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### Recent Operating Results of the Five New Wet FGD Installations

F or Ameren Corporation

Bruce C. Studley: VP, After Market Services

Hitachi Power Systems America, Ltd.

Robert Nicolo: AQCS Product Director

Hitachi Power Systems America, Ltd.

Steve M osch: Director, Air Quality Control Systems Engineering

Hitachi Power Systems America, Ltd.

ABSTRACT

Hitachi Power Systems America, Ltd. has recently completed the Start

- Up, Performance

Testing and several months of operation on the five (5) We t Limest one F orced Oxidation

Scrubbers (W FGD ) installed in Missouri and Illinois for Ameren. Ameren Corporation is

the parent of utility compan ies that serve 2.4 million electric customers and 1 million

natural gas customers in a 64,000 square

- mile area of Missou ri and Illinois.

This paper will discuss the project backgrounds along with the design and operating

performance of the advanced SO 2 reduction technology that was implemented on these

five units.

The performance of these WFGD s has delivered ultralow SO 2 emissions which also

demonstrates the capability to reliably deliver CO 2 capture ready clean flue gas for future

carbon capture programs where single digit PPM SO 2 emissions are required. The paper

will discuss the advanced design features and performanc e of these W FGD systems

including SO 2 , SO 3 , PM, and mercury capture efficiencies. These installations are reliably

achieving over 99% SO 2 reductions without the use of additives, internal packing/trays or

other chemical additions.

With the new Utility MA CT requirements expected to be finalized soon, these uni ts will

have the advantage of t he ir excellent multi

- pollutant control aspects. It will be most

important to achieve lower acid gasses, mercury, and filterable PM emissions in light of the

new regulat ions.2

INTRODUCTION

Ameren as part of their continued investments in environmental improvements at their

operating plants awarded in April 2006 five (5) WFGD s along with the associated w et

l imestone grinding systems, piping, rotating equipment, valves and instrumentation and

controls to Hitachi Power Systems America , Ltd. (HPSA). The WFGDs are located at

three of Ameren’s coal fired power plants as shown in Figures 1, 2 and 3 which include;

Sioux Units 1 & 2 (2 x 535 MW) West Alton, MO

Duck Creek Unit 1 (465 MW) Canton, IL

Coffeen Unit 1 (360 MW) & Unit 2 (590 MW) Coffeen, IL

Advanced design features were employed into the WFGDs to accommodate the wide

range of inlet flue gas sulfur and chlorine concentrations and to maximize SO 2 removal

efficiency. The vessels themselves, or spray towers, are made of carbon steel which was

flake glass lined to allow continuous operation to chloride levels as high as 50,000 ppm.

With respect to the scrubber inlet ducts they were made of Hastelloy C276 (UNS N10276).

With all five wet limestone forced oxidation scrubbers successfully coming online between

May 2009 and January 2011 performance has been superior with the ability of achieving

over 99% SO 2 reductions without the use of additives or internal packing /trays

. The

performance to date of these WFG D s has consistently delivered ultralow SO 2 emissions in

addition to the removal of other pollutants

. Beyond SO 2 capture, the WFGDs also

effectively remove SO 3 , particulate matter, and oxidized mercury, etc . The design basis for

the WFGD s includ ed S O 2 removal efficiency of 99%, SO 3 removal efficiency of 60%,

mercury (Hg) removal as it pertains to oxidized mercury of 90% and particulate (PM)

removal to less than 0.015 lb/MMBtu. In addition, the WFGDs have all operated t o date

with an availability of 100 %.

Fig. 1 Sioux Units 1 & 2 F ig. 2 Duck Creek Unit 1

Fig. 3 Coffeen Units 1 & 23

WFGD DESIGN AND EQUIPME NT SELECTION

HPSA’s advanced spray tower streamlined design for high efficiency and low power

consumption and equipment selection was based on optimizing both the installed and

overall life cycle costs. Wherever possible the duplication of equipment was maximized to

simplify operations and maintenance along with stocking of spare parts. Key design

criteria included an SO 2 removal efficiency of 99% while using limestone slurry with up to

95% passing through a 325 mesh screen with the potential to operate at chloride levels as

high as 50,000 ppm, while producing gypsum with an oxidation level of greater than or

equal to 99%.

Basic design criteria for the WFGDs with respect to incoming flue gas as specified by

Ameren is presented in Table 1.

Table 1

– B asic Design Criteria

Sioux 1 & 2 Duck Creek Coffeen 1 Coffeen 2

Absorber MW 535 465 360 590

Coal Type Bituminous/PRB Bituminous Bituminous Bituminous

Sulfur Content (%) 2.15 3.41 3.47 3.47

Inlet S0 2 Conc (ppmd

– 3% O 2 ) 2,048 3,325 3,304 3,304

Inlet SO 3 Conc. (ppmd

– 3% O 2) 14

- 17 15

– 23 49

– 55 46

– 51

Inlet Dust (lb/10 6 Btu) 0.07 0.109 0.071 0.071

Gas Flow Rate (acfm) 1,915,000 1,485,900 1,337,200 2,214,400

Inlet Temp. (deg. F) 340 305 305 305

Process design criteria included having a gas v elocity from 13 to 14 feet/second, a liquid to

gas ratio (L/G) ranging from 140 to 160 gallons/10 3 ACF, a gas contact time in excess of

2.0 seconds, a liquid residence time of 6 minutes, and sufficient solids residence time in

hours to assure guaranteed gy psum production.

With respect to materials of construction, which were selected for the high chloride

operating condition, Figure 4 below describes both the vessel and its major components.4 Fig. 4 Materia ls of Construction

It is worth noting that with respect to the Sioux WFGDs that Ameren Misssouri after

construction of the absorbers had been initiated elected to line the inside of the vessels

with Stebbins tiles versus the flake glass lining. This required a structural review of the

vessels primarily at the transition cones because of the additional loading on the vessel

walls caused by the tiles, which simply required the installation of additional external

stiffeners. In order to minimize any differential expansion between the vessel walls and

the internal tile and grout a high reflectance white paint was used externally.

With respect to absorber island equipment selection the duplication of equipment between

plants was maximized to simplify overall operations and maintenance along with stocking

of spare parts. Pertinent details of major support equipment are outlined below:

All R ecycle S lurry P umps are Weir model 800TYGSL with varying motor sizes and

gear boxes.

All ab sorber Bleed Pumps are Weir model EEAH with a capacity of 1,600 gpm.

All Oxidation Air Blowers are Siemens

– Turblex model KA with varying motor sizes

and gearboxes.

All O xidation A ir A gitators are Philadelphia Mixing Solutions model 3850 with 75 HP

motors

. All Absorber S pray N ozzles are Spraying Systems type 4B

- Hollow Cone made of

silicon carbide.

All Mist Eliminators are Munters model DV

- 210 vertical flow 2

- stage elements.5

All Limestone Mills are Metso horizontal wet ball mills rated at 38 tph wi th Stock

Equipment weigh belt feeders.

PERFORMANCE RELATED PROCESS DESIGN FEATURE S

Incorporation of Hitachi’s key process design criteria was essential in being able to

guarantee an SO 2 removal efficiency of 99% while producing a high quality gypsum

bypr oduct. As shown in Figure 5 the spray zone section and configuration of the different

levels of spray headers and nozzles coupled with the quantity of slurry being recycled is

critical. A typical spray header and nozzle arrangement design for an individu al level is

shown in Figure 6.

Fig. 5 Absorber Cross Section Fig. 6 Spray Header Design

The overall result of properly incorporating the key process design criteria when coupled

with a high gas velocity of 13 to 14 feet/second produces the following:

High spray flux which minimizes velocity variation

High spray flux which maximizes gas to liquid contact

Higher spray density near absorber walls increases spray coverage and eliminates

sneakage

Pr ogressive flux density moves the gas away from the a bsorber wall toward the

center6

Figure 7 shows two spray header levels with nozzles trussed together with direct bonding

of the SiC spray nozzles. Figure 8 displays the overlapping high density spray pa tterns

resulting in the generation of fine droplets.

Fig. 7 Typical Spray Headers F ig. 8 Overlapping High Density

Spray Patterns

The design of the absorber reaction tank is also import ant when coupled with in

- situ forced

oxidation employing side mounted agitators and air lances. The result being a high level of

solids for enhanced SO 2 removal and better dewatering coupled with sufficient residence

time to ensure good gypsum crystal grow th. Figure 9 shows a typical agitator and air

lance arrangement which are spaced at the appropriate locations around the tank, while

Figure 10 displays the dispersion of air bubbles.

Fig. 9 Agitator and Air Lance Fig. 10 Di spersion of Air Bubbles to

Allow Forced Oxidation7

Elimination of the maximum amount of mist which is allowed to leave the

absorber is also a key feature. This was accomplished through the two stage mist

eliminators installed at the top of t he absorber just upstream of the outlet duct.

Figure 11 displays a typical mist eliminator arrangement which results in a

maximum entrained moisture carry over at the outlet of less than or equal to 0.070

grains/scf.

F ig. 11 Mist Eliminator Arrangement

OPERATING PERFORMANCE OF THE WFGDs

At the conclusion of the construction effort of all five (5) WFGDs, along with other

modifications and improvements being made by Ameren, tie

- in outages of sufficient

duration were und er taken and the units returned to service. Upon reaching continuous full

load operation of the boilers the scrubbers were fine tuned and all in a position to initiate

performance testing within four (4) weeks. Actual performance test dates for the indiv idual

units were:

Duck Creek Unit 1 May 20, 21, 2009

Coffeen Unit 1 February 3, 4, 5, 2010

Coffeen Unit 2 May 11, 2010

Sioux Unit 1 January 18, 19, 20, 2011

Sioux Unit 2 December 16, 17, 2010

It is important to also realize that the type of coa l being burned at all three Ameren plants

had changed significantly from the basic criteria of primarily all bituminous coal to a large

percentage of Power River Basin (PRB) coal. Specifically, the fuel blend of coal used

during the tests and currently be ing consumed is:

Duck Creek 70% PRB/30% Bituminous

Coffeen 95% PRB/5% Bituminous

Sioux 80% PRB/20% Bituminous8

Results of the performance tests undertaken with respect to emissions are shown in the

following tables, and appreciating the significan t changes in the actual coal being burned

from the design criteria, clearly indicates the ability of all five (5) WFGDs to perform at

levels well in excess of the guarantee levels. Because of the identical design parameters

of the units at Coffeen and Sio ux their test results have been averaged.

Table 2

– Duck Creek Performance Test Results

Parameter Guarantee Test Result

Particulate Emissions ≤ 0.015 lb/MMBtu 0.0045 lb/MMBtu

SO 2 Removal ≥ 99% Removal 99.83% Removal

SO 2 Emissions ≤ 0.064 lb/MMBtu 0 .0038 lb/MMBtu

SO 3 Removal ≥ 60% Removal 72.1% Removal

Mercury Removal ≥ 90% Removal of Oxidized Mercury 99.0% Removal

Table 3

– Coffeen Performance Test Results

Parameter Guarantee Test Result

Particulate Emissions ≤ 0.015 lb/MMBtu 0.0047 lb/MMBtu

SO 2 Removal ≥ 99% Removal 99.95% Removal

SO 3 Removal ≥ 60% Removal 67.45% Removal

Mercury Removal (Note) ≥ 90% Removal of Oxidized Mercury 84.35% Removal

Note: The slightly lower % removal of Oxidized Mercury is a result of the test being

conducted w h ile firing a 95% PRB/5% bituminous blend with very low speciation of

Mercury into the ionic form. Consequently, one of the outlet results was below the

quantitative limit. In addition, it should be noted the Hitachi guarantee is based on

firing an Illino is coal that has an estimated chlorine content of 0.12%, while the

tested fuel has an estimated chlorine content of less than 0.02%. This chlorine

content is critical in speciating Mercury into the ionic form.

Table 4

– Sioux Performance Test Results

P arameter Guarantee Test Result

Particulate Emissions ≤ 0.015 lb/MMBtu 0.0062 lb/MMBtu

SO 2 Removal ≥ 99% Removal 99.65% Removal

SO 2 Emissions ≤ 0.04lb/MMBtu 0.005 lb/MMBtu

SO 3 Removal ≥ 60% Removal 72.25% Removal

Mercury Removal ≥ 90% Removal of Oxidiz ed Mercury 98.7% Removal

In addition, the non

- emission guarantees associated with a gypsum oxidation level of ≥

99%, and the limestone consumption and power consumption levels required were all

satisfactor ily obtained.9

CONCLUSIONS

The successful installation of all five (5) WFGDs and their ongoing continuous ability

to consistently deliver ultralow SO 2 emissions in addition to the removal of other

pollutants, has clearly established the ability to maximize the removal of critical

pollutants from these coal fired electrical plants through the use of Hitachi’s

advanced spray tower wet scrubbers.

Ameren’s continued investments in environmental improvements at their operating

plants is a clear indication of their commitment to providing their custo mers with

clean, reliable energy, while preserving, protecting and improving the environment.

Hitachi’s WFGD experience on a worldwide basis with the completion of these five

units and those currently in design and construction totals at 75 installations. Inlet

SO 2 concentrations range from 500 to 4,000 ppm with absorber capacities to 1,050

MWs.