Gabriel ARPA, Kyuro SASAKI and Yuichi SUGAI
Department of Earth Resources Engineering,Faculty of Engineering, Kyushu University, Fukuoka 812-8581,
Japan
KAINANTU UNDERGROUND MINE STOPE VENTILATION
MEASUREMENT USING TRACER GAS AND NUMERICAL
SIMULATION
BACKGROUND
Continuous research into improving airflow quality and quantity is an on going activity. Tracer gas can be an effective method to assess mine ventilation system.
Determine complex airflow patterns and flow volume, where velocity is too low, openings too large, or cross section geometry too complex.
Accurate determination of ventilation assessment parameters; Re-circulations, - Leakages, -residence time
Simulate and model the spread of contaminants.
Tracer gas can give effective information of airflow in highly irregular airflow paths and can be an effective method to assess mine ventilation system and airflow dynamics.
Tracer gas can be used to:
REVIEW
2. Check for possible short cuts /leakages (Widodo et al. 2006)
However, there is little research on shorter mine airways and mine face, and the effect of dead ends and open spaces along airway routes.
3. Flow dynamics along airway routes. (Taylor et al. 1953, Sasaki et al. 2002, Widodo et al. 2006)
1.Check for air Leakage. (Hardcastle et al. 1993)
OBJECTIVE
To Study:
Airflow through narrow vein shrinkage stope by using tracer gas technique and numerical simulation.
The effect of dead end drives, openings and empty spaces along the airway route on airflow quantity and quality.
METHOD
By pulse injection of SF6 from upstream positions and measure the concentration with elapsed time at a downstream position.
RESEARCH APPROACH
Ventilation Survey
Tracer Gas Measurement
Numerical Simulation
FIELD MEASUREMENT
Lae
Madang
The Kainantu Mine
KAINANTU MINE OVERVIEW
Mining Method: Narrow Vein Shrinkage stope
Production: 300 ton ore/day
Semi-mechanized operation
MINE VENTILATION
Ascension – Through flow system
Fan 1 Fan 2 Fan3
4th Outlet 4th Outlet 4th Outlet
P (Pa) 500 400 400
Q (m3/s) 35 25 25
Schematic of ventilation systemMain intake (1300 Portal)
4th Outlet
Fan 3 Fan 2
Fan 1
Gas Monitor system
Lap top
Stop watch
Portable scale
Balloons
Sulfur hexafluoride (SF6)
MEASUREMENT SYSTEM
Photoacoustic gas monitor (Brual & Kjear 1302)
Resolution = 10 ppb
Absolute accuracy = +/- 50 ppb
Sampling rate = 40 sec
Raise
Sampling
Pulse release of SF6
MonitorLap top
Lower level
Upper level
Not to scale
MEASUREMENT PROCEDURE
SF6 release and measurement stope 20L20R ( Shrinkage stope)
SF6 release and measurement stope 20L24R ( Shrinkage stope)
Level 19
Level 20
SF6 monitoring point
SF6 Release point.
4 0 m
Raise 2 Raise 1 (No break through)
30 m
30 m
Broken ore25 m
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m70 m
15 m
3 m
4 m
1 m
1 m
Drives
Raises
NUMERICAL SIMULATION
dtE
tvX
tEA
QCtC
x
t
x
iii
4exp
2
)()(
2
02/1
1
Where:
Ci gas concentration at a downstream node
Ci-1 gas concentration at an upstream node
t elapsed time from gas injection
Qi air flow rate on an airway
τ time interval
A cross sectional area of an airway
Ex effective turbulent diffusion coefficient in flow direction
X distance between two nodes and
ν average gas convection velocity in an airway
(Sasaki & Dindiwe, 2002)
Ci
Ci-1Airflow
DownstreamUpstream
EFFECT OF DEAD SPACES & OPENING ON AIRLOW
Airways without dead spaces
Airways with dead spaces
Con
c.
Time
Con
c.
Time
Additional Route
Route 1
RESULTS
Level 20
SF6 release and measurement stope 20L20R ( Shrinkage stope)
Av. Velo.(m/s)
Level Raise 0.2-0.4 1-1.3
0.0
2.0
4.0
6.0
8.0
10.0
0 5 10 15 20 25 30 35Time (mins)
SF6
conc
. (pp
m)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces)Sum. total flow (Route 1, 2 & 3)
Level 19
Level 20
SF6 monitoring point
SF6 Release point.
4 0 m
Raise 2
Raise 1 (No break through)
30 m
30 m
Broken ore 25 m
31 m3/min
54 m3/min
6.3 m3/min
RESULTS
70 m 30 m
SF6 release and measurement stope 20L24R ( Shrinkage stope)
Av. Velo.(m/s)
Level Raise 0.2-0.4 1-1.3
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m70 m
15 m
0.0
2.0
4.0
6.0
8.0
0 5 10 15 20 25 30 35Time (min.)
SF6
conc
. (pp
m)
Measurement 40 sec. intervalSimulated, route 1Simulated ,route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces) Sum. total flow (Route 1, 2 & 3)
3.5 m3/min27 m3/min
40.5 m3/min
0.0
4.0
8.0
12.0
16.0
20.0
0 5 10 15Time (min)
SF6 c
onc.
(ppm
)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow(Route 1 & 2)Simulated, route 3(Open spaces)Sum. total flow(Route 1, 2 & 3)
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m30 m
15 m
RESULTS
Av. Velo.(m/s)
Level Raise 0.2-0.4 1-1.3
SF6 release and measurement stope 19L16R ( Shrinkage stope)
2.5 m3/min26 m3/min
34.5 m3/min
0.0
2.0
4.0
6.0
8.0
10.0
0 5 10 15 20 25 30 35Time (mins)
SF6
conc
. (pp
m)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces)Sum. total flow (Route 1, 2 & 3)
0.0
2.0
4.0
6.0
8.0
0 5 10 15 20 25 30 35Time (min.)
SF6
conc
. (pp
m)
Measurement 40 sec. intervalSimulated, route 1Simulated ,route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces) Sum. total flow (Route 1, 2 & 3)
0.0
4.0
8.0
12.0
16.0
20.0
0 5 10 15Time (min)
SF6 c
onc.
(ppm
)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow(Route 1 & 2)Simulated, route 3(Open spaces)Sum. total flow(Route 1, 2 & 3)
One Raise Open
Both Raise Open
Better air flow in the stope with one raised, then the stopes with both raises open.
RESULTS
DISCUSSION and CONCLUSION
Airflow rates of the stopes were evaluated with matching measured concentration-time curves with numerical ones by a numerical diffusion model in considering diffusion in open and empty spaces
Most importantly, an additional airway branch was constructed. The additional branch in the numerical model has a much longer airway length and an increased cross-sectional area with low air flow velocity. The new method has greatly improved the tailing effect .
Therefore it can be concluded that openings, dead end drives and other open spaces have no relation on flow rates, but affect the airflow quality provided from the inlet portal
Better understanding of airflow routes can be achieved by studying the arrival times and the peak of the concentration time curve for the various routes simulated.
END OF PRESENTATION!!!
THANK YOU VERY MUCH FOR YOUR
KIND ATTENTION!!!!!!!!!!
Raise 1 Raise 2
Level 20 drive
Plan view, level 20
Level 20 drive
Airflow route 3.
(Dead end drives, voids and open spaces)
Airflow route 1 Airflow route 2
Raise 1
Raise
1
Raise 2
Raise
2
A
B
Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3)
SF6 release and measurement stope 20L20R ( Shrinkage stope)
Additional airflow route to simulate for open spaces, dead end drive, voids etc..
RESULTS
Level 19
Level 20
SF6 monitoring point
SF6 Release point.
4 0 m
Raise 2
Raise 1 (No break through)
30 m
30 m
Broken ore
25 m
Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3)
Raise 1 Raise 2
Level 20 drive
Plan view, level 20
Level 20 drive
Airflow route 3.
(Dead end drives, voids and open spaces)
Airflow route 1 Airflow route 2
Raise 1
Raise
1
Raise 2
Raise
2
A
B
70 m 30 m
SF6 release and measurement stope 20L24R ( Shrinkage stope)
Additional airflow route to simulate for open spaces, dead end drive, voids etc..
RESULTS
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m70 m
15 m
Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3)
Raise 1 Raise 2
Level 20 drive
Plan view, level 20
Level 20 drive
Airflow route 3.
(Dead end drives, voids and open spaces)
Airflow route 1 Airflow route 2
Raise 1
Raise
1
Raise 2
Raise
2
A
B
70 m 30 m
SF6 release and measurement stope 19L16R ( Shrinkage stope)
Additional airflow route to simulate for open spaces, dead end drive, voids etc..
RESULTS
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 18
Level 19
Broken ore
30 m30 m
15 m
Measured MIVENAAirway Length X-Area Q Velocity Diff. Coef. Velocity Velocity
m m 2 m 3 /min m/s m 2 /s m/s m/s
Route 1 1 -> 2 30 12 200 0.28 0.75 0.32 0.332 -> 3 20 1 30 0.5 0.75 0.6 0.583 -> 4 27 1 30 0.5 0.75 0.45 0.54 -> 5 8 1 85 1.42 0.75 0.98 1.5
Route 2 1 -> 2 30 12 200 0.28 0.4 0.32 0.332 -> 6 30 12 170 0.24 0.4 0.3 0.326 -> 4 22 1 55 0.92 0.4 0.87 0.914 -> 5 8 1 85 1.42 0.4 1.2 1.24
Route 3 1 -> 2 30 12 200 0.28 0.4 x x2 -> 13 40 16 55 0.06 0.4 x x13 -> 4 22 1 55 0.92 0.4 x x4 -> 5 8 1 85 1.42 0.4 x x
Tracer Gas Simulation
Measured MIVENA
Airway Length X-Area Q Velocity Diff Coef. Velocity Velocity
m m 2 m 3 /min m/s m 2 /s m/s m/s
Rout 1 8 -> 9 80 14 170 0.2 0.6 0.26 0.18
9 -> 10 25 1.5 25 0.28 0.6 0.31 0.23
10 -> 11 30 1.5 15 0.17 0.6 0.2 0.21
11 -> 12 8 1.5 75 0.83 0.6 0.85 0.91
Route 2 8 -> 9 80 14 170 0.2 0.45 0.26 0.21
9 -> 13 30 14 145 0.17 0.45 0.21 0.19
13 -> 11 33 1.5 60 0.67 0.45 0.7 0.71
Route 3 8 -> 9 80 14 170 0.2 2 x x
9 -> 14 110 20 70 0.06 2 x x
14 -> 11 33 1.5 60 0.67 2 x x
11 -> 12 8 1.5 75 0.83 2 x x
Tracer Gas Simulation
Stope 20L24R
Stope 20L20R
Most importantly, improvement has been made at the tailing effect between the simulation and tracer gas measurement by reconstructing an additional branch to represent the delayed arrival of air due to the open spaces along the airways. The additional branch in the numerical model has a much longer airway length and an increased cross-sectional area with low air flow velocity. Therefore it can be concluded that openings, dead end drives and other open spaces have no relation on flow rates, but affect the airflow quality provided from the inlet portal.
0.0
2.0
4.0
6.0
8.0
10.0
0 5 10 15 20 25 30 35Time (mins)
SF6
conc
. (pp
m)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces)Sum. total flow (Route 1, 2 & 3)
Level 19
Level 20
SF6 monitoring point
SF6 Release point.
4 0 m
Raise 2
Raise 1 (No break through)
30 m
30 m
Broken ore 25 m
0.0
2.0
4.0
6.0
8.0
0 5 10 15 20 25 30 35Time (min.)
SF6
conc
. (pp
m)
Measurement 40 sec. intervalSimulated, route 1Simulated ,route 2Sum. total flow (Route 1 & 2)Simulated, route 3 (Open spaces) Sum. total flow (Route 1, 2 & 3)
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m70 m
15 m
0.0
4.0
8.0
12.0
16.0
20.0
0 5 10 15Time (min)
SF6 c
onc.
(ppm
)
Measurement, 40 sec. intervalSimulated, route 1Simulated, route 2Sum. total flow(Route 1 & 2)Simulated, route 3(Open spaces)Sum. total flow(Route 1, 2 & 3)
SF6 Releasepoint.
SF6 measurement point
Raise 1
30 m
Raise 2
Level 19
Level 20
Broken ore
30 m70 m
15 m
Dt
tux
DtA
Vtxc
4
)(exp
2),(
2
Where:
C(x,t) gas concentration at a downstream
V Volume of gas released
t elapsed time from gas injection
A cross sectional area of an airway
D Virtual diffusion coefficient in flow direction
X distance between two nodes and
u average uniform flow velocity of the airway
Taylor’s et al., 1953 & 1954
Best Matching & Tailing Effect
Airways without dead spaces
Airways with dead spaces
Con
c.
Time
MeasuredSimulated
Con
c.
Time
MeasuredSimulated
Tailing Effect
Simulated route 1
additional route
Additional Route
Route 1
Between Measured & Simulated
VENTILATION NETWORK
Construction of entire ventilation network using Mine ventilation simulator, MIVENA Ver.6 (Sasaki & Dindiwe, 2002)
Datadase window
Kainantu ventilation network (MIVENA)
Analysis windowKainantu ventilation layout
20L20R 20L24R19L16R
Normal
Leak