FUEL CELL SYSTEM AND METHOD FOR PERFORMING THERMAL REGENERATION OF DESULFURIZATION ADSORBATES

Abstract

The present invention relates to a fuel cell system (100a, 100b, 100c) comprising a fuel cell stack (5) having an anode portion (5a) and a cathode portion (5b), a reformer (3) for reforming fuel for use in the anode portion (5a) of the fuel cell stack (5), and a fuel tank (1) for providing the fuel to the reformer (3), wherein downstream of the fuel tank (1) and upstream of the reformer (3) there is located a desulphurization unit (2) with an adsorber (2a) for the adsorptive desulphurization of fuel, which is conducted from the fuel tank (1) via the desulphurization unit (2) to the reformer (3), wherein the adsorber (2a) is provided with anodes (5a) and cathode portions (5b) and/or an internal combustion engine (11) of the fuel cell system (100a; 100b; 100c) is in fluid communication by means of a regeneration fluid line (12), wherein fluid heated by the regeneration fluid line (12) can be conveyed from the anode portion (5a) and cathode portion (5b) and/or from the internal combustion engine (11) to the adsorber (2a). The invention also concerns a method for the thermal regeneration of desulphurization adsorbates and a motor vehicle equipped with the fuel cell system (100a, 100b, 100c) in accordance with the invention.

Claims

1. A fuel cell system comprising a fuel cell stack having an anode portion a cathode portion, a reformer for reforming fuel for use in the anode portion of the fuel cell stack, and a fuel tank for providing the fuel to the reformer, wherein downstream of the fuel tank and upstream of the reformer there is located a desulphurization unit with an adsorber for the adsorptive desulphurization of fuel, which is conducted from the fuel tank via the desulphurization unit to the reformer, wherein the adsorber has at least an anode portion and cathode portion or an internal combustion engine of the fuel cell system is in fluid connection by means of a regeneration fluid line, wherein fluid heated by the regeneration fluid line can be conveyed from at least the anode portion and cathode portion or from the internal combustion engine to the adsorber.

2. The fuel cell system according to claim 1, wherein the adsorber with anode portion and cathode portion is in fluid connection by means of a regeneration fluid line via at least one auxiliary power unit operated by the fuel cell system, wherein fluid heated by the regeneration fluid line can be conveyed from the anode portion and cathode portion via the auxiliary power unit to the adsorber.

3. The fuel cell system according to claim 2, wherein the auxiliary power unit has an exhaust gas burner, which is located for heating the reformer, wherein the exhaust gas burner, is in fluid connection with the adsorber by means of the regeneration fluid line.

4. The fuel cell system according to claim 3, wherein the exhaust gas burner is in fluid communication with a fluid connection of the cathode portion for conveying cathode exhaust gas into the exhaust gas burner.

5. The fuel cell system according to claim 2, wherein the adsorber is in fluid communication with a fluid connection of the anode portion for conveying anode portion exhaust gas into the adsorber by means of the regeneration fluid line, preferably the regeneration fluid line and the anode portion regeneration fluid line.

6. The fuel cell system according to claim 2, wherein a humidification unit for humidifying the heated fluid, which is conveyed to the adsorber, is at least located in the regeneration fluid line downstream of the auxiliary power unit or the internal combustion engine and upstream of the adsorber.

7. The fuel cell system according to claim 2, wherein an additional burner for further heating the heated fluid, which is conveyed to the adsorber, is at least located in the regeneration fluid line downstream of the auxiliary power unit or the internal combustion engine.

8. The fuel cell system according to claim 2, wherein the auxiliary power unit is located in an exhaust gas fluid line for discharging exhaust gas of the adsorber into the environment of the fuel cell system downstream of the adsorber.

9. A method for performing a thermal regeneration of desulphurization adsorbates, which result from an adsorptive desulphurization of a fuel, in a fuel cell system comprising a fuel cell stack having an anode portion and a cathode portion, a reformer for reforming fuel for use in the anode portion of the fuel cell stack, and a fuel tank for providing the fuel to the reformer, wherein downstream of the fuel tank and upstream of the reformer there is located a desulphurization unit with an adsorber for the adsorptive desulphurization of fuel, which is conducted from the fuel tank via the desulphurization unit to the reformer, wherein the adsorber has at least an anode portion and cathode portion or an internal combustion engine of the fuel cell system is in fluid connection by means of a regeneration fluid line, wherein fluid heated by the regeneration fluid line can be conveyed from at least the anode portion and cathode portion or from the internal combustion engine to the adsorber, wherein the adsorber has at least an anode portion and cathode portion or an internal combustion engine of the fuel cell system is in fluid connection by means of a regeneration fluid line, wherein, for thermal regeneration of the desulphurization adsorbates, fluid heated by the regeneration fluid line is conveyed from at least the anode portion and cathode portion or from the internal combustion engine to the adsorber for heating the adsorber.

10. The method according to claim 9, wherein the adsorber is in fluid communication with the anode portion and the cathode portion via at least one auxiliary power unit operated by the fuel cell system by means of a regeneration fluid line, wherein, for the thermal regeneration of the desulphurization adsorbates, fluid heated by the regeneration fluid line is conveyed from the anode portion and the cathode portion via the auxiliary power unit to the adsorber.

11. The method according to claim 10, wherein the auxiliary power unit has an exhaust gas burner which is located for heating the reformer, the exhaust gas burner, being in fluid connection with the adsorber by means of the regeneration fluid line and for thermal regeneration of the desulphurization adsorbates, fluid heated by the regeneration fluid line being conveyed from the exhaust gas burner to the adsorber.

12. The method according to claim 10, wherein the adsorber with a fluid connection of the anode portion for conveying anode portion exhaust gas into the adsorber by means of the regeneration fluid line is in fluid communication, wherein an activity value for the activity of an adsorbent in the adsorber in an oxygen-containing atmosphere is detected, and if it is determined that the activity value is below a predefined threshold value, anode portion exhaust gas is conveyed into the exhaust gas burner through the regeneration fluid line as part of the thermal regeneration of the desulphurization adsorbates.

13. The method according to claim 10, wherein a humidifying unit is located downstream of at least the auxiliary power unit or the internal combustion engine and upstream of the adsorber, wherein the heated fluid is humidified upstream of the adsorber by means of the humidifying unit before it is conveyed into the adsorber.

14. The method according to claim 10, wherein an additional burner is located downstream of at least the auxiliary power unit or the internal combustion engine and upstream of the adsorber, wherein the temperature of the heated fluid is detected in the regeneration fluid line upstream of the adsorber, and when it is determined that the detected temperature of the heated fluid is below a predefined threshold value, the heated fluid upstream of the adsorber is further heated by means of the additional burner before it is conveyed into the adsorber.

15. The method according to claim 10, wherein the following steps are performed within the scope of the thermal regeneration of the desulphurization adsorbates: heating of adsorbent in the adsorber to a first temperature by means of heated fluid from at least the anode portion and cathode portion or the auxiliary power unit or from the internal combustion engine, decomposition of absorbed compounds of the fuel and evaporation of the decomposed components at the second temperature are higher than at the first temperature, decomposition of intermediate products and regeneration of the adsorbent at a third temperature higher than the second temperature, and cooling at least said adsorbent or said adsorber to a fourth temperature lower than said first temperature.

16. The method according to claim 15, wherein at least the first temperature is in a range between 100 C. and 350 C., the second temperature is in a range between 350 C. and 450 C., or the third temperature is in a range between 450 C. and 550 C.

17. A motor vehicle having a fuel cell system comprising a fuel cell stack having an anode portion and a cathode portion, a reformer for reforming fuel for use in the anode portion of the fuel cell stack, and a fuel tank for providing the fuel to the reformer, wherein downstream of the fuel tank and upstream of the reformer there is located a desulphurization unit with an adsorber for the adsorptive desulphurization of fuel, which is conducted from the fuel tank via the desulphurization unit to the reformer, wherein the adsorber has an anode portion and a cathode portion or an internal combustion engine of the fuel cell system is in fluid connection by means of a regeneration fluid line, wherein fluid heated by the regeneration fluid line can be conveyed from the anode portion and cathode portion or from the internal combustion engine to the adsorber configured to perform a method for performing a thermal regeneration of desulphurization adsorbates, which result from an adsorptive desulphurization of a fuel, in the fuel cell system, wherein the adsorber has an anode portion and cathode portion or an internal combustion engine of the fuel cell system is in fluid connection by means of a regeneration fluid line, wherein, for thermal regeneration of the desulphurization adsorbates, fluid heated by the regeneration fluid line is conveyed from the anode portion and cathode portion or from the internal combustion engine to the adsorber for heating the adsorber.

Description

[0041] Is it shown schematically:

[0042] FIG. 1 block diagram to illustrate a fuel cell system according to a first embodiment of the present invention,

[0043] FIG. 2 block diagram for representing a fuel cell system according to a second embodiment of the present invention,

[0044] FIG. 3 block diagram to represent a fuel cell system according to a third embodiment of the present invention,

[0045] FIG. 4 a flow chart to explain a method according to an embodiment according to the invention.

[0046] FIG. 5 time diagram explaining a method according to an embodiment.

[0047] Elements with the same function and mode of action have the same reference signs in FIGS. 1 to 5.

[0048] FIG. 1 schematically shows a fuel cell system 100a according to a first embodiment. The fuel cell system 100a comprises a fuel cell stack 5 with an anode portion 5a and a cathode portion 5b. The fuel cell system 100a further comprises a reformer 3 for reforming fuel for use in anode portion 5a of fuel cell stack 5. In addition, the fuel cell system 100a has a fuel tank 1 to provide the fuel for the reformer 3. A desulfurization unit 2 with an adsorber 2a for adsorptive desulfurization of fuel, which is conducted from the fuel tank 1 via the desulfurization unit 2 to the reformer 3, is located downstream of the fuel tank 1 and upstream of the reformer 3.

[0049] The adsorber 2a is in fluid connection with an auxiliary power unit 4 operated by the fuel cell system 100a with an exhaust gas burner 4a, 4b by means of a regeneration fluid line 12. Accordingly, heated fluid can be conveyed through the regeneration fluid line 12 from the auxiliary power unit 4 to the adsorber 2a.

[0050] In a dashed variant, the adsorber 2a is additionally or instead directly connected to the fuel cell stack via the anode regeneration fluid line 12a, with which anode exhaust gas from the fuel cell stack 5 is conveyed to the adsorber 2a, and via the cathode regeneration fluid line 12b, with which cathode exhaust gas from the fuel cell stack 5 is conveyed to the adsorber 2a.

[0051] The exhaust burner 4a, 4b is located to heat the reformer 3 at or annularly around it. The exhaust gas burners 4a, 4b are configured with a first exhaust gas burner unit 4a and a second exhaust gas burner unit 4b, which are separated from each other in terms of flow technology and are, for example, both configured in a semi-annular shape. The first exhaust gas burner unit 4a is also in fluid communication with a cathode portion 5b fluid connection for conveying cathode portion exhaust gas into the exhaust gas burner through the regeneration fluid line 12.

[0052] In the fuel cell system 100a shown in FIG. 1, the adsorber 2a is also in fluid communication with a fluid connection of the anode portion 5a, for conveying anode portion exhaust gas into the adsorber 2a, by means of the regeneration fluid line 12 or the anode regeneration fluid line 12a.

[0053] Furthermore, a humidification unit 6 for humidifying the heated fluid, which is conveyed to the adsorber, is located in the regeneration fluid line 12 downstream of the auxiliary power unit 4, in particular the first exhaust gas burner unit 4a, and upstream of the adsorber 2a. Downstream of the auxiliary power unit 4, in particular the first exhaust gas burner unit 4a, and downstream of the humidifying unit 6 and upstream of the adsorber 2a, an additional burner 7 is located for further heating of the heated fluid which is conveyed to the adsorber.

[0054] The auxiliary power unit 4, in particular the second exhaust gas burner 4b, is located in an exhaust gas fluid line 13 for discharging exhaust gas of the adsorber 2a into the environment or to an output 10 of the fuel cell system 100a downstream of the adsorber 2a.

[0055] The fuel cell system 100a also has a blower 8 which is in fluid connection with the adsorber 2a for rinsing. The blower 8 is also in fluid connection with a preheater 9, which is located to preheat the cathode portion 5b and is correspondingly in fluid connection with it.

[0056] FIG. 2 shows a fuel cell system 100b according to a second embodiment. The fuel cell system 100b shown in FIG. 2 essentially corresponds to the fuel cell system 100a shown in FIG. 1. In order to avoid a redundant description, only the distinguishing features between the two embodiments are subsequently described.

[0057] The fuel cell system 100b according to FIG. 2 has an internal combustion engine 11. The fuel cell system 100b shown is configured as a drive system for a hybrid electric vehicle. According to this embodiment, the adsorber 2a is in fluid connection with the internal combustion engine 11 by means of the regeneration fluid line 12, whereby heated fluid can be conveyed from the internal combustion engine 11 to the adsorber 2a by means of the regeneration fluid line 12.

[0058] FIG. 3 shows a fuel cell system 100c according to a third embodiment. The fuel cell system 100c shown in FIG. 3 corresponds essentially to the fuel cell systems 100a, 100b shown in FIG. 1 and FIG. 2. In order to avoid a redundant description, only the distinguishing features between the different embodiments are subsequently described.

[0059] The fuel cell system 100c according to FIG. 3 has, like the fuel cell system 100b according to the second embodiment, an internal combustion engine 11. According to the third embodiment, the adsorber 2a is in fluid connection with the internal combustion engine 11 and the auxiliary power unit 4 by means of the regeneration fluid line 12, whereby fluid heated by the regeneration fluid line 12 can be conveyed from the internal combustion engine 11 and from the auxiliary power unit 4 to the adsorber 2a. In addition, the anode regeneration fluid line 12a and the cathode portion regeneration fluid line 12b are shown in dotted lines.

[0060] With reference to FIG. 4, a method for performing a thermal regeneration of desulphurization adsorbates resulting from an adsorptive desulphurization of a fuel in a fuel cell system 100a in accordance with the first embodiment form is then described. The adsorptive desulfurization is based on selective interaction of heterocyclic sulfur compounds and the surface of the adsorbent. To desulphurization the fuel, it only has to be pumped through the adsorber with a low volume flow (Liquid Hourly Space Velocity LHSV preferably less than 1.7 h1). If the adsorbent is loaded, i.e. if, for example, 10 ppmw sulphur is reached at the adsorber output, either the adsorbent must be exchanged or regenerated. For regeneration, the fuel in the adsorber must be emptied. This results in a volume of approx. 0.8 liters of fuel per liter of adsorbent.

[0061] In the method subsequently explained with reference to FIG. 4, for thermal regeneration of the desulphurization adsorbates, fluid heated by the regeneration fluid line is conveyed from the auxiliary power unit 4 to the desulphurization unit 2 for heating the adsorber 2a.

[0062] More precisely, in a first step S1, heated fluid is first conveyed or directed through the regeneration fluid line 12 from the auxiliary power unit 4 in the direction of the adsorber 2a in order to heat the adsorber 2a for the thermal regeneration of the desulphurization adsorbates. To be more precise, the heated fluid is led through the regeneration fluid line 12 from the exhaust gas burner, in particular the first exhaust gas burner unit 4a, to the adsorber 2a.

[0063] In a second step, S2a, an activity value is determined for the activity of an adsorbent in the adsorber in an oxygen-containing atmosphere. If it is determined that the activity value is below a predefined threshold, the method proceeds to step 3a. There, anode portion exhaust gases are conveyed into the exhaust gas burner through the regeneration fluid line 12. If it is determined that the activity value is greater than or equal to the predefined threshold, the method proceeds directly to step S4.

[0064] In a step S2b following step S1, a moisture content of the heated fluid is also detected. If it is found in step S2b that the moisture content determined is below a predefined threshold, the method proceeds to step S3b. There the heated fluid is moistened upstream of the adsorber 2a by means of the moistening unit 6 before it is conveyed into the adsorber 2a. If it is found that the moisture content detected is greater than or equal to the predefined threshold, the method proceeds directly to step S4.

[0065] In a step S2c following step S1, the temperature of the heated fluid is also detected upstream of adsorber 2a. If it is determined in step S2c that the detected temperature is below a predefined first threshold value, the method proceeds to step S3c. There the heated fluid is further heated upstream of the adsorber 2a by means of the additional burner 7 before it is conveyed into the adsorber 2a. If it is determined that the detected temperature of the heated fluid is greater than or equal to a predefined second threshold value greater than the first predefined threshold value, the method proceeds to step S3d. There the heated fluid is mixed with air, especially ambient air, to lower the temperature of the heated fluid (shown only with reference to FIG. 2). If it is determined that the detected temperature of the heated fluid is greater than or equal to the predefined first threshold and less than the predefined second threshold, the method proceeds directly to step S4.

[0066] In step S4, the heated and, if necessary, post-treated fluid is conveyed into the adsorber 2a.

[0067] With reference to FIG. 5, a method according to a further embodiment of the invention is then explained in which, in particular, a predefined temperature curve for desulphurization or desulphurization including regeneration is presented.

[0068] According to the method shown in FIG. 5, the adsorbent in the adsorber 2a is heated to a temperature of approx. 150 C. in a first step A by means of heated fluid from the auxiliary power unit 4 and/or from the internal combustion engine 11.

[0069] In a second step B, adsorbed components of the fuel are decomposed and evaporated at a temperature of approx. 300 C. In this step, the remaining liquid fuel is vaporized.

[0070] In a third step C, adsorbed components are further decomposed and evaporated at a temperature of approx. 450 C. Steps B and C can also be performed in a single step.

[0071] In a fourth step D, intermediate products are decomposed at a temperature of approx. 525 C. and regeneration of the adsorbent is initiated. If water or steam is added in a targeted manner by the humidification unit 6, the required temperature in step D can be lowered to approx. 450 C.

[0072] In a fifth, optional step E, the adsorbent is activated using various gases, in particular an anode portion exhaust gas. The fifth step E can be performed at least partially at the same time as the fourth step D. The temperature in the fifth step E depends on the adsorbent used.

[0073] In a final sixth step, the adsorbent and thus also the adsorber 2a are cooled to a temperature of approx. 20 C. by flushing with air, whereby this flushing method preferably takes place indirectly, so that there is no direct contact between the air and the adsorber 2a.

[0074] In addition to the embodiments described above, the invention naturally permits further embodiment principles. For example, at least one auxiliary power unit may alternatively or additionally have a starting burner and/or another heat source which are operated in the fuel cell system anyway and can generate the heated fluid in question.

REFERENCE CHARACTER LIST

[0075] 1 Fuel tank [0076] 2 Desulphurization unit [0077] 2a Adsorber [0078] 3 Reformer [0079] 4 Auxiliary power unit (exhaust burner) [0080] 4a First exhaust gas burner unit [0081] 4b Second exhaust gas burner unit [0082] 5 Fuel cell stack [0083] 5a Anode portion [0084] 5b Cathode portion [0085] 6 Humidification unit [0086] 7 Additional burner [0087] 8 Blower [0088] 9 Preheater [0089] 10 Output [0090] 11 Internal combustion engine [0091] 12 Regeneration fluid line [0092] 12a Anode regeneration fluid line [0093] 12b Cathode regeneration fluid line [0094] 13 Exhaust gas fluid line [0095] 100a, 100b, 100c Fuel cell system