Mitsubishi Heavy Industries Technical Review Vol. 46 No. 2 (June. 2009)
1Development of IGCC Commercial Plant
with Air-blown Gasifier
TAKAO HASHIMOTO

KOICHI SAKAMOTOYUUICHIROU KITAGAWAYOSHINORI HYAKUTAKENORISHIGE SETANIThe development of integrated coal gasification combined-cycle (IGCC) power
generation, a coal-based high-efficiency power generation system, and its commercialization
with the capture and sequestration of the CO2 produced during electric power generation hasreceived special attention. This will reduce CO2 emissions and prevent global warming whileproviding a stable energy supply. This paper reports on the development of a commercial IGCC
plant and efforts to apply CO2 capture technology to Mitsubishi Heavy Industries’ (MHI’s)
IGCC.

|1. Introduction
The consumption of coal, a fossil fuel with a long-term stable supply and low cost, willcontinue to increase significantly in step with the global increase in energy consumption. On theother hand, the use of coal is becoming increasingly difficult, mainly due to global warming. The
development of highly efficient technology to reduce CO2 emissions, therefore, has become anurgent priority. Studies are globally underway to develop the technology required to capture andsequester CO2 generated during power generation as a step in reducing CO2 emissions. This has
focused special attention on integrated coal gasification combined-cycle (IGCC) power generation
as a thermal power generation technology that can capture CO2 with the highest efficiency andeconomy; i.e., it is one of the cleanest coal technologies. This paper first outlines the status of
IGCC development, and then reports on the current development program for IGCC commercial
plants and the accompanying CO2 capture technology.

|2. IGCC development status
IGCC is a power generation system designed to run more efficiently than conventional
pulverized coal-fired systems by combining coal gasification with a gas turbine combined-cyclesystem. In collaboration with the government, nine electric utility companies, J-POWER, and theCentral Research Institute of Electric Power Industry (CRIEPI), Mitsubishi Heavy Industries(MHI) has been making efforts to develop a highly efficient and reliable air-blown IGCC plant
optimized for power generation. A 250 MW IGCC demonstration plant, which is called “Nakoso”
according to the place name where the plant is located, was constructed as the final step before
commercialization following the operation of a 2 t/day Process Development Unit (PDU) andtesting at a 200 t/day (equivalent to 25 MW) pilot plant.
The IGCC demonstration plant project was led by Clean Coal Power R&D Co. Ltd., which
was founded in the collaboration in June 2001. MHI concluded an EPC single-point turn-key
contract for all the IGCC plant, by supplying the gasifier, gas cleanup system, gas turbine, steamturbine, and exhaust heat recovery steam generator (HRSG). After all of the effort, MHI
successfully completed the design, construction, and delivery of the equipment in 2007.
A series of demonstration test started in the “Nakoso” IGCC plant in September 2007 andsuccessfully proceeded on schedule. The plant reached its rated load of 250 MW in March 2008,
and completed more than 2,000 hours of long-term continuous operation in September 2008.
Figure 1 shows its operational performance compared with the other IGCC plants in westerncountries. They use oxygen-blown gasifiers originally developed for the application to chemicalplants, and many of them could not achieve long-term continuous operation even 10 years after theinitial start of operations. The achievement of such operation by ”Nakoso” only one year after
startup demonstrated extremely high reliability of MHI’s air-blown IGCC system.

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 2 (June. 2009)
2Figure 1 Consecutive operating hours of IGCC plants as a function of years after startup

Table 1 lists the plant performance measurement results and shows that the targeted power
output and efficiency were fully achieved. The carbon conversion rate was almost 100% because of
perfect gasification reaction without any carbon in the slag. The obtained environmental emission
values, which were much better than planned, show that its environmental performance is muchhigher than that of conventional pulverized coal-fired systems. Testing for more improved
efficiency and reliability as well as the verification of long-term reliability and maintainability willtake place shortly during a 5,000 hour continuous endurance test which is planned to start in 2009.
Table 1 IGCC demonstration test results
Ambient temperature
Gross power output
Gas turbine output
Steam turbine output
Net plant efficiency
Cold gas efficiency
Carbon conversion rate
Produced gas HHV wet
Produced gascomposition

Environmental value(16% O2 basis)

CO
CO2
H2CH4
N2 and others
SOx
NOx
Particulate matter

13.1oC
250 MW (planned: 250 MW)
124 MW
126 MW
42.9 % (lower heating value, LHV) (planned: 42% minimum)
77.2%> 99.9%5.4 MJ/m3N (1,290kcal/ m3N)
30.5%
2.8%
10.5%
0.7%
55.5%
1.0 ppm (planned: 8 ppm maximum)
3.4 ppm (planned: 5 ppm maximum)<0.1 mg/ m3N (planned: 3.3 mg/m3N maximum)|3. IGCC commercial plant development program overview
3.1Air-blown IGCC commercial plant

Table 2 summarizes the principal specifications of the IGCC demonstration plant and an
IGCC commercial plant. The commercial plant uses the air-blown gasifier, which will haveapproximately twice the capacity of that used in the demonstration plant. The increase in thegasifier diameter, however, remains by approximately 20% which allows full application of thescale-up law because the operating pressure in the gasifier of the commercial plant comes to behigher than the demonstration plant.
Table 2 Specifications of the IGCC demonstration plant and commercial plants
Parameter

Units

Gross Power Output
Type of coalGasifier
Gas cleanup system
Gas turbine
Gross Power Plant efficiency
SOx
Environmental
Targets
NOx(16% O2 basis)
Particulate matter
Start of operation

MW%, LHV
ppm
ppm
mg/m3N-IGCC demonstration
plant
250
Bituminous
Dry feed, air-blown
Wet desulfurization
M701DA
48
8542007

Commercial plant(50Hz / 60Hz)
600 / 500
Bituminous
Dry feed, air-blown
Wet desulfurizationM701G / M501G
538542014, at the earliest

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 2 (June. 2009)
3The commercial plant uses the same dry feed system, in which inert gas such as nitrogen isused as the carrying medium, as in the IGCC demonstration plant. The adoption of this systembrings various advantages, which include the use of wide variety of coal and the increase in plant
efficiency. The usable coal types include low-grade coal, such as high-moisture sub-bituminous. Itis difficult to be used in a slurry feed system through which the slurry, a mixture of coal and water,
is supplied to the gasifier.
A highly reliable combustor for coal gasification is used for the gas turbine. It is based on aproven, natural gas-fired, high-efficiency G-series gas turbine with a combustion temperature of
1,500°C class, and builds on our experience with low-calorie gas-fired gas turbines, such as thoseusing blast furnace gas. The IGCC commercial plant with the latest gas turbines can dramatically
improve the net plant efficiency, allowing a significant reduction in the CO2 emission compared toconventional pulverized coal-fired plants.

3.2

Coal gasifier design

The design of the standard air-blown coal gasification equipment for IGCC has already been
completed and is ready for application to commercial plants. Figure 2 shows a full view of thestandard coal gasification facility, which is compatible with the model M501G (one of the G-series)
gas turbine. Equipment plans corresponding to customers’ needs can thus be prepared very quickly.
In addition, further improvement of the reliability and operation flexibility is underway basedon all the lessons learned from the IGCC demonstration plant. Especially, the experience gained
during the site construction and commissioning were utilized in the “Design for X” approach, inwhich the input from everyone involved in the project and proposals for the improvement based on
the design reviews were incorporated to increase the product reliability of the commercial plants.

Figure 2 Standard coal gasification facility compatible with the M501G gas turbine|4. CO2 capture by IGCC
4.1

Present status of CO2 capture projects in Japan and abroad

Since the CO2 emissions from coal-fired power plants presently count one third of theworld’s total, a significant improvement in the efficiency of coal-fired power plants and their CO2
Capture and Sequestration (CCS) capability is essentially the most effective measure against global
warming over the short and medium terms.
In May 2007 at the Heiligendamm Summit, the former Japanese Prime Minister Abe gave
his long-term vision for cutting the world’s carbon emissions down to half by 2050 in his
presentation “Cool Earth 50.” The CCS combined with IGCC, to realize a zero-emission coal-fired
power generation system, is positioned as one of the “Innovative Technology Developments”. In
addition, Japan CCS Co., Ltd., was founded in May 2008 with investment from 29 companies,
including electric utility companies and oil companies, in order to promote a full-scale
investigation of CCS and a large-scale demonstration test program for a system combining IGCCand CCS.
In the United States, the Future Gen project, mainly supported by the U.S. Department ofEnergy (DOE), started in February 2003 to develop a zero-emission IGCC plant that could captureMitsubishi Heavy Industries Technical Review Vol. 46 No. 2 (June. 2009)490% or more of the CO2. However, a change in the project policy was announced in January 2008
to fund only the CCS equipment for the IGCC with CO2 capture , which will start operation by
2015. Under the Obama administration, the policy focuses on the development of clean coaltechnology that includes CCS, and plans for multiple projects dedicated to the construction ofIGCC commercial plants with CO2 capture are underway.
In Europe, a program to promote the construction of up to 12 CCS demonstration plants by
2015 was established in the “Energy Policy for Europe”, announced by the European Commission
in January 2007, and with funding of approximately 3 billion Euros for CCS-related projects.
In addition, the commercialization of an Enhanced Oil Recovery (EOR) method that injects
CO2 into oil wells to increase oil production is underway worldwide, and is expected to be aneffective way to utilize CO2 captured from coal-fired plants.

4.2

IGCC system with CO2 captureStanding on the situation of much more interest in CO2 reduction, including CCS in Japanand foreign countries, MHI has been making efforts to realize commercial IGCC plants which cancontribute worldwide reduction in CO2 emission.
There are two methods in capturing CO2 from coal-fired power plants: (1) to capture CO2from syngas before combustion (pre-combustion capture) or (2) to capture CO2 from boiler tail-end
flue gas (post-combustion capture). The IGCC uses the pre-combustion capture because of thehighest capability in capturing CO2 at the condition of a small amount of process gas under higher
pressure; this results in higher plant efficiency than using the post-combustion capture method andleads to higher economical merit.
Figure 3 shows a block flow diagram of the air-blown IGCC system combined with CO2capture. Carbon monoxide (CO) in syngas produced in the gasifier is converted to CO2 andhydrogen (H2) in the CO shift reactor by a chemical reaction with water or steam (H2O). The CO2
is then separated from the syngas and captured in the acid gas removal (AGR) system used fordesulfurization and CO2 capture. The H2-rich syngas remaining after the removal of CO2 is used asfuel for the gas turbine. MHI’s gas turbines, with abundant supply records, have achieved
considerable success over a wide range of operating conditions using H2-rich gas. The captured
CO2 is pressurized by the compressor and transported for sequestration. In the IGCC system withCO2 capture, the optimization of the CO shift converter and the entire CO2 capture system arenecessary according to the required capture rate of CO2 and the purity of the captured CO2.

Figure 3 Block flow diagram of air-blown IGCC system with CO2 capture

Figure 4 shows a relation between the CO2 capture rate and net plant efficiency.
The air-blown IGCC performs better than the oxygen-blown at all capture rates. Thisis because the net plant efficiency of the oxygen-blown IGCC is significantly reducedby the power required for oxygen production in the air separation unit (ASU). Inaddition, the net plant efficiency decreases as the CO2 capture rate increases for both
air-blown and oxygen-blown IGCCs. This is due to the increase in energy consumed by
the auxiliary equipments in the AGR system and the CO2 compressor. However, theMitsubishi Heavy Industries Technical Review Vol. 46 No. 2 (June. 2009)5superiority of the air-blown IGCC compared to the oxygen-blown is kept in allconditions, and there is an absolute efficiency difference of 4%–5%Figure 5 compares a capital cost of the air-blown IGCC plant with CO2 capture and that of
the oxygen-blown. Finally, in terms of capital cost ($/kW), the air-blown IGCC is better than theoxygen-blown which has significant drawbacks in the ASU cost and its auxiliary power
consumption.

Figure 4 Comparison of net plant efficiency
with CO2 capture for air-blown andoxygen-blown IGCCs

Figure 5 Comparison of capital cost and net
power output with CO2 capture for
air-blown and oxygen-blown IGCCs|5. Conclusion
IGCC is a power generation method that will play the most important role in coal-fired
power generation in the 21st century because of the growing importance of coal resources and theirutilization. The high efficiency and reliability of MHI’s air-blown IGCC have been ensured
through the various activities like the successful long-term continuous operation in the IGCC
demonstration plant. More sophisticated high-efficiency high-reliability air-blown IGCC
commercial plants have been already in the course of development and are ready for realization.
MHI will make every effort to realize the commercial plants which contributes to combating
global warming. Although it significantly reduces CO2 emissions, the incorporation of the CCS
into IGCC poses challenges, including the reduction in the plant efficiency and the increase in thecapital cost. Nevertheless, we believe that the IGCC with or without CO2 capture based on MHI’s
technology will play a key role in the field of saving climate change.

Authors
Takao Hashimoto
General Manager
IGCC & Gasification Business
Power Systems Headquarters

Koichi Sakamoto
Deputy General Manager
IGCC & Gasification Business
Power Systems Headquarters

Yuuichirou Kitagawa
ManagerBoiler Engineering Department
Power Systems Headquarters

Yoshinori Hyakutake
Manager
Power Systems Project Engineering
Department, Power Systems Plant
Engineering & Construction Division
Power Systems Headquarters

Norishige Setani
Power Systems Project
Engineering Department, Power
Systems Plant Engineering &Construction Division
Power Systems Headquarters