Co2 capture-technologies

CO2 CAPTURE TECHNOLOGIES
TECHNOLOGY OPTIONS FOR CO2 CAPTURE
JANUARY 2012

GLOBAL CCS INSTITUTE – CO2 CAPTURE TECHNOLOGIES
CO2 Capture Technologies, Section 1 1
CONTENTS
TECHNOLOGY OPTIONS FOR CO2 CAPTURE ..........................................................................3
Brief description of major technologies for CO2 capture ..........................................................3
The importance of improved efficiency.....................................................................................4
Technology readiness level (TRL) ............................................................................................5
Commercial demonstration of advanced coal technologies.....................................................6
EPRI comments ..................................................................................................................6
Integrated CCS demonstration is crucially needed ............................................................6
Commercial deployment of CCS technology............................................................................6
Advantages and disadvantages of major CO2 capture technologies.......................................7
Post combustion capture advantages.................................................................................7
Post combustion capture challenges ..................................................................................7
Pre combustion capture advantages ..................................................................................7
Pre combustion capture challenges....................................................................................8
Oxy combustion advantages...............................................................................................8
Oxy combustion challenges ................................................................................................8
ACRONYMS AND SYMBOLS ..................................................................................................9

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EPRI
This document has been derived from material in the report sponsored by the Global Carbon Capture and
Storage Institute, Canberra, Australia. CO2 Capture Technologies July 2011.
CO2 Capture Technologies: Report sponsored by the Global Carbon Capture and Storage Institute, EPRI, Palo
Alto, CA: <2011>. < E236656>.

TECHNOLOGY OPTIONS FOR CO2 CAPTURE
Brief description of major technologies for CO2 capture
The main competing technologies for CO2 capture from fossil fuel usage are:
 Post Combustion Capture (PCC) from the flue gas of Combustion-based plants;
 Pre Combustion Capture from the Syngas in Gasification based plants; and
 Oxy Combustion – the direct combustion of fuel with Oxygen.
These three approaches are shown diagrammatically for coal based power systems in Figure 1-1.
Figure 1-1 Technical Options for CO2 Capture from Coal Power Plants
Post combustion capture (PCC) at near atmospheric pressure can be applied to newly designed plants or
retrofitted to existing coal plants after suitable flue gas clean up. Absorption processes are currently the most
advanced of the PCC technologies. The PCC technologies can also be used in other industries besides power
e.g. cement, oil refining, and petrochemicals.
Pre-combustion capture in the IGCC power application comprises gasification of the fuel with oxygen or air
under high pressure, the use of the shift reaction followed by CO2 removal using Acid Gas Removal (AGR)
processes with hydrogen rich syngas supplied to the gas turbine based power block. Pre combustion capture
can be added to existing IGCC plants but in the future IGCC plants will almost certainly be designed with
capture from the start. The pre-combustion capture of CO2 using AGR processes is also practiced
commercially in natural gas processing, natural gas reforming and coal gasification plants.
Oxy combustion is the combustion of fuel with oxygen. In an Oxy coal power plant, flue gas is recycled to the
oxygen fired boiler to keep the boiler temperature at the level acceptable for boiler tube material integrity. The

flue gas containing mostly CO2 is purified, dried and compressed. The Oxy technology may also be applied to
existing plants but in most cases a new boiler and steam turbine would probably be justified.
Within each of the three major capture categories there are multiple pathways using different technologies
which may find particular application more favourably in certain climate conditions, locations, elevations and
coal types.
The importance of improved efficiency
The addition of CO2 capture incurs a very significant loss of efficiency and power output that has a large effect
on the LCOE economics since the capital cost has to be spread over less MWh and the fuel cost per MWh is
increased. This document is focused on the CO2 capture technologies and potential improvements to reduce
the energy losses and capital costs associated with capture. However, a major contribution to the reduction of
CO2 from fossil based plants will be achieved through increases in the efficiency of the basic technologies of
pulverized coal combustion and combustion (gas) turbines.
For example, considerable work is underway to develop and qualify advanced materials that will enable the
use of ultra supercritical steam conditions with higher temperatures (up to 700-750°C) and pressures (up to
350 bar). This, in turn, will lead to higher plant efficiencies and lower CO2 emissions per MWh. As illustrated in
Figure 1-2 a 20% reduction in CO2 emissions can be achieved through efficiency improvement. EPRI studies
indicate that this CO2 emissions reduction from efficiency improvement can be accomplished at lower cost per
tonne of CO2 removed than from CO2 capture.
For PCC, the major energy losses are incurred in sorbent regeneration and CO2 compression. Current PCC
R&D is focused on improved sorbents that require less energy for regeneration and/or could be regenerated at
pressure, thereby reducing the CO2 compression energy required.
Figure 1-2 PC Plant Efficiency and CO2 Reduction
SubcriticalPlantRange
Commercial
Supercritical
PlantRange
AdvancedUltra-
Supercritical
PlantRange2 Percentage Point Efficiency Gain = 5% CO2 Reduction
SubcriticalPlantRange
Commercial
Supercritical
PlantRange
AdvancedUltra-
Supercritical
PlantRange2 Percentage Point Efficiency Gain = 5% CO2 Reduction

There are also major developments underway to increase the firing temperatures (up to 1600°C) and
efficiencies of gas turbines. These developments will in turn reduce the CO2 emissions from natural gas
combined cycle (NGCC) and Integrated Gasification Combined Cycle (IGCC) plants.
For IGCC pre combustion capture, the major energy losses are incurred in the air separation unit (ASU),
water-gas shift, gas cooling and CO2 separation areas. The IGCC R&D is focused on improvements to the
ASU, gasification, shift catalysts, and in the processes and equipment that reduce the energy loss of the
separation of hydrogen from CO2 and of CO2 compression. The use of higher firing temperature higher
efficiency gas turbines will further increase plant efficiency and reduce the CO2 emitted per MWh. These gas
turbines will also be of larger sizes that will provide further economies of scale and improve economics.
For oxy combustion the major energy penalty is in the ASU area. Current oxy combustion R&D is focused on
energy improvements to the ASU, potential reduction of recycle gas and CO2 purification energy losses. . The
use of higher temperature materials in the boiler and steam turbine will further increase efficiency and reduce
the CO2 emitted per MWh.
Technology readiness level (TRL)
Throughout this chapter the term Technology Readiness Level (TRL) will be used to indicate the development
level of the technologies described. The following outline of the TRL concept has been mostly taken from the
Global CCS Institute Report #4 of the Strategic Analysis Series.
This TRL approach can be particularly useful in tracking the status of individual technologies throughout the
stages of the R&D timeline. The nine TRLs are listed in Table 1-1.
The achievement of a given TRL will inform process developers and organizations of the resources required to
achieve the next level of readiness. An achievement of TRL-9 indicates that the first successful operation at
normal commercial scale has been achieved and that the technology can be deployed with risks that are
comparable to those undertaken on other commercial technologies. Progressively higher technical and
financial risks are required to achieve the TRLs up to and including TRL-9.
Table 1-1 The nine technical readiness levels
TRL-9 Full-Scale Commercial Deployment
TRL-8 Sub-Scale Commercial Demonstration Plant (>25% commercial
scale)
TRL-7 Pilot Plant (>5% commercial scale)
TRL-6 Component Prototype Demonstration (0.1-5% of full scale)
TRL-5 Component Prototype Development
TRL-4 Laboratory Component Testing
TRL-3 Analytical, ‘Proof of Concept’
TRL-2 Application Formulated
TRL-1 Basic Principles Observed
More detailed information on the background justification for the TRL rankings in this document are included
and discussed in the separate sections of this document that cover each of the three major capture pathways.
While the actual TRL levels of technologies and sectors have not changed since 2009 there has been
significant progress towards higher TRL in most areas.

Commercial demonstration of advanced coal technologies
The development of emission controls on coal fired power plants can be used as an example of technology
progression through the required TRLs. In the mid-20th
century, coal-fired power plants had limited controls for
sulphur dioxide (SO2), nitrogen oxides (NOx) or mercury emissions. Throughout the past 50 years, various
technologies to control these pollutants have progressed from about TRL-4 to full commercial availability. This
experience has shown that the achievement of TRL-9 can take approximately 20 or more years. This long
development period is largely dictated by costs, design, construction and operational testing activities
associated with the pilot plants (to achieve TRL-7), sub-scale commercial demonstration plants (to achieve
TRL-8) and the first full-scale, commercial deployment (TRL-9).
EPRI comments
The use of TRL in the context of advanced coal technologies has some drawbacks. The TRL classification
system was devised by NASA to assess technology readiness only. It was not designed to address ‘economic’
readiness. Thus, a technology may reach TRL-9 and be technically mature and still not meet project economic
requirements. The TRL system does not address the economic feasibility of deploying the technology.
In the past few years, ‘full scale’ coal-fired power plants purchased by utilities have a net capacity exceeding
400 MWe and largely greater than 600 MWe. For the purposes of a TRL assessment of advanced coal
technology, it is suggested that TRL-9 would be achieved by a power plant in the capacity range 400-800 MWe
(net). By this metric, successful operation of the Kemper County (524 MWe) would achieve TRL-9, albeit at a
CO2 capture rate less than the 90% commonly imagined. Successful operation of Boundary Dam (110 MWe)
and FutureGen (200 MWe) would achieve TRL-8: sub-scale commercial demonstration plant. Technology
suppliers to Boundary Dam and FutureGen may claim ‘commercial’ operation, but it would be operation at a
scale significantly less than that commonly purchased by utilities.
Integrated CCS demonstration is crucially needed
Although current technology needs further improvements, it is extremely important to demonstrate CCS on a
commercial scale as soon as possible. This is needed for the demonstration of capture technology operating in
an integrated mode in a real power plant and in a real power grid environment. It is also necessary to
demonstrate sequestration/storage at sufficient scale that has credibility for further deployment. Unless
progress is made at the commercial CCS demonstration scale to answer these two basic issues it will become
increasingly difficult to justify continued R&D funding on potential improvements to capture and storage
technologies.
If multiple CCS demonstrations with improved technologies are to be achieved at large-scale (i.e., TRL-9) by
2020 to proceed with commercial deployment, then many technologies need to be approaching the pilot plant
stage (TRL-7) today. However, currently there are very few organizations funding demonstrations at one-tenth
to full commercial-scale. Some pilot plant scale capture projects have been funded but advancing to sub-
commercial scale demonstrations and larger will require an order of magnitude greater level of funding.
The total capital cost of investment for PCC demonstration would be significantly lower if PCC was retrofitted
to an existing coal plant than if a new SCPC with PCC was constructed. However, the technical risk is probably
not very different from that associated with a newly built SCPC with PCC. PCC retrofit to an existing plant will
also incur a loss of power output of perhaps 30% so that replacement power may be needed.
Commercial deployment of CCS technology
Sub-scale commercial demonstration projects are being developed in the US and Europe and the Boundary
Dam PCC plant is under construction. The initial integrated full scale commercial sized CCS coal based
demonstration projects will only proceed with significant government support. The Kemper County IGCC plant
is currently the only full scale CCS plant that is fully funded and in construction. While integrated commercial
CCS demonstration projects are clearly a pre-requisite, full scale commercial deployment will only proceed is

there is a value attributable to the reduction of CO2 emissions (or possible sale) and that CCS is found to be a
competitive abatement choice.
It can be noted that some pre combustion and post combustion capture industrial projects have been able to
proceed because of the value attributable to the sale of the CO2 for EOR.
Advantages and disadvantages of major CO2 capture technologies
Post combustion capture advantages
 Can be retrofitted to existing plants allowing the continued operation of valuable resources
 In either new build or retrofit application it enables the continued deployment of the well established
Pulverized Coal (PC) technology familiar to power industries worldwide
 The continued development of improved materials for Ultra Supercritical (USC) plants will increase the
efficiency and reduce the CO2 emissions of future PC plants
 The widespread R&D on improved sorbents and capture equipment should reduce the energy penalty of
PCC capture
 Sub-scale demonstration of PCC is proceeding. The 110 MW Boundary Dam project of Saskatchewan
Power with PCC using the Cansolv process is under construction with planned operation in 2014.
Post combustion capture challenges
 Amine processes are commercially available at relatively small scale and considerable re-engineering and
scale-up is needed
 The addition of capture with current amine technologies results in a loss of net power output of about 30%
and a reduction of about 11 percentage points in efficiency. In the case of retrofit this would imply the need
for replacement power to make up for the loss.
 Most sorbents need very pure flue gas to minimize sorbent usage and cost. Typically < 10 ppmv or as low
as 1 ppmv of SO2 plus NO2 is required depending on the particular sorbent
 Steam extraction for solvent regeneration reduces flow to low-pressure turbine with significant operational
impact on its efficiency and turn down capability.
 Water use is increased significantly with the addition of PCC particularly for water cooled plants where the
water consumption with capture is nearly doubled per net MWh. For air cooling the water consumption is
also increased with capture by about 35% per net MWh.
 Plot space requirements are significant. The back-end at existing plants is often already crowded by other
emission control equipment. Extra costs may be required to accommodate PCC at some more remote
location.
Pre combustion capture advantages
 Pre combustion capture using the water-gas shift reaction and removal of the CO2 with AGR processes is
commercially practiced worldwide.
 Pre combustion capture of the CO2 under pressure incurs less of an energy penalty (~20%) than current
PCC technology (~30%) at 90% CO2 capture.
 Ongoing R&D on improved CO shift catalysts, higher temperature gas clean up and membrane separation
technology for hydrogen and CO2 has the potential to produce a step-change reduction in the energy
penalty of capture
 Water use, while still substantial, is lower than with PCC
 The ongoing continued development of larger more efficient gas turbines can markedly improve the
efficiency of future IGCC plants
 The Kemper County plant in Mississippi, an IGCC plant with pre combustion capture, is under construction
with planned operation in 2014.

Pre combustion capture challenges
 While the energy loss with addition of pre-combustion capture is lower than with the addition of PCC the
energy loss is still significant
 The commercial demonstration of large F or G gas turbines firing hydrogen has yet to be demonstrated in
an IGCC plant with capture
 In the event of a need to vent the CO2 additional purification may be needed
 IGCC is not yet very widely used in the power industry
 The capital costs of IGCC without capture are much higher than SCPC without capture. The IGCC costs
need to be reduced to compete more effectively.
Oxy combustion advantages
 Oxy-combustion power plants should be able to deploy conventional, well-developed, high efficiency
steam cycles without the need to remove significant quantities of steam from the cycle for CO2 capture.
 The added process equipment consists largely of rotating equipment and heat exchangers; equipment
familiar to power plant owners and operators. (No chemical operations or significant on-site chemical
inventory).
 Ultra-low emissions of conventional pollutants can be achieved largely as a fortuitous result of the CO2
purification processes selected, and at little or no additional cost.
 On a cost per tonne CO2 captured basis, it should be possible to achieve 98+% CO2 capture at an
incrementally lower cost than achieving a baseline 90% CO2 capture.
 Development of chemical looping combustion with advanced ultra-supercritical steam cycles could result in
an oxy-combustion power plant (with CO2 capture) that is higher efficiency than air-fired power plants
being built today (without CO2 capture).
 The best information available today (with the technology available today) is that oxy-combustion with CO2
capture should be at least competitive with pre- and post-combustion CO2 capture and may have a slight
cost advantage.
Oxy combustion challenges
 It is not possible to develop sub-scale oxy-combustion technology at existing power plants. An oxy-
combustion power plant is an integrated plant and oxy-combustion technology development will require
commitment of the whole power plant to the technology. Thus, the technology development path for oxy-
combustion may be more costly than that for either pre-combustion or post-combustion capture which can
be developed on slip streams of existing plants.
 The auxiliary power associated with air compression in a cryogenic air separation unit and CO2
compression in the CO2 purification unit will reduce net plant output by up to 25% compared to an air fired
power plant with the same gross capacity (without CO2 capture).
 There is no geological or regulatory consensus on what purity levels will be required for CO2 compression,
transportation and storage. For this reason, most oxy-combustion plant designs include a partial
condensation CO2 purification system to produce CO2 with purity comparable to that achieved by amine
post combustion capture. Oxy-combustion costs may be reduced if the purity requirements could be
relaxed.
 Air-fired combustion is commonly anticipated for start-up of oxy-combustion power plants. The very low
emissions achieved by oxy-combustion with CO2 purification cannot be achieved during air-fired start-up
operations without specific flue gas quality controls for air-fired operations that are redundant during
steady state oxy-fired operations. If a significant number of annual restarts are specified, either these
added flue gas quality controls will be required (at additional capital cost) or provisions must be made to
start up and shut down the unit only with oxy-firing and without venting significant amounts of flue gas.
 Plot space requirements are significant for the air separation unit and CO2 purification units.

ACRONYMS AND SYMBOLS
AFBC Atmospheric Fluidized Bed Combustion
AGR Acid gas removal
AQCS Air Quality Control System
ASU Air Separation Unit
B&W Babcock & Wilcox
Bara Bars absolute
Barg Bars gauge
BFW Boiler feedwater
BP British Petroleum
Btu British thermal unit
CC Combined Cycle
CCGT Combined Cycle Gas Turbine
CCPI Clean Coal Power Initiative
CCS CO2 capture and Storage (or Sequestration)
CCT Clean Coal Technology
CF Capacity Factor
CFB Circulating fluidized bed
CHP Combined Heat and Power
CO2 Carbon dioxide
COE Cost of electricity
COP ConocoPhillips
CT Combustion Turbine
DOE U. S. Department of Energy
DOE NETL Department of Energy National Energy Technology Laboratory
ECUST East China University of Science and Technology
EEPR European Energy Programme for Recovery
EIA Energy Information Administration
EOR Enhanced Oil Recovery
FBC Fluidized-bed combustion/combustor
FEED Front End Engineering Design
FGD Flue gas desulphurization
FOAK First of a kind
F-T Fischer Tropsch
ft3
Cubic feet
FW Foster Wheeler
FWI Foster Wheeler Italiana
GHG Greenhouse Gas
GI Gasification Island
GJ Gigajoule
gpm Gallons per minute (US)
GT Gas Turbine
H2S Hydrogen sulfide
HgA Mercury absolute
HHV Higher heating value
HRSG Heat recovery steam generator
HP High pressure
IEA International Energy Agency
IGCC Integrated Gasification Combined Cycle
IP Intermediate pressure
IPP Independent power producer
kJ Kilojoules
KBR Kellogg, Brown & Root

LCA Life Cycle Analysis
LCOE Levelized Cost of Electricity
LHV Lower heating value
LP Low pressure
LSTK Lump Sum Turnkey
mt Metric ton
MDEA MethylDiethanolamine
MMBtu Million Btu
MPa Mega Pascal
MTG Methanol to Gasoline
MTO Methanol to Olefins
NCCC National Carbon Capture Center
NDRC National Development and Reform Commission (China)
NETL National Energy Technology Laboratory
NGCC Natural Gas Combined Cycle
NH3 Ammonia
Nm3
Normal cubic meters
NOX Nitrogen oxides
NSPS New Source Performance Standards
OCGT Open Cycle Gas turbine
O&M Operation and maintenance
PC Pulverized Coal
PCC Post Combustion Capture
ppmv parts per million by volume
PRB Powder River Basin (Coal)
PSDF Power System Development Facility
psia Pounds per square inch absolute
psig Pounds per square inch gage
R&D Research & Development
RD&D Research, Development and Demonstration
RQ Radiant Quench (GE)
RTI Research Triangle Institute
RWE Rheinische Westphalien Electricidadeswerke
SCFD Standard Cubic Feet per day
SNG Substitute Natural Gas
SCPC Supercritical Pulverized Coal
SCR Selective catalytic reduction
SO2 Sulphur dioxide
SRU Sulphur Recovery Unit
st Short ton (2000 pounds)
stpd Short tons per day
TCR Total Capital Requirement
TFC Total Field Cost
TPC Total Plant Cost
USC Ultra Supercritical
US EPA US Environmental Protection Agency
WGCU Warm gas clean up

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