Important Questions of MINE PLANNING AND ECONOMICS

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

1. A) Why mine planning is important? What are the technical and economic in information formation required for mine planning. —   — 6 Marks Importance of mine planning: Mine planning helps h elps to reduce the following risks Mineral risk, Promoters and sponsors risk, Project completion risk, Capital cost and delay dela y risk, Operation risk, Market risk, Sovereign risk such as economic environment, political and regulatory environment and foreign currency risk Technical and economic information: Topography and contour, Climatic conditions, Surface, Water (potable and process), Mine Water as determined by prospect holes, Ore body bod y characteristics, Host rock characteristics, Ground water data, Locations for concentrator/ coal washery –  washery –  factors  factors to consider for optimum location, Tailing pond area, Roads, Power, Smelting (in case of metal mines), Land ownership, Government B) Explain the methodology with examples to calculate the coal reserve from ex exploratory ploratory bore holes. —   — 5 Marks

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

From the slice plan the areas and average thickness will be considered for calculating reserve= =Area*Average Thickness

C) What are the parameters effecting the pit design?-design? -- -3 Marks parameters rameters affecting the pit design:  design:  The following are the key pa   Topography opography,, Geology, Grade, Localization of the mineralization,   Extent of the deposit, Property boundaries,Production rates,  rates,     Road grades, Mining costs, Processing costs,  costs,     Metal recovery, Marketing considerations,   Bench height, Pit slopes, Cutoff grade, Strip Ratios (SR).  (SR).   4) What should be considered during designing d esigning of Haul road?--3 Marks 1. Minimum costs on a net present value valu e basis for the transport of mineral and waste throughout the life of the mine.  mine.   2. A minimum of traffic congestion and the maintenance of safe, ready access to the mining operations.  operations.  3. The avoidance of areas where slope stability problems could occur.  occur.  4. The use of long-life haul roads rather than short-life roads. This reduces haul road overall construction costs and operating costs as well as reducing the demand for haul road construction materials which may not be available in sufficient quantities from the overburden.   overburden.

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

D) What are the factors to be considered in designing a sampling campaign for mineral propert property y evaluation?--3 Factors to be considered in designing de signing a sampling campaign for mineral property evaluation  evaluation   Objectives of sampling-prospecting,  sampling-prospecting,  Population to be sampled  sampled  Data to be collected Choice of sampling unit to adequately adequatel y represent the population population   Organization of field data  data  Cost involved Type of minerals  minerals  Amount of money available  available  Accessibility of various parts of the mineral deposit  deposit  Avoid over precision to reduce cost  cost   2 a)  Calculate overall bench slope angle from the following information; Bench face angle=750; height of bench= 30m; width of safety bench= 25m; width of working  bench= 50m, no. of safety benches=3; no. of working benches=2 ------------------6 ------------------6 Marks

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

 b)  List various factors affecting the choice of cut-off grade for a mineral deposit.-----4 depos it.-----4 Marks Width of the ore body Reserve Mining methods Mining, processing, capital cost, Mechanization Type of ore

c)  Calculate NPV for given cash flow –  flow  – 10 10 marks Initial investment = Rs 100,000 Project life= 10 years Salvage value= Rs 20,000 Annual receipts= Rs 40,000 Annual disbursements= Rs 22,000 Minimum acceptable rate of return (discount rate)=12% 1.  Annual receipt=40,000(P/A, 12%, 10)=2,26,000 2.  Salvage value=20,000(P/A, 12%, 10) =6,440 Total inflow=2,32,440 1.  Annual disbursement=22,000(P/A, 12%, 10)=1,24,300 2.  Initial investment=100,000 Total cash out flow=2,24,430  NPV=2,32,440-2,24,430 =8140

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

3 a)  Find out the milling rate, mine production rate, mine life and overall stripping ratio from the information given below; Metal demand=5000 te/years; ore reserve=7.8 x 106 te; Tonnes to be mined= 30.8 x 10 6; Avg. grade=0.92%; mill recovery=80%; refinery recovery=97%; working days=250 per year -----8 Marks 1.  2.  3.  4. 

Stripping ratio= (30.8/7.8)=3.94 Production rate per year= 5000/(.92/100*80/100*97/100)=8,49,185te Mine life=(7.8*1000000)/8,49,185= 9.2years Milling rate=849185 te/year or 849185/250=3397te/day

(a)  Explain the following terms: (i)  Cash flow

(ii) Recovery and dilution ------4 Marks

Cash flow: This is the flow of cash from the project owners for the capital expenditure to get the project into operation (negative) and the flow of cash from the project to the owners own ers after all costs (which should be positive). Recovery and dilution: Dilution refers to the waste material that is not separated from the ore during the operation and is mined with ore. This waste material is mixed with ore and sent to the processing plant. Ore recovery can be defined by the percentage of minable reserves extracted in the mining process. The issue of balancing dilution and ore recovery is a challenging one as profitability is to be optimized while not effecting the efficiency of operation (b)  A company has 2 project proposals proposals (A & B). Initial costs are Rs. 10,00,000 and Rs. 6,00,000 respectively. The expected cash flows for 5 years of the two projects are given in the following table. Which project is more acceptable? Assume a discount rate of 9%. Year 1 2 3 4 5 Project A

4,00,000

4,00,000

4,40,000

4,80,000

4,40,000

Project B ------8 Marks

3,90,000

3,90,000

3,90,000

3,90,000

3,90,000

 NPA(A)=-1000000+[4/(1.09)+4/(1.09)^2+4.4/(1.09)^3+4.8/(1.09)^4+4.4/(1.09)^  NPA(A)=-1000000+[4/(1.09)+4/(1.09)^2+4.4/(1.09)^3+4.8/(1.09)^4+4.4/(1.09)^5]x100000 5]x100000 =-1000000+[3.67+3.37+3.40+3.40+2,86]x100000

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

=-10000000+1670000=670000/ NPV(B)=-600000+[3.9/(1.09)+3.9/(1.09)^2+3.9/(1.09)^3+3.9/(1.09)^4+3.9/(1.09)^5]x100000 =-600000+[3.58+3.28+3.01+2.76+2.54]x100000 =-600000+15.17x10000=9,17,000/Project B is more acceptable 4 A 1000m level is to be developed in rock by means of drill drill and blasts with burn cut pattern. pattern. The geometric dimensions and drilling data are as under drive width = 4.5m, height = 3m, relief hole diameter = 54mm, production hole diameter = 40mm, drill hole length= 3m, advancement = 90%, explosive used in the cartr cartridge idge form having diameter 3 of 32mm, density of explosive is 1gm/cm Assume other relevant information and calculate the followings for the full length excavation 1. Powder factor   — 6 Marks 2. Excavation duration — 6 Marks 3. Manpower --4 Marks 4. Machine---4 Marks

Answer required 1. Number of holes to be calculated 2. Charge per hole and total charge per round 3. Rock volume calculation 4. Cycle time to be calculated 5. Powder factor calculation 6. Drawing the firing sequence 7. Manpower calculation 8. Machine requirement

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

1 Estimation of number of holes

Cut holes burden values on the basis of given equations (8cm, 12cm, 25cm, 53cm)

Stoping and contour holes burden will of 20*d and spacing will be (1.1-1.25)*B (B=0.8m and S=0.9-1m) Explosive per hole=charge length*area of cartridge*density of explosive =200*3.14*32*32*1/400*1gm=1.6kg Total hole for charging=44 Total charge=44*1.6kg=71kg Volume of rock broken=4.5*3*3*90/100= 37m3

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

Powder factor=total explosive/rock volume broken=71/37=1.9kg/m3

Cycle time to be calculated for drilling @60m/hr by b y jumbo drill Length of drilling=45*3=135m Drilling time=2.5hrs Charging and stemming time, connection, firing and fume clearance time=2hrs Loading and transportation times (considering LHD of 1m3, 37m3 to be handled) and LPDT of 20m3 to be deployed=1hr Servicing timing=support, ventilation, surveying, pumping etc. =2 hr Total times=2.5+2+1+2 almost one shift of 8hrs Total duration= Advance per shift=3*0.9=2.7m Duration=1000/2.7=371 shifts=371/3=124 days

Machine =1 Jumbo+1LHD+1or 2 LPDT as main while grouting, auxiliary fan, pump etc for others (per shift)

Manpower= drilling -2, LHD-2, LPDT-2, supporting-2, fan-2, pump-2, blasting-3, supervisor-1 Total=16 per shift, 48 per day (Answer will depends on students assumptions so accordingly it will be checked and marks will be provided)

5 An underground coal mine is being planned for exploitation by Bord an and d Pillar mining system for production of 800 tonnes per day from a 3.0m thick coal seam occurring at a depth of 150m. Assume other relevant information and give Development layout--5 Marks Explosive per day — 5 Marks Manpower per day-5 Marks Machines requirement against the targeted production--5 Marks

Development layout: Incline/ shaft and levels with pillar size of 25m x 25m

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

Development by drilling and blasting A hand held coal drill d rill of 38 mm diameter is being used to drill blast holes of 6 feet length. The drilling pattern is wedge cut in a gallery galler y size of 3.6m x 2.1 2.1m. m. A total of 14 holes per round are drilled for the blasting of the development face. Cartridged permitted explosives (32mm in diameter, weighing 185gm)/P5 The mean depth of blast holes, in various rounds of solid blasts, in general, was 1.8m. The charge per round varied from 4.81 kg to 9.62 kg and the maximum charge per delay varied from 1.48 kg to 3.33 kg

 Number of faces to be blasted to get 800 te/day

 

Model Answer: MNC301-Mine planning and economics. Monsoon Semester-2021

Volume of coal from one face=3.6mx 3m x 1.8m=20m3=20*90/100=18*1.4=25te  Number of blast per day=800/25=32 Explosive per day Blast having hole=14 Charge per hole in degree one mine=1kg Explosive per blast=14kg

Powder factor=25/14te/kg=1.8te/kg Total explosive per day=800/1.8=445kg  Number of faces require per shift=32/3=11

Machine-coal drill-4crew, LHD-4crew, chain conveyor-4crew, belt conveyorconve yor- 2crew, supporting cerew-2, ventilation crew-2 etc Manpower= drilling-12, blasting-8, chain conveyor-8, belt conveyor-4, conve yor-4, supporting-4, ventilation4 Total manpower per shift=40 , per day-120+ others (Answer will depends on students assumptions so accordingly it will be checked and marks will be provided)