Symbol	Description	Unit
$\mathrm{Ar}$	Archimedes number	–
${\mathrm{C}}_{\mathrm{D}}$	Drag coefficient for a single particle	–
${\mathrm{C}}_{\mathrm{D}}\left(\mathrm{Re}, \mathsf{\epsilon }\right)$	Drag coefficient to account for mutual interactions between particles	–
${\mathrm{d}}_{\mathrm{i}}$	Characteristic diameter; i vol.−% underflow	µm
${\mathrm{d}}_{\mathrm{p}}$	Mean particle size	µm
$\mathrm{Fe}$	Amount of iron in the sample	mol
${\mathrm{Fr}}^{*}$	Modified Froude number	–
$\mathrm{g}$	Gravity	m/s2
$\mathrm{GOD}$	Gas oxidation degree	–
${\mathrm{K}}_{\mathrm{l}}$	Constant for laminar term	–
${\mathrm{K}}_{\mathrm{t}}$	Constant for turbulent term	–
$\mathrm{M}$	Liatschenko number	–
$\mathrm{n}$	Load factor	–
$\mathrm{O}$	Amount of oxygen in the sample	mol
$\mathrm{p}$	Pressure gauge	barg
$\mathrm{RD}$	Reduction degree	%
$\mathrm{Re}$	Reynolds number	–
$\mathrm{T}$	Temperature	K
$\mathrm{u}$	Superficial gas velocity in the reactor	m/s
${\mathrm{u}}_{\mathrm{mf}}$	Minimum fluidization velocity	m/s
${\mathrm{u}}_{\mathrm{slip}}$	Slip velocity	m/s
$\mathsf{\alpha }$	Index to account for the mutual interactions between particles	–
$∆\mathrm{P}$	Pressure drop caused by gas flow through a packed bed	Pa
$\mathsf{\epsilon }$	Void fraction of the bulk material	–
${\mathsf{\epsilon }}_{\mathrm{f}}$	Void fraction of the bed material in the fluidized state	–
${\mathsf{\epsilon }}_{\mathrm{mf}}$	Void fraction of the bed material at the point of incipient fluidization	–
$\mathsf{\zeta }$	Gas utilization	%
${\mathsf{\eta }}_{\mathrm{f}}$	Dynamic gas viscosity	Pa*s
${\mathsf{\rho }}_{\mathrm{Bulk}}$	Bulk density	kg/m3
${\mathsf{\rho }}_{\mathrm{f}}$	Density of the fluidizing medium	kg/m3
${\mathsf{\rho }}_{\mathrm{p}}$	True particle density	kg/m3
$\mathsf{\varphi }$	Sphericity	–