Environmental Engineering Reference
In-Depth Information
million tons. Another example is enhanced oil produc-
tion from wells where injecting CO
increases the pres-
sure in the oil reservoir, pushing out more oil to be
recovered. In this case the CO
comes from other indus-
trial processes and is typically sent by pipeline to the oil
field where it is pumped underground. Both of these
examples are much simpler than CCS at a power plant
where a very hot gas stream has to be treated, but they do
give an experience base, though a small one, on which to
base part of the cost analysis. There is a scale-up issue.
A
red electrical plant produces in a few
hours what the Norwegian gas
-gigawatt coal-
field produces in a day, and
there are many thousands of such coal-
red generating
plants.
The problem for a power plant in the carbon capture
part of CCS is the separation of the CO
from the much
larger amount of nitrogen in the gas stream. Air used to
burn coal
% that is
oxygen combines with the fuel to make CO
. Two pro-
cesses are being investigated: separation before or after
combustion. In the
is
% nitrogen and only the
first case, the oxygen is separated from
the nitrogen in air, and only the oxygen goes into the
combustion chamber and ideally only pure CO
comes
out. It can be cooled, compressed, and pumped off in a
pipeline to a storage site. In the second case the hot
mixture of CO
and nitrogen is cooled and passed
through a chemical process that absorbs the CO
, and
the nitrogen is sent back into the atmosphere. The CO
absorber is then reheated, the CO
comes out, is com-
pressed, and sent on its way. In either case the carbon
capture process uses lots of energy, and the MIT study
estimates that the CC part of CCS lowers the overall
