- Email: [email protected]
Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique
Minerals Engineering xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique Jennifer Rachel Radman a,⇑, Raymond Langlois a, Thomas Leadbeater b, James Finch a, Neil Rowson c, Kristian Waters a a b c
Department of Mining & Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec H3A OC5, Canada School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
a r t i c l e
i n f o
Article history: Received 1 August 2013 Revised 16 March 2014 Accepted 18 March 2014 Available online xxxx Keywords: Classification Hydrocyclones Mineral processing PEPT Positron emission particle tracking
a b s t r a c t For the past 120 years, hydrocyclones have been used a wide variety of industrial applications, with their main use in mineral processing being as a classifier. Hydrocyclone characterization relies heavily on empirical and phenomenological models. There is a need to develop a method by which the flow patterns can be quantified under industrial conditions. Positron emission particle tracking (PEPT), developed by the University of Birmingham in the late 1980s, has proven to be a powerful in situ visualization tool for engineering applications. This paper presents data on the motion of quartz particles in a two-inch hydrocyclone using the PEPT technique. Quartz tracer particles were labeled using the direct activation technique. The particle size range was between 2000 and +150 lm which illustrates the flow pattern of particles reporting to the underflow. Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved.
1. Introduction Hydrocyclones are widely used in industrial processes with their main use in mineral processing being as a classifier. They are deceptively simple processing units as they have no moving parts, however, their performance is complex and difficult to predict. The feed enters tangential to the hydrocyclone body under pressure which establishes the primary outer spiral which flows downwards towards the apex forming the underflow. A secondary spiral is set up simultaneously rotating upwards to the vortex finder forming the overflow. These two spiral flows make up the main flow pattern. The classical theory considers that orbiting particles within the flow pattern are subjected to two opposing forces – an outward centrifugal force and an inward drag force. Faster settling particles will move towards the outer wall of the hydrocyclone where the primary spiral flow takes them to the apex while slower settling particles move towards the secondary spiral which takes them to the vortex finder. The centrifugal field of the hydrocyclone flow is superimposed by an intensive and rapid mixing effect, mainly caused by the macroturbulence of the flow (Schubert, 2010). The turbulence level within small hydrocyclones is strongly
⇑ Corresponding author. Tel.: +1 514 398 1454. E-mail address: [email protected] (J.R. Radman).
affected by the rotation of the flow (Dyakowski and Williams, 1993). The internal flow of the hydrocyclone is complex and remains a challenge to visualize under practical, i.e., opaque, conditions. Positron emission particle tracking (PEPT), developed at University of Birmingham in the 1980s, has been successfully used to visualize flow in a number of unit operations. These include: mixing vessels (Barigou, 2004; Marigo et al., 2013); fluidised beds (Van de Velden et al., 2008); tumbling mills (Bbosa et al., 2011; Volkwyn et al., 2011); and more recently in flotation cells (Waters et al., 2008; Fan et al., 2009; Cole et al., 2010) and spiral concentrators (Waters et al., 2012). The strength of PEPT is that opaque systems can be investigated whereas previous tracking methods require direct visualization of particles (Dabir and Petty, 1986; Hsieh and Rajamani, 1988; Jirun et al., 1990; Monredon et al., 1992; Fisher and Flack, 2002 Lim et al., 2010; Marins et al., 2010). The research presented in this paper is the visualization of real-time flow of a particle inside a two-inch hydrocyclone by the PEPT technique. Recently, Chang et al. (2011) reported the underflow trajectory of a single resin bead particle labeled with ion-exchange technique inside a hydrocyclone using PEPT. The main drawback to their work from a mineral processing point of view is the lack of a slurry system. This paper tracks a quartz particle in a slurry system under a closed loop system. The tracer particle is of the same type of
http://dx.doi.org/10.1016/j.mineng.2014.03.019 0892-6875/Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
2
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
material as the rest of the system and enters the feed inlet without any preferential orientation. Running the system on a 100% recycle allowed multiple passes of the tracer through the PEPT camera. 2. Materials and methods 2.1. Apparatus and procedure The test rig was a two-inch diameter Mozley standard hydrocyclone with quartz. The total height of the hydrocyclone was 376.5 mm with the inlet height was 36.5 mm, the conical body height was 300 mm and the apex height was 40 mm. The slurry was re-circulated until the desired pressure was stabilized. The quartz tracer particles were introduced into the sump tank. A summary of the test conditions and settings is shown in Table 1. Measurements were made in the presence of an air core at ambient atmospheric conditions. The inlet flow rate was adjusted by the bypass valves. Fig. 1. X, Y and Z position for coarse quartz particle run for a typical pass: f = 0.05; N = 250.
2.2. Tracer particles The tracer particles were two size classes of quartz activated using the direct labeling technique (Fan et al., 2006a,b). The coarse run used a 2000 + 1700 lm quartz tracer particle labeled with 4 109–1 1010 Bq of 18F via the direct activation mechanism. The creation of the fine particle was through the breakage of a larger particle, followed by screening and selection as described by Boucher et al. (2014). One kilogram of quartz was added to 25 L of water (3.8% solids by mass) in a sump tank. Prior to adding the tracer, the system was operated until the pressure stabilized. By re-circulating multiple passes over the lifetime of the tracer built up the average flow pattern. The two size classes of quartz tracer are above the approximate cut-size of the two-inch hydrocyclone (20–50 lm), i.e., under the experimental conditions the tracer particles should report to the underflow (Chandrasekhar and Raghavan, 2004).
A typical pass for the coarse quartz tracer particle is shown in Fig. 1 inside the standard two inch hydrocyclone reporting to the underflow. Fig. 2 shows the trajectory for pass one, the grayscale gradient shows the time from the particle entering the field of view and exits. The particle enters through the feed inlet at t = 0 and rotates downwards along the hydrocyclone wall in a counterclockwise direction. The diameter of the vortex decreases as the particle moves into the cylindrical section of the hydrocyclone and tapers within the conical section of the hydrocyclone in its downward progression towards the apex. From Fig. 2, the conical section at between y = 300 and y = 50, the particle no longer has a continuous downward trajectory but
2.3. Positron camera The University of Birmingham ADAC Forte positron camera was used to track the trajectory of the tracer particles (Parker et al., 2002). The PEPT geometry with respect to the camera detectors is that the x-axis is from the back of the detector to the front, the y-axis is the vertical and the z-axis is across the front, from left to right. The 3D trajectory is obtained by the triangulation algorithm developed by the University of Birmingham, details of which can be found in Leadbeater and Parker (2009) and Leadbeater et al. (2012). 3. Results and discussion 3.1. Coarse tracer particle Throughout the experiment, the coarse quartz tracer particles passed through the detector field of view. This allowed the camera to capture the fast moving particle in the primary vortex. The results of a run consist of a set of single particle locations in 3D with time. Table 1 Test conditions and settings. Vortex finder diameter (mm)
Apex diameter (mm)
Sump tank volume (L)
Pressure bar (psi)
14
4.7
25
20–35
Fig. 2. Trajectory of coarse quartz particle run for a typical pass, with the particle reporting to the underflow: f = 0.05; N = 250.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
3
the particle moves upwards before continuing downwards. This extends the particle’s residence time inside the conical section. The particle is also drawn towards the hydrocyclone left side cone wall in this downward flow and moves upwards before spirally downwards and out the apex beginning at y = 50 mm. The particle does not uniformly rotate downwards towards the apex. Around the midpoint inside the conical section of the hydrocyclone, the particle’s pitch becomes smaller and moves radially inwards into a tighter vortex and upwards towards the vortex finder before continuing downwards. In Fig. 3, the frequency of coarse quartz tracer’s appearance in different sections of the standard hydrocyclone for all the passes recorded is shown. A, B and C denote the three main sections of the hydrocyclone: A represents the feed inlet and vortex finder section; B is the conical section; C is the apex section. 3.2. Fine tracer particle A typical pass for the fine quartz tracer particle is shown in Figs. 4 and 5 shows the location of the particle as a function of time for a typical pass. Fig. 4 shows that there are significant gaps in the radial positions (X-Horizontal and Z-Horizontal) that render the fitting of a
Fig. 5. Trajectory of a typical pass of the fine quartz tracer: f = 0.05; N = 10.
Fig. 3. Frequency of particle appearance in different sections of the hydrocyclone in coarse quartz run.
true trajectory impossible, but the vertical position does give an indication of the horizontal velocity and the changes with time and height. Fig. 5 confirms that the rate of location acquisition data for the fine particle does not lend itself to a comprehensive determination of the trajectory of the particle. The lines connecting the points are added as indicators linking the consecutive point found. There will, naturally, be location between the points that are missing and so a valid trajectory cannot be proposed, with a spiralling motion expected. This is exemplified by the final connecting line implying that the particle passes through the wall of the hydrocyclone, which cannot occur. The error associated with the low value of N used here is going to be significantly greater than for the larger particle, which has a higher activity. This will have to be addressed in future PEPT analyses with hydrocyclones, in order to have greater confidence in the data. 4. Conclusions
Fig. 4. X, Y and Z position for fine quartz particle run for a typical pass of the fine tracer: f = 0.05; N = 10.
PEPT has been shown to be a powerful tool in tracking the position of a relatively large quartz particle in a hydrocyclone. This work on a slurried feed extends upon previous work on hydrocyclones, which was limited to resin beads in water. In addition, it has been shown to be possible to obtain the position of finer particles in the hydrocyclone. This is the first time that a particle of the bulk material has been tracked in a hydrocyclone using PEPT. The current work was unable to accurately develop the trajectory of the fine particles, and future work will extend upon this. It is envisaged that with improved labeling and a higher resolution tracking this will be possible. The improvements to the resolution of the PEPT technique will come through the use of a more sensitive camera, such as that at the University of Cape Town, or through setting PEPT modules to a specific geometry as per the modular camera that the University of Birmingham.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
4
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
Acknowledgments The work was funded through the Natural Sciences and Engineering Research Council of Canada Collaborative Research and Development Grant in collaboration with Vale Base Metals, Teck, Xstrata Process Support, Barrick Gold, Shell Canada, Corem, SGS Lakefield Research, SGS Canada and CHEMIQA (CRDPJ-445682-12). References Barigou, M., 2004. Particle tracking in opaque mixing systems: an overview of the capabilities of PET and PEPT. Chem. Eng. Res. Des. 82 (9), 1258–1267. Bbosa, L.S., Govender, I., Mainza, A.N., Powell, M.S., 2011. Power draw estimations in experimental tumbling mills using PEPT. Miner. Eng. 24 (3–4), 319–324. Boucher, D., Deng, Z., Leadbeater, T., Langlois, R., Renaud, M., Waters, K., 2014. PEPT studies of heavy particle flow within a spiral concentrator. Miner. Eng.,. Chandrasekhar, S., Raghavan, P., 2004. A novel approach to correlate brightness of kaolin with the iron and titanium contents. In: Rao, G.V., Misra, V.N. (Eds.), Mineral Processing Technology. Allied Publishers Pvt. Ltd., Bhubaneswar, India. Chang, Y.-F., Ilea, C.G., Aasen, Ø.L., Hoffmann, A.C., 2011. Particle flow in hydrocyclone investigated by positron emission particle tracking. Chem. Eng. Sci. 66 (18), 4203–4211. Cole, K.E., Waters, K.E., Fan, X., Neethling, S.J., Cilliers, J.J., 2010. Combining positron emission particle tracking and image analysis to interpret particle motion in froths. Miner. Eng. 23 (11–13), 1036–1044. Dabir, B., Petty, C.A., 1986. Measurements of mean velocity profiles in a hydrocyclone using laser doppler anemometry. Chem. Eng. Commun. 48 (4– 6), 377–388. Dyakowski, T., Williams, R.A., 1993. Modelling turbulent flow within a smalldiameter hydrocyclone. Chem. Eng. Sci. 48 (6), 1143–1152. Fan, X., Parker, D.J., Smith, M.D., 2006a. Enhancing 18F uptake in a single particle for positron emission particle tracking through modification of solid surface chemistry. Nucl. Instrum. Methods Phys. Res., Sect. A 558, 542–546. Fan, X., Parker, D.J., Smith, M.D., 2006b. Labelling a single particle for positron emission particle tracking using direct activation and ion-exchange techniques. Nucl. Instrum. Methods Phys. Res., Sect. A 562, 345–350. Fan, X., Waters, K.E., Rowson, N.A., Parker, D.J., 2009. Modification of ilmenite surface chemistry for enhancing surfactants adsorption and bubble attachment. J. Colloid Interface Sci. 329 (1), 167–172. Fisher, M.J., Flack, R.D., 2002. Velocity distributions in a hydrocyclone separator. Exp. Fluids 32, 302–312.
Hsieh, K.T., Rajamani, K., 1988. Phenomenological model of the hydrocyclone: Model development and verification for single-phase flow. Int. J. Miner. Process. 22 (1–4), 223–237. Jirun, X., Qian, L., Jicun, Q., 1990. Studying the flow field in a hydrocyclone with no forced vortex: Part I: Average velocity. Filtr. Sep. 27 (4), 276–278. Leadbeater, T.W., Parker, D.J., 2009. A high speed PC-based data acquisition and control system for positron imaging. Nucl. Instrum. Methods Phys. Res., Sect. A 604 (1–2), 355–358. Leadbeater, T.W., Parker, D.J., Gargiuli, J., 2012. Positron imaging systems for studying particulate, granular and multiphase flows. Particuology 10 (2), 146– 153. Lim, E.W.C., Chen, Y.-R., Wang, C.-H., Wu, R.-M., 2010. Experimental and computational studies of multiphase hydrodynamics in a hydrocyclone separator system. Chem. Eng. Sci. 65, 6415–6424. Marigo, M., Davies, M., Leadbeater, T., Cairns, D.L., Ingram, A., Stitt, E.H., 2013. Application of Positron Emission Particle Tracking (PEPT) to validate a Discrete Element Method (DEM) model of granular flow and mixing in the Turbula mixer. Int. J. Pharm. 446 (1–2), 46–58. Marins, L.P.M., Duarte, D.G., Loureiro, J.B.R., Moraes, C.A.C., Silva Freire, A.P., 2010. LDA and PIV characterization of the flow in a hydrocyclone without an air-core. J. Petrol. Sci. Eng. 70, 168–176. Monredon, T.C., Hsieh, K.T., Rajamani, R.K., 1992. Fluid flow model of the hydrocyclone: an investigation of device dimensions. Int. J. Miner. Process. 35 (1–2), 65–83. Parker, D.J., Forster, R.N., Fowles, P., Takhar, P.S., 2002. Positron emission particle tracking using the new Birmingham positron camera. Nucl. Instrum. Methods Phys. Res., Sect. A 477 (1–3), 540–545. Schubert, H., 2010. Which demands should and can meet a separation model for hydrocyclone classification? Int. J. Miner. Process. 96 (1–4), 14–26. Van de Velden, M., Baeyens, J., Seville, J.P.K., Fan, X., 2008. The solids flow in the riser of a Circulating Fluidised Bed (CFB) viewed by Positron Emission Particle Tracking (PEPT). Powder Technol. 183 (2), 290–296. Volkwyn, T.S., Buffler, A., Govender, I., Franzidis, J.P., Morrison, A.J., Odo, A., van der Meulen, N.P., Vermeulen, C., 2011. Studies of the effect of tracer activity on time-averaged positron emission particle tracking measurements on tumbling mills at PEPT Cape Town. Miner. Eng. 24 (3–4), 261–266. Waters, K., Langlois, R., Leadbeater, T., 2012. Using positron emission particle tracking to understand spiral concentrators, In: Doll, A., Kracht, W., Kuyvenhoven, R. Gecamin, (Eds.), 9th International Mineral Processing Conference – Procemin 2012, Santiago, Chile. Waters, K., Rowson, N.A., Fan, X., Parker, D.J., Cilliers, J.J., 2008. Positron emission particle tracking as a method to map the movement of particles in the pulp and froth phases. Miner. Eng. 21, 877–882.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
Contents lists available at ScienceDirect
Minerals Engineering journal homepage: www.elsevier.com/locate/mineng
Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique Jennifer Rachel Radman a,⇑, Raymond Langlois a, Thomas Leadbeater b, James Finch a, Neil Rowson c, Kristian Waters a a b c
Department of Mining & Materials Engineering, McGill University, 3610 University Street, Montreal, Quebec H3A OC5, Canada School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
a r t i c l e
i n f o
Article history: Received 1 August 2013 Revised 16 March 2014 Accepted 18 March 2014 Available online xxxx Keywords: Classification Hydrocyclones Mineral processing PEPT Positron emission particle tracking
a b s t r a c t For the past 120 years, hydrocyclones have been used a wide variety of industrial applications, with their main use in mineral processing being as a classifier. Hydrocyclone characterization relies heavily on empirical and phenomenological models. There is a need to develop a method by which the flow patterns can be quantified under industrial conditions. Positron emission particle tracking (PEPT), developed by the University of Birmingham in the late 1980s, has proven to be a powerful in situ visualization tool for engineering applications. This paper presents data on the motion of quartz particles in a two-inch hydrocyclone using the PEPT technique. Quartz tracer particles were labeled using the direct activation technique. The particle size range was between 2000 and +150 lm which illustrates the flow pattern of particles reporting to the underflow. Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved.
1. Introduction Hydrocyclones are widely used in industrial processes with their main use in mineral processing being as a classifier. They are deceptively simple processing units as they have no moving parts, however, their performance is complex and difficult to predict. The feed enters tangential to the hydrocyclone body under pressure which establishes the primary outer spiral which flows downwards towards the apex forming the underflow. A secondary spiral is set up simultaneously rotating upwards to the vortex finder forming the overflow. These two spiral flows make up the main flow pattern. The classical theory considers that orbiting particles within the flow pattern are subjected to two opposing forces – an outward centrifugal force and an inward drag force. Faster settling particles will move towards the outer wall of the hydrocyclone where the primary spiral flow takes them to the apex while slower settling particles move towards the secondary spiral which takes them to the vortex finder. The centrifugal field of the hydrocyclone flow is superimposed by an intensive and rapid mixing effect, mainly caused by the macroturbulence of the flow (Schubert, 2010). The turbulence level within small hydrocyclones is strongly
⇑ Corresponding author. Tel.: +1 514 398 1454. E-mail address: [email protected] (J.R. Radman).
affected by the rotation of the flow (Dyakowski and Williams, 1993). The internal flow of the hydrocyclone is complex and remains a challenge to visualize under practical, i.e., opaque, conditions. Positron emission particle tracking (PEPT), developed at University of Birmingham in the 1980s, has been successfully used to visualize flow in a number of unit operations. These include: mixing vessels (Barigou, 2004; Marigo et al., 2013); fluidised beds (Van de Velden et al., 2008); tumbling mills (Bbosa et al., 2011; Volkwyn et al., 2011); and more recently in flotation cells (Waters et al., 2008; Fan et al., 2009; Cole et al., 2010) and spiral concentrators (Waters et al., 2012). The strength of PEPT is that opaque systems can be investigated whereas previous tracking methods require direct visualization of particles (Dabir and Petty, 1986; Hsieh and Rajamani, 1988; Jirun et al., 1990; Monredon et al., 1992; Fisher and Flack, 2002 Lim et al., 2010; Marins et al., 2010). The research presented in this paper is the visualization of real-time flow of a particle inside a two-inch hydrocyclone by the PEPT technique. Recently, Chang et al. (2011) reported the underflow trajectory of a single resin bead particle labeled with ion-exchange technique inside a hydrocyclone using PEPT. The main drawback to their work from a mineral processing point of view is the lack of a slurry system. This paper tracks a quartz particle in a slurry system under a closed loop system. The tracer particle is of the same type of
http://dx.doi.org/10.1016/j.mineng.2014.03.019 0892-6875/Crown Copyright Ó 2014 Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
2
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
material as the rest of the system and enters the feed inlet without any preferential orientation. Running the system on a 100% recycle allowed multiple passes of the tracer through the PEPT camera. 2. Materials and methods 2.1. Apparatus and procedure The test rig was a two-inch diameter Mozley standard hydrocyclone with quartz. The total height of the hydrocyclone was 376.5 mm with the inlet height was 36.5 mm, the conical body height was 300 mm and the apex height was 40 mm. The slurry was re-circulated until the desired pressure was stabilized. The quartz tracer particles were introduced into the sump tank. A summary of the test conditions and settings is shown in Table 1. Measurements were made in the presence of an air core at ambient atmospheric conditions. The inlet flow rate was adjusted by the bypass valves. Fig. 1. X, Y and Z position for coarse quartz particle run for a typical pass: f = 0.05; N = 250.
2.2. Tracer particles The tracer particles were two size classes of quartz activated using the direct labeling technique (Fan et al., 2006a,b). The coarse run used a 2000 + 1700 lm quartz tracer particle labeled with 4 109–1 1010 Bq of 18F via the direct activation mechanism. The creation of the fine particle was through the breakage of a larger particle, followed by screening and selection as described by Boucher et al. (2014). One kilogram of quartz was added to 25 L of water (3.8% solids by mass) in a sump tank. Prior to adding the tracer, the system was operated until the pressure stabilized. By re-circulating multiple passes over the lifetime of the tracer built up the average flow pattern. The two size classes of quartz tracer are above the approximate cut-size of the two-inch hydrocyclone (20–50 lm), i.e., under the experimental conditions the tracer particles should report to the underflow (Chandrasekhar and Raghavan, 2004).
A typical pass for the coarse quartz tracer particle is shown in Fig. 1 inside the standard two inch hydrocyclone reporting to the underflow. Fig. 2 shows the trajectory for pass one, the grayscale gradient shows the time from the particle entering the field of view and exits. The particle enters through the feed inlet at t = 0 and rotates downwards along the hydrocyclone wall in a counterclockwise direction. The diameter of the vortex decreases as the particle moves into the cylindrical section of the hydrocyclone and tapers within the conical section of the hydrocyclone in its downward progression towards the apex. From Fig. 2, the conical section at between y = 300 and y = 50, the particle no longer has a continuous downward trajectory but
2.3. Positron camera The University of Birmingham ADAC Forte positron camera was used to track the trajectory of the tracer particles (Parker et al., 2002). The PEPT geometry with respect to the camera detectors is that the x-axis is from the back of the detector to the front, the y-axis is the vertical and the z-axis is across the front, from left to right. The 3D trajectory is obtained by the triangulation algorithm developed by the University of Birmingham, details of which can be found in Leadbeater and Parker (2009) and Leadbeater et al. (2012). 3. Results and discussion 3.1. Coarse tracer particle Throughout the experiment, the coarse quartz tracer particles passed through the detector field of view. This allowed the camera to capture the fast moving particle in the primary vortex. The results of a run consist of a set of single particle locations in 3D with time. Table 1 Test conditions and settings. Vortex finder diameter (mm)
Apex diameter (mm)
Sump tank volume (L)
Pressure bar (psi)
14
4.7
25
20–35
Fig. 2. Trajectory of coarse quartz particle run for a typical pass, with the particle reporting to the underflow: f = 0.05; N = 250.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
3
the particle moves upwards before continuing downwards. This extends the particle’s residence time inside the conical section. The particle is also drawn towards the hydrocyclone left side cone wall in this downward flow and moves upwards before spirally downwards and out the apex beginning at y = 50 mm. The particle does not uniformly rotate downwards towards the apex. Around the midpoint inside the conical section of the hydrocyclone, the particle’s pitch becomes smaller and moves radially inwards into a tighter vortex and upwards towards the vortex finder before continuing downwards. In Fig. 3, the frequency of coarse quartz tracer’s appearance in different sections of the standard hydrocyclone for all the passes recorded is shown. A, B and C denote the three main sections of the hydrocyclone: A represents the feed inlet and vortex finder section; B is the conical section; C is the apex section. 3.2. Fine tracer particle A typical pass for the fine quartz tracer particle is shown in Figs. 4 and 5 shows the location of the particle as a function of time for a typical pass. Fig. 4 shows that there are significant gaps in the radial positions (X-Horizontal and Z-Horizontal) that render the fitting of a
Fig. 5. Trajectory of a typical pass of the fine quartz tracer: f = 0.05; N = 10.
Fig. 3. Frequency of particle appearance in different sections of the hydrocyclone in coarse quartz run.
true trajectory impossible, but the vertical position does give an indication of the horizontal velocity and the changes with time and height. Fig. 5 confirms that the rate of location acquisition data for the fine particle does not lend itself to a comprehensive determination of the trajectory of the particle. The lines connecting the points are added as indicators linking the consecutive point found. There will, naturally, be location between the points that are missing and so a valid trajectory cannot be proposed, with a spiralling motion expected. This is exemplified by the final connecting line implying that the particle passes through the wall of the hydrocyclone, which cannot occur. The error associated with the low value of N used here is going to be significantly greater than for the larger particle, which has a higher activity. This will have to be addressed in future PEPT analyses with hydrocyclones, in order to have greater confidence in the data. 4. Conclusions
Fig. 4. X, Y and Z position for fine quartz particle run for a typical pass of the fine tracer: f = 0.05; N = 10.
PEPT has been shown to be a powerful tool in tracking the position of a relatively large quartz particle in a hydrocyclone. This work on a slurried feed extends upon previous work on hydrocyclones, which was limited to resin beads in water. In addition, it has been shown to be possible to obtain the position of finer particles in the hydrocyclone. This is the first time that a particle of the bulk material has been tracked in a hydrocyclone using PEPT. The current work was unable to accurately develop the trajectory of the fine particles, and future work will extend upon this. It is envisaged that with improved labeling and a higher resolution tracking this will be possible. The improvements to the resolution of the PEPT technique will come through the use of a more sensitive camera, such as that at the University of Cape Town, or through setting PEPT modules to a specific geometry as per the modular camera that the University of Birmingham.
Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019
4
J.R. Radman et al. / Minerals Engineering xxx (2014) xxx–xxx
Acknowledgments The work was funded through the Natural Sciences and Engineering Research Council of Canada Collaborative Research and Development Grant in collaboration with Vale Base Metals, Teck, Xstrata Process Support, Barrick Gold, Shell Canada, Corem, SGS Lakefield Research, SGS Canada and CHEMIQA (CRDPJ-445682-12). References Barigou, M., 2004. Particle tracking in opaque mixing systems: an overview of the capabilities of PET and PEPT. Chem. Eng. Res. Des. 82 (9), 1258–1267. Bbosa, L.S., Govender, I., Mainza, A.N., Powell, M.S., 2011. Power draw estimations in experimental tumbling mills using PEPT. Miner. Eng. 24 (3–4), 319–324. Boucher, D., Deng, Z., Leadbeater, T., Langlois, R., Renaud, M., Waters, K., 2014. PEPT studies of heavy particle flow within a spiral concentrator. Miner. Eng.,
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Please cite this article in press as: Radman, J.R., et al. Particle flow visualization in quartz slurry inside a hydrocyclone using the positron emission particle tracking technique. Miner. Eng. (2014), http://dx.doi.org/10.1016/j.mineng.2014.03.019