CONTROL OF SULFUR DIOXIDE AND SULFUR TRIOXIDE USING MAGNESIUM-ENHANCED LIME Joseph Potts and Erich Loch Cinergy Corporation Lewis Benson, Robert Roden.

CONTROL OF SULFUR DIOXIDE AND SULFUR TRIOXIDE USING MAGNESIUM-ENHANCED LIME

Joseph Potts and Erich LochCinergy Corporation

Lewis Benson, Robert Roden and Kevin SmithCarmeuse North America

Control of SO2 and SO3 Using Magnesium-enhanced Lime

Overview Of Talk

• Background on control of SO3 with Mg(OH)2 and Ca(OH)2

• Magnesium-enhanced lime FGD process with byproduct Mg(OH)2

• Results of 800 MW and 1300 MW demonstrations of SO3 control with byproduct Mg(OH)2

• Description of 1300 MW byproduct Mg(OH)2 and SO3 control system

• SO3 control costs – byproduct Mg(OH)2 vs. commercial Mg(OH)2


SO3 Emission from Coal-fired Plants

• From oxidation of SO2 in furnace and SCR Up to 3% oxidation, 70 ppmv SO3

• Can foul heat transfer surfaces• Can cause visible plume• TRI substance


Background on SO3 control with Mg(OH)2

• Furnace injection of magnesium hydroxide to control SO3

Reacts selectively with SO3 to form water-soluble MgSO4, but not with SO2

Decades of experience in oil-fired units Some use in coal-fired units Increases melting point of slag


Magnesium-Enhanced Lime FGD Process Description

• Wet FGD process (Thiosorbic® process)• Uses lime reagent with 3-6 wt.% MgO,

balance CaO

• Mg increases SO2 removal and allows low L/G 21 L/G (3 l/Nm3) for 91% removal with 4% sulfur

coal

• Low chemical scaling potential Liquid in absorber only 10% gypsum-saturated

• Lime is source of Mg for byproduct Mg(OH)2


800 MW and 1300 MW Demonstrations of Furnace Injection of Mg(OH)2

• DOE/NETL program by URS co-sponsored by EPRI, First Energy, AEP, TVA, and Carmeuse

• Objectives 90% SO3 removal Reduce plume opacity Study balance-of-plant effects on:

Slag accumulation SCR catalyst ESP Fly ash composition


Mg(OH)2 Injection Locations

Mg(OH)2 Injection

Locations

Furnace

Selective Catalytic

Reduction

ESP WetFGD



• 800 MW unit AH, ESP (100 SCA), magnesium-enhanced

lime wet FGD Baseline SO3 32-39 ppmv at ESP outlet

• 1300 MW unit SCR, AH, ESP (400 SCA), magnesium-

enhanced lime wet FGD Baseline SO3 37 ppmv at economizer

outlet, 65 ppmv at SCR outlet


SO3 Removal in 800 MW Furnace

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8Mg:SO3 Ratio (baseline on ESP outlet SO3)

SO

3 R

em

ov

al

at

ES

P O

utl

et

Long-term test

Short-term test


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8Mg:SO3 Molar Ratio based on economizer outlet SO3 concentration

SO

3 R

emo

val

SO3 Removal in 1300 MW Furnace


SO3 Removal Across 1300 MW Furnace and SCR

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6 7 8

Mg:SO3 Molar Ratio (based on baseline SCR outlet SO3)

SO

3 R

emov

al a

t E

SP

Out

let



• No adverse impact on SCR catalyst or slagging

• ESP impact 800 MW – adverse when SO3 reduced to 3-

4 ppmv 1300 MW - no adverse impact

Opacity monitor readings reduced from 16-20% to 10-15%

• Byproduct and commercial Mg(OH)2 gave similar results



• Visible opacity significantly reduced• Flyash composition within spec for

sulfate


Hydrated Lime [Ca(OH)2] Injection for SO3 Control

• 12 micron avg. particle size, 16 m2/gram• Demonstrated at 1300 MW for control of

SO3 following SCR Injected after air heater

• Demonstrated at 1300 MW (Zimmer station) with post-SCR SO3 concentrations Injected after ESP Captured in FGD absorber and completely

utilized



MagnesiumHydroxide

Gypsumto Oxidizer

Pre-TreatedFGD Effluent

GypsumByproduct

PrecipitationTank

pH 9.5 - 10

InertsCompressed

Air

FlueGas

Absorber

Belt Filter

LimeSlurryTank

Slaker

Water

Cleaned Gas

MagnesiumEnhanced

Lime

Oxidizer

ByproductMagnesiumHydroxide

System

Magnesium-Enhanced FGD Processwith Byproduct Mg(OH)2


Byproduct Mg(OH)2 System at Zimmer

MgSO4 + Ca(OH)2 + 2H2O →

CaSO4•2H2O (gypsum) + Mg(OH)2

MagnesiumHydroxide Slurry

to SO Control3 TPH Mg(OH)

3

2

Gypsumto Oxidizer

7 TPH

Pre-TreatedFGD Effluent

to Ponds550 gpm

PrecipitationTank

pH 9.5 - 10.5

FGD Effluent631 gpmLime

4 TPHCa(OH)2

M


• Babcock & Wilcox design

• 54 ft (16.5 m) high straight shell

• L/G is 21 gal/1000 acfm (3 l/m3) for 91% SO2 removal

Magnesium-Enhanced Lime Absorberat Zimmer Station


Ex-Situ Oxidizer at Zimmer Station


Byproduct Mg(OH)2 from Magnesium-Enhanced Lime Wet FGD Process

• Byproduct process developed by Carmeuse

• Piloted in 1995 at Cinergy’s Zimmer station with support of EPRI, Ohio Coal Development Office and Cinergy

• Two plants currently producing byproduct Mg(OH)2

• Pre-treats FGD wastewater Reduces dissolved solids by 80%, metals


Composition of Byproduct Mg(OH)2

Mg(OH)2, wt. % 73 Gypsum, wt. % 21 Inerts, wt. % 6 Total Suspended Solids in slurry, %

20

BET Specific Surface Area, m2/g

55

Median Particle Size, microns

3

2 m ic ro n s


1300 MW SO3 Control System Design Parameters at Zimmer Station

• Mg(OH)2 injection system design 3 TPH Mg(OH)2

Mg:SO3 ratio = 8

90% removal of furnace-generated SO3

• Ca(OH)2 injection system 4 TPH Ca(OH)2

Ca:SO3 ratio 7.7

90% removal of SO3 post-SCR


SO3 Control Costs with Mg(OH)2

• Study by Carmeuse of 1300 MW byproduct Mg(OH)2 system $5.4 million capital cost O&M cost $67/ton Mg(OH)2

Compares with commercial Mg(OH)2 cost of ~$210/ton

$2.5 million/yr savings 2 year payback Wastewater pre-treatment at low cost


Conclusions

• Injection of byproduct Mg(OH)2 demonstrated at 800 and 1300 MW for 90% capture of furnace-generated SO3

• Byproduct Mg(OH)2 system being installed in 1300 MW plant, start-up 1st quarter 2004

• Byproduct process pre-treats FGD wastewater

• Byproduct Mg(OH)2 cost compares favorably with cost of commercial Mg(OH)2

• Hydrated lime controls SO3 formed during SCR

CONTROL OF SULFUR DIOXIDE AND SULFUR TRIOXIDE USING MAGNESIUM-ENHANCED LIME Joseph Potts and Erich Loch Cinergy Corporation Lewis Benson, Robert Roden.

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