(154g) Bimetallic Chemical Looping Gasification with Oxygen Uncoupling –Feasibility Study and Process Analysis

In a
typical chemical looping gasification (CLG) process, an iron oxide based oxygen
carrier is used to indirectly convert carbonaceous fuels into separate streams
of sequestrable CO₂, hydrogen,
and heat/electricity. Although the novel process concept has the potential to
be both clean and efficient, the reactions between the oxygen carrier particles
and fuels are often kinetically limited, especially when solid fuels such as
coal and/or biomass are used. In order to enhance the rates of the aforementioned
reactions, it is proposed that a secondary metal oxide be incorporated to the iron
oxide based oxygen carrier. For instance, when copper (II) or manganese
(III/IV) oxide is used as the secondary metal oxide, molecular oxygen can be
released from the bimetallic oxygen carrier through ?oxygen uncoupling?, i.e. decomposition
of the secondary metal oxide at high temperature. As a result, both the in-situ
solid fuel gasification and iron oxide reduction reactions can be kinetically
promoted. The present study explores the technical feasibility of this novel
bimetallic CLG process concept. A potential configuration for the bimetallic
CLG process is first proposed. This is followed by thermodynamic analysis of
key reactors to arrive at the maximum fuel and oxygen carrier conversions
considering thermodynamic equilibrium limitations. Finally, ASPEN Plus®
simulation is carried out to evaluate the energy conversion efficiency of the
bimetallic CLG process. Preliminary kinetic data for coal char conversion with
bimetallic oxygen carrier are also presented. The present study indicates that
the incorporation of the oxygen uncoupling metal oxide has the potential to
enhance the fuel and oxygen carrier conversions without adversely affecting the
overall efficiency of the CLG process.