Philip Elliott, Thomas Riethmann,

Dr. Hermann Brüggendick, Dr. Hermann Winkler, Dr. Bernhard W. Vosteen, Hans Hartenstein

Full Scale Testing of a Novel Mercury Control Strategy

February 2010 – EUEC Conference
This diagram shows, that the ways to influence the me

are limited.

Mercury can either be prevented from entering the prremoved from the process via ash, waste water, flue (e.g. gypsum).If byproducts are sold the amount of mercury in them Regulation limits the amount of mercury discharged vwaste water.

coal incl. mercury

Power Plant 

Process

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 

The Path of Mercury
PAC Injection Prior to Particulate Control 

Device

• Injection of PAC to Combine with Mercury• Captured in Baghouse or Precipitator• Requires 3-10 lbs of PAC per MMacfm 

Captured in Wet FGD

• Oxidized Mercury Dissolved in Scrubber 

Slurry

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 

Typical Methods for Mercury Capture
DeNOx

WFGD

ESP

CaBr2

1st Hydrocyclone 2nd Hydro

cyclone

Hg-free Gypsum

PAC

Low-Hg Sludge Fraction

Enhanced Mercury AbatementCaBr2 to Coal and PAC to WFGD 

with Selective Mercury Precipitation in WWT
Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 

Comparison of Technologies

Traditional PAC Injection Evonik Technology

Baghouse Required No Baghouse Required

Contamination of Fly Ash No Contamination of Fly 

Ash

Requires 3-10 lbs of PAC per MMacfm

Requires 0.2 lbs PAC per MMacfm

Wet FGD Evonik Technology

Reemission of Mercury Very limited reemission

Contamination of Gypsum Gypsum Quality not 

Affected
Purpose of Test

1. To Determine if ≥90 % Reduction without 

SCR is Possible

2. To Determine if CaBr2 Injection Affects FGD 

and WWT Process

3. To Determine if PAC Injection Affects FGD 

and WWT Processes

4. To Determine what Chemical Factors Affects 

the Process

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
PAC Dosing station

CaBr2-Dosing

WFGD

Absorber

Kessel

coal blend~ 1ppm Hg

Tagesbunker

feeder

coal

mill fly-ash recycle 

Unit 5

375 MWth

G

~

Hg-speciesafter boiler

Hg-species after FGD

Tail-End SCR – Plant Marl (375MW)

WFGD

Quench

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
1. Injected a 52 % Solution of CaBr

2 onto 

each of the 3 Coal Belts

2. Three injection points into each feeder3. Injection rates to maintain 250 ppm of Br 

in coal with respect to Hg

Injection of CaBr

2 Onto Coal 

Feeders

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
1. Injection Through a Solution of Activated 

Carbon and Water

2. Injected into the Scrubber through the 

Absorber Recycle Pump

3. Maintain a Constant Concentration of 

PAC in the Absorber

Injection of PAC into FGD

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
Baseline Results at Marl Unit 5

Flue Gas In

Hg Outlet<0.3 Hg2+

2.2 Hgo

<2.5 Hg total

Hg Inlet8.5 Hg2+1.5 Hgo10.0 Hg total

Flue Gas Outlet

Hg-concentration in absorber solution approx. 300-500 ppb

Hg 

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
55 gpm wastewater 

discharge

Flue Gas In

Hg Outlet<0.4 Hg2+

0.1 Hgo

<0.5 Hg total

Hg Inlet9.9 Hg2+

0.1 Hgo10.0 Hg total

discontinuous dosing of PAC (make-up)

Hg-concentration in absorber solution after initial dosing of PAC appr

Flue Gas Outlet

Hg 

CaBr2 & PAC Results at Marl Unit 5

PAC

CaBr2

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
Chemical Process Effect

Changed Slurry Chemistry to Determine Affect
• 0.2 lbs PAC added per MMacfm of flue gas lowers the 

Hg-concentration from 10.0 μg/m

3 to below 0.5 μg/m

3

Hg in the purified gas. 

• Oxidized Hg is adsorbed within the FGD, elemental Hg 

passes through (nearly) unaffected. Hg oxidation e.g. by CaBr

2 is required.

• The PAC/gypsum mixture can be separated completely 

using hydrocyclones (gypsum whiteness unaffected).

• Various chemical factors affect capture rate• Costs:

- Investment costs for PAC dosing station: $ 250,000 - Operating costs: 

13 tons PAC/a x $0.50/lb = $ ~ 13,000/year

Conclusions

Evonik Energy Services LLC © 2010. We reserve all right in this document and in the information contained therein. Reproduction, use or disclosure to 
Questions ?

Contact North America: Philip Elliott Email: philip.elliott@evonik-es.usContact Europe: Thomas RiethmannEmail: thomas.riethmann@evonik.com
28.05.2008 | Evonik_BL_Renewable_Energies_E.ppt