Effect of mineralogy on reducibility of calcined nickel saprolite ore by hydrogen

Abstract

The aim of the work reported here was to examine the effect of mineralogy on reducibility of three different nickel saprolite ores originating from Brazil (Mirabela deposit) and from Colombia (Cerro Matoso S.A. deposit) as well as find the optimal reduction conditions for the ores. The reduction experiments were carried out in a thermobalance furnace at constant temperatures 600, 750 and 900uC in H 2 /N 2 (72%/28%) gas mixture, followed with scanning electron microscopy (SEM-EDS) and chemical analyses. The results clearly indicate that the reducibility of the ores depends on the initial mineralogy of the ore and on the phases formed during heating, before the reduction stage. The presence of antigorite in Colombia-1 ore results in a simultaneous dehydroxylation and transformation of magnesium silicate to olivine and pyroxene during heating. Due to the recrystallisation, the degree of removable oxygen R t is decreased when increasing the temperature from 750 to 900uC. The low reducibility at 900uC was also confirmed by chemical analysis. Colombia-2 and Mirabela do not, however, contain antigorite and heating the samples resulted in formation of an easily reducible intermediate phase. Thus, the recrystallisation is not initiated at 750uC like in Colombia-1 and their R t values were also enhanced at 900uC. According to SEM-EDS results, a complex series of phase and microstructure changes has been observed along with the formation of Fe-Ni alloy particles.

Effect of mineralogy and reducing agent on reduction of saprolitic nickel ores

“…Therefore, in the case of the Colombian ores, the reduction rate of removable oxygen at 750uC after a reduction time of 45 min was not as high as that of the Mirabela. For comparison, the CO reduction results, together with the results of reduction experiments for the same ores in an H 2 /N 2 (72% : 28%) atmosphere performed earlier by the present authors (Bunjaku et al, 2012), are shown in Figs. 5-7.…”

“…More particularly, when saprolitic ore is reduced in a conditioned gaseous atmosphere, both nickel and iron are formed simultaneously by reduction and the resultant ferronickel has a comparatively low nickel content (Szekely and Evans, 1971;Bunjaku et al, 2012).…”

Review of applicable desulphurization models for crude ferronickel refining

“…Nickel's economical, strategic and metallurgical importance has been thoroughly discussed in many works (Bolt 1967; Elias 2002; Halikia et al 2002; Zevgolis 2004; Mäkinen & Taskinen 2008; Mudd 2009; Rhamdhani et al 2009; Rhamdhani et al 2009; Bunjaku et al 2011; Kobayashi et al 2011; Bunjaku et al 2012; Bunjaku et al 2012; Swinbourne 2014). From cradle to grave, significant works measuring its technical competencies have been investigated by many researchers (Gleeson 2003; Guo 2009; Habashi 2009; Solar & Mostaghel 2015).…”

Efeito Da Pré-Redução Com Hidrogênio, Na Presença De Nacl, Sobre a Lixiviação Amoniacal De Um Minério Saprolítico De Ni

“…ser encontrados na literatura (Watanabe et al, 1987;Utigard et al, 2005;O'connor et al, 2006;Chang et al, 2008;Rhamdhani et al, 2009b;a;Zevgolis et al, 2010;Bunjaku et al, 2012;Samouhos et al, 2012;Li, Y.-J. et al, 2013;Rao et al, 2013;Pickles et al, 2014;Pickles e Elliott, 2015).…”

“…al (2012) estudaram a redução de três minérios saprolíticos de níquel utilizando gás hidrogênio como fase redutora e mostraram que a composição mineralógica desses minérios é um fator que influência diretamente na sua redutibilidade, os autores observaram que a presença de vermiculita em um minério brasileiro tornou o mesmo mais redutível, o que foi atribuído à formação de piroxênios que são minerais mais fáceis de serem reduzidos. No entanto, da quantidade total de ferro e níquel presente nesse mesmo minério, os melhores valores de redutibilidade obtidos foram de apenas 38%, o que é mais uma evidência da grande dificuldade em promover a redução do níquel dessa fração mineralógica do depósito laterítico (Bunjaku et al, 2012). Wang et al (2013) estudaram a redução de um minério laterítico com altos teores de silício (17%) e magnésio (17,4%) pelo carbono sólido e por CO(g).…”