Enhanced mercury control in coal-fired power plants

• US 20030161771A1
• Filed: 02/14/2002
• Published: 08/28/2003
• Est. Priority Date: 02/14/2002
• Status: Active Grant

• Current Assignee: Hazelmere Research Ltd.
• Original Assignee: Hazelmere Research Ltd.
• Inventors: Oehr, Klaus H.
• Granted Patent: US 6,808,692 B2
• Time in Patent Office: Days
• US Class Current: 423/210
• CPC Class Codes: B01D 53/64 Heavy metals or compounds thereof, e.g. mercury

Abstract

A method of treating a coal combustion flue gas, which includes injecting a molecular halogen or thermolabile molecular halogen precursor able to decompose to form molecular halogen at flue gas temperature. The molecular halogen coverts elemental mercury to mercuric halide adsorbable by alkaline solids such as subbituminous or lignite coal ash, alkali fused bituminous coal ash capturable in whole or part by electrostatic precipitators (ESPs), baghouses (BHs), fabric filters (FFs), dry flue gas desulphurization solids, with or without subsequent adsorption by a liquid such as a flue gas desulphurization scrubbing liquor.

Claims

1. A method of treating coal combustion flue gas containing mercury, comprising:

injecting one of molecular halogen and a thermolabile molecular halogen precursor into said flue gas to effect oxidation of elemental mercury to a mercuric halide and providing one of a liquid and alkaline solid particles in said flue gas in order to adsorb at least a portion of said mercuric halide.

2. The method as claimed in claim 1, wherein said molecular halogen and/or thermolabile molecular halogen precursor contains one of chlorine, bromine and iodine.

3. The method as claimed in claim 2, wherein said thermolabile molecular halogen precursor contains a hypohalite.

4. The method as claimed in claim 3, wherein said hypohalite is a hypochlorite.

5. The method as claimed in claim 4, wherein said hypochlorite is calcium hypochlorite.

6. The method as claimed in claim 5, wherein the calcium hypochlorite is in aqueous solution.

7. The method as claimed in claim 6, wherein calcium chloride is a component of the calcium hypochlorite containing solution.

8. A method as claimed in claim 1, wherein the alkaline solid particles are alkaline coal fly ash particles.

9. A method as claimed in claim 8, wherein the coal fly ash particles are those derived from combustion of subbituminous or lignite coal.

10. A method as claimed in claim 1, wherein the alkaline solid particles are those derived from the fusion of coal ash with alkali and an alkali flux.

11. A method as claimed in claim 1, wherein the alkaline solid particles are those derived from the decomposition of a thermolabile halogen precursor.

12. A method as claimed in claim 1, wherein the alkaline solid particles are those derived from flue gas desulphurization solids.

13. The method as claimed in claim 1, wherein the resulting treated flue gas containing alkaline solid particles is passed through an electrostatic precipitator.

14. The method as claimed in claim 1, wherein the resulting treated flue gas containing alkaline solid particles is passed through a baghouse.

15. The method as claimed in claim 1, wherein the resulting treated flue gas containing alkaline solid particles is passed through a fabric filter.

16. The method as claimed in claim 1, wherein the resulting treated flue gas is passed through a flue gas desulphurization system (FGD) containing a liquid..

17. The method as claimed in claim 11, wherein the alkaline particles contain lime.

18. The method as claimed in claim 1, wherein the mercuric halide containing alkaline solids is used as a cementitious product.