Reducing mercury emissions from the burning of coal

• US 8,658,115 B2
• Filed: 08/05/2013
• Issued: 02/25/2014
• Est. Priority Date: 03/17/2005
• Status: Active Grant

• Current Assignee: Nox Ii Ltd. (Arthur J Gallagher & Company)
• Original Assignee: Nox Ii Ltd. (Arthur J Gallagher & Company)
• Inventors: Comrie, Douglas C.
• Primary Examiner(s): VANOY, TIMOTHY C
• Application Number:
  US13/958,950
• Publication Number:
  US 20130312646A1
• Time in Patent Office: 204 Days
• Field of Search: 423/210, 110/342, 110/203, 106/602, 106/705, 106/709, 588/404, 588/412, 588/256, 588/257, 446/20, 446/21
• US Class Current: 423/210
• CPC Class Codes: B01D 53/508 by treating the gases with solids
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury
• CPC Class Codes: C04B 18/065 Residues from coal gasification
• CPC Class Codes: C04B 18/162 Cement kiln dust; Lime kiln dust
• CPC Class Codes: C04B 20/023 Chemical treatment
• CPC Class Codes: C04B 2103/0088 Compounds chosen for their latent hydraulic characteristics, e.g. pozzuolanes
• CPC Class Codes: C04B 28/04 Portland cements
• CPC Class Codes: C04B 40/0039 Premixtures of ingredients
• CPC Class Codes: C04B 40/0608 Dry ready-made mixtures, e.g. mortars at which only water or a water solution has to be added before use
• 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 10/02 for reducing smoke development
• CPC Class Codes: C10L 9/10 by using additives
• CPC Class Codes: F23J 15/003 for supplying chemicals to fumes, e.g. using injection devices
• CPC Class Codes: F23J 2215/60 Heavy metals; Compounds thereof
• CPC Class Codes: F23J 7/00 Arrangement of devices for supplying chemicals to fire
• CPC Class Codes: F23K 1/00 Preparation of lump or pulverulent fuel in readiness for delivery to combustion apparatus
• CPC Class Codes: F23K 2201/505 with additives
• CPC Class Codes: Y02E 20/32 Direct CO2 mitigation
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete
• CPC Class Codes: Y10S 423/05 Automatic, including computer, control

Abstract

Sorbent components containing halogen, calcium, alumina, and silica are used in combination during coal combustion to produce environmental benefits. Sorbents such as calcium bromide are added to the coal ahead of combustion and other components are added into the flame or downstream of the flame, preferably at minimum temperatures to assure complete formation of the refractory structures that result in various advantages of the methods. When used together, the components

• • reduce emissions of elemental and oxidized mercury;
  • increase the level of Hg, As, Pb, and/or Cl in the coal ash;
  • decrease the levels of leachable heavy metals (such as Hg) in the ash, preferably to levels below the detectable limits; and
  • make a highly cementitious ash product.

Claims

1. A method of improving the leaching quality of ash produced by burning mercury-containing coal, comprising adding silica and alumina to the coal in a sufficient amount to cause a geopolymer to form upon combustion, combusting the coal in the presence of the added silica and alumina to produce coal ash and heat energy, and measuring the leaching of mercury from the ash.

2. A method according to claim 1, wherein the coal ash is fly ash.

3. A method according to claim 1, comprising adding a sorbent comprising silica and alumina onto the coal upstream of the furnace.

4. A method according to claim 3, wherein the sorbent comprises alkali powders.

5. A method according to claim 1, wherein the ash sequesters one or more of mercury, lead, arsenic, cadmium, antimony, cobalt, copper, manganese, and zinc.

6. A method according to claim 1, comprising adjusting the amount of silica and alumina added depending on the measured level of leaching.

7. A method according to claim 3, wherein the sorbent comprises greater than 5 wt. % alumina.

8. A method according to claim 3, wherein the sorbent comprises greater than 8 wt. % alumina.

9. A method according to claim 1, further comprising adding a halogen compound onto the coal upstream of the furnace.

10. A method according to claim 9, wherein the halogen compound comprises calcium bromide.

11. A method according to claim 1, comprising adding an aluminosilicate material selected from micas, clays, talc, and chrysotiles onto the coal.

12. A method according to claim 11, comprising adding a clay selected from chlorites, glauconite, illite, polygorskite, pyrophillite, sauconite, vermiculite, kaolinite, calcium montmorillonite, and sodium montmorillonite.

13. A method of increasing the cementitious properties of coal ash while reducing mercury emissions arising from the combustion of coal, comprising adding a sorbent composition onto the coal prior to combustion and/or adding a sorbent composition into the furnace along with the coal, wherein the sorbent composition comprises calcium, silica, alumina, iron oxide, and alkalis selected from Na₂O and K₂O.

14. A method according to claim 13, wherein the sorbent comprises 2-15 wt. % Al₂O₃, 30-75 wt. % CaO, 5-20 wt. % SiO₂, 1-10 wt. % Fe₂O₃, and 0.1-5 wt. % alkalis.

15. A method according to claim 14, wherein the sorbent comprises 2-10 wt. % Al₂O₃, 40-70 wt. % CaO, 5-15 wt. % SiO₂, and 2-9 wt. % Fe₂O₃.

16. A method according to claim 13, wherein the sorbent composition comprises cement kiln dust.

17. A method according to claim 13, further comprising adding a halogen compound onto the coal upstream of the furnace.

18. A method according to claim 17, wherein the halogen compound comprises a bromine compound.

19. A method according to claim 18, wherein the halogen compound comprises calcium bromide.

20. A method according to claim 13, further comprising recycling the coal ash for use in portland cement manufacture.