Field Testing o

Activated Carbon Inj

Options for Mercury Co

TXU’s Big Brown St

John Pavlish

Energy & Environmental Resear

DOE NETL Mercury Control Technology 

December 13, 2006

Pittsburgh, Pennsylvania
Acid Gas Solutions

A Lhoist Group Company

Project Participan

Project Participan
December 2006 3

Big Brown Power Station Big Brown Power Station, 
December 2006 4

Big Brown Unit Inform

Big Brown Unit Inform

Big Brown Station, Freestone County, near 

• Plant capacity: Approximately 1200 MW 

capacity with two 600-M

• Test unit: Tested one-quarter of B

baghouse Module 2-4 (

• Boiler type: Tangentially fired with e

feeders per unit

• Typical fuel: 70% Texas lignite–30% • SO2 control: None• NOx control: Low-NOx burners• Particulate 

control: COHPACTM configurat
December 2006 5

Field Testing Object

Field Testing Object

• Establish baseline Hg concentrations and sp

FF 2-4.

• Screen control technologies with short-durati

tests, including ACI-only, enhanced ACI, and 

• Perform a monthlong test with the most prom

and evaluate long-term Hg capture and balan(BOP) issues.

70% Lignite–30% Powder River Bas

• Establish baseline Hg concentrations and sp

FF 2-4.

• Parametric tests, including ACI-only and enh

100% PRB (under separate project)
Mercury Control Options 

Mercury Control Options 

Big Brown Configurat

Big Brown Configurat

TXU’s Big Brown Unit –

S

a

mpli

ng Locations

1) Coal: H

g, Cl, Pro

x./Ult., Heating Val

u

e

2a) Ash: H

g, Cl, LOI, C

2b) Ash: H

g, Cl, LOI, C

3) ESP Inlet Flue Gas: OH

4) Bag

h

o

u

se Inlet Flu

e 

5) Bag

h

o

u

se Outlet Flu

6)

A

CI and Additiv

e In

Coal

Bunker

Feeders

(8)

Pulverizers

(8)

Air

Heaters

ESPs

ID Fans

Fabric 

1

3

4

2a

6

Additive

Standard AC

&

Treated/Enhanced AC

2b

Unit 2 

Boiler

Side B ~ 300 Mw

FF4 ~ 150 Mw
December 2006 7

Baseline Coal Compar

Baseline Coal Compar

70–30 Blend and 100% PRB 

30 Blend and 100% PRB 

Nominal

70–30 Blend * 

Hg, ppm (dry) 0.287 Cl, ppm (dry) 17** Moisture, % 31.17 Ash, % 9.91 Sulfur, % 0.68 Heating Value, Btu/lb 7531 Fd, dscf/106 Btu 9729 Hg, μg/dNm3, 3% O2 37.01 

All values on an as-received basis unless otherwise noted.* Assumed ratio based on plant information.** Single value.
December 2006 8

Baseline* Hg Speciation for 7

Baseline* Hg Speciation for 7

Average of 1/18/06, 1/19/06, and 

Average of 1/18/06, 1/19/06, and 

Coal Inlet OH Inlet CMM Outlet OH 

0

102030405060

Mercury Concentration, μg/dNm3 (3% O2)

 Coal Based OH Particulate-b OH Oxidized Hg OH Elemental H CMM Total Gas 

* Measurement taken at inlet and outlet of FF2-4.
December 2006 9

Baseline* Hg Speciation for 

Baseline* Hg Speciation for 

Average of 3/30/06, 3/31/06, and 

Average of 3/30/06, 3/31/06, and 

Coal Inlet OH Inlet CMM Outlet OH 

0

102030

Mercury Concentration, μg/dNm3 (3% O2)

 Coal Based OH Particulate-bo OH Oxidized Hg OH Elemental Hg CMM Total Gas P

* Measurement taken at inlet and outlet of FF2-4.
December 2006 10

Parametric Results Sum

Parametric Results Sum

70–30 Blend 30 Blend

0123456

0

102030405060708090

100

% Hg Removal across FF 2-4

Sorbent Feed, lb/Macf

 AC Component of AC Enhanced AC AC Only Total AC and SEA4
December 2006 11

Comparison of Parametric 

Comparison of Parametric 

70–30 Blend and 100% 

30 Blend and 100% 

0123456

0

102030405060708090

100

% Hg Removal across FF 2-4

Sorbent Feed, lb/Macf

 100% PRB, Enhance 70/30 Blend, Enhanc 70/30 Blend, AC On 100% PRB, AC Only
December 2006 12

Comparison of Blend and PRB H

Comparison of Blend and PRB H

(based on CMM data) (based on CMM data)

FF 2-4

Inlet

μg/dNm3,

3% O2

FF 2-4

Outlet

μg/dNm3,

3% O2

FF 

Rem

%

Blend Baseline 23.3 26.0 0 PRB Baseline 7.2 8.4 0 Blend withEnhanced AC*

18.1 5.1 7

PRB withEnhanced AC*

8.5 1.6 8

* Enhanced AC rate was 1.5 lb/Macf
December 2006 13

Comparison of Blend Param

Comparison of Blend Param

to Gaston Results to Gaston Results

0123456

0

102030405060708090

100

 Gaston AC Only (Norit  TXU-BB Enhanced AC TXU-BB AC Only TXU-BB AC+SEA4

% Hg Removal across FF 2-4

Sorbent Feed, lb/Macf
December 2006 14

Monthlong Monthlong Test Ratio

Test Ratio

Enhanced ACI at a target rate of 1.5 l

following) was selected for the monbecause it had a favorable balance following factors:

• Hg removal goals, parametric testin

>55% capture was possible.

• Preliminary economics based on so

consumption and equipment needs

• Reducing plant impacts by minimiz

quantity of injected sorbent. Could when dP was below 10 in. W.G.
December 2006 15

Hg Sampling Throughout Hg Sampling Throughout Mon

Mon

Coal, OH, and CMM, 70 Coal, OH, and CMM, 70–30 

30 

0

102030405060

Mar 16-17 Mar 20-22 A

CMM Out

OH Out

Coal

CMM In

OH In

Mercury Concentration, μg/dNm3 (3% O2)

 Coal Based OH Particulate OH Oxidized  OH Elementa CMM Total Ga

Coal

OH In

CMM In

OH Out

CMM Out

Coal

OH In

CMM In

OH Out

CMM Out

Coal

Feb 27-Mar 1

Hg Control:1.5 lb/MacfEnhanced AC
December 2006 16

Big Brown Field Testi

Big Brown Field Testi

Balance Balance-of-Plant (BOP) Is

Plant (BOP) Is

• Bag Blinding—Following Hg field testing

drag across FF 2-4 had reached a point wnot confident in its performance for the upsummer season; therefore, the plant initiareplacement of FF 2-4 in May 2006. Becaconfounding factors, the exact cause is sinvestigation.

• Plugged Hoppers/Deposits—During the 

was discovered that two of the eight hoppand H) on FF 2-4 were plugged and filled these two hoppers, unusual deposits werwith the loose ash, which was reported to and smoldering.
December 2006 17

Th

Access Door
December 2006 18

Hoppers C and H Hoppers C and H – Ash 

Ash 

• When opened for the bag 

change, both Hoppers C and H were completely full of ash to a height above the access door.

• The operators did note that 

ash had collected in the inlet duct and was probably at least to that level and, therefore, completely filling the bottom cone.

• They did not think ash 

contacted the bags since that would require the entire inlet duct to become blocked.

Bag 

Possible As
December 2006 19

Conclusions Conclusions

Big Brown Hg Field Tes

Big Brown Hg Field Te

• Under baseline test conditions, mercury capture a

baghouse is effectively zero for both the 70–30 bPRB.

• Both the AC+SEA4 and enhanced AC options pe

AC alone. Testing showed that >70% capture couwith rates lower than 2 lb/Macf.

• Hg removal efficiencies were similar for the 70–30 

PRB, but emissions were much lower with the PRlower Hg-in-coal content.

• Month-long testing with the enhanced AC showed 

removal greater than 70%, however, there were finterruptions in the ACI feed and the ACI equipme

steady state conditions with the target ACI rate of average removals were greater than 80%.

• The narrow and limited operating margin of the C

pressure proved to be the limiting factor for applyinjection at Big Brown. Short term tests were succ

long-term sustainable ACI operation, substantial 

plant are required to provide a greater operating m
December 2006 20

Conclusions Conclusions

Big Brown Balance of Plan

Big Brown Balance of Plan

• The residual drag across FF 2-4 appears to have 

amount that was unexpected based on past expe

investigation into the root cause is still underway operating conditions as well as the effects of sorb

• The plugged hoppers and the associated deposit

result of the hopper heaters being off for compartThe heaters being off likely led to formation of deeventually grew to a size large enough and strong hopper C and H discharge. Subsequently, this led of ash and AC of adequate quantity to promote se

eventual ignition. The deposits are a mix of hydraheated to varying degrees, and ash sintered with 

smoldering ash-AC mixture. More work is needed exact mechanism of self ignition and conditions uoccur.