Part 2 CCT Overview
Environmental Protection Technologies (CO2 Recovery Technologies)

5A2. CO2 Recovery and Sequestration Technology
Technology overview

1. CO2 recovery technology(1) CO2 recovery technology (for natural gas, syngas, and flue gas)

resulting in global warming, which can only be prevented through theCO2 separation/recovery is widely prevalent in the natural gas andmitigation of CO2 emissions. There are, however, many difficulties insyngas fields and has been carried out for decades. The CO2 inrecovering and sequestering CO2 from movable bodies such as

natural gas is not only useless because it decreases the caloric

automobiles and vessels, naturally rendering it easier to recover CO2

value of natural gas, but also because it creates problems at

from stationary sources, like boilers, gas turbines, etc.

LNG/ethane recovery plants by solidifying into dry ice. CO2 is hence(3) Characteristics and superiority of technology to recover CO2 fromremoved to prevent such problems.

exhaust gas

In a plant where natural gas or naphtha is reformed to manufacture

The Kansai Electric Power Co., Inc. and Mitsubishi Heavy

H2, CO2 is separated after being converted from the CO produced

Industries, Ltd. began a joint R&D program in 1990 to recover CO2

with hydrogen as syngas. In an ammonia/urea plant, CO2 isfrom the exhaust gas of power plants and other facilities as aseparated from the gas mixture of H2, N2, and CO2 to produce urea,global-warming countermeasure. First, they assessed theusing H2/N2-derived synthetic ammonia and separated CO2.

conventional "monoethanolamine" (MEA) liquid absorbent-based

Previously, however, CO2 separation/recovery from flue gas was nottechnology considered at that time a CO2 recovery process thatin such large demand, finding limited applications only in food

could save the largest amount of energy. It is a process developed

processing and dry ice. When CO2 is separated from natural gas orby the former Dow Chemical Co. and later assigned to Fluor

syngas, the separation is relatively easy because of the highDaniel,pressure of the gas. To the contrary, CO2 separation/recovery fromdisadvantageous for use in large plants as a measure against

flue gas is difficult in many technological respects due to the very low

global warming because of such problems as the large amount ofpressure of flue gas as well as the presence of oxygen, SOx, NOx,energy required for CO2 recovery and the great loss in the liquidand soot and dust in the flue gas.

absorbent due to its rapid degradation. Kansai Electric Power andInc.

ThisMEA-based

technology

wasfound(2) Necessity to recover CO2 from fixed sources

Mitsubishi Heavy Industries started with basic research to explore

Most fossil fuels (oil, natural gas, and coal) in the world are used asa new liquid absorbent, resulting in the successful development offuel for boilers, gas turbines, and internal combustion engines,

a novel energy-saving liquid absorbent less prone to degradation. It

releasing CO2 into the atmosphere as exhaust gas. As a result, it is

has already been put into practical use for the manufacture of urea

alleged that the atmospheric concentration of CO2 has increased,in Malaysia.

2. CO2 sequestration technology
Geological sequestration and ocean sequestration are being

displacing the water. This is already underway in Norway. For

widely studied and a commercial project of the former has

Japan, Norway-like CO2 sequestration into aquifers distributed

already begun. Geological CO2 sequestration is being carriedover continental shelves are considered the most realistic.

out, using the Enhanced Oil Recovery (EOR) method or the coal

Other than into aquifers, CO2 can also be sequestered into

seam sequestration-accompanied Coal Bed Methane Recovery

closed oil/gas fields where production has already been

method. Aquifer sequestration and sequestration into closed

terminated. Closed oil/gas fields once were active oil/gas fields

oil/gas fields are options as well, if the only objective is CO2

because their geological structures did not permit oil/gas leaks.

sequestration. Figure 1 shows a conceptual view of CO2

Therefore, such closed oil/gas fields are considered secure CO2

recovery-EOR combination.

sequestration sites.

CO2-EOR commercialization started in the 1970’s mainly in theUnited States, enhancing oil production by approximately
200,000 barrels/day. Outside the United States, Canada, Turkey,and Hungary also utilize the CO2 recovery-EOR combination.
Underground aquifers are widely distributed on the earth wherever
sedimentary layers are located. Even in Japan, where aquifers are
scarce and small in structure because of Japan’s volcanic andearthquake history, surveys are underway for possible CO2
sequestration sites. If a geological underground layer has cavities,
CO2 can be sequestered in these cavities, which indigenously
contain water (mainly salt water), by pumping in CO2, thereby

Photo 1 Conceptual view:
CO2 recovery from power plant flue gas for EOR

Reference

Masaki Iijima et al., "CO2 Recovery/Effective Utilization/Fixation and Commercialization," MHI Technical Journal, 39 (5), 286, 2002.
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