Abstract
Two bimetallic Fe-Cu and Fe-Ca oxygen carriers were studied for chemical looping gasification (CLG) of biomass. The SEM results indicated that there was no obvious agglomeration on the bimetallic Fe-Cu oxygen carrier supported on Al2O3 and Fe-Ca oxygen carrier after five redox cycles while agglomeration occurred on CuO supported on Al2O3 due to the low melting point of CuO. The XRD results indicated the presence of copper-ferrite and calcium-ferrite phases in the bimetallic materials. The two bimetallic oxygen carriers can be re-oxidized with air to form a crystalline that is similar to the fresh materials. The Fe-Ca oxide became active at 360 °C which was lower than 380 °C for the Fe-Cu oxygen carrier. The high thermal stability and redox reactivity of bimetallic Fe-Cu and Fe-Ca oxygen carriers make the bimetallic oxygen carriers more suitable for recycling during CLG. The method for preparing Fe-Cu oxygen carriers had no significant impact on biomass conversion efficiency but had significant effect on the quality of syngas. Proper control of the biomass/oxygen carrier mass ratio is critical to achieve high selectivity towards gasification instead of combustion. The Fe-Ca oxygen carrier could achieve higher selectivity towards gasification than the Fe-Cu oxygen carrier.
Highlights
Biomass can be partially oxidized in a gasification process to produce syngas that mainly consists of H2, CO, CO2 and CH4
The lattice oxygen of metal oxides has been studied as an alternative oxygen source for the combustion and gasification of fuels in a chemical looping process [4,5,6]
A typical chemical looping gasification (CLG) process takes place in two interconnected reactors including a fuel reactor where a fuel such as biomass and coal is partially oxidized by a metal oxide as an oxygen source and an air reactor where the reduced metal oxide is re-oxidized with air for recycling
Summary
Biomass can be partially oxidized in a gasification process to produce syngas that mainly consists of H2 , CO, CO2 and CH4. Conventional gasification technologies use steam, air and pure oxygen as gasifying agents. The lattice oxygen of metal oxides has been studied as an alternative oxygen source for the combustion and gasification of fuels in a chemical looping process [4,5,6]. A typical chemical looping gasification (CLG) process takes place in two interconnected reactors including a fuel reactor where a fuel such as biomass and coal is partially oxidized by a metal oxide as an oxygen source and an air reactor where the reduced metal oxide is re-oxidized with air for recycling
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