Use of Alkaline-Earth Hydroxides for Reduction of

Plume Visibility inCoal-Fired Power Plants

Lewis BensonCarmeuse Technology

Mark ThomasCinergy

Power-Gen International 2005Las Vegas, Nevada

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Overview Of Talk • SO3 removal performance requirements

• Applicability of injection of alkaline earth compounds - hydrated lime, magnesium hydroxide

• Full-scale injection applications

• Results of full-scale demonstrations of SO3 control with calcium and magnesium hydroxides

• Tests of improved hydrated lime performance with higher surface area and humidification

• Balance-of-plant effects

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Performance Requirements for SO3 Control and Applicable Technology

• Retrofit Return to pre-SCR SO3 in stack: ~50%

reduction Good fit for alkali injection

“Clear stack” - < ~5 ppm SO3, ~90% reduction

Potential fit for alkali injection Demonstrated with SBS process

• New Power Plant < 2 ppm SO3

Wet ESP Alkali injection ahead of baghouse

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Conditions Favoring Alkali Injection

• Existing FGD system with difficult retrofit for a WESP

• Existing FGD system with multiple absorber modules

• Little impact on sale of fly ash• Problems with sulfuric acid corrosion

in ductwork.

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Compounds Tested for Injection for SO3 Control in Coal-fired Plants

Magnesium hydroxide

Furnace

WetFGD

Hydrated lime

dolomite, lime kiln dust, magnesite

Magnesium oxideMicronized limestone

AmmoniaTrona

Soda ash

Sodiumbisulfite

ESP

SCR

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Full-Scale Calcium Hydroxide Injection Applications

• Hydrated lime – pre-ESP Zimmer – 1300 MW – 20 mo. in service Cumberland – 2 x 1300 MW – in engineering

• Hydrated lime – pre-wet FGD Widows Creek 8 - 550 MW – 1 yr in service 650 MW – 3 mo. in service

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Full-scale Magnesium Hydroxide Injection Applications

• Magnesium hydroxide Zimmer – upper furnace - 20 mo. in service Fuel Chem TIFI / TDI – furnace / air

preheater

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Pilot-scale Magnesium Hydroxide Injection Testing

• NETL DOE / Consol / Alstom / Allegheny Energy - 1.6 MW pilot Injection ahead of Alstom pilot air preheater 4 moles Mg(OH)2 per mole SO3 inlet >90% SO3 capture from ~10-30 ppmv SO3

10 day continuous operation with <240 F flue gas exit

• Carmeuse / Consol / Alstom / Allegheny Energy – 1.6 MW pilot SCR-like SO3 conc. ~50 ppmv Demonstrate >90% SO3 capture, air preheater

cleanliness with <240 F flue gas exit temperature for 3 month continuous operation

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Key Properties of Hydrated Limesfor SO3 Control

Ca(OH)2, wt. % 92 - 95 Specific Surface Area, m2/g

10 - 25

Average Particle Size, microns

4 - 10

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Key Properties of Magnesium Compoundsfor SO3 Control

Mg(OH)2

Byproduct Mg(OH)2

MgO

Solids, % 60 20 --- Mg(OH)2, wt. % 98 60-65 --- MgO, wt. % --- --- 97 Specific Surface Area, m2/g

12 55-75 40

Average Particle Size, microns

3 3 5

Control of SO3 Using Ca(OH)2 and Mg(OH)2

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 Lime (Thiosorbic®) Wet FGDwith Byproduct Mg(OH)2 Production

for SO3 control

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Injection Locations for Mg(OH)2 in NETL Demonstrations

Commercial Mg(OH)2

orByproduct Mg(OH)2

37 ppmv SO3 at economizer

outlet65 ppmv SO3 at SCR outlet

Control of SO3 Using Ca(OH)2 and Mg(OH)2

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 Furnace in 1300 MW NETL DemonstrationBaseline SO3 37 ppmv at economizer outlet

Control of SO3 Using Ca(OH)2 and Mg(OH)2

SO3 Removal Across 1300 MW Furnace and SCR in NETL Demonstration

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

Baseline SO3 65 ppmv at SCR outlet

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Injection Locations for Mg(OH)2 and Ca(OH)2 for 1300 MW unit

50-75 gpm Mg(OH)2

slurry

Furnace SCR

ESP WetFGD

1-3 TPH hydrated

lime

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Balance-of-Plant Issues with Mg(OH)2 and Hydrated Lime Injection in 1300 MW unit

• Furnace Magnesium salt deposit on economizer tubes

• ESP Mg(OH)2

no significant effect

Hydrated lime No significant adverse effect at addition rate of 3 TPH

• No accumulation in ESP, downstream ducts Slight build-up at air in-leaks

• Flyash sales continue for concrete, other

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Alkali Injection Short-term Performance Tests

• Hydrated lime – pre-wet FGD 650 MW

• Hydrated lime – pre-ESP Zimmer – 1300 MW Gibson 5 - 625 MW

Control of SO3 Using Ca(OH)2 and Mg(OH)2

SO3 Reduction w/ Mg(OH)2 and Hydrated Lime Injection1300 MW, 3 TPH hydrated lime w/ 13 SSA, 75 gpm 15% commercial Mg(OH)2 slurry to furnace, SCR off

Lime, TPH Stack SO3, ppmv

2 2.5

3 3.4

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Effect of Specific Surface Area of Hydrated Lime on SO3 Reduction

1300 MW, 1.8 TPH hydrated lime, 50 gpm byproduct Mg(OH)2 slurry to furnace, SCR off

SSA, m2/gram Stack SO3, ppmv

No lime addition 15

13 12

21 6.5

23 4

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Effect of Humidification on Hydrated Lime for SO3 Reduction

625 MW, 1.8 TPH hydrated lime w/~23 SSA, pre-ESP, SCR off

TPH limegpm water

SSA m2/gram

Stack SO3 ppmv

--- --- --- 15.6

1.1-1.3 --- 23 5.7

1.1-1.3 30 23 3.5

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Summary

• Injection of hydrated lime & magnesium hydroxide applicable for SO3 control

• Full-scale injection applications• Options for hydrated lime injection

location: pre-ESP, pre-FGD, pre-baghouse

• Options for magnesium hydroxide injection: upper furnace, post furnace

• Improved SO3 performance with higher surface area hydrated lime and humidification

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Summary

• Furnace injection of Mg(OH)2 proven at 1300 MW for efficient capture of furnace-generated SO3; additional injection of hydrated lime ahead of ESP reduced stack SO3 <5 ppm

• ESP performance with calcium or magnesium hydroxide depends on ESP design, improves with humidification

Control of SO3 Using Ca(OH)2 and Mg(OH)2

Contact information:

• Bob Roden – Carmeuse FGT Technical Marketing Manager – 412-777-0722 office: 412-889-9662 cell; bob.roden@carmeusena.com

• Lew Benson – Carmeuse FGT Technical Manager – 412-777-0723; 412-818-9839 or 412-225-8816 cell; lew.benson@carmeusena.com

• Mark Thomas – Cinergy – 513-287-3802: office: 513-312-0124 cell; mark.thomas@cinergy.com