Method of exhaust gas treatment for a gas turbine system and exhaust gas treatment assembly

1. method for operating a gas turbine system, the gas turbine system including a compressor for compression of inlet air, a combustor for combustion of a fuel gas with compressed inlet air to form an exhaust gas, a heat recovery steam generator for receiving a portion of the exhaust gas, a scrubber for scrubbing the fuel gas with a scrubbing fluid before the fuel gas it is fed into the combustor, a direct contact cooler for cooling the portion of the exhaust gas with a cooling fluid after the portion of the exhaust gas is discharged from the heat recovery steam generator, the method comprising:

introducing scrubbing fluid having sulfide absorbed from the fuel gas discharged from the scrubber into the direct contact cooler, contacting the scrubbing fluid having the sulfide with the portion of the exhaust gas the direct contact cooler receives from the heat recovery steam generator in the direct contact cooler in order to remove a portion of nitrogen oxide therefrom; and

feeding the portion of the exhaust gas from the direct contact cooler to the compressor after the contacting of the scrubbing fluid having the sulfide with the portion of the exhaust gas is performed.

2. The method according to claim 1 , wherein the gas turbine system further comprises a cooling tower providing cooling for the direct contact cooler by means of the cooling fluid, and the method further comprising: introducing cooling fluid discharged from the cooling tower into the direct contact cooler.

3. The method according to claim 1 , wherein the gas turbine system further includes a heat exchanger for providing cooling for the direct contact cooler.

4. The method according to claim 1 , further comprising:

introducing a reagent, for removing nitrogen oxide into the direct contact cooler.

5. The method according to claim 1 , further comprising:

introducing an oxidant for oxidizing nitrogen oxide, into the direct contact cooler.

6. The method according to claim 1 , further comprising:

introducing a pH control reagent into the direct contact cooler.

7. The method according to claim 4 , wherein the reagent includes at least one of Fe(II), EDTA, NTA and DPTA.

8. The method according to claim 5 , wherein the oxidant includes at least one of hydrogen peroxide, ozone and plasma.

9. The method according to claim 6 , wherein the pH control reagent includes at least one of NaOH, NaHCO3 and Na2CO3.

10. An exhaust gas treatment assembly for a gas turbine system, wherein the gas turbine system includes a compressor for compression of inlet air, a combustor for combustion of a fuel gas with compressed inlet air to form an exhaust gas, the assembly comprising:

a heat recovery steam generator for collecting a portion of the exhaust gas,

a scrubber for scrubbing the fuel gas with a scrubbing fluid before the fuel gas-is fed into the combustor,

a direct contact cooler for cooling exhaust gas discharged from the heat recovery steam generator with a cooling fluid,

wherein:

the scrubber is fluidly connected with the direct contact cooler to introduce scrubbing fluid having sulfide absorbed from the fuel gas discharged from the scrubber into the direct contact cooler,

the heat recovery steam generator is fluidly connected with the direct contact cooler so that exhaust gas discharged from the heat recovery steam generator is passable into the direct contact cooler to contact the scrubbing fluid having the sulfide absorbed from the fuel gas with the exhaust gas discharged from the heat recovery steam generator in the direct contact cooler to remove a portion of nitrogen oxide from the exhaust gas, and

the direct contact cooler is fluidly connected with the compressor to feed exhaust gas discharged from the direct contact cooler into the compressor.

11. The exhaust gas treatment assembly according to claim 10 , further comprising:

a reagent supply conduit connected to the direct contact cooler such that reagent is introducible into the direct contact cooler to remove nitrogen oxide from the exhaust gas in the direct contact cooler;

an oxidant supply conduit connected to the direct contact cooler such that an oxidant is introducible into the direct contact cooler to oxidize nitrogen oxide in the direct contact cooler; and

a pH control reagent supply conduit connected to the direct contact cooler such that a pH control reagent is introducible into the direct contact cooler.

12. The exhaust gas treatment assembly according to claim 10 , further comprising:

a cooling tower to provide cooling fluid for the direct contact cooler, the cooling tower being fluidly connected with the direct contact cooler to introduce cooling fluid discharged from the cooling tower into the direct contact cooler.

13. The exhaust gas treatment assembly according to claim 10 , further comprising:

a heat exchanger for providing the cooling fluid for the direct contact cooler.

14. A method for operating a gas turbine system, the method comprising:

passing fuel gas through a scrubber such that scrubbing fluid absorbs sulfide from the fuel gas within the scrubber prior to the fuel gas being fed to a combustor for combustion;

discharging the scrubbing fluid having sulfide absorbed from the fuel gas to a direct contact cooler;

contacting the scrubbing fluid having the sulfide absorbed from the fuel gas with exhaust gas in the direct contact cooler to remove nitrogen oxides from the exhaust gas;

feeding exhaust gas from the direct contact cooler to a mixer for mixing with air to form a mixture after the exhaust gas has contacted the scrubbing fluid having the sulfide absorbed from the fuel gas; and

feeding the mixture from the mixer to a compressor for compressing the mixture prior to feeding the mixture to the combustor for combustion of the fuel gas.

15. The method of claim 14 , comprising:

feeding at least one reagent and at least one oxidant into the direct contact cooler to facilitate removal of nitrogen oxides from the exhaust gas in the direct contact cooler.

16. The method of claim 15 , further comprising:

feeding a pH control agent into the direct contact cooler to control a pH level within the direct contact cooler.

17. The method of claim 15 , comprising:

passing exhaust gas from the combustor through a heat recovery steam generator prior to the exhaust gas being fed to the direct contact cooler.

18. The method of claim 16 comprising:

feeding a cooling fluid into the direct contact cooler such that the cooling fluid contacts the exhaust gas in the direct contact cooler to cool the exhaust gas.

19. The method of claim 18 , wherein the cooling fluid is comprised of water.

20. The method of claim 19 , wherein the scrubbing fluid is comprised of water.