In connection with the continuously increasing demand for lime in ferrous metallurgy, there is a need to intensify the roasting process and optimize the operating parameters of shaft furnaces, which are widely used for the production of lime. For this, first of all, it is necessary to know the regularities of the course of physicochemical and thermophysical processes. The paper considers issues related to the determination of the optimal specific fuel consumption for calcining limestone, which is determined primarily by the cost of heat for the decomposition of carbonates. This can be done only on the basis of compiling the heat balances of the operating shaft furnace, which necessitates the determination of a whole set of thermophysical properties of limestone and lime. As an example of the use of the obtained data, the heat balance of a shaft transfer furnace for calcining limestone is given, from which it can be seen that most of the heat is spent on the decomposition of carbonates. The results obtained in the work can be used to optimize the operating parameters of not only mine, but also rotary kilns designed for calcining limestone.