Greatnorthernpowerdevelopmentandindustrial

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Unformatted text preview: commercialized
and
operational
technology.
 Henceforth,
the
environmental
impacts
and
costs
of
SNG
refer
to
steam‐oxygen
gasification.
However,
it
 should
be
noted
that
the
higher
a
plant’s
thermal
efficiency,
the
lower
its
CO2
emissions
will
be.
 Therefore,
CO2
emissions
from
the
hydrogasification
and
steam
catalytic
gasification
processes
should
 be
lower
than
those
of
the
steam‐oxygen
gasification
process.
 3.1.
Environmental
Implications
of
SNG
 The
coal‐to‐SNG
process
is
capable
of
achieving
very
low
sulfur
emissions.
The
sulfur
is
emitted
as
 hydrogen
sulfide
(H2S)
and
can
be
removed
by
the
acid
gas
removal
(AGR)
system.
The
acid
gas
(CO2
and
 H2S)
can
be
separated
in
the
Selexol
or
Rectisol
process
in
a
SNG
plant.
The
H2S
can
be
utilized
in
a
Claus
 Climate
Change
Policy
Partnership
 11
 Synthetic
Natural
Gas
(SNG):
Technology,
Environmental
Implications,
and
Economics
 plant
to
generate
elemental
sulfur.
Mercury
can
be
removed
in
the
water
quench
during
the
syngas
 cleaning.
The
removal
level
should
be
sufficient
to
meet
the
permitted
emissions
level.
However,
if
 required,
a
carbon
bed
could
be
used
for
additional
mercury
removal.
NOx
emissions
from
the
process
 would
be
very
low;
the
only
NOx
emissions
would
be
from
the
boiler
used
to
generate
steam
and
power
 for
the
process.
Considering
that
the
sulfur
is
removed
by
Claus
plant,
the
coal‐to‐SNG
should
be
 considered
a
clean
coal
technology.
 CO2
Emissions
 CO2
and
H2S
are
emitted
from
the
acid
gas
removal
plant.
Separate
streams
of
CO2
and
H2S
can
be
 obtained
from
the
AGR
process.
CO2
is
either
captured
or
released
into
the
atmosphere.
Approximately
 two‐thirds
of
the
carbon
content
of
the
coal
is
converted
into
CO2
in
the
SNG
process
and
the
remaining
 carbon
beco...
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