Abstract: A three-dimensional mathematical model, based on differential balances of mass and momentum, has been developed to describe the two-phase flow of gas and liquid through the dropping zone of the blast furnace. Agreement between observed and calculated valuesverifies the validity of this model. On the basis of this model, various parameters for the surrounding of the dry zone of Blast Furnace Cl-BF of the Capital Iron and Steel Company have been computed, from which a diagram for demarcation of fluidization of coke and flooding of slag has been proposed.