Overview of CO2 Reduction byIGCC Technology
TAKAO HASHIMOTO*1

KATSUHIRO OTA*11

HIROMI ISHII*1

YUUICHIROU KITAGAWA*2

YOSHINORI KOYAMA*3

KOICHI SAKAMOTO*Coal is an important source of energy, accounting for about 25% of the world's primary energy and about 20% of Japan's. Yet theCO2 emission per heating value from coal is quite large. An important challenge, for the continued use of coal, has been to reduce
CO2 emission by enhancing efficiency. Studies have recently been conducted on CCS (carbon capture and sequestration) in order toreduce CO2 emission further. The Integrated coal Gasification Combined Cycle (IGCC) has been attracting attention as the mostefficient and economic coal firing thermal power generation technology for capturing CO2 . This paper reports on the forefront trends
in IGCC and CO2 capture.

especially attractive to them.
With encouragement from Incentive Tax Credit (ITC) in
the Energy Policy Act enforced in August 2005, some IGCC
projects targeting commercial operation in the 2010s arebeing studied. The adoption of ITC in three IGCC projects
was announced in December 20 06, and plans for more
projects are scheduled to be announced in April 2008.
Electric Power companies are actively pursuing businessprojects for commercial plants. AEP (American ElectricPower), for example, applied for an IGCC of the 600 MW classwith the Public Utilities Commission in West Virginia in June
2007. Duke Energy, meanwhile, adopted an IGCC of the 600
MW class for ITC.
On the other hand, studies on the FEED (Front End
Engineering and Design: Detailed design for project costestimation) of these projects have shown that all rely onslurry-feed oxygen-blown gasifiers based on technologies
from other companies. The projects thus have low net plant
power efficiency (38.6%) (under HHV base), with CCS (carbon
capture and sequestration) positioned as a future installation
plan. The power plants clearly need to elaborate their plansand discussions for efficiency enhancement and improved
environmental performance.
2.2 Plan for air-blown IGCC commercial plant
To meet the market need for vitalized business projects forcommercial plants, efficiency enhancement, and improved
environmental performance, Mitsubishi Heavy Industries,
Ltd. (MHI) has started a study on a highly efficient IGCC
commercial plant adopting a 1500°C class gas turbine.
Figure 1 shows the external appearance of an air-blown
IGCC commercial plant. Table 1 shows a comparison of themain specification data between the IGCC demonstration
plant and a commercial plant. The gasifier in the commercial

1. IGCC development
Integrated coal Gasification Combined Cycle (IGCC)
is a power plant system designed to run more efficiently
than conventional coal firing systems by combining coalgasification with a gas turbine combined-cycle power plant.
Nine electric power companies in our countr y havebeen working with Electric Power Development Co., Ltd.
and Central Research Institute of Electric Power Industry(CR IEPI) to develop a more efficient and highly reliable
air-blown IGCC, with subsidy funding from the national
government. From 1986 to 1996, the collaborators built
and operated a pilot plant test on the scale of 200 t/day(corresponding to 25 MW ) in a project entrusted by theAgency for Natural Resources and Energy and the New
Energy and Industrial Technology Development Organization(NEDO). And from the beginning of this decade, Clean Coal
Power R&D Co., Ltd. (established in June 2001) has been
moving forward with the test operation of a 250 MW-class
IGCC demonstration plant (hereinafter “IGCC demonstrationplant”).
The gas turbine of the IGCC demonstration plant wasignited in May 2007, and the gasifier was ignited four months
later, in September. Tests are scheduled to continue until
2010.

2. Plan for IGCC commercial plant
2.1 Plan for IGCC commercial plant in the United States
Power producers in the United States are carrying forward
many plans for coal firing power plants to make effective useof abundant domestic energy resources, and to reduce theirreliance on natural gas (an increasingly expensive resource).
T he improved env ironment al per for mance of IGCC is*1 Power Systems Headquarters*2 Nagasaki Shipyard & Machinery Works*3 Nagasaki Research & Development Center, Technical Headquarters

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)18

Sulfurrecovery Sulfur
unit
CO2CO+H2O CO2+H2
SteamCoal

CO shiftconverterAir-blown
gasifier

N2O2ASU

AGR

Air
compressor

AirGT

CO2compressor

CO2 storageH2-rich syngas
AirCompGST

G

Gasification airHRSG

ASU : Air separation unit

Fig. 2 Block flow diagram of the air-blown IGCC system with CO 2 capture

Table 1 Comparisons of main specification data between IGCC
demonstration plant and commercial plant
Item
Gross power output(MW)

DemonstrationplantCommercialplant250

500 (60 Hz)

Type of coal(−) Bituminous coal Bituminous coalGasifier(−)

Gas cleanup system(−)

Gas turbine(−)

Dry feed
Air blown

Dry feed
Air blown

WetWetdesulfurization desulfurization
M701DA

M501G

Net power plant efficiency (%, HHV)

40.5

46SOx(ppm)
Environmental NOx(ppm)
Targets(16% O2 basis) Particulate(mg/m3N)
matter

8855Start of operation(−)

combustion.
Because IGCC can capt ure CO 2 f rom syngas underpressurized condition, the treated gas volume is small andthe CO2 concentration is high. Compared with CO2 capture
from boiler flue gas, the capture of CO2 from syngas requires
only a small loss of plant ef f iciency and only a modest
increase in power generation cost.
Figure 2 shows block f low diagram of the air-blown
IGCC system with CO 2 capture. Carbon monoxide (CO) insyngas produced in gasifier is converted, along with water,
into CO 2 and hydrogen (H 2) in a CO shift converter. CO 2
is separated and captured from syngas in the AGR (AcidGas Removal: Gas cleanup including desulfurization / CO 2capture). The H 2 -rich syngas from which the CO2 has been
removed is used as fuel in the gas turbine. In the IGCC with
CO2 capture, the CO shift converter and CO2 capture system
must be optimized according to the required rate of CO 2capture.
Figure 3 shows the comparisons of capital cost and net
power output between an air-blown IGCC and oxygen-blown
IGCC during CO2 capture.
Though the air-blown gasification produces much more

442007

Earliest : 2012

plant has an assumed scale-up to twice the capacity ratio of
the IGCC demonstration plant. The gas turbine will adopt
a combustor capable of firing syngas at high efficiency,
based on many of the techniques MHI has used to achieve
outstanding performance with its low-calorie firing gasturbines. The IGCC commercial plants incorporating MHI’slatest gas turbines can reduce CO2 per kilowatt-hour by about
15% compared with conventional coal firing plants, because of
the improved net plant efficiency.
MHI also studies the use of PRB (Powder River Basin)coal, an inexpensive coal found in abundance in the UnitedStates, for IGCC commercial plants. While the slurry feedsystem cannot easily adopt PRB coal because of the highwater content (20 to 30 wt%), MHI’s dry feed system cangenerate electric power with high efficiency using this coal.

140
100

Capital cost (%)

120
100

100100(Net power output)

100

92 105

80

9780

60

60

4040
202003. CO2 capture by IGCCCountries all over the world are studying IGCC systemswith CO 2 capture, to address the crisis of global warming.
Generally there are two methods to capture CO2 for the coalfiring power plant: (1) a method to capture CO2 from boiler
flue gas; (2) a method to capture CO 2 from syngas before

Capital Capital costcostagainst( $ ) net power
output( $/kW )Air blown

Capital Capital costcostagainst( $ ) net power
output( $/kW )Oxygen blown

Net power output (%)

Fig. 1 External appearance of an air-blown IGCC
commercial plant0Fig. 3 Comparisons of capital cost and net power output between
the air-blown IGCC and oxygen-blown IGCC during CO 2capture

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)19

raw syngas than oxygen-blown gasification on a volume
basis, the gasifier and AGR in the air-blow gasification IGCC
system have only a small influence on capital cost. On theother hand, the net power output in air-blown gasification islarger. Thus, air-blown gasification has advantages in termsof capital cost ($/kW).

reduce CO 2 emissions, there are several challenges posedby declines in efficiency, higher capital costs, and variationin the geological potential to store CO2 in the regions whereplants are built. We therefore intend to study not only thepower generation equipment, but total system configuration
as well.

4. Conclusion
IGCC is a core technology used in the next-generationof coal firing power plants. Our company is conducting
various demonstration tests using a 250 MW class IGCC
demonstration plant to confirm the reliability and safety. We
are also acquiring lesson-learnt data from a demonstration
plant that can ref lect to commercial plant design andestablish an air-blown IGCC system with high efficiency andhigh reliability.
Ultimately, we will realize IGCC commercial plants withthe additional capability of CCS, to respond to environmental
requirements. While CCS has the potential to substantially

Takao Hashimoto

Katsuhiro Ota

Koichi Sakamoto

Hiromi Ishii

Yuuichirou Kitagawa

Yoshinori Koyama

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 1 (Mar. 2008)20