The fluidized bed reactor was pre-heated to 800 °
C under N2 atmosphere (1.0 L/min, about 29.6 cm/s), then 6.00 g carbon-
coated iron ore were fed into the reactor (about 1.3 cm initial bed
height) and N2 was immediately altered to the desired reducing gas
(1.5 L/min, about 44.4 cm/s).