Document ID: EPA-HQ-OAR-2003-0048-0054
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-02-23T05:00Z

"
Hunt,
Tim"
<
Tim_
Hunt@
afandpa
To:
Mary
Kissell/
RTP/
USEPA/
US@
EPA,
Jim
.
org>
Eddinger/
RTP/
USEPA/
US@
EPA
cc:
"
Rob
Kaufmann
(
rckaufma@
gapac.
com)"
12/
22/
2003
01:
40
PM
<
rckaufma@
gapac.
com>,
Victor
Dallons
<
victor.
dallons@
weyerhaeuser.
com>,
'
Dave
Harvey'
<
dave.
harvey@
lpcorp.
com>,
"
Jim
Jackson
(
jimjackson@
bc.
com)"
<
jimjackson@
bc.
com>
Subject:
MACT
Overlap
Mary
Tom
and
Jim,

As
you
know,
we
have
been
concerned
about
certain
units
at
wood
products
facilities
like
thermal
oil
heaters
being
regulated
twice
under
both
Plywood
MACT
and
Boiler
MACT
(
see
AF&
PA
March
comments).
Here
is
a
brief
paper
that
outlines
what
we
believe
is
a
straightforward
solution
to
this
concern.

We
would
be
glad
to
talk
about
it
further.

Happy
Holidays,

<<
Boiler­
PWCP
MACT
Overlap
final
12­
22­
03.
doc>>

Timothy
Hunt
Senior
Director,
Air
Quality
Programs
American
Forest
and
Paper
Association
Suite
800
1111
19th
St.,
NW
Washington,
DC
20036
phone:
202­
463­
2588
fax:
202­
463­
2423
Tim_
Hunt@
afandpa.
org
(
See
attached
file:
Boiler­
PWCP
MACT
Overlap
final
12­
22­
03.
doc)
12/
22/
03
PWCP
and
Boiler
MACT
Overlap
Issues
Issue:

Some
facilities
incorporate
small
steam
generators/
thermal
oil
heaters
as
part
of
an
integrally­
designed
combustion
system
with
the
primary
purpose
of
providing
heat
for
direct­
fired
dryers.
Air
pollution
control
devices
for
the
system
are
usually
located
after
the
dryers.
These
indirect
heat
exchangers
provide
steam
or
thermal
oil
for
board
press
heating
and,
in
some
limited
instances,
log
thawing
vats/
ponds.
The
indirect
heating
function
typically
accounts
for
less
than
25%
of
the
total
heat
capacity
of
the
combustion
system
when
operating
at
full
capacity.
When
the
direct­
fired
dryers
go
down
due
to
malfunctions,
maintenance,
or
other
reasons,
emissions
from
the
limited
continued
operation
of
the
indirect
heat
exchangers
may
result
in
combustion­
related
emissions
being
directly
vented
to
the
atmosphere,
with
no
emission
control
beyond
that
provided
by
the
system's
combustion
controls.
Unless
explicitly
addressed
in
the
Plywood
and
Composite
Wood
Products
(
PCWP)
MACT
rule,
the
Boiler/
Process
Heater
MACT
provisions
could
apply
when
these
indirect
heat
exchanger
emissions
bypass
the
directheated
dryers
during
dryer
outages.
Industry
is
concerned
that
expensive
emission
control
equipment
would
be
required
by
the
Boiler/
Process
Heater
MACT
rule
that
would
not
be
needed
most
of
the
unit's
operating
time.
EPA
is
concerned
that
mills
may
exhaust
uncontrolled
boiler/
process
heater
emissions
for
an
inordinate
amount
of
time
under
the
conditions
described
above.

Discussion:

In
a
number
of
instances,
the
combustion
equipment
providing
heat
input
to
the
subject
indirect
heat
exchangers
is
fully
integrated
into
the
dryer's
overall
direct­
fired
heat
source.
The
units
at
issue
are
biomass­
fired
units.
These
units
are
among
those
reviewed
as
part
of
the
MACT
floor
determination
process
for
the
PCWP
MACT.
A
portion
of
the
dryer
heat
system's
thermal
output
may
be
passed
through
a
water
or
hot
oil
heat
exchanger
for
use
elsewhere,
typically
as
a
heat
source
for
presses.
Under
normal
operation,
the
portion
of
the
combustion
gas
directed
through
the
heat
exchangers
is
passed
directly
through
to
the
direct­
fired
dryer
along
with
the
rest
of
the
combustion
gas
from
the
integrated
heat
source.
As
noted
by
EPA,
however,
the
dryers
integrated
with
these
units
do
indeed
need
to
be
taken
off­
line
from
time­
to­
time,
usually
due
to
some
sort
of
malfunction
(
overheating,
a
fire
within
the
dryer
or
piping,
temperature/
moisture
probe
failure,
conveyor
problems,
etc.)
that
requires
prompt
(
in
many
cases,
instantaneous)
action
and/
or
maintenance
to
avoid
severe
equipment
damage
and/
or
employee
hazard.

Also,
during
a
mill
shutdown,
some
indirect
heat
continues
to
be
needed
in
the
mill.
The
presses
may
be
operated
for
a
short
period
after
the
dryers
go
down
in
order
to
empty
the
dry
flake
storage
bins
(
OSB,
PB).
When
the
dryer
is
shut
down,
(
and
subsequently,
when
it
is
in
start­
up
mode),
there
still
is
a
need
to
keep
the
associated
1
presses
operating
at
a
minimum
idle
heat
level.
This
is
necessary
to
avoid
thermal
stress
damage
(
warping,
leaks)
to
the
press
and
it's
associated
heating
system.
In
addition,
at
a
limited
number
of
OSB
plants
located
in
cold
weather
areas,
heat
is
needed
in
the
log
thawing
vats/
ponds
to
keep
them
from
freezing,
and
is
also
needed
during
start­
up
to
bring
the
log
vats/
ponds
up
to
temperature.
In
addition,
the
combustion
devices
are
kept
in
idle
mode
even
when
no
heat
is
needed
to
avoid
thermal
stresses
to
the
combustion
unit
resulting
from
cooling
and
re­
heating.
In
these
cases,
thermal
oil
continues
to
circulate
in
the
system,
and
the
oil
heat
is
dumped
via
a
heat
exchanger
to
the
atmosphere.

When
events
require
diversion
of
combustion
gas
away
from
the
dryer
system,
the
combustion
system
is
throttled
back.
Since
storage
of
dryer
product
must
be
kept
small
for
fire
and
explosion
prevention
considerations,
the
pressing
operation
can
only
operate
for
a
short
time
with
the
dryers
out
of
service.
For
this
reason,
the
combustion
source
associated
with
the
dryer/
indirect
heat
exchanger
will
be
quickly
throttled
back
and
operated
at
a
substantially
lower
than
normal
load
to
maintain
temperature
on
the
press
in
an
idle
mode.
Emissions
will
be
reduced
accordingly.
In
addition,
when
routine
maintenance
is
performed
on
the
boiler/
indirect
heat
exchanger
or
presses
in
addition
to
the
dryers,
the
heat
exchanger
units
will
be
shut
down
as
part
of
normal
operating
procedures.

The
events
where
the
indirect
heat
exchangers
will
be
kept
running,
and
thus
vented
directly
to
the
atmosphere
are
described
in
more
detail
as
follows.
Many
mills
take
an
8­
hour
maintenance
down­
day
every
2
weeks.
There
are
also
longer
periodic
outages
for
other
maintenance
and
repairs
as
well
as
various
process
emergencies.
The
indirect
heat
exchangers
may
be
operated
during
these
periods
if
there
is
no
press
and/
or
log
vat
maintenance
underway.
AF&
PA
supplied
EPA
with
considerable
dryer
downtime
with
respect
to
our
comments
on
maintenance
downtime
allowances.
During
these
documented
downtime
periods,
the
thermal
oil
heaters
or
boilers
are
operated
at
a
reduced
heat
input
and
output
rate,
typically
at
less
than
20%
of
their
normal
heat
input.
In
more
unusual
circumstances,
such
as
after
a
more
significant
dryer
fire,
the
shutdown
may
last
a
day
or
longer,
but
the
plant
cannot
run
long
in
this
mode.
Almost
immediately,
the
heat
exchanger
firing
levels
and
associated
emissions
will
be
minimized
during
these
periods,
as
only
a
small
amount
of
thermal
energy
will
be
needed
to
keep
the
presses
in
a
heated
idle
mode.
Due
to
NSPS
considerations,
some
plants
have
the
ability
to
switch
over
to
natural
gas
combustion
to
maintain
the
minimal
heat
loads
necessary
to
keep
the
presses
in
idle
mode
during
dryer
outages,
but
this
practice
will
not
be
applicable
to
all
facilities,
nor
does
the
switch
occur
instantaneously.
However,
for
facilities
with
unlimited
access
to
natural
gas,
the
ability
to
switch
fuels
would
be
an
acceptable
work
practice
to
minimize
emissions
during
dryer
outages.

Suggested
Resolution:

The
pending
PCWP
MACT
rule
should
address
this
issue
by
(
1)
directing
that
indirect
heat
exchangers
that
normally
exhaust
to
direct
 
fired
dryers
be
included
in
the
2
PWPC
MACT
source
definition
and
be
specifically
excluded
from
the
Boiler
MACT
source
definition,
and
(
2)
that
emissions
from
these
indirect
heat
exchangers
be
addressed
either
by
procedures
contained
in
the
facilities'
required
SSM
plan
or
as
a
permitted
alternate
operating
mode.
Addressing
emissions
during
these
events
via
the
facility's
SSM
plan
is
appropriate
since
most
atmospheric
venting
of
the
indirect
heat
exchanger
exhaust
is
associated
with
dryer
malfunctions,
the
need
for
an
orderly
shut
down
of
the
related
heat
source,
the
need
to
maintain
a
minimum
level
of
heat
to
protect
the
press,
and/
or
the
need
to
start
the
dryer(
s)
up
slowly
thereafter.
Addressing
the
emissions
under
an
alternative
operating
mode
may
be
appropriate
for
longer
planned
dryer
outages
where
some
heat
is
needed
to
maintain
other
mill
operations
such
as
heating
buildings
or
keeping
log
ponds
from
freezing.
Since
these
indirect
heat
exchangers
are
part
of
an
integrated
combustion
system
whose
primary
function
is
to
provide
heat
to
direct­
fired
dryers,
they
should
not
be
addressed
under
the
pending
Boiler/
Process
Heater
MACT
rule
in
view
of
that
rule's
long­
standing
determination
that
direct­
fired
process
units
are
properly
addressed
in
the
respective
MACT
rules
for
their
industrial
category
and
in
view
the
fact
that
these
specific
units
are
included
in
the
"
MACT
Floor"
for
the
PCWP
MACT.

Dryer
outage
events,
either
planned
or
unplanned,
could
be
incorporated
into
SSM
plans
by
considering
them
to
be
dryer
shutdowns.
The
General
Provisions
define
shutdowns
as
a
cessation
of
a
source
or
any
portion
of
an
affected
source
for
any
purpose.
Cessation
is
a
pause
in
operation.
The
length
of
time
a
cessation
occurs
is
not
defined
by
the
rule.
Under
this
interpretation
of
the
rule,
a
facility
would
have
to
decide
how
long
it
could
operate
a
process
heater
at
reduced
output
before
shutting
it
down
completely
in
order
to
comply
with
the
general
duty
provision
to
minimize
emissions,
and
include
the
decision
process
in
the
SSM
plan.

The
other
approach
would
be
to
incorporate
the
dryer
bypass
into
the
facility
Title
V
permit
as
an
alternative
operating
scenario
subject
to
complete
permit
authority
and
public
review.
Using
the
alternative
operating
scenario
approach
would
allow
facilities
to
tailor
their
operating
approach
to
their
unique
operating
and
physical
plant
situations.
Based
on
the
data
already
provided
to
EPA,
we
have
concluded
that
the
MACT
floor
for
these
events
is
no
control,
and
is
properly
evaluated
under
the
PWCP
MACT
rule.

AF&
PA
requests
that
the
PWCP
MACT
rule
specify
that
indirect
heat
exchanger
emissions
that
are
normally
routed
to
direct­
fired
dryers
be
subject
to
the
PCWP
MACT
requirements.
Specific
language
should
be
included
in
the
PCWP
MACT
preamble
directing
that
venting
of
these
units
is
part
of
the
MACT
floor
and
should
be
addressed
under
the
facility's
SSM
Plan
or
under
approved
Title
V
alternative
operating
scenarios.
This
coverage
should
also
be
recognized
in
the
preamble
to
the
Boiler/
Process
Heater
MACT
to
avoid
confusion
over
applicability.