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

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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

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