Hydrogen reduction of oxidized nickel concentrates

Abstract

Thermal gravimetric analysis was used to investigate the weight change of Ni/Cu/Co calcines upon heating in an inert as well as hydrogen atmosphere. The two calcines investigated contained approximately 50 wt pct combined of hematite and magnetite in addition to sulfides of Ni, Cu, Co, and Fe. Mass spectrometry was used to analyze the gas species evolved during heating and reduction.The calcine samples are 100 pct less than 100 m with hematite/magnetite rims around a central sulfide core. When heating the calcines at 10°C/min in hydrogen, reduction starts at around 400°C and is nearly complete at about 700°C with all the reducible oxygen removed. Isothermal reduction tests show that at temperatures from 650°C to 800°C, half the oxygen is removed in less than 4 min. The TGA results combined with microscopic analysis show that the reduction followed a uniform internal reduction model. The reduced calcines will quickly get re-oxidized if they are allowed to contact air while they remain hot.

Reduction kinetics of Goro nickel oxide using hydrogen

“…The reduction experiments were carried out in a thermal gravimetric analysis unit (SETARAM TGA-92) with a detection limit of 10 g and a maximum heating rate of 30 • C/min (Crowe and Utigard, 2003). The samples, with sizes from 40 to 150 mg, were heated in alumina crucibles in a controlled gas environment.…”

Sulfate Formation and Decomposition of Nickel Concentrates

“…It could be possible to implement a heating stage before the calcine is sent to the electric furnaces, thereby collecting a large amount of SO 2 in a well-controlled and confined space, rather than to allow it to be released within the smelting furnace. Previous work (Crowe and Utigard [14] ) has shown that using a reducing atmosphere in a pretreating step can affect sulfate decomposition strongly.…”

“…This finding is consistent with the decompositions of the pure sulfates shown in Figure 9. Above this temperature, we might obtain local melting of the sulfide core with the formation of oxysulfide melts, [8,14,15] leading to accelerated kinetics and steady release of SO 2 by reaction. [6] The equilibrium constant for that reaction increases from 7250 at 773 K (500°C) to more than 10 10 at 1273 K (1000°C).…”