utility mact working group
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Utility MACT Working Group. Negative Removals -- A Review Bill Maxwell, OAQPS/ESD. Purpose. To present a review of test reports from units showing negative mercury removals during ICR speciated mercury emissions tests Not to definitively answer all questions. Background - All tests. - PowerPoint PPT PresentationTRANSCRIPT
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Utility MACT Working Group
Negative Removals -- A Review
Bill Maxwell, OAQPS/ESD
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Purpose
To present a review of test reports from units showing negative mercury removals during ICR speciated mercury emissions tests
Not to definitively answer all questions
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Background - All testsNegative mercury removals were
indicated at 31 test sites when calculated either from coal-to-stack or across the tested control device 12 sites showed negative removals only
when calculated from coal-to-stack Because of differences in test
methodologies, for this analysis, this is not a calculation that we feel should be used
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General theories -- coal to stackRepresentativeness of sample
For some sites, coal analyses during testing did not match similar ICR analyses for surrounding period
Method and location of sample acquisition different than that for ICR samples
Timing of coal sampling vs. when that flue gas gets to stack sample train
Does not negate usefulness of coal-to-stack analyses overall
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Background -- Control device only19 remaining test sites indicated negative
removals across the tested control device Reviewed each test report in greater detail Cannot definitively say “here is the reason”
for any site Have plausible theories for most sites that are
felt to reasonably account for, or at least contribute strongly to, the negative removalsSome sites fall under more than one theory
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General theories - control device
Coal typeLow level of mercury presentNormal sampling distribution around
“0”Use of hot-side ESPSampling locationsTest/analytical method problems
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Coal type15 of the 19 sites burned
subbituminous or lignite coals Generally have higher proportion of
elemental mercury in flue gas Not expected to be removed Subject to loss during sample handling
Ontario-Hydro method has been modified to add stabilizer to permanganate solution that inhibits loss of elemental mercury
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Low level of mercury presentOntario-Hydro method validated at 2 ug/m3
For units having emissions near this level (may vary somewhat between labs), small variations in numerical measurements lead to large variations in percentages
Indicates care must be taken in use of significant figures and in precision of any standard
Also creates problems with non-detect values
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Normal sampling distribution around “0”Normal variability in sampling would
lead one to expect a distribution of results around any value When that value is “0” -- normal distribution
may indicate negative removals Normal sampling/analytical variability in
each sample exacerbates problem more at low removal levels than at higher removal levels
Would apply to coal-to-stack values also
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Example for tests with +/- 30% error: Poor mercury control
Gas concentrations, ug/dscminlet outlet
30% high 13 13average 10 1030% low 7 7
There are nine combinations for these 6 values above Gas concentrations, ug/dscm
inlet outlet % control1 13 13 0.0%2 10 13 -30.0%3 7 13 -85.7%4 13 10 23.1%5 10 10 0.0%6 7 10 -42.9%7 13 7 46.2%8 10 7 30.0%9 7 7 0.0%
This example illustrates that negative reported values of percent removal are expected when there is poor mercury control in the unit.
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Example for tests with +/- 30% error: Good mercury control
Gas concentrations, ug/dscminlet outlet
30% high 13 1.3average 10 130% low 7 0.7
There are nine combinations for these 6 values above Gas concentrations, ug/dscm
inlet outlet % control1 13 1.3 90.0%2 10 1.3 87.0%3 7 1.3 81.4%4 13 1 92.3%5 10 1 90.0%6 7 1 85.7%7 13 0.7 94.6%8 10 0.7 93.0%9 7 0.7 90.0%
This example illustrates that negative reported values of percent removal are not expected when there is good mercury control in the unit.
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Use of hot-side ESP
5 of 19 units utilized hot-side ESP controls Not expected to exhibit effective
mercury removal due to relatively high temperatures
Adds to problem of normal distribution of data around “0” removal
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Sampling locationSeveral sites had multiple inlet and/or
scrubber by-pass configurations Multiple modules for control devices complicate
inlet duct configurations and sampling locationsInlet sites in general were less adequate than outlets
Scrubber by-pass to meet SO2 requirements May be biasing the inlet data +/- Indicates that “percent removal” format may not
be appropriate if taken across control
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Test/analytical method problemsOntario-Hydro, at the time of testing,
was a new test method with few testing or analytical firms familiar with its use Is not an “easy” method and requires strict
adherence to procedures, QA/QC, etc. Some test contractors indicated problems
with blank levels, lost samples (dropped impingers, etc.), etc.
Sample hold times sometimes exceeded
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How the theories fit the units
Following slides fit tested sites to the theories noted earlier
Some sites fit more than one theoryGenerally cannot say “Eureka”
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Negative removal coal to stack only Cliffside Unit 1 Clifty Creek Unit 6 Columbia Unit 1 Gibson Unit 3 (both
sets of tests) Leland Olds Unit 2 Limestone Unit LIM1
Navajo Unit 3 Newton Unit 2 Rawhide Unit 101 Sherburne County
Unit 3 Stanton Station Unit
10 Wyodak Unit BW91
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Coal type
Big Brown Unit 1Cholla Unit 2Cholla Unit 3Clay Boswell Unit 4Colstrip Unit 3Coronado Unit U1BGeorge Neal South
Unit 4GRDA Unit 2
Laramie River Unit 3Lawrence Unit 4Monticello Unit 1Nelson Dewey Unit 1Platte Unit 1Sam Seymour Unit 3Stanton Station Unit 1
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Low level of mercury present
Bay Front Unit 5 . . . . . Cholla Unit 3. . . . . . . .Clay Boswell Unit 4 . . .Coronado Unit U1B . . .Laramie River Unit 3 . .Lawrence Unit 4 . . . . .Nelson Dewey Unit 1 .Presque Isle Unit 9 . . .Valley Unit 2. . . . . . . .
2.5 - 4 ug/m3
1 - 2 ug/m3
5 - 6 ug/m3
2.5 - 3 ug/m3
2.5 - 3.5 ug/m3
~5 ug/m3 (+ non detects)2 - 3 ug/m3
1 - 2 ug/m3
1 - 2 ug/m3
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Normal sampling distribution around “0” GRDA Unit 2 . . . . . . . . . . . . . . . . . Lawrence Unit 4. . . . . . . . . . . . . . . Platte Unit 1 . . . . . . . . . . . . . . . . . Big Brown Unit 1 . . . . . . . . . . . . . . Cholla Unit 2 . . . . . . . . . . . . . . . . . Coronado Unit U1B. . . . . . . . . . . . . Nelson Dewey Unit 1. . . . . . . . . . . . Presque Isle Unit 9 . . . . . . . . . . . . . Stanton Station Unit 1. . . . . . . . . . . Valley Unit 2. . . . . . . . . . . . . . . . . .
+18 to - 24% - 2 to - 34%+27 to - 33%+ 1 to - 13%+23 to - 33% - 11 to - 21%+ 2 to - 23%+ 0 to - 6%+ 2 to - 9%+ 6 to - 25%
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Use of hot-side ESP
Cholla Unit 3Gaston Unit 1Nelson Dewey Unit 1Platte Unit 2Presque Isle Unit 9
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Sampling locations
Big Brown Unit 1Clay Boswell Unit 4Colstrip Unit 3Coronado Unit U1B
(scrubber by-pass)George Neal South
Unit 4
Laramie River Unit 3
Lawrence Unit 4Sam Seymour Unit
3 (also scrubber by-pass)
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Contractor/method problems Bay Front Unit 5 . . . . . . . .
Cholla Unit 2. . . . . . . . . . . Cholla Unit 3. . . . . . . . . . . Gaston Unit 1 . . . . . . . . . . George Neal South Unit 4. . Laramie River Unit 3 . . . . .
Reported “suspect” elemental data for 2 of 3 of outlet runsNumerous problemsNumerous problemsPossible sample hold problemPossible bad test runPossible sample hold problemProbable bad test run
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ConclusionsNegative removals are expected for
some tests on units with poor mercury removal Negative removals are primarily a
combined function ofActual low removal efficienciesInherent variability in test and analytical
procedures Other factors may also be involved but
believed to be of lessor importance
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Conclusions - MoreNegative removals are not expected
for tests on units with good mercury removal Test data with good mercury removal
used for setting emission standardsAdditional testing would not impact final
MACT levels
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So where does this leave us...Ontario-Hydro method is not inherently
flawed Nothing in the data to so indicate Modifications have been made to stabilize
elemental mercury in permanganate solution Data do indicate caution in setting level of
standardTruly positive removal numbers are validMercury is not being generated
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Examples
Laramie River Unit 3Coronado Unit U1B
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Laramie River Unit 3Uses subbituminous coalSample storage conditions (~20 °C) and
holding times (> 45 days) may have been violated prior to analysis
Low mercury valueMultiple inlet ductsOne inlet run considerably different from
5 other runs at same or similar site
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Laramie River Unit 3 -- cont.Inlet concentration,
ug/ dscmOutlet concentration,
ug/ dscmLaramie River Unit 1: 1 4.593 2.835
Laramie River Unit 1: 2 5.055 3.501
Laramie River Unit 1: 3 4.562 3.286
Laramie River Unit 3: 1 0.389 2.368
Laramie River Unit 3: 2 5.263 2.761
Laramie River Unit 3: 3 5.621 3.281
Laramie Units 1 and 3 are same type of boiler, burn the same coal, and in similar quantities
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Coronado Unit U1B
Uses subbituminous coalLow mercury valueUses scrubber by-pass as part of SO2
control Sampled inlet upstream of by-pass duct Sampled outlet upstream of by-pass duct Actual impact on percent removal
calculations is unknown
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List of Units Exhibiting Negative Removals Across Control or Coal-to-Stack
Facility/ Unit Coal type Control Removal coal-to-stack, %
Removal acrosscontrol, %
Bay Front 5 Bit Mech collector -47.4 -57.1
Big Brown 1 Lignite CSESP/ FF 10.0 -8.1
Cholla 2 Sub Wet scrub 24.5 -4.4
Cholla 3 Sub HSESP 64.2 -36.3
Clay Boswell 4 Sub Wet scrub 11.4 -21.9
Cliffside 1 Bit HSESP -12.4 30.4
Clifty Creek 6 Sub HSESP -30.5 34.0
Colstrip 3 Sub Wet scrub 14.7 -7.8
Columbia 1 Sub HSESP -25.2 12.0
Coronado U1B Sub Wet scrub 30.6 -15.2
Gaston 1 Bit HSESP -40.0 -17.2
George Neal South 4 Sub CSESP 21.9 -9.6
Gibson 3 (both sets of tests) Bit CSESP -201; -16.9 5.0; 35.7
GRDA 2 Sub SDA/ CSESP -1.0 -2.8
Laramie River 3 Sub SDA/ CSESP 70.4 -78.5
Lawrence 4 Sub Wet scrub -23.2 -17.4
Leland Olds 2 Lignite CSESP -12.8 4.9
Limestone LIM1 Lignite Wet scrub -7.5 51.0
Monticello 1-2 Lignite Fabric filter -20.4 -21.3
Navajo 3 Bit Wet scrub -20.5 21.0
Nelson Dewey 1 Sub HSESP 55.6 -9.0
Newton 2 Bit CSESP -19.2 8.2
Platte 1 Sub HSESP -67.5 -2.9
Presque Isle 9 Bit/Pet coke HSESP 9.9 -3.6
Rawhide 101 Sub SDA/FF -25.6 31.8
Sam Seymour 3 Sub Wet scrub 56.2 -20.3
Sherburne County 3 Sub SDA/FF -9.7 4.5
Stanton 1 Lignite CSESP 44.1 -3.6
Stanton 10 Lignite SDA/FF -7.0 1.5
Valley 2 Bit FF -109 -6.8
Wyodak BW91 Sub SDA/ CSESP -144 43.5