DE19852844C2 - Arrangement for generating electrical energy with a fuel cell and a fuel source for the fuel required for the fuel cell - Google Patents

Description

The present invention relates to an arrangement for generating electrical Energy according to the preamble of claim 1, as known from DE 196 52 341 A1.

Fuel cells have been known for a long time and have particularly in the field the automotive industry has become significantly more important in recent years. Similar to battery systems, fuel cells generate electrical energy chemical way, the individual reactants being fed continuously and the reaction product is continuously removed. Here lies the Fuel cells are based on the basic functioning that is electrical connecting neutral molecules or atoms and thereby electrons change. This process is called the redox process. In the Fuel cell, the oxidation and reduction processes are spatially separated. The Electrons released during the reduction can be viewed as a current through a For example, consumers control the electric motor of an automobile.

As gaseous reactants for the fuel cell, for example Hydrogen is used as fuel and oxygen as oxidant. Do you want that Fuel cells with an easily available and storable fuel such as Operate natural gas or methanol, you must first through the hydrocarbon Convert reforming to a hydrogen-rich gas. This is in the essentially decomposed to hydrogen and carbon dioxide. Furthermore also arises  Carbon monoxide (CO), which is a gas harmful to the fuel cell and therefore must be removed before the fuel enters the fuel cell.

In the fuel cell, carbon monoxide can do this from a certain concentration cause the power output by the fuel cell to decrease and the Efficiency of the fuel cell is reduced. Usually an attachment of carbon monoxide in the fuel cell by breaking it down into at regular intervals with a suitable gas, for example oxygen, is rinsed. However, it has the concentration of carbon monoxide in the fuel cell exceeded a certain limit, those in the fuel cell are due to the Carbon monoxide reactions are irreversible, making the fuel cell suffers a permanent loss of performance and may need to be replaced.

Thus, there is a need to control the amount of harmful carbon monoxide in the To be able to measure fuel cells in order to clean or flush the Fuel cells can make before irreversible damage comes.

Carbon monoxide can be measured using infrared spectrometers or by means of Gas chromatography can be measured. However, both methods have the disadvantage that they on the one hand very complex and on the other hand associated with considerable costs. These known methods are therefore for the measurement of carbon monoxide in Fuel cells, especially if they are to be used in automobiles, not profitable or not practical due to the necessary equipment.

From EP 0 834 948 A2 a device and a method are already known for reduce the carbon monoxide content in a hydrogen-rich gas. there the carbon monoxide reacts with the presence of a suitable catalyst an oxygen-containing oxidizing gas. Since this oxidative reaction is exothermic, it is water cooling still required. The concentration of the Hydrogen-rich gas located carbon monoxide is over a special Sensor measured. This sensor measures the current carbon monoxide content in the hydrogen-rich gas. If a certain limit is exceeded, the  Oxidation step initiated. The main disadvantage of such a sensor is that it structurally complex and therefore not cheap. Furthermore, such a sensor requires a complex electrical circuit for its operation.

In Sciene Tools, The LKB-Instruments Journal, April 1958, pages 9 to 11 are a method and an apparatus for the detection of carbon monoxide in air described, using an oxidizing agent for oxidizing carbon monoxide that changes color during the reaction. This oxidizer is not in dosed the gas stream and carried it with it, but remains in place and Location within the measuring device. As a control variable for the dimensioning of the the terminal voltage or Current density of the fuel cell used.

In the "Textbook of Inorganic Chemistry" by H. Remy, Akademische Verlagsgesellschaft, 7th edition, Leipzig 1954 , Volume I, pages 375, 376 and 674, some oxidizing agents for the removal of CO are mentioned in connection with breathing apparatus; there is no relation to the problem of protecting a fuel cell from damage.

The present invention is based on the cited prior art The task is based on a device for generating electrical energy and for detecting and / or removing provide disruptive oxidizable substances from a fuel with which the mentioned disadvantages can be avoided. In particular, a device are provided with which the in a simple and inexpensive manner Carbon monoxide content determined in the fuel cell or the carbon monoxide in Fuel can be removed.

This task is carried out with a device with the Merk paint the claim 1 solved. Advantageous Next educations are specified in the subclaims.  

Such a device is a simple and inexpensive way quantitative measurement of interfering oxidizable substances - for example of Carbon monoxide - made possible in fuel. It also takes place through the Device according to the invention also cleaning the fuel from the interfering oxidizable substances. The oxidizing agent must be so be selected so that interfering side reactions have as little influence as possible.

Changing the color of the oxidizing agent makes it particularly simple visual inspection of the fuel for corresponding disruptive oxidizable substances allows. The measurement of the pH of the oxidizing agent or of its Change also enables other types of displays to indicate the presence of disruptive oxidizable substances can be represented in the fuel. such Displays can be used as a pointer display, pen, screen or the like be trained.

The same applies to the measurement of thermal or electrical conductivity.

Basically, the invention is not limited to certain oxidizing agents. Rather, the basic idea of the present invention is to be seen in that an interfering oxidizable substance in the fuel, which in this is to be detected or removed from it with a specific one oxidizable substance suitable oxidizing agent is associated. On Suitable oxidizing agent is an agent that leads to selective oxidation of the interfering oxidizable substance, i.e. not the actual fuel oxidized to a significant extent. Preferably the oxidizing agent is a solid Material. The difference between the interfering oxidizable substance and the oxidizing agent  setting reactions can be displayed in a suitable manner, as in the further course of the description will be explained in more detail.

The interfering oxidizable substances can preferably be oxidizable gases, and here especially carbon monoxide. The device is therefore particularly suitable for the harmful carbon dioxide in a hydrocarbon reformed Detect or remove fuel.

The oxidizing agent Cr ₂ O ₇ ^2- or MnO ₄ can be advantageous. These oxidizing agents are particularly suitable for the detection of carbon monoxide. However, other oxidizing agents are also conceivable. It is only important that the oxidizing agents can react in a suitable manner with the interfering oxidizable substance to be detected or removed and that the influence of any interfering side reactions is excluded as far as possible.

For example, if carbon monoxide is to be detected or removed in the fuel as a disruptive oxidizable substance, Cr ₂ O ₇ ^2- is preferably used as a suitable oxidizing agent. The corresponding redox equations are as follows:

Cr ₂ O ₇ ^2- + 14H ⁺ + 6e ^- → 2Cr ³⁺ + 7H ₂ O (1)

CO + ½O ₂ → CO ₂ + 2e (2)

This gives the overall redox equation as follows:

Cr ₂ O ₇ ^2- + 14H ⁺ + 3CO + 3 / 2O ₂ → 2Cr ³⁺ + 7H ₂ O + 3CO ₂ (3)

When the oxidant reacts with the carbon monoxide, it colors the oxidizing agent changes from orange to yellow / green and the pH increases.

In a further embodiment, the oxidizing agent can be provided in a container be, preferably made of a transparent material. It is a transparent material particularly advantageous if the change in the oxidizing agent is visual Color change should be displayed. To the degree of presence of disturbing To be able to display oxidizable substances as precisely as possible can on the container a corresponding scaling can also be provided.

In addition, a device for measuring the pH can also be used be provided. The pH value of the oxidizing agent measured in this device or its change, if necessary, in a suitable device processed or further processed and then in one as described above Way.

Overall, an arrangement for Generating electrical energy provided by a fuel cell, a Fuel source for the fuel required for the fuel cell and has at least one supply line from the fuel source to the fuel cell, the a device for detecting and / or removing disruptive has oxidizable substances.  

The device can advantageously be used to detect and / or remove the disruptive oxidizable substances in the flow direction of the fuel in front of the fuel cell be connected to the supply line.

However, since the device is intended to protect the fuel cell it is appropriate that they in the vicinity of the fuel cell or is arranged directly on this.

The device is preferably for detecting and / or removing the disruptive oxidizable substances connected to the feed line or the fuel cell in such a way that at least a partial flow of the fuel through or into the device is or can be introduced. In such an embodiment, the Device preferably as a kind of detector for the detection of disturbing oxidizable substances used in fuel. The device is over, for example a corresponding supply line is connected to the main supply line, so that a partial flow of the fuel can flow into the device. If the demonstrable disruptive oxidizable substance, for example carbon monoxide, is contained in the fuel, this is with the oxidizing agent in the device in the same way as above  react as described. For example, this causes a change in color of the Oxidizing agent, which over the operating time or the loading time of the Oxidizing agent progresses with the interfering oxidizable substance. If For example, if a previously defined limit is reached, this is above a correspondingly advanced discoloration of the oxidizing agent visually detectable. The device can thus act as a limit detector and thus as a maintenance indicator for serve the fuel cell. If the corresponding limit is reached, means this means that there is also a corresponding limit value for the interfering oxidizable substance is reached within the fuel cell, and that this by an appropriate Measure must be cleaned or rinsed. The oxidizing agent must then a next operating period is either regenerated (i.e. oxidized) or fresh Material can be exchanged.

A corresponding discoloration of the oxidizing agent can also mean that the interfering oxidizable substances are not satisfactory in corresponding Devices for processing the fuel are removed. In this case the change in the oxidant produced or measured by the reaction also be used as an indication that the upstream of the fuel cell Components for generating the fuel are serviced or checked have to.

In a further embodiment, the device for detecting and / or removing the interfering oxidizable substances be connected to the feed line such that the entire fuel flow is or can be passed through this. A such an arrangement is advantageous, for example, if the disturbing ones Oxidizable substances in the fuel are not only displayed, but also removed should. For example, the oxidizing agent can be in the form of a salt bed through which the fuel flows. By the reaction of the disturbing oxidizable substance with the oxidizing agent is bound in the oxidizing agent and can therefore no longer enter the fuel cell. In the presence of disruptive oxidizable substances, for example harmful carbon monoxide, for example, the pH and / or the color of the oxidizing agent changes.  

These two changes are a good indicator of how effective the oxidizing agent is. Furthermore, by changing the pH or the discoloration, it can easily be indicated when the oxidizing agent has been used up. As soon as a corresponding limit value has been reached, the oxidizing agent can either be regenerated by suitable measures - for example by flushing with H ₂ O ₂ - or the device for detecting and / or removing the interfering oxidizable substances can be removed and replaced by a new device ,

In any case, the embodiments described above prevent that a critical limit of interfering oxidizable substances in the fuel cell is achieved.

A device for processing the fuel is preferably in the direction of flow of the Fuel in front of the device for detecting and / or removing the disruptive oxidizable substances and / or provided in front of the fuel cell and with the supply line connected. Such a device for processing the fuel is for example, necessary if the fuel is not used as pure hydrogen Is available, but initially reformed from natural gas, methanol or the like must become.

Advantageously, the one described above arrangement according to the invention and / or Methods for the detection and / or removal of oxidizable substances, in particular of carbon monoxide in the fuel for a fuel cell, in particular for a fuel cell for operating an electric motor for a vehicle used.  

Although the automotive industry offers z. Currently the greatest possible uses for Fuel cells, but other possible uses are also conceivable. To call are, for example, fuel cells for mobile devices such as computers or mobile Phones to power plants. Fuel cell technology is also suitable for the decentralized energy supply of houses, industrial plants or the like.

The present invention is not limited to particular types of fuel cells that the invention can be used in connection with all types of fuel cells can. Such fuel cells are, for example, alkaline fuel cells (AFC), proton-conducting fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), Molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC) or like.

However, the present invention may preferably be used in conjunction with Fuel cells with polymer membranes (PEM) can be used. This Fuel cells have a high electrical efficiency, they only cause minimal emissions, have an optimal partial load behavior and are in essentially free of mechanical wear. PEM fuel cells preferably operated with natural gas or methanol. When reforming this Fuels in a hydrogen-rich gas as fuel for the fuel cell falls In addition to carbon dioxide, the harmful carbon monoxide, which is caused by the invention demonstrated in the fuel in a simple and inexpensive manner or else can be removed from this.

As fuel for the fuel cells, for example, but not exclusively, Hydrogen, methanol, gasoline, natural gas, coal gas, biogas or the like are used become. By the present invention, however, any disruptive oxidizable substance in the Detected fuel from or from suitable oxidizing agents be removed.

The invention will now be described by way of example using exemplary embodiments explained in more detail with reference to the accompanying drawing. Show it:

Figure 1 shows a first embodiment of the arrangement for generating electrical energy. and

Fig. 2 shows another embodiment of the arrangement for generating electrical energy.

In Fig. 1, an arrangement 10 is illustrated for generating electrical energy. The arrangement 10 can serve, for example, to provide electrical energy for the electric motor of a vehicle. For this purpose, the arrangement 10 has a fuel cell 12 , which is designed, for example, as a PEM fuel cell. The fuel cell 12 is operated with hydrogen as fuel, which in turn is reformed from natural gas or methanol. For this purpose, the arrangement 10 initially has a fuel source 11 in which the methanol or the natural gas is stored. In order to be able to reform hydrogen gas from the methanol or natural gas, a device 14 for processing the fuel is also provided, which is connected to the fuel source 11 via a feed line 13 . In the device 14 for processing the fuel, the methanol or the natural gas is reformed into hydrogen gas. The reformed hydrogen gas is fed via the feed line 13 from the device 14 for processing the fuel into the fuel cell 12 . In addition to carbon dioxide, the reformed hydrogen gas also contains carbon monoxide, which, however, is harmful to the fuel cell 12 since it reduces the power output of the fuel cell 12 from a certain content. Therefore, the fuel cell 12 must be flushed with oxygen at regular intervals, for example, in order to remove the carbon monoxide. If this measure is not carried out, irreversible reactions occur at a certain concentration point of carbon monoxide, so that the fuel cell 12 becomes unusable and must be replaced.

In order to be able to detect the harmful carbon monoxide in the fuel, the arrangement 10 has a device 15 for detecting and / or removing interfering oxidizable substances - in this case carbon monoxide - in / from the fuel. The device 15 is arranged in the flow direction S _{B of} the fuel, which is represented by a corresponding arrow, in front of the fuel cell 12 . The device 15 is advantageously located in the vicinity of the fuel cell 12 , but it can also be connected directly to it. The device 15 consists of a container 20 , which is made of a transparent material, preferably a plastic material. In the container 20 there is an oxidizing agent 16 suitable for the carbon monoxide, in this case Cr ₂ O ₇ ^2- . The container 20 of the device 15 is connected to the supply line 13 via a supply line 18 .

The functioning of the arrangement 10 is now described below:
The gaseous hydrogen fuel emerging from the device 14 for processing the fuel flows in the flow direction S _B shown by the arrow in the direction of the fuel cell 12 . Shortly before reaching the fuel cell 12 , part of the fuel flow is derived. This partial flow is fed into the device 15 via the feed line 18 . In the presence of carbon monoxide in the fuel, the carbon monoxide reacts with the oxidizing agent 16 , which is located in the container 20 of the device 15 . The reaction turns the oxidizing agent green. This green discoloration can be detected visually due to the transparent container material. In the presence of carbon monoxide in the fuel, the oxidizing agent 16 will change color more and more over the operating time of the arrangement 10 . The progressive discoloration can be detected, for example, by means of a suitable scale 17 on the container 20 . If a certain limit value has been reached, that is to say if a certain degree of discoloration of the oxidizing agent has occurred, this means that a limit value for carbon monoxide pollution has also occurred in the fuel cell 12 . The device 15 thus functions as a limit detector and thus as a maintenance indicator. Reaching the limit value signals that the fuel cell 12 must be flushed with oxygen, for example, in order to reduce the carbon monoxide load and to avoid irreversible reactions in the fuel cell 12 . Reaching the visually verifiable limit value can also mean that the device 14 for the preparation of the fuel has to be serviced, for example by exchanging catalysts or readjusting regulators.

Since the discoloration of the oxidizing agent 16 caused by the reaction of the oxidizing agent 16 with the carbon monoxide is not reversible, the discoloration shown in the device 15 is a summed total display of the exposure to carbon monoxide, but not an indication of the current loading of the fuel cell 12 with carbon monoxide. For this reason, the device 15 must be replaced by a corresponding new device after the limit value has been reached. However, since the device 15 is composed of structurally simple and inexpensive components and elements, this exchange is possible without great expense and effort.

FIG. 2 shows a further embodiment of the arrangement 10 for generating electrical energy, the same components being provided with the same reference symbols as in FIG. 1. The arrangement 10 shown in FIG. 2 for generating electrical energy in turn has a fuel source 11 , a device 14 for processing the fuel and a fuel cell 12 , which are connected to one another via a feed line 13 . The individual functions of the respective components correspond to those of the exemplary embodiment shown in FIG. 1. In contrast to FIG. 1, the device 15 serves for the detection and / or removal of interfering oxidizable substances, and here of carbon monoxide, in / from the fuel mainly for removing the carbon monoxide from the fuel. For this purpose, the device 15 , viewed in the flow direction S _{B of} the fuel, is arranged in front of the fuel cell 12 in such a way that the entire fuel stream flows through the device 15 before it enters the fuel cell 12 . In this case, the oxidizing agent 16 is designed as a salt bed in the container 20 . The change in the oxidizing agent 16 by the reaction with the carbon monoxide is not measured this time by the discoloration of the oxidizing agent 16 , but by the change in its pH value. For this purpose, the device 15 is connected to a suitable device 19 for measuring the pH value which is known in principle in the prior art.

The fuel emerging from the device 14 for processing the fuel flows through the oxidizing agent 16 . In the presence of carbon monoxide, the pH of the oxidizing agent changes. This change is measured by the device 19 and further processed according to need and application and displayed in a suitable manner. The change in pH is a good indicator of how effective oxidant 16 is in the device. Furthermore, the change in the pH value can indicate when the oxidizing agent in the device 15 has been used up. By measuring the pH value, it can be quickly indicated whether carbon monoxide is getting into the device 15 . After a predetermined limit value has been reached, the oxidizing agent 16 must either be regenerated or replaced by fresh oxidizing agent. The exchange of the oxidizing agent 16 is carried out in a simple manner in that the entire device 15 is exchanged. Reaching a pH limit value can also signal that, as in the exemplary embodiment according to FIG. 1, the components upstream of the device 15 - such as the fuel source 11 and the device 14 for processing the fuel - have to be serviced.

LIST OF REFERENCE NUMBERS

10

Arrangement for generating electrical energy

11

fuel source

12

fuel cell

13

supply

14

Device for processing the fuel

15

Device for the detection / removal of interfering oxidizable substances

16

oxidant

17

scaling

18

supply

19

Device for measuring the pH

20

container
S _B

Flow direction of the fuel

Claims (9)

1. Arrangement for generating electrical energy, with a fuel cell, a fuel source for the fuel required for the fuel cell, at least one supply line from the fuel source to the fuel cell, a device for detecting and / or removing interfering oxidizable substances contained in the fuel, wherein a oxidant is employed, which reacts in the presence of interfering substances in the oxidizable fuel thereto, and characterized by a measuring device by
that the device ( 15 ) for detecting and / or removing the interfering oxidizable substances has an oxidizing agent ( 16 ) for the interfering oxidizable substances through which the fuel flows,
that the oxidizing agent ( 16 ) changes its color and / or its pH and / or its thermal and / or its electrical conductivity when reacting with the interfering oxidizable substances and
that the measuring device (scale 17 , device 19 ) for determining the total content of the interfering oxidizable substances contained in the fuel during the operating time of the fuel cell due to the change in color and / or pH and / or the thermal and / or electrical conductivity of the Oxidizing agent is formed. 2. Arrangement according to claim 1, characterized in that the oxidizing agent ( 16 ) is Cr ₂ O ₇ ^2- or MnO ₄ . 3. Arrangement according to claim 1 or 2, characterized in that the oxidizing agent ( 16 ) in a container ( 20 ), preferably made of a transparent material, is arranged. 4. Arrangement according to one of claims 1 to 3, characterized in that a device ( 19 ) for measuring the pH of the oxidizing agent ( 16 ) is provided as the measuring device. 5. Arrangement according to one of claims 1 to 4, characterized in that the device ( 15 ) for detecting and / or removing the interfering oxidizable substances in the flow direction of the fuel in front of the fuel cell ( 12 ) is connected to the feed line ( 13 ) or that the device ( 15 ) is connected directly to the fuel cell ( 12 ). 6. Arrangement according to one of claims 1 to 5, characterized in that the device ( 15 ) for detecting and / or removing the interfering oxidizable substances is connected to the feed line ( 13 ) or the fuel cell ( 12 ) such that at least one partial flow of the fuel is or can be passed through the device ( 15 ) or into it. 7. Arrangement according to claim 6, characterized in that the device ( 15 ) for detecting and / or removing the interfering oxidizable substances is connected to the feed line ( 13 ) such that the entire fuel flow is or can be passed through it. 8. Arrangement according to one of claims 1 to 7, characterized in that a device ( 14 ) is provided for processing the fuel and that the device ( 14 ) in the flow direction of the fuel before the device ( 15 ) for detecting and / or removing the interfering oxidizable substances provided in front of the fuel cell ( 12 ) and connected to the feed line ( 13 ). 9. Use of an arrangement according to one of claims 1 to 8 to operate a vehicle being the one in the fuel contained annoying oxidizable substance coals is monoxide.