Method and device for parallel condensation and evaporation for fuel cell system

Abstract

According to the invention, a method for parallel condensation and evaporation is provided for a fuel cell system with a condensation/evaporation device. In this case, the condensation-evaporation device (KVV) has a condensation chamber and an evaporation chamber, which are thermally coupled to one another via a heat exchanger so that water vapor contained in the condensation chamber in exhaust gas of a fuel cell stack is condensed into water and in the evaporation chamber a liquid fuel of a two-phase mixture comprising the liquid fuel and a gas phase, are at least partially vaporized to fuel vapor. In this case, the energy required for evaporation is at least partially provided by waste heat from an exhaust gas of a fuel cell stack of a fuel cell and the associated energy withdrawal from the exhaust gas of a fuel cell stack is used for condensation. The present invention is characterized in that the gas phase comprises a carrier gas which is CO.sub.2.

Claims

1. A method of parallel condensing and vaporizing for a fuel cell system with a condensing/vaporizing apparatus, wherein the condensing-vaporizing apparatus (KVV) has a condensing chamber and an evaporation chamber which are thermally coupled to each other via a heat exchanger in such a way that water vapor contained in the condensing chamber in an exhaust gas of a fuel cell stack is condensed into water and in the evaporation chamber, a liquid fuel of a two-phase mixture comprising the liquid fuel and a gas phase, is at least partially evaporated to fuel vapor wherein the energy required for evaporation is at least partially provided by waste heat from the exhaust gas of the fuel cell stack of a fuel cell and the associated energy withdrawal from the exhaust gas of the fuel cell stack is used for condensation, wherein the gas phase comprises a carrier gas that is CO.sub.2.

2. The method according to claim 1, wherein the carrier gas is circulated in the fuel cell system.

3. The method according to claim 1, wherein exhaust gas from which the water is condensed out is a cathode and/or anode exhaust gas of the fuel cell stack.

4. The method according to claim 1, wherein in the evaporation chamber, the carrier gas is brought into contact with liquid fuel in such a way that saturation of the carrier gas with fuel vapor is achieved.

5. The method according to claim 1, wherein the exhaust gas is pre-cooled before entering the condensing chamber by means of at least one cooling device.

6. The method according to claim 1, wherein an aqueous fuel solution is provided as fuel.

7. The method according to claim 1, wherein, in the evaporation chamber, the liquid fuel is heated to or above a boiling point for the liquid fuel.

8. The method according to claim 1, wherein the heat exchanger is specifically a heat exchanger apparatus, and a cooling side of the condensing chamber is adjacent to the heat exchanger apparatus and to an evaporation chamber wall.

9. The method according to claim 1, wherein the fuel cell system uses a reformer, and the reformer reaction results in products including H.sub.2 and CO.sub.2 from liquid fuel.

10. The method according to claim 1, wherein the fuel cell system is a system in which fuel is introduced directly into an anode compartment of the fuel cell and reacts on an anode catalyst to form CO.sub.2.

Description

(1) The above statements on the method according to the invention apply equally to the device and vice versa. The invention will be explained in more detail below with reference to the drawings. These show in

(2) FIG. 1 a schematic representation of a HT/NT PEM fuel cell system with a condensation-evaporation device according to the invention,

(3) FIG. 2 a schematic representation of a DMFC fuel cell system with a condensation-evaporation device according to the invention,

(4) FIG. 3 a schematic representation of a further exemplary embodiment of an NT-PEM fuel cell system with a condensation-evaporation device according to the invention, and

(5) FIG. 4 a schematic representation of an exemplary embodiment of a two-part methanol pre-evaporator or evaporation chamber with an interposed exhaust gas cooler, and

(6) FIG. 5 a schematic representation of an embodiment of a condensation-evaporation device according to the invention and a CO.sub.2 separator.

(7) In the following, a condensation-evaporation device 1 according to the invention is described based on an HT-PEM fuel cell system 2 with methanol as fuel (FIG. 1).

(8) This system 2 comprises a fuel cell stack 3 having an anode side 4 and a cathode side 5, a reforming device 6, and the condensation evaporation device 1.

(9) The condensation/evaporation apparatus 1 comprises a condensation chamber 7 for condensing water from the water vapor contained in the cathode exhaust gas of the fuel cell stack 3 and an evaporation chamber 8 for at least partially evaporating methanol to methanol vapor. The condensation chamber 7 and the evaporation chamber 8 are thermally coupled via a heat exchanger 9 or the condensation chamber 7 and the vaporization chamber 8 are an integral part of the heat exchanger apparatus 9.

(10) The heat exchanger apparatus 9 is designed, for example, as a plate heat transfer device. The plate heat transfer device 9 has corrugated profiled plates (not shown), which are composed such that in each successive chamber once the (to be heated) evaporation chamber and then the heat-emitting (condensation chamber) medium flows (alternately). These chambers form according to the condensation chamber 7 and the evaporation chamber 8.

(11) The cathode side 5 of the fuel cell stack 3 has an inlet 10 for supplying cathode air. For supplying cathode air, a pump or a blower 11 may be provided.

(12) A cathode outlet 12 is connected via a line section 13 to an inlet 14 of the condensation chamber 7 of the condensation-evaporation device 1.

(13) In this line section 13, a pre-cooler 15 is integrated. The pre-cooler 15 may include, for example, a heat exchanger 16 and a fan 17 and a temperature sensor (not shown) to cool cathode exhaust gas.

(14) An outlet 18 of the condensation chamber 7 is connected via a line section 20 to a media unit 19, which is designed, for example, as an evaporator or as a humidifying device.

(15) In the line section 20, the phase separation device 21 is integrated so that the liquid phase of the media unit 19 is supplied and the gas phase is discharged from the system or can escape. In this line section 20, a pump (not shown) may be integrated to produce condensate.

(16) An anode outlet 22 of the fuel cell stack 3 is connected via a line section 23 to an inlet 24 of the evaporation chamber 8. In this line section 23, a pump 25 is integrated.

(17) Furthermore, a catalytic burner 26 is connected to this line section 23 to prevent a discharge of exhaust gases such as hydrogen or carbon monoxide to the environment. The oxidation takes place via a supply of air oxygen into the exhaust gas stream. The heat generated in this case can be supplied via a thermal coupling, for example, the media unit.

(18) Furthermore, a fuel container 27 is provided, which also opens into the evaporation chamber 8 and is connected thereto via a line section 29. Between evaporation chamber 8 and fuel tank 27, a pump 28 is provided. Instead of the pump 28 a metering device (not shown) may also be provided which comprises, for example, two pumps, an intermediate reservoir or a pump with mass flow meter.

(19) An outlet 30 of the evaporation chamber 8 is likewise connected to the media unit 19 by means of a line section 31.

(20) The media unit is connected via a line section 32 to an anode inlet 33.

(21) In this line section 32, the reformer device 6 is integrated. The reformer device 6 may comprise one or more series-connected reformers or shift stages.

(22) Alternatively, the heat transfer device may also be designed as spiral heat exchangers, tube heat exchangers or tube bundle heat exchangers, U-tube heat exchangers, jacket tube heat exchangers, heating coils or cooling coils or as countercurrent layer heat exchangers.

(23) The operation of this fuel cell system will be explained below.

(24) In this fuel cell system, it is provided that the anode of the fuel cell stack is supplied by means of reformate directly via the reformer device 6. Furthermore, the fuel cell system 2 has a CO.sub.2 cycle. CO.sub.2 as a carrier gas as well as water and fuel vapor are fed to the reformer device 6 via this circuit.

(25) In the reformer device 6, a steam reforming takes place in which hydrogen and carbon dioxide is produced from methanol and water (CH.sub.3OH+H.sub.2O.fwdarw.3H.sub.2+CO.sub.2), in which case water is used as the oxidant to produce hydrogen.

(26) The condensation-evaporation device 1 is formed to recover product water from the cathode exhaust gas.

(27) In such a fuel cell system 2, the cathode exhaust gas contains more water vapor as the reaction product of the cathode reaction than is required for the hydrogen recovery. The cooling energy of the fuel vapor amount that enters the adjusted carrier gas volume flow is still too low to cool the exhaust gas to the required temperatures, and to condense out enough water. Therefore, the pre-cooler 15 is provided.

(28) In the media unit 19, methanol is evaporated or taken up in vapor form by a carrier gas stream and fed to the reforming device 6.

(29) In the condensation chamber 7 of the condensation-evaporation device 1, the cathode exhaust gas is cooled by the thermal contact with the evaporation chamber 8 via the heat exchanger apparatus. In this way, water is condensed out of the water vapor contained in the cathode exhaust gas and is the system 2 again.

(30) The separation of the condensate from the exhaust stream can be done for example in the phase separation device 21 by gravity or a pump. The condensate is then fed to the media unit 19, in which also the CO.sub.2-fuel vapor stream is introduced.

(31) If the media unit 19 is designed as a moistening device, a new equilibrium of the vapor pressures of water and fuel vapor in the carrier gas arises in the liquid phase of the moistening device, depending on the molarity of the fuel solution and temperature present there.

(32) This means that in the case where only fuel is evaporated, water vapor is additionally taken up in the gas phase. Depending on the vapor pressure of the supplied gas, additional fuel vapor is taken up by the gas phase or condensed into the fuel solution.

(33) The media unit 19 may also be an evaporator device in which fuel and water is completely evaporated.

(34) In addition, in addition to the pre-cooler 15 by air, further pre-cooling may be provided, e.g. by thermal contact (by means of a heat exchanger) with a liquid medium (water, fuel or fuel solution) in the media unit 19, the pre-cooled from the fuel cell 3 gas. This heat exchanger may be formed by a plate heat exchanger or corresponding piping with cooling fins extending into the liquid.

(35) A further exemplary embodiment of the condensation-evaporation device 1 will be described below with reference to an NT-PEM fuel cell system 2 (FIG. 1).

(36) Unless otherwise described, this embodiment corresponds to the embodiment described above. Identical components are provided with the same reference numerals.

(37) According to this embodiment, the reforming device 6 is multi-stage or formed with at least one shift stage.

(38) When using a low-temperature fuel cell, there is a more complex reforming with shift stages at lower temperatures and/or selective oxidation and/or a reformer with suitable catalysts to have the lowest possible carbon monoxide (e.g. 50 ppm), or to have in addition to carbon dioxide and water vapor, no other substances in the hydrogen, if possible.

(39) Otherwise, the inventive method is carried out analogously to the above-described HT-PEM fuel cell system.

(40) When using a solid oxide fuel cell (SOFC), however, the reformer can be omitted or adapted to the requirements of the system.

(41) In the following, another embodiment of the condensation-evaporation device 1 will be described with reference to a DMFC fuel cell system 2 (FIG. 2).

(42) Unless otherwise described, this embodiment corresponds to the embodiments described above. Identical components are provided with the same reference numbers.

(43) The cathode outlet 12 of the fuel cell stack is connected via the line section 13 to the condensation chamber 7 of the condensation evaporation device 1.

(44) In this line section 13, a heat exchanger apparatus 34 is integrated for pre-condensation.

(45) The outlet 18 of the condensation chamber 7 is connected via the line section 20 with a special methanol solution tank 35, which serves as a buffer memory. This container 35 contains two phases, a liquid phase (methanol solution) and a gas phase (anode exhaust gas (CO.sub.2)).

(46) In the line section 20, the phase separation device 21 is integrated so that the liquid phase is supplied to the container 35 and the gas phase can escape from the system.

(47) Fuel tank 27 is connected via the line section 29 to the inlet 24 of the evaporation chamber.

(48) At the inlet 24 of the evaporation chamber 8, a distribution device 36 is provided for the uniform or optimal loading of the evaporation chambers with CO.sub.2 and fuel, primarily in direct current. The direct current prevents excessive cooling of the carrier gas and thus its absorption capacity of fuel. The distribution device 36 can also be designed as a valve device for controlling corresponding volume flows.

(49) For circulating the methanol solution, a line section 37 from the anode outlet 22 to the methanol solution vessel 35 is provided.

(50) Furthermore, in this system, a further gas cycle, wherein in the gas cycle circuit anode exhaust gas is used as a carrier gas, may be provided.

(51) In this gas cycle, a portion of the CO.sub.2 resulting from the anode reaction which emerges from the fuel cell stack 3 as anode exhaust gas is recirculated.

(52) The unneeded remainder of this gas can be removed via a gas outlet 45 which is connected to line section 38.

(53) For recirculation, a line section 38 leads from a chamber of the methanol solution tank 35 containing the gas phase to the inlet 24 of the evaporation chamber 8.

(54) In addition, a heat exchanger apparatus 39 and a phase separation device 40 can be integrated in this line section 38 or in the gas circuit.

(55) The phase separation device 40 has a return line 41 to the methanol solution tank 35.

(56) In the methanol solution tank 19, the two-phase mixture of the anode fluid flows from the anode outlet 22, the gas being separated therein and partially recirculated to the vaporization chamber of the KVV 1, for example by means of a pump.

(57) The non-circulated part is discharged from the system via a conduit section 44. For its purification, an afterburner can be used again.

(58) To increase the methanol uptake in the evaporation chamber 8 of the KVV 1, the CO.sub.2 phase can be cooled in the heat exchanger apparatus 39 before it enters the KVV 1 to condense water vapor and methanol vapor and be deposited in the phase separation device 21.

(59) However, the heat exchanger apparatus 39, which is, for example, air-cooled or can be cooled by thermal coupling to the condensation chamber, and the phase separation device 40 are not absolutely necessary in a DMFC fuel cell system 2. Particularly, when operating with low methanol concentrations one can do without it

(60) In order to achieve a lower methanol concentration in the carrier gas, a methanol-depleted zone in the methanol solution container 35 can also be formed. Then, the gas chamber of the container 35 is divided into an upper chamber and a lower chamber (not shown). In the upper space, the anode fluid depleted in the fuel cell 3 is introduced. In this case the methanol solution flows in the lower space with the liquid phase of the buffer storage by gravity or a conveyor. The gas phase (mainly CO.sub.2) in the upper chamber is partially conveyed to the evaporation chamber 8 and the remainder is discharged from the system as anode exhaust gas (not shown).

(61) Alternatively, carrier gas with a lower methanol vapor pressure can also be taken away via an additional phase separation in line section 37 from the anode fluid. (not shown).

(62) In the evaporation chamber 8, there is contact between CO.sub.2 with supplied methanol from a methanol CO.sub.2 tank or fuel tank 27 and to its evaporation. The effluent mixture of methanol and CO.sub.2 is then introduced into the methanol solution tank 35.

(63) The methanol solution tank 35 is connected to the anode inlet 33 of the fuel cell stack 3 via a pipe section 46.

(64) The phase separation device 40 is connected to the methanol solution container 35 via a line section 41.

(65) Usually, DMFC systems have a buffer with a methanol solution consisting of methanol and water to supply the anode electrodes. This solution, after passing through the anode and depleted there, is returned to the storage. The storage is supplied with water and methanol or methanol solution to compensate for the depletion. In systems that are supplied exclusively with pure methanol, water must be recovered from the cathode exhaust gas. This is made possible by condensation of product water in the cathode.

(66) In order to use the KVV 1 in DMFC fuel cell systems 2, it is necessary to provide carrier gas, that is, to provide the gas cycle described above.

(67) In evaporation chamber 8, there is contact between CO.sub.2 with supplied methanol from the fuel tank 27 and to its evaporation. The effluent mixture of methanol and CO.sub.2 is then introduced into the methanol solution of the buffer tank 35. In the methanol solution (low-molar, e.g., 0.5-3 molar), the methanol mostly condenses again, releasing heat of vaporization, thereby establishing a higher temperature level within the solution, which transfers to the fuel cell through which the methanol solution flows. When the temperature of the fuel cell increases, e.g. from 70° C. to 85° C., a significant increase in performance can be expected.

(68) The KVV 1 can also serve only to increase the operating temperature, if it can be dispensed by supplying a methanol-water mixture (for example, from the buffer tank (not shown)) on the water condensation. In this case, the cathode condensate is not supplied to the methanol solution container, but discharged, for example, with the exhaust gas. In the evaporation chamber of the KVV the methanol solution is then fed instead of pure methanol and is evaporated.

(69) The cathode condensation is carried out as described in the first performance example.

(70) In a gaseous supply one of the DMFC, e.g. by means of a humidification-processing device, by which vapors are delivered to the CO.sub.2 phase from the methanol solution, a part of the gaseous anode fluid (CO.sub.2, water, and methanol vapor) exiting from the anode compartment is led into the evaporation chamber 8 of the KVV 1.

(71) In the following, another embodiment of the condensation-evaporation device will be described with reference to another NT-PEM fuel cell system (FIG. 3).

(72) Unless otherwise described, this embodiment corresponds to the embodiment described above. The same components have the same reference numerals.

(73) Also, according to this embodiment, the reformer device 6 may be formed in multiple stages.

(74) After the reformer device 6, according to this embodiment, a separator 50 (51, 52) for separating hydrogen from the reformate is provided. In this separator 50, which can be heated, the hydrogen is separated via membranes (e.g., metallic palladium/silver membranes) from the reformate. The membrane is provided between chambers 51 and 52 of the separator 50, 6. In the chamber 51, reformate flows in. In this case most of the hydrogen passes through the membrane in chamber 52 and is supplied from there to the anode inlet 33 of the fuel cell stack.

(75) In this case, it is not that the anode off gas is used as the gas phase for receiving fuel in the evaporation space 8, but it is e.g. taken in the CO2 phase from chamber 51 after the hydrogen separation and passed over the line section 48 in the evaporation chamber 8 of the KVV 1.

(76) Furthermore, the evaporation chamber 8 opens into a further chamber 43 for overheating, which is thermally isolated from the condensation chamber 7 and is not thermally coupled thereto. In this chamber a further energy input takes place in such a way that the fuel is completely evaporated.

(77) Water from the phase separator 21 is supplied to the further chamber 43 from the phase separator 21, which is also preferably completely evaporated in chamber 43.

(78) Accordingly, not only the fuel evaporated in the CO.sub.2 phase fuel, but also water is evaporated.

(79) The evaporation chamber 8 is thus extended according to the alternative embodiment shown here with the further chamber 43 for complete evaporation or overheating to a superheating device 44, in which the remaining non-evaporated liquid fuel or the fuel solution is heated above the boiling point, so that they evaporate. With this structure one can do without a media unit.

(80) Chamber 43 may be thermally insulated from the condensation chamber by means of insulation (not shown). However, it is also possible to dispense with the insulation. The chamber is designed or arranged in such a way that the energy input into the condensation chamber is low or the cooling effect of the evaporation chamber is only slightly reduced.

(81) Chamber 43 can be heated by a heater 47, which is for example designed as a heat exchanger, which is supplied with hot gases from the catalytic burner 26, so that a pure gaseous supply of reformer or fuel cell with the reactants is possible.

(82) Furthermore, a fuel cell system according to the present invention, that is, according to all the embodiments described above, comprises a control device (not shown). The control device is designed to adjust the temperature in such a way that the amount of water required for the reformer or anode reaction is condensed out in the condensation-evaporation device. For this purpose, the control device controls one or more of the input described parameters and or components of the fuel cell system.

(83) The embodiments described above can be combined with each other, even if the above possible combination options are only partially shown.

(84) Methanol is used as fuel in the description of the present invention by way of example only. Other liquid fuels, such as other alcohols, e.g. ethanol, formic acid, gasoline, diesel, dimethyl ether, LPG can be used. In principle, especially substances with high vapor pressures (a low boiling point, for example below 85° C.) and a high enthalpy of evaporation are suited. These properties apply particularly to methanol.

(85) For lower boiling point materials, the process can be optimized by using appropriate pressures (higher pressures in the evaporation chamber) or in case of high boiling points with lower pressures.

(86) By the application described in this invention, product water is recovered particularly from the cathode exhaust gas. Recovery of product water from the anode exhaust gas is also possible, but not preferred. Furthermore, other gases such as reformate can be dried.

(87) According to a further aspect of the present invention, the gas stream discharged from the phase separation device 21 can be thermally coupled to a further device of the fuel cell system 2 to temper this further device. Another device may be one or more line sections and or one or more components of the fuel cell system.

(88) This exploits the fact that the invention enables a temperature level independent of the environment with which the fluids escape from the CVT.

(89) This property can advantageously be used to cool or temper components or fluids at a stable temperature level.

(90) For example, pump 25 delivering the carrier gas can be stably operated by cooling or tempering the carrier gas fluid to a predetermined temperature level by means of a heat exchanger. This is done by the fuel cell exhaust gas from the KVV flows on the cold side of a heat exchanger after the phase-separating device in countercurrent and flows on the hot side of the heat exchanger, the carrier gas. In addition, the cooled fluid can also temper or cool components such as pumps or electronics by means of a thermal contact

(91) Another effect of the present invention is to increase the operating temperature of DMFC systems and thus the power density of the fuel cell.

(92) Instead of pure fuel, a fuel solution can also be evaporated to moisten the fuel cell or to provide the water vapor necessary for operation.

(93) By means of the condensation according to the invention, product water which is required for operation can also be used at high outside temperatures, e.g. in hot areas. This applies to all embodiments of the present invention.

(94) The heat exchange device requires a small space because a sufficient temperature difference across the evaporation chamber can be set (e.g., higher than the cooling air) and heat is not released into the gas but into the liquid. This is possible with much smaller areas than with gases.

(95) If several parallel chambers are used for fuel evaporation, as for example in a plate heat exchanger, a fine distribution can be provided at the common input for fuel and gas, which distributes the gas reliably to the chambers.

(96) This can be achieved by a distribution device 36, such as a gas distributor or distributor structure, which distributes the gas into the chambers uniformly via capillaries. The distributor structure may also be formed via a feed line which has small openings in each gas chamber.

(97) To ensure the tiltability of the device, a hydrophilic, coarse-pored material can be introduced, which flows through the gas and then distributes it finely and prevents sloshing of the fuel during tilting movements, so that no liquid fuel can get into the media unit and fuel only in gaseous state can be fed into the media unit.

(98) A further improvement can be achieved by hydrophilizing the surfaces used. As a result, a fuel film can form on heat exchanger surfaces and this can more efficiently absorb the heat of the exhaust gas flowing on the other side.

(99) Other embodiments are also possible: e.g. a heat exchanger or a pipe, the cathode exhaust gas flows through (condensation side, interior) and is wetted from the outside with fuel (evaporation chamber, exterior chamber). On the outer surfaces of the heat exchanger, the carrier gas (CO.sub.2 phase) flows with the help of an enclosure. This heat exchanger (condensation chamber) can also be in a container with methanol and that way be partially or completely covered with methanol, wherein the CO.sub.2 phase is bubbled through methanol and thereby saturated with methanol.

(100) In the embodiments explained above with reference to FIGS. 1 to 3, it is shown by way of example in the figures that the condensing chamber 7 and the vaporization chamber 8 of the condensation-evaporation device 1 are supplied with the corresponding media in such a way that the media are guided in direct current he follows. According to alternative embodiments, which correspond to the above embodiments in all other technical features except for the DC-current, it is preferably provided that the condensing chamber 7 and the evaporation chamber 8 of the condensation-evaporation device 1, the corresponding media are supplied in such a way that a leadership of the media takes place in the countercurrent.

(101) According to an alternative embodiment, which otherwise corresponds to the embodiments illustrated in FIGS. 1 and 3, the condensation chamber 7 is formed at least in two parts.

(102) Accordingly, the condensation chamber 7 comprises a first condensation chamber 7a and a second condensation chamber 7b, which are each independently coupled to the evaporation chamber 8 thermally via the heat exchanger apparatus 9 (FIG. 4). The first and the second condensation chamber 7a, 7b and the evaporation chamber 8 may be an integral part of the heat exchanger apparatus 9.

(103) Here, it is provided to arrange the heat exchanger 16 between the first and the second condensation chamber 7a, 7b or to switch between them.

(104) Since the exhaust gases to be cooled require a relatively large surface of the heat exchanger 16 in order to be cooled, it is advantageous to form the condensation chamber 7a, 7b in two parts, so that the heat exchanger 16 does not have to cool the exhaust gas until after reaching the dew point. The surface of the heat exchanger 16 with the evaporating and condensing media is then significantly lower with the same performance as a heat transfer with a larger surface of the heat exchanger. With a cooling of the exhaust gas to be cooled with a smaller surface of the heat exchanger 16, the lower temperatures are compared with the methanol evaporation in an advantageously efficient manner. Otherwise, this embodiment comprises the features of the embodiments described with reference to FIG. 1 or 3.

(105) In this case the leadership of the media takes place in countercurrent.

(106) According to an alternative embodiment (FIG. 5), which otherwise also corresponds to the embodiments shown in FIGS. 1 and 3 and can be combined with the embodiment shown in FIG. 4, the CO.sub.2 in the anode exhaust gas is depleted via a separator 60 (for example via an amine scrubber), so that the entire from the anode outlet of the anode 4 flowing over-stoichiometric, necessary for the reforming process water is recirculated via the media unit 19. As a result, the loss of water is minimized, and only the stoichiometrically consumed water must be replaced, so that in this case the heat exchanger 16 can also be made substantially smaller.

(107) In principle, this method can also be used for more efficient dehumidifying of the refractory gas by passing reformate into the condensate chamber instead of exhaust gas. This is particularly advantageous for fuel cells that require dry reformate like the HT-PEM fuel cells.

LIST OF REFERENCE NUMBERS

(108) 1 condensation-evaporation apparatus

(109) 2 fuel cell system

(110) 3 fuel cell stack

(111) 4 anode side

(112) 5 cathode side

(113) 6 reforming apparatus

(114) 7 condensation chamber 7a first condensation chamber 7b second condensation chamber 8 evaporation space

(115) 9 heat exchanger apparatus

(116) 10 intake

(117) 11 pump

(118) 12 cathode outlet

(119) 13 line section

(120) 14

(121) 15 pre-cooler

(122) 16 heat exchanger

(123) 17 aeration system

(124) 18 outlet

(125) 19 media unit

(126) 20 line section

(127) 21 phase-separation device

(128) 22 anode outlet

(129) 23 line section

(130) 24 intake

(131) 25 pump

(132) 26 catalytic burner

(133) 27 fuel tank

(134) 28 pump

(135) 29 line section

(136) 30 outlet

(137) 31 line section

(138) 32 line section

(139) 33 anode inlet

(140) 34 heat exchanger

(141) 35 methanol solution tank/buffer

(142) 36 distribution facility

(143) 37 line section

(144) 38 line section

(145) 39 heat exchanger apparatus

(146) 40 phase-separation device

(147) 41 line section

(148) 42 shift stage

(149) 43 chamber

(150) 44 overheating device

(151) 45 line section

(152) 46 line section

(153) 47 heater

(154) 48 line section

(155) 50 separator

(156) 51 chamber

(157) 52 chamber

(158) 60 separator