Influence of the properties of refractory powders on their granulation and the properties of the granules

Abstract

In blast furnace production it is advantageous to use compact stoves with spherical checkers*, a subcupola temperature of 1550~ and a service temperature for the checkers in the upper layer of 1450~ diminishing over the height of the stoves, and also to use compact stoves with multilayer checkers made from refractories in temperature ranges corresponding to the service temperatures of each material.In connection with this, it has become necessary to develop a technology for granulated bodies based on aluminosilicate powders with various A1203 concentrations.Moreover, it is desirable to investigate the influence of the alumina's concentration of the s-form, which is determined by the grade of the alumina, and also by the method of treating the aluminum oxide for granulation, since the previously developed technology [i] is based on the use of scarce grade-GK alumina.The preparation of the starting materials, whose properties are shown in Tablel, includes vibrogrinding @ to a predominant grain size of minus i0 ~m.The specific surface of the powders, determined by the nitrogen-adsorption method, with the required grinding fineness (90% grains measuring less than i0 ~m) with an increase in the A1203 content in the alumina of various grades and high-alumina chamotte is increased (Fig. la). This is due to the better grindability of the alumina, which is connected with the marked brittleness of its particles, in contrast to particles of chamotte powders, which, because of the high content of glass phase, possess a higher impact strength. The specific surface of the powders is determined by the concentration of fine fractions (minus 5 ~m), which is seen from In [2] it is shown that the bulk density and angle of natural slope of powders significantly affect the densification of the material. The bulk density of powders was determined according to GOST 11035-64, pouring the powders through a funnel into the measuring metal nozzle of 1000-cm 3 capacity, the internal diameter of the nozzle being 45 mm. The angle of natural slope was determined by forming the powdered body in the shape Of a cone, for which the powder was poured through a funnel onto a flat surface; the cone was then measured with the aid of a protractor [3].During the process of granulation the granules undergo continuous densification, so we studied the influence of the bulk density and angle of natural fall on the granulation capacity of the powders and the resulting granules. Figure 2 shows that, with an increase in the specific surface of the powders, there is a reduction in their bulk density.Moreover, an increase in the content of A1203 in chamotte powders increases their bulk density (Fig. 3); the same is noted for spinel powders, although their bulk density is lower than that of chamotte powders, despite their higher true density. This is a result, firstly, of the somewhat greater specific surface, and secondly, of the peculiarity of the structure of the particles of alumina, including the presence of internal pores in the crystals.The powders were ...