JPH0847621A - Device for removing carbon monoxide - Google Patents

Abstract

PURPOSE:To imcrease the efficiency of oxidation reaction of carbon monoxide by a catalyst to improve the carbon monoxide removal efficiency. CONSTITUTION:A carbon monoxide removing device 16 is provided with three oxidation reactors, a lst to a 3rd ones in a reformed gas pipe line 36 in series. While reformed gas is passed through each oxidation reactor together with oxygen, CO is oxidized and removed by a catalyst in each oxidation reactor. The oxidation reactors are each fed with air by the quantity (L/3) one-third of the total amount L of introduced air determined by the detected CO concentration of a CO concentration sensor at the upstream side of a lst oxidation reactor 30. Further, for the 2nd and the 3rd oxidation reactors, the air quanity is increased and decreased to correct it by the detected CO concentration of a CO concentration sensor at the upstream side thereof. In this way, a catalyst in each oxidation reactor is simultaneously made under a state in which reformed gas contg. CO and air (oxygen) of a flow rate corresponding to the CO concentration coexist, and CO oxidation reaction proceeds in each oxidation reactor almost at the same time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a removing device for oxidizing and removing carbon monoxide from a gas containing carbon monoxide.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental protection, replacement of engines using combustion energy of gasoline or light oil has been demanded, and it has been put into practical use to obtain driving energy for vehicles from fuel cells. . This fuel cell requires hydrogen-rich gas and oxygen-rich gas as fuel gas. A so-called reformed gas generated by steam reforming a hydrocarbon compound such as methanol is generally used as the hydrogen-rich gas, and air that is easily available is generally used as the oxygen-rich gas.

It is well known that in a steam reforming reaction of a hydrocarbon compound such as methanol, carbon monoxide is produced as an intermediate product in the course of the reaction. Since this carbon monoxide poisons the catalyst of the electrode in the fuel cell and causes deterioration of the cell performance, various techniques have been proposed so as not to introduce carbon monoxide into the fuel cell together with hydrogen gas.

First, in the steam reformer, which is a source of carbon monoxide, the reaction temperature and steam ratio of the reforming reaction are controlled to
It is common practice to reduce the amount of carbon monoxide produced. Further, in a hydrogen-rich gas (reformed gas) supply system, carbon monoxide in the reformed gas is oxidized by a specific catalyst such as ruthenium or rhodium as disclosed in Japanese Patent Laid-Open No. 5-201102. As carbon, carbon monoxide is removed from the reformed gas.

In this case, the catalyst is housed in an elongated steel tube container (reaction container), and the reforming gas is introduced into the reaction container along with its longitudinal direction together with air. Then, while the reformed gas passes through the reaction vessel, carbon monoxide in the reformed gas is oxidized and removed by the catalyst.

[0006]

However, in the above-mentioned conventional carbon monoxide removing apparatus, the following problems remain unsolved.

At the gas inlet side of the reaction vessel, the reformed gas and air are mixed and flow in, so that the catalytic oxidation reaction between oxygen in the air and carbon monoxide in the reformed gas rapidly progresses. At this time, a part of hydrogen of the reformed gas reacts with oxygen in the air (oxidation reaction) by the catalyst and is consumed, and water is generated. On the other hand, on the gas outlet side of the reaction vessel, oxygen is consumed due to the oxidation reaction on the inlet side and oxygen deficiency occurs, and carbon monoxide, which is an object of oxidation, also decreases.
Therefore, the oxidation reaction of carbon monoxide does not proceed as much as the gas outlet side. However, due to the nature of the reaction by the catalyst, the situation of lack of oxygen has a greater effect on the progress of the oxidation reaction than the situation of decrease of carbon monoxide.

By the way, since the oxidation reaction of carbon monoxide by the catalyst is an exothermic reaction and the amount of heat generation increases with the progress of the oxidation reaction, the amount of heat generation is larger on the gas inlet side of the reaction vessel and smaller on the gas outlet side. Therefore, the temperature in the reaction vessel is not uniform along the longitudinal direction of the reaction vessel, in other words, along the flow direction of the reformed gas, and the temperature of the catalyst in the reaction vessel also varies accordingly. Therefore, the catalyst involved in the reaction cannot be placed at an appropriate temperature in the longitudinal direction of the reaction vessel (gas flow direction), and the efficiency of the oxidation reaction is reduced, so that carbon monoxide cannot be efficiently removed. I was afraid. Taking a specific catalyst as an example, when a platinum catalyst (Pt catalyst) is used, the optimum carbon monoxide oxidation temperature is 120 to 140 ° C. It greatly exceeds the temperature and drops below the exit side.

Although it is possible to use a heating device or a cooling device to control the temperature in the reaction vessel to be uniform along the longitudinal direction of the reaction vessel, it is not practical for the following reason. . In other words, even if the gas outlet side of the reaction vessel is heated and controlled, oxygen is still actively consumed at the gas inlet side, so the situation of lack of oxygen and reduction of carbon monoxide at the gas outlet side cannot be eliminated. Absent. Therefore, the oxidation reaction of carbon monoxide on the gas outlet side does not actively proceed regardless of the presence or absence of temperature control, and the efficiency of the oxidation reaction cannot be improved. Further, when the gas inlet side is cooled in addition to the gas outlet side heating, the reaction by the catalyst on the gas inlet side can be suppressed to some extent, and the situation such as oxygen shortage on the gas outlet side can be somewhat improved. However, since heating and cooling are controlled at the same time, energy loss used for temperature adjustment becomes large, which is not practical.

Further, it is possible to adopt a structure in which a large amount of oxygen is supplied so that the oxygen reaches the gas outlet side as well, but this is not practical for the following reasons. That is, if the oxygen supply amount becomes excessive, the reaction with oxygen via the catalyst proceeds further, so that the hydrogen consumption amount in the reformed gas and the water generation amount also increase. Therefore, the amount of hydrogen in the reformed gas is reduced, which is not preferable.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the efficiency of carbon monoxide oxidation reaction by a catalyst and improve the efficiency of carbon monoxide removal.

[0012]

In order to achieve the above object, the means adopted in the carbon monoxide removing apparatus according to claim 1 is a removal method for oxidizing and removing carbon monoxide from a gas containing carbon monoxide. In the device, a catalyst housing containing a catalyst involved in the oxidation reaction of carbon monoxide in the presence of oxygen is provided in the gas passage pipe so that the gas passes through the housing of the catalyst. The gist of the present invention is to provide oxygen introducing means for introducing oxygen into the catalyst containing portion of the catalyst containing body from a plurality of locations along the flow.

Further, the means adopted in the carbon monoxide removing apparatus according to claim 2 is a removing apparatus for oxidizing and removing the carbon monoxide from a gas containing carbon monoxide, which is carried out in the presence of oxygen. A catalyst containing body containing a catalyst involved in the oxidation reaction of carbon is provided in the gas passage pipe so that the gas passes through the containing portion of the catalyst, and the gas passage pipe is provided on the upstream side of the catalyst containing body. An oxygen introduction means for introducing oxygen is provided, and the gist of the catalyst containing body is that the catalyst is contained so that the amount of the catalyst per unit volume on the upstream side with respect to the downstream side of the gas flow is reduced. To do.

[0014]

In the carbon monoxide removing apparatus having the above structure, oxygen is introduced into the catalyst storage portion of the catalyst storage body from a plurality of locations along the gas flow by the oxygen introducing means. Therefore, carbon monoxide and oxygen are simultaneously mixed in each of the oxygen-introduced portions, and the situation of oxygen deficiency does not occur. For this reason, the oxidation reaction of carbon monoxide proceeds substantially simultaneously by the catalyst at each of the oxygen introduction points. Therefore, the amount of heat generated by the progress of the oxidation reaction also increases substantially simultaneously at a plurality of points along the gas flow, so that the variation in the temperature distribution of the stored catalyst in the gas flow direction is suppressed, and the catalyst It is possible to put it at an appropriate temperature in the flow direction.

In the carbon monoxide removing device according to the second aspect of the invention, oxygen is introduced into the gas passage pipe on the upstream side of the catalyst containing body by the oxygen introducing means so that the catalyst in the catalyst containing body is changed into the gas flow. On the upstream side, carbon monoxide and oxygen are mixed.
However, since the amount of the catalyst per unit volume stored in the catalyst storage body is small on the upstream side of the gas flow, the rapid progress of the oxidation reaction of carbon monoxide by the catalyst is suppressed on the upstream side. Thereby, on the upstream side, heat generation and oxygen consumption due to the oxidation reaction are suppressed. Since oxygen consumption is suppressed on the upstream side, a relatively large amount of oxygen is mixed on the downstream side so that oxygen deficiency does not occur. Moreover, on the downstream side, since the amount of the catalyst per unit volume stored in the catalyst storage body is large, it does not interfere with the progress of the carbon monoxide oxidation reaction in combination with the fact that oxygen is not insufficient. Therefore, the oxidation reaction of carbon monoxide by the catalyst can be made to proceed almost uniformly along the gas flow in the catalyst housing. As a result, it is possible to suppress variations in the temperature distribution of the stored catalyst in the gas flow direction and to keep the catalyst at an appropriate temperature in the gas flow direction.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the carbon monoxide removing apparatus according to the present invention will be described with reference to the drawings. First,
A fuel cell system to which the carbon monoxide removing apparatus of the first embodiment is applied will be briefly described.

As shown in FIG. 1, the fuel cell system 10
Are a reformer 12 that reforms methanol with steam to produce a hydrogen-rich reformed gas, a fuel cell 14 that uses hydrogen gas and oxygen gas as fuel gas, and oxidizes carbon monoxide in the gas in the presence of oxygen. Carbon monoxide removal device (hereinafter CO
A removing device) 16.

The reformer 12 includes a reforming reaction section 18 containing a methanol reforming catalyst (eg, Cu--Zn type catalyst, Cu--Cr type catalyst, etc.), and methanol reforming in the reforming reaction section 18. And a heating unit 20 for heating the catalyst for use to the appropriate temperature. Then, the reformer 12 receives the supply of water and methanol to the reforming reaction unit 18, and the reforming reaction unit 1
Hydrogen-rich reformed gas (H ₂ : 75%) is generated by advancing the following two-step chemical reactions by the methanol reforming catalyst of No. 8, and this reformed gas is sent downstream together with steam.

CH ₃ OH → 2H ₂ + CO CO + H ₂ O → H ₂ + CO ₂

Therefore, the reformed gas sent from the reformer 12 is a mixed gas that occupies most of hydrogen and carbon dioxide, but it contains about 1% of carbon monoxide (CO) which is an intermediate product of the above reaction. Includes about 0.1 to 5%. And this CO
The contained reformed gas is sent to the CO removing device 16.

In the chemical reaction described above, the methanol reforming catalyst in the reforming reaction section 18 has an appropriate temperature (for example, 200
~ 300 ° C). Therefore, the reformer 12
Receives the supply of methanol and hydrogen (gas) as heat generation energy sources to the heating unit 20, burns methanol and hydrogen in the reformer 12, and heats the reforming reaction unit 18 by the combustion heat. In addition, this hydrogen gas is used in the fuel cell 1
Excess hydrogen gas from 4 is used.

The CO removing device 16 receives supply of the reformed gas and air from the heating section 20, oxidizes and removes CO in the reformed gas, and sends out the hydrogen-rich reformed gas to the fuel cell 14. The detailed configuration of the CO removal device 16 and the CO oxidation removal will be described later.

The fuel cell 14 has an electrolyte membrane (for example, a solid polymer electrolyte membrane) 22 that selectively permeates hydrogen ions.
Is sandwiched between the anode 24 and the cathode 26, and exhibits an electromotive force through an electrochemical reaction of the fuel gas supplied to the anode and the cathode. That is, when the fuel cell 14 receives the reformed gas (hydrogen-rich) after CO oxidation removal through the CO removal device 16 to the anode 24 and the air supply to the cathode 26, the fuel cell 14 can generate the electricity represented by the following reaction formula. Allow a chemical reaction to proceed.

The anode (hydrogen ^{_{electrode): H 2 → 2H + +}} 2e - ... cathode (oxygen ^{electrode): 2H + + 2e - +} (1/2) O 2 → H 2 O ...

The hydrogen ions produced by the reaction of the formula at the anode 24 are in the hydrated state of H ⁺ ( _x H ₂ O), and the electrolyte membrane 2
The hydrogen ions that permeate (diffuse) 2 and permeate the membrane are subjected to the reaction of the formula at the cathode 26. As a result, the fuel cell 14 exhibits an electromotive force and supplies the electromotive force to an external load such as a motor. In this case, as shown in the figure, the surplus reformed gas from the anode 24 is heated by the heating unit 20 of the reformer 12.
And excess air is discharged from the cathode 26 to the atmosphere. Then, in the heating unit 20, the unused hydrogen (hydrogen not provided in the formula) in the reformed gas sent from the anode 24 is burned with methanol.

A check valve, a fluid pressure pump, etc. are provided at appropriate places in the supply lines for methanol, water, air, etc. in the fuel cell system 10 described above. Further, each pump is, of course, drive-controlled, for example, in the case of a water pump and a methanol pump, so that the molar ratio of the two becomes a predetermined value, but since it is not directly related to the gist of the present invention, its description will be omitted. It will be omitted.

Next, the detailed structure of the CO removing device 16 will be described. As shown in the block diagram of FIG. 2, the CO removal device 16 includes a first oxidation reactor 30 and a second oxidation reactor 32 which are divided into three in the flow direction of the gas (reformed gas from the reformer 12). The third oxidation reactor 34 is provided in series with a reformed gas pipe 36 that is a reformed gas passage from the reformer 12.
Then, the reformed gas is sequentially passed through each of the oxidation reactors from the upstream side thereof, and then is sent to the fuel cell 14. Further, in the reformed gas pipeline 36, CO concentration sensors 31a, 31b, 31c that detect the CO concentration in the gas passing through the pipelines are installed upstream of the respective oxidation reactors. Therefore, each CO concentration sensor detects the CO concentration in the gas flowing into each oxidation reactor, and the signal is sent to a controller (not shown).

First oxidation reactor 30 and second oxidation reactor 3
Each of the oxidation reactors of the second and third oxidation reactors 34 stores a catalyst (for example, a Pt catalyst) involved in the CO oxidation reaction (2CO + O ₂ → 2CO ₂ ) in the presence of oxygen on a carrier. Then, CO is oxidized by this catalyst to CO ₂ and CO in the gas is removed.

In addition to the above, the CO removing device 16 includes a first oxidation reactor 30, a second oxidation reactor 32, and a third oxidation reactor 34.
An air introducing pipe 38 for introducing air into the reforming gas pipe 36 is provided upstream of the respective oxidation reactors and downstream of the corresponding CO concentration sensor, and the branch pipes 38a, 38b, 38c of the pipes are provided. Have joined. In addition, each branch pipe 38
The a, 38b, and 38c are provided with flow rate adjusters 40a, 40b, and 40c that adjust the flow rate of the air passing through the pipelines. The flow rate adjusters 40a, 40b, 40c are
It is connected to a control device (not shown), and the flow rate is adjusted by a control signal from this control device. Since the control device outputs a control signal of a flow rate according to the CO concentration detected by the CO concentration sensor to each flow rate regulator, each flow rate regulator introduces air with a flow rate according to the CO concentration into the corresponding oxidation reactor. .
Therefore, the catalyst in each oxidation reactor is placed in a state in which the reformed gas containing CO and air having a flow rate according to the CO concentration are mixed, that is, CO and oxygen are mixed.

Here, the relationship between the amount of air introduced into each oxidation reactor and the CO concentration detected by the CO concentration sensor upstream of each oxidation reactor will be described in detail. First, the first oxidation reactor 3
The total amount of air to be introduced (total amount of introduced air) L is determined according to the CO concentration detected by the 0 upstream CO concentration sensor 31a. The total amount of introduced air L is an air amount that is sufficient to oxidize all of the detected concentrations of CO into CO ₂ and is determined in consideration of the amount of oxygen that reacts with hydrogen in the reformed gas by the catalyst. . The total amount of introduced air L is oxygen (air)
Corresponds to the amount of air introduced in the prior art in which is introduced into the reformed gas only upstream of the reactor.

The flow rate adjusters 40a, 40b, 4
0c adjusts the flow rate of the pipe line to 1/3 of the total amount L of introduced air, and L / 3 of air is introduced to each corresponding oxidation reactor. After that, in the second oxidation reactor 32 and the third oxidation reactor 34, the amount of introduced air of L / 3 is further adjusted as follows. That is, the amount of air introduced into both oxidation reactors is determined by the CO concentration sensor 31 upstream of both oxidation reactors.
The increase / decrease is corrected according to the CO concentration detected by b and 31c. Specifically, the amount of air of L / 3 ± α is introduced into the second oxidation reactor 32, and the amount of air of L / 3 ± β is introduced into the third oxidation reactor 34.

Therefore, the CO removing apparatus 16 of the first embodiment
In the respective oxidation reactors of the first oxidation reactor 30, the second oxidation reactor 32, and the third oxidation reactor 34, the mixture of carbon monoxide and oxygen is simultaneously expressed, and the amount of CO depends on the CO concentration. Oxygen deficiency does not occur by introducing air. Therefore, in the CO removal device 16, the oxidation reaction of carbon monoxide by the catalyst simultaneously proceeds in each oxidation reactor. Therefore, the amount of heat generated by the progress of the oxidation reaction also increases in each oxidation reactor at substantially the same time, which suppresses the variation in the temperature distribution of the catalyst housed in each oxidation reactor. As a result, according to the CO removal device 16, the catalyst of each oxidation reactor can be placed at an appropriate temperature, so that the efficiency of the oxidation reaction of carbon monoxide by the catalyst is increased and the removal efficiency of carbon monoxide is improved. Can be improved.

Further, in the CO removing device 16, the first oxidation reactor 30, the second oxidation reactor 32, and the third oxidation reactor 3
The catalyst of each oxidation reactor of No. 4 is not placed in an oxygen-deficient state, and the downstream oxidation reactor (second oxidation reactor 32
In addition, a CO mixed gas (reformed gas) after a portion of CO is oxidized and removed by the upstream oxidation reactor is flown into the third oxidation reactor 34). Therefore, even if the CO concentration, the gas temperature, etc. of the reformed gas from the reformer 12 fluctuate, the reformed gas whose fluctuation is suppressed is controlled by the second oxidation reactor 32 and the third reformer.
Since the CO can be removed by the oxidation reactor 34, the fuel cell 1
A hydrogen-rich reformed gas with a surely reduced CO concentration is sent to No. 4. Therefore, the CO removal device 16 can reliably prevent CO poisoning of the catalyst at the anode of the fuel cell 14 and avoid deterioration of cell performance.

Next, the above-mentioned effects of the CO removing device 16 will be described with specific numerical values. Each of the first oxidation reactor 30, the second oxidation reactor 32, and the third oxidation reactor 34 is a tubular body having a cross-sectional area of 2 cm ² and a length of 5 cm. The Pt catalyst is supported on a carrier. Stored (catalyst load:
2 g / liter). Then, from the reformer 12, the reformed gas (H ₂ : 75%, CO ₂ :
24%, CO: 1%) was sent out at a flow rate of 10 liters / min.

Under these conditions, air was introduced into the respective oxidation reactors from the branch pipes 38a, 38b, 38c as described above. Then, when the CO concentration of the reformed gas in the reformed gas pipe 36 was measured downstream of the third oxidation reactor 34, it was 10 ppm. On the other hand, the branch pipe 38a
In the case where air is introduced only at a predetermined flow rate (0.5 liter / min), that is, in the case of the conventional technique in which oxygen is introduced into the reformed gas only upstream of the reactor, the third oxidation reactor 3
The CO concentration in the 4 downstream was 200 ppm. From this, it was found that the CO removal device 16 improved the CO removal efficiency as compared with the conventional case.

Next, the CO removing device 16 of the second embodiment will be described. The CO removing device 16 of the second embodiment is
The structure of the oxidation reactor and the structure of introducing air are different from those of the first embodiment. Therefore, in the following explanation,
Descriptions of members having the same functions as those of the first embodiment will be omitted.

As shown in the schematic sectional view of FIG. 3, the CO removing device 16 of the second embodiment is provided with only one oxidation reactor 42 in the middle of the reformed gas pipeline 36, and the reactor concerned has ,
A Pt catalyst that participates in the oxidation reaction of CO in the presence of oxygen is supported and stored on the carrier 44. Therefore, the reformed gas flowing from the reformed gas pipe 36 is sent to the fuel cell 14 while being in contact with the Pt catalyst.

Further, in the oxidation reactor 42, in the vicinity of the connecting portion with the reformed gas pipe 36, that is, on the reformed gas inlet side,
An air introduction pipe line 46 for introducing air is connected. Inside the oxidation reactor 42, the air introducing pipe 46 has a spiral shape as shown in the drawing, and its end is closed. A large number of air discharge holes 48 are formed at appropriate intervals in the spiral portion of the air introduction pipe line 46, that is, in the inside of the oxidation reactor of the air introduction pipe line 46, up to the pipe end. .

Therefore, when air is introduced from the air introduction pipe line 46, the introduced air is discharged from the air discharge hole 48 of the spiral portion of the air introduction pipe line 46 to every corner inside the oxidation reactor 42. To be done. In other words, air is introduced into the oxidation reactor 42 from a plurality of locations along the flow of the reformed gas in the oxidation reactor 42 (portions where the air discharge holes 48 are formed). Therefore, in the CO removing apparatus 16 of the second embodiment, CO is removed at a plurality of locations along the reformed gas flow in the oxidation reactor 42 (perforated locations of the air discharge holes 48).
A mixture of reformed gas containing air and air, that is, CO
A state where oxygen and oxygen are mixed is developed at the same time, and the situation of lack of oxygen does not occur.

Therefore, the CO removing device 16 of the second embodiment
Then, the oxidation reaction of carbon monoxide by the catalyst is simultaneously advanced at a plurality of points along the flow of the reformed gas in the oxidation reactor 42. Therefore, the amount of heat generated by the progress of the oxidation reaction also increases substantially simultaneously at a plurality of points along the reformed gas flow in the oxidation reactor 42, so that the catalyst from the gas inlet side to the outlet side of the oxidation reactor 42 is increased. Suppresses variations in temperature distribution. As a result, even with the CO removing device 16 of the second embodiment, the catalyst from the gas inlet side to the outlet side of the oxidation reactor 42 can be placed at an appropriate temperature, so that the oxidation of carbon monoxide by the catalyst is performed. The efficiency of the reaction can be increased and the efficiency of removing carbon monoxide can be improved.

Next, a description will be given of an embodiment in which the amount of the catalyst is specified when the catalyst is stored. C of the third embodiment
As shown in the schematic cross-sectional view of FIG. 4, the O remover 16 has only one oxidation reactor 50 in the middle of the reformed gas pipeline 36.
And an air introduction conduit 52 for introducing air into the reformed gas conduit 36 is provided upstream thereof.

The oxidation reactor 50 accommodates the Pt catalyst, which participates in the oxidation reaction of CO in the presence of oxygen, as a pellet catalyst as follows. That is, on the gas inlet side of the oxidation reactor 50, a pellet-shaped Pt catalyst 54a having an outer diameter of about 6 mm is stored in a layered manner over a predetermined range, and downstream thereof, a pellet-shaped Pt catalyst 54b having an outer diameter of about 3 mm. Of the Pt catalyst 54 having an outer diameter of about 1 mm is housed in layers over a predetermined range, that is, on the downstream side, that is, on the gas outlet side of the oxidation reactor 50.
c are stored in layers over a predetermined range. Therefore, the reformed gas flowing in from the reformed gas pipe 36 is sequentially brought into contact with the pellet-shaped Pt catalysts having different outer diameters, and the fuel cell 14
Send to.

Since the outer diameter of each pellet-shaped Pt catalyst stored in the oxidation reactor 50 in three layers is smaller than the gas inlet side of the oxidation reactor 50, the pellet-shaped Pt catalyst in each layer is formed. The surface area of the catalyst increases in the order of layers from the gas inlet side. Therefore, the oxidation reactor 5
The catalyst amount at 0 gradually increases from the gas inlet side to the gas outlet side, that is, from the upstream side to the downstream side of the reformed gas flow in the oxidation reactor 50. Then, the reformed gas and air are mixed by introducing air from the air introduction conduit 52 to the reformed gas conduit 36 on the upstream side of the oxidation reactor 50, and the reformed gas containing CO and the air are mixed. The gas in the above state, that is, the state in which CO and oxygen are mixed is sent to the oxidation reactor 50.

In this oxidation reactor 50, since the amount of catalyst on the gas inlet side is small as described above, the rapid progress of the carbon monoxide oxidation reaction by the Pt catalyst is suppressed, and the oxidation reactor 50 is suppressed. On the gas inlet side, the heat generation and oxygen consumption associated with the oxidation reaction are suppressed. Oxygen consumption is suppressed on the gas inlet side, and pellets P on the downstream side are suppressed.
Since a relatively large amount of oxygen-containing gas flows into the storage range of the t catalyst 54b and the pellet-shaped Pt catalyst 54c, oxygen deficiency does not occur. Moreover, since the amount of the stored catalyst is large on the downstream side, it does not interfere with the progress of the oxidation reaction of carbon monoxide by the catalyst in combination with the fact that oxygen is not insufficient. Therefore, the oxidation reaction of carbon monoxide by the catalyst can proceed almost uniformly along the flow of the reformed gas in the oxidation reactor 50. Therefore, variations in the temperature distribution of the catalyst in each layer housed in the oxidation reactor 50 are suppressed. As a result, the CO removing apparatus 1 of the third embodiment
According to No. 6, since the catalyst in each layer from the gas inlet side to the outlet side of the oxidation reactor 50 can be placed at an appropriate temperature, the efficiency of the carbon monoxide oxidation reaction by the catalyst can be increased and The removal efficiency can be improved.

Further, a CO removal device with improved carbon monoxide removal efficiency can be provided by a very simple modification in which the oxidation reactor 50 is replaced with an oxidation reactor in an existing device. Therefore, according to the CO removing device 16 of the third embodiment, the reason for the effectiveness of the existing equipment can be considered.

Next, the CO removing device 16 of the fourth embodiment will be described. The CO removing device 16 of the fourth embodiment is
The method of adjusting the catalyst amount of the catalyst is different from that of the third embodiment. That is, as shown in the schematic cross-sectional view of FIG. 5, the CO removing apparatus 16 of the fourth embodiment has the following configuration in the oxidation reactor 56 provided only in the middle of the reformed gas pipeline 36. Store the catalyst.

As shown in the figure, the oxidation reactor 56 includes four catalyst storage cell chambers 56a to 56 along the flow of the reformed gas.
It is divided and divided into d. Then, in the catalyst storage cell chamber 56a on the inlet side of the reformed gas, a metal carrier cell carrying a Pt catalyst involved in the CO oxidation reaction in the presence of oxygen is stored so that the number of cells is 31 / cm ^2. ing.
The metal carrier cells described above are housed in the catalyst housing cell chamber 56b downstream thereof so that the number of cells is 47 / cm ² . The catalyst storage cell chamber 56c has 32 cells.
/ Cm ² and so as, as the number of cells is 78 / cm ² to catalyst storage cell chamber 56d, the metal carrier respectively are accommodated.

Therefore, also in the fourteenth embodiment, the surface area of the Pt catalyst in each catalyst storage cell chamber increases from the gas inlet side to the cell chamber in the same manner as in the third embodiment. Therefore, the amount of catalyst in the oxidation reactor 56 gradually increases from the upstream side to the downstream side of the reformed gas flow in the oxidation reactor 56. As a result,
According to 16th of the fourth embodiment, as in the third embodiment, the oxidation reaction of carbon monoxide by the catalyst is performed by placing the catalyst from the gas inlet side to the outlet side of the oxidation reactor 56 at an appropriate temperature. The efficiency of carbon monoxide removal can be improved by increasing the efficiency of.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment and can be implemented in various modes without departing from the scope of the present invention. Of course.

For example, in the CO removing device 16 of the first embodiment, when introducing air into each of the first oxidation reactor 30, the second oxidation reactor 32, and the third oxidation reactor 34, C
Introducing air at a flow rate according to the O concentration, and for the second oxidation reactor 32 and the third oxidation reactor 34, the upstream C
Although the flow rate is corrected by the O concentration, the present invention is not limited to this. In other words, the configuration may be such that only the same flow rate of air is introduced into each of the first to third oxidation reactors. Even if configured in this manner, the situation of oxygen deficiency does not occur in each oxidation reactor, so the efficiency of the CO oxidation reaction is increased and the CO removal efficiency is improved by uniformizing the temperature distribution in the gas flow direction of the catalyst. Can be improved. Further, since the flow rate control is unnecessary, the structure can be simplified.

Further, in the CO removing device 16 of the first embodiment, the CO concentration sensor may be one upstream of the first oxidation reactor 30. Even in this case, the first oxidation reactor 3
0 or the CO concentration downstream of the second oxidation reactor 32, the CO concentration in the original reformed gas, the amount of air introduced into each oxidation reactor, the first oxidation reactor 30 and the second oxidation reactor 32 It is calculated from the CO removal amount (predicted value) and the like, and the flow rate of air according to the calculated CO concentration is adjusted to the second oxidation reactor 32 and the third oxidation reactor 3.
Can be introduced in 4. Therefore, in the case of such a configuration, the configuration can be simplified, the number of parts can be reduced, and the cost can be reduced by reducing the number of installed CO concentration sensors.

Further, in the CO removing apparatus 16 of the first embodiment, three oxidation reactors were used, but the first oxidation reactor 30
It goes without saying that a simple structure including the second oxidation reactor 32 and the second oxidation reactor 32 can be used.

In the CO removing device 16 of the second embodiment,
When the air discharge hole 48 is formed in the spiral portion of the air introduction pipe line 46, the perforation density may be different between the gas inlet side and the gas outlet side of the oxidation reactor 42. For example,
It is also possible to configure so that the perforation density of the air exhaust holes 48 gradually increases from the gas inlet side of the oxidation reactor 42, specifically, the number of the air exhaust holes 48 perforated from the gas inlet side gradually increases. . Furthermore, the internal portion of the oxidation reactor 42 of the air introduction pipe line 46 may be formed in a mesh shape, a tree shape, or the like instead of the spiral shape.

In the CO removing device 16 of the third embodiment,
As the amount of catalyst gradually increased from the upstream side to the downstream side of the reformed gas flow, it was decided to use a pellet catalyst as the catalyst and change its outer diameter. However, changing the size of the catalyst as a monolithic catalyst instead of a pellet catalyst,
By changing the size of the carrier supporting the catalyst, the amount of the catalyst can be gradually increased from the upstream side to the downstream side of the reformed gas flow. Alternatively, even if the carriers have the same shape, carriers having different catalyst loadings are used to gradually increase the catalyst amount of the catalyst stored in the oxidation reactor 50 from the upstream side to the downstream side of the reformed gas flow. It can also be configured as follows.

Further, in the third and fourth CO removing devices 16, the catalyst amount is changed in multiple stages, but there are two stages in which the catalyst amount is small on the gas inlet side of the oxidation reactor and large on the outlet side. It is also possible to adopt a configuration having a catalytic amount.

Further, each of the above-mentioned embodiments has the CO removing device 1
6 has been described as applied to the fuel cell system 10, but it goes without saying that it can be applied to any device as long as it needs to remove carbon monoxide in the gas by oxidation.

[0057]

As described above in detail, in the carbon monoxide removing apparatus according to the first and second aspects, the catalyst is prevented from flowing in the gas flow direction by suppressing the variation of the temperature distribution in the gas flow direction of the catalyst. Can be placed at a suitable temperature for
Therefore, according to the carbon monoxide removing apparatus of the first and second aspects, the efficiency of the carbon monoxide oxidation reaction by the catalyst can be increased and the carbon monoxide removing efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system 10.

FIG. 2 is a block diagram showing a schematic configuration of a CO removal device 16 of the first embodiment.

FIG. 3 is a sectional view showing a schematic configuration of a CO removal device 16 of a second embodiment.

FIG. 4 is a sectional view showing a schematic configuration of a CO removing device 16 of a third embodiment.

FIG. 5 is a sectional view showing a schematic configuration of a CO removing device 16 of a fourth embodiment.

[Explanation of symbols]

 10 ... Fuel cell system 12 ... Reformer 14 ... Fuel cell 16 ... CO removal device 18 ... Reforming reaction part 20 ... Heating part 22 ... Electrolyte membrane 24 ... Anode 26 ... Cathode 30 ... First oxidation reactor 31a, 31b, 31c ... CO concentration sensor 32 ... 2nd oxidation reactor 34 ... 3rd oxidation reactor 36 ... Reforming gas pipeline 38 ... Air introduction pipeline 38a, 38b, 38c ... Branch pipe 40a, 40b, 40c ... Flow rate regulator 42 ... Oxidation reactor 44 ... Carrier 46 ... Air introduction pipe line 48 ... Air discharge hole 50 ... Oxidation reactor 52 ... Air introduction pipe line 54a ... Pellet Pt catalyst 54b ... Pellet Pt catalyst 54c ... Pellet Pt catalyst 56 ... Oxidation Reactor 56a-56d ... Catalyst storage cell chamber

Claims (2)

[Claims] 1. A removal device for oxidatively removing carbon monoxide from a gas containing carbon monoxide, the catalyst housing containing a catalyst involved in the oxidation reaction of carbon monoxide in the presence of oxygen, A catalyst storage part is provided in the gas passage pipe so that the gas passes, and an oxygen introduction means for introducing oxygen into the catalyst storage part of the catalyst storage body from a plurality of locations along the gas flow. An apparatus for removing carbon monoxide, comprising: 2. A removal device for oxidizing and removing carbon monoxide from a gas containing carbon monoxide, comprising: a catalyst container containing a catalyst involved in the oxidation reaction of carbon monoxide in the presence of oxygen; A catalyst storage part is provided in the gas passage pipe so that the gas passes, and an oxygen introduction unit for introducing oxygen into the gas passage pipe is provided on the upstream side of the catalyst storage body. An apparatus for removing carbon monoxide, characterized in that the catalyst is contained so that the amount of the catalyst per unit volume on the upstream side with respect to the downstream side of the gas flow is reduced.