1
A
list
of
contaminants
is
attached.
One
exception
is
vanadium
oxide
in
the
HFO
which
is
used
in
SCR
systems
as
a
NOx
reduction
catalyst.
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
ANN
ARBOR,
MI
48105
December
16,
2003
OFFICE
OF
AIR
AND
RADIATION
MEMORANDUM
SUBJECT:
Summary
of
Conference
Call
with
Argillon
on
December
10,
2003
FROM:
Mike
Samulski
Assessment
and
Standards
Division
TO:
Docket
OAR­
2003­
0190
On
December
10,
2003,
Mike
Samulski,
Jean­
Marie
Revelt,
and
Alan
Stout
from
the
U.
S.
EPA
engaged
in
a
conference
call
with
Gary
Keefe,
Michael
Joisten,
and
Ingo
Willering
of
Argillon.
The
topic
of
the
discussion
was
the
feasibility
of
using
selective
catalytic
reduction
(
SCR)
to
achieve
NOx
reductions
from
diesel
marine
engines.
Argillon
manufactures
the
SINOx
®
catalyst
used
in
many
SCR
applications,
including
marine
vessels.

This
memo
summarizes
information
shared
by
Argillon.
In
addition,
attached
are
three
documents
on
the
SINOx
®
SCR
system
that
were
referenced
in
these
discussions.
The
first
attachment
is
a
list
of
marine
vessels
using
SINOx
®
SCR.
The
second
attachment
is
a
presentation
made
in
2002
by
Siemens
(
former
parent
company
for
SINOx
®
manufacture)
on
the
application
of
the
SINOx
®
SCR
system
to
marine
diesel
engines.
The
third
attachment
is
a
list
of
toxic
agents
for
SINOx
®
catalysts.

Fuel
Sulfur
Heavy
fuel
oil
(
HFO)
burned
by
ocean­
going
ships
can
have
fuel
sulfur
levels
as
high
as
4.5%
with
an
average
around
3%.
Sulfur
itself
does
not
poison
SCR
catalysts.
In
stationary
source
applications,
SCR
units
are
used
on
coal
fired
plants
with
sulfur
levels
around
5%.
However,
HFO
contains
other
contaminants,
such
as
heavy
metals,
that
will
poison
the
catalyst.
1
Also,
as
discussed
below,
ammonium
sulfate
formation
is
an
issue.
The
SINOx
®
SCR
system
is
currently
used
on
26
vessels
(
see
attachment
1).
For
most
of
these
vessels,
the
propulsion
engines
operate
on
HFO
with
a
sulfur
content
around
1%
and
the
auxiliary
engines
generally
operate
on
marine
distillate
oil
with
a
2
Note:
marine
diesel
engines
can
have
annual
hours
of
operation
ranging
from
less
than
200
hrs/
yr
for
recreational
craft
up
to
more
than
6,000
hrs/
yr
for
ocean­
going
vessels.
The
lives
of
these
engines
can
often
be
measured
in
decades.

­
2­
sulfur
content
around
0.5%.
These
vessels
are
operated
in
the
Baltic
where
lower
sulfur
fuel
is
available
because
Sweden
requires
that
its
vessels
operate
on
1%
sulfur
fuel
or
less.

SCR
systems
need
a
reducing
agent,
generally
aqueous
urea,
to
reduce
NOx.
The
heat
in
the
exhaust
creates
ammonia
from
the
urea
which
reacts
with
NOx
in
the
catalyst
to
form
N
2
and
water.
However,
ammonia
can
also
react
with
SO
3
in
the
exhaust
to
form
ammonia
sulfate.
If
the
ammonia
sulfate
condenses
on
the
catalyst,
it
can
deactivate
the
catalyst
over
time.
To
ensure
the
durability
of
the
catalyst,
urea
is
not
injected
until
the
exhaust
temperature
is
high
enough
to
prevent
ammonia
sulfate
formation
and
condensation.
Slide
12
in
the
second
attachment
includes
a
graph
presenting
the
relationship
between
fuel
sulfur
content
and
minimum
operation
temperature.
For
very
low
sulfur
fuel
(<
0.05%),
urea
can
be
injected
into
the
exhaust
stream
at
temperatures
as
low
as
260

C.
However,
as
the
sulfur
content
of
the
fuel
increases,
the
exhaust
stream
must
be
hotter
before
urea
can
be
injected.
For
marine
vessels
running
on
1%
sulfur
fuel,
the
urea
is
not
injected
until
the
exhaust
temperature
downstream
of
the
catalyst
reaches
300­
320

C.

Maintenance
Argillon
reported
that
no
special
maintenance
is
needed
for
the
SINOx
®
SCR
system.
Typical
maintenance
includes
inspecting
pumps
and
the
dosing
unit
for
leaks
and
periodically
changing
filters.
This
is
consistent
with
standard
maintenance
for
other
pumps
on
vessels.
The
catalysts
typically
have
a
guaranteed
useful
life
of
16,000
to
24,000
hours2
and
can
be
monitored
either
by
visually
inspecting
for
plugging
or
using
a
differential
pressure
measurement.
If
a
continuous
NOx
monitoring
system
is
used,
this
monitoring
system
can
be
used
to
provide
feedback
on
the
operation
of
the
SCR
unit.

When
the
engine
is
operated
on
heavier
fuel
oils
(
typically
above
0.5%
sulfur),
a
soot
blower
is
used
to
prevent
catalyst
plugging
caused
by
ash
in
the
exhaust
fuel.
A
soot
blower
uses
compressed
air
to
blow
out
any
soot
that
may
be
collecting
in
the
catalyst.
The
soot
blower
generally
operates
for
a
few
seconds
every
1
to
2
hours.
The
purpose
of
the
soot
blower
is
to
prevent
the
early
stages
of
plugging
and
would
not
be
effective
for
cleaning
out
a
catalyst
that
has
already
been
plugged.

Temperature
As
discussed
above,
the
minimum
exhaust
temperature
at
which
the
SCR
unit
can
operate
is
a
function
of
fuel
sulfur.
Even
with
very
low
sulfur
fuel,
the
SCR
unit
requires
an
exhaust
temperature
of
260

C
to
operate.
When
the
exhaust
temperature
is
too
low
(
measured
downstream
of
the
catalyst)
the
urea
injection
is
discontinued.
The
heat
capacity
of
the
catalyst
helps
stabilize
the
temperature
which
helps
avoid
any
deactivation
during
short
periods
of
transience
or
idle.
Also,
the
urea
injection
is
switched
on
at
a
higher
temperature
than
that
at
which
it
is
switched
off.
This
helps
­
3­
stabilize
the
urea
dosing.
Running
the
exhaust
through
the
SCR
catalyst
without
urea
injection
does
not
hurt
the
system.
As
a
matter
of
fact,
the
SCR
unit
could
be
switched
on
and
off
during
engine
operation
without
damaging
the
system
because
there
are
no
unique
startup
and
shutdown
procedures.

At
idle
and
light
loads,
marine
diesel
engines
generally
operate
at
exhaust
temperatures
below
260

C.
As
the
power
increases,
so
does
the
exhaust
temperature.
The
load
at
which
the
exhaust
temperature
becomes
hot
enough
for
the
SCR
to
function
properly
is
a
function
of
engine
design
(
and
fuel
sulfur
as
discussed
above).
For
lower
speed
engines
and
higher
sulfur
fuels,
the
load
becomes
higher
at
which
the
exhaust
temperature
would
be
hot
enough
to
activate
the
SCR
system.
In
addition,
the
amount
of
time
that
an
engine
operates
at
higher
loads
can
vary
greatly
by
application.
Examples
of
this
are
discussed
below.

The
highest
temperature
operation
recommended
by
Argillon
for
the
SINOx
SCR
system
is
510

C.
Above
this
temperature
there
is
a
change
in
the
crystal
structure
of
the
titanium
dioxide
which
reduces
the
inner
surface
area
of
the
catalyst.
This
irreversibly
deactivates
the
catalyst.
510

C
is
significantly
higher
than
is
typically
seen
in
marine
diesel
engine
exhaust
due
to
the
high
efficiency
of
these
engines.

Application
Most
of
the
applications
currently
using
SCR
operate
primarily
at
higher
loads
such
as
ferries
or
power
generation
units.
Ferries
generally
operate
at
their
cruising
speed
with
limited
time
at
low
load
when
the
vessels
come
to
dock.
This
constraint
is
important
because
not
all
marine
engines
are
operated
in
this
way.
For
instance,
Argillon
referred
to
a
tug
application
where
the
vessel
primarily
idled
or
operated
at
light
loads
moving
around
the
harbor
and
only
at
high
loads
for
10­
15
minute
increments
when
pushing
ships.
In
this
case,
the
limited
amount
of
high
load
operation
(
therefore
high
exhaust
temperatures)
would
limit
the
emission
reduction
potential
of
SCR
for
this
vessel.

Emission
standards
for
commercial
marine
diesel
engine
standards
are
generally
based
on
measured
emissions
over
the
E3
or
E2
duty
cycles.
The
E3
duty
cycle
is
for
engines
operating
on
a
propeller
curve
and
the
E2
duty
cycle
is
for
engines
operating
at
constant
speed.
These
duty
cycles
do
not
include
an
idle
mode
and
are
weighed
towards
higher
power.
Argillon
stated
that
they
generally
report
their
emission
reductions
based
on
the
E3
duty
cycle,
however,
they
have
investigated
the
effectiveness
of
SCR
versus
engine
load.
During
testing
on
a
high­
speed,
fourstroke
engine
used
in
a
chemical
tanker,
Argillon
found
that
the
SCR
could
be
activated
at
28%
load
when
200
ppm
S
(
0.02%
S)
fuel
was
used.
On
another
high­
speed
engine
using
200
ppm
S
fuel,
they
observed
85%
NOx
reductions
at
40%
load
and
above.
Argillon
is
in
the
process
of
applying
SCR
to
a
50
MW
engine
operating
on
2%
sulfur
HFO.
To
achieve
the
temperature
needed
to
activate
the
SCR,
the
SCR
catalyst
is
placed
upstream
of
the
turbocharger
turbine.

For
diesel
truck
engines,
the
catalyst
volume
is
on
the
order
of
three
times
the
engine
displacement.
However,
for
larger
engines
used
in
marine
applications,
the
volume
to
displacement
ratio
is
typically
higher
because
of
lower
back
pressure
restrictions
set
by
the
manufacturers.
In
­
4­
marine
applications
there
may
be
other
sources
of
back
pressure
as
well
such
as
boilers
and
silencers.
Catalysts
are
larger
when
a
lower
cell
density
is
used
in
the
catalyst
to
minimize
the
pressure
drop
across
the
catalyst.
For
stationary
source
and
marine
applications,
there
is
generally
enough
space
to
fit
the
SCR
system
in
the
existing
exhaust
systems.
However,
for
locomotive
applications,
less
space
is
available
which
presents
a
packaging
challenge.
One
solution
may
be
to
size
the
catalyst
to
the
locomotive
while
giving
on
total
emission
reduction.
For
instance,
a
catalyst
targeting
a
50%
reduction
in
NOx
rather
than
an
80%
reduction,
would
be
about
20%
smaller.
From
a
functionality
standpoint,
SCR
could
be
used
on
any
size
engine,
including
high­
speed
marine
engines
with
water
cooled
exhaust.
However,
for
very
small
engines,
the
cost
may
be
a
limiting
factor.

Emission
Reductions
The
proposed
Tier
IV
HC+
NOx
emission
limits
for
the
European
Union
range
from
1.5
to
2.2
g/
kW­
hr.
Argillon
stated
that
these
limits,
which
are
based
on
the
ISO
duty
cycles
mentioned
above,
could
be
met
through
the
use
of
SCR.
SCR
can
be
used
to
achieve
more
than
an
80%
NOx
reduction
over
the
ISO
test
procedures
and
more
than
a
90%
NOx
reduction
at
continuous
rated
power.
In
addition,
HC
and
PM
can
be
reduced
through
oxidation
in
the
catalyst.
PM
reductions
are
generally
due
to
oxidation
of
the
soluble
organic
fraction
of
the
PM
and
are
a
function
of
fuel
quality.
To
increase
these
reductions,
and
to
reduce
CO,
an
oxidation
catalyst
could
be
installed
downstream
of
the
SCR
unit.
In
this
case,
the
fuel
sulfur
would
need
to
be
low
enough
to
prevent
poisoning
of
the
oxidation
catalyst
and
to
prevent
the
formation
of
direct
sulfate
PM.
Manufacturers
of
oxidation
catalysts
typically
guarantee
their
catalysts
up
to
0.4%
S.

Over
an
oxidizing
catalyst,
sulfur
can
oxidize
to
form
SO
3
which,
in
turn,
will
combine
with
water
to
create
sulfuric
acid/
sulfate
PM.
If
the
fuel
sulfur
is
high
enough,
the
formation
of
sulfate
PM
can
outweigh
the
PM
reduction
due
to
oxidation.
Argillon's
experience
is
that,
with
an
SCR
catalyst
only,
the
sulfate
formation
will
outweigh
the
PM
reduction
when
the
fuel
sulfur
level
is
above
2.0%.
With
the
use
of
an
oxidation
catalyst,
the
sulfate
PM
formation
would
be
higher.

Argillon
stated
that
ammonia
slip
is
not
an
issue
with
their
SCR
system,
so
they
do
not
need
a
downstream
oxidation
catalyst.
To
control
ammonia
slip,
ammonia
is
measured
during
the
calibration
of
the
SCR
system.
The
calibration
provides
a
margin
of
safety
in
the
urea
dosage
to
prevent
ammonia
slip.
In
addition,
the
catalyst
will
adsorb
ammonia
which
will
later
react
with
NOx
to
form
N
2
and
water.
They
stated
that
ammonia
sensors
are
not
currently
available
for
use
on
ships
and
that
all
of
their
ammonia
measurements
are
made
in
the
laboratory
using
expensive
laser­
based
measuring
equipment.

Implications
­
5­
The
following
table
presents
the
issues
for
applying
SCR
to
marine
and
locomotive
applications.
This
is
not
to
say
that
these
issues
could
not
be
resolved
given
time
and
effort.
The
main
design
constraints
appear
at
this
time
to
be
packaging,
duty
cycle,
and
fuel
used.

Application
Issues
for
SCR
Application
Packaging
Duty
Cycle
Fuel
Locomotives
limited
space
on
locomotives
may
limit
potential
reductions
okay
okay
Marine,
Distillate
Fuel
probably
okay,
but
have
not
yet
applied
to
marine
applications
less
than
600
kW
okay
for
some
applications,
but
may
be
an
issue
for
others
okay
Marine,
Residual
Fuel
okay
okay
overall;
however,
low
load
operation
near
ports
may
be
an
issue
too
high
sulfur
affects
minimum
operation
temperature;
may
have
to
switch
to
lower
sulfur
fuel
attachments
