POWER May 2011 - 40

THE FUTURE OF COAL
variety of R&D efforts are under way to reduce
these penalties.
The DOE/NETL currently is funding
development of pre-combustion CO2
capture
technologies that have the potential to
provide significant improvements in cost
and performance compared with current
solvents. Research is focusing on alternative
physical solvents, solid sorbents, and
membrane-based systems for the separation
of hydrogen and CO2
.
EPRI recently completed a study for the
Canadian Clean Power Coalition that explored
each area of a base IGCC plant for
technology advancements that could improve
the efficiency and/or cost of the plant. Results
showed recent developments in coal preparation
and feeding, air separation, gasification,
syngas and CO2
production could deliver a coal-fired power
plant, including 90% CO2
plant efficiency higher than a present-day
IGCC plant without CO2
capture.
Oxy-combustion. Oxy-combustion separates
oxygen from air and combines it with
recycled flue gas, so that combustion occurs
in the presence of oxygen and CO2
ing a flue gas rich in CO2
, produc(70%
to 90%, dry
basis). This combustion process allows the
CO2
produced during coal combustion to be
more easily purified and compressed prior to
transport and storage.
capture, with net
Oxy-coal technologies are at an earlier
stage of development than pre- or post-combustion
CO2
date, no commercial-scale oxy-combustion
power plants are in operation.
In the U.S., the DOE/NETL-funded FutureGen
2.0 project plans to repower Ameren
Energy Resources' 200-MW oil-fired
Meredosia Unit 4 with Babcock & Wilcox's
oxy-coal technology and to construct a CO2
pipeline and geological storage facility. The
project plans to capture over 90% of the
CO2
and sequester 1.2 million tons/year. The
processing, and power
schedule calls for the engineering and environmental
assessments to be completed by
2012 and the plant to begin operation in 2016.
(See " Oxy-Combustion: A Promising Technology
for Coal-Fired Plants, " Jan. 2010.)
Two commercial oxy-coal plants are
planned in Europe-Vattenfall's 250-MWe
plant in Germany and Endesa's 300-MWe
plant in Spain-and a 30-MWe pilot plant is
under construction in Australia by CS Energy.
Oxygen-fired IGCC and oxy-combustion
processes require large amounts of oxygen,
which imposes a significant cost and energy
penalty. An innovative technology called ion
transport membrane (ITM), developed by Air
Products (AP) under a cooperative agreement
with the DOE, could help reduce these costs.
The ITM process uses a ceramic material under
temperature and pressure to ionize and
3. Net power output and efficiency for IGCC with and without CO2 capture.
Source: EPRI
PRB cases - net output
Net efficiency
1,200
1,000
800
600
400
200
38.2%
29.8%
31.1%
PRB cases - total aux load
P8 cases - net output
40.0%
P8 cases - total aux load
38.8%
31.5%
38.1%
30.2%
37.8%
30.3%
41.9%
31.6%
45%
40%
35%
30%
25%
20%
15%
10%
5%
0%
capture technologies, and to
separate oxygen molecules from the air, and
unlike conventional cryogenic air-separation
units, it requires no electric power. EPRI has
been involved in the project since 2008, when
EPRI formed a collaborative to perform technical
tasks, assess overall progress, and provide
industry input to AP and the DOE.
Estimates by AP and EPRI suggest that oxygen
plant capital costs and operating power
consumption could be reduced in IGCC applications
by using ITM. Other potential benefits
include reduced cooling water and plant
space requirements. Preliminary modeling of
ITM applied to oxy-combustion shows similar
economic and efficiency benefits.
Retrofit CO2 Capture. The U.S. has
more than 330 GWe of existing capacity in
PC plants. To meet anticipated greenhouse
gas reduction targets, the U.S. electric power
industry may need to retrofit existing coal
plants with PCC systems. More broadly,
some analysts believe worldwide PCC retrofit
is essential to stabilize atmospheric CO2
The challenges of retrofitting plants for
.
carbon capture are significant: Sites would
need space for capture and compression
equipment (about 6 acres for a 500-MW
unit), the low-pressure steam turbine potentially
could need to accommodate extraction
of 25% to 30% of its steam for the CCS system,
the demand for cooling water supply
could increase by as much as 100%, and pollutant
controls may need to be upgraded to
be capable of reducing emissions below currently
permitted values to protect the solvent
used in some of the capture processes.
EPRI is in the midst of a large, multi-company
project to conduct plant-specific studies
to determine the thermal and economic impacts
of retrofitting a plant with an advanced
amine PCC technology. The studies are being
conducted at five plant sites, representative of
typical configurations across North America.
The project team is modeling the process flow
and the heat and mass balances to identify
the most practical CO2
capture configuration
based on each site's constraints, determine
the space required for the capture technology,
estimate the performance and costs for
the capture and compression systems, and
reveal each plant's features that materially
affect cost and feasibility of retrofitting.
New Capture Processes. Many reNotes:
P8 = Pittsburgh #8 coal, R/Q = Energy Radiant Quench gasifier, SGC = syngas cooler, WQ = Water Quench
gasifier.
40
www.powermag.com
search teams, including EPRI, are doing
considerable work to develop new capture
processes (primarily for post-combustion
applications) aimed at significantly reducing
the costs and inherent energy penalty.
In particular, the DOE/NETL is funding
development of several advanced PCC
technologies. In some cases, through its
Technology Watch function, EPRI has
identified potential new breakthrough proPOWER
| May 2011
Case 1: Siemens
Case 2: Siemens, CCS
Case 6: Shell SGC
Case 7: Shell SGC, CCS
Case 10: Shell WQ
Case 11: Shell WQ, CCS
Case 13: Siemens
Case 14: Siemens CCS
Case 15: GEE R/Q
Case 16: GEE R/Q, CCS
Case 21: Shell SGC
Case 22: Shell SGC, CCS
Net/gross power output (MWe)
Net plant efficiency (HHV)

http://www.powermag.com

POWER May 2011

Table of Contents for the Digital Edition of POWER May 2011