(60d) Development of Freeze Granulated Oxygen Carriers for Chemical Looping Combustion of Solid Fuels

Chemical
looping combustion (CLC) is proving to be a promising technology for the
combustion of carboneous fuels producing electricity and a sequestration-ready
concentrated CO₂ stream.  Recently, more attention is being given
to its application to solid fuels.  The University of Kentucky Center for
Applied Energy Research is presently developing a integrated process to apply
CLC to coal combustion.  A first step in this work is the development of suitable
oxygen carriers (OCs) specifically for the application of CLC to solid
fuels. 

The
materials investigated in this study included Fe₂O₃, NiO and
CuO on a supported matrix. The unsupported forms of the metal oxides were
examined as well for comparison. All tested OCs were produced by freeze
granulation with subsequent freeze drying and high temperature calcination. Reaction
rates were examined by a thermal analyzer-differential scanning
calorimeter-mass spectrometer (TG-DSC-MS). A mixture of H₂/CO/CO₂/Ar
was used as the reducing gae and O₂/Ar was the oxidizing gas
mixture.  Oxidation/reduction cycles of the OCs were carried out both in dry
and wet gases to simulate actual conditions in a CLC reactor.  Reaction rates,
the extent of oxidation/reduction, recycle stability, the effect of water
vapor, and OC durability will be discussed. The data show that the supported
OCs on alumina all have fewer tendencies to agglomerate after multiple oxidation-reduction
cycles than unsupported OCs.