Steamoxygengasificationprocessdiagram compressionand

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Unformatted text preview: oblem
with
producing
SNG
from
coal
is
the
additional
CO2
created
by
the
process.
This
paper
analyzes
 SNG
generation
technology
and
the
current
state
of
SNG
development
and
discusses
how
carbon
 capture
and
sequestration
(CCS)
technology
could
affect
SNG.
It
examines
the
technology’s
economic
 and
environmental
implications
to
determine
under
what
conditions
SNG
production
becomes
 economically
viable.
 2.
Coal­to­SNG
Technology
 2.1.
Brief
Description
 Steam‐oxygen
gasification,
hydrogasification,
and
catalytic
steam
gasification
are
the
three
gasification
 processes
used
in
coal‐to‐SNG.
The
proven
and
commercialized
method
of
gasification
for
the
coal‐to‐ SNG
process,
however,
is
the
steam‐oxygen
gasification
process.
 2.1.1.
Steam‐oxygen
gasification
 In
the
steam‐oxygen
process
of
converting
coal
to
SNG,
coal
is
gasified
with
steam
and
oxygen.
The
 gasification
process
produces
carbon
monoxide
(CO),
hydrogen
(H2),
carbon
dioxide
(CO2),
methane
 (CH4),
and
higher
hydrocarbons
such
as
ethane
and
propane.
The
gas
composition
depends
upon
the
 gasifier
conditions,
i.e.,
temperature
and
pressure.
At
higher
temperatures
and
pressures,
the
major
 products
are
CO
and
H2.
Three
moles
of
H2
are
required
to
react
with
each
mole
of
CO
to
produce
one
 mole
of
CH4.
The
concentration
of
H2
in
syngas
is
increased
by
a
step
called
the
water‐gas
shift
reaction,
 which
is
followed
by
a
gas
cleaning.
The
cleaned
gas,
consisting
primarily
of
CO
and
H2,
reacts
in
the
 methanation
reactor
in
the
presence
of
a
catalyst
to
produce
CH4
and
H2O.
The
resulting
gas,
after
H2O
 condensation
and
polishing,
if
required,
is
synthetic
natural
gas
(SNG).
Figure
1
shows
the
flow
diagram
 of
steam‐oxygen
gasification.
The
essential
components
of
the
process
are
the
air
separation
unit,
the
 gasifier,
the
water‐gas
shift
reactor,
syngas
cleanup,
and
the
methanation
reactor.
Each
component
is
 described
below.
 
 Air
Separation
Unit
 Oxygen
required
in
the
gasifier
is
either
supplied
by
vendors
or
generated
on‐site
using
an
air
separation
 unit
(ASU).
Cryogenic
air
separation
is
the
technology
generally
used
in
the
ASU.
 
 Gasifier
 The
most
important
and
basic
component
of
the
coal‐to‐SNG
process
is
the
gasifier.
Thegasifier
 converts
coal
into
syngas
(primarily
CO
and
H2)
using
steam
and
ox...
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This essay was uploaded on 03/18/2014 for the course ENG 316K taught by Professor Kruppa during the Spring '08 term at University of Texas at Austin.

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