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

Hsuan-Chih Wu ； Young Ku

《Aerosol and Air Quality Research》 19卷8期 (2019/08) Pp. 1920-1936

https://doi.org/10.4209/aaqr.2018.06.0222

摘要

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 Fe_2O_3/Al_2O_3 and Fe_2O_3/Al_2O_3/TiO_2 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 (k_g) for the reduction of Fe_2O_3/Al_2O_3 and Fe_2O_3/Al_2O_3/TiO_2 by CO were found to be 0.16 and 0.22 mm s^(-1), respectively, and using the Fe_2O_3/Al_2O_3 and Fe_2O_3/Al_2O_3/TiO_2 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 Fe_2O_3/Al_2O_3 than with the Fe_2O_3/Al_2O_3/TiO_2 due to a high flow rate for the former being used. When Fe_2O_3/Al_2O_3/TiO_2 was used as the oxygen carrier, the particles, which contained a large percentage of Fe_2O_3, exhibited high reactivity to syngas (CO/H_2); thus, less Fe_2O_3/Al_2O_3/TiO_2 than Fe_2O_3/Al_2O_3 was required to combust the charcoal.

關鍵字

Chemical looping process ； Charcoal combustion ； Hematite ； Reduction kinetic ； Moving bed reactor