METHOD AND SYSTEM FOR CONTROLLING MERCURY EMISSIONS FROM COAL-FIRED THERMAL PROCESSES

• US 20160074808A1
• Filed: 11/23/2015
• Published: 03/17/2016
• Est. Priority Date: 02/04/2010
• Status: Active Grant

• Current Assignee: ADA-ES, Inc. (Advanced Emissions Solutions, Inc.)
• Original Assignee: ADA-ES, Inc. (Advanced Emissions Solutions, Inc.)
• Inventors: Sjostrom, Sharon, Lagarenne, Jon, Senior, Connie
• Granted Patent: US 9,884,286 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B01D 2251/108 Halogens or halogen compounds hydrogen halides B01D2251/50
• CPC Class Codes: B01D 2253/10 Inorganic adsorbents
• CPC Class Codes: B01D 2257/602 Mercury or mercury compounds
• CPC Class Codes: B01D 46/00 Filters or filtering processes specially modified for separating dispersed particles from gases or vapours filtering elements B01D24/00-B01D35/00; filtering material B01D39/00; their regeneration outside the filters B01D41/00
• CPC Class Codes: B01D 53/50 Sulfur oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: B01D 53/8625 Nitrogen oxides
• CPC Class Codes: C10L 10/00 Use of additives to fuels or fires for particular purposes additives for liquid carbonaceous fuels characterised by their chemical nature C10L1/10; using binders for briquetting solid fuels C10L5/10; using additives to improve the combustion of solid fuels C10L9/10
• CPC Class Codes: C10L 2290/141 of additive or catalyst
• CPC Class Codes: C10L 3/101 Removal of contaminants
• CPC Class Codes: F23J 15/003 for supplying chemicals to fumes, e.g. using injection devices
• CPC Class Codes: F23J 15/02 of purifiers, e.g. for removing noxious material traps for solid residues F23J3/04
• CPC Class Codes: F23J 2215/60 Heavy metals; Compounds thereof
• CPC Class Codes: F23J 7/00 Arrangement of devices for supplying chemicals to fire

Abstract

The present disclosure is directed to the use of elemental or speciated iodine and bromine to control total mercury emissions.

Claims

1. A method, comprising:

providing a mercury-containing gas stream comprising vapor-phase mercury, a vapor-phase iodine, and particulates;

passing the mercury-containing gas stream through a selective catalytic reduction zone; and

thereafter removing particulates from the mercury-containing gas stream to form a treated stream, at least a portion of the vapor-phase mercury being removed from the mercury-containing gas stream with removal of the particulates, 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;

(iv) a concentration of the iodine is about 30 ppmw or less relative to a weight of a mercury-containing feed material producing the vapor-phase mercury.

2. The method of claim 1, wherein (i) is true.

3. The method of claim 2, wherein the mercury-containing gas stream comprises about 1.5 ppmw or less vapor-phase iodine.

4. The method of claim 1, wherein (ii) is true.

5. The method of claim 4, wherein the molar ratio is no more than about 250.

6. The method of claim 1, wherein (iii) is true.

7. The method of claim 6, wherein a temperature of the mercury-containing gas stream ranges from about 325 to about 450°

C. and wherein the concentration of vapor-phase iodine at the air preheater outlet ranges from about 0.2 to about 2 ppmw.

8. The method of claim 1, wherein (iv) is true.

9. The method of claim 1, wherein the feed material natively comprises no more than about 3 ppmw total iodine and no more than about 10 ppmw total bromine, wherein the halogen-containing additive is contacted with the feed material, wherein the halogen-containing additive comprises no more than about 25% of halogens other than iodine and/or bromine, and wherein a total halogen concentration relative to a weight of the feed material is about 15 ppmw or less.

10. The method of claim 6, wherein the iodine is contacted with vapor-phase mercury upstream of the air preheater.

11. The method of claim 9, wherein the feed material is combustible, wherein the combustible feed material is combusted to produce the mercury-containing gas stream, wherein the vapor-phase iodine causes removal of at least about 75% of elemental and speciated mercury from the mercury-containing gas stream, and wherein the combustible feed material, when combusted, produces an unburned carbon particulate level of no more than about 20% by weight of the combustible feed material.

12. The method of claim 1, further comprising:

while vapor phase iodine and mercury are in the mercury-containing gas stream, introducing, into the mercury-containing gas stream, a reactive surface agent to collect at least most of the iodine and mercury.

13. The method of claim 12, wherein the reactive surface agent is one or more of a zeolite, silica, alumina, silica alumina, gamma-alumina, activated alumina, acidified alumina, a metal oxide particle, aluminosilicate, ion exchange resin, clay, a transition metal sulfate, a ceramic, an alkaline material, trona, an alkali metal bicarbonate, an alkali metal bisulfate, an alkali metal bisulfite, sulfide, elemental sulfur, circulating fluidized bed ash, fluidized catalytic cracker fines, and fumed silicate, and wherein one or more of a mean, median, and P₉₀ size of the reactive surface agent is no more than about 100 microns.

14. The method of claim 1, wherein a concentration of the vapor-phase mercury in the mercury-containing gas stream is at least about 0.001 ppmw, wherein a molar ratio, in the mercury-containing gas stream, of vapor phase iodine to total gas-phase mercury is no more than about 250, wherein a concentration of the vapor-phase iodine in the mercury-containing gas stream is about 1.5 ppmw or less, and wherein the selective catalytic reduction catalyst at least one of catalyzes the formation of diatomic iodine and oxidizes at least some of the vapor-phase mercury.

15. The method of claim 1, further comprising:

passing the mercury-containing gas stream through at least one of a baghouse, a spray dryer absorber, and an electrostatic precipitator to form a treated gas stream; and

thereafter passing the treated gas stream through a wet scrubber, the wet scrubber having a scrubber slurry sorbing no more than about 20% of the total mercury.

16. The method of claim 1, further comprising:

passing the mercury-containing gas stream through at least one of a first particulate removal device to remove at least most of the mercury and form a first gas stream; and

passing the first gas stream through a preheater to form a second gas stream; and

passing the second gas stream through a second particulate removal device to remove at least most of any remaining mercury from the second gas stream and form a treated gas stream.

17. The method of claim 1, wherein the mercury-containing gas stream is derived from combustion of a combustible feed material and wherein the feed material is one of a high- and medium-sulfur coal and wherein a concentration of at least one of sulfur trioxide and nitrogen dioxide gas in the mercury-containing gas stream is at least about 5 ppmv.

18. The method of claim 1, wherein the mercury-containing gas stream is derived from combustion of a combustible feed material and wherein the feed material is a high alkali coal.

19. The method of claim 1, 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 10:

1.

20. The method of claim 12, wherein the reactive surface agent is introduced by a dry scrubber and wherein the dry scrubber is located upstream of a particulate removal device.

21-67. -67. (canceled)