DE102008060533A1 - Liquid separator for a fuel cell system - Google Patents

Abstract

A liquid separator (42, 44, 46) for a fuel cell system comprises a sump (48) having a gas inlet (62), a gas outlet (64) and a water outlet (66), a water drain line (52) connected to the water outlet (46). 66) and a drain valve (54) disposed in the water drain line (52). In order to ensure fast functioning of the liquid separator (42, 44, 46) during a freeze start, at least one heatable structural element (70) is arranged and formed in the collecting container (48) in such a way that it is heated in an ice block (68) in the Sump (48) generates at least one connected to the water outlet (66) channel.

Description

The The invention relates to a liquid separator, in particular a liquid separator for a fuel cell system, and a fuel cell system with at least one such Liquid separator.

Under A fuel cell becomes both a single fuel cell (in short: single cell) as well as a series connection of two or more single cells to a fuel cell stack (short: Stack) Understood.

Usually is used in a fuel cell to generate electrical energy anode-side hydrogen or a hydrogen-rich gas as fuel and cathode side oxygen or an oxygen-rich Gas such as ambient air supplied as an oxidizing agent. The electrodes of the fuel cell are through an ion exchange membrane (eg polymer electrolyte membrane) separated from each other.

The hydrogen molecules supplied at the anode-side react on the anode catalyst in the anode region according to the equation H ₂ → 2 · H ⁺ + 2 · e ^- and thereby give electrons to the electrode to form positively charged hydrogen ions (protons). The protons thus formed in the anode region then diffuse through the ion exchange membrane to the cathode region. There, they react on a cathode catalyst with the cathode-side supplied oxygen and the supplied via an external circuit electrons according to the equation O ₂ + 4 · H ⁺ + 4 · e ^- → 2 · H ₂ O to water.

In The fuel cell system is thus the reaction product of the electrochemical Processes formed in the fuel cell water. About that In addition, it often becomes common with the anode area or the cathode region added reactants additional Water entered into the fuel cell system. For example may contain moisture in the anode gases or in the ambient air be.

liquid However, water can be used in the fuel cell system, especially in the Block the fuel cell provided flow channels and so a uniform distribution of gaseous Affecting reactants in the system or in the fuel cell. This can negatively affect the degree of conversion of the reactants in the fuel cell and thus affect the efficiency of the system. Further, in the fuel cell system existing liquid Water freezes at low temperatures, causing damage to the System components and blockages of flow channels can lead. In a mobile application of the fuel cell, for example, for a drive of a vehicle, it is also necessary, an emission of liquid Avoid water as this is at low outside temperatures Ice formation on a road and thus a traffic hazard could lead.

Therefore Fuel cell systems usually contain several Liquid separators, which are in different places in The system is arranged to remove liquid water from the Gas flows or the system to remove.

The structure of a conventional fuel cell system, as for example in the DE 10 2004 056 952 A1 is described in is 3 illustrated.

This in 3 exemplified fuel cell system includes a fuel cell 10 with an anode area 12 and a cathode region 14 passing through an ion exchange membrane 16 are separated from each other. The fuel cell system usually includes a plurality of such fuel cells 10 , which are arranged one behind the other or stacked to form a stack.

The cathode area 14 the fuel cell 10 is through a compressor 18 via a cathode gas supply line 20 Supplied air or an oxygen-rich gas. For the derivation of in the fuel cell 10 resulting cathode exhaust gases is the cathode region of the fuel cell 10 with a cathode exhaust gas discharge line 22 connected.

In order to be conductive for the hydrogen ions, the ion exchange membrane must 16 the fuel cell 10 be constantly moistened. For this purpose, in the cathode gas supply line 20 a humidification system 24 arranged, which humidifies the cathode-side supplied air with water. The humidification system 24 is preferably also with the cathode exhaust gas discharge line 22 in conjunction and is designed as a gas-gas membrane humidifier.

The anode area 12 the fuel cell 10 is connected to an anode gas supply line 26 in connection through which the anode area 12 Hydrogen is supplied. For dosing the hydrogen supply in the anode area 12 is in this anodes gas supply line 26 a first valve 28 arranged. An anode exhaust gas discharge line 30 is designed as a recirculation line, in which a recirculation fan 32 is arranged to leave the anode area 12 the fuel cell 10 To lead exiting anode exhaust gases in the circulation. In the anode exhaust gas discharge line 30 are preferably sensors 34 . 36 provided to measure the pressure, the temperature and the relative humidity of the anode exhaust gases and the hydrogen concentration in the anode exhaust gases.

Further, there is the anode exhaust gas discharge line 30 preferably also via a second valve 38 with a flushing line 40 in connection. After switching off the fuel cell system, the second valve 38 be opened to the anode area 12 the fuel cell 10 with one through the purge line 40 supplied purge gas such as air to rinse.

For the reasons set forth above, it is preferable in the cathode gas supply line 20 a first liquid separator 42 , in the anode gas supply line 26 a second liquid separator 44 and in the anode exhaust gas discharge line 30 another liquid separator 46 arranged. Each of these liquid separators 42 . 44 . 46 generally contains a collection container 48 and a level sensor 50 for detecting the liquid level in the collecting container 48 , One fluid outlet of each reservoir 48 is with a water drainage pipe 52 connected, in each case a drain valve 54 is arranged. If a level sensor 50 Indicates that the water level in the sump 48 the associated liquid separator 42 . 44 . 46 has reached a predetermined value, the corresponding drain valve 54 opened, so that in the sump 48 collected water through the liquid outlet and the respective water drain line 52 can be removed from the fuel cell system.

In connection with the described liquid separators 42 . 44 . 46 In particular, after switching off the fuel cell system is the problem that in the collection containers 48 as well as in the water drainage pipes 52 to the drain valves 54 Collected liquid water at low outside temperatures can freeze, resulting in collection containers 48 , the water drainage pipes 52 and the drain valves 54 Ice blocks can form that prevent water drainage. If the fuel cell system is started at very low temperatures (so-called freeze start), then the sump 48 , the water drainage pipes 52 and the drain valves 54 the existing liquid separator 42 . 44 . 46 be heated to melt the ice blocks existing there and the functioning of the liquid separator 42 . 44 . 46 produce as quickly as possible after the start of operation. In the prior art corresponding heating elements are used for this purpose.

For example, from the DE 10 2007 051 811 A1 a divertable via a shared solenoid discharge valve for use in a fuel cell system known.

Next discloses the DE 100 13 687 B4 a fuel cell system in which at least partially heatable media lines are provided.

Of the Invention is based on the object, a liquid separator to create a fuel cell system at a so-called freeze start is fast functioning.

These Task is solved by a liquid separator with the features of claim 1. Advantageous embodiments and further developments of the invention are in the dependent Claims specified.

One Liquid separator according to the present The invention comprises a collection container having a gas inlet, a gas outlet and a water outlet, a water drain line, the connected to the water outlet, and a drain valve, the in the water drain line is arranged on. additionally is in the collecting container at least one heatable structural element is arranged and designed such that it is heated when in a block of ice in the collection at least one with generated connected to the water outlet channel.

With the heatable structural element in the collecting container specifically required for the function of the collection container Areas, namely those for the formation of channels for a drain of liquid water to the water outlet heated in the water drain line. this leads to for quickly producing the functionality of the liquid separator, without to melt the entire block of ice, as with conventional liquid separators the case is. By limiting the areas to be heated in the collection can the functionality the liquid separator in a so-called freeze start Not only very fast, but also guaranteed with only a small amount of energy become.

In a preferred embodiment of the invention, the at least one heatable structural element is formed from a material which has a higher thermal conductivity than a material of the collecting container. As a result, the heat is introduced in a more targeted manner in the collecting container by the heat input limited even further becomes.

In In a further embodiment of the invention, the at least one Heatable structural element using the heat energy a fuel cell, a starting heater or a working medium, preferably a cooling medium, the fuel cell system to be heated. There to thaw the liquid separator Any existing heat sources of the fuel cell system be used, is the energy input for the heat input into the collecting tank of the liquid separator very low.

alternative or additionally, the at least one heatable structural element also using an electric heating element or a Hydrogen combustion in the liquid separator itself to be heated.

In an embodiment of the invention, the at least a heatable structural element a in the sump protruding rib element.

In another embodiment of the invention, the at least a heatable structural element connected to the water outlet pipe element with openings in the pipe wall.

In In yet another embodiment of the invention are also the drain valve and / or the water drain line at least partially heated.

According to one Another aspect of the invention includes a fuel cell system a fuel cell having an anode region and a cathode region, a cathode gas supply line, a cathode exhaust gas discharge line, an anode gas supply line, an anode exhaust gas discharge line and at least a liquid separator described above.

at the liquid separator of the fuel cell system, formed in accordance with the present invention is, it is for example a liquid separator in the cathode gas supply line, a liquid separator in the anode gas supply line and / or a liquid separator in the anode exhaust gas discharge pipe of the fuel cell system.

Above and other features and advantages of the invention will become apparent from the following description of preferred embodiments better understood with reference to the accompanying drawings. Showing:

1 a schematic representation of the structure of a liquid separator of the present invention;

2 a partial perspective view, partially in section, of a Flüssigkeitsabscheiders according to a preferred embodiment of the invention; and

3 a schematic block diagram of a fuel cell system, in which the liquid separator of the present invention can be used in an advantageous manner.

The liquid separator of the present invention can be advantageously used in a fuel cell system as shown in FIG 3 is exemplified and has already been explained above. However, the invention is of course not limited to this application, in particular not limited to a fuel cell system constructed in this way. In addition, the present invention is advantageously usable in both mobile and stationary applications.

In the in 3 illustrated fuel cell system, the description of which should not be repeated here again, the liquid separator 42 in the cathode gas supply line 20 , the liquid separator 44 in the anode gas supply line 26 and / or the liquid separator 46 in the anode exhaust gas discharge line 30 be designed as an inventive liquid separator.

The basic principle and operation of a liquid separator of the present invention will now be described with reference to FIG 1 explained in more detail.

The liquid separator 42 . 44 . 46 has a housing 60 in which the collection container 48 is arranged, which is often funnel-shaped, as in 1 indicated. In the upper area of the collection container 48 are a gas inlet 62 and a gas outlet 64 intended. Through the gas inlet 62 a gas flows together with liquid water contained in it into the sump, the liquid water is in the bottom area of the sump 48 collected, and the dehumidified gas leaves the sump 64 through the gas outlet.

In the bottom area of the collection container 48 there is a water outlet 66 that with a water drainage pipe 52 connected is. In this water drainage line 52 is a drain valve 54 arranged to the flow path through the water drain line 52 to open and lock. A sensor (not shown in FIG 1 ) detects the level of liquid water in the sump. At a predetermined level, the drain valve then becomes 54 Open to collect the liquid water from the collection container 48 for example, to the environment, to another water separator, to a media line of the fuel cell system or to the cathode gas supply line into the fuel cell.

As in 1 illustrated, it may happen at very low ambient temperatures that the liquid water in the reservoir 48 freezes and settles in the bottom of the collection container 48 an ice block 68 then forms the water outlet 66 blocked. Similarly, at low outdoor temperatures, the drain valve 54 and the water drainage line 52 upstream of the drain valve 54 be blocked by frozen water. Of course, the risk of this ice formation is particularly when the fuel cell system is switched off, because then the flow paths through the liquid separator 42 . 44 . 46 no longer be flowed through, in particular no longer be flowed through with a medium whose temperature is sufficiently high to prevent freezing of the water.

At a start of the fuel cell system from the in 1 shown state, ie at a so-called freeze start, in the collection container 48 of the liquid separator 42 . 44 . 46 usually an ice block 68 is present, the the water outlet 66 blocked, must now as soon as possible, the functionality of the liquid separator 42 . 44 . 46 be guaranteed. In other words, must be achieved as quickly as possible, that liquid water from the reservoir 48 in the water drainage line 52 can drain away.

Unlike conventional systems, this is not the complete ice block for this purpose 68 melted, which requires a relatively large amount of energy. Instead, in the sump 48 , especially in its lower area, where usually the block of ice 68 forms, at least one structural element 70 arranged or formed, which is heated and which forms at least one channel through its heated structure in the block of ice, through the liquid water from the reservoir 48 over the water outlet 66 in the water drainage line 52 can flow. To increase the reliability, it may be advantageous to use several independent channels through the at least one structural element 70 to create.

Ie. to achieve the functionality of the liquid separator 42 . 44 . 46 does not have the entire block of ice 68 be melted, but it is sufficient a small portion of it. For this reason, only a small amount of energy is needed to allow the drainage of liquid water.

A further limitation of the heat input region and thus of the required energy expenditure can be achieved by the at least one structural element 70 is made of a material with a good thermal conductivity (eg aluminum, copper), while the remaining (wall) areas of the collecting container 48 consist of a material with a lower thermal conductivity (eg plastic). This effect can be due to special coatings heat transfer to the block of ice 68 or the collection container 48 be reduced.

The structural element 70 in the collection container 48 as well as the water drainage line 54 including the drain valve 52 inside the housing can be heated in various ways. For example, the desired heating may be achieved using the heat energy of the fuel cell, a starting heater, or an operating medium, preferably a cooling medium, of the fuel cell system. Because here to thaw the liquid separator 42 . 44 . 46 Any existing heat sources of the fuel cell system are used, the energy required for the heat input into the sump of the liquid is very low. Alternatively or additionally, the at least one heatable structural element 70 , the drain valve 54 and the water drainage line 52 inside the case 60 also be heated using an electric heating element or a hydrogen combustion in the liquid separator itself.

The area of the water drainage line 52 outside the case 60 of the liquid separator 42 . 44 . 46 is preferably also heated, for example by an electric heating element 72 ,

The heatable structural element 70 For example, by rib structures on the inner wall of the collecting container 48 be formed in its bottom area. If the rib structures are heated, channels are very quickly formed in the depressions between the ribs of the rib structures.

Another preferred embodiment of the at least one structural element 70 will be referred to below 2 described in more detail.

In the embodiment of 2 is the heatable structural element 70 in the collection container 48 formed from a tubular element that connects to the water outlet 66 and the water drainage line 52 is connected and in the interior of the collection container 48 protrudes. The height of the pipe element 70 in the collection container 48 is sized so that it is greater than the height of an expected block of ice 68 is. For example, it corresponds to what serpegel level at which the sensor 50 during operation of the fuel cell system, the drain valve 54 Pressed to remove the liquid water from the sump 48 to expire.

The pipe element 70 is in 2 shown with a substantially circular cross-section. But there are also other cross-sectional shapes for the pipe element conceivable, for example, elliptical, square, rectangular, polygonal. As in further 2 recognizable, is the pipe element 70 with a variety of openings 76 provided in the form of holes, slots, slots or the like.

Below the collection container 48 is a radiator 78 arranged. This radiator 78 stands with the pipe element 70 in the collection container 48 in very good thermal contact, for example, it is integrally formed with this of a material with good thermal conductivity. As in 2 are shown in the radiator 78 channels 80 designed for a heating medium. This heating medium is in a preferred embodiment of the invention, the cooling medium of the fuel cell system, which is during operation of the fuel cell 10 heated. As explained above, the radiator 78 but also be heated in other ways to the pipe element 70 to warm up.

Has himself in the collection container 48 after switching off the fuel cell system, an ice block 68 If the system is to be restarted from this state (freeze start), then the radiator will be formed 78 below the collection container 48 and thus also the pipe element 70 in the interior of the collection container 48 heated (for example, using the cooling medium of the fuel cell system). By heating the pipe element 70 the ice block melts 68 first in the immediate vicinity of the tubular element 70 as well as inside the pipe element 70 , Thus, first several channels form in the block of ice 68 through which liquid water in the sump 48 above the ice block 68 is recollected, to the water outlet 66 of the collection container 48 and continue through the water drainage line 52 can drain away. Over time, of course, here is the entire block of ice 68 melted.

Because the ice block 68 very targeted only in a small sub-volume directly inside the pipe element 70 and around it is melted, a relatively low energy consumption is sufficient. In addition, the small volume fraction of the ice block 68 be melted very quickly, so that the functionality of the liquid separator 42 . 44 . 46 can be made very quickly at a freeze start.

While in the embodiment of 2 only one pipe element 70 is present in the collecting container, it is also possible to provide a plurality of tubular elements or a branched tubular element system or to combine one or more tubular elements with the above-mentioned rib structures.

In the embodiment of 2 is the water drainage pipe 52 following the water outlet 66 of the collection container 48 ie upstream of the drain valve 54 , with an electric heating element 74 formed, which the water drain line 52 warmed up during a freeze start and also during operation at low ambient temperatures, thus thawing ice in the line or preventing ice formation.

In a variant of this embodiment, the water drain line 52 in the case 60 of the liquid separator 42 . 44 . 46 but like the structural element 70 or its radiator 78 also be heated by the cooling medium of the fuel cell system.

The heating of the structural element 70 , the water drainage pipe 52 and the drain valve 54 is preferably carried out only at low ambient temperatures, where it must be assumed that ice formation has taken place in these components. For this purpose, one or more temperature sensors (not shown) are provided.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102004056952 A1 [0008]
• DE 102007051811 A1 [0016]
• - DE 10013687 B4 [0017]

Claims (14)

Liquid separator ( 42 . 44 . 46 ), in particular for a fuel cell system, with a collecting container ( 48 ), which has a gas inlet ( 62 ), a gas outlet ( 64 ) and a water outlet ( 66 ) having; a water drainage pipe ( 52 ) connected to the water outlet ( 66 ) connected is; and a drain valve ( 54 ) located in the water drainage line ( 52 ), characterized in that in the collecting container ( 48 ) at least one heatable structural element ( 70 ) is arranged and designed such that when heated in an ice block ( 68 ) in the collecting container ( 48 ) at least one with the water outlet ( 66 ) connected channel. Liquid separator according to claim 1, characterized in that the at least one heatable structural element ( 70 ) is formed of a material having a higher thermal conductivity than a material of the collecting container ( 48 ). Liquid separator according to claim 1 or 2, characterized in that the at least one heatable structural element ( 70 ) using the heat energy of a fuel cell ( 10 ), a starting heater or an operating medium of the fuel cell system can be heated. Liquid separator according to claim 3, characterized in that the at least one heatable structural element ( 70 ) is heatable using a cooling medium of the fuel cell system. Liquid separator according to claim 1 or 2, characterized in that the at least one heatable structural element ( 70 ) is heatable using an electric heating element. Liquid separator according to claim 1 or 2, characterized in that the at least one heatable structural element ( 70 ) using hydrogen combustion in the liquid separator ( 42 . 44 . 46 ) is itself heatable. Liquid separator according to one of the preceding claims, characterized in that the at least one heatable structural element ( 70 ) into the collecting container ( 48 ) has protruding rib member. Liquid separator according to one of the preceding claims, characterized in that the at least one heatable structural element ( 70 ) with the water outlet ( 66 ) connected pipe element having openings in the pipe wall. Liquid separator according to one of the preceding claims, characterized in that the drain valve ( 54 ) is a heated drain valve. Liquid separator according to one of the preceding claims, characterized in that the water drain line ( 52 ) is at least partially heated. Fuel cell system, with a fuel cell ( 10 ) with an anode region ( 12 ) and a cathode region ( 14 ); a cathode gas supply line ( 20 ); a cathode exhaust gas discharge line ( 22 ); an anode gas supply line ( 26 ); an anode exhaust gas discharge line ( 30 ); and at least one liquid separator ( 42 . 44 . 46 ), characterized in that the at least one liquid separator ( 42 . 44 . 46 ) is designed according to one of the preceding claims. Fuel cell system according to claim 11, characterized in that in the cathode gas supply line ( 20 ) a liquid separator ( 42 ) is arranged according to one of claims 1 to 10. Fuel cell system according to claim 11 or 12, characterized in that in the anode gas supply line ( 26 ) a liquid separator ( 44 ) is arranged according to one of claims 1 to 10. Fuel cell system according to one of claims 11 to 13, characterized in that in the anode exhaust gas discharge line ( 30 ) a liquid separator ( 46 ) is arranged according to one of claims 1 to 10.