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US 8,124,036 B1Granted
Additives for mercury oxidation in coal-fired power plants
AssigneeADA-ES, Inc.
InventorsKenneth E. Baldrey, Sharon Sjostrom, Nina Bergan French, Michael D. Durham
Life of this patent
Estimating the term…
Abstract
The present invention is directed to an additive, primarily for combustion of low sulfur and high alkali coals, that includes a transition metal to impact positively bottom ash slag and optionally a halogen to effect mercury oxidation and collection in the flue gas.
Claims66
A method, comprising:
- (a) combusting a coal feed comprising mercury and iron to form a flue gas comprising elemental mercury derived from the mercury in the coal feed and fly ash, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash);
- (b) contacting an additive with (i) the coal feed, prior to step (a), and/or (ii) the flue gas resulting from step (a), the additive comprising a transition metal and at least one of bromine and iodine, wherein the additive comprises no more than about 5 wt. % (dry basis) carbon, wherein an atomic ratio of chlorine to bromine in the coal feed ranges from about 1:1 to about 250:1, and wherein, in either option (i) or (ii), the additive promotes post-combustion oxidation of the elemental mercury;
- and
- (c) collecting the oxidized mercury and fly ash to provide a treated flue gas.
1 more element
A method, comprising:
- (a) contacting a coal feed, prior to combustion, with an additive, wherein the coal feed comprises mercury, alkali, and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash) as Fe2O3, the alkali content of the coal feed is at least about 20 wt. % (dry basis of the ash) alkali, wherein the coal feed comprises no more than about 500 ppm halogens, and wherein the additive comprises a transition metal and at least one of bromine and iodine, wherein the additive comprises no more than about 1 wt. % carbon, and wherein the additive promotes oxidation of the elemental mercury;
- (b) combusting, by a wet bottom boiler, the coal feed to form a flue gas comprising elemental mercury derived from the mercury in the coal feed and fly ash;
- and
- (c) collecting the oxidized mercury and fly ash to provide a treated flue gas.
1 more element
A flue gas treatment method, comprising:
- (a) providing a coal feed, the coal feed having a Loss on Ignition (“LOI”) of at least about 10% and comprising mercury, alkali, and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash) as Fe2O3, the alkali content of the coal feed is at least about 20 wt. % (dry basis of the ash) alkali, and wherein the coal feed comprises no more than about 500 ppm halogens;
- (b) contacting the coal feed, prior to combustion, with an additive, the additive comprising a transition metal and a halogen, wherein the additive promotes oxidation of the elemental mercury;
- (c) combusting, by a wet bottom boiler, the coal feed to form a flue gas comprising elemental mercury derived from the mercury in the coal feed and fly ash;
- and
- (d) collecting the oxidized mercury and fly ash to provide a treated flue gas, wherein:
- the additive further comprises a mineralizer;
- the mineralizer is zinc oxide;
- and
- the additive comprises at least about 1 wt. % (dry basis) mineralizer, wherein the additive comprises no more than about 5 wt. % (dry basis) carbon.
6 more elements
A flue gas treatment method, comprising:
- (a) providing a coal feed, the coal feed having a Loss on Ignition (“LOI”) of at least about 10% and comprising mercury and iron, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash);
- (b) combusting the coal feed to form a flue gas comprising elemental mercury derived from the mercury in the coal feed and fly ash;
- (c) contacting an additive with (i) the coal feed, prior to step (b), and/or (ii) the flue gas resulting from step (b), the additive comprising a transition metal and at least one halogen, wherein the additive comprises no more than about 5 wt. % (dry basis) carbon, and wherein, in either option (i) or (ii), the additive promotes post-combustion oxidation of the elemental mercury;
- and
- (d) collecting the oxidized mercury and fly ash to provide a treated flue gas, wherein:
- the coal feed is contacted with the additive prior to step (b);
- and
- the additive comprises:
- (a) at least about 50 wt. % (dry basis) iron;
- (b) at least about 1 wt. % (dry basis) halogens;
- and
- (c) a mineralizer.
9 more elements
A method, comprising:
- (a) combusting a coal feed comprising mercury and iron to form a flue gas comprising elemental mercury derived from the mercury in the coal feed and fly ash, wherein the iron content of the coal feed is less than about 10 wt. % (dry basis of the ash);
- (b) contacting an additive with (i) the coal feed, prior to step (a), and/or (ii) the flue gas resulting from step (a), the additive comprising a transition metal and at least one of bromine and iodine, wherein the additive includes no more than about 5 wt. % (dry basis) carbon, wherein the additive includes no more than about 0.5 wt. % (dry basis) sulfur, wherein an atomic ratio of chlorine to bromine in the coal feed ranges from about 1:1 to about 250:1, and wherein, in either option (i) or (ii), the additive promotes post-combustion oxidation of the elemental mercury;
- and
- (c) collecting the oxidized mercury and fly ash to provide a treated flue gas.
1 more element
Dependencies are inferred from the claim text.