JP2005093214A - Method of supplying liquefied petroleum gas to hydrogen production system for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of supplying liquefied petroleum gas having low fluctuation in composition, and stable sulfur content in a hydrogen producing system, and to provide a superior fuel cell system equipped with a fuel cell using the hydrogen gas generated at the hydrogen production system. <P>SOLUTION: The hydrogen production system has (A) a liquefied petroleum gas supply side container, and (B) a preparatory side container thereof, storing liquefied petroleum gas as a fuel supply means. The method of supplying the liquefied petroleum gas to the hydrogen production system of the fuel cell is carried out, by continuously supplying the liquefied liquid petroleum gas to the hydrogen production system, by switching the fuel supplying means from the (A) container to the (B) container, while the pressure-drop of the (A) container, where the switching is carried out before the pressure of the container (A) becomes lower than 0.11 MPaG. This method is utilized in the fuel cell system. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for supplying a liquefied petroleum gas having a stable sulfur content to a hydrogen production system for a fuel cell.

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 natural gas as a raw material, further petroleum liquefied petroleum gas, naphtha, The use of petroleum-based hydrocarbons such as kerosene has been studied.
When producing hydrogen using these gaseous or liquid hydrocarbons, there is generally a method of treating the hydrocarbons by partial oxidation reforming, autothermal reforming or steam reforming in the presence of a reforming catalyst. It is used.
When producing hydrogen for fuel cells by reforming liquefied petroleum gas or city gas, it is required to reduce the sulfur content in the gas in order to suppress poisoning of the reforming catalyst.
Moreover, when propylene, butene, etc. are used as a raw material for petrochemical products, it is required to reduce the sulfur content in order to prevent poisoning of the catalyst.
In order to maximize the performance of the desulfurizing agent used, it is desirable to use liquefied petroleum gas or the like having as low a sulfur content as possible.

  When the sulfur compounds in the liquefied petroleum gas are analyzed in detail, in general, in addition to methyl mercaptan and carbonyl sulfide, dimethyl sulfide (DMS), t-butyl mercaptan (TBM), and methyl ethyl sulfide are added as odorants. (MES) and the like are included. Various adsorbents for adsorbing and removing such a sulfur content from a fuel gas such as liquefied petroleum gas are known (see, for example, Patent Documents 1 to 4). However, some of these adsorbents exhibit high desulfurization performance at about 150 to 300 ° C., but the actual condition is that the desulfurization performance at room temperature is not always satisfactory.

In addition, when liquefied gas such as liquefied petroleum gas is supplied to the fuel cell hydrogen production system by the natural vaporization method, the liquefied petroleum gas is temporarily stored in a container and supplied from the container to the system. As the amount of gas decreases, the composition of the gas supplied from the container varies. When supplying the liquefied petroleum gas from two or more containers, an automatic switching device is used. However, a widely used type is where the pressure of the container supplying the gas is reduced to 0.1 MPaG. Switch to spare container. However, when attention is paid to the sulfur concentration in the supply gas, the concentration increases from several mass ppm at the beginning of supply to several tens mass ppm when the pressure of the container is reduced to 0.1 MPaG.
Therefore, when hydrogen is produced from liquefied petroleum gas as a fuel for a stationary fuel cell, it undergoes desulfurization and reforming processes as described above. However, the productivity of the fuel cell hydrogen production system is improved and the quality is stabilized. In order to achieve this, it is desirable that the composition change of the liquefied gas as a raw material is small.

JP 2001-286753 A JP 2001-305123 A Japanese Patent Laid-Open No. 2-302496 (page 2) JP 2001-123188 A (page 3)

  Under such circumstances, the present invention provides a method for supplying a liquefied petroleum gas in which the composition variation of the liquefied petroleum gas being supplied is small and the sulfur content is stable when the liquefied petroleum gas is supplied to the fuel cell hydrogen production system. Is intended to provide. It is another object of the present invention to provide an excellent fuel cell system having a fuel cell that uses hydrogen gas produced by the hydrogen production system as fuel.

  As a result of intensive studies to achieve the above object, the inventors of the present invention switched to a preliminary container before the pressure of the container on the liquefied petroleum gas supply side dropped below a specific pressure, It has been found that by supplying to a production system, liquefied petroleum gas having a small composition change and a stable sulfur content can be supplied. The present invention has been completed based on such findings.

That is, the present invention
(1) As a fuel supply means, it has (A) a liquefied petroleum gas supply side container and (B) its spare side container which contain liquefied petroleum gas, and (A) B) By switching to the container, when continuously supplying the fuel cell hydrogen production system, the switching is performed before (A) the pressure of the container is less than 0.11 MPaG. A method for supplying liquefied petroleum gas to a hydrogen production system for fuel cells,
(2) (A) The liquefied petroleum gas supply method to the fuel cell hydrogen production system according to (1), wherein the pressure in the container is switched in the range of 0.13 to 0.3 MPaG.
(3) The liquefied petroleum gas supply method to the fuel cell hydrogen production system according to (1) and (2) above, further comprising a desulfurization means for removing sulfur from the liquefied petroleum gas on the outlet side of the fuel supply means, and (4) A fuel cell system using the liquefied petroleum gas supply method of (1) to (3),
Is to provide.

  According to the present invention, fluctuations in sulfur concentration in liquefied petroleum gas can be suppressed to a small level, and by adding desulfurization means, a liquefied petroleum gas having a lower sulfur concentration and being stable can be provided.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic process diagram showing an embodiment of a method for supplying liquefied petroleum gas according to the present invention. 1 is a supply side container (A), 2 is a backup side container (B), 3 is a flow meter, 4 is an automatic switching valve, 5 is a flow meter, 6 is a three-way valve, 7 is a sulfur content measuring means before desulfurization treatment , 8 is a three-way valve, 9 is a desulfurizer containing a desulfurizing agent, 10 is a three-way valve, 11 is a sulfur content measuring means after desulfurization treatment, 12 is an outlet to the next process, and 13 is an outlet to the next process. .
Although the container shown in FIG. 1 is a combination of two, the number is not particularly limited as long as it is two or more.

First, liquefied petroleum gas is supplied from the container 1 on the supply side (A), but before the pressure in the container (A) 1 becomes less than 0.11 MPaG (MPaG is the gauge pressure expressed in MPa). It is necessary to switch to the spare side container 2 by the automatic switching valve 4 (B).
By switching, the container (B) 2 becomes a supply side container, and liquefied petroleum gas is supplied from the container (B) 2. Accordingly, the container (A) 1 is changed to a spare side container. By repeating this change alternately, liquefied petroleum gas can be continuously supplied to the fuel cell hydrogen supply system.
The container containing the liquefied petroleum gas is preferably used in a temperature range of −20 ° C. to 50 ° C., more preferably 0 ° C. to 40 ° C.
If the operating temperature is lower than −20 ° C., the pressure of the liquefied petroleum gas container is lowered, so that the liquefied petroleum gas in the container cannot be sufficiently consumed. It is.
The pressure range for switching is not particularly limited as long as it is 0.11 MPaG or more, but is usually preferably in the range of 0.13-0.3 MPaG, more preferably in the range of 0.15-0.25 MPaG.
By setting the switching pressure within the above range, it is possible to supply liquefied petroleum gas having a small composition variation and low sulfur content, and the amount of residual liquefied petroleum gas in the container does not increase.

Subsequently, the liquefied petroleum gas supplied to the container (A) 1 or the container (B) 2 can measure the sulfur content before the desulfurization treatment by the sulfur content measuring means 7. If the sulfur content is usually 0.05 mass ppm or less, the liquefied gas can be supplied to the fuel cell hydrogen supply system from 12 which is the outlet of the next step.
Next, when the sulfur content of the liquefied petroleum gas exceeds 0.05 ppm by mass, desulfurization treatment is performed by the desulfurizer 9 filled with a desulfurizing agent as desulfurization means. The sulfur content after the desulfurization treatment can be measured by the sulfur content measuring means 11 in the liquefied petroleum gas subjected to the desulfurization treatment. The liquefied petroleum gas desulfurized to a sulfur content of generally 0.05 mass ppm or less is supplied to the fuel cell hydrogen supply system from the outlet 13 of the next process.

As described above, the load on the desulfurization agent can be reduced because there is little variation in the sulfur content contained in the liquefied petroleum gas in the step before entering the desulfurization means.
The desulfurization agent used in the desulfurization means in the present invention is not particularly limited, and those conventionally used as a desulfurization agent, for example, activated carbon, zeolite, or a metal oxide-based adsorbent are used. These desulfurization agents may be used alone or in combination of two or more.
As desulfurization conditions, the normal temperature is selected in the range of 0 to 200 ° C., and the GHSV (gas hourly space velocity) is selected in the range of 200 to 60,000 h ⁻¹ , preferably 400 to 4,000 h ^−1. .

Next, the desulfurized liquefied petroleum gas is brought into contact with a partial oxidation reforming catalyst, an autothermal reforming catalyst, or a steam reforming catalyst to perform partial oxidation reforming, autothermal reforming, or steam reforming, respectively. Manufacturing.
In this reforming treatment, the concentration of the sulfur compound in the desulfurized hydrocarbon-containing gas is preferably 0.05 mass ppm or less, and particularly preferably 0.01 mass ppm or less from the viewpoint of the life of each reforming catalyst.
The partial oxidation reforming is a method for producing hydrogen by a partial oxidation reaction of hydrocarbons, and in the presence of a partial oxidation reforming catalyst, usually a reaction pressure of normal pressure to 5 MPa, a reaction temperature of 400 to 1,100 ° C. The reforming reaction is carried out under the conditions of GHSV 1,000 to 100,000 h ⁻¹ and oxygen (O ₂ ) / carbon ratio 0.2 to 0.8.
Autothermal reforming is a method in which partial oxidation reforming and steam reforming are combined, and usually in the presence of an autothermal reforming catalyst, reaction pressure is normal pressure to 5 MPa, reaction temperature is 400 to 1,100. The reforming reaction is performed under the conditions of ° C., oxygen (O ₂ ) / carbon ratio of 0.1 to 1, steam / carbon ratio of 0.1 to 10, and GHSV of 1,000 to 100,000 h ⁻¹ .

Furthermore, steam reforming is a method for producing hydrogen by bringing steam into contact with a hydrocarbon, usually in the presence of a steam reforming catalyst, at a reaction pressure of normal pressure to 3 MPa, a reaction temperature of 200 to 900 ° C., steam. The reforming reaction is performed under the conditions of / carbon ratio of 1.5 to 10 and GHSV of 1,000 to 100,000 h ⁻¹ .
In the present invention, the partial oxidation reforming catalyst, the autothermal reforming catalyst, and the steam reforming catalyst can be appropriately selected from conventionally known catalysts, but are particularly ruthenium-based and nickel-based. System catalysts are preferred. Moreover, as a support | carrier of these catalysts, the support | carrier containing at least 1 type chosen from manganese oxide, a cerium oxide, and a zirconia can be mentioned preferably. The support may be a support made of only these metal oxides, or may be a support made by adding the above metal oxide to another refractory porous inorganic oxide such as alumina.

The second invention of the present application is a fuel cell system comprising a reformer and a fuel cell using hydrogen gas produced by the reformer as a fuel, and will be described in detail with reference to FIG. explain.
The fuel desulfurized by the desulfurizer 9 shown in FIG. 1 and passed through the outlet 13 to the next process is mixed with water from a water tank (not shown) through the water pump 20 and then introduced into the vaporizer 16 to be vaporized. Then, it is mixed with the air sent out from the air blower 25 and fed into the reformer 21. The reformer 21 is filled with the above-described reforming catalyst, and the above-described reforming reaction is performed from the fuel mixture (a gas mixture containing liquefied petroleum gas, water vapor, and oxygen) fed into the reformer 21. To produce hydrogen.

  The hydrogen or synthesis gas 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 22 and the CO selective oxidizer 23. Examples of the catalyst 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 22, and a CO selective oxidizer 23 for a ruthenium-based catalyst, Examples thereof include platinum-based catalysts and mixed catalysts thereof.

The fuel cell 24 is a solid polymer fuel cell having a polymer electrolyte 24C between a negative electrode 24A and a positive electrode 24B. The hydrogen-rich gas obtained by the above method is introduced into the negative electrode side, and the air sent from the air blower 25 is introduced into the positive electrode side after 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 24A and 24B. To do. In that case, platinum black or a Pt catalyst supported on activated carbon or a Pt—Ru alloy catalyst is used for the negative electrode, and platinum black or a Pt catalyst supported on activated carbon is used for the positive electrode.

  The excess hydrogen can be used as fuel by connecting the burner 21A of the reformer 21 to the negative electrode 24A side. Further, an air / water separator 26 is connected to the positive electrode 24B side, water and exhaust gas generated by the combination of oxygen and hydrogen in the air supplied to the positive electrode 24B side are separated, and water is used for generation of water vapor. can do. Since heat is generated in the fuel cell 24 with power generation, an exhaust heat recovery device 27 can be attached to recover the heat for effective use. The exhaust heat recovery device 27 is attached to the fuel cell 24 and deprives heat generated during the reaction, a heat exchanger 27B for exchanging heat deprived by the heat exchanger 27A with water, The heat exchanger 27C and a pump 27D that circulates the refrigerant to the heat exchangers 27A and 27B and the cooler 27C are provided, and the hot water obtained in the heat exchanger 27B 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.
Example 1
A switch having a replenishment start pressure of 0.15 MPaG was manufactured (switch A).
Gas was supplied at 240 g / h via the switch A from two containers filled with liquefied petroleum gas having a sulfur concentration of 4.9 ppm by mass in a new container. The supply of gas from each container is monitored with a flow meter, and a commercial desulfurization agent (product made by Zude Chemie Catalysts Co., Ltd., from the start of the gas supply from the backup side container until the supply of gas from the use side container ceases) Name G-132B) Desulfurization was performed by flowing gas into a reaction tube filled with 20 cm ³ . During this time, the sulfur concentration in the feed gas before the desulfurization treatment and the sulfur concentration after the desulfurization treatment were analyzed. The results are shown in Table 1.

Example 2
A switch with a replenishment start pressure of 0.25 MPaG was manufactured (switch B).
Gas was supplied at 240 g / h from two containers filled with liquefied petroleum gas having a sulfur concentration of 4.9 mass ppm into a new container via the switch B. The supply of gas from each container is monitored with a flow meter, and a commercial desulfurization agent (product made by Zude Chemie Catalysts Co., Ltd., from the start of the gas supply from the backup side container until the supply of gas from the use side container ceases) Name G-132B) Desulfurization was performed by flowing gas into a reaction tube filled with 20 cm ³ . During this time, the sulfur concentration in the feed gas before the desulfurization treatment and the sulfur concentration after the desulfurization treatment were analyzed. The results are shown in Table 1.

Comparative Example 1
Using a switch (switch C) with a replenishment start pressure of 0.10 MPaG, 240 g / h from two containers filled with liquefied petroleum gas having a sulfur concentration of 4.9 mass ppm into the new container via switch C Gas was supplied. The supply of gas from each container is monitored with a flow meter, and a commercial desulfurization agent (product made by Zude Chemie Catalysts Co., Ltd., from the start of the gas supply from the backup side container until the supply of gas from the use side container ceases) Name G-132B) Desulfurization was performed by flowing gas into a reaction tube filled with 20 cm ³ . During this time, the sulfur concentration in the feed gas and the sulfur concentration in the outlet gas after desulfurization were analyzed. The results are shown in Table 1.

The following can be seen from Table 1.
When the pressure on the supply side container does not become less than 0.11 MPaG, that is, when the pressure on the use side container is 0.11 MPaG or more and preferably in the range of 0.30 MPaG or less, it is As a result, the liquefied petroleum gas with a stable sulfur content can be supplied to the hydrogen production system for fuel cells in the next process and the desulfurizing agent can be supplied. The load can be reduced.

It is a schematic process drawing which shows one embodiment of the liquefied petroleum gas supply method of this invention. It is a schematic process drawing which shows one embodiment of the fuel cell system of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supply side container 2 Spare side container 3 Flowmeter 4 Automatic change-over valve 5 Flowmeter 6 Three-way valve 7 Sulfur content measuring means before desulfurization process 8 Three-way valve 9 Desulfurizer 10 Three-way valve 11 Sulfur content measuring means after desulfurization process 12 Outlet to next process 13 Outlet to next process 14 Fuel cell system 15 Hydrogen production system 16 Vaporizer 17 Water supply pipe 18 Fuel introduction pipe 19 Connection pipe 20 Water pump 21 Reformer 21A Reformer burner 22 CO conversion 23 CO selective oxidizer 24 Fuel cell 24A Fuel cell negative electrode 24B Fuel cell positive electrode 24C Fuel cell polymer electrolyte 25 Air blower 26 Air / water separator 27 Waste heat recovery device 27A Heat exchanger 27B Heat exchanger 27C Cooler 27D Refrigerant circulation pump

Claims (4)

As a fuel supply means, it has (A) a liquefied petroleum gas supply side container and (B) its spare side container, which contain liquefied petroleum gas. In order to supply continuously to the hydrogen production system for fuel cells, the switching is performed before (A) the pressure in the container does not drop below 0.11 MPaG. To supply liquefied petroleum gas to industrial hydrogen production systems. (A) The method for supplying liquefied petroleum gas to a hydrogen production system for a fuel cell according to claim 1, wherein the pressure in the container is switched in the range of 0.13 to 0.3 MPaG. The method for supplying liquefied petroleum gas to a fuel cell hydrogen production system according to claim 1 or 2, further comprising a desulfurization means for removing sulfur from the liquefied petroleum gas on the outlet side of the fuel supply means. The fuel cell system using the liquefied petroleum gas supply method of any one of Claims 1-3.

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