(43d) High Temperature Oxygen Production

A potential
alternative to produce clean coal technologies would be to combust fossil fuels
in pure oxygen instead of air, which contains approximately 78% nitrogen by
volume. If nitrogen was removed from the process, flue gas streams would have a
much higher concentration of CO₂, reducing or eliminating the need
for costly CO₂ capture. Moreover, NO_X emissions and the
subsequent need for processing would be reduced significantly. The main problem
with this method is separating oxygen from the air. This is usually completed
cryogenically which requires a lot of energy (for a typical 500MW coal-fired
power station supplying pure oxygen requires at least 15% of the electricity
the plant generates annually). Cryogenic air separation technology for
producing high purity oxygen is energy intensive and requires air to be cooled
to about - 300 degree Fahrenheit for separation. The cold oxygen must be heated
to high temperatures in order to couple this air separation process with coal
power plants. The high cost of producing oxygen, however, has made oxy-combustion
a cost-prohibitive option for commercial use in most power plants. Developing
technologies in oxygen and ion transport membranes have the potential to reduce
the cost of oxygen production and increase oxy-combustion's cost-effectiveness.

In this research, multicomponent
oxides containing Mn in different oxidation states were explored as reactants
for two-step high temperature high purity oxygen production. High temperature
reduction and oxidation of these compounds were carried out in an inert gas and
air atmosphere, respectively, using TGA-DSC. For synthesized manganese-based oxide
materials to separate air, they should be able to incorporate oxygen atoms in
to their crystal structure and release oxygen at the same or elevated
temperatures while varying the oxygen partial pressure of the system.

The results obtained
from TGA-DSC showed all investigated compounds can produce high purity oxygen
at elevated temperatures. Details of multicomponent oxides  preparation, characterization,
and high temperature conversion of the oxides under reduction and oxidation
conditions  will be discussed.