Modeling of metalized pellets firing with the account of physico-chemical transformations in them

Abstract

The engineering mathematical model of development of physical and chemical transformations is considered in the volume of pellet, consisting of granules of iron-stone, limestone and coke (carbon-containing fuel). It is shown that according to the experimental information there are mathematical models, using the three-stage chart of renewal. Strict mathematical description of process of renewal on this chart requires the joint decision of kinetics tasks of successiveparallel reactions and diffusion of multicomponent gas in the pores of ore piece. Such approach cannot be used in the mathematical model of process of metallised pellets burning because of its complication. This complication increases at the account of characteristic feature of the gas and temperature mode of burning machine, producing metallised pellets: change of gas composition during material movement (transition from an oxidizing atmosphere to restoration or neutral). For the decision of the task of ore granule renewal it is important to know the distribution curves of the concentrations of reducing agents and gaseous reaction products along the radius. Because of complication of the equalizations of diffusion, heating of granules and chemical kinetics, the close method of decision of Stefan problem, developed by L.S. Leybenzon, is used, essence of which is in supposition, quasi stationary distribution has time in the volume of granule to be set. All oxide reduction reactions occur not on the surface of the micropores of the corresponding granule layer, but on the frontal surfaces separating these layers and the restoration of the central volume of the original magnetite does not develop until the neighboring hematite region is recovered to Fe3O4. At such conditions all complication of the simplified mathematical model is compensated by the proper choice of algorithm of numeral decision of the equalizations system. As a row of simplifications doesn’t correspond to reality (for example, the layer of metallic iron is not skipped by a gas-reducer), it is necessary to use effective coefficients, the value of which is set during the model adaptation. © 2018, National University of Science and Technology MISIS. All rights reserved.