ANALYSIS OF THE ELECTROLYTIC REDUCTION AND OF ITS POLLUTANT EMISSIONS IN A PRIMARY ALUMINUM FACTORY IN THE HISTORICAL CITY OF OURO PRETO/MG

Abstract

This work is a result of an environmental project developed as a mandatory requirement of the Environmental Projects Course of the Industrial Chemistry undergraduate course of the Federal University of Ouro Preto (UFOP/MG). Firstly, the project consisted of a technical visit supervised by specialized technicians at the plant of a primary aluminum production industry in the city of Ouro Preto/MG, the Novelis do Brazil Ltda. The goals were to know and describe the production process of this factory and then, using data collected during the visit and others made available by the company to the state environmental agency (FEAM), to give a technical and critical opinion about of the possible environmental impacts of this industrial activity to the environment of the municipality in question. For this purpose, the main sectors of the plant were visited, i.e., the unit of bauxite processing and calcined aluminum production (Al₂O₃), the aluminum electrolyte reduction cells, and the gaseous and/or particulate matter control/treatment systems. The study shown that Novelis Company produced primary aluminum with good quality, but there was a high consumption of electricity in the reduction, which required own production of a part of its total energy necessary. The Soderberg paste was used as a self-cooking electrode (anode), but its potential pollutants have led the factory to implement a Complete Environmental Management System (EMS), aiming to accomplish with the ISO 9002 and 14001 standards. Among the improvements, the Novelis implemented an innovator gas dry washing and particulate control system, so called Dry Scrubber, which has demonstrated an efficiency of 96–99% in controlling emissions at this industrial plant.