Phase distribution and stepwise kinetics of iron oxides reduction during chemical looping hydrogen generation in a packed bed reactor

Abstract The reduction performance greatly impacts the efficiency of chemical looping hydrogen generation (CLHG) using iron oxides. This work studied the feature of packed bed technology for CLHG. First, a prevention strategy of fuel breakthrough was applied to simulate an industrial process. 25% solid conversion and 2000 μmol H 2 /g Fe 2 O 3 hydrogen production were achieved. Then, a novel idea to directly investigate the reduced particle bed using sub-layers was performed to characterize the reactor. Fe, FeO and Fe 3 O 4 distributed in an orderly manner due to the plug flow gas–solid contact pattern in the reactor. The quantitative calculation showed that the area of Fe 3 O 4  → FeO took up 80% space of the bed. The kinetic reason for this phenomenon was explored by means of a thermodynamically controlled method. The continuous reduction of iron oxides was successfully decoupled into three independent reactions and the step of Fe 3 O 4  → FeO was found as the limiting step with a maximum reaction rate of 0.0008 s −1 .