Gabriel ARPA, Kyuro SASAKI and Yuichi SUGAI Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka , 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 SF 6 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 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 4 th Outlet 4 th Outlet 4 th Outlet P (Pa) Q (m 3 /s) ３５ ２５ ２５ Schematic of ventilation system Main intake (1300 Portal) 4 th Outlet Fan 3Fan 2 Fan 1

Gas Monitor system Lap top Stop watch Portable scale Balloons Sulfur hexafluoride (SF 6 ) MEASUREMENT SYSTEM Photoacoustic gas monitor (Brual & Kjear 1302) Resolution = 10 ppb Absolute accuracy = +/- 50 ppb Sampling rate = 40 sec Raise Sampling Pulse release of SF 6 Monitor Lap top Lower level Upper level Ｎｏｔ ｔｏ ｓ ｃａｌｅ

MEASUREMENT PROCEDURE SF 6 release and measurement stope 20L20R ( Shrinkage stope) SF 6 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 Broken ore 25 m SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 70 m 15 m 3 m 4 m 1 m Drives Raises

NUMERICAL SIMULATION Where: C i gas concentration at a downstream node C i-1 gas concentration at an upstream node telapsed time from gas injection Q i air flow rate on an airway τ time interval A cross sectional area of an airway E x effective turbulent diffusion coefficient in flow direction X distance between two nodes and νaverage gas convection velocity in an airway (Sasaki & Dindiwe, 2002) CiCi C i-1 Airflow Downstream Upstream

EFFECT OF DEAD SPACES & OPENING ON AIRLOW Airways without dead spaces Airways with dead spaces Conc. Time Conc. Time Additional Route Route 1

RESULTS Level 20 SF 6 release and measurement stope 20L20R ( Shrinkage stope) Av. Velo.(m/s) LevelRaise Level 19 Level 20 SF6 monitoring point SF6 Release point. ４0m４0m Raise 2 Raise 1 (No break through) 30 m Broken ore 25 m 31 m 3 /min 54 m 3 /min 6.3 m 3 /min

RESULTS 70 m 30 m SF 6 release and measurement stope 20L24R ( Shrinkage stope) Av. Velo.(m/s) LevelRaise SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 70 m 15 m 3.5 m 3 /min 27 m 3 /min 40.5 m 3 /min

SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 15 m RESULTS Av. Velo.(m/s) LevelRaise SF 6 release and measurement stope 19L16R ( Shrinkage stope) 2.5 m 3 /min 26 m 3 /min 34.5 m 3 /min

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!!!!!!!!!!

Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3) SF 6 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. ４0m４0m Raise 2 Raise 1 (No break through) 30 m Broken ore 25 m

Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3) 70 m 30 m SF 6 release and measurement stope 20L24R ( Shrinkage stope) Additional airflow route to simulate for open spaces, dead end drive, voids etc.. RESULTS SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 70 m 15 m

Schematic of airflow. A) Plan of 20 level, B) Arrangement of additional branch (Route 3) 70 m 30 m SF 6 release and measurement stope 19L16R ( Shrinkage stope) Additional airflow route to simulate for open spaces, dead end drive, voids etc.. RESULTS SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 18 Level 19 Broken ore 30 m 15 m

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.

Level 19 Level 20 SF6 monitoring point SF6 Release point. ４0m４0m Raise 2 Raise 1 (No break through) 30 m Broken ore 25 m

SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 70 m 15 m

SF 6 Release point. SF 6 measurement point Raise 1 30 m Raise 2 Level 19 Level 20 Broken ore 30 m 70 m 15 m

Where: C(x,t)gas concentration at a downstream VVolume of gas released telapsed time from gas injection A cross sectional area of an airway D Virtual diffusion coefficient in flow direction X distance between two nodes and uaverage uniform flow velocity of the airway Taylor’s et al., 1953 & 1954

Best Matching & Tailing Effect Airways without dead spaces Airways with dead spaces Conc. Time Measured Simulated Conc. Time Measured Simulated 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 window Kainantu ventilation layout 20L20R20L24R 19L16R

Ｎｏｒ ｍａｌ Ｌｅａ ｋ