Microstructural, thermochemistry and mechanical evaluation of self-reducing pellets using electric arc furnace (EAF) dust containing zinc for Waelz process

Abstract

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.

Conversion Termoquímica Y Análisis Microestructural De Briquetas Auto-Reductoras Hechas De Cáscarilla Resultante De La Laminación Proveniente Del Proceso De Conformado Del Acero en Caliente (Mill Scale), Y Grafito Reciclado

“…Hernández Buitrago et. al., [16], proponen que las posibles reacciones de reducción para estos óxidos en el rango de 700 a 1200ºC serían según las reacciones:…”

Direct reduced iron and zinc recovery from electric arc furnace dust

“…The secondary use of zinccontaining materials in steel-smelting furnaces leads to the accumulation of zinc in the lining of blast furnaces and their destruction. 7 Therefore, one of the main stages of the processing of such materials should be the removal of zinc, [8][9][10] which can be carried out by pyrometallurgical (mainly in ferrous metallurgy), 11,12 hydrometallurgical (mainly in non-ferrous metallurgy) and other methods for process intensification, like microwave-assisted separation, 13 in-process separation, 14 etc. 15,16 In the case of the pyrometallurgical method, during roasting with carbon at temperatures of 950-1050 °C, zinc is formed in a gaseous state and sublimates.…”

Spent Mushroom Substrate and Electric Arc Furnace Dust Recycling by Carbothermic Reduction Method

“…Alternatively, using biomass to replace or partially replace coal and coke can reduce CO 2 emissions and potentially improve the process efficiency [ 16 , 17 ]. Others had used charcoal and petroleum coke for the carbothermic reduction of EAFD and had reported higher compressive strength and improved reduction of charcoal containing pellets [ 18 ].…”