Hot-side method and system
The present disclosure is directed to the use of elemental or speciated iodine and bromine to control total mercury emissions.
1. A method, comprising:
generating, from a mercury-containing feed material, a mercury-containing gas stream comprising vapor-phase elemental mercury and a vapor-phase halogen;
passing the mercury-containing gas stream through a scrubber to remove at least a portion of the vapor-phase halogen and/or a halogen-containing derivative thereof and form a halogen-containing scrubbing medium and a treated gas stream; and
removing the halogen from the halogen-containing scrubbing medium to form a treated scrubbing medium for recycle to the scrubber and a removed halogen and/or halogen-containing material,
wherein the mercury-containing feed material is coal, wherein the mercury-containing gas stream is formed by combusting coal, wherein the vapor-phase halogen is generated at least in part from a halogen-containing additive in contact with the coal, and wherein the vapor-phase halogen is introduced into the gas stream downstream of a coal combustion zone.
2. The method of claim 1 , wherein the halogen in the removed halogen and/or halogen-containing material is one or more of bromine and iodine and wherein the scrubber is a wet or dry scrubber and wherein the vapor-phase halogen is generated at least in part from a native halogen-content of the coal.
3. The method of claim 1 , wherein the scrubber removes at least most of the vapor-phase halogen from the mercury containing gas stream and wherein the scrubber removes at least most of an acid gas from the mercury containing gas stream.
4. The method of claim 1 , wherein at least most of the halogen on the halogen-containing scrubbing medium is removed as the removed halogen and/or halogen-containing material.
5. The method of claim 1 , wherein the scrubber is a wet scrubber and is capable of removing one or more of HCl, HBr, and HF from the mercury containing gas stream.
6. The method of claim 1 , wherein the halogen is removed from the halogen-containing scrubbing medium by one or more of membrane separation, precipitation, adsorption, and/or absorption.
7. The method of claim 6 , wherein the halogen-containing scrubbing medium is contacted with an oxidant to assist halogen removal.
8. The method of claim 1 , wherein the scrubber is a wet scrubber and wherein the halogen is removed from the halogen-containing scrubbing medium by one or more of an ion exchange resin, solvent extraction, adsorption, absorption, precipitation, and membrane filtration.
9. The method of claim 1 , wherein the vapor phase halogen can oxidize elemental mercury in the mercury containing gas stream and further comprising:
recycling the removed halogen and/or halogen-containing material to the generating step, whereby the vapor-phase halogen is derived from the removed halogen and/or halogen-containing material.
10. The method of claim 9 , further comprising regenerating the removed halogen and/or halogen-containing material prior to recycle.
11. The method of claim 1 , wherein a concentration of the vapor-phase halogen in the treated gas stream is no more than about 25 ppm.
12. The method of claim 1 , wherein the vapor-phase halogen is iodide.
13. The method of claim 1 , wherein the vapor-phase halogen is bromide.
14. A method, comprising:
generating, from a mercury-containing feed material, a mercury-containing gas stream comprising vapor-phase elemental mercury and a vapor-phase halogen;
passing the mercury-containing gas stream through a scrubber to remove at least a portion of the vapor-phase halogen and/or a halogen-containing derivative thereof and form a halogen-containing scrubbing medium and a treated gas stream; and
removing the halogen from the halogen-containing scrubbing medium to form a treated scrubbing medium for recycle to the scrubber and a removed halogen and/or halogen-containing material,
wherein the vapor-phase halogen is generated at least in part from a halogen-containing additive in contact with the coal and wherein the scrubber is a wet scrubber and is capable of removing one or more of HCl, HBr, and HF from the gas stream.
15. The method of claim 14 , wherein the scrubber removes at least most of the vapor-phase halogen from the mercury containing gas stream and wherein the scrubber removes at least most of an acid gas from the mercury containing gas stream and wherein the vapor-phase halogen is generated at least in part from a native halogen-content of the coal.
16. The method of claim 14 , wherein at least most of the halogen on the halogen-containing scrubbing medium is removed as the removed halogen and/or halogen-containing material.
17. The method of claim 16 , wherein the halogen-containing scrubbing medium is contacted with an oxidant to assist halogen removal.
18. The method of claim 14 , wherein the halogen is removed from the halogen-containing scrubbing medium by one or more of an ion exchange resin, solvent extraction, adsorption, absorption, precipitation, and membrane filtration.
19. The method of claim 14 , wherein the vapor-phase halogen can oxidize elemental mercury in the mercury containing gas stream and further comprising:
recycling the removed halogen and/or halogen-containing material to the generating step, whereby the vapor-phase halogen is derived from the removed halogen and/or halogen-containing material.
20. The method of claim 19 , further comprising regenerating the removed halogen and/or halogen-containing material prior to recycle.
21. The method of claim 14 , wherein a concentration of the vapor-phase halogen in the treated gas stream is no more than about 25 ppm.
22. The method of claim 14 , wherein the vapor-phase halogen is iodide.
23. The method of claim 14 , wherein the vapor-phase halogen is bromide.
24. The method of claim 14 , wherein the mercury-containing feed material is coal, wherein the mercury-containing gas stream is formed by combusting coal and wherein the vapor-phase halogen is formed from a native halogen-content of the coal.
25. The method of claim 14 , wherein the mercury-containing feed material is coal, wherein the mercury-containing gas stream is formed by combusting coal, and wherein the vapor-phase halogen is formed from a halogen-containing additive combusted with the coal.
26. The method of claim 14 , wherein the mercury-containing feed material is coal, wherein the mercury-containing gas stream is formed by combusting coal, and wherein the vapor-phase halogen is introduced into the mercury containing gas stream downstream of a coal combustion zone.