Problem 3: (20 Points) A tabular orebody is to be mined with a room and piilar method. The management requested the ventilation engineer of the mine to calculate the optimal number of intake and return airways, using the PV concept and with the following available information: K (for intakes) = 55 x 10-40 |b-min/ft (9.174 x 10-2 kg/m) K (for returns) = 75 x 10-40|b-min-/ft (9.174 x 10-2 kg/m) Life 18 years Interest on capital 11% Ore density 141 lb/ft? (2,255 kg/m?) Taxes, insurance, maintenance 3% L 5,000 ft (1,524 m) Le 0 Power cost $0.055/kWh Overall efficiency of mine fan, no = 70% Q = 500,000 cfm (326 m/s) Distance between x-cuts = 40 ft (12 m) Distance between entries = 40 ft (12 m) = = = = Cost differential Operation $2.50/ton ($2.75/t) = 24 hrs/day, 365 days/yr Due to stress conditions at the mine, the openings (airways) should be driven in an ovaloid shape, as shown. DE (3 201 (6 + 20" 16 Airway layout Cost of taxes, insurance and maintenance is shared between production and development of the mine, thus ignored for ventilation calculation. 1. Determine the cost recovery factor of the first and second entries 2 point 2. Determine the PV of fix cost for 10 entries 4.5 points 3. Determine the power cost hp-yr 1 point 4. Determine the area and perimeter 2 point 5. Determine head lost for 1 entry 1 point 6. Determine input power for 1 entry 1 point 7. Determine the PV factor 1 point 8. Determine the operating cost and PV cost for 10 entries 5.5 points 9. Provide the graphical costs for all intake entries 2 point