Abstract:
A two-dimensional finite difference model has been developed to describe the reduction of kilogram
quantities of dehydrated phosphogypsum. The model’s scope has been limited to focus on the heat
transfer and reactions that occur within a mass of material contained in a vessel inside a furnace rather
than also including the effects of heat transfer to the vessel. Changes in the heat transfer properties (k,
ρ, and Cp) are incorporated as the composition of the mass changes as the chemical reactions progress.
The model is validated against experimental data, with samples heated to 1000°C at 3°C min−1 while
purging with nitrogen gas. A sensitivity analysis of model predictions to the pre-exponential factor of
the reaction rate constant of the main chemical reaction and the thermal conductivity of the powder bed
indicated that, at the envisaged process conditions, the behaviour of the system depends much more on
the rate of heat transfer than on the rate of the chemical reaction. The model demonstrated a significant
increase in accuracy when the thermal conductivity was modelled to increase linearly with temperature
compared to assuming a constant value.
