Reducibility of laterite ores

Kawahara, Masayasu; Toguri, J. M.; Bergman, R. A.

doi:10.1007/bf02654202

Cited by 24 publications

(24 citation statements)

References 2 publications

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“…Therefore, the initial minerals of the Mirabela and Colombia-2 ores behave differently in the reduction process in various reducing gases compared to the initial minerals in the Colombia-1 ore (Tables 1 and 2). Hence, the experimental results of the current study confirmed that the reducibility of the pellets depends on the initial mineralogy of the ores (Kawahara et al, 1988;Utigard and Bergman, 1992;Nath et al, 1995;Pietilä , 2011) and on the phases formed during heating and their NiO activity (Mukhopadhyay and Jacob, 1995). Therefore, information on the mechanism of phase transformation of the minerals, especially serpentine and other clay silicates, during the roasting reduction process is important for the improvement of the overall nickel yield from saprolitic ores (Hallet, 1997;Bunjaku et al, 2010;Bunjaku et al, 2012).…”

Section: Resultssupporting

confidence: 89%

“…Consequently, nickel oxide that separates from the disintegrated nickel magnesia silicate crystal may recombine to form poorly reducible olivine (Mg,Ni) 2 SiO 4 or/and easily reducible pyroxene (Mg,Ni)SiO 3 if they are heated to y850uC or higher (Kawahara et al, 1988;Valix and Cheung, 2002). Therefore, the initial minerals of the Mirabela and Colombia-2 ores behave differently in the reduction process in various reducing gases compared to the initial minerals in the Colombia-1 ore (Tables 1 and 2).…”

Section: Resultsmentioning

confidence: 99%

“…In conventional bromine-methanol leaching using the ICP technique, the reduced pellets were leached out in a bromine-methanol solution. Thereafter, the individual metals contained in the extraction liquid were determined with the ICP technique (Kawahara et al, 1988;Li and Coley, 2000). The accessible oxygen presented in Table 1 is defined as oxygen contained in NiO, Fe x O and CoO, and the degree of removable oxygen as R t , after the time t relative to the nickel, iron and cobalt in CO/CO 2 , is calculated (see equations (1) and (2)) in a similar way to that in H 2 /N 2 done earlier by the present authors (Bunjaku et al, 2012).…”

Section: Methodsmentioning

confidence: 99%

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

Bunjaku

Kekkonen

Pietilä

et al. 2012

Mineral Processing and Extractive Metallurgy

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The aim of this work was to explore the effect of mineralogy and gas reductant on the reduction of nickel laterites. Three different nickel saprolitic ores reduced by carbon monoxide were examined, and the results were compared with hydrogen reduction of the same ores. The reduction experiments were carried out in a thermobalance furnace which allows continuous measurement of mass change. The ores were reduced in CO/CO 2 (72% : 28%) at 750 and 900uC for 90 min. Chemical analysis was utilised to determine the degree of metallisation of the reduced pellets. It was found that the reduction rate and degree of removable oxygen at 750 and 900uC in CO/CO 2 was lower compared to reduction experiments in H 2 /N 2 (72% : 28%). The reducibility of the samples seems to depend on mineralogy and their modes of decomposition and recrystallisation. The results clearly indicate that using various reducing gases has an impact on the reduction behaviour and generation of metallics of nickel saprolitic ores.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

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

Bunjaku

Kekkonen

Pietilä

et al. 2012

Mineral Processing and Extractive Metallurgy

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“…It has been suggested (Hang and Brindley, 1973;Kawahara et al, 1988;Harris et al, 2009;Zevoglis 7 Micrograph of Mirabela after being reduced at 600uC by H 2 /N 2 (72%/28%) gas mixture 8 Isopleth of system Fe-O-Ni showing equilibrium phases over oxygen pressure range of P O2 510 4 -10 215 Pa (0?1-10 29 atm) at 800-1000uC (http://www.npl.co.uk/advanced-materials/measurements-techniques/modelling/mtdata) et al, 2010; that after the recrystallisation and especially after the formation of olivine in which nickel is firmly bonded, the reduction becomes more difficult. This is in agreement with the results obtained for Colombia-1 ore in the present study.…”

Section: Resultsmentioning

confidence: 99%

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

Bunjaku

Kekkonen

Taskinen

2012

Mineral Processing and Extractive Metallurgy

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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.

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“…Kawahara et al [15] investigated the reducibility of laterite ores using hydrogen over a temperature range of 400 to 1000 • C. The reducibility was based on the degree of reduction of the oxides of iron, nickel and cobalt to their metallic forms. The nickel reduction degree varied from 19% to 70%, and the reduction process was concluded after 40 min.…”

Section: Reduction Roast and Upgradementioning

confidence: 99%

Factors Affecting the Upgrading of a Nickeliferous Limonitic Laterite Ore by Reduction Roasting, Thermal Growth and Magnetic Separation

et al. 2017

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Abstract:There is considerable interest in the development of new processes to extract the nickel from the oxidic nickeliferous laterite deposits, as the global nickel sulphide resources are rapidly becoming more difficult to access. In comparison to sulphide ores, where the nickel-containing mineral can be readily concentrated by flotation, nickel laterites are not amenable to significant upgrading, due to their complex mineralogy. In this paper, firstly, a brief overview of the conventional techniques used to process the nickeliferous limonitic laterites is given, as well as a review of current research in the area. Secondly, a thermodynamic model is developed to simulate the roasting process and to aid in the selection of process parameters to maximize the nickel recovery and grade and also to minimize the magnetite content of the concentrate. Thirdly, a two-stage process involving reduction roasting and thermal growth in either a tube furnace or a rotary kiln furnace, followed by magnetic separation, was investigated. Thermogravimetric, differential thermal and mineral liberation analyses techniques were utilized to further understand the process. Finally, the nickel grades and recovery results were compared to those available in the literature.

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Reducibility of laterite ores

Cited by 24 publications

References 2 publications

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

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

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

Factors Affecting the Upgrading of a Nickeliferous Limonitic Laterite Ore by Reduction Roasting, Thermal Growth and Magnetic Separation

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