Document ID: EPA-HQ-OAR-2009-0234-19980
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2011-12-21T05:00Z

Date:	September 30, 2011

Subject:	National Emission Standards for Hazardous Air Pollutants
(NESHAP) for Coal- and Oil-Fired Electric Utility Steam Generating Units

Response to Comments Regarding Inaccurate Heat Rates in MACT Floor
Analysis

From:	Shelly Johnson

To:	William Maxwell

OAQPS/SPPD/ESG (D243-01)

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

Background

The EPA proposed National Emission Standards for Hazardous Air
Pollutants (NESHAP) for Coal- and Oil-Fired Electric Utility Steam
Generating Units (EGUs) on May 3, 2011.  The public comment period ended
on July 5, 2011.  The Electric Power Research Institute (EPRI) commented
on the unit heat rates used in the maximum achievable control technology
(MACT) floor analysis. They stated, “Heat rates were calculated
incorrectly for 53 EGUs listed in the MACT floor spreadsheets. These
errors resulted in emissions on a pound per megawatt-hour (lb/MWh) basis
that are two to six times too low. EGUs affected by this error include
several identified as lowest emitting in the MACT floor spreadsheets.”
In addition to this comment, EPA has received other comments indicating
that the heat rates used to convert emissions on a lb/MMBtu basis to a
lb/MWh basis are not realistic.

This memorandum addresses the work done to identify facilities with heat
rates that appear to be inaccurate, and to revise that information in
the EGU MACT Information Collection Request (ICR) database.

Discussion

The heat rates used in the MACT floor analysis are calculated based on
data provided by each company in response to the EGU MACT ICR. The
boiler information table contains detailed boiler-specific operating
parameters for each boiler at a facility. These parameters include the
present maximum heat input (MMBtu/hr) and summer gross generating
capacity (MWe). These company-provided parameters are used to calculate
the heat rate for each boiler. The heat rate is calculated by dividing
the maximum heat input by the summer gross generating capacity to obtain
a heat rate in units of MMBtu/MWh. 

Most boilers have a calculated heat rate between 8 and 14 MMBtu/MWh. The
boilers with calculated heat rates lower than 8 MMBtu/MWh, and plants
with multiple boilers serving one generator were reviewed to confirm the
maximum heat input and summer gross generating capacity values that were
provided in response to the ICR.

The most common reason for the low calculated heat rates is that the
generation values for the turbine generator were entered for each boiler
that supplies steam to the generator. For instance, if twin boilers
provide steam to a single turbine generator that produces 200 MW of
electricity, each boiler is (ostensibly) responsible for one-half of the
electricity generated. Therefore, the summer gross generating capacity
value should have been reported as 100 MWe for each boiler; however, in
many cases the full 200 MW was entered as the capacity for each boiler. 

Conclusion

In total, 25 facilities were contacted to confirm the maximum heat
inputs and gross generating capacities of 59 boilers. All of the 53
units EPRI suggested are included in the 59 boilers that were corrected.
For the 11 facilities that did not respond to our request for additional
information, the heat inputs and generating capacities were revised
based on information included in the NEEDS database (v4.10).  The
original values from the ICR response and the corrected values are shown
in Attachment 1, Table A-1. All revisions have been made in the ICR
database and will be reflected in future outputs of the MACT floor data.



ATTACHMENT 1

Table A-  SEQ Table \* ARABIC  1 : Boilers with corrected maximum heat
inputs and summer gross generating capacities.

  PAGE   \* MERGEFORMAT  2