MATHEMATICAL MODEL OF BURNING PROCESS OF COAL-ORE PELLETS ON CONVEYOR MACHINE

Development of mathematical models of coal-ore pellets burning process was executed on the conveyor machine. The problems of heat transfer between gas and material in the transversally blown dense laye r are considered. The description is given for the following aspects: the phenomena of drying and cooling of materials (inclu ding by air-and-water mixture), oxidation processes of ore constituents of pellets, dissociation of limestone and burning of fuel constituents of material. Equalizations of the engineering mathematical models of iron oxides recovery and burning of fuel granules and of heating of machine’s fi re grate (carts) are resulted. When calculating the development of physicochemical transformations in the volume of the pellet, it was assumed that any chemical reaction from the surface of the granules of a particular component proceeds over the entire inner and outer surfaces of the pellet, and the process potential (the diff erence in the concentration of gaseous reactant) is a function of the pellet’s radius, the diff usion coeffi cient of reagent in micropores of the pellet. At the same time, the response in the individual pellet is frontal, and the completion degree of the process can be expressed through the radii of unreacted pellet volumes. Among all physicochemical phenomena accompanying the process of calcination of coal-ore pellets, this mathematical model directly takes into account only the main ones, which are refl ected in the material balance and can be verifi ed experimentally. Finite-diff erence approximation of equations of the mathematical model together with the expressions for calculating the thermophysical characteristics of heat carriers, heat and mass transfer coeffi cients, thermochemical and kinetic constants, etc. have formed the basis of a numerical model of a conveyor burning machine that produces metallized pellets. The implementation of this model in the particular case is presented in the article.

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