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Evaluation of Iron-based Oxygen Carrier Supported on Alumina/Titania for Charcoal Combustion through Chemical Looping Process

Category: Control Techniques and Strategy

Volume: 19 | Issue: 8 | Pages: 1920-1936
DOI: 10.4209/aaqr.2018.06.0222
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Hsuan-Chih Wu, Young Ku

  • Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan

Highlights

  • Fe2O3/Al2O3/TiO2 and Fe2O3/Al2O3 particles provided with high reactivity for CO/H2.
  • Higher mass transfer coefficient was observed for Fe2O3/Al2O3/TiO2 reduction.
  • Over 47% of maximum carbon conversions were reached for charcoal combustion in MBR.
  • Less oxygen carriers are required for charcoal combustion with Fe2O3/Al2O3/TiO2.
  • Roughly 255W was released for CLC of charcoal with Fe2O3/Al2O3/TiO2.

Abstract

Hematite supported on alumina or alumina/titania was fabricated to serve as an oxygen carrier in the chemical looping combustion (CLC) of charcoal. The reduction rate of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 particles increased with the reactor inlet’s CO concentration and displayed a slight effect from elevated operating temperatures. Applying the shrinking core model, the mass transfer coefficients (kg) for the reduction of Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 by CO were found to be 0.16 and 0.22 mm s–1, respectively, and using the Fe2O3/Al2O3 and Fe2O3/Al2O3/TiO2 to combust charcoal resulted in carbon conversion rates of approximately 61.8% and 47.2%, respectively, when the inlet steam flow rate was set to 221.4 mmol min–1. Significantly, a higher inlet steam flow rate may not be advantageous when employing iron-based oxygen carriers. More heat was released during combustion with the Fe2O3/Al2O3 than with the Fe2O3/Al2O3/TiO2 due to a high flow rate for the former being used. When Fe2O3/Al2O3/TiO2 was used as the oxygen carrier, the particles, which contained a large percentage of Fe2O3, exhibited high reactivity to syngas (CO/H2); thus, less Fe2O3/Al2O3/TiO2 than Fe2O3/Al2O3 was required to combust the charcoal.

Keywords

Chemical looping process Charcoal combustion Hematite Reduction kinetic Moving bed reactor


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