Dynamic Simulation ofSize Reduction Operations from

Mine-to-Mill

byJ.A. Herbst and W.T. Pate

J.A. H

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Outline

✦ Introduction✦ A General Flowsheet

Simulator✦ Comminution Objects✦ Simulation Case Study✦ Future Capabilities✦ Conclusions

Kona

HawaiiMauiMolokai

Oahu

Kauai

Honolulu

Tahiti

California Mexico

Hilo

J.A. Herbst & Associates

Australia

The Cost of ComminutionWorldwide

Energy Consumed Worldwide≅≅≅≅ 2.6 x 1010 US$/year

Wear Parts Consumed Worldwide= 5 billion US$/year

100%100%

00Product Size

Ener

gy E

ffici

ency

50%50%

Typical Breakdown ofComminution Costs

Explosive Fracturing 1%

Coarse Crushing 2%

Fine Crushing 20%

Grinding 77%

Mine-to-Mill Simulation

Real World Model Object FlowsheetSimulator

Benefits ofObject Oriented Programming

A software object contains code and data which simulate thepertinent characteristics of a physical device or stream

PROGRAM MAINCALL MINE ( )CALL TRUCK ( )CALL CRUSH(FEED,CRUSHPROD)CALL STORAGE ( ) CALL SCREEN(FEED,SCREENPROD)CALL MILL(FEED,MILLPROD)SUBROUTINE MINE ( )SUBROUTINE TRUCK ( )SUBROUTINE MILL(FEED,MILLPROD)SUBROUTINE STORAGE ( )SUBROUTINE CRUSH(FEED,CRUSHPROD)SUBROUTINE SCREEN(FEED,SCREENPROD)

Object Oriented Traditional

When process objects are connected by streams they are linked for computation

Conceptual Design of MinOOcad

ProcessObject

ObjectProperties

ObjectDisplay

StreamObject

StreamObject

( )ttO ∆+2

( )ttO ∆+1

( )tI

Object Menu

ContainerStream

Object #1

StreamObject #M

ProcessObject #2

ProcessObject #N

ProcessObject #1

ProcessObject #3

Implementation ofMinOOcad

Models of Flowsheet Elements

SLOW

FAST

INTERMEDIATE

0 1 10

Response

t/ττττ Longest Dwell Time

Coarse OreStorage

Dynamic/Multi-Components

Accumulation = Input - Output+ Generation

ScreenStream

ε

P80

T

P

( )dt MOut,ij f Mij= - + ’sdMi,j MIn,i,j

• •

Particle Size Decreasing

ABAB

BB

AA

Comminution Objects- The Ball Mill

Feature 1Visualization

Feature 2Dynamic

PerformanceControl

Feature 3Scale-up/Design

Feature 4Capital/

Operating Cost

$$

ManagerComputationProcedures

Input and Output User Interface

KnowledgeBase

Ball Mill Object

Comminution Objects

MineTruckStorageCrushersConveyorsScreensBall Mill - Pebble MillSAG - AG MillsSumpsHydrocyclones

Simulation Case Study

MinePrimaryCrusher

PrimaryMills

SecondaryMills

BallMill

Coarse OreStorage

SAGMILL

SAGMILL

MinOOcad Flowsheet

Tool Bar and Property Page

Property Pages

Zoom on Property Page

Outputs

Date Time, hr Feedrate Feed waterJetwater Mill rpm6/14/98 18:00 0.00000 2037.9 673.3 75.0 10.016/14/98 18:02 0.03333 2010.7 672.4 75.0 10.016/14/98 18:04 0.06667 2021.5 673.0 74.9 10.016/14/98 18:06 0.10000 2051.2 673.6 74.9 10.016/14/98 18:08 0.13333 2080.9 677.6 74.9 10.016/14/98 18:10 0.16667 2059.8 690.0 74.9 10.016/14/98 18:12 0.20000 2076.0 687.8 74.9 10.016/14/98 18:14 0.23333 2096.1 682.5 74.8 10.016/14/98 18:16 0.26667 2116.2 678.1 74.8 10.016/14/98 18:18 0.30000 2112.2 679.5 74.8 10.016/14/98 18:20 0.33333 2099.1 675.8 74.8 10.016/14/98 18:22 0.36667 2095.3 675.5 74.8 10.016/14/98 18:24 0.40000 2093.0 665.2 74.7 10.016/14/98 18:26 0.43333 2090.6 665.4 74.7 10.016/14/98 18:28 0.46667 1507.2 666.8 74.7 10.016/14/98 18:30 0.50000 1663.9 684.5 74.7 10.01

Spreadsheet Graphic

Base Case - At Steady State

SAG Mill %L=12

Ball Mill %L=70

0.01

0.10

1.00

10 100 1000 10000 100000 1000000

Particle Size, microns

Frac

tion

Pass

ing Mine

% L =0

Gyratory% L=0

PredictedOperating Data

Dynamic SituationsSimulated

✦ Increase in Powder Factor at Mine

✦ Increase in Truck Haul Time

✦ Decrease in Stockpile Inventory

Increase in Powder Factor

10000

100000

1000000

0 2 4 6 8 10 12

Time, hr

Min

e, C

rush

er a

nd S

tock

pile

P80

, m

icro

ns

10

100

1000

SA

G a

nd B

all M

ill P

80,

mic

rons

SAG Mill

Ball M ill

M ine

Stockpile

Crusher

Powder factor increased by 150%

SAG Mill

Ball Mill

Mine

Stockpile

Crusher

Increase in Truck Haul Time

0

200

400

600

800

1000

0 2 4 6 8 10 12 14

Time, hr

Tonn

age,

tph

0

10

20

30

40

50

60

70

80

Mag

netit

e Li

bera

tion,

%H

aul T

ime,

min

.

Truck haul time increased by 25%

Truck tonnage

SAG mill tonnage

Ball mill magnetite liberation

Stockpile tonnage

Truck haul time

SAG Mill Tonnage

Ball Mill Magnetite Liberation

Stockpile Tonnage

Truck Haul Time

Truck Haul Time Increased by 25%

Decrease in Stockpile Inventory

10

100

1000

10000

100000

1000000

2 4 6 8

Time, hr

P80

, m

icro

ns

100

200

300

400

500

Tonn

age,

mtp

h

M ine P80

Crusher P80

SAG mill tph

Stockpile tph

Ball mill P80

SAG mill P80

Ball Mill P80

SAG Mill P80

Stockpile tphSAG Mill

tph

Mine P80Crusher P80

Downstream Impacts

0

200

400

600

800

1000

2 4 6 8

Time, hr

Hol

dup,

t o

r To

nang

e, tp

h

0

1000

2000

3000

4000

5000

Pow

er, k

w

S tockpile tonnage

SAG mill power

SAG mill rock tons

SAG mill tonnage

Begin stockpile inventory change

50

75

100

125

150

175

2 4 6 8Time, hr

P80

, m

icro

ns

22

24

26

28

30

32

% o

f Mag

netit

e Li

bera

ted

Begin change in stockpileinventory

Ball mill P80

Ball mill magnetite liberated

Future Possibilities✦ Operating costs calculated on a minute-to-minute

basis over the entire flowsheet✦ Enterprise-wide control system capability integrated

into simulator✦ Incorporating the impact of maintenance using

realistic wear and replacement models✦ Embedding into control system software for on-line

decision making

Conclusions✦ Comminution comprises the most energy intensive and

costly set of unit operations at a mine/mill site.✦ Opportunities exist to improve "enterprise-wide financial

performance" through understanding and exploitingdynamic/steady state interactions between comminutionoperations.

✦ A Windows based generic flowsheet simulator,MinOOcad, has been developed to allow dynamicsimulation for any number of elements

✦ Advanced comminution models embedded in welldesigned software objects can provide realistic simulationsoff all flowsheet elements.

✦ Potential uses for MinOOcad are broad and exciting.