The Largest and the Highest
Performance Flue Gas
Desulfurization Plant for Fossil
Power Plants in the World
Machinery & Steel Structures Headquarters
Environment & Energy Business Department

While sulfur oxides (SOx) and nitrogen oxides (NOx) emissions from coal-fired power plants are regulated drastically in the U.S., Mitsubishi Heavy Industries, Ltd. (MHI) established a joint corporation, Advatech LLC, with theURS Corporation, which is an American engineering company, in May 2002, and delivered on time a flue gas desulfurization (FGD) plant which was the first Advatech LLC plant, and started operation from the middle of October
2006. The FGD plant for Unit 3 of the Paradise Fossil Plant (unit gross generation capacity 1056 MW) that wasordered from Tennessee Valley Authority (TVA), which is the largest U.S. utility, is the largest in the world and thehighest performance plant in which more than 98% of the sulfur dioxide (SO2) can be removed in single module.

costs with highly efficient performance, MHI has designed the double contact flow scrubber (DCFS), which
is a fountain-like spray type absorption tower equippedwith single stage upward DCFS spray as shown inFigFig.. 1 , which has met these goals, and 76 units havealready been installed, and received high evaluations
from users.
Because of the quickly increasing demand for desulfurization in the U.S., Advatech LLC was established in
2002 and was awarded the desulfurization facility by theTVA for Unit 3 of the Paradise Fossil Plant in the sameyear.
This paper presents an overview of the scrubber design for the TVA Paradise FGD system, and outlines its
recent operating status.

1. Introduction
Taking the initiative with the rise of global environmental regulations in recent years, MHI has developeda desulfurization technology using a wet limestone-gypsum process, and has been building flue gas
desulfurization (FGD) facilities for fossil power plants
since 1972.
As of April, 2007, MHI has delivered the wet limestone-gypsum process to 191 FGD plants, and has a highshare of the global market.
Although flue gas desulfurization facilities must have
low capital, and operation and maintenance (O&M)

Clean Gas

2. Overview of Desulfurization Plant for Paradise Fossil Plant

Dirty Gas

2.1. Overview of Paradise Fossil Plant
The TVA is the nation's largest public power provider
and has power stations in the states of Tennessee, Alabama, Georgia, and a part of Kentucky, with 33,000
megawatts of dependable generating capacity.
Paradise Fossil Plant(1) is located in western Kentuckyon the Green River near the village of Paradise, and has
three coal-fired boilers with a total of 2,273 megawattsof dependable generating capacity, and was built between
1963 and 1970.
Units 1 and 2 installed FGD scrubbers in 1983, andthe amount of SO 2 emissions from the three-unit plant
has been reduced by 93% by installing an FGD scrubber
to Unit 3 when combined with the operation of the othertwo scrubbers.

Fig. 1 Twin tower of double-contact-flow-scrubber (DCFS)

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

1New Inlet Duct

New Inlet Duct

Twin Tower
DCFS Absorber
Absorber Recycle Pump

FGD Booster Fan
Slurry Bleed Tank

Forced Ox Compressor Bldg

Fig. 3 Layout of the new FGD system at Paradise Unit 3Fig. 2 View of Paradise Fossil Plant

Fig. 4 Cross-section of the Unit 3 scrubber

2.2. Outline of FGD System for the Paradise Unit 3A cross-section of the Unit 3 scrubber is shown in
FigFig.. 4 . A co-current & counter-current DCFS (twin tower)
is adopted, and upward single stage sprays are installed
on a single spray header located in the lower sections of
the first and second towers. The Unit 3 scrubber is thelargest single scrubber module in the world with thehighest performance and can treat 4 million acfm of fluegas, removing more than 98 percent of the SO2. The key
design system parameters of the scrubber are shown inTable 1
1.

A view of Paradise Fossil Plant is shown in Fig. 22,and the layout of the new FGD system at Paradise Unit
3 is shown in Fig. 33.
Paradise Fossil Plant Unit 3 also has a selective catalytic reduction system, the same as the two other units,
which reduce NOx emissions from the plant. The boiler
exhaust gas which has had the NOx removed is fed tofour electrostatic precipitators to remove particulatematter via an air heater. The gas is then passed into asingle scrubber DCFS module via four fans, and the gas
with SO2 removed is discharged from the new wet stack.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)

2Table 1 Key design system parameters of the FGD system
Description

Units

Value

Unit Gross Generation Capacity

MW

1 056

Boiler TypeBalanced Draft Cyclone

Inlet Flue Gas Flowrate

acfm

4 028 000

Inlet Flue Gas Flowrate

lb/hr

12 020 000

Inlet Flue Gas Temperature

F350

Design Fuel Sulfur Content% - dry basis

3.4

Design Inlet SO2 Loading

lbs SO2 /MMBtu

5.1

Design Inlet SO2 Loading

ppm-dry

2 121%98gallons

1 371 000

#2 346

Recycle Slurry Solids% by wt30Recycle Slurry Chloride Concentration

ppm-dry

1 780

tph

50%pass-325 mesh

90

Gypsum Solids Production Rate

tph75

Limestone Consumption Rate

tph47

Makeup Water Consumption Rate

gpm

2 200

Height of New Wet Stack

ft600

FGD System SO2 Removal Efficiency
Recycle Tank Volume
Fountain Nozzles

Limestone Prep System Capacity
Limestone Slurry Grind Size

Air
Reducer

Motor
Bearing

Impeller (Arm)Fine
Bubbles

Equipment Redundancy
Recycle Pumps

10+1

Ball Mills

1+1

Ox Air Blowers

2+1

ARS

3+0

Fig. 5 Air rotary sparger

the first tower. After the flue gas exits from the sprayzone of the second tower, it passes through a two-stage
vertical flow mist eliminator to separate the mists andis discharged from the stack.
As mentioned above, the DCFS has no internal structure in the gas-liquid contact zone other than the singlestage spray pipes, so that maintenance is very easy on internal inspections. Since the spray pipes themselves arealways washed by the slurry there is no gypsum scaling.
The recycle pump bay is located in front of the second
tower. Recycle pumps discharge into two common external recycle headers which provide slurry for the first andsecond tower's spray pipes. By using a modular approach,the size of the absorber tower can be easily expanded byincreasing the width of the absorber tower with the samelength of spray pipes, and the number of pipes and pumps
to accommodate the different volumes of flue gas.
In addition, the collected gypsum slurry is discharged
into a pond in this plant.
2.3. Outline of the Other Equipment
The following latest equipment has been adopted inthis FGD system which realizes even higher efficiency.
(1) Air Rotary Sparger (ARS)
Sulfite ions in the absorbent must be oxidized tosulfate ions in order to recover the gypsum from theabsorbed SO 2 . MHI has developed an arm rotary
sparger (ARS) which provides oxidation air to the reaction tank and mixes with the slurry for commercialplants. As air is provided to four impellers (arms)
through a shaft, it can be dispersed in fine bubbles by
the shear of rotating arms as shown in Fig. 55.

Absorber Dimensions
Lengthft

Widthft70

Heightft

125

Materials of Construction

114

NameCommon

UNS

Inlet-Wet/Dry Interface

C-276

N10276

1st Tower Contact Zone

2 550

S32550254 Smo

S31254

2nd Tower

2 205

S32205

Recycle Tank

2 205

S32205

1st to 2nd Tower Crossover

2 205

S32205

Stack Liner

Roll Bond C-276

N10276

Inlet Ductwork

Corten SteelSpray Header

304 SS

Mist Eliminator

317 L

Outlet Ductwork

The first tower is called a co-current scrubber: fluegas is released from the top of first tower and contacts
the recycle slurry that is sprayed upward from the spraynozzles, and goes down through the scrubber contacting
falling droplets. The droplets of slurry fall into a reaction tank at the bottom of the scrubber. As the gas leaves
the first tower, it traverses the top of slurry in the reaction tank before entering the second tower.
The second tower is called a counter-current scrubber: the gas enters the second tower and goes up throughthe scrubber contacting the recycle slurry sprayed upward, and the droplets fall into the reaction tank as in

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)3

Table 2 Summary of Advatech projects in the US
Capacity

Description

Startup

Status

TVAWidows Creek #8550 MW

Retrofit FGD

Dec 2003

Complete

TVA

Paradise #31 056 MW

New FGD

Oct 2006

Complete

TVA

Bull Run #1950 MW

New FGD

Oct 2008

Under Construction

TVA

Kingston #6-9

200 MW x 4

New FGD

Oct 2009

Under Construction

TVA

Kingston #1-5

200 MW x 5

New FGD

Apr 2010

Under Construction

TVAJohn Sevier #1-4

712 MW (188 MW x 4)

New FGD

Oct 2011

Conceptual Design

Southern Company

Gorgas #8, 9 and 10

Total 1 021 MW

New FGD

Dec 2007

Under Construction

Southern Company

Hammond #1-4

Total 800 MW

New FGD

Jul 2008

Under Construction

Southern CompanyMiller #3 &4

750 MW x 2

New FGD

2009-2010

Designing

Southern Company

Miller #1&2

750 MW x 2

New FGD

2010-2011

Designing

Southern Company

Scherer #1-4

923 MW x 4

New FGD

2011-2014 Conceptual Design

Southern Company

Daniel #1&2

530 MW x 2

New FGD

2011

Conceptual Design

IP&L-AES

Harding Street Station #7465 MW

New FGD

Aug 2007

Under Construction

Utility

Plant

The ARS for the Paradise No. 3 scrubber was delivered by MHI. Three units are mounted on the topof the reaction tank between the first and second towers which agitate the whole reaction tank, and are
the largest ARS units in the world.
(2) Limestone Reagent Preparation System
Limestone which is stored in a silo is fed to a ballmill with the process water and is crushed. The resulting slurry is sent to a holding tank, where it ispumped to a hydro cyclone classifier, where unacceptably large limestone particles are recycled to the ballmill. The grinding is accomplished by one or more
additional ball mills.

operation in October and is being prepared for performance testing currently scheduled for summer 2007.

4. Recent Future Work
The summary of Advatech's FGD projects in the U.S.
is shown in Table 2
2. MHI has been already awarded five
new FGD systems and one project to retrofit with DCFS
from TVA, and will develop the further sales based on
the success of this project.
Moreover, we think that we can contribute to the further sales promotion of desulfurization systems byapplying MHI technology as a multi-emission control
technology for the new regulations being enforced inthe U.S.

3. Status of Operating the Unit 3 FGD System
Construction of the third Paradise scrubber was completed in October 2006. The Unit 3 FGD system started

Reference(1) http://www.tva.gov/sites/paradise.htm

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 44 No. 2 (Jul. 2007)4