Sulfurization- Desulfurization of Iron-Calcium Oxygen Carriers during Chemical Looping Combustion of Syngas

Received: November 7, 2022
Revised: July 18, 2023
Accepted: September 3, 2023

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Cite this article:

Chen, Y.L., Ku, Y., Chang, Y.C. (2023). Sulfurization- Desulfurization of Iron-Calcium Oxygen Carriers during Chemical Looping Combustion of Syngas. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.220398

ABSTRACT

Chemical looping combustion of SO₂-containing syngas with various fabricated iron-calcium oxygen carriers was studied to comprehend the sulfurization and desulfurization of oxygen carriers during combustion. Experimental results indicated calcium-iron oxygen carriers fabricated with CaO:Fe₂O₃ weight ratio of 3:7 and calcined at 800°C (CaFe-378) was suitable for chemical looping combustion of syngas. CaFe₂O₄ was noticed to be the dominant crystalline phase in CaFe-378 even after 10 redox operations. Reduction kinetics for chemical looping combustion of both H₂ or CO in syngas with CaFe-378 were adequately described by the 2-dimension diffusion model. The activation energies of H₂ and CO with CaFe-378 were determined to be 35.4 kJ mol^-1 and 46.0 kJ mol^-1, respectively. Calcium sulfide (CaS) was generated during the chemical looping combustion of SO₂-containing syngas with CaFe-378. CaS was further oxidized to CaSO₄ on the surface of CaFe-378 during air regeneration, which might inhibit the complete regeneration of iron oxides. Satisfactory regeneration of sulfurized oxygen carriers was accomplished by introducing hydrogen after the air-regeneration because of the reduction of calcium sulfate to calcium oxide.

Keywords: Chemical looping combustion, CaO/Fe2O3 oxygen carrier, Sulfurization desulfurization