JP2000169106A - Method and device for converting carbon monoxide in reformed hydrogen - Google Patents

Abstract

(57) [Problem] To improve the conversion efficiency of CO contained in reformed hydrogen and reduce the CO concentration. SOLUTION: In a hydrogen generator 10 for reforming a hydrocarbon feedstock to generate reformed hydrogen, a CO shift unit 14
Two CO shift tanks 18 and 22 are provided. A highly active catalyst such as Pt is accommodated inside the first CO shift tank 18, and the CO in the injected reformed hydrogen is brought into contact with oxygen at a predetermined temperature to shift the CO to a predetermined value. Second CO shift tank 2
Reference numeral 2 contains a low-activity catalyst such as Ru, and converts and removes unconverted CO and CO regenerated by the reverse shift reaction in the first CO shift tank 18. That is, the first CO
In the shift tank 18, most of the CO in the reformed hydrogen is converted in the presence of the high-activity catalyst, and at least the low-activity catalyst in the second CO shift tank 22 is reduced to a level that does not receive CO poisoning.
On the other hand, a low activity catalyst has a low CO conversion activity, but has a very low or suppressed reverse shift reaction. Therefore, a low concentration of CO can be converted and removed without regenerating CO by the reverse shift reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a converter for converting CO mixed in reformed hydrogen in an apparatus for generating reformed hydrogen by reforming a hydrocarbon-based raw material.

[0002]

2. Description of the Related Art Conventionally, as an industrial production method of hydrogen,
A steam reforming method, a partial oxidation method, and the like are known. These methods use hydrocarbons in natural gas or petroleum-based fluids, such as methane and methanol, as raw materials, and reform the raw materials by contacting them with steam at high temperature or partially oxidizing them to produce hydrogen. To manufacture. The hydrogen produced here is widely used in the chemical industry and the like.

[0003] In recent years, the above-mentioned method for producing hydrogen by reforming hydrocarbons has also been used in fuel cells. That is, the fuel cell has a mechanism in which electrons are supplied from hydrogen at a fuel electrode (anode), and oxygen receives electrons at a cathode to generate electric energy and water. Manufactured by reforming hydrogen. As described above, since the fuel cell generates power using hydrogen and oxygen as raw materials, it has excellent environmental characteristics,
As a future energy supply system, it is expected to be widely used from a power supply for a large spacecraft to a power supply for a small vehicle.

However, in a fuel cell, for example, a phosphoric acid electrolyte fuel cell (PAFC), a catalyst layer containing a noble metal such as platinum is used for an electrode, and the catalyst layer is formed by reforming the hydrocarbon. Poisoning by the by-product CO may make power generation difficult or impossible. Therefore, it is necessary to remove CO from the reformed hydrogen generated by reforming the hydrocarbon raw material. As a method for removing CO from such reformed hydrogen, there is a CO conversion method in which CO is converted and removed.

This CO conversion method is a reaction in which CO is converted into CO ₂ by contacting a CO conversion catalyst, for example, platinum or the like, with oxygen at a high temperature not subject to CO poisoning. In such a conventional CO shift reaction using a platinum catalyst or the like, the CO concentration in the reformed hydrogen can be reduced to about 20 ppm to 100 ppm. By keeping the temperature of the fuel cell at 80 ° C. or higher for the CO remaining at such a low concentration, the fuel cell can be operated without causing the problem of CO poisoning on the platinum electrode.

[0006]

However, the temperature of the fuel cell gradually rises due to the current generated by the start-up of the cell and the internal resistance, and becomes a set operating temperature. When the temperature is low, there is a problem that the power generation efficiency is reduced due to the influence of CO poisoning. In addition, the above-mentioned problem of CO poisoning is solved by raising the temperature of the fuel cell. However, raising the temperature of the fuel cell increases the internal resistance of the fuel cell, thereby lowering the cell efficiency. Was causing it. Therefore, this CO
If the concentration can be reduced as much as possible, battery efficiency can be improved.

In a fuel cell of a low temperature type solid electrolyte type having an operation temperature as low as room temperature to 80 ° C. or less,
This makes the platinum electrode susceptible to poisoning by CO. Therefore, as fuel for this low-temperature solid electrolyte fuel cell,
At present, pure hydrogen is used without using reformed hydrogen. However, if the CO in the reformed hydrogen can be extremely reduced, the low-temperature solid electrolyte fuel cell can be operated using reformed hydrogen that is cheaper than pure hydrogen. The range of application can be expanded.

On the other hand, the above-mentioned conventional reformed hydrogen after CO conversion includes, in addition to the CO that remains unconverted, CO that is regenerated from CO ₂ by a reverse shift reaction that occurs during CO conversion.
Is included. In other words, in order to reduce the CO concentration, it is not enough to simply transform and remove unconverted CO,
Reverse shift reaction (CO ₂ + H ₂ → CO + H ₂ O) is suppressed and C
It is necessary to prevent the regeneration of O.

Further, in recent years, fuel cells are expected to be applied to power supplies for automobiles, home electric appliances, and the like, and in response to this demand, downsizing of the hydrogen generator is required.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to further reduce the CO concentration in reformed hydrogen. Another object is to reduce the size of a device for generating reformed hydrogen.

[0011]

Means for Solving the Problems In order to achieve the above object, the present invention provides a method in which CO mixed with reformed hydrogen produced by reforming a hydrocarbon-based raw material is brought into contact with oxygen in the presence of a catalyst. A CO conversion method for converting CO in the reformed hydrogen at a predetermined temperature in the presence of a highly active catalyst to reduce the CO to a predetermined value; and
A second CO conversion step of converting and removing CO contained in the reformed hydrogen after the O conversion step at a predetermined temperature in the presence of a low activity catalyst.

The above-mentioned invention is intended to increase the CO conversion rate by combining the advantages of a high activity catalyst and a low activity catalyst. That is, a catalyst having a high CO conversion efficiency has a characteristic that it has relatively low CO poisoning and a high efficiency of promoting the CO conversion reaction, and also promotes a reverse shift reaction in which CO is regenerated. On the other hand, a low activity catalyst is susceptible to CO poisoning and has a low efficiency of promoting a CO shift reaction, but has a characteristic that the activity of causing a reverse shift reaction is extremely low.

Therefore, in the first CO conversion step, most of the CO in the reformed hydrogen is positively converted by the highly active catalyst to reduce the CO to a predetermined value. The “predetermined value” is a value that does not poison the low activity catalyst used in the next step, and is determined by the type of the low activity catalyst used, the CO conversion temperature, and the like. CO remaining in this process includes:
CO regenerated by reverse shift reaction other than undenatured CO
Is also included. This low-concentration CO is subjected to CO conversion by the following CO conversion reaction using a low-activity catalyst, whereby CO is removed. By performing CO conversion in two stages using two catalysts having different characteristics in this manner, CO can be efficiently removed, and an increase in CO concentration due to CO regeneration can be reduced or prevented. As a result, when the reformed hydrogen CO-converted by the method of the present invention is used in a fuel cell, the operating temperature of the fuel cell can be reduced, and thereby the cell efficiency can be increased.

In the above, "contact with oxygen"
The reason is that it is not always necessary to make contact with oxygen gas, but it may be brought into contact with air containing oxygen, and as a result, may be brought into contact with oxygen.

In the present invention, a highly active catalyst is a catalyst having a high activity for promoting a CO conversion reaction and a catalyst having low CO poisoning, such as a Pt-based catalyst. Further, the low activity catalyst refers to a catalyst having an activity of promoting a CO shift reaction and having a very low or suppressed activity of promoting a reverse shift reaction, such as a Ru catalyst. For example, by using a Pt catalyst as a high-activity catalyst and using a Ru catalyst as a low-activity catalyst, for example, CO
Can be converted to about 1 ppm, whereby a cell efficiency close to that of pure hydrogen can be achieved. Further, the reformed hydrogen that has been CO-converted by the present method can be used as a fuel for a low-temperature solid electrolyte fuel cell, which conventionally used only pure hydrogen.

The present invention also relates to a CO conversion apparatus for converting CO contained in reformed hydrogen produced by reforming a hydrocarbon-based material by contacting it with oxygen in the presence of a catalyst. A first CO that has an introduction path for introducing hydrogen, contains a highly active catalyst therein, and converts CO in the injected reformed hydrogen into contact with oxygen at a predetermined temperature to convert the CO to a predetermined value. The shift unit is connected to the first CO shift unit via a transfer path, contains a low-activity catalyst therein, and converts CO in reformed hydrogen introduced through the transfer path into oxygen at a predetermined temperature. And a second CO shift unit for converting and removing the first CO shift unit and oxygen supply means for supplying oxygen to the first CO shift unit and the second CO shift unit.

According to the above invention, most of the CO in the reformed hydrogen is converted by contact with oxygen in the presence of the highly active catalyst in the first CO conversion section, whereby CO is reduced.
Here, the reformed hydrogen with reduced CO is transferred to the next second CO shift section through the transfer path. In the second CO shift section, the low activity catalyst can perform the CO shift reaction without being poisoned because the CO concentration is reduced. Under a low activity catalyst, the reverse shift reaction is low, and the reverse shift reaction can be suppressed by adjusting the temperature and the like. As a result, according to the two-stage CO shift section, the CO in the reformed hydrogen can be extremely reduced.

In the above invention, a Pt catalyst is used as the high activity catalyst, and a Ru catalyst is used as the low activity catalyst.

Although the Pt catalyst has an activity to promote the reverse shift reaction, it promotes the oxidation reaction with a high activity and can reduce it to about 50 ppm. And to this extent C
By reducing O, it becomes possible to further reduce to 5 ppm or less by the Ru catalyst without poisoning the Ru catalyst in the second CO shift part.

The CO converter according to the present invention is further provided with an oxygen sensor provided in the transfer path for detecting the oxygen concentration in the gas sent out to the transfer path, and connected to the oxygen sensor and detected by the oxygen sensor. Control means for controlling the shift reaction of the first CO shift section based on the oxygen concentration;
Is further provided.

According to the above invention, it is expected that the reverse shift reaction in the first CO shift section is also suppressed. That is, a highly active catalyst such as a Pt catalyst is used in the first CO conversion section, and this highly active catalyst promotes an oxidation reaction for converting CO and also promotes a reverse shift reaction. However, this reverse shift reaction may be controllable based on the oxygen content in the CO shift. Therefore, the oxygen concentration in the gas sent from the first CO shift unit is measured by the oxygen sensor installed in the transfer path, and the reaction of the first CO shift unit is controlled by the control means based on the measured value. To suppress the reverse shift reaction. Thereby, the regeneration of CO due to the reverse shift reaction is suppressed or prevented, and the CO reduction efficiency in the first CO shift section can be improved.

In the CO converter according to the present invention, the oxygen supply means is connected to the reformed hydrogen introduction passage, and oxygen is supplied together with the reformed hydrogen from the reformed hydrogen introduction passage to the first CO conversion unit. Oxygen supply amount detection means for detecting the amount of oxygen supply in the second CO shift section based on the temperature of the second CO shift section; and Means for controlling the shift reaction of the first CO shift section to adjust the amount of oxygen consumed, wherein oxygen consumption in the first CO shift section is adjusted by the oxygen shift control means, A part of the oxygen supplied from the reforming hydrogen introduction path is supplied to the second CO shift section.

According to the above invention, the gas containing oxygen is fed into the reforming hydrogen introduction passage by the gas supply means, and the oxygen consumption in the first CO shift section is adjusted by the oxygen consumption adjusting means. A part of the oxygen supplied from is supplied also to the second CO shift section. As a result, it is not necessary to separately provide a supply source for supplying oxygen to the second CO shift section, and the size of the shift converter can be reduced.

Further, the hydrogen generator of the present invention comprises a reforming section for reforming a hydrocarbon-based material by contacting it with reforming air containing oxygen in the presence of a reforming catalyst to produce reformed hydrogen. A CO conversion unit for converting CO in reformed hydrogen by contacting it with oxygen in the presence of a catalyst, wherein the CO conversion unit comprises any one of the CO converters of the present invention, A pipe for passing a cooling medium is provided in each of the first CO shift section and the second CO shift section, and the cooling medium flowing through one pipe is used as the hydrocarbon-based material, and the cooling medium flowing through the other pipe is modified. It is characterized by quality air.

Conventionally, the raw material before reforming was vaporized by an evaporator or the like and then sent to the reforming section. However, according to the invention, the heat of reaction generated during CO conversion is absorbed by the raw material passing through the pipe. Heating and evaporation of the raw material,
Cooling of the transformer can be performed simultaneously. Also,
During the reforming of the raw material, the reforming air is supplied to the reforming section, and it is preferable from the viewpoint of the reforming efficiency that the reforming air is heated in advance to give the reforming energy. By passing the reforming air through the pipe, the reforming air can be heated simultaneously with the cooling of the CO shift section. Therefore, according to the present invention, there is no need to provide an evaporator or an air heater in the reforming section, and the apparatus can be downsized. In addition, the first CO metamorphic section and the second C
Cooling is performed by a cooling medium different from that of the O shift unit, and it is possible to individually cool to a temperature suitable for CO shift. Therefore, it is possible to improve the CO shift efficiency in both CO shift units. In particular, in the first CO shift section, it is desirable to use a hydrocarbon-based material having a high heat of reaction and high cooling efficiency as a cooling medium for the first CO shift section in order to shift a large amount of CO. On the other hand, since the second CO shift section has a lower reaction heat than the first CO shift section, it is preferable to cool the second CO shift section with a gas having a low cooling capacity, such as reforming air. By cooling with the reforming air in this way, it is possible to prevent the formation of a temperature distribution in the second CO shift portion and to cool the second CO shift portion uniformly.

According to the present invention, the pipe through which the reforming air flows is provided with an outlet for blowing out a part of the air into the first CO shift section or the second CO shift section. Oxygen is supplied by the reforming air.

According to the above invention, a part of the reforming air is supplied to the first CO shift section or the second CO shift section, whereby the first CO shift section or the second CO shift section is supplied to the first CO shift section or the second CO shift section. Is
There is no need to provide a separate means for supplying oxygen. As a result, the size of the device can be reduced.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 shows the overall configuration of a fuel cell to which a hydrogen generator according to a first embodiment is connected.

The hydrogen generator 10 for generating hydrogen, which is the fuel of the fuel cell 26, is provided with a raw material storage section 11 for storing a reforming raw material. The raw material of the system is contained. The hydrocarbon-based raw material is not particularly limited, and for example, methanol, methane, propane, butane, gasoline and the like can be used.

The reforming section 12 connected to the raw material storage section 11
Reforms hydrocarbon feedstock to produce reformed hydrogen. The reforming method in the reforming section 12 may employ any of a steam reforming method, a partial oxidation method, a hydrocracking method, and the like. In each of these reforming methods, a reforming catalyst is used at the time of reforming, and this reforming catalyst is appropriately selected depending on the reforming method to be used. For example, in the case of a methanol steam reforming method, a Cu-based catalyst such as a Cu-Zn catalyst can be suitably used. In the case of the methane partial oxidation method, a Ni-based or Pd-based catalyst can be used. These catalysts are supported on a suitable carrier and arranged in the reforming section so that they can come into contact with the hydrocarbon feed.

Further, the configuration of the reforming section 12 can be appropriately determined according to the reforming method to be adopted. For example, when the steam reforming method is adopted, a heating evaporator for evaporating a raw material and a steam generator for generating steam can be included in addition to a reforming furnace containing a Cu-based catalyst or the like. And
And steam generated in the heating evaporator vaporized raw material evaporated in the steam generator feed to the reforming furnace, the presence of a catalyst, the raw material steam reforming to produce a reformed hydrogen containing H _2. In the case of the partial oxidation method, a heating evaporator for evaporating the raw material and an air heater for supplying reforming air with reforming energy can be included in addition to the reforming furnace containing the Ni-based catalyst. Then, the vaporized raw material and the heated reforming air are sent to the reformer, and the raw material is reformed in the presence of the catalyst to generate reformed hydrogen.

The reformed hydrogen generated in the reforming section 12 contains CO that poisons the catalyst layer of the fuel cell 26.
In order to remove this CO from the reformed hydrogen, the CO shift unit 1
4 are provided. The CO shift section 14 is connected to the reforming section 12 through the introduction path 13, and the reformed hydrogen of the reforming section 12 is sent to the CO shift section 14 through the introduction path 13. The CO shift converter 14, the CO in reformed hydrogen is contacted with oxygen in the presence of a catalyst, removing the CO is transformed into CO ₂ is selectively oxidized. In the present embodiment, the following two shift tanks 18 and 22 are provided in the CO shift unit 14 in order to shift and remove CO as much as possible.

That is, the first CO shift tank 18 is directly connected to the introduction path 13, and the introduction path 13 has an air source 16 as an oxygen supply source for supplying oxygen required for CO shift.
Is connected. In addition, the first CO shift tank 18
Is a highly active catalyst that catalyzes CO conversion with high activity inside,
For example, a Pt-based catalyst is accommodated in a suitable carrier, for example, alumina. This Pt-based catalyst is relatively less susceptible to CO poisoning even if the reformed hydrogen contains a high concentration of CO, and can also prevent CO poisoning by keeping it at a high temperature. On the other hand, the reverse shift reaction highly active catalysts such as Pt-based catalysts for reproducing CO from CO ₂ (CO ₂ +
H ₂ → CO + H ₂ O). Therefore,
The first CO shift tank 18 has a role of greatly reducing CO in the reformed hydrogen fed from the introduction path 13 while allowing a slight reverse shift reaction to occur.

Since the above-mentioned CO conversion reaction involves heat generation, a cooling unit 24 is connected to the first CO conversion tank 18 in order to remove the heat and maintain the temperature suitable for the CO conversion catalyst. In particular, since a large amount of CO is converted in the first CO shift tank 18 and a large amount of reaction heat is generated, it is preferable to adopt a configuration capable of efficiently removing heat. For example, a method in which a cooling medium having a high cooling capacity such as a liquid is passed through a cooling pipe or the like in the first CO shift tank 18 can be adopted.

Next, the second CO shift tank 22 is connected to the first CO shift tank 18 via a transfer path 19, and the transfer path 19 has an air for supplying oxygen required for CO shift. Source 20 is connected. In addition, the second CO shift tank 2
2 contains a low activity catalyst for converting low concentrations of CO. This low activity catalyst is required to have a high activity such as a Pt catalyst as long as it can convert the CO left unconverted in the first CO shift tank 18 and the CO regenerated by the reverse shift reaction. And not. Rather, the low activity catalyst is preferably a catalyst that does not promote the reverse shift reaction or can suppress the reverse shift reaction. Such low activity catalysts, for example, Ru, Ni, Fe, their alloys,
It can be selected from ceramics, nitrides, and the like, and is preferably a Ru catalyst. This Ru catalyst is susceptible to CO poisoning when the CO concentration is high,
If the concentration is reduced, it is possible to maintain CO
CO conversion can be performed with poisoning prevented and reverse shift suppressed. Therefore, the second CO shift tank 2
In 2, the CO remaining in the reformed hydrogen transferred from the first CO shift tank 18 is shift-removed while the reverse shift reaction is suppressed.

In the second CO shift tank 22, C
Cooling unit 25 to remove reaction heat generated during O
Is connected. Since the amount of CO shift in the second CO shift tank 22 is smaller than that in the first CO shift tank 18, the heat generated correspondingly is small. Therefore, the cooling unit 25 is not required to have a higher cooling capacity than the cooling unit 24 provided in the first CO shift tank 18. For example, the cooling unit 25 performs cooling by using a cooling medium having a low cooling capacity such as a gas,
Maintain a temperature suitable for the O transformation reaction.

The reformed hydrogen generated by the hydrogen generator 10 can be used for various purposes. Here, a fuel cell 26 is connected to the hydrogen generator 10 and the reformed hydrogen generated in the fuel cell 26 is connected. High-quality hydrogen is supplied as fuel. Since the reformed hydrogen generated by the hydrogen generator 10 has a further reduced CO content as compared with a conventional hydrogen generator, it is also suitably used for a fuel cell requiring a hydrogen fuel having a low CO concentration. be able to. This fuel cell 2
6, for example, a phosphoric acid electrolyte fuel cell (PAF
C) and a low-temperature solid electrolyte fuel cell to which pure hydrogen has been conventionally supplied as a fuel. This fuel cell 2
In 6, reformed hydrogen is supplied to the fuel electrode (anode), and oxygen is supplied to the cathode from an air source 28 connected to the fuel cell 26.

Next, the operation of the hydrogen generator will be described.
The case where a Pt catalyst is used as the high activity catalyst and a Ru catalyst is used as the low activity catalyst will be described as an example.

The hydrocarbon-based reforming raw material is stored in the storage section 11, and the stored raw material is supplied to the reforming section 12. In the reforming section 12, the raw material is reformed, and reformed hydrogen is generated and CO is by-produced. For example, when methanol is reformed, hydrogen and carbon dioxide are generated, and at this time, CO is by-produced. The concentration of the by-produced CO varies depending on the type of hydrocarbon raw material, the reformer, the reforming method, and the like, but may be, for example, about 5000 to 10,000 ppm.

The reformed hydrogen containing such a high concentration of CO is introduced into the CO shift section 14, and is first oxidized by the supplied oxygen in the presence of a Pt catalyst in the first CO shift tank 18, to thereby reduce CO 2. Transformed to ₂ . However, in the first CO shift tank 18, the CO shift is efficiently performed, but the CO is slightly regenerated by the reverse shift reaction.
For example, the CO concentration is reduced only to about 20 to 200 ppm. Here, the reformed hydrogen containing a low concentration of CO is then transferred to a second CO shift tank 22, where the reformed hydrogen is further oxidized and converted under a Ru catalyst. When a Ru catalyst is used, the temperature of the second CO shift tank 22 is maintained at, for example, 100 to 130 ° C., so that the Ru catalyst is not poisoned with CO and the reverse shift reaction is suppressed. Catalyzes CO conversion in the hot state. By this CO conversion reaction using the Ru catalyst, CO can be removed to 5 ppm or less.

FIG. 2 shows the results obtained when the reformed hydrogen produced here was used in a low-temperature solid electrolyte fuel cell and the power generation characteristics were measured. Here, two types of reformed hydrogen (1 ppm or less, 5 ppm or less C
In order to investigate the power generation characteristics of O-containing reformed hydrogen, pure hydrogen and two types of reformed hydrogen (15 ppm-containing and 20 ppm CO-containing reformed hydrogen) generated by a conventional hydrogen generator were used as comparison targets. .

As shown in FIG. 2, when the CO concentration in the reformed hydrogen was 5 ppm or less, there was almost no difference between the pure hydrogen and the power generation efficiency. On the other hand, it was shown that when about 15 to 20 ppm of CO was contained as in conventional reformed hydrogen, the power generation characteristics were significantly reduced.

By installing a two-stage CO shift tank in the CO shift section as described above, it is possible to reduce the CO concentration. Particularly, in a battery which generates power at a low temperature, such as a low-temperature solid fuel cell. Also, power generation characteristics equivalent to pure hydrogen were obtained. This makes it possible to reduce the start-up time when starting up the battery.

[Second Embodiment] In the second embodiment,
An oxygen sensor is further provided in the transfer path of the first embodiment. FIG. 3 is an enlarged sectional view of the configuration around the oxygen sensor.

In FIG. 3, an oxygen sensor 34 is connected to the transfer path 32 to measure the amount of oxygen used in the first CO shift tank 30.
Is provided. The first CO shift tank 30 contains a highly active catalyst such as Pt, and a CO shift reaction is performed by the catalyst. However, as described above, since this catalyst also catalyzes a reverse shift reaction for regenerating CO, it can be reduced to only about 20 ppm in the first CO shift tank 30. Here, this first CO shift tank 3
In order to suppress the reverse shift reaction within zero as much as possible, an oxygen sensor 34 is installed, and the amount of oxygen used in the first CO shift tank 30 is monitored.

That is, the reverse shift reaction is related to the amount of oxygen used or present in the first CO shift tank 30 as shown in FIG. That is, the first CO shift tank 30
The reformed hydrogen and oxygen are supplied to the first CO shift tank 3 so that the oxygen concentration becomes higher than the CO concentration near the inlet 30a.
0, the CO concentration near this inlet 30a,
Since the oxygen concentration is high, the oxidation reaction proceeds efficiently. On the other hand, in the vicinity of the outlet 30b, CO and oxygen are consumed by the CO conversion, and conversely, the catalyst is expected to proceed with the reverse shift reaction using the H ₂ and CO ₂ having the increased concentrations to regenerate CO.

Therefore, in the present embodiment, the oxygen sensor 34 in the transfer path measures the oxygen concentration discharged from the first CO shift tank 30, and monitors whether the oxygen concentration is such that the reverse shift reaction hardly occurs. This oxygen sensor 34 has a first C
A control unit 36 for controlling the operation of the O shift tank 30 is connected,
In the oxygen sensor 34, for example, the degree to which oxygen slightly remains as indicated by an arrow A in FIG.
If the temperature falls below the level, a signal is output to the control unit 36 to control the operation of the first CO shift tank 30. For the control of this operation, for example, a method of changing the temperature, the pressure, and the like can be adopted. By controlling the first CO shift tank 30 in this way, the reverse shift reaction is suppressed and C
O regeneration is prevented. Thereby, the first CO shift tank 30
Can be further reduced.

Although the case where only the oxygen sensor is provided is shown here, it is also preferable to provide a CO sensor in addition to the oxygen sensor. When a CO sensor is installed, for example, oxygen and CO discharged from the first CO shift tank 30
The concentration indicated by arrow A in FIG. 4, that is, the ratio at which CO disappears and a small amount of oxygen (for example, about 0.1%) remains can be monitored. . Here, when the ratio deviates from this ratio, as described above, these sensors output a signal to the control unit and the first CO
The operation of the shift tank 30 is controlled.

If the reverse shift reaction in the first CO shift tank can be accurately suppressed by installing the oxygen sensor and the control unit, the CO concentration in the reformed hydrogen in the first CO shift tank is reduced to 5 ppm or less. Is also possible. In this case, the second CO shift tank may be deleted from the CO shift section.

[Third Embodiment] In the third embodiment shown in FIG. 5, the CO converter 37 in the first embodiment is used.
Air source 38 necessary for CO conversion to reduce the size of
Is installed only in the introduction path 39 for introducing reformed hydrogen into the CO shift section 37, and the first CO
Oxygen is supplied to the shift tank 40 and the second CO shift tank 41.

Specifically, as shown in FIG. 5, an air source 38 is connected to an introduction path 39, and the air source 38 is required for a first CO shift tank 40 and a second CO shift tank 41. Pump in air containing oxygen. That is, the oxygen sent from the air source 38 is first used in the first CO shift tank 40, and the oxygen remaining unused is sent to the second CO shift tank 41 together with the reformed hydrogen and the like. .

On the other hand, the second CO shift tank 41 is provided with a temperature sensor 42 as a means for measuring the amount of oxygen supplied into the first CO shift tank 40. CO
The transformation reaction is a reaction that oxidizes CO and is accompanied by heat generation. Therefore, by measuring the temperature in the second CO shift tank 41, it is possible to determine how much oxygen is being sent.

A controller 43 for controlling the operation of the first CO shift tank 40 is connected to the temperature sensor 42. The control unit 43 detects the oxygen supply amount based on the temperature of the temperature sensor 42, and suppresses the operation of the first CO shift tank 40 when it is determined that the amount is small. The supply of oxygen to the second CO shift tank 41 is balanced. Here, the control unit 43 is connected to the cooling unit 44, and the temperature of the first CO shift tank 40 is adjusted by the cooling unit 44 to adjust the reaction of the first CO shift tank 40.

As described above, by making it possible to supply oxygen from one air source 38 to the two CO shift tanks 40 and 41, the size of the apparatus can be reduced, and the cost of manufacturing the apparatus can be reduced by reducing the number of air sources. It is also possible to plan.

[Fourth Embodiment] FIG. 6 shows a hydrogen generator according to a fourth embodiment. In the present embodiment, in order to reduce the size of the apparatus, as a cooling medium for cooling the first CO shift tank and the second CO shift tank, a raw material for producing reformed hydrogen and a reforming medium used for reforming the raw material are used. Quality air is used.

Regarding the reforming in the reforming section 48, an evaporator for heating and evaporating a raw material such as a hydrocarbon and a reforming air or water are used regardless of whether a steam reforming method or a partial oxidation method is employed. A heater for heating and heating is required. On the other hand, the CO shift reaction in the CO shift section involves heat generation. Therefore, while the heat generated during CO conversion is absorbed by the raw material and the reforming air, and the raw material is heated and evaporated,
It becomes possible to cool the CO shift section. In order to perform such heat exchange, specifically, a pipe for sending out a raw material and a pipe for supplying air for reforming can be configured as follows.

One end of a raw material pipe 46 for sending out the raw material is connected to the storage part 45 for storing the raw material.
The other end of 6 extends to the reforming section 48 through the inside of the first CO shift tank 47. The material of the raw material pipe 46 is not particularly limited, but the portion 46a passing through the inside of the first CO shift tank 47 is
It is preferable to use a material having good thermal conductivity so as to easily absorb the heat generated in the step. Further, for the portion 46b between the first CO shift tank 47 and the reforming section 48, it is preferable to use a material having high heat retention so as not to release the absorbed heat. In this case, the raw material pipe 46 may be configured by connecting a plurality of materials, but the entirety is formed of a material having good thermal conductivity, and the portion after passing through the first CO shift tank 47 is By covering the pipe 46 with a heat insulating material or the like, heat insulation can be maintained.

The reforming air required for the reforming in the reforming section 48 is supplied from an air source 52 installed near the second CO shift tank 50. This air source 52 includes
One end of an air pipe 54 for delivering air is connected, and the other end of the air pipe 54 passes through the second CO shift tank 50 and is connected to the reforming section 4.
8 The material of the air pipe 54 is also not particularly limited, as in the case of the raw material pipe 46. However, the heat generated in the second CO shift tank 50 is transmitted to the portion 54a passing through the inside of the second CO shift tank 50. It is preferable to use a material having good thermal conductivity so as to be easily absorbed. Also,
For the portion 54b between the second CO shift tank 50 and the reforming section 48, it is preferable to use a material having high heat retention so as not to release the absorbed heat.

As described above, the raw material pipe 46 for sending out the raw material
When passing through the inside of the first CO shift tank 47, the raw material acts as a cooling medium, absorbs heat generated during CO combustion in the first CO shift tank 47, and the first CO shift tank 47 It will be cooled to the temperature. On the other hand, the raw material flowing through the raw material pipe absorbs the heat to obtain the reforming energy, so that it is not necessary to provide an evaporator in the reforming section.

Also, as for the reforming air, when the air pipe 54 passes through the second CO shift tank 50, it absorbs the heat generated during the combustion of CO and obtains the reforming energy.
The second CO shift tank 50 is cooled to a predetermined temperature. Therefore, this air can also be directly sent to a reformer or the like without heating or the like in the reforming section. Further, by passing the raw material and the reforming air as a cooling medium, it is not necessary to separately install a cooling unit for cooling each of the CO shift tanks 47 and 50, and the hydrogen generator can be downsized.

In the above, the raw material pipe 46 can be passed through the inside of the second CO shift tank 50 and the air pipe 54 can be passed through the inside of the first CO shift tank 47.
Preferably, as described above, the raw material pipe 46 is placed inside the first CO shift tank 47, and the air pipe 54 is placed in the second CO shift tank 47.
It passes through the inside of the shift tank 50. First CO shift tank 47
In order to convert most of the by-product CO in the reforming section 48 to an amount that can be removed in the second CO shift tank 50, most of the CO is removed from the first CO shift tank 4.
It is transformed by 7. Therefore, the calorific value associated with the CO conversion is large, and the large calorific value generated here is preferably absorbed by a raw material having a relatively high absorption capacity.

On the other hand, in the second CO shift tank 50, since the calorific value at the time of CO shift is small, when this is absorbed in the raw material, the temperature is too low, which may affect the CO shift efficiency. Therefore, by using air having a relatively low heat absorption capacity as a cooling medium, the second CO shift tank 50 can be maintained at a predetermined temperature uniformly, and as a result, the second CO shift tank 50 CO conversion efficiency can be maintained and improved.

As described above, in this embodiment, the size of the apparatus can be reduced as described above, and further, the medium for cooling the first CO shift tank and the second CO shift tank are made different, so that the It is also possible to improve the efficiency of the CO conversion reaction. In particular, the amount of heat generated by the reaction is greatly different in each of these shift shift tanks, and the optimum temperature for the CO shift reaction is also different because the catalyst used is different. Therefore, by making the cooling medium different in this way, it becomes possible to individually adjust the temperature according to the needs of each of the metamorphic tanks.

[Fifth Embodiment] FIG.
And 8. In this embodiment, a part of the cooling air for cooling the second CO shift tank is supplied into the second CO shift tank and used for CO shift. FIG. 7 shows the entire configuration of the second CO shift tank 60, and FIG. 8 shows the configuration of the catalyst and piping inside the second CO shift tank 60.

In FIG. 7, the second CO for removing CO is
The metamorphic tank 60 is provided with a cooling air source 64 in the vicinity,
One end of a pipe 66 is connected to the cooling air source 64. The pipe 66 passes through the inside of the second CO shift tank 60, and the other end is connected to an introduction path and a reforming section (not shown) of the second CO shift tank 60.

As shown in FIG. 8, this pipe 66 is connected to a plurality of cooling plates 74 inside the second CO shift tank 60. These cooling plates 74 can efficiently absorb the heat generated during CO conversion,
It is installed so as to sandwich it. Also, this cooling plate 7
4 has a configuration in which a large number of fine tubes 76 are arranged, and cooling air from a cooling air source 64 passes through the small tubes 76. Further, the cooling plate 74 includes
Air outlet 78 toward the direction in which reformed hydrogen is introduced
Are formed, a part of the air passing through the cooling plate 74 is blown out, and mixed with the reformed hydrogen.

As described above, by supplying a part of the cooling air into the second CO shift tank 60, the cooling of the second CO shift tank 60 and the second The required air supply to the CO shift tank 60 can be performed at the same time. In addition, it is possible to reduce the size of the apparatus by reducing the number of air sources.

[0069]

As described above, according to the present invention, the CO concentration can be extremely reduced while preventing the regeneration of CO by the reverse shift reaction. The reformed hydrogen subjected to CO conversion by the present CO converter can achieve a cell efficiency close to pure hydrogen when used in a fuel cell. In addition, the present hydrogen generator can contribute to downsizing of the device while efficiently using thermal energy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a hydrogen generator according to a first embodiment.

FIG. 2 is a graph comparing the battery efficiency of reformed hydrogen generated by the hydrogen generator of the first embodiment with pure hydrogen and conventional reformed hydrogen.

FIG. 3 is a partially enlarged view around a first CO shift tank in a hydrogen generator according to a second embodiment.

FIG. 4 is a graph showing O ₂ and CO concentrations in a state where an oxidation reaction is occurring and a state where a reverse shift reaction is occurring in a first CO shift tank.

FIG. 5 shows CO in the hydrogen generator of the third embodiment.
It is a figure showing the whole transformation part composition.

FIG. 6 is a diagram illustrating an overall configuration of a hydrogen generator according to a fourth embodiment.

FIG. 7 is a cross-sectional view of a second CO shift tank in the hydrogen generator of the fifth embodiment.

FIG. 8 is a diagram showing an internal configuration of a second CO shift tank in the hydrogen generator of the fifth embodiment.

[Explanation of symbols]

10 Hydrogen generator, 11,45 storage unit, 12,48
Reforming section, 13 Introductory path, 14, 37 CO shift section, 1
6, 20, 38, 52 air source, 18, 30, 40,
47 first CO shift tank, 19, 32 transfer route, 22,
41, 50, 60 Second CO shift tank, 26 fuel cell, 34 oxygen sensor, 36 control unit, 42 temperature sensor, 43 control unit, 46 raw material piping, 54 air piping, 66 piping, 78 outlet.

Claims (8)

[Claims] 1. A CO conversion method in which CO mixed in reformed hydrogen generated by reforming a hydrocarbon-based raw material is brought into contact with oxygen in the presence of a catalyst to convert CO. In the presence of a high activity catalyst, a first CO conversion step of converting at a predetermined temperature to reduce to a predetermined value, CO remaining in the reforming hydrogen after the CO reduction step at a predetermined temperature in the presence of a low activity catalyst Second CO to be transformed and removed
And a metamorphosis step. 2. The CO conversion method according to claim 1, wherein the high activity catalyst is a Pt catalyst, and the low activity catalyst is a Ru catalyst. 3. A CO shift converter for converting CO mixed in reformed hydrogen generated by reforming a hydrocarbon-based raw material by contacting oxygen in the presence of a catalyst, wherein the reformed hydrogen is introduced. A first CO conversion unit that has an introduction path, accommodates a highly active catalyst inside, and makes CO in the injected reformed hydrogen contact with oxygen at a predetermined temperature to convert and reduce the CO to a predetermined value; The reformer is connected to the first CO conversion section via a transfer path, accommodates a low-activity catalyst therein, and contacts CO in reformed hydrogen introduced through the transfer path with oxygen at a predetermined temperature to perform conversion. A CO converter comprising: a second CO converter to be removed; and oxygen supply means for supplying oxygen to the first CO converter and the second CO converter. 4. The CO converter according to claim 3, wherein the high activity catalyst is a Pt catalyst, and the low activity catalyst is a Ru catalyst. 5. An oxygen sensor provided in the transfer path for detecting an oxygen concentration in gas sent out to the transfer path; and an oxygen sensor connected to the oxygen sensor and based on the oxygen concentration detected by the oxygen sensor. 5. The CO converter according to claim 3, further comprising: a control unit configured to control a conversion reaction of the first CO conversion unit. 6. 6. The oxygen supply means is connected to the reformed hydrogen introduction passage, and oxygen is supplied from the reformed hydrogen introduction passage to the first CO shift section together with the reformed hydrogen; Oxygen supply amount detection means for detecting the oxygen supply amount in the second CO shift section based on the temperature of the section, and the first supply section is connected to the oxygen supply amount detection means and based on the detected oxygen supply amount. An oxygen consumption control means for controlling a shift reaction of the CO shift section to adjust oxygen consumption, wherein the oxygen consumption in the first CO shift section is adjusted by the oxygen shift control means, and the reformed hydrogen introduction path is provided. The CO converter according to any one of claims 3 to 5, wherein a part of the oxygen supplied from the CO is supplied to the second CO conversion unit. 7. A hydrocarbon-based raw material in the presence of a reforming catalyst,
It has a reforming section that reforms by contacting with reforming air containing oxygen to generate reformed hydrogen, and a CO converting section that reforms CO in reformed hydrogen by contacting with oxygen in the presence of a catalyst. A hydrogen generator, wherein the CO shift unit is constituted by the CO shift converter according to any one of claims 3 to 6, and a pipe that allows a cooling medium to pass through each of the first CO shift unit and the second CO shift unit. Provided, a cooling medium flowing through one of the pipes as the hydrocarbon-based raw material,
A hydrogen generator, wherein a cooling medium flowing through the other pipe is used as reforming air. 8. A pipe through which the reforming air flows, the first C
The hydrogen outlet according to claim 7, wherein an outlet for blowing a part of the air is provided in the O shift part or the second CO shift part, and oxygen is supplied by the air blown out from the outlet. Generator.