Method and system for controlling mercury emissions from coal-fired thermal processes
First Claim
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1. A method, comprising:
- in a mercury-containing gas stream comprising vapor-phase mercury and vapor-phase iodine and having a temperature ranging from about 325 to about 450°
C., the vapor-phase iodine being derived, at least in part, from an iodine-containing additive, separating at least about 50% of the vapor-phase mercury from the mercury-containing gas stream, wherein at least one of the following is true;
(i) the mercury-containing gas stream comprises about 3.5 ppmw or less vapor-phase iodine;
(ii) in the mercury-containing gas stream, a molar ratio of vapor-phase iodine to vapor-phase mercury is no more than about 600;
(iii) at an air preheater outlet, a concentration of vapor-phase iodine ranges from about 0.1 to about 10 ppmw; and
(iv) a concentration of the vapor-phase iodine is about 30 ppmw or less relative to a weight of a solid mercury-containing feed material producing the vapor-phase mercury.
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Abstract
The present disclosure is directed to the use of elemental or speciated iodine to control total mercury emissions.
318 Citations
49 Claims
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1. A method, comprising:
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in a mercury-containing gas stream comprising vapor-phase mercury and vapor-phase iodine and having a temperature ranging from about 325 to about 450°
C., the vapor-phase iodine being derived, at least in part, from an iodine-containing additive, separating at least about 50% of the vapor-phase mercury from the mercury-containing gas stream, wherein at least one of the following is true;(i) the mercury-containing gas stream comprises about 3.5 ppmw or less vapor-phase iodine; (ii) in the mercury-containing gas stream, a molar ratio of vapor-phase iodine to vapor-phase mercury is no more than about 600; (iii) at an air preheater outlet, a concentration of vapor-phase iodine ranges from about 0.1 to about 10 ppmw; and (iv) a concentration of the vapor-phase iodine is about 30 ppmw or less relative to a weight of a solid mercury-containing feed material producing the vapor-phase mercury. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method, comprising:
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contacting a mercury-containing solid feed material with an iodine-containing additive to form a treated feed material, wherein an iodine concentration of the iodine-containing additive relative to a weight of the feed material is about 30 ppmw or less; thereafter generating, from the treated feed material, a mercury-containing gas stream comprising vapor-phase mercury and iodine; and removing at least about 50% or more of the mercury from the mercury-containing gas stream. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A method, comprising:
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contacting a solid mercury-containing feed material with an iodine-containing additive to form a treated feed material; generating, from the treated feed material, a mercury-containing gas stream comprising vapor-phase mercury and iodine, wherein the vapor-phase iodine comprises both a hydrogen-iodine species and diatomic iodide and wherein a molecular ratio of diatomic iodide to the hydrogen-iodine species is at least about 25;
1; andremoving at least most of the mercury from the mercury-containing gas stream. - View Dependent Claims (42, 43, 44, 45, 46, 47, 48, 49)
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Specification