Determinação dos parâmetros físico-químicos dos ânodos usando métodos de controlo de sua qualidade. caso: Mozal

Abstract

In factories where precooked anodes are used for electrolytic cells, the anode cooking step represents an important step in the production of the primary metal since the performance of the ovens influences the quality of the carbon block consumed in the alumina reduction reaction for the aluminum. For that, several methods of quality control of precooked anodes are used. As a general objective, the following was formulated: to apply the quality control methods of the anodes used in the aluminum production process. Specifically, the selection of parameters for anode quality control, determination of the physical-chemical parameters of the anodes and finally applied the statistical analysis of the results obtained. The present work is the product of a work placement that lasted for a period of three months. It was enriched by professional experience at the aluminum smelter factory, Mozal. The tests were carried out at the Central Laboratory of the same factory. During the normal anode block production process, 15 samples were taken from specific areas in the cooking oven. These zones are at the bottom, at half height and at the top of the oven. Of these samples, 3 were selected randomly per day and used in the study. Because the quantity produced varied, the number of samples taken for the study was also not constant. At the end of the study, 20 was taken as the final sample number. These samples were subjected to the following tests: CO2 reactivity, air permeability, thermal conductivity, air reactivity, thermal expansion coefficient, mechanical flexibility, electrical resistivity and impurity determination by XRF. Based on the results obtained, the methods used for the quality control of anodes have proven to be reliable and safe: the anodes have low reactivity to air, low air permeability, high thermal conductivity and mechanical resistance, which contributes to greater operational stability of the cells electrolytic and, consequently, greater productivity. It was seen that the impurities of vanadium and nickel, present in the analyzed samples, negatively influence the reactivity to air, catalyzing the parasitic reactions of carbon consumption. Excess sodium and calcium can cause the destruction of the refractory material in the anode cooking ovens.