1
MEMORANDUM
DATE:
February
19,
2004
SUBJECT:
Selection
of
Operating
Parameters
for
the
Stationary
Reciprocating
Internal
Combustion
Engines
Final
Rule
FROM:
Tanya
Ali
Alpha­
Gamma
Technologies,
Inc.

TO:
Sims
Roy,
EPA
OAQPS
ESD
Combustion
Group
On
December
19,
2002,
EPA
proposed
national
emission
standards
for
hazardous
air
pollutants
(
NESHAP)
for
stationary
reciprocating
internal
combustion
engines
(
RICE)
(
67
FR
77830).
In
the
proposed
rule,
EPA
specified
that
sources
had
to
meet
certain
operating
limitations,
in
addition
to
meeting
emission
limitations.
The
EPA
received
several
comments
on
the
proposed
rule
from
industry.
In
general,
industry
was
opposed
to
the
type
and
level
of
operating
limitations
proposed
by
EPA.
The
purpose
of
this
memorandum
is
to
document
information
supporting
EPA's
selection
of
operating
parameters
and
operating
limitations
for
the
stationary
RICE
final
rule.

Operating
Limitations
Proposed
Operating
Limitations
For
existing,
new,
and
reconstructed
4
stroke
rich
burn
(
4SRB)
engines
complying
with
the
requirement
to
reduce
formaldehyde
emissions
by
75
percent
or
more
using
non­
selective
catalytic
reduction
(
NSCR),
EPA
specified
that
sources
had
to:

(
1)
maintain
their
catalyst
so
that
the
pressure
drop
across
the
catalyst
does
not
change
by
more
than
2
inches
of
water
from
the
pressure
drop
across
the
catalyst
measured
during
the
initial
performance
test;

(
2)
maintain
their
catalyst
so
that
the
temperature
rise
across
the
catalyst
is
no
more
than
5
percent
different
from
the
temperature
rise
across
the
catalyst
measured
during
the
initial
performance
test;
and
2
(
3)
maintain
the
temperature
of
their
stationary
RICE
exhaust
so
that
the
catalyst
inlet
temperature
is
greater
than
or
equal
to
750

F
and
less
than
or
equal
to
1,250

F.

For
new
and
reconstructed
2
stroke
lean
burn
(
2SLB)
stationary
RICE,
new
and
reconstructed
4
stroke
lean
burn
(
4SLB)
stationary
RICE,
and
new
and
reconstructed
compression
ignition
(
CI)
stationary
RICE
complying
with
the
requirement
to
reduce
carbon
monoxide
(
CO)
emissions
using
an
oxidation
catalyst,
EPA
specified
that
sources
had
to:

(
1)
maintain
their
catalyst
so
that
the
pressure
drop
across
the
catalyst
does
not
change
by
more
than
2
inches
of
water
from
the
pressure
drop
across
the
catalyst
measured
during
the
initial
performance
test;
and
(
2)
maintain
the
temperature
of
their
stationary
RICE
exhaust
so
that
the
catalyst
inlet
temperature
is
greater
than
or
equal
to
500

F
and
less
than
or
equal
to
1,250

F.

For
stationary
RICE
complying
with
the
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust,
EPA
specified
that
sources
had
to:

(
1)
maintain
an
operating
load
greater
than
or
equal
to
95
percent
of
the
operating
load
established
during
the
initial
performance
test;
or
(
2)
maintain
a
fuel
flow
rate
greater
than
or
equal
to
95
percent
of
the
fuel
flow
rate
established
during
the
initial
performance
test;
and
(
3)
comply
with
any
additional
operating
limitations
approved
by
the
Administrator.

During
the
public
comment
period,
EPA
received
several
different
comments
from
industry
regarding
the
proposed
operating
parameters
and
operating
limitations.
The
following
sections
summarize
the
comments
received
on
the
proposed
operating
parameters
and
operating
limitations
and
document
EPA's
selection
of
operating
parameters
and
operating
limitations
for
the
final
rule.

Catalyst
Pressure
Drop
Several
commenters
expressed
that
the
pressure
drop
requirement
should
be
removed.
In
general,
commenters
were
of
the
opinion
that
although
a
significant
change
in
pressure
drop
across
the
catalyst
may
provide
an
indication
that
the
catalyst
has
become
fouled,
EPA
has
not
provided
any
evidence
to
suggest
that
an
increase
in
2
inches
of
water
leads
to
the
catalyst
performance
being
impacted.
In
fact,
3
commenters
stated
that
industry
data
show
that
the
pressure
drop
across
the
catalyst
can
increase
by
more
than
2
inches
of
water
without
impacting
the
catalyst
performance.
In
addition,
commenters
also
stated
that
the
pressure
drop
is
not
something
that
vendors
treat
as
a
continuous
operating
parameter
requirement,
but
is
a
maintenance
requirement
on
some
engines.

Catalyst
vendors
have
indicated
to
EPA
that
the
pressure
drop
across
the
catalyst
may
be
a
good
parameter
to
indicate
catalyst
performance
and
that
an
increase
in
pressure
drop
is
an
indication
of
poor
catalyst
performance
(
Document
ID
Nos.
OAR­
2002­
0059­
0189
and
0190
and
A­
95­
35
II­
E­
103
and
104).
The
pressure
drop
across
the
catalyst
can
indicate
if
the
catalyst
is
damaged
or
fouled.
If
the
catalyst
is
damaged
or
becomes
fouled,
the
catalyst
performance
would
decrease.
For
these
reasons,
EPA
felt
it
was
appropriate
to
include
a
requirement
to
monitor
the
pressure
drop
as
it
can
serve
as
a
surrogate
of
catalyst
performance
and
can
provide
an
indication
of
decreasing
catalyst
efficiency.
The
EPA
feels
that
this
requirement
is
appropriate
for
the
final
rule.

The
EPA
determined
based
on
information
from
catalyst
vendors
that
an
operating
limitation
of
2
inches
of
water
was
appropriate
as
such
a
pressure
drop,
as
compared
to
the
pressure
drop
measured
during
the
initial
performance
test,
might
indicate
that
the
catalyst
has
been
damaged
or
fouled.
Miractech
Corporation
stated
in
their
catalyst
manual
for
oxidation
catalyst
and
NSCR
that
if
the
pressure
drop
changes
by
more
than
2
inches
of
water
column,
the
catalyst
should
be
inspected
for
damage
or
fouling
(
Document
ID
Nos.
OAR­
2002­
0059­
0482
and
A­
95­
35
II­
D­
64).
For
this
reason,
EPA
feels
it
is
on
firm
ground
establishing
such
an
operating
limitation
for
sources
using
NSCR
or
oxidation
catalyst
in
the
final
rule.
It
should
be
noted
that
periods
when
the
pressure
drop
strays
from
the
established
ranges
are
not
considered
violations.
These
periods
are
considered
deviations,
which
might
result
in
further
examination
by
the
enforcing
agency.

As
discussed
above,
EPA
feels
it
is
appropriate
to
maintain
the
requirement
that
the
pressure
drop
across
the
catalyst
not
change
by
more
than
two
inches
of
water
from
the
pressure
drop
across
the
catalyst
measured
during
the
initial
performance
test
as
an
operating
limitation
in
the
final
rule
for
sources
using
NSCR
or
oxidation
catalyst.
However,
the
EPA
has
reevaluated
its
position
regarding
requiring
sources
to
monitor
the
pressure
drop
across
the
catalyst
on
a
continuous
basis
and
is
no
longer
requiring
sources
to
install
a
continuous
parameter
monitoring
system
to
monitor
this
parameter
continuously.
The
pressure
drop
across
the
catalyst
is
not
likely
to
change
within
short
periods
of
time,
but
is
a
parameter
the
owner
or
operator
might
see
changing
over
a
longer
period
of
time,
not
within
hours
or
days.
This
is
consistent
with
comments
that
stated
that
vendors
do
not
treat
pressure
differential
as
a
continuous
operating
parameter
requirement.
Rather
it
is
presented
as
a
maintenance
requirement
for
catalysts
on
some
engines.
For
this
reason,
EPA
feels
it
is
appropriate
to
require
4
sources
that
must
comply
with
the
pressure
drop
requirement
to
measure
this
parameter
monthly
in
the
final
rule.
The
EPA
does
not
expect
the
pressure
drop
across
the
catalyst
to
change
significantly
more
frequently
than
monthly.

It
should
be
noted
that
in
the
final
rule,
the
requirement
to
measure
the
pressure
drop
across
the
catalyst
monthly
applies
to
sources
complying
with
any
emission
limitation
requirement
of
the
final
rule
using
NSCR
or
oxidation
catalyst.
Sources
that
comply
with
any
of
the
emission
limitations
that
do
not
use
NSCR
or
oxidation
catalyst
do
not
have
to
measure
the
pressure
drop
across
the
catalyst
monthly,
but
must
instead
petition
the
Administrator
for
approval
of
operating
limitations
or
approval
of
no
operating
limitations.
These
sources
must
measure,
maintain,
and
monitor
the
operating
parameters
that
were
approved
by
the
Administrator,
if
any.

Catalyst
Temperature
Rise
Several
commenters
stated
that
the
temperature
rise
requirement
should
be
removed.
In
general,
commenters
stated
that
a
wide
range
of
temperature
differentials
may
be
experienced
across
NSCR
catalysts.
A
NSCR
catalyst
is
more
likely
to
show
a
positive
temperature
change
across
the
catalyst,
however,
very
low,
or
even
negative,
temperature
changes
are
possible
while
the
catalyst
is
functioning
normally.
Also,
commenters
stated
that
EPA
has
not
provided
any
data
to
support
the
proposed
operating
limitation
of
5
percent
temperature
rise,
as
compared
to
the
temperature
rise
measured
during
the
initial
performance
test.
One
commenter
questioned
why
a
higher
temperature
differential
should
not
be
allowed.
As
an
example,
the
commenter
stated
that
what
if
the
temperature
differential
is
10
percent,
and
asked
would
this
not
represent
a
higher
degree
of
oxidation.

Based
on
the
comments
received,
EPA
agrees
with
the
commenters
that
such
a
requirement
would
be
inappropriate
and
most
likely
would
not
provide
an
accurate
representation
of
how
the
catalyst
is
performing.
Therefore,
EPA
has
not
included
the
requirement
to
maintain
the
catalyst
such
that
the
temperature
rise
across
the
catalyst
stays
within
5
percent
of
the
temperature
rise
measured
during
the
initial
performance
test
in
the
final
rule.
The
EPA
feels
that
maintaining
the
catalyst
inlet
temperature
continuously
and
measuring
the
pressure
drop
across
the
catalyst
monthly
is
sufficient
to
ensure
compliance
in
between
periodic
stack
testing.

Catalyst
Inlet
Temperature
Several
commenters
contended
that
the
temperature
ranges
at
the
catalyst
inlet
should
be
revised.
Commenters
supported
an
operating
range
of
450

F­
1,350

F
for
lean
burn
engines.
Emissions
data
from
EPA's
testing
at
Colorado
State
University
demonstrate
that
the
proposed
emission
limitations
were
achieved
when
the
catalyst
inlet
temperature
was
as
low
as
450

F.
In
addition,
information
in
EPA's
docket
5
suggests
that
1,350

F
should
be
allowed
as
the
upper
limit
for
catalyst
inlet
temperature
operating
limitations.

The
EPA
required
the
catalyst
inlet
temperature
to
be
maintained
to
ensure
proper
operation
of
the
oxidation
catalyst.
The
EPA
stated
in
the
preamble
to
the
proposed
rule
that,
in
general,
the
oxidation
catalyst
performance
will
decrease
as
the
catalyst
inlet
temperature
decreases.
Also,
if
the
catalyst
inlet
temperature
is
too
high,
oxidation
catalyst
performance
could
be
affected.
Finally,
the
oxidation
catalyst
inlet
temperature
cannot
be
too
low,
or
the
reduction
of
HAP
emissions
may
be
compromised.
For
these
reasons,
EPA
proposed
that
sources
complying
with
the
CO
reduction
requirement
using
an
oxidation
catalyst
maintain
the
catalyst
inlet
temperature
within
500­
1,250

F.

The
EPA
agrees
that
the
lower
end
of
the
operating
limitation
temperature
range
should
start
at
450

F
for
2SLB,
4SLB,
and
CI
engines
using
oxidation
catalyst.
The
level
of
the
standard
for
2SLB
engines
in
the
final
rule
is
58
percent
CO
reduction.
Similar
CO
reduction
was
observed
at
CSU
for
2SLB
engines
where
the
exhaust
temperature
was
450

F.
For
this
reason,
the
EPA
has
specified
in
the
final
rule
that
the
lower
end
of
the
operating
limitation
is
450

F.
Furthermore,
EPA
feels
that
the
oxidation
catalyst
will
perform
adequately
at
a
temperature
of
1,350

F.
This
was
discussed
in
the
memorandum
entitled
"
Control
Technologies
for
Stationary
RICE"
available
from
EPA's
Edocket
Website
as
Document
ID
Number
OAR­
2002­
0059­
0064
(
A­
95­
35
II­
B­
41).
Comments
received
also
stated
that
Waukesha
Pearce
Industries,
Inc.
includes
1,350

F
in
their
limited
warranty
statements
for
oxidation
catalysts.
For
these
reasons,
EPA
agrees
with
the
commenters
and
feels
that
the
higher
end
of
the
operating
limitation
temperature
range
should
end
at
1,350

F.
The
EPA
has
written
the
temperature
range
requirement
for
catalyst
inlet
temperatures
to
be
between
450

F
and
1,350

F
in
the
final
rule
for
2SLB,
4SLB,
and
CI
engines
using
oxidation
catalyst.
For
4SRB
engines,
the
temperature
range
required
for
catalyst
inlet
temperatures
is
the
same
as
proposed,
i.
e.,
the
catalyst
inlet
temperature
must
be
between
750

F
and
1,250

F.

Note
that
in
the
final
rule,
the
requirement
to
maintain
the
catalyst
inlet
temperature
applies
to
sources
complying
with
any
emission
limitation
requirement
using
NSCR
or
oxidation
catalyst.
Sources
that
comply
with
any
of
the
emission
limitations
that
do
not
use
NSCR
or
oxidation
catalyst
do
not
have
to
maintain
the
catalyst
inlet
temperature,
but
must
instead
petition
the
Administrator
for
approval
of
operating
limitations
or
approval
of
no
operating
limitations.

Load/
Fuel
Flow
Several
commenters
stated
that
the
operating
load
and
fuel
flow
rate
operating
limitations
should
be
removed.
Certain
commenters
expressed
that
the
requirement
to
6
maintain
an
operating
load
or
fuel
flow
rate
may
under
many
circumstances
be
impractical.
This
would
be
particularly
problematic
for
stationary
engines
used
in
variable
load
applications
and
could
potentially
limit
engine
operation.

The
EPA
understands
that
maintaining
the
operating
load
or
fuel
flow
rate
within
95
percent
of
the
operating
load
or
fuel
flow
rate
established
during
the
initial
performance
test
may
be
impractical
for
many
engines,
especially
those
used
in
load
following
applications
such
as
engines
operating
on
pipelines
which
must
respond
to
unpredictable
pipeline
conditions.
Therefore,
the
EPA
has
not
included
the
requirement
to
maintain
load
or
fuel
flow
rate
in
the
final
rule.
The
EPA
feels
that
maintaining
the
catalyst
inlet
temperature
continuously
and
measuring
the
pressure
drop
across
the
catalyst
monthly
is
sufficient
to
ensure
compliance
in
between
periodic
stack
testing
for
sources
complying
with
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust
using
NSCR
or
oxidation
catalyst.

Sources
that
comply
with
the
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust
that
do
not
use
NSCR
or
oxidation
catalyst
must
petition
the
Administrator
for
approval
of
operating
limitations
or
approval
of
no
operating
limitations.

Deviations
Periods
when
operating
parameters
stray
from
the
operating
limitations
are
considered
deviations.
For
sources
that
must
measure
the
pressure
drop
monthly,
periods
when
the
pressure
drop
across
the
catalyst
is
greater
than
2
inches
of
water
from
the
pressure
drop
across
the
catalyst
measured
during
the
initial
performance
test
are
considered
deviations.
For
sources
that
must
maintain
the
temperature
of
their
stationary
RICE
exhaust,
periods
when
the
catalyst
inlet
temperature
is
outside
of
the
acceptable
range
as
defined
in
the
final
rule
are
considered
deviations.

Deviations
from
operating
limitations
must
be
reported
in
the
semiannual
compliance
report.
However,
a
deviation
is
not
a
direct
violation
of
the
stationary
RICE
final
rule,
but
requires
that
the
owners
and
operators
take
action
to
assure
that
the
catalyst
system
is
still
functional.
The
owner
and
operator
would
have
to
explain
the
cause(
s)
of
deviation
and
determine
whether
or
not
the
deviation
is
an
indication
of
declining
catalyst
performance
in
their
semiannual
compliance
report.
Depending
on
the
cause(
s)
of
the
deviation,
owners
and
operators
may
have
to
wash,
service,
or
replace
the
catalyst.
Deviations
may
result
in
the
enforcing
agency
requiring
the
owner
or
operator
to
conduct
a
performance
test.

Conclusion
In
the
final
rule,
EPA
has
allowed
sources
the
flexibility
of
complying
with
either
7
emission
limitation
requirement
(
percent
reduction
or
concentration
limit),
regardless
of
which
control
technique
is
applied.
Sources
that
use
an
oxidation
catalyst
are
not
limited
to
meeting
the
requirement
to
reduce
CO
emissions,
but
have
the
option
to
comply
with
either
the
CO
percent
reduction
requirement
or
with
the
formaldehyde
concentration
limit.
Similarly,
4SRB
engines
that
use
NSCR
are
not
limited
to
meeting
the
requirement
to
reduce
formaldehyde
emissions,
but
have
the
option
to
comply
with
either
the
formaldehyde
percent
reduction
requirement
or
with
the
formaldehyde
concentration
limit.
Sources
that
do
not
use
oxidation
catalyst
or
NSCR,
may
also
choose
to
comply
with
either
the
percent
reduction
requirement
or
with
the
formaldehyde
concentration
limit.

As
previously
noted
in
this
memorandum,
sources
that
comply
with
any
emission
limitation
requirement
and
use
NSCR
or
oxidation
catalyst,
must
also
comply
with
operating
limitations
that
apply
to
that
engine
subcategory.
Sources
that
comply
with
any
emission
limitation
requirement
that
do
not
use
NSCR
or
oxidation
catalyst
do
not
have
to
comply
with
the
operating
limitations
specified
in
the
final
rule,
but
must
instead
petition
the
Administrator
for
approval
of
operating
parameters
and
limitations
that
the
source
feels
will
be
indicators
of
performance
and
emission
levels.
Sources
also
have
the
option
of
petitioning
the
Administrator
for
approval
of
no
operating
limitations.
The
following
table
shows
the
operating
limitations
of
the
final
rule.

Table
1.
Operating
Limitations
for
the
Final
Rule
Subcategory
Operating
Limitations
4SRB
stationary
RICE
complying
the
with
requirement
to
reduce
formaldehyde
emissions
and
using
NSCR;

and
4SRB
stationary
RICE
complying
with
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust
and
using
NSCR.
Maintain
your
catalyst
so
that
the
pressure
drop
across
the
catalyst
does
not
change
by
more
than
2
inches
of
water
from
the
pressure
drop
across
the
catalyst
that
was
measured
during
the
initial
performance
test;

and
maintain
the
temperature
of
your
stationary
RICE
exhaust
so
that
the
catalyst
inlet
temperature
is
greater
than
or
equal
to
750

F
and
less
than
or
equal
to
1,250

F.
Subcategory
Operating
Limitations
8
2SLB,
4SLB,
and
CI
stationary
RICE
complying
with
the
requirement
to
reduce
CO
emissions
and
using
an
oxidation
catalyst;

and
2SLB,
4SLB,
and
CI
stationary
RICE
complying
with
the
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust
and
using
an
oxidation
catalyst.
Maintain
your
catalyst
so
that
the
pressure
drop
across
the
catalyst
does
not
change
by
more
than
2
inches
of
water
from
the
pressure
drop
across
the
catalyst
that
was
measured
during
the
initial
performance
test;

and
maintain
the
temperature
of
your
stationary
RICE
exhaust
so
that
the
catalyst
inlet
temperature
is
greater
than
or
equal
to
450

F
and
less
than
or
equal
to
1,350

F.

4SRB
stationary
RICE
complying
with
the
requirement
to
reduce
formaldehyde
emissions
and
not
using
NSCR;

and
2SLB,
4SLB,
and
CI
stationary
RICE
complying
with
the
requirement
to
reduce
CO
emissions
and
not
using
an
oxidation
catalyst;

and
Stationary
RICE
complying
with
the
requirement
to
limit
the
concentration
of
formaldehyde
in
the
stationary
RICE
exhaust
and
not
using
NSCR
or
an
oxidation
catalyst.
Comply
with
any
operating
limitations
approved
by
the
Administrator.
