The increment of recycling of steel using electric arc furnace and the tendency to coat of steel products with zinc, in order to prevent corrosion, has increased the proportion of galvanized scrap used worldwide in the recent years. Approximately 10 to 20 Kg/t of cast steel is generated in casting arcs. These collected dusts electric arc furnace (EAF dust) contains iron, zinc, lead, and cadmium. Mainly in the form of oxides and their wastes are considered hazardous typically in countries such as Brazil, U.S., Japan and Germany. It is estimated that from the total of 7.5 million metric tons of EAF dust generated worldwide only 45% is recycled. With Waelz process, the EAF dust can be treated to recover zinc by means of reductionvolatilization-oxidation reactions occurring within the rotary kiln. In this work the thermodynamics of the Waelz process is studied to optimize the recovery of volatiles especially zinc. Kinetic parameters were evaluated trough series of ten experiments, comprise the major process factors such as type of reductants (charcoal and petroleum coke), time (20-120 minutes) and temperature (450-1150°C). The mechanical behavior of the pellets was evaluated by compressive cold strength and drop tests. Characterization was performed using scanning electron microscopy, microanalysis EDS, X-ray diffraction, X-ray fluorescence, granulometric analysis by laser diffraction, as well as measurements of moisture, bulk density and percentage of volatiles, fixed carbon and ash. The small pellets (10mm) with charcoal used as a reductant, presented a higher compression and higher recovery of volatiles than those with petroleum coke.

ResumoUma grande quantidade de poeiras e fumos contendo óxidos de ferro, zinco, alumínio, cálcio, chumbo, magnésio e cádmio são habitualmente gerados durante a produção do aço em usinas siderúrgicas semiintegradas. Processos hidrometalúrgicos e pirometalúrgicos têm sido desenvolvidos para o tratamento da poeira de aciaria elétrica (PAE). O processo Waelz, que recupera parte destes resíduos por meio de reações metalúrgicas de redução e oxidação em um forno rotativo, é uma tecnologia de destaque empregada para a recuperação dos metais voláteis, e tem sido a mais usada nos últimos 40 anos. Neste trabalho, foi realizado um estudo termodinâmico do processo Waelz, visando à otimização das condições metalúrgicas necessárias para garantir a recuperação dos metais voláteis (em especial zinco), de forma a assegurar a minimização de impactos ambientais e maximização de opções de processamento para a recuperação do zinco contido. As variáveis cinéticas foram estudadas por meio da execução de uma serie de 6 experimentos, englobando os principais fatores do processamento, tais como: tipo de redutor e tempo/temperatura de processamento. Também foi avaliado o comportamento mecânico das pelotas para cada formulação. Caracterizações por meio de microscopia eletrônica com microanálise via EDS, difração de raios X, fluorescência de raios X, análise granulométrica a laser, resistência à compressão, porcentagem de matéria volátil, carbono fixo e cinzas foram empregados. Palavras-chave: Pelotas autorredutoras; Recuperação do zinco; Tratamento de resíduo de aciaria; Processo Waelz. EVALUATION MICROSTRUCTURAL, TERMOCHEMISTRY AND MECHANICAL OF BEHAVIOR PELLETS AUTO REDUCING OF ELECTRIC ARC FURNACE DUST CONTANING ZINC FOR WAELZ PROCESS AbstractA high amount of residues such as dust and fumes containing iron oxides, zinc, aluminum, calcium, lead, magnesium and cadmium are usually generated during the steel production in steel mills, which produce it from scrap melting. Hydrometallurgical and pyrometallurgical processes have been developed to the treatment of electric arc furnace dust (EAF). The Waelz process, that recovers part of these residues through metallurgical reactions of oxidation and reduction in a rotary kiln, is a leading technology used for the recovery of volatile metals, and has been widely used over the past 40 years. In this work, an initial thermodynamic and kinetic study of the Waelz reduction process was conducted, aiming to optimize the metallurgical conditions needed to ensure the recovery of volatile metals (especially zinc) and therefore assure the minimization of environmental impacts and maximization of more sustainable processing options and with higher added value due to the increase of zinc recovery from the dust and metallurgical residues. Kinetic variables were studied by running a series of six experiments, covering the main processing variables such as content and type of the binder, content and type of the reducer and processing time/temperature. The behavior and thermomechanical properties will also be as...