1
Memorandum
and
attachment
from
W.
Maxwell,
EPA/
CG,
to
Utility
MACT
Project
Files,
December
2003.
Power
plant
efficiency
table.
TO:
Bill
Maxwell,
U.
S.
Environmental
Protection
Agency,
OAQPS
(
C439­
01)

FROM:
Jeffrey
Cole,
RTI
International
DATE:
December
2003
SUBJECT:
MACT
Floor
Unit
Conversion
from
Input­
based
Standard
to
Output­
based
Standard
in
the
Proposed
National
Emission
Standards
for
Hazardous
Air
Pollutants;
and,
in
the
Alternative,
Proposed
Standards
of
Performance
for
New
and
Existing
Stationary
Sources:
Electric
Utility
Steam
Generating
Units
Since
all
the
reported
data
obtained
throughout
the
development
of
the
proposed
rule
are
in
the
current
input­
based
format
of
pounds
per
trillion
British
thermal
units
(
lb/
TBtu)
heat
input,

EPA
applied
an
efficiency
factor
to
the
current
format
to
develop
the
output­
based
HAP
limits
(
pounds
per
megawatt­
hour;
lb/
MWh).
The
efficiency
factor
approach
was
selected
because
the
alternative
of
converting
all
the
reported
data
in
the
database
to
an
output­
basis
would
require
extensive
data
gathering
and
analyses.
Applying
a
baseline
gross
efficiency
would
essentially
convert
the
selected
heat
input­
based
HAP
level
to
an
output­
based
emission
limit.

The
output­
based
standard
must
be
associated
with
a
baseline
efficiency.
Most
existing
electric
utility
steam
generating
plants
fall
in
the
range
of
24
to
35
percent
efficiency1.
However,

newer
units
operate
around
35
percent
efficiency;
therefore,
35
percent
was
selected
as
the
baseline
efficiency
for
new
units;
32
percent
was
selected
as
the
baseline
efficiency
for
existing
units.
2
Memorandum
and
attachments
from
W.
Maxwell,
EPA/
CG,
to
Utility
MACT
Project
Files,
November
26,
2003.
Analysis
of
variability
in
determining
MACT
floor
for
coalfired
electric
utility
steam
generating
units.
2
The
efficiency
of
electric
utility
steam
generating
units
usually
is
expressed
in
terms
of
heat
rate,
which
is
the
ratio
of
heat
input,
based
on
higher
heating
value
(
HHV)
of
the
fuel,
to
the
energy
(
i.
e.,
electrical)
output.
The
heat
rate
of
a
utility
steam
generating
unit
operating
at
32
percent
efficiency
is
11.3
joules
per
watt
hour
(
10,700
Btu
per
kilowatt
hour;
Btu/
kWh);
the
heat
rate
for
units
operating
at
35
percent
efficiency
is
10.3
joules
per
watt
hour
(
9,800
Btu/
kWh).

Equation
1.
Conversion
factor
for
Hg
or
Ni
from
TBtu
to
lb/
MWh
for
Existing
Sources
1
TBtu/
1,000,000,000,000
Btu
*
3.414
Btu/
W­
h
*
1,000,000
W­
h/
MW­
h
*
(
1/
0.32)
=
10.7
x
10­
6
TBtu/
MW­
h
Equation
2.
Conversion
factor
for
Hg
or
Ni
from
TBtu
to
lb/
MWh
for
New
Sources
1
TBtu/
1,000,000,000,000
Btu
*
3.414
Btu/
W­
h
*
1,000,000
W­
h/
MW­
h
*
(
1/
0.35)
=
9.8
x
10­
6
TBtu/
MW­
h
Existing
coal­
fired
electric
utility
units
have
to
meet
a
MACT
floor
based
on
the
top
12
percent
of
the
bituminous
coal­
fired
data
(
4
units),
the
top
12
percent
of
the
subbituminous
coal­
fired
data
(
4
units),
the
top
5
lignite­
fired
units,
the
top
2
refuse
coal­
fired
units,
and
the
top
2
IGCC
units.
The
average
is
adjusted
for
variability
and
a
confidence
interval
of
97.5
percent.
2
This
MACT
floor
limit
is
then
converted
from
input­
based
standard
(
lb/
TBtu)
to
output­
based
standard
(
lb/
MWh)
by
multiplying
by
10.7
x
10­
6.

Newly
constructed
coal­
fired
electric
utility
units
have
to
meet
a
MACT
floor
based
on
the
top
unit
in
all
coal
ranks
or
process
types.
This
top
unit
is
the
unit
with
the
lowest
emission
level
after
adjusting
for
variability
and
a
confidence
interval
of
97.5
percent.
This
MACT
floor
limit
is
then
converted
from
input­
based
standard
(
lb/
TBtu)
to
output­
based
standard
(
lb/
MWh)
by
multiplying
by
9.8
x
10­
6.
