JPH08133701A - Carbon monoxide remover - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the carbon monoxide concentration in the hydrogen-rich fuel gas supplied to the fuel cell to 100 ppm or less, even immediately after starting the carbon monoxide removing device or during intermittent operation. Stable and excellent power generation performance. A reforming device 1 is provided in an oxidation reactor 36 carrying a selective oxidation catalyst for preferentially activating carbon monoxide oxidation reaction.
The fuel gas from 0 and the oxidant gas (air) from the air pump 26 are supplied. Flow rate of fuel gas is 3
The temperature in the oxidation reactor is detected by the temperature detector 44. When the temperature of the selective oxidation catalyst has not reached the activation temperature range immediately after the start of the apparatus or the like, an excessive amount of the oxidizing gas is supplied to the oxidation reactor via the oxidizing gas supply device 46 by the control of the controller 52 (FIG. 3). The reaction of oxidizing the hydrogen in the fuel gas progresses in parallel with the supplied carbon monoxide oxidation reaction, and the exothermic reaction rapidly raises the temperature of the oxidation catalyst. After the oxidation catalyst reaches the activation temperature range, the oxidant gas supply amount to the oxidation reactor is controlled so that the optimum oxygen / carbon monoxide molar ratio for activating the carbon monoxide oxidation reaction is obtained. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon monoxide removing device, and more particularly to a device for removing hydrogen rich gas supplied to a fuel cell operating at a relatively low temperature such as a phosphoric acid fuel cell or a solid polymer electrolyte fuel cell. The present invention relates to a carbon monoxide removing device used for always maintaining a low concentration of carbon monoxide.

[0002]

2. Description of the Related Art In a fuel cell power generation device in which a fuel electrode and an oxidation electrode are arranged on both sides of an electrolyte, and hydrogen and oxygen are supplied to the fuel electrode and the oxidation electrode, respectively, to obtain a cell reaction, power generation efficiency is improved. In order to increase the temperature and prevent air pollution, it is desirable to supply a gas as rich as hydrogen in the fuel electrode.

For this reason, a reforming device for producing a hydrogen-rich reformed gas by reforming a raw fuel gas containing hydrocarbons such as methanol or alcohols as a main component by the action of a reforming catalyst is provided in a fuel cell. Although it is provided in advance, carbon monoxide produced as a by-product of this reforming reaction poisons the electrode catalyst (Pt) of the fuel cell and deteriorates the performance of the fuel cell. In particular, high-performance phosphoric acid fuel cells and solid polymer electrolyte fuel cells, which have been developed in recent years, operate in a relatively low temperature range, so that the characteristics are greatly deteriorated due to catalyst poisons.

Therefore, it is necessary to reduce the concentration of carbon monoxide contained in the reformed gas immediately after the reforming reaction to about 1% to 100 ppm or less at the time of supplying it to the fuel electrode of the fuel cell. In JP-A-3-276577, a carbon monoxide removing device is provided between the reforming device and the fuel cell, which is filled with an oxidation catalyst that preferentially oxidizes carbon monoxide in the reformed gas. Is proposed.

[0005]

An oxidation catalyst such as Pt / Al ₂ O ₃ is used in the carbon monoxide removing apparatus in the above-mentioned prior art, and the activation temperature range of the carbon monoxide oxidation reaction is 70 to 200. C., and if the oxidation catalyst is maintained in this temperature range, it is possible to reduce the carbon monoxide concentration in the reformed gas to 100 ppm or less and supply it to the fuel electrode of the fuel cell.

However, in order to keep the temperature of the oxidation catalyst in the above-mentioned temperature range for activation of the oxidation reaction, it is necessary to provide a temperature control device having both a cooling function and a heating function on the oxidation catalyst carrier, and moreover, at this temperature. Even if the control device is provided, until the temperature of the oxidation catalyst carrier incorporated in the carbon monoxide removing device reaches 70 ° C. immediately after the reforming device and the carbon monoxide removing device are activated, the carbon monoxide removing device is It cannot exert its carbon monoxide removing ability. Further, even when the reformer is operated intermittently, the catalyst temperature fluctuates due to the intermittent start-up and stop of the carbon monoxide removing device, which causes the same problem as described above.

[0007]

Therefore, the present invention solves the problems of the prior art described above, and the carbon monoxide concentration in the reformed gas is set to 100 even immediately after the activation of the carbon monoxide removing device.
It is an object of the present invention to provide a carbon monoxide removing device capable of reducing the concentration to ppm or less and preventing poisoning deterioration of an electrode catalyst of a fuel cell.

In order to achieve this object, the present invention is a carbon monoxide removing apparatus for oxidizing and removing carbon monoxide in hydrogen-rich fuel gas, which comprises an oxidation reactor carrying an oxidation catalyst and the oxidation reactor. Flow rate detection means for detecting the flow rate of the fuel gas supplied to the reactor, oxidant gas supply means for supplying the oxidant gas to the oxidation reactor, and temperature detection means for detecting the temperature in the oxidation reactor. An oxidant gas supply amount adjusting means for adjusting the oxidant gas supply amount from the oxidant gas supply means in accordance with the temperature detected by the temperature detecting means. A carbon removal device is provided.

[0009]

[Effect] Immediately after the activation of the carbon monoxide removing device, if the oxidation catalyst for selectively activating the carbon monoxide oxidation reaction is below the activation temperature, an excessive amount of the oxidant gas is oxidized together with the fuel gas. The reactions introduced into the reactor and oxidizing the hydrogen in the fuel gas are carried out in parallel, and the self-heating associated with this reaction rapidly heats the oxidation catalyst in the oxidation reactor.
After the temperature of the oxidation catalyst rises and enters the active temperature range, an amount of the oxidant gas suitable for the carbon monoxide oxidation reaction is supplied to remove the carbon monoxide contained in the fuel gas.

[0010]

FIG. 1 shows a system configuration of a fuel cell power generator using a carbon monoxide removing device according to an embodiment of the present invention.

Liquid methanol is introduced into the combustion section 12 of the fuel reforming apparatus 10 from the tank 22 by the pump 24, and air from the air pump 26 is introduced into the combustion section 12 of the fuel reforming apparatus so that the liquid methanol is liquefied on the combustion catalyst. A heat source gas is generated by burning methanol. In this embodiment, the catalyst combustion section 12 is composed of the combustion catalyst, so that the heater 14 is provided to heat the combustion catalyst to the activation temperature. The heat source is not limited to the above,
For example, the heat source gas may be generated by burning hydrogen gas or liquid methanol with a burner using air as a combustion aid. The heat source gas is used as a heat source for the vaporization reaction, the reforming reaction, and the shift reaction in the vaporization section 16, the reforming section 18, and the shift conversion section 20, which will be described later.

A mixed liquid fuel of methanol and water (mixing ratio 1: 1 to 1: 4), which is a reforming raw material, is contained in a tank 28 and is directly supplied from the tank 28 or via a refrigerant pump 30 as described later. Cooling layer 42 of the oxidation reactor 36
After being passed as a refrigerant to the reforming catalyst of the adjacent reforming unit 18, the reforming fuel gas introduced into the vaporizing unit 16 of the fuel reforming device 10 by the pump 32 and sequentially vaporized in the vaporizing unit 16 is applied to the reforming catalyst of the adjacent reforming unit 18. Introduced into the reforming reaction (CH ₃ OH (g) + H
_A hydrogen-rich reformed gas is generated by ₂ O (g) → 3H ₂ + CO ₂ .

The reforming section 18 is a carrier for the reforming catalyst, and the reforming catalyst composed of, for example, Cu / Zn is supported on the reforming section structure by impregnation, thermal spraying, electrodeposition, sputtering, coating, or the like. The reforming section structure is maintained by the heat source gas in the activation temperature range of the reforming catalyst of 250 to 300 ° C. The reformed gas produced by the reforming reaction under the reforming catalyst is rich in hydrogen, but contains surplus steam, carbon dioxide, and a trace amount (about 1%) of carbon monoxide.

The reformed gas produced by the reforming reaction is introduced from the reforming section 18 to the adjoining shift conversion section 20, and is monoxidized by the shift reaction (CO + H ₂ O → H ₂ + CO ₂ ) under the shift conversion catalyst. Carbon is removed and the concentration of carbon monoxide in the reformed gas is reduced to about 0.5%. The active temperature range of the shift reaction is 150 to 230 ° C., and the heat source gas is used as the heat source in the shift conversion section.

The reformed gas that has undergone the shift reaction in the shift conversion section 20 is introduced into the gas introduction manifold 38 of the oxidation reactor 36 after the flow rate of the gas supplied to the oxidation reactor 36 is detected by the flow meter 34.

An example of the structure of the oxidation reactor 36 is shown in FIG. 2, in which a catalyst packing layer 40 and a cooling layer 42 through which a refrigerant passes are laminated alternately adjacent to the gas introduction manifold 38. The body is placed to form the oxidation reactor 36. The structure of the oxidation reactor 36 shown in FIG. 2 is not limited, and for example, a cooling pipe 42 through which a refrigerant flows may be arranged around one catalyst packing 40.

The catalyst packed layer 40 contains Pt, Ru, Pd,
Noble metals such as Rh are granular Al2O3, TiO2, SiO
What is carried on 2 etc. is filled. Alternatively, a catalyst-filled layer may be formed by supporting the above-mentioned noble metal on a honeycomb structure.

The above-mentioned oxidation catalyst has an activation temperature range (70-
At 200 ° C., a reaction for oxidizing carbon monoxide (C
Since O + 1 / 2O ₂ → CO ₂ ) is activated preferentially,
The concentration of carbon monoxide contained in the reformed gas can be reduced.

A predetermined refrigerant is introduced into the cooling layer 42 in order to cool the oxidation catalyst carried on the catalyst packed layer 40 so as to keep it in the above-mentioned activation temperature range. As the refrigerant, cooling water or any other material can be used, but in the present embodiment, the water / methanol mixed solution in the tank 28 is used, and is introduced into the cooling layer 42 via the refrigerant pump 30. are doing. The refrigerant after passing through the cooling layer 42 is
It is supplied to the vaporization section 16 of the reformer 10 by the pump 32. With such a configuration, the water / methanol mixed liquid that is the reforming raw material is heated by heat exchange while flowing through the cooling layer 42 as a refrigerant, so that the amount of heat required in the vaporization section 16 is reduced.

Although not shown in FIG. 2, the oxidation reactor 3
6 is provided with a temperature detector 44 for detecting the temperature of the catalyst carried in the catalyst packed bed 40. Temperature detector 44
The detected temperature signal by the sensor is sent to the controller 52 (FIG. 3) together with a signal indicating the reformed gas flow rate measured by the flow meter 34. The controller 52 responds to these input values, as described later, by the oxidant gas supply device 46.
The amount of oxidant gas supplied from and the discharge pressure of the refrigerant pump 30 are controlled.

The reformed gas, the carbon monoxide concentration of which has been reduced to 100 ppm or less in the carbon monoxide removing device 36, is introduced into a humidifier 48 consisting of a constant temperature water tank and a heater, and then a solid polymer electrolyte fuel cell 50. Is supplied to the fuel electrode (-). Since the reformed gas is cooled and humidified in the humidifier 48, the fuel cell is 50 to 10
The optimum operating temperature range of 0 ° C. is maintained, and the electrolyte membrane is hydrated to maintain its wet state. Air serving as an oxidant gas is supplied from the air pump 26 to the oxidizing electrode (+) of the fuel cell 50.

The control by the controller 52 in this embodiment is performed as follows. (1) When the catalyst temperature is 70 ° C. or lower When the temperature detector 44 detects that the temperature of the oxidation catalyst supported on the catalyst packed bed 40 is 70 ° C. or lower immediately after the oxidation reactor 36 is started. , Controller 52
Receiving the detection signal, controls the operation of the oxidant gas supply device 46 so as to supply an excess amount of the oxidant gas to the oxidation reactor 36 with respect to the reformed gas supply amount. That is, O2 / CO suitable for the carbon monoxide oxidation reaction by the above-mentioned catalyst
The (molar ratio) is 1.0 to 3.0, but an excess amount of the oxidant gas over the proper molar ratio is supplied to the oxidation reactor 36. For example, the vol% of the oxidant gas in the mixed gas after supplying the oxidant gas to the reformed gas is set to 20 to 70%. When an excessive amount of oxidant gas is supplied in this way, a reaction for oxidizing hydrogen in the reformed gas in parallel with the carbon monoxide oxidation reaction (H ₂ + 1 / 2O ₂ → H ₂ O)
Is activated. Since this reaction is an exothermic reaction, the catalyst temperature rises as the reaction progresses, and it is possible to raise the temperature of the oxidation catalyst in the catalyst-packed bed 40 to its activation temperature range within a short time after starting.

At this time, since it is not necessary to cool the oxidation catalyst, the refrigerant pump 30 is deactivated. (2) When the catalyst temperature reaches 70 ° C. It is known from the detection signal from the temperature detector 44 that the reaction for oxidizing hydrogen in the state of the above (1) has progressed and the catalyst temperature has reached 70 ° C. At this time, the controller 52 controls the operation of the oxidant gas supply device 46 in order to advance the reaction of preferentially oxidizing carbon monoxide in the reformed gas.
That is, O2 / CO suitable for the carbon monoxide oxidation reaction
The oxidant gas corresponding to (molar ratio) = 1.0 to 3.0 is controlled to be supplied to the oxidation reactor 36. For example,
The vol% of the oxidant gas in the mixed gas after supplying the oxidant gas to the reformed gas is set to 1 to 10%.

At the same time, the controller 52 controls the refrigerant pump 3
The discharge pressure of 0 is adjusted to cool the catalyst so that the catalyst temperature does not exceed the upper limit of activation temperature (200 ° C.). As a result, the catalyst is maintained in the active temperature range, and the carbon monoxide concentration in the reformed gas can be surely reduced to 100 ppm or less. (3) When the catalyst temperature again becomes 70 ° C. or lower When the oxidation reactor 36 is also intermittently operated due to the intermittent operation of the fuel reforming device 10, the catalyst temperature once reaches its active temperature range. After the temperature rises, the temperature may fall and the temperature may drop to 70 ° C. or lower. When this is detected by the temperature detector 44, the control by the controller 52 is switched to the state (1) again.

[0025]

EFFECTS OF THE INVENTION According to the present invention, since the carbon monoxide removal treatment is efficiently performed by the action of the selective oxidation catalyst even immediately after the activation of the carbon monoxide removal device, the carbon monoxide content is always kept below the predetermined level. The fuel gas can be supplied to the fuel cell in a state where the concentration is reduced, deterioration of the electrode catalyst of the fuel cell can be prevented, stable performance can be given to the fuel cell, and a long life can be achieved.

In the conventional carbon monoxide removing device, a temperature control device having a heating function and a cooling function is used in order to keep the oxidation catalyst in the active temperature range. Can heat the catalyst by utilizing the self-heating due to the hydrogen oxidation reaction,
External heating by means such as a heater is unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic system configuration diagram of a solid polymer electrolyte fuel cell including a carbon monoxide removing device according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing the configuration of the oxidation reactor in FIG.

FIG. 3 is an explanatory view showing a control system of each element related to the oxidation reactor in FIG.

[Explanation of symbols]

 10 Fuel Reforming Device 26 Air Pump 28 Raw Fuel Tank 30 Refrigerant Pump 34 Reformed Gas Flow Meter 36 Oxidation Reactor 40 Selective Oxidation Catalyst Packing Bed 42 Cooling Bed 44 Temperature Detector 46 Oxidant Gas Supply Device 50 Fuel Cell

Claims (4)

[Claims] 1. A carbon monoxide removing device for oxidizing and removing carbon monoxide in a hydrogen-rich fuel gas, comprising: an oxidation reactor carrying an oxidation catalyst; and a fuel gas supplied to the oxidation reactor. Flow rate detecting means for detecting a flow rate, oxidant gas supply means for supplying an oxidant gas to the oxidation reactor,
Temperature detecting means for detecting the temperature in the oxidation reactor, and oxidant gas supply amount adjusting means for adjusting the oxidant gas supply amount from the oxidant gas supply means in accordance with the temperature detected by the temperature detecting means. An apparatus for removing carbon monoxide, comprising: 2. The oxidant gas supply amount adjusting means comprises:
When the detection signal indicating the fuel gas flow rate detected by the flow rate detection means and the detection signal indicating the temperature detected by the temperature detection means are input and the temperature is lower than a predetermined temperature, the fuel gas flow rate is determined. A control command is output to the oxidant gas supply means so that the supply amount of the oxidant gas with respect to the predetermined value or more, and the temperature is equal to or higher than the predetermined temperature, the oxidant gas with respect to the fuel gas flow rate 2. The carbon monoxide removing apparatus according to claim 1, wherein a control command is output to the oxidant gas supply means so that the supply amount of the oxygen is less than a predetermined value. 3. The carbon monoxide removing apparatus according to claim 2, wherein the predetermined temperature is set in correspondence with an activation temperature at which the oxidation catalyst activates a carbon monoxide oxidation reaction. 4. The oxygen / carbon monoxide molar ratio suitable for the carbon monoxide oxidation reaction activated by the oxidation catalyst when the temperature is equal to or higher than a predetermined temperature. Is supplied to the oxidation reactor in a predetermined amount, and when the temperature is lower than the predetermined temperature, an excess amount of oxidant gas exceeding the predetermined amount is supplied to the oxidation reactor. 3. The carbon monoxide removing apparatus according to claim 2, wherein the oxidant gas supply means is controlled so that reactions of oxidizing hydrogen in the fuel gas are performed in parallel.