Influência da adição de cargas inorgânicas no desempenho de produtos refratários obtidos a partir de borras de alumínio

Abstract

White dross is a reject generated during aluminium production. It contains several oxides that can be useful to the refractories and cement industries. However, white dross can be hazardous both to human health and the environment. In this work, white dross was evaluated as a prospective raw material for the production of refractories. For this purpose, the dross was subjected to calcination followed by comminution and classification. In order to improve the mechanical properties of the refractory, two different kinds of electrofused particles were used separately as reinforcement: mullite and alumina. Particles of the TP-325 mullite were added to the white dross powder in proportions varying from 5 to 35% weight. The AL-L 280 alumina particles were added to another batch of refractories, in two different amounts (20 and 30% wt.). All materials were characterized by X-ray fluorescence, X-ray diffraction, and thermogravimetric analysis. Mixtures of residual powder and particles were compression molded as prismatic bars under a pressure of 30 MPa. Pressed bars were sintered in air at 1400ºC for 2h, and the heating rate was 5ºC/min. Mechanical and physical properties of the sintered parts were determined by means of linear shrinkage, water absorption, apparent porosity, density, MOR (three-point bending) and SEM analysis. The results obtained in this work indicate that the mixtures of white dross and 15% mullite allowed for a better compaction and density, producing parts with higher mechanical strength than the mixtures with alumina. Pyrometric cone tests at 1400ºC show the refractoriness of the parts up to that temperature. Therefore, under the conditions of this research work, white dross with additions of mullite particles has proven to be a prospective candidate for the production of refractory parts.