Jordan, LukeVan Vuuren, David2023-08-282023-08-282022-10Jordan, L.A, and van Vuuren, D. 2022 Heat-constrained modelling of calcium sulphate reduction. Journal of the Southern African Institute of Mining and Metallurgy, vol. 122, no. 10, pp. 607–616. http://dx.DOI.org/10.17159/2411-9717/1530/2022.2225-6253 (print)2411-9717 (online)10.17159/2411-9717/1530/2022http://hdl.handle.net/2263/92080A 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.en© Southern African Institute of Mining and Metallurgy.Carbothermal reductionPhosphogypsumModellingWaste treatmentArticle