JPH08217403A - Reformer - Google Patents

Abstract

PURPOSE: To provide a low-cost reformer effective for preventing the deposition of carbon in the steam-reforming process of a fuel and suppressing the increase in the methane content of the reformed gas. CONSTITUTION: This reformer produces a hydrogen-rich gas by the steam- reforming reaction of a fuel with steam on a reforming catalyst filled in a reforming tube 2. The catalyst layer in the reforming tube 2 has a double-layer structure consisting of a noble metal catalyst layer 11 placed at the inlet side of the feedstock gas 1 composed of steam and fuel and a base metal catalyst layer 12 placed at the outlet side of the reformed gas 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reformer for producing a hydrogen-rich gas by reacting fuel with steam.

[0002]

2. Description of the Related Art The outline of a conventional reformer will be described with reference to FIG. In FIG. 2, the raw material gas 1 consisting of preheated fuel gas and steam is supplied to the reforming pipes 2 installed in a predetermined number according to the design value of the hydrogen generation amount inside the reforming device, and the inside of the reforming pipe 2 is supplied. The catalyst layer 3 is used for steam reforming of the fuel to generate hydrogen. The heat of reaction required for the steam reforming reaction, which is an endothermic reaction, is obtained by burning the fuel gas 5 and the air 6 in the reformer burner 4 and converting the high temperature combustion gas 7 into the reforming pipe 2
Flow from the gas outlet side of the catalyst layer 3 to the gas inlet side,
It is supplied by exchanging heat with the catalyst layer 3. The temperature of the catalyst layer 3 is about 400 ° C. at the gas inlet and about 70 at the gas outlet.
It is 0 ° C. and has a temperature distribution from the gas inlet to the gas outlet. The catalyst layer 3 is usually filled with one type of steam reforming catalyst having catalytic activity for the steam reforming reaction in each fuel. The catalyst is in the form of particles to increase the effective surface area. For steam reforming of hydrocarbon fuels such as methane and propane, application of a noble metal-based catalyst such as a Ru-based catalyst has been studied in recent years because it has a high catalytic activity and hardly causes carbon deposition. However, a noble metal catalyst such as a Ru-based catalyst is more expensive than a base metal catalyst such as a Ni-based catalyst that has been widely used, and when a noble metal-based catalyst is used, a methanation represented by the following formula is used. There is a problem that methane is often generated by the reaction and the methane concentration in the reformed gas is high.

[0003]

[Equation 1]

Using a normal pressure fixed bed flow type reaction apparatus whose configuration is shown in FIG. 3, Ni-Al ₂ O ₃ which is a base metal catalyst is used.
FIG. 6 shows the reformed gas composition excluding steam when the catalyst and the Ru—Al ₂ O ₃ catalyst, which is a noble metal-based catalyst, are filled in the reactor 78 to perform steam reforming of propane.

The atmospheric fixed bed flow reactor comprises a gas supply section, a steam supply section and a reaction section. The gas supply unit includes pipes for supplying propane 68, hydrogen 51, and nitrogen 52, stop valve 57, 58, 70,
Regulator 55, 56, 69, pressure gauge 59, 60, 7
1, a check valve 64, 65, 66, 67, a thermal mass flow controller 72, and float type flow meters 53 and 54. The flow rate of propane 68 is controlled by the Samar mass flow controller 72, and the flow rate of hydrogen 51 and nitrogen 52 is controlled by the float type flow meters 53 and 54. The steam supply unit includes a balance 63, a water tank 62, a pump 61, a vaporizer 73, and a temperature control unit 74. A predetermined amount of water is sent from the water tank 62 to the carburetor 73 by the pump 61 to generate water vapor. In the vaporizer 73, steam and propane 68 are mixed. The vaporizer 73 raises the temperature in advance to a predetermined temperature by the temperature control unit 74 before supplying the water to vaporize the water. The reaction part includes a heater 76 for keeping heat of the pipe, an electric furnace 77, and a reactor 7.
8, trap 79, temperature control unit 75 and 8
It consists of 1. The reactor 78 is heated in the electric furnace 77 to a temperature required for the steam reforming reaction. The temperature control unit 75 controls the temperature of the electric furnace 77. In addition, the pipe has a heater 7 up to a predetermined temperature in order to prevent condensation of water vapor.
The temperature is raised at 6. The steam reforming of propane 68 is performed inside the reactor 78 filled with the catalyst to generate hydrogen. 80 is drainage and 82 is exhaust.

In the steam reforming experiment using the atmospheric pressure fixed bed flow reactor, the temperature of the catalyst layer was controlled at a constant temperature of 500 ° C. in the electric furnace 77 in order to facilitate the analysis. From FIG. 6, as described above, when the Ni—Al ₂ O ₃ catalyst was used, the methane concentration in the reformed gas was low, but carbon deposition occurred, while the Ru—Al ₂ O ₃ catalyst was used. It can be seen that when carbon is used, carbon deposition does not occur, but the methane concentration in the reformed gas is about 5% higher than that of the Ni-Al ₂ O ₃ catalyst, and the hydrogen concentration is relatively low. In a propane steam reforming experiment using an atmospheric fixed bed flow reactor, the packed catalyst volume was 11.4 cm ³ , the steam carbon ratio, which is the ratio of steam to carbon in the fuel, was 3.0, and the propane Supply amount 44.8 cm ³ · min
^-1 , and the Ni-Al ₂ O ₃ catalyst contains a cylindrical catalyst having a diameter of 4.6 mm and a height of 4.4 mm containing 12 wt% of Ni, and the Ru-Al ₂ O ₃ catalyst contains 1 wt% of Ru. A spherical catalyst having a diameter of 5.5 mm was used.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and prevents carbon deposition during steam reforming of fuel and suppresses an increase in the amount of methane produced in the reformed gas. An object is to provide a reformer at low cost.

[0008]

In order to achieve the above object, the reforming apparatus of the present invention provides a steam reforming reaction by supplying a fuel and steam and performing a steam reforming reaction on a reforming catalyst filled in a reforming tube. In a reformer that produces a hydrogen-rich gas, the catalyst layer inside the reforming tube has a two-layer structure, a precious metal catalyst layer is provided on the inlet side of the raw material gas consisting of steam and fuel, and on the outlet side of the reformed gas. It is characterized in that a base metal catalyst layer is provided. Further, the reforming apparatus of the present invention is characterized in that the noble metal catalyst layer is a Ru catalyst layer and the base metal catalyst layer is a Ni catalyst layer.

[0009]

According to the present invention, the catalyst layer inside the reforming tube of the reformer has a two-layer structure, and the noble metal catalyst layer is provided on the inlet side of the raw material gas consisting of fuel and water vapor. The main feature is to provide a base metal catalyst layer on the outlet side. It differs from the conventional technique in that the catalyst layer inside the reforming tube is divided into two layers, a noble metal catalyst layer and a base metal catalyst layer, and the noble metal catalyst layer is provided on the gas inlet side. By having a two-layer structure, the steam reforming reaction that causes carbon precipitation occurs selectively in the noble metal catalyst layer near the gas inlet, so that carbon precipitation is suppressed, and in the base metal catalyst layer, the methanation reaction occurs. Since the production of methane is suppressed and the decomposition of methane produced by the methanation reaction is promoted, the prevention of carbon deposition and the suppression of the increase in methane concentration in the reformed gas can be achieved at the same time.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. One embodiment of the present invention is shown in FIG. 2 in FIG.
Those having the same reference numerals as those in FIG. The conventional reformer shown in FIG. 2 has a structure in which the catalyst layer inside the reforming tube 2 is divided into two layers, a noble metal catalyst layer 11 on the gas inlet side and a base metal catalyst layer 12 on the gas outlet side. Is very different. Ru-A as the precious metal catalyst layer 11
An l ₂ O ₃ catalyst layer is provided on the gas inlet side, and a base metal catalyst layer 1
The effect of providing a Ni-Al ₂ O ₃ catalyst layer on the gas outlet side as No. 2 is the steam reforming of propane carried out using the atmospheric pressure fixed bed flow reactor shown in FIG. The quality test results will be described as an example. The reaction conditions such as the catalyst used, the packed catalyst volume, the steam carbon ratio, the catalyst layer temperature, and the propane supply amount are the same as those described in the conventional example. Provided Ru-Al ₂ O ₃ catalyst layer on the gas inlet side in FIG. 7, Ru-Al ₂ O obtained when a Ni-Al ₂ O ₃ catalyst layer on the gas outlet side
₃ shows the relationship between the ratio of the catalyst layer volume to the total catalyst layer volume and carbon deposition. It can be seen from FIG. 7 that carbon deposition does not occur if the Ru—Al ₂ O ₃ catalyst layer is provided in an amount of 30% or more of the total catalyst layer volume. Of the steam reforming characteristics of propane in the Ru-Al ₂ O ₃ catalyst layer and the Ni-Al ₂ O ₃ catalyst layer carried out under the same conditions as the steam reforming experiment of propane carried out using the atmospheric pressure fixed bed flow reactor The simulation result is shown in FIG. From FIG. 4, the reaction rate of propane was higher in the Ru-Al ₂ O ₃ catalyst layer, which was 30% of that in the catalyst layer.
It can be seen that propane is all reacted at the position.
Ru-A excluding water vapor when the Ru-Al ₂ O ₃ catalyst layer is provided on the gas inlet side at 20% and 30% of the total catalyst layer volume
The measurement result of the gas composition of the l ₂ O ₃ catalyst layer is shown in FIG.
FIG. 9 shows the measurement results of the gas composition at the outlet of all catalyst layers. From FIG. 8, it can be seen that unreacted propane is contained in about 2% only in the case of 20%. This is consistent with the simulation result shown in FIG. Therefore, since the ratio of the Ru-Al ₂ O ₃ catalyst layer necessary for the propane to sufficiently react with the ratio of the Ru-Al ₂ O ₃ catalyst layer necessary for preventing the carbon precipitation was equal, the carbon precipitation was It is presumed that propane occurs near the gas inlet of the catalyst layer in the process of being decomposed by the steam reforming reaction, and if the region where the propane decomposition reaction occurs is the Ru-Al ₂ O ₃ catalyst layer, the remaining portion of the catalyst layer is It can be said that carbon deposition does not occur even in the Ni—Al ₂ O ₃ catalyst layer. Ru-Al ₂ on the gas inlet side
O ₃ catalyst layer is provided, the total catalyst propane reformed gas composition and Ru-Al ₂ O ₃ catalyst layer volume in the case of using a two-layer structure catalyst layer in which a Ni-Al ₂ O ₃ catalyst layer on the gas outlet side The relationship of the ratio to the layer volume is shown in FIG. It can be seen from FIG. 5 that when the ratio of the Ru—Al ₂ O ₃ catalyst layer exceeds 30%, the methane concentration in the reformed gas increases and the hydrogen concentration relatively decreases. A Ru-Al ₂ O ₃ catalyst layer is provided on the gas inlet side for 20 times.
% And 30%, the methane concentration at the Ru-Al ₂ O ₃ catalyst layer outlet is about 17% as shown in FIG.
Since the methane concentration at the catalyst layer outlet shown in FIG. 9 is higher than 12 to 13%, the Ni-Al ₂ O ₃ catalyst layer has the effect of suppressing the production of methane by the methanation reaction and the Ru-Al ₂ O. _{3 It} can be said that it also has the effect of decomposing methane generated in the catalyst layer. Therefore, by making the ratio of the Ru-Al ₂ O ₃ catalyst layer as small as possible within the range where carbon precipitation does not occur, it is possible to prevent carbon precipitation and suppress increase of methane concentration in the reformed gas at the same time in steam reforming of propane. It is possible to achieve.

From the above results, the Ru-Al ₂ O ₃ catalyst layer which is the noble metal catalyst layer 11 is provided on the gas inlet side, and the Ni-Al ₂ O ₃ catalyst layer which is the base metal catalyst layer 12 is provided on the gas outlet side. If the ratio of each catalyst layer is optimized by using the provided two-layer catalyst layer, the amount of methane produced in the reformed gas will be increased and the amount of hydrogen produced will be relatively increased in steam reforming of propane, which is a hydrocarbon. It is concluded that carbon precipitation can be prevented without reducing

In the examples, the Ru-based catalyst is used as the noble metal-based catalyst and the Ni-based catalyst is used as the base metal-based catalyst. However, the Rh-based catalyst, Ir-based catalyst,
Pd-based catalysts, Pt-based catalysts, and Re-based catalysts, Co-based catalysts, and Fe-based catalysts as base metal-based catalysts are also applicable.

[0013]

As described above, according to the present invention, the catalyst of the reformer has a two-layer structure, and the noble metal-based catalyst is effective in preventing carbon deposition on the catalyst during the steam reforming reaction. Layer and a base metal catalyst layer that is effective in suppressing the generation of methane by the methanation reaction and decomposing methane produced by the methanation reaction. There is an advantage that carbon precipitation can be prevented and the increase in the amount of methane in the reformed gas can be suppressed even under the condition that the amount of water vapor is small, without significantly increasing the cost.

In particular, when the present invention is applied to the reformer for an on-site type fuel cell, the amount of reforming steam can be reduced without a large increase in catalyst cost and deterioration in reforming performance, and the exhaust heat can be relatively removed. By increasing the amount of recovery steam, the overall efficiency of the fuel cell power generator can be increased.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a reformer showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a conventional reformer.

FIG. 3 is a structural explanatory view showing an example of an atmospheric pressure fixed bed flow type reaction apparatus used in a propane steam reforming experiment for verifying the effectiveness of the present invention.

[Fig. 4] Ru-Al ₂ carried out under the same conditions as the steam reforming experiment of propane carried out using an atmospheric fixed bed flow reactor.
O ₃ is a characteristic diagram showing an example of a simulation result of the steam reforming characteristics of propane in the catalyst layer and Ni-Al ₂ O ₃ catalyst layer.

FIG. 5: A Ru—Al ₂ O ₃ catalyst layer is provided on the gas inlet side,
Gas outlet side to the Ni-Al ₂ O ₃ in the case where the catalyst layer using a two-layer structure catalyst layer in which a propane reformed gas composition and Ru-A
It is a characteristic view which shows an example of the relationship of the ratio of the 1 ₂ O ₃ catalyst layer volume to the total catalyst layer volume.

[Fig. 6] Ni-A using an atmospheric fixed bed flow reactor
l ₂ O ₃ catalyst and Ru-Al ₂ O ₃ catalyst a diagram illustrating an example of the reformed gas composition excluding water vapor when performing steam reforming of propane was charged to each reactor.

FIG. 7 is a view showing a Ru—Al ₂ O ₃ catalyst layer provided on the gas inlet side,
R when a Ni-Al ₂ O ₃ catalyst layer is provided on the gas outlet side
It is an explanatory diagram showing an example of the relationship between the ratio and the carbon deposition with respect to the total catalyst layer volume of u-Al ₂ O ₃ catalyst layer volume.

FIG. 8 shows the measurement results of the Ru—Al ₂ O ₃ catalyst layer outlet gas composition excluding water vapor when the Ru—Al ₂ O ₃ catalyst layer is provided on the gas inlet side at 20% and 30% of the total catalyst layer volume. It is explanatory drawing which shows an example.

FIG. 9 is an explanatory diagram showing an example of measurement results of the gas composition of all catalyst layer outlets excluding water vapor when the Ru-Al ₂ O ₃ catalyst layer is provided on the gas inlet side at 20% and 30% of the total catalyst layer volume. Is.

[Explanation of symbols]

 1 ... Raw material gas 2 ... Reforming tube 3 ... Catalyst layer 4 ... Reforming device burner 5 ... Fuel gas 6 ... Air 7 ... Combustion gas 8 ... Reforming gas 9 ... Reforming tube 10 ... Thermal conductive material 11 ... Noble metal catalyst Layer 12 ... Base metal catalyst layer 51 ... Hydrogen 52 ... Nitrogen 53 ... Float type flow meter 54 ... Float type flow meter 55 ... Regulator 56 ... Regulator 57 ... Stop valve 58 ... Stop valve 59 ... Pressure gauge 60 ... Pressure gauge 61 ... Pump 62 ... Water tank 63 ... Balance 64 ... Check valve 65 ... Check valve 66 ... Check valve 67 ... Check valve 68 ... Propane 69 ... Regulator 70 ... Stop valve 71 ... Pressure gauge 72 ... Thermal mass flow controller 73 ... Vaporizer 74 ... Temperature control unit 75 ... Temperature control unit 76 ... Heater 77 ... Electric furnace 78 ... Reactor 79 ... Trap 80 ... Drainage 1 ... temperature control unit 82 ... exhaust

Claims (2)

[Claims] 1. A reformer for producing a hydrogen-rich gas by performing a steam reforming reaction on a reforming catalyst which is supplied with fuel and steam and filled in a reforming tube, wherein a catalyst layer inside the reforming tube is provided. Is a two-layer structure, wherein the noble metal catalyst layer is provided on the inlet side of the raw material gas consisting of steam and fuel, and the base metal catalyst layer is provided on the reformed gas outlet side. 2. The reformer according to claim 1, wherein the noble metal-based catalyst layer is a Ru-based catalyst layer, and the base metal-based catalyst layer is a Ni-based catalyst layer.