(280a) Investigation of CuO-Based Oxygen Carriers As CLOU Materials for Solid Fuels

Chemical-looping
combustion (CLC) is a promising combustion technique with efficient CO₂-capture
at low cost due to inherent gas separation. In a CLC process, a metal oxide is
circulated between two reactors, wherein they undergo changes from an oxidized
form in the air reactor to a reduced one in the fuel reactor. In the case of
chemical-looping with oxygen uncoupling (CLOU), the oxygen carrier releases oxygen
in the gas phase in the fuel reactor as shown in the figure. This enables a high
rate of conversion of char from solid fuels, as it eliminates the need for the
gasification step needed in normal CLC with solid fuels.

Only certain pure
metal oxides of Co, Cu and Mn have an equilibrium
partial pressure of oxygen suitable for CLOU. Due to its favorable
thermodynamics (facile redox properties) and agile kinetics (high reactivity),
CuO is a promising CLOU material, in addition to being an excellent oxygen
carrier in the combustion of gaseous fuels.

In this work, the
performance of CuO-based oxygen carriers supported on ZrO₂
stabilized by calcium oxide, magnesia and ceria will be presented to assess
their suitability as oxygen carriers for solid fuel combustion. The samples were
prepared by freeze-granulation and the reactivity was examined in a laboratory
fluidized bed reactor under cyclic oxidizing and reducing conditions,
simulating the CLOU process. Owing to the fast release of oxygen by CLOU
particles, the reaction rates were investigated using coke as the fuel of
choice. The influence of reaction temperature and oxygen concentration on the
rate of reaction was also studied.

Schematic
of the chemical-looping combustion via oxygen uncoupling (CLOU) process