Computational Fluid Dynamics (CFD) modelling of a dust collection system in an underground mine crushing plant was carried out. Dust was collected/absorbed through the holes along the top edge of Run of Mine (ROM) bin. The dust collection performance of the system is summarised. The detail results are presented in the form of velocity vectors and dust concentration iso-surface contours. Time dependent dust concentration isosurfaces are also presented. Dust was found to be well contained within the crusher bin and stands out as a viable option. However, the velocity magnitudes were found to be very high in and around the whole exits, which has the potential to lead to undesirable pressure drop and generation of noise

Alam, F.

Khan, M.

Naser, J.

University of Queensland eSpace

16th Australasian Fluid Mechanics Conference 
Crown Plaza, Gold Coast, Australia 
2-7 December 2007 
 
Evaluation of a Proposed Dust Ventilation/Collection System in an Underground Mine 
Crushing Plant 
 
J. Naser1, F. Alam2, M. Khan3 
Faculty of Engineering & Industrial Science 
1Swinburne University of Technology, Victoria, 3122 AUSTRALIA 
2School of Aerospace, Mechanical and Manufacturing Engineering 
RMIT University, Melbourne, VIC 3083, AUSTRALIA 
3Centre for Multiphase Processes, University Newcastle, NSW 2308, Australia 
 
             
Abstract 
Computational Fluid Dynamics (CFD) modelling of a dust 
collection system in an underground mine crushing plant was 
carried out. Dust was collected/absorbed through the holes along 
the top edge of Run of Mine (ROM) bin. The dust collection 
performance of the system is summarised. The detail results are 
presented in the form of velocity vectors and dust concentration 
iso-surface contours. Time dependent dust concentration iso-
surfaces are also presented. 
 
Dust was found to be well contained within the crusher bin and 
stands out as a viable option. However, the velocity magnitudes 
were found to be very high in and around the whole exits, which 
has the potential to lead to undesirable pressure drop and 
generation of noise.  
 
Introduction
Extraction of ore using block caving method is common in 
underground mines. The ore extracted from draw point is hauled 
to underground crushing station using load haul dump (LHD) 
trucks and tipped or dropped into ore or ROM bin. A typical 
LHD truck tipping into a ROM bin is shown in Fig.1. Dust is 
released during the tipping process. The released dust often 
causes visibility problem to the LHD drivers. The 
released/dispersed dust is expected go out along with the 
outgoing ventilation air. In the conventional approach the 
outgoing dust laden air is collected through an exit in the ceiling. 
The dispersion of dust is governed by local airflow controlled by 
the mechanical ventilation system and is made very complex by 
the localised turbulent air motion generated by large volumes of 
material undergoing drop feed [1]. Computational Fluid 
Dynamics (CFD) simulation has been successfully used in the 
past [2] to evaluate the ventilation of underground crushing plant. 
The study [2] also carried out experimentation to qualitatively 
validate the CFD results and gain more insight into the physics of 
the dust dispersion by the drop feed. 
 
This paper undertakes CFD modelling of a less conventional dust 
collection systems proposed for a mine, details not disclosed for 
confidentiality reasons. Dust was collected/absorbed through the 
holes along the top edge of ROM bin. The idea was to contain the 
dust released from the bin to within the bin. Fig. 2 shows the 
geometry of the four tunnels and the bin, hereafter referred to as 
tipple, investigated in this study. The merits of the proposed dust 
collection system were evaluated and remarks/recommendations 
made. Simulations were conducted for three cases: empty, half, 
and full ore bin scenarios. 
 
The paper presents the flow geometries investigated, 
computational grid used for modelling the geometry and the 
computational results obtained under the specified operating 
conditions. The CFD software FIRE [3] was used for this 
investigation. 
 
Fig.1 Typical LHD trucks tipping into a ROM bin 
 
Fig.2 Geometry of the tipple showing the 20 cm holes on the 
edge of ROM bin 
 
 
Computational Method 
A typical computational grid arrangement, out of the three used 
for different bin content scenarios (empty, half empty & full) is 
shown in Fig. 3. The solution domain and the computational 
grids were constructed from the CAD drawings. Time averaged 
equations were solved to obtain the values of velocities, pressure, 
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dust concentrations and turbulence parameters. The multi-phase 
capability available in FIRE was used to model the air-dust flow 
system. Air was considered as the continuous phase (1st Phase) 
and dust, with a density of 2000kg/m3 and a uniform particle size 
of 5 micron, was considered as the dispersed (2nd phase). Both 
transient and steady state conditions were modelled. In the 
transient or time dependent situation, efforts were made to 
simulate the cyclic loading pattern observed in the real life 
operation (one LHD feed per min). A 5m3 of air-dust mixture 
(representing the volume of air displaced from the bin by each 
LHD feed) with a dust loading of 1% was released from the 
bottom of the bin over a period of 5 sec. (i.e a flow rate of 
1m3/sec) The cycle was repeated every 60 seconds and a total of 
10 cycles, i.e. a total of 600 seconds in real time was simulated. 
Under the steady state situation a continuous release of 
5m3/60=0.0833m3/sec. of air-dust mixture was maintained from 
the bottom of the bin. The simulations were carried out under iso-
thermal (200C) conditions. The volume flow rates of air through 
each tunnel and the air-dust mixture released from the bin, for all 
the three case scenarios investigated, are given in the table 1. 
 
table 1 Volume flow rates (boundary conditions) 
Air Volume flow rates 
m3/sec 
Inlets 
Steady Transient  
(60 sec/cycle) 
Dust loading % 
volume 
Tunnel-1 20.1 20.1 0.0 
Tunnel-2 3.3 3.3 0.0 
Tunnel-3 10.8 10.3 0.0 
Tunnel-4 22.6 22.6 0.0 
Bin 
(bottom of 
bin) 
0.0833 1.0 for first 5 
sec 
0.0 for next 55 
sec 
 
1.0 
 
 
 
Fig.3 A typical computational grid used (empty bin scenario) 
 
Results and Discussions 
The overall dust collection performance is summarised in table 2. 
The detail results are presented in the form of velocity vectors on 
vertical and horizontal planes and dust concentration iso-surface 
contours in the solution domain. As the time dependent effects 
were introduced through air-dust mixture released from the 
bottom of the bin (see table 1), it was not expected to alter the 
overall flow dynamics of the domain substantially. However, the 
dust concentration pattern will be altered. Hence, the dust 
concentration iso-surface contours obtained for both transient and 
steady state cases are presented in this paper. The time dependent 
videos of dust concentration iso-surfaces were also developed but 
could not be made available with this paper. The velocity vectors 
obtained for steady state cases are presented in this paper. 
 
 
Dust Collection Performance Summary  
Dust released and dust collected under the steady state cases are 
presented in table 2. Dust was found to be well contained within 
the bin. This is further demonstrated in Figs. 10 to 15. Thus the 
proposed system of collecting dust through the holes along the 
top edge of ROM bin appears to be a viable option. 
 
table 2 Dust collection summary 
Dust 
collection 
For exit 
through 20cm 
holes in the 
bin 
Dust 
released 
from the 
bottom of 
the bin 
Kg/sec 
Dust 
collected 
Kg/sec 
 
Remarks 
 
 
Empty bin 
 
1.67 
 
0.84 
50% dust is extracted, 
the rest is contained 
within the bin and 
doesn’t flow out of the 
bin.  
  
Half-empty 
bin 
 
1.67 
 
1.01 
60% dust is extracted, 
the rest is contained 
within the bin and 
doesn’t flow out of the 
bin. 
 
 
 Full bin 
 
1.67 
 
1.1 
65% dust is extracted, 
the rest is contained 
within the bin and 
doesn’t flow out of the 
bin. 
 
 
 
Fig. 4 Velocity vectors on a vertical plane through the centre of 
Tunnel 1 & 4, (empty bin scenario) 
 
 
Velocity and Dust Concentration 
The velocity vectors on a vertical plane through the centre of 
Tunnels 1 & 4, (Fig. 4) clearly show that, at the entrance to the 
tipple, the flow bifurcates, with the majority of the flow bending 
downwards towards the exit holes and a small portion bending 
upward forming two vortices near the ceiling. This upward 
stream has the potential to carry the dust, which may come from 
tunnel, to the two vortices near the ceiling and form dust cloud. 
The velocity magnitudes in bin, below the exit-hole level, were 
very small.  
 
The volume flow rate through tunnel-2 is very small (see table 1). 
The velocity vectors in Fig. 5 show that the flow doesn’t have 
enough momentum to penetrate into the tipple and is quickly 
sucked in towards the exit holes. The volume flow rate through 
tunnel-3 is also relatively low (see table 1) and is also quickly 
sucked in towards the exit holes Fig. 6. Flows coming through 
tunnels 3 & 4 doesn’t show the tendency of bifurcation observed 
in those of tunnel 1 & 4 (Fig.4). It may be possible to remove the 
formation of vortices near the ceiling and hence the potential of 
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dust cloud formation there by adjusting/balancing the flow rates 
through the tunnels. 
 
 
 
Fig. 5 Velocity vectors on a vertical plane through the centre of 
Tunnel 2 (empty bin scenario) 
 
 
 
Fig. 6 Velocity vectors on a vertical plane through the centre of 
Tunnel 3 (empty bin scenario) 
 
 
Fig. 7 Velocity vectors on a horizontal plane through the centre 
of Tunnels (empty bin scenario) 
 
 
Velocity vectors on a horizontal plane through the centre of 
tunnels (Fig. 7) show that the higher flow rates through tunnels-1 
& 4 leads to greater penetration into the tipple, whereas the least 
flow rate through tunnel-2 leads to lowest penetration. 
 
 
Fig. 8 Velocity vectors on a horizontal plane through 20cm holes 
in the bin (empty bin scenario) 
 
 
 
Fig. 9 Velocity contours on a horizontal plane through 20cm 
holes in the bin (empty bin scenario) 
 
 
Velocity vectors and contours (Figs. 8 & 9) on a horizontal plane 
through 20cm holes in the bin clearly show that the velocity 
magnitudes are very high in and around the holes and reach a 
maximum of 102m/s. This high velocity (which is in the 
compressible flow regime) may lead to high pressure drop and 
generation of noise. Efforts may me made to reduce these high 
velocities by using bigger whole diameters. 
 
 
 
Fig. 10 Dust iso-contours or iso-surface (100mg/m3) (empty bin 
scenario) (A snap shot of transient/time dependent case) 
 
1413
 
Fig. 11 Dust iso-contours or iso-surface (100mg/m3) (empty bin 
scenario) (steady state case) 
 
 
Dust iso-contours or iso-surface (100mg/m3) are presented in 
Figs. 10 & 11. It may be mentioned here that the dust 
concentration inside the iso-surface envelope is greater than 
100mg/m3. It is encouraging to see that the dust is well contained 
within the bin. However, the dust generated by the movement of 
LHD in the tunnels is ignored in this study. The dust generated 
by LHD movement and the pattern of flow coming into the tipple 
through tunnels-1 & 4 (Fig 4a) has the potential to form dust 
cloud near the ceiling. This can be investigated as an extension of 
this study. 
 
The results for half-empty and full bin scenarios, not presented in 
this paper, show very similar behaviour to that observed for 
empty bin scenario presented above. However, for the benefit of 
the readers, dust iso-contours (100mg/m3) for full bin scenarios, 
are presented in Figs. 13 & 14. Again, dust appears to be 
contained within the bin for both the transient and steady state 
simulations for the full bin case. 
 
 
 
Fig. 13 Dust iso-contours or iso-surface (100mg/m3) (full bin 
scenario) (A snap shot of transient/time dependent case) 
 
 
Fig. 14 Dust iso-contours or iso-surface (100mg/m3) (full bin 
scenario) (steady state case) 
 
Conclusions  
Dust collection through the holes along the top edge of ROM bin 
appears to be a viable option for collecting dust from an 
underground crushing plant. Under the conditions and 
assumptions made of the present study, dust released from the bin 
was found to be contained within the bin. The dust generated by 
the movement of loading trucks in the tunnels was ignored in this 
study. This can be investigated as an extension of this study. 
Efforts may also be made to reduce the high velocities observed 
in the bin holes by using bigger diameter holes. 
 
References 
[1] Johansen, S.T., & Laux, H., Simulation of granular flows, 
Proceedings of RELPOWFLO III, The international 
symposium on the reliable flow of particulate solids, 
Telemark College, Porsgrunn, Norway, 11-13 August 1999 
[2] Silvester, S.A., Lowndes, I.S., Kingman, S.W., The 
ventilation of an underground crushing plant, Mining 
Technology, Dec. 2004, Vol.113 
[3] FIRE, user guide, www.avl.com 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Evaluation of a Proposed Dust Ventilation/Collection System in an Underground Mine Crushing Plant

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Evaluation of a Proposed Dust Ventilation/Collection System in an Underground Mine Crushing Plant

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