XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2797
Positron Emission Particle Tracking (PEPT)
Positron Emission Particle Tracking (PEPT) (shown in
Figure 4) is another 3D particle tracking technique devel-
oped in recent years. Initially developed for medical imag-
ing, it was first applied to engineering at the University
of Birmingham, United Kingdom. The basic principle of
PEPT is based on positron annihilation. A single (“tracer”)
particle is labeled with a radionuclide that decays via beta-
plus decay, generating two gamma photons, each with an
energy of 511 keV, moving in precisely opposite directions.
An array of detectors (a PET “camera”) is used to simulta-
neously detect the two gamma rays, which defines the line
along which the annihilation occurred, as shown schemati-
cally in Figure 4. Detection of a few such events in a very
short time interval allows the position of the tracer particle
to be triangulated in three dimensions. The tracer particle’s
location in space may be found at a frequency of up to
250 Hz, where the accuracy depends on the tracer particle’s
speed and activity.
Most of the work applying PEPT to turbulent flows
deals with velocity measurement. The quality of the mea-
surements in flotation processes is related to the spatial and
temporal precision of the PET scanner and the characteris-
tics of the tracer (Cole, et al., 2014). Their results showed
that tracer particles require sufficient activity for accurate
tracking. Guida et al.(2009) employed PEPT to study
the mixing of a concentrated suspension of coarse glass
particles and liquid in a vessel stirred by a pitched blade
turbine. The Lagrangian trajectory of a single positron-
emitting particle was visualized, and then used to obtain
the detailed Eulerian path of the two-phase flow inside the
vessel. Pianko-Oprych et al. (2009) compared the velocity
measurements made by PEPT with those made using PIV
of water in the same vessel and found excellent agreement.
Excellent velocity measurement results were also obtained
for solid suspensions with concentrations as high as 5wt%,
which was not achievable using PIV. Chiti et al. (2011)
used PEPT to study the turbulent flow in a baffled ves-
sel agitated by a Rushton turbine. The Lagrangian veloc-
ity obtained from the PEPT was converted to an Eulerian
velocity that was then compared with LDA measurement
results in the literature. The excellent agreement between
the two results shows that the PEPT technique obtained
accurate velocity data in the vessel.
The PEPT can reveal particle trajectories in opaque
turbulent flows inside small laboratory-scale vessels.
Measuring velocity fluctuation with PEPT is challenging
because the water surrounding the tracer absorbs a portion
of the γ-rays, decreasing the signal-to-noise ratio (Chiti,
et al., 2011). The main challenge is how to determine the
tracer location within dynamic multiphase flows (Cole,
et al., 2022). Recent developments show that PEPT can
detect turbulent structures at macroscale lengths by calcu-
lating the turbulent kinetic energy (TKE) experienced by a
PEPT tracer particle (Cole, et al., 2023).
Constant Temperature Anemometer (CTA)
Constant Temperature Anemometer (CTA) is a thermal
measurement technique employing a hot wire heated by a
supplied current/voltage to measure mean and rms veloci-
ties in turbulent flows. Amini et al. (2013, 2016a, 2016b,
2017, 2020) developed a scale-up technique using a con-
stant temperature anemometer to measure turbulence in
flotation cells. Figure 5 demonstrates the CTA setup for a
5L flotation cell in which our experiments were conducted.
A 60 L flotation cell was set up in a similar fashion.
Figure 4. Schematic of the PEPT
Figure 5. (a) An experimental setup for CTA to be used in a
5 L cell (1: CTA module, 2: computer, 3: traverse, 4: probe
holder bar, 5: air valve, 6: 5 L bottom driven flotation cell).
(b) A conical film probe
Positron Emission Particle Tracking (PEPT)
Positron Emission Particle Tracking (PEPT) (shown in
Figure 4) is another 3D particle tracking technique devel-
oped in recent years. Initially developed for medical imag-
ing, it was first applied to engineering at the University
of Birmingham, United Kingdom. The basic principle of
PEPT is based on positron annihilation. A single (“tracer”)
particle is labeled with a radionuclide that decays via beta-
plus decay, generating two gamma photons, each with an
energy of 511 keV, moving in precisely opposite directions.
An array of detectors (a PET “camera”) is used to simulta-
neously detect the two gamma rays, which defines the line
along which the annihilation occurred, as shown schemati-
cally in Figure 4. Detection of a few such events in a very
short time interval allows the position of the tracer particle
to be triangulated in three dimensions. The tracer particle’s
location in space may be found at a frequency of up to
250 Hz, where the accuracy depends on the tracer particle’s
speed and activity.
Most of the work applying PEPT to turbulent flows
deals with velocity measurement. The quality of the mea-
surements in flotation processes is related to the spatial and
temporal precision of the PET scanner and the characteris-
tics of the tracer (Cole, et al., 2014). Their results showed
that tracer particles require sufficient activity for accurate
tracking. Guida et al.(2009) employed PEPT to study
the mixing of a concentrated suspension of coarse glass
particles and liquid in a vessel stirred by a pitched blade
turbine. The Lagrangian trajectory of a single positron-
emitting particle was visualized, and then used to obtain
the detailed Eulerian path of the two-phase flow inside the
vessel. Pianko-Oprych et al. (2009) compared the velocity
measurements made by PEPT with those made using PIV
of water in the same vessel and found excellent agreement.
Excellent velocity measurement results were also obtained
for solid suspensions with concentrations as high as 5wt%,
which was not achievable using PIV. Chiti et al. (2011)
used PEPT to study the turbulent flow in a baffled ves-
sel agitated by a Rushton turbine. The Lagrangian veloc-
ity obtained from the PEPT was converted to an Eulerian
velocity that was then compared with LDA measurement
results in the literature. The excellent agreement between
the two results shows that the PEPT technique obtained
accurate velocity data in the vessel.
The PEPT can reveal particle trajectories in opaque
turbulent flows inside small laboratory-scale vessels.
Measuring velocity fluctuation with PEPT is challenging
because the water surrounding the tracer absorbs a portion
of the γ-rays, decreasing the signal-to-noise ratio (Chiti,
et al., 2011). The main challenge is how to determine the
tracer location within dynamic multiphase flows (Cole,
et al., 2022). Recent developments show that PEPT can
detect turbulent structures at macroscale lengths by calcu-
lating the turbulent kinetic energy (TKE) experienced by a
PEPT tracer particle (Cole, et al., 2023).
Constant Temperature Anemometer (CTA)
Constant Temperature Anemometer (CTA) is a thermal
measurement technique employing a hot wire heated by a
supplied current/voltage to measure mean and rms veloci-
ties in turbulent flows. Amini et al. (2013, 2016a, 2016b,
2017, 2020) developed a scale-up technique using a con-
stant temperature anemometer to measure turbulence in
flotation cells. Figure 5 demonstrates the CTA setup for a
5L flotation cell in which our experiments were conducted.
A 60 L flotation cell was set up in a similar fashion.
Figure 4. Schematic of the PEPT
Figure 5. (a) An experimental setup for CTA to be used in a
5 L cell (1: CTA module, 2: computer, 3: traverse, 4: probe
holder bar, 5: air valve, 6: 5 L bottom driven flotation cell).
(b) A conical film probe