POWER January 2011 - 54

CARBON CAPTURE
What is Oxy-Combustion?
The oxy-combustion system consists of the
familiar coal-fired power plant's boiler and
environmental cleanup equipment (in the
case of FutureGen 2.0, supplied by Babcock &
Wilcox). These components have been redesigned
to burn coal with a mixture of nearly
pure oxygen and recycled flue gas (which is
primarily CO2) rather than air. An air separation
unit (ASU) produces the oxygen used for
combustion of the coal (Figure 2). The concentrated
stream of CO2 that leaves the boiler
is ready for cleaning and compression by the
compression and purification unit (CPU). The
CO2 is then transported in a pipeline to a permanent
storage facility. For FutureGen 2.0, Air
Liquide is supplying the ASU and the CPU.
use. In 2001, B&W partnered with AL, which
brought expertise in air separation, compression,
and purification to the team. The team
worked to improve the overall efficiency and
economics of the entire oxy-combustion plant
design. This collaboration led to several engineering
studies and cost estimates for both
retrofit and greenfield applications. That work
included testing oxy-combustion at 1.5 MWth
at the B&W R&D Center between 2001 and
2004 and large pilot-scale tests at the 30MWth
CEDF in 2007 and 2008.
The 30-MWth CEDF is a mini power plant
that includes a specially designed boiler with
a full complement of flue gas cleanup systems.
The CEDF is " catch-and-release " system
for CO2
of CO2
process, the CO2
; although a high-purity stream
is produced by the oxy-combustion
from the pilot facility is not
compressed and stored but is released to atmosphere.
All of the other processes for flue
gas cleaning were included as part of the system
testing.
The CEDF was the first in the world to
oxy-combust bituminous, subbituminous,
and lignite coals at this scale. Two process
configurations were tested:
■ Cold recycle, in which all of the flue gas
passes through the environmental clean-up
equipment, is cooled to remove substantial
moisture, and then is recycled to the boiler
at approximately 150F.
■ Warm recycle, in which the secondary flue
gas is taken after the air heater with only
particulates removed before being recycled
to the boiler at approximately 350F.
The remainder of the flue gas passes
through the environmental clean-up equipJanuary
2011 | POWER
2. Three building blocks. The oxy-coal combustion power plant substitutes nearly pure
oxygen mixed with recycled flue gas for air in the combustion of coal to produce a CO2 gas
stream ready for cleaning and compression in the compression and purification unit (CPU).
From the CPU the essentially pure CO2 is transported as a liquid via pipeline to the CO2 storage
facility. Source: FutureGen Alliance
ASU
Boiler island
Nitrogen (N2) out
Recycled flue gas
CPU
Other gases (NCGs)
Air in
Air
separation
unit
Oxygen
(O2)
CO2 and
flue gas
Boiler
Environmental
cleanup
equipment
Ash H2O SO2
Coal in
Other captured
emissions
CO2 capture
(liquid)
CO2 compression
3. The path to success. The B&W/AL oxy-combustion research and development pathway
to commercial deployment has accelerated with the team's recent selection as supplier of the oxy
technology for FutureGen 2.0. Source: Babcock & Wilcox Power Generation Group and Air Liquide
1,000
Integration
study
Engineer100
ing
studies
(25-790 MW)
10
SBS I pilot tests
1
2003
2005
2007
2009
2011
2013
2015
Notes: BWRC = Babcock & Wilcox (B&W) Research Center, Callide = Air Liquide oxy pilot plant in Australia, CEDF = Clean
Environment Development Facility, SBS = B&W Small Boiler Simulator, Lacq = Air Liquide oxy pilot plant in Lacq, France
ment and the flue gas cooler. Testing confirmed
control philosophies for transitioning
from air to oxy-combustion and flue gas recycle
control. The tests showed 50% to 70%
reduction in NOx
removal of SO2
and met expectations for
, SO3, and particulates. In an
oxy-combustion plant, the small amount of
remaining pollutants from the power block
are then removed in the compression and
purification unit (CPU). Figure 3 shows the
B&W/AL technology's pathway to commercial
deployment.
Beginning in 2008, the team focused on
optimization and integration of the three
blocks: the power block (including steam cywww.powermag.com
cle
and balance of plant), air separation unit
(ASU), and CPU. This work led to selection
of the warm recycle process for low-sulfur
fuels. Based on this work, a 150-MW gross
demonstration plant design was developed.
Designs for commercial plants up to 700
MW gross are now in progress.
Unique System Design
The biggest impact on plant efficiency
and project cost is the addition of the ASU
and CPU. B&W and AL have made significant
investments in improving system
designs and component efficiency and
have achieved impressive gains. Although
53
SBS II pilot tests
ASU efficiency
optimization
30 MWth CEDF
demo
EPRI 700 MW
reference
650 MWe
engineering
study
FG 2.0
200 MWe demo
Lacq oxy-gas test,
burners & CPU test,
BWRC component test
Callide CPU demo
Plant size (MWe)

http://www.powermag.com

POWER January 2011

Table of Contents for the Digital Edition of POWER January 2011