Mirant: Who We Are

INDEPENDENT POWER COMPANY  Make and sell electricity 

competitively, reliably, ethically, and safely 

 10 power plants in the US Approximately 10,000 MW of 

generating capacity ~ 10 million homes

 Coal, natural gas, and oil fuel 

electric generation fleet

 Mid

-Atlantic’s generation output

sold to PJM wholesale electricity marketMirant emplo s nearl 1 600 

1

 Mirant employs nearly 1,600 

employees in the U.S.
Summary of Mid-Atlantic Air Pollution Control Projects

 Investing for the Future: Air Quality Control Systems (>$

 Flue Gas Desulphurization (aka FGD or Scrubbers)

– U 9 % l f SO U

p to 95% removal of SO f MD fl 

2

for MD fleet

– Morgantown, Chalk Point and Dickerson Scrubbers placed in ser

December, 2009

 Selective Catalytic Reduction (SCR) 

– Up to 90% removal of NOx for MD fleet– Morgantown 

• Unit 1 placed in service June 2007• Unit 2 placed in service May 2008

– Chalk Point 

• Unit 1 placed in service May 2008

– Dickerson

• Selective Non-Catalytic Reduction (SNCR); Units 1, 2, 3 placed 

J l 2009 J

uly 2009

 Together, FGDs and SCRs reduce ionic Hg by >80%
SO2 Control System at Dickerson

 Flue Gas Desulphurization System 

 O t f U it 1 2 d 3 One system for Units 1, 2 and 3 ‘Wet’ scrubber technology

 Removes ~ 95% of SO from Flue Gas 2

 MDE regulations set annual tonnage limits  Nearly 30,000 tons/year removed from the units

 Creates a Commercially Saleable By-Product SO2 reductions help the State of Maryland achieve compli

the National Ambient Air Quality Standard (NAAQS) for pamatter smaller than 2 5 microns (PM 2 5) matter smaller than 2.5 microns (PM 2.5)
Dickerson Generating Station

 Three coal-fired boilers, 

182 MW each

 Two Combustion Turbines (CTs), 

167 MW each

 One 13 MW Blackstart CT Water source: Potomac River E i i t l it E

missions con

trol units:

- Selective non-catalytic reduction (SNCR) - Electrostatic Precipitators

- Baghouse- Flue Gas Desulfurization (FGD) System
Purpose of FGD:

To reduce the SO2, NOx, and Hg emissions of coal combuchemical reactions between water, flue gas, and limestone

Limestone arrives in 

trains

Mixed with water to 

create slurry

Stack gases 

to absorber v

• Clean f• Wastew

Gypsu

Wastewater (from 

IWWTP) and river water

•
FGD Chemistry

• SO2 in flue gas reacts with water to create su

acid (H2SO3 acid (H ) 2SO3

H SO reacts with the calcium carbonate 

2SO3 reacts with the calcium carbonate 

in limestone slurry to create calcium sulfit(CaSO ) and liberates CO as a gas & H 

3), and liberates CO2 as a gas & H

liquid 

• O2 is added by natural and forced oxidatio

CaSO3 + 1⁄2 O2 combine to produce gypsu

(CaSO4)
FGD W t W t T t 

FGD

Was

te 

W

a

ter 

Trea

tme

Physical Chemical Treatment

 Metals Reduction

Biological Treatment

 Nitrogen Reduction

7
Physical Chemical System

Alkali (pH control)

Organosulfide (metals precip.)

Ferric Chloride 

(coagulant)

Polymer

Hydrochloric

FGD Purge from Hydroclones

Hydrochloric

Acid

Recycle Sludge 

Clarification

Gravit

Filtrat

Equalization

Dewaterin

g

Sludge

Recycle Sludge Filtrat

Sludge 

g

Tank

Filtrate

Cake

Backwash Stream
Biological Treatment Stage

Performed downstream of physical-chemical 

treatment, after removal of TSS and 

metals

 Nitrogen removal

–

Activated Sludge reactors to 

remove N

– Nitrogen levels of discharge 

less than 4 ppm
FGD Wastewater Treatment 

Physical Chemical System

Treatment Effectiveness

Constituent Typical Influent (mg/L) Typical Efflu

Treatment Effectiveness

TSS 10,000 - 40,000 <30

pH 4.5 - 6.0 6.5 - 

As 0.05 - 3.0 <0.

Cd 0 04 . - 0 5. <0 

.

Cr 0.3 - 5.0 <0.

Cu 0.1 - 0.85 <0.Hg 0.05 - 0.8 <0.0

Ni 0.2 - 6.0 <0

Pb 0.1 - 3.0 <0.

Zn 0.4 - 8.0 <0.

Total N Total

N 20-290

<4.
Nitrogen Sources

 Makeup Water

River Water River WaterSewage Treatment Plant EffluentIndustrial WWTP effluent

Flue Gas

 A i Sli f SCR/SNCR E i t Ammonia Slip 

from SCR/SNCR

Equipmen

t

 Nitrous Oxide (NOx)

 95% NO and 5% NO

2

 Nitrogen (N

2

)

FGD System Nitrogen Containing Additives

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FGD System Nitrogen Containing Additives

 Polymers, DBA, etc