JPH05306103A - Radiation heat-transmission type reformer - Google Patents

Abstract

PURPOSE:To effectively utilize a catalyst on the raw gas inlet side and to improve reforming efficiency in the radiation heat-transmission type reformer by injecting a specified amt. of air which is mixed with a raw gas before the raw gas enters a catalytic body. CONSTITUTION:A gas-impermeable partition wall 5 is provided in a closed vessel 10 to divide the vessel into a combustion section 1 and a heat receiving section 3. A porous heat radiator 2 is provided in the combustion section 1 and a catalytic body 4 in the heat receiving section 3. A high-temp. gas is supplied to the radiator 2, and the catalytic body 4 is heated by the heat radiated from the high-temp. gas. A raw gas 8 is supplied to the heat receiving section 3 from a raw gas pipe 11, brought into contact with the catalytic body 4 and reformed. In this case, the air 21 corresponding to <=38% of the raw gas is supplied through an air pipe 20 before the raw gas 8 enters the catalytic body 4 and mixed with the raw gas 8. Consequently, heat is generated by the oxidation of the raw gas and reformed gaseous hydrogen with air to compensate for the temp. decrease in the catalytic body 4 due to the steam reforming reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a radiant heat transfer reformer used in a fuel cell power plant or other application.

 (Prior Art) A fuel cell generally produces electric power by electrochemically reacting hydrogen and oxygen. Among the fuel cells, the molten carbonate fuel cell or solid oxide fuel cell can use carbon monoxide directly as a fuel without using hydrogen.

However, as the fuel for power generation plants, the normally used hydrocarbons such as natural gas and naphtha cannot be used directly as fuels for fuel cells, so the following reformers are used. That is, the raw material gas in which methane gas and steam are mixed to obtain hydrogen gas is subjected to steam reforming represented by CH ₄ + H ₂ O → CO + 3H ₂ to obtain a product gas in which hydrogen and carbon monoxide are mixed. It is a thing.

 In recent years, a new type of radiant heat transfer reformer has been developed, which uses a porous radiant body as a heating body as an example of the reformer to improve the heat transfer effect, and Fig. 2 shows the most practical one among them. (This is disclosed in Japanese Patent Publication No. 62-172615).

In FIG. 4, 1 is a combustion chamber, 2 is a porous heat radiation body, 3 is a heat receiving chamber, 4 is a porous heat receiving body having a substantially uniform pore size in which a catalyst is uniformly supported throughout, and 5 is The inside of the cylindrical container 10 is partitioned into the combustion chamber 1 and the heat receiving chamber 3, and a partition wall for preventing the raw material gas (gas mixture of CH ₄ and H ₂ O) 8 from leaking, 6 is a high temperature obtained by combustion of fuel Combustion gas, 7 is exhaust gas, 9 is a product gas obtained by mixing H ₂ and CO obtained by decomposition of the raw material gas 8, 11 is a raw material gas supply pipe, 12 is a burner having many ejection ports 12a, and 13 is exhaust gas A pipe, 14 is a product gas extraction pipe.

 In the above reaction apparatus, the high temperature combustion gas 6 injected from the burner 12 and burned passes through the heat radiator 2 and is discharged from the exhaust gas pipe 13 as the exhaust gas 7. The sensible heat of the burning gas 6 is absorbed by the heat radiating body 2 by convective heat transfer when passing through the heat radiating body 2, and the heat radiating body 2 is heated and radiant heat is released into the device and radiated. When the partition wall 5 is made of a metallic material or ceramic, the radiant heat is received by the heat receiving body 4 as heating and re-radiation of the partition wall 5, and when the partition wall 5 is a transparent material such as quartz glass. The heat is received by the heat receiving body 4 through the partition wall 5, and the heat receiving body 4 is heated.

 The raw material gas 8 is heated and decomposed by the heat receiving body 4 when passing through the heat receiving body 4, and becomes a produced gas 9 in which H and CO are mixed, and is sent to the outside of the apparatus through a produced gas extraction pipe 14.

 As described above, the heat absorbed by the heat radiating body 2 is applied to the heat receiving body 4 by radiation, and the source gas 8 is passed through the heat receiving body 4 to be heated and decomposed into the presence of a catalyst, thereby reforming. When the generated gas 9 is obtained, the heat is effectively used and the raw material gas 8 is decomposed effectively by the compact device.

 (Problems to be Solved by the Invention) In the conventional apparatus described above, since the inside of the partition wall 5 is a hydrogen-rich gas and the outside is a combustion gas containing a large amount of high-temperature air, the conventional partition wall 5 is used. Some of them are made of metal such as heat-resistant steel or heat-resistant alloy that can withstand high temperatures. In addition to this, there is a conventional partition wall 5 made of colorless and transparent quartz glass. However, in the case of a reformer, the latter metal, which has a high mechanical strength at high temperatures, is used because the latter will burn a large amount when it breaks.

 Therefore, the radiant heat from the heat radiation body 2 outside the partition wall 5 is transferred to the partition wall 5 by heat conduction through the partition wall 5 itself and radiated from the upper part of the partition wall 5 to the outside, resulting in a heat loss. The temperature of the partition wall 5 is reduced by this amount, and the amount of heat radiated and transmitted from the inner surface of the partition wall 5 to the internal heat receiving body 4 is reduced. The steam reforming reaction is carried out in the heat receiving body 4 as described above, but since this reaction is an endothermic reaction, the temperature decreases when there are many reactions. Therefore, the amount of the source gas 8 is limited.

 To explain this, the temperature distribution of the heat receiving body 4 is relatively low in a certain area from the inlet side, and is rapidly increased by the heat radiation from the partition wall 5 at the outlet side of the heat receiving body 4, and the steam reforming reaction of the endothermic reaction is It is slow at low temperatures and accelerates at higher temperatures.

 Therefore, the reaction does not proceed much on the low temperature side of the heat receiver 4, and the reaction mainly occurs on the high temperature side. As a result, the heat absorption of the heat receiver 4 is mainly performed in the portion close to the partition wall 5, the catalyst on the low temperature side is not effectively used, and the reforming efficiency is poor.

 It is an object of the present invention to provide a radiant heat transfer type reforming apparatus that can effectively utilize a catalyst on the inlet side of a raw material gas and improve reforming efficiency.

 [Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a heating chamber and a heated chamber by providing a partition wall made of a gas impermeable material in a closed container. The heating chamber is provided with a porous radiator, the heating chamber is provided with a contact medium, and a high-temperature gas is passed through the radiator to be discharged to the outside of the container. In a reformer for heating a catalyst body in the heated chamber through a partition wall and passing a raw material gas introduced into the heated chamber to the catalyst body to obtain a reformed gas, the raw material gas is the catalyst. Before entering the medium, an air amount of 38% or less of the raw material gas or an oxygen amount of 8.0% or less of the raw material gas is injected to mix the air or oxygen with the raw material gas. Air supply to the inlet side of the catalyst body It is characterized by the provision of a feeding means.

 (Operation) According to the present invention, the mixed gas of the raw material gas and air or oxygen enters the heat receiver to cause a partial oxidation reaction. In this case, the reaction formula when the combustion catalyst is added or when the combustion catalyst is not added is as follows.

CH ₄ +20 ₂ → CO ₂ + 2H ₂ O (1) CH ₄ + H ₂ O → CO + 3H ₂ (2) CH ₄ + CO ₂ → 2CO + 2H ₂ (3) CO + H ₂ O → CO ₂ + H ₂ (4) Above The reactions of equations (2) and (3) are reactions involving a large endotherm, but since equation (1) is an exothermic reaction, the rate of temperature decrease due to the reactions of equations (2) and (3) is small. You can do it.

 Therefore, the catalyst on the raw material gas inlet side, which has not been effectively used in the past, can be effectively used, and the reforming efficiency is improved. Therefore, if the reforming gas conditions are the same as in the conventional device, reforming can be performed with a small amount of catalyst volume.

 (Example) Hereinafter, the Example of this invention is described. FIG. 1 is a vertical sectional view showing an embodiment thereof, and here, the same parts as those of the conventional apparatus shown in FIG.

 In FIG. 2, the raw material gas 8 is supplied from the raw material gas pipe 11 into the heat receiving chamber 3 in the container 10. Separately from this, the compressed air 21 (38% or less of the flow rate of the raw material gas) 21 from the air supply means (not shown) is supplied to the heat receiving chamber 3 through the air tube 20. And a plurality of small holes 22 are formed at the lower end of the air tube 20, and a plurality of ribs 23 are attached to the outer peripheral surface of the air tube 20. There is.

 Then, the catalyst body 4 as the heat receiving body is divided into a plurality of layers by the plurality of catalyst body divided layers 4a, 4b, 4c ... In the flow direction of the raw material gas 21, and each catalyst body divided layer 4a. , 4b, 4c ... All carry a reforming catalyst body.

 The operation of the first embodiment configured as above will be described. The compressed air 21 is jetted from a large number of small holes 22 formed in the peripheral surface of the lower end portion of the air pipe 20 to the raw material gas 8 of the raw material gas supply pipe 11 on the outer periphery of the air pipe 20 to compress the compressed air and the raw material gas. Are mixed well.

Since the temperature is as low as about 400 ° C. in this portion, methane gas (CH ₄ ) does not burn. However, the temperature at the inlet of the heat receiver 4 is about 500 ° C. even with the conventional device of FIG. 2, and the temperature at the outlet of the heat receiver 4 is about 800 ° C. Therefore, in the first embodiment, since the air pipe 20 supplies an air amount of 38% or less of the amount of the raw material gas, the air and methane and the reformed hydrogen gas are oxidized to generate heat. Therefore, it is possible to compensate for the decrease in the temperature of the heat receiver 4 due to the steam reforming reaction.

 Therefore, the amount of methane remaining in the produced gas 9 obtained by the reforming reaction becomes small, and the methane conversion rate also improves.

 As a result of the experiment conducted in the above-mentioned embodiment, that is, the example in which the reforming catalyst bodies are put in the respective catalyst body dividing layers 4a, 4b, 4c, it is only necessary to mix the air amount of about 3% of the raw material gas amount. It was revealed that the outlet temperature of the heat receiving body 4 increased from 730 ° C to 750 ° C, and the methane conversion rate increased from 78% to 85%.

 In the above-described embodiment, when the oxidation combustion catalyst layer is provided in the first layer 4a of the catalyst divided layers 4a, 4b, 4c on the inlet side of the heat receiving body 4, the temperature difference between the respective parts is equalized. Therefore, better results were obtained as the modification performance than the above-mentioned examples. Therefore, as mentioned above, it is possible to improve the reforming performance by simply mixing a small amount of air into the raw material gas.

 This is shown in Fig. 2 which shows the results of examining the total conversion rate of methane by conducting a concrete reaction in a reforming reaction. The horizontal axis is the amount of injected air, which is shown as a ratio to the amount of raw material gas. The vertical axis shows the amount changed by injecting air, based on when the air injection amount is zero.

 Curve A shows the amount of methane burned by the injected air, which raises the temperature and the reforming reaction progresses due to the temperature rise, improving the methane conversion rate.

Curve B shows the decrease of methane because methane is burned by the injected air. Here, the total conversion rate of methane is shown by a curve C, and Φ _A , Φ _B , and Φ _C are respectively expressed as Φ _C = (1 + Φ _A ) × (1-Φ _B ).

In curve A, when air is injected into the raw material gas, it greatly rises, but since the methane conversion rate does not exceed 100%, the improvement is saturated at Φ _A = 25%. The curve B increases linearly with the injected air amount. Therefore, the total improvement in conversion rate was the highest when the amount of injected air was about 11%. When the amount of injected air is set to 38% or more, the total conversion rate is not improved and deteriorates. Therefore, the limit of the amount of injected air is 38% or less.

 The first embodiment described above shows the case where an air amount of 38% or less of the raw material gas amount is mixed. Instead of this air, an oxygen amount of 8.0% or less of the raw material gas amount is supplied from the air tube 20. The same effect can be obtained by inserting it.

 Similar to Fig. 2, Fig. 3 shows the results of an experiment in which the reforming reaction was carried out and the total conversion rate of methane was investigated. The horizontal axis shows the amount of injected oxygen, which is shown as the ratio to the amount of raw material gas. is there. The vertical axis shows the amount of change due to oxygen injection when the oxygen injection amount is zero. As is clear from this characteristic diagram, the maximum improvement in the total conversion was obtained when the injected oxygen amount was about 2.5%. When the injected oxygen amount is 8% or more, the total conversion rate is not improved but deteriorates. Therefore, the limit of the amount of injected oxygen is 8% or less.

 In the above-mentioned first embodiment, the approaching flow from the inner side toward the outer partition wall 5 is described by introducing the raw material gas 8 into the heat receiving body 4. The flow in this case is more effective by injecting air, but the flow opposite to this, that is, the case where the heat flows from the outside to the inside of the heat receiving body 4, can also be implemented. In the case of this reverse flow, the temperature distribution is high on the outside and low on the inside, so the position where the oxidation catalyst layer is provided is particularly effective on the inside.

 [Effects of the Invention] According to the present invention described above, it is possible to provide a radiant heat transfer type reforming apparatus capable of obtaining a very good steam reforming product gas simply by mixing air or oxygen into the raw material gas. ..

[Brief description of drawings]

 FIG. 1 is a vertical sectional view showing a first embodiment of a radiant heat transfer type reforming apparatus of the present invention, and FIG. 2 is a characteristic diagram showing a change in performance depending on an air injection amount when the present invention is carried out, FIG. 3 is a characteristic diagram showing a change in performance depending on the oxygen injection amount when the present invention is carried out, and FIG. 4 is a vertical sectional view showing an example of a radiant heat transfer reformer of a conventional device. DESCRIPTION OF SYMBOLS 1 ... Combustion chamber, 2 ... Thermal radiator, 3 ... Heat receiving body, 5 ... Partition wall, 10 ... Container, 11 ... Raw material gas supply pipe, 20 ... Air pipe, 22 ... Small hole.

Claims (2)

[Claims] 1. A closed chamber is provided with a partition wall made of a gas impermeable material to form a heating chamber and a heated chamber, the heating chamber is provided with a porous radiator, and the heated chamber is also described above. A catalyst body is provided in the chamber, and a high-temperature gas is passed through the radiator to be discharged to the outside of the container, whereby the catalyst body in the heated chamber is heated by the radiant heat of the high-temperature gas through the partition wall. In a reformer for obtaining a reformed gas by passing a raw material gas introduced into a heated chamber to the catalyst body, an air of 38% or less of the raw material gas amount before the raw material gas enters the catalyst body. A radiant heat transfer reformer characterized by comprising an air supply means for injecting an amount of the air, mixing the air with the raw material gas, and supplying the mixed gas to the inlet side of the catalyst body. 2. A closed chamber is provided with a partition wall made of a gas impermeable material to form a heating chamber and a heated chamber, the heating chamber is provided with a porous radiator, and the heated chamber is also described above. A catalyst body is provided in the chamber, and a high-temperature gas is passed through the radiator to be discharged to the outside of the container, whereby the catalyst body in the heated chamber is heated by the radiant heat of the high-temperature gas through the partition wall. In a reformer for obtaining a reformed gas by passing a raw material gas introduced into a heated chamber through the catalyst body, the raw material gas is 8.0% or less of the raw material gas before entering the catalyst body. A radiant heat transfer reformer characterized by being provided with an oxygen supply means for injecting the oxygen amount of the above, mixing the oxygen with the raw material gas and supplying the mixed gas to the inlet side of the catalyst body.