Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)20

CO2 Recovery Technology for Coal-Fired Power Plants

MASAKI IIJIMATATSUTO NAGAYASUSUSUMU OKINOYOSHINORI KAJIYA|1. Introduction
As long as fossil fuels continue to be used, CO2 capture and storage (CCS) is an essential
countermeasure against global warming. This is particularly important for coal-fired power plants
because they produce relatively large amounts of CO2. The important issues in CCS include theability to capture large volumes of CO2 from coal-fired power plants as well the reduction of theenergy and cost required to do so. This report explains trends in CO2 capture technologies,
describes CCS projects around the world, and introduces the features of technologies developed by
Mitsubishi Heavy Industries (MHI).

|2. CO2 sources1
About 13.5 billion tons of CO2 are produced every year by stationary sources; this is about
60% of CO2 emissions worldwide. Fossil-fuel CO2 emissions cannot be effectively reduced without
CCS from these stationary sources. More than 70% of the CO2 emission from stationary sources
comes from thermal power generation facilities that burn coal, gas, and oil. Therefore, a reductionin the CO2 emissions from thermal power generation facilities would be effective in reducing
overall CO2 emissions. Coal-fired plants are responsible for 60% of the emissions from thermal
generation facilities.
In other words, more than 20% of worldwide CO2 emissions come from coal-fired power
plants. Coal reserves are widely distributed, and coal is significantly cheaper than oil or natural gas.
For these reasons, the quantity of coal consumed for power generation is expected to increase evenfurther, resulting in even more CO2 emissions. Because of this, CCS for coal-fired power plants
will have a big impact on the reduction of CO2 emissions.

|3. CO2 capture technology
3.1

CO2 capture overview1

Three types of CO2 capture systems are available (1) post-combustion CO2 capture (postcombustion), (2) oxy-fuel combustion (oxy-fuel), and (3) pre-combustion CO2 capture(pre-combustion).
(1) Post combustion CO2 capture
Chemical absorption is currently used to capture CO2 from flue gases but has not beenused on a large scale for recovering CO2 from entire power plants. Other methods such as
physical absorption, adsorption and membrane separation are being studied, but these have notyet been put into practical use. Currently, three practical chemical absorption methods are inoperation:
 Kerr-McGee ABB Lummus Crest process, which uses 15–20 wt% monoethanolamine(MEA) Flour Daniel ECONAMINE process, which uses 30 wt% MEA
 the Kansai Electric Power Co., Ltd. / MHI KM-CDR process that uses KS-1 solvent
The most energy efficient process is MHI’s KM-CDR process; it uses about 20% lessenergy than the others.

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)21(2) Oxy-fuelOxygen is produced by air separation, and CO2-rich flue gas is recirculated through theboiler to reduce the combustion temperature. The CO2 concentration of flue gas is 80–98% by
volume, enabling 100% CO2 capture.
(3) Pre-Combustion CO2 capture
In this method, H2, CO, and CO2 are generated by steam reforming of natural gas or apartial oxidation from natural gas or coal. CO is treated by a CO shift reaction to give CO2 andH2. After that CO2 is separated and H2 is produced. This method is used commercially toproduce ammonia and hydrogen.

3.2Features of MHI’s CO2 capture technology

MHI began researching and developing technology for capturing the CO2 from the flue gasesof power plants in 1990 in conjunction with Kansai Electric Power Co., Inc. One of the first issues
was the reduction of the energy required for CO2 capture. As the result of an extensive research anddevelopment program, MHI has developed many proprietary technologies including a
reduced-energy solvent (KS-1), a practical reduced-energy regeneration system, and a system forthe optimal integration of steam between a power-generation facility and a CO2 capture facility.

|4. Trends in CCS projects
4.1

Present situation of CCS projects

The widespread global implementation of CCS faces several hurdles. The CCS projects now
underway were designed to reduce current CO2 or future emissions, and most operate at relatively
low cost. Some came about through the provision of incentives, such as the CO2 tax in Norway, orthrough the use of recovered CO2 for enhanced oil recovery, as seen in Weyburn (Canada).

4.2

Prospects for the future

CCS demonstration tests are about to begin in Europe and include a new project in Britain.
CCS will not progress smoothly without demonstration tests directed by the government. Inaddition, widespread CCS requires finding suitable storage locations and regulatory certainty withregard to relevant laws and international rules; and economic incentive mechanisms such as CO2
emission trading and funding.

|5. MHI Experience
5.1

Commercial experience

MHI has developed the technology for capturing CO2. Commercial achievements based on
MHI’s KM-CDR process include four operational natural gas-fired plants, another three plants
currently under construction, and one more plant in the planning stages (Figure 1).

(1) Malaysia: 200 ton/day, (2) Japan: 330 ton/day, inin operation since 1999
operation since 2005
(Petronas)(chemical company)(3) India: 450 ton/day, in
operation since 2006
(IFFCO/AONLA)(4) India: 450 ton/day, in
operation since 2006
(IFFCO/PHULPUR)

Figure 1 MHI’s commercial plants

5.2

Experience with coal CO2 capture

The commercial viability of CO2 capture from coal-fired power plants is one of the important
issues for CCS. MHI has constructed a 10-ton CO2/day demonstration plant at a coal-fired power
station in Matsushima, Japan to capture CO2 from flue gas produced by a pulverized-coal-fired
boiler. This project received funding from the Research Institute of Innovative Technology for theEarth (RITE) and was carried out jointly with the Electric Power Development Co., Ltd.

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)22(J-POWER). MHI completed more than 4,000 hours of demonstration operation at this site in 2006
and 2007 to confirm the practicality of the KM-CDR process. Based on this success, MHI will
demonstrate a medium-scale plant with a capacity of several hundred to a thousand tons of CO2/day
as the next step, with the eventual aim of developing a large-scale commercial plant.

|6. Conclusion
As long as fossil fuels continue to be used, CCS is an essential countermeasure against globalwarming. This report has focused on technologies for the capture of CCS, introduced the trends in
CO2 capture technologies around the world, and described the features of MHI’s technologies. Theissues related to CO2 capture at coal-fired power plants include reducing the energy and cost
involved. MHI will continue with research and development to deal with these issues andcontribute to practical countermeasures against global warming.

References
1.

IPCC Special Report on Caron Dioxide Capture and Storage, 2005

Authors
Masaki Iijima
Manager,
Environmental/Chemical Plant
Project Department,
Plant and Transportation Systems
Engineering & Construction Center

Tatsuto Nagayasu
Manager,
Environmental/Chemical Plant
Planning Department,
Plant and Transportation Systems
Engineering & Construction Center

Susumu Okino
Manager,
Chemical Process Research Group,
Hiroshima Research &Development Center, Headquarters

Yoshinori Kajiya
Environmental/Chemical Plant
Planning Department,
Plant and Transportation Systems
Engineering & Construction Center