Desulfurizer for fuel gas for fuel cell and desulfurization method using the same

Abstract

A desulfurizer for fuel gas for a fuel cell includes: a first adsorption tank including an adsorber having selective adsorption capacity for a thiophene-based compound and a second adsorption tank including an adsorber having selective adsorption capacity for a mercaptan-based compound. The desulfurizer uses separate adsorbers having selective adsorption capacity for a thiophene-based compound and a mercaptan-based compound, in multiple stages to perform a more efficient and economical desulfurizing of a fuel gas to remove various sulfur compounds, especially thiophene-based compounds and mercaptan-based compounds compared to a desulfurizer using a single adsorber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic graph illustrating an electrode voltage of a conventional fuel cell against concentration of H₂S;

FIG. 2 is a block diagram conceptually illustrating the constitution of a conventional fuel processor for a fuel cell;

FIG. 3 is a schematic drawing of a desulfurizer according to an embodiment of the present invention;

FIG. 4 is a graph showing the adsorptivity and adsorption selectivity of Na—Y against fuel gas containing tetrahydrothiophene (THT) and tertiarybutylmercaptan (TBM);

FIG. 5 is a graph showing the adsorptivity and adsorption selectivity of Ag—Y against fuel gas containing THT and TBM;

FIG. 6 is a graph showing the adsorption performance of ETAS-10, which has different structure and different chemical properties from a Y-zeolite, against a fuel gas containing THT and TBM;

FIG. 7 is a graph of the amount of adsorbed THT from a fuel gas containing only THT with respect to the Ag ion-exchange level of an Ag ion-exchanged Na—Y zeolite;

FIG. 8 is a graph of an amount of adsorbed TBM from a fuel gas containing only TBM with respect to the Ag ion-exchange level of an Ag ion-exchanged Na—Y zeolite;

FIG. 9 is a graph illustrating the desulfurization adsorption performance of a two-step desulfurizer according to an embodiment of the present invention, wherein a first adsorption tank on an upper section is charged with Na—Y zeolite and a second adsorption tank on a lower section is charged with Ag—Y zeolite, using a fuel gas containing THT and TBM;

FIG. 10 is a graph illustrating the desulfurization adsorption performance of a conventional desulfurizer charged with only Na—Y, using a fuel gas containing THT and TBM;

FIG. 11 is a graph illustrating the desulfurization adsorption performance of a conventional desulfurizer charged with only Ag—Y, using a fuel gas containing THT and TBM; and

FIG. 12 is a graph illustrating the desulfurization adsorption performance of a two-step desulfurizer, wherein a first adsorption tank on an upper section is charged with Ag—Y zeolite and a second adsorption tank on a lower section is charged with Na—Y zeolite, using a fuel gas containing THT and TBM.

Claims

1. A desulfurizer for fuel gas for a fuel cell containing at least one sulfur compound, comprising: a first adsorption tank comprising first adsorber having a selective adsorption capacity for thiophene-based compounds; anda second adsorption tank comprising second adsorber having a selective adsorption capacity for mercaptan-based compounds.

2. The desulfurizer of claim 1, wherein the first adsorption tank is in a first section of the desulfurizer and the second adsorption tank is in a second section of the desulfurizer downstream from the first section.

3. The desulfurizer of claim 1, wherein the first adsorption tank is in an upper section of the desulfurizer and the second adsorption tank is in a lower section of the desulfurizer.

4. The desulfurizer of claim 1, wherein the adsorber of the first adsorption tank is an Na—Y zeolite.

5. The desulfurizer of claim 1, wherein the adsorber of the second adsorption tank is an Ag—Y zeolite.

6. The desulfurizer of claim 4 wherein the Si/Al ratio of the Na—Y zeolite is in the range of 2 to 5.

7. The desulfurizer of claim 5 wherein the Si/Al ratio of the Ag—Y zeolite is in the range of 2 to 5.

8. The desulfurizer of claim 4, wherein a Na/Al ratio of the Na—Y zeolite is in the range of 0.1 to 1.0.

9. The desulfurizer of claim 5, wherein the Ag/Al ratio of the Ag—Y zeolite is in the range of 0.2 to 0.7.

10. The desulfurizer of claim 4, wherein the adsorber of the first adsorption tank is prepared by pretreating a Na—Y zeolite at 350 to 450° C. for 3 to 5 hours in air.

11. The desulfurizer of claim 5, wherein the Ag—Y zeolite is formed by pretreating an Na—Y zeolite at 350 to 450° C. for 3 to 5 hours in air and then ion-exchanging the pretreated Na—Y zeolite in an Ag precursor solution at 25 to 30° C. for 30 min. to 2 hours.

12. The desulfurizer of claim 1, wherein the first adsorber has a selective adsorption capacity for at least one compound selected from the group consisting of thiophenol, alkylthiophene, and benzothiophene.

13. The desulfurizer of claim 12, wherein the alkylthiophene comprises at least one material selected from the group consisting of 2-methylthiophene, 3-methylthiophene, ethylthiophene, dimethyl thiophene, trimethylthiophene, and tetrahydrothiophene (THT); andwherein the benzothiophene comprises at least one material selected from the group consisting of benzothiophene, dibenzothiophene, methylbenzothiophene, and dimethylbenzothiophene.

14. The desulfurizer of claim 1, wherein the first adsorber has a selective adsorption capacity for tetrahydrothiophene.

15. The desulfurizer of claim 1, wherein the second adsorber has a selective adsorption capacity for at least one compound selected from the group consisting of 1-ethanethiol, 1-propanethiol, 2-propanethiol, 2-butanethiol, t-butyl mercaptan (TBM), 2-methyl-2-propanethiol, pentanethiol, hexanethiol, heptanethiol, octanethiol, nonanethiol, and thiophenol.

16. The desulfurizer of claim 1, wherein the second adsorber has a selective adsorption capacity for tertiarybutylmercaptan.

17. The desulfurizer of claim 1, further comprising a guard bed in front of the first and/or second adsorption tanks to remove moisture and impurities in the fuel gas.

18. The desulfurizer of claim 17, wherein the guard bed comprises at least one material selected from the group consisting of a zeolite, a silica gel, and an activated carbon.

19. The desulfurizer of claim 1, further comprising an indicator after the second adsorption tank to indicate the concentration of a sulfur compound in the desulfurized fuel gas.

20. A fuel processor for a fuel cell comprising a desulfurizer, a reformer and at least one carbon monoxide removal apparatus, wherein the desulfurizer comprises: a first adsorption tank comprising an adsorber having a selective adsorption capacity for a thiophene-based compound; anda second adsorption tank comprising an adsorber having a selective adsorption capacity for a mercaptan-based compound.

21. A fuel cell system comprising a fuel processor and a fuel cell stack, wherein the fuel processor comprises a desulfurizer that comprises: a first adsorption tank comprising an adsorber having a selective adsorption capacity for a thiophene-based compound; anda second adsorption tank comprising an adsorber having a selective adsorption capacity for a mercaptan-based compound.

22. A method of desulfurizing a fuel gas for a fuel cell containing sulfur compounds, the method comprising: first removing thiophenes from the fuel gas using a first adsorber having a selective adsorption capacity for thiophene-based compounds; andthen removing mercaptans that remain in the fuel gas using a second adsorber having an adsorption capacity for mercaptan-based compounds.

23. The method of claim 22, wherein the removing of thiophenes and the removing of mercaptans are performed at 0 to 50° C.

24. The method of claim 22, wherein the removing of thiophenes and the removing of mercaptans are performed under 0.5 to 2.5 atm.

25. The method of claim 22, wherein the fuel gas is a city gas containing thiophenes and mercaptans.

26. The method of claim 22, wherein the first adsorber is an Na—Y zeolite and the second adsorber is an Ag—Y zeolite.

27. The method of claim 22, wherein the method is carried out by passing the fuel gas through a first adsorption tank comprising the first adsorber; and then passing the fuel gas through a second adsorption tank comprising the second adsorber.