Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
2001-10-05
2004-10-19
Gulakowski, Randy (Department: 1746)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S010000, C429S010000, C429S006000, C429S006000, C429S006000, C429S006000, C429S006000, C261S096000, C261S099000, C261S102000, C261S104000, C261S142000, C261S154000
Reexamination Certificate
active
06805988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a humidifying apparatus for a water permeable fuel cell that uses, for example, a hollow fiber membrane.
2. Description of the Related Art
A fuel cell mounted on a fuel cell vehicle has a structure wherein an electrode membrane structure providing an anode electrode and a cathode electrode on either side of a solid polymer electrolyte membrane is laminated on a separator that forms the gas passage for supplying various reaction gasses to both sides of this electrode membrane structure and at the same time supports the electrode membrane structure from both sides.
In this fuel cell, hydrogen gas is supplied to the anode electrode as a reaction gas for the fuel, and oxygen or air is supplied to the cathode electrode as a reaction gas for oxidation, and the chemical energy involved in the oxidation-repipeion reaction of these gases is extracted as direct electrical energy.
That is, at the anode electrode side the hydrogen gas is ionized and diffuses through a solid polymer electrolyte, and the electrons migrate to the cathode electrode side by passing through the external load, and the electrical energy can be extracted by a series of electrochemical reactions that generate water by reacting with oxygen.
However, in this fuel cell, when the solid polymer electrolyte membrane dries out, the ion conductivity decreases, leading to a decrease in the energy conversion efficiency Therefore, in order to maintain satisfactory ion conduction, moisture must be supplied to the solid polymer electrolyte membrane.
In order to attain this object, in this type of fuel cell, a humidifying apparatus is provided that supplies the reaction gas for the fuel and the reaction gas for the oxidizing agent after they have been humidified, supplies moisture to the solid polymer electrolyte membrane, and thereby maintains the satisfactory reaction.
A water permeable humidifying apparatus providing a hollow fiber membrane that permits the permeation of steam in the direction of the thickness of the membrane, such as that disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 8-273687, is known as a humidifying apparatus of this type.
FIG. 8
is a structural diagram of a fuel cell system providing the conventional humidifying apparatus. The air that is used as a reaction gas for the oxidizing agent is pressurized by the super charger
81
, supplied to the humidifying apparatus
80
A on the cathode electrode side via the pipe
82
for the reaction gas for the oxidizing agent, and supplied to the cathode electrode of the fuel cell
83
(below, referred to as the FC stack) after being moisturized in the humidifying apparatus
80
A on the cathode electrode side. In addition, after the oxygen in the air supplied to the cathode electrode is used as the oxidizing agent, it is discharged from the FC stack
83
as off gas. The off gas that includes moisture generated during the reaction in the FC stack
83
is sent to the humidifying apparatus
80
A on the cathode electrode side via the pipe
84
for the off gas from the FC stack
83
, the steam in the off gas in the humidifying apparatus
80
A on the cathode electrode side is taken up by the reaction gas for the oxidizing agent, and thereafter, is discharged.
In addition, the hydrogen gas used as the reaction gas for the fuel is supplied to the humidifying apparatus
80
B on the anode electrode side via the gas pipe
85
for the fuel supply, is moisturized in the humidifying apparatus
80
B on the anode electrode side, and then supplied to the anode electrode of the FC stack
83
. In addition, a part of the oxygen supplied to the anode electrode is used as fuel and supplied to the oxidation-reduction reaction. After this one part of the oxygen gas has been supplied to the reaction, it becomes off gas and is discharged from the FC stack
83
.
However, the solid polymer electrolyte membrane possesses the property that steam is caused to permeate from the side having a high moisture concentration to the side having a low concentration, where the solid polymer electrolyte membrane serves as a boundary, as a result of the ion hydration effect. As described above, the moisture concentration of the off gas flowing through the cathode electrode side is higher than that of the off gas flowing through the anode electrode side because it includes moisture generated during the reaction, but due to the ion hydration effect, the moisture in the off gas flowing through the cathode electrode side becomes steam, permeates the solid polymer electrolyte membrane, and diffuses into the off gas flowing through the anode electrode side. Therefore, moisture is included in the off gas on the anode electrode side.
The off gas on the anode electrode side that includes this moisture is sent to the humidifying apparatus
80
B on the anode electrode side from the FC stack
83
via the off gas pipe
86
, the steam in the off gas in the humidifying apparatus
80
B on the anode electrode side is delivered to the reaction gas for the fuel, and subsequently, discharged.
Here, a humidifying module, which is the essential structural component of the humidifying apparatus
80
A on the cathode electrode side and the humidifying apparatus
80
B on the anode electrode side, will be explained referring to FIG.
7
.
In the humidifying module
30
, a plurality of bundled tube shaped porous hollow fiber membranes
32
comprising a steam permeable membrane (water permeable membrane) are accommodated, partition members
33
that bundle both ends of the hollow fiber membranes
32
are joined airtight to the outer surface of the hollow fiber membrane
32
or the inner surface of the hollow fiber membrane
32
and the outer peripheral surface of the housing
31
. One end of the housing
31
communicates with the inlet head
34
, and the other end communicates with the outlet head
35
. In addition, gas inlet holes
36
a
and gas outlet holes
26
b
are provided more inward than both of the partition members
33
, which are the peripheral part of the housing
31
. The gas inlet holes
36
a
and gas outlet holes
36
b
communicate with an round internal passage of the round inlet cover
37
a
and the round outlet cover
37
b
that are respectively provided along the exterior peripheral surface of the housing
31
.
In addition, in this humidifying module
30
, the reaction gas is supplied to the round internal passage of the round inlet cover
37
a
, is introduced into the housing
31
from the gas inlet hole
36
a
, and flows in the round internal passage of the round outlet cover
37
b
from the outlet hole
36
b
after passing through the hollow fiber membrane
32
in the housing
31
. In contrast, the off gas is supplied to the inlet head
34
, enters into hollow part of the hollow fiber membrane
32
after being supplied to the housing
31
from the inlet head
34
, and flows to the outlet head
35
from the other end of the housing
31
after passing through this hollow part. When the reaction gas and the off gas are caused to flow in this manner, the moisture in the off gas is taken up by the reaction gas via the hollow fiber membrane
32
, and thereby, the reaction gas is humidified. Moreover, as one manner of using the humidifying module
30
, the off gas can flow into the hollow part of the hollow fiber membranes
32
, and the reaction gas can flow between the hollow fiber membranes
32
, and in this manner as well, the moisture in the off gas can be taken up by the reaction gas via the hollow fiber membrane
32
to produce the humidifying.
In addition, the humidifying apparatus
80
A on the cathode electrode side and the humidifying apparatus
80
B on the anode electrode side can be provided with a plurality of humidifying modules
30
, and in this case, the reaction gas supply pipes communicate with the inlet head
34
of each of the humidifying modules
30
, the reaction gas discharge pipe communicates with the outlet head
35
of each of the humidifying modules
30
, the off gas supply pipe c
Katagiri Toshikatsu
Katano Kouji
Kusano Yoshio
Shimanuki Hiroshi
Gulakowski Randy
Honda Giken Kogyo Kabushiki Kaisha
Lahive & Cockfield LLP
Laurentano, Esq. Anthony A.
Winter Gentle E.
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