Minimizing Quarrying Costs by Correct Shotrock Fragmentation And

Minimizing Minimizin g Quarryi Quarrying ng Costs by Corre Correct ct Shotrock Fragmentation and In-pit Crushing

Oct. 2006, Rev A Jarmo Eloranta

Contents • Quarry process in general Comparison of different different shotrock shotrock fragmentat fragmentations ions • Comparison

• Comparison of different crushing methods • Conclusions • Enclosures

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Contents • Quarry process in general Comparison of different different shotrock shotrock fragmentat fragmentations ions • Comparison

• Comparison of different crushing methods • Conclusions • Enclosures

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Challenge in Quarry Development

‘real’ optimum

Source: Technical University Trondheim, Norway

$/to n What about the hauling distance?

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Distance

Quarry Process Stationary Crushers

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Quarry Process Mobile Crusher(s)

Mobile primary crushing

All crushers mobile

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Example of Quarry Cost distribution

Crushing & Screening Drilling

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Blasting Loading Hauling

Approach Based on Two Phases • Comparison of different shotrock fragmentations, including:

- drilling and blasting - boulder handling - loading - hauling - crushing (traditional stationary) • Comparison of different crushing methods, including:

- stationary - inpit, semimobile - inpit, fully mobile 7

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Optimum drilling and blasting Cost Effective Quarry Practise

Optimum crushing

Comparison of Different Shotrock Fragmentations

Comparison of different shotrock fragmentations

Starting Point: Stationary Three-stage Plant with a Capacity of 1600t/h. Final Product 0-20mm MAIN DATA

Drillig: Nr.of units Drilling pattern (m2) Blasting: Specific charge (kg/m3) K50 (mm), L Number of operators Loading by excavators Bucket size (m3) Nr.of units Hauling by trucks: Pay-load (t) Distance (km) Nr.of units Crushing: Primary crusher type Nr.of primary units Nr.of sec.&tertary units General Drillability & blastability Work index (kWh/t) Drill hole dia (mm) Bench height (m) Explosive Interest rate (%) / Quarry life (y) Fuel price ($/liter) / Energy ($/kWh) Wages ($/hour)

Case 1

Case 2

Case 3

Case 4

Case 5

3 9

4 6,4

5 5,8

6 4,5

8 3,3

0,53 410

0,76 290

0,9 250 18-22

1,15 200

1,56 150

12 2-7 depending on blast configuration (or bigger buckets) 50 2 8-10 depending on blast configuration Nordberg C160 jaw 2 5 45 / 0,7 15 89 10 Anfo 10 / 20 0,5 / 0,1 17

All together more than 50 different cases were analysed 9

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General Selection of Drilling Method

) i s p ( S C U , h t g n e r t S e v i s s e r p m o C

Top Hammer

Down-the-Hole

(Pneumatic & Hydraulic)

(Pneumatic)

50,000 100,000 40,000 80,000 30,000 60,000 20,000 40,000 10,000

Rotary

(Drag bits)

(Roller bits)

2

3

Source: Metso Minerals & Tamrock studies

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20,000

Rotary

1

10

120,000

4

5

6

7

8

9

10 11

12 13

14 15

Drillhole Diameter (‘’)

) b l ( t h g i e W n w o d l l u P y r a t o R


Impact of drillhole diameter to drilling and blasting costs

Impact of drillhole diameter to drilling and blasting costs K50 = 250, drillability = medium, blastability = good

] t / D S U [ s t s o c l a t o T

1,50 1,40 1,30 1,20 1,10 1,00 0,90 0,80 0,70 0,60 0,50 0,40 0,30 0,20 0,10 0,00

0,50

0,30 0,20 0,10 0,00 64

89 Drillhole diameter [mm]


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Blasting

0,40

115

] t / D S U [ s t s o C

Drilling Drilling Blasting


Impact of Drillhole Diameter

Boulder count

) n o t / D S U ( t s a l B & l l i r D

Blasting


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Fragment elongation ratio % Fines in shotrock Micro-crack damage of fragments

Drilling

Hole Diameter (mm )

Fines in feed

n o t r e p y t i t n a u Q

Hole Diameter (mm )

Cost1.pre/A. Lislerud


Boulder Handling Sort boulders from muck pile Downsize the boulders Minimize boulder count using tighter drill patterns or reduced uncharged height

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Example of Direct Costs Caused by Boulders. Customer case, breakage before loading

Hammering Costs ($/tonnes) h60 / s r 50 e d l u40 o b f 30 o r e 20 b m u10 n

0 0

0,05

0,1

0,15 $/tonnes

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0,2

0,25

0,3


Key Issue • Removal of bolder breakage outside process

• -> improved plant utilization

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Impact of Blast Distribution on Loading Costs

K50 definition

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Loading Operations; Examples

Typical toe problem requiring auxiliary hyd. excavator work and/or use of secondary blasting

Auxiliary machines required for quarry floor cleanup after blasting for loaders with poor mobility Source: Metso Minerals & Tamrock studies

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Tight muckpile (poor diggability) due to insufficient heave and throw


Optimum Shotrock Profiles for Loading Operations

Hmax

Front Shovels

Wheel Loaders

High productivity Minimal cleanup area Safe for operator

Low productivity Muckpile too tight Muckpile too high Dangerous for

operator

Hmax dependent on loader size and type for optimum loading capacity conditions

Hmax

New floor

Shotrock throw onto old (poor loadability) floor


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Front Shovels Loaders

Wheel

Moderate productivity productivity Large cleanup area loose Safe for operator operator

High Muckpile is Safe for


And Feeding by Excavator

Cat recommendations

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Impact of Blast Distribution on Hauling Costs with Dumbers

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Why Coarser Blast Distribution Impacts on Loading and Hauling Costs? • Material is more difficult to load due to:

- more likely toe problems - bigger boulders • Scope of equipment changes due to more difficult and/or longer cycle times

• With respect to the equipment there is

- more wear - more maintenance

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Results K50 is 50% point of fraction distribution

Total costs / produced ton 4 ] n o t d e c u d o r p / D S U [ s t s o C

Case

3

Hauling Loading Hammering Crushing Blasting Drilling

2

1 0

Case 1 Case 2 Case 3 Case 4 Case 5

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K50 (mm)

Case 1

410

Case 2

290

Case 3

250

Case 4

200

Case 5

150


Conclusions of Shotrock Fragmentation

• From the total product cost point of view, there is an optimum shotrock fragmentation. In the case study, the optimum was k 50 ~ 250 mm.

• The crushing cost share is almost unchanged with different K 50 values because the blast impacts only on primary crushing

• Even smaller drillhole diameters than used here (89mm) can be economical, because: - Smaller drillhole diameters produce fewer fines. In many cases this is considered waste - There are fewer boulders to be handled

- There are fewer micro cracks in the blasted rock, due to more ‘gentle blasting’. In many cases, this generates better final aggregate quality

• Boulder management is important

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Comparison of Different Crushing Methods

Comparison of different crushing methods

Starting Points for Crushing Method Comparisons

• k50=250mm is being used as shotrock fragmentation • The following quarrying methods are under comparison:

- stationary: -

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• Material is transported by dump trucks into crushing plants inpit, semimobile • material is transported by dump trucks into the semimobile primary jaw crusher, and from there by conveyors to the secondary & tertiary crushing plants inpit, fully mobile • primary crushing done at a quarry face with a highly mobile track mounted jaw crusher, and taken from there by conveyors into the secondary and tertiary crushing plants. No dump trucks are used.


Stationary Crushers Primary crusher cannot normally be moved

Typical distance 2km

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Semimobile Inpit Crushing Primary crusher can be moved but only on a non-frequent basis.

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In-pit Fully Mobile Crushing Primary crusher is track mounted, compact and movable within 5-10 minutes.

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In-pit Fully Mobile Crushing Movable and steerable Lokolink conveyor system is a key component

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Truck Transport Versus Conveyor Belt

2,50

Horizontal Hauling USD/t Belt; Cost per ton

2,00 Truck; Cost per ton 1,50

t / D S U

1,00

0,50

0,00 0,5 1,0 2,0 3,0 4,0 5,0 0,5 1,0 2,0 3,0 4,0 5,0 0,5 1,0 2,0 3,0 4,0 5,0 0,5 1,0 2,0 3,0 4,0 5,0 0,5 0,5 0,5 0,5 0,5 0,5 1 1 1 1 1 1 5 5 5 5 5 5 10 10 10 10 10 10 L (km) & Capacity (million t/y)

Cost comparison between conveyor belt transport and dump truck haulage hauling distance and annual capacity.

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Truck Transport Versus Conveyor Belt Vertical Hauling USD/t

s : 1 t o 8) 1,40 1,20

Belt; Cost per ton

1,00

Truck; Cost per ton

t 0,80 / D S U 0,60

0,40 0,20 0,00 50 0,5

100 0,5

150 0,5

200 0,5

50 1

100 1

150 1

200 1

50 5

100 5

150 5

200 5

50 10

100 10

150 10

200 10

H (m) & Capacity (million t/y)

Cost comparison between conveyor belt transport and dump truck haulage as a function of vertical hauling distance and annual capacity given a haulage length to height ratio of 8 : 1.

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Starting Point: Three Different Plant Configurations with a Capacity of 1600t/h. Final Product 0-20mm

Primary crusher type Size Number of units Loaders, excavators: Bucket size (m3) Number of units Dump trucks: Size (t) Number of units Haulage distance (km) Conveyor length (km) Number of operators Secondary & tertiary crushers and screens *) Other variables *) = K10 in Hong-Kong

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Stationary plant

Semimobile primary plant

Fully mobile in-pit primary plant

Fixed Jaw C160 2

Semimobile Jaw C140 2

Track mounted Jaw C125 2

12 2

5,5 3

5,5 2

50 8 2 20

35 7 1 1 20 Secondaries: 2 * Nordberg OC 1560 Tertiaries: 3 * Nordberg HP500 Seven Screens: 10-20m2 As in previous drilling & blasting example

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Results Total costs / produced ton K50 = 250mm, Feed rate 1600t/h ] n o t

d e c u d o r p / D S U [ s t s o C

3,5 3 Hauling Loading Hammering Crushing Blasting Drilling

2,5 2 1,5 1 0,5 0

Stationary

Semimobile

Fully mobile

Difference between stationary and fully mobile is about 25%.

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Another Example Total costs / produced ton Spreadsheet lines 141 - 146

Costs [USD/produced ton] 0

0,5

1

1,5

2

2,5

3

3,5

Case 6a: K50=410 Case 7a: K50=290

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y r a m i r r e p h y r s a u r n c o i t a t S

Case 8a: K50=250 Case 10a: K50=200

y r a r m e i r h p s e u l i r c b o M

Case 11a: K50=150 Case 16a: K50=410 Case 17a: K50=290 Case 18a: K50=250 Case 19a: K50=200

Case 20a: K50=150

Drilling Total 2

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Blasting

Crushing

Hammering

Loading

Hauling

Tools Available 1) Process Integration and Optimization (PIO) Services This is not a case of … • Increasing the powder factor to increase plant throughput

•

Opt(blast) +…+ Opt(crush)

Max($$$)

2) Calculation & simulation tools

Total Cost vs. work category Utilities

2,00

Crushing

n o 1,00 t / $

Haulage

0,00

It is… The development of a quarrying and processing strategy which minimizes the overall cost per tonne treated and maximizes company profit. Opt(blast +…+

crush&screen) = Max($$$) 35

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DT-system

LT-system

Total Cost vs. cost category 1,50

Capital

1,00

Mainten an Energy

n o t 0,50 / $

0,00 DT-system

LT-system

Work continues …

Conclusions for Quarry Development • From the total product cost point of view, there is an optimum shotrock fragmentation.

• Oversize boulder frequency has a significant impact on capacity and cost.

• A smaller drillhole diameter produces fewer

fines. In many cases, this is considered waste.

• The crushing cost share is almost unchanged

with different K50 values when the crushing method is the same. The optimum selection is dependent on: - Rock type due to abrasion - ‘Case-specific factors’ like the life of the quarry, investment possibilities etc.

• Whole quarry process optimization instead of the suboptimization of individual components

• Inpit crushing can generate remarkable benefits 36

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Enclosures • Operational targets for a typical aggregate producer • K50 feed sizes • Example: Norwegian case

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Operational Targets for a Typical Aggregate Producer

USD / tonne

Product price curve v e r s u s product quality Product cost curve

Opt.

Shotrock fragmentation

Return 38

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K50 Feed Sizes

% 100

K410 80

K290

K250 K200

60

K150 40

20

0

Return

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Example: Norwegian Case

shotrock

Rock type

Anorthosite

Explosive

Slurrit 50-10

Blast size tonnes

~50 000

40

0 - 300 mm weigh t

32 - 70 mm

25 70 weigh t

0 - 32 mm


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m m 2 35 3 0 f o 30 e g a t n e 20 c r e P

Ø114 Ø102 Ø89

Large SUB’ from prior bench level

Ø76

80

90

100

110

120

Hole diameter (mm)

Return

Basic Selection of Loading Equipment

Source: Cat presentations

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Minimizing Quarrying Costs by Correct Shotrock Fragmentation And

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