Investigations on the carbothermic reduction of chromite ores

Abstract

Experimental studies were carried out on the reducibility of two different chromite ores using different reducing carbonaceous reducing agents in the temperature range 1173 to 1573 K. "Friable lumpy" ores and "hard lumpy" ores were used in the experiments. Petroleum coke, devolatilized coke, (DVC) and graphite were used as reducing agents. It was found that iron was practically completely reduced before the commencement of the reduction of chromium in the ore. The reduction of iron was controlled by diffusion. The activation energy for this process was estimated to be 130 kJ/mole. The reduction of chromium was controlled by either chemical reaction or nucleation. Rate of reduction was highest when raw petroleum coke was used as the reducing agent. The DVC was less effective compared to raw coke, whereas the rate of reduction was lowest when graphite was used as the reducing agent.

Direct Production of Ferrochrome by Segregation Reduction of Chromite in the Presence of Calcium Chloride

“…As shown, the finer size fractions contain higher amounts of the gangue minerals, evidenced by the lower Cr 2 O 3 and higher SiO 2 concentrations. XRD (Rigaku D/MAX 2500, Rigaku Ltd., Tokyo, Japan) analysis of the 37-75 µm size fraction (Figure 1) indicates that the main gangue minerals are clinochlore (Mg,Fe) 5 Al(Si 3 Al)O 10 (OH) 8 , magnesite (MgCO 3 ), and phlogopite KMg 3 (Si 3 Al)O 10 (OH) 2 . Chromite size fraction of 180-300 µm has much less gangue, with only clinochlore identified by XRD (Figure 1).…”

“…In addition to the reduction of chromite directly by solid carbon (Equation (1)), chromite can also be reduced by gaseous CO forming CO2 (Equation (4)), resulting in the evolution of minor amounts of CO2 at approximately 150 min when pellets were heated ( Figure 14). The CO2 can be further consumed by the Boudouard reaction, i.e., Equation (5). The absence of this minor CO2 peak when the powder sample was used ( Figure 14) strongly suggests that the Boudouard reaction was greatly promoted.…”

“…The SAF process for ferrochrome production is extremely electric energy-intensive [3], with the specific energy consumption (SEC) in the range of 2.4-4.8 MWh per ton of ferrochrome produced [4]. Among the various SAF smelting technologies, pre-reduction of chromite before SAF smelting generally results in a lower SEC, because significant amounts of energy that are required for both heating the feed material and for enabling the endothermic reduction reactions are supplied by burning fuels in the pre-reduction stage, which is generally carried out in rotary kilns [5]. The premus process operates at a pre-reduction degree of~50% Cr metallization, achieving a low SEC of 2.4 MWh/t [6].…”

Briquette smelting in electric arc furnace to recycle wastes from stainless steel production

“…These together make carbon as a reducing agent more environmentally and economically attractive than silicon. Carbon was then selected as the main reducing agent for recovery the metals from the waste briquettes [13][14][15][16] .…”

Modelling of the Refining Processes in the Production of Ferrochrome and Stainless Steel

“…Dawson & Edwards (1986), Niayesh & Dippenaar (1992), Xiao et al (2004), Chakraborty et al (2005) and Zhao & Hayes (2010), the influece of the electric current on the reduction reactions is usually omitted as anything else but a heat source . Experiments conducted by Rousu et al (2010) indicated the enhancing effect of electric current on the reduction reactions thus giving a little information concerning the dependancies between the current and the reactions.…”