New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace(EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite(Zn Fe2O4), which accounts for more than half of total zinc in the EAF dust, into Zn O and Ca2Fe2O5 by Ca O addition. The EAF dust was mixed with Ca O powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All Zn Fe2O4 was transformed into Zn O and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient Ca O to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess Ca O beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than Zn Fe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when Ca O was added.

Activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag and their application to the recycling of Ni–Co–Fe-based end-of-life superalloys via remelting

To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life（EoL） superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al_2O_3-SiO_2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al_2O_3-SiO_2 slag. The activity coefficients of NiO and CoO in CaO-Al_2O_3-SiO_2 slag both show a positive deviation from Raoult＇s law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B =（%CaO）/（%SiO_2） = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.

Up-grading of natural ilmenite ore by combining oxidation and acid leaching

Rutile （TiO2） is heavily used in pigments mid colormlts, mid the most abundmlt source of rutile is ilmeinte. Upon oxidation of ilmeinte, mtile cml be formed wiffl modest energy consumption; furfflermore, after leaching, only a few byproducts are formed. Unfortunate- ly, one drawback is file necessarily long oxidative process of typically used mefflods. In fflis study, we show fflat a fluidized bed reactor cml be used to oxidize ilmeinte ore to rapidly form ruffle mid pseudobrookite （Fe2TiOs） phases. Ilmeinte was oxidized wiffl 5vo1% 02 in Ar at temperatures of 1173 K or 1223 K mid subsequently leached using a diluted H2SO4 solution to dissolve file pseudobrookite phase. The effects of acid concentration, temperature, mid cooling rate after oxidation were investigated. We show fflat file ilmeinte was rapidly oxidized to form rutile mid pseudobrookite phases at 1173 mid 1223 K in a 5vo1% O2/95vo1% Ar environment wifflin 40 min. The fmal maximum mtile yield was 84.2mo1% after leaching in （1 ＋ 1） H2SO4 solution at 393 K for 12 h.