AbstractAn impinging‐stream reactor, developed and tested for calcination of phosphate with low organic matter content, has proven to be an efficient device for conducting this process.Modeling of the calcination process has been done along two lines. Considering a single particle and assuming that calcination rate is controlled by the heat transfer in the particle, resulted in a criterion for testing the effect of temperature on the enrichment of P205 and other phenomena. Performing a heat balance on the reactor and on the particle, and incorporating physical concepts, led to correlations with only one adjustable parameter for the conversion of carbonates as a function of the operating parameters.The major conclusion drawn from implementation of the model was that phosphate calcination is governed by the internal resistance of the particle to the heat transfer. The calcination efficiency results, as well as the practical experience gained in this study, indicated that the impinging‐stream calciner may provide a promising tool for phosphate enrichment, and more generally, for processes involving gas‐solid contact at high tempera