Study of Heat Exchange Processes During Roasting of Iron-ore Pellets

The method for approximate calculation of heat exchange in a layer of iron-ore pellets is developed, based on the regularities of heat transfer in the stationary layer. It is noted that the duration of oxidizing roasting of iron-ore pellets on a belt of the conveyor-type machine is influenced by the conditions of heat exchange, distribution of temperatures of gas and material along the height of the layer; the physical and chemical processes occurring in the layer of pellets during its heating (magnetite oxidation, decomposition of carbonates, etc.) have a great influence. Most of them flow with the release or absorption of heat. As a result, the calculation of heat exchange in the roasting layer of pellets is a complex problem. It is shown that it is not possible to obtain a solution of the system of equations describing the heat exchange in a layer of pellets in the general case, but only approximately using stepwise approximation of the boundary conditions and parameters of the problem,or by a numerical method with the help of a computer, which is considered in this article. With the help of the drawn-up program, the calculation of heat exchange in the layer of pellets has been carried out with respect to the mode of their roasting on a conveyor-type machine. The considered method has a great practical application, since it allows determining the optimal duration of the pellet roasting process, taking into account the effect on heat exchange of various factors, and consequently, the specified degree of completeness of all physicochemical transformations in the treated layer to obtain a high-quality product. Keywords: heat exchange, calculation method, iron-ore pellets, physical and chemical processes, layer, conveyor-type machine, roasting, temperature, solution, approximation, parameters, problem, numerical methods, duration, boundary condition