JP2002003865A - Carbon monoxide remover - Google Patents

Abstract

PROBLEM TO BE SOLVED: To level the temperature distribution of a catalyst layer along the flow direction of a gas in a carbon monoxide remover the reactor of which is packed with a catalyst. SOLUTION: A heat pipe 3 (a heat-conductive rod) is inserted along the flow direction of a gas in a catalyst 2 layer charged in a reactor 1. The length L of the heat pipe 3 is at least 50% of the length L0 of the catalyst layer charged; and the cross section S of the heat pipe 3 is 1-62% of the cross section S0 of the reactor 1. This heat pipe 3 enables sharp temperature rise occurring in the inlet side 1a region of the reactor 1 to be inhibited and enables the temperature distribution of the catalyst layer along the flow direction of the gas to be leveled by heat conduction to the outlet side 1b region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon monoxide remover for removing CO from a gas containing CO.
An object of the present invention is to provide a carbon monoxide remover having excellent removal ability.

[0002]

2. Description of the Related Art In a fuel cell system, a hydrogen-rich fuel gas is supplied to an anode of a fuel cell.
An oxidant is supplied to the cathode and electrochemically reacted to generate power. As the hydrogen-rich fuel gas, reforming obtained by steam reforming a hydrocarbon-based gas such as natural gas or a raw fuel such as methanol in a reformer can be used.

[0003] By the way, in the steam reforming reaction by the reformer, carbon monoxide is generated together with hydrogen, and this carbon monoxide degrades a catalyst such as platinum used for the anode. It is desirable that the carbon concentration be as low as possible. Therefore, conventionally, a carbon monoxide converter and a carbon monoxide remover are provided at the subsequent stage of the reformer, and after the carbon monoxide concentration is reduced to about 100 ppm, the reformed gas is supplied to the anode. Here, the carbon monoxide remover is:
The reactor is configured by being filled with a selective oxidation catalyst,
By introducing reformed gas together with air into the reactor, carbon monoxide is selectively oxidized and removed.

[0004]

In order to efficiently remove carbon monoxide using a carbon monoxide remover, it is necessary to maintain the selective oxidation catalyst filled in the reactor within an appropriate temperature range. is necessary. However, since the reaction in the carbon monoxide remover is an exothermic reaction, a reaction occurs rapidly near the inlet of the reformed gas, and the temperature rises near the inlet, so that the catalyst flows along the flow direction of the reformed gas. Temperature distribution becomes non-uniform. For this reason, it has been difficult to maintain the temperature of the catalyst in an appropriate temperature range over the entire reactor, and there has been a problem that carbon monoxide cannot be efficiently removed.

The present invention has been made to solve such a conventional problem, and it is intended to suppress a rapid rise in the temperature of the catalyst layer near the inlet in the reactor and to level the temperature of the catalyst layer. It is an object of the present invention to provide a carbon monoxide remover that can be used.

[0006]

As a means for achieving this object, the present invention relates to a carbon monoxide remover in which a catalyst is filled in a reactor, wherein the catalyst layer is contained in the catalyst layer. The point is that a thermally conductive rod is inserted along the flow direction of the gas passing through. Further, in this carbon monoxide remover, the heat conductive rod is a heat pipe, and the cross section of the heat conductive rod is
1 to 62% of the cross-sectional area of the reactor, the length of the thermally conductive rod inserted into the catalyst layer is 50% or more of the entire length of the catalyst layer, It is characterized by the following.

According to the present invention, a thermally conductive rod is inserted along a gas flow direction into a catalyst layer filled in a reactor accompanied by an exothermic reaction. As a result, heat can be transferred from the high heat side to the low heat side, and the temperature distribution of the catalyst layer can be leveled to achieve uniform catalytic reaction.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a carbon monoxide remover according to the present invention will be described with reference to the accompanying drawings. Figure 1
(A), (b) is a schematic sectional view showing a basic structure of a carbon monoxide remover, in which 1 is a cylindrical reactor, in which a catalyst 2 is filled inside and a catalyst layer is provided in the catalyst layer. A heat conductive rod, in this case a heat pipe 3, is inserted along the axial direction of the reactor 1.

In the heat pipe 3, a working fluid is sealed in a cylindrical vacuum sealed container, and the heat pipe 3 exhibits a heat conducting function through the working fluid. That is, the working fluid is supplied to one end 3a of the heat pipe 3 (the inlet side 1a of the reactor 1 where the temperature becomes high).
Area), heats and evaporates. At that time, it absorbs the heat of evaporation and moves to the other end 3b (the outlet side 1b area where the temperature is low), where it is condensed to release heat of condensation, and the liquid is condensed. Is returned to the inlet end 3a via the wick 3c mounted in the heat pipe 3.
The wick 3c is for moving the condensed working fluid by capillary action. Accordingly, the heat pipe 3 does not require any external power, and the working fluid can self-circulate to transmit heat energy from the high temperature side to the low temperature side. In this case, as the working fluid, Freon, methanol, ammonia, water, or the like which can be used at 150 ° C. to 300 ° C. in consideration of the catalyst temperature in the reactor 1 is suitable.

[0010] Since the size (length, cross-sectional area, etc.) of such a heat pipe 3 is an important factor in relation to the catalyst layer in the reactor 1, an experiment was first conducted on the length. FIG.
Shows the experimental results of the temperature distribution of the catalyst layer when the length L of the heat pipe 3 is 50% of the length L ₀ of the catalyst packed bed in the reactor 1, that is, when L = １ ／ L _0. . According to this, in both the case of the present invention shown by the solid line and the case of the conventional example shown by the broken line, the temperature of the catalyst layer rises in the region 1a on the inlet side of the reactor 1. However, in the case of the present invention, since heat is transferred from the inlet side 1a region to the outlet side 1b region by the heat pipe 3 inserted into the reactor 1,
The temperature of the catalyst layer in the reactor 1 is lower in the region 1a on the inlet side than in the conventional example and higher in the region 1b on the outlet side than in the conventional example. Therefore, in the case of the present invention, as shown in FIG. 2, the temperature difference between the temperature in the inlet side 1a region and the temperature in the outlet side 1b region becomes smaller than before, and the catalyst layer temperature in the reactor 1 decreases. The leveling could be leveled than before.

From the results of this experiment, the effectiveness of heat conduction by the heat pipe 3 is sufficiently recognized, and the temperature distribution of the catalyst layer in the reactor 1 is almost leveled except for a region where the temperature rises sharply at the inlet side 1a. In addition, the temperature control became easy, and a proper reaction temperature of the catalyst 2 (depending on the type), for example, 140 ° C. to 190 ° C. could be secured.

FIG. 3 shows a temperature distribution experiment result of the catalyst layer when the length L of the heat pipe 3 is 100% (L = L ₀ ) with respect to the length L _{0 of the} catalyst packed layer. In this case, since the end 3a of the heat pipe is located on the inlet side 1a of the reactor 1, the working fluid in the heat pipe 3 evaporates efficiently with the rapid temperature rise on the inlet side 1a, By absorbing a large amount of heat of evaporation, a rapid rise in temperature of the catalyst layer is suppressed.
As a result, the catalyst temperature on the inlet side 1a becomes lower than in the case of FIG. From there, a large amount of heat of condensation is released when condensing along with the large amount of heat of evaporation absorbed in the region 1b on the outlet side. Accordingly, the temperature distribution of the catalyst layer shows a gentler downward line than in the case of FIG. 2, and the temperature difference between the inlet side 1a region and the outlet side 1b region becomes smaller.

From the results of this experiment, it was found that the effect of heat conduction by the heat pipe 3 was superior to that of FIG. 2, and that the temperature distribution of the catalyst layer could be leveled sufficiently. That is, while suppressing the rapid temperature rise of the catalyst at the inlet side 1a of the reactor 1, the upper limit of the temperature distribution at the inlet side 1a of the catalyst layer is lowered by a large amount of heat conduction through the working fluid, while the outlet side The lower limit of the temperature distribution in 1b can be raised.

FIG. 4 shows the experimental results of the temperature distribution of the catalyst layer when the length L of the heat pipe 3 is 40% (L = 0.4L ₀ ) with respect to the length L _{0 of the} catalyst packed layer. In this case, the catalyst temperature rises to almost the same level as in the conventional example with the rapid temperature rise at the inlet side 1a, and the working fluid of the heat pipe 3 is heated and evaporated at the place where the temperature rises. However, the amount of evaporation is small. Therefore, from there exit 1
In region b, sufficient heat conduction is not performed, and the temperature distribution of the catalyst layer is slightly higher than that of the conventional example, but follows a downward line substantially similar to that of the conventional example.

In this case, the effectiveness of heat conduction by the heat pipe 3 was not recognized to be sufficient, and it was found that the temperature distribution of the catalyst layer could not be leveled sufficiently. Therefore, it is preferable that the length of the heat pipe 3 inserted in the catalyst layer be 50% or more of the length of the catalyst packed layer. The insertion position of the heat pipe 3 is not limited to the position shown in FIGS. 2 and 3, but may be near the center of the catalyst layer. Further, one end of the heat pipe 3 may be inserted into the area 1a on the inlet side, and the other end may be taken out of the reactor 1. In this case, the heat in the region 1a on the inlet side can be radiated to the outside via the heat pipe 3, so that the temperature of the catalyst layer in the region 1a on the inlet side can be lowered and the temperature of the catalyst layer can be leveled. be able to.

Next, an experiment was conducted on a preferable sectional area of the heat pipe 3. FIG. 5 shows the results of the experiment.
With 1-62% cross-sectional area S of the heat pipe 3 with respect to the cross-sectional area _{S 0} of the reactor 1, the CO concentration at the outlet side 1b can be 100ppm or less, and 2-58% This allows the CO concentration at the outlet side 1b to be 50 ppm or less, and the CO concentration at the outlet side 1b can be reduced to 10 to 50%.
The CO concentration at b could be reduced to about 10 ppm.
This is considered to be because the temperature distribution of the catalyst layer by the heat pipe 3 could be leveled as described above, so that CO could be effectively removed. Therefore, the cross-sectional area of the heat pipe 3 is preferably 1 to 62%, more preferably 2 to 58%, further preferably 10 to 50% with respect to the cross-sectional area of the reactor 1. .

In the carbon monoxide remover, a hydrogen-rich gas containing CO is passed through a catalyst together with oxygen to selectively oxidize CO and lower the CO concentration. An experiment was conducted on a preferable oxygen supply amount at that time. FIG. 6 shows the experimental results.
When the ratio of O ₂ to CO contained in the hydrogen-rich gas is 0.75 to 1, the CO concentration at the outlet side 1b is reduced to 10%.
ppm or less.

The heat pipe 3 is made of, for example, 17 to 25% by weight of Cr and 10 to 35% of Ni from the viewpoints of good thermal conductivity, excellent heat resistance and non-permeability of hydrogen.
Alloys containing% by weight are suitable. Further, in the present invention, the same effect can be obtained by inserting not only the heat pipe but also another heat conductive rod into the catalyst.

[0019]

As described above, according to the present invention, in a carbon monoxide remover accompanied by an exothermic reaction, a thermally conductive rod such as a heat pipe is provided on a catalyst layer filled in the reactor. Since it is inserted along the flow direction, it is necessary to suppress the temperature rise due to sudden catalytic reaction occurring at the inlet side of the reactor, and to level the temperature distribution of the catalyst layer along the gas flow direction in the reactor. And temperature control can be facilitated. Therefore, an excellent effect is obtained such that the function of the carbon monoxide remover is enhanced and a stable hydrogen-rich gas having a low CO concentration can be supplied to the fuel cell.
Further, by using a heat pipe as the heat conductive rod and specifying the length and cross-sectional area of the heat pipe with respect to the reactor, the material of the heat pipe, the working fluid, and the like, the above effects can be further enhanced.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a carbon monoxide remover according to the present invention, wherein (a) is a schematic longitudinal sectional view, and (b) is a schematic transverse sectional view.

FIG. 2 is a temperature distribution diagram of a catalyst layer when a heat pipe having a length of 50% with respect to the length of a catalyst packed bed is inserted.

FIG. 3 is a temperature distribution diagram of the catalyst layer when a heat pipe having a length of 100% with respect to the length of the packed bed of the catalyst is inserted.

FIG. 4 is a temperature distribution diagram of the catalyst layer when a heat pipe having a length of less than 50% of the length of the packed bed of the catalyst is inserted.

FIG. 5 is a diagram showing the relationship between the ratio of the cross-sectional area of the heat pipe to the cross-sectional area of the reactor and the outlet CO concentration.

FIG. 6 is a diagram showing the relationship between outlet CO concentration due to O ₂ / CO.

[Explanation of symbols]

 1. Reactor 2. Catalyst 3. Heat pipe (thermally conductive rod)

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Fujio 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. (reference) 4G040 EA02 EA03 EA06 EB31 EB43 EB46 EC07 4H060 AA02 BB11 CC18 FF02 GG02 5H027 AA02 BA01 BA17

Claims (4)

[Claims] 1. A carbon monoxide remover having a catalyst filled in a reactor, wherein a thermally conductive rod is inserted into the catalyst layer along a flow direction of a gas passing through the catalyst layer. A carbon monoxide remover characterized by being worn. 2. The carbon monoxide remover according to claim 1, wherein said heat conductive rod is a heat pipe. 3. The carbon monoxide remover according to claim 1, wherein a cross-sectional area of the heat conductive rod is 1 to 62% of a cross-sectional area of the reactor. 4. The catalyst according to claim 1, wherein the length of the thermally conductive rod inserted into the catalyst is 50% or more of the entire length of the catalyst layer. A carbon monoxide remover according to item 1.