EP1336213A1

EP1336213A1 - Method for regenerating co contamination in ht-pem fuel cells and a corresponding fuel-cell system

Info

Publication number: EP1336213A1
Application number: EP01993032A
Authority: EP
Inventors: Joachim Grosse; Manfred Poppinger; Rolf BRÜCK; Meike Reizig
Original assignee: Emitec Gesellschaft fuer Emissionstechnologie mbH; Siemens AG
Current assignee: Siemens AG; Vitesco Technologies Lohmar Verwaltungs GmbH
Priority date: 2000-10-30
Filing date: 2001-10-30
Publication date: 2003-08-20
Also published as: CN1473370A; AU2002215835A1; WO2002037591A1; KR20030044062A; JP2004513486A; CA2427133A1; DE10053851A1; US20030203248A1

Abstract

The HT-PEM fuel cells that are constantly operated at high temperatures are less sensitive to CO contamination than PEM fuel cells that are operated at normal temperatures. The aim of the invention is to regenerate possible CO contamination caused by the starting of the fuel cell. To achieve this, the HT-PEM fuel cell is operated in pulse mode for a predetermined period during the warm-up phase or at operating temperature. This permits the regeneration of the electrodes of the fuel cells, which have CO deposits. To carry out a regeneration method of a control and/or regulation device (120) in a fuel-cell system comprising at least one fuel cell module that consists of a stack of HT-PEM fuel cells, with a control and/or regulation device for process management allocated thereto, said system is provided with a pulse device (125), which activates a pulse-mode operation for the fuel-cell stack (110), in accordance with predeterminable parameters.

Description

LO υ f ιv>'H ¹ μ- ¹ π o Cπ o Cn o Cπ

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Φ CD t ι-i N p "N cn O Φ φ ^ rt ι-i" N Φ μ- <P P Hi Ω

P 2J CD P φ ≥! H H- rt li P 3 Φ Φ μ- <li K Φ MP SD P ^J

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P f "H CD P Ω • P 1 ιP P Hi Φ P rt SD tr tr P Φ P 1 o tr rt O Hi rt ü Φ

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P H- rt o Cfl Φ P ü rt H P Cfl P H H H tr P Φ P H H <ιp Ü

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P P CD SD H- rt tS ÖJ C • Φ O? P • 6 P tr I »XJ φ μ- ii li CΛ H

CΛ CD Cfl P P Hi n S H φ SD P 1 Φ φ Φ li Ω H P φ Hi rt ι

P r P SD Hl rt s; DI Φ li cn O <! μ- H - li φ Ü OP ^J P φ P P> O μ-

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P ^J Hi N ιP P ι P σ> Φ cn H <P ^J P iQ • ö PO: Φ PI TJ CΛ ii rt Φ NP r + N φ φ P Φ op rt P ^" φ φ h- ¹ P Φ φ li P 'ü o <i φ OP φ P

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<J ^ 0 ^ Φ n cn Hi tr P P P φ Φ SD P Φ Cd ^ H P Hi INI Φ

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PP r- ^> M p: H- Hi φ φ cn Φ cn H- <! K 0 ι-3 ü SD li P 'O PJ tr

CD rt P h- ¹ cn Φ Hi P μ- cn ij φ φ P Φ H- P 1 li Hi H ¹ VP Φ li tr ω Φ P φ cn ιQ N H- P φ PHP 3 Φ ιQ IM Φ Hi Φ φ μ ^j μ-

O: CD ι-i rt P t φ rt Φ Φ «P H- ι-i P P Ω 1_i tr Φ P N P ι SD l-h Φ rt P ~ - P o U3 cn iQ P tr SD φ cn Φ φ Φ U3 K

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CD PP H- Φ O £ SD Φ H- ¹ H- POP Φ Λ (D Φ Φ rt H ö φ 1

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/ (0 co CD P P 'φ s: 3 P Φ Φ μ- p- 0 H φ ii M SD φ Φ g

H Φ P SD SD P μ- 1 rt n Φ ü SD * <μ- P tr 1 1

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lichten W _O 00/02156 A2 states that special so-called HTM- _b between HT-PEM fuel cells tolerate CO impurities in the fuel gas of up to 10,000 pp. For the stationä ^¬ ren operation so CO assignments can advertising put into the purchase. Nevertheless, efforts are made to remove CO deposits on the electrodes, particularly when or after starting the fuel cell.

The object of the invention is therefore to propose a method specifically for the HT-PEM fuel cell, with which possible CO deposits on the electrodes are prevented, and to create an associated fuel cell system.

The object is achieved with respect to the method according to the invention by the measures of claim 1 and with respect to the fuel cell system by the features of claim 9. Further developments of the method and the associated system are specified in the dependent claims.

In the invention, the HT-PEM fuel cell is pulsed for a predetermined period during the heating from the cold to the operationally warm state. The pulse operation achieves with sufficient certainty a regeneration of any CO-coated electrodes of the HT-PEM fuel cells.

The measure according to the invention can advantageously take place as a function of the poisoning state, provided that a suitable sensor for detecting the poisoning state is present. The cell voltage generated by the fuel cell or its change is appropriate here. The measures according to the invention can also be carried out as a precaution after each cold start, so that the formation of CO deposits on electrodes is prevented and thus possible poisoning of the membrane electrode units (MEAs) is excluded. Within the scope of the invention is advantageous when the Regenerati ^¬ on he _d _C O-poisoning is performed once per operating cycle of HT-PEM fuel cell. The Regene ^¬ takes place ration by pulse operation at temperatures between 60 ° C and 300 ° C, preferably between 120 and 200 ° C.

Further details and advantages of the invention result from the following description of figures of exemplary embodiments with reference to the drawing in conjunction with the patent claims. They each show as graphical representations

1, the co-dependence is operated at a voltage of the PEM fuel cell stack _^ at low temperatures, Figure 2 is a corresponding illustration for a HT-PEM fuel cell stack,

Figure 3 and Figure 4 shows the influence of pulsing on the operation of a HT-PEM fuel cell stack

FIG. 5 shows a fuel cell system with an HT-PEM fuel cell stack and an associated control or. Control device.

PEM fuel cells are sufficiently known from the prior art, so that their structure is no longer described in detail in the present context. Such PEM fuel cells are based essentially on proton exchange in a solid electrolyte (proton exchange membrane), the term “PEM * also being derived from the structure of the fuel cell with a polymer electrolyte membrane. The heart of such PEM fuel cells is the so-called MEA or membrane electrode assembly (membrane electrode assembly), in which a suitable membrane made of organic material as the electrolyte or its carrier electrodes are applied as the cathode and anode of the fuel cell on both sides. co CO M r ¹

Cπ O Cn o cπ O Cπ

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Φ CΛ P Φ PHHP ^J rt o? ^ q Φ s; P Cd P Λ tr li P φ rt Cd ü P • Hi Φ μ- CΛ

Hi P

P et Cfl φ o SD D O: P P J Φ • 3 ^ q P CΛ * «φ P Hi μ- rt rt

0 ^ Φ P ^* μ- P et Cfl? Ό PPH y rt <Φ μ- P Φ rt M cn P rt O g

CΛ H Hl μ- μ- • P Φ P φ SD TS P ιq P ii Φ PH) P cn HOPP φ Φ Hl M μ- Hi ι rt φ P ü P 3 φ φ SD μ- μ- ii rt rt rt μ - ü Dd P 3

P P H Hi>

Ω NP μ- μ- PPPP ιq P tr φ P l 3 Hl Φ φ H ¹ Φ Φ 3 li t? rt cn isi p- Φ H et ^ q 3 3 <SD ^ Φ f Φ tr φ p: rt li μ- H ¹ tr Φ r Φ tr φ cn

Φ rt Tl μ- o φ O μ- 3 ^ q tr μ- μ- li Ω <P - HO: Φ μ ^j

P Φ P • tr P rt P CΛ CΛ P 3 μ- φ Φ φ P s; SD - rt Φ o P p: P "μ- H" μ- H Φ Φ μ ^j OH rt P cn ≥i μ- PP Φ P Φ μ- P <PP Öd Φ P φ μ-

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M P 3 N Φ P - - P μ- rt rt Cfl P Hi O tr P H P P μ- Hi P CΛ

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P ^ CΛ l er P o P o O φ φ Φ Φ tr O P μ- p: i, O O n φ φ li Cf s. P-

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P Φ PPM TS rt U5 HP μ- S Φ P α cn H φ P Φ P μ- P p: P ¹ P 2, μ-

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CD CΛ Cd

P P Cfl et Φ μ- Φ <q Cfl Φ Φ J tr Ω φ P P P s: g CΛ M

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H μ- Φ P Ω P O ü CΛ o P Λ "ι φ Hl μ-» li ιq P rt li

Hi P o PPS t μ ^j Φ P Φ P ü P ^J rt rt Ω μ- P m Φ φ fl P tr CΛ

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- tq μ- <! rt Ω P. SD: μ- o P r Φ P P Ti Φ Hi p: o Hl Φ

^ Φ Ω O n P ^J Φ φ PP ^J ü CΛ p: H Φ Cd μ- M Φ μ- μ- o vq s: Hl ii c φ Hi P • P Φ ü φ HP o tr Φ PH Φ Ω HP li φ μ- ii s; r + rt μ- Hi PPH φ CΛ N φ φ O Φ P Φ - Φ P Ω CΛ 3 H ü φ T o Φ Φ PN Φ PPP CΛ P »CΛ H Φ P? d φ t rt P tr μ- PP μ- M tr Φ Φ 3 P ιq Cd P Φ CΛ tr Hl HP Φ rt P »Φ Φ Ω g

Φ μ- cn P Φ Φ H r + P φ μ- H ¹ Φ ιq ιq μ-? 5 ii ü CΛ ti P tr I μ-

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M P tr <! IV) Φ Hl ^ P Φ li o P ιq Φ rt

SD g SD t ii Φ Φ ιq φ φ σ n ii Hi P H "P Φ O Φ 1 0 μ- Cfl I P Φ H tr Φ CΛ

SH o SD φ P ^■ μ- fi φ CΛ P

H μ- Cfl 1 o P o rt P ιq CΛ tr Ω P Φ P P Cfl

SD 1 1 1 PPOP cn P φ tr H et P 1 1 1 1 l 1 1 I 1 1

high _S i tromdichten the voltages U steep wastes for ^¬ len to zero.

Such characteristics are known. It is also known that when the electrodes are coated with CO, the fuel cells become inoperable.

1 shows four characteristic curves 11 are illustrated to 14 for low temperature ^¬ tur PEM fuel cells, the different CO concentrations as a parameter, namely in detail 0 ppm with characteristic curve 11, 100 ppm in curve 12, 1000 ppm with characteristic curve 13 and 10,000 ppm characteristic curve 14. The result is that at higher CO contents, which lead to CO deposits on the electrodes, the voltages collapse even at low current densities, for example at 1000 ppm CO at approximately 1.1 A / cm ² compared to approximately 2 A / cm ² at 0 ppm CO.

FIG. 2 shows two characteristic curves 21 and 22 with 0 ppm CO and 1000 ppm CO, especially for the high-temperature PEM fuel cell, that their voltage-current density dependencies are practically identical. This corresponds to the well-known fact that the HT-PEM is largely insensitive to contamination with CO.

If one considers the CO poisoning as a function of the temperature, this results in particular at low temperatures, i.e. in the low-temperature PEM fuel cell, a rapid drop in cell voltage that occurs at high temperatures, i.e. at high temperature PEM, asymptotically goes to zero.

When the HT-PEM fuel cell is in operation, potential poisoning of the electrodes can now be excluded by starting the fuel cell from the cold stand during the heating of the fuel cell or after reaching the operating temperature condition of Brennstoffzel ^¬ le for a predetermined period, the HT-PEM fuel cell is operated in pulse mode. This can on the one hand gene by temporary short-circuiting or reversing the polarity and secondly by switching off the hydrogen supply at load operation SUC ^¬.

The pulsed operation regenerates the electrodes covered with CO and thus puts the HT-PEM fuel cell in the ideal state.

It therefore makes sense to find suitable criteria for determining the poisoning status of the HT-PEM fuel cell. The line voltage gradient can be used as such a criterion, for example, since a drop in the cell voltage indicates poisoning. The pulse operation can therefore advantageously be carried out as a function of the drop in the cell voltage.

For this purpose, FIGS. 3 and 4 show the individual voltages U of high-temperature PEM fuel cell units as characteristic curves 31 and 41 with different CO poisonings as a function of time t, pulse operation taking place over different time intervals with a given current density. It is discharged via a defined resistor with a specified discharge time. The characteristic curve 31 stands for a CO content of 100 ppm with a pulse of 10 min at 300 mA / m ² and 20 s discharge time. The characteristic curve 41, on the other hand, stands for a CO content of 1000 ppm with a pulse of 5 min at 300 A / cm ² and 20 s discharge time.

In FIGS. 3 and 4, pulse operation takes place when the HT-PEM fuel cell is heated, that is to say before the respective operating temperature has been reached, since electrode deposits with carbon monoxide (CO) can occur at the low temperatures. Instead, the pulse mode can also be zen, _d . _h . Warm operating condition is reached. It can thus be ensured that the HT-PEM fuel cell is regenerated depending on the poisoning state. The cell voltage or its change can be recorded as a trigger for an automatic regeneration of the HT-PEM fuel cell. This means that the pulse operation takes place depending on the dynamic voltage behavior.

It turns out that with the described method, the clamping voltage of the ^¬ HT-PEM fuel cell also CO impurities in the fuel gas is in the range of 100 and 1000 ppm CO occupancy can be kept constant. This confirms a major advantage of the HT-PEM fuel cell.

In FIG. 5, 110 shows a fuel cell module, which consists of a stack of individual HT-PEM fuel cells 111, 111 ^Λ , ... and is referred to in the technical field as a fuel cell stack or "stack *" for short. The process gas, ie hydrogen or hydrogen-rich gas as the fuel gas on the one hand and oxygen or air as the oxidant on the other hand, are supplied centrally. The stack 110 contains lines for the process gases, which are not discussed further in the present context.

In FIG. 5 there is a control device 120 with which the process in the fuel cell stack 110 is controlled in a known manner. The control device has discrete inputs 121, 121,... For setting process parameters and, for example, an output 131 for a common, possibly bidirectional data bus. several outputs 131, 131 ^Λ , ... for individual control lines.

According to FIG. 5, the control device 120 is assigned a pulse device 125, which enables pulse operation of the fuel cell system. There is also a timer 126 which operates the pulse device 125 in predefinable operating modes. K) I— ¹ o Cπ O Cπ r öd <l α EU ιq N Hi N 03 P ^* PPMP cn o ii o μ- ι-3 φ Φ P Φ P o P Φ tr Cd ti P μ- o φ P Φ 1 Hi t 3 ü P CΛ φ H Hi rt o P Tl p: ü q P ti Φ PPP

O P cn T> M t Φ Φ Φ CΛ φ φ Cd P cn ιq P

CΛ o φ g ü P rt tr P φ P P cn φ rt

Φ et 0 vP 1 rt ü μ- 0: tr H μ- cn P - «« μ- μ- O n Φ Cd o μ- CΛ »i P cn Φ Ω et P O

P Hi P H s; P P rt P ti φ <P tr O ιq ιq P

CΛ Hi tr φ φ μ- rt P Φ μ- P et Hi ιp φ

Ω INI μ- li P ü μ- P φ «3 ti PP Hi <Hi P tr φ CΛ PPPP φ CΛ cn ιQ μ- NO • μ ^j H rt CΛ φ P Hi 0 Cfl 3 Φ P μ- O μ- rt 3 ii H CΛ NP μ- φ Φ O 0 OH ΓJJ: tr o Φ Φ OPMH CΛ fco σ P

O P Hl 3> Φ H μ- P CΛ μ- Φ Ti Φ cn et s: 0 Hi μ- et rt φ N rt P P li tr

• Φ O s; N M ιq ti Φ P s: P P N cn P φ

CΛ μ- Φ μ- μ- μ- Φ CΛ P Φ rt P P Cfl

Φ P ü P φ φ P ¹ li cn PH "PPPO

PPP μ ^j N μ- tr tr P rt Φ P Ω P Ω P rt li Φ Φ P CΛ PP Φ P cn Φ ^ r ιq P ¹ P μ ^j Ω PH "≤ Hi ιq μ- P cn φ μ- tr P Φ P Tl P rt N CΛ Φ P? T: NH

Ω LP σ μ- Φ P ü _* φ Φ φ PO: P><Φ tr Φ Φ p P 3 μ- PJHPPP? R

Φ Hl μ- p CΛ φ s: rt CΛ P CΛ P Φ H ¹ tr p: P CΛ tr P Φ tr o μ-> M vq Φ ti μ- Φ f-3 tr μ- H ¹ O Φ P Φ H cn Φ PP cn μ-

Φ li P et N P rt ιq φ Φ Hl P O 3 oo

3 rt cn i r-> ii P ii φ μ- W p: μ- <q tr

TJ tr H rt μ- cn P μ- P r t P cn -> φ φ O φ Φ rt P φ et H li H ιq%

H P CΛ tr P Ω tr φ μ- O rt ii P Hi

P φ o Cd PP tr P Ω P φ Φ P w P rt li P φ P P. P Φ Φ tr Φ Ü P rt ⁴

P P et 3 Φ LJ- μ- H et P CΛ μ- μ- Ü ü P φ H μ- H P Φ P et P φ M Φ Φ

Hi P ti μ- rt Φ P φ P 3 P μ- P μ- P

Φ Ω Φ φ Cd H φ H P ιq μ- cn ^ q rt φ

P tr tr φ ti 3? rt O P φ H P

CΛ μ- CΛ μ- φ K K rt tv> ü ti P rt Φ rt P 3 N P P f-3 μ- π «φ • H

Φ P • <Φ P 1 P 1 <l o P cπ P

H CΛ ι-3? R CΛ Tl Tl μ- tr tr 3 Cd

Φ H "? Rt M rt M Φ φ N P φ ii

Hi 3 P φ o g CΛ g ii μ- φ P P tr Φ

O P: S CΛ ιq Hi 1 rt 1 rt P ti ti Φ P

P H φ φ Hi Cd P Cd Cf 3 P P

H Φ P N ti ii ii s: tr o M P ω

P P ii φ φ Φ et φ Φ Φ P H P g rt

M μ- rt Hl H P P ii H o Hi ι μ- O

O φ P O P P P P P CΛ X P Φ rt Hi

0 li H "rt Φ cn P CΛ Φ Ω μ- Cfl P- rt Hi

O K tr ιq μ- et P rt P t P cn Φ Φ INI

H φ Φ o O O P P Φ tr 1 H P P P Hl M Hi; r φ <P rt P μ- TJ Φ • ü Hi O Hi P μ- o ^ q Φ

CΛ M μ- P Ω 1 Ω 1 P rt K rt N φ g Ω φ tr tr P φ 1 Φ P P 1 tr H 1 1 P li 1

Claims

claims

1. A process for regeneration of CO poisoning in HT-PEM fuel cell comprising the following steps: - the HT-PEM fuel cell is starting in cold state ge ^¬,

- The HT-PEM fuel cell is then operated in pulse mode for a predetermined period of time,

- The pulse mode regenerates the CO poisoning, in particular the poisoning of electrodes covered with CO, of the HT-PEM fuel cell.

2. The method according to claim 1, so that the pulse operation takes place during the heating of the HT-PEM fuel cell to the operating temperature.

3. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the pulse operation after heating, i.e. in the warm operating state, the HT-PEM fuel cell takes place.

4. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the HT-PEM fuel cell is operated in pulse mode depending on the poisoning state

5. The method according to any one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the HT-PEM fuel cell is operated as a function of the cell voltage in pulse mode.

6. The method according to claim 1, characterized in that the HT-PEM fuel cell is operated in pulse mode after each cold start.

7. _V out according to one of the preceding claims, ^¬ du rchgekennzeichnet that a regeneration of the HT-PEM fuel cell is carried out once per cycle of operation.

8. The method according to claim 6, so that the regeneration of the HT-PEM fuel cell takes place at temperatures between 60 ° C and 300 ° C, preferably between 120 ° C and 200 ° C.

9. Fuel cell system with at least one fuel cell module from a stack of HT-PEM fuel cells (fuel cell stack) and an associated control and / or regulating device for process control, characterized in that the control and / or regulating device (120) is assigned a pulse device (125) which, depending on predefinable parameters, activates the fuel cell stack (110) for pulsed operation.

10. The fuel cell system as claimed in claim 10, so that a timer (126) for activating the pulse device (125) is present.

11. Fuel cell system according to claim 9, d a d u r c h g e k e n n z e i c h n e t that means for detecting the

Output voltage of the fuel cell stack (110) or for detecting changes in the voltage are present.

12. Fuel cell system according to claim 11, d a d u r c h g e k e n n z e i c h n e t that the activation of the

Fuel cell stacks (110) for pulse operation are triggered by a predeterminable voltage change gradient of the fuel cell stack (110).

13. Fuel cell system according to claim 9, characterized in that sensors for detection of CO occupancies are present in the HT-PEM fuel cells.

14. The fuel cell system according to claim 11, so that the activation of the fuel cell stack (110) for pulse operation is sensor-controlled.