Processes of the action of iron and its compounds on a refractory lining

Abstract

Iron and its oxides participate in all processes of failure of the refractory linings of metallurgical equipment.This may be explained by the high thermodynamic activity of iron in both the liquid and solid phases.Investigations of the parameters of formation of iron oxides and their interaction with refractory oxides under equilibrium conditions are known [i, 2]. However, the real processes of action of iron and its oxides on refractories have still been studied insufficiently and generalization of information on the mechanisms of these processes is of interest.Based on the temperature conditions of service, equipment in which such action occurs primarily in the solid and highly viscous phase such as machines and equipment for firing of pellets (temperature in the working space from 800 to 1300~and equipment in which the interaction occurs primarily in the liquid phase such as open hearth, double bath, and electric furnaces and oxygen converters (temperature in the melting space 1600-1800~ may be conditionally distinguished.Conveyor Firing Machines for Pellets.The iron materials, dust and the pellets themselves, especially their finest (finer than 0.I nun) portion, have a significant influence on the refractory lining.The polydispersed red-brown dust consists primarily of magnetite and hematite with some quantity of calcium ferrites, quartz, and glass. The pellets have a black color with a reddish tint and consist primarily of magnetite and hematite with some quantity of silicate and ferrite phases. A layer of crust is formed on the surface of the machine lining, which is an indication of the thermoplastic state of a portion of the material.In appearance Rig. i) the crust hasa grayish black lustrous color anda flaky surface, ina number of cases with swelling.The flakiness is oriented in the direction of flows of gaseous products in the machine.The crust is practieally nonmagnetic, has a porous structure, and consists of poorly sintered rubbly material, fine formless particles with sharp edges and isometric spherical drops. Their mineral composition consists of concretions of fine grains of hematite and an insignificant quantity of calcium ferrites, quartz, and glass, that is, similar to the composition of the dust and pellets [3]. The chemical composition* of the crust is (wt.%) 77.96 Fe203, 7.37 A1203, 11.56 SiO2, and 1.56 CaO (the content of these same oxides in the pellets is 84.2, 1.87, 9.9, and 2.98%, respectively).The refractoriness of the crust is 1500-1550~ Therefore in the working space of the firing machines there are no materials the refractoriness of which is significantly lower than the temperature of this space. As the result of this the formation of the iron crust is the basic form of interaction of the reactants of the working space with the refractory lining.A Grate--Furnace--Cooler Firing Machine.The lining of this machine is also characterized by the formation on practically all portions of crusts with a refractoriness of 1330-1480~ with a temperature in the working space of the machine of up ...