28 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
produced at a remote mine, the cost of shipment of the
concentrate to a smelter may be prohibitive, especially if
the grade of the concentrate is low in nickel content. The
cost of making metallic nickel is significant. At the same
time, as the demand for nickel in batteries increases, it is
not required to make nickel metal as the final product. In
fact, nickel in a form that can go easily to make battery
grade nickel salts may be preferred as demand growth in the
battery sector will dominate through to 2050 (IEA).
A hydrometallurgical process has been developed that
provides an alternative route to making mixed hydroxide
product containing nickel and cobalt hydroxide. The pro-
cess yields high extraction and recovery of nickel, cobalt,
and copper from the nickel concentrate, forms a stable envi-
ronmental residue and avoids the production of gases and
dusts. The production of the mixed hydroxide of high qual-
ity is an alternative to smelting, converting, and refining.
The West Musgrave Project in Australia was used as a
basis for this study (Dreisinger et al., 2023).
Hydrometallurgical Process Description
Figure 5 shows a typical flowsheet for the process. The
nickel concentrate containing a range of minerals compris-
ing pentlandite, violarite, pyrrhotite, pyrite, chalcopyrite,
and various gangue minerals such as silicates, is prepared
by mineral flotation. The concentrate is thickened to form
a slurry and pumped to a holding tank ahead of a pres-
sure autoclave. A surfactant (sodium and/or calcium lig-
ninsulfonate) is added to the concentrate. Lignin sulfonates
disperse liquid sulfur at elevated temperature and maintain
high extraction rates of metals such as nickel, cobalt, and
copper from sulfide minerals.
Also added to the autoclave are oxygen gas and cooling
solution. The cooling solution is a solution that is recycled
from thickening and washing the autoclave discharge and
contains high levels of nickel, cobalt, copper, and sulfuric
acid. The cooling solution also contains some chloride ion
obtained by adding a salt such as NaCl or an acid such
as HCl to the cooling solution before pumping into the
autoclave. The autoclave temperature rises to 120–159 °C
due to the heat of reaction of the oxidation of the sulfide
minerals in the autoclave. The temperature is controlled by
addition of cooling solution. The preferred temperature of
operation is about 150–155 °C to maximize the kinetics of
the process while avoiding formation of viscous sulfur. The
oxygen gas feeding the autoclave is injected by spargers or
drawn into the slurry by gas-pumping impellers. Chloride
addition minimizes the oxidation of sulfur to sulfuric acid
to minimize the consumption of oxygen and the require-
ment for neutralization of excess acid.
The key chemical reactions occurring in the autoclave
are shown below in simplified form.
Figure 4. Simplified flowsheet for the CMCSL process
produced at a remote mine, the cost of shipment of the
concentrate to a smelter may be prohibitive, especially if
the grade of the concentrate is low in nickel content. The
cost of making metallic nickel is significant. At the same
time, as the demand for nickel in batteries increases, it is
not required to make nickel metal as the final product. In
fact, nickel in a form that can go easily to make battery
grade nickel salts may be preferred as demand growth in the
battery sector will dominate through to 2050 (IEA).
A hydrometallurgical process has been developed that
provides an alternative route to making mixed hydroxide
product containing nickel and cobalt hydroxide. The pro-
cess yields high extraction and recovery of nickel, cobalt,
and copper from the nickel concentrate, forms a stable envi-
ronmental residue and avoids the production of gases and
dusts. The production of the mixed hydroxide of high qual-
ity is an alternative to smelting, converting, and refining.
The West Musgrave Project in Australia was used as a
basis for this study (Dreisinger et al., 2023).
Hydrometallurgical Process Description
Figure 5 shows a typical flowsheet for the process. The
nickel concentrate containing a range of minerals compris-
ing pentlandite, violarite, pyrrhotite, pyrite, chalcopyrite,
and various gangue minerals such as silicates, is prepared
by mineral flotation. The concentrate is thickened to form
a slurry and pumped to a holding tank ahead of a pres-
sure autoclave. A surfactant (sodium and/or calcium lig-
ninsulfonate) is added to the concentrate. Lignin sulfonates
disperse liquid sulfur at elevated temperature and maintain
high extraction rates of metals such as nickel, cobalt, and
copper from sulfide minerals.
Also added to the autoclave are oxygen gas and cooling
solution. The cooling solution is a solution that is recycled
from thickening and washing the autoclave discharge and
contains high levels of nickel, cobalt, copper, and sulfuric
acid. The cooling solution also contains some chloride ion
obtained by adding a salt such as NaCl or an acid such
as HCl to the cooling solution before pumping into the
autoclave. The autoclave temperature rises to 120–159 °C
due to the heat of reaction of the oxidation of the sulfide
minerals in the autoclave. The temperature is controlled by
addition of cooling solution. The preferred temperature of
operation is about 150–155 °C to maximize the kinetics of
the process while avoiding formation of viscous sulfur. The
oxygen gas feeding the autoclave is injected by spargers or
drawn into the slurry by gas-pumping impellers. Chloride
addition minimizes the oxidation of sulfur to sulfuric acid
to minimize the consumption of oxygen and the require-
ment for neutralization of excess acid.
The key chemical reactions occurring in the autoclave
are shown below in simplified form.
Figure 4. Simplified flowsheet for the CMCSL process