Ammonia capturing by CO

1. A method for capturing ammonia present in combustion flue gas subjected to CO 2 removal, using a water wash unit that comprises at least first and second stages included in a chilled ammonia process, comprising the steps of:

providing CO 2 loaded liquid comprising CO 2 dissolved in the liquid;

providing wash water liquid;

combining the CO 2 loaded liquid with the wash water liquid to form a CO 2 enriched wash water liquid

providing the CO 2 enriched wash water liquid at each of the first and second stages of the water wash unit;

bringing the combustion flue gas into contact with the CO 2 enriched wash water liquid by adding the CO 2 enriched wash water liquid to said water wash; and

forming a reduced ammonia flue gas stream and a used wash water stream.

2. The method according to claim 1 , wherein the concentration of ammonia in the CO 2 enriched wash water liquid added to the first stage is 0.5 to 3 mol/liter.

3. The method according to claim 1 , wherein the wash water liquid comprises 0.0005 mol/l to 0.2 mol/l ammonia (NH 3 ) before it is combined with the CO 2 loaded liquid.

4. The method according to claim 1 , wherein the wash water unit operates at 1° C. to 10° C.

5. The method according to claim 1 , wherein the ratio of moles of ammonia (NH 3 ) to moles of carbon dioxide (CO 2 ) for the CO 2 enriched wash water liquid is kept at about 0.05 to 10.

6. A method for capturing ammonia present in combustion flue gas subjected to CO 2 removal, using a water wash unit that comprises at least first and second stages included in a chilled ammonia process, comprising:

providing CO 2 loaded liquid comprising CO 2 dissolved in the liquid;

providing wash water liquid;

combining the CO 2 loaded liquid with the wash water liquid to form a CO 2 enriched wash water liquid;

providing the CO 2 enriched wash water liquid to the water wash unit; and

bringing said combustion flue gas into contact with said CO 2 enriched wash water liquid to form a cleaned flue gas stream and a used wash liquid.

7. The method of claim 6 , further comprising:

providing a portion of the CO 2 enriched wash water liquid to the water wash unit to each of the first and second stages.

8. The method according to claim 5 , wherein the ratio of moles of ammonia (NH 3 ) to moles of carbon dioxide (CO 2 ) for the CO 2 enriched wash water liquid is kept at about 0.1 to 5.

9. The method according to claim 5 wherein the ratio of moles of ammonia (NH 3 ) to moles of carbon dioxide (CO 2 ) for the CO 2 enriched wash water liquid is kept at about 1 to 4.

10. A method for capturing ammonia present in combustion flue gas subjected to CO 2 removal, using a water wash unit that comprises at least first and second stages, the method comprising:

providing a CO 2 loaded liquid comprising CO 2 dissolved in the liquid;

providing wash water liquid;

combining the CO 2 loaded liquid with the wash water liquid to form CO 2 enriched wash water liquid;

providing the CO 2 enriched wash water liquid to the water wash unit to each of the at least first and second stages;

bringing said combustion flue gas into contact with said CO 2 enriched wash water liquid to form a reduced ammonia flue gas stream and a used wash water stream;

wherein the concentration of ammonia in the CO 2 enriched wash water liquid added to the first stage is 0.5 to 3 mol/liter; and

wherein the concentration of ammonia in the CO 2 enriched wash water liquid added to the second stage is 0.005 to 0.2 mol/liter.

11. The method according to claim 10 , wherein the wash water liquid comprises 0.0005 mol/l to 0.2 mol/l ammonia (NH 3 ) before it is combined with the CO 2 loaded liquid.

12. The method according to claim 10 , wherein the wash water unit operates at 1° C. to 10° C.

13. The method according to claim 10 , wherein the ratio of moles of ammonia to moles of carbon dioxide for the CO 2 enriched wash water liquid is kept at about 0.05 to 10.

14. The method according to claim 1 , wherein the concentration of ammonia in the CO 2 enriched wash water liquid added to the second stage is 0.005 to 0.2 mol/liter.

15. The method according to claim 3 , wherein the concentration of ammonia in the wash water entering the second stage is lower than the concentration of ammonia entering the first stage.