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.
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.
3 . The method of claim 1 , wherein the scrubber removes at least most of the vapor-phase halogen from the gas stream and wherein the scrubber removes at least most of an acid gas from the 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 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 halogen can oxidize elemental mercury in the 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 . The method of claim 1 , 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.
15 . The method of claim 1 , 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.
16 . The method of claim 1 , 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 gas stream downstream of a coal combustion zone.