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1 Use of Gas Mixing Equations and Simulation Approaches in Design of Mine Inertisation Systems HW Wu and ADS Gillies 13th United States/North American.

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Presentation on theme: "1 Use of Gas Mixing Equations and Simulation Approaches in Design of Mine Inertisation Systems HW Wu and ADS Gillies 13th United States/North American."— Presentation transcript:

1 1 Use of Gas Mixing Equations and Simulation Approaches in Design of Mine Inertisation Systems HW Wu and ADS Gillies 13th United States/North American Mine Ventilation Symposium, June 2010

2 2 Objective of the study To examine gas mixing and dilution approaches to give a better understanding of how acceptable levels of mine atmosphere contaminants can be evaluated. To examine gas mixing and dilution approaches to give a better understanding of how acceptable levels of mine atmosphere contaminants can be evaluated. As an example the interaction between gases from inertisation systems and the underground mine atmosphere can be evaluated to assist in design of the mine inertisation system. As an example the interaction between gases from inertisation systems and the underground mine atmosphere can be evaluated to assist in design of the mine inertisation system. Inertisation approaches include use of engine exhausts, nitrogen, carbon dioxide, and diesel fired boiler units. Inertisation approaches include use of engine exhausts, nitrogen, carbon dioxide, and diesel fired boiler units.

3 3 Introduction New approaches allowing improvement in understanding use of inertisation techniques have been examined. New approaches allowing improvement in understanding use of inertisation techniques have been examined. Case studies used to examine available calculation or computer simulation approaches for predicting induced inertisation gas interaction with the mine ventilation system. Case studies used to examine available calculation or computer simulation approaches for predicting induced inertisation gas interaction with the mine ventilation system. Comparisons are made of the use of different approaches to estimate the time required to inert a sealed underground atmosphere situation. Comparisons are made of the use of different approaches to estimate the time required to inert a sealed underground atmosphere situation.

4 4 Approaches Adopted Two direct calculation approaches are Two direct calculation approaches are the application of commonly accepted rules of thumb for fluid dilution or flushing of a mined space with a minimum diluting gas requirement of for instance of three times the void volume, and the application of commonly accepted rules of thumb for fluid dilution or flushing of a mined space with a minimum diluting gas requirement of for instance of three times the void volume, and the direct utilization of gas mixing and dilution equations (Hartman, et al 1997). the direct utilization of gas mixing and dilution equations (Hartman, et al 1997). The use of advanced fire simulation network software, Ventgraph. The use of advanced fire simulation network software, Ventgraph.

5 5 Inertisation System - GAG-3A jet engine exhaust unit (Gorniczy Agregat Gasniczy)

6 6 Inertisation System - Liquefied nitrogen

7

8 Inertisation System - Tomlinson Boiler

9 Inertisation System - Membrane Floxal units

10 GAG Docking Point

11 11 Case Study I: Nitrogen inertisation To provide an estimation of the time required to inert a single entry development in an underground coal mines using a membrane nitrogen gas unit. To provide an estimation of the time required to inert a single entry development in an underground coal mines using a membrane nitrogen gas unit. Parameters of the single entry roadway are: Parameters of the single entry roadway are: Total length of sealed zone 280m with brattice sail partition, Total length of sealed zone 280m with brattice sail partition, Dimension of the single entry roadway 2.6m by 5.3m., and Dimension of the single entry roadway 2.6m by 5.3m., and Gas make CH 4 is 14 m 3 /hour; CO 2 is 7.2 m 3 /hour. Gas make CH 4 is 14 m 3 /hour; CO 2 is 7.2 m 3 /hour. Parameters of the inertisation system proposed Parameters of the inertisation system proposed A nitrogen gas inert unit with inert line into the sealed zone and an inert capacity of 1,100 m 3 /hour or m 3 /s. A nitrogen gas inert unit with inert line into the sealed zone and an inert capacity of 1,100 m 3 /hour or m 3 /s. Inert gas output oxygen level of 0.01 percent. Inert gas output oxygen level of 0.01 percent.

12 12 Layout of the seal and inertisation arrangements

13 13 Dilution or flushing rule of thumb Time determined from inert gas flow rate and mined void volume WhereY is volume of working space in m 3, is time in seconds, is time in seconds, Q is inertisation unit output, m 3 /s C is a constant set at for instance 3. C is a constant set at for instance 3.

14 14 Gas mixing and dilution Equation WhereY, Q and are as defined previously Q g is the gas inflow, m 3 /s x is conc. of contaminant in the mixture, x 0 is conc. of contaminant in the space initially, B is conc. of contaminant in normal intake air

15 15 Times required with various constant values used – Rule of Thumb Constant Values Used Time Required for the Inert system to achieve (hours)

16 16 Times required to achieve various oxygen levels - Gas Equation Resulting oxygen Level in the Sealed area (%) Time Required for the Inert system to achieve (hours)

17 17 Correlation between constant vales, C and the resulting oxygen levels for dilution or flushing rule of thumb

18 18 Times required to achieve various oxygen levels – Rule of Thumb Constant Values Used Time Required for the Inert system to achieve (hours) Resulting oxygen Level (%)

19 19 Snapshot from Ventgraph simulation after 10.2 hours with oxygen level at about 1.1% percent

20 20 Predicted Gas Concentration in the Purge Pipe over time from Ventgraph simulation outputs

21 21 Case Study I Summary Based on the simple gas dilution or flushing rule of thumb with three times volume, it will take the membrane nitrogen inerting system about 10.5 hours to inert (O 2 ~1.1%) the sealed area. Based on the simple gas dilution or flushing rule of thumb with three times volume, it will take the membrane nitrogen inerting system about 10.5 hours to inert (O 2 ~1.1%) the sealed area. When applying the gas mixing and dilution equation, it would take the membrane nitrogen inertisation system about 10.7 hours to achieve an oxygen level of 1.0 percent. When applying the gas mixing and dilution equation, it would take the membrane nitrogen inertisation system about 10.7 hours to achieve an oxygen level of 1.0 percent. From Ventgraph simulation it will take 10.2 hours for the membrane nitrogen inerting system to reduce the oxygen level in the sealed area down to 1.1 percent with the assumptions of leakages (every 50m) from the wide side of the heading to the narrow side behind the brattice. From Ventgraph simulation it will take 10.2 hours for the membrane nitrogen inerting system to reduce the oxygen level in the sealed area down to 1.1 percent with the assumptions of leakages (every 50m) from the wide side of the heading to the narrow side behind the brattice.

22 22 Case Study II: Diesel Fired Boiler to provide an estimation of the time required to inert a sealed coal Mains development in case of emergency using a diesel fired boiler inertisation unit. to provide an estimation of the time required to inert a sealed coal Mains development in case of emergency using a diesel fired boiler inertisation unit. Parameters of the sealed Mains roadways are: Parameters of the sealed Mains roadways are: 66 roadways with a total length of 2,273m. 66 roadways with a total length of 2,273m. Dimension of the roadway 2.7m by 5.0m. Dimension of the roadway 2.7m by 5.0m. Parameters of the inertisation system proposed Parameters of the inertisation system proposed Three inertisation boreholes, one 0.76m and two 0.56m in diameter are located at 4 ct between B and C Headings. Three inertisation boreholes, one 0.76m and two 0.56m in diameter are located at 4 ct between B and C Headings. The boreholes are 54 m in length with a surface steel manifold structure to connect the boreholes to the inertisation unit. The boreholes are 54 m in length with a surface steel manifold structure to connect the boreholes to the inertisation unit.

23 23 Layout of the Mains development area and inert boreholes arrangements

24 24 Times required to achieve various oxygen levels – Rule of Thumb Constant Values Used Time Required for the Inert system to achieve (hours) Resulting oxygen Level (%)

25 25 Times required to achieve various oxygen levels - Gas Equation Resulting oxygen Level in the Sealed area (% ) Time Required for the Inert system to achieve (hours)

26 26 Snapshots from Ventgraph simulation after 50.5 hours with oxygen level at about 3.0 percent with Portal seals, R=1,000 Ns 2 /m 8

27 27 Predicted oxygen levels over time from Ventgraph outputs (Portal seals, R=1,000 Ns 2 /m 8 )

28 28 Times required to achieve various oxygen levels – Ventgraph Resulting oxygen level (%) Time required to achieve inert level in hours for varying seal resistances R=100 Ns 2 /m 8 R=1,000 Ns 2 /m 8 R=10,000 Ns 2 /m

29 29 Case Study II Summary Based on the simple gas dilution or flushing rule of thumb with three times volume, it will take the diesel boiler inerting system about 50.1 hours to fully inert the sealed Mains area. Based on the simple gas dilution or flushing rule of thumb with three times volume, it will take the diesel boiler inerting system about 50.1 hours to fully inert the sealed Mains area. When applying the gas mixing and dilution equation, it would take the diesel boiler inertisation system about 49.0 hours to achieve an oxygen level of 3.0 percent. When applying the gas mixing and dilution equation, it would take the diesel boiler inertisation system about 49.0 hours to achieve an oxygen level of 3.0 percent. From Ventgraph simulation it will take between 42.6 to 53.5 hours for the diesel boiler inerting system to reduce the oxygen level in the sealed Mains area down to 3.0 percent with assumptions of resistance values for the portal seals ranging from 100 to 10,000 Ns 2 /m 8. From Ventgraph simulation it will take between 42.6 to 53.5 hours for the diesel boiler inerting system to reduce the oxygen level in the sealed Mains area down to 3.0 percent with assumptions of resistance values for the portal seals ranging from 100 to 10,000 Ns 2 /m 8.

30 30 Conclusions Case studies have been developed to examine usage of induced inertisation tools available to the Australian coal mining industry. Case studies have been developed to examine usage of induced inertisation tools available to the Australian coal mining industry. Comparisons made of estimations of the time required to inert include Comparisons made of estimations of the time required to inert include the application of commonly accepted rules of thumb for fluid dilution or flushing with minimum three times quantity of inert gas requirements, the application of commonly accepted rules of thumb for fluid dilution or flushing with minimum three times quantity of inert gas requirements, the utilization of gas mixing and dilution equations, and the utilization of gas mixing and dilution equations, and the use of advanced fire simulation network software for and modelling of the mine ventilation system. the use of advanced fire simulation network software for and modelling of the mine ventilation system.

31 31 Conclusions These approaches all give reasonable estimation of the times required to inert a sealed area. These approaches all give reasonable estimation of the times required to inert a sealed area. However use of rule of thumb or the gas equation calculations does not taken into consideration leakages in mine ventilation systems and assumes prefect gas mixing. However use of rule of thumb or the gas equation calculations does not taken into consideration leakages in mine ventilation systems and assumes prefect gas mixing. Use of the Ventgraph fire simulation program is able to take these into account but needs careful modelling to reflect the behavior of the mine ventilation network under consideration. Use of the Ventgraph fire simulation program is able to take these into account but needs careful modelling to reflect the behavior of the mine ventilation network under consideration. The direct calculations are simpler and more approximate but do not require the effort to set up the more complicated fire simulation model. The direct calculations are simpler and more approximate but do not require the effort to set up the more complicated fire simulation model. Cont.


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