Syngas chemical looping combustion using a highly performing fluidizable oxygen carrier

Abstract

• A high performing 20 wt%Ni-1 wt%Co-5 wt%La/γ-Al 2 O 3 oxygen carrier is reported. • The preparation method secures a stable fluidizable OC with enhanced reactivity. • This OC carrier is suitable for biomass gasification derived syngas combustion. • This OC yields up to 92% CO 2 yields in the 550-650 º C range. • This OC is free from NiAl 2 O 4 formation in the targeted temperature operating range. Biomass steam gasification produces a blend of H 2 , CO, CH 4 and CO 2 , designated as syngas. Syngas can be further combusted using fluidizable oxygen carriers (OC). This operation which is known as Chemical Looping Combustion (CLC), is valuable for syngas combustion as it involves nickel oxidation and nickel reduction, which are both exothermic reactions. To improve syngas CLC and establish its application, a new Ni-based oxygen carrier was studied using a Co and La modified γ-Al 2 O 3 support. This type of OC considerably limits the NiAl 2 O 4 formation. A Highly Performing Oxygen Carrier (HPOC) was engineered using a special preparation methodology to exclude NiAl 2 O 4 species formation. The evaluation of this HPOC was developed using the fluidized CREC Riser Simulator reactor at mild CLC 550–650 °C temperatures. Reaction conditions employed ranged from 2 to 40 s and used a 0.5–1 fuel to oxygen stoichiometric supply ratio (ψ). It is shown that under these conditions, the HPOC demonstrates a stable performance, yielding 75–92% CO 2 , displaying a 1.84–2.75 wt% (gO 2 /gOC) oxygen transport capacity with 40–60% solid phase oxygen conversion.