MP244rev6

Impacts of Texas Lignite on SCR Catalyst Lif

Performance

2007 EPRI SCR Workshop

Pensacola, FL

November 12 to 14, 2007

Dave Broske

EPRI

Charlotte, NC

Bennett Jones

Luminant Power

Dallas, TX

Randy Smith

FERCo

Laguna Hills, CA
MP244rev6

2

Project Participants

y JEC, Inc. – Ed Cichanowiczy Sargent & Lundy – Raj Gaikwady Hitachi – Bill Grettay Luminant Power – Bob Wiemuthy Sandow SES – Brad Masek, Luis Cordova, David S
MP244rev6

3

Test Program Drivers

Program Objective: Develop knowledge of SCR cataly

performance and longevity to apply to full-size SCR 

on Texas lignite-fired units.

Regulatory Drivers: 2009 NOx CAIR; 2015 NOx CAIR; S

approval specifies SCR on Sandow 4; approved Oak Units 1 & 2 PSD permits requires SCRs (BACT)

With the exception of a limited number of units operati

Eastern Europe, essentially no experience with coaclassified as lignite. Eastern Europe units firing lignutilize a lignite-like coal primarily from Czechoslovathe ash, sulfur & silica contents do not reflect U.S. l

For both northern and Texas lignites, effectively no ex

to draw upon in the design of an SCR NOx control p
MP244rev6

4

Earlier Testing

Martin Lake “in-situ” test program – Report 1004732 De

y Mini-reactor testing performed in May 2002 thro

2003

y Showed no significant issues with maintaining a

over ~ 14 months for both honeycomb and plate samples

y Only 4” x 4” catalyst cross sectiony Lignite/PRB blend

In-situ results validated moving to pilot-scale SCR sys

slipstream reactor
MP244rev6

5

Test Program Overview and Design Parame

y One-year test period on 100% Texas Lignite firingy One catalyst layer; focus on simulating catalyst ero

poisoning with catalyst activity measured intermitte

y Reactor sized to minimize the deposition and accum

of ash adjacent to the reactor wall

y Downward flow direction; controlled flue gas extrac

rate (through the use of both bypass and isolation vcapability of reducing flue gas temperature at the ex

point and a venturi to monitor flow rate

y Monthly in-situ activity measurementsy Physical samples collected at 6 and 12 months for v

analysis

y Hg and SO3 oxidation measurements at 1, 6 and 12 
MP244rev6

6

Host Site 

Sandow Steam Electric Station Unit 4 y Twin-furnace, tangentially-fired, CE unity Originally 575MW, later upgraded to 640 MWy Started operation 1980 y ESP and limestone scrubbery Spring 2010 full-scale SCR

y Year-round operationy Two reactorsy 3 + 1 configuration
MP244rev6

7

Slipstream Overview 

y Sargent & Lundy Catalyst sectioy Single catalyst 

1 meter in lengt

y Flue gas flow ~

(velocity ~13 ft/

y Driving force p

heater pressure 

y Active control o

flow rate

y LPA screen on 
MP244rev6

8

Inlet Scoop and LPA Screen
MP244rev6

9

Reactor Inlet Ductwork

y Horizontal duct f

scoop 7 in x 24 i

y Inlet gas sample 

and ammonia inj

y Expansion to 24 
MP244rev6

10

Reactor Housing 

y Sootblowersy Large catalyst loading y Small inspection dooy Inlet & outlet samplin

Hg and SO3 oxidation 
MP244rev6

11

Slipstream Reactor Control System 

y Automatic control of 

rate and temperature

y Automatic shutdown 

triggers based on Saload

y Automatic catalyst s

backpurge cycles

y Mass flow controller 

injection 

y 2-stream (inlet/outlet

analysis system (NO

monitoring catalyst a

y Full access for contr

remote activity testininternet/VPN connec
MP244rev6

12

Control System User Interface
MP244rev6

13

Fly Ash Deposition Issues

Catalyst conditioinstallation

Typical condition found after shutting reactor down for inspection
MP244rev6

14

Splitter Vanes and Sootblowers Above Cata

Condition upon i

Typical condition foshutting reactor dowinspection

y Note deposits accumulated on 

surfaces above catalyst

y Sootblowers found to be 

ineffective in clearing deposits after a host unit outage
MP244rev6

15

Sootblowers

y Original design had the sootblowers positioned 48 inches 

the catalyst surface, with 1/8” diameter jets

y Pilot-scale performance showed this design to be ineffecty Numerical (EPRI) and cold-flow (FERCo) modeling studies 

performed to redesign the sootblowers

y Distance above the catalyst was reduced to 18 inchesy Jet diameter was increased to 3/8”

y Marked increased effectiveness in clearing surface depos

host unit outage
MP244rev6

16

Catalyst Cleaning and Sampling: 10/4/07

y All eight modules remove

cleaned with compressed 

y Sample plates removed fr

modules, for analysis by v

y After cleaning and 

reassembly, catalyst pressure drop was reduced from ~1.25” H2O to ~0.48”

H2O (close to that when 

new)
MP244rev6

17

Catalyst Pressure Drop Trends

Catalyst 

Sootblowers installed

Catalyst plugg
MP244rev6

18

Activity Test Protocol 

Reactor Potential = -ln(1- ∆NO)

Sandow Unit 4 Pilot SCR 3/2/07

0

102030405060708090

100

0.0 0.5 1.0 1.5 2.0

NH3/NO

NO Removal (%)

y Measure NO re

function of NH3 

rate

y Calculate RP fr

maximum NO r

y RP calculation 

both K/K0 and b

y K = -AV·ln(1- ∆N

y Need geometric 

of catalyst to cafrom NO remov
MP244rev6

19

Reactor Potential Results

RP/RP0 Versus Catalyst dP Over Eight Months of Ope

y After 5 month

RP/RP0 down 

has doubled t

y At 3500 hours 

catalyst pluggclimbs to 1.1” 

drops to 0.5

y After catalyst 

hrs) dP was reH2O and RP/R

0.88

y Majority of ini

was due to pluthan catalyst d

y Currently at 5

RP/RP0 = 0.77 

Sandow Unit 4 Pilot SCR

0.00.20.40.60.81.01.2

0 1000 2000 3000 4000 5000 6000

Operating Hours

RP/RPo, Catalyst dP ("H2O) RP/RPo

Catalyst dP
MP244rev6

20

Summary

y Deposition of fly ash accumulated on surfaces abov

catalyst has been an issue after host unit outages

y Initial sootblower design proved to be ineffective in 

surface deposits from catalyst

y Redesigned sootblower system showed marked inc

effectiveness

y However, significant catalyst plugging had already o

and physical cleaning of the modules was necessar

y After cleaning:

y Catalyst pressure drop was reduced to the level 

installed in March (~0.48” H2O)

y RP/RP0 increased dramatically from 0.50 to 0.88

y Testing is continuing