528
Particle Transport and Separation Using an Electrostatic
Traveling Wave
Yueau Yu, Jan Cilliers, Yanghua Wang
Resource Geophysics Academy, Imperial College London, London, UK
Department of Earth Science and Engineering, Imperial College London, London, UK
Kathryn Hadler
Department of Earth Science and Engineering, Imperial College London, London, UK
European Space Resources Innovation Centre (ESRIC), Esch-sur-Alzette, Luxembourg
Stanley Starr
Department of Earth Science and Engineering, Imperial College London, London, UK
ABSTRACT: An Electrostatic Traveling Wave (ETW) transports particle through electric forces, without fluids
or moving parts. We detail the relationships between particle size, motion direction and field frequency. At the
“crossover frequency”—a particle is equally likely to move along or against the traveling wave. The crossover
frequency decreases as particle size increases, and the proportion of particles moving against the wave direction
increases as frequency increases. We have demonstrated experimentally the separation of particles with different
sizes (average at 38 and 116 µm) by manipulating their travel directions. This shows the potential of the ETW
technology in dry mineral processing.
INTRODUCTION
Mineral processing aims to extract valuable minerals from
their ores and reduce the bulk of the ore which must be
transported and processed by the smelter (Barry A. Wills,
2006). This enrichment process significantly increases the
contained value of the ore. Conventional processing tech-
niques, such as wet separation, consumes large quantities of
water (HirajimaPetrusOosako et al., 2010, Borm, 1997).
The water supply in many remote mining locations is becom-
ing increasingly unreliable and the cost of water resources
in mining areas like Australia and Chile is increasing
(OshitaniFranks and Griffin, 2010, TripathyBanerjeeSuresh
et al., 2017). To reduce these costs and risks, dry mineral
processing is becoming more attractive. In the processing
of particles when conducting research, dry particle manip-
ulation is crucial (YanoKubotaMiyamoto et al., 2006,
Kawamoto and Tsuji, 2011). Dry processing offers addi-
tional benefits, in reducing transport costs, the need for
dewatering and the handling of tailings.
An electrostatic traveling wave (ETW) field can be
produced by a set of electrodes, insulated from each other
and connected to AC poly-phase voltage sources. Neutral
or charged fine particles brought into the ETW field will
move with a trajectory determined by the electrical force,
gravitational and drag forces, and other forces depen-
dent on their physical properties. The ETW, in large part,
depends on dielectrophoresis (DEP), first defined by Pohl
as the interaction between non-uniform electric fields with

Previous Page Next Page

Extracted Text (may have errors)

528
Particle Transport and Separation Using an Electrostatic
Traveling Wave
Yueau Yu, Jan Cilliers, Yanghua Wang
Resource Geophysics Academy, Imperial College London, London, UK
Department of Earth Science and Engineering, Imperial College London, London, UK
Kathryn Hadler
Department of Earth Science and Engineering, Imperial College London, London, UK
European Space Resources Innovation Centre (ESRIC), Esch-sur-Alzette, Luxembourg
Stanley Starr
Department of Earth Science and Engineering, Imperial College London, London, UK
ABSTRACT: An Electrostatic Traveling Wave (ETW) transports particle through electric forces, without fluids
or moving parts. We detail the relationships between particle size, motion direction and field frequency. At the
“crossover frequency”—a particle is equally likely to move along or against the traveling wave. The crossover
frequency decreases as particle size increases, and the proportion of particles moving against the wave direction
increases as frequency increases. We have demonstrated experimentally the separation of particles with different
sizes (average at 38 and 116 µm) by manipulating their travel directions. This shows the potential of the ETW
technology in dry mineral processing.
INTRODUCTION
Mineral processing aims to extract valuable minerals from
their ores and reduce the bulk of the ore which must be
transported and processed by the smelter (Barry A. Wills,
2006). This enrichment process significantly increases the
contained value of the ore. Conventional processing tech-
niques, such as wet separation, consumes large quantities of
water (HirajimaPetrusOosako et al., 2010, Borm, 1997).
The water supply in many remote mining locations is becom-
ing increasingly unreliable and the cost of water resources
in mining areas like Australia and Chile is increasing
(OshitaniFranks and Griffin, 2010, TripathyBanerjeeSuresh
et al., 2017). To reduce these costs and risks, dry mineral
processing is becoming more attractive. In the processing
of particles when conducting research, dry particle manip-
ulation is crucial (YanoKubotaMiyamoto et al., 2006,
Kawamoto and Tsuji, 2011). Dry processing offers addi-
tional benefits, in reducing transport costs, the need for
dewatering and the handling of tailings.
An electrostatic traveling wave (ETW) field can be
produced by a set of electrodes, insulated from each other
and connected to AC poly-phase voltage sources. Neutral
or charged fine particles brought into the ETW field will
move with a trajectory determined by the electrical force,
gravitational and drag forces, and other forces depen-
dent on their physical properties. The ETW, in large part,
depends on dielectrophoresis (DEP), first defined by Pohl
as the interaction between non-uniform electric fields with

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 529
polarized particles and liquids (Pohl, 1951, Pohl, 1958).
Due to the advantages of a simple structure, it requires no
water and operates with low-energy, ETW methods have
grown in popularity for applications in dry mineral pro-
cessing, space technology and dust mitigation.
The early work were inspired the transport of charged
aerosols in a spatially periodic, non-uniform field. More
systematic experimental and simulation research were
developed later to build practical applications systems,
such as biological cell separation apparatus and xerographic
system that can transport toner particles. However, these
applications are still in the theoretical and experimental
stages. EDS is a recently developed and relatively mature
technology that may have potential applications on dust
mitigation systems, particularly on solar panels and devices
in space. This auto surface cleaning system is economic and
environmental friendly. Many research groups have done
experimental and simulation research to evaluate the effects
of electrode configurations, humidity, voltage amplitude,
voltage frequency, and wave forms on the dust removal effi-
ciency on different types of particles and dust deposition
modes. The performance of EDS have been improved a lot
and outdoor field tests show promising results. The applica-
tion of EDS in space environments, such as on the Moon
or Mars, have also attracted increasing attention. The miti-
gation of dust simulant of Mars JSC-1, lunar JSC-1a, and
Minnesota simulant were tested under Martian and lunar
conditions. The feasibility of EDS system was proved and
space experiments are also part of the planning. In addi-
tion, more controlled movement of particle by using ETW
methods was researched recently such as particle size sepa-
ration in the area of ISRU.
In the review of ETW methods, we found that the diver-
sity of application fields weakens the integration between
different lines of research and hinders the development and
implementation of practical ETW systems. Motion of par-
ticles in an ETW system is affected by many parameters.
Different research groups use different experimental and
simulation models, which leads to different conclusions
at different scales. The comparison relationship between
simulation and experimental results is not straightforward,
making it difficult to reproduce and apply published mod-
els. And there is a lack of simple design rules that a designer
could use to create a system to meet a stated set of design
requirements. One of the gaps identified was that the results
of experiment and simulation lack effective quantitative
comparison methods, and the simulation model has not
been adequately validated. Single particle simulations and
single particle experiment can provide comparison for each
other that validate each other effectively. These conclusions
also provide direct and accurate information for the design
of an ETW system for particle transport.
In this paper, an ETW experimental system of particle
separation was developed based on the previous conclu-
sions and guidance. The experimental results show that
larger particles tend to move backward at lower frequencies,
at which frequency smaller particles may still move forward
effectively. A “crossover” frequency is defined, which means
a particle has an equal chance to move forward or back-
ward. And the crossover frequency decreases as the particle
size increases. Finally, a mixture of different sizes of 30 to
50 µm and 75 to 110 µm particles have been tested and
show good separation performance.
MATERIAL AND EXPERIMENT SET-UP
This section details each component. The components and
their relationship is as shown in Figure 1, including the
fabrication of the ETW board, the function generator and
its operation, details, and operation of the power supply
system, and the observation system using high-speed video
and photography.
ETW Conveyor Board Fabrication
The generation of an ETW requires a series of parallel elec-
trodes supplied with a multi-phase time-varying voltage. In
this research, the design and manufacture of the ETW con-
veyor board used printed circuit board (PCB) technology.
A basic PCB is made up of an insulating material sheet and
a tightly bonded layer of copper foil on the substrate. The
layout design of the electrodes was done by computer, and
which then transformed into the physical ETW board. The
desired electrode configuration is formed by chemically
etching the copper that is retained on the board.
A three-phase design of the ETW system was selected,
because it represents the minimum number of phases nec-
essary to create a traveling wave field that controls the
direction of particle movement. This also allows compari-
son with simulation results using a three-phase model. The
three-phase voltages are delivered to three sets of electrodes
separately. This requires an additional layer of PCB to con-
nect these three sets of electrodes independently.
The design of the electrode configuration was made in
Kicad software, shown in Figure 2. Red tracks represent the
electric circuits in the front layer, while blue tracks repre-
sent the electric circuits in the back layer. The electrodes
on the top surface are interconnected with the connecting
electrodes on the back via the pads. They are copper-filled
holes, which connect the electrodes on the corresponding
positions of the front and back sides. The four mounting
holes were designed for the support structure of the board.

Previous Page Next Page

Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 529
polarized particles and liquids (Pohl, 1951, Pohl, 1958).
Due to the advantages of a simple structure, it requires no
water and operates with low-energy, ETW methods have
grown in popularity for applications in dry mineral pro-
cessing, space technology and dust mitigation.
The early work were inspired the transport of charged
aerosols in a spatially periodic, non-uniform field. More
systematic experimental and simulation research were
developed later to build practical applications systems,
such as biological cell separation apparatus and xerographic
system that can transport toner particles. However, these
applications are still in the theoretical and experimental
stages. EDS is a recently developed and relatively mature
technology that may have potential applications on dust
mitigation systems, particularly on solar panels and devices
in space. This auto surface cleaning system is economic and
environmental friendly. Many research groups have done
experimental and simulation research to evaluate the effects
of electrode configurations, humidity, voltage amplitude,
voltage frequency, and wave forms on the dust removal effi-
ciency on different types of particles and dust deposition
modes. The performance of EDS have been improved a lot
and outdoor field tests show promising results. The applica-
tion of EDS in space environments, such as on the Moon
or Mars, have also attracted increasing attention. The miti-
gation of dust simulant of Mars JSC-1, lunar JSC-1a, and
Minnesota simulant were tested under Martian and lunar
conditions. The feasibility of EDS system was proved and
space experiments are also part of the planning. In addi-
tion, more controlled movement of particle by using ETW
methods was researched recently such as particle size sepa-
ration in the area of ISRU.
In the review of ETW methods, we found that the diver-
sity of application fields weakens the integration between
different lines of research and hinders the development and
implementation of practical ETW systems. Motion of par-
ticles in an ETW system is affected by many parameters.
Different research groups use different experimental and
simulation models, which leads to different conclusions
at different scales. The comparison relationship between
simulation and experimental results is not straightforward,
making it difficult to reproduce and apply published mod-
els. And there is a lack of simple design rules that a designer
could use to create a system to meet a stated set of design
requirements. One of the gaps identified was that the results
of experiment and simulation lack effective quantitative
comparison methods, and the simulation model has not
been adequately validated. Single particle simulations and
single particle experiment can provide comparison for each
other that validate each other effectively. These conclusions
also provide direct and accurate information for the design
of an ETW system for particle transport.
In this paper, an ETW experimental system of particle
separation was developed based on the previous conclu-
sions and guidance. The experimental results show that
larger particles tend to move backward at lower frequencies,
at which frequency smaller particles may still move forward
effectively. A “crossover” frequency is defined, which means
a particle has an equal chance to move forward or back-
ward. And the crossover frequency decreases as the particle
size increases. Finally, a mixture of different sizes of 30 to
50 µm and 75 to 110 µm particles have been tested and
show good separation performance.
MATERIAL AND EXPERIMENT SET-UP
This section details each component. The components and
their relationship is as shown in Figure 1, including the
fabrication of the ETW board, the function generator and
its operation, details, and operation of the power supply
system, and the observation system using high-speed video
and photography.
ETW Conveyor Board Fabrication
The generation of an ETW requires a series of parallel elec-
trodes supplied with a multi-phase time-varying voltage. In
this research, the design and manufacture of the ETW con-
veyor board used printed circuit board (PCB) technology.
A basic PCB is made up of an insulating material sheet and
a tightly bonded layer of copper foil on the substrate. The
layout design of the electrodes was done by computer, and
which then transformed into the physical ETW board. The
desired electrode configuration is formed by chemically
etching the copper that is retained on the board.
A three-phase design of the ETW system was selected,
because it represents the minimum number of phases nec-
essary to create a traveling wave field that controls the
direction of particle movement. This also allows compari-
son with simulation results using a three-phase model. The
three-phase voltages are delivered to three sets of electrodes
separately. This requires an additional layer of PCB to con-
nect these three sets of electrodes independently.
The design of the electrode configuration was made in
Kicad software, shown in Figure 2. Red tracks represent the
electric circuits in the front layer, while blue tracks repre-
sent the electric circuits in the back layer. The electrodes
on the top surface are interconnected with the connecting
electrodes on the back via the pads. They are copper-filled
holes, which connect the electrodes on the corresponding
positions of the front and back sides. The four mounting
holes were designed for the support structure of the board.

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 527
Lv, N. N., Chen, H., Su, C., Wang, H. C., Dong, Y. C., &
Wu, L. S. (2023). Kinetics Investigation of Phosphorus
Leaching from Steelmaking Slag. Mineral Processing
and Extractive Metallurgy Review, 44(8), 571–576.
Martins, A. C. P., De Carvalho, J. M. F., Costa, L. C. B.,
Andrade, H. D., de Melo, T. V., Ribeiro, J. C. L., &
Peixoto, R. A. F. (2021). Steel slags in cement-based
composites: An ultimate review on characteriza-
tion, applications and performance. Construction and
Building Materials, 291, 123265.
Menad, N., Kanari, N., &Save, M. (2014). Recovery of
high grade iron compounds from LD slag by enhanced
magnetic separation techniques. International Journal
of Mineral Processing, 126, 1–9.
Mercado-Borrayo, B. M., González-Chávez, J. L.,
Ramírez-Zamora, R. M., &Schouwenaars, R. (2018).
Valorization of metallurgical slag for the treatment of
water pollution: an emerging technology for resource
conservation and re-utilization. Journal of Sustainable
Metallurgy, 4, 50–67.
Nippon Steel, 2024, Promotion of innovative technology
development (https://www.nipponsteel.com/en/csr
/env/warming/future.html)
Pasetto, M., Baliello, A., Giacomello, G., &Pasquini, E.
(2017). Sustainable solutions for road pavements: A
multi-scale characterization of warm mix asphalts con-
taining steel slags. Journal of Cleaner Production, 166,
835–843.
REDMS, Product Profile, IMSC Group,https://www.imsc
-group.com/rare-earth-drum-magnetic-separators
(page accessed on 22nd May 2024).
Tang, Z., Liang, J., Jiang, W., Liu, J., Jiang, F., Feng, G.,
...&Wang, T. (2020). Preparation of high strength
foam ceramics from sand shale and steel slag. Ceramics
International, 46(7), 9256–9262.
Tripathy, S. K., Singh, V., Murthy, Y. R., Banerjee, P. K.,
&Suresh, N. (2017). Influence of process param-
eters of dry high intensity magnetic separators on
separation of hematite. International Journal of Mineral
Processing, 160, 16–31.
Tripathy, S. K., Banerjee, P. K., Suresh, N., Murthy, Y. R.,
&Singh, V. (2017a). Dry high-intensity magnetic sep-
aration in mineral industry—a review of present status
and future prospects. Mineral Processing and Extractive
Metallurgy Review, 38(6), 339–365.
Tripathy, S. K., Rao, D. S., Eswaraiah, C., &Sahoo, D.
(2021). Applied Mineralogical Investigation on the
Nature of Phosphorous in the Basic Oxygen Furnace
Slag. Transactions of the Indian Institute of Metals, 74(9),
2319–2334.
Wan, J., Du, H., Gao, F., Wang, S., Gao, M., Liu, B., &
Zhang, Y. (2021). Direct leaching of vanadium from
vanadium-bearing steel slag using NaOH solutions: a
case study. Mineral Processing and Extractive Metallurgy
Review, 42(4), 257–267.
WSA, (2021). Steel industry co-products, Fact Sheet, World
Steel Association, Brussels, Belgium, Apr. 2021.
Wu, Q., &Huang, Z. (2021). Preparation and performance
of lightweight porous ceramics using metallurgical steel
slag. Ceramics International, 47(18), 25169–25176.
Wu, Z. Huang, Wu, Q., &Huang, Z. (2021). Preparation
and performance of lightweight porous ceramics using
metallurgical steel slag. Ceramics International, 47(18),
25169–25176.
Zhang, J., Zhang, W., &Xue, Z. (2017). Oxidation kinet-
ics of vanadium slag roasting in the presence of calcium
oxide. Mineral Processing and Extractive Metallurgy
Review, 38(5), 265–273.
Zheng, Y., Luo, X., Yang, J., Huo, W., &Kang, C.
(2020). A novel approach to fabricate foam ceram-
ics from steel slag. Advances in Materials Science and
Engineering, 2020, 1–7.
Zhu, L. (2020). Influence of waste residue treatment in
metallurgical iron and steel plant on environmental
protection. China Metal Bull., 191–192.

Previous Page Next Page

Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 527
Lv, N. N., Chen, H., Su, C., Wang, H. C., Dong, Y. C., &
Wu, L. S. (2023). Kinetics Investigation of Phosphorus
Leaching from Steelmaking Slag. Mineral Processing
and Extractive Metallurgy Review, 44(8), 571–576.
Martins, A. C. P., De Carvalho, J. M. F., Costa, L. C. B.,
Andrade, H. D., de Melo, T. V., Ribeiro, J. C. L., &
Peixoto, R. A. F. (2021). Steel slags in cement-based
composites: An ultimate review on characteriza-
tion, applications and performance. Construction and
Building Materials, 291, 123265.
Menad, N., Kanari, N., &Save, M. (2014). Recovery of
high grade iron compounds from LD slag by enhanced
magnetic separation techniques. International Journal
of Mineral Processing, 126, 1–9.
Mercado-Borrayo, B. M., González-Chávez, J. L.,
Ramírez-Zamora, R. M., &Schouwenaars, R. (2018).
Valorization of metallurgical slag for the treatment of
water pollution: an emerging technology for resource
conservation and re-utilization. Journal of Sustainable
Metallurgy, 4, 50–67.
Nippon Steel, 2024, Promotion of innovative technology
development (https://www.nipponsteel.com/en/csr
/env/warming/future.html)
Pasetto, M., Baliello, A., Giacomello, G., &Pasquini, E.
(2017). Sustainable solutions for road pavements: A
multi-scale characterization of warm mix asphalts con-
taining steel slags. Journal of Cleaner Production, 166,
835–843.
REDMS, Product Profile, IMSC Group,https://www.imsc
-group.com/rare-earth-drum-magnetic-separators
(page accessed on 22nd May 2024).
Tang, Z., Liang, J., Jiang, W., Liu, J., Jiang, F., Feng, G.,
...&Wang, T. (2020). Preparation of high strength
foam ceramics from sand shale and steel slag. Ceramics
International, 46(7), 9256–9262.
Tripathy, S. K., Singh, V., Murthy, Y. R., Banerjee, P. K.,
&Suresh, N. (2017). Influence of process param-
eters of dry high intensity magnetic separators on
separation of hematite. International Journal of Mineral
Processing, 160, 16–31.
Tripathy, S. K., Banerjee, P. K., Suresh, N., Murthy, Y. R.,
&Singh, V. (2017a). Dry high-intensity magnetic sep-
aration in mineral industry—a review of present status
and future prospects. Mineral Processing and Extractive
Metallurgy Review, 38(6), 339–365.
Tripathy, S. K., Rao, D. S., Eswaraiah, C., &Sahoo, D.
(2021). Applied Mineralogical Investigation on the
Nature of Phosphorous in the Basic Oxygen Furnace
Slag. Transactions of the Indian Institute of Metals, 74(9),
2319–2334.
Wan, J., Du, H., Gao, F., Wang, S., Gao, M., Liu, B., &
Zhang, Y. (2021). Direct leaching of vanadium from
vanadium-bearing steel slag using NaOH solutions: a
case study. Mineral Processing and Extractive Metallurgy
Review, 42(4), 257–267.
WSA, (2021). Steel industry co-products, Fact Sheet, World
Steel Association, Brussels, Belgium, Apr. 2021.
Wu, Q., &Huang, Z. (2021). Preparation and performance
of lightweight porous ceramics using metallurgical steel
slag. Ceramics International, 47(18), 25169–25176.
Wu, Z. Huang, Wu, Q., &Huang, Z. (2021). Preparation
and performance of lightweight porous ceramics using
metallurgical steel slag. Ceramics International, 47(18),
25169–25176.
Zhang, J., Zhang, W., &Xue, Z. (2017). Oxidation kinet-
ics of vanadium slag roasting in the presence of calcium
oxide. Mineral Processing and Extractive Metallurgy
Review, 38(5), 265–273.
Zheng, Y., Luo, X., Yang, J., Huo, W., &Kang, C.
(2020). A novel approach to fabricate foam ceram-
ics from steel slag. Advances in Materials Science and
Engineering, 2020, 1–7.
Zhu, L. (2020). Influence of waste residue treatment in
metallurgical iron and steel plant on environmental
protection. China Metal Bull., 191–192.