C b ti Additi f SCR Com

bustion Additives 

for SCR

Performance Optimization

2012 Power Plant Air Pollutant C“ S ontrol 

“Mega” 

Symposium

Baltimore, Maryland, August 20-23, 2012

Mandar Gadgil

AQCS Engineer

B&W PGG

E

Bla

Elizabeth Hansen 

Business Development Manager 

B&W PGG
Presentation Overview Presentation Overview

Ì Deactivation by flue gas constituents

derived from different fuels

Ì Combustion additive development development

Ì Field test results

Ì Economic analysis of combustion

additive i j ti n ec on

Deactivation of SCR Catalyst by Ars

Deactivation of SCR Catalyst by Ars

Ì Experienced on eastern bituminous and Illinois Basin coals

Ì Independent of staged or un

‐staged combustion

Ì Cli a

cium i j ti n ec on ties up gas

p

hase arsenic, re

d i uc ng concen

t ti ra o

phase arsenic reaching catalyst and thereby the rate of deactivati

Ì Recommended calcium to arsenic ratio is set based on coal being f

Ì Trusted mitigation technique uses injection of combustion additive
Deactivation of SCR Catalyst by Alk

Deactivation of SCR Catalyst by Alk

Ì Potassium and sodium induced catalyst deactivation observed in b

combustion

Ì Independent of staged or un

‐staged combustion

Ì Some western bituminous coals also have about

1

‐1.5%

K in ash

Ì North Dakota lignite has about

5

‐7% Na in ash

Ì Deactivation Deactivation mainly by reaction reaction between between acid sites on catalyst catalyst and 

Ì Strength of acidic DeNO

x sites is weakened by the base

Ì Mitigation could be possible using combustion additives (more dat
Deactivation of SCR Catalyst by Phosp

Deactivation of SCR Catalyst by Phosp

Ì Deactivation by phosphorus many times experienced with PRB co

Ì Combustion conditions play major role in the deactivation proces

Ì Commonly observed under staged combustion conditions as com

unstaged combustion

Ì Poor combustion leads to deactivation of catalyst by phosphorus

Ì Gas phase phosphorus phosphorus at SCR inlet is important important contributor contributor to de

de
Staged/Poor Combustion Effects Staged/Poor Combustion Effects

Ì Carbothermic reduction of

phosphorus

‐bearing minerals

due to staging in lower furnace

Ì Even unstaged, if poor

combustion exists in furnace furnace the

same effect is observed

Ì Load cycling with different mill

combination in service service is also

expected to cause combustion

environment similar to staging
Gas Phase Phosphorus Samplin

Gas Phase Phosphorus Samplin

80

Gas Phase

P at 100% PRB Staged Units

60

70

b

gas phase P at plant

A 

Gas pahse P at Wyegn 

Gas phase P at Plant

A 

Gas phase P at Wygen 

40

50

Phase P in ppb

20

30

Gas P

0

10

1 2 3 4

5 6 7 8 9 10 11 Run 12 id
Deactivation by Gas Phase Phosph

Deactivation by Gas Phase Phosph

Ì Chemical deactivation

Ì V

‐

P bond formation indicated gas phase phosphorus adsorbs on

active sites just like ammonia does

Ì Phosphorus adsorption more prominent on lower layers, causing

more deactivation than first layer

• In presence of ammonia, phosphorus adsorption

may be suppressed

• Second and third layers see less ammonia than

first layer

• More

P accumulation accumulation at outlet section section than inlet within

a log
Combustion Additive Developme

Combustion Additive Developme

Ì B&W investigations investigations for binding binding gas phase phosphorus phosphorusÌ Impact on boiler performance

Ì Technical feasibility of injection

Ì Short term testing

Ì Long term testing

Ì International 

p g atent 

granted 

Ì US patent pending
Long Term Injection Long Term Injection

Ì To demonstrate demonstrate

a reduction reduction in the

rate of catalyst deactivation

Ì Wygen 2 ,100 MW unit with

SCR, SDA and bag house

Ì Wyodak mine PRB coal

Ì Staged combustion

Ì Ei d xperience

d rapid ca

tl t a ys

t

deactivation due to phosphorus

previously with new catalyst

Ì At th

e time

o

f t ti es ng, catl t a ys

t was

6.9 mm pitch, single

layer, regenerated
Long Term Injection Long Term Injection

Ì Completed Completed 13 000+ , hours of continuous continuous injection injection of additive additiveÌ Plant coal flow is around 135,000 lbs per hour

Ì Test injection rate of about 50 lb/hr

Ì Simple pneumatic additive injection system
Using Combustion Additive for

SCR Catalyst Deactivation Deactivation Mitigat

Mitigat
Expected Catalyst Performance T

Expected Catalyst Performance T

1.10 80.9

1

0.60.70.8

Original expecteddeactivation for

W

y

2

0 30.40.5

y

0.6 k/ko @ 16,000 hrs

0.10.20.3

0

0 2000 4000 6000 8000 10000 12000 14000 
Actual Catalyst Performance Actual Catalyst Performance

1.1

Oii l

d

0 80.9

1 Original expecte

d

deactivation for Wy 2

0.6 k/ko @ 16,000 hrs

0.60.70.80 30.40.5

Actual deactivation for Wy 2

0.10.20.3 0.45 k/ko

@ 6,800 hrs

0

0 2000 4000 6000 8000 10000 12000 14000 
Wygen 2 Catalyst Performanc

2 Catalyst Performanc

1.1

Original expected

Ko

0 80.9

1

Original expected

deactivation for Wy 20.6 k/ko @ 16,000 hrs

activity K/K

0.60.70.8

Catalyst

0 30.40.5

Actual Wy 2 deactivation with additive

Actual deactivation for Wy 2

0.10.20.3 y

0.45 k/ko @ 6,800 hrs

0

0 2000 4000 6000 8000 10000 12000 
Wygen 2 Performance with Addit

2 Performance with Addit
Wygen 3 Performance without Ad

3 Performance without Ad

Coal Flow

Ammonia Flow

Catalyst DP
Observations

Ì Completed 13,000+ hours of continuous injection of additive

Ì With additive injection, the rate of deactivation slowed significan

staged combustion unit

Ì No negative impact observed on furnace or any back‐end equipm

Ì Worked well even with regenerated catalyst

Ì Universal app y licability independent of catalyst type and pitch

Ì Wygen 3 with same coal and same staged combustion following t

deactivation trend without the additive injection
Projections of Catalyst Life Projections of Catalyst Life

Ì Based on deactivation rate at Wygen 2 with additive injection, the 

catalyst life for different different scenarios: scenarios:

Unit No. of la

yers

End of life

activity

K/K

Expected

life

H

y K/Ko ours

Wy 3 no additive 2 0.43 16,000

W

y

2 with additive 1 0.6 16,000

Wy

2 with additive 2 0.6 24,000

Wy 2 with additive 3 0.6 36,000

Ì Significant improvement in life of catalyst can be achieved due to 

deactivation
How does a slower rate of deactivation benefit new or ex

• Extending life further with the same volume 

Parameter With additive WithouUnit size >650 MWe >65Inlet NO

x 0.26 0

Outlet NO

x 0.05 0

Slip

2 ppm

2 

Initial volume 680 m3 68

Expected life 26,000 16

No of change events in 20 years 6 
Blended Additive Developmen

Blended Additive Developmen

Ì Demonstrate reduction in gas phase phosphorus entering SCR an

simultaneous increase in Hg oxidation

Ì Demonstrate Hg emissions compliance with oxidation and remov

only

Ì Demonstrate same Hg oxidation using blended powder additive a

demonstrated using liquid bromine

Ì Developed

a blended additive (FeCo3+CaBr2) to achieve simultan

phosphorus reduction and Hg oxidation

Ì Tested at 300 MW PRB unit with SCR, CDS and bag house AQCS tr
Results of Hg Oxidation Test Results of Hg Oxidation Test

Day Additive Plant load Coal Hg in

% Stack 

MW lb/Tbtu Oxidized

Hg

@ air

heater

outlet

Hg inlb/Tbtu

outlet

1 Baseline 250 7 30 4.8 

2 liquid chlorine 250 8.1 51 1.8 3 liquid bromine 275 13 76 1.1 4 powder bromine 250 8.5 76 1.2 5 powder chlorine 150 13 71 1.8 
Observations from Blended Additive 

Observations from Blended Additive 

3⁄4 Overall higher

% Hg oxidation over baseline due to halogen inject

3⁄4 Similar

% Hg oxidation achieved by both liquid and powdered bro

injection

3⁄4 With bromine injection, stack Hg was at or below 1.2 lb/Tbtu com

set by MATS

3⁄4 Confirms the capability to achieve Hg compliance using SCR, CDS 

house without ACI injection

3⁄4 No increase in stack HCl and HBr emissions observed with injectio
Economic Benefits of Blended Add

Economic Benefits of Blended Add

3⁄4 Significant savings in compliance cost due to elimination

/ reduct

ACI

3⁄4 As the poisoning of catalyst is mitigated, Hg oxidation with haloge

achieve Hg emission compliance without carbon for long term

3⁄4 Additional revenue from sale of ash due to elimination of carbon

3⁄4 Reduction in ash disposal cost because of ash sale
Questions

mgadgil@bab