3859
Pilot Plant for Wet Grinding with Vertical Roller Mill
O. Schindler, T. Zinke, H. Lieberwirth
Institute for Mineral Processing Machines and Recycling Systems Technology TU Bergakademie Freiberg, Freiberg
Saxony, Germany
ABSTRACT: Confined bed comminution (e.g., HPGR, VRM) in dry grinding for cement and ore processing
offers energy efficiency advantages over tumbling mills. But moist feed material with its higher drying energy
consumption diminishes this benefit. A novel approach introduces a VRM in overflow mode for wet grinding.
TU Bergakademie Freiberg and Loesche collaborated on a pilot-scale circuit with a vibrating screen, hydro-
cyclones, and a centrifuge for solid/liquid separation. This may present a promising solution for more efficient ore
liberation via wet grinding. The paper details the first comparison of dry and wet grinding with the pilot plant.
INTRODUCTION
The raw materials industry currently faces contradictory
trends and challenges. These include an increasing demand
for raw materials, a decrease in ore grades, a finer intergrowth
of valuable minerals with gangue, and a rapidly increasing
cost of exploration and production. (Schodde, 2019).
The demand for raw materials is increasing and is
partly linked to efforts for eliminating the use of fos-
sil fuels. The World Energy Outlook Special Report
(International Energy Agency, 2021), for example, shows
that the requirement for certain strategic materials of an
electrically powered car is approximately five times higher
than that of a conventional car with an internal combus-
tion engine. The copper requirement alone is more than
twice higher as before. According to the same study, power
generation from renewable energies will require signifi-
cantly higher amounts of these key metal materials in the
future. Additionally there is the exponentially increasing
demand due to the growing world population and, in par-
allel, the trend toward increasing BIP per capita, which in
itself results in an exponentially increasing demand for raw
materials (Krausmann et al., 2009). Both effects lead to
assumptions that primary copper demand may increase by
approximately 50% from 25 mio. t in 2022 to 37 mio. t
in 2030 (Energy Transitions Commission, 2023) or similar
(Yergin et al., 2022 McKinsey &Company, 2023).
The aim to reduce costs and CO2 emissions, leads also
to reducing the specific energy consumption a in almost all
areas of life. Processing plants are not excluded because the
energy demand for comminution plants alone accounts for
approximately 1 to 2 %of the worldwide energy consump-
tion (Segura-Salazar et al., 2021). A study conducted by
WEIR Minerals underlines this, concluding that an average
mine for the extraction of copper, gold, iron ore and nickel
requires approximately 25 %of the energy for the commi-
nution process alone (Leonida, 2020).
For a processing plant producing 100,000 t of cop-
per concentrate per day, Wills and Finch (Wills and Finch,
2016) stated that the cost share for grinding is approxi-
mately 47 %of the overall costs, mainly due to the energy
consumption. Schlesiger et al. investigated the direct oper-
ating costs for concentrating copper from 0.5 %to 30 %.
With a total amount of 4.80 $/t, alone 3.10 $/t is caused by
milling with tumbling mills and size classification. This rep-
resents more than 64 %of the operating costs (Schlesinger
et al., 2011).
Deposits with high ore grades are gradually exhausted
and replaced by new ones, often with lower grades and
Pilot Plant for Wet Grinding with Vertical Roller Mill
O. Schindler, T. Zinke, H. Lieberwirth
Institute for Mineral Processing Machines and Recycling Systems Technology TU Bergakademie Freiberg, Freiberg
Saxony, Germany
ABSTRACT: Confined bed comminution (e.g., HPGR, VRM) in dry grinding for cement and ore processing
offers energy efficiency advantages over tumbling mills. But moist feed material with its higher drying energy
consumption diminishes this benefit. A novel approach introduces a VRM in overflow mode for wet grinding.
TU Bergakademie Freiberg and Loesche collaborated on a pilot-scale circuit with a vibrating screen, hydro-
cyclones, and a centrifuge for solid/liquid separation. This may present a promising solution for more efficient ore
liberation via wet grinding. The paper details the first comparison of dry and wet grinding with the pilot plant.
INTRODUCTION
The raw materials industry currently faces contradictory
trends and challenges. These include an increasing demand
for raw materials, a decrease in ore grades, a finer intergrowth
of valuable minerals with gangue, and a rapidly increasing
cost of exploration and production. (Schodde, 2019).
The demand for raw materials is increasing and is
partly linked to efforts for eliminating the use of fos-
sil fuels. The World Energy Outlook Special Report
(International Energy Agency, 2021), for example, shows
that the requirement for certain strategic materials of an
electrically powered car is approximately five times higher
than that of a conventional car with an internal combus-
tion engine. The copper requirement alone is more than
twice higher as before. According to the same study, power
generation from renewable energies will require signifi-
cantly higher amounts of these key metal materials in the
future. Additionally there is the exponentially increasing
demand due to the growing world population and, in par-
allel, the trend toward increasing BIP per capita, which in
itself results in an exponentially increasing demand for raw
materials (Krausmann et al., 2009). Both effects lead to
assumptions that primary copper demand may increase by
approximately 50% from 25 mio. t in 2022 to 37 mio. t
in 2030 (Energy Transitions Commission, 2023) or similar
(Yergin et al., 2022 McKinsey &Company, 2023).
The aim to reduce costs and CO2 emissions, leads also
to reducing the specific energy consumption a in almost all
areas of life. Processing plants are not excluded because the
energy demand for comminution plants alone accounts for
approximately 1 to 2 %of the worldwide energy consump-
tion (Segura-Salazar et al., 2021). A study conducted by
WEIR Minerals underlines this, concluding that an average
mine for the extraction of copper, gold, iron ore and nickel
requires approximately 25 %of the energy for the commi-
nution process alone (Leonida, 2020).
For a processing plant producing 100,000 t of cop-
per concentrate per day, Wills and Finch (Wills and Finch,
2016) stated that the cost share for grinding is approxi-
mately 47 %of the overall costs, mainly due to the energy
consumption. Schlesiger et al. investigated the direct oper-
ating costs for concentrating copper from 0.5 %to 30 %.
With a total amount of 4.80 $/t, alone 3.10 $/t is caused by
milling with tumbling mills and size classification. This rep-
resents more than 64 %of the operating costs (Schlesinger
et al., 2011).
Deposits with high ore grades are gradually exhausted
and replaced by new ones, often with lower grades and