CN1523697A

CN1523697A - A highly effective humidifying equipment adapted to low-voltage operation of fuel battery

Info

Publication number: CN1523697A
Application number: CNA031154824A
Authority: CN
Inventors: 胡里清; 李拯; 夏建伟
Original assignee: Shanghai Shen Li High Tech Co Ltd
Current assignee: State Grid Corp of China SGCC; Shanghai Municipal Electric Power Co; Shanghai Shenli Technology Co Ltd
Priority date: 2003-02-21
Filing date: 2003-02-21
Publication date: 2004-08-25
Anticipated expiration: 2023-02-21
Also published as: CN100346516C

Abstract

This invention relates to a high efficient humidifying device including multiple double-pole plates, multiple membrane plates, a top plate, a bottom plate and slip liners, the front of the double pole plate is set with many parallel skirts, its back is set with multiple parallel skirts vertical to the front ones, the said membrane plates are pervious gas membranes, the said double-pole plates, membrane plates and top and bottom plates make up of the humidifying part and the slip liners are set at the four sides of the humidifying part.

Description

High-efficiency humidifying device suitable for low-voltage operation of fuel cell

Technical Field

The invention relates to an auxiliary device of a fuel cell, in particular to a high-efficiency humidifying device suitable for low-voltage operation of the fuel cell.

Background

An electrochemical fuel cell is a device that is capable of converting hydrogen fuel and an oxidant into electrical energy and reaction products. The inner core component of the device is a Membrane Electrode (MEA), which is composed of a proton exchange Membrane and two porous conductive materials sandwiched between two surfaces of the Membrane, such as carbon paper. The membrane contains a uniform and finely dispersed catalyst, such as a platinum metal catalyst, for initiating an electrochemical reaction at the interface between the membrane and the carbon paper. The electrons generated in the electrochemical reaction process can be led out by conductive objects at two sides of the membrane electrode through an external circuit to form a current loop.

At the anode end of the membrane electrode, fuel can permeate through a porous diffusion material (carbon paper) and undergo electrochemical reaction on the surface of a catalyst to lose electrons to form positive ions, and the positive ions can pass through a proton exchange membrane through migration to reach the cathode end at the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (e.g., oxygen), such as air, forms negative ions by permeating through a porous diffusion material (carbon paper) and electrochemically reacting on the surface of the catalyst to give electrons. The anions formed at the cathode end react with the positive ions transferred from the anode end to form reaction products.

In a pem fuel cell using hydrogen as the fuel and oxygen-containing air as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of the fuel hydrogen in the anode region produces hydrogen cations (or protons). The proton exchange membrane assists the migration of positive hydrogen ions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other to cause explosive reactions.

In the cathode region, oxygen gains electrons on the catalyst surface, forming negative ions, which react with the hydrogen positive ions transported from the anode region to produce water as a reaction product. In a proton exchange membrane fuel cell using hydrogen, air (oxygen), the anode reaction and the cathode reaction can be expressed by the following equations:

and (3) anode reaction:

and (3) cathode reaction:

in a typical pem fuel cell, a Membrane Electrode (MEA) is generally placed between two conductive plates, and the surface of each guiding plate in contact with the MEA is die-cast, stamped, or mechanically milled to form at least one or more guiding grooves. The guide electrode plates can be plates made of metal materials or plates made of graphite materials. The diversion pore canals and the diversion grooves on the diversion electrode plates respectively guide the fuel and the oxidant into the anode area and the cathode area on two sides of the membrane electrode. In the structure of a single proton exchange membrane fuel cell, only one membrane electrode is arranged, and a flow guide polar plate of anode fuel and a flow guide polar plate of cathode oxidant are respectively arranged on two sides of the membrane electrode. The flow guide polar plates are used as a current flow collection mother plate and mechanical supports at two sides of the membrane electrode, and flow guide grooves on the flow guide polar plates are also used as channels for fuel and oxidant to enter the surfaces of the anode and the cathode and as channels for taking away water generated in the operation process of the fuel cell.

In order to increase the total power of the whole proton exchange membrane fuel cell, two or more single cells can be connected in series to form a battery pack in a straight-stacked manner or connected in a flat-laid manner to form a battery pack. In the direct-stacking and serial-type battery pack, two surfaces of one polar plate can be provided with flow guide grooves, wherein one surface can be used as an anode flow guide surface of one membrane electrode, and the other surface can be used as a cathode flow guide surface of another adjacent membrane electrode, and the polar plate is called a bipolar plate. A series of cells are connected together in a manner to form a battery pack. The battery pack is generally fastened together into one body by an upper end plate, a lower end plate and a tie rod.

A typical battery pack generally includes: (1) the fuel (such as hydrogen, methanol or hydrogen-rich gas obtained by reforming methanol, natural gas and gasoline) and the oxidant (mainly oxygen or air) are uniformly distributed in the diversion trenches of the anode surface and the cathode surface; (2) cooling fluid (such as water) is uniformly distributed into cooling channels in each battery pack through an inlet and an outlet of the cooling fluid and a flow guide channel, and heat generated by electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell is absorbed and taken out of the battery pack for heat dissipation; (3) the outlets of the fuel gas and the oxidant gas and the corresponding flow guide channels can carry out liquid and vapor water generated in the fuel cell when the fuel gas and the oxidant gas are discharged. Typically, all fuel, oxidant, and cooling fluid inlets and outlets are provided in one or both end plates of the fuel cell stack.

The proton exchange membrane fuel cell can be used as a power system of all vehicles, ships and other vehicles, and can also be used as a portable, movable and fixed power generation device.

The core component of the proton exchange membrane fuel cell is a membrane electrode, and the proton exchange membrane is the core component of the membrane electrode. At present, a proton exchange membrane used in a membrane electrode of a proton exchange membrane fuel cell needs water molecules to keep moisture in the running process of the cell, and only hydrated protons can freely pass through the proton exchange membrane and reach the cathode end of the electrode from the anode end of the electrode to participate in electrochemical reaction. Otherwise, when a large amount of dry air or fuel hydrogen is supplied to the fuel cell and leaves the fuel cell, water molecules in the proton exchange membrane are easy to be carried away, so that the proton exchange membrane is in a dry water loss state, protons cannot freely pass through the proton exchange membrane, the internal resistance of the electrode is increased rapidly, and the performance of the cell is reduced rapidly. The air or fuel hydrogen supplied to the fuel cell generally needs to be humidified to increase the relative humidity of the air or hydrogen entering the fuel cell to avoid water loss from the proton exchange membrane.

The humidification devices currently applied to proton exchange membrane fuel cells mainly comprise the following components:

1. before dry air and fuel hydrogen enter the fuel cell, the dry air and the fuel hydrogen contact with purified water in a humidifying device and collide with each other, so that water molecules and air molecules are uniformly mixed to form gaseous air, and when the water molecules enter the fuel cell, the air reaches a certain relative humidity.

2. Before dry air or fuel hydrogenand pure water enter a fuel cell, the dry air or fuel hydrogen and the pure water are not in direct contact in a humidifying device, but are separated by a layer of membrane which can allow water molecules to freely penetrate but not allow gas molecules to penetrate, when the dry air flows through one side of the membrane and the pure water flows through the other side of the membrane, the water molecules can automatically penetrate through the other side of the membrane from one side of the membrane, so that the air molecules and the water molecules are mixed to reach air with certain relative humidity. Such membranes may be proton exchange membranes such as Nafion membranes from dupont, and the like.

3. The patent application number: 02217654.3 discloses a humidifying device (Shanghai Shenli science and technology Co., Ltd.) for exchanging water by using dry air before entering a fuel cell and wet air after exiting the fuel cell, wherein the humidifying device is composed of a rotary inner container, water absorbing materials are filled in the rotary inner container, when the dry air passes through the rotary inner container, water molecules on the surface of the filling materials in the inner container are taken away, and the wet air and the water pass through the surface of the filling materials in the inner container to adsorb the water molecules again.

The above several humidification methods all have technical drawbacks:

(1) the 1 st and 2 nd humidifying devices need to provide purified water additionally, and the supply of the purified water is mainly controlled by devices such as a water pump, a pipeline and the like, so that the complexity of the humidifying device is greatly increased, and the energy consumption is increased.

(2) When purified water is supplied to the 1 st and 2 nd humidifying devices, the purified water is consumed continuously and must be supplied intime, which causes the cost of the operation process of the fuel cell to be increased and the operation to be inconvenient.

(3) When dry air or fuel hydrogen takes away water molecules, a large amount of heat needs to be absorbed to promote vaporization of the water molecules, and the 1 st method needs an external heat source.

(4) The 3 rd humidifying device needs a motor to drive the humidifying liner device to rotate, thereby increasing the energy consumption and complexity of the humidifying device.

(5) The approach used in the humidification device of type 2 is as described in US Patent 5,382,478, and the humidification device segments may be incorporated into the fuel cell stack or may exist separately outside the fuel cell stack as shown in fig. 1a, 1b, 1c, 1d, 1e, 1 f.

The humidifying device is composed of a plurality of guide plates as shown in figure 2a and a plurality of diaphragm plates as shown in figure 2b in engineering manufacture, wherein the diaphragm plates are a proton exchange membrane which can permeate water but can not permeate the air, such as Nafion membranes of DuPont company, and a plurality of guide holes and guide grooves are arranged on the guide plates.

The design principle of the humidifying device is that fluid needing to be humidified, such as air and hydrogen, flows in the diversion trench on the diversion plate on one side of the membrane, purified water flows in the diversion trench on the diversion plate on the other side of the membrane, and water molecules can automatically permeate the other side of the membrane from one side of the membrane.

However, the design of this humidifier has the following technical drawbacks:

① the diversion plate has many diversion holes, the area of each diversion hole can not be large, otherwise the effective area of the humidifying diversion plate can be reduced seriously;

② the diversion plate has many diversion trenches, because of the size and position limitation of each diversion hole, the diversion trench is forced to have a bending part (as figure 2a) in the design;

therefore, the design of the humidifying device can only be suitable for the condition of high-pressure operation of the fuel cell, and when fluid such as air to be humidified passes through the humidifying device, pressure loss is inevitably caused due to the restriction of the size of the flow passage and fluid resistance caused by the bending of the diversion trench. That is, there is a large pressure drop loss between the pressure of the fluid entering the humidifier and the pressure of the fluid exiting the humidifier.

Disclosure of Invention

The present invention is directed to overcoming the above-mentioned drawbacks of the prior art and providing a high efficiency humidifier with a simple structure and low cost, which is suitable for low-voltage operation of fuel cells.

The purpose of the invention can be realized by the following technical scheme: a high-efficiency humidifying device suitable for low-voltage operation of a fuel cell is characterized by comprising a plurality of bipolar plates, a plurality of diaphragm sheets, an upper end plate, a lower end plate and a flow collecting sleeve; the front side of the bipolar plate is provided with a plurality of parallel diversion trenches, the back side of the bipolar plate is provided with a plurality of parallel diversion trenches which are arranged at an angle of 90 degrees with the diversion trenches on the front side, and the diaphragm is a water-permeable air-barrier film; a diaphragm is clamped between the bipolar plates to form a humidifying unit, the humidifying unit is overlapped up and down, and an upper end plate and a lower end plate are respectively arranged at the upper end and the lower end of the humidifying unit to form a humidifying part; one side of the humidifying part becomes an inlet of fluid, the opposite side of the inlet becomes an outlet of fluid, the other side of the humidifying part becomes an inlet of the other fluid, and the opposite side of the inlet becomes an outlet of the other fluid; the collecting sleeve is arranged on four sides of the humidifying part to form the humidifying device.

The bipolar plate is made of metal material, thin plastic or graphite material or composite material.

The flow guide grooves on the bipolar plate are a plurality of parallel straight grooves or wavy grooves.

The membrane sheet comprises a base material, and an ion-containing resin impregnated on the base material.

The base material is a porous material.

The porous material is selected from one of porous ceramics, porous stainless steel, sand core glass, porous polytetrafluoroethylene and polyethylene plastic film.

The resin containing ions is selected from one of polystyrene sulfonic acid resin and poly-perfluorosulfonic acid resin.

The flow guide grooves on the front and back of the bipolar plate are arranged in the same direction.

Compared with the prior art, the invention has the following characteristics:

1. the fuel cell is used for discharging heat, humid air and water for humidification, and no external pure water is needed for humidifying dry gas entering the humidifying device;

2. no external heat source is required to be provided or extra power is consumed;

3. the structure is compact;

4. the device is suitable for low-pressure operation of the fuel cell, and the fluid entering the humidifying device has small fluid resistance due to the large enough flow guide channels and the fact that the fluid passes through a plurality of parallel straight flow guide grooves, namely, the fluid needing to be humidified has little pressure loss after entering and exiting the humidifying device.

Drawings

FIG. 1a is a schematic view of a first prior art humidifier;

FIG. 1b is a schematic view of a second prior art humidifier;

FIG. 1c is a schematic view of a third prior art humidifier;

FIG. 1d is a schematic diagram of a fourth prior art humidifier;

FIG. 1e is a schematic diagram of a fifth conventional humidifier;

FIG. 1f is a schematic view of a sixth prior art humidifier;

FIG. 2a is a schematic structural diagram of a bipolar plate of a conventional humidifier, and its flow guide grooves and flow guide holes;

FIG. 2b is a schematic structural view of a diaphragm and a flow guide hole thereof of a conventional humidifying device;

FIG. 3 is a schematic structural view of a bipolar plate and its front surface channels according to the present invention;

FIG. 4 is a schematic structural view of a bipolar plate and its backside channels according to the present invention;

FIG. 5 is a schematic view of the structure of a membrane sheet according to the present invention;

FIG. 6 is a schematic view showing the structure of a humidifying part of the present invention;

FIG. 7 is a schematic view of the construction of the humidifying device of the present invention;

FIG. 8 is a schematic structural view of another embodiment of a bipolar plate and its front channels according to the present invention;

FIG. 9 is a schematic structural view of another embodiment of a bipolar plate and its backside channels according to the present invention;

FIG. 10 is a schematic view of another embodiment of the humidifier apparatus of the present invention.

Detailed Description

As shown in fig. 3 to 7, a high-efficiency humidifying device suitable for low-voltage operation of a fuel cell comprises a plurality of bipolar plates 1, a plurality of diaphragm sheets 2, an upper end plate 3, a lower end plate 4 and a collecting sleeve 5; the front surface of the bipolar plate 1 is provided with a plurality of parallel diversion trenches 11, the back surface of the bipolar plate 1 is provided with a plurality of parallel diversion trenches 12 which are arranged at an angle of 90 degrees with the diversion trenches on the front surface, and the diaphragm 2 is a water-permeable air-barrier film; a diaphragm is clamped between the bipolar plates to form a humidifying unit, the humidifying unit is overlapped up and down, and an upper end plate 3 and a lower end plate 4 are respectively arranged at the upper end and the lower end to form a humidifying part Z; one side A of the humidifying part Z becomes an inlet of fluid, the opposite side of the inlet becomes an outlet of fluid, the other side B of the humidifying part becomes an inlet of other fluid, and the opposite side of the inlet becomes anoutlet of other fluid; the collecting sleeve 5 is arranged on four sides of the humidifying part to form the humidifying device.

The humidifying device of the invention is in a square structure, and a thin film which can allow water molecules to freely permeate each other but can not allow gas molecules to permeate each other is arranged between the bipolar plate and the bipolar plate.

The material of the bipolar plate is typically a metallic material (e.g., stainless steel) or a thin plastic or graphite material that facilitates heat transfer, or a composite bipolar plate that carries fuel cell gases (e.g., air or hydrogen) on one side and wet, hot air or hydrogen) on the other side, and the flow channels may be parallel straight channels or parallel undulating curved channels (that facilitate heat and mass transfer, but offer less resistance). The membrane sheet between the bipolar plate and the bipolar plate can be a proton exchange membrane, such as a dupont Nafion membrane, or the substrate can be a porous material, such as a porous ceramic, a porous stainless steel, sand core glass, a porous polytetrafluoroethylene, a polyethylene and other plastic film, many pores in the porous material are filled with the proton exchange resin (water-insoluble ionic resin), and the resin molecules can freely exchange water molecules but do not allow gas molecules to permeate, such as perfluorosulfonic acid resin, polystyrene sulfonic acid resin and the like.

In order to reduce the fluid resistance, the front and back surfaces of all the bipolar plates are parallel straight-through or wave guide grooves, after the bipolar plates and the diaphragm sheets are assembled together to form a square stack (humidifying part Z), one side (A surface) of the whole stack can be used as a fluid inlet, the whole opposite side of the inlet can be used as a fluid outlet, the other side (B surface) of the whole stackcan be used as another fluid inlet, the whole opposite side of the inlet can be used as a fluid outlet, and the four sides are led out by using sleeve pipes to form a complete humidifying device.

As shown in fig. 8-10, it is another embodiment of the present invention, the front and back surfaces of the bipolar plate flow guiding plate of this embodiment are the same parallel straight-through flow channel groove flow guiding field, the humidifying device is equipped with additional flow collecting sleeves on four sides to lead out two inlets, and two outlets become the complete humidifying device.

Claims

1. A high-efficiency humidifying device suitable for low-voltage operation of a fuel cell is characterized by comprising a plurality of bipolar plates, a plurality of diaphragm sheets, an upper end plate, a lower end plate and a flow collecting sleeve; the front side of the bipolar plate is provided with a plurality of parallel diversion trenches, the back side of the bipolar plate is provided with a plurality of parallel diversion trenches which are arranged at an angle of 90 degrees with the diversion trenches on the front side, and the diaphragm is a water-permeable air-barrier film; a diaphragm is clamped between the bipolar plates to form a humidifying unit, the humidifying unit is overlapped up and down, and an upper end plate and a lower end plate are respectively arranged at the upper end and the lower end of the humidifying unit to form a humidifying part; one side of the humidifying part becomes an inlet of fluid, the opposite side of the inlet becomes an outlet of fluid, the other side of the humidifying part becomes an inlet of the other fluid, and the opposite side of the inlet becomes an outlet of the other fluid; the collecting sleeve is arranged on four sides of the humidifying part to form the humidifying device.

2. A high efficiency humidification device as claimed in claim 1 wherein the bipolar plate is made of metal or thin plastic or graphite or composite material.

3. A high efficiency humidifier apparatus suitable for low pressure operation of fuel cells as claimed in claim 1, wherein said channels of said bipolar plate are a plurality of parallel straight channels or wave shaped channels.

4. A high efficiency humidification device as claimed in claim 1 suitable for low pressure operation of fuel cells wherein the membrane sheet comprises a porous substrate and an ion containing resin impregnated on the substrate.

5. A high efficiency humidification device as claimed in claim 4 wherein the substrate is a porous material.

6. The device of claim 5, wherein said porous material is selected from the group consisting of porous ceramics, porous stainless steel, sand glass, porous polytetrafluoroethylene, and polyethylene plastic film.

7. A high efficiency humidification device as claimed in claim 4 suitable for low pressure operation of fuel cells wherein the ion containing resin is selected from one of polystyrene sulfonic acid resin and polyperfluorosulfonic acid resin.

8. A high efficiency humidifier apparatus suitable for low pressure operation of fuel cells as claimed in claim 1, wherein the channels on the front and back sides of the bipolar plate are arranged in the same direction.