A utilização do carvão antracito como fonte de carbono em forno rotativo na produção de chumbo secundário: um estudo de caso

Abstract

Approximatly 80% of global lead production is intended for the manufacture of lead-acid batteries. Due to being a heavy metal with high toxicity, improper disposal of espent batteries poses risks to human health and the environment. CONAMA Resolution No. 257/1999 defines that unusable batteries must be returned to the supplier to be reused, recycled or disposed of in an environmentally correct way. The process of obtaining secondary lead from the recycling of lead-acid batteries is mostly pyrometallurgical, occurring in four main stages: scrap crushing, melting in rotary furnaces, refining and casting. In the metal smelting stage, three raw materials are used, responsible for reducing lead oxides, sulfates and sulfides: a carbon source, a material with a high iron content and sodium carbonate. Seeking to optimize the process and increase the yield of raw lead in the furnaces, the present work has studied the use of anthracite coal as an alternative fixed carbon source to the commonly used petroleum coke, due to its higher available carbon content. Pilot scale tests were carried out with different furnace charge compositions, and later full scale tests were carried out. The results obtained in the industrial process were not satisfactory. Therefore, the second stage of the work was to investigate the possible root cause of the problem using thermogravimetric analyzes and propose improvements for the development of future work.