Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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I. Non-Low Rank Virgin Coal Standard

Interagency reviewers have concerns that the heat rate reported for Nucla Unit 001 is incorrect. As a result, Nucla Unit 

001 is not the single best performing source for Hg emissions. After discounting Nucla Unit 001, no clear single best 

performing source emerges to set the Hg emission limit for new units not burning low-rank, virgin coal. 

The Hg emission limit for new units should be informed by the $100 million mercury control program that was conducted

by DOE between 2001–2008. DOE found that 90% removal is achievable, cost-effective, and accomplishes deep 

reduction in mercury emissions.

Nucla Unit 001 is not the single best performing source for Hg emissions for units not burning low-rank virgin 

coal.

Reviewers are concerned that the heat rate reported for Nucla Unit 001 is inaccurate. The heat rate that was reported for 

the Nucla unit was 9,382 Btu/kWhi. Upon inspection, this heat rate appears too low for a relatively small (100 MW), 21-

year-old fluidized bed boiler. 

Since heat rates for existing coal units are widely available, reviewers performed a cross-check in an attempt to verify it. 

Using publicly available data from the U.S. Department of Energy’s (DOE) Energy Information Administration (EIA), a 

much higher heat rate was identified for the Nucla unit. The average heat rate from 2003 – 2011 was 12,080 Btu/kWh, 

according to EIA dataii. This heat rate was further verified using the power plant database available in Ventyx’s Energy 

Velocity suite. 

Reviewers have reviewed EPA's comment about gross vs. net heat rate and it is well taken. The heat rate reported to EPA 

by Nucla (9,382 Btu/kWh) is gross, while the heat rate we are citing (12,080 Btu/kWh) is net. The difference between 

gross and net heat rate lies in the parasitic power load at Nucla, which is unknown. While it is not possible to factor this

parasitic load into the calculations (since it wasn't reported), we can apply engineering judgment to determine if the 

difference between EPA's (gross) heat rate our (net) heat rate seems reasonable.

A recent study by NETL ("Cost and Performance Baseline for Fossil Energy Plants, Volume 3," 

http://www.netl.doe.gov/energy-analyses/baseline_studies.html) evaluated cost and performance of atmospheric CFBs 

very similar to Nucla. The pollution control configuration assumed for this study was identical to Nucla: fabric filter and

SNCR (no FGD, which has a large parasitic load). In this study, the difference between gross and net heat rates was 5%. 

We would expect the Nucla gross/net heat rate spread to be similar, or at the very least, close. However, the difference 

between EPA's (gross) heat rate our (net) heat rate is approaching 30%. This summary is shown in the table below. On 

this basis, we believe that an incorrect gross heat rate may have been reported to EPA, and this ultimately led to Nucla 

being identified as the single best performing source for Hg emissions.

Gross 

heat rate, 

Btu/kWh

Net heat 

rate, 

Btu/kWh

Percent 

Difference

CFB 

(NETL 

study)

8,347 8,770 5%

Nucla 9,382 

(EPA)

12,080 

(EIA, 

Ventyx)

29%
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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Nucla Unit 001 incorrectly identified as single best performing source for Hg emissions. Heat rates were used to convert 

mercury concentration from pounds per million Btu coal heat input to pounds per megawatt-hour of energy produced (a 

standard calculation used in the industry) according to the following conversion (the incorrect heat rate has been 

highlighted). The specific values that resulted in Nucla Unit 001 being identified as the single best performing source are 

used in the example calculation: 

5.3 × 10

 



×



10

×

,  

 ×

10h

h

= 5 × 10

 

h

The resulting mercury emission rate, 5 x 10-8 Lb Hg/MWh, identified Nucla Unit 001 as the single best performing source 

for coal units not burning low-rank, virgin coal. The other two incorrectly calculated emission rates are shown in Table 1

for reference. The highlighted value in Table 1 is the result that incorrectly identified Nucla Unit 001 as the single best 

performing source for coal units not burning low-rank, virgin coal.

Table 1 – Nucla Unit 001 Calculated Mercury Emission Rates.

Mercury Emitted, 

Lb/mmBtu

Mercury Emitted, Lb/MWh

5.3 x 10-9

5.0 x 10-8

6.0 x 10-95.6 x 10-8

9.9 x 10-99.2 x 10-8

Nucla Unit 001 native mercury removal as indicated is implausibly high. A cross-check on the mercury emissions shown 

in Table 1, using well-known and widely available information about mercury co-benefit capture, suggests that the Nucla 

unit should not be achieving the high degree of native mercury removal that was calculated by EPA.

Nucla Unit 001 burns bituminous coal, and is equipped with a fabric filter and selective non catalytic reduction system for 

NOx control. Based on this configuration, the native mercury removal is expected be in the range of 84-93%iii. However 

the co-benefit capture reported by the Nucla unit is in excess of 99.7% for all three data points collected (shown in Table 2

2). 

Reviewers find these figures to be implausibly high. Reviewers point out that DOE conducted a $100 million mercury 

control testing program at actual power plants from 2001 – 2008, and removal rates this high were never observed, even 

for coal units equipped with activated carbon injection (ACI). The removal rates indicated for Nucla Unit 001, which 

does not have ACI installed, do not seem reasonable when compared to published, well-documented native mercury 

removal rates.

Table 2 – Nucla Unit 001 Native Mercury Removal Summary

Inlet mercury, 

Lb/mmBtu

Outlet mercury, 

Lb/mmBtu

Percent native 

mercury removal

3.9 x 10-65.3 x 10-999.9%

3.9 x 10-66.0 x 10-999.8%

3.9 x 10-69.9 x 10-999.7%

After recalculating Nucla Unit 001, no clear single best performing source emerges to set the Hg emission limit for new 

units not burning low-rank, virgin coal. Having established that Nucla Unit 001 is a questionable choice for selection as 

the single best performing source, the remaining units are referred to and shown in Table 3. Spruance Genco 3A/B are 

discounted, for the same reason that EPA discounted Spruance Genco 2A/B. AES Greenidge Unit 4 retired on September 
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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21, 2012. Seward Units 1 and 2 should be discounted because they burn coal refuse, not virgin coal. Only a single data 

point exists for Roanoke Valley 1, and it is unclear how EPA treats a single or two points in their analysis.

Table 3 – Ranking Order for Single Best Performing Source, Units not Burning Low-Rank, Virgin Coal

Rank Unit Potential Issues

5,6 Spruance Genco 3A/B

Control technology and unit size are not representative 

of 2012 RACT/BACT/LAER technologies or sizes of 

utility units likely to be constructed in future.

7 AES Greenidge Unit 4 Retired on September 21, 20121

8 Seward Unit 1 Burns coal refuse, not virgin coal

9 Seward Unit 2 Burns coal refuse, not virgin coal

10 Roanoke Valley 1 Only 1 data point available

The Hg emission limit for new units should be informed by the $100 million mercury control field test program that was 

conducted by DOE between 2001 – 2008. DOE conducted extensive Hg removal testing on actual flue gas at a range of 

power plants. The host sites spanned a variety of coal types and boiler configurations, along with nearly every 

combination of pollution control technology that is currently being used in industry. The knowledge and experience 

gained as a result of the DOE program should be used to inform the Hg emission limit, based on the removal capability of 

the technology.

The Hg limit for new units should be based on 90% removal, in accordance with the capability of the technology. The 

comprehensive results of DOE’s mercury control program are shown in 

 

1

Letter from William R. Bady, Director of AEE2, LLC to Jaclyn Brilling, Secretary of NY State Public Service Commission dated 

September 18, 2012. This letter can be found at 

http://www.nyiso.com/public/webdocs/services/planning/planned_gen_retirements/Westover_Unit_8_Retirement_Notice_09-18-

12.pdf
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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Figure 1 and Figure 2. Although removal rates are dependent upon many factors including the coal being burned, sorbent 

type, and pollution control configuration, it is evident that 80-90% mercury removal is achievable. If it is assumed that 

new coal units are equipped with fabric filter (to comply with the filterable particulate matter emission requirement under 

MATS) and (wet or dry) FGD (to comply with the acid gas emission requirement under MATS), then 90% Hg removal 

appears achievable according to 
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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Figure 1 and Figure 2. 
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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Figure 1 – Untreated Activated Carbon Injection Performance Curvesiv

Figure 2 – Chemically Treated Activated Carbon Injection Performance Curvesiv

II. Form of the Standards

One substantial revision to the proposed rule we feel is appropriate is that both input and output based standards 

for new units should be provided as is the case for existing units under the MATS rule. Providing only output 

based standards combines efficiency requirements with emission limits unnecessarily complicating compliance.
Summary of Interagency Working Comments on Draft Language under EOs12866 and 

13563 Interagency Review. Subject to Further Policy Review.

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Factors unrelated to HAPS emissions and controls performance such as ambient temperatures, unit capacity 

factors (driven by power demand), and available fuel supply impact unit efficiency and should not be threats to 

compliance with MATS limits for new units.

III. RTI memo, Floor analysis 

Step 6 states: “This step was dependent on the quantity and type of data available in the record for the best performing 

source. If data from three or more stack tests were available for the best performing source, test averages (typically the 

average of 3 runs) were used in the MACT floor calculations. If data from less than three stack tests were available in the 

record (i.e., one or two stack tests were available), data from the individual test runs were used in the MACT floor 

calculations.”

In the case of Subcategory 2 for Mercury emissions (first entry on page 6), the new UPL was determined using 6 runs. It 

is unclear if the UPL was set based on the single best run, or if the average of these 6 runs was used. It seems from the 

methodology that the single best run was used because it has less than three tests, however there may be enough data in 6 

runs to justify using the average (give that the data is normally distributed). It should also be noted that this was the only 

emission limit that was lowered due to the revised calculation approach.

However, in other cases, test averages were used, which is stated as the average of the individual runs. It does not seem 

appropriate to average test runs when multiple tests are available and use a different method due to the lack of a specified 

number of test runs.

 

i UPL_Coal_Hg_Nucla_110612.xlsm

iihttp://www.eia.gov/beta/enerdat/#/topic/1?agg=2,0,1&fuel=vvg&geo=g&sec=g&freq=M&start=200101&end=201208&ctype=linech

art&maptype=0&rse=0

iii “Mercury Capture and Fate Using Wet FGD at Coal-Fired Power Plants,” Feeley et. al., U.S. Department of Energy/National Energy 

Technology Laboratory, August 2006

iv “An Update on DOE/NETL’s Mercury Control Technology Field Testing Program,” Feeley et. al., U.S. Department of 

Energy/National Energy Technology Laboratory, July 2008