably in the range of 1.5 to 5, and more preferably in the range of 2 to 4.
Moreover, it is preferable to perform steam reforming while maintaining the inlet temperature of the steam reforming catalyst layer at 630 ° C. or lower. When the inlet temperature is 630 ° C. or lower, the raw material is not thermally decomposed, so that carbon deposition through the carbon radicals on the catalyst or the reaction tube wall hardly occurs. From the above viewpoint, the inlet temperature of the steam reforming catalyst layer is preferably 600 ° C. or lower. The catalyst layer outlet temperature is not particularly limited, but is preferably in the range of 650 to 800 ° C. When the temperature is 650 ° C. or higher, the amount of hydrogen generated is sufficient, and when it is 800 ° C. or lower, the reaction apparatus does not need to be made of a heat-resistant material, which is economically preferable.

As reaction conditions in the partial oxidation reforming treatment, the pressure is usually normal pressure to 5 MPa · G, the temperature is 400 to 1100 ° C., the oxygen (O ₂ ) / carbon (molar ratio) is 0.2 to 0.8, and the liquid The space-time velocity (LHSV) is 0.1 to 100 h ⁻¹ .
As reaction conditions in the autothermal reforming treatment, the pressure is usually normal pressure to 5 MPa · G, the temperature is 400 to 1100 ° C., the steam / carbon (molar ratio) is 0.1 to 10, and oxygen (O ₂ ). / carbon (molar ratio) is 0.1, a liquid hourly hourly space velocity (LHSV) can be 0.1～2H ^-1, gas hourly space velocity (GHSV) conditions of 1000～100000H ^-1 is employed.
In addition, since CO obtained by the steam reforming, partial oxidation reforming or autothermal reforming adversely affects hydrogen generation, it is preferable to convert CO to CO ₂ by reaction and remove it.
Thus, according to the method of the present invention, hydrogen for fuel cells can be produced efficiently.

The fuel cell system of the present invention is characterized by using hydrogen produced as described above, and specifically comprises a raw material supply device, a desulfurization device, a reforming device, and a fuel cell. Examples of the fuel cell in this fuel cell system include a solid oxide fuel cell (SOFC), a solid polymer fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), and a molten carbonate fuel cell (MCFC). It may be.
Next, a fuel cell system using a gaseous hydrocarbon compound as a raw material for a fuel cell will be described with reference to FIG. The fuel in the gaseous hydrocarbon compound cylinder 21 is introduced into the desulfurizer 23 in the hydrogen production system 20 through the fuel supply line 22 by a natural vaporization method. The desulfurizer 23 has a first-stage desulfurizer and a second-stage desulfurizer, the first-stage desulfurizer is connected to the fuel supply line 22, and the second-stage desulfurizer is connected to the fuel introduction pipe 12, and the first-stage desulfurizer and the second-stage desulfurizer are connected in series. It is connected. The desulfurizer 23 can be filled with, for example, activated carbon, zeolite, or a metal-based adsorbent. The fuel desulfurized by the desulfurizer 23 is mixed with water from the water tank via the water pump 24 and the water supply pipe 11 and then sent to the reformer 31 together with the air sent from the air blower 35. The reformer 31 is filled with a reforming catalyst, and hydrogen is produced from the fuel mixture (mixed gas containing hydrocarbon compound, water vapor and oxygen) sent to the reformer 31 by any of the reforming reactions described above. Is manufactured. Reference numeral 38 denotes a fuel gas flow rate adjusting valve.

  The hydrogen produced in this way is reduced to the extent that the CO concentration does not reach the characteristics of the fuel cell through the CO converter 32 and the CO selective oxidizer 33. Examples of catalysts used in these reactors include an iron-chromium-based catalyst, a copper-zinc-based catalyst, or a noble metal-based catalyst for the CO converter 32, and a ruthenium-based catalyst, platinum for the CO selective oxidizer 33. Examples thereof include a system catalyst or a mixed catalyst thereof. When the CO concentration in the hydrogen produced by the reforming reaction is low, the CO converter 32 and the CO selective oxidizer 33 may not be attached.

The fuel cell 34 is an example of a polymer electrolyte fuel cell including a polymer electrolyte 34C between a negative electrode 34A and a positive electrode 34B. The hydrogen-rich gas obtained by the above method is introduced into the negative electrode side, and the air sent from the air blower 35 is introduced into the positive electrode side after performing appropriate humidification treatment if necessary (humidifier not shown). Is done.
At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds on the negative electrode side, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds on the positive electrode side, and a direct current is generated between both electrodes 34A and 34B. To do. In that case, platinum black or an activated carbon-supported Pt catalyst or Pt-Ru alloy catalyst is used for the negative electrode, and platinum black or an activated carbon-supported Pt catalyst is used for the positive electrode.

  The surplus hydrogen can be used as fuel by connecting the burner 31A of the reformer 31 to the negative electrode 34A side. Further, an air / water separator 36 is connected to the positive electrode 34B side, water and exhaust gas generated by the combination of oxygen and hydrogen in the air supplied to the positive electrode 34B side are separated, and water is used for generation of water vapor. can do. Since heat is generated in the fuel cell 34 with power generation, an exhaust heat recovery device 37 can be attached to recover the heat for effective use. The exhaust heat recovery device 37 is attached to the fuel cell 34 to deprive the heat generated during the reaction, a heat exchanger 37A, a heat exchanger 37B for exchanging the heat deprived by the heat exchanger 37A with water, 37C and a pump 37D that circulates the refrigerant to the heat exchangers 37A and 37B and the cooler 37C, and the hot water obtained in the heat exchanger 37B can be effectively used in other facilities.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Production Example 1
Ion exchange in which 36.01 kg of nickel sulfate hexahydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) and 8.52 kg of copper sulfate pentahydrate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) were heated to 80 ° C. Dissolved in 400 L of water, 720 g of pseudo boehmite (67 mass% as C-AP, Al ₂ O ₃ , produced by Catalyst Kasei Kogyo Co., Ltd.) was mixed with it to obtain Preparation A. Separately, 30.00 kg of sodium carbonate was dissolved in 400 L of ion-exchanged water heated to 80 ° C., and 9.36 kg of water glass (JIS-3, Si concentration 29 mass%, manufactured by Nippon Chemical Industry Co., Ltd.) was added. Preparation liquid B was obtained.
While maintaining the temperature of each of preparation solutions A and B at 80 ° C., both were introduced into a stainless steel reaction tube having an inner diameter of 8 mm and a length of 10 cm to obtain a precipitation cake. Thereafter, the precipitated cake was washed and filtered using 6000 L of ion-exchanged water, and the product was dried for 12 hours with a 120 ° C. blower dryer, and then calcined at 350 ° C. for 3 hours. The calcined product has a nickel content (NiO equivalent) of 64% by mass, a copper content (CuO equivalent) of 16% by mass, a silica-alumina content of 20% by mass, and a Si / Al ratio (atomic ratio) of 4. .8.
Next, 5 mass% alumina sol in terms of alumina was added to the fired product and kneaded, followed by extrusion using a die having a diameter of 1 mm. Subsequently, the drying process was performed in 120 degreeC oven for 3 hours, and also it baked at 350 degreeC for 3 hours, and obtained the desulfurization agent a.

Example 1
The following tests were performed on the fuel cell system shown in FIG. 150 g and 80 g of the desulfurizing agent a obtained in Production Example 1 were charged in a front-stage desulfurizer and a rear-stage desulfurizer made of stainless steel having a diameter of 2.5 cm, respectively. The pre-stage desulfurizer and the post-stage desulfurizer are connected in series. Carbonyl sulfide, dimethyl sulfide, dimethyl disulfide and t-mercaptan are added to desulfurized propane gas (manufactured by Takachiho Chemical Co., Ltd.) so that the sulfur concentration is 1.25 ppm by mass, respectively, under normal pressure and room temperature. The PEFC fuel cell was supplied to the pre-desulfurizer at 2 L / min, which is a supply speed corresponding to 1 kW output. It was -97 degreeC when the moisture concentration of the sulfur containing propane gas at the time of supply was measured as a dew point using the dew point meter.
After 1780 hours have passed since the supply of the sulfur-containing propane gas was started, the moisture was diluted with nitrogen gas, and this nitrogen gas was converted into sulfur-containing propane gas until the dew point measured by the dew point meter was −35 ° C. Added. After 1785 hours from the start of supply of the sulfur-containing propane gas, the sulfur content concentration at the outlet of the post-desulfurizer was measured and found to be less than 0.05 mass ppm. After 1800 hours had elapsed from the start of the supply of the sulfur-containing propane gas, the supply of the sulfur-containing propane gas was stopped, and the desulfurization agent in the former stage desulfurizer was taken out. The operation from filling the desulfurizing agent into the pre-desulfurizer, supplying the sulfur-containing propane gas, and taking out the desulfurizing agent is one cycle.

After the completion of the first cycle, 150 g of the desulfurizing agent a was continuously charged in this first-stage desulfurizer, and the same operation as described above was repeated, and the second, third, and fourth cycles were tested. In each cycle, the sulfur concentration after 1785 hours from the start of supply of the sulfur-containing propane gas was less than 0.05 ppm by mass. The total amount of desulfurizing agent used until the end of the fourth cycle is 680 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0. .53.
After the completion of the first cycle, the sulfur concentration in the desulfurizing agent taken out from the former desulfurizer was measured, and it was found that 2.0 g of sulfur was contained. Moreover, after the 4th cycle was complete | finished, when the desulfurization agent was taken out from the back | latter stage desulfurizer and the sulfur content density | concentration in a desulfurization agent was measured, it turned out that 0.5 g of sulfur content is contained. It can be seen that the sulfur adsorption amount per 1 kW of the fuel cell output is 2 g or more in the front-stage desulfurizer and 0.5 g or more in the rear-stage desulfurizer.

Comparative Example 1
In Example 1, the amount of the desulfurizing agent a in the latter-stage desulfurizer was set to 20 g, and at the end of each cycle, the used desulfurizer a in the latter-stage desulfurizer was replaced with 20 g of a new desulfurizer a. The test was conducted in the same manner as in Example 1.
In each cycle, the sulfur concentration after 1785 hours from the start of supply of the sulfur-containing propane gas was 1.3 ppm by mass in the first cycle, 1.0 ppm by mass in the second cycle, and 1.5 ppm in the third cycle. The mass ppm was 1.2 mass ppm at the fourth cycle. The total amount of desulfurizing agent used until the end of the fourth cycle is 680 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0. .13.
After the first cycle was completed, the desulfurization agent was taken out from the pre-stage desulfurizer and the post-stage desulfurizer, and the concentration of sulfur in the desulfurizer was measured. It was found that the desulfurizing agent contained 0.1 g of sulfur.

Example 2
The following tests were performed on the fuel cell system shown in FIG. 150 g and 80 g of the desulfurizing agent a obtained in Production Example 1 were charged in a front-stage desulfurizer and a rear-stage desulfurizer made of stainless steel having a diameter of 2.5 cm, respectively. The pre-stage desulfurizer and the post-stage desulfurizer are connected in series. Carbonyl sulfide, dimethyl sulfide, dimethyl disulfide and t-mercaptan are added to desulfurized propane gas (manufactured by Takachiho Chemical Co., Ltd.) so that the sulfur concentration is 1.25 ppm by mass, and supplied at normal pressure and room temperature. The pre-desulfurizer was supplied at a rate of 2 L / min.
After 1780 hours have passed since the supply of the sulfur-containing propane gas was started, carbonyl sulfide, dimethyl sulfide, dimethyl disulfide and t-mercaptan were added to the sulfur-containing propane gas, and the respective sulfur content concentrations were 2.5. It adjusted so that it might become mass ppm. After 1785 hours from the start of supply of the sulfur-containing propane gas, the sulfur content concentration at the outlet of the post-desulfurizer was measured and found to be less than 0.05 mass ppm. After 1800 hours had elapsed from the start of the supply of the sulfur-containing propane gas, the supply of the sulfur-containing propane gas was stopped, and the desulfurization agent in the former stage desulfurizer was taken out. The operation from filling the desulfurizing agent into the pre-desulfurizer, supplying the sulfur-containing propane gas, and taking out the desulfurizing agent is one cycle.
After the completion of the first cycle, 150 g of the desulfurizing agent a was continuously charged in this first-stage desulfurizer, and the same operation as described above was repeated, and the second, third, and fourth cycles were tested. In each cycle, the sulfur concentration after 1785 hours from the start of supply of the sulfur-containing propane gas was less than 0.05 ppm by mass. The total amount of desulfurizing agent used until the end of the fourth cycle is 680 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0. .53.

Comparative Example 2
In Example 2, the amount of the desulfurizing agent a in the latter-stage desulfurizer was set to 20 g, and the used desulfurizer a in the latter-stage desulfurizer was replaced with 20 g of a new desulfurizer a at the end of each cycle. The test was conducted in the same manner as in Example 2.
In each cycle, the sulfur concentration after 1785 hours from the start of supply of the sulfur-containing propane gas was 2.5 mass ppm in the first cycle, 2.1 mass ppm in the second cycle, and 2.3 in the third cycle. The mass ppm was 2.0 mass ppm at the fourth cycle. The total amount of desulfurizing agent used until the end of the fourth cycle is 680 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0. .13.
After the completion of the first cycle, the desulfurization agent was taken out from the pre-stage desulfurizer and the post-stage desulfurizer, and the concentration of sulfur in the desulfurization agent was measured. This desulfurization agent was found to contain 0.1 g of sulfur.

Example 3
The following tests were performed on the fuel cell system shown in FIG. 150 g and 240 g of the desulfurizing agent a obtained in Production Example 1 were charged in a front-stage desulfurizer and a rear-stage desulfurizer made of stainless steel having a diameter of 2.5 cm, respectively. The pre-stage desulfurizer and the post-stage desulfurizer are connected in series. Carbonyl sulfide, dimethyl sulfide, dimethyl disulfide and t-mercaptan are added to desulfurized propane gas (manufactured by Takachiho Chemical Co., Ltd.) so that the sulfur concentration is 1.25 ppm by mass, and supplied at normal pressure and room temperature. The pre-desulfurizer was supplied at a rate of 2 L / min.
After 2780 hours have passed since the start of the supply of the sulfur-containing propane gas, carbonyl sulfide, dimethyl sulfide, dimethyl disulfide and t-mercaptan were added to the sulfur-containing propane gas, and each sulfur content concentration was 2.5. It adjusted so that it might become mass ppm. After 2785 hours from the start of supply of the sulfur-containing propane gas, the sulfur content concentration at the outlet of the post-stage desulfurizer was measured and found to be less than 0.05 mass ppm. After 2800 hours had elapsed from the start of the supply of the sulfur-containing propane gas, the supply of the sulfur-containing propane gas was stopped, and the desulfurization agent in the former stage desulfurizer was taken out. The operation from filling the desulfurizing agent into the pre-desulfurizer, supplying the sulfur-containing propane gas, and taking out the desulfurizing agent is one cycle.
After the completion of the first cycle, 150 g of the desulfurizing agent a was continuously charged in this first-stage desulfurizer, and the same operations as described above were repeated, and the second to eighth cycle tests were performed. In each cycle, the concentration of sulfur after 2800 hours from the start of supply of the sulfur-containing propane gas was less than 0.05 ppm by mass. The total amount of desulfurizing agent used up to the end of the eighth cycle is 1440 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-stage desulfurizer is 1. .6.

Example 4
The following tests were performed on the fuel cell system shown in FIG. 150 g and 30 g of the desulfurizing agent a obtained in Production Example 1 were charged in a front-stage desulfurizer and a rear-stage desulfurizer made of stainless steel having a diameter of 2.5 cm, respectively. The pre-stage desulfurizer and the post-stage desulfurizer are connected in series. Carbonyl sulfide, dimethyl sulfide, dimethyl disulfide, and t-mercaptan are added to desulfurized propane gas (manufactured by Takachiho Chemical Industry Co., Ltd.) so that the sulfur concentration is 1.25 ppm by mass, and supplied at normal pressure and room temperature. The pre-desulfurizer was supplied at a rate of 2 L / min. It was -97 degreeC when the moisture concentration of the sulfur containing propane gas at the time of supply was measured as a dew point using the dew point meter.
After 1780 hours have passed since the supply of the sulfur-containing propane gas was started, the moisture was diluted with nitrogen gas, and this nitrogen gas was converted into sulfur-containing propane gas until the dew point measured by the dew point meter was −35 ° C. Added. After 1785 hours from the start of supply of the sulfur-containing propane gas, the sulfur content concentration at the outlet of the post-desulfurizer was measured and found to be less than 0.05 mass ppm. After 1800 hours had elapsed from the start of the supply of the sulfur-containing propane gas, the supply of the sulfur-containing propane gas was stopped, and the desulfurization agent in the former stage desulfurizer was taken out. The operation from filling the desulfurizing agent into the pre-desulfurizer, supplying the sulfur-containing propane gas, and taking out the desulfurizing agent is one cycle.
After the completion of the first cycle, 150 g of the desulfurizing agent a was continuously charged in this first-stage desulfurizer, and the same operation as described above was repeated to carry out the second cycle test. In the second cycle, the sulfur concentration after 1785 hours from the start of supply of the sulfur-containing propane gas was less than 0.05 ppm by mass. The total amount of desulfurizing agent used up to the end of the second cycle is 330 g, and the ratio (b / a) of the mass (b) of the desulfurizing agent in the post-desulfurizer to the mass (a) of the desulfurizing agent in the pre-desulfurizer is 0. .2.

  According to the desulfurization method of the present invention, the sulfur content of the fuel cell fuel can be efficiently removed to a very low concentration with a minimum amount of the desulfurization agent, and the temporary impurities and the sulfur content concentration of the fuel can be reduced. In addition, since leakage of sulfur compounds to the downstream side can be controlled, poisoning due to sulfur in the reformer catalyst and the fuel cell catalyst mounted in the fuel cell system can be prevented. Hydrogen for batteries can be produced efficiently.

It is a schematic flowchart which shows an example of the fuel cell system of this invention.

Explanation of symbols

1: Fuel cell system 11: Water supply pipe 12: Fuel introduction pipe 20: Hydrogen production system 21: Gaseous hydrocarbon compound cylinder 22: Fuel supply line 23: Desulfurizer 24: Water pump 31: Reformer 31A: Reformation Burner 32: CO converter 33: CO selective oxidizer 34: Fuel cell 34A: Fuel cell negative electrode 34B: Fuel cell positive electrode 34C: Fuel cell polymer electrolyte 35: Air blower 36: Air / water separator 37: Waste heat recovery Device 37A: Heat exchanger 37B: Heat exchanger 37C: Cooler 37D: Refrigerant circulation pump 38: Flow rate adjusting valve

Claims (14)

  A method of desulfurizing fuel for a fuel cell using a desulfurization apparatus that is disposed in a fuel cell system and includes a first-stage desulfurizer and a second-stage desulfurizer, and periodically replacing a desulfurization agent in the first-stage desulfurizer, A method for desulfurizing a fuel for a fuel cell, comprising using a desulfurizing agent in a post-desulfurizer semipermanently.   2. The fuel cell according to claim 1, wherein the ratio (b / a) of the mass (b) of the desulfurizer in the post-desulfurizer to the mass (a) of the desulfurizer in the pre-stage desulfurizer is 0.2-2. Fuel desulfurization method.   The method for desulfurizing a fuel for a fuel cell according to claim 1 or 2, wherein the adsorption amount of sulfur per 1 kW of fuel cell output is 2 g or more in the former stage desulfurizer and 0.5 g or more in the latter stage desulfurizer.   The fuel cell fuel desulfurization method according to any one of claims 1 to 4, wherein the fuel cell fuel is a gaseous hydrocarbon compound.   The desulfurizing agent charged in the first-stage desulfurizer and the second-stage desulfurizer is a desulfurization agent having an ability to adsorb carbonyl sulfide, hydrogen sulfide, mercaptans, sulfides, and disulfides. Fuel cell fuel desulfurization method.   The desulfurizing agent is (A) a desulfurizing agent containing zeolite and / or (B) a desulfurizing agent containing at least one selected from metal elements, metal oxides and metal component-supported oxides. A method for desulfurizing a fuel cell fuel according to claim 1.   The fuel cell fuel desulfurization method according to claim 6, wherein the zeolite is a zeolite having a beta (BEA) structure and / or a zeolite having a faujasite (FAU) structure.   The desulfurizing agent containing zeolite is selected from the group consisting of Ag component, Cu component, Ni component, Zn component, Mn component, Fe component, Co component, alkali metal component, alkaline earth metal component and rare earth metal component together with zeolite. The method for desulfurizing a fuel for a fuel cell according to claim 6 or 7, comprising at least one metal component.   A desulfurization agent containing at least one selected from metal elements, metal oxides and metal component-supported oxides is an Ag component, Cu component, Ni component, Zn component, Mn component, Fe component, Co component, Al component, Si The fuel cell fuel desulfurization method according to any one of claims 6 to 8, comprising at least one metal component selected from the group consisting of a component, an alkali metal component, an alkaline earth metal component, and a rare earth metal component.   A method for producing hydrogen for a fuel cell, comprising reforming the fuel for a fuel cell desulfurized by the desulfurization method according to claim 1.   The method for producing hydrogen for a fuel cell according to claim 10, wherein the reforming is steam reforming, partial oxidation reforming, or autothermal reforming.   The method for producing hydrogen for a fuel cell according to claim 10 or 11, wherein the catalyst used for reforming is a ruthenium catalyst or a nickel catalyst.   The method for producing hydrogen for a fuel cell according to claim 12, wherein the carrier component of the catalyst used for reforming contains at least one selected from manganese oxide, cerium oxide, and zirconium oxide. A fuel cell system using hydrogen produced by the method according to claim 10.

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