Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
2000-05-01
2003-07-01
Gulakowski, Randy (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S006000
Reexamination Certificate
active
06586126
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a temperature controller (control system) for a fuel gas in a fuel cell system which generates an electric power by supplying a modified hydrocarbon gas as a fuel gas to a fuel cell.
BACKGROUND OF THE INVENTION
A fuel cell system is an electric power system mainly composed of a fuel cell. The fuel cell generates an electric power by supplying hydrogen as a fuel gas to a hydrogen pole of the fuel cell and supplying an oxidizing gas containing oxygen gas such as air to an oxygen pole of the fuel cell. The fuel cell system directly converts a chemical energy to an electric energy and has a high power efficiency. In addition, the fuel cell system is assumed to be very clean power generating system which discharges negligible amount of environmental contaminating substances and, thus, has been under the examination of applicability to a wide variety of fields.
In such a fuel cell system, from the view points of difficulty to handle hydrogen and diversification of fuel sources, a gas except for hydrogen is utilized as a fuel gas. For example, a hydrocarbon fuel such as methane (CH
4
) or methanol (CH
3
OH) is reformed in a reformer to generate hydrogen, and the modified gas comprising hydrogen as a main ingredient is utilized in many cases. In the case of a vehicle like an automobile, on which fuel cell is carried, the use of hydrogen is inconvenient in the requirement of a long period of time for filling hydrogen and in the difficulty in carrying a large amount of hydrogen, resulting in a shortened mileage. For this reason, it has been considered that a liquid fuel like methanol is charged into an automobile, to be utilized as the fuel by modifying the liquid fuel in the reformer to generate a gas containing hydrogen as a main ingredient. Since methanol can be charged just like refueling and a mileage in this case is in no way to inferior to that in the case of the present automobile utilizing gasoline, making it possible to treating the automobile just like gasoline based car. What is more, in the case of utilizing methanol, since the methanol molecule only has one hydrogen atom, the amount of hydrogen generated is large and the proportion of carbon dioxide discharged is small in comparison with any other hydrocarbon fuel having a larger number of carbon atoms.
With reference to
FIG. 5
, the conventional fuel cell system
50
will be specifically described. The hydrocarbon fuel (methanol in this case) is introduced to a reformer
61
of a fuel gas generator
60
together with water and air at which the hydrocarbon fuel is modified to produce a fuel gas. While carbon monoxide (hereinafter sometimes referred to as “CO” ) is contained in the resulting fuel gas generated in the reformer only in a trace amount, CO, which poises the catalyst in a fuel cell
52
, is converted into carbon dioxide by a CO remover
62
to be removed. The chemical reaction within the CO remover
62
, of course, has an optimal temperature range. If the temperature is lower than this range, the proportion of converting (removing) CO becomes low, and conversely, if it is higher than this range, there is a possibility to bring about “converse shift” or “methanation” where the hydrogen generated unduly undergoes oxidation.
Since the fuel gas generated in the reformer
61
has a high temperature (e.g., 300° C.), the fuel gas is allowed to cool down to an appropriate temperature (e.g., 100° C.) by means of a heat exchanger
71
in
at an inlet side, and then introduced into the carbon monoxide remover
62
. The fuel gas from which CO has been removed by the CO remover
62
is introduced into the fuel cell
52
. Since the chemical reaction within the carbon monoxide remover
62
is exothermic, the temperature of the fuel gas is increased (e.g., 180° C.). On the other hand, the working temperature of the solid macromolecule fuel cell is from normal temperature to approximately 150° C., a heat exchanger
71
out
at an outlet side is placed between the CO remover
62
and the fuel cell
52
to cool the fuel gas (e.g., cooled to 80° C.). Subsequently, an electric powder is generated due to the reaction between the fuel gas supplied at the side of the hydrogen pole and air supplied at the side of the oxygen pole to supply electric power to a motor etc.
As described above, it is important to control the temperature of the fuel gas at the inlet and outlet of the carbon monoxide remover
61
in the fuel cell system
50
, and the temperature is controlled by a temperature control system
70
.
The temperature control system
70
has a circulating channel
76
for circulating a coolant medium (cooling water), having a radiator
72
, a thermostat
73
for controlling the temperature of the coolant medium, a circulating pump
75
and the like in addition to the heat exchanger
71
in
at an inlet side and the heat exchanger
71
out
at an outlet side. In this temperature control system
70
, the coolant medium circulating within the circulating channel
76
is controlled so as to keep its temperature at a constant level.
However, since the temperature control system
70
as described above has a configuration that the temperature of the coolant medium is controlled within a constant level by a thermostat
73
, and the temperature of the fuel gas is controlled by the coolant medium having the constant temperature, the temperature of the fuel gas is decided basically by the ability of the heat exchanger
71
, the temperature of the fuel gas at the inlet of the heat exchanger
71
and the flow amount. For this reason, the temperature of the fuel gas at the inlet of the CO remover
62
and that at the inlet of the fuel cell
52
cannot be controlled at a desirable level in a precision manner. Particularly, when the thermal load at the heat exchanger
71
is rapidly increased, as in the case where the temperature of the fuel gas is rapidly increased, the temperature control of the fuel gas utilizing the coolant medium having a constant temperature, has a restriction and, thus the temperature of the fuel gas at the outlet of the heat exchanger
71
is unduly increased. This problem cannot be solved if the flow amount of the coolant medium (cooling water) become variable.
Furthermore, in the case of carrying the fuel cell system on an automobile, since the fuel cell system is used in the state of a high variation in the thermal load of the fuel cell
52
, it is required to keep the temperature of fuel gas at a constant level, quickly corresponding to the variation in the load according to driving operation.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide a temperature control system for controlling a temperature of a fuel gas in a fuel cell system, which can quickly respond to the sharp variation in thermal load in an exchanger to control the temperature of the fuel gas to a desirable value in a precision manner.
We have studied to solve the problems associated with the prior art and to attain the object described above. As a result, we have found the fact that when a mechanism for controlling the temperature of the fuel gas is added to a thermostat for controlling the temperature by keeping the temperature of a coolant medium at a constant level, the temperature can be controlled at a desirable level in a precision manner due to the synergism between them, and completed the present invention.
The temperature control system for controlling a fuel gas of fuel cell of the present invention comprises a fuel reformer for reforming a hydrocarbon fuel into a reformed gas mainly comprising hydrogen, carbon monoxide remover or removing a carbon monoxide in the reforming gas and said reformed fuel gas is supplied to said fuel cell, said temperature control system comprising:
at least one heat exchanger which exchanges heat between the fuel gas and a coolant medium, said heat exchanger being placed at an inlet side and/or outlet side of said carbon monoxide remover,
a radiator which radiates the heat exchanged by said heat exchanger,
a thermostat which
Ogawa Takayuki
Okamoto Hideo
Takase Hidehiko
Arent Fox Kintner Plotkin & Kahn
Gulakowski Randy
Honda Giken Kogyo Kabushiki Kaisha
Wills M.
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