The digestion kinetics of low-grade phosphate ores in intital operation has been investigated under the non-steady state, where concentration of phosphoric acid is variable. A new model equation is presented according to the concentration variation of phosphoric acid in the bulk liquid phase. The kinetics behavior of the digestion process was studied in the ranges 323K～358K.The obtained results show that rate constant of reaction and the weight fraction of phosphate ores conversion increase with reaction temperature rising. The activation energy has been calculated to be 71.86KJ/mol while the pre-exponential factor is 6.521×106. Comparing with experimental data and theoretical calculating value, it indicates that the model fits the experimental data perfectly. The conclusion may provide theoretical base for optimizing process conditions and devising reactors.
