Desulfurization kinetics of high lead and zinc sulfide containing slag with oxygen blowing

Abstract

The desulfurization process of lead and zinc slag is an important smelting process to obtain lead and zinc. The aim of this paper is to study the desulfurization process of high lead and zinc sulfide containing slag with oxygen blowing. The predominance area diagrams of the Pb-Zn-Fe-SO system (Pb/(Fe+Pb+Zn)=0.176, Zn/(Fe+Pb+Zn)=0.56) at various temperature were thermodynamically constructed. The physical properties, the chemical composition and the phase transformation of the desulfurization slag were investigated. The thermodynamic results indicated that lead, zinc, and iron can be oxidized to form high lead and zinc slag. The experimental results illustrated that the sulfur content in the oxidation slag can be reduced to less than 1% as temperature increased up to 1573 K. The XRD analysis of as-quenched slag shows the PbS and ZnS phase decreased, while zincite and spinel phase (Zn x Fe 3-x O 4+y) emerged and increased as the reaction time increased. The desulfurization process of molten slag were considered to be the first-order reaction and the apparent activation energy was estimated to be 44.46 kJ/mol. Under the experimental conditions, the mass transfer in the gas and liquid phase was likely to be the restrictive step.

Study on hydrogen smelting reduction behaviour in synthetic molten HIsarna slag

“…To investigate the effect of surface area between gas and the molten slag on reaction, a gas injection experiment was conducted. During the injection of H 2 -Ar into the molten slag, the reaction would mainly occur between the bubbles and FeO in the molten slag [26,27]. The detailed reaction mechanism for the case of gas injection is described as follows and it is schematically presented in Figure 10(c). The small H 2 -Ar gas bubbles are formed at the outlet of the injection lance. The hydrogen diffuses in the gas boundary layer of the individual bubble and reaches the gas/slag interface. Fe 2+ diffuses in the molten slag and reaches the gas/slag interface of each bubble. The H 2 -Ar bubbles react with Fe 2+ at gas/slag interface. Product irons are formed at the surface of the bubbles.…”

“…k FeO could be replaced by k inj as the migration of Fe ions in the molten slag is the control step in the current research [26,27].…”

“…The contact time, t e could be determined using Equation (10) [27,28]: where d b is an equivalent diameter of the gas bubble (m); and v is a velocity of the rising gas bubble (m s −1 ).…”

“…To investigate the effect of surface area between gas and the molten slag on reaction, a gas injection experiment was conducted. During the injection of H 2 -Ar into the molten slag, the reaction would mainly occur between the bubbles and FeO in the molten slag [26,27]. The detailed reaction mechanism for the case of gas injection is described as follows and it is schematically presented in Figure 10(c).…”

“…where D FeO is the diffusion coefficient of FeO in the liquid film (m 2 s −1 ), and t e is a contact time between gas bubbles and the molten slag during gas injection (s). k FeO could be replaced by k inj as the migration of Fe ions in the molten slag is the control step in the current research [26,27].…”