New pyrometallurgical process of EAF dust treatment with CaO addition

Abstract

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 (ZnFe 2 O 4 ), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca 2 Fe 2 O 5 by CaO addition. The EAF dust was mixed with CaO 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 ZnFe 2 O 4 was transformed into ZnO and Ca 2 Fe 2 O 5 at a minimum temperature of 900°C within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe 2 O 4 . 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 CaO was added.

Mining and metallurgical wastes: a review of recycling and re-use practices

“…Furthermore, hydrometallurgical processes using conventional leaching and chelating media also suffer from poor selectivity and codissolution, thereby increasing the complexity of downstream solution purification processes. As a result, several alternative leaching and pretreatment processes have been proposed, or are being investigated, in order to improve the kinetics and economics of the leaching processes Abott et al, 2006Abott et al, , 2009Steer and Griffiths, 2013;Bakkar, 2014;Chairaksa-Fujimoto et al, 2015;Miki et al, 2016;Chairaksa-Fujimoto et al, 2016;Binnemans and Jones, 2017;Xing, Wang, and Chen, 2017).…”

“…Pretreatment and leaching of ferrous dusts-As discussed in the preceding sections, the presence of the refractory ZnFe 2 O 4 spinel presents challenges to the conventional leaching of these materials in aqueous media. As such, several studies have focused on the thermal pretreatment of Zn-bearing dusts before the leaching process (Chairaksa-Fujimoto et al, 2015;Miki et al, 2016;Chairaksa-Fujimoto et al, 2016;Yakornov et al, 2017). Chairaksa-Fujimoto et al (2015) investigated the effect of CaO addition on the conversion of ZnFe 2 O 4 in industrial EAF dust.…”

“…As such, several studies have focused on the thermal pretreatment of Zn-bearing dusts before the leaching process (Chairaksa-Fujimoto et al, 2015;Miki et al, 2016;Chairaksa-Fujimoto et al, 2016;Yakornov et al, 2017). Chairaksa-Fujimoto et al (2015) investigated the effect of CaO addition on the conversion of ZnFe 2 O 4 in industrial EAF dust. Their findings confirmed that the ZnFe 2 O 4 spinel can be decomposed by thermal treatment in the temperature range 900-1100ºC and in the presence of a stoichiometric amount of reactive CaO to produce ZnO and Ca 2 Fe 2 O 5 , as shown in Equation [2](Chairaksa-Fujimoto et al 2015:…”

“…Based on the thermodynamic feasibility of reaction [2] at the temperatures investigated, the authors have demonstrated that 100% of the ZnO can be selectively leached in conventional acidic or alkaline media after 4 hours, compared to 40% leaching efficiency in the case of the as-received sample (Chairaksa-Fujimoto et al, 2015, 2016.…”

Immobilization of Chromium in Stainless Steel Slag Using Low Zinc Electric Arc Furnace Dusts

“…Several different methods have been proposed for recycling of EAF dusts, including pyrometallurgical, hydrometallurgical and hybrid processes (thermal reduction followed by leaching), which are mainly proposed to extract crude zinc from EAF dusts rich in ZnO. [17,[20][21][22][23][24][25][26][27] However, most Chinese steel electrical arc furnaces produce steel using scrap steels combined with a certain amount of liquid metal, so the zinc content in EAF dusts is relatively low (< 10 pct [28] ) compared with other countries (> 20 pct [23,24,27] ). The economic benefit of recovering zinc from low-zinc-content EAF dusts is limited.…”