XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 35
This can be done by adding NaOH to MgCl2 solution
or by reversing the order of addition. The goal is to provide
a near complete removal of Mg as Mg(OH)2 from solution,
requiring a near stoichiometric addition of NaOH.
Chlor-Alkali plant. The final solution is NaCl and
H2O with some minor contaminants in solution. This
solution is directed to a chlor-alkali plant for manufacture
of NaOH, Cl2, and H2. This involves many steps. The Cl2
and H2 are burned and water-scrubbed to form strong HCl
solution for recycle to leaching.
EXPERIMENTAL RESULTS
Raw Materials for Leaching
The nickel saprolite sample was provided by SGS Canada
from an existing inventory of material.
Table 4. Composition of Raw Materials for Extraction
Analysis(%) Nickel Saprolite
Ni 1.81
Co 0.052
Cu 0.005
Zn 0.02
Fe 18.0
Mg 12.2
Al 2.19
Cr 0.78
Mn 0.65
Ca 0.33
Si 15.6
Na 0.02
S 0.02
60
65
70
75
80
85
90
95
100
600 700 800 900 1000
Acid Addition (kg HCl/t)
Mg Fe Ni
60
65
70
75
80
85
90
95
100
600 700 800 900 1000
Acid Addition (kg HCl/t)
SiO2
Figure 8. Batch leaching of saprolite. Typical conditions: Temperature 100 °C, 4 h, 87 g/L Mg (as MgCl
2 )
The samples were either used as received or ground to
finer size as required. Typical particle sizes were 100%
1 mm for saprolite and 150 mm for the asbestos tailing
and olivine.
HCl Leaching Test Results
A series of HCl leaching tests was performed to assess the
extraction of the key elements (Ni/Co/Mg/Fe/Al) and the
quality of silica residue produced as a product.
Cementitious Properties of the Leach Residues
An extensive study of the cementitious properties of the
leach residues is currently being conducted by the LMC
laboratory EPFL (Lausanne, Switzerland). The micro-silica
leach residue product has a reactivity similar to fly ash. This
is important as fly ash availability will decrease over time
with reduced use of carbon-based fuels. Micro-silica can be
used to replace fly ash. Further testing has shown that with
up to 30% substitution for Ordinary Portland Cement
(OPC) the compressive strength of mortars is unaffected,
the compressive strength of concrete is increased 14–19%
and the concrete containing Atlas micro-silica has a 10-fold
improvement in chloride penetration resistance compared
to reference OPC.
Bench and Pilot Plant Results
Following an extensive bench test program, the Atlas
Materials process was piloted on a sample of nickel sap-
rolite ore for a total of 10 days. All the key metrics were
achieved in the pilot plant operation.
Extraction
(%)
Residue
Silica
Grade
(%)
This can be done by adding NaOH to MgCl2 solution
or by reversing the order of addition. The goal is to provide
a near complete removal of Mg as Mg(OH)2 from solution,
requiring a near stoichiometric addition of NaOH.
Chlor-Alkali plant. The final solution is NaCl and
H2O with some minor contaminants in solution. This
solution is directed to a chlor-alkali plant for manufacture
of NaOH, Cl2, and H2. This involves many steps. The Cl2
and H2 are burned and water-scrubbed to form strong HCl
solution for recycle to leaching.
EXPERIMENTAL RESULTS
Raw Materials for Leaching
The nickel saprolite sample was provided by SGS Canada
from an existing inventory of material.
Table 4. Composition of Raw Materials for Extraction
Analysis(%) Nickel Saprolite
Ni 1.81
Co 0.052
Cu 0.005
Zn 0.02
Fe 18.0
Mg 12.2
Al 2.19
Cr 0.78
Mn 0.65
Ca 0.33
Si 15.6
Na 0.02
S 0.02
60
65
70
75
80
85
90
95
100
600 700 800 900 1000
Acid Addition (kg HCl/t)
Mg Fe Ni
60
65
70
75
80
85
90
95
100
600 700 800 900 1000
Acid Addition (kg HCl/t)
SiO2
Figure 8. Batch leaching of saprolite. Typical conditions: Temperature 100 °C, 4 h, 87 g/L Mg (as MgCl
2 )
The samples were either used as received or ground to
finer size as required. Typical particle sizes were 100%
1 mm for saprolite and 150 mm for the asbestos tailing
and olivine.
HCl Leaching Test Results
A series of HCl leaching tests was performed to assess the
extraction of the key elements (Ni/Co/Mg/Fe/Al) and the
quality of silica residue produced as a product.
Cementitious Properties of the Leach Residues
An extensive study of the cementitious properties of the
leach residues is currently being conducted by the LMC
laboratory EPFL (Lausanne, Switzerland). The micro-silica
leach residue product has a reactivity similar to fly ash. This
is important as fly ash availability will decrease over time
with reduced use of carbon-based fuels. Micro-silica can be
used to replace fly ash. Further testing has shown that with
up to 30% substitution for Ordinary Portland Cement
(OPC) the compressive strength of mortars is unaffected,
the compressive strength of concrete is increased 14–19%
and the concrete containing Atlas micro-silica has a 10-fold
improvement in chloride penetration resistance compared
to reference OPC.
Bench and Pilot Plant Results
Following an extensive bench test program, the Atlas
Materials process was piloted on a sample of nickel sap-
rolite ore for a total of 10 days. All the key metrics were
achieved in the pilot plant operation.
Extraction
(%)
Residue
Silica
Grade
(%)